,transcriber's ,note ,in ,,problem ,i1 ,,chapter ,,iii1 ,section #de 7originally page #ch71 chemical formulas represent the numbers of atoms in a molecule with patterns like this3 ,c#aad4 ,throughout this e,book1 pairs of underscores enclose italicized text1 ,small-caps text appears as ,,all-,,caps1 and pairs of equals signs enclose boldface text4 ,works by the same ,author4 ,,problems ,,of ,,life ,,and ,,mind4 ,the ,foundations of a ,creed4 ,two ,volumes4 ,octavo4 ,per volume1 #c4jj4 ,,contents3 ,the ,method of ,science and its ,applications to ,metaphysics--,the ,rules of ,philosophizing--,psychological ,principles--,the ,limitations of ,knowledge--,the ,principles of ,certitude--,from the ,known to the ,unknown--,matter and ,force--,force and ,cause--,the ,absolute in the ,correlations of ,feeling and ,motion4 ,,the ,,story ,,of ,,goethe',s ,,life4 ,new ,edition4 ,one volume4 #afmo4 ,with ,portrait4 #a4ej4 99499 ,for sale by all ,booksellers4 ,sent1 post-paid1 on receipt of price by the ,publishers1 ,,houghton1 ,,mifflin ,,co41 ,,boston4 ,,the ,,physical ,,basis ,,of ,,mind4 ,with ,illustrations4 ,,being ,,the ,,second ,,series ,,of ,,problems ,,of ,,life ,,and ,,mind4 ,,by ,,george ,,henry ,,lewes4 ,illustration3 ,the ,riverside ,press4 ,,boston ,,and ,,new ,,york3 ,,houghton1 ,,mifflin ,,and ,,company4 ,the ,riverside ,press1 ,cambridge4 #ahia4 ,,author',s ,,edition4 ,from ,advance ,sheets4 ,the ,riverside ,press1 ,cambridge1 ,mass41 ,u4 ,s4 ,a4 ,printed by ,h4 ,o4 ,houghton ,company4 ,,preface4 ,the title indicates that this volume is restricted to the group of material conditions which constitute the organism in relation to the physical world--a group which furnishes the data for one half of the psychologist's quest2 the other half being furnished by historical and social conditions4 ,the ,human ,mind1 so far as it is accessible to scientific inquiry1 has a twofold root1 man being not only an animal organism but an unit in the social organism2 and hence the complete theory of its functions and faculties must be sought in this twofold direction4 ,this conception 7which has been declared 8to amount to a revolution in ,psychology071 although slowly prepared by the growing conviction that ,man could not be isolated from ,humanity1 was first expounded in the opening volume of these ,problems of ,life and ,mind2 at least1 ,i am not aware that any predecessor had seen how the specially human faculties of ,intellect and ,conscience were products of social factors co-operating with the animal factors4 ,in considering the ,physical ,basis a large place must be assigned to the mechanical and chemical relations which are involved in organic functions2 yet we have to recognize that this procedure of ,analysis is artificial and preparatory1 that none of its results are final1 none represent the synthetic reality of vital facts4 ,hence one leading object of the following pages has been everywhere to substitute the biological point of view for the metaphysical and mechanical points of view which too often obstruct research--the one finding its expression in spiritualist theories1 the other in materialist theories2 both disregarding the plain principle that the first requisite in a theory of biological phenomena must be to view them in the light of biological conditions3 in other words1 to fix our gaze upon what passes in the organism1 and not on what may pass in the laboratory1 where the conditions are different4 ,analysis is a potent instrument1 but is too often relied on in forgetfulness of what constitutes its real aid1 and thus leads to a disregard of all those conditions which it has artificially set aside4 ,we see this in the tendency of anatomists and physiologists to assign to one element1 in a complex cluster of co-operants1 the significance which properly belongs to that cluster3 as when the property of a tissue is placed exclusively in a single element of that tissue1 the function of an organ assigned to its chief tissue1 and a function of the organism to a single organ4 ,another object has been to furnish the reader uninstructed in physiology with such a general outline of the structure and functions of the organism1 and such details respecting the sentient mechanism1 as may awaken an interest in the study1 and enable him to understand the application of ,physiology to ,psychology4 ,if he comes upon details which can only interest specially educated students1 or perhaps only by them be really understood1 he can pass over these details1 for their omission will not seriously affect the bearing of the general principles4 ,i have given the best ,i had to give2 and must leave each reader to find in it whatever may interest him4 ,the uses of books are first to stimulate inquiry by awakening an interest2 secondly1 to clarify and classify the knowledge already gained from direct contemplation of the phenomena4 ,they are stimuli and aids to observation and thought4 ,they should never be allowed to see for us1 nor to think for us4 ,the volume contains four essays4 ,the first1 on the ,nature of ,life1 deals with the speciality of organic phenomena1 as distinguished from the inorganic4 ,it sets forth the physiological principles which ,psychology must incessantly invoke4 ,in the course of the exposition ,i have incorporated several passages from four articles on ,mr4 ,darwin's hypotheses1 contributed to the ,fortnightly ,review during the year #ahfh4 ,i have also suggested a modification of the hypothesis of ,natural ,selection1 by extending to the tissues and organs that principle of competition which ,mr4 ,darwin has so luminously applied to organisms4 ,should this generalization of the 8struggle for existence0 be accepted1 it will answer many of the hitherto unanswerable objections4 ,the second essay is on the ,nervous ,mechanism1 setting forth what is known and what is inferred respecting the structure and properties of that all-important system4 ,if the sceptical and revolutionary attitude1 in presence of opinions currently held to be established truths1 surprises or pains the reader unprepared for such doubts1 ,i can only ask him to submit my statements to a similar scepticism1 and confront them with the ascertained evidence4 ,after many years of laborious investigation and meditation1 the conclusion has slowly forced itself upon me1 that on this subject there is a 8false persuasion of knowledge0 very fatal in its influence1 because unhesitatingly adopted as the ground of speculation both in ,pathology and ,psychology4 ,this persuasion is sustained because few are aware how much of what passes for observation is in reality sheer hypothesis4 ,i have had to point out the great extent to which ,imaginary ,anatomy has been unsuspectingly accepted2 and hope to have done something towards raising a rational misgiving in the student's mind respecting 8the superstition of the nerve-cell0--a superstition which ,i freely confess to have shared in for many years4 ,the third essay treats of ,animal ,automatism4 ,here the constant insistance on the biological point of view1 while it causes a rejection of the mechanical theory1 admits the fullest recognition of all the mechanical relations involved in animal movements1 and thus endeavors to reconcile the contending schools4 ,in this essay ,i have also attempted a psychological solution of that much-debated question--the relation between ,body and ,mind4 ,this solution explains why physical and mental phenomena must necessarily present to our apprehension such profoundly diverse characters2 and shows that ,materialism1 in attempting to deduce the mental from the physical1 puts into the conclusion what the very terms have excluded from the premises2 whereas1 on the hypothesis of a physical process being only the objective aspect of a mental process1 the attempt to interpret the one by the other is as legitimate as the solution of a geometrical problem by algebra4 ,in the final essay the ,reflex ,theory is discussed2 and here once more the biological point of view rectifies the error of an analysis which has led to the denial of ,sensibility in reflex actions1 because that analysis has overlooked the necessary presence of the conditions which determine ,sensibility4 ,in these chapters are reproduced several passages from the ,physiology of ,common ,life4 ,according to my original intention1 this volume was to have included an exposition of the part ,i conceive the brain to play in physiological and psychological processes1 but that must be postponed until it can be accompanied by a survey of psychological processes which would render the exposition more intelligible4 ,,the ,,priory1 ,march1 #ahgg4 ,,contents4 ,,problem ,i4 ,,the ,,nature ,,of ,,life4 ,,chapter ,i4 ,,page ,,the ,,problem ,,stated #c 7,the ,position of ,biology7 #d 7,organisms7 #h 7,vital ,force7 #ad 7,vital ,force controlling ,physical and ,chemical ,forces7 #af ,,chapter ,,ii4 ,,definitions ,,of ,,life #bd ,,chapter ,,iii4 ,,organism1 ,,organization1 ,,and ,,organic ,,substance #cg 7,organism and ,medium7 #de 7,the ,hypothesis of ,germinal ,matter7 #eg 7,organisms and ,machines7 #fg ,,chapter ,,iv4 ,,the ,,properties ,,and ,,functions #gj 7,does the ,function determine the ,organ87 #gh ,,chapter ,v4 ,,evolution #hi 7,natural ,selection and ,organic ,affinity7 #aae 7,recapitulation7 #aeb ,,problem ,,ii4 ,,the ,,nervous ,,mechanism4 ,,chapter ,i4 ,,survey ,,of ,,the ,,system1 #aeg 7,the ,early ,forms of ,nerve-,centres71 #afh 7,the ,peripheral ,system71 #aga 7,ganglia and ,centres71 #agb ,,chapter ,,ii4 ,,the ,,functional ,,relations ,,of ,,the ,,nervous ,,system1 #agf ,,chapter ,,iii4 ,,neurility1 #ahi 7,origins of ,nerve-,force71 #bja 7,the ,hypothesis of ,specific ,energies71 #bjg ,,chapter ,,iv4 ,,sensibility1 #baa ,,chapter ,v4 ,,action ,,without ,,nerve-,,centres1 #bbg ,,chapter ,,vi4 ,,what ,,is ,,taught ,,by ,,embryology81 #bcg ,,chapter ,,vii4 ,,the ,,elementary ,,structure ,,of ,,the ,,nervous ,,system1 #bea 7,difficulties of the ,investigation71 #beb 7,the ,nerve-,cell71 #beh 7,the ,nerves71 #bgj 7,the ,neuroglia71 #bgc 7,the ,relations of the ,organites71 #bgh 7,recapitulation71 #bii ,,chapter ,,viii4 ,,the ,,laws ,,of ,,nervous ,,activity #caj 7,the ,energy of ,neurility7 #caa 7,the ,propagation of ,excitation7 #cad 7,stimuli7 #cba 7,stimulation7 #cbd 7,the ,law of ,discharge7 #cbf 7,the ,law of ,arrest7 #ccc 7,the ,hypothesis of ,inhibitory ,centres7 #ccf 7,anatomical ,interpretations of the ,laws7 #cci ,,problem ,,iii4 ,,animal ,,automatism4 ,,chapter ,i4 ,,the ,,course ,,of ,,modern ,,thought #cde ,,chapter ,,ii4 ,,the ,,vital ,,mechanism #cfc ,,chapter ,,iii4 ,,the ,,relation ,,of ,,body ,,and ,,mind #cgf ,,chapter ,,iv4 ,,consciousness ,,and ,,unconsciousness #cii ,,chapter ,v4 ,,voluntary ,,and ,,involuntary ,,actions #dae ,,chapter ,,vi4 ,,the ,,problem ,,stated #dca ,,chapter ,,vii4 ,,is ,,feeling ,,an ,,agent8 #ddj ,,problem ,,iv4 ,,the ,,reflex ,,theory4 ,,chapter ,i4 ,,the ,,problem ,,stated #dfg ,,chapter ,,ii4 ,,deductions ,,from ,,general ,,laws #dij ,,chapter ,,iii4 ,,inductions ,,from ,,particular ,,observations #eji 7,cerebral ,reflexes7 #eaa 7,discrimination7 #ebj 7,memory7 #ebb 7,instinct7 #ebb 7,the ,acquisition of ,instinct7 #ecf 7,acquisition7 #edf ,,chapter ,,iv4 ,,negative ,,inductions #eej ,,problem ,i4 ,,the ,,nature ,,of ,,life4 8,la ,physiologie a pour but d'exposer les phnomnes de la vie humaine et les conditions d'o ils dpendant4 ,pour y arriver d'une manire sre1 il faut ncessairement avant tout dterminer quels sont les phnomnes qu'on dsigne sous le nom de vie en gnral4 ,c'est pourquoi la premire chose faire est d'tudier les proprits gnrales du corps qu'on appelle organiques ou vivans40--,,tiedemann1 ,trait de ,physiologie de l',homme1 ,i4 #b4 8,some weak and inexperienced persons vainly seek by dialectics and far-fetched arguments either to upset or establish things that are only to be founded on anatomical demonstration and believed on the evidence of the senses4 ,he who truly desires to be informed of the question in hand must be held bound either to look for himself1 or to take on trust the conclusions to which they who have looked have come40--,,harvey1 ,second ,dissertation to ,riolan4 ,,the ,,nature ,,of ,,life4 ,,chapter ,i4 ,,the ,,problem ,,stated4 #a4 ,although for convenience we use the terms ,life and ,mind as representing distinct orders of phenomena1 the one objective and the other subjective1 and although for centuries they have designated distinct entities1 or forces having different substrata1 we may now consider it sufficiently acknowledged among scientific thinkers that every problem of ,mind is necessarily a problem of ,life1 referring to one special group of vital activities4 ,it is enough that ,mind is never manifested except in a living organism to make us seek in an analysis of organic phenomena for the material conditions of every mental fact4 ,mental phenomena when observed in others1 although interpretable by our consciousness of what is passing in ourselves1 can only be objective phenomena of the vital organism4 #b4 ,on this ground1 if on this alone1 an acquaintance with the general principles of structure and function is indispensable to the psychologist2 although only of late years has this been fully recognized1 so that men profoundly ignorant of the organism have had no hesitation in theorizing on its highest functions4 ,in saying that such knowledge is indispensable1 ,i do not mean that in the absence of such knowledge a man is debarred from understanding much of the results reached by investigators1 nor that he may not himself make useful observations and classifications of psychological facts4 ,it is possible to read books on ,natural ,history with intelligence and profit1 and even to make good observations1 without a scientific groundwork of biological instruction2 and it is possible to arrive at empirical facts of hygiene and medical treatment without any physiological instruction4 ,but in all three cases the absence of a scientific basis will render the knowledge fragmentary and incomplete2 and this ought to deter every one from offering an opinion on debatable questions which pass beyond the limit of subjective observations4 ,the psychologist who has not prepared himself by a study of the organism has no more right to be heard on the genesis of the psychical states1 or of the relations between body and mind1 than one of the laity has a right to be heard on a question of medical treatment4 ,,the ,,position ,,of ,,biology4 #c4 ,science is the systematic classification of ,experience4 ,it postulates unity of ,existence with great varieties in the ,modes of ,existence2 assuming that there is one ,matter everywhere the same1 under great diversities in the complications of its elements4 ,the distinction of ,modes is not less indispensable than the identification of the elements4 ,these ,modes range themselves under three supreme heads3 ,force1 ,life1 ,mind4 ,under the first1 range the general properties exhibited by all substances2 under the second1 the general properties exhibited by organized substances2 under the third1 the general properties exhibited by organized animal substances4 ,the first class is subdivided into ,physics1 celestial and terrestrial1 and ,chemistry4 ,physics treats of substances which move as masses1 or which vibrate and rotate as molecules1 without undergoing any appreciable change of structural integrity2 they show changes of position and state1 without corresponding changes in their elements4 ,chemistry treats of substances which undergo molecular changes of composition destructive of their integrity4 ,thus the blow which simply moves one body1 or makes it vibrate1 explodes another4 ,the friction which alters the temperature and electrical state of a bit of glass1 ignites a bit of phosphorus1 and so destroys its integrity of structure1 converting phosphorus into phosphoric acid4 #d4 ,the second class1 while exhibiting both physical and chemical properties1 is markedly distinguished by the addition of properties called vital4 ,their peculiarity consists in this3 they undergo molecular changes of composition and decomposition which are simultaneous1 and by this simultaneity preserve their integrity of structure4 ,they change their state1 and their elements1 yet preserve their unity1 and even when differentiating continue specific4 ,unlike all other bodies1 the organized are born1 grow1 develop1 and decay1 through a prescribed series of graduated evolutions1 each stage being the indispensable condition of its successor1 no stage ever appearing except in its serial order4 #e4 ,the third class1 while exhibiting all the characteristics of the two preceding classes1 is specialized by the addition of a totally new property1 called ,sensibility1 which subjectively is ,feeling4 ,here organized substance has become animal substance1 and ,vegetality has been developed into ,animality by the addition of new factors1--new complexities of the elementary forces4 ,many1 if not most1 philosophers postulate an entirely new ,existence1 and not simply a new ,mode1 to account for the manifestations of ,mind2 they refuse to acknowledge it to be a vital manifestation1 they demand that to ,life be added a separate substratum1 the ,soul4 ,this is not a point to be discussed here4 ,we may be content with the assertion that however great the phenomenal difference between ,humanity and ,animality 7a difference we shall hereafter see to be the expression of a new factor1 namely1 the social factor71 nevertheless the distinctive attribute of ,sensibility1 out of which rise ,emotion and ,cognition1 marks the inseparable kinship of mental with vital phenomena4 ,thus all the various ,modes of ,existence may1 at least in their objective aspect1 be ranged under the two divisions of ,inorganic and ,organic1--,non-living and ,living1--and these are respectively the objects of the cosmological and the biological sciences4 #f4 ,the various sciences in their serial development develop the whole art of ,method4 ,mathematics develops abstraction1 deduction1 and definition2 ,astronomy abstraction1 deduction1 and observation2 ,physics adds experiment2 ,chemistry adds nomenclature2 ,biology adds classification1 and for the first time brings into prominence the important notion of conditions of existence1 and the variation of phenomena under varying conditions3 so that the relation of the organism to its medium is one never to be left out of sight4 ,in ,biology also clearly emerges for the first time what ,i regard as the true notion of causality1 namely1 the procession of causes1--the combination of factors in the product1 and not an ab extra determination of the product4 ,in ,vitality and ,sensibility we are made aware that the causes are in and not outside the organism2 that the organic effect is the organic cause in operation2 that there is autonomy but no autocracy2 the effect issues as a resultant of the co-operating conditions4 ,in ,sociology1 finally1 we see brought into prominence the historical conditions of existence4 ,from the due appreciation of the conditions of existence1 material and historical1 we seize the true significance of the principle of ,relativity4 #g4 ,having thus indicated the series of the abstract sciences we have now to consider more closely the character of ,biology4 ,the term was proposed independently yet simultaneously in ,germany and ,france1 in the year #ahjb1 by ,treviranus and ,lamarck1 to express 8the study of the forms and phenomena of ,life1 the conditions and laws by which these exist1 and the causes which produce them40 ,yet only of late years has it gained general acceptance in ,france and ,england4 ,the term ,cosmology1 for what are usually called the ,physical ,sciences1 has not yet come into general use1 although its appropriateness must eventually secure its recognition4 ,biology1--the abstract science of ,life1--embracing the whole organic world1 includes ,vegetality1 ,animality1 and ,humanity2 the biological sciences are ,phytology1 ,zology1 and ,anthropology4 ,each of the sciences has its cardinal divisions1 statical and dynamical1 namely1 ,morphology--the science of form1--and ,physiology--the science of function4 ,morphology embraces--#a1 ,anatomy1 i4 e4 the description of the parts then and there present in the organism2 and these parts1 or organs1 are further described by the enumeration of their constituent tissues and elements2 and of these again the proximate principles1 so far as they can be isolated without chemical decomposition4 #b1 ,organogeny1 i4 e4 the history of the evolution of organs and tissues4 ,physiology embraces the properties and functions of the tissues and organs--the primary conditions of ,growth and ,development out of which rise the higher functions bringing the organism into active relation with the surrounding medium4 ,the first group of properties and functions are called those of vegetal1 or organic life2 the second those of animal1 or relative life4 ,,organisms4 #h4 ,it will be needful to fix with precision the terms1 ,organism1 ,life1 ,property1 and ,function4 ,an organism1 although usually signifying a more or less complex unity of organs1 because the structures which first attracted scientific attention were all thus markedly distinguished from inorganic bodies1 has by the gradual extensions of research been necessarily generalized1 till it now stands for any organized substance capable of independent vitality3 in other words1 any substance having the specific combination of elements which manifests the serial phenomena of growth1 development1 and decay4 ,there are organisms that have no differentiated organs4 ,thus a microscopic formless lump of semifluid jelly-like substance 7,protoplasm7 is called an organism1 because it feeds itself1 and reproduces itself4 ,there are advantages and disadvantages in such extensions of terms4 ,these are notable in the parallel extension of the term ,life1 which originally expressing only the complex activities of complex organisms1 has come to express the simplest activities of protoplasm4 ,thus a ,monad is an organism2 a ,cell is an organism2 a ,plant is an organism2 a ,man is an organism4 ,and each of these organisms is said to have its ,life1 because 8,through all the mighty commonwealth of things ,up from the creeping worm to sovereign man0#a there is one fundamental group of conditions1 one organized substance1 one vitality4 ,obviously this unity is an abstraction4 ,in reality1 the life manifested in the ,man is not the life manifested in the ,monad3 he has ,functions and ,faculties which the ,monad has no trace of2 and if the two organisms have certain vital characteristics in common1 this unity is only recognized in an ideal construction which lets drop all concrete differences4 ,the ,life is different when the organism is different4 ,hence any definition of ,life would be manifestly insufficient which while it expressed the activities of the ,monad left unexpressed the conspicuous and important activities of higher organisms4 ,a sundial and a repeater will each record the successive positions of the sun in the heavens2 but although both are instruments for marking time1 the sundial will not do the work of the repeater2 the complexity and delicacy of the watch mechanism are necessary for its more varied and delicate uses4 ,a semifluid bit of protoplasm will feed itself2 but it will not feed and sustain a complex animal2 nor will it feel and think4 #i4 ,neglect of this point has caused frequent confusion in the attempts to give satisfactory definitions4 ,biologists ought to have been warned by the fact that some of the most widely accepted definitions exclude the most conspicuous phenomena of ,life1 and are only applicable to the vegetable world1 or to the vegetal processes in the animal world4 ,a definition1 however abstract1 should not exclude essential characters4 ,the general consent of mankind has made ,life synonymous with ,mode of ,existence4 ,by the life of an animal is meant the existence of that animal2 when dead the animal no longer exists2 the substances of which the organism was composed exist1 but under another mode2 their connexus is altered1 and the organism vanishes in the alteration4 ,it is a serious mistake to call the corpse an organism2 for that special combination which constituted the organism is not present in the corpse4 ,this misconception misleads some speculative minds into assigning life to the universe4 ,the universe assuredly exists1 but it does not live2 its existence can only be identified with life1 such as we observe in organisms1 by a complete obliteration of the speciality which the term ,life is meant to designate4 ,yet many have not only pleased themselves with such a conception1 but have conceived the universe to be an organism fashioned1 directed1 and sustained by a soul like that of man--the anima mundi4 ,this is to violate all scientific canons4 ,the life of a plant-organism is not the same as the life of an animal-organism2 the life of an animal-organism is not the same as the life of a human-organism2 nor can the life of a human-organism be the same as the life of the world-organism4 ,the unity of ,existences does not obliterate the variety of ,modes2 yet it is the speciality of each ,mode which ,science investigates2 to some of these ,modes the term ,life is consistently applied1 to others not2 and if we merge them all in a common term1 we must then invent a new term to designate the ,modes now included under ,life4 #aj4 ,in resisting this unwarrantable extension of the term ,i am not only pointing to a speculative error1 but also to a serious biological error common in both spiritualist and materialist schools1 namely that of assigning ,life to other than organic agencies4 ,instead of recognizing the speciality of this ,mode of ,existence as dependent on a speciality of the organic conditions1 the spiritualist assigns ,life to some extra-organic ,vital ,principle1 the materialist assigns it to some inorganic agent--physical or chemical4 ,waiving for the present all discussion of ,vitalism1 let us consider in what sense we must separate organic from all inorganic phenomena4 #aa4 ,there is a distinction between inorganic and organic which may fitly be called radical3 it lies at the root of the phenomena1 and must be accepted as an ultimate fact1 although the synthesis on which it depends is analytically reducible to a complication of more primitive conditions4 ,it has been already indicated in #e4 ,all organisms above the very simplest are syntheses ,of three terms3 ,structure1 ,aliment1 and ,instrument4 ,crystals1 like all other anorganisms have structure1 and in a certain sense they may be said to grow 7,mineralia crescunt71 though the growth is by increase and not by modification3#b the motherlye1 which is the food of the crystal1 is never brought to the crystal1 nor prepared for it1 by any instrumental agency of the crystal4 ,organisms are exclusively instrumental2 the organ is an instrument4 ,the structural integrity of an organism is thus preserved through an alimentation which is effected through special instruments4 ,nothing like this is visible in anorganisms4 ,the increase of a crystal is further distinguishable from the growth of an organism1 in the fact ,of its being simple accretion without development2 and the structure of the crystal is distinguishable from that of an organism in the fact that its integrity is preserved by the exclusion of all molecular change1 and not by the simultaneous changes of molecular decomposition and recomposition4 ,inorganic substances are sometimes as unstable as organic1 sometimes even more unstable2 but their instability is the source of their structural destruction--they change into other species2 whereas the instability of organized substances 7not of organic7 is the source of their structural integrity3 the tissue is renovated1 and its renovation is a consequence of its waste4 #ab4 ,but while the distinction is thus radical1 when we view the organism from the real--that is1 from the synthetic point of view--we must also urge the validity of the analytical point of view1 which seizes on the conditions here complicated in a special group1 and declares these conditions to be severally recognizable equally in anorganisms and in organisms4 ,all the fundamental properties of ,matter are recognizable in organized ,matter4 ,the elementary substances and forces familiar to physicists and chemists are the materials of the biologist2 nor has there been found a single organic substance1 however special1 that is not reducible to inorganic elements4 ,we see1 then1 that organized ,matter is only a special combination of that which in other combinations presents chemical and physical phenomena2 and we are prepared to find ,chemistry and ,physics indispensable aids in our analysis of organic phenomena4 ,aids1 but only aids2 indispensable1 but insufficient4 #ac4 ,there is therefore an ambiguity in the common statement that organized matter is not ordinary matter4 ,indisputable in one sense1 this is eminently disputable when it is interpreted as evidence of a peculiar ,vital ,force 8wholly unallied with the primary energy of ,motion40 ,if by 8ordinary matter0 be meant earths1 crystals1 gases1 vapors1 then assuredly organized matter is not ordinary4 8,between the living state of matter and its non-living state10 says ,dr4 ,beale1 8there is an absolute and irreconcilable difference2 so far from our being able to demonstrate that the non-living passes by gradations into or gradually assumes the scale or condition of the living1 the transition is sudden and abrupt1 and matter already in the living state may pass into the non-living condition in the same sudden and complete manner40#c ,the ambiguity here is sensible in the parallel case of the difference between crystallizable and coagulable matter1 or between one crystal and another4 ,if we can decompose the organic into the inorganic1 this shows that the elements of the one are elements of the other2 and if we are not yet able to recompose the inorganic elements into organic matter 7not at least in its more complex forms71 may this not be due to the fact that we are ignorant of the proximate synthesis1 ignorant of the precise way in which the elements are combined8 ,i may have every individual part of a machine before me1 but unless ,i know the proper position of each1 ,i cannot with the parts reconstruct the machine4 ,indeed the very common argument on which so much stress is laid in favor of some mysterious ,principle as the source of organic phenomena1 namely1 that human skill is hopelessly baffled in the attempt to make organic substances1 still more a living cell1 is futile4 ,men can make machines1 it is said1 but not organisms1 ergo organisms must have a spiritual origin4 ,but the fact is that no man can make a machine1 unless he take advantage of the immense traditions of our race1 and apply the skill of millions who have worked and thought before him1 slowly and tentatively discovering the necessary means of mechanical effect4 ,the greatest thinker1 or the deepest scholar1 who did not place himself in the line of the tradition1 and learn the principles of mechanism1 and the properties of the materials1 would be as incapable of making a watch1 as the physiologist now is of making a cell4 ,but the skill of man has already succeeded in making many organic substances1 and will perhaps eventually succeed in making a cell1 certainly will1 if ever the special synthesis which binds the elements together should be discovered4 ,not that such a discovery would alter the position of ,biology in relation to ,chemistry4 ,the making of albumen1 nay1 the construction of an organism in the laboratory1 would not in the least affect the foundation of ,biology1 would not obliterate the radical difference between organisms and anorganisms4 ,it is the speciality of organic phenomena which gives them a special place1 although the speciality may only be due to a complication of general agencies4 ,,vital ,,force4 #ad4 ,a similar ambiguity to that of the phrase 8ordinary matter0 lies in the equally common phrase 8,vital ,force10 which is used to designate a special group of agencies1 and is then made to designate an agent which has no kinship with the general group2 that is to say1 instead of being employed in its real signification--that which alone represents our knowledge--as the abstract statical expression of the complex conditions necessary to the manifestation of vital phenomena1 or as the abstract dynamical expression of the phenomena themselves1 it is employed as an expression of their unknown ,cause1 which1 because unknown1 is dissociated from the known conditions1 and erected into a mysterious ,principle1 having no kinship with ,matter4 ,in the first sense the term is a shorthand symbol of what is known and inferred4 ,the known conditions are the relations of an organism and its medium1 the organism being the union of various substances all of which have their peculiar properties when isolated2 properties that disappear in the union1 and are replaced by others1 which result from the combination--as the properties of chlorine and sodium all disappear in the sea-salt which results from their union2 or as the properties of oxygen and the properties of hydrogen disappear and are replaced by the properties of water4 ,when therefore ,vital ,force is said to be exalted or depressed1 the phrase has rational interpretation in the alteration which has taken place in one or more of the conditions1 internal and external3 a change in the tissues1 the plasma1 or the environment1 exalts or depresses the energy of the vital manifestations2 and to suppose that this is effected through the agency of some extra-organic ,principle is a purely gratuitous fiction4 #ae4 ,that we are ignorant of one or more of the indispensable conditions symbolized in the abstract term ,vitality or ,vital ,force1 is no reason for quitting the secure though difficult path of ,observation1 and rushing into the facile but delusive path of ,fiction1 which proposes metempirical ,agents 7in the shape of ,vital and ,psychical ,principles7 to solve the problems of ,life and ,mind4 ,we may employ the term ,vital ,force to label our observations1 together with all that still remains unobserved2 and we are bound to recognize the line which separates observation from inference1 what is proved from what is inferred2 but while marking the limits of the known1 we are not to displace the known in favor of the unknown4 ,it is said that because of our ignorance we must assume these causes of ,life and ,mind to be unallied with known material causes1 and belonging to a different order of existences4 ,this is to convert ignorance into a proof2 and not only so1 but to allow what we do not know to displace what we do know4 ,the organicist is ready to admit that much has still to be discovered2 the vitalist1 taking his stand upon this unknown1 denies that what has been discovered is really important1 and declares that the real agent is wholly unallied to it4 ,how can he know this8 ,he does not know it2 he assumes it2 and the chief evidence he adduces is that the ordinary laws of inorganic matter are incapable of explaining the phenomena of organized matter2 and that physical and chemical forces are controlled by vital force4 ,i accept both these positions1 stripping them1 however1 of their ambiguities4 ,the laws of ordinary matter are clearly incompetent in the case of matter which is not ordinary1 but specialized in organisms2 and when we come to treat of ,materialism we shall see how unscientific have been the hypotheses which disregard the distinction4 ,the question of control is too interesting and important to be passed over here4 ,,vital ,,force ,,controlling ,,physical ,,and ,,chemical ,,forces4 #af4 ,the facts relied on by the vitalists are facts which every organicist will emphasize1 though he will interpret them differently4 ,when1 for example1 it is said that 8,life resists the effect of mechanical friction10 and the proof adduced is the fact that the friction which will thin and wear away a dead body is actually the cause of the thickening of a living--the skin of a laborer's hand being thickened by his labor2 the explanation is not that ,life1 an extra-organic agent1 8resists mechanical friction0--for the mechanical effect is not resisted 7the skin is rubbed off the rower's hand sooner than the wood is rubbed off the oar7--but that ,life1 i4 e4 organic activity repairs the waste of tissue4 #ag4 ,again1 although many of the physical and chemical processes which invariably take place under the influences to which the substances are subjected out of the organism1 will not take place at all1 or will take place in different degrees1 when the substances are in the organism1 this is important as an argument against the notion of vital phenomena being deducible from physical and chemical laws1 but is valueless as evidence in favor of an extra-organic agent4 ,let us glance at one or two striking examples4 #ah4 ,no experimental inquirer can have failed to observe the often contradictory results which seemingly unimportant variations in the conditions bring about2 no one can have failed to observe what are called chemical affinities wholly frustrated by vital conditions4 ,even the ordinary laws of ,diffusion are not always followed in the organism4 ,the ,amba1 though semifluid1 resists diffusion when alive2 but when it dies it swells and bursts by osmosis4 ,the exchange of gases does not take place in the tissues1 precisely as in our retorts4 ,the living muscle respires1 that is1 takes up oxygen and gives out carbonic acid1 not on the principle of simple diffusion1 but by two separable physiological processes4 ,the carbonic acid is given out1 even when there is no oxygen whatever present in the atmosphere1 and its place may then be supplied by hydrogen2 and this physiological process is so different from the physical process which goes on in the dead muscle 7the result of putrefaction71 that it has been proved by ,ranke to go on when the temperature is so low that all putrefaction is arrested4 ,the same experimenter finds#d that whereas living nerve will take up1 by imbibition1 #aj per cent of potash salts1 it will not take up #a per cent of soda salts1 presented in equal concentration2 and he points to the general fact that the absorption of inorganic substances does not take place according to the simple laws of diffusion1 but that living tissues have special laws1 the nerve1 for instance1 having a greater affinity for neutral potash salts than for neutral soda salts4 ,let me add1 by way of anticipating the probable argument that may urge this in favor of ,vital ,principle which is lightly credited with the prescience of final causes1 that so far from this 8elective affinity0 of the tissues being intelligent and always favorable1 ,ranke's experiments unequivocally show that it is more active towards destructive1 poisonous substances1 than towards the reparative1 alimentary substances2 which is indeed consistent with the familiar experience that poisons are more readily absorbed than foods1 when both are brought to the tissues4 ,thus it is well known that of all the salts the sulphate of copper is that which plants most readily absorb--and it kills them4 ,the special affinities disappear as the vitality disappears1 and dying plants absorb all salts equally4 #ai4 ,the more the organism is studied1 the more evident it will become that the simple laws of diffusion1 as presented in anorganisms rarely if ever take effect in tissues2 in other words1 what is called ,imbibition in ,physics is the somewhat different process of ,absorption in ,physiology4#e ,the difference is notable in this capital fact1 that whereas the physical diffusion of liquids and gases is determined by differences of density1 the physiological absorption of liquids and gases is determined by the molecular organization of the tissue1 which is perfectly indifferent to1 and resists the entrance of1 all substances incapable of entering into organic combination1 either as aliment or poison4 ,a curious example of the indifference of organized substances to some external influences and their reaction upon others1 is the impossibility of provoking ciliary movement in an epithelial cell1 during repose1 by any electrical1 mechanical1 or chemical stimuli except potash and soda4 ,virchow discovered that a minute quantity of either of these1 added to the water in which the cell floated1 at once called forth the ciliary movements4 #bj4 ,the true meaning of the resistance of ,vitality to ordinary chemical affinity is1 that the conditions involved in the phenomena of ,vitality are not the conditions involved in the phenomena of ,chemistry2 in other words1 that in the living organism the substances are placed under conditions different from those in which we observe these substances when their chemical affinities are displayed in anorganisms4 ,but we need not go beyond the laboratory to see abundant examples of this so-called resistance to chemical affinity1 when the conditions are altered4 ,the decomposition of carbonates by tartaric acid is a chemical process which is wholly resisted if alcohol instead of water be the solvent employed4 ,the union of sulphur with lead is said to be due to the affinity of the one for the other2 but no one supposes this affinity to be irrespective of conditions1 or that the union will take place when any one of these conditions is absent4 ,if we fuse a compound of lead and iron in a crucible containing sulphur1 we find it is the iron1 and not the lead1 which unites with the sulphur2 yet we do not conclude that there is a ,crucible ,principle which frustrates chemical affinity and resists the union of sulphur and lead2 we simply conclude that the presence of the iron is a condition which prevents the combination of the sulphur with the lead3 not until all the iron has taken up its definite proportion of sulphur will the affinity of the lead come into play4 ,this is but another illustration of the law that effects are processions of their causes1 summations of the conditions of their existence4 ,if the fire burns no hole in the teakettle so long as there is water to conduct the heat away1 this is not due to any principle more mysterious than the presence of a readily conducting water4#f #ba4 ,in accordance with the law of ,causation just mentioned1 which has been expounded in detail in our ,first ,series 7,vol4 ,,ii4 p4 #cce71 the special combinations of ,matter in organisms must present special phenomena4 ,therefore since the province of ,biology is that of explaining organic phenomena by means of their organic conditions1 it must be radically distinguished from the provinces of ,physics and ,chemistry1 which treat not of organized but of inorganic matter4 ,it is idle1 it is worse1 for it is misleading1 to personify the organic conditions1 known and inferred1 in a ,vital ,principle2 idle1 because we might with equal propriety personify the conditions of crystallization in a ,crystal ,principle2 misleading1 because the artifice is quickly dropped out of sight1 and the abstract term then becomes accepted as an entity1 supposed to create or rule the phenomena it was invented to express4 #bb4 ,inquirers are but too apt to misconceive the value of ,analysis1 which is an artifice of ,method indispensable to research1 though needing the complementary rectification by ,synthesis before a real explanation can be reached4 ,analysis decomposes the actual fact into ideal factors1 separates the group into its components1 and considers each of these1 not as it exists in the group1 in the reality1 but as it exists when theoretically detached from the others4 ,the oxygen and hydrogen into which water is decomposed did not exist as these gases in the water2 the albumen and phosphate we extract from a nerve did not exist as isolated albumen and phosphate in the nerve1 they were molecularly combined4 ,in like manner the physical and chemical processes which may analytically be inferred in vital processes do not really take place in the same way as out of the organism4 ,the real process is always a vital process1 and must be explained by the synthesis of all the co-operant conditions4 ,the laws of ,physics and ,chemistry formulate abstract expressions of phenomena1 wherever and whenever these appear1 without reference to the modes of production2 and in this sense the movement of a limb is no less a case of ,dynamics than the movement of a pulley--the decomposition of a tissue is a case of ,chemistry no less than the decomposition of a carbonate2 the electromotor phenomena observed in muscle are as purely physical as those observed in a telegraph4 ,but when a biologist has to explain the movements of the limbs1 or the decompositions of tissues1 he has to deal with the phenomena and their modes of production1 he has a particular group before him1 and must leave out nothing that is characteristic of it4 ,the movements of the pulley do not depend on ,contractility and ,sensibility1 which in turn depend on ,nutrition4 ,the decomposition of the carbonate does not depend on conditions resembling those of a living tissue4 ,vaucanson's duck was surprisingly like a living duck in many of its movements2 but in none of its actions was there any real similarity to the actions of a bird1 because the machine was unlike an organism in action4 ,the antithesis of mechanism and organism will be treated of in #gh4 #bc4 ,we conclude1 then1 that defining physical phenomena as the movements which take place without change of structure1 and chemical phenomena as the movements with change of structure1 although both classes may be said to take place in the organism1 and to be the primary conditions on which organic phenomena depend1 they do not embrace the whole of the conditions1 nor are the sciences which formulate them capable of formulating either the special phenomena characteristic of organisms or their special modes of production4 ,the biologist will employ chemical and physical analysis as an essential part of his method2 but he will always rectify what is artificial in this procedure1 by subordinating the laws of ,physics and ,chemistry to the laws of ,biology revealed in the synthetic observation of the organism as a whole4 ,the rectification1 here insisted on1 will be recognized as peculiarly urgent in ,psychology1 which has greatly suffered from the misdirection of ,analysis4 #bd4 ,no one will misunderstand this specialization of ,biology to mean a separation of ,life from the series of objective phenomena1 and the introduction of a new entity2 the specialization points to a ,mode of ,existence4 ,all classifications are artifices1 but they have their objective grounds2 the ground of difference on which ,biology is separated from ,chemistry and ,physics1 though all three may be merged in a common identity1 is such as to justify the term radical4 ,a vital process is no more to be considered physico-chemical1 because physico-chemical conditions are presupposed in it1 than a feeling is to be considered a nutritive process1 because ,nutrition is presupposed in all ,feeling4 ,organic substances have been made by chemists1 and inorganic 8cells0 have also been made2 but these substances were not organized1 these 8cells0 would not live4 ,the germ-cell is the workshop of generation1 the secreting-cell the workshop of secretion1 the muscle-cell the workshop of contraction4 ,what is required over and above organic substances and cell-forms1 is that special state called organization4 ,see #di4 ,those who contemplate the manifestations without also taking into account their modes of production may see nothing but physico-chemical facts in vital facts4 ,it is by a similar limitation of the point of view that ,vitality is often confounded with ,movement1 and portions of organic matter are said to live1 simply on the evidence of their movements4#g ,,chapter ,,ii4 ,,definitions ,,of ,,life4 #be4 ,biology1 the science of ,life1 being thus assigned its place in the hierarchy of objective laws1 we now proceed to consider what the term ,life symbolizes4 ,by a large preliminary simplification1 ,life may be defined as the mode of existence of an organism in relation to its medium4 ,to render this of any value1 however1 a clear conception of the organism is first indispensable2 and this must be preceded by an examination of the various attempts to define life in anticipation of such a clear conception4 #bf4 ,every phenomenon1 or group of phenomena1 may be viewed under two aspects--the statical1 which considers the conditions of existence2 and the dynamical1 which considers these conditions in their resultant1--in their action4 ,the statical definition of ,life will express the connexus of the properties of organized substance1 all those conditions1 of matter1 form1 and texture1 and of relation to external forces1 on which the organism depends4 ,these various conditions1 condensed into a single symbol1 constitute ,vitality or ,vital ,force1 and are hence taken as the ,cause of vital phenomena4 ,the dynamical definition will express the connexus of ,functions and ,faculties of the organism1 which are the statical properties of organized substance in action1 under definite relations4 ,it is obvious that the term ,life must vary with the varying significates it condenses1--every variation in the complexity of the organism will bring a corresponding fulness in the signification of the term4 ,the life of a plant is less significant than the life of an animal2 and the life of a mollusc less than that of a fish4 ,but not only is the term one of varying significance1 it is always an abstract term which drops out of sight particular concrete differences1 registering only the universal resemblances4 99 99 99 99 99 #bg4 ,it would be a profitless labor to search out1 and a wearisome infliction to set down1 the various definitions which have been proposed and accepted2 but certain characteristic examples may be selected4 ,all that ,i am acquainted with belong to two classes3 #a1 the meta-physiological hypothesis of an extra-organic agent1 animating lifeless matter by unknown powers2 #b1 the physiological hypothesis which seeks the cause of the phenomena 7i4 e4 the conditions7 within the organism itself1--a group of conditions akin to those manifested elsewhere1 but differently combined4 ,the first hypotheses are known under the names of ,animism and ,vitalism1--more commonly the latter4 ,the second are known as ,organicism and ,materialism1--but the latter term only applies to some of the definitions4 #bh4 ,under ,vitalism are included all the hypotheses of a soul1 a spirit1 an archus1 a vital principle1 a vital force1 a nisus formativus1 a plan or divine idea1 which have from time to time represented the metaphysical stage of ,biology4 ,the characteristic of that stage is the personification of a mystery1 accompanied by the persuasion that to name a mystery is to explain it4 ,in all sciences when processes are imperfectly observed1 the theory of the processes 7which is a systematic survey of the available evidence marshalled in the order of causal dependence7 is supplemented by hypothesis1 which fills up with a guess the gap left by observation4 ,the difference between the metaphysical and the positive stages of a science lies in the kind of guess thus introduced to supplement theory1 and the degree of reliance accorded to it4 ,i have more than once insisted on the scientific canon that 8to be valid1 an explanation must be expressed in terms of phenomena already observed02 now it is quite clear that most of the extra-organic hypotheses do not fulfil this condition2 no one having ever observed a spirit1 an archus1 or a vital principle2 but only imagined these agents to explain the facts observed4 ,as an example of the difference1 and a proof that the value of an hypothesis does not rest on the facility with which it connects observations1 and seems to explain them1 take the three hypotheses of animal spirits1 nervous fluid1 and electricity1 by which neural processes have been explained4 ,the animal spirits are imaginary2 the nervous fluid is without a basis in observation1 no evidence of such a fluid having been detected2 but electricity 7or1 speaking rigorously1 the movements classed as electrical71 although not proved to be the agent in nerve-action1 is proved to exist in nerves as elsewhere1 and its modes of operation are verifiable4 ,it1 therefore1 and it alone of the three hypotheses1 is in conformity with the scientific canon4 ,it may not1 on full investigation1 meet all requirements2 it may be rejected as imperfect2 but it is the kind of guess which scientific theory demands4 ,the second difference noticeable between the metaphysical and the positive stages is the degree of reliance accorded to hypothesis2 which is very much the same as that noticeable in the uncritical and critical attitudes of untrained and trained intellects4 ,the one accepts a guess as if it were a proof2 is fascinated by the facility of linking together isolated observations1 and1 relying on the guess as truth1 proceeds to deduce conclusions from it2 the other accepts a guess as an aid in research1 trying by its aid to come upon some observation which will reveal the hidden process2 but careful never to allow the guess to supersede observation1 or to form a basis of deductions not immediately verified4 #bi4 ,a glance at the metaphysiological definitions will detect both the kind of guess and the kind of reliance which prevailed4 ,the mystery was not simply recognized1 it was personified as an entity3 ,will and ,intelligence were liberally accorded to it1 for it was supposed to shape matter1 and direct force into predestined paths by prescience of a distant end4 ,the observed facts of the egg passing through successive changes into a complex organism were so marvellous1 so unlike any facts observable in the inorganic world1 that they seemed to demand a cause drawn from higher sources4 ,the mystery of life obtruded itself at every turn4 ,it was named1 and men fancied it explained4 ,but in truth no mystery is got rid of by explanation1 however valid2 it is only shifted farther back4 ,explanation is the resolution of a complex phenomenon into its conditions of existence--the product is reduced to its factors2 the explanation is final when this resolution has been so complete that a reconstruction of the product is possible from the factors4 ,the vast majority of explanations--especially in the organic region--are no more than what mathematicians call 8a first approximation40 ,it is through successive approximations that science advances2 but even when the final stage is reached a mystery remains4 ,we may know that certain elements combine in certain proportions to produce certain substances2 but why they produce these1 and not different substances1 is no clearer than why muscles contract or organisms die4 ,this ,why is1 however1 an idle question4 ,that alone which truly concerns us is the ,how1 and not the ,why4 #cj4 ,biology is still a long way off the ,how4 ,but it can boast of many approximations2 and its theories are to be tested by the degree of approximation they effect4 ,in this light the physiological1 intra-organic1 hypotheses manifestly have the advantage4 ,many of them are indeed very unacceptable2 they are guided by a mistaken conception of the truths reached by ,analysis4 ,for when men first began to discard the extra-organic hypotheses1 and to look into the organism itself1 they were so much impressed by the mechanical facts observed1 that they endeavored to reduce all the phenomena to ,mechanics4 ,the circulation became simply a question of hydraulics4 ,digestion was explained as trituration4 ,the chemists then appeared1 and their shibboleths were 8affinities0 and 8oxidations40 ,with ,bichat arose the anatomical school1 which decomposing the organism into organs1 the organs into tissues1 and these tissues into their elements1 sought the analytical conditions of existence of the organism in the properties of these tissues1 and the functions of these organs4 ,the extra-organic agent was thus finally shown to be not only a fiction1 but a needless fiction4 ,every student of the history of the science will note how from the very necessities of the case the metaphysiologists1 without relinquishing their ,vital ,principle1 have been led more and more to enter on the track of the physiologists1 pursuing their researches more and more into the processes going on in the organism1 and assigning more and more causal efficiency to these1 with a corresponding restriction of the province of their extra-organic cause4 ,hence in the ranks of the vitalists have been found some of the very best observers and theorists2 but they were such in despite of1 and not in consequence of1 their hypothesis1 which was only invoked by them when evidence was at fault4 ,nor1 unscientific as vitalism is1 can we deny that it has been so far serviceable to the science1 that it has corrected the materialist error of endeavoring to explain organic phenomena by physico-chemical laws2 and has persistently kept in view the radical difference between organic and inorganic4 #ca4 ,these remarks may justify a selection of definitions1 classified under the two heads4 ,the selection is fitly opened by the ,aristotelian definition which prevailed for centuries4 ,aristotle distinguishes ,life1 which he says means 8the faculties of self-nourishment1 self-development1 and self-decay10 from the ,vital ,principle4 ,every natural body manifesting life may be regarded as an essential existence 772 but then it is an existence only as a synthesis 7 72 and since an organism is such a synthesis1 being possessed of ,life1 it cannot be the ,vital ,principle 774 ,therefore it follows that the ,vital ,principle must be an essence1 as being the ,form of a natural body holding life in potentiality4 ,the ,vital ,principle is the primary reality of an organism4 8,it is therefore as idle to ask whether the ,vital ,principle and ,organism are one1 as whether the wax and the impress on it are one4444 ,thus if an eye were an animal1 ,vision would be its ,vital ,principle3 for ,vision is1 abstractedly considered1 the essence of the eye2 but the eye is the body of ,vision1 and if ,vision be wanting1 then1 save in name1 it is no longer an eye40 ,apart from certain metaphysical implications1 inevitable at that period1 there is profound insight in this passage4 ,his adversary ,telesio quite misconceives the meaning here assigned to the ,vital ,principle4#h #cb4 ,let us pass over all the intermediate forms of the hypothesis1 and descend to ,kant1 who defines ,life 8an internal principle of action0 7this does not distinguish it from fermentation72 an organism he says is 8that in which every part is at once means and end40 8,each part of the living body has its cause of existence in the whole organism2 whereas in non-living bodies each part has its cause in itself40 ,johannes ,mller adopts a similar view3 8,the harmonious action of the essential parts of the individual subsist only by the influence of a force1 the operation of which is extended to all parts of the body1 and does not depend on any single parts2 this force must exist before the parts1 which are in fact formed by it during the development of the embryo4444 ,the vital force inherent in them generates from the organic matter the essential organs which constitute the whole being4 ,this rational creative force is exerted in every animal strictly in accordance with what the nature of each requires40 #cc4 ,this is decidedly inferior to ,aristotle1 who did not confound the vegetative with the rational principle4 ,it rests on the old metaphysical error of a vis medicatrix1 an error which cannot sustain itself against the striking facts which constantly point to a vis destructrix1 a destructive tendency quite as inexorable as the curative tendency4 ,and the experimental biologist soon becomes impressed with the fact that the tissues have indeed a selective action1 by which from out the nutrient material only these substances are assimilated which will enter into combination with them2 but this selective action is fatal1 no less than reparative3 substances which poison the tissue are taken up as readily as those which nourish it4 ,the idea of prescience1 therefore1 cannot be sustained2 it is indeed seldom met with now in the writings of any but the ,montpellier school1 who continue the traditions of ,stahl's teaching4 ,it has been so long exploded elsewhere that one is surprised to find an ,english physiologist clinging to a modification of it--,i mean ,dr4 ,lionel ,beale1 who repeatedly insists on ,life as 8a peculiar ,force1 temporarily associated with matter10 a 8power capable of controlling and directing both matter and force10 an 8undiscovered form of force having no connection with primary energy or motion40 8,the higher phenomena of the nervous system are probably due primarily to the movements of the germinal matter due to vital power1 which vital power of this the highest form of germinal matter is in fact the living ,i40 #cd4 ,apart from the primary objection to all these definitions1 namely1 that they seek to express organic phenomena in terms of an extra-organic principle1 to formulate the facts observed in terms of a cause inferred1 there is the fatal objection that they speak confidently on what is avowedly unknown4 ,if the force be1 as ,dr4 ,beale says1 8undiscovered10 on what grounds can he assert that it has no connection with the forces which are known8 ,all that the observed facts warrant is the assertion that organic phenomena are special 7which no one denies71 and must therefore depend on special combinations of matter and force4 ,but on this ground we might assume a crystallizing ,force1 and a coagulating ,force1 having no connection with the molecular forces manifested elsewhere3 these also are special phenomena1 not to be confounded with each other4 #ce4 ,schelling defines ,life as 8a principle of individuation0 and a 8cycle of successive changes determined and fixed by this internal principle40 ,which is so vague that it may be applied in very different senses4 ,bichat's celebrated definition 7which is only a paraphrase of a sentence in ,stahl71 8the sum of the functions which resist ,death10 although an endeavor to express the facts from the ,intra-organic point of view1 is not only vague1 but misrepresents one of the cardinal conditions1 by treating the ,external ,medium as antagonistic to ,life1 whereas ,life is only possible in the relation to a ,medium4 #cf4 ,were it not so vague1 the definition proposed by ,dugs and ,bclard would be unexceptionable3 the former says it is 8the special activity of organized beings02 the latter1 8the sum of the phenomena proper to organized bodies40 ,when supplemented by a description of organized bodies1 these formul are compendious and exact4 ,the same remark applies to the definition of ,lamarck3 8that state of things which permits organic movements2 and these movements1 which constitute active life1 result from a stimulus which excites them40 #cg4 ,de ,blainville1 and after him ,comte and ,charles ,robin1 define it thus3 8,life is the twofold internal movement of composition and decomposition at once general and continuous40 ,this1 excellent as regards what is called vegetal life1 is very properly objected to by ,mr4 ,herbert ,spencer in that it excludes those nervous and muscular functions which are the most conspicuous and distinctive of vital phenomena4 ,the same objection must be urged against ,professor ,owen's definition3 8,life is a centre of intussusceptive assimilative force capable of reproduction by spontaneous fission40 #ch4 ,in #ahec1 after reviewing the various attempts to express in a sentence what a volume could only approximately expound1 ,i proposed the following3 8,life is a series of definite and successive changes1 both of structure and composition1 which take place within an individual without destroying its identity40 ,this has been criticised by ,mr4 ,herbert ,spencer and by ,dr4 ,lionel ,beale1 and if ,i had not withdrawn it before their criticisms appeared1 ,i should certainly have modified and enlarged it afterwards4 ,i mention it1 however1 because it is an approach to a more satisfactory formula in so far as it specifies two cardinal characteristics distinguishing organisms from all anorganisms1 namely1 the incessant evolution through definite stages1 and the preservation of specific integrity throughout the changes2 not only the organism as a whole is preserved amidst incessant molecular change1 but each tissue lives only so long as the reciprocal molecular composition and decomposition persist4 ,on both of these points ,i shall have to speak hereafter4 ,the definition1 however1 is not only defective in its restriction to the molecular changes of ,nutrition1 taking no account of the ,properties and ,functions of the organism2 but defective also in giving no expression to equally important relations of the organism to the medium4 #ci4 ,this last point is distinctly expressed in ,mr4 ,spencer's definition3 8,life is the continuous adjustment of internal relations to external relations40 ,considered as a formula of the most general significance1 embracing therefore what is common to all orders of vital phenomena1 this is the best yet proposed4#i ,if ,i propose another it will not be to displace but to run alongside with ,mr4 ,spencer's2 and this only for more ready convenience4 ,before doing so ,i must say a few words by way of clearing the ground4 #dj4 ,what does the term ,life stand for8 ,what are the concrete significates of this abstract symbol8 ,as before stated1 it is sometimes a compendious shorthand for the special phenomena distinguishing living from non-living bodies2 and sometimes it expresses not these observed phenomena1 but their conditions of existence1 which are by one school personified in an abstract and extra-organic cause4 ,thus the life of an animal1 a man1 or a nation1 means--#a1 the special manifestations of these organisms1 and groups of organisms2 or #b1 the causes which produce these manifestations4 ,we are often misunderstood by others1 and sometimes vague to ourselves1 when we do not bear these two different meanings in view4 ,it was probably some sense of this which made ,aristotle distinguish ,vitality from ,life1 as that of the one uniform cause separated from its multiple effects2 it was certainly the motive of ,fletcher1 who thus expressly limits the meanings3 8,vitality or ,irritability1 the property which characterizes organized beings of being acted on by certain powers otherwise than either strictly mechanically or strictly chemically2 ,life1 the sum of the actions of organized beings resulting directly from their vitality so acted on40#aj ,vitality and ,life being thus discriminated as the statical and the dynamical aspects of the organism1 we find in relation to the former two radically opposed conceptions3 the metaphysiological or extra-organic1 and the physiological or intra-organic4 ,the first conceives ,vitality to be a ,vital ,principle1 or extra-organic agent1 sometimes a soul1 spirit1 archus1 idea1 and sometimes a force1 which easily becomes translated into a property4 ,the conception of an entity must be rejected1 because it is metempirical and unverifiable1 #cd4 ,the conception of a force must be rejected1 because it is irreconcilable with any definite idea we have of force4 ,what the term ,force signifies in ,physics and ,chemistry1 namely1 mass animated by velocity1 or directed pressure1 which is the activity of the agent1--is precisely that which these vitalists pertinaciously exclude4 ,they assume a force which has nothing in common with mass and velocity2 which is not a resultant1 but a principle2 which instead of being a directed quantity1 is itself autonomous and directive1 shaping matter into organization1 and endowing it with powers not assignable to matter4 ,if this vital force has any mass at its back1 it is a spiritual mass2 if it is directed1 the direction issues from a 8,mind somewhere40 ,now this conception is purely metempirical4 ,not only is it inexact to speak of ,vitality as a force1 it is almost equally inexact to speak of it as a property2 since it is a term which includes a variety of properties2 and when ,fletcher assigns the synonym of ,irritability1 this at once reveals the inexactness2 for beside this property1 we must place ,assimilation1 ,evolution1 ,disintegration1 ,reproduction1 ,contractility1 and ,sensibility1--all characteristic properties included in ,vitality4 #da4 ,having thus rejected the conceptions of entity1 force1 and property1 we are left in presence of--#a1 the organic conditions as the elements1 and #b1 of their synthesis 7in the state called organization7 as the personified principle4 ,vital forces1 or the vital force1 if we adopt the term for brevity's sake1 is a symbol of the conditions of existence of organized matter2 and since organisms are specially distinguishable from anorganisms by this speciality of their synthesis1 and not by any difference in the nature of the elements combined1 this state of organization is the 8force0 or 8principle0 of which we are in quest4 ,to determine what ,life means1 we must observe and classify the phenomena presented by living beings4 ,to determine what ,vitality--or organization--means1 we must observe and classify the processes which go on in organized substances4 ,these will occupy us in the succeeding chapters2 here ,i may so far anticipate as to propose the following definitions3-- #db4 ,life is the functional activity of an organism in relation to its medium1 as a synthesis of three terms3 ,structure1 ,aliment1 and ,instrument2 it is the sum of functions which are the resultants of ,vitality2 ,vitality being the sum of the properties of matter in the state of organization4 #dc4 ,vital phenomena are the phenomena manifested in organisms when external agencies disturb their molecular equilibrium2 and by organisms when they react on external objects4 ,thus everything done in an organism1 or by an organism1 is a vital act1 although physical and chemical agencies may form essential components of the act4 ,if ,i shrink when struck1 or if ,i whip a horse1 the blow is in each case physical1 but the shrinking and the striking are vital4 ,every part of a living organism is therefore vital1 as pertaining to ,life2 but no part has this ,life when isolated2 for ,life is the synthesis of all the parts3 a federation of the organs when the organism is complex1 a federation of the organic substances when the organism is a simple cell4 #dd4 ,all definitions1 although didactically placed at the introduction of a treatise1 are properly the final expression of the facts which the treatise has established1 and they cannot therefore be fully apprehended until the mind is familiarized with the details they express4 ,much1 therefore1 which to the reader may seem unintelligible or questionable in the foregoing definition1 must be allowed to pass until he has gone through the chapters which follow4 ,,chapter ,,iii4 ,,organism1 ,,organization1 ,,and ,,organic ,,substance4 #de4 ,there is a marked difference between organic and organised substances4 ,the organic are non-living1 though capable of living when incorporated in organized tissue 7albumen is such a substance72 or they may be incapable of living because they have lived1 and are products of waste1 e4 g4 urea4 ,the organized substance is a specific combination of organic substances of various kinds1 a combination which is organization4 ,any organized substance is therefore either an independent organism1 or part of a more complex organism4 ,protoplasm1 either as a separate organism or as a constituent of a tissue1 is organized substance4 ,organic substances are numerous and specific4 ,they are various combinations of proximate principles familiar to the chemist1 which may conveniently be ranged under three classes3 ,the first class of organic substances comprises those composed of principles having what is called a mineral origin2 these generally quit the organism unchanged as they entered it4 ,the second class comprises those which are crystallizable1 and are formed in the organism1 and generally quit it in this state as excretions4 ,the third class comprises the colloids1 i4 e4 substances which are coagulable and not crystallizable1 and are formed in and decomposed in the organism1 thus furnishing the principles of the second class4 ,all the principles are in a state of solution4 ,water is the chief vehicle of the materials which enter and the materials which quit the organism2 and bodies in solution are solvents of others1 so that the water thus acquires new solvent properties4 #de;a4 ,two points must be noted respecting organic substances3 they are mostly combinations of higher multiples of the elements2 and their combinations are not definite in quantity4 ,albumen1 for example1 has 7according to one of the many formulas which have been given7 an elementary composition of #baf atoms of ,carbon1 #afi of ,hydrogen1 #bg of ,nitrogen1 #c of ,sulphur1 and #fh of ,oxygen2 whereas in its final state1 in which it quits the organism as ,urea1 it is composed of #b atoms of ,carbon1 #d of ,hydrogen1 #b of ,nitrogen1 and #b of ,oxygen1 all the ,sulphur having disappeared in other combinations4 ,in like manner in the organism ,stearin falls from ,c#aad1 ,h#aaj1 ,o#ab1 to ,oxalic ,acid1 which is ,c#d1 ,h#b1 ,o#h4 ,it is obvious that the necessary modifiability of organic substance is due to this multiplicity of its elementary parts and the variety of its molecular structure4 #de;b4 ,nor is the indefiniteness of the quantitative composition less important1 though seldom adequately appreciated1 or even suspected4 ,robin and ,verdeil#aa are the only writers ,i can remember who have distinctly brought the fact into prominence4 ,that all inorganic substances are definite in composition1 every one knows4 ,quicklime1 for example1 may be got from marble1 limestone1 oyster-shells1 or chalk2 but however produced1 it always contains exactly #bej ounces of calcium to #ajj ounces of oxygen2 just as water is always ,,oh#b4 ,not so the pre-eminently vital substances1 those which are coagulable and not crystallizable3 no precise formula will express one of these2 for the same specific substance is found to vary from time to time1 and elementary analyses do not give uniform results4 ,thus1 if after causing an acid to combine with one of these substances1 we remove the acid1 we are not certain of finding the substance as it was before--as we are1 for example1 after urea is combined with nitric acid and then decomposed4 ,the same want of definiteness is of course even more apparent in the combinations of these proximate principles into organized substance4 ,protoplasm differs greatly in different places4 ,epithelial cells differ4 ,muscular and nervous fibres are never absolutely the same in different regions4 ,a striped and unstriped muscular fibre1 the muscular fibre of a sphincter or of a limb1 a nerve-fibre in a centre1 in a trunk1 or in a gland1 will present variations of composition4 ,the elastic fibres of the ligaments are larger in the horse than in man2 and in other animals they are smaller4 ,these differences are sometimes due to the constituents1 and sometimes to the arrangement of the constituents2 the conversion of ,albumen into ,fibrine without elementary loss or addition1 is a good example of the latter4 ,that the tissues of one man are not absolutely the same as the tissues of another1 in the sense in which it is true to say that the chalk of one hill is the same as that of another1 or as gold in ,australia is the same as gold in ,mexico1 is apparent in their very different reactions under similar external conditions3 the substance which poisons the one leaves the other unaffected4 ,the man who has once had the small-pox1 or scarlet fever1 is never the same afterwards1 since his organism has now become insusceptible of these poisons4 ,and ,sir ,james ,paget has called attention to the striking fact revealed in disease1 namely1 that in the same tissue--say the bone or the skin--a morbid substance fastens only on certain small portions leaving all the rest unaltered1 but fastens on exactly corresponding spots of the opposite sides of the body2 so that on both arms1 or both legs1 only the corresponding bits of tissue will be diseased4 8,manifestly when two substances display different relations to a third their composition cannot be identical2 so that though we may speak of all bone or of all skin as if it were all alike1 yet there are differences of intimate composition4 ,no power of artificial chemistry can detect the difference2 but a morbid material can40#ab ,it is to this variability of composition that we must refer individual peculiarities1 and those striking forms of variety known as idiosyncrasies1 which cause some organisms to be affected by what seem inexplicable influences--physical and moral4 ,in spite of all these variations1 however1 there are certain specific resemblances dependent of course on similarity of composition and structure1 so that the muscle of a crustacean is classed beside the muscle of a vertebrate1 although the elementary analysis of the two yields different results4 ,nerve-tissue1 according to my experience1 is the most variable of all1 except the blood2 variable not only from individual to individual1 and from genus to genus1 but even in the same individual it never contains the same quantities of water1 phosphates1 etc4 ,hence it is that different nerves manifest different degrees of excitability1 and the same nerve differs at different times4 ,thus the fifth pair1 in a poisoned animal1 retains its excitability long after the others are paralyzed2 and the patient under chloroform feels a prick on the brow or at the temples1 when insensible at any other spot4 ,the pneumogastric which is excitable during digestion is--in dogs at least--inexcitable when the animal is fasting4 #df4 ,the organic substances are what analysis discovers in organized substances1 but none of them1 not even the highest1 is living1 except as organized4 ,albumen alone1 or ,stearin alone1 is as incapable of ,vitality1 as ,plumbago1 or ,soda2 but all organic substances are capable of playing a part in vital actions2 and this part is the more important in proportion to their greater molecular variety4 ,organization is a special synthesis of substances belonging to all three classes2 and the organized substance1 thus formed1 alone merits the epithet living4 ,we see how organized substances1 being constituted by principles derived from the inorganic world1 and principles derived from the organic world1 have at once a dependence on the external ,medium1 and an independence of it1 which is peculiar to living beings4 ,an analogous dependence and independence is noticeable with respect to the parts2 and this is a character not found in inorganic compounds4 ,the organism1 even in its simplest forms1 is a structure of different substances1 each of which is complex4 ,while one part of a crystal is atomically and morphologically identical with every other1 and is the whole crystal 8writ small10 one part of an organism is unlike another1 and no part is like the whole4 ,hence the dependence of one organ and one tissue on another1 and each on all4 ,yet1 while every part is1 so to speak1 a condition of existence of every other1 and the unity of the organism is but the expression of this solidarity1--wherever organized substance has been differentiated into morphological elements 7cells1 etc471 each of these has its own course of evolution independently of the others1--is born1 nourished1 developed1 and dies4 #dg4 ,the interdependence of nerve and muscle is seen in this1 that the more the muscle is excited the feebler its contractions become2 this decrease in contractility is compensated by an increased excitability in its nerve2 so that while the muscle demands a more powerful stimulus1 the nerve acquires a more energetic activity4 ,ranke's curious and careful experiments seem to prove that this depends on the wearied muscle absorbing more water1 owing to the acids developed by its activity1 and on the nerve losing this water--a nerve being always more irritable when its quantity of water diminishes4 #dh4 ,herein we see illustrated the great law of organized activity1 that it is a simultaneity of opposite tendencies1 as organized matter is a synthesis of compositions and decompositions1 always tending towards equilibrium and disturbance1 storing up energy and liberating it4 ,unlike what is observed in unorganized matter1 the conditions of waste bring with them conditions of repair1 and thus--within certain limits--every loss in one direction is compensated by gain in another4 ,there is a greater flow of nutrient material1 or1 more properly speaking1 a greater assimilation of it by the tissue1 where there has been made a greater opening for it by previous disintegration4 ,the alkaline state of the nutrient material1 and the acid state of the material that has been used1--the alkaline state which characterizes repose and assimilation1 and the acid state which characterizes activity and deassimilation1 are but cases of this general law2 on the synthesis of these opposite tendencies depends the restless change1 together with the continued specific integrity1 of organized matter4 #di4 ,the state of organization may therefore be defined as the molecular union of the proximate principles of the three classes in reciprocal dissolution4 ,an organism is formed of matter thus organized1 which exists in two states--the amorphous and the figured4 ,the amorphous substances are liquid1 semi-liquid1 and solid2 the figured are the cells1 fibres1 and tubes1 called 8anatomical elements40 ,for these ,i prefer the term suggested1 ,i believe1 by ,milne ,edwards1 namely1 organites1 because they are the individual elements which mainly constitute the organs1 and are indeed by many biologists considered as elementary organisms4 ,these organites1 which go to form the tissues1 and by the tissues the organs1 have their specific form1 volume1 structure1 and chemical reactions4 ,they exist in textures or tissues1 or separately 7e4 g4 blood corpuscles71 and are in many respects like the simplest organisms known1 such as ,monads1 ,vibrios1 ,amb1 etc4 #ej4 ,the simplest form of life is not--as commonly stated--a cell1 but a microscopic lump of jelly-like substance1 or protoplasm1 which has been named sarcode by ,dujardin1 cytode by ,haeckel1 and germinal matter by ,lionel ,beale4 ,this protoplasm1 although entirely destitute of texture1 and consequently destitute of organs1 is nevertheless considered to be living1 because it manifests the cardinal phenomena of ,life3 ,assimilation1 ,evolution1 ,reproduction1 ,mobility1 and ,decay4 ,examples of this simplest organism are ,monads1 ,protamb1 and ,polythalamia4#ac ,few things are more surprising than the vital activity of these organites1 which puzzle naturalists as to whether they should be called plants or animals4 ,all microscopists are familiar with the spectacle of a formless lump of albuminous matter 7a ,rhizopod7 putting forth a process of its body as a temporary arm or leg1 or else slowly wrapping itself round a microscopic plant1 or morsel of animal substance1 thus converting its whole body into a mouth and a stomach2 but these phenomena are surpassed by those described by ,cienkowski1#ad who narrates how one ,monad fastens on to a plant and sucks the chlorophyll first from one cell and then from another2 another ,monad1 unable to make a hole in the cell-wall1 thrusts long processes of its body into the opening already made1 and drags out the remains of the chlorophyll left there by its predecessor2 while a third ,monad leads a predatory life1 falling upon other ,monads that have filled themselves with food4 ,here1 as he says1 we stand on the threshold of that dark region where ,animal ,will begins2 and yet there is here only the simplest form of organization4#ae #ea4 ,now let our glance pass on to the second stage--the ,cell4 ,here we have a recognized differentiation in the appearance of a nucleus amid the protoplasm4 ,the nucleus is chemically different from the substance which surrounds it2 and although perhaps exaggerated importance has been attributed to this nucleus1 and mysterious powers have been ascribed to it1 yet as an essential constituent of the cell it commands attention4 ,indeed1 according to the most recent investigations1 the definition of a cell is 8a nucleus with surrounding protoplasm40 ,the cell-wall1 or delicate investing membrane--that which makes the cell a closed sac--is no longer to be regarded as a necessary constituent1 but only as an accessory4#af #eb4 ,the cell may be either an organism or an organite4 ,it may lead an isolated life as plant or animal1 or it may be united with others and lead a more or less corporate existence2 but always1 even as an element of a higher organism1 it preserves its own individuality4 ,at first we see that the corporate union is very slight1 merely the contact of one cell with another of its own kind1 as in the filament of a ,conferva4 ,rising higher1 we see the cell united with others different from it2 plants and animals appear1 having structures composed of masses of various cells4 ,rising still higher1 we see animal forms of which the web is woven out of myriads upon myriads of cells1 with various cell-products1 processes1 fibres1 tubes4 ,,organism ,,and ,,medium4 #ec4 ,but we have only one half of the great problem of life1 when we have the organism2 and it is to this half that the chief researches have been devoted1 the other falling into neglect4 ,what is that other8 ,the ,medium in which the organism lives4 ,every individual object1 organic or inorganic1 is the product of two factors3--first1 the relation of its constituent molecules to each other2 secondly1 the relation of its substance to all surrounding objects4 ,its properties1 as an object or an organism1 are the results of its constituent molecules1 and of its relation to external conditions4 ,organisms are the results of a peculiar group of forces1 exhibiting a peculiar group of phenomena4 ,viewing these in the abstract1 we may say that there are three regulative laws of life3--7#a7 ,the ,lex ,formationis--the so-called nisus formativus1 or 8organizing force02 7#b7 the ,lex ,adaptationis1 or adaptive tendency2 7#c7 the ,lex ,hereditatis1 or tendency to reproduce both the original form and its acquired modifications4 ,we have always to consider the organizing force in relation to all surrounding forces--a relation succinctly expressed in the word ,adaptation4 ,just as water is water only under a certain relation of its constituent molecules to the temperature and atmospheric pressure--just as it passes into other forms 7ice or steam7 in adapting itself to other conditions2 so1 likewise1 the organism only preserves its individuality by the adjustment of its forces with the forces which environ it4 #ed4 ,this relation of ,organism and ,medium1 the most fundamental of biological data1 has had a peculiar fortune3 never wholly unrecognized1 for it obtrudes itself incessantly in the facts of daily experience1 it was very late in gaining recognition as a principle of supreme importance2 and is even now often so imperfectly apprehended that one school of philosophers indignantly rejects the idea of the ,organism and ,medium being the two factors of which ,life is the product4 ,not only is there a school of vitalists maintaining the doctrine of ,life as an entity independent both of ,organism and ,medium1 and using these as its instruments2 but there is also a majority among other biologists1 who betray by their arguments that they fail to keep steadily before them the fundamental nature of the relation4 ,something of this is doubtless due to the imperfect conception they have formed of what constitutes the ,medium2 instead of recognizing in it the sum of external conditions affecting the organism--i4 e4 the sum of the relations which the organism maintains with external agencies1--they restrict1 or enlarge it1 so as to misapprehend its significance--restrict it to only a few of the conditions1 such as climate1 soil1 temperature1 etc41 or enlarge it to embrace a vast array of conditions which stand in no directly appreciable relation to the organism4 ,every one understands that an organism is dependent on proper food1 on oxygen1 etc41 and will perish if these are withheld1 or be affected by every variation in such conditions4 ,every one understands that an animal which can devour or be devoured by another1 will flourish or perish according to the presence of its prey or its enemy4 ,but it is often forgotten that among external existences1 all those which stand in no appreciable relation to the organism are not properly to be included in its ,medium4 ,in consequence of this oversight we frequently hear it urged as an objection to the ,evolution ,hypothesis1 that manifold organisms exist under the same external conditions1 and that organisms persist unchanged amid a great variety of conditions4 ,the objection is beside the question4 ,in the general sum of external forces there are certain items which are nearly related to particular organisms1 and constitute their ,medium2 those items which are so distantly related to these organisms as to cause no reactions in them1 are1 for them1 as if non-existent4#ag ,of the manifold vibrations which the ether is supposed to be incessantly undergoing1 only certain vibrations affect the eye as light2 these constitute the ,medium of ,sight2 the others are as if they were not4 ,only certain vibrations of the air affect the ear as ,sound2 to all other vibrations we are deaf2 though ears of finer sensibility may detect them and be deaf to those which affect us4 #ee4 8,the external conditions of existence0 is therefore the correct definition of the ,medium4 ,an animal may be surrounded with various foods and poisons1 but if its organism is not directly affected by them they cannot be food or poison to it4 ,an animal may be surrounded with carnivorous rivals1 but if it is not adapted to serve them as food1 or is too powerful to be attacked by them1 they only indirectly enter into its ,medium1 by eating the food it would eat4 ,the analogy is similar with anorganisms and their relation to their media4 ,every physical or chemical phenomenon depends on the concurrence of definite conditions3 namely1 the substance which manifests the change1 and the medium in which the change is manifested4 ,alter the medium1 solid1 liquid1 or gaseous1 change its thermal or electrical state1 and the phenomenon is altered4 ,but although similar alterations in the medium notoriously influence the organism1 yet1 because a great many variations in external conditions are unaccompanied by appreciable changes in the organism1 there are biologists who regard this as a proof of ,life being independent of physical and chemical laws2 an error arising from their not recognizing the precise nature of organic conditions4 #ef4 ,to give greater precision to the conception of a ,medium it will be desirable to adopt the distinction much insisted on by ,claude ,bernard1 namely1 #a1 an ,external or ,cosmical ,medium1 embracing the whole of the circumstances outside the organism1 capable of directly affecting it1 and #b1 an ,internal or ,physiological ,medium1 embracing the conditions inside the organism1 and in direct relation with it--that is to say1 the plasma in which its tissues are bathed1 by which they are nourished4 ,to these add its temperature and electrical conditions4 ,bernard only includes the nutritive fluid2 but inasmuch as each organism possesses a temperature and electrical state of its own1 and these are only indirectly dependent on the external temperature and electricity1 and as it is with these internal conditions that the organism is in direct relation1 ,i include them with the plasma among the constituents of the ,physiological ,medium4 ,any change in the ,external ,medium1 whether of temperature or electricity1 of food or light1 which does not disturb the ,internal ,medium1 will of course leave the organism undisturbed2 and for the most part all the changes in the ,external ,medium which do affect the organism1 affect it by first changing the ,internal ,medium4 ,external heat or cold raises or depresses the internal temperature indirectly by affecting the organic processes on which the internal temperature depends4 ,we see here the rationale of acclimatization4 ,unless the organism can adapt itself to the new ,external ,medium by the readjustment of its ,internal ,medium1 it perishes4 #eg4 ,we are now enabled to furnish an answer to the very common objection respecting the apparent absence of any direct influence of external conditions4 ,let the objection first be stated in the words of a celebrated naturalist1 ,agassiz3 8,it is a fact which seems to be entirely overlooked by those who assume an extensive influence of physical causes upon the very existence of organized beings1 that the most diversified types of animals and plants are everywhere found under identical circumstances4 ,the smallest sheet of fresh water1 every point of the sea-shore1 every acre of dry land1 teems with a variety of animals and plants4 ,the narrower the boundaries which are assigned as the primitive home of all these beings1 the more uniform must be the conditions under which they must be assumed to have originated2 so uniform indeed that in the end the inference would be that the same physical causes can produce the most diversified effects40 ,obviously there is a complete misstatement of the argument here2 and the excess of the misstatement appears in the following passage3 8,the action of physical agents upon organized beings presupposes the very existence of those beings40 ,who ever doubted it8 8,the simple fact that there has been a period in the history of our earth when none of these organized beings as yet existed1 and when1 nevertheless1 the material constitution of our globe and the physical forces acting upon it were essentially the same as they are now1 shows that these influences are insufficient to call into existence any living being40#ah ,although most readers will demur to the statement that because the material constitution of our globe was 8essentially the same0 before and after animal life appeared1 therefore there could have been no special conditions determining the appearance of ,life1 the hypothesis of ,evolution entirely rejects the notion of organic forms having been diversified by diversities in the few physical conditions commonly understood as representing the ,medium4 ,mr4 ,darwin has the incomparable merit of having enlarged our conception of the conditions of existence so as to embrace all the factors which conduce to the result4 ,in his luminous principle of the ,struggle for ,existence1 and the ,natural ,selection which such a struggle determines1 we have the key to most of the problems presented by the diversities of organisms2 and the ,law of ,adaptation1 rightly conceived1 furnishes the key to all organic change4 #eh4 ,in consequence of the defective precision with which the phrase 8,medium10 or its usual equivalent 8physical conditions10 is employed1 several biological errors pass undetected4 ,haeckel#ai calls attention to the common mistake of supposing the organism to be passive under the influence of external conditions1 whereas every action1 be it of light or heat1 of water or food1 necessarily calls forth a corresponding reaction1 which manifests itself in a modification of the nutritive process4 ,he points out the obverse of this error in the current notion that ,habit is solely due to the spontaneous action of the organism1 in opposition to the influence of external agency1--as if every action were not the response to a stimulus4 ,corresponding with the fluctuations in the ,medium there must necessarily be fluctuations of ,adaptation1 and ,i think we may safely assume that it is only when these fluctuations cease that the ,adaptation becomes ,habit4 ,this is the interpretation of the phrase 8,habit is second ,nature10 and is very different from the common interpretation which attributes it to the use or disuse of organs2 as if use or disuse were a spontaneous uncaused activity4 #ei4 ,the organism1 simple or complex1 is1 we have already seen1 built up from materials originally derived from the ,external ,medium1 but proximately from the ,internal ,medium4 ,this statement1 however1 requires some qualification1 especially in view of the hypothesis that organized substance was originally created such as we now find it1 and not evolved from inorganic materials4 ,whether this hypothesis be adopted1 or rejected1 we have the fact that the immense majority of organisms now existing--if not all--are products of pre-existing organisms2 and therefore organized matter is now mainly1 if not solely1 formed by organized matter4 ,we take1 therefore1 as our point of departure1 the protoplasm2 this is the first of the three terms of the vital synthesis3 ,structure1 ,aliment1 and ,instrument4 ,the evolution of this is proximately dependent on the pabulum afforded it in the ,internal ,medium1 which is the true nutrient material1 and to which what is usually called food stands in an external relation3 for between the reception of food and its assimilation by the organite1 there is an indispensable intermediary stage1 through which matter passes from the unorganized to the organized state4 ,this intermediate is now recognized in plants as in animals4 ,the old belief that plants were nourished directly from the soil and atmosphere can no longer be sustained4 ,the process of ,nutrition is alike in both3 in both the materials drawn from the ,external ,medium are formed into proximate principles and organic substances4 ,it is daily becoming more and more probable that the inorganic materials1 water and oxygen1 so freely entering into the organism1 never pass directly from the ,external ,medium to the tissues1 but have to pass through the ,internal ,medium where they are changed1 so that the water is no longer free1 but exists in a fixed state which has no analogue out of the living substance4 ,only a part of the water can be pressed out mechanically2 the rest--that which is already incorporated with the other elements--can only be got rid of in a vacuum and at a high temperature4 ,oxygen1 also1 comports itself differently in the tissue2 as is proved by the fact that its physiological absorption is markedly different from any chemical oxidation in a dead or decomposing tissue4#bj ,be this as it may1 we know that organic substances have to be unbuilt and rebuilt in the organism2 that the albumen of our food never passes directly into the albumen of our tissues2 any more than the milk drunk by a nursing mother will pass into her breasts1 and increase her supply1 except by nourishing her4 #fj4 ,in the ,first ,series of these ,problems the term ,bioplasm was employed to designate this organized part of the ,internal ,medium4 ,i was led to adopt it as a corresponding term to that of ,psychoplasm1 by which ,i wished to designate the sentient material of the psychological medium4 ,there can be little doubt that the term ,bioplasm was an unconscious reproduction of the title of ,dr4 ,beale's work1 which ,i must have seen advertised4 ,i withdraw it now that ,i have read ,dr4 ,beale's work1 and see that the signification he attaches to the term is almost identical with ,protoplasm4 ,in lieu thereof1 the term ,plasmode 7from plasma1 anything formed1 and odos1 a pathway7 may be substituted3 it represents the nutrient material on its way to form ,protoplasm1 which is formative material2 while the materials formed may be termed ,organites and ,products3 the organite being the cell or cell-derivative 7fibre1 tube72 the products being the gaseous liquid and solid derivatives of vital processes1 which are secretions when they form intercellular substance or return into the plasmode and re-enter the vital circle2 excretions when they are rejected1 as incapable of further assimilation4 ,the liver-cell will furnish an example of each kind of product4 ,the bile1 though containing principles serviceable in the chemical transformations1 is for the most part excreted2 but besides bile1 the liver-cell produces starchy and saccharine principles which are true secretions1 and re-enter the plasmode4 #fa4 ,the organite is thus composed of sap1 substance1 and product2 the organism1 of plasmode1 tissue1 and product4 ,a glance at the vegetable-cell shows it to be constituted by the primordial utricle1 or protoplasm1 the outermost layer of which is condensed into a membrane1 or cell-wall1 and the cavity thus enclosed is filled with sap4 ,the cell-wall grows as the protoplasm grows1 and the protoplasm draws its material from the plasmode4 ,a glance at the blood1 the great reservoir of the river of life1 shows us plasmode in the serum1 and organites in the corpuscles2 the one distinguished by sodic salts1 the other by potassic salts4 ,the plasmode1 or serum1 is in a constant change of composition and decomposition1 giving up to the various tissue-organites and intercellular plasmodes the requisite materials1 and receiving from organites and plasmodes the products of their changes4 ,the serum is fed from the food and the tissues2 and it feeds the several plasmodes which bathe the several tissues4 ,passing into the capillaries1 it becomes transformed as it passes through their walls into the intercellular spaces1 saturating the acid products of the cell-activities with its alkalies1 and furnishing the protoplasms with their needed materials4 #fb4 ,it will be understood that1 although in appearance these stages are sharply defined1 in reality they are insensible4 ,but from the analytical point of view we may regard ,nutrition as the office of the plasmode1 and ,evolution as the office of the protoplasm4 ,although evolution or genesis of form depends on assimilation1 it is not a necessary consequence3 the plasmode or the protoplasm might preserve such perfect equality in the waste and repair1 such complete equilibrium1 as not to undergo any development4 ,the ova1 for example1 which exist in the ovaries at birth are not all subsequently developed2 and if with modern embryologists we conclude that there is no replacement of these by proliferation we shall in them have examples of organites remaining unchanged through a period of fifty years4#ba ,but such an equilibrium is perhaps only possible in complete inactivity4 #fc4 ,again1 although the office of the plasmode is primarily that of forming protoplasm1 ,i think there is evidence to suggest that it not only does this1 but that some of it is used in the direct development of energy1 especially heat and electricity4 ,the various forms of starch and sugar taken in with the food or formed in the liver1 certainly do not as such enter into protoplasm4 ,the same with alcohol4 #fd4 ,it is perhaps in forgetfulness of the artificial nature of analytical distinctions that controversies rage respecting what are called intercellular substances and cell-walls4 ,now that the wall is no longer regarded as an essential constituent of the cell1 but as a secondary formation1 two opinions are maintained3 first1 that it is merely a concentration of the external layer of protoplasm2 secondly1 that it is a product of secretion from the protoplasm4 ,both positions may be correct4 ,certainly in some cases there is no other appreciable difference between wall and protoplasm than that of a greater consistence2 whereas in many other cases there exists a decided difference in their chemical reactions1 showing a difference of composition4 ,taking both orders of fact1 we may conclude that the cell-wall is sometimes part of the organite1 and sometimes product3 a blood-cell and a cartilage-cell may be cited as examples of each4 ,and this argument applies to the intercellular substance also4 #fe4 ,the terms plasmode and protoplasm are general1 and include many species4 ,there are different plasmodes for the different tissues1 so that we find phosphates of soda in the blood-serum1 phosphates of potash in the nerve-plasma1 phosphates of magnesia in the muscle-plasma1 and phosphates of lime in the bone-plasma2 having severally to form the specifically different protoplasms of these tissues4 ,observe1 moreover1 the gradations of these in respect of their physical state3 the blood being the most liquid1 the nerve a degree more solid1 the muscle still more solid1 and the bone almost entirely solid2 and since solubility of material is a necessary condition of the chemical changes1 we can understand how the blood1 the nerve1 the muscle1 and the bone represent degrees of vital activity3 the greater the instability of organized substance1 the more active its molecular renovation4 ,many serious errors result from overlooking the specific differences of protoplasms2 among them may be mentioned that very common one of asserting that the ovum of a man is not distinguishable from the ovum of any other mammal1 nor the ovum of a mammal from that of a reptile2 nay1 we sometimes see it stated that the protoplasm from which a mammal may be developed is the same as that which is the germ of an oak4 ,so long as this simply asserts that we have at present no means of distinguishing them by any chemical or physical tests1 there can be no objection raised2 but it is a serious misconception1 which any embryological investigation ought to rectify1 to suppose that the ovum is not specific from the first4 #ff4 ,between the organites and their plasmodes there is the necessary relation1 which corresponds with the relation between organisms and their mediums4 ,once formed1 the organites are arranged side by side1 or end on end1 into textures or tissues1 and these are grouped into organs1 every organ being constituted by a collection of tissues1 as every apparatus is by a collection of organs1 and the organism by the federation of all the parts4 ,we have more than once insisted on the necessity of synthetic interpretation to complete the indications of analysis3 which means that no account of vital phenomena is real unless it takes in all the co-operant factors1 both those of the organism and the medium4 ,neglect of this canon vitiates ,dr4 ,beale's otherwise remarkable labors4 ,,the ,,hypothesis ,,of ,,germinal ,,matter4 #fg4 ,it may help to elucidate certain important points if ,i here examine the hypothesis which ,dr4 ,beale has worked out with such patient skill1 but with what seem to me such unphysiological results4 ,he deserves1 ,i think1 more applause than has been awarded to him1 not only for the admirable patience with which he has pursued the idea1 but also for the striking definiteness of the idea itself--always a great advantage in an hypothesis1 since it gives precision to research4 ,if biologists have paid but little attention to it1 this is no doubt due to the theoretical1 still more than to the observational contradictions it presents4 ,histologists dispute his facts1 or his interpretations2 while other biologists do not see their way in the application of his hypothesis4 ,respecting all disputed points of observation ,i shall be silent1 for ,i have myself made no systematic researches in this direction1 such as would entitle me to form an estimate of the evidence4 ,but my dissent from the hypothesis is founded on biological principles so fundamental that ,i should be willing to take my stand entirely on the facts he himself puts forward4#bb #fh4 ,the hypothesis is that nothing in the organism has any claim to vitality except the minute masses of protoplasm 7by him called bioplasm71 which in the egg represent1 he thinks1 about the one-thousandth part of the whole mass1 the rest being lifeless matter1 namely1 pabulum1 and formed material4 ,this bioplasm is the germinal matter out of which1 by a process of dying1 arise the tissues and humors constituting the formed material--these1 with the pabulum which feeds the germinal matter1 being all dead material4 ,the germinal matter itself1 though living1 only lives because there is temporarily associated with it that ,vital ,force of which we have already spoken 7 #ad74 ,in virtue of this association1 a particle of matter not exceeding the one hundred-thousandth of an inch in diameter is said to be alive2 and1 presumably1 to contain within it all those manifold powers which the term ,life condenses4 ,the pabulum brought under the influence of this ,vital ,force is transformed into germinal matter which1 escaping from this mysterious influence1 dies into tissue4 ,muscle-fibres and nerve-fibres are thus not living parts1 nor are their actions vital4 ,so that1 to be consistent1 we must not speak of the organism as living1 but as a dead structure produced by the ,vital ,force1 and set in action by the aid of scattered bits of germinal matter4 ,he has not1 ,i think1 stated whether each of these bioplasms has its own ,vital ,force1 so that the organism is the theatre of millions of ,vital ,forces2 or whether it is one ,vital ,force which animates the whole organic world of plants and animals4 ,but nothing can be less equivocal than his position respecting the lifelessness of every part of the organism except the germinal matter4 #fi4 ,the germinal matter may be selected as the primary stage of the formed material1 the initial point of growth1 and thus stand for the pre-eminently distinctive centre of ,nutrition2 but were we to limit all ,nutrition to the germinal matter1 as defined by ,dr4 ,beale1 and deny the co-operation of all the formed material1 we should still not be justified in restricting ,life to simple ,nutrition4 ,we cannot exclude such phenomena as those of ,sensation and ,motion1 nor can we assign these to the germinal matter4#bc ,to suppose this1 would be equivalent to saying that the steam which issues from a teakettle is capable of the actions of a locomotive engine4 ,the steam from the kettle is like the steam from the boiler1 it has molecular energy1 and by this will co-operate in the production of mechanical work1 if the mechanism be adjusted to it4 ,the molecular energy of the protoplasm in muscular fibre may be indispensable to the movements of the muscles1 but these1 and not the protoplasmic movements alone1 are muscular contractions4 ,an hypothesis1 therefore1 which is obliged to declare that muscle-fibre and nerve-fibre are not living1 even when active in the organism1 seems to me defective at its base4 ,if we view these apart from the organism1 they may1 like all the other formed materials1 be regarded as dead2 and no one doubts that epidermis1 nail1 horn1 hair1 and bone are dead in this sense1 that they cannot live independently1 and do not reproduce themselves4 ,but so long as even these form constituents of the living organism1 they also are living 7 #db74bd ,it is only by a misconception of the analytical artifice that so simple a truth could have been missed4 #gj4 ,but this misconception meets us at many a turn4 ,the ,vitalist hypothesis of an extra-organic agent of course refuses to regard ,life as the expression of all the co-operant conditions2 and even opponents of that hypothesis often fall into the same error of principle1 when they attempt to explain ,life by localizing it in the cells2 which is simply a morphological substitution for the once popular doctrine that only the vascular parts were organized1 and every part destitute of blood-vessels was dead4 ,this idea seemed supported by the facts of the most highly vascular parts being the most vital1 and of a parallelism existing between the vital activity of those organs which when injected seemed almost entirely composed of blood-vessels1 as the liver and brain1 and those which showed scarcely a trace of vessels1 as cartilage and bone2 it seemed supported also by the appearance of blood-vessels in all new formations1 and by the idea of the blood as the nutrient fluid4 ,then came the cell-doctrine1 and the belief that the cell was the really ultimate morphological element--which may be true--and that 8here alone there is any manifestation of life to be found1 so that we must not transfer the seat of vital action anywhere beyond the cell10#be--which is very questionable4 #ga4 ,we have already seen that the cell is an anatomical element1 or organite2 the organism is but an aggregate of organites and their plasmodes4 ,but ,biology1 which deals with the organism as a whole1 and with functions which are the resultants of all the vital properties1 must not be restricted to any single factor1 however important4 ,it would assuredly be deemed absurd to say that diamond rings and lead-pencils were the same1 because the diamond and the plumbago1 which are the specific elements of each1 are both the same chemical element1--carbon4 ,the substance is really different in diamond and plumbago1 is different in properties1 and is1 in rings and pencils1 united with different substances into objects having very different properties4 ,whatever analysis may discover as to the identities of organic structures1 we cannot explain a single vital phenomenon without taking into account the three terms1 ,structure1 ,aliment1 and ,instrument2 and whenever a cell is said to be the seat of vital action1 these three terms must be implied4 ,in ,dr4 ,beale's hypothesis the restriction is carried to its extreme2 not content with the cell1 he withdraws vital action from the cell as a whole1 assigning it to the protoplasm and nucleus--cell-contents and cell-wall being1 in his view1 dead4 ,if it be true that the protoplasm is alone concerned in ,nutrition1 yet ,nutrition is not ,life4 ,occupied mainly with formative processes1 it leaves other indispensable processes to other parts4 ,he instances the removal of all the tissues during the metamorphoses of insects3--8new organs and textures are laid down afresh and developed ab initio1 instead of being built up upon those first formed40 ,but to show how he restricts the idea of ,life1 he adds3 8,such complete change1 however1 necessitates a state of existence during which action or function remains in complete abeyance40#bf ,the muscles and nerves which are instrumental in this functional life are said to be dead4 ,it is true that the muscle-fibre does not develop fresh fibres4 ,but it is equally true that the protoplasm of muscle does not alone execute muscular contraction4 ,each has its special office4 ,hence ,i reject the idea that formed material is dead4 ,he further says 8formed material may be changed1 it cannot change itself40 ,the antithesis is doubly inexact3 #a1 nothing changes itself1 but only yields to pressure1 or reacts on being stimulated2 and #b1 all the evidence at hand is against the notion that the formed material is not the seat of incessant molecular change2 it is wasted and repaired molecule by molecule4 ,klliker properly protests against the growing tendency of histologists to deify protoplasm1 and to make it the sole seat of vital changes1 the cell-wall and cell-products having also1 he says1 their physiological importance4 ,it is manifestly erroneous to deny vital changes to the red blood-corpuscles on the ground of their no longer containing germinal matter4#bg #gb4 ,the analytical view may separate certain parts as active1 and other parts as passive1 and thus regard the cells as the seats of vital activity1 the intercellular substance as merely accessory and instrumental2 but the real or synthetical view must recognize both parts as equally indispensable1 equally vital4 ,take cartilage1 for instance1 with its enormous preponderance of intercellular substance 7formed material71 and consider how absolutely impossible any of its uses would be were it reduced to the germinal matter of its corpuscles6 ,and so of all the tissues4 #gc4 ,if formed material is not to be excluded from the living parts of the organism1 neither is the plasmode1 out of which the germinal matter arises1 since here we have the nutritive changes in their highest activity2 and because the property of ,nutrition is here most active1 the other property of ,development is in abeyance4 ,dr4 ,beale holds that pabulum necessarily becomes germinal matter2 but when we come to treat of ,nutrition it will appear that this is not more true than that ,food necessarily becomes ,tissue3 some of it does2 but much of it is used up for heat and other purposes4 #gd4 ,what is true and important in the distinction between germinal matter and formed material is1 that from the former onwards there is a gradual process of devitalization1 the older parts of every organite and tissue approaching more and more to the state of inorganic matter4 ,but to show how vain is the attempt to restrict ,vitality to any one out of a complex of co-operant factors1 we might set up a chemical hypothesis to the effect that ,vitality depends on phosphates1 and with it explain the phenomena quite as well as with the hypothesis of germinal matter4 ,for not only is it found that the productive quality of a soil depends on its richness in phosphates1 but1 as ,lehmann has shown1 wherever cells and fibres make their appearance phosphates are found1 even in the lowest organisms1 which1 however1 contain but little4 ,phosphates abound in seeds and ova1 in muscles and ganglia1 and are deficient in the woody parts of plants and the elastic fibres of animals4 ,the infant absorbs phosphates in large quantities and excretes them in small quantities4 ,nervous activity is accompanied by the consumption of a third more phosphorus than accompanies muscular activity4 ,phosphates are among the most energetic of organic stimulants4 ,but who would endow the phosphates with ,vitality1 on the ground of their indispensable presence in all vital processes8 #ge4 ,life1 as we saw1 is the expression of the whole organism4 ,many of the parts are incapable of manifesting any vital phenomena except in connection with all the rest2 and of those parts which may be separated from the organism and continue to manifest some vital phenomena1 none are capable of manifesting all4 ,when the connexus of the parts is destroyed the organism is dead4 ,long after that cessation which we call ,death1 there are still evidences of ,vitality in some of the parts3 the heart will continue to beat1 the glands will secrete1 the hair will grow1 the temperature will still be above that of the surrounding medium1 the muscles will be excitable2 these vital properties are the activities of organized substances1 and so long as the state of organization is preserved they are preserved2 but the ,life1 which is the synthesis of all the vital properties1 vanishes with the destruction of that synthesis4 #gf4 ,may we not generalize this1 and say that every special form of existence1 organic or inorganic1 is determined by the synthesis of its elements8 ,atoms are grouped into molecules1 molecules into masses1 masses into systems4 ,out of the textureless germinal membrane and the yolk1 with no additions from without except oxygen and heat1 are developed all the textures and organs of the chick2 and this chick weighs no more than the egg out of which it was evolved4 ,the development has been a succession of syntheses--epigenesis upon epigenesis4 ,we may1 if we please1 regard each organite1 as it appears1 living its separate life1 and each tissue its separate life2 but we must not confound under the same symbol modes of existence so widely different as the activities of an organite1 and the activities of an organism constituted by millions of organites4 #gg4 ,if therefore we cannot restrict ,life to the processes of ,nutrition1 ,dr4 ,beale's hypothesis1 whatever value it may have as explaining histogenesis1 is quite unacceptable4 ,neither ,vital ,force nor ,bioplasm covers the whole ground4 ,for the former there is no better evidence than our ignorance of the real synthesis2 for the latter the evidence is positive in its nature1 but its interpretation is questionable4 ,dr4 ,beale selects as the germinal matter those portions of tissue which are susceptible of being deeply stained by the carmine solution1 the formed material being only stained in a faint degree2 the nucleus and nucleolus are the portions of germinal matter which are most deeply stained2 and hence he concludes that the older the matter the fainter will be its coloration4 ,there is no dispute as to the value of the staining process1 invented by ,gerlach1 for the discrimination of chemically different parts of a tissue2 and ,dr4 ,beale has made excellent use of it in his researches4#bh ,but ,i altogether dispute the conclusion that the staining process reveals the parts which are exclusively vital2 and for this reason3 it depends solely on the acid reaction of those parts2 and we cannot divorce the acid from the alkaline agencies1 both being indispensable4 ,nay1 it has been proved that in the living animal no organized substance can be stained4 ,lord ,godolphin ,osborne first discovered1 in #ahef1 that the protoplasm of growing wheat was susceptible of coloration2#bi but ,gerlach1 in #aheh1 found that this never took place in the animal during life4 ,he kept tadpoles and intestinal worms for weeks in colored fluids1 without a single spot becoming stained2 although no sooner did these animals die than the staining began4 ,nor even when he injected the colored fluids under the skin and into the stomach1 was the slightest coloration produced4#cj ,to ,gerlach's testimony may be added that of ,stein1 who1 in his magnificent work on ,infusoria1 says that not only has no foreign substance ever been found in the protoplasm of the ,opalina1 but in the ,acineta1 and all the embryos of the higher ,infusoria known to him1 he has been unable to color the living substance4#ca ,this resistance of the living protoplasm is surely a serious objection to the hypothesis that only those parts of the dead organism which are stained were the truly vital parts4 ,ranke sums up the results of his experiments thus3 8,they all show that the living cell resists the imbibition of every substance which it cannot assimilate4 ,it is precisely the impossibility of staining the cell that proves this conclusively1 since every particle of carmine absorbed would have revealed its presence40 ,it is not to be supposed that ,dr4 ,beale was unacquainted with ,gerlach's experiments4 ,he has at any rate so far qualified the statement of his hypothesis as to admit that it is only after death that the germinal matter is stained4 8,the living matter0 7he says1 ,how to ,work with the ,microscope1 p4 #ajg7 8possesses an acid reaction1 or to speak more correctly1 an acid reaction is always developed immediately after its death40 ,now1 since this acid reaction only presents itself after death1 and it is this which is revealed by the carmine1 we have no right to conclude that the carmine singles out the vital parts4 ,every one knows that the living muscle and nerve1 when in repose1 present an alkaline or faintly neutral reaction1 and after excitation this is changed into an acid reaction1 which increases with the exhaustion of the tissue4 ,in strict logic1 therefore--if we could logically apply such a test--it is the unstained parts that ought to be called vital4 ,but1 in truth1 alkalinity and acidity are equally indispensable4 #gh4 ,the main object of my bringing this question forward was to illustrate the danger of being misled by analysis3 a danger we shall see to be very serious in psychological inquiries4 ,the aid derived from analysis need never be undervalued2 all that we have to bear in mind is that it is only a logical artifice1 and that our real explanation must always be synthetic4 ,because of the tendency to rely on analysis there has been an imperfect discrimination of the profound difference between ,,organisms ,,and ,,machines2 and while on the one hand the legitimate striving of the biologist to display the mechanism of organic actions has been denounced by a certain school as ,materialism and a hateful attempt to 8rob ,life of its mystery10 there has been on the other hand a misconception of this mechanism1 as if its dependent actions were of the nature of machines1 that is to say1 as if organized mechanisms were strictly comparable with machines constructed of inorganic parts4 ,no doubt the laws of ,mechanics are the same in both1 for these are abstract laws which take no account of concrete differences4 ,but when elaborate parallels are drawn up between steam-engines and animal organisms1 the coal consumed in the one likened to the food in the other1 and the force evolved in the combustion in both being the same1 there is a complete obliteration of all that specially distinguishes vital activity4 #gi4 ,between an organism and a machine there is the superficial resemblance that both have a complex structure1 and are constructed of different and dependent parts4 ,but underneath this resemblance there is a radical diversity4#cb ,the arrangement of parts in the organism is more than a juxtaposition1 it is a solidarity1 arising from the fact of their being all differentiations from a common substance which is a special combination of the three classes of proximate principles4 ,thus they are not parts which have been put together1 but which have been evolved1 each out of a pre-existing part1 and each co-operating in the very existence of the other4 ,the machine is made of independent and primarily unrelated parts2 its integrity depends on the continued preservation of the substance of each part2 waste is here destruction4 ,the organism is constituted by interdependent and primarily related parts2 its integrity depends on the continued destruction and renovation of their substance2 waste is a condition of vitality4 ,the actions of the machine are subordinated2 the actions of an organism are co-ordinated4 ,the lever moves a wheel1 and the wheel in moving liberates a spring1 each transmitting a communicated impulse1 but otherwise each acts independently--no slight modification in the structure or movement of the wheel will modify the structure or the movements of the lever1 no alteration in the tension of the spring will affect the structure of the wheel4 ,but in the organism all are parts of one sympathetic whole2 each reacts on each2 each is altered by the other4 ,not a nerve is stimulated1 nor a muscle moved1 but the entire organism is affected4 ,a condensation here is the cause of a greater imbibition there4 ,the injection of salt or sugar under the skin of the frog's leg will produce cataract in its eye4 ,the activity of a secreting cell in the ovary1 or liver1 alters the condition of the brain2 the activity of the brain will check the secretion of a gland1 or relax the sphincters of the bladder4 ,when we observe the growth of horns1 or the appearance of the beard1 concomitant with the secretion of spermatic cells--and especially when we observe with these a surprising change in the physical and moral capabilities and tendencies of the organism--we understand how the remotest parts of this mechanism are bound together by one subtle yet all-powerful tie4 ,nothing of this is visible in a machine4 ,in a machine the material is so far of secondary importance that it may be replaced by materials of various kinds3 a pulley may be worked with a hempen cord1 a silken cord1 or an iron chain2 a wheel may be wood1 iron1 copper1 brass1 or steel2 the actions will in each case be similar4 ,not so the organic mechanism3 the slightest variation1 either in composition or intimate structure1 will affect1 and may frustrate the organic activity4 ,it is only in the skeleton that the specific character of the materials may be changed2 and here only in the substitution of one phosphate for another in the solid masonry4#cc #hj4 ,another marked characteristic of the organism is that it has a connexus of actions1 the simultaneous effect of a continuous evolution1 appearing in stages and ages4 ,and in the animal organism there is a consensus as well as a connexus1 through which there is evolution of ,mind2 and in the ,social ,organism an evolution of ,civilization4 ,this consensus forms an intermediate stage through which the animal actions are sensitive as well as nutritive1 and the nutritive are regulated by the sensitive4 ,it is obvious that nothing like this is to be found in a machine2 and we conclude1 therefore1 that any view of the organism which regards its mechanism without taking in these cardinal characteristics must be radically defective4 ,we no more deny the existence of mechanical phenomena in denying that the organism is like a machine1 than we deny the existence of chemical phenomena in denying that ,vitality is chemical4 ,,chapter ,,iv4 ,,the ,,properties ,,and ,,functions4 #ha4 ,the terms ,property and ,function are not always used with desirable precision4 ,there is1 however1 a marked distinction between the property which characterizes a tissue in whatever organ the tissue may be found1 and the function which is exhibited by an organ composed of several tissues4 ,we ought never to speak of a function unless we imply the existence of a correlative organ2 and it is therefore incorrect to speak of the function of ,nutrition1 since all the tissues nourish themselves2 but we may speak of certain organs as special instruments in facilitating ,nutrition4 ,thus also with respiration1 usually1 but not accurately1 spoken of as the function of the lungs2 the lungs being simply the most effective of the instruments by which the interchange of gases 7which also takes place in every tissue7 is facilitated4 ,if by ,respiration we mean ,breathing1 then1 indeed1 ,respiration is the function of the lungs2 if we mean the absorption of oxygen and the exhalation of carbonic acid1 ,respiration is a general property of vital tissue4 ,a fragment of muscle removed from the body respires1 so long as its organization is intact2 but it does not breathe--it has no accessory instruments1 nor does it need them4 ,the co-operation of nerve centres1 diaphragm1 ribs1 circulating system1 etc41 necessary in the complex organism to bring the due amount of oxygen to the tissues1 and convey away the carbonic acid1 is here needless4 ,in the ascending animal series we find this necessity growing with the complexity of the organism4 ,the whole skin respires in the amphibia1 and to some extent in man also3 a frog will live for ten or fourteen days after extirpation of its lungs1 the skin respiring sufficiently to keep up a feeble vitality4 ,but the skin does not suffice2 and1 very early1 certain portions are specialized into organs 7at first in the shape of external gills1 and finally as internal lungs71 for the more energetic1 because more specialized1 performance of this office4 ,in the simpler organisms the blood is easily reached by the air2 therefore no instrument is needed4 ,in primitive societies the transport of goods is effected by men and women carrying them2 in civilized societies by the aid of horses and camels1 and wagons drawn by oxen2 till finally these are insufficient1 and railways are created1 whose power of transport transcends the earlier methods1 as the breathing of a mammal transcends the respiration of a mollusc4 ,breathing is the special function of an organ--the lungs 7or more strictly1 the thoracic apparatus7--as ,railway ,transport is a special social function4 ,although each of the tissues forming this organ can1 and does1 exhale carbonic acid and absorb oxygen--and each of the railway servants can1 and does1 transport objects to and from the locomotive--yet the main work is thrown upon the special apparatus4 #hb4 ,what is meant by properties of tissue and functions of organs may be thus illustrated4 ,let us suppose ourselves investigating the structure of a ship4 ,we find it composed of various materials--wood1 iron1 copper1 hemp1 canvas1 etc42 and these under various configurations are formed into particular parts serving particular purposes1 such as deck1 masts1 anchor1 windlass1 chains1 ropes1 sails1 etc4 ,in all these parts the materials preserve their properties2 and wherever wood or iron may be placed1 whatever purpose the part may serve1 the properties of wood and iron are unaffected2 and it is through a combination of these properties that the part is effective2 while through the connection of one part with another the purpose becomes realized4 ,the purposes to which masts1 ropes1 or sails are subservient may be called their functions2 and these of course only exist1 as such1 in the ship4 ,it is the same with the organism4 ,we find it composed of various ,tissues1 and these are combined into various ,organs or ,instruments4#cd ,the properties of ,tissues remain the same1 no matter into what ,organs they may be combined2 they preserve and exert their physical1 chemical1 and vital properties1 as wood and iron preserve their properties4 ,each ,tissue has its characteristic quality2 and the ,organ which is constructed out of a combination of several ,tissues1 more or less modified1 is effective solely in virtue of these properties1#ce while the ,function of that organ comes into play through its combination with other organs4 ,for example1 muscular tissue has a vital property which is characteristic of it1 ,contractility2 and muscles are organs constituted by this tissue and several others2#cf such organs have the general function of ,contraction1 but whether this shall be specially manifested in the beating of the heart1 the winking of the eyelid1 the movement of the chest1 or the varied movements of the limbs1 will depend on the anatomical connections4 ,the reader unfamiliar with ,biology is requested to pay very particular attention to this point2 he will find many obscurities dissipated if he once lays hold of the 8principal connections40 #hb;a4 ,although ,bichat's conception was of great value1 it was not sufficiently disengaged from the metaphysical mode of viewing biological phenomena4 ,both he and his disciples will be found treating ,properties as entities1 and invoking them as causes of the phenomena instead of recognizing them simply as abstract expressions of the phenomena4 ,readers of my ,first ,series will remember how often ,i have had occasion to point out this common error3 men having baptized observed facts with a comprehensive name1 forget the process of baptism1 and suppose the name to represent a mysterious agency4 ,the fact that gases combine is expressed in the term affinity2 and then ,affinity is understood to be the cause of the combinations4 ,the fact that bodies tend towards each other is called their gravitation1 and ,gravitation is then said to cause the tendency4 ,the doctrine of vital properties has been thus misunderstood4 ,while no one imagines that he can operate on affinity otherwise than by operating on the known conditions under which gases combine1 many a biologist and physician speaks as if he could operate on the ,irritability of a tissue1 or the ,co-ordination of muscles1 by direct action on these abstractions4 ,let it be therefore once for all expressly stated that by the property of a tissue is simply meant the constant mode of reaction of that tissue under definite conditions4 ,the property is not a cause1 otherwise than the conditions it expresses are a cause4 ,and these conditions are first those of the organized structure itself1 and secondly those of the medium in which it lives4 ,oxygen unites with ,hydrogen to form water1 but only under certain pressures2 so likewise muscles manifest ,contractility on being stimulated 7that is their mode of reaction71 but only under certain degrees of temperature1 humidity1 and a certain chemical composition of the plasmode4 ,the property is so truly an expression of the co-operant conditions1 that it is found to vary with those conditions1 and to vanish when they vary beyond a certain limit4 ,an attempt has been made to restrict the notion of a property to an ultimate fact4 ,whatever is not reducible to known conditions is to be accepted as a property4 ,combustion1 for example1 is reducible to the molecular combination of oxygen and some other gas2 but this combination itself is not reducible1 and it is therefore christened affinity4 ,i cannot accept this view4 ,admitting our inability to say why gases combine under certain conditions 7and in this sense all facts are inexplicable and ultimate1 unless we take the how as ample explanation of the why71 ,i must still say that since affinity itself depends on the co-operation of known conditions1 it is not less explicable than combustion4 ,but the point is unimportant3 what we have here to settle is the meaning of a property of tissue1--and that is the mode of reaction which that tissue manifests under constant conditions1 internal and external4 #hc4 ,the evolution of ,life is the evolution of special properties and functions from general properties and functions4 ,the organism rises in power as it ramifies into variety4 ,out of a seemingly structureless germinal membrane1 by successive differentiations certain portions are set apart for the dominant1 or exclusive1 performance of certain processes2 just as in the social organism there is a setting apart of certain classes of men for the dominant or exclusive performance of offices1 which by their co-operation constitute ,society4 ,the soldier fights1 but ceases to build or reap1 weave or teach2 the mason builds2 the agriculturist sows and reaps2 the priest and thinker teach2 the statesman governs4 ,in simple societies each does all1 or nearly all2 but the social life thus manifested is markedly inferior to the energetic life of a complex society4 ,so with organisms4 ,an amba manifests the general properties of ,nutrition1 ,reproduction1 ,sensibility1 and ,movement4 ,but it has no special organs1 consequently no special functions4 ,the polype has a certain rudimentary specialization of parts3 it has a simple alimentary cavity1 and prehensile tentacles2 and although by these it can seize and digest its prey1 it can only do so in a limited way--all the manifold varieties and power of prehension and digestion observed in more complex organisms are impossible with such organs as the polype possesses4 #hd4 ,differences of structure and connection necessarily bring about corresponding differences in ,function1 since ,function is the directed energy of the ,properties of tissues4 ,one organ will differ from another in structure1 as the liver from the pancreas1 or the kidney from the spleen2 or one organ may closely resemble another but differ from it only in connections1 as a sensory and a motor nerve1 or an extensor and a flexor muscle4 ,we must therefore always bear both points in mind4 ,every modification1 structural or connectional1 is translated by a corresponding modification in the office4 ,the hand and the foot show this well4 ,the tissues are the same in both1 the properties are the same1 and both have the same general function of ,prehension2 but their morphological differences carry corresponding differences in their uses4 ,suppose we have a galvanic battery1 we know that its electric force may be variously applied4 ,two pieces of charcoal fixed to the ends of its conducting wires give us the electric light2 replacing the charcoal by a telegraphic apparatus we can transmit a message from one continent to the other2 the wires dipped in a solution effect a chemical decomposition1 dipped into a mixture of gases they effect a chemical composition4 ,in these1 and many other applications1 the property of the battery is constant2 but the functions it subserves have varied with the varying co-operants4 ,so with the properties of tissue4#cg ,not only have we to bear in mind the organic connections of the tissues1 but also the relation of the organs to their media4 ,swimming and ,walking1 for example1 are both functions of the locomotive apparatus1 but they are specially differenced by the media in which the animal moves4 #he4 ,the properties of tissues are their peculiar modes of reaction1 and each tissue has its dominant characteristic1 such as the ,contractility of the muscle1 and the ,neurility of the nerve4 ,but there has of late years sprung up a misleading conception1 partly a consequence of the cell-theory1 and partly of the almost inevitable tendency of analysis to disregard whatever elements it provisionally sets aside2 this conception is the removal of the property from its tissue1 and the localization of it in one of the organites--cell or fibre4 ,this has been conspicuously mischievous in the case of the nerve-cell1 which has been endowed with mysterious powers1 and may be said to have usurped the place of nerve-tissue4 ,i shall have to speak of this in the next problem4 ,here ,i only warn the student against the common error4 ,the properties of a tissue depend on the structure and composition of that tissue1 together with its plasmode and products2 they vary as these vary4 ,to select any one element in this complex1 and ascribe the reaction of the tissue to that1 is only permissible as a shorthand expression4 #hf4 ,what has just been expounded may be condensed in the following biological law3-- ,identity of tissue everywhere implies identity of property2 and similarity of tissue corresponding similarity of property4 ,identity of organic connection everywhere implies identity of function2 and similarity of organic connection similarity of function4 #hg4 ,this law1 first formulated by me in #ahei1 and then applied to the interpretation of nervous functions1 was so little understood that for the most part it met with either decided denial or silent neglect2 no doubt because of the general disinclination to admit that the properties and functions of the spinal cord could be similar to those of the brain1 in correspondence with the similarity of their tissues and organic connections4 ,even ,professor ,vulpian1 who adopted it1 as well as my principal interpretations1 hesitated1 and relapsed into the orthodox view in assigning three different properties to one and the same tissue in cord1 medulla oblongata1 and cerebrum4#ch ,in the course of our inquiries we shall so frequently have to invoke this law that ,i earnestly beg the reader to meditate upon it1 and ask himself upon what other grounds1 save those of structure and connection1 the properties and functions can possibly rest8 ,if on no other1 then similarity in structure and connection by logical necessity involves similarity in property and function4 ,,does ,,the ,,function ,,determine ,,the ,,organ8 #hh4 ,closely connected with this law1 which simply formulates the self-evident principle that every action is rigorously determined by the nature of the agent1 and the conditions under which the act takes place1 is the surprising question whether functions are dependent upon organs1 or organs dependent on functions8--a question which sometimes takes this shape3 ,is ,life the result of organization1 or is organization the result of ,life8 ,the vitalist1 who holds that ,life is an extra-organic agent1 is logical in declaring organization to be the consequence of ,life2#ci but there are many organicists who conclude from certain facts that organs are developed by functions1 and that organization is a result of ,life4 ,there seems1 however1 to be some equivoque here4 ,i cannot otherwise understand how ,mr4 ,spencer should have written3 8,there is one fact implying that ,function must be regarded as taking the precedence of ,structure4 ,of the lowest rhizopods which present no distinctions of parts1 and nevertheless feed and grow and move about1 ,professor ,huxley has remarked that they exhibit ,life without ,organization40#dj ,the equivoque here arises from the practice of calling all living bodies 8organisms10 even those destitute of the differentiations called organs2 but if we substitute the term 8living body0 in lieu of 8organism10 the equivoque will disappear1 and ,function no longer seem to precede ,structure4 ,neither ,mr4 ,spencer nor ,mr4 ,huxley would affirm that ,life can be manifested without a living body2 and every living body must have a structure of some sort--unless by structure be meant a special configuration of parts4 ,the properties of a body1 whether it be simple or complex in structure1 result from the properties of its components2 and the vital phenomena vary with these varying components4 ,the substance of a ,rhizopod is indeed simple as compared with that of higher organisms1 but is complex as compared with anorganisms2 and corresponding with this simplicity of structure there is simplicity of vital function4#da #hi4 ,the properties of steam are exhibited by the kettle on the fire1 no less than by the gigantic engine which animates a manufactory2 but the uses of steam 7the functions of the engine7 vary with the varying structure1 and the applications of that structure to other structures4 ,precisely analogous is the case of the organ and its function1 in relation to the living substance of which it is a peculiar modification4 ,vital actions are manifested by a lump of protoplasm2 but these actions are as sharply demarcated from the actions of more highly organized animals1 as the phenomena of a steam-engine are from those of a teakettle4 #ij4 ,mr4 ,spencer has nowhere defined what he means by ,structure1 nor given a definition of ,organ1 and this neglect makes it difficult rightly to appreciate his view4 ,but whether we take structure to signify the substance of the living body1 or the differentiations of that substance into separate tissues and organs1 in either case the actions 7functions7 of which this structure is the agent must be rigorously determined by it4 ,mr4 ,spencer has avowed this in declaring that the 8general physiologist may consider functions in their widest sense as the correlatives of tissue40 ,is this true in the widest sense and not true in the narrowest8 ,i am puzzled to find him insisting that 8function from beginning to end is the determining cause of structure4 ,not only is this manifestly true where the modification of structure arises by reaction from modification of function2 but it is also true where a modification of structure otherwise produced apparently initiates a modification of function40 ,such language would be consistent were he a vitalist who believed in a ,principle independent of ,matter which shapes matter into organic forms2 but as a positive thinker he can scarcely escape the admission that since ,function is the activity of the ,agent 7,function in the widest sense being the action of the whole ,organism1 and in its narrowest sense the action of the special ,organ7 there cannot be an activity preceding the agent4 ,i suspect that he does not always bear in mind the distinction between ,property and ,function1 and consequently is led into statements at variance with the principles he professes4 ,as far as ,i understand the course of his thought1 it runs somewhat thus3 ,with the increased use of an organ its volume may be increased1 its structure altered2 this alteration will1 by reaction1 cause alterations in other organs1 and thus the result of a change in the habitual activities of an animal will be an alteration in the arrangement of its parts4 #ia4 ,we speak loosely of an organ being developed by increased activity2 but this is loose speech1 and investigation shows that the organ is not developed by1 but accompanies the increased activity1 every increment of activity being necessarily preceded by a corresponding increment of structure4 ,this is evident priori3 the force manifested is inherent in the structure manifesting it4 ,thus we ought not to say 8the vascular system furnishes good instances of the increased growth that follows increased function02 we ought to say1 8that permits increased function40 ,the muscle having a contractile power represented by #aj1 expends1 we will suppose1 #g units of force in its normal activity1 and these are replaced by its normal nutrition4 ,if from an extra demand upon it #i units are expended1 the muscle becomes fatigued1 if #aj1 exhausted1 and it will no longer contract1 the whole disposable sum of its contractility being dissipated4 ,during all these stages the structure of the muscle--or to prevent all equivoque1 let us say the substance of the muscle--has been changing1 not indeed in any degree appreciable to the eye1 but appreciable by the more decisive tests of chemical and physiological reactions4 ,yet inasmuch as in the ordinary course of things the waste is quickly repaired1 the muscle in repose once more regains its original state1 once more represents #aj units of contractility4 ,now let us consider what takes place when extra labor is thrown upon the muscle1 when exercise causes growth4 ,at the outset of a walking tour we may not be able to compass more than twenty miles a day1 at its close we manage thirty4 ,is it the increased activity of the function which has caused this increase of structure8 ,in one sense1 yes2 but let us understand it4 ,had the increase of activity been temporary1 there would have been only a temporary increase of structure4 ,but when the ordinary expenditure of #g units rises to #i1 on several successive days1 this extra expenditure of tissue has had to be met by an extra nutrition--i4 e4 more plasmode has been formed and more protoplasm4 ,it is a physiological law1 easily explained1 that1 within due limits1 extra waste brings about extra repair3 as the channels are widened and multiplied1 the derived currents become stronger1 and the increased flow of nutrition which was temporary becomes permanent1 because this increase is no longer dependent on an extra stimulus1 but on an enlarged channel4#db ,when the channels have not become multiplied or enlarged1 which must be the case whenever the extra stimulus is fluctuating and temporary1 the extra expenditure is not followed by increased size of the muscle3 the currents resume their old directions1 no longer being diverted4 #ib4 ,let the social organism furnish us with an illustration4 ,at the present moment there is a movement against the retail shopkeepers of ,london in favor of ,co-operative ,stores4 ,the stimulus of getting better goods and cheaper1 attracts the flow of custom from its old channels2 and if this continue a certain time the new arrangements will be so thoroughly organized1 and will work so easily1 that ,co-operative ,stores will to a great extent supplant the retail shops4 ,but if from any causes the stimulus slackens before this reorganization has passed from the oscillating into the permanent stage--if the goods are not found to be superior1 or the cheapness not worth the extra trouble--the old influences 7aiding our indolence7 which have been long and continuously at work1 will cause the social organism to resume its old aspect1 and the co-operative 8varieties0 will disappear1 or exist beside the ancient 8species40 ,in the one case as in the other a glance at the process is enough to detect that the increase in the activity has been preceded by a corresponding increase in the structure4 ,the muscle has not been enlarged by extra activity1 but with it4 ,the co-operative action has grown with each additional co-operator4 ,looking at the cases from afar we may justly say that development has been due to function2 but looking to the process we see that each increment of activity was necessarily dependent on an increment of substance4 ,when changes of habit or adaptation are said to produce modifications in structures1 this is true in as far as one modification of structure necessarily brings with it correlative modifications1 the growth of one part affecting the growth of all more or less2 but we must remember that to render the structure capable of new adaptations corresponding modifications must have been going on4 ,the retail shopkeepers might securely laugh at the co-operative movement if the respectable families would not or could not become co-operant4 ,when ,mr4 ,spencer urges that 8not only may leaf-stalks assume to a great degree the character of stems when they have to discharge the functions of stems by supporting many leaves1 and very large leaves1 but they may assume the characters of leaves when they have to undertake the functions of leaves10 ,i would ask if he is not reversing the actual process8 ,the stem cannot assume the functions of a leaf until it has first assumed the character of a leaf4 ,the assumptions of both must be gradual1 and pari passu4 #ic4 ,the hand is an organ1 its function is prehension4 ,the performance of this function in any of its numerous applications is rigorously limited by the structure of the hand--the bones1 muscles1 nerves1 circulating and absorbent vessels1 connective tissue1 fat1 etc4 ,fatigue the nerve1 and the function will be feebly performed2 exhaust it1 and the function ceases2 diminish the action of the heart1 tie an artery1 or vitiate the structure of the blood1 and the function will be correspondingly affected2 stiffen the tendons1 soften the bones1 diminish the synovial fluid1 or increase the fat--in short1 make any alteration whatever in the structure of the hand1 and an alteration is necessarily produced in its function4 ,so rigorously is function dependent upon structure1 that the hand of one man will execute actions which are impossible to another4 ,the hand of a baby is said to be the same in structure as the hand of a man2 and since the powers 7functions7 of the two are notoriously different1 we might rashly conclude that here function was dissociated from structure4 ,the case is illustrative4 ,in baby and man the structure is similar1 not the same2 the resemblance is of kind1 not of degree2 and the function likewise varies with the degree4 ,the penny cannon which delights the child is similar in structure to the ten-pounder which batters down walls2 and though1 speaking generally1 we may say that the function of both is to fire gunpowder for human ends1 no one expects the penny cannon to be employed in warfare4 ,in physiology1 as in mechanics1 the effect varies with the forces involved4 ,there can be no doubt that an exaggerated activity will produce a modification in the active organ1 for this is only the familiar case of increased growth with increased exercise1 and this is the biological meaning in which ,function can be said not1 indeed1 to create1 but to modify an existing ,organ4 ,preceding the activity there must be the agent4 ,every organ although having its special function has also the properties of all the tissues which constitute it4 ,the function is only the synthesis of these properties to which a dominant tissue gives a special character4 ,the eye1 for example1 though specially characterized by its retinal sensibility to light1 is largely endowed with muscles1 and its movements are essential to ,vision4 ,the intestinal canal1 again1 though specially characterized by its secretions for the decomposition of food1 has muscles which are essential to ,digestion4 ,in many animals1 especially vegetable-feeders1 there is an exaggeration of the muscular activity in certain parts of the intestinal canal which is only possible through a corresponding development of the muscular tissue1 so that in some birds1 crustaceans1 and molluscs we find a gizzard1 which is wholly without a mucous membrane to secrete fluids1 and which aids ,digestion solely by trituration4 #id4 ,mr4 ,spencer1 as ,i have already suggested1 seems to have been led into his view by not keeping distinctly present to his mind the differences between ,properties of tissue and ,function1 the activity of an organ4 8,that function takes precedence of structure10 he says1 8seems implied in the definition of ,life4 ,if ,life consist of inner actions so adjusted as to balance outer actions--if the actions are the substance of ,life1 while the adjustment constitutes its form2 then may we not say that the actions formed must come before that which forms them--that the continuous change which is the basis of function must come before the structure which brings the function into shape80 ,the separation of 8actions formed0 from 8that which forms them0 is inadmissible4 ,an action cannot come before the agent3 it is the agent in act4 ,the continuous change1 which is the basis of ,vitality1 is a change of molecular arrangements2 and the organ which gives a special direction to the vital activity1 e4 g4 which shapes the property of ,contractility into the function of ,prehension1 this organ must itself be formed before it can manifest this function4 ,it is true that in one sense the organs are formed by1 or are differentiated in1 a pre-existent organism2 true that the general activity of living substance must precede the special activity of any organ1 as the expansions of steam must precede any steam-engine action2 but the general activity depends on the general structure2 and the special actions on the special structures4 ,if by ,organization we are to understand not simply organized substance1 but a more or less complex arrangement of that substance into separate organs1 the question is tantamount to asking whether the simplest animals and plants have life8 ,and to ask the question1 whether ,life precedes organic substance8 is tantamount to asking whether the convex aspect of a curve precedes the concave6 or whether the motions of a body precede the body6 ,to disengage ourselves from the complicated suggestions of such a word as ,life1 let us consider one of the vital phenomena1 ,contraction4 ,this is a phenomenon manifested by simple protoplasm1 and by the highly differentiated form of protoplasm known as muscle4 ,in one sense it would be correct to say that ,contractility as a general property of tissue precedes ,contraction1 which is specialized in muscle4 ,but it would be absurd to say that muscular contraction preceded the existence of muscle1 and formed it4 ,the contractions of the protoplasm are not the same as muscular contractions any more than the hand of a baby is the same as a man's2 the general property which both have in common depends on the substance both have in common2 the special property which belongs to the muscle depends on its special structure4 ,an infinite activity of the contractile protoplasm would be incompetent to form a muscle1 unless it were accompanied by that peculiar change in structure which constitutes muscle4 ,the teakettle might boil forever without producing a steam-engine or the actions of a steam-engine4 ,that which is true of one function is true of all functions1 and true of ,life1 which is the sum of vital activities4 #ie4 ,it is this haziness which made ,agassiz 8regret to observe that it has almost become an axiom that identical functions presuppose identical organs4 ,there never was a more incorrect principle leading to more injurious consequences40#dc ,and elsewhere he argues that organs can exist without functions4 ,but this is obviously to pervert the fundamental idea of an organ4 8,the teeth of the whale which never eat through the gums1 and the breasts of the males of all classes of mammalia10 are cited by him as examples of such organs without functions2 but in the physiological significance of the term these are not organs at all4 ,it is no more to be expected that the breasts of the male should act in lactation1 than that the slackened string of a violin should yield musical tones2 but the breasts of the male may be easily stimulated into yielding milk1 and the slackened string of the violin may be tightened so as to yield tone4 ,even the breasts of the female do not yield milk except under certain conditions1 and in the absence of these are on a par with those of the male4 #if4 ,organized substance has the general properties of ,assimilation1 ,evolution1 ,sensibility1 and ,contractility2 each of the special tissues into which organized substance is differentiated manifests a predominance of one of these properties4 ,thus although the embryo-cells all manifest contractility1 it is only the specialized muscle-cell which continues throughout its existence to manifest this property1 and in a dominant form2 the muscle-cell also assimilates and develops1 but besides having these properties in common with all other cells1 it has the special property of contracting with an energy not found in the others4 ,all cells respire2 but the blood-cells have this property of absorbing oxygen to a degree so far surpassing that of any other cell that physiologists have been led to speak of their containing a peculiar respiratory substance4 ,in like manner all1 or nearly all1 the tissues contain myeline--which indeed is one of the chief constituents of the yolk of eggs--but only in the white sheath of the nerves is it detached and specialized as a tissue4 #ig4 ,but while ,sensibility and ,contractility are general properties of organized substance1 specialized in special tissues2 ,sensation and ,contraction are functions of the organs formed by such tissues2 and these organs are only found in animal organisms4 ,it is a serious error1 which we shall hereafter have to insist on1 to suppose that ,sensation can be the property of ganglionic cells1 or1 as it is more often stated1 the property of the central gray matter4 ,sensation is the function of the organism2 it varies with the varying organ2 the sensation of ,touch not being the same as the sensation of ,sight1 or of ,sound4 #ih4 ,we may consider the organism under two aspects--that of ,structure and that of ,function4 ,the latter has two broad divisions corresponding with the vegetal and animal lives2 the one is ,nutrient1 the other ,efficient4 ,the one prepares and distributes ,food1 the other distributes ,motion4 ,of course this separation is analytical4 ,in reality the two are interblended2 and although the neuro-muscular system is developed out of the nutritive system1 it is no sooner developed than it plays its part as ,instrument in the preparation and distribution of ,aliment4 ,this not being a treatise on ,physiology1 there can be no necessity for our here considering the properties and functions in detail4 ,what is necessary to be said on ,sensibility and ,contractility will find its place in the course of future chapters2 for the present we will confine ourselves to ,evolution on account of its psychological1 no less than its physiological1 interest4 ,,chapter ,v4 ,,evolution4 #ii4 ,that organized substance has the property of nourishing itself by assimilating from its internal medium substances there present in an unorganized state1 and that this is followed by a development or differentiation of structure1 is familiar to every inquirer4 ,every one who has pursued embryological researches1 and in a lesser degree every one who has merely read about them1 must have been impressed by this marvel of marvels3 an exceedingly minute portion of living matter1 so simple in aspect that a line will define it1 passes by successive modifications into an organism so complex that a treatise is needed to describe it2 not only do the cells in which the ovum and the spermatozoon originate1 pass into a complex organism1 reproducing the forms and features of the parents1 and with these the constitutional peculiarities of the parents 7their longevity1 their diseases1 their mental dispositions1 nay1 their very tricks and habits71 but they may reproduce the form and features1 the dispositions and diseases1 of a grandfather or great-grandfather1 which had lain dormant in the father or mother4 ,consider for an instant what this implies4 ,a microscopic cell of albuminous compounds1 wholly without trace of organs1 not appreciably distinguishable from millions of other cells1 does nevertheless contain within it the 8possibilities0 of an organism so complex and so special as that of a ,newton or a ,napoleon4 ,if ever there was a case when the famous ,aristotelian notion of a 8potential existence0 seemed justified1 assuredly it is this4 ,and although we can only by a fallacy maintain the oak to be contained in the acorn1 or the animal contained in the ovum1 the fallacy is so natural1 and indeed so difficult of escape1 that there is no ground for surprise when physiologists1 on first learning something of development1 were found maintaining that the perfect organism existed already in the ovum1 having all its lineaments in miniature1 and only growing into visible dimensions through the successive stages of evolution4#dd ,the preformation of the organism seemed an inevitable deduction from the opinions once universal4 ,it led to many strange1 and some absurd conclusions2 among them1 to the assertion that the original germ of every species contained within it all the countless individuals which in process of time might issue from it2 and this in no metaphysical 8potential0 guise1 but as actual boxed-up existences 7embots72 so that ,adam and ,eve were in the most literal sense progenitors of the whole human race1 and contained their progeny already shaped within them1 awaiting the great accoucheur1 time4 #ajj4 ,this was the celebrated 8embotement0 theory4 ,in spite of obvious objections it gained scientific acceptance1 because physiologists could not bring themselves to believe that so marvellous a structure as that of a human organism arose by a series of successive modifications1 or because they could not comprehend how it was built up1 part by part1 into forms so closely resembling the parent-forms4 ,that many and plausible reasons pleaded in favor of this opinion is evident in the fact that illustrious men like ,haller1 ,bonnet1 ,vallisneri1 ,swammerdamm1 ,raumur1 and ,cuvier1 were its advocates2 and if there is not a sigle physiologist of our day who accepts it1 or who finds any peculiar difficulty in following the demonstrations of embryologists1 how from the common starting-point of a self-multiplying epithelial cell parts so diverse as hairs1 nails1 hoofs1 scales1 feathers1 crystalline lens1 and secreting glands may be evolved1 or how from the homogeneous germinal membrane the complex organism will arise1 there are very few among the scorners of the dead hypothesis who seem capable of generalizing the principles which have destroyed it1 or can conceive that the laws of ,evolution apply as rigorously to the animal and vegetable kingdoms as to the individual organisms4 ,the illustrious names of those who advocated the preformation hypothesis may serve to check our servile submission to the authorities so loudly proclaimed as advocates of the fixity of species4 ,the more because the two doctrines have a common parentage4 ,the one falls with the other1 and no array of authorities can arrest the fall4 ,that the manifold differentiations noticeable in a complex organism should have been evolved from a membrane wholly destitute of differences is a marvel1 but a marvel which ,science has made intelligible4 ,yet the majority of those to whom this has been made intelligible still find an impossibility in admitting that the manifold forms of plant and animal were successively evolved from equally simple origins4 ,they relinquish the hypothesis of preformation in the one case1 and cling to it in the other4 ,evolution1 demonstrable in the individual history1 seems preposterous in the history of the class4 ,and thus is presented the instructive spectacle of philosophers laughing at the absurdities of 8preformation10 and yet exerting all their logic and rhetoric in defence of 8creative fiats0--which is simply the preformation hypothesis 8writ large40 #aja4 ,it would not be difficult to show that the doctrine of ,epigenesis1 with which ,wolff forever displaced the doctrine of ,preformation1 leads by an inevitable logic to the doctrine of universal ,evolution2 and that we can no more understand the appearance of a new organism which is not the modification of some already existing organism1 than we can understand the sudden appearance of a new organ which is not the modification of some existing structure4 ,in the one case as in the other we may disguise the process under such terms as creative fiat and preformation2 but these terms are no explanations2 they re-state the results1 they do not describe the process2 whereas ,epigenesis describes the process as it passes under the eye of science4 #ajb4 ,if any reader of these pages who1 from theological or zological suspicion of the ,development ,hypothesis1 clings to the hypothesis of a creative ,plan which once for all arranged the organic world in ,types that could not change1 will ask what rational interpretation can be given to the succession of phases each embryo is forced to pass through1 it may help to give him pause4 ,he will observe that none of these phases have any adaptation to the future state of the animal1 but are in positive contradiction to it1 or are simply purposeless2 whereas all show stamped on them the unmistakable characters of ancestral adaptations and the progressions of ,organic ,evolution4 ,what does the fact imply8 ,there is not a single known example of a complex organism which is not developed out of simpler forms4 ,before it can attain the complex structure which distinguishes it1 there must be an evolution of forms similar to those which distinguish the structures of organisms lower in the series4 ,on the hypothesis of a ,plan which prearranged the organic world1 nothing could be more unworthy of a supreme intelligence than this inability to construct an organism at once1 without previously making several tentative efforts1 undoing to-day what was so carefully done yesterday1 and repeating for centuries the same tentatives1 and the same corrections1 in the same succession4 ,do not let us blink this consideration4 ,there is a traditional phrase much in vogue among the anthropomorphists1 which arose naturally enough from the tendency to take human methods as an explanation of the divine--a phrase which becomes a sort of argument--8,the ,great ,architect40 ,but if we are to admit the human point of view1 a glance at the facts of embryology must produce very uncomfortable reflections4 ,for what should we say to an architect who was unable1 or being able was obstinately unwilling1 to erect a palace except by first using his materials in the shape of a hut1 then pulling it down and rebuilding them as a cottage1 then adding story to story and room to room1 not with any reference to the ultimate purposes of the palace1 but wholly with reference to the way in which houses were constructed in ancient times8 ,what should we say to the architect who could not form a museum out of bricks and mortar1 but was forced to begin as if going to build a mansion3 and after proceeding some way in this direction1 altered his plan into a palace1 and that again into a museum8 ,yet this is the sort of succession on which organisms are constructed4 ,the fact has long been familiar2 how has it been reconciled with ,infinite ,wisdom8 ,let the following passage answer for a thousand3--8,the embryo is nothing like the miniature of the adult4 ,for a long while the body in its entirety and its details presents the strangest of spectacles4 ,day by day and hour by hour the aspect of the scene changes1 and this instability is exhibited by the most essential parts no less than by the accessory parts4 ,one would say that ,nature feels her way1 and only reaches the goal after many times missing the path1--on dirait que la nature ttonne et ne conduit son uvre bon fin qu'aprs s'tre souvent trompe40#de ,writers have no compunction in speaking of ,nature feeling her way and blundering2 but if in lieu of ,nature1 which may mean anything1 the ,great ,architect be substituted1 it is probable that the repugnance to using such language of evasion may cause men to revise their conceptions altogether2 they dare not attribute ignorance and incompetence to the ,creator4 #ajc4 ,obviously the architectural hypothesis is incompetent to explain the phenomena of organic development4 ,evolution is the universal process2 not creation of a direct kind4 ,von ,baer1 who very properly corrected the exaggerations which had been put forth respecting the identity of the embryonic forms with adult forms lower in the scale1 who showed that the mammalian embryo never was a bird1 a reptile1 or a fish1 nevertheless emphasized the fact that the mammalian embryo passes through all the lower typical forms2 so much so that1 except by their size1 it is impossible to distinguish the embryos of mammal1 bird1 lizard1 or snake4 8,in my collection10 he says1 8there are two little embryos which ,i have omitted to label1 so that ,i am now quite incompetent to say to what class they belong4 ,they may be lizards1 they may be small birds1 or very young mammals2 so complete is the similarity in the mode of formation of the head and trunk4 ,the extremities have not yet made their appearance4 ,but even if they existed in the earliest stage we should learn nothing from them1 for the feet of lizards1 mammals1 and the wings of birds1 all arise from the same common form40 ,he sums up with his formula3 8,the special type is always evolved from a more general type40#df ,such reminiscences of earlier forms are intelligible on the supposition that originally the later form was a modification of the earlier form1 and that this modification is repeated2 or on the supposition that there was a similarity in the organic conditions1 which similarity ceased at the point where the new form emerged4 ,but on no hypothesis of creative ,plan are they intelligible4 ,they are useless structures1 failing even to subserve a temporary purpose4 ,sometimes1 as ,mr4 ,darwin remarks1 a trace of the embryonic resemblance lasts till a late age3 8,thus birds of the same genus1 and of closely allied genera1 often resemble each other in their first and second plumage3 as we see in the spotted feathers in the thrush group4 ,in the cat tribe most of the species are striped and spotted in lines2 and stripes or spots can plainly be distinguished in the whelp of the lion and the puma4 ,we occasionally1 though rarely1 see something of this kind in plants4444 ,the points of structure in which the embryos of widely different animals of the same class resemble each other often have no direct relation to their conditions of existence4 ,we cannot1 for instance1 suppose that in the embryos of the vertebrata the peculiar loop-like courses of the arteries near the bronchial slits are related to similar conditions in the young mammal which is nourished in the womb of its mother1 in the egg of a bird which is hatched in a nest1 and in the spawn of a frog under water40 #ajd4 ,it would be easy to multiply examples1 but ,i will content myself with three4 ,the tadpole of the ,salamander has gills1 and passes his existence in the water2 but the ,salamandra atra1 which lives high up among the mountains1 brings forth its young full-formed4 ,this animal never lives in the water4 ,yet if we open a gravid female1 we find tadpoles inside her with exquisitely feathered gills1 and 7as ,i have witnessed7 these tadpoles 8when from the mother's womb untimely ripped10 if placed in water1 swim about like the tadpoles of water newts4 ,obviously this aquatic organization has no reference to the future life of the animal1 nor has it any adaptation to its embryonic condition2 it has solely reference to ancestral forms1 it repeats a phase in the development of its progenitors4 ,again1 in the embryo of the naked ,nudibranch1 we always observe a shell1 although the animal is without a shell1 and there can be no purpose served by the shell in embryonic life4#dg ,finally1 the human embryo has a tail1 which is of course utterly purposeless1 and which1 although to be explained as a result of organic laws1 is on the creative hypothesis only explained as an adherence to the general plan of structure--a specimen of pedantic trifling 8worthy of no intellect above the pongo's40#dh #aje4 ,humanly appreciated1 not only is it difficult to justify the successive stages of development1 the incessant building up of structures immediately to be taken down1 but also to explain why development was necessary at all4 ,why are not plants and animals formed at once1 as ,eve was mythically affirmed to be taken from ,adam's rib1 and ,minerva from ,jupiter's head8 ,the theory of ,evolution answers this question very simply2 the theory of ,creation can only answer it by affirming that such was the ordained plan4 ,but the theory of ,evolution not only gives the simpler and more intelligible answer to this question1 it gives an answer to the further question which leaves the theory of ,creation no loophole except a sophism--namely1 why the formation of organisms is constantly being frustrated or perverted8 ,and1 further1 it gives an explanation of the law noticed by ,milne ,edwards1 that ,nature is as economical in her means as she is prodigal in her variation of them3 8,on dirait qu'avant de recourir des ressources nouvelles elle a voulu puiser1 en quelque sorte1 chacun des procds qu'elle avait mis en jeu40#di ,the applause bestowed on ,nature for being economical is a curious transference to ,nature of human necessities4 ,why1 with a whole universe at her disposal1 should ,nature be economical8 ,why must she always be working in the same groove1 and using but a few out of the many substances at her command8 ,economy is a virtue only in the poor4 ,if ,nature1 in organic evolutions1 is restricted to a very few substances1 and a very few modes of combination1 always creating new forms by modification of the old1 and apparently incapable of creating an organism at once1 this must imply an inherent necessity which is very unlike the free choice that can render economy a merit4 #ajf4 ,there may indeed be raised an objection to the ,development ,hypothesis on the ground that if the complex forms were all developed from the simpler forms1 we ought to trace the identities through all their stages4 ,if the fish developed into the reptile1 the reptile into the bird1 and the bird into the mammal 7which ,i1 for one1 think questionable71 we ought to find1 it is urged1 evidence of this passage4 ,and at one time it was asserted that the evidence existed2 but this has been disproved1 and on the disproof the opponents of ,evolution take their stand4 ,although ,i cannot feel much confidence in the idea of such a passage from ,type to ,type1 and although the passage1 if ever it occurred1 must have occurred at so remote a period as to leave no evidence more positive than inference1 ,i cannot but think the teaching of ,embryology far more favorable to it than to our opponents4 ,supposing1 for the sake of argument1 that the passage did take place1 ought we to find the embryonic stages accurately reproducing the permanent forms of lower types8 ,von ,baer thinks we ought2 and lesser men may follow him without reproach4 ,but it seems to me that he starts from an inadmissible assumption1 namely1 that the development must necessarily be in a straight line rather than in a multiplicity of divergent lines4 8,when we find the embryonic condition10 he says1 8differing from the adult1 we ought to find a corresponding condition somewhere in the lower animals40#ej ,not necessarily4 ,we know that the mental development of a civilized man passes through the stages which the race passed through in the course of its long history1 and the psychology of the child reproduces the psychology of the savage4 ,but as this development takes place under conditions in many respects different1 and as certain phases are hurried over1 we do not expect to find a complete parallel4 ,it is enough if we can trace general resemblances4 ,von ,baer adds1 8,that certain correspondences should occur between the embryonic states of some animals and the adult states of others seems inevitable and of no significance7874 ,they could not fail1 since the embryos lie within the animal sphere1 and the variations of which the animal body is capable are determined for each type by the internal connection and mutual reaction of its organs1 so that particular repetitions are inevitable40 ,a profound remark1 to which ,i shall hereafter have occasion to return1 but its bearing on the present question is inconclusive4 ,the fact that the embryonic stages of the higher animals resemble in general characters the permanent stages of the lower animals1 and very closely resemble the embryonic stages of those animals1 is all that the ,development ,hypothesis requires4 ,nor is its value lessened by the fact that many of the details and intermediate stages seem passed over in the development of the higher forms1 for the recapitulation can only be of outlines1 not of details2 since there are differences in the forms1 there must be differences in their histories4 #ajg4 ,in the preceding observations the object has simply been to show that the phenomena to be explained can be rationally conceived as resulting from gradual ,evolution1 whereas they cannot be so rationally interpreted on any other hypothesis4 ,and here it may be needful to say a word respecting ,epigenesis4 ,the ,preformation hypothesis1 which regarded every organism as a simple educt and not the product of a germ1 was called by its advocates an evolution hypothesis--meaning that the adult form was an outgrowth of the germ1 the miniature magnified4 ,wolff1 who replaced that conception by a truer one1 called his1 by contrast1 ,epigenesis1 meaning that there was not simply out-growth but new growth4 8,the various parts10 he says1 8arise one after the other1 so that always one is secreted from 7excernirt71 or deposited 7deponirt7 on the other2 and then it is either a free and independent part1 or is only fixed to that which gave it existence1 or else is contained within it4 ,so that every part is the effect of a pre-existing part1 and in turn the cause of a succeeding part40#ea ,the last sentence expresses the conception of ,epigenesis which embryologists now adopt2 and having said this1 we may admit that ,wolff1 in combating the error of preformation1 replacing it with the truer notion of gradual and successive formation1 was occasionally open to the criticism made by ,von ,baer1 that he missed the true sense of ,evolution1 since the new parts are not added on to the old parts as new formations1 but evolved from them as transformations4 8,the word ,evolution1 therefore1 seems to me more descriptive of the process than ,epigenesis4 ,it is true that the organism is not preformed1 but the course of its development is precisely the course which its parents formerly passed through4 ,thus it is the ,invisible--the course of development--which is predetermined40#eb ,when the word ,epigenesis is used1 therefore1 the reader will understand it to signify that necessary succession which determines the existence of new forms4 ,just as the formation of chalk is not the indifferent product of any combination of its elements1 carbon1 oxygen1 and calcium1 but is the product of only one series of combinations1 an evolution through necessary successions1 the carbon uniting with oxygen to form carbonic acid1 and this combining with the oxide of calcium to form chalk1 so likewise the formation of a muscle1 a bone1 a limb1 or a joint has its successive stages1 each of which is necessary1 none of which can be transposed4 ,the formation of bone is peculiarly instructive1 because the large proportion of inorganic matter in its substance1 and seemingly deposited in the organic tissue1 would lead one to suppose that it was almost an accidental formation1 which might take place anywhere2 yet although what is called connective tissue will ossify under certain conditions1 true bone is the product of a very peculiar modification1 which almost always needs to be preceded by cartilage4 ,that the formation of bone has its special history may be seen in the fact that it is the last to appear in the animal series1 many highly organized fishes being without it1 and all the other systems appearing before it in the development of the embryo4 ,thus although the mother's blood furnishes all the requisite material1 the ftus is incapable of assimilating this material and of forming bone1 until its own development has reached a certain stage4 ,moreover1 when ossification does begin1 it generally begins in the skull 7in man in the clavicle72 and the only approach to an internal skeleton in the ,invertebrates is the so-called skull of the ,cephalopoda4 ,not only is bone a late development1 but cartilage is also2 and although it is an error to maintain that the ,invertebrates are wholly destitute of cartilage1 its occasional presence having been fully proved by ,claparde and ,gegenbaur1 the rarity of its presence is very significant4 ,the animals which can form shells of chalk and chitine are yet incapable of forming even an approach to bone4 #ajh4 ,epigenesis depends on the laws of succession1 which may be likened to the laws of crystallization1 if we bear in mind the essential differences between a crystal and an organism1 the latter retaining its individuality through an incessant molecular change1 the former only by the exclusion of all change4 ,when a crystalline solution takes shape1 it will always take a definite shape1 which represents what may be called the direction of its forces1 the polarity of its constituent molecules4 ,in like manner1 when an organic plasmode takes shape--crystallizes1 so to speak--it always assumes a specific shape dependent on the polarity of its molecules4 ,crystallographers have determined the several forms possible to crystals2 histologists have recorded the several forms of ,organites1 ,tissues1 and ,organs4 ,owing to the greater variety in elementary composition1 there is in organic substance a more various polar distribution than in crystals2 nevertheless1 there are sharply defined limits never overstepped1 and these constitute what may be called the specific forms of ,organites1 ,tissues1 ,organs1 ,organisms4 ,an epithelial cell1 for example1 may be ciliated or columnar1 a muscle-fibre striated or non-striated1 a nerve-fibre naked or enveloped in a sheath1 but the kind is always sharply defined4 ,an intestinal tube may be a uniform canal1 or a canal differentiated into several unlike compartments1 with several unlike glandular appendages4 ,a spinal column may be a uniform solid axis1 or a highly diversified segmented axis4 ,a limb may be an arm1 or a leg1 a wing1 or a paddle4 ,in every case the anatomist recognizes a specific type4 ,he assigns the uniformities to the uniformity of the substance thus variously shaped1 under a history which has been similar2 the diversities he assigns to the various conditions under which the processes of growth have been determined4 ,he never expects a muscular tissue to develop into a skeleton1 a nervous tissue into a gland1 an osseous tissue into a sensory organ4 ,he never expects a tail to become a hand or a foot1 though he sees it in monkeys and marsupials serving the offices of prehension and locomotion4 ,he never expects to find fingers growing anywhere except from metacarpal bones1 or an arm developed from a skull4 ,the well-known generalization of ,geoffroy ,st4 ,hilaire that an organ is more easily annihilated than transposed1 points to the fundamental law of ,epigenesis4 ,in the same direction point all the facts of growth4 ,out of a formless germinal membrane we see an immense variety of forms evolved2 and out of a common nutritive fluid this variety of organs is sustained1 repaired1 replaced2 and this not indifferently1 not casually1 but according to rigorous laws of succession2 that which precedes determining that which succeeds as inevitably as youth precedes maturity1 and maturity decay4 ,the nourishment of various organs from plasmodes derived from a common fluid1 each selecting from that fluid only those molecules that are like its own1 rejecting all the rest1 is very similar to the formation of various crystals in a solution of different salts1 each salt separating from the solution only those molecules that are like itself4 ,reil long ago called attention to this analogy4 ,he observed that if in a solution of nitre and sulphate of soda a crystal of nitre be dropped1 all the dissolved nitre crystallizes1 the sulphate remaining in solution2 whereas on reversing the experiment1 a crystal of sulphate of soda is found to crystallize all the dissolved sulphate1 leaving the nitre undisturbed4 ,in like manner muscle selects from the blood its own materials which are there in solution1 rejecting those which the nerve will select4 #aji4 ,nay1 so definite is the course of growth1 that when a limb or part of a limb is cut off from a crab or salamander1 a new limb or new part is reproduced in the old spot1 exactly like the one removed4 ,bonnet startled the world by the announcement that the ,nas1 a worm common in ponds1 spontaneously divided itself into two worms2 and that when he cut it into several pieces1 each piece reproduced head and tail1 and grew into a perfect worm4 ,this had been accepted by all naturalists without demur1 until ,dr4 ,williams1 in his 8,report on ,british ,annelida1 #ahea10 declared it to be a fable4 ,in #aheh1 under the impulse of ,dr4 ,williams's very emphatic denial1 ,i repeated experiments similar to those of ,bonnet1 with similar results4 ,i cut two worms in half1 and threw away the head-bearing segments1 placing the others in two separate vessels1 with nothing but water and a little mud1 which was first carefully inspected to see that no worm lay concealed therein4 ,in a few days the heads were completely reformed1 and ,i had the pleasure of watching them during their reconstruction4 ,when the worms were quite perfect1 ,i again cut away their heads1 and again saw these reformed4 ,this was repeated1 till ,i had seen four heads reproduced2 after which the worms succumbed4 #aaj4 ,the question naturally arises1 ,why does the nutritive fluid furnish only material which is formed into a part like the old one1 instead of reproducing another part1 or one having a somewhat different structure8 ,the answer to this question is the key to the chief problem of organic life4 ,that a limb in situ should replace its molecular waste by molecules derived from the blood1 seems intelligible enough 7because we are familiar with it71 and may be likened to the formation of crystals in a solution2 but how is it that the limb which is not in existence can assimilate materials from the blood8 ,how is it that the blood1 which elsewhere in the organism will form other parts1 here will only form this particular part8 ,there is1 probably1 no one who has turned his attention to these subjects who has not paused to consider this mystery4 ,the most accredited answer at present before the world is one so metaphysiological that ,i should pass it by1 were it not intimately allied with that conception of ,species1 which it is the object of these pages to root out4 ,it is this3 #aaa4 ,the organism is determined by its ,type1 or1 as the ,germans say1 its ,idea4 ,all its parts take shape according to this ruling plan2 consequently1 when any part is removed1 it is reproduced according to the ,idea of the whole of which it forms a part4 ,milne ,edwards1 in a very interesting and suggestive work1 concludes his survey of organic phenomena in these words3 8,dans l'organisme tout semble calcul en vue d'un rsultat dtermin1 et l'harmonie des parties ne rsulte pas de l'influence qu'elles peuvent exercer les unes sur les autres1 mais de leur co-ordination sous l'empire d'une puissance commune1 d'un plan prconu1 d'une force pr-existante40#ec ,this is eminently metaphysiological4 ,it refuses to acknowledge the operation of immanent properties1 refuses to admit that the harmony of a complex structure results from the mutual relations of its parts1 and seeks outside the organism for some mysterious force1 some plan1 not otherwise specified1 which regulates and shapes the parts4 ,von ,baer1 in his great work1 has a section entitled1 8,the nature of the animal determines its development02 and he thus explains himself3 8,although every stage in development is only made possible by the pre-existing condition which is another mode of expressing ,epigenesis1 nevertheless the entire development is ruled and guided by the ,nature of the animal which is about to be 7von der gesammten ,wesenheit des ,thieres welches werden soll71 and it is not the momentary condition which alone and absolutely determines the future1 but more general and higher relations40#ed ,one must always be slow in rejecting the thoughts of a master1 and feel sure that one sees the source of the error before regarding it as an error2 but in the present case ,i think the positive biologist will be at no loss to assign ,von ,baer's error to its metaphysical origin4 ,without pausing here to accumulate examples both of anomalies and slighter deviations which are demonstrably due to the 8momentary conditions0 that preceded them1 let us simply note the logical inconsistency of a position which1 while assuming that every separate stage in development is the necessary sequence of its predecessor1 declares the whole of the stages independent of such relations6 ,such a position is indeed reconcilable on the assumption that animal forms are moulded 8like clay in the hands of the potter40 ,but this is a theological dogma1 which leads to very preposterous and impious conclusions2 and whether it leads to these conclusions or to others1 positive ,biology declines theological explanations altogether4 ,von ,baer1 although he held the doctrine of ,epigenesis1 coupled it1 as many others have done1 with metaphysical doctrines to which it is radically opposed4 ,he believed in ,types as realities2 he was therefore consistent in saying1 8,it is not the ,matter and its arrangements which determine the product1 but the nature of the parent form--the ,idea1 according to the new school40 ,how are we to understand this ,idea8 ,if it mean an independent ,entity1 an agency external to the organism1 we refuse to acknowledge its existence4 ,if it mean only an a posteriori abstraction expressing the totality of the conditions1 then1 indeed1 we acknowledge that it determines the animal form2 but this is only an abbreviated way of expressing the law of ,evolution1 by which each stage determines its successor4 ,the ,type does not dominate the conditions1 it emerges from them2 the animal organism is not cast in a mould1 but the imaginary mould is the form which the polarities of the organic substance assume4 ,it would seem very absurd to suppose that crystals assumed their definite shapes 7when the liquid which held their molecules in solution is evaporated7 under the determining impulse of phantom-crystals1 or ,ideas2 yet it has not been thought absurd to assume phantom forms of organisms4 #aab4 ,the conception of ,type as a determining influence arises from that fallacy of taking a resultant for a principle1 which has played so conspicuous a part in the history of philosophy4 ,like many others of its class it exhibits an interesting evolution from the crude metaphysical to the subtle metaphysical point of view1 which at last insensibly blends into the positive point of view4 ,at first the ,type or ,idea was regarded as an objective reality1 external to the organism it was supposed to rule4 ,then this notion was replaced by an approach to the more rational interpretation1 the idea was made an internal not an external force1 and was incorporated with the material elements of the organism1 which were said to 8endeavor0 to arrange themselves according to the ,type4 ,thus ,treviranus declares that the seed 8dreams of the future flower02 and 8,henle1 when he affirms that hair and nails grow in virtue of the ,idea1 is forced to add that the parts endeavor to arrange themselves according to this ,idea40#ee ,even ,lotze1 who has argued so victoriously against the vitalists1 and has made it clear that an organism is a vital mechanism1 cannot relinquish this conception of legislative ,ideas1 though he significantly adds1 8these have no power in themselves1 but only in as far as they are grounded in mechanical conditions40 ,why then superfluously add them to the conditions8 ,if every part of a watch1 in virtue of the properties inherent in its substance1 and of the mutual reactions of these and other parts1 has a mechanical value1 and if the sum of all these parts is the time-indicating mechanism1 do we add to our knowledge of the watch1 and our means of repairing or improving it1 by assuming that the parts have over and above their physical properties the metaphysical 8tendency0 or 8desire0 to arrange themselves into this specific form8 ,when we see that an organism is constructed of various parts1 each of which has its own properties inalienable from its structure1 and its uses dependent on its relation to other parts1 do we gain any larger insight by crediting these parts with desires or 8dreams0 of a future result which their union will effect8 ,that which is true in this conception of legislative ,ideas is that when the parts come together there is mutual reaction1 and the resultant of the whole is something very unlike the mere addition of the items1 just as water is very unlike oxygen or hydrogen2 further1 the connexus of the whole impresses a peculiar direction on the development of the parts1 and the law of ,epigenesis necessitates a serial development1 which may easily be interpreted as due to a preordained plan4 #aac4 ,in a word1 this conception of ,type only adds a new name to the old difficulty1 adding mist to darkness4 ,the law of ,epigenesis1 which is simply the expression of the material process determined by the polarity of molecules1 explains as much of the phenomena as is explicable4 ,a lost limb is replaced by the very processes1 and through the same progressive stages as those which originally produced it4 ,we have a demonstration of its not being reformed according to any ,idea or ,type which exists apart from the immanent properties of the organic molecules1 in the fact that it is not reformed at once1 but by gradual evolution2 the mass of cells at the stump are cells of embryonic character1 cells such as those which originally 8crystallized0 into muscles1 nerves1 vessels1 and integument1 and each cell passes through all its ordinary stages of development4 ,it is to be remembered that so intimately dependent is the result on the determining conditions1 that any external influence which disturbs the normal course of development will either produce an anomaly1 or frustrate the formation of a new limb altogether4 ,one of my tritons bit off the leg of his female2#ef the leg which replaced it was much malformed1 and curled over the back so as to be useless2 was this according to the ,idea8 ,i cut it off1 and examined it2 all the bones were present1 but the humerus was twisted1 and of small size4 ,in a few weeks a new leg was developed1 and this leg was normal4 ,if the ,idea1 as a ruling power1 determined the growth of this third leg1 what determined the second1 which was malformed8 ,are we to suppose that in normal growth the ,idea prevails1 in abnormal the conditions8 ,that it is the polarity of the molecules which at each moment determines the group those molecules will assume1 is well seen in the experiment of ,lavalle mentioned by ,bronn4#eg ,he showed that if when an octohedral crystal is forming1 an angle be cut away1 so as to produce an artificial surface1 a similar surface is produced spontaneously on the corresponding angle1 whereas all the other angles are sharply defined4 8,valentin10 says ,mr4 ,darwin1 8injured the caudal extremity of an embryo1 and three days afterwards it produced rudiments of a double pelvis1 and of double hind limbs4 ,hunter and others have observed lizards with their tails reproduced and doubled4 ,when ,bonnet divided longitudinally the foot of the salamander1 several additional digits were occasionally formed40#eh ,where is the evidence of the ,idea in these cases8 #aad4 ,i repeat1 the reproduction of lost limbs is due to a process which is in all essential respects the same as that which originally produced them2 the genesis of one group of cells is the necessary condition for the genesis of its successor1 nor can this order be transposed4 ,but--and the point is very important--it is not every part that can be reproduced1 nor is it every animal that has reproductive powers4 ,the worm1 or the mollusk1 seems capable of reproducing every part2 the crab will reproduce its claws1 but not its head or tail2 the perfect insect of the higher orders will reproduce no part 7indeed the amputation of its antennae only is fatal71 the salamander will reproduce its leg1 the frog not4 ,in human beings a muscle is said never to be reproduced2 but this is not the case in the rare examples of supplementary fingers and toes1 which have been known to grow again after amputation4 ,the explanation of this difference in the reproductive powers of different animals is usually assigned to the degree in which their organisms retain the embryonic condition2 and this explanation is made plausible by the fact that the animals which when adult have no power of replacing lost limbs1 have the power when in the larval state4 ,but although this may in some cases be the true explanation1 there are many in which it fails1 as will be acknowledged after a survey of the extremely various organisms at widely different parts of the animal series which possess the reproductive power4 ,even animals in the same class1 and at the same stage of development1 differ in this respect4 ,i do not attach much importance to the fact that all my experiments on marine annelids failed to furnish evidence of their power of reproducing lost segments2 because it is difficult to keep them under conditions similar to those in which they live4 ,but it is significant that1 among the hundreds which have passed under my observation1 not one should have been found with a head-segment in the process of development1 replacing one that had been destroyed2 and this is all the more remarkable from the great tenacity of life which the mutilated segments manifest4 ,quatrefages had observed portions of a worm1 after gangrene had destroyed its head and several segments1 move about in the water and avoid the light6#ei #aae4 ,a final argument to show that the reproduction is not determined by any ruling ,idea1 but by the organic conditions and the necessary stages of evolution1 is seen in the reappearance of a tumor or cancer after it has been removed4 ,we find the new tissue appear with all the characters of the normal tissue of the gland1 then rapidly assume one by one the characters of the diseased tissue which had been removed2 and there as on is1 that the regeneration of the tissue is accompanied by the same abnormal conditions which formerly gave rise to the tumor3 the directions of 8crystallization0 are similar because the conditions are similar4 ,in every case of growth or regrowth the conditions being the same1 the result must be the same4 #aaf4 ,it seems a truism to insist that similarity in the results must be due to similarity in the conditions2 yet it is one which many theorists disregard2 and especially do we need to bear it in mind when arguing about ,species4 ,i will here only touch on the suggestive topic of the analogies observed not simply among animals at the extreme ends of the scale1 but also between animals and plants where the idea of a direct kinship is out of the question4 ,my very imperfect zological knowledge will not allow me to adduce a long array of instances1 but such an array will assuredly occur to every well-stored mind4 ,it is enough to point to the many analogies of ,function1 more especially in the reproductive processes--to the existence of burrowers1 waders1 flyers1 swimmers in various classes--to the existence of predatory mammals1 predatory birds1 predatory reptiles1 predatory insects by the side of herbivorous congeners1--to the nest-building and incubating fishes2 and in the matter of ,structure the analogies are even more illustrative when we consider the widely diffused spicula1 set1 spines1 hooks1 tentacles1 beaks1 feathery forms1 nettling-organs1 poison-sacs1 luminous organs1 etc42 because these have the obvious impress of being due to a community of substance under similar conditions rather than to a community of kinship4 ,the beak of the tadpole1 the cephalopod1 the male salmon1 and the bird1 are no doubt in many respects unlike2 but there is a significant likeness among them1 which constitutes a true analogy4 ,i think there is such an analogy between the air-bladder of fishes and the tracheal rudiment which is found in the gnat-larva 7,corethra plumicornis74#fj ,very remarkable also is the resemblance of the avicularium1 or 8bird's-head process10 on the polyzoon known popularly as the ,corkscrew ,coralline 7,bugula avicularia71 which presents us in miniature with a vulture's head--two mandibles1 one fixed1 the other moved by muscles visible within the head4 ,no one can watch this organ snapping incessantly1 without being reminded of a vulture1 yet no one would suppose for a moment that the resemblance has anything to do with kinship4 #aag4 ,such cases are commonly robbed of their due significance by being dismissed as coincidences4 ,but what determines the coincidence8 ,if we assume1 as we are justified in assuming1 that the possible directions of ,organic ,combination1 and the resultant forms1 are limited1 there must inevitably occur such coincident lines3 the hooks on a ,climbing ,plant will resemble the hooks on a ,crustacean or the claws of a ,bird1 as the one form in which under similar external forces the more solid but not massive portions of the integument tend to develop4 ,i am too ill acquainted with the anatomy of plants to say how the hooks so common among them arise2 but from examination of the ,blackberry1 and comparison of its thorns with the hooks and spines of the ,crustacea1 ,i am led to infer that in each case the mode of development is identical--namely1 the secretion of chitine from the cellular matrix of the integument4 ,another mode of evading the real significance of such resemblances is to call them analogies1 not homologies4 ,there is an advantage in having two such terms1 but we ought to be very clear as to their meaning and their point of separation4 ,analogy is used to designate similarity in ,function with dissimilarity in ,structure4 ,the wing of an insect1 the wing of a bird1 and the wing of a bat are called analogous1 but not homologous1 because their anatomical structure is different3 they are not constructed out of similar anatomical parts4 ,the fore-leg of a mammal1 the wing of a bird1 or the paddle of a whale1 are called homologous1 because in spite of their diverse uses they are constructed out of corresponding anatomical parts4 ,to the anatomist such distinctions are eminently serviceable4 ,but they have led to some misconceptions1 because they are connected with a profound misconception of the relation between ,function and ,organ4 ,embryology teaches that the wing of the bird and the paddle of the whale are developed out of corresponding parts1 and that these are not like the parts from which the wing of an insect or the flying-fish will be developed2 nevertheless1 the most cursory inspection reveals that the wing of a bird and the paddle of a whale are very unlike in structure no less than in function1 and that their diversities in function correspond with their diversities in structure2 whereas the wing of the insect1 of the bird1 and of the bat1 are in certain characters very similar1 and correspondingly there are similarities in their function4 ,it is1 however1 obvious that the resemblance in function is strictly limited to the resemblance in anatomical structure2 only in loose ordinary speech can the flight of an insect1 a bird1 or a bat be said to be 8the same03 it is different in each--the weight to be moved1 the rapidity of the movement1 the precision of the movements1 and their endurance1 all differ4 ,,natural ,,selection ,,and ,,organic ,,affinity4 #aah4 ,it is impossible to treat of ,evolution without taking notice of that luminous hypothesis by which ,mr4 ,darwin has revolutionized ,zology4 ,there are two points needful to be clearly apprehended before the question is entered upon4 ,the first point relates to the lax use of the phrase 8conditions10 sometimes more instructively replaced by 8conditions of existence40 ,inasmuch as ,life is only possible under definite relations of the organism and its medium1 the 8conditions of existence0 will be those physical1 chemical1 and physiological changes1 which in the organism1 and out of it1 co-operate to produce the result4 ,there are myriads of changes in the external medium which have no corresponding changes in the organism1 not being in any direct relation to it 7see #ed74 ,these1 not being co-operant conditions1 must be left out of the account2 they are not conditions of existence for the organism1 and therefore the organism does not vary with their variations4 ,on the other hand1 what seem very slight changes in the medium are often responded to by important changes in the vital chemistry1 and consequently in the structure of the organism4 ,now the nature of the organism at the time being1 that is to say1 its structure and the physico-chemical state of its tissues and plasmodes1 is the main condition of this response2 the same external agent will be powerful1 or powerless1 over slightly different organisms1 or over the same organism at different times4 ,usually1 and for convenience1 when biologists speak of conditions1 they only refer to external changes4 ,this usage has been the source of no little confusion in discussing the ,development ,hypothesis4 ,mr4 ,darwin1 however1 while following the established usage1 is careful in several places to declare that of the two factors in ,variation--the nature of the organism and the nature of the conditions--the former is by far the more important4 #aah;a4 ,a still greater modification of terms must now be made4 ,instead of confining the 8struggle for existence0 to the competition of rivals and the antagonism of foes1 we must extend it to the competition and antagonism of tissues and organs4 ,the existence of an organism is not only dependent on the external existence of others1 and is the outcome of a struggle2 but also on the internal conditions which co-operate in the formation of its structure1 this structure being the outcome of a struggle4 ,the organism is this particular organism1 differing from others1 because of the particular conditions which have co-operated4 ,the primary and fundamental struggle must be that of the organic forces at work in creating a structure capable of pushing its way amid external forces4 ,the organism must find a footing in the world1 before it can compete with rivals1 and defend itself against foes4 ,owing to the power of reproduction1 every organism has a potential indefiniteness of multiplication2 that potential indefiniteness is1 however1 in reality restricted by the supply of food1 and by the competition of rivals for that supply4 ,the multiplication of any one species is thus kept down by the presence of rivals and foes3 a balance is reached1 which permits of the restricted quantities of various species4 ,this balance is the result of a struggle4 ,now let me call attention to a similar process in the formation of the organism itself4 ,every organite1 and every tissue1 has a potential growth of indefinite extent1 but its real growth is rigorously limited by the competition and antagonism of the others1 each of which has its potential indefiniteness1 and its real limits4 ,something1 in the food assimilated1 slightly alters the part which assimilates it4 ,this change may be the origin of other changes in the part itself1 or in neighboring parts1 stimulating or arresting the vital processes4 ,a modification of structure results4 ,or there may be no new substance assimilated1 but external forces may call a part into increased activity--which means increased waste and repair2 and this increase here is the cause of a corresponding decrease somewhere else4 ,whatever the nature of the change1 it finds its place amid a complex of changes1 and its results are compounded with theirs4 ,when organites and tissues are said to have a potential indefiniteness of growth1 there is assumed a potential indefiniteness in the pabulum supplied3 if the pabulum were supplied1 and if there were no antagonism thwarting its assimilation1 growth would of course continue without pause1 or end2 but in reality this cannot be so4 ,for1 take the blood as the vehicle of the pabulum--not only is its quantity limited1 and partly limited by the very action of the tissues it feeds1 but even in any given quantity there is a limit to its composition--it will only take up a limited quantity of salts1 iron1 albumen1 etc42 no matter how abundant these may be in the food4 ,so again with the plasmodes of the various tissues--they have each their definite capacities of assimilation4 ,what has already been stated respecting chemical affinity 7 #bj7 is equally applicable to organic affinity2 as the presence of fused iron in the crucible partially obstructs the combination of sulphur and lead1 so the presence of connective tissue partially obstructs the combination of muscle protoplasm with its pabulum4 #aah b4 ,owing to the action and reaction of blood and plasmode1 of tissues on tissues1 and organs on organs1 and their mutual limitations1 the growth of each organism has a limit1 and the growth of each organ has a limit4 ,beyond this limit1 no extra supply of food will increase the size of the organism2 no increase of activity will increase the organ4 8,man cannot add a cubit to his stature40 ,the blacksmith's arm will not grow larger by twenty years of daily exercise1 after it has once attained a certain size4 ,increase of activity caused it to enlarge up to this limit2 but no increase of activity will cause it to pass this limit4 ,why8 ,because here a balance of the co-operating formative forces has been reached4 ,larger muscles1 or more muscle-fibres1 demand arteries of larger calibre1 and these a heart of larger size2 with the increase of muscle would come increase of connective tissue2 and this tissue would not only compete with the muscle for pabulum1 but by mechanical pressure would diminish the flow of that pabulum4 ,and why would connective tissue increase8 ,because1 in the first place1 there is a formative association between the two1 so that owing to a law1 not yet understood1 the one always accompanies the other2 and1 in the second place1 there is a functional association between the two1 a muscle-fibre being inoperative unless it be attached to a tendon1 or connective tissue2 it will contract out of the body although separated from its tendon or other attachment2 but in the body its contraction would be useless without this attachment4 ,we must bear in mind that muscle-fibres are very much shorter than ordinary muscles2 according to the measurements of ,w4 ,krause they never exceed #d cm in length1 and usually range between #b and #c cm2 their fine points being fixed to the interstitial connective tissue1 as the whole muscle is fixed to its tendon4 ,the function of the muscle is thus dependent on a due balance of its component tissues2 if that balance is disturbed the function is disturbed4 ,should1 from any cause1 an excess of muscle-fibre arise1 the balance would be disturbed2 should an encroachment of connective tissue1 or of fat1 take place1 there would be also a defect of function4 ,here we have the co-operation and limitation of the tissues illustrated2 let us extend our glance1 and we shall see how the co-operation and limitation of the organs come into play1 so that the resulting function depends on the balance of their forces4 ,the contractile power of each individual muscle is always limited by the resistance of antagonists1 which prevent the muscle being contracted more than about a third of its possible extent1 i4 e4 possible when there are no resistances to be overcome4 ,not only the increasing tension of antagonist muscles1 but the resistance of tendons1 bones1 and softer parts must be taken into account4 ,thus1 the increase of the blacksmith's muscular power would involve a considerable increase in all the tissues of the arm2 but such an increase would involve a reconstruction of his whole organism4 ,whenever there is an encroachment of one tissue on another1 there is a disturbance of the normal balance1 which readily passes into a pathological state4 ,if the brain is overrun with connective tissue1 or the heart with fatty tissue1 we know the consequences4 ,if connective tissue is deficient1 epithelial runs to excess1 no longer limited by its normal antagonist1 and pus1 or cancer1 result4 #aah;c4 ,it is unnecessary here to enlarge on this point4 ,i have adduced it to show that we must extend our conception of the struggle for existence beyond that of the competition and antagonism of organisms--the external struggle2 and include under it the competition and antagonism of tissues and organs--the internal struggle4 ,variability is inherent in organic substances1 as the result of their indefiniteness of composition 7 #de;b74 ,this variability is indefinite1 and is rendered definite by the competition and antagonism1 so that every particular variation is the resultant of a composition of forces4 ,the forces in operation are the internal and external conditions of existence--i4 e4 the nature of the organism1 and its response to the actions of its medium4 ,a change may take place in the medium without a corresponding response from the organism2 or the change may find a response and the organism become modified4 ,every modification is a selection1 determined by laws of growth2 it is the resultant of a struggle between what1 for want of a better term1 may be called the organic affinities--which represent in organized substances what chemical affinities are in the anorganized4 ,just as an organism which has been modified and thereby gained a superiority over others1 has by this modification been selected for survival--the selection being only another aspect of this modification--so one tissue1 or one organ1 which has surpassed another in the struggle of growth1 will thereby have become selected4 ,natural ,selection1 or survival of the fittest1 therefore1 is simply the metaphorical expression of the fact that any balance of the forces which is best adapted for survival will survive4 ,unless we interpret it as a shorthand expression of all the internal and external conditions of existence1 it is not acceptable as the origin of species4 #aah;d4 ,mr4 ,darwin has so patiently and profoundly meditated on the whole subject1 that we must be very slow in presuming him to have overlooked any important point4 ,i know that he has not altogether overlooked this which we are now considering2 but he is so preoccupied with the tracing out of his splendid discovery in all its bearings1 that he has thrown the emphasis mainly on the external struggle1 neglecting the internal struggle2 and has thus in many passages employed language which implies a radical distinction where--as ,i conceive--no such distinction can be recognized4 8,natural ,selection10 he says1 8depends on the survival under various and complex circumstances of the best-fitted individuals1 but has no relation whatever to the primary cause of any modification of structure40#fa ,on this we may remark1 first1 that selection does not depend on the survival1 but is that survival2 secondly1 that the best-fitted individual survives because of that modification of its structure which has given it the superiority2 therefore if the primary cause of this modification is not due to selection1 then selection cannot be the cause of species4 ,he separates ,natural ,selection from all the primary causes of variation1 either internal or external--either as results of the laws of growth1 of the correlations of variation1 of use and disuse1 etc41 and limits it to the slow accumulations of such variations as are profitable in the struggle with competitors4 ,and for his purpose this separation is necessary4 ,but biological philosophy must1 ,i think1 regard the distinction as artificial1 referring only to one of the great factors in the production of species4 ,and for this reason3 ,selection only comes into existence in the modifications produced either by external or internal changes2 and the selected change cannot be developed further by mere inheritance1 unless the successive progeny have such a disposition of the organic affinities as will repeat the primary change4 ,inherited superiority will not by mere transmission become greater4 ,the facts which are relied on in support of the idea of 8fixity of species0 show at any rate that a given superiority will remain stationary for thousands of years2 and no one supposes that the progeny of an organism will vary unless some external or internal cause of variation accompanies the inheritance4 ,mr4 ,darwin agrees with ,mr4 ,spencer in admitting the difficulty of distinguishing between the effects of some definite action of external conditions1 and the accumulation through natural selection of inherited variations serviceable to the organism4 ,but even in cases where the distinction could be clearly established1 ,i think we should only see an historical distinction1 that is to say1 one between effects produced by particular causes now in operation1 and effects produced by very complex and obscure causes in operation during ancestral development4 #aah;e4 ,the reader will understand that my criticism does not pretend to invalidate ,mr4 ,darwin's discovery1 but rather to enlarge its terms1 so as to make it include all the biological conditions1 and thus explain many of the variations which ,natural ,selection--in the restricted acceptation--leaves out of account4 ,mr4 ,darwin draws a broad line of distinction between ,variation and ,selection1 regarding only those variations that are favorable as selected4 ,i conceive that all variations which survive are by that fact of survival1 selections1 whether favorable or indifferent4 ,a variety is a species in formation2 now ,selection itself is not a cause1 or condition1 of variation1 it is the expression of variation4 ,mr4 ,darwin is at times explicit enough on this head3 8,it may metaphorically be said that ,natural ,selection is daily and hourly scrutinizing throughout the world the slightest variations2 rejecting those that are bad1 preserving and adding up all that are good2 silently and insensibly working1 whenever and wherever opportunity offers1 at the improvement of each organic being in relation to its organic and inorganic conditions of life40#fb ,but the metaphorical nature of the term is not always borne in mind1 so that elsewhere ,natural ,selection is said to 8act on and modify organic beings10 as if it were a positive condition and not the expression of the modifying processes4 ,because grouse are largely destroyed by birds of prey1 any change in their color which would render them less conspicuous would enable more birds to escape2 but it is obvious that this change of color will be due to ,organic ,affinity2 and only when the change is effected will there have been that selection which expresses it4 ,mr4 ,darwin's language1 however1 is misleading4 ,he says3 8,hence ,natural ,selection might be most effective in giving the proper color to each kind of grouse1 and in keeping that color when once acquired40 ,this is to make ,selection an agent1 a condition of the development of color2 which may be accepted if we extend the term so as to include the organic changes themselves4 ,again3 8,some writers have imagined that ,natural ,selection induces variability1 whereas it only implies the preservation of such variations as are beneficial to the being under its conditions of life40 ,it1 however1 is made to imply more than this1 namely1 the accumulation and further modification of such variations4 8,the mere existence of individual variability and of some well-marked varieties1 though necessary as the foundation1 helps us but little in understanding how species arise in nature4 ,how have all those exquisite adaptations of one part of the organization to another part1 and to the conditions of life1 and of one organic being to another being1 been perfected80 ,my answer to this question would be3 ,by ,organic ,affinity1 and the resulting struggle of the tissues and organs1 the consequences of which are that very adaptation of the organism to external conditions1 which is expressed as the selection of the structures best adapted4 ,the selections are the results of the struggle1 according to my proposed extension of the term 8struggle40 ,mr4 ,darwin defines the struggle3 8,the dependence of one being on another1 and including 7what is more important7 not only the life of the individual but success in leaving progeny40 ,this definition seems defective1 since it omits the primary and more important struggle which takes place between the organic affinities in operation4 ,to succeed in the struggle with competitors1 the organism must have first acquired--by selection--a superiority in one or more of its organs4 #aah;f4 ,a little reflection will disclose the importance of keeping our eyes fixed on the internal causes of variation1 as well as on the external conditions of the struggle4 ,mr4 ,darwin seems to imply that the external conditions which cause a variation are to be distinguished from the conditions which accumulate and perfect such variation1 that is to say1 he implies a radical difference between the process of variation and the process of selection4 ,this1 ,i have already said1 does not seem to me acceptable2 the selection1 ,i conceive1 to be simply the variation which has survived4#fc ,if it be true that a ,variety is an incipient ,species and shows us ,species in formation1 it is in the same sense true that a variation is an incipient organ4 ,a species is the result of a slowly accumulating divergence of structure2 an organ is the result of a slowly accumulating differentiation4 ,at each stage of differentiation there has been a selection1 but we cannot by any means say that this selection was determined by the fact of its giving the organism a superiority over rivals1 inasmuch as during all the early stages1 while the organ was still in formation1 there could be no advantage accruing from it4 ,one animal having teeth and claws developed will have a decided superiority in the struggle over another animal that has no teeth and claws2 but so long as the teeth and claws are in an undeveloped state of mere preparation they confer no superiority4 #aah;g4 ,natural ,selection is only the expression of the results of obscure physiological processes2 and for a satisfactory theory of such results we must understand the nature of the processes4 ,in other words1 to understand ,natural ,selection we must recognize not only the facts thus expressed1 but the factors of these facts1--we must analyze the 8conditions of existence40 ,as a preliminary analysis we find external conditions1 among which are included not only the dependence of the organism on the inorganic medium1 but also the dependence of one organism on another1--the competition and antagonism of the whole organic world2 and internal conditions1 among which are included not only the dependence of the organism on the laws of composition and decomposition whereby each organite and each tissue is formed1 but also the dependence of one organite and one tissue on all the others--the competition and antagonism of all the elements4 ,the changes wrought in an organism by these two kinds of conditions determine ,varieties and ,species4 ,although many of the changes are due to the process of natural selection brought about in the struggle with competitors and foes1 many other changes have no such relation to the external struggle1 but are simply the results of the organic affinities4 ,they may or they may not give the organism a greater stability1 or a greater advantage over rivals2 it is enough that they are no disadvantage to the organism1 they will then survive by virtue of the forces which produced them4 #aai4 ,the position thus reached will be important in our examination of the ,theory of ,descent by which ,mr4 ,darwin tentatively1 and his followers boldly1 explain the observed resemblances in structure and function as due to blood-relationship4 ,the doctrine of ,evolution affirms that all complex organisms are evolved by differentiation from simpler organisms1 as we see the complex organ evolved from simpler forms4 ,but it does not necessarily affirm that the vast variety of organisms had one starting-point--one ancestor2 on the contrary1 ,i conceive that the principles of ,evolution are adverse to such a view1 and insist rather on the necessity of innumerable starting-points4 ,let us consider the question4 ,that the ,theory of ,descent explains many of the facts must be admitted2 but there are many which it leaves obscure2 and ,mr4 ,darwin1 with that noble calmness which distinguishes him1 admits the numerous difficulties4 ,whether these will hereafter be cleared away by an improvement in the ,geological ,record1 now confessedly imperfect1 or by more exhaustive exploration of distant countries1 none can say2 but1 to my mind1 the probability is1 that we shall have to seek our explanation by enlarging the idea of ,natural ,selection1 subordinating it to the laws of ,organic ,affinity4 ,it does not seem to me1 at present1 warrantable to assume ,descent as the sole principle of morphological uniformities2 there are other grounds of resemblance beyond those of blood-relationship2 and these have been too much overlooked2 yet a brief consideration will disclose that similarity in the physiological laws and the conditions of ,organic ,affinity must produce similarity in organisms1 independently of relationship2 just as similarity in the laws and conditions of inorganic affinity will produce identity in chemical species4 ,we do not suppose the carbonates and phosphates found in various parts of the globe1 or the families of alkaloids and salts1 to have any nearer kinship than that which consists in the similarity of their elements and the conditions of their combination4 ,hence1 in organisms1 as in salts1 morphological identity may be due to a community of conditions1 rather than community of descent4 ,mr4 ,darwin justly holds it to be 8incredible that individuals identically the same should have been produced through ,natural ,selection from parents specifically distinct10 but he1 since he admits analogous variations1 will not deny that identical forms might issue from parents having widely different origins1 provided that these parent forms and the conditions of their reproduction were identical1 as in the case of vegetable and animal resemblances4 ,to deny this would be to deny the law of causation4 ,and that which is true of identical forms under identical conditions is true of similar forms under similar conditions4 ,when ,history and ,ethnology reveal a striking uniformity in the progression of social phases1 we do not thence conclude that the nations are directly related1 or that the social forms have a common parentage2 we conclude that the social phases are alike because they have had common causes4 ,when chemists point out the uniformity of type which exists in compounds so diverse in many of their properties as water and sulphuretted or selenetted hydrogen1 and when they declare phosphoretted hydrogen to be the congener of ammonia1 they do not mean that the one is descended from the other1 or that any closer link connects them than that of resemblance in their elements4 ,in the case of vegetal and animal organisms1 we observe such a community of elementary substance as of itself to imply a community in their laws of combination2 and under similar conditions the evolved forms must be similar4 ,with this community of elementary substance1 there are also diversities of substance and of co-operant conditions2 corresponding with these diversities there must be differences of form4 ,thus1 although observation reveals that the bond of kinship does really unite many widely divergent forms1 and the principle of ,descent with ,natural ,selection will account for many of the resemblances and differences1 there is at present no warrant for assuming that all resemblances and differences are due to this one cause1 but1 on the contrary1 we are justified in assuming a deeper principle which may be thus formulated3 ,all the complex organisms are evolved from organisms less complex1 as these were evolved from simpler forms2 the link which unites all organisms is not always the common bond of heritage1 but the uniformity of organized substance acting under similar conditions4 ,it is therefore consistent with the hypothesis of ,evolution to admit a variety of origins or starting-points1 though not consistent to admit the sudden appearance of complex ,types1 such as is implied in the hypothesis of specific creations4 #aai a4 ,the analogies of organic forms and functions demand a more exhaustive scrutiny than has yet been given them4 ,why is it that vessels1 nerves1 and bones ramify like branches1 and why do these branches take on the aspect of many crystalline forms8 ,why is it that cavities are constantly prolonged in ducts1 e4 g4 the mouth succeeded by the sophagus1 the stomach by the intestines1 the bladder by the urethra1 the heart by the aorta1 the ovary by the oviduct1 and so on8 ,why are there never more than four limbs attached to a vertebral column1 and these always attached to particular vertebr8 ,why is there a tendency in certain tissues to form tubes1 and in these tubes commonly to assume a muscular coat8#fd ,to some of these queries an answer might be suggested which would bring them under known physical laws4 ,i merely notice them here for the sake of emphasizing the fact that such analogies lie deeply imbedded in the laws of evolution1 and that what has been metaphorically called organic crystallization will account for many similarities in form1 without forcing us to have recourse to kinship4 ,to take a very simple case4 ,no one will maintain that the crystalline forms of snow have any kinship with the plants which they often resemble4 ,mr4 ,spencer has noticed the development of a wing-bearing branch from a wing of the ,ptilota plumosa1 when its nutrition is in excess4 8,this form1 so strikingly like that of the feathery crystallizations of many inorganic substances1 proves to us that in such crystallizations the simplicity or complexity of structure at any place depends on the quantity of matter that has to be polarized at that place in a given time4 ,how the element of time modifies the result1 is shown by the familiar fact that crystals rapidly formed are small1 and that they become larger when they are formed more slowly40#fe ,it may be objected1 and justly1 that in the resemblance between crystals and organisms the analogy is purely that of form1 and usually confined to one element1 whereas between organisms there is resemblance of substance no less than of form1 and usually the organisms are alike in several respects4 ,the answer to this objection is1 that wherever there is a similarity in the causal conditions 7substance and history7 there must be a corresponding similarity in the results2 if this similarity extends to only a few of the conditions1 the analogy will be slight2 if to several1 deep4 ,but whether slight or deep we are not justified1 simply on the ground of resemblance1 in assuming1 short of evidence1 that because they are alike1 two organisms are related by descent from a common ancestor4 #abj4 ,let us glance at a few illustrations4 ,it has been urged as a serious objection to ,mr4 ,darwin's hypothesis1#ff that it fails to explain the existence of phosphorescent organs in a few insects2 and certainly1 when one considers the widely different orders in which these organs appear1 and their absence in nearly related forms1 it is a difficulty4 ,in noctiluc1 earthworms1 molluscs1 scolopendra1 and fireflies1 we may easily suppose the presence of similar organic conditions producing the luminosity2 but it requires a strong faith to assign ,descent as the cause4#fg ,we may say the same of the electric organs possessed by seven species of fish1 belonging to five widely separated genera4 ,although each species appears to have a limited geographical range1 one or the other is found in almost every part of the globe4 ,these organs occupy different positions1 being now on each side of the head1 now along the body1 and now along the tail2 and in different species they are innervated from different sources4 ,their intimate structure also varies2 as appears from the remarkable investigations of ,max ,schultze4#fh ,they cannot1 therefore1 be homologous4 ,how could they have arisen8 ,not by the slow accumulations of ,natural ,selection1 because1 until the organs were fully formed1 they could be of no advantage in the struggle2 hence the slow growth of the organ must have proceeded without the aid of an advantage in the struggle--in each case from some analogous conditions which produced a differentiation in certain muscles4 ,the fundamental resemblance to muscles was pointed out by ,carus long ago4 ,it has been insisted on by ,leydig3#fi and ,owen says1 8,the row of compressed cells constituting the electric prism of the ,torpedo offers some analogy to the row of microscopic discs of which the elementary muscle fibre appears to consist40#gj ,we must not1 however1 forget that these resemblances are merely such as suggest that the electric organ is a differentiation of the substance which elsewhere becomes muscular1 and that ,dr4 ,davy was justified in denying the organ to be muscular4#ga ,that it is substituted for muscle cannot be doubted4 ,now1 although we are entirely ignorant of the conditions which cause this differentiation of substance which elsewhere becomes muscular1 but here becomes electric organs1 we can understand that1 when once such a development had taken place1 if it in any way profited the fish in its struggle for existence1 ,natural ,selection would tend to its further increase and propagation4 ,so far ,mr4 ,darwin carries us with him2 but we decline proceeding further4 ,the development of these organs in fishes so widely removed1 does not imply an ancestral community4 ,it is interpretable as mere growth on a basis once laid2 and therefore would occur with or without any advantage in the struggle with rivals4 ,the similarity in concurrent conditions is quite enough to account for the resemblance in structure4 ,this1 with his accustomed candor1 ,mr4 ,darwin admits4 8,if the electric organs10 he says1 8had been inherited from one ancient progenitor thus provided1 we might have expected that all electric fishes would be specially related to each other4 ,nor does ,geology at all lead to the belief that formerly most fishes had electric organs which most of their modified descendants have lost40 #aba4 ,it may seem strange that he should urge a difficulty against his hypothesis when it could be avoided by the simple admission that even among nearly allied animals great differences in development are observable1 and the electric organs might be ranged under such diversities4 ,but ,mr4 ,darwin has so thoroughly wrought out his scheme1 that he foresees most objections1 and rightly suspects that if this principle of divergent development be admitted1 it will cut the ground from under a vast array of facts which his hypothesis of ,descent requires4 ,the sudden appearance of new organs1 not a trace of which is discernible in the embryo or adult form of organisms lower in the scale1--for instance1 the phosphorescent and electric organs1--is like the sudden appearance of new instruments in the social organism1 such as the printing-press and the railway1 wholly inexplicable on the theory of ,descent1#gb but is explicable on the theory of ,organic ,affinity4 ,for observe3 if we admit that differentiations of structure1 and the sudden appearance of organs1 can have arisen spontaneously--i4 e4 not hereditarily--as the outcome of certain changed physical conditions1 we can hardly refuse to extend to the whole organism what we admit of a particular organ4 ,if1 again1 we admit that organs very similar in structure and function spontaneously appear in organisms of widely different kinds--e4 g4 the phosphorescent and electric organs--we must also admit that similar resemblances may present themselves in organisms having a widely different parentage2 and thus the admission of the spontaneous evolution of closely resembling organs carries with it the admission of the spontaneous evolution of closely resembling organisms3 that the protoplasm of muscular tissue should1 under certain changed conditions1 develop into the tissue of electric organs1 is but one case of the law that organized substance will develop into organisms closely resembling each other when the conditions have been similar4 #abb4 ,it is to be remarked that ,mr4 ,darwin fixes his attention somewhat too exclusively on the adaptations which arise during the external struggle for existence1 and to that extent neglects the laws of organic affinity2 just as ,lamarck too exclusively fixed his attention on the influence of external conditions and of wants4 ,not that ,mr4 ,darwin can be said to overlook the organic laws2 he simply underestimates the part they play4 ,occasionally he seems arrested by them1 as when instancing the 8trailing palm in the ,malay ,archipelago1 which climbs the loftiest trees by the aid of exquisitely constructed hooks1 clustered around the ends of the branches1 and this contrivance no doubt is of the highest service to the plant2 but as there are nearly similar hooks on many trees which are not climbers1 the hooks on the palm may have arisen from unknown laws of growth1 and have been subsequently taken advantage of by the plant undergoing further modification and becoming a climber40 #abc4 ,i come round to the position from which ,i started1 that the resemblances traceable among animals are no proof of kinship2 even a resemblance so close as to defy discrimination would not1 in itself1 be such a proof4 ,the absolute identity of chalk in ,australia and in ,europe is a proof that there was absolute identity in the formative conditions and the constituent elements1 but no proof whatever that the two substances were originally connected by genesis4 ,in like manner the similarity of a plant or animal in ,africa and ,europe may be due to a common kinship1 but it may also be due to a common history4 ,it is indeed barely conceivable that the history1 from first to last1 would ever be so rigorously identical in two parts of the globe as to produce complex identical forms in both2 because any diversity1 either in structure or external conditions1 may be the starting-point of a wide diversity in subsequent development2 and the case of organic combinations is so far unlike the inorganic1 that while only one form is possible to the latter 7chalk is either formed or not formed71 many forms are possible to organic elements owing to the complexity and indefiniteness of organic composition4 ,but although forms so allied as those of ,species are not readily assignable to an identical history in different quarters of the globe1 it is not only conceivable1 but is eminently probable1 that ,orders and ,classes have no nearer link of relationship than is implied in their community of organized substance and their common history4 ,the fact that there is not a single mammal common to ,europe and ,australia is explicable1 as ,mr4 ,darwin explains it1 on the ground that migration has been impossible to them2 but it is also explicable on the laws of ,evolution--to have had mammals of the same species and genera would imply a minute coincidence in their history1 which is against the probabilities4 ,again1 in the ,oceanic ,islands there are no ,batrachians2 but there are ,reptiles1 and these conform to the reptilian type4 ,mr4 ,darwin suggests that the absence of ,batrachia is due to the impossibility of migration1 their ova being destroyed by salt water4 ,but may it not be due to the divergence from the reptilian type1 which was effected elsewhere1 not having taken place in these regions8 ,when we find the metal ,tin in ,prussia and ,cornwall1 and nowhere else in ,europe1 must we not conclude that in these two countries1 and nowhere else1 a peculiar conjunction of conditions caused this peculiar evolution8 #abd4 ,the question at issue is1 ,are the resemblances observable among organic forms due to remote kinship1 and their diversities to the divergences caused by adaptation to new conditions8 or are the resemblances due to similarities1 and the diversities to dissimilarities in the substance and history of organic beings8 ,are we to assume one starting-point and one centre of creation1 or many similar starting-points at many centres8 ,so far from believing that all plants and animals had their origin in one primordial cell1 at one particular spot1 from which descendants migrated and became diversified under the diverse conditions of their migration1 it seems to me more consistent with the principle of ,evolution to admit a vast variety of origins more or less resembling each other2 and this initial resemblance will account for the similarities still traceable under the various forms2 while the early differences1 becoming intensified by development under different conditions1 will yield the diversities4 ,the evolution of organisms1 like the evolution of crystals1 or the evolution of islands and continents1 is determined1 #ast1 by laws inherent in the substances evolved1 and1 #b;d1 by relations to the medium in which the evolution takes place4 ,this being so1 we may priori affirm that the resultant forms will have a community strictly corresponding with the resemblance of the substances and their conditions of evolution1 together with a diversity corresponding with their differences in substance and conditions4 ,it is usually supposed that the admission of separate 8centres of creation0 is tantamount to an admission of 8successive creations0 as interpreted by the majority of those who invoke 8creative fiats40 ,but the doctrine of ,evolution1 which regards ,life as making its appearance consequent upon a concurrence of definite conditions1 and regards the specific forms of ,life as the necessary consequences of special circumstances1 must also accept the probability of similar conditions occurring at different times and in different places4 ,upon what grounds1 cosmical or biological1 are we to assume that on only one microscopic spot of this developing planet such a group of conditions was found--on only one spot a particle of protein substance was formed out of the abundant elements1 and under conditions which caused it to grow and multiply1 till in time its descendants overran the globe8 ,the hypothesis that all organic forms are the descendants of a single germ1 or of even a few germs1 and are therefore united by links of kinship more or less remote1 is not more acceptable than the hypothesis that all the carbonates and phosphates1 all the crystals1 and all the strata found in different parts of the globe1 are the descendants of a single molecule1 or a few molecules2 or1--since this may seem too extravagant1--than that the various maladies which afflict organic beings are1 in a literal sense1 members of families having a nearer relationship than that of being the phenomena manifested by similar organs under similar conditions--a conception which might have been accepted by those metaphysical pathologists who regarded ,disease as an entity4 ,few philosophers have any hesitation in supposing that other planets besides our own are peopled with organic forms1 though1 from the great differences in the conditions1 these forms must be extremely unlike those of our own planet4 ,if separate worlds1 why not separate centres8 ,the conclusion seems inevitable that wherever and whenever the state of things permitted that peculiar combination of elements known as organized substance1 there and then a centre was established--,life had a root4 ,from roots closely resembling each other in all essential characters1 but all more or less different1 there have been developed the various stems of the great tree4 ,myriads of roots have probably perished without issue2 myriads have developed into forms so ill-adapted to sustain the fluctuations of the medium1 so ill-fitted for the struggle of existence1 that they became extinct before even our organic record begins2 myriads have become extinct since then2 and the descendants of those which now survive are like the shattered regiments and companies after some terrific battle4 #abe4 ,there seems to me only one alternative logically permissible to the ,evolution ,hypothesis1 namely1 that all organic forms have had either a single origin1 or else numerous origins2 in other words1 that a primordial cell was the starting-point from which all organisms have been successively developed2 or that the development issued from many independent starting-points1 more or less varied4 ,this is apparently not the aspect presented by the hypothesis to many of its advocates2 they seem to consider that if all organic forms are not the lineal descendants of one progenitor1 they must at any rate be the descendants of not more than four or five4 ,the common belief inclines to one4 ,mr4 ,darwin1 whose caution is as remarkable as his courage1 and whose candor is delightful1 hesitates as to which conclusion should be adopted3 8,i cannot doubt10 he says1 8that the theory of descent1 with modifications1 embraces all the members of the same class4 ,i believe that animals have descended from1 at most1 only four or five progenitors1 and plants from an equal or lesser number4 ,analogy would lead me one step further1 namely1 to the belief that all animals and plants have descended from some one prototype4 ,but analogy may be a deceitful guide40 #abf4 ,i cannot see the evidence which would warrant the belief that ,life originated solely in one microscopic lump of protoplasm on one single point of our earth's surface2 on the contrary1 it is more probable that from innumerable and separate points of this teeming earth1 myriads of protoplast sprang into existence1 whenever and wherever the conditions of the formation of organized substance were present4 ,it is probable that this has been incessantly going on1 and that every day new protoplasts appear1 struggle for existence1 and serve as food for more highly organized rivals2 but whether an evolution of the lower forms is1 or is not1 still going on1 there can be no reluctance on the part of every believer in ,evolution to admit that when organized substance was first evolved1 it was evolved at many points4 ,if this be so1 the community observable in organized substance1 wherever found1 may as often be due to the fact of a common elementary composition as to the fact of inheritance4 ,if this be so1 we have a simple explanation both of the fundamental resemblances which link all organisms together1 and of the characteristic diversities which separate them into kingdoms1 classes1 and orders4 ,the resemblances are many1 and close1 because the forms evolved had a similar elementary composition1 and their stages of evolution were determined by similar conditions4 ,the diversities are many1 because the forms evolved had from the first some diversities in elementary composition1 and their stages of evolution were determined under conditions which1 though similar in general1 have varied in particulars4 ,indeed1 there is no other ground for the resemblances and differences among organic beings than the similarities and dissimilarities in their ,substance and ,history2 and1 whether the similarities are due to blood-relationship1 or to other causes1 the results are the same4 ,there is something seductive in the supposition that ,life radiated from a single centre in ever-increasing circles1 its forms becoming more and more various as they came under more various conditions1 until at last the whole earth was crowded with diversified existences4 8,from one cell to myriads of complex organisms1 through countless ons of development10 is a formula of speculative grandeur1 but ,i cannot bring myself to accept it2 and ,i think that a lingering influence of the tradition of a 8creative fiat0 may be traced in its conception4 ,may we not rather assume that the earth at the dawn of ,life was a vast germinal membrane1 every slightly diversified point producing its own vital form2 and these myriads upon myriads of forms--all alike and all unlike--urged by the indwelling tendencies of development1 struggled with each other for existence1 many failing1 many victorious1 the victors carrying their tents into the camping ground of the vanquished4 ,the point raised is the immense improbability of organized substance having been evolved only in one microscopic spot2 if it were evolved at more than one spot1 and under slightly varying conditions1 there would necessarily have arisen in these earliest formations the initial diversities which afterwards determined the essential independence and difference of organisms4 #abi4 ,let us for a moment glance at the resemblances and diversities observable in all organisms4 ,all have a common basis1 all being constructed out of the same fundamental elements3 carbon1 hydrogen1 nitrogen1 and oxygen2 these 7the organogens1 as they are named71 with varying additions of some other elements1 make up what we know as ,organic ,substance1 vegetal and animal4 ,another peculiarity all organisms have in common1 namely1 that their matter is neither solid nor liquid1 but viscid4 ,beside this community of ,substance we must now place a community of ,history4 ,all organisms grow and multiply by the same process2 all pass through metamorphic stages ending in death2 all1 except the very simplest1 differentiate parts of their substance for special uses1 and these parts 7cilia1 membranes1 tubes1 glands1 muscles1 nerves7 have similar characters in whatever organism they appear1 and their development is always similar1 so that the muscles or nerves of an intestinal worm1 a lobster1 or a man1 are in structure and history fundamentally alike4 ,when1 therefore1 we see that there is no biological character of fundamental importance which is not universal throughout the organic world1 when we see that in ,structure and ,history all organisms have a community pervading every variety1 it is difficult not to draw the conclusion that some hidden link connects all organisms into one2 and when1 further1 it is seen that the most divergent forms may be so arranged by the help of intermediate forms only slightly varying one from the other1 that the extreme ends--the monad and the man--may be connected1 and a genealogical tree constructed1 which will group all forms as modified descendants from a single form1 the hypothesis that kinship is the bidden link of which we are in search becomes more and more cogent4 #acj4 ,but now let the other aspect be considered4 ,if there is an unmistakable uniformity1 there is also a diversity no less unmistakable4 ,the chemical composition of organic substances is various4 ,unlike inorganic substances1 the composition of which is rigorously definite1 organic substances are1 within narrow limits1 variable in composition 7 #de74 ,i pass over the resemblances and differences observed in the earliest stages of development1 marked as they are1 and direct attention to the fact1 that down at what must be considered the very lowest organic region1 we meet with differences not less striking than those met with in the highest1 we find structures 7if structures they may be called71 which cannot be affiliated1 so widely divergent is their composition4 ,the structureless vibrio1 for example1 is not only capable of living in a medium destitute of ,oxygen1 but is1 according to ,m4 ,pasteur1 actually killed by oxygen2 whereas the equally simple bacteria can no more dispense with ,oxygen than other animals can4 ,consider for a moment the differences implied in the fact that one organism cannot even form an enveloping membrane to contain its protoplasm1 whereas another contrives to secrete an exquisite shell2 yet between the naked ,rhizopod and the shelled ,rhizopod our lenses and reagents fail to detect a difference4 ,one ,monad can assimilate food of only one kind1 another ,monad assimilates various kinds4#gc ,what a revelation of chemical differences appears in the observations of ,m4 ,pasteur respecting the vibrio and bacteria1 in a fermentescible liquid--the former beginning the putrid fermentation which the latter completes6 ,we cannot doubt that some marked difference must exist between the single-celled organism which produces alcoholic fermentation1 and that which produces acetic fermentation1 and that again which produces butyric fermentation2 and if we find distinctions thus established at the lowest region of the organic series1 we need not marvel if the distinctions become wider and more numerous as the series becomes more diversified4 ,the structure and development of an organism are dependent on the affinities of its constituent molecules1 and it is a biological principle of great importance which ,sir ,james ,paget insists on1 when he shows how 8the existence of certain materials in the blood may determine the formation of structures in which they may be incorporated40#gd ,any initial diversity may thus become the starting-point of a considerable variation in subsequent evolution4#ge ,thus1 supposing that on a given spot there are a dozen protoplasts closely resembling each other1 yet each in some one detail slightly varying2 if this variation is one which1 by its relations to the external medium1 admits of a difference in the assimilation of materials present in the medium1 it may be the origin of some new direction in development1 and the ultimate consequence may be the formation of a shell1 an internal skeleton1 a muscle1 or a nerve4 ,were this not so1 it would be impossible to explain such facts as that chitine is peculiar to the ,articulata1 cellulose to ,molluscoida1 carbonates of lime to ,mollusca and ,crustacea1 and phosphates to ,vertebrata--all assimilated from the same external medium4 ,but we see that from this medium one organism selects the materials which another rejects2 and this selection is determined by the nature of the structure3 which assimilates only those materials it is fitted to assimilate4 ,we hear a great deal of ,adaptation determining changes of structure and function1 and are too apt to regard this process as if it were not intimately dependent on a corresponding structural change4 ,by no amount of external influence which left the elementary composition of the structure unchanged1 could an organism with only two tissues be developed into an organism with three or four4 ,by no supply or stimulus1 could an animal incapable of assimilating peroxide of iron acquire red blood corpuscles1 although it might have the iron without the corpuscles2 nor could an oyster form its shell unless capable of assimilating carbonate of lime4 ,for myriads of years1 in seas and ponds1 under endless varieties of external conditions1 the amb have lived and died without forming a solid envelope1 although the materials were abundant1 and other organisms equally simple have formed envelopes of infinite variety4 ,in all the seas1 and from the earliest ages1 zoophytes have lived1 and assumed a marvellous variety of shapes and specialization of functions2 but although some of them have acquired muscles1 none have acquired true nerves1 none bone4 ,ages upon ages rolled on before fishes were capable of forming bone2 and thousands are still incapable of forming it1 though living in the same waters as the osseous fishes4 #aca4 8,looking to the dawn of life10 says ,mr4 ,darwin 7repeating an objection urged against his hypothesis71 8when all organic beings1 as we imagine1 presented the simplest structure1 how could the first steps in advancement1 or in the differentiation and specialization of parts have arisen8 ,i can make no sufficient answer2 and can only say that1 as we have no facts to guide us1 all speculation would be baseless and useless40 ,where ,mr4 ,darwin hesitates1 lesser men need extra caution2 but ,i must risk the danger of presumption1 at least so far as to suggest that while an answer to this question is difficult on that dynamical view of ,evolution which regards ,function as determining ,structure1 it is less difficult on the statico-dynamical view propounded in these pages2 the difficulty which besets the explanation when all the manifold varieties of organic forms are conceived as the successive divergences from an original starting-point1 is lessened when a variety of different starting-points is assumed1 in each of which some initial diversity prepared the way for subsequent differentiations2 just as we know that between the ovum of a vertebrate and the ovum of an invertebrate1 similar as they are1 there is a diversity which manifests itself in their subsequent evolution4 ,if ,function is determined by ,structure1 and ,evolution is the product of the two1 it is clear that the different directions in the lines of development will have their origin in structural differences1 and not in the action of external circumstances1 unless these previously bring about a structural change4 ,the action of the medium on the organism is assuredly a potent factor which ,biology cannot ignore3 but the organism itself is a factor1 and according to its nature the influence of the medium is defined4 7 #aah47 #acb4 ,quitting for a moment the track of this argument1 let us glance at the resemblances and differences observable in ,plants and ,animals1 because most people admit that these have separate origins4 ,the resemblances are scarcely less significant than those existing among animals4 ,both have a similar basis of elementary composition2 not only are both formed out of protoplasts with similar properties1 but in both the first step from the protoplasm to definite structure is the ,cell4 ,and the life of this ,cell is remarkably alike in both1 its phases of development being in many respects identical2 nay1 even such variations as obtain in the cell-membranes are curiously linked together by a community in the formative process4#gf ,in both ,plants and ,animals we find individuals constituted--#ast1 by single cells2 #b;d1 by groups of cells undistinguishable among each other2 and #c;d1 by groups of differentiated cells4 ,in both we find colonies of individuals leading a common life4 ,in both the processes of ,nutrition and ,reproduction are essentially similar2 both propagate sexually and asexually2 both exhibit the surprising phenomena of parthenogenesis and alternate generations4 ,in both there are examples of a free-roving embryo which in maturity becomes fixed to one spot1 losing its locomotive organs and developing its reproductive organs4 ,in both the development of the reproductive organs is the climax which carries ,death4 ,so close is the analogy between plant-life and animal-life1 that it even reaches the properties usually held to be exclusively animal2 ,i mean that even should we hesitate to accept ,cohn's discovery of the muscles in certain plants1#gg we cannot deny that plants exhibit ,contractility2 and should we refuse to interpret as ,sensibility the phenomena exhibited by the ,sensitive ,plants1 we cannot deny that they present a very striking analogy to the phenomena of ,sensibility exhibited by animals4 #acc4 ,it is unnecessary to continue this enumeration1 which might easily be carried into minute detail4 ,a chapter of such resemblances would only burden the reader's mind1 without adding force to the conclusion that a surprising community in ,substance and ,life-history must be admitted between ,plants and ,animals4 ,this granted1 we turn to the differences1 and find them no less fundamental and detailed4 ,chemistry tells us nothing of the differences in the protoplasms from which animals and plants arise2 but that initial differences must exist is proved by the divergence of the products4 ,the vegetable cell is not the animal cell2 and although both plants and animals have albumen1 fibrine1 and caseine1 the derivatives of these are unlike4 ,horny substance1 connective tissue1 nerve tissue1 chitine1 biliverdine1 creatine1 urea1 hippuric acid1 and a variety of other products of evolution or of waste1 never appear in plants2 while the hydrocarbons so abundant in plants are1 with two or three exceptions1 absent from animals4 ,such facts imply differences in elementary composition2 and this result is further enforced by the fact that where the two seem to resemble1 they are still different3 the plant protoplasm forms various cells1 but never forms a cartilage-cell or nerve-cell2 fibres1 but never a fibre of elastic tissue2 tubes1 but never a nerve tube2 vessels1 but never a vessel with muscular coatings2 solid 8skeletons10 but always from an organic substance 7cellulose71 not from phosphates and carbonates4 ,in no one character can we say that the plant and the animal are identical2 we can only point throughout the two kingdoms to a great similarity accompanying a radical diversity4 #acd4 ,having brought together the manifold resemblances1 and the no less marked diversities1 we must ask what is their significance8 ,do the resemblances imply a community of origin1 an universal kinship8 ,if so1 the diversities will be nothing more than the divergences which have been produced by variations in the ,life-history of the several groups4 ,or--taking the alternative view--do the diversities imply radical differences of origin8 ,if so1 the resemblances will be nothing more than the inevitable analogies resulting from ,organized ,substance being everywhere somewhat similar in composition1 and similar in certain phases of evolution4 ,to state the former position in the simplest way1 we may assume that of two masses of protoplasm having a common parentage1 one1 by the accident of assimilating a certain element not brought within the range of the other1 thereby becomes so differentiated as to form the starting-point of a series of evolutions widely divergent from those possible to its congener2 and at each stage of evolution the introduction of a new element 7made possible by that stage7 will form the origin of a new variation4 ,it is thus feasible to reduce all organic forms to a primordial protoplasm1 in the evolutions of which successive differentiations have been established4 ,on the other hand1 it is equally feasible to assume that the existence of radical differences must be invoked to account for the possibility of the successive differentiations4 #ace4 ,the hunt after resemblances has led to much mistaken speculation2 and with reference to the topic now before us1 it may be urged1 that although by attaching ourselves to the points of community1 in disregard of the diversities1 we may make it appear that all animals have a common parentage1 and that plants and animals are merely divergent groups of the same prototype1 a rigorous logic will force us onwards1 and compel us to admit that a kinship no less real unites the organic with the inorganic world4 ,for upon what principle are we to pause at the cell or protoplasm8 ,if by a successive elimination of differences we reduce all organisms to the cell1 we must go on and reduce the cell itself to the chemical elements out of which it is constructed2 and inasmuch as these elements are all common to the inorganic world1 the only difference being one of synthesis1 we reach a result which is the stultification of all classification1 namely1 the assertion of a kinship which is universal4 ,we must bear in mind that all things may be reduced to a common root by simply disregarding their differences4 ,all things are alike when we set aside their unlikeness4 #acf4 ,suppose1 for the sake of illustration1 we regard an ,orchestra in the light of the ,development ,hypothesis4 ,the various instruments of which it is composed have general resemblances and particular differences1 not unlike those observable in various organisms2 and as we proceed in the work of classification we quickly discover that they may be arranged in groups analogous to the ,sub-kingdoms1 ,classes1 ,orders1 ,genera1 and ,species of the organic world4 ,each group has its cardinal distinction1 its initial point of divergence4 ,all musical instruments resemble each other in the fundamental character of producing ,tone by the vibrations of their substance4 ,this may be called their organic basis4 ,the first marked difference which determines the character of two sub-kingdoms 7namely1 instruments of ,percussion and ,wind instruments7 arises from a difference in the method of impressing the vibrations2 and the grand divisions of these sub-kingdoms arise from the nature of the vibrating substances4 ,each type admits of many modifications1 but the primary distinction is ineffaceable4 ,we can conceive the ,pipe modified into a ,flute1 a ,flageolet1 a ,clarionet1 a ,hautbois1 a ,bassoon1 or a ,fife1 by simple accessory changes2 to modify the ,pipe into a ,trumpet1 and thus produce the peculiar timbre of the trumpet1 would be impossible except by the substitution of a new material2 by replacing the wood with metal we may adhere to the old ,type1 but we have created a new ,class4 7,attention is requested to this point1 because the current views respecting the transmutation of tissues1 which seem to lend a decisive support to the hypothesis of the transmutation of species are very commonly vitiated by the confusion of transformation with substitution4 ,no anatomical element is transformed into another specifically different--an epithelial-cell into a nerve-cell1 for instance--but one anatomical element is frequently substituted for another47 ,to convert the ,pipe or the ,trumpet into a ,violin or a ,drum would be impossible4 ,we can follow the modifications of a ,tambourine into a ,drum or ,kettle-drum1 but no modifications of these will yield the ,cymbals4 ,that is to say1 the vibrating materials--wood1 metal1 parchment1 and the combination of wood and strings--have peculiar properties1 and the instruments formed of such materials must necessarily from the very first belong to different groups1 each subdivision of the groups being dependent on some characteristic difference in methods of impressing the vibrations1 or in the materials4 ,although all musical instruments have a common property and a common purpose1 we do not regard them as transformations of one primitive instrument2 their kindred nature is a subjective conception2 the analogies are numerous and close1 but we know their origin4 ,it is obvious that men being pleased by musical tones1 have been led by their delight to construct instruments whenever they have discovered substances capable of musical vibrations1 or methods of impressing such vibrations4 ,by substituting the bow for the plectrum or the fingers1 they may have changed the ,lyre into the ,violin1 ,viola1 ,violoncello1 and ,bass4 7,it seems historically probable that the real origin of the ,violin class was an instrument with one string played on by a bow47 ,by grouping together ,pipes of various sizes they got the ,panpipes2 by substituting metal and enlarging the blowing apparatus they got the ,organ4 ,by beating on stretched parchment with the finger1 they got the ,tambourine and ,tom-,tom2 by doubling this and using a stick they got the ,drum4 ,by beating metal with metal they got the ,cymbals2 by beating wood they got the ,castanets4 #acg4 ,the application of this illustration is plain4 ,just as a wind-instrument is incapable of becoming a stringed instrument1 so a ,mollusc1 with all its muscles unstriped1 and its nervous system unsymmetrical1 is incapable of becoming a ,crustacean1 with all its muscles striped and its nervous system symmetrical4 ,indeed there are probably few biologists of the present day who imagine the transmutation of one kind into the other to be possible2 but many biologists assume that both may have been evolved from a common root4 ,the point is beyond proof2 yet ,i think there is a greater probability in the assumption that both were evolved from different roots4 ,at any rate1 one thing is certain2 a divergence could only have been effected by a series of substitutions2 and the question when and how these substitutions took place is unanswerable3 one school believes them to have been creative fiats1 the other school believes them to have been transmutations4 #ach4 ,when we see an annelid and a vertebrate resembling each other in some special point which is not common either to their classes or to any intermediate classes--as when we see the wood-louse 7,oniscus7 and the hedgehog defend themselves in the same strange way by rolling up into a ball--we cannot interpret this as a trace of distant kinship4 ,when we see a breed of pigeons and a breed of canaries turning somersaults1 and one of the ,bear family 7,ratel7 given to the same singular habit1 we can hardly suppose that this is in each case inherited from a common progenitor4 ,when we see one savage race tipping arrows with iron1 and another1 ignorant of iron1 using poison1 there is a community of object effected by diversity of means2 but the analogy does not necessarily imply any closer connection between the two races than the fact that men with similar faculties and similar wants find out similar methods of supplying their wants4 ,even those who admit that the human race is one family1 and that the various peoples carried with them a common fund of knowledge when they separated from the parent stock1 may still point to a variety of new inventions and new social developments which occurred quite independently of each other1 yet are strikingly alike4 ,their resemblance will be due to resemblance in the conditions4 ,the existence1 for example1 of a religious worship1 or a social institution1 in two nations widely separated both in time and space1 and under great historical diversities1 is no absolute proof that these two nations are from the same stock1 and that the ideas have the same parentage4 ,it may be so2 it may be otherwise4 ,it may be an analogy no more implying kinship than the fact of ants making slaves of other ants 7and these the black ants67 implies a kinship with men4 ,given an organization which in the two nations is alike1 and a history which is in certain characteristics analogous1 there must inevitably result religious and social institutions having a corresponding resemblance4 ,i do not wish to imply that the researches of philologists and ethnologists are misdirected1 or that their conclusions respecting the kinship of mankind are to be rejected2 ,i only urge the consideration that perhaps too much stress is laid on community of blood1 and not enough on community of conditions4 ,,recapitulation4 #aci4 ,the various lines of argument may here be recapitulated4 ,the organic world presents a spectacle of endless diversity1 accompanied by a pervading uniformity4 ,the general resemblances in forms and functions are more or less masked by particular differences4 ,the resemblances1 it is said1 may be all due to kinship1 all the living individuals having descended from a primordial cell2 and at each stage of the descent the adaptations to new conditions may have issued in deviations from the ancestral form1 while the process of ,natural ,selection giving stability to those variations which best fitted the organism in the struggle of existence1 has made greater and greater gaps1 and produced more marked diversities among the descendants4 ,this is the ,darwinian ,theory3 8,on my theory unity of ,type is explained by unity of ,descent40 #adj4 ,by the general consent of biologists1 this theory is held to explain many if not all the observed facts4 ,it is a very luminous suggestion2 but it requires an enlargement so as to include ,organic ,affinity2 and when once this fundamental principle is admitted1 it brings with it very serious doubts as to the theory of ,descent4 ,we are then entitled to assume that many of the most striking resemblances1 instead of being due to kinship1 are due simply to the general principle that similar causes must have similar effects1 and that organic substances having a very close resemblance1 organized substances must have similar stages of evolution under similar conditions2 and thus organs will necessarily take on very similar forms in very different organisms 7for example1 the eye of the cephalopod and the eye of the vertebrate71 and organisms having widely different parentage may closely resemble each other4 ,if we are entitled to assume that protoplasm appeared not in one microscopic spot alone1 but in many places and in vast quantities--and this is surely the more justifiable assumption--then we must also admit that these germinal starting-points were from the first1 or very shortly afterwards1 differentiated by variations in their elementary composition4 ,now we know that a very minute change in composition may lead to immense differences in evolution4 ,thus the descendants of two slightly different progenitors may1 by continual differentiation1 become very markedly unlike2 yet1 because of the original resemblance of their substances1 they will reveal a pervading similarity4 ,while it is thus conceivable that all organisms may resemble each other1 and all differ1 owing to the similarities and diversities in the 8conditions of existence0 7and among those conditions that of descent is of wide range71 it is not very readily conceivable how advantage in the external struggle could have determined the varieties of form and function1 because many differentiations give no superiority in the struggle4 ,as ,mr4 ,st4 ,george ,mivart urges1 8,natural ,selection utterly fails to account for the conservation and development of the minute and rudimentary beginnings1 the slight and infinitesimal commencements of structures1 however useful those structures may afterwards become40#gh ,and this is undeniable on the supposition that ,natural ,selection is an agency not identical with the variations of growth1 but exclusively confined to the accumulation of favorable variations4 #ada4 ,in estimating the two hypotheses--,first1 of ,descent from one primordial germ1 and the modifications due to ,natural ,selection1 or1 as ,i should say1 expressed in ,selection2 and ,secondly1 of ,descent from innumerable germs having initial differences1 which differences radiated into the marked modifications1 there is this superiority to be claimed for the first1 that it is more easily handled as an aid to research1 and is therefore more decidedly useful4 ,the laws of ,organic ,affinity are at present too obscure for any successful application4 ,i only wish to point out that the theory of ,descent is an imaginary construction of what may have been the process of species-formation1 not a transcription of the process observed4 ,it constructs an imaginary ,type as progenitor of a long line of widely different descendants4 ,the annelid which is taken as the ancestor of the vertebrates is not any annelid known either to zologists or geologists1 but a generalized and imaginary type4 ,so daringly liberal is the imagination in endowing the ancestor with whatever may be required for the descendants1 that ,mr4 ,darwin thinks it probable1 from what we know of the embryos of vertebrates1 that these animals 8are the modified descendants of some ancient progenitor which was furnished in its adult state with branchi1 a swim-bladder1 four simple limbs1 and a long tail1 all fitted for an organic life10 7p4 #ecc72 and ,dr4 ,dohrn conceives the original type to have contained within itself all that has been subsequently evolved in the highest vertebrate1 the other and less elaborate organisms being mere degradations from this type4#gi ,this use of the imagination1 although not without advantages1 is also not without dangers4 ,it may direct research1 it must not be suffered to replace research4 ,,problem ,,ii4 ,,the ,,nervous ,,mechanism4 8,all the functions of the nervous system are as dependent upon its structure and nature1 as the accurate indication of time upon the construction of the chronometer40--,,prochaska4 8,unser ,wissen wird nie vollendet1 ist und bleibt ,stckwerk2 dessen ,ergnzung das ,streben und ,hoffen der forschenden ,denker bleiben wird fr alle ,zeit40--,,radenhausen1 ,osiris4 8,our nimble souls ,can spin an insubstantial universe ,suiting our mood1 and call it possible1 ,sooner than see one grain with eye exact1 ,and give strict record of it40 ,,george ,,eliot1 ,the ,spanish ,gypsy4 8,if we compare the teachings of our books with what ,nature is constantly showing1 we find there is no agreement between those two sources of learning40--,,brown ,s,,quard4 ,,the ,,nervous ,,mechanism4 ,,chapter ,i4 ,,survey ,,of ,,the ,,system4 #a4 ,our knowledge of mental processes is derived from reflection on our personal experiences1 combined with inferences from our observation of other men and animals1 under similar conditions4 ,the processes are complex and variable2 so complex and variable1 that knowledge of their component factors can only be gained through long tentative study1 aided by fortunate circumstances which present these factors separately1 or at any rate in such marked predominance as to fix attention4 ,this subjective analysis of the processes has to be supplemented by1 and confirmed by an objective analysis of1 the conditions1 external and internal3 the facts of ,feeling have to be traced to facts of ,physiology1 which will exhibit that ,physical ,basis of ,mind so earnestly sought by the inquirer4 ,both the subjective and the objective analysis are at present in a very imperfect state4 ,although there is much confident assertion and 8false persuasion of knowledge0 in both regions1 there is1 unhappily1 little that can be seriously accepted as demonstrated4 ,in the present volume we shall concern ourselves almost exclusively with the objective analysis1 and do our utmost to mark what is mere inference from what is verified observation4 ,it is only by ,observation that facts can be settled2 however ,analogy and ,inference may suggest where the truth may lie1 they are finger-posts1 not goals4 ,at the best they only tell us what ,observation would reveal could the processes be submitted to ,sense4 ,in a loose and general way every one knows that the ,nervous ,system is a dominant agent in all sentient processes2 although not by any means the only agent1 yet1 because of its predominance1 it is artificially accepted as the only one4 ,with the greater complexity of this system1 there is observed a corresponding increase in the variety of sentient phenomena4 ,the labors of anatomists have secured a tolerably exact plan of the topographical distribution of this system2 a somewhat chaotic mass of observation and inference passes as a description of its elementary structure4 ,the labors of physiologists have succeeded to a small extent in localizing certain functions in certain organs of this system4 ,but imperfect as our knowledge of the elementary structures is1 our knowledge of the functions is still more so4 ,i wish ,i could say otherwise1 and that ,i could ask my readers to accept with confidence what teachers confidently propound4 ,the attitude of scepticism is always repulsive2 the sceptic is seldom received without disfavor1 because he throws on us the labor of investigation there where we wish for the confidence of knowledge4 ,yet it is only by facing the facts that we can hope one day to solve the great questions4 #b4 ,the nervous system has1 in our artificial view of it1 two divisions3 the ,peripheral1 which connects the organism with the external world2 and the ,central1 which connects each part of the organism with all the other parts4 ,although the system is constituted by various tissues--neural1 connective1 vascular1 and elastic--it receives its characteristic designation from nerve-fibrils1 nerve-fibres1 and nerve-cells2 just as the muscular system receives its designation from contractile cells and fibres4 ,this neural tissue assumes three well-marked forms3 #a1 nerves1 which are bundles of fibres and fibrils1 enclosed in a membranous sheath2 #b1 ganglia1 which are clusters of cells1 fibres1 and fibrils1 sometimes enclosed in a sheath1 sometimes not2 #c1 centres1 which are artificial divisions of the neural axis1 serving as points of union for different organs4 ,in the ,invertebrata the neural axis is the chain of ganglionic masses running along the ventral side1 and giving off the nerves to organs of sense1 and to the muscles4 ,it may be seen represented in ,fig4 #a4 ,illustration3 ,fig4 #a4--,nervous system of a beetle4 ,the small round masses1 or ganglia1 are seen to be connected by longitudinal fibres1 and from the ganglia issue fibres to the limbs1 organs of sense1 and viscera4 ,in the ,vertebrata the axis is dorsal1 and is called the cerebro-spinal axis1 including brain and spinal cord4 ,when we look at this structure superficially we see various nerves radiating from it to skin1 glands1 and muscles2 but a closer examination1 enlightened by knowledge of function1 shows that some of these nerves pass into it from the various surfaces and sense-organs1 and are therefore called afferent or sensory2 whereas another set passes out of it to glands and muscles1 and these nerves are therefore called efferent or motory4 ,there are also fibres which1 passing from one part of the great centre to another1 are called commissural4 ,to this brief account of the cerebro-spinal system may be added a word on the connected chain of ganglia and nerves known as the ,sympathetic1 because it was formerly supposed to be the organ through which the various 8sympathies0 were effected4 ,it is now held to be the system devoted to the viscera and blood-vessels2 but there is still great want of agreement among physiologists as to whether it is an independent system1 having a special structure somewhat different from that of the cerebro-spinal1 or whether it is simply a great plexus of nerves and ganglia1 only topographically distinguishable from the rest of the nervous system4 ,into this point it is unnecessary for me to enter here4 ,enough to say1 that ,i entirely agree with ,sigmund ,mayer in adopting the second view4#hj ,in no histological character1 yet specified1 are the sympathetic nerves and ganglia demarcated from the others4 ,there are1 indeed1 more non-medullary fibres 7the gray fibres of ,remak7 in the sympathetic2 but the same fibres are also abundant in the cerebro-spinal system2 and the sympathetic has also its large medullary fibres4 #c4 ,the ,centres are composed of two substances3 the gray and the white4 ,the gray substance is often called the vesicular because of its abundant cells2 but it has even more fibres than cells1 and the white substance has also a few cells4#ha ,the gray substance is distributed over the surface of the brain--in the convolutions2 and in various other parts of the encephalon4 ,it surrounds the central canal which forms the ventricles of the brain and is continued as a very small cavity all down the spinal cord4 ,besides entering into the important and conspicuous masses known as the cerebral ganglia--7the optic thalami1 and corpora striata7--the gray substance is massed in the corpora quadrigemina1 crura cerebri pons varolii1 and medulla oblongata4 ,we shall have occasion to refer to each of those parts4 ,until modern times all the masses included in the skull under the familiar term ,brain 7or the technical term ,encephalon7 were regarded as the only centre1 and also as the origin of all the nerves4 ,nor has this notion even yet entirely disappeared1 although the spinal cord is known not to be a large nerve trunk1 but a centre or connected chain of centres1 structurally and functionally similar to the cranial centres4 ,the shadow of the ancient error still obscures interpretation of the part this spinal cord plays in the sentient mechanism2 and thus although the cord is universally admitted to be a centre for 8sensitive impressions10 it is usually excluded from ,sensation4 ,this widespread and misleading notion will be critically examined in a future problem4 #d4 ,beginning our survey of the cerebro-spinal axis with the ,spinal ,cord1 we observe it to consist3 #a1 of central gray substance surrounding the scarcely visible canal1 which is all that remains of the primitive groove in the germinal membrane 7 #i72 #b1 irregular gray masses1 called the anterior and posterior horns1#hb connected with the anterior and posterior roots of the spinal nerves2 and #c1 strands of white fibres enclosing this central substance1 and called the anterior lateral and posterior columns4 ,like the ,cerebrum1 it is a double organ formed by two symmetrical halves1 as the cerebrum is of two hemispheres4 ,each half innervates the corresponding half of the body4 ,the cord is unlike the cerebrum in external form1 though very like it in internal structure4 ,the gray structure is mainly external in the cerebrum1 and is internal in the cord4 ,from the anterior side of the cord 7that which in animals is the under side7 the motor nerves issue2 from the posterior 7in animals the upper7 side1 issue the sensory nerves4 ,on each of the sensory nerves there is a ganglion4 ,the roots of each nerve1 formed of several rootlets issuing from the anterior and posterior columns1 subsequently unite together1 and proceed in a single sheath to muscles and skin1 separating again1 however1 before they reach muscles and skin4 ,fig4 #b represents this arrangement4 ,illustration3 ,fig4 #b4--;,a portion of the spinal cord with its nerves 7after ,bernard74 ,the left-hand figure shows the anterior side2 the right-hand the posterior4 ,a the anterior1 and ,p1 the posterior root1 they meet at g1 the ganglion2 c and d are filaments connecting two posterior roots4 #e4 ,there are thirty-one pairs 7sometimes thirty-two7 of such nerves--namely1 eight cervical1 twelve thoracic1 five lumbar1 five sacral1 and one 7or two7 coccygeal4 ,figs4 #c to #f represent transverse sections1 which display the entrance of the roots of the nerves into the anterior and posterior horns4 #f4 ,similar masses of gray substance in the ,medulla ,oblongata 7which is the name given to the cord when it passes into the skull7#hc are supposed to be the origins of some other nerves 7the cranial74 ,illustration3 ,fig4 #c4--,transverse section of one half of the spinal cord in the lumbar region 7after ,klliker74 a1 anterior root entering the anterior gray horns1 m and l1 where cells are clustered2 c1 central canal2 d and e1 the anterior and posterior commissures uniting the two halves of the cord2 b1 posterior root entering the posterior gray horn4 ,illustration3 ,fig4 #d4--,transverse section of both halves of the cord1 cervical region4 a1 ,fissure separating the anterior columns2 b1 fissure of the posterior4 ,illustration3 ,fig4 #e4--,transverse section of the cord in the dorsal region4 ,illustration3 ,fig4 #f4--,transverse section in the lumbar region4 ,although the ,medulla ,spinalis is unquestionably continued as the ,medulla ,oblongata1 the arrangement of its tissues here becomes gradually changed1 and so complicated that it baffles the scalpel4 ,anatomists are1 however1 agreed on the one point of fundamental importance to us here--namely1 that there is only a rearrangement1 not a new tissue4 ,accepting the artificial division into two organs1 we may say that their functions are different1 inasmuch as they are different in their anatomical connections--they innervate different parts2 but as nerve-centres they have one and the same property4 ,on its posterior surface the ,medulla ,oblongata opens as the fourth ventricle4 ,it is then no longer a closed canal1 but an expansion of the spinal canal1 which is covered by the ,cerebellum4 ,on its anterior surface projects the pons varolii4 ,figs4 #g and #h represent these4 ,illustration3 ,fig4 #g4--;,back1 or upper view of the ,medulla ,oblongata as it continues the ,med4 ,spinalis4 #a1 ,section of the thalami2 #b1 corpora quadrigemina 7the two lower bodies are imperfectly represented in the engraving72 #c1 section of the crura cerebelli2 #d1 the fourth ventricle2 #e1 the restiform bodies2 #f1 the calamus scriptorius4 ,illustration3 ,fig4 #h4--;,front1 or under view of the ,med4 ,oblong4 #a1 ,optic nerves cut off at the chiasma2 #b1 crura cerebri2 #c1 pons varolii2 #d1 olivary bodies2 #e1 anterior pyramids2 #f1 spinal columns4 ,while thus on the one hand continuing the ,medulla ,spinalis1 the ,medulla ,oblongata is seen on the other hand to be continuous with the ,brain--its white columns passing upwards in the crura cerebri1 its cavity repeated in the other ventricles4 ,above it lie the ganglionic masses1 the corpora quadrigemina1 optic thalami1 and corpora striata4 ,crowning these are the big and little brains1 ,cerebrum and ,cerebellum4 ,figs4 #i and #aj represent this relation of ,medulla ,spinalis1 ,medulla ,oblongata1 and ,brain4 ,fig4 #aa is a purely artificial diagram which will give the reader some idea of the disposition of the white and gray substances4 ,illustration3 ,fig4 #i4--;,human ,brain in ,profile4 #a1 ,cerebrum2 #b1 cerebellum2 #c1 pons varolii and medulla oblongata4 ,illustration3 ,fig4 #aj4--,one half of the ,brain in ,profile1 from the inside4 #a1 ,convolutions of the cerebrum2 #b1 corpus callosum or great commissure uniting the two hemispheres2 #c1 arbor vit or branching arrangement of gray and white matter in the cerebellum2 #d1 pons varolii and medulla4 ,illustration3 ,fig4 #aa4--;,diagram of a vertical section of the ,brain 7after ,dalton74 #a1 ,olfactory ganglion2 #b1 cerebral hemisphere2 #c1 corpus striatum2 #d1 thalamus2 #e1 corpora quadrigemina2 #f1 cerebellum2 #g1 ganglion of the pons varolii2 #h1 olivary body4 #g4 ,in man the ,cerebrum is to the ,cerebellum as #i to #a4 ,in the lower vertebrates the preponderance is still greater4 ,the cerebrum is in our artificial systems commonly divided into three lobes4 ,the frontal lobe is that portion which lies in front of the deep fissure named after ,rolando2 between that fissure and the 8internal perpendicular fissure0 lies the parietal lobe2 behind this we have the occipital lobe2 and1 below the fissure of ,sylvius1 the tempero-sphenoidal lobe4 ,each lobe is again subdivided according to its convolutions4 ,the disposition of the fibres in the brain is far too complex to be accurately followed4 ,all that we can say is1 that there are strands which connect one convolution with another1 strands which connect one hemisphere with another1 strands which connect cerebrum with cerebellum1 and strands which connect the cerebrum with the lower ganglia4 ,it is important to conceive this distinctly2 for we shall hereafter see that the function of the ,brain 7by brain is here meant both ,cerebrum and ,cerebellum7 is not that of innervation1 but of incitation and regulation4 ,to speak metaphorically1 it is the coachman who holds in his hands the reins1 and guides the team4 ,one cardinal fact should arrest attention1 namely1 that not a single nerve in the body has its origin or centre of innervation in the cerebrum and cerebellum4 ,the olfactory and optic nerves do indeed seem to issue from the cerebrum2 and are commonly described as cerebral nerves4 ,but the facts of ,development1 minute ,anatomy1 and ,experiment prove this to be inexact4 ,although ,i shall continue to speak of the olfactory and optic nerves in accordance with universal usage1 not wishing to burden the reader with unnecessary innovations1 ,i must at the outset express my opinion that these nerves cannot be brought under the same general type as the other sensory nerves4 ,embryology and ,anatomy suggest that they have no more claim to the title than the crura cerebri4 ,of this hereafter4 ,setting these aside1 no one now refuses to acknowledge that ,cerebrum and ,cerebellum1 although centres of ,incitation and ,association1 are not the centres of direct ,innervation3 the organic mechanism in all its physiological processes will act independently of them 7so far as such artificial distinctions are admissible at all74 ,this does not throw a doubt on their physiological functions1 nor on their participation in the normal execution of physiological processes4 #h4 ,from this rapid survey two important points may be selected for special attention4 ,first1 the continuity of the neural axis throughout2 secondly1 the fundamental similarity of its structure1 underlying great variations in its form and connections4 ,this1 which is the anatomical expression of the ,unity of the nervous system1 will become more evident after we have expounded what ,embryology and ,microscopic ,anatomy teach4 ,we may therefore digress here awhile to consider ,,the ,,early ,,forms ,,of ,,nerve ,,centres4 #i4 ,in the outermost layer of the germinal membrane of the embryo a groove appears1 which deepens as its sides grow upwards1 and finally close over and form a canal4 ,this canal is composed of cells all alike4 ,its foremost extremity soon bulges into three well-marked enlargements1 which are then called the primitive cerebral vesicles4 ,the cavities of these vesicles are continuous4 ,except in position and size1 there are no discernible differences in these vesicles1 which are known as the ,fore-brain1 ,middle-brain1 and ,hind-brain4 #aj4 ,the ,fore-brain soon buds off from each side a small vesicle4 ,this is the optic vesicle1 the first rudiment of what subsequently becomes optic nerve and retina4 ,at this period it is simply a vesicle with a hollow stem1 the cavity being continuous with the cavity of the cerebral vesicle1 and the walls continuous with the cerebral wall4 ,it thus appears that the retina and optic 8nerve0 are primitive portions of the brain--a detached segment of the general centre1 identical in structure with the cerebral vesicle1 and not unlike in form4 ,a cup-like depression quickly forms the optic vesicle into an inner and an outer fold4 ,the inner or concave fold becomes the retina1 and the outer or convex fold 7that nearest to the brain7 becomes its choroid membrane4 ,on the fourth day of incubation the retina of the chick is composed of spindle-shaped cells1 all alike4 ,on the seventh day there is a differentiation into layers1 one of which on the eighth day is granular2 on the tenth two are granular2 and on the thirteenth ganglionic cells appear4 ,some of the cells have elongated into radial fibres 7known as ,mller's fibres72 and with the appearance of rods and cones the normal retinal elements are complete4 #aa4 ,the researches of ,foster and ,balfour#hd confirm the statement that all the different parts of the retina 7whether nervous or connective7 are derived from one and the same layer of embryonic cells1 which originally formed a portion of the first cerebral vesicle4 #ab4 ,meanwhile the hollow stem of this optic vesicle begins to develop fibres amidst the nuclei of its walls4 ,the 8optic nerve0 arises3 it is still hollow2 and in birds remains so through life4 ,the fibres as they are developed grow forwards towards the retina1 and spread over its internal surface4 ,they also grow forwards towards the brain1 and spread over its substance2 but it is not1 as might be supposed1 and is generally believed1 with the cerebral hemispheres 7or that portion of the ,fore-brain from which these are derived71 but with the ,middle-brain 7which becomes the corpora quadrigemina71 that the optic fibres are in connection4#he #ac4 ,this will be understood when the further development is traced4 ,the ,fore-brain1 after budding off the optic vesicles1 buds off two larger vesicles--the future cerebral hemispheres4 ,this is noticeable on the second day of incubation1 and by the third day each vesicle is as large as the whole of the original ,fore-brain4 ,their development is essentially like that of the optic vesicles2 both as to the cellular and the fibrous elements4 ,the convolutions1 corpus callosum1 nucleus lentiformis1 and corpora striata are then indicated4 ,meanwhile1 that which originally was the ,fore-brain has lapsed into the secondary rank as ,intermediate-brain 7,zwischenhirn71 and becomes the parts surrounding the third ventricle1 namely1 the thalami1 corpora candicantia1 infundibulum1 and what is called the 8posterior perforated substance40 #ad4 ,the ,middle-brain1 or ,second ,vesicle1 develops the corpora quadrigemina from the roof of its cavity1 and the crura cerebri from its floor4 ,the ,hind-brain1 or ,third ,vesicle1 divides into two1 like the ,first ,vesicle2 it buds off the hemispheres of the cerebellum2 its cavity forms the fourth ventricle2 its walls the medulla oblongata4 #ae4 ,it thus appears that the primitive membrane forms into a canal1 which enlarges at one part into three vesicles1 and from these are developed the encephalic structures4 ,the continuity of the walls and cavities of these vesicles is never obliterated throughout the subsequent changes4 ,it is also traceable throughout the medulla spinalis4 ,and microscopic investigation reveals that underneath all the morphological changes the walls of the whole cerebro-spinal axis are composed of similar elements on a similar plan4#hf #af4 ,two conclusions directly follow from this exposition3--first1 that since the structure of the great axis is everywhere similar1 the properties must be similar2 secondly1 that since there is structural continuity1 no one part can be called into activity without at the same time more or less exciting that of all the rest4 ,,the ,,peripheral ,,system4 #ag4 ,following the analytical division1 we now come to the ,peripheral ,system of nerves and ganglia4 ,the separation1 ,i must often repeat1 is purely artificial2 but the artifice has conveniences4 ,we separate in the same way the heart from veins and arteries1 and the capillary circulation from the arterial4 ,each nerve has its direct connection with a particular centre1 and indirectly with the whole system4 ,it has its circumscribed territory1 and individual office4 ,except in a few cases of anastomosis1 the action of one nerve does not involve that of another3 only one muscle or one group of muscles is moved1 without exciting motion in a neighbor4 ,it is through the centres that these individual territories are united2 and a wave of excitation always passes throughout the central substance4 ,thus the centres are not simply organs of association1 consequently of regulation1 but are the nexus whereby the diversity of the actions is integrated into the unity of consensus4 #ah4 ,nothing further need at present be stated respecting the nerves2 but it is needful to give precision to the ideas of ,,ganglia ,,and ,,centres1 usually spoken of as if they were convertible terms4 ,that this is inexact may be readily shown1 and that it is misleading appears in its causing physiologists to credit every ganglion1 wherever found1 with central functions2 and1 by an almost inevitable extension of the error1 has led to the assignment of central functions to a single ganglionic cell6 ,this is but part of that 8superstition of the cell0 against which ,i shall have to protest4 ,i will not here raise the doubt which presses from various sides respecting the central functions of the ganglia in the heart and intestines1 because the reader perhaps shares the general opinion on that point2 but let me simply ask what central function can possibly be assigned to the ganglia on each of the spinal sensory nerves8 above all to those grouped and scattered ganglionic cells which are found at the peripheral termination of some nerves1 and in the very trunks of others8 ,there may1 indeed1 be imagined a central function for the ganglia in the mesentery1 and even in the choroid coat of the retina1 on the hypothesis 7quite gratuitous1 ,i think7 of their regulating the circulation2 but even this explanation cannot be adopted with respect to the ganglionic cells which appear in the course of the nerve4#hg ,the meaning of a physiological centre is1 that it is a point to which stimulations proceed1 and from which they are reflected4 ,the meaning of a ganglion is1 that it is a group of nerve cells dispersed among1 or in continuation with1 nerve fibres3 it may be a centre of reflection1 or it may not2 and in the latter case its physiological office is at present undetermined4 ,a ganglion is no more a centre in virtue of its cell-group than a muscle is a limb4 ,all function depends on connection1 and central function demands a connection of afferent and efferent parts4 #ai4 ,the ganglia found in the ventral cord of the ,invertebrate 7see ,fig4 #a7 are centres1 each of which has considerable independence1 each regulating a single segment of the body1 or a group of similar segments4 ,as the scale of animal complexity ascends1 these separated centres tend more and more to coalesce1 and with this coalescence comes an increasing combination of movements4#hh ,observe the caterpillar slowly crawling over a leaf2 each segment of its body moves in succession2 but when this caterpillar becomes a butterfly the body moves rapidly1 and all at once4 ,open the caterpillar1 and you find its nervous centres are thirteen separate ganglia1 each presiding over a distinct part of the body1 and each capable of independent action4 ,open the butterfly1 and you find the thirteen ganglia greatly changed3 the second and third are fused into one2 the fourth1 fifth1 and sixth into another2 the eleventh and twelfth into another2 the only trace of the original separation is in a slight constriction of the surface4 ,the movements of the caterpillar were few1 simple1 slow1 and those of the butterfly are many1 varied1 and rapid4 #bj4 ,in the ,vertebrates the coalescence of ganglia is such that the spinal axis is one great centre4 ,we do indeed anatomically and physiologically subdivide it into several centres1 because several portions directly innervate separate organs2 but its importance lies in the intimate blending of all parts1 so that fluctuating combinations of its elements may arise1 and varied movements result4 ,each centre combines various muscles2 the axis is a combination of centres4 ,the brainless frog1 for instance1 has still the spinal cord1 and therefore the power not only of moving either of his limbs1 but also of combining their separate movements3 if grasped1 he struggles and escapes2 if pricked1 he hops away4 ,but these actions1 although complex1 are much less complex and varied than the actions of the normal frog4 ,there is not only a coalescence of ganglia1 but a greater and greater concentration of the substance in the upper portions of the axis4 ,in the inferior vertebrates1 and in the mammalian embryo1 the spinal cord occupies the whole length of the vertebral canal from the head to the tip of the tail2 and here the centres of reflexion correspond with the several segments4 ,but as the cranial mass develops there is a withdrawal of neural substance from the lower parts1 and the centres of reflexion are then some way removed from the segments they innervate4 ,in the animal development there is even a greater and greater predominance of the upper portions1 so that the brain and medulla oblongata are of infinitely more importance than the spinal cord4 #ba4 ,besides the central group of elements which belong to fixed and definite actions1 we must conceive these elements capable of variable combinations1 like the pieces of colored glass in a kaleidoscope1 which fall into new groups1 each group having its definite though temporary form4 ,the elements constitute really a continuous network of variable forms4 ,it is to such combinations1 and not to fixed circumscribed ganglia1 that we must refer the subordinate centres of the axis4 ,we speak of a centre for ,respiration1 a centre for ,laughing1 a centre for ,crying1 a centre for ,coughing1 and so on1 with as much propriety as we speak of a centre for ,swallowing or for ,walking4 ,not that in these cases there is a circumscribed mass of central substance set apart for the innervation of the several muscles employed in these actions1 and for no other purpose4 ,each action demands a definite group of neural elements1 as each geometric form in the kaleidoscope demands a definite group of pieces of glass2 but these same pieces of glass will readily enter into other combinations2 and in like manner the muscles active in ,respiration are also active in ,laughing1 ,coughing1 etc41 though differently innervated and co-ordinated4 #bb4 ,the physiological rank of a centre is therefore the expression of its power of fluctuating combination4 ,the medulla oblongata is higher than the medulla spinalis1 because of its more varied combinations2 the cerebrum is higher than all1 because it has no fixed and limited combinations4 ,it is the centre of centres1 and as such the supreme organ4 ,,chapter ,,ii4 ,,the ,,functional ,,relations ,,of ,,the ,,nervous ,,system4 #bc4 ,the distinguishable parts of this system are the central axis1 the cranial nerves1 and the spinal nerves1 with the chain of ganglia and nerves composing the ,sympathetic4 ,let us briefly set down what is known of their special offices4 ,men very early discovered that the nerves were in some way ministrant to ,sensation and ,movement2 a divided nerve always being accompanied by insensibility and immobility in the limb4 ,galen1 observing that paralysis of movement sometimes occurred without insensibility1 suggested that there were two kinds of nerve2 but no one was able to furnish satisfactory evidence in support of this suggestion until early in the present century1 when the experiments of ,charles ,bell1 perfected by those of ,majendie and ,mller1 placed the suggestion beyond dispute4 ,illustration3 ,fig4 #ab4--,transverse sections of spinal cord 7dorsal region74 #bd4 ,fig4 #ab is a diagram 7not a drawing of the actual aspect1 which would be hardly intelligible to readers unversed in such matters7 representing two transverse sections of the spinal cord just where the nerve-roots issue4 ,the gray substance is somewhat in the form of a rude ,h1 in the dorsal region1 and of the expanded wings of a butterfly in the lumbar enlargements 7,figs4 #d-f72 the extremities of this gray substance are the anterior and posterior horns4 ,we have already said that from the anterior horns of each half issue the roots of the motor nerves1 which pass to the muscles4 ,from the posterior horns issue the sensory nerves1 which1 soon after leaving the cord1 enter the ganglia before joining the motor nerves1 and then pass to the skin1 in the same sheath with their companions1 separating again as they reach the muscles and surfaces where they are to be distributed4 ,when this mixed nerve is cut through1 or tied1 all sensation and movement disappear from the parts innervated4 ,but if only one of the roots be cut through1 above the ganglion1 there will then be only a loss of movement or a loss of sensation4 ,thus suppose the section be made at a1 b1 ,a3 we have then divided a sensory nerve1 and no pinching or pricking of the part innervated by that nerve will be felt2 but movement will take place if the under nerve be irritated1 or if a sensation elsewhere be excited4 ,now reverse the experiment1 as at ,b1 c1 d4 ,then1 pricking of the skin will be felt1 but no movement will respond4 ,the nerve which enters the cord at the upper 7posterior7 part is therefore a sensory nerve2 that which enters at the under 7anterior7 part is motor4 ,the direction is in each case indicated by the arrow4 ,the central end b1 if irritated1 will produce sensation2 whereas the peripheral end a produces neither sensation nor movement4 ,the central end d produces neither sensation nor movement2 the peripheral end c produces movement4 #be4 ,two facts are proved by these experiments4 ,first1 that the co-operation of the centre is necessary for ,sensation1 but not for ,movement4 ,although normally all the muscles of the trunk are moved only when their centre has been excited1 yet any irritation applied directly to the muscle nerve1 even when separated from its centre1 produces a movement4 ,and to this we may add that a slighter stimulus will move the muscle by direct irritation of the nerve1 than by indirect irritation through the centre2 a slighter stimulus also will suffice when applied to the nerve than when applied to the muscle itself4 #bf4 ,the second fact proved is known as ,bell's ,law1 that the sensory and motor channels are respectively the posterior and anterior nerves4 ,the fact is indisputable1 but its theoretic interpretation can no longer be accepted in its original form4 ,bell supposed the two nerves to be different in kind1 endowed with different specific energies1 the one sensitive1 the other motor4 ,the majority of writers still express themselves as if they adopted this view4 ,we shall1 however1 presently see reason for replacing it by the more consistent interpretation which assigns one and the same property to both nerves1 marking their distinction by the terms afferent and efferent2 the one set being anatomically so disposed that it conveys stimuli from the surfaces to the centre1 and the other set conveying stimuli from the centre to the muscles1 glands1 and other cells4#hi #bg4 ,bell's discovery was rapidly generalized4 ,the principle of localization was extended to all nerves1 and of course to the posterior and anterior columns of the spinal cord1 which indeed were assumed to be continuations of the nerves4 ,bell1 who was greater as an anatomist than as a philosopher1 always maintained that anatomical deduction was superior to experiment4 ,but this was to misunderstand the reach of deduction1 which is only valid to the extent of its premises4#ij ,in the present case1 the premises assumed that the posterior columns were continuations of the posterior roots1 and carried impressions to the brain1 the anterior columns carrying back from the brain the 8mandates of the will40 ,experiment has1 however1 decisively shown that it is not through the posterior columns that sensory impressions travel to the brain1 but through the central gray substance4 #bh4 ,the spinal cord with its central gray substance is at each point a centre of reflexion4 ,connected as it is with different organs1 we artificially consider it as a chain of different centres1 and try to detect the functional relations of its parts4 ,the inquiry is important1 but we must bear in mind the cardinal principle that diversity of ,function depends on the organs innervated1 and not on a diversity of ,property in the nervous tissue4 ,although all nerves have a common structure and common property1 yet we distinguish them as sensory and motor2 and the sensory we subdivide into those of ,special ,sensation and those of ,systemic ,sensation4 ,the motor we divide into muscular1 vasomotor1 and glandular4 ,the hypothesis of specific energies must be relinquished 7 #fc74 ,in like manner all centres have a common structure and a common property1 with a great diversity of functional relations4 ,here also the hypothesis of specific energies has been generally adopted1 owing to a mistaken conception of the biological principle just mentioned4 ,the cerebral hemispheres are credited with the properties of sensation1 thought1 and volition2 the cerebellum with the property of muscular co-ordination2 the spinal cord with the property of reflexion4 #bi4 ,no attempt to assign the true functional relations of the centres will be made at the present stage of our exposition4 ,we must learn more of the processes in ,sensation1 ,thought1 and ,volition1 before we can unravel the complex physiological web on which they depend4 ,but here1 provisionally1 may be set down what observation and experiment have disclosed respecting the part played by certain centres4 ,we know1 for example1 that when the cerebral hemispheres are carefully removed from a reptile or a bird1 all the essentially vital functions go on pretty much as before1 but a great disturbance in some of the psychical functions is observed4 ,the brainless bird eats1 drinks1 sleeps1 moves its limbs separately and in combination1 manifests sensibility to light1 sound1 and touch1 performs such instinctive actions as preening its feathers1 or thrusting the head under the wing while roosting4 ,throw it into the air and it will fly4 ,in its flight it will avoid obstacles1 and will alight upon a ledge1 or your shoulder4 ,but it will not fly unless thrown into the air2 it will not escape through the open door or window2 it will avoid objects1 but will show no fear of them1--alighting on your head1 for example1 without hesitation4 ,it is sensitive to light1 and may in a certain sense be said to see2 but it fails to perceive what is seen4 ,it will eat and drink1 if food and water be administered1 but it will starve near a heap of grain and never peck it1 not even if the beak be thrust into the heap4 ,a grain1 or strip of meat1 may be thrust inside the beak2 there it will remain unswallowed1 unless it touches the back of the mouth1 then swallowing at once follows the stimulus4 ,the bird with its brain will fly away if you turn the finger1 or stick1 on which it is perching2 without its brain1 it makes no attempt to fly1 but flutters its wings1 and balances itself4 ,if you open the mouth of a cat1 or rabbit1 and drop in some bitter fluid1 the animal closes its mouth firmly1 and resists your efforts to repeat the act2 without its brain1 the animal shows the same disgust at the taste1 but never resists the preliminaries of the repetition4 #cj4 ,these1 and analogous facts1 have been noted by various experimenters4 ,they are very far from proving what is usually concluded2 but they prove the important negative position that the cerebrum is not the centre of innervation for any of the organs on which the observed actions depend4 ,thus1 the cerebrum is not necessary to sight3 ergo it does not innervate the eye4 ,it is not necessary to hearing3 ergo it does not innervate the ear4#ia ,it is not necessary to breathing1 swallowing1 flying1 etc43 ergo it does not innervate the organs of these functions4 ,what then is lost8 ,we have only to remember that the cerebrum is continuous with the thalami and corpora striata1 and1 through its crura1 with the medulla oblongata and medulla spinalis1 to foresee that its removal must more or less affect the whole neural axis1 and consequently disturb the actions of the whole organism2 this disturbance will often have the appearances which would be due to the removal of a central apparatus1 so that we shall be apt to attribute the cessation of a function to the loss of its organ1 when in fact the cessation is due simply to an arrest of the organ by irritation4 ,thus the cessation of consciousness1 or of any particular movements1 when the cerebrum is removed1 is no decisive proof that the cerebrum is the organ of consciousness1 or of the movement in question4 ,this point will be duly considered hereafter4 ,what we have now to consider is the facts observed after removal of the cerebrum4 ,first1 we observe a loss of that power of combining present states with past states1 present feelings with feelings formerly excited in conjunction with them1 the power which enables the animal to adjust its actions to certain sensations now unfelt but which will be felt in consequence of the adjustment4 ,secondly1 we observe a loss of ,spontaneity3 the bird1 naturally mobile and alert1 now sits moveless for hours in a sort of stupor1 occasionally preening its feathers1 but rarely quitting its resting-place4 ,all the most conspicuous phenomena which we assign to ,intelligence and ,will seem absent4 ,the sensations are altered and diminished4 ,many ,instincts have disappeared1 but some remain4 ,the sexual feeling is preserved1 although the bird has lost all power of directing its actions so as to gratify the desire4 ,but these effects are only observed when the whole of both hemispheres have been removed4 ,if a small portion remain the bird retains most of its faculties1 though with less energy4 ,in frogs and fishes there is little discernible effect observed when a large portion of the cerebrum is removed4 #ca4 ,now take away from this mutilated bird its cerebellum3 all the functions continue as before except that some combined movements can no longer be effected2 flight is impossible2 walking is a mere stagger4 ,remove only the lateral lobes1 and though flight is still possible great incoherence of the wings is observed1 whereas walking is not much affected4 ,if only the cerebellum be removed1 the cerebrum being intact1 the phenomena are very different4 ,all the perceptions and almost all the emotions1 all the spontaneity and vivacity are retained2 but the sexual instinct1 which was manifested when the cerebrum was removed1 is now quite gone4 ,what we call ,intelligence seems unaffected4 ,the bird hears1 and understands the meaning of the sounds1 sees and perceives1 sees and fears1 sees and adjusts its movements with a mental vision of unseen consequences4#ib #cb4 ,are we from these facts to conclude that the cerebrum is the 8organ of the mind02 that it is 8the seat0 of sensation1 thought1 emotion1 volition2 and that the cerebellum is the 8seat0 of the sexual instinct1 and muscular co-ordination8 ,such conclusions have found acceptance1 even from physiologists who would have been startled had any one ventured to affirm that the medulla oblongata was the 8organ0 of ,respiration1 because ,respiration ceases when this centre is destroyed4 ,i shall have to combat this notion at various stages of my exposition4 ,here let me simply say that it is irreconcilable with any clear conception of organ and function2 and is plainly irreconcilable with any survey of psychical phenomena in animals in whom the cerebrum does not exist1 and in animals from whom it has been removed4 ,what the facts indisputably prove is that the cerebrum has an important part in the mechanism by which the most complex psychical combinations are effected1 and that the cerebellum has an important part in the mechanism by which the most complex muscular combinations are effected4 ,the supreme importance of the cerebrum may be inferred from its dominating all the other centres1 and from its preponderance in size4 ,in man it stands to all the other cranial centres together in the relation of #aa to #c4 ,it is about five times as heavy as the spinal cord--that is to say from #a1ajj to #a1djj grammes1 compared with #bg to #cj grammes4 ,the quantity of blood circulating through it is immense4 ,haller estimated the cranial circulation as one fifth of the whole circulation4 ,if1 therefore1 the ,nervous ,centres are agents in the production of ,sensation and ,intelligence1 by far the largest share must be allotted to the cranial centres1 and of these the largest to the ,cerebrum4 #cc4 ,it is1 however1 one thing to recognize the ,cerebrum as having an important part in the production of psychical phenomena1 another thing to localize all the phenomena in it as their organ and seat--a localization which soon becomes even more absurd1 when of all the cerebral structure the multipolar cells alone are admitted as the active agents6 ,as was said just now1 we recognize in the ,medulla ,oblongata the nervous centre of ,respiration1 but we do not suppose that ,respiration has its seat there1 nor that this centre is absolutely indispensable for the essential part of the process4 ,we respire by our skin1 as well as by our lungs2 many animals respire who have nothing like a medulla oblongata2 as many animals feel1 and manifest will1 who have nothing like a cerebrum4 ,the destruction of centres is of course a disturbance of the mechanisms which they regulate4 ,but even the observed results of a destruction require very close examination1 and are liable to erroneous interpretations4 ,the disappearance of a function following the destruction1 or disease of a particular part1 is not to be accepted as a proof that this part is the organ of the lost function2 because precisely the same phenomena may often be observed following the destruction of a totally different part4#ic ,but one result may always be relied on1 and that is the persistence of a function after removal of a particular part4 ,thus there is a certain spot of the cerebral convolutions from which movements of the limbs are excited when the electrodes are applied to it2 removal of the substance is immediately followed by paralysis of the limbs4 ,are we to conclude that this spot is the organ of the function8 ,it is true that the function is called into action by a stimulus applied to this spot3 true that the function suddenly vanishes when the substance of this spot is destroyed4 ,nevertheless1 what seems a loss of function is only a disturbance4 ,in two or three days the paralysis begins to disappear1 and at the end of a week the limbs are moved nearly in the normal manner4 ,and the same is true when the spot in question is destroyed on both sides4 ,the recovery of the function shows that the absent part was not its organ4 ,there is a paradoxical experiment recorded by ,m4 ,paul ,bert which may be cited here4 ,he removed the right cerebral hemisphere from a chameleon1 and found that the limbs on the left side were paralyzed2 but on his then removing the left cerebral hemisphere the limbs of the left side recovered their activity4 ,a similar result was obtained by ,lussana and ,lemoigne by extirpation of the thalami4 ,when we find combined movements persisting after the cerebellum has been destroyed1 we may be sure that the cerebellum is not the organ by which such combinations take place2 and when we find sensation and volition manifested after the cerebrum has been removed1 we may be sure that the cerebrum is not the organ for these sensations and volitions4 #cd4 ,and this we do find4 ,physiologists1 indeed1 for the most part1 deny it2 or rather1 while they admit the observed facts1 they refuse to admit the only consistent interpretation1 biassed as they are by the traditional conception of the brain4 ,after having for many years persistently denied ,sensibility to any centre except the cerebrum1 they are now generally agreed in including the medulla oblongata within the privileged region2 but they still exclude the medulla spinalis4 #ce4 ,if all the cranial centres as far as the medulla oblongata are removed from young rabbits1 dogs1 or cats1 there are unmistakable evidences of ,sensibility in their cries when their tails are pinched1 their moving jaws 7as in mastication7 when bitters are placed in their mouths1 and their raised paws rubbing their noses1 when irritating vapors are applied4 ,it is said indeed that the cries are no signs of pain2 and this is probable2 but they are assuredly signs of ,sensibility4 #ce4 ,the frog thus mutilated has lost indeed all its special senses1 except ,touch1 but it still breathes1 struggles when grasped1 thrusts aside the pincers which irritate it1 or wipes away acid dropped on its skin4 ,if the eye be lightly touched1 the eyelid closes2 if the touch be repeated three or four times1 the foreleg is raised to push the irritant away2 if still repeated1 the head is turned aside2 but however prolonged the irritation1 the frog neither hops1 nor crawls away1 as he does when the cerebellum remains4 ,place the brainless frog on his back1 and if the medulla oblongata remains he will at once regain the normal position2 but if that part is absent he will lie helpless on his back4 ,the power of preserving equilibrium in difficult positions--which of course implies a nice co-ordination of muscles--resides in the so-called optic lobes of the frog 7what in mammals are called the corpora quadrigemina74 #cg4 ,with the destruction of each part of the central mass there will necessarily be some disturbance of the mechanism2 but difficult as may be the task of detecting by experiment what is the normal action of any one part1 there ought to be no hesitation in recognizing the persistence of functions after certain parts are destroyed4 ,the spinal cord is anatomically known to be the centre from which the limbs1 trunk1 and genito-urinary organs are innervated4 ,so long as the mechanism of the actions involving such organs is intact1 no removal of other parts will prevent this mechanism from exhibiting its normal action4 ,there may indeed arise1 and there has arisen1 the doubt whether ,sensibility is involved in the action of any nerve centre below the medulla oblongata4 ,but this doubt is founded on the traditional hypothesis respecting the seat of ,sensation1 and is flagrantly at variance with the logical conclusions of ,anatomy and ,experiment4 #ch4 ,anatomy shows that the structure of the spinal cord is in all essential characters the same as that of the medulla oblongata2 and indeed that the whole central axis has one continuous tissue1 somewhat variously arranged1 and in relation with various organs4 ,abundant ,experiment has shown that the spinal cord1 apart from the encephalon1 is capable of acting as a sensorial and volitional centre4 ,the striking facts advanced by ,pflger1 ,auerbach1 and myself1 have not been impugned2#id but their interpretation has been generally rejected4 ,we showed that a brainless frog responded to stimulation in actions which bore so close a resemblance to actions admitted to be sensorial and volitional--showed the frog adapting itself to new conditions1 and acquiring dexterity in executing actions which at first were impossible or difficult1 devising combinations to effect a purpose which never by any possibility could have formed part of its habits--manifesting1 in a word1 such signs of ,sensibility1 that no one witnessing the experiments could hesitate as to the interpretation1 had he not been biassed by the traditions of the schools4 #ci4 ,our opponents argued that in spite of all appearances there were profound differences between the actions of the normal and the brainless animal1 and that the latter were due simply to ,reflex ,action4 ,i also insist on profound differences2 but underlying these there are fundamental identities4 ,as to the ,reflex ,action1 two points will hereafter be brought forward3 #a1 that all central action is reflex1 the cerebral no less than the spinal2 #b1 that the hypothesis of ,reflex ,action being purely mechanical1 and distinguished from ,voluntary ,action in not involving ,sensibility1 is an hypothesis which must be relinquished4 #dj4 ,postponing1 however1 all discussion of these points1 let me here say that the doctrine maintained in these pages is that the whole cerebro-spinal axis is a centre of ,reflexion1 its various segments taking part in the performance of different kinds of combined action4 ,it has one common property1 ,sensibility2 and different parts of it minister to different functions--the optic centre being different from the auditory1 the cerebral from the spinal2 and so on4 ,to make this intelligible1 however1 we must first learn what is known respecting the properties of nerve-tissue4 ,,chapter ,,iii4 ,,neurility4 #da4 ,observation having found that the activity of a nerve was always followed by a sensation when the nerve ended in a centre1 and by a movement when the nerve ended in a muscle1 ,theory was called upon to disclose the nature of this peculiar property of nerves4 ,that a peculiar and mysterious power did act in the nerves no one doubted2 the only doubt was as to its nature4 ,the ancient hypothesis of ,animal ,spirits seemed all that was needed4 ,the spirits coursed along the nerves1 and obeyed the mandates of the ,soul4 ,when this hypothesis fell into discredit1 its place was successively taken by the hypotheses of ,nervous ,fluid1 ,electricity1 and ,nerve ,force4 ,the ,fluid1 though never manifested to ,sense1 was firmly believed in1 even so late as the days of ,cuvier2#ie but when the so-called electrical currents were detected in nerves1 and the nervous phenomena were shown to resemble electrical phenomena1 there was a general agreement in adopting the electrical hypothesis4 ,the brain then took the place of a galvanic battery2 the nerves were its electrodes4 #db4 ,closer comparison of the phenomena detected various irreconcilable differences1 which1 if they proved nothing else1 proved that nerve-action took place under conditions so special as to demand a special designation4 ,electricity itself is so little understood1 that until its nature is more precisely known1 we cannot confidently say more than that nerve-action resembles electrical-action2 meanwhile the speciality of neural conditions renders all deduction illusory which is based on electrical-action as observed under other conditions4 ,in presence of these difficulties1 cautious physiologists content themselves with assigning the observed phenomena to the observed and inferred conditions1 condensing these in the convenient symbol 8nerve-force10 without pretending to any specification of the nature of that force4 ,it may be a wave of molecular movement dependent on isometric change or on metamorphic change4 ,it may be the liberation of molecular tension resembling electricity2 it may be electricity itself4 ,but whatever the nature of the change1 it is an activity of the tissue1 and as such comes under the general dynamic conception of ,force or ,energy4 #dc4 ,in this sense the term has nothing equivocal or obscure4 ,it is a shorthand expression symbolizing certain well-defined observations4 ,nevertheless1 it is a term which we shall do well to avoid when possible1 and to replace by another having less danger of misinterpretation2 the reason being that ,force has become a sort of shibboleth1 and a will-o'-wisp to speculative minds4 ,all that we know of ,force is ,motion4 ,but this is too meagre for metempirical thinkers1 who disdain the familiar experiences expressed in the term ,motion1 and demand a transcendent cause 8to account0 for what is observed4 ,they seek an entity to account for the fact4 ,motion is a very definite conception1 expressing precise experiences2 we know what it means1 and know that the laws of moving bodies admit of the nicest calculation4 ,a similar precision belongs to ,force when understood as 8mass acceleration10 or ,m ,v4 ,but this does not content those metaphysicians who understand by ,force 8the unknown reality behind the phenomena0--the cause of ,motion4 ,this cause they refuse to recognize in some antecedent motion 7what ,i have termed a 8differential pressure071 but demand for it a physical or metaphysical agent3 the physical agent being a subtle fluid of the nature of ,ether1 or a nerve atmosphere surrounding the molecules2 the metaphysical agent being a ,spirit or aggregate of ,soul-atoms4 ,the second alternative we may decline here to discuss4 ,the first alternative is not only a pure fiction1 but one which is inconsistent with the demonstrable velocity of the neural process1 which is not greater than the pace of a greyhound1 whereas the velocities of light and electricity are enormously beyond this4 ,it is inconsistent also with the observation that a much feebler current of electricity is requisite for the stimulation of a muscle through its nerve than when directly applied to the muscle3 a proof that the nerve does not act solely by transmission of electricity--unless we gratuitously assume that the nerve is a multiplicator4 ,when it is said that the living nerve is incessantly liberating ,force which can be communicated to other tissues1 the statement is acceptable only if we reject the metaphysical conceptions it will too generally suggest--the conceptions of ,force as an entity1 and of its being passed from one object to another like an arrow shot from a bow4 ,the physical interpretation simply says that the molecules of the nerve are incessantly vibrating1 and with varying sweep2 these vibrations1 when of a certain energy1 will set going vibrations in another substance by disturbing the tension of its molecules1 as the vibrations of heat will disturb the tension of the gunpowder molecules1 and set them sweeping with greater energy3 this is the communication of the force4 ,just as we say that a magnet communicates magnetic force to a bit of iron1 though all we mean is that the magnet has so altered the molecular condition of the iron as to have given it the movements called magnetism--in short1 has excited in the iron the dormant property of becoming magnetic--so we say the nerve communicates its force to the muscle1 exciting in the muscle its dormant property of contraction4 ,but in truth nothing has passed from magnet to iron1 or from nerve to muscle4 #dd4 ,do what we will1 however1 there is always1 in the present condition of philosophical chaos1 the danger of being misunderstood when we employ the term ,nerve-force2 and ,i have proposed the term ,neurility as an escape from the misleading suggestions4 ,it is a symbol expressing the general property of nerve-tissue4 ,for reasons presently to be stated1 ,i restrict ,neurility to the peripheral system1 employing ,sensibility for the central system4 ,the excited muscle manifests its special property of ,contractility2 the excited nerve manifests its special property of ,neurility2 the excited centre manifests its special property of ,sensibility4#if ,the terms are simply descriptive1 and carry with them no hypothesis as to what ,neurility is in its hidden process1 nor how ,sensibility arises in a nerve-centre1 and not elsewhere4 ,we know that a stimulated muscle contracts1 and we express the fact by assigning to muscular tissue the property of ,contractility4 ,we know that a stimulated nerve translates an impulse from one point to another1 and excites the muscle to contract2 and we express the fact by assigning to nerve-tissue the property of transmitting stimulation1 which is further specified1 as unlike other transmissions1 by the term ,neurility4 #de4 ,what is the meaning attached to the term ,property1 and how it is distinguished from ,function1 has been already expounded in ,problem #a1 #ha-f4 ,there also was laid down the principle of identity of structure implying identity of property4 ,inasmuch as observation reveals a fundamental similarity in the structure of the nervous tissue throughout the animal kingdom1 we must conclude the existence of a fundamental similarity in the property of that tissue3 a conclusion confirmed by observation4 ,there is a corresponding agreement in the organs and functions2 so that1 within certain limits1 the experiments performed on an insect may be verified on a mammal4 ,everywhere nerve-tissue has certain characters in common1 accompanied by variations in the degree and mode of manifestation corresponding with variations in structure and connection4 ,obvious as the fact is1 we must emphasize the great variety which accompanies the underlying uniformity1 for this is recognizable both in the individual organism and in the animal kingdom at large4 ,even such seemingly individual terms as nerve-cell and nerve-fibre are in truth generic2 and the description which accurately represents one cell or fibre needs modifying for others4 ,properties are generalized expressions2 they result from the composition1 the structure1 and the texture of a substance4 ,thus one bar of iron may differ from another of equal bulk in being more or less crystalline in structure1 though having the same composition and the same texture4 ,this difference will modify the mode of manifestation of the iron-properties4 ,cast-iron pillars1 for example1 will support1 as a roof1 a weight which would break them if suspended2 wrought-iron pillars of similar bulk will bear a weight suspended which would crush them as a roof4 ,yet both cast and wrought iron pillars have the same properties1 because they have the same composition and similar structure2 the variation of structure only producing a difference in the modes4 ,texture may also vary4 ,the bar of iron may be beaten into a plate1 rolled into a cylinder1 or split into wire-work1 without any change in its properties1 but with marked differences in its modes of manifestation1 and in the uses to which it may be applied4 ,these uses are of course dependent on the connections established between the iron and other things4 ,in ,physiology1 uses are called functions4 #df4 ,nerve-tissue must be understood as having everywhere the same general ,property4 ,in one animal and in another1 in one part and in another1 ,neurility is the same in kind1 but not everywhere manifesting the same degree1 nor applied to the same ,function4 ,the composition of nerve-tissue varies1 but not more than the composition of all other organized substances2 the structure is variable1 but only within a small range2 the texture also2 while the connections are very various4 ,hence1 whatever the variations in composition or structure1 the nerve-fibre has everywhere one fundamental property1 which in connection with a muscle has the functional activity of exciting contraction2 in connection with a gland of exciting secretion2 and in connection with a centre of exciting reflexion4#ig #dg4 ,had a clear idea of ,function as dependent on connexion been present to their minds certain physiologists would hardly have raised the mirage of 8,nerve-force10 a mysterious entity endowed with 8specific energies10 and capable of producing vital and psychical phenomena by an occult process2 nor would others have been led to the monstrous hypothesis of particular nerve-cells being endowed with thought1 instinct1 and volition4 ,they would have sought an explanation of functions in the combined properties of the co-operant organs and tissues4 ,they would not have endowed one nerve with ,sensibility1 and another nerve of identical structure with ,motility2#ih one nerve with a motor property1 and another with the opposite property of inhibition4 ,they would have seen that all nerves have the same property1 but different uses when in different connexions4 #dh4 ,throughout the animal kingdom we see movement following on stimulation4 ,stimulation may be defined the change of molecular equilibrium4 ,the stimulation of a muscle is produced indirectly through a change in the nerve1 or directly through a change in the muscle itself4 ,in the simplest organisms there is no trace of nerve-tissue2 but their substance manifests ,irritability 7or as it is often called ,sensibility72 and a stimulus to one part is propagated throughout--the whole body moves when touched4 ,even in ,polypes1 where there is the beginning of a differentiation1 the motion is slowly propagated from one part to the rest4 ,a single tentacle retracts when touched2 but the movement rarely ends there2 it is slowly communicated from one tentacle to the other1 and from them to the whole mass4 ,touching the body1 however1 will not1 if the touch be slight1 cause the tentacles to move2 so that we see here a beginning of that principle of specialization which is so manifest in the higher organisms3 the tentacles have become the specially sensitive parts4 ,ascending higher in the scale of organisms we find those which habitually move particular parts without at the same time necessarily moving the rest2 and this independence of parts1 accompanying a more perfect consensus1 we find to be developed pari passu with a nervous system4 ,an immense variety of part-movements1 with varying combinations of such movements1 is the physiological expression of the more complex nervous system4 #dh a4 ,deferring what has to be said of ,sensibility till the next chapter1 we may here touch on its relation to ,irritability1 which is often used as its synonym4 ,objectively it cannot be distinguished from ,irritability1 nor indeed from the most general phenomenon of reaction under stimulation2 in this it is an universal property4 ,but subjectively it is distinguishable as a peculiar mode of reaction1 only known in nerve-tissues4 ,while all tissues are irritable1 and react on being stimulated1 each tissue has its special mode of reaction4 ,the secreting-cell reacts differently from the muscle-cell4 ,the reaction of the nerve is the innervation of a centre or a muscle2 the reaction of an innervated centre is sensation2 of a muscle1 contraction4 ,there are three aspects of neural reaction3 excitation1 propagation of the disturbance1 and innervation4 ,the first is expressed by irritability1 the second by conductibility1 the third by sensibility2 but these are only artificial distinctions in the general phenomenon of transmitted excitation4 ,the nerve substance is specially distinguished by its instability of molecular equilibrium2 it undergoes chemical change with a readiness comparable to that of explosive substances4 ,hence its facility of propagation of disturbance4 ,there is irritability and propagation of disturbance in muscular tissue1 notably evident in the continuous tissue of the heart1 intestines1 and ureter2 but the propagation is slow and diffusive2 whereas in the nerve it is rapid1 and restricted along a definite path4 ,by this rapidity and restriction the force of the impact is increased2 and thus a slight stimulus applied to the nerve is capable of disturbing the state of the muscle4 #di4 ,thus while molecular movement is a fundamental condition of ,vitality1 and is incessant throughout organized substance1 the massive movements of the organism1 and the movements of particular parts1 are the directed quantities of this molecular agitation4 ,they are due to stimulation4 ,we distinguish this from mechanical impulsion4 ,it is a vital process involving molecular change2 it is not simply the communication of motion from without1 but the excitation of motion within4 ,it is not like the blow which merely displaces an object1 but like the blow which disturbs its molecular equilibrium4 ,the effect1 therefore1 depends on this molecular condition3 the blow which scatters a heap of gunpowder will explode a fulminating salt1 and this1 in exploding1 will excite the gunpowder to explode4 ,the stimulus which is too feeble to excite contraction in a muscle will be powerful enough to excite the neurility of a nerve1 and that will excite the contractility of the muscle4 ,the nerve-force is simply neural stimulus4 ,it acts upon the other tissues as the nitrogenous salt upon the gunpowder4 ,although it is now common to speak of nerves as transmitting waves of molecular motion1 and to regard nerves as the passive medium for the 8transference of force10 whereby the force is thus made an abstract entity1 we must always remember that such phrases are metaphors1 and that the truer expression will be not 8transference of force10 but the 8propagation of excitation40 ,i mean that it is not the force of the impact nor its energy which a nerve transmits1 it is the vibratory change produced in the nerve by the impact1 which excites another change in the organ to which the nerve goes4 ,we know by accurate measurements that the excitation of a nerve lasts much longer than the stimulus1 a momentary impact producing an enduring agitation4 ,we know also that the excitation of a centre lasts longer than the muscular contraction it has initiated4 ,we know1 moreover1 that a nerve may be totally incapable of conducting an external stimulus1 yet quite capable of conducting a central stimulus2 were it a passive conductor like a wire this would not be so4#ii #ej4 ,the nerve is essentially an exciter of change1 and thereby a regulator4 ,a muscle in action does not appreciably determine action in any other 7except in the comparatively rare cases of anastomosing muscles72 a secreting cell does not propagate its excitation to others4 ,the nerve1 on the contrary1 not only propagates its excitation1 and awakens the activity of the muscle or gland with which it is connected1 but through the centre affects the whole organism-- 8,ein ,schlag tausend ,verbindungen schlgt40 ,thus it is that stimulation which in the simpler organisms was diffused throughout the protoplasm1 has in the complex organisms become the specialized property of a particular tissue4 #ea4 ,two general facts of supreme importance must now be stated3 ,one is the law of stimulation--every excitation pursues the path of least resistance4 ,the second is the condition of stimulation--unlike mechanical impulsion1 it acts only at insensible distances4 #eb4 ,this means that although a nerve may be excited by any stimulus external to it which changes its molecular condition1 no propagation of that change 7i4 e4 no stimulation through the nerve7 is possible except through continuity of substance4 ,mere physical contact suffices to excite the nerve2 but if there be an interruption of continuity in the nerve itself1 no stimulus-wave passes across that line4 ,cut a nerve1 and bring the divided surfaces once more into close contact1 there will still be such a solution of continuity as to arrest the stimulus-wave1 mere physical contact not sufficing for the propagation4 ,whereas across the cut ends of a divided nerve1 even visibly separated1 the electric current easily passes4 ,this necessity for the vital continuity of tissue in the propagation of stimulation must always be borne in mind4 ,the presence of a membrane1 however delicate1 or of any tissue having a different molecular constitution1 suffices to arrest or divert the wave4 ,i conceive1 therefore1 that it is absolutely indispensable that a nerve should terminate in and blend with a muscle or a centre1 otherwise no stimulation of muscle or centre will take place through the nerve4 ,illustration3 ,fig4 #ac4 #ec4 ,the difference between excitation from contact and stimulation from continuity may be thus illustrated4 ,in ,fig4 #ac we see the legs of a frog attached to the spine by the lumbar nerves 7l71 and lying on the muscles 7m7 of one leg is the nerve 7c7 of another frog's leg4 ,applying the electrodes to 7l71 the muscles 7m7 are violently contracted2 not only so1 but their contraction excites the other nerve 7c71 and the leg attached to this nerve is thereby thrown into contraction4 ,this 8secondary contraction10 as ,dubois ,reymond calls it1 might be supposed to be due to a diffusion of the electrical current2 but that it is due to a change in the muscles 7m7 is proved by delicate experiments showing that the movements in the detached leg are of precisely the same kind as those in the legs directly stimulated4 ,if there is only a muscular shock in the one case1 there is only a muscular shock in the other2 if there is tetanus in the one1 there is tetanus in the other2 if the muscles of the first leg are fatigued and respond slowly and feebly1 the response of the second is slow and feeble4 ,moreover1 the secondary contraction may be produced by chemical or mechanical stimulus1 as well as by the electrical4 #ed4 ,although the contraction of a muscle is thus seen to be capable of exciting a nerve in contact with it1 the reverse is not true3 we can produce no contraction in a muscle by exciting a nerve simply in contact with the muscle1 and not penetrating its tissue and terminating there4 ,accordingly we always find a nerve when about to enter a muscle or a centre losing its protecting envelopes2 it gradually becomes identified as a protoplasmic thread with the protoplasm of the muscle or the centre4 #ee4 ,neurility1 then1 is the propagation of molecular change4 ,two offices are subserved by the nervous system1 which may respectively be called ,excitation--the disturbance of molecular tension in tissues1 and consequent liberation of their energies2 and ,co-ordination--the direction of these several energies into combined actions4 ,thus1 when the muscle is in a given state of molecular tension1 the stimulation of its nerve will change that state1 causing it to contract if it be in repose4 ,but this stimulation1 which will thus cause a contraction1 will be arrested1 if at the same time a more powerful stimulation reaches the antagonist muscle1 or some distant centre3 then the muscle only tends to contract4 ,,origin ,,of ,,nerve-,,force4 #ef4 ,after this brief account of ,neurility we may pass to the consideration of its origin4 ,are we to understand that this property belongs to the nerves themselves in the sense in which ,contractility belongs to the muscles8 or are we to accept the teaching which assigns the origin of 8nerve-force0 to the ganglia1 and regards the nerves simply as passive conductors of a force developed in the cells8 #eg4 ,it is now many years since ,i ventured to criticise the reigning doctrine1 and to urge the necessity ,of consistently carrying out the distinction between ,property and ,function4 ,i called attention to the positive evidence which contradicted the idea of passive conduction2 and pointed out the illusory nature of the favorite analogy1 in which ganglia were likened to batteries1 and nerves to the conducting wires4 ,but the old image still exerts its empire2 and writers are still found speaking of the brain as a telegraphic bureau1 the ganglia as stations1 and the nerves as wires4 ,in the cells of the gray substance they place a constantly renewing reservoir of nerve-force4 ,there the force is elaborated1 stored up1 and from thence directed along the nerves4 ,the sensory nerve 8transmits an impression to the brain0--as the wire transmits a message to the bureau4 ,the motor nerve1 in turn1 8transmits the mandates of the will0--and all is clear6 ,clear1 until we come to translate metaphors into visible facts1 or try to conjure up some mental image of the process4 ,for myself1 ,i can only conceive nerve-force as the activity of the nerve1 and not of something else4 ,this becomes still more evident when ,i find that the activity is equally manifest after its imaginary source has been removed4 ,transmitting impressions1 or messages1 implies as a preliminary that there should be an impressible agent1 or a message-sender1 at the periphery4 ,no one supposes that simply touching one end of a wire would send an 8impression0 or a 8message0 to the battery2 or that without the battery this touch would evolve a current4 ,the battery is indispensable2 in it is evolved the current which the wire transmits4 ,not so the ganglion1 or brain4 ,remove the wire from its connection with the battery1 and it is a bit of wire1 nothing more4 ,but remove a nerve from its connection with a ganglion1 and it is still active as nerve1 still displays its ,neurility when excited1 still moves the muscle as before4 ,the amputated limb will move when its nerves are stimulated1 just as when a reflex from its centre moved it4 ,every one knew the fact2 it was staring them in the face1 yet they disregarded it4 ,even the old anatomist1 ,willis1 had recorded experiments which ought to have opened their eyes4 ,he tied the phrenic nerve1 and found that1 when he irritated it below the ligature1 the diaphragm moved2 but when he irritated it above the ligature1 no movement followed4 ,since his days1 thousands of experiments have shown that the presence of a ganglion is not necessary to the action of a nerve4#ajj #eh4 ,of course an explanation was ready4 ,the nerve was said to have been 8endowed with force0 from its ganglion during their vital connection2 and this force1 stored up in the nerve1 was disposable for some time after separation from the ganglion4 ,we need not pause to criticise this misty conception of one part 8endowing0 another with force2 the plain facts afford the best answer4 ,there seemed1 indeed1 a confirmation of the hypothesis in the fact that although the nerve separated from its ganglion was capable of excitation1 yet after a few excitations it was exhausted1 and ceased to stimulate the muscle4 ,it seemed like the piece of magnetized iron which would act as a temporary magnet1 though quickly losing this borrowed power4 ,but the whole fabric fell--or ought to have fallen--when extended observation discovered that this exhausted nerve would1 if left in repose1 recover its lost power4 ,a nerve preserves its excitability as long as it preserves its structural integrity1 and recovers its power in recovering that integrity4 ,the length of time varies4#aja ,gratiolet found the muscles in the leg of a tortoise1 which had been amputated a week before1 contract when the nerves were irritated2 and ,schiff found the divided nerve of a winter frog excitable at the end of three weeks4 ,even after all excitability has disappeared1 it will reappear if arterial blood be injected2 just as muscles which have already begun to assume cadaveric rigidity recover their contractility after transfusion4 ,nor is this all4 ,the separated nerve finally degenerates1 and loses all its structural characters and physiological properties2 yet under favorable conditions it will regenerate--recover its structures and properties2 and this even apart from a centre1 as ,vulpian showed4 ,very noticeable is the fact that the force said to be produced in the centre1 and only 8conveyed0 by the nerve1 vanishes gradually from the centre to the periphery1 and recovers from the periphery to the centre--the part of the nerve which is farthest from the centre being excitable when the part nearest the centre is still inexcitable4 ,again1 when a nerve is pinched1 contraction in the muscle follows2 but the pinch has for a time so disturbed the structural integrity of the nerve 7at that spot7 that no irritant applied to the spot1 or between it and the centre1 will be followed by contraction1 whereas below the spot an irritation takes effect4 ,this is another form of the experiment of ,willis4 ,even in its normal state1 the nerve has different degrees of excitability in different parts of its course1--a fact discovered by ,pflger which is quite irreconcilable with the hypothesis of passive conduction4 ,doubts have been thrown on ,pflger's interpretation1#ajb namely1 that there is an avalanche-like accumulation of energy proportionate to the length of the stimulated portion2 but the fact remains1 that one and the same irritant applied successively to two different points of a nerve does not irritate the muscle in the same degree4 ,munk also finds the velocity of transmission in a motor nerve increases as it approaches its termination in the muscle4#ajc #ei4 ,nothing can be more unlike the conduction of an electric current than this excitation of ,neurility2 nothing more accordant with the idea of it as a vital property of the tissue4 ,the notion of its being derived from a centre is on a par with the notion first successfully combated by ,haller1#ajd that the muscle derived its ,contractility from the nerves2 or the analogous notion that the electric organ in fishes derived its property from the brain4 ,indeed1 it was in support of the hypothesis that the brain was a battery1 and nerves the conductors1 that the phenomena observed in electrical fishes were frequently cited4 ,the electric organ was seen to be connected with the brain2 its discharges were under the control of the animal1 and were destroyed on one side when the brain on the corresponding side was destroyed4 ,but ,charles ,robin long ago suggested1 what indeed ought never to have been doubted1 that the brain was not the source of the electricity2 but that the tissue of the electric organ itself had this special property1 which the nerve merely called into activity4 ,the suggestion has been experimentally verified by ,m4 ,moreau1 who divided all the nerves supplying the electric organ on one side1 and1 having thus cut off all communication with the brain1 produced electrical discharges by irritating the nerves2 precisely as the muscles are made to contract when the divided nerves are irritated4 ,had the experiment ceased here1 it might have been interpreted on the old hypothesis3 the electric organ might be supposed to have a certain amount of electric force condensed in it1 stored up there1 as it is said to be in the nerves1 and discharged when the organ is irritated4 ,but experiment has decided this point also4 ,electric fishes notoriously exhaust their power by a few discharges1 and recover it after repose4 ,when ,m4 ,moreau had exhausted his mutilated fishes1 he replaced them in the water1 and allowed them repose4 ,on again irritating the divided nerves1 the discharges were again produced4#aje #fj4 ,on all sides the idea of nerves deriving their power from another source than their own substance is seen to be untenable4 ,a priori this might have been concluded4 ,neurility is the vital property of nerve-tissue4 8,nerve-force0 is nerve-action--molecular changes in the nerve itself1 not in some remote substance4 ,that nerve and centre are vitally connected is true2 and what their physiological relations are will hereafter be examined2 but we must dismiss the idea of nerves having the relation to centres that electrodes have to batteries4 #fa4 ,in proposing the term ,neurility1 ,i not only wished to get rid of the ambiguities which hovered round 8nerve-force0 and 8nerve-current10 but to recall the physiological principle that properties are dependent on structures2 and therefore that the special property of nerve-tissue is conditioned by its structure4 ,neurility is1 of course1 an abstraction2 but so is the nerve an abstraction4 ,the concrete manifestations are the several nerve-actions4 ,these we classify and specify4 ,one class we call sensory1 another class motor2 not because the nerve-action itself is different1 but because it is in each class in a different functional relation to other parts4 ,in classing men as governors and governed1 employers and employed1 we do not suppose anthropological distinctions1 but only differences in their social functions4 #fb4 ,this is the modification of the ,law of ,bell to which reference was made in #bf4 ,it replaces the idea of two different kinds of nerve1 sensory and motor1 by that of two different anatomical connections4 ,i need not reproduce here the argument with which ,i formerly criticised the supposed distinction between sensory and motor nerves2 because the old idea is rapidly falling into discredit1 and physiologists so eminent as ,vulpian and ,wundt have explicitly announced their adhesion to the principle of identity1--a principle which1 as ,vulpian truly remarks1 dominates the whole physiology of the nervous system4#ajf ,,the ,,hypothesis ,,of ,,specific ,,energies4 #fc4 ,one development of the theory of ,bell1 respecting the different kinds of nerve1 has been the still accredited hypothesis that each nerve has a 8specific energy10 or quality1 in virtue of which it acts and reacts only in one way4 ,the optic nerve1 no matter how stimulated1 only responds by a sensation of color1 the auditory nerve only by a sensation of sound2 and so on4 ,this hypothesis1 which 7as ,i learn from a correspondent7#ajg was originally propounded by ,bell himself1 was developed and made an ,european doctrine by ,johannes ,mller1 first in his remarkable treatise1 ber die phantastischen ,gesichtserscheinungen 7#ahbf71 and afterwards in his ,physiology4 ,like all good hypotheses1 it has been fruitful2 and ,helmholtz still holds it to be of extraordinary importance for the theory of perception4 ,although combated by a few physiologists1 it has kept its place firm in the general acceptance2 no doubt because it forms a ready explanation of the facts4 ,but1 as ,i often have to remark1 explanation is not demonstration4#ajh #fd4 ,the first criticism to be made on the hypothesis is that it commits the error of confounding function with property1 assigning as a specific quality of the nerve the reaction of the organ innervated4 ,thus ,mller speaks of the specific energy as 8the essential condition of the nerves in virtue of which they see light and hear sound40 ,but the optic nerve no more sees1 than the liver-nerve secretes bile4 ,that the optic nerve is one element in the mechanism on which vision depends1 is all that we can say1 ,mller declares that it is not sufficient to assume each nerve to be so constituted that it has a susceptibility to certain stimuli rather than to others2 but that 8with ,aristotle we must ascribe to each a peculiar energy as its vital quality4 ,sensation10 he adds1 8consists in the sensorium receiving through the medium of the nerves a knowledge of certain qualities1--a condition1 not of the external bodies1 but of the nerves themselves10--and these qualities are different in different nerves4 ,in other words1 he assumes a special substance for each special energy4 ,the sensation of color depends on the special ,visual substance 7,sehsinnsubstanz72 the sensation of sound on the ,auditory substance 7,hrsinnsubstanz72 and so on4 #fe4 ,we have here an hypothesis analogous to that of ,innate ,ideas1 or a priori ,forms of ,thought4 ,it is1 in fact1 only a reproduction of that conception carried into the sphere of ,sense4 ,no one thinks of assigning specific energies to the several muscles1 yet a movement of prehension is as different from a movement of extension1 a peristaltic movement is as different from a movement of occlusion1 as a sensation of sound is from a sensation of color4 ,if movement is common to both of the one class1 feeling is common to both of the other3 the forms and mechanism are different and specific4 ,muscles have the common property of contracting under stimulation2 whatever be the nature of the stimulus1 each muscle has its own particular response1 or mode of reaction3 the flexor always bending1 never extending the limb2 the sphincter always closing1 never opening the orifice4 ,the movements of the heart are not the same as those of the eye2 both are unlike the movements of the intestine4 ,there are muscles which respond to some stimuli1 and not to others4 ,those of the eye1 or of the vocal chords1 respond to impulses which would leave the masseter or biceps unstirred4 ,according to ,marey1 the hyoglossus of a frog will become tetanic under a stimulus of only ten pulses in a second2 whereas the gastrocnemius of that same frog resists a stimulus of less than twenty in a second4 ,we find the retina responding to ethereal pulses which leave the auditorius unaffected2 we find the muscles of a gnat's wing so exquisitely susceptible that the wing beats eight thousand times in a second1--a delicacy in comparison with which even our muscles of the eye are coarse4 #ff4 ,the facts which the hypothesis of specific energies is called on to explain are more consistently interpreted on the admission of a common property in nerve-tissue1 manifesting different degrees of excitability1 and entering into different mechanisms1 so that the functional results differ4 ,a nerve which may be stimulated from the skin will not respond at all1 or not in the same way1 if the stimulus be applied under the skin4 ,are we to suppose that the specific energy resides in one part of the nerve1 and not in another8#aji ,that the optic nerve responds to stimuli which will not sensibly excite a motor nerve1 depends on the terminal structures through which the stimulation is excited2 for the optic nerve itself1 apart from the retinal expansion1 is as insensible to light as the motor nerve is4 ,and the specific sensation1 or movement1 which results from stimulation of a nerve depends not on the nerve1 but on the mechanism of which the nerve is one element4 ,sensations of touch1 temperature1 and pain are assuredly specific2 they are as unlike each other as a sensation of taste is unlike a sensation of smell4 ,yet the same nerves1 variously stimulated1 produce all three sensations4 #fg4 ,we conclude1 therefore1 that the phrase 8specific energy0 is an elliptical expression for the particular office of a nerve4 ,in this meaning there is no obscurity4 ,the optic nerve is not a vasomotor nerve1 the skin nerve is not a muscle nerve2 the auditory nerve is a nerve of special sensation1 the vagus is a nerve of systemic sensation2 and so on4 ,neither movement nor sensation belongs to the nerves themselves4 ,,chapter ,,iv4 ,,sensibility4 #fh4 ,the principles laid down in the preceding chapter are equally applicable to the central system4 ,but here greater difficulties await us4 ,we cannot expect traditional views to be easily displaced1 when they have taken such hold on the mind1 as is the case with regard to ,sensibility4 ,to admit that all nerves have a common property1 and that their functional relations depend on the organs which they innervate1 demands small relinquishment of cherished opinions4 ,but to admit that all nerve-centres have a common property1 and that their functional relations depend on their anatomical connections1 is to sweep away at once a mass of theoretic interpretations which from long familiarity have acquired an almost axiomatic force4 ,that the brain1 and the brain only1 is the source and seat of ,sensibility is the postulate of modern ,physiology4 #fi4 ,the question is one of extreme complexity1 but may be greatly simplified1 if we can manage to reduce it to purely physiological terms1 and consider the phenomena in their objective aspect4 ,in dealing with nerves and their actions this was comparatively easy2 we had for the most part only physiological processes to unravel4 ,it is otherwise in dealing with nerve-centres--the subjective or psychological aspect of the phenomena inevitably thrusts itself on our attention2 and all the mysteries of ,feeling and ,thought cloud our vision of the neural process4 ,do what we will1 we cannot altogether divest ,sensibility of its psychological connotations1 cannot help interpreting it in terms of ,consciousness2 so that even when treating of sensitive phenomena observed in molluscs and insects1 we always imagine these more or less suffused with ,feeling1 as this is known in our own conscious states4 #gj4 ,feeling is recognized as in some way or other bound up with neural processes2 but ,physiology proper has only to concern itself with the processes2 and the question whether these can1 and do1 go on unaccompanied by ,feeling1 is1 strictly speaking1 one which belongs to ,psychology4 ,it demands as a preliminary that the term ,feeling be defined2 and the answer will depend upon that definition1 namely1 whether ,feeling be interpreted as synonymous with ,consciousness in the restricted sense1 or synonymous with the more general term ,sentience4 ,if the former1 then since there are unquestionably neural processes of which we are not conscious1 we must specify the particular groups which subserve ,feeling2 as we specify the particular groups which subserve the sensations of ,sight1 ,hearing1 ,taste1 etc42 and localize the separate functions in separate organs4 ,if the latter1 then1 since all neural processes have a common character1 we have only to localize the particular variations of its manifestation1 and distinguish sensitive phenomena as we distinguish motor phenomena4 #ga4 ,it is absolutely certain that the ,feeling we attribute to a mollusc is different from that which we attribute to a man2 if only because the organisms of the two are so widely different1 and have been under such different conditions of excitation4 ,if every feeling is the functional result of special organic activities1 varying with the co-operant elements1 we can have no more warrant for assuming the existence of the same particular forms of ,feeling in organisms that are unlike1 than for assuming the #dgth proposition of ,euclid to be presented by any three straight lines4 ,the lines are the necessary basis for the construction1 but they are not the triangle1 except when in a special configuration4 ,this is not denying that animals feel 7in the general sense of that term71 it is only asserting that their feelings must be very unlike our own4 ,even in our own race we see marked differences--some modes of feeling being absolutely denied to individuals only slightly differing from their fellows4 ,if1 however1 we admit that different animals must have different modes of ,feeling1 we must also admit that the neuro-muscular activities are generically alike in all1 because of the fundamental similarity in the structures4 ,whether we shall assign ,feeling to the mollusc or not will depend on the meaning of the term2 but1 at all events1 we require some term general enough to include the phenomena manifested by the mollusc1 and those manifested by all other animals4 ,sensibility is the least objectionable term4 ,unless we adopt some such general designation1 physiological and psychological interpretations become contradictory and obscure4 ,the current doctrine which assigns ,sensibility to the brain1 denying it to all other centres1 is seriously defective1 inasmuch as it implies that tissues similar in kind have utterly diverse properties2 in other words1 that the same nerve-tissue which manifests ,sensibility in the brain has no such property in the spinal cord4 #gb4 ,how is this tenable8 ,no one acquainted at first hand with the facts denies that the objective phenomena exhibited by the brainless animal have the same general character as those of the animal possessing a brain3 the actions of the two are identical in all cases which admit of comparison4 ,that is to say1 the objective appearances are the same2 differing only in so far as the mechanisms are made different by the presence or absence of certain parts4 ,the brain not being a necessary part of the mechanical adjustments in swimming1 or pushing aside an irritating object1 the brainless frog swims and defends itself in the same way as the normal frog4 ,but no sooner do we pass from the objective interpretation1 and introduce the subjective element of ,feeling among the series of factors necessary to the product--no sooner do we ask whether the brainless frog feels the irritation against which it struggles1 or wills the movements by which it swims--than the question has shifted its ground1 and has passed from ,physiology to ,psychology4 ,the appeal is no longer made to ,observation1 but to ,interpretation4 ,observation tells us here nothing directly of ,feeling4 ,what it does tell us1 however1 is the identity of the objective phenomena2 and ,physiology demands that a common term be employed to designate the character common to the varied phenomena4 ,sensibility is such a term4 ,but most modern physiologists1 under the bias of tradition1 refuse to extend ,sensibility to the spinal cord1 in spite of the evidences of the spinal cord possessing that property in common with the brain4 ,they prefer to invoke a new property2 they assign spinal action to a ,reflex ,mechanism which has nothing of the character of ,sensibility1 because they have identified ,sensibility with ,consciousness1 and have restricted ,consciousness to a special group of sensitive phenomena4 #gc4 ,nor is it to be denied that on this ground they have a firm basis4 ,every one could testify to the fact that many processes normally go on without being accompanied by consciousness1 in the special meaning of the term4 ,reflex actions1--such as winking1 breathing1 swallowing1--notoriously produced by stimulation of sensitive surfaces1 take place without our 8feeling0 them1 or being 8conscious0 of them4 ,hence it is concluded that the ,reflex mechanism suffices without the intervention of ,sensibility4 ,i altogether dispute the conclusion2 and in a future ,problem will endeavor to show that ,sensibility is necessary to ,reflex ,action4 ,but without awaiting that exposition we may at once confront the evidence1 by adducing the familiar fact that 8unconscious0 processes go on in the brain as well as in the spinal cord2 and this not simply in the sphere of ,volition1 but also in the sphere of ,thought4#aaj ,we act and think 8automatically0 at times1 and are quite 8unconscious0 of what we are doing1 or of the data we are logically grouping4 ,we often think as unconsciously as we breathe2 although from time to time we become conscious of both processes4 ,yet who will assert that these unconscious processes were independent of ,sensibility8 ,who will maintain that because cerebral processes are sometimes unaccompanied by that peculiar state named ,consciousness1 therefore all its processes are unaccompanied by ,feeling8 ,and if here we admit that the ,reflex mechanism in the brain is a sensitive mechanism1 surely we must equally admit that the similar ,reflex mechanism in the spinal cord is sensitive8 #gd4 ,let it be understood that ,sensibility is the common property of nerve-centres1 and physiological interpretations will become clear and consistent4 ,consciousness1 as understood by psychologists1 is not a property of tissue1 it is a function of the organism1 dependent indeed on ,sensibility1 but not convertible with it4 ,there is a greater distinction between the two than between ,sensation1 the reaction of a sensory organ1 and ,perception1 the combined result of sensory and cerebral reactions2 or than that between ,contractility1 the property of the muscles1 and ,flying1 the function of a particular group of muscles4 ,it is not possible to have ,consciousness without ,sensibility2 but perfectly possible to have ,sensations without ,consciousness4 ,this will perhaps seem as inconceivable to the reader as it seemed to ,schrder van der ,kolk4#aaa #ge4 ,let us illustrate it by the analogy of ,pain4 ,there is a vast amount of sensation normally excited which is totally unaccompanied by the feelings classed as painful4 ,the action of the special senses may be exaggerated to an intolerable degree1 but the exaggeration never passes into pain3 the retina may be blinded with excess of light1 and the ear stunned with sound--the optic nerve may be pricked or cut--but no pain results4 ,the systemic sensations also are habitually painless1 though they pass into pain in abnormal states4 ,clearly1 then1 ,pain is not the necessary consequence of ,sensibility2 and this is true not only of certain sensitive parts1 but of all2 as is proved in the well-known facts of ,analgesia1 in which complete insensibility of the skin as regards ,pain co-exists with vivid sensibility as regards ,touch and ,temperature4 ,hence the majority of physiologists refuse to acknowledge that the struggles and cries of an animal1 after removal of the brain1 are evidences of pain2 maintaining that they are 8simply reflex actions40 ,this is probable2 the more so as we know the struggles and cries which tickling will produce1 yet no pain accompanies tickling4 ,but if the struggles and cries are not evidence of pain1 they are surely evidence of ,sensibility4 #gf4 ,now for the term ,pain in the foregoing paragraph substitute the term ,consciousness1 and you will perhaps allow that while it may be justifiable to interpret the actions of a brainless animal as due to a mechanism which is unaccompanied by the specially conditioned forms of ,sensibility classed under ,consciousness--just as it is unaccompanied by the specially conditioned forms of ,perception and ,emotion--there is no justification for assuming the mechanism not to have been a sensitive mechanism4 ,the wingless bird cannot manifest any ,of the phenomena of flight2 but we do not therefore deny that its other movements depend on ,contractility4 #gg4 ,difficult as it must be to keep the physiological question apart from the psychological when treating of ,sensibility1 we shall never succeed in our analysis unless the two questions are separately treated4 ,the physiologist considers organisms and their actions from their objective side1 and tries to detect the mechanism of the observed phenomena4 ,these he has to interpret in terms of ,matter and ,motion4 ,the psychologist interprets them in terms of ,feeling4 ,the actions which we see in others we cannot feel1 except as visual sensations2 the changes which we feel in ourselves we cannot see in others1 except as bodily movements4 ,the reaction of a sensory organ is by the physiologist called a sensation1--borrowing the term from the psychologist2 he explains it as due to the stimulus which changes the molecular condition of the organ2 and this changed condition1 besides being seen to be followed by a muscular movement1 is inferred to be accompanied by a change of ,feeling4 ,the psychologist has direct knowledge only of the change of ,feeling which follows on some other change2 he infers that it is originated by the action of some external cause1 and infers that a neural process precedes1 or accompanies1 the feeling4 ,obviously there are two distinct questions here1 involving distinct methods4 ,the physiologist is compelled to complete his objective observations by subjective suggestions2 compelled to add ,feeling to the terms of ,matter and ,motion1 in spite of the radical diversity of their aspects4 ,the psychologist also is compelled to complete his subjective observations by objective interpretations1 linking the internal changes to the external changes4 ,a complete theory must harmonize the two procedures4 #gh4 ,in a subsequent ,problem we shall have to examine the nature of ,sensation in its psychological aspect2 here we have first to describe its physiological aspect4 ,to the psychologist1 a sensation is simply a fact of ,consciousness2 he has nothing whatever to do with the neural process1 which the physiologist considers to be the physical basis of this fact2 and he therefore regards the physiologists as talking nonsense when they talk of 8unconscious sensations10 the phrase being to him equivalent to 8unfelt feelings10 or 8invisible light40 ,it is quite otherwise with the physiologist1 who viewing a sensation solely as a neural process1 the reaction of a sensory organ1 can lawfully speak of unconscious sensations1 as the physicist can speak of invisible rays of light1--meaning those rays which are of a different order of undulation from the visible rays1 and which may become visible when the susceptibility of the retina is exalted4 ,he knows that there are different modes1 and different complexities of neural process2 to one class he assigns consciousness1 to the other unconsciousness4 ,if he would be severely precise1 he would never speak of sensation at all1 but only of sensory reaction4 ,but such precision would be pedantic and idle4 ,he wants the connotations of the term sensation1 and therefore uses it4 #gi4 ,the functional activity of a gland is stimulated by a neural process reflected from a centre2 by a similar process a muscle is called into action4 ,no one supposes that the neural process is1 in the one case secretory1 in the other motory3 in both it is the same process in the nerve2 and our investigation of it would be greatly hampered if we did not disengage it from all the suggestions hovering around the ideas of secretion and muscular action4 ,in like manner we must disengage the neural process of a sensory reaction from all the suggestions hovering around the idea of ,consciousness1 when that term designates a complex of many reactions4 ,in ,problem ,,iii4 we shall enter more particularly into the distinction between ,sensibility and ,consciousness2 for the present it must suffice to say that great ambiguity exists in the current usage of these terms4 ,sometimes ,consciousness stands as the equivalent of ,sensibility2 sometimes as a particular mode of ,sensibility known as ,reflection1 ,attention1 and ,thought4 ,the former meaning is an extension of the term similar to that given to the word ,rose1 which originally meaning ,red came to be restricted to a particular red flower2 and after other flowers of the same kind were discovered which had yellow and white petals1 instead of red1 the term rose still adhered even to these4 8,yellow ,rose0 is therefore as great a verbal solecism as unconscious sensation4 ,we have separated the redness from the rose1 and can then say that the color is one thing1 the flower another4 ,by a similar process of abstraction we separate ,consciousness from ,sensation1 and we can then say that there are sensations without consciousness4 ,in consequence of this1 psychologists often maintain that to have a sensation and be conscious of it are two different states4 ,we are said to hear a sound1 and yet not to be conscious of hearing it4 ,the sound excites a movement1 but it does not excite our consciousness4 ,now although it is true that there are roses which are not red1 it is not true that there are roses which have no color at all4 ,although it is true that there are sensations which are not of the particular mode of ,sensibility which psychologists specially designate as ,consciousness1 it is not true that there are sensations which are not modes of ,sensibility4 #hj4 ,and what is ,sensibility which1 on its subjective side1 is ,sentience8 ,in one sense it may be answered that we do not know4 ,in another sense it is that which we know most clearly and positively3 ,sentience forms the substance of all knowledge4 ,being the ultimate of knowledge1 every effort must be vain which attempts to explain it by reduction to simpler elements4 ,the human mind1 impatient of ultimates1 is always striving to pierce beyond the fundamental mysteries2 and this impatience leads to the attempts so often made to explain ,sensibility by reducing it to terms of ,matter and ,motion4 ,but inasmuch as a clear analysis of ,matter and ,motion displays that our knowledge of these is simply a knowledge of modes of ,feeling1 the reduction of ,sentience or ,sensibility to ,matter and ,motion is simply the reduction of ,sensibility to some of its modes4 ,this point gained1 a clear conception of the advantages of introducing the ideas of ,matter and ,motion will result4 ,it will then be the familiar and indispensable method of explaining the little known by the better known4 ,the objective aspect of things is commonly represented in the visible and palpable2 because what we can see we can also generally touch1 and what we can touch we can taste and smell2 but we cannot touch an odor nor a sound2 we cannot see them2 we can only connect the odorous and sonorous objects with visible or palpable conditions4 ,everywhere we find sensations referred to visible or palpable causes2 and hence the desire to find this objective basis for every change in ,sensibility4 ,the sensation1 or state of consciousness1 is the ultimate fact2 we can only explain it by describing its objective conditions4 #ha4 ,thus much on the philosophical side4 ,returning to our physiological point1 we must say that a sensation is1 objectively1 the reaction of a sensory organ1 or organism2 subjectively1 a change of feeling4 ,objectively it is a phenomenon of movement1 but distinguishable from other phenomena by the speciality of its conditions4 ,it is a vital phenomenon1 not a purely mechanical phenomenon4 ,although the molecular movement conforms1 of course1 to mechanical principles1 and may be viewed abstractly as a purely mechanical result1 yet1 because it takes place under conditions never found in machines1 it has characters which markedly separate it from the movements of machines4 ,among these differential characters may be cited that of selective adaptation1#aab which is most conspicuous in volition4 #hb4 ,in the early stages of animal evolution there is no differentiation into muscle and nerve4 ,the whole organism is equally sensitive 7or irritable7 in every part4 ,muscles appear1 and then they are the most sensitive parts4 ,nerves appear1 and the seat of ,sensibility has been transferred to them2 not that the muscles have lost theirs1 but their irritability is now represented by their dominant character of ,contractility1 and the nerves have taken on the special office of ,sensibility4 ,that is to say1 while both muscle and nerve form integral elements of the sensitive reaction1 the process itself is analytically conceived as a combination of two distinct properties1 resident in two distinct tissues4 #hc4 ,carrying further this analytical artifice1 ,i propose to distinguish the central organs as the seat of ,sensibility1 confining ,neurility to the peripheral nerves4 ,in physiological reality both systems1 central and peripheral1 are one2 the separation is artificial4 ,strictly speaking1 therefore1 ,neurility--or nerve-action--is the general property of nerve-tissue1 central and peripheral4 ,but since ,neurility may be manifested by nerves apart from centres1 whereas ,sensibility demands the co-operation of both1 and since we have often to consider the central process in itself1 without attending to the process in the nerves1 it is well to have two characteristic terms4 ,i shall therefore always use the term ,sensibility for the reactions of the nervous centres1--,sentience being its psychological equivalent2 although the reader will understand that in point of fact there is no break1 nor transformation1 as the wave of change passes from sensory nerve to centre1 and from centre to motor nerve3 there is one continuous process of change4 ,but just as we analytically distinguish the sensory from the motor element of this indissoluble process1 so we may distinguish the ingoing and outgoing stages from the combining stage4 ,sensibility1 then1 represents the property of combining and grouping stimulations4 #hd4 ,fully aware of the misleading connotations of the term1 and of the difficulty which will be felt in disengaging it from these1 especially in reference to ,consciousness1 ,i have long hesitated before adopting it4 ,but the advantages greatly outweigh the disadvantages4 ,sensibility has long been admitted to express the peculiar modes of reaction in plants and animals low down in the scale4 ,no one hesitates to speak of a sensitive plant1 or a sensitive surface4 ,the tentacles of a polype are said to be sensitive2 though probably no one thereby means that the polype has what psychologists mean by ,consciousness4 ,by employing the general term ,sensibility to designate the whole range of reactions peculiar to the nerve-centres1 when these special organs exist1 it will be possible to interpret all the physiological and psychological phenomena observed in animals and men on one uniform method4 ,the observed variations will then be referable to varieties in organisms4 #he4 ,suppose1 for illustration1 an organism like the human except that it is wholly deficient in ,sight1 ,hearing1 ,taste1 and ,smell4 ,it has no sense but ,touch--or the general reaction under contact with external objects4 ,it will move on being stimulated1 and will combine its movements differently under different stimulations4 ,it will feel1 and logically combine its feelings4 ,but its mass of feeling will be made of far simpler elements than ours2 its combinations fewer2 and the contents of its ,consciousness so very different from ours that we are unable to conceive what it will be like2 we can only be sure that it will not be very like our own4 ,this truncated ,organism will have its ,sensibility2 and we must assign this property to its central nerve-tissue1 as we assign our own4 ,if now we descend lower1 and suppose an organism with no centres whatever1 but which nevertheless displays evidence of ,sensibility--feelings and combinations of movements--we must then conclude that the property specialized in a particular tissue of the highly differentiated organism is here diffused throughout4 ,it is obvious that the sensations or feelings of these supposed organisms will have a common character with the feelings of more highly differentiated organisms1 although the modes of manifestation are so various4 ,if we recognize a common character in muscular movements so various as the rhythmic pulsation of the heart1 the larger rhythm of inspiration and expiration1 the restless movements of the eye and tongue1 the complexities of manipulation1 the consensus of movements in flying1 swimming1 walking1 speaking1 singing1 etc41 so may we recognize a common character in all the varieties of sensation4 ,the special character of a movement depends on the moving organ4 ,the special character of a sensation depends on the sensory organ4 ,contractility is the abstract term which expresses all possible varieties of contraction4 ,sensibility--or ,sentience--is the abstract term which expresses all possible varieties of sensation4 #hf4 ,the view here propounded may find a more ready acceptance when its application to all physiological questions has been tested1 and it is seen to give coherence to many scattered and hitherto irreconcilable facts4 ,meanwhile let a glance be taken at the inconsistencies of the current doctrine4 ,that doctrine declares one half of the gray substance of the spinal cord to be capable only of receiving a sensitive stimulation1 the other half capable only of originating a motor stimulation4 ,we might with equal propriety declare that one half of a muscle is capable only of receiving a contractile stimulation1 and the other half of contracting4 ,the ingoing nerve1 passing from the surface to the posterior part of the spinal cord1 excites the activity of the gray substance into which it penetrates2 with the anterior part of this gray substance an outgoing nerve is connected1 and through it the excitation is propagated to a muscle3 contraction results4 ,such are the facts4 ,in our analysis we separate the sensory from the motor aspect1 and we then imagine that this ideal distinction represents a real separation4 ,we suppose a phenomenon of ,sensibility independent of a phenomenon of ,contractility--suppose the one to be 8transformed0 into the other--and we then marvel 8how during this passage the excitation changes its nature40#aac #hg4 ,before exerting ingenuity in explaining a fact1 it is always well to make sure that the fact itself is correctly stated4 ,does the neural excitation change its nature in passing from the posterior to the anterior gray substance8 ,i can see no evidence of it4 ,indeed the statement seems to confound a neural process with a muscular process4 ,the neural process is one continuous excitation along the whole line of ingoing nerve1 centre1 and outgoing nerve1 which nowhere ceases or changes into another process1 until the excitation of the muscle introduces a new factor4 ,so long as the excitation keeps within the nerve-tissue1 it is one and the same process of change2 its issue in a contraction1 a secretion1 or a change in the conditions of consciousness1 depends on the organs it stimulates4 #hh4 ,i have already called attention to the artificial nature of all our distinctions1 and the necessity of such artifices4 ,they are products of that 8,secondary power ,by which we multiply distinctions1 then ,deem that our puny boundaries are things ,that we perceive1 and not that we have made40#aad ,the distinction of ,central and ,peripheral systems is not simply anatomical1 it has a physiological justification in this1 that the ,central ,system is the organ of connection4 ,any one part of it directly excited by an ingoing nerve propagates that excitation throughout the whole central mass1 and thus affects every part of the organism4 ,therefore we place ,sensibility in it4 ,but this general ,property subserves various ,functions1 according as the ,central ,system is variously related to different organs4 ,this fact has given rise to the idea that different portions of the cerebro-spinal axis have different properties--which is a serious error4 ,what is certain is that the ,cerebrum must have a different function from that of the ,thalami1 and the ,cerebellum one different from the ,medulla ,oblongata2 while that of the ,medulla ,spinalis is different from all4 ,precisely on the same grounds that a muscle-nerve has a different office from a skin-nerve1 or the pneumogastric from the acoustic4 ,but all nerves have one ,neurility in common2 all centres have one ,sensibility in common4 ,,chapter ,v4 ,,action ,,without ,,nerve-,,centres4 #hi4 ,it has long been one of the unquestioned postulates of ,physiology that no nerve-action can take place without the intervention of a centre2 and as a corollary1 that all movement has its impulse--reflex or volitional--from a centre4#aae ,the postulate rests on the assumption that nerves derive their 8force0 from their centre4 ,this assumption we have seen to be erroneous4 ,yet1 in consequence of its acceptance1 experimenters have failed to notice the many examples of nerve-action independent of centres4 ,indeed1 except ,schiff1 ,goltz1 and ,engelmann1 ,i can name no one who has ventured to suggest that movements may be excited through nerves without the co-operation of centres2#aaf nor have even they explicitly formulated the conclusion to which their observations point4 ,it is true that the majority of muscular movements are determined by a reflex from centres2 and that any break in the triple process of the ingoing nerve1 centre1 and outgoing nerve1 prevents such movements4 ,it is true that the more conspicuous and harmoniously co-ordinated phenomena belong to this class4 ,but it is also demonstrable that many nerve-actions may1 and some do1 take place by direct stimulation of the nerve1 or direct stimulation of the muscle1 without the intervention of a centre1 without even the intervention of a ganglion4 ,this must obviously be the case in animals which have no centres2 and even in some which have well-developed nervous centres1 there is every reason to believe that these centres often act rather in the way of co-ordinating than of directly stimulating actions4 #ij4 ,i was first led to doubt the reigning doctrine by a surprising observation 7frequently repeated7 after ,i had removed the whole nervous centres from a garden snail 7,helix pomatia74 ,the muscular mass called 8the foot0 was thrown into slow but energetic contraction whenever the skin was pricked with the point of a scalpel1 or touched with acid2 nay1 even when a glass rod dipped in the acid was brought close to1 without absolutely touching1 the skin1 the foot curled up1 and then slowly relaxed4 ,the same effect was produced on the 8mantle0--where there was of course no centre4 ,but direct irritation of the muscles under the skin produced no such contraction2 only through the skin could the stimulation take effect4 ,in one case ,i observed this strange phenomenon five hours after removal of the centres4 ,it was a great puzzle4 ,at first ,i concluded that there must be minute ganglia in the skin1 serving as reflex-centres4 ,i searched for them in vain2 and although a longer search on better methods might possibly have detected ganglionic cells1 ,i soon relinquished the search1 because ,i had other grounds for believing that even the presence of abundant ganglia would not suffice1 until some better proof were afforded that such ganglia were reflex-centres4 #ia4 ,that direct stimulation of the nerve suffices to move the muscles1 is familiar to all experimenters4 ,there is no centre1 or ganglion1 in the amputated leg of the frog1 which nevertheless contracts whenever the sciatic nerve is stimulated4 ,and after the nerve has been exhausted1 and refuses to respond to any stimulus1 the muscle itself may be directly stimulated4 ,inasmuch as the movement depends on the contractility of the muscles1 a stimulation through centre1 through motor-nerve1 or through muscle1 will be followed by contraction4 ,let us take a clear case of reflex action4 ,the pupil of the eye contracts when a beam of light falls on it1 and dilates when the beam is shut off4 ,the path of the neural process is normally this3 the light stimulates the optic nerve1 which in turn stimulates the corpora quadrigemina2 7here the nerves which move the eye are experimentally proved to be stimulated27 and it is through these that the pupil is caused to contract4 ,if the optic nerve be divided1 no such reflex takes place--proving that the contraction does not1 at least normally1 come from the ciliary ganglion4 ,but now it is matter of observation that the pupil will contract and dilate under the stimuli of light and darkness1 when there is no such reflex pathway open4 ,removal of the eye from the body obliterates this path1 cuts the eye off from all connection with the centre4 ,brown ,squard removed both eyes from a frog1 placed one in a dark box1 and left the other exposed to the light3 the pupil of the former was found dilated1 that of the latter contracted4 ,on reversing the experiment1 and placing the eye with contracted pupil in the dark box1 he found it there dilate1 while the dilated pupil exposed to the light contracted4#aag ,in frogs with very irritable tissues1 ,i have found not only the pupil contracting1 after the whole cranial cavity has been emptied1 but even the eyelid close1 on irritating the conjunctiva#aah--yet this is one of the typical reflex actions6 ,i am disposed to think that even the action of swallowing may be faintly excited by stimulation of the pharynx of a brainless frog2 but ,i have not observations sufficiently precise to enable me to speak confidently4 ,goltz has1 however1 shown that after removal of brain and spinal cord and heart1 there is spontaneous and active movement in sophagus and stomach4#aai ,this will no doubt be referred to the agency of the ganglionic plexus2 but similar movements have been observed by ,engelmann in the ureter1 and in isolated fragments of the ureter in which not a ganglionic cell was present4#abj #ib4 ,that nerves are stimulated by internal changes has long been recognized with reference to 8subjective sensations40 ,the divided nerve1 in that portion which remains connected with the centre1 will at times cause great pain4 ,obscure organic conditions1 changes of temperature1 states of the blood1 excite the nerves1 and the patient feels as if the surface of the amputated limb were irritated4 ,it is all very well to call these 8subjective sensations02 that does not alter the fact of the nerve being called into activity by other than the normal stimuli from the surface2 in like manner muscular movements 7which are not to be explained as 8subjective movements07 will be excited by organic stimuli when motor-nerves are separated from their centres4 ,in each case it has sufficed that the nerve should be excited2 and when excited1 no matter by what means1 the effect is always similar4 #ic4 ,here are a few facts4 ,stimulation of the nerves which send filaments to the chromatophores of the skin in reptiles causes the skin to become paler1 and even colorless3 the color-specks disappear under this contractile stimulus4 ,this being known1 ,goltz deprived a frog of brain1 spinal cord1 and heart1 thus eliminating all possible influence from them1 slit up the skin of the back1 and displayed the nerves which pass from each side of the spine to the skin2 these nerves he then divided on the right side1 and observed the skin on this side slowly become paler and paler1 till finally it was as yellow as wax2 the left side1 having its nerves intact1 retained its color4 ,two conclusions seemed to him warranted by this experiment3 ,first1 that even in the dead frog the nerves separated from their centre were still active2 secondly1 that the irritation of the nerves resulting from their section was the cause of the color-specks disappearing4 ,this second conclusion was strengthened when he found that the irritation was increased when he cut the nerves bit by bit4 ,it is not at present1 ,i believe1 clearly made out that the color-specks of the ,cephalopoda are in direct connection with nerves2 but it is tolerably certain that they are in some way under the influence of nervous stimulation1 directly or indirectly4 ,d',orbigny1 indeed1 goes so far as to say they are dependent on the will of the animal4#aba ,this seems very lax language2 but restricting ourselves to the fact of nervous influence1 the experiments of ,goltz receive further illustration in an observation ,i have elsewhere recorded4#abb ,i found that a strip of skin taken from the dead body of a calamary 7,loligo7 showed the color-specks expanding and contracting with vigor4 #id4 ,the heart is well known to beat after death1 if death be not the result of a gradual decay4 ,sometimes1 indeed1 its muscular irritability is so active that the heart will beat for hours4 ,e4 ,rousseau observed it beating in a woman twenty-seven hours after she had been guillotined4#abc ,not only will it beat after death1 but in many animals even after removal from the body3 the heart of a young puppy1 or kitten1 will beat for three or four hours after its removal2 that of a full-grown dog1 or cat1 not one hour2 whereas the beating of that of a tortoise1 or a frog1 will1 under proper precautions1 be preserved for days--and even after it has stopped1 it may be stimulated to fresh pulsations4 ,physiologists explain this spontaneous movement of the heart as due to the ganglia in its substance4 ,this explanation1 which is founded on what ,i cannot but regard as a purely imaginary view of the functions of ganglionic cells1 must stand or fall with that hypothesis4 ,a long and arduous investigation has led me to doubt whether in any case the heart's movements are primarily due to its ganglia2 at all events1 the same spontaneous movements are observed in the hearts of molluscs and crustaceans1 which are without even a trace of ganglia2 and in the hearts of mammalian embryos long before ganglia or nerve-fibres make their appearance4 ,not less certain is it that movements of contraction and dilatation are produced in the blood-vessels independently of all central influence4 ,this has been decisively proved by the ,italian physiologist1 ,mosso1 when experimenting on an organ isolated from the organism2 and although the vessels have their nerve cells and fibres1 he justly doubts whether it is to these that the stimulation is due1 because the phenomena are observed after the nervous vitality has disappeared4 ,goltz severed all the tissues in the leg of a rabbit1 so that the only connection of the leg with the rest of the body was through the crural vein and artery1 which kept up the circulation2 yet although the nerves of the skin were thus separated from their centre1 so that no sensation could be produced by stimulating the skin of the leg1 consequently no reflex from the centre on the vessels1 ,goltz found that a marked reddening of the skin from congestion of the capillaries followed the application of mustard to the skin4 ,physiologists who believe that the constriction and dilatation of blood-vessels are due to the action of the ganglionic cells distributed over the walls of the vessels will explain ,goltz's observation as a case of reflex action2 but those who agree with me that such an hypothesis respecting the part played by the cells is untenable1 will class the observation among other cases of direct stimulation4 #ie4 ,but passing from these perhaps questionable cases1 let us glance at other cases4 ,the mobile iris of the bird displays movements after the nerves have been divided4 ,even the voluntary striped muscles are not altogether motionless4 ,schiff divided the hypoglossus on one side1 and found1 of course1 the tongue paralyzed on that side2 but he also found that on the third day after the operation some of the muscles of that side were quivering3 the agitation spread to others1 till by the end of the fourth day all the fibres were rhythmically contracting4 ,from this time onwards1 the contractions were incessant2 though they were never able to move the tongue1 because the fibres did not contract simultaneously4 ,schiff also observed that the hairs over the eyes and the 8whiskers0 of cats1 rabbits1 and guinea pigs were for months after section of their nerves in incessant rhythmical vibration4 ,this was observed when the animals were asleep as when awake4 ,valentin records the spontaneous movements in the diaphragm of animals just killed2 and this even after section of the phrenic nerve4 ,the same movements may be seen in the operculum of fishes4 ,henle observed the spontaneous contractions of the intercostal muscles2 which ,schiff confirms1 adding that the movements observed by him in cats and birds were not simply contractions of some fibres1 but of all the muscles1 so that three or four excised ribs rhythmically contracted and expanded4 ,i have performed a great many experiments with a view of determining this question1 but the phenomena were so variable that ,i refrain from adducing any1#abd and merely state the general result as one in harmony with the foregoing examples4 ,the great variability of the phenomena depends upon the variable conditions of muscular irritability and anatomical relations4 ,when the heart of one woman is found beating twenty-seven hours after death1 while in most men and women it ceases after a few minutes1 we must be prepared to find different1 and even contradictory phenomena under varying unknown conditions4 ,there is1 however1 a general agreement among experimenters that muscular irritability increases after separation from nerve-centres1 and then quickly decreases again4 #if4 ,although the stimulation of muscles usually comes through a nerve-centre1 yet since the muscles do not derive their ,contractility from nerve-centres any stimulation will suffice4 ,now since we have abundant proof that sensory nerves are stimulated by certain organic changes1 by poisons in the blood1 excess of carbonic acid1 etc41 we are justified in concluding that motor nerves will be stimulated in like manner1 and thus muscular movement be produced occasionally without the intervention of a centre4 ,pressure on a motor nerve1 or the irritation which results from inflammation1 will determine contraction1 or secretion directly4 ,recently1 ,erb and ,westphal have disclosed the fact that the leg will be suddenly jerked out if the patella be gently tapped2 and they prove this not to be a reflex action1 because it follows with the same certainty after the skin has been made insensible4#abe ,there are doubtless many other phenomena which1 though commonly assigned to reflex stimulation1 are really due to direct stimulation4 ,research might profitably be turned towards the elucidation of this point4 ,since there is demonstrable evidence that a nerve when no longer in connection with its centre1 or with ganglionic cells1 may be excited by electricity1 pressure1 thermal and chemical stimuli1 we must conclude that even when it is in connection with its centre1 any local irritation from pressure1 changes in the circulation1 etc41 will also excite it4 ,but as such local excitations will have only local and isolated effects1 they will rarely be conspicuous4 ,,chapter ,,vi4 ,,what ,,is ,,taught ,,by ,,embryology8 #ig4 ,subject to the qualification expressed in the last chapter1 stimulation of muscles and glands involves a neural process in ingoing nerve1 centre1 and outgoing nerve4 ,these are the triple elements of the 8nervous arc40 ,if muscles were directly exposed to external influences1 they would be stimulated without the intervention of a centre2 but as a matter of fact they never are thus exposed1 being always protected by the skin4 ,did the skin-nerves pass directly to the muscles underneath1 they would move those muscles1 without the intervention of a centre2 but as a matter of fact the skin-nerves pass directly to a centre1 so that it is only through a centre that they can act upon the muscles4 ,were muscles and glands directly connected with sensitive surfaces1 their activity would indeed be awakened by direct stimulation2 but unless the muscles were so connected the one with the other1 by anastomosis of fibres or continuity of tissue1 that the movement of one was the movement of all1 there would need to be some other channel by which their separate energies should be combined and co-ordinated4 ,in the higher organisms anastomosis of muscles is rare1 and the combination is effected by means of the nerves4 #ih4 ,although analysis distinguishes the two elements of the neuro-muscular system1 assigning separate properties to the separate tissues1 an interpretation of the phenomena demands a synthesis1 so that a movement is to be conceived as always involving ,sensibility1 and a sensation as always involving ,motility4#abf ,in like manner1 although analysis distinguishes the various organs of the body1 assigning separate functions to each1 our interpretation demands their synthesis into an organism2 and we have thus to explain how the whole has different parts1 and how these different parts are brought into unity4 ,embryology helps us to complete the fragmentary indications of ,anatomy and ,physiology4 #ii4 ,take a newly laid egg1 weigh it carefully1 then hatch it1 and when the chick emerges1 weigh both chick and shell3 you will find that there has been no increase of weight4 ,the semifluid contents have become transformed into bones1 muscles1 nerves1 tendons1 feathers1 beak1 and claws1 all without increase of substance4 ,there has been differentiation of structure1 nothing else4 ,oxygen has passed into it from without2 carbonic acid has passed out of it4 ,the molecular agitation of heat has been required for the rearrangements of the substance4 ,without oxygen there would have been no development4 ,without heat there would have been none4 ,had the shell been varnished1 so as to prevent the due exchange of oxygen and carbonic acid1 no chick would have been evolved4 ,had only one part of the shell been varnished1 the embryo would have been deformed4 #ii;a4 ,the patient labors of many observers 7how patient only those can conceive who have made such observations67 have detected something of this wondrous history1 and enabled the mind to picture some of the incessant separations and reunions1 chemical and morphological4 ,each stage of evolution presents itself as the consequence of a preceding stage1 at once an emergence and a continuance2 so that no transposition of stages is possible2 each has its appointed place in the series 7,,problem ,i4 #ajg74 ,for in truth each stage is a process--the sum of a variety of co-operant conditions4 ,we1 looking forward1 can foresee in each what it will become1 as we foresee the man in the lineaments of the infant2 but in this prevision we always presuppose that the regular course of development will proceed unchecked through the regular succession of special conditions3 the infant becomes a man only when this succession is uninterrupted4 ,obvious as this seems1 it is often disregarded2 and the old metaphysical conception of potential powers obscures the real significance of ,epigenesis4 ,the potentiality of the cells of the germinal membrane is simply their capability of reaching successive stages of development under a definite series of co-operant conditions4 ,we foresee the result1 and personify our prevision4 ,but that result will not take place unless all the precise changes that are needful serially precede it4 ,a slight pressure in one direction1 insufficient to alter the chemical composition of the tissue1 may so alter its structure as to disturb the regular succession of forms necessary to the perfect evolution4 #ajj4 ,the egg is at first a microscopic cell1 the nucleus of which divides and subdivides as it grows4 ,the egg becomes a hollow sphere1 the boundary wall of which is a single layer of cells1 all so similar that to any means of appreciation we now possess they are indistinguishable4 ,they are all the progeny of the original nucleus and yolk1 or cell contents4 ,very soon1 however1 they begin to show distinguishable differences1 not perhaps in kind1 but in degree4 ,the wall of this hollow sphere is rapidly converted into the germinal membrane1 out of which the embryo is formed4 ,kowalewsky 7confirmed by ,balfour7 has pointed out how in the ,amphioxus the hollow sphere first assumes an oval shape1 and then1 by an indentation of the under side1 with corresponding curvature of the upper side1 presents somewhat the shape of a bowl4 ,the curvature increases1 and the curved ends approaching each other1 the original cavity is reduced to a thin line separating the upper from the under surface4 ,the cavity of the body is formed by the curving downwards of this double layer of the germinal membrane4 #aja4 ,this is not precisely the course observable in other vertebrates2 but in all1 the germinal membrane1 which lies like a watch-glass on the surface of the yolk1 is recognizable as two distinct layers of very similar cells4 ,what do these represent8 ,they are the starting-points of the two great systems3 ,instrumental and ,alimental4 ,the one yields the dermal surface2 the other the mucous membrane4 ,each follows an independent though analogous career4 ,the yolk furnishes nutrient material to the germinal membrane1 and so passes more or less directly into the tissues2 but unlike the germinal membrane1 it is not itself to any great extent the seat of generation by segmentation4 ,there are two yolks3 the yellow and the white 7which must not be confounded with what is called the white of egg72 and their disposition may be seen in the diagram 7,fig4 #ad7 copied from ,foster and ,balfour's work4 ,the importance of the white yolk is that it passes insensibly into a distinct layer of the germinal membrane1 between the two primary layers4#abg ,each of the three layers of the germinal membrane has its specific character assigned to it by embryologists1 who1 however1 are not all in agreement4 ,some authorities regard the topmost layer as the origin of the nervous system1 the epidermis1 with hair1 feathers1 nails1 horns1 the cornea and lens of the eye1 etc4 ,to the middle layer are assigned the muscular and osseous systems1 the sexual organs1 etc4 ,to the innermost layer1 the alimentary canal1 with liver1 pancreas1 gastric and enteric glands4 ,other authorities are in favor of two primary layers3 one for the nervous1 muscular1 osseous1 and dermal systems2 the other for the viscera and unstriped muscles4 ,between these two layers1 a third gradually forms1 which is specially characterized as the vascular4 ,illustration3 ,fig4 #ad4--;,diagrammatic section of an unincubated hen's egg4 bl1 blastoderm2 w y1 white yolk2 y y1 yellow yolk2 v t1 vitelline membrane2 x and w1 layers of albumen2 ch l1 chalaza2 a ch1 air-chamber2 i s m1 internal layer of shell membrane2 s m1 external layer2 s1 shell4 #ajb4 ,messrs4 ,foster and ,balfour1 avoiding the controverted designations of serous1 vascular1 and mucous layers1 or of sensorial1 motor germinative1 and glandular layers1 employ designations which are independent of theoretic interpretation1 and simply describe the position of the layers1 namely1 epiblast for the upper1 mesoblast for the middle1 and hypoblast for the under layer4 ,from the epiblast they derive the epidermis and central nervous system 7or would even limit the latter to the central gray matter71 together with some parts of the sense-organs4 ,from the mesoblast1 the muscles1 nerves 7and probably white matter of the centres71 bones1 connective tissue1 and blood-vessels4 ,from the hypoblast1 the epithelial lining of the alimentary canal1 trachea1 bronchial tubes1 as well as the liver1 pancreas1 etc4#abh ,klliker's suggestion is much to the same effect1 namely1 that the three layers may be viewed as two epithelial layers1 between which subsequently arises a third1 the origin of nerves1 muscles1 bones1 connective tissue1 and vessels4#abi #ajc4 ,the way in which the history may be epitomized is briefly this3 ,there are two germinal membranes1 respectively representing the ,instrumental and ,alimental ,systems4 ,each membrane differentiates1 by different appropriations of the yolk substance1 into three primary layers1 epithelial1 neural1 and muscular4 ,in the epiblast1 or upper membrane1 these layers represent3 #a1 the future epidermis with its derivatives--hair1 feathers1 nails1 skin glands1 and chromatophores2 #b1 the future nervous tissue2 #c1 the future muscular tissue4#acj 7,bone1 dermis1 connective tissue1 and blood-corpuscles are subsequent formations47 ,the hypoblast1 or under membrane1 in an inverted order presents a similar arrangement3 #a1 the unstriped muscular tissue of viscera and vessels2 #b1 the nervous tissue of the sympathetic system2 #c1 the epithelial lining of the alimentary canal with its glands4 ,fundamentally alike as these two membranes are1 they have specific differences2 but in both we may represent to ourselves the embryological unit constituted by an epithelial cell1 a nerve-cell1 and a muscle-cell4 ,all the other cells and tissues are adjuncts1 necessary1 indeed1 to the working of the vital mechanism1 but subordinated to the higher organites4 #ajd4 ,this conception may be compared with that of ,his in the division of ,archiblast and ,parablast assigned by him to the germ and accessory germ4#aca ,we can imagine1 he says1 the whole of the connective substances removed from the organism1 and thus leave behind a scaffolding in which brain and spinal cord would be the axis1 surrounded by muscles1 glands1 and epithelium1 and nerves as connecting threads4 ,all these parts stand in more or less direct relation to the nervous system4 ,all are continuous4 ,by a similar abstraction we can imagine this organic system removed1 and leave behind the connected scaffolding which is formed from the accessory germ2 but this latter has only mechanical significance2 the truly vital functions belong to the other system4 #aje4 ,the researches of modern histologists have all converged towards the conclusion that the organs of ,sense are modifications of the surface1 with epithelial cells which on the one side are connected with terminal hairs1 or other elements adapted to the reception of stimuli1 and are connected on the other side through nerve-fibres with the perceptive centres4 ,it has been shown that nerve-fibres often terminate in 7or among7 epithelial cells--sensory fibres at the surface1 and motor-fibres in the glands4#acb ,whether the fibres actually penetrate the substance of the cell1 or not1 is still disputed4 ,enough for our present purpose to understand that there is a physiological connection between the two1 and above all that sensory nerves are normally stimulated through some epithelial structure or other4 ,illustration3 ,fig4 #ae4--,transverse section of a ,blastoderm incubated for eighteen hours4 ,the section passes through the medullary groove1 m e4 ,a1 epiblast4 ,b1 mesoblast4 ,c1 hypoblast4 m f1 medullary fold1 c h1 notochord4 #ajf4 ,and this becomes clear when we go back to the earliest indications of development4 ,look at ,fig4 #ae1 representing a transverse section of the germinal membranes in a chick after eighteen hours' incubation4 ,here the three layers1 ,a1 ,b1 and ,c1 have the aspect of simple cells very slightly differing among each other4 ,yet since each layer has ultimately a progeny which is characteristically distinguishable1 we may speak of each not as what it now is1 but what it will become4 ,although the most expert embryologist is often unable to distinguish the embryo of a reptile from that of a bird or of a mammal1 at certain stages of evolution1 so closely does the one resemble the other1 yet inasmuch as the embryo of a reptile does not1 cannot become a bird1 nor that of a bird a mammal1 he is justified in looking forward to what each will become1 and in calling each embryo by its future name4 ,on the same ground1 although we cannot point to any such distinction between the layers of the blastoderm as ,i have indicated in the separation of ,instrumental and ,alimental ,systems1 nor specify any characters by which the cells can be recognized as epithelial1 neural1 and muscular1 yet a forward glance prefigures these divisions4 ,we know that the first result of the segmentation of the yolk is the formation of cells all alike1 which in turn grow and subdivide into other cells4 ,we know that these cells become variously modified both in composition and structure1 and that by such differentiations the simple organism becomes a complex of organs4 #ajg4 ,but here it is needful to recall a consideration sometimes disregarded1 especially by those who speak of ,differentiation as if it were some magical ,formative ,principle1 quite independent of the state of the organized substance which is formed4 ,there is a luminous conception--first announced by ,goethe1 and subsequently developed by ,milne ,edwards--which regards the organism as increasing in power and complexity by a physiological 8division of labor10 very similar to that division of employments which characterizes the developed social organism4 ,but the metaphor has sometimes been misleading2 it has been interpreted as indicating that ,function creates ,organ 7see ,,problem ,i4 #hh71 and as if ,differentiation itself were something more than the expression of the changes resulting from the introduction of different elements4 ,in the ,social ,organism a 8division of labor0 presupposes that laborers with their labor-materials are already existing2 the change is one of rearrangement3 instead of each laborer employing his skill in doing many kinds of work1 he restricts it to one kind1 which he is then able to do with less loss of time and power4 ,thus is social power multiplied without increase of population1 and the social organism becomes more complex by the differentiation of its organs4 ,it is not precisely thus with the ,animal ,organism during its evolution4 ,indeed to suppose that the differentiation of the germinal membrane into special tissues and organs takes place by any such division of employments1 is to fall into the ancient error of assuming the organism to exist preformed in the ovum4 ,the unequivocal teaching of ,epigenesis is that each part is produced out of the elements furnished by previous parts2 and for every differentiation there must be a difference in composition1 structure1 or texture--the first condition being more important than the second1 the second more important than the third4 ,the word protoplasm has almost as wide a generality as the word animal1 and is often used in forgetfulness of its specific values3 the protoplasm of a nerve-cell is not the same as that of a blood-cell1 a muscle-cell1 or a connective-tissue cell1 any more than a bee is a butterfly1 or a prawn a lobster4 ,no sooner has the specific character been acquired1 no sooner is one organite formed by differentiation1 than there is an absolute barrier against any transformation of it into any other kind of organite4 ,the nerve-cell1 muscle-cell1 and epithelial cell have a common starting-point1 and a community of substance2 but the one can no more be transformed into the other than a mollusc can be transformed into a crustacean4 ,in the homogeneous cellular mass which subsequently becomes the 8vertebral plates10 a group of cells is very early differentiated3 this is the rudimentary spinal ganglion1 which becomes enveloped in a membrane1 and then pursues a widely different course from that of the other cells surrounding it1 so that 8the same cell which was formerly an element of the vertebral plate now becomes a nerve-cell1 while its neighbors become cartilage-cells40#acc ,indeed all the hypotheses of transformation of tissues by means of ,differentiation are as unscientific as the hypotheses of the transformation of animals4 ,in the organism1 as in the ,cosmos1 typical forms once attained are retained4 ,there probably was a time in the history of the animal series when masses of protoplasm by appropriating different materials from the surrounding medium were differentiated into organisms more complex and more powerful than any which existed before4 ,but it is obvious that from a common starting-point there could have been no variations in development without the introduction of new elements of composition3 there might have been many modifications of structure1 but unless these facilitated modifications of composition1 there could never have resulted the striking differences observed in animal organisms4#acd #ajh4 ,to return from this digression1 we may liken the three primary layers of the germinal membranes to the scattered and slightly different masses of protoplasm out of which the animal kingdom was developed4 ,in this early stage there are no individualized organites--no nerve-cells or muscle-cells4 ,they are cells ready to receive modifications both of composition and structure1 appropriating slightly different elements from the yolk1 and according to such appropriation acquiring different properties4 ,and this is necessarily so1 since the different cells have not exactly the same relation to the yolk1 nor are they in exactly the same relation to the incident forces which determine the molecular changes4 ,the uppermost layer 7epiblast7 under such variations develops into epithelium and central nerve-tissue2 the epithelial cell cannot develop into a nerve-cell1 the two organites are markedly unlike1 yet both spring from a common root4 ,another modification results in the development of muscle-cells from the inner layer4 #aji4 ,hence we can understand how the surface is sensitive even in organisms that are without nerve-tissue2 and also how even in the highest organisms there is an intimate blending of epithelial with neural tissues4 ,the same indication explains the existence of neuro-muscular cells in the ,hydra1 recorded by ,kleinenberg1 and of neuro-muscular fibres in the ,bero1 by ,eimer4#ace ,in the simpler organisms the surface is at once protective1 sensitive1 and absorbent4 ,it shuts off the animal from the external medium1 and thus individualizes it2 at the same time it connects this individual with the medium2 for it is the channel through which the medium acts1 both as food and stimulus4 ,the first morphological change is one whereby a part of the surface is bent inwards1 and forms the lining of the body's cavity4 ,soon there follows such a modification of structure between the outer and inner surfaces 7ectoderm and endoderm7 that the one is mainly sensitive and protective1 the other mainly protective and absorbent4 ,the outer surface continues indeed to absorb1 but its part in this function is insignificant compared with that of the inner surface1 which not only absorbs but secretes fluids essential to assimilation4 ,the inner surface1 although sensitive1 is subjected to less various stimulation1 and its sensibility is more uniform4 #aaj4 ,the uppermost of the primary layers we have seen to be epithelial2 and we know that the first lines of the central nervous system are laid there4 ,a depression called the medullary groove is the first indication of the future cerebro-spinal axis4 ,some writers--,klliker1 for instance--regard this medullary groove as continuous with but different from the epithelial layer2 others maintain that it lies underneath the epithelium1 just as we see it in later stages1 when the differentiation between epithelial and nerve cell has taken place4 ,since no one disputes the fact that when the groove becomes a closed canal its lining is epithelial1 one of two conclusions is inevitable3 either the cells of the primary layer develop in the two diverse directions1 epithelial and neural2 or else epithelial cells can be developed on the surface of neural cells and out of them4 ,the latter conclusion is one which1 involving the conception of transformation1 would seem to be put out of court4 ,i think1 then1 we must admit that the under side of the primary layer of cells becomes differentiated into nerve-cells2 and this is in accordance with the observations of ,messrs4 ,foster and ,balfour4#acf #aaa4 ,while there is this intimate morphological and physiological blending of epithelial and neural organites1 there is an analogous relation between neural and muscular organites4 ,as the neural layer lies under the epithelial1 the muscular lies under the neural4 ,the surface stimulation passes to the centre1 and is reflected on the muscles4 ,embryology thus teaches why a stimulus from the external medium must be propagated to a nerve-centre before it reaches the muscles2 and why a stimulus on one part of the surface may set all the organism in movement1 by passing through a centre which co-ordinates all movements4 ,this1 of course1 only applies to the higher organisms4 ,in the simpler structures the sensitive surface is directly continuous with the motor organs4 ,it is unnecessary here to pursue this interesting branch of our subject2 nor need we follow the analogous evolution of the second germinal membrane representing the ,alimental ,system4 ,our attention must be given to what is known and inferred respecting the elementary structure of the nerves and centres1 on which mainly the interest of the psychologist settles1 since to him the whole of ,physiology is merged in nerve actions4 ,,chapter ,,vii4 ,,the ,,elementary ,,structure ,,of ,,the ,,nervous ,,system4 #aab4 ,the progress of science involves an ever-increasing ,analysis4 ,investigation is more and more directed towards the separated details of the phenomena previously studied as events2 the observed facts are resolved into their component factors1 complex wholes into their simpler elements1 the organism into organs and tissues4 ,but while the analytical process is thus indispensable1 it is1 as ,i have often to insist1 beset with an attendant danger1 namely1 that in drawing the attention away from one group of factors to fix it exclusively on another1 there is a tendency to forget this artifice1 and instead of restoring the factors provisionally left out of account1 we attempt a reconstruction in oblivion of these omitted factors4 ,hence1 instead of studying the properties of a tissue in all the elements of that tissue1 and the functions of an organ in the anatomical connections of that organ1 a single element of the tissue is made to replace the whole1 and very soon the function of the organ is assigned to this particular element4 ,the 8superstition of the nerve-cell0 is a striking illustration4 ,the cell has usurped the place of the tissue1 and has come to be credited with central functions2 so that wherever anatomists have detected ganglionic cells1 physiologists have not hesitated to place central functions4 ,by such interpretations the heart and intestines1 the glands and blood-vessels1 have1 erroneously1 ,i think1 their actions assigned to ganglionic cells4 ,it is unnecessary to point out the radical misconception which thus vitiates a great mass of anatomical exposition and physiological speculation4 ,i only call the reader's attention to the point at the outset of the brief survey we have now to make of what is known respecting the elementary structure of the nervous system4 ,,difficulties ,,of ,,the ,,investigation4 #aac4 ,so great and manifold are the difficulties of the search1 that although hundreds of patient observers have during the last forty years been incessantly occupied with the elementary structure of the nervous system1 very little has been finally established4 ,indeed1 we may still repeat ,lotze's sarcasm1 that 8microscopic theories have an average of five years' duration40 ,this need not damp our ardor1 though it ought to check a too precipitate confidence4 ,nothing at the present moment needs more recognition by the student than that the statements confidently repeated in text-books and monographs are very often for the most part only ingenious guesses1 in which ,observation is to ,imagination what the bread was to the sack in ,falstaff's tavern bill4 ,medical men and psychologists ought to be warned against founding theories of disease1 or of mental processes1 on such very insecure bases2 and physiological students will do well to remember the large admixture of ,hypothesis which every description of the nervous system now contains4 ,not that the potent aid of ,hypothesis is to be undervalued2 but its limits must be defined4 ,it may be used as a finger-post1 not as a foundation4 ,it may suggest a direction in which truth may be sought2 it cannot take the place of ,observation4 ,it may link together scattered facts2 it must not take the place of a fact4 ,we are glad of corks until we have learned to swim4 ,we are glad of a suggestion which will for the nonce fill up the gaps left by observation1 and hold the facts intelligibly together4 ,and both as suggestion and colligation1 ,hypothesis is indispensable4 ,indeed1 every discovery is a verified hypothesis2 and there is no discovery until verification has been gained3 up to this point it was a guess1 which might have been erroneous--a torchbearer sent out to look for a missing child in one direction1 while the child was wandering in another2 only when he finds the child can we acknowledge that the torchbearer pursued the right path4 ,hypothesis satisfies the intellectual need of an explanation1 but we must be wary lest we accept this fulfilment of a need as equivalent to an enlargement of knowledge2 we must not accept explanation as demonstration1 and suppose that because we can form a mental picture of the possible stages of an event1 therefore this picture represents the actual stages4 ,let us be alert1 forewarned against the tendency to seek evidence in support of a conclusion1 instead of seeking to unfold the conclusion step by step from the evidence4 ,to seek for evidence in support of a guess is very different from seeking it in support of a conclusion2 which latter practice is like that of people asking advice1 and only following it when it chimes in with their desires4 #aad4 ,is not the warning needed1 when we find anatomists guided by certain 8physiological postulates10 and consequently seeing only what these postulates demand8 ,for example1 there is the postulate of 8isolated conduction10 which is said to require that every nerve-fibre should pursue its course singly from centre to periphery4 ,accordingly the fibres are described as unbranched4 ,whatever may be the demand of the postulate1 or the felt necessity of the deduction1 the fact is that nerve-fibres do branch off during their course at various points2 nay1 it is doubtful whether any lengthy fibre is unbranched4 ,other postulates demand what fact plainly denies4 ,it is said to be 8necessary0 that every cell should have at least two fibres1 and that sensory and motor nerves should be directly connected through their respective cells4 ,these things cannot be seen1 but they are described with unhesitating precision4 ,diagrams are published in which the sensory fibres pass into the cells of the posterior horn of the spinal cord1 and these cells send off prolongations to the cells of the anterior horn1 and thence the motor fibres pass out to the muscles3 an absolutely impossible arrangement1 according to our present data6 ,again1 the postulate that nerve-force originates in the cells1 and that nerve-functions depend on cells1 required that the cells should be most abundant where the function was most energetic4 ,of course they were found most abundant in the required places--no notice whatever being taken of the facts which directly contradicted the deduction4 #aae4 ,among the serious obstacles to research we must reckon this tendency to substitute ,imaginary ,anatomy for ,objective ,anatomy4 ,i am conscious of the tendency in myself1 as ,i note it in others2 and have constantly to struggle against it1 though not perhaps always aware of it4 ,many a time have ,i had to relinquish plausible explanations1 which would have supported my speculations could ,i but have believed that they represented the facts2 but being unable to believe this1 ,i had to remember that hypotheses and explanations appear and disappear--only the solid fact lives4 ,if there is one lesson emphatically taught by ,philosophy1 it is the unwisdom of founding our conclusions on our desires rather than on the objective facts4 #aaf4 ,in the following pages a constantly critical attitude is preserved3 this is simply to keep active the sense of how much is still needed to be done before a satisfactory theory of the nervous system can be worked out4 ,the objective difficulties are greater than in any other department of ,anatomy4 ,the problem is to form a precise picture of what the organites are1 and of how they are arranged in the living tissue2 yet our present means of investigation involve as a preliminary that we should alter that arrangement1 removing some elements of the tissue1 and changing the state of others1 without knowing what were their precise state and arrangement before the change4 ,place a piece of nerve-tissue under the microscope1 without having subjected it to various mechanical and chemical operations1 and you can see next to nothing of its structure4 ,you must tear the parts asunder1 and remove the fat and nerve-sap 7plasmode7 before you can see anything2 you must coagulate the albumen1 and otherwise chemically alter the substances before a thin section can be made2 you must get rid of the tissues in which it is embedded1 without knowing what are the connections thus destroyed4 ,living neurine has no greater consistence than cream1 often no greater than oil4 ,how1 then1 can thin sections be made until this viscid substance has been hardened by alcohol or acids8 ,but substances thus acted on lose their constituent water1 which can no more be removed without alteration of their structure1 than it can be removed from certain salts without destruction of their special properties4 ,losing their water alone1 they become deformed4 ,they lose much more4 ,sometimes the loss can be estimated1 as in the case of the hyaline substance investing the nucleus during the process of segmentation in embryonic cells1 which may be seen to disappear when a weak solution of acid is applied4#acg ,at other times we are unable to say what has disappeared4 ,under different modes of preparation very different appearances are observed1 and anatomists are accordingly at variance4 ,yet unless some hardening method be adopted little can be seen6 ,stilling1 who has given his life to the study1 declares that no results are reliable which are obtained from the unprepared tissue1 because the mechanical isolation of the elements destroys the textural arrangement4#ach ,there is one method of hardening1 and only one1 which we can be certain does not chemically alter the structure1 and that is the freezing method4 ,the experiments of ,dr4 ,weir ,mitchell and ,dr4 ,richardson prove this1 because they prove that the brain of the living animal may be frozen and frozen again and again1 yet recover its vital activity when thawed4 ,professor ,rutherford has invented an admirable instrument for making sections of the frozen tissue1 of any delicacy that may be required2 but with the thinnest section there will still be certain difficulties of observation1 unless the tissue has undergone a staining process4 ,whatever is seen1 however1 in the frozen tissue is to be accepted as normal4 #aag4 ,two points must be determined before reliance can be placed on observations of tissues chemically acted on3 ,first1 we must prove that the forms now visible existed before the preparation--the chemical action merely unveiling them2 secondly1 we must estimate the part played by the elements which have been removed in order to make the rest visible4 ,we know1 for example1 that the nucleus often exists in the cell1 though an acid may be needed to make it visible4 ,we also know that cells which during life are quite free from visible granules are distinctly granulated after death1 even without external chemical action4 ,imagine the explanation of a steam-engine to be attempted by first taking it to pieces1 and examining these pieces1 with no account of the coals and steam which had previously been removed in order to facilitate the examination4 ,when we know the part played by coals and steam1 we may disregard these items of the active machine4 ,so when we know the part played by water1 fat1 amorphous substance1 and plasmode1 we may describe nerve-tissue without taking these into account4 #aah4 8,you have convinced me10 said ,rasselas to ,imlac1 8that it is impossible to be a poet40 ,my readers may1 perhaps1 infer from this enumeration of the difficulties that a knowledge of the minute anatomy of the nervous system is impossible4 ,not so2 but a knowledge of these difficulties should impress us with the necessity for a vigilant scepticism1 and the search after new methods4 ,if the difficulties are fairly faced1 they may be finally overcome4 ,what we must resign ourselves to at present is the conviction that our knowledge is not sufficiently accurate to be employed as a basis of deduction in the explanation of physiological and psychological processes4#aci #aai4 ,having said so much1 let me add that there are some positive materials1 and these yearly receive additions4 ,the organites are described with a general agreement as to their composition and structure--although there is much that is hypothetical even here4 ,neurine is known under two aspects3 the amorphous and the figured4 ,the figured1 which is the better known1 comprises cells of different kinds1 fibres and fibrils4 ,the amorphous1 more generally called ,neuroglia1 or nerve-cement1 is less understood1 and is indeed by many authorities excluded altogether from the nerve-tissue proper1 and relegated to the class of connective tissues4 ,,the ,,nerve-,,cell4 #abj4 ,it is unfortunate that the term nerve-cell is applied to organites of very variable structure4 ,nerve-cell is a generic term of which the species are many2 under it are designated organites in different stages--as infancy1 childhood1 and manhood are all included under ,man4 ,most commonly by nerve-cell is understood the ganglionic corpuscle1 conspicuous in its size and its prolongations1 such as it appears in the great centres1 and in ganglia4 ,it also designates smaller different organites1 sometimes called 8nuclei0 7,kerne71 sometimes grains 7,krner74 ,there would be advantage in designating the earlier stages as neuroblasts1 reserving the word cells for the more developed forms4 ,such a distinction would facilitate the discussion of whether nerve-fibres had or had not their origin in cells2 because while ,i1 for one1 see very coercive evidence against the accepted notion that all the fibres have their origin in the processes of ganglionic corpuscles1 ,i see no reason to doubt that both fibres and corpuscles have their origin in neuroblasts4 ,of this anon4 ,the cell is a composite organite1 the primary element being a microscopic mass of protoplasm1 or what may more conveniently be termed neuroplasm4 ,it appears as finely granulated and striated or fibrillated substance on a hyaline ground1 with water1 fat1 and diffused pigment in varying quantities4 ,the cell contains a nucleus1 and nucleolus--sometimes two4 ,like other animal cells1 it sometimes has a distinct cell-wall1 sometimes not4 ,its size and shape are variable3 sometimes distinctly visible to the naked eye1 generally visible only under the microscope4#adj ,it is round1 oval1 pyramidal1 club-shaped1 pear-shaped1 or many-cornered4 ,it has one1 two1 three1 or many outgrowths called 8processes10 and according to the processes it is known as unipolar1 bipolar1 and multipolar4 ,when there are no processes the cell is called apolar4 ,some idea of these processes may be formed if they are likened to the pseudopodia of ,amb and ,foraminifera4 ,compare ,fig4 #af1 a nerve-cell1 figured by ,gerlach1 with ,fig4 #ag1 one highly magnified1 in which ,max ,schultze's hypothesis is represented4 ,illustration3 ,fig4 #af4--,nerve-cell from anterior horn of spinal cord 7man71 magnified #aej diameters4 a1 cell process unbranched passing into or joining an axis cylinder1 the other processes are branched2 b1 pigment4 ,the nucleus and nucleolus are visible4 ,illustration3 ,fig4 #ag4--,nerve-cell from the anterior gray substance of the spinal cord of a calf magnified #fjj4 a1 the axis cylinder2 b1 the branched process4 ,the neuroplasm is represented as distinctly fibrillated1 with granular substance interspersed4 ,nucleus and nucleolus very distinct4 #aba4 ,such is a general description of the nerve-cell as it is seen in various places1 and under various modes of preparation4 ,how much is due to preparation we cannot positively say4 ,while we always discover fibrine in the blood after it is withdrawn from the vessels1 we know that fibrine as such does not exist in the circulating blood4 ,and if neurine is a semi-liquid substance1 we may doubt whether in the living cell it is fibrillated4 ,doubts have been thrown even on the normal existence of the granular substance1 which has been attributed to coagulation4 ,thus we know that the nucleus of the white blood-corpuscle appears perfectly homogeneous until subjected to heat1 yet at a certain temperature 7#hf ,f47 it assumes the aspect of a fine network4 ,haeckel observed the hyaline substance of the neurine in crayfish become troubled and changed directly any fluid except its own blood-serum came in contact with it4 ,leydig noticed the transparent ganglion of a living ,daphnia become darker and darker as the animal died2 and ,i saw something like this1 after prolonged struggles of a ,daphnia to escape from a thread in which its leg was entangled4 ,charles ,robin1 indeed1 asserts that the passage from the hyaline to the finely granulated state is a characteristic of the dying cell4#ada ,on the other hand1 it should be noted that ,max ,schultze describes a fibrillated appearance in cells just removed from the living animal1 and placed in serum4 ,when1 therefore1 one observer describes the neuroplasm as being clear as water1 another as finely granular1 and a third as fibrillated1 we must conclude that the observations refer to cells1 #a1 under different states of vitalization1 or1 #b1 under different modes of preparation4 ,on the first head we note that some nerve-cells are so perishable that ,trinchese declares he could find no cells in the ganglia of a cuttlefish which had been dead twenty-four hours1 although they were abundant in one recently killed4#adb ,on the second head we note that the changes wrought by modes of preparation cannot be left out of consideration4 ,auerbach notices that the cells and fibres apparent in the plexus myentericus after an acid has been applied1 cannot be detected before that application--nothing is visible but a pale gelatinous network1 with here and there knots of a paler hue2 and ,i remember my surprise on examining the fresh spinal cord of a duck-embryo1 and finding no trace of cells such as ,i had that very morning seen in the cord of a chick of earlier date1 but which had been soaked in weak bichromate of potash4 ,now we have excellent grounds for believing that in both cases these organites were present1 and that it was the reagent which disclosed their presence in the chick2 and so in other cases we must ask whether the forms which appear under a given mode of preparation are simply unmasked1 or are in truth produced by the reagent8 ,this question we can rarely answer4 ,if one of the very large cells be taken from the ganglion of a living mollusc1 and be gently pressed till it bursts1 the discharged contents will be seen to be of a hyaline viscid substance1 with fine granules but no trace of fibres4 ,yet we must not rashly generalize from this1 and declare that in the vertebrate cells the substance is not also fibrillated4 ,as a good deal of speculation rests on the assumption of the fibrillated cell-contents1 ,i have thought it worth while to note the uncertainty which hovers round it4 #abb4 ,among the uncertainties must be reckoned the question as to the cell-processes4 ,the existence of apolar and unipolar cells is flatly denied by many writers1 who assert that the appearances are due to the fragility of the processes4 ,fragile the processes are1 and evidence of their having been broken off meet us in every preparation2 but the denial of apolar and unipolar cells seems to me only an example of the tendency to substitute hypothesis for observation 7 #aad74 ,the 8postulate0 which some seem to regard as a 8necessity of thought0 that every nerve-cell shall have at least two fibres1 one ingoing1 the other outgoing1 is allowed to override the plain evidence4#adc ,it originated in the fact first noticed by ,wagner and ,charles ,robin that certain cells in the spinal ganglia of fishes are bipolar4 ,the fact was rapidly generalized1 in spite of its not being verified in other places2 the generalization was accepted because 7by a strange process of reasoning running counter to all physiological knowledge7 it was thought to furnish an elementary illustration of the reflex process4 ,as the centre had its ingoing and outgoing nerve1 so the cell was held to be a centre 8writ small10 and required its two fibres1 ,no one paused to ask1 how a cell placed in the track of an ingoing nerve could fulfil this office of a reflex centre2 no one supposed that the portion of the sensory fibre which continued its course1 after the interruption of the cell1 was a motor fibre4 ,what does ,observation teach8 ,it teaches that at first all nerve-cells are apolar4 ,even in the cortex of the cerebrum1 where 7unless we include the nuclei and grain-like corpuscles under cells7 all the cells are finally multipolar1 there is not one which has a process1 up to the seventh or eighth day of incubation 7in the chick72 from that day1 and onwards1 cells with one process appear2 later on1 cells with two1 and later still1 with three4 ,by this time all the apolar cells have disappeared4 ,they may therefore be regarded as cells in their infancy4 ,however that may be1 we must accept the fact that apolar cells exist2 whether they can co-operate in neural functions1 is a question which must be decided after the mode of operation of cells is placed beyond a doubt4 #abc4 ,if apolar cells are embryonic forms of cells which afterwards become multipolar1 this interpretation will not suffice for the unipolar cells4 ,they are not only abundant1 but are mature forms in some organs1 and in some animals2 though in some organs they may truly be regarded as embryonic4 ,thus in the human embryo up to the fourth month all the cells of the spinal cord are said to be unipolar1#add later on they become multipolar4 ,but in birds1 rabbits1 dogs1 and even man1 the cells in the spinal ganglia are mainly 7if not wholly7 unipolar2#ade nor is there any difficulty in observing the same fact in the sophageal ganglia of molluscs 7see ,fig4 #bb74 ,such are the observations4 ,they have indeed been forced into agreement with the bipolar postulate1 by the assumption that the single process branches into two1 one afferent1 the other efferent4#adf ,but before making observation thus pliant to suit hypothesis1 it would be well to look more closely into the evidence for the hypothesis itself4 ,for my own part1 ,i fail to see the justification of the postulate2 whereas the existence of unipolar cells is an observation which has been amply verified4 ,illustration3 ,fig4 #ah4--,supposed union of two nerve-cells and a fibre4 ,the processes subdivide into a minute network1 in which the fibre also loses itself4 #abd4 ,bipolar cells abound2 multipolar cells are still more abundant2 and these are the cells found in the gray substance of the neural axis4 ,deiters1 in his epoch-making work1#adg propounded an hypothetic schema which has been widely accepted4 ,finding that the large cells in the anterior horn of the spinal cord gave off processes of different kinds1 one branched1 the other unbranched1 he held that the latter process was the origin of the axis cylinder of a nerve-fibre1 whereas the branched process was protoplasm which divided and subdivided1 and formed the connection between one cell and another4 ,gerlach has modified this by supposing that the minute fibrils of the branching process reunite and form an axis cylinder 7,fig4 #ah74 ,there is no doubt that some processes terminate in a fine network2 and there is a probability 7not more7 that the unbranched process is always continuous with the axis cylinder of a motor nerve1 as we know it sometimes is with that of a dark-bordered fibre in the white substances4 ,this1 though probable1 is1 however1 very far from having been demonstrated4 ,once or twice ,klliker1 ,max ,schultze1 and ,gerlach have followed this unbranched process as far as the root of a motor nerve2 and they infer that although it could not be traced further1 yet it did really join an axis cylinder there4 ,in support ,of this inference came the observations of ,koschennikoff1#adh that in the cerebrum and cerebellum1 processes were twice seen continuous with dark-bordered nerve-fibres4 ,but the extreme rarity of such observations amid thousands of cells is itself a ground for hesitation in accepting a generalized interpretation1 the more so since we have ,henle's observation of the similar entrance of a branched process into the root4#adi ,now it must be remembered that the branched process is by no anatomist at present regarded as the origin of the axis cylinder2 so that if it can enter the root without being the origin of a nerve-fibre1 we are not entitled to assume that the entrance of the unbranched process has any other significance 7on this head compare #ade71 especially when we reflect that no trustworthy observer now professes to have followed a nerve-fibre of the posterior root right into a multipolar cell4 ,figures1 indeed1 have been published which show this1 and much else2 but such figures are diagrams1 not copies of what is seen4 ,they belong to ,imaginary ,anatomy4#aej ,the relation of the cell-process to the nerve-fibre will be discussed anon4 ,illustration3 ,fig4 #ai4--;,anastomosing nerve-cells 7after ,gratiolet74 a1 body of the cell2 c1 process of uniting two cells2 d1 branching process4 #abe4 ,a word in passing on the contradictory assertions respecting the anastomosis of nerve-cells4 ,that the gray substance forms a continuum of some kind is certain from the continuity of propagation of a stimulus4 ,but it is by no means certain that one cell is directly united to its neighbor by a cell-process4 ,eminent authorities assert that such direct union never takes place2 others1 that it is a rare and insignificant fact2 others1 that it is constant1 and 8demanded by physiological postulates40 ,i will not1 in the presence of distinct affirmations1 venture to deny that such appearances as are presented in ,fig4 #ai may occasionally be observed2 the more so as ,i have myself seen perhaps half a dozen somewhat similar cases2 but it is the opinion of ,deiters and ,klliker that all such appearances are illusory4#aea ,granting that such connections occur1 we cannot grant this to be the normal mode2 especially now the more probable supposition is that the connection is normally established by means of the delicate ramifications of the branching processes4 ,imaginary ,anatomy has not been content with the cells of the anterior horn being thus united together1 to admit of united action1 but has gone further1 and supposed that the cells of the posterior horn1 besides being thus united1 send off processes which unite them with the cells of the anterior horn--and thus a pathway is formed for the transmission of a sensory impression1 and its conversion into a motor impulse4 ,what will the reader say when informed that not only has no eye ever beheld such a pathway1 but that the first step--the direct union of the sensory nerve-fibre with a cell in the posterior horn--is confessedly not visible8 #abf4 ,the foregoing criticisms will perhaps disturb the reader who has been accustomed to theorize on the data given in text-books2 but he may henceforward be more cautious in accepting such data as premises for deduction1 and will look with suspicion on the many theories which have arisen on so unstable a basis4 ,when we reflect how completely the modern views of the nervous system1 and the physiological1 pathological1 and psychological explanations based on these views1 are dominated by the current notions of the nerve-cell1 it is of the last importance that we should fairly face the fact that at present our knowledge even of the structure of the nerve-cell is extremely imperfect2 and our knowledge of the part it plays--its anatomical relations and its functional relations--is little more than guesswork6 ,,the ,,nerves4 #abg4 ,we now pass to the second order of organites2 and here our exposition will be less troubled by hesitations1 for although there is still much to be learned about the structure and connections of the nerve-fibres1 there is also a solid foundation of accurate knowledge4 ,illustration3 ,fig4 #bj4--;a1 axis cylinder formed by the fibrils of the cell contents1 and at a' assuming the medullary sheath2 b1 naked axis cylinder from spinal cord4 ,a nerve is a bundle of fibres within a membranous envelope supplied with blood-vessels4 ,each fibre has also its separate sheath1 having annular constrictions at various intervals4 ,it is more correctly named by many ,french anatomists a nerve-tube rather than a nerve-fibre2 but if we continue to use the term fibre1 we must reserve it for those organites which have a membranous sheath1 and thereby distinguish it from the more delicate fibril which has none4 ,the nerve tube or fibre is thus constituted3 within the sheath lies a central band of neuroplasm identical with the neuroplasm of nerve-cells1 and known as the axis cylinder2 surrounding this band is an envelope of whitish substance1 variously styled myeline1 medullary sheath1 and white substance of ,schwann3 it is closely similar to the chief constituent of the yolk of egg1 and to its presence is due the whitish color of the fibres1 which in its absence are grayish4 ,the axis cylinder must be understood as the primary and essential element1 because not only are there nerve-fibrils destitute both of sheath and myeline yet fulfilling the office of ,neurility1 but at their terminations1 both in centres and in muscles1 the nerve-fibres always lose sheath and myeline1 to preserve only the neuroplasmic threads of which the axis cylinder is said to be composed4 ,in the lowest fishes1 in the invertebrates1 and in the so-called sympathetic fibres of vertebrates1 there is either no myeline1 or it is not separated from the neuroplasm4 #abh4 ,nerve-fibres are of two kinds--#a4 ,the dark-bordered or medullary fibres1 which have both sheath and myeline1 as in the peripheral system2 or only myeline1 without the sheath1 as in the central system4 #b4 ,the non-medullary fibres1 which have the sheath1 without appreciable myeline--such are the fibres of the olfactory1 and the pale fibres of the sympathetic4 ,nerve-fibrils are neuroplasmic threads of extreme delicacy1 visible only under high magnifying powers 7#gjj-hjj71 which abound in the centres1 where they form networks4 ,the fibrils also form the terminations of the fibres4 ,many fibrils are supposed to be condensed in one axis cylinder4 ,this is represented by ,max ,schultze in ,figs4 #ag and #bj4 #abi4 ,as may readily be imagined1 the semi-liquid nature of the neuroplasm throws almost insuperable difficulties in the way of accurately determining whether the axis cylinder in the living nerve is fibrillated or not2 whether1 indeed1 any of the aspects it presents in our preparations are normal4 ,authorities are not even agreed as to whether it is a pre-existent solid band of homogeneous substance1 or a bundle of primitive fibrils1 or a product of coagulation4#aeb ,rudanowsky's observations on frozen nerves convinced him that the cylinder is a tubule with liquid contents4#aec ,my own investigations of the nerves of insects and molluscs incline me to the view of ,dr4 ,schmidt of ,new ,orleans1 namely1 that the cylinder axis consists of minute granules arranged in rows and united by a homogeneous interfibrillar substance1 thus forming a bundle of granular fibrils enclosed in a delicate sheath#aed--;in other words1 a streak of neuroplasm which has a fibrillar disposition of its granules4 ,we ought to expect great varieties in such streaks of neuroplasm2 and it is quite conceivable that in the ,rays and the ,torpedo there are axis cylinders which are single fibrils1 and others which are bundles1 with finely granulated interfibrillar substance4#aee ,the fibres often present a varicose aspect1 as represented in ,fig4 #ba4 ,it is1 however1 so rarely observed in the fresh tissue1 that many writers regard it 7as well as the double contour7 as the product of preparation4#aef ,it is1 indeed1 always visible after the application of water4 ,we need say no more at present respecting the structure of nerve-fibres1 except to point out that we have here an organite not less complex than the cell4 ,illustration3 ,fig4 #ba4--,nerve-fibres from the white substance of the cerebrum4 a1 a1 a1 the medullar contents pressed out of the tube as irregular drops4 ,,the ,,neuroglia4 #acj4 ,besides cells and fibres1 there is the amorphous substance1 which constitutes a great part of the central tissue1 and also enters largely into the peripheral tissue4 ,it consists of finely granular substance1 and a network of excessively delicate fibrils1 with nuclei interspersed4 ,its character is at present sub judice4 ,some writers hold it to be nervous1 the majority hold it to be simply one of the many forms of connective tissue3 hence its name neuroglia1 or nerve-cement4 ,in the convolutions of the frozen brain ,walther finds the cells and fibres imbedded in a structureless semi-fluid substance wholly free from granules2 the granules only appear there when cells have been crushed4 ,it is to this substance he attributes the fluctuation of the living brain under the touch1 like that of a mature abscess2 the solidity which is felt after death is due to the coagulation of this substance4 ,unhappily we have no means of determining whether the network visible under other modes of investigation is present1 although invisible1 in this substance4 ,the neuroglia1 as it appears in hardened tissues1 must therefore be described with this doubt in our minds4 ,if we examine a bit of central gray substance where the cells and fibres are sparse1 we see1 under a low power1 a network of fibrils in the meshes of which lie nerve-cells4 ,under very high powers we see outside these cells another network of excessively fine fibrils embedded in a granular ground substance1 having somewhat the aspect of hoar-frost1 according to ,boll4 ,it is supposed that the first network is formed by the ultimate ramifications of the nerve-cell processes1 and that the second is formed by ramifications of the processes of connective cells4 ,in this granular1 gelatinous1 fibrillar substance nuclei appear1 together with small multipolar cells not distinguishable from nerve-cells except in being so much smaller4 ,these nuclei are more abundant in the tissue of young animals1 and more abundant in the cerebellum than in the cerebrum4 ,the granular aspect predominates the fresher the specimen1 though there is always a network of fibrils2 so that some regard the granules as the result of a resolution of the fibrils1 others regard the fibrils as the linear crystallization 7so to speak7 of the granules4#aeg #aca4 ,such is the aspect of the neuroglia4 ,i dare not venture to formulate an opinion on the histological question whether this amorphous substance is neural1 or partly neural and partly connective 7a substance which is potentially both1 according to ,deiters and ,henle71 or wholly connective4 ,the question is not at present to be answered decisively1 because what is known as connective tissue has also the three forms of multipolar cells1 fibrils1 and amorphous substance2 nor is there any decisive mark by which these elements in the one can be distinguished from elements in the other4 ,the physical and chemical composition of ,neuroglia and ,neuroplasm are as closely allied as their morphological structure4 ,and although in the later stages of development the two tissues are markedly distinguishable1 in the early stages every effort has failed to furnish a decisive indication4#aeh ,connective tissue is dissolved by solutions which leave nerve-tissue intact4 ,can we employ this as a decisive test8 ,no1 for if we soak a section of the spinal cord in one of these solutions1 the pia mater and the membranous septa which ramify from it between the cells and fibres disappear1 leaving all the rest unaltered4 ,this proves that ,neuroglia is at any rate chemically different from ordinary connective tissue1 and more allied to the nervous4 ,as to the staining process1 so much relied on1 nothing requires greater caution in its employment4 ,stieda found that the same parts were sometimes stained and sometimes not2 and ,mauthner observed that in some cells both contents and nucleolus were stained1 while the nucleus remained clear1 in other cells the contents remained clear2 and some of the axis cylinders were stained1 the others not4#aei ,lister found that the connective tissue between the fibres of the sciatic nerve1 as well as the pia mater1 were stained like the axis cylinders2#afj and in one of my notes there is the record of both 7supposed7 connective cells and nerve-cells being stained alike1 while the nerve-fibres and the 7supposed7 connective fibres were unstained4 ,whence ,i conclude that the supposition as to the nature of the one group being different from that of the other was untenable1 if the staining test is to be held decisive4 #acb4 ,the histological question is raised into undue importance because it is supposed to carry with it physiological consequences which would deprive the neuroglia of active co-operation in neural processes1 reducing it to the insignificant position of a mechanical support4 ,i cannot but regard this as due to the mistaken tendency of analytical interpretation1 which somewhat arbitrarily fastens on one element in a complex of elements1 and assigns that one as the sole agent4 ,whether we call the neuroglia connective or neural1 it plays an essential part in all neural processes1 probably a more important part than even the nerve-cells1 which usurp exclusive attention6 ,to overlook it1 or to assign it a merely mechanical office1 seems to me as unphysiological as to overlook blood-serum1 and recognize the corpuscles as the only nutrient elements4 ,the notion of the neuroglia being a mere vehicle of support for the blood-vessels arises from not distinguishing between the alimental and instrumental offices4 ,in the function of a limb1 bone is a co-operant4 ,in the function of a centre1 connective tissue is a co-operant2 so that even if we acknowledge neuroglia to be a special form of connective tissue1 it is an agent in neural processes2 what its agency is1 will be hereafter considered4 ,following ,bidder and ,kupffer1 the ,dorpat school proclaimed the whole of the gray substance of the posterior half of the spinal cord to be connective tissue2 and ,blessig maintained that the whole of the retina1 except the optic fibres1 was connective tissue4#afa ,even those anatomists who regarded this as exaggerated1 admitted that connective tissue largely enters into the gray substance1 especially if the granular ground substance be reckoned as connective1 the nerve-cells being very sparse in the posterior region4 ,be it so4 ,let us admit that the gray matter of the frog's spinal cord is mainly composed of neuroglia1 in which a very few multipolar nerve-cells are embedded4 ,what must our conclusion be8 ,why1 that since this spinal cord is proved to be a centre of energetic and manifold reflex actions--even to the extent of forcing many investigators to attribute sensation and volition to it--this is proof that connective tissue does the work of nerve-tissue1 and that the neuroglia is more important than nerve-cells6 ,three hypotheses are maintainable--#a4 ,the neuroglia is the amorphous ground-substance of undeveloped tissue 7neuroplasm7 out of which the cells and fibres of nerve-tissue and connective tissue are evolved4 #b4 ,it is the product of dissolved nerve cells and fibres4 #c4 ,it is the undeveloped stage of connective tissue4 ,for physiological purposes we may adopt any one of these views1 provided we keep firm hold of the fact that the neuroglia is an essential element1 and in the centres a dominant element4 ,to make this clear1 however1 we must inquire more closely into the relations of the three elements1 nerve-cells1 fibres1 and neuroglia4 ,,the ,,relations ,,of ,,the ,,organites4 #acc4 ,in enumerating among the obstacles to research the tendency to substitute hypothetic deductions in place of objective facts1 ,i had specially in my mind the wide-reaching influence of the reigning theories of the nerve-cell4 ,had we a solidly established theory of the cell1 equivalent1 say1 to our theory of gas-pressure1 we should still need caution in allowing it to override exact observation2 but insecure as our data are1 and hypothetical as are the inferences respecting the part played by the cell1 the reliance placed on deductions from such premises is nothing less than superstition4 ,science will take a new start when the whole question is reinvestigated on a preliminary setting aside of all that has been precipitately accepted respecting the office of the cell4 ,this exercise of the imagination1 even should the reigning theories subsequently be confirmed1 would not fail to bring many neglected facts into their rightful place4 ,i am old enough to remember when the cell held a very subordinate position in ,neurology1 and now my meditations have led me to return1 if not to the old views of the cell1 at least to something like the old estimate of its relative importance4 ,its existence was first brought prominently forward by ,ehrenberg in #ahcd1 who described its presence in the sympathetic ganglia2 and by ,remak in #ahcg1 who described it in the spinal ganglia4 ,for some time afterwards the ganglia and centres were said to contain irregular masses of vesicular matter which were looked on as investing the fibres2 what their office was1 did not appear4 ,but there rapidly arose the belief that the cells were minute batteries in which 8nerve-force0 was developed1 the fibres serving merely as conductors4 ,once started on this track1 ,hypothesis had free way1 and a sort of fetichistic deification of the cell invested it with miraculous powers4 ,in many works of repute we meet with statements which may fitly take their place beside the equally grave statements made by savages respecting the hidden virtues of sticks and stones4 ,we find the nerve-cells credited with 8metabolic powers10 which enable them to 8spiritualize impressions1 and materialize ideas10 to transform sensations into movements1 and elaborate sensations into thoughts2 not only have they this 8remarkable aptitude of metabolic local action10 they can also 8act at a distance40#afb ,the savage believes that one pebble will cure diseases1 and another render him victorious in war2 and there are physiologists who believe that one nerve-cell has sensibility1 another motricity1 a third instinct1 a fourth emotion1 a fifth reflexion3 they do not say this in so many words1 but they assign to cells which differ only in size and shape1 specific qualities4 ,they describe sensational1 emotional1 ideational1 sympathetic1 reflex1 and motor-cells2 nay1 ,schrder van der ,kolk goes so far as to specify hunger-cells and thirst-cells4#afc ,with what grace can these writers laugh at ,scholasticism8 #acd4 ,the hypothesis of the nerve-cell as the fountain of nerve-force is supported by the gratuitous hypothesis of cell-substance having greater chemical tension and molecular instability than nerve-fibre4 ,no evidence has been furnished for this2 indeed the only experimental evidence bearing on this point1 if it has any force1 seems directly adverse to the hypothesis4 ,i allude to the experiments of ,wundt1 which show that the faint stimulus capable of moving a muscle when applied directly to its nerve1 must be increased if the excitation has to pass through the cells by stimulation of the sensory nerve4#afd ,wundt interprets this as proving that the cells retard every impulse1 whereby they are enabled to store up latent force4 ,the cells have thus the office of locks in a canal1 which cause the shallow stream to deepen at particular places4 ,i do not regard this interpretation as satisfactory2 but the fact at any rate seems to prove that so far from the cells manifesting greater instability than the fibres1 they manifest less4 #ace4 ,the hypothesis of nerve-force being developed in the ganglia1 gradually assumed a more precise expression when the nerve-cells were regarded as the only important elements of a ganglion4 ,it has become the foundation-stone of ,neurology1 therefore very particular care should be taken to make sure that this foundation rests on clear and indisputable evidence4 ,instead of that1 there is absolutely no evidence on which it can rest2 and there is much evidence decidedly opposed to it4 ,neither structure nor experiment points out the cells as the chief agents in neural processes4 ,let us consider these4 ,fig4 #bb shows the contents of a molluscan ganglion which has been teased out with needles4 ,illustration3 ,fig4 #bb4--;,cells1 fibres1 and amorphous substance from the ganglion of a mollusc 7after ,bucholtz74 ,the cells are seen to vary in size1 but in all there is a rim of neuroplasm surrounding the large nucleus1 and from this neuroplasm the fibre is seen to be a prolongation4 ,the dotted substance in the centre is the neuroglia4 ,except in the possession of a nucleus1 there is obviously here no essential difference in the structure of cell and fibre4 ,illustration3 ,fig4 #bc--;,fibres from the auditory nerve4 a1 the axis cylinder2 b1 the cellular enlargement2 c1 the medullary sheath4 ,now compare this with ,fig4 #bc1 representing three fibres from the auditory nerve4 ,here the cell substance1 as ,max ,schultze remarks1 8is a continuation of the axis cylinder1 and encloses the nucleus4 ,the medulla commonly ceases at the point where the axis enters the cell1 to reappear at its exit2 but it sometimes stretches across the cell to enclose it also3 so that such a ganglion cell is in truth simply the nucleated portion of the cylinder axis40#afe ,there are many places in which fibres are thus found with cells inserted in their course as swellings3 in the spinal ganglia of fishes these are called bipolar cells2 they are sometimes met with even in the cerebellum2 but oftener in peripheral nerves1 where they are mostly small masses of granular neuroplasm from which usually a branching of the fibre takes place4 ,the point to which attention is called is that in some cases1 if not in all1 the nerve-fibre is structurally continuous with the cell contents4 ,the two organites--fibre and cell--differ only as regards the nucleus and pigment4 ,haeckel1 who affirms that in the crayfish 7,astacus fluviatilis7 he never saw a cell which did not continue as a fibre1 thinks there is always a marked separation of the granular substance from its 8hyaline protoplasm10 and that only this latter forms the axis cylinder4 ,but although my observations agree with this as a general fact1 ,i have seen even in crayfish the granular substance prolonged into the axis cylinder2 and in other animals the granular substance is frequently discernible4 ,indeed it may be said that anatomists are now tolerably unanimous as to the axis cylinder being identical with the protoplasmic cell substance4 ,if this be so1 we have only to recall the principle of identity of property accompanying identity of structure1 to conclude that whatever properties we assign to the cells 7unless we restrict these to the nucleus and pigment7 we must assign to the axis cylinders4 ,we can therefore no longer entertain the hypothesis of the cells being the fountains or reservoirs of ,neurility2 the less so when we reflect that cells do not form the hundredth part of nerve-tissue3 for even the gray substance bears but a small proportion to the white2 and of the gray substance1 ,henle estimates that one half is fibrous1 the rest is partly cellular1 partly amorphous4 ,those who derive ,neurility from the cells1 forget that although the organism begins as a cell1 and for some weeks consists mainly of cells1 yet from this time onwards there is an ever-increasing preponderance of cell-derivatives--fibres1 tubes1 and amorphous substance--and corresponding with this is the ever-increasing power and complexity of the organism4 #acf4 ,from another point of view we must reject the hypothesis4 ,not only does the evidence which points to the essential continuity in structure of nerve cell and fibre discredit the notion of their physiological diversity1 but it is further supported by the fact that although the whole nervous system is structurally continuous1 an immense mass of nerve-fibres have no immediate connection with ganglionic cells3--neither springing from nor terminating in such cells1 their activity cannot be assigned to them4 ,to many readers this statement will be startling4 ,they have been so accustomed to hear that every fibre begins or terminates in a cell1 that a doubt thrown on it will sound paradoxical4 ,but there is an equivoque here which must be got rid of4 ,when it is said that every fibre has its 8origin0 in a cell1 this may be true if origin mean its point of departure in evolution1 for 8cells0 are the early forms of all organites2 but although every organite is at first a cell1 and in this sense a nerve-fibre must be said to originate in a cell1 we must guard against the equivoque which arises from calling the highly differentiated organite1 usually designated ganglionic cell1 by the same name as its starting-point4 ,on this ground ,i suggest the term neuroblast1 in lieu of nerve-cell1 for the earlier stages in the evolution of cell and fibre4 ,both ,embryology and ,anatomy seem to show that cell and fibre are organites differentiated from identical neuroblasts1 with a somewhat varying history1 so that in their final stages the cell and fibre have conspicuous differences in form with an underlying identity2 just as a male and female organism starting from identical ova1 and having essential characters in common1 are yet in other characters conspicuously unlike4 ,the multipolar cell is not necessarily the origin of a nerve-fibre1 although it is probable that some short fibres have their origin in the prolongations of cells4 ,although the latter point has not1 ,i think1 been satisfactorily established1 except in the invertebrata1 ,i see no reason whatever to doubt its probability2 what seems the least reconcilable with the evidence is the notion that all fibres arise as prolongations from ganglionic cells1 instead of arising independently as differentiations from neuroblasts4 ,the reader will observe that my objection to the current view is purely anatomical2 for the current view would suit my physiological interpretations equally well1 and would be equally irreconcilable with the hypothesis of the cell as the source of ,neurility1 so long as the identity of structure in the axis cylinder and cell contents is undisputed4 #acg4 ,the evidence at present stands thus3 ,there are numerous multipolar cells which have no traceable connection with nerve-fibres2 and fibres which have no direct connection with multipolar cells4 ,by the first ,i do not mean the disputed apolar cells1 ,i mean cells in the gray substance of the centres which send off processes that subdivide and terminate as fibrils in the network of the ,neuroglia 7,figs4 #af1 #ah74 ,it is indeed generally assumed that these have each one process--the axis-cylinder process--which is prolonged as a nerve-fibre2 nor would it be prudent to assert that such is never the case2 though it would be difficult to distinguish between a fibre which had united with a process and a fibre which was a prolongation of a process1 in both cases the neuroplasm being identical4 ,i only urge that the assumption is grounded not on anatomical evidence1 but on a supposed necessary postulate4 ,all that can be demonstrated is that some processes terminate in excessively fine fibrils2 and occasionally in thousands of specimens processes have been traced into dark-bordered fibres4 ,it is true that they often present appearances which have led to the inference that they did so terminate--appearances so deceptive that ,golgi and ,arndt independently record observations of unbranched processes having the aspect of axis cylinders being prolonged to a considerable distance 7#fjj in one case71 yet these were found to terminate not in a dark-bordered fibre1 but in a network of fibrils4#aff #ach4 ,while it is thus doubtful whether dark-bordered fibres are always immediately connected with cells1 it is demonstrable that multitudes of fibres have only an indirect connection with cells1 being developed as outgrowths from other fibres4 ,dr4 ,beale considers that in each such outgrowths have their origin in small neuroplasmic masses 7his 8germinal matter074 ,that is another question4 ,the fact here to be insisted on is that we often find groups of cells with only two or three fibres1 and groups of fibres where very few cells exist4 ,schrder van der ,kolk says that in a sturgeon 7,accipenser sturio7 weighing #abj pounds he found the spinal cord scarcely thicker than that of a frog2 the muscles of this fish are enormous1 and its motor nerves abundant2 yet these nerves entered the cord by roots no thicker than a pig's bristle2 and in the very little gray matter of the cord there was only a cell here and there found after long search4 ,are we to suppose that these rare cells were the origins of all the motor and sensory nerves8 ,a similar want of correspondence may be noticed elsewhere4 ,thus in the spinal cord of the ,lamprey my preparations show very few cells in any of the sections1 and numerous sections show none at all4 ,stieda counted only eight to ten cells in each horn of some osseous fishes1 except at the places where the spinal roots emerged4 ,in the eel and cod he found parts of the cord quite free from cells1 and in other parts found two1 three1 never more than ten4 ,in birds he counted from twenty-five to thirty4 ,particular attention is called to this fact of the eel's cord being thus deficient1 because every one knows the energetic reflex action of that cord1 each separate segment of which responds to peripheral stimulation4 ,it may indeed be urged that these few cells were the origin of all the fibres1 the latter having multiplied by the well-known process of subdivision2 and in support of this view the fact may be cited of the colossal fibres of the electric fishes1 each of which divides into five-and-twenty fibres1 and in the electric eel each fibre is said by ,max ,schultze to divide into a million of fibrils4 ,but ,i interpret this fact otherwise4 ,it seems to me to prove nothing more than that the neuroplasm has differentiated into few cells and many fibres4 ,and my opinion is grounded on the evidence of ,development1 presently to be adduced4 ,if we find 7and this we do find7 fibres making their appearance anywhere before multipolar cells appear1 the question is settled4 #aci4 ,dr4 ,beale regards the large caudate cells of the centres as different organites from the oval and pyriform cells1 and thinks they are probably stations through which fibres having different origins merely pass1 and change their directions2 and ,max ,schultze says that no single fibril has been found to have a central origin2 every fibril arises at the periphery1 and passes through a cell1 which is thus crossed by different fibrils4#afg 7,comp4 ,fig4 #ag47 ,the teaching of ,development is on this point of supreme importance4 ,unhappily there has not yet been a sufficient collection of systematic observations to enable us to speak very confidently as to the successive stages1 but some negative evidence there is4 ,the changes take place with great rapidity1 and the earliest stages have hardly been observed at all4 ,although for several successive years ,i watched the development of tadpoles1 the difficulties were so great1 and the appearances so perplexing1 that the only benefit ,i derived was that of being able the better to understand the more successful investigations of others4 ,four or five days after fecundation is the earliest period of which ,i have any recorded observation2 at this period the cerebral substance appeared as a finely granular matter1 having numerous lines of segmentation marking it off into somewhat spherical and oval masses1 interspersed with large granules and fat globules4 ,here and there hyaline substance appeared between the segments4 ,similar observations have since been recorded by ,charles ,robin in the earliest stages of the ,triton4#afh ,he says that when the external gills presented their first indications1 nuclei appeared1 each surrounded by a rim of hyaline substance1 from which a pale filament was prolonged at one end1 sometimes one at both ends1 and this filament subdivided as it grew in length until it had all the appearance of an axis cylinder4 ,this1 however1 he says1 is a striation1 not a fibrillation2 he refuses to admit that the axis cylinder is a bundle of fibrils4 ,he further notices the simultaneous appearance of amorphous substance2 and as this is several days before there is any trace of a pia mater1 or proper connective tissue1 he urges this among the many considerations which should prevent the identification of neuroglia with connective tissue4 ,in a very young embryo of a mole 7,i could not determine its age7 the cortex of the hemispheres showed granular amorphous substance1 in which were embedded spherical masses of somewhat paler color1 which had no nuclei1 and were therefore not cells4 ,besides these1 there were nucleated masses 7apolar cells1 therefore7 and more developed cells1 unipolar1 bipolar1 and tripolar4 ,not a trace of a nerve-fibre was visible4 ,in agreement with this are the observations of ,masius and ,van ,lair1 who cut out a portion of the spinal cord in a frog1 and observed the regenerated tissue after the lapse of a month4 ,it contained apolar1 bipolar1 and multipolar cells1 together with 8corpuscles without processes1 for the most part larger than the cells1 and appearing to be mere agglomerations of granules10--these latter ,i suppose to have been what ,i describe as segmentations of the undeveloped substance4 ,gray fibres1 with a few varicose fibres1 also appeared4#afi #adj4 ,the admirable investigations of ,franz ,boll have given these observations a new significance4 ,he finds in the cerebral substance of the chick on the third or fourth day of incubation a well-marked separation between the neuroglia and nerve-tissue proper4 ,fig4 #bd1 ,a1 represents three nerve-cells1 each with its nucleus and nucleolus1 and each surrounded with its layer of neuroplasm4 ,the other four masses he regards as nuclei of connective tissue4 ,three days later the distinction between the two is more marked 7,fig4 #bd1 ,b74 ,not only have the nerve-cells acquired an increase of neuroplasm1 they also present indications of their future processes1 which at the twelfth day are varicose 7,fig4 #bd1 ,c74 7,all this while the connective corpuscles remain unchanged47 ,although ,boll was unable to trace one of these processes into nerve-fibres1 he has little doubt that they do ultimately become 7unite with87 axis cylinders4 ,illustration3 ,fig4 #bd4--;,embryonic nerve-cells4 ,illustration3 ,fig4 #be4--;,embryonic nerve-fibres4 ,it is difficult to reconcile such observations with the hypothesis of the cells being simply points of reunion of fibrils4 ,we see here multipolar cells before any fibrils appear4 ,respecting the development of the white substance1 i4 e4 the nerve-fibres1 ,boll remarks that in the corpus callosum of the chick the first differentiation resembles that of the gray substance4 ,the polygonal and spindle-shaped cells represented in ,fig4 #be1 ,a1 are respectively starting-points of connective and neural tissues4 ,the spindle-shaped cells elongate1 and rapidly become bipolar4 ,this is supposed to result in the whole cell becoming transformed into a fibre1 the nucleus and nucleolus vanishing2 but the transformation is so rapid that he confesses that he was unable to trace its stages2 all that can positively be asserted is that one or two days after the appearance presented in ,fig4 #be1 ,b1 the aspect changes to that of fibrils4 ,the columns of polygonal cells between which run these fibrils1 he regards as the connective corpuscles described by several anatomists in the white substance both of brain and cord1 and which are sometimes declared to be multipolar nerve-cells4#agj #ada4 ,dr4 ,schmidt's observations on the human embryo were of course on tissue at a very much later stage4 ,according to him1 the fibrils of the axis cylinders are formed by the linear disposition and consolidation of elementary granules4 ,the fibrils thus formed are separated by interfibrillar granules which in time become fibrils4 ,not earlier than three months and a half does the formation of individual axis cylinders begin by the aggregation of these fibrils into minute bundles1 which are subsequently surrounded by a delicate sheath4#aga #adb4 ,with respect to the transition of the spindle-shaped cells into fibrils1 since there is a gap in the observations of ,boll1 and since those of ,schmidt are subsequent to the disappearance of the cells1 and in both cases all trace of nucleus has disappeared1 ,i suggest that we have here an analogy with what ,weismann has recorded of the metamorphoses of insects4 ,in the very remarkable memoir of that investigator#agb it is shown that the metamorphoses do not take place by a gradual modification of the existing organs and tissues1 but by a resolution of these into their elements1 and a reconstruction of their elements into tissues and organs4 ,the muscles1 nerves1 trache1 and alimentary canal1 undergo what may be called a fatty degeneration1 and pass thence into a mere blastema4 ,it is out of these ruins of the old tissues that the new tissues are reconstructed4 ,on the fourth day the body of the pupa is filled with a fluid mass--a plasma composed of blood and dissolved tissues4 ,the subsequent development is thus in all essential respects a repetition of that which originally took place in the ovum4#agc ,two points are especially noticeable3 ,first1 that in this resolved mass of granules and fat globules there quickly appear large globular masses which develop a fine membrane1 and subsequently nuclei4 ,a glance at the figure #ea of ,weismann's plates reveals the close resemblance to the earliest stages of nerve-cells2 and the whole process recalls the regeneration of nerves and nerve-centres after their fatty degeneration4 ,secondly1 the nerves reappear in their proper places in the new muscles1 and this at a time when the nerve-centres are still unformed2 so that the whole peripheral system is completely rebuilt in absolute independence of the central system4 ,the idea1 therefore1 that nerve-fibres are the products of ganglia must be relinquished4 ,this idea is further discountenanced by ,boll's observations1 which show that the fibre-cells are from the first different from the ganglionic cells2 and by the observations of ,foster and ,balfour1 that 8fibres are present in the white substance on the third day of incubation02 whereas cell processes do not appear until the eighth day4 ,foster and ,balfour are inclined to believe 8that even on the seventh day it is not possible to trace any connection between the cells and fibres40 ,in the later stages1 the connection is perhaps established4#agd #adc4 ,we may1 ,i think1 conclude from all this that in the higher vertebrates the white substance of brain and cord is not the direct product of the gray substance2 in other words1 that here nerve-fibres1 even if subsequently in connection with the ganglionic cells1 have an independent origin4 ,they may grow towards and blend with cell processes2 they are not prolongations of those processes4 ,they may be identical in structure and property1 as one muscle is identical with another1 but one is not the parent of the other4 #add4 ,sigmund ,mayer emphatically declares that in no instance has he traced a cell process developed into a dark-bordered nerve-fibre4 ,the process1 he says1 may often be traced for a certain distance alongside of a fibre2 but it then suddenly ceases1 whereas the fibre is seen continuing its course unaltered4 ,still more conclusive is the evidence afforded by nerves having only very few fibres 7#b-d sometimes in the frog71 which have1 nevertheless1 a liberal supply of cells1 visible without preparation4 ,valentin counted twenty-four cells in a nerve which had but two fibres4#age ,now although it is possible to explain the presence of numerous fibres with rare cells either as due to subdivisions of fibres1 or to the fibres having cells elsewhere for their origin1 it is not thus that we can explain the presence of numerous cells which have no fibres developed from their processes4 #ade4 ,with regard to this observation of the cell process running alongside of the fibre1 the recent researches of ,ranvier may throw some light on it4 ,he describes the cells in the spinal ganglia as all unipolar2 each single process pursues a more or less winding course as a fibril1 often blending with others1 till it reaches one of the fibres from the sensory root4 ,it blends with this fibre at the annular constriction of the fibre1 becoming here incorporated with it1 so that a ,t-shaped fibre is the result4#agf ,if this should be confirmed1 it would reconcile many observations2 but it would greatly disturb all current interpretations4 ,ranvier remarks that it is no longer tenable to suppose that the ganglionic cell is a centre1 sensory or motor1 receiving the excitation or sending forth a motor impulse2 for if the fibril issuing from a cell becomes laterally soldered to a nerve-fibre1 there is no possibility of saying in which direction this cell receives the excitation1 nor in which it transmits the impulse4 #adf4 ,we have seen good reason to conclude that the essential element of the nerve--the axis cylinder--is the same substance as the neuroplasm which forms the essential element of the cell4 ,at any rate1 we are quite certain that the cell process is neuroplasm4 ,on this ground there is no difficulty in understanding that a cell process may sometimes be drawn out into an axis cylinder 7as indeed we see to be the case in the invertebrata and electric fishes72 while again in numerous other cases the nerve-fibre has an independent origin1 being1 in short1 a differentiation from the neuroplasm which has become a fibre instead of a cell4 ,it is clear from the observations of ,rouget on ,development1 and of ,sigmund ,mayer on ,regeneration1 that fibres1 nuclei1 and cells become differentiated from the same neuroplasm1 those portions which are not converted into fibres remaining first as lumps of neuroplasm1 then acquiring a nucleus1 and some of these passing into cells4 ,i mean that between fibres1 nuclei1 and cells there are only morphological differences in an identical neuroplasm4#agg ,if this is in any degree true1 it will not only explain how fresh fibres may be developed in the course of fibres1 branching from them as from trunks1 and branchlets from branchlets1 twigs from branchlets1 the same conditions of growth being present throughout2 it will also completely modify the notion of any physiological distinction between cell and fibre greater than can be assigned to the morphological differences4 ,we shall then no longer suppose that the cell is the fountain whence the fibre draws its nutrition and its 8force02 and this will be equally the case even if we admit that a cell is1 so to speak1 the germ from which a whole plexus of fibres was evolved1 for no one will pretend that the 8force0 of an organism is directly derived from the ovum1 or that the ovum nourishes the organism4 #adg4 ,at this stage of the discussion it is needful to consider a point which will spontaneously occur to every instructed reader1 ,i mean the interesting fact discovered by ,dr4 ,waller1 that when a sensory root was divided1 the portion which was still in connection with the ganglion remained unaltered1 whereas the portion which was only in connection with the spinal cord degenerated2 and vice versa1 when a motor root was divided1 the portion connected with the cord remained unaltered1 the portion severed from the cord degenerated4 ,the observation has been frequently confirmed1 and the conclusion drawn has been that the cells in the ganglion of the posterior root are the nutritive centres of posterior nerves1 the cells in the anterior horn of the cord being the nutritive centres of the anterior nerves4 ,another interpretation is however needed1 the more so because the fact is not constant4#agh ,true of some nerves1 it is not true of others4 ,vulpian found that when he cut out a portion of the lingual nerve1 and transplanted it by grafting under the skin of the groin1 where of course it was entirely removed from all ganglionic influence1 it degenerated1 but it also regenerated4 ,pathological observations convinced ,meissner that the ganglia are wholly destitute of an influence on the nutrition of the vagus2 and ,schiff proved experimentally that other ganglia were equally inoperative1 since motor nerves could be separated from the spinal cord without degeneration4#agi ,not however to insist on this1 nor on the other facts of regeneration1 in the absence of ganglionic influence1 let us remark that ,dr4 ,waller's examples would not be conclusive unless the teaching of ,embryology could be disproved4 ,that nerves degenerate when separated from ganglia is a fact2 but it is also a fact that muscles degenerate when separated from a nerve-centre2 yet we do not suppose the nerve-centre to nourish the muscles4 ,and against the fact that the sensory nerve remains unaltered only in that portion which is connected with the ganglion1 we must oppose the observations of ,klliker and ,schwalbe1#ahj who affirm that none of the fibres which enter the posterior columns of the spinal cord have any direct connection with the cells of the ganglion on the posterior root4 ,the cells of this ganglion they declare to be unipolar 7in the higher vertebrates71 and the fibres in connection with these cells are not those which pass to the cord1 but all of them pass to the periphery4 ,according to ,ranvier1 the fibres from the cells join the fibres of the posterior root4 ,schwalbe found that if the spinal nerve be firmly grasped and steadily drawn1 it will often be pulled from its sheath1 and the ganglion laid bare2#aha in this ganglion all the cells are found undisturbed1 which could not be the case had fibres from those cells entered the cord1 since the traction would necessarily have disturbed them4 ,,recapitulation4 #adh4 ,at the opening of this chapter mention was made of the besetting sin of the analytical tendency1 namely1 to disregard the elements which provisionally had been set aside1 and not restore them in the reconstruction of a synthetical explanation4 ,familiar experiences tell us that a stimulus applied to the skin is followed by a muscular movement1 or a glandular secretion2 sometimes this takes place without any conscious sensation2 sometimes we are distinctly conscious of the stimulus2 and sometimes we consciously will the movement4 ,these facts the physiologist tries to unravel1 and to trace the complicated processes involved4 ,the neurologist of course confines himself exclusively to the neural processes2 all the other processes are provisionally left out of account4 ,but not only so3 the analytical tendency is carried further1 and even in the neural process the organs are neglected for the sake of the nervous tissue1 and the nervous tissue for the sake of the nerve-cell4 ,the consequence has been that we have an explanation offered us which runs thus3-- #adi4 ,the nerve-cell is the supreme element1 the origin of the nerve-fibre1 and the fountain of nerve-force4 ,the cells are connected one with another by means of fibres1 and with muscles1 glands1 and centres also by means of fibres1 which are merely channels for the nerve-force4 ,a stimulus at the surface is carried by a sensory fibre to a cell in the centre2 from that point it is carried by another fibre to another cell2 and from that by a third fibre to a muscle3 a reflex contraction results4 ,this is the elementary 8nervous arc40 ,but this arc has also higher arcs with which it is in connection3 the sensory cell besides sending a fibre directly to a motor cell1 also sends one upwards to the cerebral centres2 and here again there is a nervous arc1 so that the cerebral centre sends down an impulse on the motor cells1 and the contraction which results is due to a volitional impulse4 ,the transmission of the stimulation which in the first case was purely physical1 becomes in the latter case psychical4 ,the sensory impression is in one cell transformed into a sensation1 in another cell into an idea1 in a third cell into a volition4 #aej4 ,this course is described with a precision and a confidence which induces the inexperienced reader to suppose that it is the transcript of actual observation4 ,i venture to say that it is imaginary from beginning to end4 ,i do not affirm that no such course is pursued1 ,i only say no such course was ever demonstrated1 but that at every stage the requisite facts of observation are either incomplete or contradictory4 ,first1 be it noted that the actions to be explained are never the actions of organs so simple as the description sets forth4 ,it is not by single fibres and cells that the stimulus is effected1 but by complex nerves and complex centres4 ,only by a diagrammatic artifice can the fibre represent the nerve1 and the cell the centre4 ,in reality the cells of the centre 7supposing them to be the only agents7 act in groups1 and ,anatomy should therefore show them to be mutually united in groups--which is what no ,anatomy has succeeded in showing1 unless the ,neuroglia be called upon4 ,secondly1 be it noted that the current scheme of the relations between cells and fibres is one founded on physiological postulates1 not on observation4 ,thirdly1 much of what is actually observed is very doubtful1 because we do not know whether the appearances are normal1 or due to modes of preparation and post-mortem changes4 ,we cannot at present say1 for instance1 whether the fibrillated appearance of cell contents and axis cylinder represents the living structure or not4 ,we may either suppose that the neuroplasmic pulp splits longitudinally into fibres1 or that neuroplasmic threads resolve themselves into a homogeneous pulp--the axis cylinder may be a condensation of many fibrils1 or the fibrils may be a resolution of the substance4 #aea4 ,let us contrast step by step the ,imaginary ,anatomy found in the text-books with the ,objective ,anatomy as at present disclosed by the researches of all the chief workers4 ,imaginary ,anatomy assumes that the sensory fibre passes from a surface into the cells of the posterior horn of the spinal cord4 ,objective ,anatomy sees the fibre pass into the gray substance1 but declares that no direct entrance of a fibre into a cell is there visible4 ,imaginary ,anatomy assumes that from the sensory cells of the gray substance pass fibres in connection with the motor cells of the anterior horn1 thus forming a direct channel through which the excitation of a sensory cell is transmitted to a motor cell4 ,objective ,anatomy fails to discover any such direct channel--no such fibres are demonstrable4 ,imaginary ,anatomy assumes that from the motor cells issue fibres which descend to the muscles and glands1 and carry there the motor impulses and the 8mandates of the will40 ,objective ,anatomy fails to find at the utmost more than a probability that these cells are continued as fibres1 a probability which is founded on the rare facts of cell processes having been seen extending into the roots of the nerves1 and of a cell process having occasionally been seen elsewhere continuous with a dark-bordered fibre4 ,granting1 however1 that this probability represents the fact1 we have thus only one part of the 8nervous arc0 which can be said to have been verified4 ,imaginary ,anatomy further assumes that this nervous arc is connected with cerebral centres by means of fibres going upwards from the posterior cells1 and fibres descending downwards to the anterior cells4 ,objective ,anatomy sees nothing of the kind4 ,it sees fibres entering the gray substance1 and there lost to view in a mass of granular substance1 fibrils1 neuroblasts1 and cells4 ,there may be uninterrupted fibres passing upwards and downwards2 but it is impossible to see them4 ,and if we are told that physiological interpretations demand such a structure1 we may fairly ask if this1 and this only1 is the structure which is adequate to the propagation of excitation8 ,now it seems to me that another kind of structure1 and one more closely agreeing with what is observed1 better answers the demands of ,physiology4 ,this will be more evident after the ,laws of ,nervous ,action have been expounded in the succeeding chapter4 ,meanwhile we may remark that the arrangement of cells and fibres which is imagined as the mechanism of propagation and reflexion is absolutely irreconcilable with the teaching of ,experiment3 for the spinal cord may be cut through anywhere1 without destruction of the transmission of sensory and motor excitations1 provided only a small portion of gray substance be left to establish the continuity of the axis4 ,divide all the substance of the posterior half in one place1 and all the substance of the anterior half in another1 yet so long as there is a portion of gray substance left as a bridge between the lower and upper segments1 the transmission of sensory and motor excitations will take place4 #aeb4 ,in other essential respects we have to note that the anatomical evidence for the current interpretations is absolutely deficient or contradictory4 ,there is no adequate warrant for the assumption that all nerves have their origin in ganglia1 all fibres in cells4 ,such evidence as at present exists is against that supposition1 and in favor of the supposition that both cell and fibre are differentiations of a common neuroplasm1 sometimes directly1 sometimes indirectly continuous4 ,fibres1 and plexuses of fibres1 interspersed with cells irregularly distributed--now singly1 now in small groups1 now in larger and larger groups--constitute the figured elements of nerve-tissue2 and even if we set aside the amorphous substance as indifferent or subordinate1 we have still no ground for assigning the supremacy1 much less the sole significance1 to the cells4 ,the grounds of this denial have been amply furnished in our exposition4 ,for1 let it be granted that nerve-cells are the origins of the fibres and the sources of their nutrition--a point which is eminently disputable--this would in no sense help the physiological hypothesis of the cell as the fountain of ,neurility4 ,if the fibre is simply the cell-contents drawn out longitudinally1 if its essential element is identical with the essential element of the cell1 then we can no more ascribe to the cell the exclusive property of ,neurility than we can draw a lump of lead out into a wire1 and then ascribe different properties to the thin end and the thick end4 ,but on this point it is needless to speculate1 since we have experimental evidence proving that the nerve-fibre has its ,neurility even when separated from the cell1 or even from the ganglion4 #aec4 ,it is possible--,i do not see sufficient evidence for a stronger assertion--that the cells are the nutritive sources of the fibres4 ,they may represent the alimental rather than the instrumental activities of nervous life4 7,compare ,,problem ,i4 #db47 ,my contention is that in any case they are not the supreme elements of the active tissue1 and in no sense can they be considered as organs4 ,only confusion of ideas could for a moment permit such language1 or could assign central functions to cells which are elements of tissue4 ,if the cell be credited with such powers anywhere1 it must be credited with them everywhere4 ,now ,i ask what conceivable central function can be ascribed to a cell which terminates the fibre in a peripheral ganglion1 or which is merely an enlargement in the course of a fibre in a nerve-bundle8 ,besides the facts already adduced1 let attention be called to this3 ,if a nerve-bundle from the submucosa of the intestine be examined1 there appear among the fibres many nuclei 7neuroblasts71 and occasionally cells1 unipolar and bipolar4 ,these cells--if we may trust the observations of ,rouget on the earliest development of nerves1 and of ,sigmund ,mayer on regenerated nerves--are simply more advanced stages of evolution of the neuroblasts2 but whatever their genesis may be1 there can be nothing in the nature of a central function assigned to them4 #aed4 ,it may be asked1 ,what part can we assign to cells in neural actions if they are apolar1 unipolar1 and even when multipolar1 isolated from each other1 and from fibres8 ,i confess that ,i have no answer ready1 not even an hypothesis4 ,until some rational interpretation of the cell be given we must be content to hold an answer in suspense4 ,what ,i would urge is that we are precipitate in assuming that the anatomical connection between one element and another must necessarily be that of a fibre4 ,in a semi-fluid substance1 such as neurine1 continuity may be perfect without solid fibres3 the amorphous substance and the plasmode may as well transmit waves of molecular motion from one part of the tissue to another1 and therefore from cell to cell1 or from cell to fibre1 as a figured substance may4 ,when the posterior root enters the gray substance of the cord1 there is no more necessity for its fibres passing directly into the cells of that gray substance1 in order to excite their activity1 than there is for a wire to pass from the bell to the ear of the servant1 who hears the vibrations of the bell through the pulsations of the intervening air upon her tympanum4 ,look at the structure of the retina1 or the cerebellum1 and you will find that the ganglionic cells which have processes passing in a direction contrary to that whence the stimulus arrives1 have none where continuity of fibre and cell would be indispensable on the current hypothesis4 ,light stimulates the rods and cones1 but there are no nerve-fibres1 hitherto discovered1 passing from these to the ganglionic cells2 instead of that there is a ground-substance thickly interspersed with granules and nuclei4 ,from the cells we see processes issue2 to the cells none are seen arriving4 ,so with the cerebellum4 ,the large cells send their processes upwards to the surface2 but downwards towards the white substance the processes are lost in the granular layer1 which most histologists regard as connective tissue4 #aee4 ,a mere glance at nervous tissue in any part will show that cells are far from forming the principal constituents4 ,in the epidermis or a gland the cell is obviously the chief element1 forming the bulk of the tissue1 and being the characteristic agent4 ,in nerve-tissue1 as in connective tissue1 the reverse is the case4 ,we must therefore cease to regard the cell as having the importance now attached to it1 and must rather throw the emphasis on the fibres and neuroglia4 #aef4 ,before quitting this subject let a word be said on the amazing classification which has attained wide acceptance 7although rejected by the most eminent authorities71 founded on the size of the cells--the large multipolar cells being specified as motor1 the smaller cells as sensory1 while those of an intermediate size are sympathetic4 ,i forbear to dwell on the development of this notion which specifies sensational1 ideational1 and emotional cells1 because this does not pretend to have a basis in observation2 whereas there are anatomical facts which give a certain superficial plausibility to the original classification4 ,the conception is profoundly unphysiological2 yet1 if the anatomical evidence were constant1 one might give it another interpretation4 ,the evidence is1 however1 not constant4 ,large cells are found in regions assigned to sensory nerves1 and small cells in motor regions4 ,in the spinal cord of the tortoise ,stieda declares that the so-called motor cells are limited to the cervical and lumbar enlargements2 all the rest of the motor region being absolutely destitute of them4#ahb ,again look at the cells of the retina--no one will assign motor functions to them--yet they are the same as those of the cerebellum and the anterior horns of the spinal cord4 7,it is worth a passing mention that the structure of the nervous parts of the retina more closely resembles that of the cerebellum than of the cerebrum47 #aeg4 ,while our knowledge of the cell is thus far indeed from having the precision which the text-books display1 and in no sense warrants the current physiological interpretations1 our knowledge of fibres and neuroglia is also too incomplete for theoretic purposes4 ,we know that the axis cylinder is the essential element2 but we are still at a loss what part is to be assigned to the medullary sheath4 ,there is indeed a popular hypothesis which pronounces it to be the means of insulating the fibre1 and thus preserving the isolated conduction of nerve-force4 ,being of a fatty nature1 this insulating office was readily suggested in agreement with the assumption that ,neurility was ,electricity4 ,now1 without discussing whether ,neurility is or is not ,electricity1 even admitting the former to be satisfactorily proved1 ,i must remark that the admission still leaves the medullary sheath incapable of fulfilling the supposed office1 since not only is there no such sheath in most of the invertebrates and in the sympathetic nerves of vertebrates1 but even in those nerves which have the sheath it is precisely in places where the insulation would be most needed--namely1 just before the terminations of the fibres in muscles and in centres--that the sheath is absent4 ,this is as if we tried to conduct water through a pipe which fell short at both ends--before it left the cistern1 and before it reached the spot to be watered4 ,if there is a tendency in ,neurility to spread wherever it is not insulated by a medullary sheath1 then before reaching the centres and the muscles1 it must1 on the insulating hypothesis1 dribble away6 #aeh4 ,the facts expressed in the 8law of isolated conduction0 are important1 and are difficult of explanation2 but it is obvious that they cannot be referred to the presence of the medullary sheath4 ,nor indeed will any insight into the propagation of stimulation through the central axis be intelligible until we have reformed our anatomical theories1 and taken the ,neuroglia into account4 ,the theory which connects every fibre directly with a cell1 and every cell with another by anastomosis--even were it demonstrated--would not explain the law of isolated conduction4 ,butzke cogently remarks#ahc that such a disposition of the elements should render all neural paths invariable2 whereas the fact is that they are very variable4 ,we learn to perform actions1 and then we unlearn them2 the paths are traversed now in one direction1 now in another4 ,fluctuation is the characteristic of central combinations4 ,and for this fluctuating combination of elements a corresponding diversity is required in the possible channels4 ,this seems to be furnished by the network of the ,neuroglia4 ,see the representation copied from ,butzke's plate1 and note how the cell-process blends with the meshes of the ,neuroglia4 ,is it fanciful to regard this network of fibrils as having somewhat the relation of capillaries to blood-vessels8 ,did we not experimentally know that the capillaries are terminal blood-vessels1 we should not suspect it from mere examination of the structure4 #aei4 ,having insisted that our knowledge is insufficient for any explanation of the 8law of isolated conduction10 ,i can only suggest a path of research which may lead to some result4 ,what we know is that some stimulations are propagated from one end of the cerebro-spinal axis to the other in definitely restricted paths1 while others are irradiated along many paths4 ,in the succeeding chapter this will be more fully considered2 what we have here to note is that the manifold irradiations of a stimulation have an anatomical substratum in the manifold sub-divisions of the network of fibrils and the amorphous substance in which they penetrate4 ,illustration3 ,fig4 #bf4--,nerve-cells with processes terminating in neuroglia4 #afj4 ,in conclusion1 ,i would say1 let no one place a too great confidence in the reigning doctrines respecting the elementary structure of the nervous system1 but accept every statement as a 8working hypothesis0 which has its value in so far as it links together verified facts1 or suggests new research1 but is wholly without value in so far as it is made a basis of deductions not otherwise verified4 ,hypotheses are indispensable to research1 but they must be accompanied by vigilant scepticism4 ,imagination is only an enemy to ,science when ,scepticism is asleep4 ,,chapter ,,viii4 ,,the ,,laws ,,of ,,nervous ,,activity4 #afa4 ,the foregoing remarks have had the object of showing how little substantial aid ,psychology can at present derive from what is known of the elementary structure of the nervous system1 indispensable as an accurate knowledge of that structure must be to a complete analysis of its functions4 ,this caution has been specially addressed to those medical and psychological students whose researches leave them insufficient leisure to pursue microscopical investigations for themselves1 and who are therefore forced to rely on second-hand knowledge1 which is usually defective in the many qualifying considerations which keep scepticism vigilant4 ,relying on positive statements1 and delusive diagrams which only display what the observer imagines1 not what he actually sees1 they construct on such data theories of disease1 or of mental processes2 or else they translate observed facts into the terms of this imaginary anatomy1 and offer the translation as a new contribution to ,science4 #afb4 ,but little aid as can at present be derived from the teaching of the microscope1 some aid ,psychology may even now derive from it4 ,the teaching will often serve1 for instance1 to correct the precipitate conclusions of subjective analysis1 which present artificial distinctions as real distinctions1 separating what ,nature has united4 ,it will show certain organic connections not previously suspected2 and since whatever is organically connected cannot functionally be separated1 such sharply marked analytical distinctions as those of periphery and centre1 or of sensation and motion1 must be only regarded as artificial aids4 ,the demonstration of the indissoluble union of the tissues is a demonstration of their functional co-operation4 ,so also the anatomical demonstration of the similarity and continuity of all parts of the central system sets aside the analytical separation of one centre from another1 except as a convenient artifice2 proving that cerebral substance is one with spinal substance1 having the same properties1 the same laws of action4 ,for the present1 ,psychology must seek objective aid from ,physiology and ,pathology rather than from elementary ,anatomy4 ,in the paragraphs which are to follow ,i shall endeavor to select the chief laws of nervous activity which the researches of physiologists and pathologists disclose4 ,by these laws we may direct and control psychological research4 ,,the ,,energy ,,of ,,neurility4 #afc4 ,vitality is characterized by incessant molecular movement1 both of composition and decomposition1 in the building up of structure and the liberation of energy4 ,the life of every organism is a complex of changes1 each of which directly or indirectly affects the statical and dynamical relations1 each being the resultant of many co-operant forces4 ,in the nourishment of every organite there is an accumulation of molecular tension1 that is to say1 stored-up energy in a latent state1 ready to be expended in the activity of that organite2 and this expenditure may take place in a steady flow1 or in a sudden gush4 ,the molecular movements under one aspect may be called convergent1 or formative3 they build the structure1 and tend to the state of equilibrium which we call the statical condition of the organite1 i4 e4 the condition in which it is not active1 but ready to act4 ,perfect equilibrium is of course never attained1 owing to the incessant molecular change3 indeed ,life is inconsistent with complete repose4 ,under another aspect the molecular movements may be called discharging3 they constitute the dynamic condition of the organite1 in which its functional activity appears4 ,the energy is now diverted1 liberated1 and the surplus1 over and above that which is absorbed in formation1 instead of slowly dribbling off1 gushes forth in a directed stream4 ,the slow formation of a secretion in a gland-cell1 and the discharge of that secretion1 will illustrate this2 or 7if muscular tone be admitted7 the incipient contraction of the chronic state1 and the complete contraction of the dynamic state1 may also be cited4 #afd4 ,the discharge which follows excitation may thus be viewed as a directed quantity of molecular movement4 ,because it is always strictly relative to the energy of tension1 and is inevitable when that tension attains a certain surplus over what is required in construction1 there is a limit1 #a1 to the growth and evolution of every organite1 and every organism 7comp4 ,problem ,i4 #aah71 and1 #b1 to its dynamical effect4 ,when there is no surplus1 the organite is incapable of discharge3 it is then exhausted1 i4 e4 will not respond to stimulus4 #afe4 ,the speciality of nerve-tissue is its pre-eminence in directive energy4 ,like all other tissues1 it grows1 develops1 and dies2 but above all others it has what we call excitability1 or readiness in discharging its energy in a directed stream4 ,by its topographical distribution it plays the functional part of exciting the activity of other tissues3 it transmits molecular disturbance from periphery to centre1 from centre to centre1 and from centre to muscles1 vessels1 and glands4 ,when a muscle is excited it moves1 and when a gland is excited it secretes2 but these actions end1 so to speak1 with themselves2 the muscle does not directly move any other muscle2#ahd the gland does not directly excite any other gland4 ,the nerve1 on the contrary1 has always a wide-spreading effect2 it excites a centre which is continuous with other centres2 and in exciting one muscle1 usually excites a group4 ,hence the nervous system is that which binds the different organs into a dynamic unity4 ,and ,comparative ,anatomy teaches that there is a parallelism between the development of this system and the efficient complexity of the organism4 ,as the tissues become more and more specialized1 and the organs more and more individualized1 they would become more and more unsuited to the general service of the organism1 were it not that a corresponding development of the nervous system brought a unifying mechanism4 ,the great instability of neurine1 in other words1 its high degree of tension1 renders it especially apt to disturb the tension of other tissues4 ,it is very variable2 and this variability will have to be taken into account in explaining the restriction of discharges to particular centres4 ,a good example of exaggerated tension is furnished by strychnine poisoning4 ,the centres are then so readily excitable that a touch1 or a puff of cold air on the skin1 will determine convulsions4 ,and it is worthy of remark that for some hours after this convulsive discharge the centres return to something like their normal state2 and the animal may then be stroked1 pinched1 or blown upon without abnormal reactions4 ,but during this interval the centres are slowly accumulating excess of tension from the poisoned blood2 and at the close1 convulsions will again follow the slightest stimulus4 ,this alternation of exhaustion and recrudescence is noticed by ,schrder van der ,kolk in the periodicity of the phenomena exhibited in spinal disease4#ahe ,,the ,,propagation ,,of ,,excitation4 #aff4 ,understanding1 then1 that the propagation of an excitation depends on the state of tension of the tissue1 and always follows the line of least resistance1 whichever that may be at the moment1 we have to inquire whether the transmission takes place only in one direction1 from periphery to centre in sensory nerves1 and from centre to periphery in motor nerves8 ,by most physiologists this is answered affirmatively4 ,indeed a special property has been assigned to each nerve1 in virtue of this imaginary limitation of centripetal and centrifugal conduction4 ,the 8nerve-current0 7accepted as a physical fact1 and not simply a metaphor7 is supposed to 8flow0 from the central cells along the motor nerve to the muscles2 but by a strange oversight the current is also made to 8flow0 towards the central cells which are said to produce it6 ,now although the fact may be1 and probably is1 that normally the sensory nerve1 being stimulated at its peripheral end1 propagates the stimulation towards the centre1 and the motor nerve propagates its central stimulation towards the periphery1 the question whether each nerve is not capable of transmission in both directions is not thus answered4 ,a priori it is irrational to assert that nerves fundamentally alike in composition and structure are unlike in properties2 and we might as well suppose that a train of gunpowder could only be fired at one end1 as to suppose that a nerve could only be excited at one end4 ,and how does the evidence support this a priori conclusion8 ,dubois ,reymond proved that each nerve conducted electricity in both directions2 but as ,neurility has not been satisfactorily shown to be identical with the electric current1 this may not be considered decisive4 ,such a doubt does not hang over the following facts4 ,m4 ,paul ,bert1 pursuing ,john ,hunter's curious experiments on animal grafting1 has grafted the tail of a rat under the skin of the rat's back1 the tip of the tail being inserted under the skin1 its base rising into the air1 so that there is here an inversion of the normal position4 ,in the course of time ,sensibility gradually reappears in this grafted tail2 and at the end of about twelve months the rat not only feels when the tail is pinched1 but knows where the irritation lies1 and turns round to bite the pincers4#ahf ,here we have a case of a sensory nerve reversed1 yet transmitting stimulation from the base to the tip of the tail1 instead of from the tip to the base1 as in a normal organ4 ,vulpian and ,philippeaux having divided two nerves1 united the central end of the sensory nerve with the peripheral end of the motor nerve2 when the organic union was complete1 and each nerve was formed out of the halves of two different nerves1 the effect of pinching one of these was to produce simultaneously pain and movement1 showing that the excitation was transmitted upwards to the centre1 and downwards to the muscles4#ahg ,it may be compared with a train of gunpowder having a loaded cannon at one end and a bundle of straw at the other1 when if a spark be dropped anywhere on this train1 the flame runs along in both directions1 explodes the cannon1 and sets alight the straw4 #afg4 ,indeed we have only to remember the semi-liquid nature of the axis cylinder to see at once that it must conduct a wave of motion as readily in one direction as in another4 ,a liquid transmits waves in any direction according to the initial impulse4 ,there is consequently no reason for asserting that because the usual direction is centripetal in a sensory nerve1 and centrifugal in a motor nerve1 each nerve is incapable of transmitting excitations in both directions4 ,and ,i think many phenomena are more intelligible on the assumption that neural transmission is in both directions4 ,if the eye is fixed steadfastly on a particular color during some minutes1 the retina becomes exhausted1 and no longer responds to the stimulus of that color3 here the stimulation is of course centripetal4 ,but if instead of looking intently on the color1 the mind 7in complete absence of light7 pictures it intently1 this cerebral image is equally capable of exhausting the retina2 and unless we believe that color is a cerebral1 not a retinal phenomenon 7which is my private opinion71 we must accept this as proof of a centrifugal excitation of a sensory tract4 ,another illustration may be drawn from the muscular sense4 ,there may be a few sensory fibres distributed to muscles2 but even if the observations of ,sachs#ahh should be confirmed1 ,i do not think that all muscle sensations can be assigned to these fibres1 but that the so-called motor fibres must also co-operate4 ,when a nerve acts upon a muscle1 the muscle reacts on the nerve2 and when a nerve acts on a centre1 the centre reacts on the nerve4 ,the agitation of the central tissue cannot leave the nerve which blends with it unaffected2 the agitation of the muscular tissue must also by a reversal of the 8current0 affect its nerve4 ,laplace points out how the movement of the hand which holds a suspended chain is propagated along the chain to its terminus1 and if when the chain is at rest we once more set that terminus in motion1 the vibration will remount to the hand4#ahi ,the contraction of a muscle will not only stimulate the sensory fibres distributed through it1 but also1 ,i conceive1 stimulate the very motor fibres which caused the contraction1 since these fibres blend with the muscle4#aij #afh4 ,to understand this1 it is necessary to remember that the stimulation of a nerve does not arise#aia in the changed state of that nerve1 but in the process of change1 i4 e4 the disturbance of the tension4 ,the duration of the stimulation is that of the changing process1 and the intensity increases with the differential of the velocity of change4 ,so that when a nerve which has been excited by a change of state returns to its former state1 this return--being another change--is a new excitation4 ,that it is not the changed state1 but the change1 which is operative1 explains the fact noted by ,brown ,squard3 a frog poisoned by strychnine1 when decapitated and all respiration destroyed1 will remain motionless for days together1 if carefully protected from all external excitation2 but its nervous system is in such a state of tension all this time that the first touch produces general convulsions4 ,freusberg also notes that if a brainless frog be suspended by the lower jaw1 and one foot be pinched1 the other leg is moved at first1 then quickly droops again1 and remains at rest until the pincers are removed from the pinched foot1 when suddenly all four legs are violently moved by the stimulation which the simple removal produces4 ,let us also add the well-known and significant fact that if a nerve be divided rapidly by a sharp razor1 neither sensation nor motion is produced1 because the intensity of a stimulus being1 to speak mathematically1 the function of the changing process1 the duration of the process is in this case too brief4 ,on the same ground the application of a stimulus will excite no movement1 if the force be very slowly increased from zero to an intensity which will destroy the nerve2 but at any stage a sudden increase will excite a movement4 #afi4 ,we may group all the foregoing considerations in this formula3 ,,law ,i4 ,every neural process is due to a sudden disturbance of the molecular tension4 ,the liberated energy is discharged along the lines of least resistance4 ,the conditions which determine the lines of least resistance are manifold and variable4 ,the nervous system is a continuous whole1 each part of which is connected with diverse organs2 but in spite of this anatomical diversity1 the deeper uniformity causes the activity of each part to depend on and involve the activity of every other1 more or less4 ,by 8more or less0 is meant1 that although the excitation of one part necessarily affects the state of all the others1 because of their structural community1 so that each sensation and each motion really represents a change in the whole organism1 yet the responsive discharge determined in each organ by this change1 depends on the tension of the organ and its centre at that moment4 ,a bad harvest really affects the whole nation2 but its effect is conspicuous on the welfare of the poor rather than of the rich1 although the price of bread is the same to rich and poor4 ,nervous centres1 and muscular or glandular organs1 differ in their excitability2 one condition of this greater excitability being the greater frequency with which they are called into activity4 ,the medulla oblongata is normally more excitable than the medulla spinalis2 the heart more than the limbs4 ,hence a stimulus which will increase the respiration and the pulse may have no appreciable effect on the limbs2 but some effect it must have4 #agj4 ,imagine all the nerve-centres to be a connected group of bells varying in size4 ,every agitation of the connecting wire will more or less agitate all the bells2 but since some are heavier than others1 and some of the cranks less movable1 there will be many vibrations of the wire which will cause some bells to sound1 others simply to oscillate without sounding1 and others not sensibly to oscillate4 ,even some of the lighter bells will not ring if any external pressure arrests them2 or if they are already ringing1 the added impulses1 not being rhythmically timed1 will arrest the ringing4 ,so the stimulus of a sensory nerve agitates its centre1 and through it the whole system2 usually the stimulation is mainly reflected on the group of muscles innervated from that centre1 because this is the readiest path of discharge2 but it sometimes does not mainly discharge along this path1 the line of least resistance lying in another direction2 and the discharge never takes this path without also irradiating upwards and downwards through the central tissue4 ,thus irradiated1 it falls into the general stream of neural processes2 and according to the state in which the various centres are at the moment it modifies their activity4 ,a nervous shock--physical or mental--sensibly affects all the organs4 ,a severe wound paralyzes1 for a time1 parts far removed from the wounded spot4 ,a blow on the stomach will arrest the heart2 a fright will do the same4 ,terror relaxes the limbs1 or sets them trembling2 so does a concussion3 if a frog be thrown violently on the ground1 all its muscles are convulsed2 but if the nerves of one limb be divided before the shock1 the muscles of that limb will not be convulsed4 #aga4 ,we are apt to regard the discharge on the moving organs as if that were the sole response of a stimulation2 but although the most conspicuous1 it is by no means the most important effect4 ,besides exciting the muscles1 more or less1 every neural process has its influence on the organic processes of secretion1 and effects thermal and electrical changes4 ,schiff has demonstrated that every sensation raises the temperature of the brain2 ,nothnagel1 that irritation of a sensory nerve causes constriction of the cerebral arteries1 and hence cerebral anmia4 ,brown ,squard and ,lombard find the temperature of a limb raised when its skin is pinched1 and lowered when the skin elsewhere is pinched4 ,georges ,pouchet has shown that fishes change color according to the brightness or darkness of the ground over which they remain2 and these changes are dependent on nervous stimulation1 mainly through the eye1 division of the optic nerves preventing the change4 ,these are so many a posteriori confirmations of what a priori may be foreseen4 ,they are cited here merely to enforce the consideration1 seldom adequately kept before the mind1 that every neural process is a change which causes other changes in the whole organism4 ,,stimuli4 #agb4 ,stimuli are classed as external and internal1 or physical and physiological4 ,the one class comprises all the agencies in the ,external ,medium which appreciably affect the organism2 the other class all the changes in the organism which appreciably disturb the equilibrium of any organ4 ,although the pressure of the atmosphere1 for example1 unquestionably affects the organism1 and determines organic processes1 it is not reckoned as a stimulus unless the effect become appreciable under sudden variations of the pressure4 ,in like manner the blood is not reckoned among the internal stimuli1 except when sudden variations in its composition1 or its circulation1 determine appreciable changes4 ,because the external stimuli1 and the so-called ,senses which respond to them1 are more conspicuous than the internal stimuli and the ,systemic ,senses1 they have unfortunately usurped too much attention4 ,the massive influence of the ,systemic ,sensations in determining the desires1 volitions1 and conceptions of mankind has not been adequately recognized4 ,yet every one knows the effect of impure air1 or a congested liver1 in swaying the mental mood2 and how a heavy meal interferes with muscular and mental exertion4#aib ,what is conspicuous in such marked effects1 is less conspicuously1 but not less necessarily1 present in slighter stimuli4 #agc4 ,a constant pressure on the tympanum excites no sound2 only a rhythmic alternation of pressures will excite the sensation4 ,a constant temperature is not felt2 only changes in temperature4 ,if ,light and ,sound were as uniform as the circulation of the blood1 or the pressure of the atmosphere1 we should be seldom conscious of the existence of these stimuli4 ,but because the changes are varied and marked1 our attention is necessarily arrested by them4 ,the changes going on within the tissues are too graduated to fix the attention2 it is only by considering their cumulative effects that we become impressed with their importance4 ,for example1 the development of the sexual glands determines conspicuous physical and moral results--we note consequent effects on voice1 hair1 horns1 structure of the skull and size of the muscles1 no less than the rise of new feelings1 desires1 instincts1 ideas4 ,any organic interference with the activity of the ovaries will alter the moral disposition of the animal3 suppression of this organic process means non-development of the feelings of maternity2 the moral superstructure is absent because its physical basis is wanting4 #agd4 ,blood supplies the tissues with their plasmodes2 a constant supply of oxygenated blood is therefore necessary to the vitality of the tissues4 ,but it is an error to suppose that oxygen is the special stimulus of nerve-centres1 or that their activity depends on their oxidation2 on the contrary1 the deficiency of oxygen or surplus of carbonic acid is that which stimulates4 ,when saturated with oxygen1 the blood paralyzes respiration2 when some of the oxygen is withdrawn1 respiration revives4 ,here--as in all other cases--we have to remember that differences in degree readily pass into differences in kind1 so that an excess of a stimulus produces a reversal of the effect2 thus although surplus of carbonic acid excites respiratory movements1 excess of carbonic acid causes ,asphyxia4 ,abundance of blood is requisite for the continuous activity of nerve-centres2 but while a temporary deficiency of blood renders them more excitable1 too great a deficiency paralyzes them4 ,anmia1 which causes great excitability1 and convulsions 7so that nerves when dying are most irritable71 may easily become the cause of the death of the tissue4 ,there are substances which can only be dissolved by a given quantity of liquid2 if this quantity be in excess1 they are precipitated from the solution4 ,there are vibrations of a given order which cause each string to respond2 change the special order1 and the string returns to its repose4 ,in the stillness and darkness of the night we are excluded from most of the external stimuli1 yet a massive stream of systemic sensations keeps the sensitive mechanism active1 and in sleep directs the dreams4 ,the cramps and epileptiform attacks which occur during sleep are most probably due to the over-excitability produced by surplus carbonic acid4 ,to temporary anmia may be assigned the strange exaggeration of our sensations during the moments which precede awakening2 and the greater vividness of dream-images4 ,it is only needful to mention in passing the varied stimuli by which cerebral changes act upon the organism4 ,the mention of a name will cause a blush1 a brightening of the eye1 a quickening of the pulse4 ,the thought of her absent infant will cause a flow of milk in the mother's breast4 #age4 ,we may formulate the foregoing considerations in another law3 ,,law ,,ii4 ,the neural excitation1 which is itself a change1 directly causes a change in the organ innervated1 and indirectly in the whole organism4 ,the significance of this law is1 that although for the convenience of research and exposition we isolate one organ from the rest of the organism1 and one process from all the co-operant processes1 we have to remember that this is an artifice1 and that in reality there is no such separation4 ,,stimulation4 #agf4 ,passing now from these general considerations to their special application1 we may formulate the law of stimulation3 ,,law ,,iii4 ,a faint or moderate stimulation increases the activity of the organ2 but beyond a certain limit1 increase of stimulation diminishes1 and finally arrests1 the activity4 ,duration of stimulation is equivalent to increase4 ,a muscle stimulated contracts2 if the stimulation be repeated1 the muscle becomes tetanized1 and in this state has reached its limit2 a fresh stimulation then relaxes the muscle4 ,a very faint stimulation of the vagus quickens the pulsation of the heart1 but a slight increase1 or duration of the stimulation1 slackens and arrests the heart4#aic ,every one knows how a moderate feeling of surprise1 pleasure1 or pain quickens the heart and the respiration2 and how a shock of surprise1 joy1 grief1 or great physical pain depresses1 and even arrests them4 ,excess of light is blinding2 excess of sound deafening4 #agg4 ,the nervous system is incessantly stimulated1 and variably4 ,hence a great variation in the excitability of different parts4 ,while the regular and moderate activity of one part is accompanied by a regular flow of blood to it1 so that there is a tolerably constant rhythm of nutrition and discharge1 any irregular or excessive activity exhausts it1 until there has been a nutritive restoration4 ,we can thus understand how one centre may be temporarily exhausted while a neighboring centre is vigorous4 ,cayrade decapitated a frog1 and suspended light weights to each of its hind legs2 when either leg was stimulated1 the weight attached to it was raised4 ,after each repetition the weight was raised less and less1 until finally the weight ceased to be raised3 the centre had been exhausted4 ,but now when the other leg1 which had been in repose1 was stimulated1 it energetically contracted1 and raised its attached weight2 showing that its centre was not exhausted by the action of the other4#aid #agh4 ,this seems in contradiction with the principle that the excitation of one centre is an excitation of all4 ,it also seems in contradiction with the principle urged by ,herzen1 that irritation of one sciatic nerve diminishes the excitability of the opposite leg2 and this again seems contradicted by the principle urged by ,setschenow1 that although moderate excitation of one sciatic nerve will diminish the excitability of the other1 a powerful excitation will increase it4 #agi4 ,all three principles are1 ,i believe1 exact expressions of experimental evidence2 and their seeming contradictions may be reconciled on a wider survey of the laws of neural activity1 interpreted according to the special conditions of each case4 ,these laws may be conveniently classified as laws of ,discharge1 and ,laws of ,arrest2 the second being only a particular aspect of the first4 ,,the ,,law ,,of ,,discharge4 #ahj4 ,the physiological independence of organs1 together with their intimate dependence in the organism1 and the fact that this organism is incessantly stimulated from many sides at once1 assure us a priori that the 8waves0 of molecular movement due to each stimulus must sometimes interfere and sometimes blend with others1 thus diverting or neutralizing the final discharge in the one case1 and in the other case swelling the current and increasing the energy of the discharge4 ,we are accustomed to speak of one part 8playing on another10 sympathizing with another1 and so on2 but what is the process expressed in these metaphors8 ,when an idea1 or a painful sensation1 quickens the pulse1 or increases the flow of a secretion1 we are not to imagine that from a spot in the cerebrum1 or the surface1 there is a nerve-fibre going directly to the heart1 or the gland1 transmitting an impulse2 in each case the central tissue has been agitated by a sudden change at the stimulated point1 and the discharge on heart and gland is the resultant of this agitation along the lines of least resistance4 ,the nerves of the great toe1 for example1 pass into the spinal cord at a considerable distance from the spot where the nerves of the arm enter it2 when1 therefore1 the great toe is pinched1 the arm does not move by direct stimulation of its nerves1 but by the indirect stimulation which has traversed the whole central substance4 #aha4 ,this is intelligible when we know that the whole central substance is continuous throughout2 but the difficulty arises when we have to explain why1 if this central substance is stimulated throughout1 only arms and legs respond2 in other words1 why the toe-centre 8plays upon0 the arm-centre1 and not on the others8 ,when a frog is decapitated1 if we gently touch one leg with the point of the scalpel1 the leg will move1 but only this leg4 ,prick more forcibly1 and both legs will move4 ,keep on pricking1 and all four legs are drawn up1 and the frog hops away4 ,each excitation was propagated along the cord2 but the discharge was restricted in the first case to one limb1 in the second to two1 in the third it involved all the muscles of the trunk4 ,at the sight of a friend a dog wags his tail gently3 as there is no direct connection between the optic nerves and the tail1 this playing of one centre on another must be by the agency of intermediate centres2 and we know that if the dog's spinal cord be divided1 this excitation from the optic centre is no longer possible1 yet the tail will wag if the abdomen be tickled1 or the leg pinched4 ,now compare the effect on the dog produced by the sight of his master1 or of a friend accustomed to take him out4 ,there is no longer a gentle wagging of the tail1 but an agitation of the whole body3 he barks1 leaps1 and runs about2 the central stimulation is discharged through many outlets2 and could we test the effect1 we should find an appreciable alteration in the thermal and electrical condition of the whole organism1 with corresponding changes in circulation1 secretion1 etc4 ,so different are the consequences of two slightly different retinal impressions mingling their stimulations with the same mass of central substance6 #ahb4 ,the discharge is determined by two conditions3 the state of tension1 and the energy of the stimulation4 ,the state of tension is increased by every stimulation which falls short of a discharge2 that is to say1 faint and frequent stimulation augments the excitability1 whereas powerful stimulation exhausts it4 ,when1 therefore1 one wave succeeds another in the same direction1 it reaches a centre more disposed to discharge2 or1 as ,cayrade expresses it1 8a certain agitation of the cells is necessary for the manifestation of their property of reaction1 in the same way that the concentric circles produced on the surface of water by a falling stone are more rapid and more numerous if a stone has already agitated the surface40 #ahc4 ,so much for the tension4 ,what has been called the energy of the stimulation is more complicated4 ,it is not measurable as a simple physical process2 we cannot say that a given quantity of any external force will determine a given discharge4 ,it is mostly complicated by psychical processes1 and these so modify the result that instead of the predicted discharge there is arrest1 or discharge from another centre4 ,press a dog's skin with increasing violence1 and the effect increases from pleasurable to painful irritation2 but whether the dog will cry out and bite1 or cry out and struggle to escape1 depends upon whether the pincher is a stranger or a friend4 ,if you hurt a dog while removing a thorn from its foot it will cry out1 but although the pain causes it to initiate a biting movement1 by the time your hand is reached that movement will have been changed1 and the dog will lick the hand which he knows is hurting him in the endeavor to relieve him of the thorn4 ,the co-operation of the mind is here evident enough4 ,a purely psychical process has interfered with the purely physiological process4 ,and ,i shall hereafter endeavor to show that psychical processes analogous in kind though simpler in degree are really co-operant in actions of the spinal cord4 ,the dog would be said to discriminate between the pain inflicted by a friend1 and the same pain inflicted by a stranger4 ,in other words1 the sensitive mechanism would be differently determined in the direction of discharge1 although the initial stimulation was the same in each case4 ,if we admit that the resulting action is in each case the consequence of the particular group of elements co-operating1 there will be no ground for denying that analogous discrimination is manifested by the brainless animal1 who also responds differently to different external stimuli1 and differently to the same stimulus under different central conditions4 ,the brainless frog croaks if its back be gently stroked with the handle of a scalpel2 but if the point be used1 or if the handle be roughly pressed1 instead of croaking1 the frog raises his leg in defence4 ,here the difference in the peripheral irritation has excited a different reaction in the centre2 and this might be interpreted as purely physical2 if now the leg be fastened1 and the movement of defence be thus prevented1 the frog will employ the other leg2 or adopt some other means of relieving itself from the irritation4 ,it was a mass of registered experiences which determined the dog not to bite his master4 ,an analogous registration of experiences determines the changed reactions of the brainless frog4 ,but this is a point which can only be touched on in passing here1 and it is touched on merely to facilitate our exposition of the complicated conditions of neural discharge4 ,these may be formulated in #ahd4 ,,law ,,iv4 ,the simultaneous influence of several stimuli1 each of which separately excites the same centre1 is cumulative3 stimuli then assist each other1 and their resultant is their arithmetical sum4 ,simultaneous stimuli1 each of which excites a different centre1 interfere with each other's energy1 and their resultant is their algebraical sum4 ,in this law there is a condensed expression of that composition of forces which may either result in ,discharge or ,arrest4 ,by simultaneity is not to be understood merely the coincidence of impressions1 but also the reverberations of impressions not yet neutralized by others4 ,thus when ,sensibility is tested by the now common method1#aie it is found that if one leg is withdrawn after a lapse of1 say1 ten pendulum beats1 the other leg1 which has not been irritated1 will nevertheless1 on irritation1 be withdrawn in less than ten beats1 provided the central agitation caused by the first stimulation has not yet subsided4 ,but1 on the contrary1 the withdrawal will be considerably deferred1 or even prevented altogether1 if at the same time that the leg is acted on by the acid1 a more powerful excitation takes place in some other part of the body4 ,in the one experiment we see simultaneous excitation in the same centre and the same direction4 ,in the other simultaneous excitation in different centres4 ,the more powerful excitation suppresses the discharge from the less powerful2 but although it prevails1 it loses just as much force as it arrests4#aif #ahe4 ,there is another very interesting experiment by ,freusberg1 which must be cited here4#aig ,when the sciatic nerve is divided1 the frog's leg is of course not withdrawn from the acidulated water1 because in that case no sensory excitation is propagated from the skin to the centre2 but although there is no stimulation from the skin1 there is one from the muscles1 as appears in the fact that if a small weight be suspended on this leg1 the other leg is more rapidly withdrawn from the acidulated water--the action of the muscles having affected the centre and increased its excitability4 #ahf4 ,when the motor group of one leg is moderately stimulated1 the discharge is confined to the muscles of that one leg2 and according to ,herzen the excitability of the motor group of the other leg is thereby somewhat diminished4 ,but if the stimulation be increased1 there is an irradiation to the other group1 which irradiation1 although not sufficient to excite a discharge1 renders it much more ready to discharge1 so that a feeble stimulus suffices4 ,this accords with ,setschenow's observations1 and is confirmed by ,freusberg's experiment1 in which1 when one leg was stimulated by acid1 if the acid were not wiped off but allowed to keep up the irritation1 the other leg moved without being irritated2 and this other leg having come to rest1 when in its turn dipped in the acid1 was more rapidly withdrawn than the first leg had been on first being stimulated2 showing that the central groups had become more excitable by the stimulation of either leg4 #ahg4 ,while it is intelligible that an excitation of one group should increase the activity of neighboring groups1 by an increase of the vascular activity of the region1 it is not so readily intelligible why the feebler excitation of one group should diminish the excitability of its neighbor2 yet the facts seem to warrant both statements4 #ahh4 ,the conditions which determine ,discharge are obscure4 ,we may1 however1 say that anatomical and physiological data force the conclusion that whenever the central tissue is powerfully stimulated in any one part1 there is either a discharge1 or a greater tension 7tendency to discharge7 in every other part2 in consequence of which1 every fresh stimulus in the same direction finds the parts more prepared to react2 while every fresh stimulus in a contrary direction meets with a proportional resistance4 ,stated thus generally1 the principle is clear enough2 but the immense complication of stimulations1 and the statical variableness of the organs1 renders its application to particular cases extremely obscure4 ,why does the ticking of a clock arrest the attention1 even with unpleasant obtrusiveness1 at one time1 and presently afterwards cease to be heard at all8 ,why does the cut of a knife cause intense pain1 and a far greater cut received during the heat and agitation of a quarrel pass unfelt8 ,why will the same external force excite convulsions in all the muscles1 and at another time scarcely be distinguishable8 ,these are consequences of the temporary condition of the centres2 but there are permanent conditions which in some organisms determine equally variable results4 ,thus the shock of terror which will simply agitate one person1 will develop an epileptic attack in another1 and insanity in a third2 just as exposure to cold will in one person congest the liver1 in another the lungs4 ,a loud and sudden sound causes winking in most persons1 and in many a sort of convulsive shock4 ,the harsh noise of a file causes a shiver in some persons1 and in others 8sets the teeth on edge10 while in others it causes an increased flow of saliva4 #ahi4 ,nerves and centres have different degrees of excitability4 ,the nerve-terminals in the skin are more sensitive to impressions than those in the mucous membrane2 those in the alimentary canal are more sensitive than those in the peritoneum2 and all nerve-terminals are more sensitive than nerve-trunks4 ,a touch on the surface of the larynx will produce a cough1 but the nerve-trunk itself may be pinched or galvanized without producing any such reflex4 ,moreover1 there is the difference of grouping4 ,if the skin of the abdomen be tickled1 there is a reflex on the adductor and extensor muscles of the leg2 but these movements are reversed if the skin of the back be tickled4 ,nor indeed are these movements invariable in either case2 the one series will sometimes quite suddenly change to the other1 if the irritation is kept up4 ,that one and the same stimulus applied to the same spot should now excite this group and now the other1 shows that both motor groups are affected1 and that the discharge takes place from the one which at the time being is in the highest tension4 ,the alternation of tension explains rhythmical discharge4 ,,the ,,law ,,of ,,arrest4 #aij4 ,the ,law of ,arrest is only another aspect of the ,law of ,discharge1 and may be regarded as the conflict of excitations4 ,if a stranger enters the room where a woman lies in labor1 there will often be caused a sudden cessation of the uterine contractions4#aih ,again1 every one knows how the breathing and the beating of the heart are arrested by the idea of danger4 ,the arrest is in each of the three cases only temporary1 because when the shock of the new stimulus has caused its discharge 7arrest71 the peripheral irritation which caused the former discharges resumes its influence1 and uterus1 heart1 and diaphragm begin to move again1 even more energetically4 ,note1 moreover1 that not only will the cerebral excitation arrest the spinal discharge--an idea check the contractions of the uterus or the heart--but the reverse also takes place4 ,the brain of the woman may be intently occupied with some scheme for the education or welfare of her expected child1 but no sooner do the labor pains set in1 than all these cerebral combinations are arrested4 #aia4 ,one sensation arrests another2 one idea displaces another4 ,if the foreleg of a headless frog be irritated1 the hind-leg will also be moved by the stimulation2 or vice versa4 ,here there has been a propagation of the excitation in either direction4 ,but if while the legs are thus irritated1 and the centres are ready to discharge1 another and more powerful irritation reach the centre--say by pinching the skin of the back--there will be no discharge on the legs4 ,if the vagus be irritated1 the heart is arrested2 but this does not take place if at the same time1 or immediately before1 the foot has been sharply pinched4 ,a few gentle taps on the abdomen suffice to stop the heart2 but if a drop of acid be previously placed on the skin1 we tap in vain1 the heart continues to beat4 ,brown ,squard cites several cases in which convulsions were arrested by irritation of sensitive surfaces2#aii and ,dr4 ,crichton ,browne records a case of a patient in whom there was abolition of spinal reflex1 due to cerebral irritation3 tickling the soles of the feet1 or pricking the toes1 which normally excites reflex movements1 in this case excited none whatever4 8,this seems to prove that nerve currents1 set in motion by irritation of the brain1 or some of its convolutions1 transmitted down the cord1 may inhibit reflex action40#bjj ,examples might indefinitely be multiplied4 ,pinch the skin of a rabbit between the eyes1 and you will observe that pulse and respiration are slackened2 but if the tail1 which is very sensitive1 be pinched1 this slackening is only momentary1 and is succeeded by a quickening--unless the pain be great4 ,even the effect of intense pain may be neutralized by stimulating the vagus--just as the effect of stimulating the vagus may be neutralized by pain4 ,claude ,bernard found that having dropped ammonia on the eyelid of a dog1 the pain caused a convulsive closure of the lid2 but on galvanizing the vagus1 the lid opened again1 to be closed when the galvanism ceased4#bja ,when the heart is beating faintly 7as in syncope71 any irritating vapor applied to the nostrils will cause a more energetic pulsation2 yet a very irritating vapor lowers the action of the heart beating normally1 and will even arrest that of a rabbit4 ,over-stimulation has almost always the opposite effect of moderate stimulation4 #aib4 ,while there seems every reason to believe that an excitation necessarily affects the whole cerebro-spinal axis1 there is no doubt that there is a certain restriction of this irradiation to definite paths1 i4 e4 the responsive discharge is confined to definite groups4 ,some of these restrictions are connate pathways3 we bring them with us at birth2 but most of them are pathways acquired after birth4 ,the boy who sheds tears at parting from his mother when he goes to school1 will shed no tears when he parts from her to go to college1 nay1 perhaps will shed none when he parts from her forever3 not that his love has lessened1 but that the idea of such expression of it as 8unmanly0 has become an organized tendency and arrests the tears4 ,a youth of southern race1 who has not learned to be ashamed of tears1 weeps freely under such circumstances4 #aic4 ,the pathways organized at birth are not many4 ,examples are the inspiration which follows expiration2 the movements of coughing when the larynx is tickled2 the movements of swallowing1 sneezing1 etc4 ,even these may be arrested for a brief time by what is called 8the will02 but when once the discharge begins in any part of the mechanism1 the whole group is necessarily involved and the action is then inevitable4 ,many of the reflex actions which are universal are nevertheless acquired4 ,winking1 for instance1 when an object approaches the eye1 is universal among us1 but is never seen in infants1 nor in animals4 ,it is even doubtful whether the drawing up of the leg when the toes are pinched is not an acquired reflex4 ,doubtful1 ,i mean1 in this sense1 that although the fact of non-withdrawal is observable in infants1 who cannot localize their sensations1 this may be due to the imperfect development of their nervous system4 ,mr4 ,spalding has proved that although the callow bird cannot fly1 the mechanism of flight is no sooner developed than the action follows at once1 without any previous tentative experiences4 #aid4 ,by experience we learn to restrict the paths of irradiation1 so as to wink with one eye while the other is unmoved1 to bend one finger while the rest are extended1 to move one limb1 or one group of muscles1 while the others are at rest2 in short1 to execute any one particular action1 and not at the same time agitate superfluously many other organs4 ,the boy when first learning to write is unable to prevent the simultaneous motions of tongue and legs1 which are ludicrously irrelevant to the purpose of writing2 but he learns to keep all his organs in subjection1 and only the eyes and hands active4#bjb ,an analogous restriction takes place in thinking4 ,a train of thought is kept up by the exclusion of all suggestions which are not pertinent2 and the power of the thinker is precisely this power of concentration4 ,,the ,,hypothesis ,,of ,,inhibitory ,,centres4 #aie4 ,the facts and their formulated laws which have just been adduced furnish a sufficient explanation of all the phenomena of arrest which of late years have been detached and assigned to a special mechanism of inhibitory nerves and centres4 ,in spite of the eminent authorities countenancing the hypothesis of a particular set of inhibitory nerves1 and particular centres of inhibition1 ,i must confess that the hypothesis appears to me inadmissible2 and that ,i side with those physiologists who hold that each nerve and each centre has its inhibitory action4 ,indeed1 if the action of arrest be1 as ,i maintain1 only another aspect of the action of discharge1 the result of the conflict of forces1 to say that all centres have the property of excitation1 is to say that all have the properties of discharge and arrest3 the discharge is only the resultant of the conflict along the line of least resistance2 the arrest is the effect of the conflict along the line of greatest resistance4 ,the observed phenomena of arrest are so varied and numerous that the upholders of the inhibitory hypothesis have been forced to invent not only arresting centres1 but centres which arrest these arresting centres6 ,dr4 ,lauder ,brunton candidly remarks3 8,at present our notions of nervous action seem to be getting as involved as the ,ptolemaic system of astronomy1 and just as epicycles became heaped upon cycles1 so nerve-centres are being added to nerve-centres4 ,and yet1 clumsy though the system may be1 it serves at present a useful purpose1 and may give real aid until a better is discovered40 ,i do not think a ,copernicus is needed to discover a better4 ,the ,law of ,arrest as a general neural law suffices1 when the right conception of a centre as a physiological rather than an anatomical designation is admitted4 7,see p4 #agc47 #aif4 ,it would be out of place here to consider the conflicting evidence which at present renders the question of the movements of the heart one of the most unsatisfactory in the whole range of experimental physiology4 ,after devoting much time to it1 and after writing a long chapter on it1 ,i suppress what ,i had written1 and content myself with the statement that no advantage whatever is derived from the hypothesis of a special mechanism of arrest1 unless perhaps in giving a temporary precision to the direction of research4 ,i mean that the search for special centres may lead to the discovery of the particular paths to which an impulse is restricted in any one action3 as1 for instance1 the vagus in retarding the pulsation of the heart4 ,if the cerebrum can determine a movement1 and combine various movements1 it is a centre of arrest2 if the cerebellum can determine and regulate movements1 it is a centre of arrest2 if the medulla oblongata can determine and regulate movements1 it is a centre of arrest2 if the medulla spinalis can determine and combine movements1 it is a centre of arrest2 if a nerve can dilate a constricted blood-vessel1 or constrict a dilated one1 it is a nerve of arrest4 ,in other words1 every centre exerts its action either in discharging1 or in arresting the discharge of some other centre4 ,the physiological process of ,arrest may be physically interpreted as ,interference2#bjc not that the process in nerve-tissue is to be understood as the same as that observed in fluids1 or that the metaphor of neural waves is to be taken for more than an intelligible picturing of the process2 the difference in the two agents forbids our admitting the resemblance to be more than analogical4 ,thus interpreted1 however1 we see that not only will one centre arrest the action of another1 but one nerve may be made to arrest itself6 ,i mean that1 under similar conditions of interference1 the stimulation which normally follows on external stimulus may be inhibited by a previous1 or a counter stimulation4 ,thus the nerve which will be stimulated by a chemical or mechanical stimulus1 wholly fails to react if a constant current is passing through it1 although this constant current does not itself cause a constant contraction4 ,remove the electrodes1 and then the chemical or mechanical stimulus takes effect4 ,or the experiment may be reversed3 let the nerve be placed in a saline solution1 and the muscles will be at once thrown into violent contraction2 if the electrodes are now applied to the nerve1 the contractions suddenly cease1 to begin again directly the electrodes are removed4 ,,anatomical ,,interpretation ,,of ,,the ,,laws4 #aig4 ,the problem for the anatomist is twofold3 ,first1 given the organ1 he has to determine its function1 or vice versa1 given the part of an organ1 to determine its functional relation2 secondly1 given the function1 he has to determine its organ4 ,the structural and functional relations of nerves and centres have been ascertained in a general way2 we are quite sure that the posterior nerves carry excitations from sensitive surfaces1 that the anterior nerves carry excitations to muscles and glands2 and that the central gray substance not only reflects a sensory excitation as a motor excitation1 but propagates an excitation along the whole cerebro-spinal axis4 ,but when we come to a more minute analysis of the functional activities1 and endeavor to assign their respective values to each part of the organic mechanism1 the excessive complexity and delicacy of the mechanism baffles research4 ,we are forced to grope our way2 and the light of the hypothetic lamps which we hold aloft as often misdirects as helps us4 ,the imaginary anatomy which at present gains acceptance1 no doubt seems to simplify explanations2 but this seeming turns out to be illusory when closely examined4 ,the imagined arrangement of fibres and cells we have seen to be not in agreement with observation2 and were it demonstrable1 it would not account for the laws of propagation4 ,suppose sensory fibres to terminate in cells1 and fibres from these to pass upwards to other sensory cells and transversely to motor cells1 how in such a connected system could irradiations take place1 if the law of isolated conduction were true8 ,and how could isolated conduction take place1 if the excitation of a part were necessarily the excitation of the whole8 ,why1 for example1 is pain not always irradiated8 ,why is it even localized in particular spots1 determining movements in particular muscles2 and when irradiation takes place1 why is it circumscribed1 or--and this is very noteworthy--manifested in two widely different places1 the intercostal and trigeminal nerves8 ,why does the irritation of intestinal worms manifest itself now by troubles of vision1 now by noises in the ear1 and now by convulsions8 #aih4 ,answers to such questions must be sought elsewhere4 ,our first search should be directed to the anatomical data1 which have hitherto been so imprudently disregarded4 ,under the guidance of the laws formulated in this chapter1 let us accept the anatomical fact of a vast network forming the ground-substance in which cells and fibres are embedded1 and with which they are continuous2 let us accept the physiological principle ,of similarity of property with similarity of composition and structure2 let us accept the hypothesis that the discharge of neural energy is dependent on the degree of stimulus and the degree of tension at the time being--and we shall have at least a general theory of the process1 though there will still remain great obscurities in particular applications4 ,we shall have before us a vast network of pathways1 all equally capable of conducting an excitation1 but not all equally and at all moments open4 ,it will always be difficult to determine what are the conditions which at any moment favor or obstruct particular openings4 ,paths that have been frequently traversed will of course be more readily traversed again2 but this very facility will sometimes be an obstacle1 since it will have caused that path to be preoccupied1 or have fatigued the organ to which it leads4 #aii4 ,since the escape of an excitation must always be along the lines of least resistance1 an obvious explanation of the restriction to certain paths has been to assume that some fibres and cells have naturally greater resistance than others4 ,but this explanation is simply a restatement of the fact in other words4 ,what is this greater resistance8 ,why is it present in one fibre rather than in another8 ,we should first have to settle whether the resistance was in the nervous pathway itself1 or in the centre1 or in the organ innervated2 an excitation might pass along the nervous tract1 yet fail to change the state of the centre1 or the organ1 sufficiently to produce an appreciable response2 and only those parts where an appreciable response was produced would then be considered as having had the pathways of propagation open4 #bjj4 ,when we reflect on the innumerable stimulations to which the organism is subjected from so many various points1 and remember further that each stimulation leaves behind it a tremor which does not immediately subside1 we shall conceive something of the excessive complexity of the mechanism1 and marvel how any order is established in the chaos4 ,what we must firmly establish in our minds is that the mechanism is essentially a fluctuating one1 its elements being combined1 recombined1 and resolved under infinite variations of stimulation4 ,if it were a mechanism of fixed relations1 such as we find in machines1 or in the 8mechanism of the heavens10 we might accept the notion of certain organites having greater resistance as a consequence of their structure1 just as one muscle resists being moved by the impulse which will move another4 ,nor is it doubtful that such differences exist in nervous organites2 but the laws of central excitation are not interpretable by any such hypothesis1 since we know that the paths which were closed against an impulse of considerable energy may be all open to an impulse of feebler energy1 and that a slight variation in the stimulus will be followed by a wide irradiation4 ,for example1 a grain or two of snuff will excite the violent and complex act of sneezing1 but the nerves of the nasal cavity may be pinched1 cut1 or rubbed1 without producing any such result4 ,one group of nervous organites will fail to involve the activity of neighboring groups2 and the simple movement of a single organ is then all that appreciably follows the stimulation2 yet by a slight change in the stimulation1 the organites are somewhat differently grouped1 and the result is a complex movement of many organs4 ,it is this fluctuation of combination in the organites which renders education and progress possible4 ,those combinations which have very frequently been repeated acquire at last an automatic certainty4 99 99 99 99 99 ,we are now in a position to examine with more precision the extremely important laws of nervous action which are involved in the phenomena designated by the terms ,reflex ,action1 ,automatic ,action1 and ,voluntary ,action4 ,,problem ,,iii4 ,,animal ,,automatism4 8,l'organisme le plus complexe est un vaste mcanisme qui rsulte de l'assemblage de mcanismes secondaires40--,,claude ,,bernard4 8,les corps vivants sont machines l'infini40--,,leibnitz4 8,noi lamentiamo con ,majendie che nel linguaggio fisiologico siensi intruse le preopinioni psicologiche col trascico inevitabile del vocaboli1 ai quali codeste preopinioni si trovano legate4 ,probabilmente questa fu una delle principali cagioni degli errori e degli equivoci anatomofisiologici1 da cui non poterono svincolarsi1 a loro insaputa1 i cultori sperimentali della scienza1 perch nell' interpretare i fenomeni osservati erano obbligati ad usare il linguaggio di una false moneta in corso40--,,lussana e ,,lemoigne1 ,fisiologia dei ,centri ,nervosi1 #ahga1 ,i4 #af4 ,,animal ,,automatism4 ,,chapter ,i4 ,,the ,,course ,,of ,,modern ,,thought4 #a4 ,modern ,philosophy has moved along two increasingly divergent lines4 ,one1 traversed by ,galileo1 ,descartes1 ,newton1 and ,laplace1 had for its goal the absolute disengagement of the physical from the mental1 i4 e4 the objective from the subjective aspect of phenomena1 so that the physical universe1 thus freed from all the complexities of ,feeling1 might be interpreted in mechanical terms4 ,as a preliminary simplification of the problem this was indispensable2 only by it could the ,first ,notion of primitive speculation be replaced by the ,theoretic ,conception of scientific speculation4#bjd ,the early thinker inevitably invested all external objects with properties and qualities similar to those he assigned to human beings1 and their actions he assigned to human motives4 ,sun1 moon1 and stars seemed living beings2 flames1 streams1 and winds were supposed to be moved by feelings such as those known to move animals and men4 ,nor was any other conception then possible3 men could only interpret the unknown by the known1 and their standard of all action was necessarily drawn from their own actions4 ,not having analyzed ,volition and ,emotion1 above all not having localized these in a neuro-muscular system1 men could not suspect that the movements of planets and plants1 and of streams and stones1 had motors of a different kind from the movements of animals4 ,the scientific conception of inert insensible ,matter was only attained through a long education in abstraction2 and is assuredly never attained by animals1 or by savages4 ,but no sooner were vital conditions recognized1 than the difference between vital and mechanical movements emerged4 ,when men learned that many of their own actions were unaccompanied either by ,love or ,hate1 by ,pleasure or ,pain1 and that many were unprompted by conscious intention1 while others were unaccompanied by conscious sensation1 they easily concluded that wherever the special conditions of ,feeling were absent1 the actions must have some other motors4 ,intelligence1 ,emotion1 ,volition1 and ,sensation being one by one stripped away from all but a particular class of bodies1 nothing remained for the other bodies but insensible ,matter and ,motion4 ,this was the ,theoretic ,conception which science substituted for the ,first ,notion4 ,it was aided by the observation of the misleading tendency of interpreting physical phenomena by the human standard1 substituting our fancies in the place of facts1 manipulating the order of the universe according to our imagination of what it might be1 or ought to be4 ,hence the vigilance of the new school in suppressing everything pertaining to the subjective aspect of phenomena1 and the insistance on a purely objective classification1 so that by this means we might attain to a knowledge of things as they are4 ,by thus withdrawing ,life and ,mind from ,nature1 and regarding the universe solely in the light of ,motion and the laws of ,motion1 two great scientific ends were furthered1 namely1 a classification of conceptions1 and a precision of terms4 ,objective phenomena made a class apart1 and the great aim of research was to find a mathematical expression for all varieties under this class4 ,masses were conceived as aggregates of ,atoms1 and these were reduced to mathematical points4 ,forces were only different modes of ,motion4 ,all the numberless differences which perception recognized as qualities in things1 were reduced to mere variations in quantity4 ,thus all that was particular and concrete became resolved by analysis into what was general and abstract4 ,the ,cosmos then only presented a problem of ,mechanics4 #b4 ,during this evolution1 the old ,dualism 7which conceived a material universe sharply demarcated from the mental universe7 kept its ground1 and attained even greater precision4 ,the logical distinction between ,matter and ,mind was accepted as an essential distinction1 i4 e4 representing distinct reals4 ,there was on the one side a group of phenomena1 ,matter and ,force2 on the other side an unallied group1 ,feeling and ,thought3 between them an impassable gulf4 ,how the two were brought into relation1 each acting and reacting on the other1 was dismissed as an 8insoluble mystery0--or relegated to ,metaphysics for such minds as chose to puzzle over questions not amenable to experiment4 ,physics1 confident in the possession of mathematical and experimental methods which yielded definite answers to properly restricted questions1 peremptorily refused to listen to any suggestion of the kind4 ,and the career of ,physics was so triumphant that success seemed to justify its indifference4 #c4 ,in our own day this analytical school has begun to extend its methods even to the mental group4 ,having reduced all the objective group to mathematical treatment1 it now tries to bring the subjective group also within its range4 ,not only has there been more than one attempt at a mathematical ,psychology2 but also attempts to reduce ,sensibility1 in its subjective no less than in its objective aspect1 to molecular movement4 ,here also the facts of ,quality are translated into facts of ,quantity2 and all diversities of ,feeling are interpreted as simply quantitative differences4 #d4 ,thus far the one school4 ,but while this ,theoretic ,conception stripped ,nature of consciousness1 motive1 and passion1 rendering it a mere aggregate of mathematical relations1 a critical process was going on1 which1 analyzing the nature of ,perception1 was rapidly moving towards another goal4 ,locke1 ,berkeley1 ,hume1 and ,kant1 directing their analysis exclusively to the subjective aspect of phenomena1 soon broke down the barriers between the physical and mental1 and gradually merged the former in the latter4 ,matter and its qualities1 hitherto accepted as independent realities1 existing where no ,mind perceived them1 were now viewed as the creations of ,mind--their existence was limited to a state of the percipient4 ,the old ,dualism was replaced by ,idealism4 ,the ,cosmos1 instead of presenting a problem of ,mechanics1 now presented a problem of ,psychology4 ,beginning with what are called the secondary qualities of ,matter1 the psychological analysis resolved these into modes of ,feeling4 8,the heat which the vulgar imagine to be in the fire and the color they imagine in the rose are not there at all1 but are in us--mere states of our organism40 ,having gained this standing-place1 there was no difficulty in extending the view from the secondary to the primary qualities4 ,these also were perceptions1 and only existed in the percipient4 ,nothing then remained of ,matter save the hypothetical unknown x--the postulate of speculation4 ,kant seemed forever to have closed the door against the real ,cosmos when he transformed it into a group of mental forms--,time1 ,space1 ,causality1 ,quantity1 etc4 ,he propounded what may be called a theory of mental ,dioptrics whereby a pictured universe became possible1 as ,experience by its own a priori laws moulded itself into a consistent group of appearances1 which produced the illusion of being a group of realities4 ,he admitted1 indeed1 that by the operation of ,causality we are compelled to believe in a ,real underlying the appearances2 but the very fact that this ,causality is a subjective law1 is proof1 he said1 of its not being an objective truth4 ,thus the aim of the mechanical conception was to free research from the misleading complexities of subjective adulterations1 and view things as they are apart from their appearances2 but this aim seemed illusory when ,psychology showed that ,time1 ,space1 ,matter1 and ,motion were themselves not objective reals except in so far as they represented subjective necessities2 and that1 in short1 things are just what they appear1 since it is only in the relation of external reals to internal feelings that objects exist for us4 #e4 ,idealism has been the outcome of the psychological method4 ,it has been of immense service in rectifying the dualistic conception1 and in correcting the mechanical conception4 ,it has restored the subjective factor1 which the mechanical conception had eliminated4 ,it has brought into incomparable clearness the fundamental fact that all our knowledge springs from1 and is limited by1 ,feeling4 ,it has shown that the universe represented in that knowledge1 can only be a picture of the system of things as these exist in relation to our ,sensibility4 ,but equally with the mechanical conception it has erred by incomplete analysis4 ,for a complete theory of the universe1 or of any one phenomenon1 those elementary conditions which analysis has provisionally set aside must finally be restored4 ,when ,quality is replaced by ,quantity1 this is an artifice of method1 which does not really correspond with fact4 ,the quality is the fact given in feeling1 which we analytically refer to quantitative differences1 but which can never be wholly resolved into them1 since it must be presupposed throughout4 ,one color1 for example1 may be distinguished from another as having more or fewer undulations2 and so we may by abstraction1 letting drop all qualitative characters1 make a scale of undulations to represent the scale of colors4 ,but this is an ideal figment4 ,it is the representation of one series of feelings by another series of different feelings4 ,no variation of undulations will really correspond with variation in color1 unless we reintroduce the suppressed quality which runs through all color4 ,attempt to make one born blind feel1 or even understand1 ,color by describing to him the kind of wave-movement which it is said to be1 and the vanity of the effort will be manifest4 ,movement he knows1 and varieties of movement as given in tactile and muscular sensations2 but no combination and manipulation of such experiences can give him the specific sensation of ,color4 ,that is a purely subjective state1 which he is incapable of experiencing1 simply because one of the essential factors is absent4 ,one set of objective conditions is present1 but the other set 7his sense-organ7 is defective4 ,without the 8greeting of the spirit0 undulations cannot become colors 7nor even undulations1 for these also are forms of feeling74 ,besides the sense-organ there is needed the feeling of ,difference1 which is itself the product of past and present feelings4 ,the reproduction of other colors1 or other shades of color1 is necessary to this perception of difference2 and this involves the element of ,likeness and ,unlikeness between what is produced and reproduced4 ,so that a certain mental co-operation is requisite even for the simplest perception of quality4 ,in fact1 psychological analysis shows that even ,motion and ,quantity1 the two objective terms to which subjective ,quality is reduced1 are themselves ,fundamental ,signatures of ,feeling2#bje so that here1 as elsewhere1 it is only by analytical artifice that the objective can be divorced from the subjective4 ,matter is for us the ,felt2 its ,qualities are differences of ,feeling4 #f4 ,not that this result is to be interpreted as freeing our ,theoretic ,conception from its objective side1 and landing us in ,idealism1 which suppresses the real universe4 ,the denial of all reality apart from our minds1 is a twofold mistake3 it confounds the conception of general relations with particular relations1 declaring that because the ,external in its relation to the sentient organism can only be what it is felt to be1 therefore it can have no other relations to other individual reals4 ,this is the first mistake4 ,the second is the disregard of the constant presence of the objective real in every fact of ,feeling3 the ,not-,self is emphatically present in every consciousness of ,self4 ,the legitimate conclusion is neither that of ,dualism nor of ,idealism1 but what ,i have named ,reasoned ,realism 7,problems1 ,vol4 ,i4 p4 #bja71 which reconciles ,common ,sense with ,speculative ,logic1 by showing that although the truth of things 7their ,wahrheit7 is just what we perceive in them 7our ,wahrnehmung71 yet their reality is this1 and much more than this4 ,things are what they are felt to be2 and what they are thought to be1 when thoughts are symbols of the perceptions4 ,idealism declares that they are nothing but this4 ,it is against this nothing but that ,common ,sense protests2 and the protest is justified by ,reasoned ,realism1 which1 taking a comprehensive survey of the facts1 thus answers the idealist3 8,your synthesis is imperfect1 since it does not include all the data--notably it excludes the fact of an objective or ,not-,self element in every feeling4 ,you may1 conceivably1 regard the whole universe as nothing but a series of changes in your consciousness2 but you cannot hope to convince me that ,i myself am simply a change in yourself1 or that my body is only a fleeting image in your mind4 ,hence although ,i conclude that the ,not-,self is to you1 as to me1 undivorceable from ,self1 inalienable from ,feeling1 in so far as it is felt1 yet there must nevertheless be for both of us an existence not wholly coextensive with our own4 ,my world may be my picture of it2 your world may be your picture of it2 but there is something common to both which is more than either--an existent which has different relations to each4 ,you are not me1 nor is the pictured ,cosmos me1 although ,i picture it4 ,looking at you and it1 ,i see a vast whole of which you are a small part2 and such a part ,i conclude myself to be4 ,it is at once a picture and the pictured2 at once subjective and objective4 ,to me all your modes of existence are objective aspects1 which1 drawing from my own experience1 ,i believe to have corresponding subjective aspects2 so that your emotions1 which to me are purely physical facts1 are to you purely mental facts4 ,and psychological analysis assures me that all physical facts are mental facts expressed in objective terms1 and mental facts are physical facts expressed in subjective terms40 #g4 ,but while ,philosophy thus replaces the conceptions of ,dualism and ,idealism by the conception of the ,two-fold ,aspect1 the special sciences in their analytical career have disregarded the problem altogether4 ,the mechanical theory of the universe not only simplified research by confining itself solely to the objective aspect of phenomena1 but by a further simplification set aside all vital and chemical relations1 to deal exclusively with mechanical relations4 ,in ascertaining the mathematical relations of the planetary system1 no elucidation could possibly be gained from biological or chemical conceptions2 the planets therefore were provisionally stripped of everything not mechanical4 ,in systematizing the laws of motion1 it was necessary to disengage the abstract relations from everything in any way resembling spontaneity1 or extra-mechanical agency3 ,matter was therefore1 by a bold fiction1 declared to be inert1 and its ,motion regarded as something superadded from without4 #g;a4 ,and this was indispensable for the construction of those ideal laws which are the objects of scientific research4 ,science1 as we often say1 is the systematization of ,experience under the forms of ideal constructions4 ,experience implies ,feeling1 and certain fundamental ,signatures1 all reducible to the primary discernment of ,likeness and ,unlikeness4 ,hence ,science is first a classification of qualities or discerned likenesses and differences2 next a measurement of quantities of discerned likenesses and differences4 ,although measurement is itself a species of classification1 it is distinguished by the adoption of a standard unit of comparison1 which1 being precise and unvarying1 enables us to express the comparisons in precise and unvarying symbols4 ,whether the unit of length adopted be an inch1 a foot1 a yard1 a mile1 the distance of the earth from the sun1 or the distances of the fixed stars1 the quantities thus measured are symbols admitting of one invariable interpretation4 ,the exactness of the mathematical sciences is just this precision and invariability of their symbols1 and is not1 as commonly supposed1 the source of any superior certainty as to the facts4 ,the classificatory sciences1 which deal with qualities rather than with quantities1 may be equally certain1 and represent fuller knowledge1 because involving more varied feelings1 but they cannot pretend to exactness4 ,even on the quantitative side1 certainty is not identical with exactness4 ,i may be quite certain that one block of marble is larger than another--meaning that it affects me more voluminously--but ,i cannot know how much larger it is1 without interpreting my feelings by the standard of quantity--the how-muchness as represented by that standard4 ,the immense advantages of exact measurement need not be insisted on4 ,the ,biological ,sciences1 which are predominantly classificatory1 can never rival the ,cosmological ,sciences in exactness2 but they may reach a fuller knowledge2 and their certainty will assume more and more the character of exactness as methods of measurement are applied to their classifications of qualities4 ,the qualitative and quantitative aspects of phenomena are handled by the two great instruments1 ,logic and ,mathematics1 the second being only a special form of the first4 ,these determine the general conceptions which are derived from our perceptions1 and the whole constitute ,experience4 #h4 ,what is the conclusion to which these considerations lead8 ,it is that the separation of the quantitative from the qualitative aspect of phenomena--the objective mechanical from the subjective psychological--is a logical artifice indispensable to research2 but it is only an artifice4#bjf ,in pursuance of this artifice1 each special science must be regarded as the search after special analytical results2 and meanwhile this method should be respected1 and no confusion of the boundaries between one science and another should be suffered4 ,mechanical problems must not be confused by the introduction of biological relations4 ,biological problems must not be restricted to mechanical relations4 ,i do not mean that the mechanical relations present in biological phenomena are not to be sought1 and1 when found1 to be expressed in mechanical terms2 ,i mean that such an inquiry must be strictly limited to mechanical relations4 ,subjective relations are not to be denied1 because they are provisionally set aside1 in an inquiry into objective relations2 but we must carefully distinguish which of the two orders we are treating of1 and express each in its appropriate terms4 ,this is constantly neglected4 ,for example1 nothing is more common than to meet such a phrase as this3 8,a sensory impression is transmitted as a wave of motion to the brain1 and there being transformed into a state of consciousness1 is again reflected as a motor impulse40 ,the several sciences having attained certain analytical results1 it remains for ,philosophy to co-ordinate these into a doctrine which will furnish general conceptions of the ,world1 ,man1 and ,society4 ,on the analytical side a mechanical theory of the universe might be perfected1 but it would still only be a theory of mechanical relations1 leaving all other relations to be expressed in other terms4 ,we cannot accept the statement of ,descartes that ,nature is a vast mechanism1 and ,science the universal application of mathematics4 ,the equation of a sphere1 however valuable from a geometrical point of view1 is useless as an explanation of the nature and properties of the spherical body in other relations4 ,and so a complete theory of the mechanical relations of the organism1 however valuable in itself1 would be worthless in the solution of a biological problem1 unless supplemented by all that mechanical terms are incompetent to express4 #i4 ,the course of biological speculation has been similar to the cosmological4 ,it also began with a ,first ,notion1 which compendiously expressed the facts of ,experience4 ,nor can any ,theoretic ,conception be finally adopted which does away with these facts1 known with positive certainty1 and popularly expressed in the phrase3 8,i have a body1 and a soul40 ,we may alter the phrase either into 8,i am a body1 and ,i am a soul02 or into1 8,my body is only the manifestation of my soul02 or1 8,my soul is only a function of my body02 but the fundamental experiences which are thus expressed are of absolute authority1 no matter how they may be interpreted4 ,that ,i have a body1 or am a body1 is not to be speculatively argued away4 ,that ,i move my arm to strike the man who has offended me1 or stretch out my hand to seize the fruit which ,i see1 is unquestionable2 that these movements are determined by these feelings1 and are never thus effected unless thus determined1 is also unquestionable4 ,here are two sets of phenomena1 having well-marked differences of aspect2 and they are grouped respectively under two general heads1 ,life and ,mind4 ,life is assigned to the physical organism1 or ,body--all its phenomena are objective4 ,mind is assigned to the psychical organism1 or ,soul--all its phenomena are subjective4 ,although what is called my ,body is shown to be a group of qualities which are feelings--its color1 form1 solidity1 position1 motion--all its physical attributes being what is felt by us in consequence of the laws of our organization2 yet inasmuch as these feelings have the characteristic marks of objectivity1 and are thereby referred to some objective existence1 we draw a broad line of demarcation between them and other feelings having the characteristic marks of subjectivity1 and referring to ourselves as subjects4 ,psychological analysis shows us that this line of demarcation is artificial1 only representing a diversity of aspect2 but as such it is indispensable to science4 ,we cannot really separate in a sensation what is objective from what is subjective1 and say how much belongs to the ,cosmos apart from ,sensibility1 and how much to the subject pure and simple2 we can only view the sensation alternately in its objective and subjective aspects4 ,what belongs to extra-mental existence in the phenomenon of ,color1 and what to the 8greeting of the spirit10 is utterly beyond human knowledge3 for the ethereal undulations which physicists presuppose as the cosmic condition are themselves subjected to this same greeting of the spirit3 they too are ideal forms of sensible experiences4 #aj4 ,this conclusion1 however1 was very slowly reached4 ,the distinction of aspects was made the ground of a corresponding distinction in agencies4 ,each group was personified and isolated4 ,the one group was personified in ,spirit--an existent in every respect opposed to ,matter1 which was the existent represented in the other group4 ,one was said to be simple1 indestructible2 the other compound1 destructible4 ,one was invisible1 impalpable1 beyond the grasp of ,sense2 the other was visible1 tangible1 sensible4 ,one was of heaven1 the other of earth4 ,thus a biological ,dualism1 analogous to the cosmological1 replaced the ,first ,notion4 ,it was undermined by advances in two directions4 ,psychology began to disclose that our conception of ,matter was1 to say the least1 saturated with ,mind1 its ,atoms confessedly being ideal figments2 and that all the terms by which we expressed material qualities were terms which expressed modes of ,feeling2 so that whatever remained over and above this was the unknown x1 which speculation required as a postulate4 ,idealism1 rejecting this postulate1 declared that ,matter was simply the projection of ,mind1 and that our ,body was the objectivation of our ,soul4 ,physiology began to disclose that all the mental processes were 7mathematically speaking7 functions of physical processes1 i4 e4 varying with the variations of bodily states2 and this was declared enough to banish forever the conception of a ,soul1 except as a term simply expressing certain functions4 #aa4 ,idealism and ,materialism are equally destructive of ,dualism4 ,the defects of particular idealist and materialist theories we will not here touch upon2 they mainly result from defects of ,method4 ,not sufficiently recognizing the primary fact testified by ,consciousness1 namely1 that ,experience expresses both physical and mental aspects1 and that a ,not-,self is everywhere indissolubly interwoven with ,self1 an objective factor with a subjective factor1 the idealist reduces ,existence to a mere panorama of mental states1 and the ,body to a group in this panorama4 ,he is thus incapable of giving a satisfactory explanation of all the objective phenomena which do not follow in the same order as his feelings1 which manifest a succession unlike his expectation1 and which he cannot class under the order of his mental states hitherto experienced4 ,he conceives that it is the ,mind which prescribes the order in ,things2 whereas experience assures us that the order is described1 not prescribed by us3 described in terms of ,feeling1 but determined by the laws of ,things1 i4 e4 the genesis of subjective phenomena is determined by the action of the ,cosmos on our ,sensibility1 and the reaction of our ,sensibility4 ,he overlooks the evidence that the mental forms or laws of thought which determine the character of particular experiences1 were themselves evolved through a continual action and reaction of the ,cosmos and the ,soul1 precisely as the laws of organic action which determine the character of particular functions were evolved through a continual adaptation of the organism to the medium4 ,these immanent laws are declared to be transcendental1 antecedent to all such action and reaction4 ,a similar exclusiveness vitiates the materialist doctrine4 ,overlooking the primary fact that ,feeling is indissolubly interwoven with processes regarded as purely physical because they are considered solely in their objective aspect1 the materialist fails to recognize the operation of psychological laws in the determination of physiological results2 he hopes to reduce ,biology to a problem of ,mechanics4 ,but ,vitality and ,sensibility are coefficients which must render the mechanical problem insoluble1 if only on the ground that mechanical principles have reference to quantitative relations1 whereas vital relations are qualitative4 ,his error is the obverse of the vitalist's error4 ,the vitalist imagines that the speciality of organic phenomena proves the existence of a cause which has no community with the forces operating elsewhere2 so1 turning his back on all the evidence1 he attempts to explain organic phenomena without any aid from ,physics and ,chemistry4 ,the materialist1 turning his back on all the evidence of quite special conditions only found at work in living organisms1 tries to explain the problem solely by the aid of ,physics and ,chemistry4 ,it is quite certain that physiological and psychological problems are not to be solved if we disregard the laws of ,evolution through ,epigenesis4 ,the mental structure is evolved1 as the physical structure is evolved4 ,it is quite certain that no such evolution is visible in anorganisms1 nor will any one suppose it to be possible in machines4 ,from the biological point of view we must therefore reject both ,idealism and ,materialism4 ,we applaud the one when it says1 8,don't confuse mental facts by the introduction of physical hypotheses02 and the other when it says1 8,don't darken physical facts with metaphysical mists40 ,we say to both1 8,by all means make clear to yourselves which aspect of the phenomena you are dealing with1 and express each in its own terms4 ,but in endeavoring to understand a phenomenon you must take into account all its ascertainable conditions4 ,now these conditions are sometimes only approachable from the objective side2 at other times only from the subjective side40 #ab4 ,while it is necessary to keep the investigation of a process on its objective side1 limited to objective conditions1 and to express the result in objective terms1 we must remember that this is an artifice2 above all1 we must remember that even within the objective limits our analyses are only provisional1 and must be finally rectified by a restoration of all the elements we have provisionally set aside4 ,thus rectified1 the objective interpretation of vital and mental phenomena has the incomparable advantage of simplifying research1 keeping it fixed on physical processes1 instead of being perturbed by suggestions of metaphysical processes4 ,and as all physical investigation naturally tends to reduce itself to a mechanical investigation1 because ,mechanics is the science of motion1 and all physical processes are motions1 we may be asked1 ,why should not the mechanical point of view be the rational standing-point of the biologist8 ,our answer is1 ,because ,mechanics concerns itself with abstract relations1 and treats of products without reference to modes of production1 i4 e4 with motions without reference to all the conditions on which they depend4 ,every physical change1 if expressed in physical terms1 is a change of position1 and is determined by some preceding change of position4 ,it is a movement having a certain velocity and direction1 which velocity and direction are determined by the velocity and direction of a force 7a pressure or a tension7 compounded with the forces of resistance1 i4 e4 counter-pressures4 ,clearly1 the nature of the forces in operation must be taken into account2 and it is this which the mechanical view disregards1 the biological regards4 ,the mechanical view is fixed on the ascertained adjustment of the parts1 so that the working of the organism may be explained as if it were a machine1 a movement here liberating a movement there4 ,the biological view includes this adjustment of parts1 but takes in also the conditions of molecular change in the parts on which the adjustment dynamically depends4 ,mechanical actions may be expressed as the enlargement or diminution of the angle of two levers2 but chemical actions are not thus expressible2 still less vital and mental actions4 #ac4 ,the organism is on the physical side a mechanism1 and so long as the mechanical interpretation of organic phenomena is confined to expressing the mechanical principles involved in the mechanical relations1 it is eminently to be applauded4 ,but the organism is something more than a mechanism1 even on the physical side2 or1 since this statement may be misunderstood1 let me say1 what no one will dispute1 that the organism is a mechanism of a very special kind1 in many cardinal points unlike all machines4 ,this difference of kind brings with it a difference of causal conditions4 ,in so far as the actions of this mechanism are those of a dependent sequence of material positions1 they are actions expressible in mechanical terms2 but in so far as these actions are dependent on vital processes1 they are not expressible in mechanical terms4 ,vital facts1 especially facts of sensibility1 have factors neither discernible in machines nor expressible in mechanical terms4 ,we cannot ignore them1 although for analytical purposes we may provisionally set them aside4 99 99 99 99 99 ,in the course of the development of the mechanical theory1 the history of which has just been briefly sketched1 biological problems have more and more come under its influence4 ,there has always been a fierce resistance to the attempt to explain vital and sentient phenomena on mechanical1 or even physical principles1 but still the question has incessantly recurred1 ,how far is the organism mechanically interpretable8 ,and while the progress of ,biology has shown more and more the machine-like adjustment of the several parts of which the organism is composed1 it has also shown more and more the intervention of conditions not mechanically interpretable4 ,we shall have to consider the question1 therefore1 under two forms4 ,first1 whether animals are machines1 and if not1 by what characters do we distinguish them from machines8 ,secondly1 in what sense can we correctly speak of ,feeling as an agent in organic processes8 ,,chapter ,,ii4 ,,the ,,vital ,,mechanism4 #ad4 ,no answer can be successfully attempted in reply to the first of the questions which closed the last chapter until we have given precision to certain terms of incessant recurrence4 ,i have often to remark on the peculiar misfortune of ,psychology1 that all its principal terms are employed by different writers1 and are understood by different readers1 in widely different senses3 they denote and connote meanings of various significance4 ,all physicists mean the same thing when they speak of weight1 mass1 momentum1 electricity1 heat1 etc4 ,all chemists mean the same thing when they speak of affinity1 decomposition1 oxygen1 carbonic acid1 etc4 ,all physiologists mean the same thing when they speak of muscle1 nerve1 nutrition1 secretion1 etc4 ,but scarcely any two psychologists mean precisely the same thing when they speak of sensation1 feeling1 thought1 volition1 consciousness1 etc42 and the differences of denotation and connotation in their uses of such terms lead to endless misunderstanding4 ,as ,rousseau says3 8,les dfinitions pourraient tre bonnes si l'on n'employait pas les mots pour les faire40 ,but since we must employ words as our signs1 our utmost care should be given to clearly marking what it is the signs signify4 #ae4 ,the question we have now before us1 whether animal actions are interpretable on purely mechanical principles8 can only be answered after a preliminary settlement of the terms4 ,the first of these terms to be settled is that of mechanism1 when applied to the vital organism4 ,if the organism is a mechanism1 its actions must of course be interpretable on mechanical principles4 ,but this general truth requires a special interpretation1 if on inquiry we find that the organism is a particular kind of mechanism1 one which is not to be classed under the same head as inorganic machines4 ,and this we do find4 ,in ,problem ,i4 #bb1 will be found a statement of the radical difference between organic and inorganic mechanisms1 due to the differences in their structures4 ,but the differences there noted do not affect the operation of abstract mechanical principles1 which are of course manifested wherever there is a dependent sequence of material changes2 and which are the same abstract principles in the mechanism of the heavens1 the mechanism of a paper-mill1 or the mechanism of an animal body4 ,in other words1 the principles are abstract1 and are abstracted from all concrete cases by letting drop what is special to each case1 retaining only what is common to all4 ,this procedure is indispensable to the ideal constructions of ,science4 ,but we cannot rightly interpret any concrete case by abstract principles alone2 we must restore the special characters which the abstraction has eliminated4 ,the most lucid explanation of the mechanism of the heavens will leave us quite in the dark respecting the action of a paper-mill1 until we have studied the mill at work1 ascertained its structure and mode of operation1 and therein detected what is common both to its mechanism and to the mechanism of the heavens4 ,thus equipped1 we approach the study of the animal mechanism1 but find ourselves wholly in the dark until we have also ascertained its structure and mode of operation2 then we may recognize in it the principles of dependent sequence which had been abstracted from the paper-mill and the heavens4 ,to neglect this concrete study1 and to argue from ,machinery to ,life in disregard of special conditions1 is not more rational than to assume that the movement of a piston is prompted by volition4 #af4 ,the recognition of special differences is no denial of fundamental identities4 ,we do not deny the presence of phenomena in organisms which belong to physical and chemical agencies1 but we assert that organisms have other phenomena besides these1 dependent on conditions not present in physical and chemical phenomena4 ,the same material elements and forces may be recognized in a moving inorganic body1 and a moving organic body2 but in the latter there is a speciality of combination with a speciality of result4 ,just as the same words and laws of grammatical construction may be recognized in prose and poetry2 yet poetry is not prose1 but has special rules of its own1 and special effects4 ,in an organism1 as in a machine1 the adjustment of the parts is a condition of the mechanical action2 the one enables us to explain the other4 ,but the parts adjusted1 and the consequences of the adjustment1 are unlike in the two cases4 ,this unlikeness is pervading and profound4 ,one cardinal difference is that the combination of the parts is in the machine a fixed1 in the organism a fluctuating adjustment2 and this fluctuation is due to certain vital processes subjectively known as sensitive guidance4 ,hence machines have fixed and calculated mechanisms2 whereas organisms are variable and to a great extent incalculable mechanisms4 #ag4 ,i conceive1 therefore1 that a theory which reduces vital activities to purely physical processes is self-condemned4 ,not that we are to admit the agency of any extra-organic principle1 such as the hypothesis of ,vitalism assumes 7,prob4 ,i4 #ad72 but only the agency of an intra-organic principle1 or the abstract symbol of all the co-operant conditions--the special combination of forces which result in organization4 ,this assures us that an organism is a peculiar kind of mechanism1 the processes in which are peculiar to it2 and among those processes there is one which results in what we call ,sensibility4 ,this ,sensibility is a factor which raises the phenomena into another order4 ,to overlook its presence is fatal to any explanation of the organic mechanism4 ,yet it is overlooked by those who tell us that when an impression on a nerve is conveyed to the brain1 and is thence reflected on the limbs--as when the retina of a wolf is stimulated by the image of a sheep1 and the spring of the wolf upon the sheep follows as a 8purely mechanical consequence--the whole process has from first to last been physical40 ,unless the term physical is here used to designate the objective sequence1 as contemplated by an onlooker1 who likens the process to the sequence observable in a machine1 ,i should say that from first to last the process has been not physical1 but vital1 involving among its essential conditions the peculiarly vital factor named ,sensibility4 ,the process taking place in the wolf's organism is one which involves conditions never found in purely physical processes4 ,we may indeed analytically disregard these4 ,we may view the process in its purely physical relations1 or in its purely chemical relations1 or in its purely mathematical 7mechanical7 relations4 ,but this is the artifice of the analytical method4 ,in reality the process is no one of these1 for it is all of these2 it is a process in a living organism1 and depends on conditions only found in living organisms--nay1 in this particular case the process depends on conditions only found in organisms like that of the wolf2 for the image of the sheep will stimulate the brain of a goat1 horse1 or elephant without producing any such movement in the organism4 #ah4 ,the importance of this point must excuse my reiteration of it4 ,we must make clear to ourselves that the organism is in its objective aspect a physiological mechanism1 in its subjective aspect a psychological mechanism3 in both aspects it is to be radically demarcated from all inorganic mechanisms4 ,in it the combination and co-ordination of movements involve conditions never present in machines2 among these conditions1 there are combinations and co-ordinations of ,sensibility1 which1 although material processes on the objective side1 are processes believed to be only present in organisms4 ,we have the strongest reasons for concluding that every feeling1 every change in ,sensibility1 has its correlative material process in the organism--is1 in short1 only the subjective aspect of the objective organic change4 ,what in ,physiology is called ,co-ordination and has reference to movements1 in ,psychology may be called ,logic1 having reference to feelings4 ,but be this latter point accepted or rejected1 the one point which admits of no dispute is that an organism is radically distinguishable from every inorganic mechanism in that it acquires through the very exercise of its primary constitution1 a new constitution with new powers4 ,its adjustment is a changing and developing mechanism4 ,that is to say1 a machine1 however complex its structure1 is constructed once for all1 and this primary constitution is final1 the adjustment of parts remaining unaltered2 and although by exercise the machine may come to work more easily1 with less friction1 it never comes to work differently1 to readjust its parts1 and develop new capabilities4 ,it has no historical factor manifest in its functions4 ,it has no experience4 ,it reacts at last as at first4 ,how different the organism6 ,this has not only variable adjustments due to internal fluctuations1 it has experience which develops new parts1 and new adjustments of old parts4 ,every organism has its primary constitution in the adjustment of parts peculiar to the species2 it has also its secondary or modified constitution1 in the adjustment which has been more or less altered by individual experiences2 it has1 thirdly1 its temporary constitution in the variable adjustment due to the varying state of tension which results from varying stimulation4 #ai4 ,a word on each4 ,there is a structural disposition of the parts which is common to large groups of organisms1 so that a corresponding similarity is observable in the reactions of these organisms4 ,thus all quadrupeds use their limbs for locomotion in very similar ways2 birds use their wings for flight in similar ways4 ,all vertebrates swallow their food1 defend themselves1 shrink when hurt1 etc41 in ways that are very similar4 ,in so far as their organizations are alike1 their actions and reactions are alike4 ,in so far as their organizations differ1 their actions and reactions differ4 ,the goose and the vulture are alike in the main lines of structure2 still more alike are duck and hen2 yet1 owing to certain unlike characters of structure1 they manifest some marked differences in action and reaction3 the goose will starve in the presence of food which the vulture gluttonously devours1 and the vulture will refuse the vegetable food which the goose devours2 the duck plunges into the water1 the hen not only refuses to enter it1 but is greatly agitated when she sees the ducklings she has hatched plunging into it4 ,that peculiar instincts1 habits1 and feelings are rigorously determined by peculiarities in the organism1 no one doubts1 when animals are in question4 ,if this is less obvious in the case of men1 the reason is that there the influence of other factors somewhat masks the operation of the primary constitution--these factors are the modified and the temporary constitutions4 ,yet even in man it is true to say that his feelings and actions are the result of his organization1 native and acquired4 #bj4 ,no two men are organized in all respects alike4 ,there are individual variations in structure1 both native and acquired4 ,these may be too slight to be appreciable by any other test than the difference of reaction under similar external stimuli2 but the variations in the sensibility to music1 color1 temperature1 sexual influence1 moral influence1 etc41 betray corresponding differences in the organisms4 ,any one variation in structure1 seemingly trivial1 may be the origin of well-marked diversity in physical and moral characters4 ,compare the bull with the ox1 or the predatory aggressive eagle with the cowardly vulture4 ,nor are the temporary modifications to be overlooked4 ,antoine ,cros mentions the case of a patient1 a young girl1 suffering from congested liver and spleen1 which of course altered the state of her blood1 and thus for a time modified her constitution4 ,her moral character was greatly altered by it4 ,she ceased to feel any affection for father or mother2 would play with her doll1 but could not be brought to show any delight in it2 could not be drawn out of her apathetic sadness4 ,things which previously had made her shriek with laughter1 now left her uninterested4 ,her temper changed1 became capricious and violent4#bjg ,congestion of the lungs1 if unaccompanied by congestion of the liver1 never produces such effects1 because not thus altering the blood4 ,the effects of liver congestion are familiar4 ,cros cites the case of a magistrate whose liver was enlarged1 and whose skin showed a markedly bilious aspect1 and in whom all affection seemed to be dead3 he did not exhibit any perversion or violence1 only want of emotive reaction4 ,if he went to the theatre he could not feel the slightest pleasure in it4 ,the thoughts of his home1 his absent wife and children1 were1 he declared1 as unaffecting to him as a problem in ,euclid4 #ba4 ,owing to the recognized dependence of peculiar instincts and modes of reaction on peculiarities of structure1 comparative anatomists are quite confident1 when they find a portion of a skull with two occipital condyles1 that the animal to which this skull belonged had red blood-corpuscles without nuclei1 and 7if a female7 suckled its young4 ,if in that fragment of skull there remain a single tooth1 it will prove that the animal was carnivorous or herbivorous1 and had1 or had not1 retractile claws4 ,from such data a general conclusion may be formed as to the instincts and habits of the animal4 ,the data disclose much of the primary constitution1 that is to say1 the mechanism which the animal brought with it into the world1 ready prepared to react in definite ways on being stimulated4 ,the connate mechanism has correlative tendencies of reaction4 ,some of these tendencies are inevitably called into play by external conditions1 and they continue unaltered amid great varieties of circumstances1 provided none of these variations directly deprive them of their appropriate stimulation4 ,such tendencies of the connate mechanism are styled automatic 7an unfortunate metaphor1 which has led to the theory of ,automatism71 and include1 besides the visceral reactions1 the more complex reactions of winking1 breathing1 swallowing1 coughing1 flying1 walking1 etc4 ,it is true that we learn to walk1 and learn to wink1 whereas the other actions require no tentative efforts directed by experience2 but the mechanism of all these actions is already laid down in the primary constitution1 and is inevitably called into play4 #bb4 ,the instincts also belong to the connate mechanism1 and in the course of the normal experience of the animal inevitably come into play2 but1 unlike the automatic tendencies of breathing1 swallowing1 and coughing1 they are capable of modification1 or even suppression1 by alterations in the course of individual experience4 ,the connate mechanism of the cat determines its dread of water1 and its enmity to the dog and mouse2 yet a cat will by the modifications of certain experiences become as ready as an otter to take to the water1 and become so fond of a dog that she will allow him to tend upon her kittens2 and so indifferent to the mouse that she will let it run over her body4 ,all this implies a new adjustment in the nervous centres1 with new modes of reaction on sensory impressions3 the inherited mechanism has been modified4 ,i need not dwell on the profound modifications which the human inherited mechanism undergoes in the course of experience--how social influences and moral and religious teachings redirect1 or even suppress1 many primary tendencies2 so that 8moral habits0 become organized1 and replace the original tendencies of the organism4 ,these1 when organized1 become the inevitable modes of reaction1 and are sometimes called secondarily automatic4 ,it is important to recognize this organization of experiences1 this acquisition of a secondary or modified constitution1 if we would explain psychological processes by physiological processes4 ,thus the processes of ,logic are automatic1 they belong to the connate primary mechanism1 and their action is inevitable1 invariable4 ,the elements of a judgment1 like the elements of a perception1 may vary1 and we therefore say that one judgment is false1 and one perception incomplete2 but the judging process is always the same1 and the perceiving process is always the same4 ,we may breathe pure air or impure air1 but the breathing process is in each case the same2 and judgment is as automatic as breathing1 not to be altered1 not to be suppressed4 ,again1 the moral terror at wickedness of any recognized kind is as automatic as the instinctive terror at danger4 ,the one has its roots in the primary disposition called love of approbation and its correlative dread of disapprobation3 the social instinct4 ,the other has its root in the primary disposition called 8instinct of self-preservation10 which is really the reflex shrinking from pain3 the physiological instinct4 #bc4 ,besides the connate and acquired mechanism1 we have now to consider the temporary and fluctuating adjustments which represent the statical condition of the organism at each moment4 ,the automatism of the primary constitution is such that previous experience and conscious effort are not needed2 nor will any experience or any effort alter the mode of reaction4 ,if a strong light falls on the eye1 the iris contracts2 if the eyeball is dry1 the eyelid drops2 if sound-waves beat upon the tympanum1 the stapedius muscle contracts2 if the lining of the throat be tickled1 the muscles involved in coughing or in vomiting contract4 ,no experience is necessary for these actions1 some of which are so complicated that if we had to learn them1 as we learn far simpler actions1 the organism would perish before the power was attained4 ,yet all of these presuppose a certain normal state of the mechanism1 any considerable variation in which will modify or suppress them4 #bd4 ,secondarily automatic actions are those which have been acquired through experiences that have modified the organism1 and produced a new adjustment of parts4 ,we learn to shield the eyes against a strong glare of light by raising the hand2 by winking we learn to shield the eye against an approaching body2 we also learn to turn the head in the direction of a sound1 and to thrust away with our hands the object that is irritating our skin4 ,experience has been necessary for all these actions1 and has finally organized the tendencies to perform them1 so that the reaction is invariable1 inevitable1 unless controlled by the will4 ,if you tickle my throat1 ,i may1 or may not1 push aside your hand2 but if the inside of my throat be tickled1 ,i must cough4 ,here we see the difference between the automatic and secondarily automatic actions4 ,the second being due to individual experience1 are more or less controllable2 and whether they are or are not controlled depends on the condition of the nerve-centres at the moment4 ,you may tickle my throat1 or irritate my skin1 without causing any movement of my hands to thwart you1 either because my nerve-centres are preoccupied by other stimulations1 and ,i am not conscious of the irritation1 or because ,i do not choose to thwart you4 #be4 ,it should be added that some secondarily automatic actions have become so firmly organized that we can only with great difficulty interfere with them4 ,others never enter into consciousness1 and are therefore often supposed to be purely mechanical4 ,the movement of the eye towards the brightest light1 and the convergence of the axes of both eyes1 are reflexes which1 although involuntary and unconscious1 are the products of education4 ,they do not belong to the connate constitution1 although they are so inevitably acquired by experience that they belong to every normal child4 ,at first the infant stares with a blank gaze1 and its eyes1 though moving under the stimulus of light1 move incoherently2 the axes never converge except by accident4 ,very early1 however1 the infant's eyes are observed to follow the movements of a bright light2 and at last they acquire so certain and rapid a power of adjustment that the eyes shift from spot to spot1 always 8fixing0 the object by bringing the most sensitive part of the retina to bear on it4 ,the incoherent movements have become precisely regulated movements4 ,it is the same with speech4 ,the vocal organs are exercised in an incoherent babble4 ,by degrees these movements become regulated so as to respond definitely to definite stimuli1 and words are formed1 then sentences1 till finally fluent speech becomes in a great degree automatic4 ,the vocal muscles respond to an auditory stimulus1 and the child repeats the word it has heard1 just as the eye-muscles respond to a retinal stimulus4 ,that we acquire the power of converging the axes1 and accommodating the lens to near objects1 is not only proved by observation of infants1 but also by cases of disease4 ,after the reflex mechanism has been long established1 so that it acts with inevitable precision1 a slight paralysis of one of the muscles has the effect of making all objects appear in a different position2 the patient trying to touch an object1 then always moves his hand on one side of it4 ,von ,graefe relates the case of a stonebreaker who always struck his hand with the hammer when he tried to strike the stone4 ,yet this very man learned to accommodate his movements to the new impressions2 so that if his paralysis had been cured1 his modified mechanism would have been ill adapted to the new conditions1 and he would once more have struck his hand instead of the stone4 #bf4 ,this digression on the native and acquired dispositions of the organism1 while it has brought into strong light all that can be cited in favor of regarding animal bodies as mechanisms1 and their actions as the direct consequences of mechanical adjustments1 has also made conspicuous the radical difference between an organism and a machine4 ,we cannot too emphatically insist on this radical difference4 ,between the group of conditions involved in the structure and action of a machine1 and the group of conditions involved in the structure and action of an organism1 there are contrasts as broad as any that can be named4 ,to overlook these in taking account solely of the conditions common to both groups is a serious error4 ,on such grounds we might insist that a tiger is a violet1 because both are organisms4 ,the biologist will admit that an organism is a mechanism1 and 7in so far as its bodily structure is concerned7 a material mechanism4 ,all the actions of this structure are therefore mechanical1 in the two senses of the term3 first1 as being the actions of material adjustments2 secondly1 as being movements1 and thereby included under the general laws of motion represented in ,mechanics2 the abstract laws of movement for an organic body are not different from the abstract laws of movement for an inorganic body4 ,so far we have been considering the abstract relations only4 ,no sooner do we consider the phenomena as concrete wholes1 than we find great diversity in the modes of production of the movements in organisms and machines4 ,now it is precisely the modes of production which have interest for us4 ,we never understand a phenomenon so as to gain any practical control over it1 or any theoretical illumination from it1 unless we have mastered some of its conditions2 our knowledge of these conditions is the measure of our power4 ,,chapter ,,iii4 ,,the ,,relation ,,of ,,body ,,and ,,mind4 #bg4 ,the second question proposed was1 ,in what sense can ,feeling be correctly spoken of as an ,agent in organic processes8 ,this brings us face to face with a much-debated topic1 the relation of ,body and ,mind2 and demands a theoretic interpretation of that ,first ,notion which expresses universal experience1 namely1 that what ,i know as ,myself is a ,body1 in one aspect1 and a ,soul1 in the other4 ,what ,i call my ,body is a persistent aggregate of objective phenomena2 and my ,soul is a persistent aggregate of subjective phenomena3 the one is an individualized group of experiences expressible in terms of ,matter and ,motion1 and therefore designated physical2 the other an individualized group of experiences expressible in terms of ,feeling1 and therefore designated psychical4 ,but1 however contrasted1 they are both simply embodiments of ,experience1 that is to say1 are ,modes of ,feeling4 ,all ,existence--as known to us--is the ,felt4 ,the laws of our organism compel us1 indeed1 to postulate an ,existent which is extra mentem--a ,real not ,ourselves--but the same laws debar us from any knowledge whatever of what this is1 or is like4 ,we know ,things absolutely in so far as they exist in relation to us2 and that is the only knowledge which can have any possible significance for us4 #bh4 ,it is impossible for me to doubt that ,i am a ,body1 though ,i may doubt whether what is thus called is anything more than a group of feelings4 ,it is impossible for me to doubt that ,i am a ,soul2 though ,i may doubt whether what is thus called is more than a group of bodily functions4 ,in separating what is unquestionable from what is questionable1 we separate the fundamental facts of consciousness from the theoretic interpretations of those facts3 no theoretic interpretation can efface or alter the facts4 ,whatever ,philosophy may discover1 it cannot displace the fact that ,i know ,i am a ,soul1 in every sense in which that phrase represents ,experience3 ,i know the ,soul in knowing its concretes 7feelings71 and in knowing it as an abstraction which condenses those concretes in a symbol4 ,the secondary question is1 ,whether this abstraction represents one ,existent1 and the abstraction ,body another and wholly different ,existent1 or the two abstractions represent only two different ,aspects8 this may be debated1 and must be answered according to theoretic probabilities4 #bi4 ,what are the probabilities8 ,we are all agreed that ,consciousness is the final arbiter4 ,its primary deliverance is simply that of a radical distinction4 ,it is silent on the nature of the distinction--says nothing as to whether the distinction is one of agents or of aspects4 ,it says1 8,i am a ,soul40 ,with equal clearness it says1 8,i am a ,body40 ,it does not say1 8,i am two things40 ,nor does the fact of a radical distinction imply more than a contrast of aspects1 such as that of convex and concave4 ,the curve has at every point this contrast of convex and concave1 and yet is the identical line throughout4 ,a mental process is at every point contrasted with the physical process assumed to be its correlate2 and this contrast demands equivalent expression in the terms of each4 ,the identity underlying the two aspects of the curve is evident to ,sense4 ,the identity underlying the mental and physical process is not evident to ,sense1 but may be made eminently probable to ,speculation1 especially when we have explained the grounds of the difference1 namely1 that they are apprehended through different modes4 ,but although ,i admit that the conclusion is only one of probability1 it is one which greatly transcends the probability of any counter-hypothesis4 ,let us see how this can be made out4#bjh #cj4 ,we start from the position that a broad line of demarcation must be drawn between the mental and the physical aspect of a process1 supposing them to be identical in reality4 ,nothing can be more unlike a logical proposition than the physical process which is its correlate2 so that ,philosophy has hitherto been forced to forego every attempt at an explanation of how the two can be causally connected3 referring the connection to a mystery1 or invoking two different agents1 spiritual and material1 moving on parallel lines1 like two clocks regulated to work simultaneously4 ,but having recognized this difference1 can we not also discern fundamental resemblances8 ,first and foremost1 we note that there is common to both the basis in ,feeling3 they are both modes of ,consciousness4 ,the ,mind thinking the logical proposition is not1 indeed1 in the same state as the ,mind picturing the physical process which is the correlate of that logical proposition--no more than ,i1 who see you move on being struck1 have the same feelings as you who are struck4 ,but the ,mind which pictures the logical proposition as a process1 and pictures the physical process as a bodily change1 is contemplating one and the same event under its subjective and objective aspects2 just as when ,i picture to myself the feelings you experience on being struck ,i separate the subjective aspect of the blow from its objective aspect4 ,secondly1 between the logical proposition and the physical process there is a community of causal dependence1 i4 e4 the mode of grouping of the constituent elements1 whereby this proposition1 and not another1 is the result of this grouping1 and not another4 ,in fact1 what in subjective terms is called ,logic1 in objective terms is ,grouping4 #ca4 ,let us approach the question on a more accessible side4 ,sensation avowedly lies at the basis of mental manifestations4 ,now1 rightly or wrongly1 ,sensation is viewed alternately as a purely subjective fact--a psychological process--and as a purely objective fact--the physiological reaction of a sense-organ4 ,it is so conspicuously a physiological process that many writers exclude it from the domain of ,mind1 assign it to the material organism1 and believe that it is explicable on purely mechanical principles4 ,this seems to me eminently disputable2 but the point is noticed in proof of the well-marked objective character which the phenomenon assumes4 ,in this aspect a sensation is simply the reaction of a bodily organ4 ,the physiologist describes how a stimulus excites the organ1 and declares its reaction to be the sensation4 ,thus viewed1 and expressed in terms of ,matter and ,motion1 there is absolutely nothing of that subjective quality which characterizes sensation4 ,yet without this quality the objective process cannot be a sensation4 ,exclude ,feeling1 and the excitation of the auditory organ will no more yield the sensation of ,sound by its reaction1 than the strings and sounding-board of a piano when the keys are struck will yield music to a deaf spectator4 ,hence the natural inference has been that inside the organism there is a listener3 the ,soul is said to listen1 transforming excitation into sensation4 ,this inference only needs a more systematic interpretation and it will represent the biological theory1 which demands something more than the reaction of the sensory organ--namely1 the reaction of the whole organism through the sensory organ4 ,i mean1 that no organ isolated from the organism is capable of a physiological reaction--only of a physico-chemical reaction2 and sensation depends on 7is7 the physiological reaction4 ,when a sense-organ is stimulated1 this stimulation is a vital process1 and is raised out of the class of physico-chemical processes by virtue of its being the indissoluble part of a complex whole4 ,interfere with any one of the co-operant conditions--withdraw the circulation1 check respiration1 disturb secretion--and the sense-organ sinks from the physiological to the physical state2 it may then be brought into contact with its normal stimuli1 but no stimulation 7in the vital sense7 will take place1 there will be no vital reaction4 ,condensing all vital processes in the symbol ,vitality1 we may say ,vitality is requisite for every physiological process4 ,a parallelism may be noted on the subjective side3 all the sentient processes may be condensed in the one symbol ,sensibility 7,feeling71 and we must then say1 ,no psychological process is possible as an isolated fact1 but demands the co-operation of others--it is a resultant of all the contemporaneous conditions of ,sensibility in the organism4 ,in ordinary language this is what is meant by saying that no impression can become a sensation without the intervention of ,consciousness--an ambiguous phrase1 because of the ambiguity of the term ,consciousness1 but the phrase expresses the fact that in ,sensation a process in the organism is necessary to the reaction of the organ4 #cb4 ,having recognized the distinction between the two processes objective and subjective1 physical and mental1 we have recognized the vanity of attempting to assign their limits1 and to say where ,motion ends and ,feeling begins1 or how ,feeling again changes into ,motion4 ,the one does not begin where the other ends4 ,according to the two-clock theory of ,dualism1 the two agents move on parallel lines4 ,on the theory of ,monism the two aspects are throughout opposed4 ,both theories explain the facts2 which explanation is the most congruous with experience8 ,against the first we may object that the hypothesis of two ,agents utterly unallied in nature wants the cardinal character of a fertile hypothesis in its unverifiableness3 it may be true1 we can never know that it is true4 ,by the very terms of its definition1 the ,spirit--if that mean more than an abstract expression of sentient states--is beyond all sensible experience4 ,this is indeed admitted by the dualists1 for they postulate a ,spirit merely because they cannot otherwise explain the phenomena of ,consciousness4 ,herein they fail to see that even their postulate brings no explanation1 it merely restates the old problem in other terms4 #cc4 ,up to the present time these same objections might have been urged with equal force against ,monism4 ,indeed1 although many philosophers have rejected the two-clock theory of ,leibnitz1 they have gained a very hesitating acceptance for their own hypothesis of identity4 ,to most minds the difficulty of imagining how a physical process could also be a psychical process1 a movement also be a feeling1 seemed not less than that of imagining how two such distinct ,agents as ,matter and ,mind could co-operate1 and react on each other1 or move simultaneously on parallel lines4 ,although for many years ,i have accepted the hypothesis of ,monism1 ,i have always recognized its want of an adequate reply to such objections4 ,unless ,i greatly deceive myself1 ,i have now found a solution of the main difficulty2 and found it in psychological conditions which are perfectly intelligible4 ,but knowing how easily one may deceive one's self in such matters1 ,i will only ask the reader to meditate with open-mindedness the considerations now to be laid before him1 and see if he can feel the same confidence in their validity4 #cd4 ,one of the early stages in the development of ,experience is the separation of ,self from the ,not-,self4 ,i look out on 8the vast extern of things10 and see a great variety of objects1 included in a visible hemisphere4 ,all these objects in various positions1 having various forms and colors1 ,i believe to be wholly detached from1 and in every way unallied to1 ,myself4 ,and what is that ,self8 ,it is my ,body as a visible and tangible object1 separated from all other visible and tangible objects by the constant presence of feelings connected with it and its movements1 and not connected with the other objects4 ,this constant presence of feelings is referred to a ,soul1 which ,i then separate from my ,body1 as an ,inner ,self2 and from this time onwards ,i speak of the ,body as mine1 and learn to regard it in much the same light as other outer objects4 ,in my nave judgment the external objects are supposed to exist as ,i see and touch them1 whether ,i or any one else see and touch them or not3 they in no sense belong to the series of feelings which constitute the ,me4 ,and since my ,body resembles these objects in visible and tangible qualities1 and also in being external to my feelings1 it also takes its place in the objective world4 ,thus arises the hypothesis of ,dualism which postulates a ,physis1 or object-world1 and an sthesis1 or subject-world3 two independent existents1 one contemplated1 the other contemplating4 #ce4 ,philosophy1 as we know1 leads to a complete reversal of this primitive conclusion1 and shows that the contemplated is a synthesis of contemplations1 the ,physis being also the sthesis4 ,psychological investigation shows that the objects supposed to have forms1 colors1 and positions within an external hemisphere1 have these only in virtue of the very feelings from which they are supposed to be separated4 ,the visible universe exists only as seen3 the objects are ,reals conditioned by the laws of ,sensibility4 ,the space in which we see them1 their geometrical relations1 the light and shadows which reveal them1 the forms they affect1 the lines of their changing directions1 the qualities which distinguish them1--all these are but the externally projected signs of feelings4 ,they are signs which we interpret according to organized laws of experience2 each sign being itself a feeling connected with other feelings4 ,we project them outside according to the 8law of eccentric projection0--which is only the expression of the fact that one feeling is a sign of some other1 and is thereby ideally detached from it4 ,according to this law ,i say1 8my ,body02 just as ,i say1 8my ,house02 or1 8my ,property40 ,misled by this1 ,dualism holds that in the very fact of detaching my ,body from my ,self1 calling it mine1 is the revelation of a distinct entity within the body4 ,but that this is illusory1 appears in the application of this same law of eccentric projection to sensations and thoughts1 which are called mine1 as my legs and arms are mine4 ,if it is undeniable that ,i say my ,body--and thus ideally detach the ,body from the ,soul--it is equally undeniable that ,i say my ,soul2 and from what is the ,soul detached8 ,in presence of this difficulty1 the metaphysician may argue that neither ,body nor ,soul can be coextensive with its manifestations1 but demands a noumenal ,real for each--a substratum for the bodily manifestations1 and a substratum for the mental manifestations4 ,this1 however1 is an evasion1 not a solution of the difficulty4 ,if we postulate an unknown and unknowable noumenon1 we gain no insight3 first1 because ,philosophy deals only with the known functions of unknown quantities1 and therefore leaves the x out of the calculation2 secondly1 because1 granting the existence of these noumena1 we can have no rational grounds for asserting that they are not of one and the same nature2 for we have no grounds for any assertion whatever about them4 ,and if it be urged against this1 that ,consciousness testifies to a distinction1 ,i answer that on a closer scrutiny it will be found to testify to nothing more than a diversity of manifestation4 ,all therefore that comes within the range of knowledge is1 ,how does this diversity arise8 #cf4 ,there are two ways1 and there are only two1 in which differences arise4 ,these are1 #a1 the modes of production of a product1 and1 #b1 our modes of apprehension of the product4 ,things may be very different1 and yet to our apprehension indistinguishable1 so that we regard them as identical2 and they may be identical1 yet appear utterly unlike4 ,a mechanical bird may seem so like a living bird1 and their actions so indistinguishable to the spectator1 that he will not suspect a difference1 or suspecting it1 will not be able to specify it4 ,of both objects1 so long as his modes of apprehending them are circumscribed1 he can only say what these imply3 he sees familiar forms1 colors1 and movements1 which he interprets according to the previous experiences of which these are the signs4 ,but by varying the modes of apprehension1 and gaining thus a fuller knowledge1 he finds that the two products have very different modes of production2 hence he concludes the products to be different3 the mechanism of the one is not the organism of the other2 the actions of the mechanical bird are not the actions of the living bird4 ,the fuller knowledge has been gained by viewing the objects under different relations1 and contemplating them in their modes of production1 not as merely visible products4 ,he sees the mechanism performing by steel springs1 wheels1 and wires1 the work which the organism performs by bones1 muscles1 and nerves2 and the farther his analysis of the modes of production is carried1 the greater are the differences which he apprehends4 #cg4 ,now consider the other side4 ,one and the same object will necessarily present very different aspects under different subjective conditions1 since it is these which determine the aspect4 ,the object cannot be to ,sight what it is to ,hearing1 to ,touch what it is to ,smell4 ,the vibrations of a tuning-fork are seen as movements1 heard as sounds4 ,in current language the vibrations are said to cause the sounds4 ,misled by this1 philosophers puzzle themselves as to how a material process 7vibration7 can be transformed into a mental process 7sensation71 how such a cause can have so utterly different an effect4 ,but ,i have formerly#bji argued at some length that there is no transformation or causation of the kind supposed4 ,the tuning-fork--or that ,real which in relation to ,sense is the particular object thus named--will1 by one of its modes of acting on my ,sensibility through my optical apparatus1 determine the response known as vibrations2 but it is not this response of the optical organ which is transformed into1 or causes the response of the auditory organ1 known as sound4 ,the auditory organ knows nothing of vibrations1 the optical nothing of sounds4 ,the responses are both modes of ,feeling determined by organic conditions1 and represent the two different relations in which the ,real is apprehended4 ,the ,real is alternately the one and the other4 ,and if the one mode of ,feeling has a physical significance1 while the other has a mental significance1 so that we regard the vibrations as objective facts1 belonging to the external world1 and the sounds as subjective facts1 exclusively belonging to the internal world1 this is due to certain psychological influences presently to be expounded4 ,meanwhile let us fix clearly in our minds that both vibrations and sounds are modes of ,feeling4 ,my consciousness plainly assures me that it is ,i who see the one1 and hear the other2 not that there are two distinct subjects for the two distinct feelings4 ,add to which1 manifold uncontradicted experiences assure me that the occasional cause--the objective factor--of the one feeling1 is also the cause of the other1 and not that the two feelings have two different occasional causes4 ,from both of these undeniable facts we must conclude that the difference felt is simply a difference of aspect1 determined by some difference in the modes of apprehension4 #ch4 ,assuming then that a mental process is only another aspect of a physical process--and this we shall find the more probable hypothesis--we have to explain by what influences these diametrically opposite aspects are determined4 ,from all that has just been said we must seek these in the modes of apprehension4 ,there can be no doubt that we express the fact in very different terms2 the question is1 ,what do these terms signify8 ,why do we express one aspect in terms of ,matter and ,motion1 assigning the process to the objective world2 and the other aspect in terms of ,feeling1 assigning the process to the subjective world8 ,let the example chosen be a logical process as the mental aspect1 and a neural process as its physical correlate4 ,the particular proposition may be viewed logically1 as a grouping of experiences1 or physiologically1 as a grouping of neural tremors4 ,here we have the twofold aspect of one and the same reality2 and these different aspects are expressed in different terms4 ,we cannot be too rigorous in our separation of the terms2 for every attentive student must have noted how frequently discussions are made turbid by the unconscious shifting of terms in the course of the argumentation4 ,this is not only the mistake of opponents who are unaware of the shifting which has occurred in each other's minds1 so that practically the adversaries do not meet on common ground1 but cross and recross each other2 it is also the mistake of the solitary thinker losing himself in the maze of interlacing conceptions instead of keeping steadily to one path4 ,only by such shifting of terms can the notion of the physical process causing1 or being transformed into1 the mental process for a moment gain credit2 and this also greatly sustains the hypothesis of ,dualism1 with its formidable objections3 ,how can ,matter think8 ,how can ,mind act on ,matter causing ,motion8 #ci4 ,those who recognized that the terms ,matter and ,mind were abstractions mutually exclusive1 saw at once that these questions1 instead of being formidable1 were in truth irrational4 ,to ask if ,matter could think1 or ,mind move ,matter1 was a confusion of symbols equivalent to speaking of a yard of ,hope1 and a ton of ,terror4 ,although ,measure and ,weight are symbols of ,feeling1 and in this respect are on a par with ,hope and ,terror1 yet because they are objective symbols they cannot be applied to subjective states1 without violation of the very significance they were invented to express4 ,no one ever asks whether a sensation of ,sound can be a sensation of ,color2 nor whether ,color can move a machine1 although ,heat can1 yet the one is no less a sensation than the other4 ,on similar grounds no one should ask whether ,matter can think1 or ,mind move ,matter4 ,the only rational question is one preserving the integrity of the terms1 namely1 whether the living1 thinking organism presents itself to apprehension under the twofold aspect--now under the modes of ,feeling classified as objective or physical2 now under the modes classified as subjective or mental4 #dj4 ,we are told that it is 8impossible to imagine ,matter thinking10 which is very true2 only by a gross confusion of terms can ,thought be called a property of cerebral tissue1 or of ,matter at all4 ,we may1 indeed1 penetrate beneath the terms which relate to aspects1 and recognize in the underlying reality not two existences1 but one4 ,our conceptions of this reality1 however1 are expressed in symbols representing different classes of feelings1 objective and subjective2 and to employ the terms of one class to designate the conceptions of the other is to frustrate the very purposes of language4 ,matter and ,mind1 ,object and ,subject1 are abstractions from sentient experiences4 ,we know them as abstractions1 and know the concrete experiences from which they are abstracted4 ,philosophers1 indeed1 repeatedly assure us that we neither know what ,matter is nor what ,mind is1 we only know the phenomenal products of the action and reaction of these two unknown noumena4 ,were this so1 all discussion would be idle2 we could not say whether ,matter was or was not capable of thinking1 whether ,mind was or was not the same as ,matter1 we could only abstain from saying anything whatever on the topic4 ,what should we reply to one who asked us to name the product of two unknown quantities8 ,so long as x and y are without values their product must be without value4 ,if the value of x be known1 and that of y unknown1 then the product still remains unknown3 x y x #j x4 ,therefore1 unless the ,objective aspect were the equivalent of the ,subjective aspect1 it could never be subjectively present4 ,feeling is but another aspect of the ,felt4 #da4 ,it is because we do know what ,matter is1 that we know it is not ,mind3 they are symbols of two different modes of ,feeling4 ,if we separate the conception of citizenship from the conception of fatherhood1 although the same man is both citizen and father1 how much more decisively must we separate the conception of ,matter1 which represents one group of feelings1 from the conception of ,mind1 which represents another8 ,one element in the former is common to the whole group1 namely1 the reference to a ,not-,self1 induced by the sensation of ,resistance1 which always ideally or sensibly accompanies the material class4 ,the axiom1 ,i feel1 ergo ,i exist1 has its correlative3--,i act1 ergo there are other existents on which ,i act2 and these are not wholly ,me1 for they resist1 oppose1 exclude me2 yet they are also one with ,me1 since they are felt by me4 ,in my ,feeling1 that which is not ,me is ,matter1 the objective aspect of the ,felt1 as ,mind is the subjective aspect4 ,but since ,hunger and ,thirst1 ,joy and ,grief1 ,pain and ,terror1 are also felt1 yet are never classed under the head of ,matter1 the grounds of the classification of feelings have to be expressed4 ,professor ,bain makes the distinction between ,matter and ,mind to rest solely on the presence or absence of ,extension3 this is the decisive mark3 ,matter he defines as the ,extended4 ,the definition is inadequate4 ,when ,i see a dog and its image reflected in a pool1 or see a dog and think of another1 in the three cases dog1 image1 and idea have ,extension2 but ,i recognize the dog as a material fact1 the idea as a mental fact2 and although the image of the dog has material conditions by which ,i am optically affected1 just as the idea has material cerebral conditions1 ,i recognize a marked difference between them and the dog1 due to the different modes of apprehension4 ,the dog is known as a persistent reality1 which1 when ,sight is supplemented by ,touch1 will yield sensations of ,resistance1 and thus disclose its materiality4 ,the image vanishes if ,i attempt to touch it2 ,i see its outlines waver and become confused with every disturbance of the surface of the pool2 the idea vanishes when another idea arises2 whence ,i conclude that neither has material reality1 because neither has the ,resistance which characterizes the ,not-,self4 ,the image and the idea may be referred to material conditions1 but so may pains1 terrors1 volitions1 yet these are all without ,extension1 simply because they are not visual feelings4 #db4 ,matter does not represent all feelings1 but only the objective sensibles2 and these are not all characterized by ,extension1 but only those which directly or indirectly involve optico-tactical experiences accompanied by muscular experiences4 ,matter is primarily the ,visible and ,resistant2 and secondarily1 whatever can be imagined as such2 so that ether1 molecules1 and atoms1 although neither visible nor tangible1 are ranged under the head of ,matter4 ,color is a feeling as ,sound and ,scent are feelings1 and although material conditions are equally presupposed in all three1 yet ,color alone has ,extension1 and because it can be imaged it has a more objective character than the others1 which having no lines and surfaces1 want the optical conditions for the formation of images1 and are less definitely connected with tactical and muscular experiences4 ,nevertheless1 since ,sound and ,scent are obviously associated with objects seen and touched1 they have a degree of materiality never assigned to such feelings as ,hunger and ,thirst1 ,pleasure1 ,terror1 and ,hope4 #dc4 ,when we refer feelings to material conditions1 we follow the natural tendency to translate the little known in terms of the better known1 and employ the symbols ,matter and ,motion1 because these furnish the intellect with images1 i4 e4 definite and exact elements to operate with4 ,in hearing a sound1 there is nothing at all like 8vibrations10 nothing like 8aerial waves0 and 8neural processes10 given in that feeling2 but on attempting to explain it1 we remove it from the sphere of ,sensation to carry it into the sphere of ,intellect1 and we must change our symbols in changing our problem2 here our only resource is to translate the subjective state into an imaginable objective process1 which can only be expressed in terms of ,matter and ,motion4 ,what we heard as ,sound is then seen as ,vibration4 ,when we are optically or mentally contemplating vibrations and neural processes1 we are supplanting one source of feeling by another1 translating an event in another set of symbols4 ,but we can no more hear the sound in seeing the vibrations1 than a blind man can see the fly in the amber which he feels with his fingers1 or than we can feel the amber he holds1 while we are only looking at it4 ,the phrase 8material conditions of ,feeling0 sometimes designates the objective aspect of the subjective process1 and sometimes the agencies in the external medium which co-operate with the organism in the production of the feelings4 ,in each case there is an attempt to explain a feeling by intelligible symbols4 #dd4 ,the ,animal probably never attempts such explanation2 satisfied with the facts1 it is careless of their factors4 ,man is never satisfied3 is restless in the search after factors2 and having found them1 seeks factors of these factors2 so that ,lichtenberg felicitously calls him 8das rastlose ,ursachenthier0--8the animal untiring in the search for causes40 ,and thus sciences arise3 we translate experiences into geometrical1 physical1 chemical1 physiological1 and psychological terms--different symbols of the different modes of apprehending phenomena4 #de4 8,i see an elephant40 ,in other words1 ,i am affected in a certain way1 and interpret my affection by previous similar experiences1 expressing these in verbal symbols4 ,but ,i want an explanation1 and this the philosopher vouchsafes to me by translating my affection into his terms4 ,he takes me into another sphere--tells me of an undulating ,ether1 the waves of which beat upon my retina--of lines of ,light refracted by media and converged by lenses according to geometric laws--of the formation thereby of a tiny image of the gigantic elephant on my retina as on the plate of a camera-obscura--this1 and much more1 is what he sees in my visual feeling1 and he bids me see it also4 ,grateful for the novel instruction1 ,i am compelled to say that it does not alter my vision of the elephant1 does not make the fact a whit clearer1 does not indeed correspond with what ,i feel4 ,it is outside knowledge1 valuable1 as all knowledge is1 but supplementary4 ,it is translation into another language4 ,and when ,i come to examine the translation1 ,i find it very imperfect4 ,i ask my instructor3 ,is it the tiny image on my retina which ,i see1 and not the big elephant on the grass8 ,and how do ,i see this retinal image1 which you explain to be upside down8--how is it carried from my retina to my mind8 ,i have no consciousness of tiny reversed image1 none of my retina1 only of a fact of feeling1 which ,i call 8seeing an elephant40 ,the camera-obscura has no such feeling--it reflects the image1 it does not see the object4 ,here my instructor1 having reached the limit of his science1#baj hands me over to the physiologist1 who will translate the fact for me in terms not of ,geometry1 but of ,anatomy and ,physiology4 ,the laws of ,dioptrics cease at this point3 the image they help to form on the retina is ruthlessly dispersed1 and all its beautiful geometric construction is lost in a neural excitation1 which is transmitted through semifluid channels of an optic tract to a semifluid ganglion1 whence a thrill is shot through the whole brain1 and is there transformed into a visual sensation4 ,again ,i fancy ,i have gained novel instruction of a valuable kind2 but it does not affect my original experience that ,i am enabled to translate it into different terms2 the less so because ,i cannot help the conviction that the translation is imperfect1 leaving out the essential points4 ,if a phrase be translated for me into ,french or ,german1 ,i gain thereby an addition to my linguistic knowledge1 but the experience thus variously expressed remains unaffected4 ,when the fact is expressed in geometrical or physiological terms1 the psychical process finds no adequate expression4 ,neither in the details1 nor in the totals1 do ,i recognize any of the qualities of my state of feeling in seeing the elephant4 ,i do not see the geometrical process1 ,i do not see the anatomical mechanism1 ,i see the elephant1 and am conscious only of that feeling4 ,you may consider my organism geometrically or anatomically1 and bring it thus within the circle of objective knowledge2 but my subjective experience1 my spiritual existence1 that of which ,i am most deeply assured1 demands another expression4 ,nay more1 on closely scrutinizing your objective explanations1 it is evident that a psychical process is implied throughout--such terms as undulations1 refractions1 media1 lenses1 retina1 neural excitation1 overtly refer1 indeed1 to the material objective aspect of the facts1 but they are themselves the modes of ,feeling by which the facts are apprehended1 and would not exist as such without the 8greeting of the spirit40 #df4 ,what1 then1 is our conclusion8 ,it is1 that to make an adequate explanation of psychical processes by material conditions we must first establish an equivalence between the subjective and objective aspects2 and1 having taken this step1 we must complete it by showing wherein the difference exists2 having established this entity and diversity1 we have solved the problem4 ,let us attempt this solution4 ,when ,i speak to you1 the spoken words are the same to you and to me4 ,you hear what ,i hear1 you apprehend what ,i apprehend4 ,but there were muscular movements of articulation felt by me and not felt by you2 to feel these you also must articulate the words2 but so long as you merely hear the words1 there is a difference in our states of feeling4 ,some of my movements you can see1 others you can imagine2 but this is not my feeling of them1 it is your optical equivalent of my muscular feeling4 ,on a similar assumption of equivalence1 a neural process is made to stand for a logical process4 ,in thinking a proposition1 we are logically grouping verbal symbols representative of sensible experiences2 and this is a quite peculiar state of ,consciousness1 wholly unlike what would arise in the mental or visual contemplation of the neural grouping1 which is its physiological equivalent4 ,but this diversity does not discredit the idea of their identity2 and although some of my readers will protest against such an idea1 and will affirm that the logical process is not a process taking place in the organism at all1 but in a spirit which uses the organism as its instrument1 ,i must be allowed in this exposition to consider the identity established1 my purpose being to explain the diversity necessarily accompanying it4 ,therefore1 ,i say1 that although a logical process is identical with a neural process1 it must appear differently when the modes of apprehending it are different4 ,while you are thinking a logical proposition1 grouping your verbal symbols1 ,i1 who mentally see the process1 am grouping a totally different set of symbols3 to you the proposition is a subjective state1 i4 e4 a state of feeling1 not an object of feeling3 to become an object1 it must be apprehended by objective modes3 and this it can become to you as to me1 when we see it as a process1 or imagine it as a process4 ,but obviously your state in seeing or imagining the process must be different from your state when the process itself is passing1 since the modes of apprehension are so different4 ,there may be every ground for concluding that a logical process has its correlative physical process1 and that the two processes are merely two aspects of one event2 but because we cannot apprehend the one aspect as we apprehend the other1 cannot see the logical sequence as we see the physical sequence1 this difference in our modes of apprehension compels us to separate the two1 assigning one to the subjective1 the other to the objective class4 ,between the sensible perception of an object and the reproduced image of the object there is chiefly a quantitative difference in the physiological and psychological processes3 the image is a faint sensation4 ,yet this quantitative difference brings with it the qualitative distinction which is indicated in our calling the one a sensation1 the other a thought4 ,the consequence has been that while all philosophers have admitted the sensation to be--at least partly--a process in the bodily organism1 the majority have maintained that the thought is no such process in the organism1 but has its seat in a spirit independent of the organism4 #dg4 ,the states of ,feeling which are associated with other states characterized as objective because overtly referring to a ,not-,self1 we group under the head of ,matter3 we assign material conditions as their antecedents4 ,whereas states of ,feeling which are not thus associated we group under the head of ,mind1 and assign internal conditions as their antecedents4 ,color and ,taste are very different states of ,feeling1 yet both are spontaneously referred to external causes1 because they are associated with visual and tactical states2 whereas ,hunger1 ,nausea1 ,hope1 etc41 have no such associations1 and their material conditions are only theoretically assigned4 ,our intelligible universe is constructed out of the elements of ,feeling according to certain classifications1 the broadest of which is that into external and internal1 object and subject4 ,the abstractions ,matter and ,mind once formed and fixed in representative symbols1 are easily accredited as two different ,reels4 ,but the separation is ideal1 and is really a distinction of ,aspects4 ,we know ourselves as ,body-,mind2 we do not know ourselves as ,body and ,mind1 if by that be meant two coexistent independent ,existents2 and the illusion by which the two ,aspects appear as two ,reals may be made intelligible by the analysis of any ordinary proposition4 ,for example1 when we say 8this fruit is sweet10 we express facts of ,feeling--actual or anticipated--in abstract terms4 ,the concrete facts are these3 a colored feeling1 a solid feeling1 a sweet feeling1 etc41 have been associated together1 and the colored1 solid1 sweet group is symbolized in the abstract term 8fruit0 ,but the color1 solidity1 and sweetness are also abstract terms1 representing feelings associated in other groups1 so that we find 8fruit0 which has no 8sweetness02 and 8sweetness0 in other things besides 8fruits40 ,having thus separated ideally the 8sweetness0 from the 8fruit0--which in the concrete sweet-fruit is not permissible--we easily come to imagine a real distinction4 ,this is the case with the concrete living organism when we cease to consider it in its concrete reality1 and fix our attention on its abstract terms--,body and ,mind4 ,we then think of ,body apart from ,mind1 and believe in them as two ,reals1 though neither exists apart4 ,there is no state of consciousness in which object and subject are not indissolubly combined4 ,there is no physical process which is not indissolubly bound up with the psychical modes of apprehending it4 ,every idea is either an image or a symbol--it has therefore objective reference1 a material aspect4 ,every object is a synthesis of feelings--it has therefore subjective reference1 a material aspect4 ,thus while all the evidence points to the identity of ,object and ,subject1 there is ample evidence for the logical necessity of their ideal separation as ,aspects4 ,this ,i have explained as a case of the general principle which determines all distinctions--namely1 the diversity in the modes of production of the products1 which--subjectively--is diversity in the modes of apprehending them4 ,the optico-tactical experiences are markedly different from the other experiences1 as being more directly referred to the ,not-,self which resists2 and because these lend themselves to ideal constructions by means of images and symbols1 it is these experiences into which we translate all the others when we come to explain them and assign their conditions4 ,for--and this is the central position of our argument--all interpretation consists in translating one set of feelings in the terms of another set4 ,we condense sets of feelings in abstract symbols2 to understand these we must reduce them to their concrete significates4 ,they are signs2 we must show what they are signs of4 ,now the symbols ,object and ,subject are the most abstract we can employ4 ,because they are universal1 they represent what cannot in reality be divorced4 ,we can1 indeed1 ideally separate ourselves from the ,cosmos2 in the same way we can ideally separate our inner ,self or ,soul from our outer ,self or ,body2 and again our ,soul from its sentient states1 our ,body from its physical changes4 ,but not so in reality4 ,the separation is a logical artifice1 and a logical necessity for ,science4 ,the necessity will be obvious to any one who reflects how the ideal constructions of ,science demand precision and integrity of terms4 ,the problem of ,automatism brings this very clearly into view4 ,the question is1 ,can we translate all psychological phenomena in mechanical terms8 ,if we can1 we ought2 because these terms have the immense advantage of being exact1 dealing as they do with quantitative relations4 ,but my belief is that we cannot--nay1 that we cannot even translate them all into physiological terms4 ,the distinction between quantitative and qualitative knowledge 7p4 #ced7 is a barrier against the mechanical interpretation4 ,physiology is a classificatory science1 not a science of measurement4 ,nor can the laws of ,mind be deduced from physiological processes1 unless supplemented by and interpreted by psychical conditions individual and social4 ,,chapter ,,iv4 ,,consciousness ,,and ,,unconsciousness4#baa #dh4 ,science demands precision of terms2 and in this sense ,condillac was justified in defining it1 8une langue bien faite40 ,the sciences of ,measurement are exact because of the precision of their terms1 and are powerful because of their exactness4 ,the sciences of ,classification cannot aspire to this precision1 and therefore1 although capable of attaining to a fuller knowledge of phenomena than can be reached by their rivals1 this advantage of a wider range is accompanied by the disadvantage of a less perfect exposition of results4 ,while physicists and chemists have only to settle the significance of the facts observed1 biologists and social theorists have over and above this to settle the significance of the terms they employ in expressing the facts observed4 ,hence more than half their disputes are at bottom verbal4 ,this is markedly the case in the question of ,automatism4 ,one man declares that animals are automata2 another that they are conscious automata2 and while it is quite possible to hold these views and not practically be in disagreement with the views of ordinary men1 or indeed with the views of spiritualist and materialist philosophers1 we can never be sure that the advocates of ,automatism do not mean what they are generally understood to mean4 ,if a man says that by an automaton he does not here mean a machine1 such as a steam-engine or a watch1 but a vital mechanism which has its parts so adjusted that its actions resemble those of a machine2 and if he adds that this automaton is also conscious of some of its actions1 though unconscious of others1 we can only object to his using terms which have misleading connotations4 ,if he mean by 8conscious automata10 that animals are mechanisms moved on 8purely mechanical principles10 their consciousness having nothing whatever to do with the production of their actions1 then indeed our objection is not only to his use of terms1 but to his interpretation of the facts4 #di4 ,the questions of fact are two3 ,are animal mechanisms rightfully classed beside machines8 and1 ,is consciousness a coefficient in the actions of animal mechanism8 ,the first has already been answered2 the second demands a preliminary settlement of the terms 8conscious10 8unconscious10 8voluntary10 and 8involuntary40 ,the aim of ,physiology is to ascertain the particular combinations of the elementary parts involved in each particular function--in a word1 the mechanism of organic phenomena2 and the modern ,reflex ,theory is an attempt to explain this mechanism on purely mechanical principles1 without the co-operation of other principles1 especially those of ,sensation and ,volition4 ,it is greatly aided by the ambiguity of current terms4 ,we are accustomed to speak of certain actions as being performed unconsciously or involuntarily4 ,we are also accustomed to say that ,consciousness is necessary to transform an impression into a sensation1 and that ,volition is the equivalent of conscious effort4 ,when1 therefore1 unconscious and involuntary actions are recorded1 they seem to be actions of an insentient mechanism4 ,the ,reflex ,theory once admitted1 a rigorous logic could not fail to extend it to all animal actions4 #ej4 ,i reject the ,reflex ,theory1 on grounds hereafter to be urged1 but at present call attention to the great ambiguity in the terms 8conscious0 and 8unconscious40 ,in one sense no definition of ,consciousness can be satisfactory1 since it designates an ultimate fact1 which cannot therefore be made more intelligible than it is already4 ,in another sense no definition is needed1 since every one knows what is meant by saying1 8,i am conscious of such a change1 or such a movement40 ,it is here the equivalent of ,feeling4 ,to be conscious of a change1 is to feel a change4 ,if we desire to express it in physiological terms1 we must define ,consciousness--8a function of the organism02 and this definition we shall find eminently useful1 because the organism being a vital mechanism1 and the integrity of that mechanism being necessary for the integrity of the function1 while every variation of the mechanism will bring a corresponding variation of the function1 we shall have an objective guide and standard in our inquiries4 ,organisms greatly differ in complexity1 yet because they also agree in the cardinal conditions of ,vitality1 among which ,sensibility is one1 we conclude that they all have ,feeling2 but the ,feeling of the one will differ from that of another1 according to the complexity of the sentient mechanism in each4 ,the perfection of this mechanism lies in the co-ordination of its parts1 and the consensus of its sentient activities2 any disturbance of that consensus must cause a modification in the total consciousness2 and when the disturbance is profound the modification is marked by such terms as 8insanity10 8loss of consciousness10 8insensibility40 ,these terms do not imply that the sentient organs have lost their ,sensibility1 but only that the disturbed mechanism has no longer its normal consensus1 no longer its normal state of ,consciousness4 ,each organ is active in its own way so long as its own mechanism is preserved2 but the united action of the organs having been disturbed1 their resultant function has been altered4 ,hence in a fit of ,epilepsy there is a complete absence of some normal reactions1 with exaggeration of others4 ,in a state of ,coma there is no spontaneity--none of the manifold adaptations of the organism to fluctuating excitations1 external and internal1 observable in the normal state4 ,the organism still manifests ,sensibility--but this is so unlike the manifestations when its mechanism is undisturbed 7and necessarily so since the ,sensibility varies with the mechanism7 that it is no longer called by the same name4 ,in the normal organism ,sensibility means ,feeling1 or ,consciousness2 but in the abnormal organism there is said to be a 8loss of ,consciousness40 ,what the physiologist or the physician means by the phrase 8loss of ,consciousness0 is intelligible1 and for his purposes unobjectionable4 ,he observes many organic processes going on undisturbed--the unconscious patient breathes1 secretes1 moves his limbs1 etc4 ,these processes are referred to the parts of the mechanism which are not disturbed2 they are obviously independent of that adjustment of the mechanism which by its consensus has the special resultant named ,consciousness2 he therefore concludes that these1 and many other organic processes1 which are neither accompanied nor followed by discriminated feelings1 are the direct consequences of the stimulated mechanism4 ,he never hesitates to adopt the popular language1 and say1 8,we sometimes act unconsciously1 perceive unconsciously1 and even think unconsciously1 all by the simple reflex of the mechanism40 ,now observe the opening for error in this language4 ,the actions are said to go on unconsciously1 and1 because unconsciously1 as pure reflexes1 which are then assigned to an insentient mechanism1 and likened to the actions of machines4 ,but1 as ,i hope hereafter to make evident1 the reflex mechanism necessarily involves ,sensibility2 and therefore reflex actions may be unaccompanied by ,consciousness--in one meaning of that term--without ceasing to be sentient1 the feelings are operative1 although not discriminated4 ,on the other hand1 there is another and very general meaning of the term ,consciousness1 which is the equivalent of ,sentience4 #ea4 ,in discussing ,automatism1 or the ,reflex ,theory1 it is absolutely necessary that we should first settle the meaning we assign to the term ,consciousness4 ,the laxity with which the term is used may be seen in the enumeration occupying six pages of ,professor ,bain's account of the various meanings4 ,psychology is often said to be 8the science of the facts of ,consciousness02 and the ,brain is often assigned as 8the organ of ,consciousness40 ,yet there are many mental processes1 and many cerebral processes1 which are declared to be unconscious4 ,obviously if ,consciousness is the function of the ,brain1 there can be no cerebral activity which is unconscious2 just as there can be no activity of the lungs which is not respiratory4 ,usage therefore points to a general and a special sense of the term4 ,the general usage identifies it with ,sensibility1 in its subjective aspect as ,sentience1 including all psychical states1 both those classed under ,sensation1 and those under ,thought4 ,these states are the 8facts of consciousness0 with which ,psychology is occupied4 ,in the special usage it is distinguished from all other psychical states by a peculiar reflected feeling of ,attention1 whereby we not only have a sensation1 but also feel that we have it2 we not only think1 but are conscious that we are thinking2 not only act1 but are conscious of what we do4 ,it is this which ,kant indicates when he defines it 8the subjective form accompanying all our conceptions 7,begriffe702 and ,jessen when he defines it 8the internal knowing of our knowing1 an in itself reflected knowing40#bab #eb4 ,we shall often have to recur to this general and this special meaning1 both of which are too firmly rooted for any successful attempt to displace them4 ,the fact that some organic processes and some mental processes take place now consciously and now unconsciously1 i4 e4 now with the feeling of reflected attention1 and now with no such feeling1 assuredly demands a corresponding expression2 nor1 in spite of inevitable ambiguities1 is there ground for regretting that the expression chosen should be only an extension of the expression already adopted for all other states of ,sentience4 ,a sentient or conscious state can only be a state of the sentient organism1 itself the unity of many organs1 each having its ,sensibility4 ,there is more or less consensus1 but there is no introduction of a new agent within the organism1 converting what was physical impression into mental reaction4 ,from first to last there has been nothing but neural processes1 and combinations of such processes--which1 viewed subjectively1 are sentient processes4 ,thus the gradations of sensitive reaction are ,sentience1 ,consentience1 and ,consciousness1 which are represented in the ,logic of ,feeling and the ,logic of ,signs4 ,the familiar term ,conscience will then represent the ,logic of ,conduct4 ,thus understood1 we may say that a man sometimes acts unconsciously1 or thinks unconsciously1 although his action and thought are ruled by ,consentience1 as he sometimes acts and thinks unconscientiously1 although he is not without obedience to ,conscience on other occasions4 ,the feeling which determines an action is operative1 although it may not be discriminated from simultaneous feelings4 ,when this is the case1 we say the feeling is unconscious2 but this no more means that it is a purely physical process taking place outside the sphere of ,sentience1 than the immoral conduct of a man would be said to be mechanical1 and not the conduct of a moral agent4 ,there is undoubtedly a marked distinction expressed in the terms ,consciousness and ,unconsciousness1 but it is not that of contrasts such as ,mental and ,physical1 it is that of grades such as ,light and ,darkness4 ,just as ,darkness is a positive optical sensation very different from mere privation--just as it replaces the sensation of ,light1 blends with it1 struggles with it1 and in all respects differs from the absence of all optical sensibility in the skin2 so ,unconsciousness struggles with1 blends with1 and replaces ,consciousness in the organism1 and is a positive state of the sentient organism1 not to be confounded with a mere negation of ,sentience2 above all1 not to be relegated to merely mechanical processes4 #eb a4 ,remember that1 strictly speaking1 ,consciousness is a psychological not a physiological term1 and is only used in ,physiology on the assumption that it is the subjective equivalent of an objective process4 ,to avoid the equivoque of 8unconscious sensation10 we may substitute the term 8unconscious neural process02 and as all neural processes imply ,sensibility1 which in the subjective aspect is ,sentience1 we say that ,sentience has various modes and degrees--such as ,perception1 ,ideation1 ,emotion1 ,volition1 which may be conscious1 sub-conscious1 or unconscious4 ,when ,leibnitz referred to the fact of 8obscure ideas10 and modern writers expressed this fact as 8unconscious cerebration10 the first phrase did not imply a process that was other than mental1 the second phrase did not imply a process that was other than physiological3 both indicated a mode of the process known as ,consciousness under other modes4 ,there are different neural elements grouped in ,ideation and ,emotion2 there are different neural elements grouped in ,consciousness1 ,sub-consciousness1 and ,unconsciousness2 but one tissue with one property is active in all4 #ec4 ,the nervous organism is affected as a whole by every affection of its constituent parts4 ,every excitation1 instead of terminating with itself--as is the case in most physical processes--or with the motor impulse it excites1 is propagated throughout the continuous tissue1 and thus sends a thrill throughout the organism4 ,the wave of excitation in passing onwards beats against variously grouped elements--temporary and permanent centres--disturbing their balance more or less1 and liberating the energy of some1 increasing the tension of others1 necessarily affecting all4 ,those groups which have their energy liberated set up processes that are either discriminated as sensations1 or are blended with the general stream1 according to their relative energy in the consensus4 ,thus the impulse on reaching the centres for the heart1 lungs1 legs1 and tail excites the innervation of these organs2 but as these are only parts of the organism1 and as all the parts enter the consensus1 and ,consciousness is the varying resultant of this ever-varying consensus1 the thrill which any particular stimulus excites will be unconscious1 sub-conscious1 or conscious1 in proportion to the extent of the irradiated disturbance1 which will depend on the statical conditions of the centres at the moment4 ,a sound sends a thrill which excites emotion1 causes the heart to beat faster1 the muscles to quiver1 the skin-glands to pour forth their secretion2 yet this same sound heard by another man1 or the same man under other conditions1 physical or historical1 merely sends a faint thrill1 just vivid enough to detach itself as a sensation from the other simultaneous excitations2 and the same sound may excite a thrill which is so faint and fugitive as to pass unconsciously4 ,physiological and psychological inductions assure us that these are only differences of degree4 ,the same kind of physiological effect accompanies the conscious and unconscious state4 ,every sensory impression1 no matter whether discriminated or not1 affects the circulation and develops heat4 ,the blood-vessels of the part impressed expand1 vessels elsewhere contract--a change in the blood pressure has been effected1 which of course implies that the whole organism has been affected4 ,delicate instruments show that at the time a sensation is produced the temperature of the brain is raised4 ,the same is true of ideation4 ,mosso has invented a method of registering the effect of thought on the circulation4 ,he finds ideation accompanied by a contraction of the peripheral vessels proportionate to the degree of intellectual effort4 ,a young man translating ,greek showed greater contraction than when he was translating ,latin4 ,during sound sleep--when we are said to be unconscious--sudden noises always cause contraction of the peripheral vessels4 ,psychological observation assures us that the conscious and unconscious states were both consentient1 and were both operative in the same degree4 ,the absorbed thinker threads his way through crowded streets1 and is sub-conscious and unconscious of the various sights1 sounds1 touches1 and muscular movements which make up so large a portion of his sentient excitation at the time2 yet he deftly avoids obstacles1 hears the sound of a hurried step behind him1 recognizes an interesting object directly it presents itself1 and can even recall in ,memory many of the uninteresting objects which he passed in sub-conscious and unconscious indifference4 #ed4 ,on all grounds1 therefore1 we must say that between conscious1 sub-conscious1 and unconscious states the difference is only of degree of complication in the neural processes1 which by relative preponderance in the consensus determine a relative discrimination4 ,we can only discriminate one thrill at a time2 but the neural excitations simultaneously pressing towards a discharge are many2 and the conditions which determine now this1 and now the other excitation to predominate by its differential pressure1 are far beyond any mechanical estimate4 ,i mention this because the advocates of the ,reflex ,theory maintain that the neural processes are the same whether a sensation be produced or not2 and that since the same actions follow the external stimulation whether sensation be produced or not1 this proves the actions to be purely mechanical4 ,i reply1 the neural processes are not the same throughout in the two cases--otherwise the effects would be the same4 ,you might as well say1 8,since the explosion of the gun is the same1 whether shotted or not1 a blank cartridge will kill02 but if you tell me that your gun killed the bird1 ,i declare that the cartridge was not a blank one4 ,whether the explosion of the gun also produced terror in one bystander1 curiosity in a second1 and attracted no notice from a third1 will be altogether another matter4 ,in like manner the sensory impression which determines a movement may or may not be accompanied or followed by other sentient states2 the fact of such movement is evidence of its sentient antecedent2 and an external stimulus that will produce this neural process1 and this consequent movement1 must produce a feeling1 although not necessarily a discriminated sensation4 ,now since1 for discrimination1 other neural processes must co-operate1 we cannot say that in the two cases all the neural processes have been the same throughout2 nor because of this difference can we say that the process of the undiscriminated sensation is a mechanical1 not a sentient process4 ,in the next problem this point will be argued more fully4 #ee4 ,the need of recognizing ,consciousness and ,consentience as degrees of energy and complexity in sentient states is apparent when we consider animal phenomena4 ,has a bee consciousness8 ,has a snail volition8 or are they both insentient mechanisms8 ,all inductions warrant the assertion that a bee has thrills propagated throughout its organism by the agency of its nerves2 and that some of these thrills are of the kind called sensations--even discriminated sensations4 ,nevertheless we may reasonably doubt whether the bee has sentient states resembling otherwise than remotely the sensations1 emotions1 and thoughts which constitute human ,consciousness1 either in the general or the special sense of that term4 ,the bee feels and reacts on feelings2 but its feelings cannot closely resemble our own1 because the conditions in the two cases are different4 ,the bee may even be said to think 7in so far as ,thought means logical combination of feelings71 for it appears to form ,judgments in the sphere of the ,logic of ,feeling-- 2 although incapable of the ,logic of ,signs-- 4 ,we should therefore say the bee has ,consentience1 but not ,consciousness--unless we accept ,consciousness in its general signification as the equivalent of ,sentience4 ,the organism of the bee differs from that of a man1 as a mud hut from a marble palace4 ,but since underlying these differences there are fundamental resemblances1 the functions of the two will be fundamentally alike4 ,both have the function of ,sentience2 as mud hut and palace have both the office of sheltering4 #ef4 ,the question of ,volition will occupy us in the next chapter4 ,restricting ourselves here to that of ,consciousness1 and recalling the distinction of the two meanings of the term1 we now approach the question of ,unconsciousness4 ,are we to understand this term as designating a purely physical state in contrast to the purely mental state of ,consciousness2 or only as designating a difference of degree8 ,this is like asking whether ,light and ,darkness are both optical feelings1 or one an optical feeling and the other a physical process8 ,on the ,reflex ,theory1 no sooner does a vital and mental process pass from the daylight of ,consciousness1 or twilight of ,sub-consciousness1 into the darkness of ,unconsciousness1 than the whole order of phenomena is abruptly changed1 they cease to be vital1 mental1 and lapse into physical1 mechanical processes4 ,the grounds of this conclusion are1 first1 the unpsychological assumption that the unconscious state is out of the sphere of ,sentience2 and secondly1 the unphysiological assumption that the ,brain is the only portion of the nervous system which has the property of ,sensibility4 ,restate the conclusion in different terms and its fallacy emerges3 8organic processes suddenly cease to be organic1 and become purely physical by a slight change in their relative position in the consensus2 the organic process which was a conscious sensation a moment ago1 when its energy was not balanced by some other process1 suddenly falls from its place in the group of organic phenomena--sentient phenomena--to sink into the group of inorganic phenomena now that its energy is balanced40 ,consider the parallel case of ,motion and ,rest in the objective sphere4 ,they are two functions of the co-operant forces1 one dynamic1 the other static2 although markedly distinguishable as functions1 we know that they are simply the co-operant forces now unbalanced and now balanced2 what we call ,rest is also a product of moving forces1 each of which is operant1 and will issue in a definite resultant when its counter-force is removed4 ,motion and ,rest are correlatives1 and both belong to the sphere of ,kinetics4 ,in like manner ,consciousness and ,unconsciousness are correlatives1 both belonging to the sphere of ,sentience4#bac ,every one of the unconscious processes is operant1 changes the general state of the organism1 and is capable of at once issuing in a discriminated sensation when the force which balances it is disturbed4 ,i was unconscious of the scratch of my pen in writing the last sentence1 but ,i am distinctly conscious of every scratch in writing this one4 ,then1 as now1 the scratching sound sent a faint thrill through my organism1 but its relative intensity was too faint for discrimination2 now that ,i have redistributed the co-operant forces1 by what is called an act of ,attention1 ,i hear distinctly every sound the pen produces4 #eg4 ,the inclusion of ,sub-consciousness within the sentient sphere is obvious2 the inclusion of ,unconsciousness within that sphere may be made so1 when we consider its modes of production1 and compare it with the extra-sensible conception of molecules and atoms4 ,the ,matter which is sensible as masses1 may be resolved into molecules1 which lie beyond the discrimination of sense2 and these again into atoms1 which are purely ideal conceptions2 but because molecules are proved1 and atoms are supposed1 to have material properties1 and to conform to sensible canons of the objective world1 we never hesitate to class them under the head of ,matter2 nor do we imagine that in passing beyond the discrimination of ,sense they lose their objective significance4 ,they are still physical1 not mental facts4 ,so with ,sentience3 we may trace it through infinite gradations from ,consciousness to ,sub-consciousness1 till it fades away in ,unconsciousness2 but from first to last the processes have been those of a sentient organism2 and by this are broadly distinguished from all processes in anorganisms4 ,the movement of a limb has quite different modes of production from the movement of a wheel2 and among its modes must be included those of ,sensibility1 a peculiarly vital property4 ,oxidation may be slow or rapid1 manifesting itself as combustion1 heat1 or flame1 but it is always oxidation--always a special chemical phenomenon4 ,and so the neural process of ,sentience1 whether conscious1 sub-conscious1 or unconscious1 is always a state of the sentient organism4 ,if a material process does not change its character1 and become spiritual1 on passing beyond the range of sensible appreciation1 why should a psychical process become material on passing beyond the range of discrimination8 ,if we admit molecules as physical units1 sentient tremors are psychical units4 ,the extra-sensible molecules have indeed their subjective aspect1 and only enter perception through the 8greeting of the spirit40 ,the sentient tremors have also their objective aspect1 and cannot come into existence without the neural tremors1 which are their physical conditions4 #eh4 ,it is only by holding fast to such a conception that we can escape the many difficulties and contradictions presented by unconscious phenomena1 and explain many physiological and psychological processes4 ,descartes--followed by many philosophers--identified ,consciousness with ,thought4 ,to this day we constantly hear that to have a sensation1 and to be conscious of it1 is one and the same state2 which is only admissible on the understanding that ,consciousness means ,sentience1 and ,sentience the activity of the nervous system viewed subjectively4 ,leibnitz pointed out that we have many psychical states which are unconscious states--to have an idea and be conscious of it1 are1 he said1 not one but two states4 ,the ,consciousness by ,descartes erected into an essential condition of ,thought1 was by ,leibnitz reduced to an accompaniment which not only may be absent1 but in the vast majority of cases is absent4 ,the teaching of most modern psychologists is that ,consciousness forms but a small item in the total of psychical processes4 ,unconscious sensations1 ideas1 and judgments are made to play a great part in their explanations4 ,it is very certain that in every conscious volition--every act that is so characterized--the larger part of it is quite unconscious4 ,it is equally certain that in every perception there are unconscious processes of reproduction and inference--there is much that is implicit1 some of which cannot be made explicit--a 8middle distance0 of sub-consciousness1 and a 8background0 of unconsciousness4 ,but1 throughout1 the processes are those of ,sentience4 #ei4 ,unconsciousness is by some writers called latent ,consciousness4 ,experiences which are no longer manifested are said to be stored up in ,memory1 remaining in the ,soul's picture-gallery1 visible directly the shutters are opened4 ,we are not conscious of these feelings1 yet they exist as latent feelings1 and become salient through association4 ,as a metaphorical expression of the familiar facts of ,memory this may pass2 but it has been converted from a metaphor into an hypothesis1 and we are supposed to have feelings and ideas1 when in fact we have nothing more than a modified disposition of the organism--temporary or permanent--which when stimulated will respond in this modified manner4 ,the modification of the organism when permanent becomes hereditary2 and its response is then called an instinctive or automatic action4 ,and as actions pass by degrees from conscious and voluntary into sub-conscious and sub-voluntary1 and finally into unconscious and involuntary1 we call them volitional1 secondarily automatic1 and automatic4 ,if any one likes to say the last are due to latent consciousness1 ,i shall not object4 ,i only point to the fact that the differences here specified are simply differences of degree--all the actions are those of the sentient organism4 #fj4 ,picture to yourself this sentient organism incessantly stimulated from without and from within1 and adjusting itself in response to such stimulations4 ,in the blending of stimulations1 modifying and arresting each other1 there is a fluctuating 8composition of forces10 with ever-varying resultants4 ,besides the stream of direct stimulations1 there is a wider stream of indirect or reproduced stimulations4 ,together with the present sensation there is always a more or less complex group of revived sensations1 the one group of neural tremors being organically stimulated by the other4 ,an isolated excitation is impossible in a continuous nervous tissue2 an isolated feeling is impossible in the consensus or unity of the sentient organism4 ,the term ,soul is the personification of this complex of present and revived feelings1 and is the substratum of ,consciousness 7in the general sense71 all the particular feelings being its states4 ,to repeat an illustration used in my first volume1 we may compare ,consciousness to a mass of stationary waves4 ,if the surface of a lake be set in motion each wave diffuses itself over the whole surface1 and finally reaches the shores1 whence it is reflected back towards the centre of the lake4 ,this reflected wave is met by the fresh incoming waves1 there is a blending of the waves1 and their product is a pattern on the surface4 ,this pattern of stationary waves is a fluctuating pattern1 because of the incessant arrival of fresh waves1 incoming and reflected4 ,whenever a fresh stream enters the lake 7i4 e4 a new sensation is excited from without71 its waves will at first pass over the pattern1 neither disturbing it nor being disturbed by it2 but after reaching the shore the waves will be reflected back towards the centre1 and there will more or less modify the pattern4 ,,chapter ,v4 ,,voluntary ,,and ,,involuntary ,,actions4 #fa4 ,much of what has been said in the preceding chapter respecting the passive side of the organism is equally applicable to the active side4 ,our actions are classed as voluntary and involuntary mainly in reference to their being consciously or unconsciously performed2 but not wholly so1 for there are many involuntary actions of which we are distinctly conscious1 and many voluntary actions of which we are at times sub-conscious and unconscious4 ,i do not propose here to open the long and arduous discussion as to what constitutes ,volition1 my present purpose being simply that of fixing the meaning of terms1 so that the question of ,automatism may not be complicated by their ambiguities4 8,voluntary0 and 8involuntary0 are1 like 8conscious0 and 8unconscious10 correlative terms2 but commonly1 instead of being understood as indicating differences of degree in phenomena of the same order1 they are supposed to indicate differences of kind--a new agent1 the ,will1 being understood in the one case to direct the ,mechanism which suffices without direction in the other4 #fb4 ,this interpretation is unphysiological and unpsychological1 since it overlooks the fact that both voluntary and involuntary actions belong to the same order of phenomena1 i4 e4 those of the sentient organism4 ,both involve the same efficient cause1 i4 e4 co-operant conditions4 ,we draw a line of demarcation between the two abstractions--as between all abstractions--but the concrete processes they symbolize have no such demarcation4 ,just as the thought which at one moment passes unconsciously1 at another consciously1 is in itself the same thought1 and the same neural process2 so the action which at one moment is voluntary1 and at another involuntary1 is itself the same action1 performed by the same mechanism4 ,the incitation which precedes1 and the feeling which accompanies the action1 belong to the accessory mechanisms1 and may be replaced by other incitations and other feelings2 as the fall of an apple is the same event1 involving the same conditions1 i4 e4 efficient cause1 whether the occasional cause be a gust of wind or the gardener's scissors1 and whether the fall be seen and heard or not4 ,i may utter words intentionally and consciously1 and ,i may utter the same words automatically1 unconsciously2 ,i may wink voluntarily1 and wink involuntarily4 ,there are terms to express these differences2 but they do not express a difference in the efficient agencies4 #fc4 ,many writers seem to think that the involuntary actions belong to the physical mechanical order1 because they are not stimulated by cerebral incitations1 and cannot be regulated or controlled by such incitations--or as the psychologists would say1 because ,consciousness in the form of ,will is no agent prompting and regulating such actions4 ,but ,i think this untenable4 ,the actions cannot belong to the mechanical order so long as they are the actions of a vital mechanism1 and so long as we admit the broad distinction between organisms and anorganisms4 ,whether they have the special character of ,consciousness or not1 they have the general character of sentient actions1 being those of a sentient mechanism4 ,and this becomes the more evident when we consider the gradations of the phenomena4 ,many1 if not all1 of those actions which are classed under the involuntary were originally of the voluntary class--either in the individual or his ancestors2 but having become permanently organized dispositions--the pathways of stimulation and reaction having been definitely established--they have lost that volitional element 7of hesitation and choice7 which implies regulation and control4 ,but even here a slight change in the habitual conditions will introduce a disturbance in the process which may awaken ,consciousness1 and the sense of effort1 sometimes even causing control4 ,an instinctive or an automatic action may be thus changed1 or arrested4 ,take as an example one of the unequivocally automatic actions1 that of ,breathing4 ,it is called automatic because1 like the actions of an automaton1 it is performed by a definitely constructed mechanism1 always working in the same way when stimulated and left to itself4 ,there must of course be a sense of effort in every impulse which has resistance to overcome1 organs to be moved2 but the mechanism of ,breathing is so delicately adjusted1 that the sense of effort is reduced to a minimum1 and we are unconscious of it1 or sub-conscious of it4 ,nevertheless1 without altering the rate or amplitude of the inspirations and expirations1 we become distinctly conscious of them1 and1 moreover1 within certain limits we can control them1 so that the ,breathing passes from the involuntary to the voluntary class4 #fd4 ,pass on to other examples4 ,what action can be more involuntary than the rhythmic movements of the heart and the contractions of the iris8 ,compared with the actions of the tongue or limbs1 these seem riveted by an iron necessity1 freed from all consciousness and control4 ,yet the movements of the heart are not only stimulated by sensations and thoughts1 they are also capable of being felt2 and the movements both of heart and iris are not wholly removed from our control4 ,that we do not habitually control 7that is1 interfere with7 the action of the heart1 the contraction of the iris1 or the activity of a gland1 is true2 it is on this account that such actions are called involuntary2 they obey the immediate stimulus4 ,but it is an error to assert that these actions cannot be controlled1 that they are altogether beyond the interference of other centres1 and cannot by any effort of ours be modified4 ,it is an error to suppose these actions are essentially distinguished from the voluntary movement of the hands4 ,we have acquired a power of definite direction in the movements of the hands1 which renders them obedient to our will2 but this acquisition has been of slow laborious growth4 ,if we were asked to use our toes as we use our fingers--to grasp1 paint1 sew1 or write with them1 we should find it not less impossible to control the movements of the toes in these directions1 than to contract the iris1 or cause a burst of perspiration to break forth4 ,certain movements of the toes are possible to us2 but unless the loss of our fingers has made it necessary that we should use our toes in complicated and slowly acquired movements1 we can do no more with them than the young infant can do with his fingers4 ,yet men and women have written1 sewed1 and painted with their toes4 ,all that is requisite is that certain links should be established between sensations and movements2 by continual practice these links are established2 and what is impossible to the majority of men1 becomes easy to the individual who has acquired this power4 ,this same power can be acquired over what are called the organic actions2 nevertheless the habitual needs of life do not tend towards such acquisition1 and without some strong current setting in that direction1 or some peculiarity of organization rendering it easy1 it is never acquired4 ,in ordinary circumstances the number of those who can write with their toes is extremely rare1 the urgent necessity which would create such a power being rare2 and rare also are the examples of those who have any control over the movement of the iris1 or the action of a gland2 but both rarities exist4 ,it would be difficult to choose a more striking example of reflex action than the contraction of the iris of the eye under the stimulus of light2#bad and to ordinary men1 having no link established which would guide them1 it is utterly impossible to close the iris by any effort4 ,it would be not less impossible to the hungry child to get on the chair and reach the food on the table1 until that child had learned how to do so4 ,yet there are men who have learned how to contract the iris4 ,the celebrated ,fontana had this power2 which is possessed also by a medical man now living at ,kilmarnock--,dr4 ,paxton--a fact authenticated by no less a person than ,dr4 ,allen ,thomson4#bae ,dr4 ,paxton can contract or expand the iris at will1 without changing the position of his eye1 and without an effort of adaptation to distance4 ,to move the ears is impossible to most men4 ,yet some do it with ease1 and all could learn to do it4 ,some men have learned to 8ruminate0 their food2 others to vomit with ease2 and some are said to have the power of perspiring at will4#baf ,now1 if once we recognize a link of sensation and motion1 we recognize a possible source of control2 and if the daily needs of life were such that to fulfil some purpose the action of the heart required control1 we should learn to control it4 ,some men have1 without such needs1 learned how to control it4 ,the eminent physiologist1 ,e4 ,f4 ,weber of ,leipzig1 found that he could completely check the beating of his heart4 ,by suspending his breath and violently contracting his chest1 he could retard the pulsations2 and after three or five beats1 unaccompanied by any of the usual sounds1 it was completely still4 ,on one occasion he carried the experiment too far1 and fell into a syncope4 ,cheyne1 in the last century1 recorded the case of a patient of his own who could at will suspend the beating of his pulse1 and always fainted when he did so4 #fe4 ,it thus appears that even the actions which most distinctly bear the character recognized as involuntary--uncontrollable--are only so because the ordinary processes of life furnish no necessity for their control4 ,we do not learn to control them1 though we could do so1 to some extent2 nor do we learn to control the motions of our ears1 although we could do so4 ,and while it appears that the involuntary actions can become voluntary1 it is familiar to all that the voluntary actions tend1 by constant repetition1 to become involuntary4 ,thus involuntary actions1 under certain limitations1 may be controlled2 on the other hand1 the voluntary are incapable of being controlled under the urgency of direct stimulation4 ,both are reflexes4 ,inasmuch as almost all actions are the products of stimulated nerve-centres1 it is obvious that these actions are reflex--reflected from those centres4 ,it matters not whether ,i wink because a sensation of dryness1 or because an idea of danger1 causes the eyelid to close3 the act is equally reflex4 ,the nerve-centre which supplies the eyelid with its nerve has been stimulated2 the stimuli may be various1 the act is uniform4 ,at one time the stimulus is a sensation of dryness1 at another an idea of danger1 at another the idea of communicating by means of a wink with some one present2 in each case the stimulus is reflected in a muscular contraction4 ,sensations excite other sensations2 ideas excite other ideas2 and one of these ideas may issue in an action of control4 ,but the restraining power is limited1 and cannot resist a certain degree of urgency in the original stimulus4 ,i can1 for a time1 restrain the act of winking1 in spite of the sensation of dryness2 but the reflex which sets going this restraining action will only last a few seconds2 after which1 the urgency of the external stimulus is stronger than that of the reflex feeling--the sensation of dryness is more imperious than the idea of resistance--and the eyelid drops4 ,if a knife be brought near the arm of a man who has little confidence in the friendly intentions of him that holds it1 he shrinks1 and the shrinking is 8involuntary10 i4 e4 in spite of his will4 ,let him have confidence1 and he does not shrink1 even when the knife touches his skin4 ,the idea of danger is not excited in the second case1 or if excited1 is at once banished by another idea4 ,yet this very man1 who can thus repress the involuntary shrinking when the knife approaches his arm1 cannot repress the involuntary winking when the same friend approaches a finger to his eye4 ,in vain he prepares himself to resist that reflex action2 in vain he resolves to resist the impulse2 no sooner does the finger approach1 than down flashes the eyelid4 ,many men1 and most women1 would be equally unable to resist shrinking on the approach of a knife3 the association of the idea of danger with the knife would bear down any previous resolution not to shrink4 ,it is from this cause that timorous women tremble at the approach of firearms4 ,an association is established in their minds which no idea is powerful enough to loosen4 ,you may assure them the gun is not loaded2 8that makes very little difference10 said a nave old lady to a friend of mine4 ,they tremble1 as the child trembles when he sees you put on the mask4 ,these illustrations show that the urgency of any one idea may1 like the urgency of a sensation1 bear down the resistance offered by some other idea2 as the previous illustrations showed that an idea could restrain or control the action which a sensation or idea would otherwise have produced4 ,according to the doctrines current1 the ,will is said to be operative when an idea determines an action2 and yet all would agree that the winking which was involuntary when the idea of danger determined it1 was voluntary when the idea of communicating with an accomplice in some mystification determined it4 #ff4 ,there is no real and essential distinction between voluntary and involuntary actions4 ,they all spring from ,sensibility4 ,they are all determined by feeling4 ,it is convenient1 for common purposes1 to designate some actions as voluntary2 but this is merely a convenience2 no psychological nor physiological insight is gained by it2 an analysis of the process discloses no element in a voluntary action which is not to be found in an involuntary action--except in the origin or degree of stimulation4 ,in ordinary language it is convenient to mark a distinction between my raising my arm because ,i will to raise it for some definite purpose1 and my raising it because a bee has stung me2 it is convenient to say1 8,i will to write this letter10 and 8this letter is written against my will--,i have no will in the matter40 ,but ,science is more exacting when it aims at being exact2 and the philosopher1 analyzing these complex actions1 will find that in each case certain muscular groups have been set in action by different sensational or ideational stimuli4 ,the action itself is that of a neuro-muscular mechanism1 which mechanism works in the same way1 whatever be the source of the original impulse4 ,the stimulation may be incited directly from the periphery1 or indirectly from a remote centre2 and the action may be arrested by a peripheral or central stimulation3 the reflex which ordinarily follows the excitation of a sensory nerve will be modified1 or arrested1 if some other nerve be at the same time stimulated4 7,see ,law of ,arrest1 ,prob4 ,,ii4 #aij47 #fg4 ,all actions are reflex1 all are the operations of a mechanism1 all are sentient1 because the mechanism has ,sensibility as its vital property4 ,in thus preserving the integrity of the order of vital phenomena1 and keeping them classified apart from physical and chemical phenomena1 we by no means set aside the useful distinctions expressed in the terms voluntary and involuntary2 any more than we set aside the distinction of vertebrate and invertebrate when both are classed under ,animal1 and separated from ,plant1 or ,planet4 ,the mechanisms of the special ,senses respond in special reactions2 the mechanisms of special actions have also their several responses4 ,the tail responds to stimulation with lateral movements1 the chest with inspiration and expiration1 and so on4 ,these responses are called automatic1 and have this in common with the actions of automata that they are uniform1 and do not need the co-operation of ,consciousness1 though they do need the operation of ,sensibility1 and are thereby distinguished from the actions of automata4 ,the facial muscles1 and the limbs1 also respond to stimulation in uniform ways1 but owing to the varieties of stimulation the actions are more variable1 and have more the character of volitional movements4 ,with this greater freedom of possible action comes the eminently mental character of choice4 ,in the cerebral rehearsal of an act not yet performed--its mental prevision--as when we intend to do something1 yet for the moment arrest the act1 so that there is only a nascent excitation of the motor process1 there is a peculiar state of ,consciousness expressive of this state of the mechanism3 we call the prevision a motive--and it becomes a motor when the intention is realized1 the nascent excitation becomes an unchecked impulse4 ,the abstract of all motives we call ,will4 ,a motive is a volition in the sphere of the ,intellect4 ,in the sphere of ,emotion it is a motor4 ,hence we never speak of the ,will of a mollusc1 or the motives of an insect1 only of their sensations and motors4 ,yet it is obvious that the reflex in operation when a snail shrinks at the approach of an object is essentially similar to the reflex in operation when the baby shrinks1 and this again is still more similar to that in operation when the boy shrinks3 the boy has the idea of danger1 which neither baby nor snail can have2 the idea is a motive1 which can be controlled by another idea2 the baby and the snail can have no such motive1 no such control--are they therefore automata8 #fh4 ,if ,i see that a donkey has wandered into my garden1 the motive which determines me to take a stick and with it drive the donkey away is a cerebral rehearsal of the effects which will follow my act4 ,the sight of the donkey has roused disagreeable feelings1 and these suggest possible means of alleviation2 out of these possibilities--reproductions of former experiences--,i choose one4 ,but if ,i seize the stick with which some one is threatening me1 ,i do not pause to choose1 ,i snatch automatically without hesitation4 ,yet this unreflecting automatic act is itself as truly volitional as my seizing the stick to drive away the donkey--it is the motor which has been organized in me by previous experiences--it is the consequence of an emotion1 not of a deliberation2 and it has not been determined by any clear prevision of consequences4 ,feeling inspires1 and feeling guides my movements1 so that if my snatch has missed the stick1 ,i snatch again1 or duck under4 ,this is the kind of ,volition we ascribe to animals4 ,it is a great part of our own4 ,by insensible degrees1 acts which originally were prompted by motives sink into the automatic class prompted by motors4 ,when an angry man snatches up a knife1 doffs bystanders aside1 and rushes on his enemy to stab him1 he does not distinctly prefigure the final result1 he only obeys each motor1 and is conscious of each step2 but had he planned the murder he would have foreseen the end1 and this prevision would have been the motive4 ,the angry man is struck with horror at the sight of the bleeding corpse1 and passionately declares he did not mean to kill4 ,nor did he will the consequences of his act1 yet he certainly willed each separate step--he recognized the knife1 saw the bystanders1 knew they would interfere with him1 willed to push them aside4 ,he may be right in declaring that the act was involuntary2 but assuredly it was not purely mechanical4 #fi4 ,again1 we are not conscious of the separate sensations which guide speech or writing2 we cannot properly be said to will the utterance of each tone1 or the formation of each letter4 ,are these processes mechanical and not volitional8 ,by no means4 ,we know that they were laboriously learned by long tentative efforts1 each of which was accompanied by distinct consciousness4 ,we also know that now when the mechanism is so easy in its adjustment as to suggest automatism1 there needs but a slight alteration in the conditions to make us distinctly conscious of the processes--the wrong word spoken1 or one letter ill formed1 suffices to arrest the easy working of the mechanism4 ,a similar mechanism operates in thinking1 which also lapses from the conscious and voluntary to the unconscious and involuntary state4 ,the logical process of ,judgment is as purely a reflex from one neural group to another1 as the physiological process of co-ordination4 ,in ordinary thinking we are as little conscious of the particular steps--our interest being concentrated on the result--as we are of the particular stages of an action4 ,the adjustments of the mechanism of ,reproduction and ,association are set going by a motive1 and kept going by psychological motors4 ,and here--as in bodily actions--there is often a conflict between motive and motors--between the foreseen result1 and the available means of reaching it--the motors usually prevailing because they represent the active side of the mechanism4 ,thus when an oculist wishes to examine a patient's eye1 he does not tell him to give a particular direction to his eye1 knowing that the motive to do so will not suffice2 instead of this he simply moves his own hand in the desired direction1 certain that the eye will by reflex irresistibly follow it4 ,nay1 there are sometimes such anomalies of innervation that the eye1 instead of obeying the motive1 moves in a contrary direction4 ,meschede mentions a patient whose movements were mostly of this anomalous kind3 when he willed to move the eyes to the right1 they moved to the left2 when he willed to move them up1 they moved down4 ,it was thus also with his hands and feet4 ,yet he was distinctly conscious that his intention had been frustrated1 and that he acted 8because he could not help it40#bag ,how insensibly a motive sinks into a motor1 that is to say1 a voluntary into an involuntary act1 may be recognized in speech1 writing1 singing1 walking1 etc41 and in the incessant movements of the eye in fixing objects4 ,aubert has well remarked that we only give definite movements to the eye when we wish to see an object distinctly4 ,whenever the indistinct vision suffices--as in walking through the streets occupied in conversation or thought--we make no such movements2 but no sooner does any object excite our attention1 than the effort to fix that object at once excites the necessary reflex4#bah #gj4 ,by the ,will1 then1 we must understand the abstract generalized expression of the impulses which determine actions1 when those impulses have an ideal origin2 by ,volition the still more generalized expression of all impulses which determine actions4 ,the one class is that of motives with ideal elements2 the other that of motors with sensational or emotional elements4 ,but both are mental states1 both are neural processes in a sentient organism2 neither is mechanical1 except in so far as all actions are expressible in mechanical terms4 ,for convenience we class actions as reflex1 automatic1 involuntary1 unconscious1 voluntary1 and conscious4 ,if we separate the reflex from the voluntary1 we need not therefore dissociate the former from ,sensibility2 and the reason why we ought not to separate it is that we know it to be sense-guided from first to last1 although the sensations may escape discrimination4 ,the feeling of ,effort1 which was formerly felt when an action was performed1 may have become so minimized that it is too faint for more than a momentary consciousness1 too evanescent for the memory to retain it2 yet the feeling must always be operant when its mechanism is in action4 ,the ease with which the mechanism works does not change the adjustment of its elements1 nor alter its character4 ,the facile unobtrusive performance of a vital function does not change it from a vital to a mechanical act4 ,mr4 ,spencer seems to me to express himself ambiguously when he says3 8,just as any set of psychical changes originally displaying ,memory1 ,reason1 and ,feeling cease to be conscious1 rational1 and emotional as fast as they by repetition grow closely organized1 so do they at the same time pass beyond the sphere of ,volition4 ,memory1 ,reason1 ,feeling1 and ,will disappear in proportion as psychical changes become automatic0#bai--;for while it is perfectly true that we only call those psychical changes 8automatic0 which have lost the special qualities called 8conscious1 rational1 and emotional10 it is not less true that they remain from first to last psychical changes1 and are thereby distinguished from physical changes4 ,to suppose that they pass from the psychical to the physical by frequent repetition would lead to the monstrous conclusion that when a naturalist has by laborious study become so familiarized with the specific marks of an animal or plant that he can recognize at a glance a particular species1 or recognize from a single character the nature of the rest1 the rapidity and certainty of this judgment proves it to be a mechanical1 not a mental act4 ,the intuition with which a mathematician sees the solution of a problem would then be a mechanical process1 while the slow and bungling hesitation of the tyro in presence of the same problem would be a mental process3 the perfection of the organism would thus result in its degradation to the level of a machine6 ,the operations of the intellect may furnish us with an illustration4 ,ideas are symbols of sensations4 ,the idea of a horse is an abstraction easily traceable to concrete sensations1 yet as an abstraction is so different a state of feeling that we only identify it with its concretes by a careful study of its stages of evolution1 namely1 sensation1 image1 reproduced images resembling yet differing from the original sensation1 a coalescence of their resemblances1 and finally the substitution of a verbal symbol for these images4 ,with this symbol the intellect operates1 and sometimes operates so exclusively with it that not the faintest trace of image or sensation is appreciable--the word horse takes the place of the image in the sequence of sensorial processes1 just as the image takes the place of the sensation4 ,it does this as a neural equivalent4 ,in the same way we substitute verbal symbols for a bag of sovereigns when we pay a creditor with a check2 he pays the check away to another2 and this monetary equivalent passes from hand to hand without a single coin making its appearance4 ,does the transaction cease to be commercial1 monetary1 in this substitution of signs8 ,no2 nor does a process cease to be psychical when an image is substituted for a sensation1 and a verbal symbol for an image4 ,this every one will admit4 ,must we not go further1 and extend the admission to automatic actions which originally were voluntary1 and have now lost all trace of ideal prevision1 and almost all traces of accompanying consciousness8 ,the motor mechanism has its symbols also2 in this sense1 that whereas the action which at first needed complex sensorial processes to set it going and keep it going1 is now determined by a single one of those processes taking the place of their resultant4 ,when a practised accountant runs his eye up a column of figures1 he does not pause to realize the values of those figures by decomposing the symbols into their numerical units1 he simply groups one symbol with another according to their intuited relations1 and the final result is reached with a certainty not less1 and a rapidity far greater1 than if it had been reached by step-by-step verification4 ,it is thus with the pianoforte-player4 ,it is thus with all automatic performances1 except those dependent on the connate adjustments of the mechanism4 ,,chapter ,,vi4 ,,the ,,problem ,,stated4 #ga4 ,if the preceding attempt to disengage the question from the ambiguities of its terms has been successful1 we shall find little difficulty in rationally interpreting all the facts adduced in favor of ,animal ,automatism1 without having recourse to a mechanical theory of biological phenomena4 ,the objections to that theory are that it employs terms which have very misleading connotations even when they do not denote phenomena of widely different orders2 so that the moral repugnance commonly felt at the attempt to treat the animal organism as if it were a machine1 is sustained by the intellectual repugnance at the attempt to explain biological phenomena on principles derived from phenomena of a simpler order4 ,remark1 in passing1 this piquant contradiction3 the ,automaton theory of ,descartes1 when applied to the animals1 generally excited ridicule or repulsion2 whereas the far more inconsistent and mechanical theory of ,reflex ,action has been almost universally welcomed as a great discovery1 though it banishes the ,sensibility which ,descartes preserved4 ,and further1 the philosophers who most loudly protested against the idea that animals were machines1 were the philosophers who most insisted that these animals were made1 not evolved--planned by their maker1 as a watch is planned by its maker1 with a distinct purpose and prevision in the disposition of every part2 whereas the philosophers who most emphatically reject this notion of organisms being made1 are often those who liken organisms to machines4 #gb4 ,the paradox propounded by ,descartes loses much of its strangeness when we understand his meaning4 ,its terms are infelicitous because of their misleading connotations4 ,when he says that all the actions of animals which seem to be due to ,consciousness are in fact produced on the same principles as those of a machine1 he means that animals have not souls to direct their actions2 but since1 on being questioned1 he is ready to admit that animals have sensation1 perception1 emotion1 and memory1 his denial of their souls practically comes to much the same as the ordinary position that animals have not ,thought nor ,consciousness of ,self4#bbj ,the admission of sensation is1 however1 quite enough to mark the essential difference between an organism and a machine4 #gc4 ,it was really a great step taken by ,descartes when he directed attention to the fact that all animal actions were executed in strict conformity with mechanical principles1 because both before his time1 and since1 we may observe a great disregard of the animal mechanism1 and a disposition to interpret the phenomena on metaphysical principles4 ,but the connotations of the term 8machine0 were such as to lead the mind away from the special conditions of the vital mechanism1 and fix it exclusively on the general conditions of machinery4 ,hence his opponents misunderstood him1 and some of his followers made the same oversight1 and ended by eliminating sensation altogether4 ,in pursuance of this mechanical point of view1 to the exclusion of the biological1 ,thought and even ,consciousness have been eliminated from among the organic agencies1 and are said to have no more influence in determining even human actions than the whistle of the steam-engine has in directing the locomotive4 ,there are thus two metaphysiological theories4 ,according to the one1 ,consciousness directs indeed the actions of the organism1 but is not itself an organic process--it sits apart1 like a musical performer playing on an instrument4 ,according to the other1 it is not a directing agency1 but an accessory product of certain organic processes1 which processes may go on quite as well without any accompaniment and interference of ,consciousness4 #gd4 ,two observations arise here4 ,first1 we observe a want of due recognition of the objective and subjective aspects1 and their respective criteria4 ,secondly1 we observe mental facts of irresistible certainty interpreted by material hypotheses of questionable value2 and not only so1 but a higher validity is assigned to the material hypotheses than to the mental facts they are invented to explain4 ,that we are conscious1 and that our actions are determined by sensations1 emotions1 and ideas1 are facts which may or may not be explained by reference to material conditions1 but which no material explanation can render more certain4 ,that animals resemble us in this as in other respects is an induction of the highest probability4 ,it is also a fact that many actions take place1 as we say1 unconsciously and involuntarily2 and that some take place now consciously1 now unconsciously4 ,these facts also we endeavor to explain3 and when we find that some of the unconscious and involuntary actions take place after the brain has been removed1 this is interpreted on the material hypothesis of the brain being the sole seat of sensation and consciousness2 and is urged in favor of the hypothesis that consciousness cannot be an agent in the mechanism4 ,here the confusion of objective and subjective aspects is patent4 ,consciousness as a subjective fact cannot be a material or objective fact4 ,but may it not be another aspect of that which is objective8 ,so long as we are dealing with the objective aspect1 we have nothing but material processes in a material mechanism before us4 ,a change within the organism is caused by a neural stimulation1 and the resulting action is a reflex on the muscles4 ,here there is simply a transference of motion by a material mechanism4 ,there is in this no evidence of a subjective agency2 there could be none4 ,but when we come to investigate the process1 we find that it differs from similar processes in anorganisms1 by the necessary co-operation of special conditions1 and among these--the vital conditions--there are those which in their subjective aspect we express not in terms of ,matter and ,motion1 but in terms of ,feeling1 i4 e4 not in objective but in subjective terms4 ,i see a stone move on being struck2 ,i also see a man shrink on being struck1 and hear a dog howl on being kicked4 ,i do not infer that the stone feels as the man and dog feel1 because ,i know the stone and the dog to be differently constituted1 and infer a corresponding difference in their reactions4 ,i infer that the man and dog feel1 because ,i know they are like myself1 and conclude that what ,i feel they feel1 under like conditions4 #ge4 ,descartes says that animals are sensitive automata4 ,they always act as we sometimes act1 i4 e4 when we are not conscious of what we do1 as in singing1 walking1 playing the piano1 etc4 ,we are said to do these things mechanically1 automatically1 and hence the conclusion that these actions are those of a pure mechanism4 ,but it would be truer to say that we never act mechanically1 we always act organically4 8,when one who falls from a height throws his hands forwards to save his head10 says ,descartes1 8it is in virtue of no ratiocination that he performs this action0 7that depends on the definition3 in the ,logic of ,feeling there is a process of ratiocination identical with that in the ,logic of ,signs74 8,it does not depend upon his mind0 7again a question of definition71 8but takes place merely because his senses being affected by present danger0 7senses1 then1 have a perception of danger87 8some change arises in his brain which determines the animal spirits to pass thence into the nerves in such a manner as is required to produce this motion1 in the same way as in a machine1 and without his mind being able to hinder it4 ,now since we observe this in ourselves1 why should we be so much astonished if the light reflected from the body of a wolf into the eye of a sheep has the same force to excite in it the motion of flight80 ,here1 both in the case of the man and the sheep1 there is presupposed the very mental experience which is denied4 ,the young child will not throw out its arm to protect itself2 but after many experiences of falling and stumbling1 there is an organized perception of the impending danger1 and the means of averting it1 and it is this which determines the throwing out of the arms4 ,if this is not a mental fact--a process of judgment--then the logical conclusion by which a financier on hearing a war rumor orders his broker to sell stock1 is not a mental fact4 ,the light reflected from the body of a wolf would not disturb the sheep unless its own1 or its inherited organized experience were ready there to respond4 ,but this organized experience1 you say1 enters into the mechanism8 ,yes2 but it cannot be made to enter into the mechanism of an automaton1 because however complex that mechanism may be1 and however capable of variety of action1 it is constructed solely for definite actions on calculated lines3 all its readjustments must have been foreseen1 it is incapable of adjusting itself to unforeseen circumstances4 ,hence every interruption in the prearranged order either throws it out of gear1 or brings it to a standstill4 ,it is regulated1 not self-regulating4 ,the organism1 on the contrary--conspicuously so in its more complex forms--is variable1 self-regulating1 incalculable4 ,it has selective adaptation 7p4 #bba7 responding readily and efficiently to novel and unforeseen circumstances2 acquiring new modes of combination and reaction4 ,an automaton that will learn by experience1 and adapt itself to conditions not calculated for in its construction1 has yet to be made2 till it is made1 we must deny that organisms are machines4 ,automatism in the organism implies ,memory and ,perception4 ,a sudden contact--a sudden noise--a vague form seen in the twilight will excite the mechanism according to its organized experiences4 ,we start automatically1 before we automatically interpret the cause2 we start first1 and then ask1 ,what is that8 ,but we do not always start at sounds or sights which have no association with previous experiences4 ,the child and the man both see the falling glass1 but the child does not automatically stretch out a hand to save the glass4 ,having once learned the action of swimming or billiard-playing1 we automatically execute these2 without consciously remembering the rules1 we unconsciously obey them2 each feeling as it rises is linked on to another1 each muscle is combined with others in a remembered synthesis4 #gf4 ,kempelen's chess-player surprised the public1 but every instructed physiologist present knew that in some way or other its movements were directed by a human mind2 simply because no machine could possibly have responded to the unforeseen fluctuations of the human mind opposed to it4 ,even the mind of a dog or a savage would be incompetent to pass beyond the range of its previous experiences1 incompetent to seize the significance of an adversary's moves on the chessboard4 ,now just as we conclude that mental agency is essential to a game of chess1 so we conclude that ,sensibility is essential to the fluctuating responses of an organism under unforeseen circumstances4 ,we can conceive an automaton dog that would bark at the presence of a beggar2 but not of an automaton dog that would bark one day at the beggar and the next day wag his tail1 remembering the food and patting that beggar had bestowed4 ,since all we know of machines forbids the idea of their being capable of adjusting their actions to new circumstances1 or of evoking through experience new powers of combination1 we conclude that wherever this capability of adaptation is present there is an agency in operation which does not belong to the class of mechanical agencies4 ,goltz has shown that a frog deprived of its brain manifests so much of vision as enables it to avoid obstacles--leaping to the right or to the left of a book placed in its path4 ,this ,professor ,huxley regards as purely mechanical3--8,although the frog appears to have no sensation of light1 visible objects act upon the motor mechanism of its body40 ,should we not rather conclude that if the frog had no sensation1 no such effect would follow8 because although a machine might be constructed to respond to variations of light and shadows1 none could be constructed 7without ,sensibility7 to respond to the fluctuating conditions as an organism responds4#bba ,were the reflex actions of the organism purely mechanical--i4 e4 involving none of those fluctuating adjustments which characterize ,sensibility--the effect would be uniform1 and proportional to the impact2 but it is variable1 and proportional to the static condition of the nervous centres at the moment4 ,exaggerate this--by strychnine1 for instance--and the slightest touch on the skin will produce general convulsions4 ,lower it--by an ansthetic--and no reflex at all will follow a stimulus4 ,in ansthesia of the mucous membrane1 no reflex of the eyelid1 no secretion of tears1 follows on the irritation of the membrane2 no sneezing follows irritation of the inside of the nose2 no vomiting follows irritation of the fauces4 #gg4 ,the question has long ceased to be whether the organism is a mechanism4 ,to the physiologist it is this before all things4 ,to the psychologist also it has of late years more and more assumed this character2 because even when he postulates the existence of a spiritual entity in the organism but not of it1 he still recognizes the necessity of a mechanism for the execution of the acts determined by the spirit2 and when the psychologist adopts the theory of spiritual phenomena as the subjective aspect of what objectively are material phenomena1 he of course regards the bodily mechanism and the mental mechanism as one and the same real4 ,this settled1 the problem of ,automatism may be thus stated3 ,granting the animal organism to be a material mechanism1 and all its actions due to the operation of that mechanism1 are we to conclude that it is an automaton essentially resembling the automata we construct1 the movements of which may1 or may not1 be accompanied by ,feeling1 but are in no case determined by ,feeling8 ,descartes says that animals are sensitive automata4 ,professor ,huxley says that both animals and men are sensitive and conscious automata2 so that misleading as the language of ,descartes and ,professor ,huxley often is in what its terms connote1 we do them great injustice if we suppose them to have overlooked the points of difference between organisms and machines which have been set forth with so much emphasis in a preceding chapter2 and the reader is requested to understand that without pretending to say how much the inevitable connotation of their language expresses their opinions1 and how much it may have only led to their being misunderstood1 my criticisms are directed against this connotation and this interpretation4 ,,chapter ,,vii4 ,,is ,,feeling ,,an ,,agent8 #gh4 ,descartes having attributed all animal actions to a sensitive mechanism1 and indeed all human actions to a similar mechanism1 endeavored to reconcile this hypothesis with the irresistible facts of ,consciousness--which assured us that our actions1 at least1 were determined by ,feeling4 ,to this end he assumed that man had a spiritual principle over and above the sentient principle4 ,the operation of this principle was1 however1 limited to ,thought2 the actions themselves were all performed by the automatic mechanism2 so that1 in strict logic1 the conclusion from his premises was the same for man as for animals4 ,this conclusion ,professor ,huxley announced in his ,address before the ,british ,association1 #ahgdbbb--to the great scandal of the general public1 which did not understand him aright2 and to the scandal also of a physiological public1 which1 strangely enough1 failed to see that it was the legitimate expression of one of their favorite theories--the celebrated ,reflex ,theory4 ,now although it is quite open to any one to reject the premises which lead to such a conclusion1 if he sees greater evidence against the conclusion than for the premises1 it is surely irrational to accept the premises as those of scientific induction1 and yet reject the conclusion because it endangers the stability of other opinions8 ,for my own part1 ,i do not accept the premises1 and my polemic will have reference to them4 #gi4 ,professor ,huxley adopts certain ,theses which represent the views generally adopted by physiologists2 to which he adds a ,thesis which is adopted by few1 and which he only puts forward hypothetically4 ,against these positions ,i place ,antitheses1 less generally adopted1 but which in my belief approximate more nearly to the inductions of experience4 ,theses4 ,antitheses4 ,i4 ,there can be no sensation ,i4 ,there is sensation without without consciousness4 consciousness1 if consciousness means a special mode of ,sentience4 ,,ii4 ,there can be no ,,ii4 ,the co-operation of the brain consciousness without the is only necessary for a special co-operation of the brain4 mode of ,sentience2 other modes are active when the brain is inactive4 ,,iii4 ,sensation and ,consciousness ,,iii4 ,unless the molecular changes are in some inexplicable way be limited to the brain as the caused by molecular changes in occasional cause1 there is the brain1 following upon these no following of sensation or as one event follows another1 motion1 no causal link between the the causal link between motion two2 but the neural process is and sensation being a mystery4 the sensation1 viewed objectively1 the sensation is the neural process1 viewed subjectively4 ,in this antithesis1 ,neural ,process is not limited to the brain1 but comprises the whole sensitive organism as the efficient cause4 ,,iv4 ,all actions which take place ,,iv4 ,all actions are the actions of unconsciously are reflex1 and a reflex mechanism1 and all are reflex actions are the operation sentient1 even when unconscious2 of an insentient mechanism2 they are therefore never purely they are therefore as purely mechanical1 but always organical4 mechanical as those of automata4 ,v4 ,the animal body is a reflex ,v4 ,sentience being necessary to mechanism2 even when the reflex action1 it is necessarily brain co-operates with the an agent4 other centres1 and produces consciousness1 this product is not an agent in determining action1 it is a collateral result of the operation4 #hj4 ,the first four ,theses are those current in our textbooks1 so that it is only the fifth which will have the air of a paradox4 ,nor1 as a paradox1 is it without advocates4 ,schiff long ago suggested it hypothetically4 ,hermann mentions it as entertained by physiologists1 whom he does not name4#bbc ,laycock1 and1 if ,i remember rightly1 ,dr4 ,drysdale1 have insisted on it2 and ,mr4 ,spalding has proclaimed it with iterated emphasis4 ,of the ,antitheses nothing need be said here1 since the whole of this volume is meant to furnish their evidence4 ,i have already stated that my polemic is against the views that ,professor ,huxley is supposed to hold by those whom his expressions mislead1 rather than against the views ,i imagine him really to hold4 ,i have little doubt that he would disavow much that ,i am forced to combat1 although his language is naturally interpreted in that sense4 ,but ,i do not know in how far he would agree with me1 and in the following remarks ,i shall confine myself to what seems to be the plain interpretation of his words1 since that is the interpretation which has been generally adopted1 and which ,i most earnestly desire to refute4 #ha4 ,to begin with this passage4 ,after stating the views of ,descartes1 he says3 8,as actions of a certain degree of complexity are brought about by mere mechanism1 why may not actions of still greater complexity be the result of a more refined mechanism8 ,what proof is there that brutes are other than a superior race of marionnettes1 which eat without pleasure1 cry without pain1 desire nothing1 know nothing1 and only simulate intelligence as a bee simulates a mathematician80 ,what proof8 ,why1 in the first place1 the proof which is implied in the 8more refined mechanism0 required for the greater complexity of actions4 ,in the next place1 the proof that the organism of the brute is very different from the mechanism of a marionnette1 and is so much more like the organism of man1 that since we know man to eat with pleasure and cry with pain1 there is a strong presumption that the brute eats and cries with somewhat similar feelings4 #hb4 ,having stated the hypothesis1 ,professor ,huxley says he is not disposed to accept it1 though he thinks it cannot be refuted4 ,his chief reason for not accepting it is that the law of continuity forbids the supposition of any complex phenomenon suddenly appearing2 the community between animals and men is too close for us to admit that ,consciousness could appear in man without having its beginnings in animals4 ,finding that animals have brains1 he justly concludes that they also must have brain functions2 and they also therefore must be credited with ,consciousness4 ,this argument seems to me to have irresistible cogency2 and to be destructive not only of the automaton hypothesis1 but equally of the hypothesis on which the ,reflex ,theory is founded4 ,if the law of continuity forbids the sudden appearance of ,consciousness1 the law of similarity of property with similarity of structure forbids the supposition that central nerve-tissue in one part of the system can suddenly assume a totally different property in another part4 ,if the brain of an animal1 a bird1 a reptile1 or a fish--and a fortiori if the sophageal ganglia of an insect or a mollusc--may be credited with ,sensibility1 because of the fundamental similarity of these structures with the structures of the human brain1 then surely the spinal cord must be credited with ,sensibility2 for the tissue of the spinal cord is more like that of the brain1 than the brain of a reptile is like the brain of a man4 ,the sudden disappearance of all ,sensibility1 on the removal of one portion of the central nervous system1 would be a violation of the law of continuity4 ,and if it be said that ,consciousness is not the same as ,sensibility1 but is a specially evolved function of a specially developed organ1 the answer will be that this is only a difference of mode1 and that the existence of ,sensibility is that which renders the automaton and reflex theories untenable4 #hc4 ,professor ,huxley would probably admit this2 for however his language may at times seem to point to another conclusion1 and is so far ambiguous1 he has expressed the view here maintained with tolerable distinctness in the following passage1 to which particular attention is called3-- 8,but though we may see reason to disagree with ,descartes' hypothesis1 that brutes are unconscious machines1 it does not follow that he was wrong in regarding them as automata4 ,they may be more or less conscious sensitive automata2 and the view that they are such conscious machines is that which is implicitly or explicitly adopted by most persons4 ,when we speak of the actions of the lower animals being guided by instinct and not by reason1 what we really mean is that though they feel as we do1 yet their actions are the results of their physical organization4 ,we believe1 in short1 that they are machines1 one part of which 7the nervous system7 not only sets the rest in motion and co-ordinates its movements in relation with changes in surrounding bodies1 but is provided with a special apparatus the function of which is the calling into existence of those states of consciousness which are termed sensations1 emotions1 and ideas40 #hd4 ,to say that they are 8conscious automata0 seems granting all that ,i demand2 but there are two objectionable positions which the phrase conceals3 first1 that ,consciousness is not a coefficient2 and secondly1 that ,reflex ,action is purely mechanical4 ,professor ,huxley nowhere1 ,i think1 establishes the distinction between ,consciousness as a term for a special mode of ,feeling1 and ,consciousness as the all-embracing term for sentient phenomena4 ,his language always implies that an action performed unconsciously is performed mechanically2 which may be acceptable if by unconsciously be meant insentiently4 ,i hold that whether consciously or unconsciously performed1 the action is equally vital and sentient4 ,in the case he has cited of a soldier now living who is subject to periodic alternations of normal and abnormal states1 in the latter states all the actions being said to be 8unconscious10 we have only to read the account to recognize ample evidence of ,sentience4 ,here is a descriptive passage3-- #he4 8,his the soldier's in the abnormal state movements remain free1 and his expression calm1 except for a contraction of the brow1 an incessant movement of the eyeballs1 and a chewing motion of the jaws4 ,the eyes are wide open1 and their pupils dilated4 ,if the man happens to be in a place to which he is accustomed he walks about as usual2 but if he is in a new place1 or if obstacles are intentionally placed in his way1 he stumbles against them1 stops1 and then feeling over the objects with his hands1 passes on one side of them4 ,he offers no resistance to any change of direction which may be impressed upon him1 or to the forcible acceleration or retardation of his movements4 ,he eats1 drinks1 smokes1 walks about1 dresses and undresses himself1 rises and goes to bed at the accustomed hours4 ,nevertheless pins may be run into his body1 or strong electric shocks sent through it1 without causing the least indication of pain2 no odorous substance1 pleasant or unpleasant1 makes the least impression2 he eats and drinks with avidity whatever is offered1 and takes asaftida or vinegar of quinine as readily as water2 no noise affects him2 and light influences him only under certain conditions40 ,there is no one of these phenomena that is unfamiliar to students of mental disease4 ,the case is chiefly remarkable from the periodicity of the recurrence of the abnormal state4 ,i have collected other cases of the kind1 and may hereafter find a fitting occasion to quote them4#bbd ,the ansthesia and 8unconsciousness0 noted1 no more prove the actions performed by this soldier to have been purely mechanical1 i4 e4 undetermined by sensation1 than ansthesia and unconsciousness prove somnambulists and madmen to be machines4 ,in the pathological state called 8ecstasy0 there is a considerable diminution of sensibility to external stimuli2 with a concentration on certain feelings1 images1 trains of thought1 exhibiting itself in expressions of emotion4 8,les malades10 says a master1 8paraissent entirement absorbs par leurs mouvements intrieurs1 ils refusent gnralement de manger1 et spcialement la volont de l'me semble compltement enchaine40#bbe #hf4 ,observe that while this soldier exhibits such insensibility to certain stimuli1 he unequivocally exhibits sensibility to other stimuli4 ,all his acts show sense-guidance4 ,sight and ,touch obviously regulate his movements4 ,and when he feels objects placed in his way1 and then passes beside them1 wherein does this differ from the normal procedure of sensitive organisms8 wherein does it resemble automata8 ,dr4 ,mesmet--from whose narrative the case is cited--remarks that the sense of ,touch seems to persist 8and indeed to be more acute and delicate than in the normal state02 upon which ,professor ,huxley has this comment3--8,here a difficulty arises4 ,it is clear from the facts detailed that the nervous apparatus by which in the normal state sensations of touch are excited is that by which external influences determine the movements of the body in the abnormal state4 ,but does the state of consciousness1 which we term a tactile sensation1 accompany the operation of this nervous apparatus in the abnormal state8 or is consciousness utterly absent1 the man being reduced to a pure mechanism8 ,it is impossible to obtain direct evidence in favor of the one conclusion or the other2 all that can be said is that the case of the frog shows that the man may be devoid of any kind of consciousness40 #hg4 ,it is here we are made vividly aware of the absolute need there is to disengage the terms employed from their common ambiguities4 ,all the evidence of a tactile sensation which can possibly be furnished1 on the objective side1 is furnished by the actions of this soldier2 to doubt it would be to throw a doubt on the sensibility of any animal unable to tell us what it felt2 nay1 even a man if he were dumb1 or spoke a language we could not understand1 could give us no other proof4 ,we conclude that the soldier had tactile sensations1 because we see him guided by them as we ourselves are guided by tactile sensations2 we know that he is an organism1 not a machine1 and therefore reject the inference that he has become reduced to a 8pure mechanism0 because it is inferred that his consciousness is absent4 ,and on what is this inference grounded8 #a1 ,the belief that the brain is the sole organ of consciousness 7,sentience7--a belief flatly disproved by the facts1 which show ,sentience when the brain has been removed2 and #b1 the belief that the decapitated frog1 because it avoids obstacles and redirects its leaps to avoid them1 does so without ,sentience4 ,according to the definition we adopt1 we may either say that the decapitated frog1 and the soldier in his abnormal state1 act without consciousness1 or with it4 ,but what does not seem permissible is to deny that their actions exhibit the clearest evidence of sense-guidance1 and the kind of volition which this sense-guidance implies2 and this is quite enough to separate them from actions of automata4 ,when a man ducks his head to avoid a stone which he sees falling towards him1 he assuredly has a sensation1 i4 e4 there is a grouping of neural elements1 which subjectively is a sensation1 and this originates a grouping of other neural elements1 the outcome of which is a muscular movement1 which subjectively is a motor sensation3 this grouping would not have been originated unless the particular grouping had preceded it2 nor would the simple retinal stimulus have excited this sensation unless the nerve-centres had been attuned to such response by many previous experiences3 the ignorant child would not duck its head on seeing the stone approach4 ,in our familiar use of the word ,consciousness it would be correct to say that the man ducks his head 8unconsciously02 and yet expressing the fact in psychological language1 we also say3 ,he ducks his head because remembering the pain of former similar experiences1 he knows that if the stone strikes him he will again be hurt as before1 therefore he wills to avoid it2 expressing it in physiological language we may say3 ,the man acts thus because he is so organized that a particular neural process is the stimulus of a particular central discharge2 and he became thus organized through a long series of anterior adjustments responding to stimuli1 each adjustment being the activity of the vital organism4 #hh4 ,there can be no doubt that the soldier had perceptions1 and that these perceptions guided his movements2 whether these shall be called 8states of consciousness0 or not1 is a question of terms4 ,now since we know that certain actions are uniformly consequent on certain perceptions1 we are justified in inferring that whenever the actions are performed1 the perceptions preceded them3 this inference may be erroneous1 but in the absence of positive evidence to the contrary it is that which claims our first assent4 ,is it evidence to the contrary that the perception may have stimulated the action1 yet been unaccompanied by the special mode named consciousness8 ,not in the least4 ,we learn to read with conscious effort2 each letter has to be apprehended separately1 its form distinguished from all other forms1 its value as a sign definitely fixed1 yet how very rarely are we 8conscious0 of the letters when we read a book8 ,each letter is perceived2 and yet this process passes so rapidly and smoothly1 that unless there be some defect in a letter1 or the word be misspelled1 we are not 8conscious0 of the perceptions4 ,are we therefore reading automata8#bbf ,we are said to walk unconsciously at times2 and the continuance of the movement is said to be due to reflex action4 ,but it is demonstrable that the cutaneous sensibility of the soles of the feet is a primary condition4 ,if the skin be insensible1 the walking becomes a stumble4 ,in learning to walk1 or dance1 the child fixes his eyes on his feet1 as he fixes them on his fingers in learning to play the piano4 ,after a while these registered sensations connected with the muscular sense suffice to guide his feet or his fingers2 but not if feet or fingers lose their sensibility4 #hi4 ,with these explanations let us follow the further details of this soldier's abnormal actions3-- 8,the man is insensible to sensory impressions made through the ear1 the nose1 the tongue1 and1 to a great extent1 the eye2 nor is he susceptible to pain from causes operating during his abnormal state4 ,nevertheless it is possible so to act upon his tactile apparatus as to give rise to those molecular changes in his sensorium which are ordinarily the causes of associated trains of ideas4 ,i give a striking example of this process in ,dr4 ,mesmet's words3 #8,il se promenait dans le jardin1 on lui remet sa canne qu'il avait laiss tomber4 ,il la palpe1 promne plusieurs reprises la main sur la poigne coude de sa canne--devient attentif--semble prter l'oreille--et tout coup appelle1 8,henri6 les voil60 ,et alors portant la main derrire son dos comme pour prendre une cartouche1 il fait le mouvement de charger son arme1 se couche dans l'herbe plat ventre dans la position d'un tirailleur1 et suit avec l'arme paule tous les mouvements de l'ennemi qu'il croit voir courte distance4' ,in a subsequent abnormal period ,dr4 ,mesmet caused the patient to repeat this scene by placing him in the same conditions4 ,now in this case the question arises whether the series of actions constituting this singular pantomime was accompanied by the ordinary states of consciousness1 the appropriate trains of ideas1 or not8 ,did the man dream that he was skirmishing8 or was he in the condition of one of ,vaucanson's automata--a mechanism worked by molecular changes in the nervous system8 ,the analogy of the frog shows that the latter assumption is perfectly justifiable40 #ij4 ,before criticising this conclusion let me adduce other illustrations of this dreamlike activity4 8,a gentleman whom ,i attended in a state of perfect apoplexy10 says ,abercrombie1 8was frequently observed to adjust his nightcap with the utmost care when it got into an uncomfortable state3 first pulling it down over his eyes1 and then turning up the front of it in the most exact manner40 ,according to the current teaching1 these actions1 which seem like evidence of sensation1 are nothing of the kind1 because--the patient was 8unconscious02 that is to say1 because he did not exhibit one complex kind of ,sensibility1 it is denied that he exhibited another kind6 he did not feel discomfort1 nor feel the movements by which it was rectified--because he could not speak1 discuss impersonal questions1 nor attend to what was said to him6 ,abercrombie cites other cases3 8,a gentleman who was lying in a state of perfect insensibility from disease of the brain0 7note the phrase1 which really only expresses the fact that external stimuli did not create their normal reactions7 8was frequently observed even the day before his death to take down a repeating watch from a little bag at the head of his bed1 put it close to his ear and make it strike the hour1 and then replace it in the bag with the greatest precision4 ,another whom ,i saw in a state of profound apoplexy1 from which he recovered1 had a perfect recollection of what took place during the attack1 and mentioned many things which had been said in his hearing when he was supposed to be in a state of perfect unconsciousness40 ,dr4 ,wigan also tells of a lady whom he knew1 and who was actually put in a coffin1 under the belief that she was dead when in a trance4 ,her sense of hearing was then preternaturally acute4 ,in her second-floor bedroom she heard what the servants said in her kitchen4 ,when her brother came to see her and he declared she should not be buried until putrefaction set in1 she felt intense gratitude and a gush of tenderness1 but was unable to move even an eyelid as a manifestation of her feeling4 ,suddenly all her faculties returned4 ,dr4 ,wigan adds that he visited the ,countess ,escalante1 one of the ,spanish refugees1 who remained in a similar state for a short period1 during which she saw her husband and children1 and was quite conscious of all they did and said--but did not recognize them as her own4 ,she was absolutely without the power of moving a finger or of opening her mouth4 ,dr4 ,neil ,arnott told me of a similar case in his practice4 ,in these last cases we learn that consciousness--in its ordinary acceptation--was present1 though bystanders could see no trace of it4 ,and very often in cases where ,consciousness1 or at any rate ,sensibility1 is clearly manifested1 its presence is denied1 because the patient on recovering his normal condition is quite unable to remember anything that he felt and did4 ,under ansthetics patients manifest sensation1 but on awaking they declare that they felt nothing--of what value is their declaration8 ,m4 ,despine tells us of a patient who under chloroform struggled1 swore1 and cried out1 8,mon ,dieu6 que je souffre60 yet when the operation was over1 and he emerged from the effects of the chloroform1 he remembered nothing of what he had felt4#bbg #ia4 ,returning now to ,dr4 ,mesmet's soldier1 and to the conclusion that his dreamlike acts were no more than the actions of one of ,vaucanson's automata1 surely we are justified in concluding1 first1 that these actions were not of the same kind as those of an automaton1 since they were those of a living organism2 secondly1 that they present all the evidence positive and inferential which ,sensibility can present in the actions we observe in another1 and do not feel in ourselves2 and thirdly1 if with physiologists we agree that the mechanism of these actions is 8worked by molecular changes in the nervous system10 there is some difficulty in understanding how ,consciousness1 which is said to be caused by such changes1 could have been absent--how the cause could operate yet no effect be produced4 #ib4 ,what automata can be made to perform is surprising enough1 but they can never be made to display the fluctuations of sense-guided actions1 such as we see in the report of ,dr4 ,mesmet's soldier3-- 8,the ex-sergeant has a good voice1 and had at one time been employed as a singer at a caf4 ,in one of his abnormal states he was observed to begin humming a tune4 ,he then went to his room1 dressed himself carefully1 and took up some parts of a periodical novel which lay on the bed1 as if he were trying to find something4 ,dr4 ,mesmet1 suspecting that he was seeking his music1 made up one of these into a roll and put it into his hand4 ,he appeared satisfied1 took up his cane1 and went down stairs to the door4 ,here ,dr4 ,mesmet turned him round1 and he walked quite contentedly in the opposite direction4 ,the light of the sun shining through a window happened to fall upon him1 and seemed to suggest the footlights of the stage on which he was accustomed to make his appearance4 ,he stopped1 opened his roll of imaginary music1 put himself in the attitude of a singer1 and sang with perfect execution three songs one after the other4 ,after which he wiped his face with his handkerchief and drank without a grimace a tumbler of strong vinegar-and-water40 #ic4 ,epileptic patients have frequently been observed going through similar dreamlike actions in which only those external stimuli which have a relation to the dream seem to take effect4#bbh ,we interpret these as phenomena of disordered mental action1 the burden of proof lies on him who says they are phenomena of pure mechanism4 ,a mail-coach does not suddenly cease to be a mail-coach and become a wheelbarrow because the coachman is drunk1 or has fallen from the box4 ,the horses1 no longer guided by the reins1 may dash off the highroad into gardens or ditches2 but it is their muscular exertions which still move the coach4 ,can any one conceive an automaton acting as the sergeant is described to be in the following passage8-- 8,sitting at a table he took up a pen1 felt for paper and ink1 and began to write a letter to his general1 in which he recommended himself for a medal on account of his good conduct and courage4 ,it occurred to ,dr4 ,mesmet to ascertain experimentally how far vision was concerned in this act of writing4 ,he therefore interposed a screen between the man's eyes and his hands2 under these circumstances he went on writing for a short time1 but the words became illegible1 and he finally stopped4 ,on the withdrawal of the screen1 he began to write again where he had left off4 ,the substitution of water for ink in the inkstand had a similar result4 ,he stopped1 looked at his pen1 wiped it on his coat1 dipped it in the water1 and began again1 with the same effect4 ,on one occasion he began to write upon the topmost of ten superposed sheets of paper4 ,after he had written a line or two1 this sheet was suddenly drawn away4 ,there was a slight expression of surprise1 but he continued his letter on the second sheet exactly as if it had been the first4 ,this operation was repeated five times1 so that the fifth sheet contained nothing but the writer's signature at the bottom of the page4 ,nevertheless1 when the signature was finished1 his eyes turned to the top of the blank sheet1 and he went through the form of reading over what he had written1 a movement of the lips accompanying each word2 moreover1 with his pen he put in such corrections as were needed40 #id4 ,dr4 ,mesmet concludes that 8his patient sees some things and not others2 that the sense of sight is accessible to all things which are brought into relation with him by the sense of touch1 and1 on the contrary1 is insensible to things which lie outside this relation40 ,in other words1 the sensitive mechanism acts1 but acts abnormally4 ,this is precisely what is observed in somnambulists4 ,yet ,professor ,huxley1 who makes the comparison1 appears to regard both states as those in which the organism is reduced to a mere mechanism1 because on recovering their normal state the patients are unconscious of what has passed2 and because the frog1 without its brain1 also manifests analogous phenomena4 ,neither premise warrants the conclusion4 ,i have already touched on the unconsciousness of past actions2 let me add the case of ,faraday1 who was assuredly not an automaton when he prepared and delivered a course of lectures which were nevertheless so entirely obliterated from his memory that the next year he prepared and delivered the same course once more1 without a suspicion that it was not a new one4 ,as to the frog1 ,i must leave that case till ,i come to examine the evidence on which the hypothesis of the purely mechanical nature of spinal action rests4 #ie4 ,the point never to be left out of sight is that actions which are known to be preceded and accompanied by sensations do not lose their special character of ,sentience1 as actions of a sentient mechanism1 because they are not also preceded and accompanied by that peculiar state which is specially called ,consciousness1 i4 e4 attention to the passing changes 7comp4 p4 #djc74 ,when we see a man playing the piano1 and at the same time talking of something far removed from the music1 we say his fingers move unconsciously2 but we do not conclude that he is a musical machine--muscular sensations and musical sensations regulate every movement of his fingers2 and if he strikes a false note1 or if one of the notes jangles1 he is instantly conscious of the fact4 ,either we must admit that his brain is an essential part of the mechanism by which the piano was played1 and its function an essential agent in the playing2 or else we must admit that the brain and its function were not essential1 and therefore the playing would continue if the brain were removed4 ,in the latter case1 we should have a musical automaton4 ,that a particular group of sensations1 such as musical tones1 will set going a particular group of muscular movements1 without the intervention of any conscious effort1 is not more to be interpreted on purely mechanical principles1 than that a particular phrase will cause a story-teller to repeat a familiar anecdote1 or an old soldier 8to fight his battles o'er again40 #if4 ,let us now pass to another consideration1 namely1 whether ,consciousness--however interpreted--is legitimately conceived as a factor in the so-called conscious and voluntary actions2 or is merely a collateral result of certain organic activities8 ,to answer this1 we must first remember that ,consciousness is a purely subjective process2 although we may believe it to be objectively a neural process1 we are nevertheless passing out of the region of ,physiology when we speak of ,feeling determining ,action4 ,motion may determine ,motion2 but ,feeling can only determine ,feeling4 ,yet we do so speak1 and are justified4 ,for thereby we implicitly declare1 what ,psychology explicitly teaches1 namely1 that these two widely different aspects1 objective and subjective1 are but the two faces of one and the same reality4 ,it is thus indifferent whether we say a sensation is a neural process1 or a mental process3 a molecular change in the nervous system1 or a change in ,feeling4 ,it is either1 and it is both1 as ,i have elsewhere explained4#bbi ,there it was argued that the current hypothesis of a neural process causing the mental process--molecular movement being in some mysterious way transformed into sensation--is not only inconceivable1 but altogether unnecessary2 whereas the hypothesis that the two aspects of the one phenomenon are simply two different expressions1 now in terms of ,matter and ,motion1 and now in terms of ,consciousness1 is in harmony with all the inductive evidence4 #ig4 8,it may be assumed10 says ,professor ,huxley1 8that molecular changes in the brain are the causes of all the states of consciousness of brutes4 ,is there any evidence that these states of consciousness may conversely cause those molecular changes which give rise to muscular motion8 ,i see no such evidence4 ,the frog walks1 hops1 swims1 and goes through his gymnastic performances1 quite as well without consciousness1 and consequently without volition1 as with it2 and if a frog in his natural state possesses anything corresponding with what we call volition1 there is no reason to think that it is anything but a concomitant of the molecular changes in the brain1 which form part of the series involved in the production of motion4 ,the consciousness of brutes would appear to be related to the mechanism of their body simply as a collateral product of its working1 and to be as completely without any power of modifying that working as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery4 ,their volition1 if they have any1 is an emotion indicative of physical changes1 not a cause of such changes40 ,particular attention is called to the passages in italics4 ,in the first is expressed a view which seems not unlike the one ,i am advocating1 but which is contradicted by the second4 ,let us consider what is implied4 #ih4 ,when ,consciousness is regarded solely under its subjective aspect there is obviously no place for it among material agencies1 regarded as objective4 ,so long as we have the material mechanism in view we have nothing but material changes4 ,this applies to the frog1 with or without its brain2 to man1 supposed to be moved by volition1 or supposed to move automatically4 ,the introduction of ,consciousness is not the introduction of another agent in the series1 but of a new aspect2 the neural process drops out of sight1 the mental process replaces it4 ,the question whether we have any ground for inferring that in the series there is included the particular neural state which subjectively is a state of ,consciousness1 must be answered according to the evidence4 ,well1 the evidence shows that the actions do involve the co-operation2 and this ,professor ,huxley expresses when he says that the molecular changes in the brain form part of the series involved in the production of motion4 ,whether we regard the process objectively as a series of molecular changes1 or subjectively as a succession of sentient changes1 the sum of which is on the one side a motor impulse1 on the other a state of consciousness1 we must declare ,consciousness to be an agent1 in the same sense that we declare one change in the organism to be an agent in some other change4 ,the facts are the same1 whether we express them in physiological or in psychological terms4 ,the physiologist1 having only the material aspect of the organism in view1 says1 8,a cerebral process initiates a motor process02 the psychologist says1 8,a sensation determines an action40 ,unless the two processes have been linked together by an organic disposition1 native or acquired1 there will be no such motor process following the cerebral process4 ,a dog standing outside the gate is unable to ring the bell1 though having seen another dog ring it1 he may wish to do so2 but the cerebral process 7his wish7 is not linked on to the needful motor process--he has not learned to realize the wish2 whereas the other dog1 having by trial hit upon the right mode of directing his muscles1 has registered this experience1 and can ring the bell4 ,the organized disposition which enables the dog to do this may truly enough be called a modification of the mechanism2 but what we have here to note is that a sensation originally determined the movement1 and always determines it4 #ii4 ,it is the unfortunate ambiguity of the word ,consciousness1 and the questionable hypothesis of the brain being the sole seat of ,sensibility1 which darken this investigation4 ,because animals1 after the brain has been removed1 are seen to perform certain actions as deftly as before1 they are said to perform these without the intervention of ,consciousness2 when all that is proved by the facts is that these actions are performed without the intervention of the brain4 ,in support of this explanation1 examples are cited of unconscious actions performed by human beings4 ,but if we assign ,sensibility not to one part of the nervous system exclusively1 but to the whole1 we can readily understand how the loss of a part will be manifested by very marked changes in the reactions of the whole1 and yet not altogether prevent the reactions of the parts remaining intact4 ,an animal must respond somewhat differently with and without a brain4 ,one marked difference is the spontaneity of the actions when the brain is intact1 and the loss of much spontaneity when the brain is injured or removed4 ,cerebral processes prompt and regulate actions1 as the pressure of the driver on the reins prompts and regulates the movements of the horses2 but the carriage is moved by the horses and not by the driver2 and the action is executed by the motor mechanism1 whether the incitation arise in a cerebral process or a peripheral stimulation4 #ajj4 ,if we admit that ,consciousness is itself an organic process1 accompanying the molecular changes as a convex surface accompanies a concave1 we must also admit that its fluctuations are adjustments and readjustments of the organic mechanism1 and that the actions are the effects of these--their resultants4 ,the loss of the brain must obviously cause a great disturbance in these adjustments4 ,we may call that a loss of ,consciousness1 if we choose to limit the term to one mode of sentient reaction4 ,but this loss of a mode does not change those reactions which persist so as to convert them into purely mechanical reactions4 ,a troop of soldiers may have lost its directing officer1 but will fight with the old weapons and the old intelligence1 though not with the same convergence of individual efforts4 ,a frog or a pigeon no more acts as well without a brain as with a brain1 than the troop of soldiers fights as well without an officer4 #aja4 ,having thus claimed a place for ,consciousness in the series of organic processes1 let us now see whether it has a place among the active agencies4 ,according to ,professor ,huxley it is not itself an agent1 but only the 8collateral product of the working of the machine40 ,it accompanies actions1 it does not direct them4 ,it is an index1 not a cause4 ,surely it seems more accurate to say that it accompanies and directs the working8 ,it accompanies the working in two senses3 first1 as the subjective aspect of the objective process2 secondly1 as the change which produces a subsequent change1 that is to say1 the movements initiated by a feeling are themselves also felt as they pass2 and this feeling enters into the general stream of simultaneous excitations out of which new movements and feelings arise2 or to express it physiologically1 the sensory impressions determine muscular movements1 which in turn react on the nerve-centres1 and these reactions blend with the general excitation of reflected and re-reflected processes4#bcj ,since every change in ,consciousness is a change in the sentient organism1 which objectively is a change in the nervous centres1 the working of the mechanism being itself a dependent series of such changes1 each movement must have a reflected influence on the general state4 ,this reflected influence may be viewed as a collateral product of the working2 but there is no real analogy between it and the whistle of the steam-engine1 because this reflected influence demonstrably does intervene in the subsequent movements4 ,the feeling which accompanies or follows a particular movement cannot indeed modify that movement1 since that is already set going1 or has passed2 here there is some analogy to the steam-whistle2 but the analogy fails in the subsequent history3 no movements whatever of the steam-engine are modified by the whistle which accompanies the working of that engine2 yet how the reflected influence modifies the working of the organism6 ,if the hand be passing over a surface1 there is1 accompanying this movement1 a succession of muscular and tactile feelings which may be said to be collateral products4 ,but the feeling which accompanies one muscular contraction is itself the stimulus of the next contraction2 if anywhere during the passage the hand comes upon a spot on the surface which is wet or rough1 the change in feeling thus produced1 although a collateral product of the movement1 instantly changes the direction of the hand1 suspends or alters the course--that is to say1 the collateral product of one movement becomes a directing factor in the succeeding movement4 ,now this is precisely what no automaton can effect1 unless for changes that are prearranged4 ,a steam-engine drives its locomotive over the rails1 be they smooth or rough1 entire or broken2 it whistles as it goes1 but no whistling directs and redirects its path4 #ajb4 ,volition is said to be an 8emotion indicative of physical changes1 not a cause of such changes40 ,here it is necessary to understand in what sense the term cause is employed4 ,i should prefer stating the proposition thus3 a volition is a state of the sentient organism1 indicative of physical changes which have taken place1 and of changes which will take place4 ,because it is the expression of the first group of changes1 it cannot be their origin2 but it can be1 and is the origin of the second group1 which it initiates4 ,the indignation excited by an insult or a blow is not the origin of the emotion or the pain1 but it is the origin of the actions which are prompted by this sentient state4 ,in fact no sooner do we admit that the organism is a sentient mechanism1 than the conclusion is irresistible that ,sensibility is a factor in the working of that mechanism4 #ajc4 8,much ingenious argument10 says ,professor ,huxley1 8has at various times been bestowed upon the question3 ,how is it possible to imagine that volition which is a state of consciousness1 and as such has not the slightest community of nature with matter and motion1 can act upon the moving matter of which the body is composed1 as it is assumed to do in voluntary acts8 ,but if1 as is here suggested1 the voluntary acts of brutes--or in other words1 the acts which they desire to perform--are as purely mechanical as the rest of their actions1 and are simply accompanied by the state of consciousness called volition1 the inquiry1 so far as they are concerned1 becomes superfluous4 ,their volitions do not enter into the chain of causation of their actions at all4444 ,as consciousness is brought into existence only as the consequence of molecular motion in the brain1 it follows that it is an indirect product of material changes4 ,the soul stands related to the body as the bell of a clock to the works1 and consciousness answers to the sound which the bell gives out when it is struck40 ,this has been answered in the foregoing pages2 nor do ,i think the reader who has recognized the ambiguity of the term ,consciousness1 and the desirability of replacing it in this discussion by the less equivocal term ,sentience1 will need more to be said4 #ajd4 ,the important question whether reflex actions are insentient1 and therefore mechanical1 will occupy us in the next problem4 ,the question of ,automatism which has been argued in the preceding chapters1 may1 ,i think1 be summarily disposed of by a reference to the irresistible evidence each man carries in his own consciousness that his actions are frequently--even if not always--determined by feelings4 ,he is quite certain that he is not an automaton1 and that his feelings are not simply collateral products of his actions1 without the power of modifying and originating them4 ,now this fundamental fact cannot be displaced by any theoretical explanation of its factors4 ,nor would this fundamental truth be rendered doubtful1 even supposing we were to grant to the full all that is adduced as evidence that some actions were the result of purely mechanical processes without sentience at all4 ,i am a conscious organism1 even if it be true that ,i sometimes act unconsciously4 ,i am not a machine1 even if it be true that ,i sometimes act mechanically4 ,,problem ,,iv4 ,,the ,,reflex ,,theory4 8,si omnes patres sic1 et ,ego non sic40--,,abelard1 ,sic et ,non4 8,will man bestimmen wo der ,mechanismus aufhrt und wo der ,wille anfngt so ist die ,frage berhaupt falsch gestellt4 ,denn man setzt hier ,begriffe einander gegenber die gar keine ,gegenstze sind4 ,vorgebildet in den mechanischen ,bedingungen des ,nervensystems sind alle ,bewegungen40--,,wundt1 ,physiologische ,psychologie4 8,sollte die so durchsichtige ,homologie zwischen ,hirn and ,rckenmark1 wie solche sich schlagend in ,bau und ,entwicklung darthut1 wesentlich andere physiologische ,qualitten bedingen80--,,luschinger in ,pflger's ,archiv1 ,bd4 ,,xiv4 #chd4 ,,the ,,reflex ,,theory4 ,,chapter ,i4 ,,the ,,problem ,,stated4 #a4 ,the peculiarity of the ,reflex ,theory is its exclusion of ,sensibility from the actions classed as reflex2 in consequence of which1 the actions are considered to be 8purely mechanical40 ,no one denies that most of the reflex actions often have conscious sensations preceding and accompanying them1 but these are said not to be essential to the performance of the actions1 because they may be absent and the actions still take place4 ,it is notorious that we breathe1 wink1 swallow1 etc41 whether we are conscious of these actions or not4 ,our conclusion therefore is that these peculiar states of ,consciousness are accessory1 not essential to the performance of these actions4 ,the fact is patent1 the conclusion irresistible4 ,but now consider the equivoque3 because an action takes place without our being conscious of it1 the action is said to have had no sensation determining it4 ,this1 which is a truism when we limit ,consciousness to one of the special modes ,of ,sensibility1 or limit sensation to this limited ,consciousness1 is a falsism when we accept ,consciousness as the total of all combined sensibilities1 or ,sensation as the reaction of the sensory mechanism4 ,that a reflex action is determined by the sensory mechanism1 no one disputes2 whether the reaction of a sensory mechanism shall be called a sensation or not1 is a question of terms4 ,i have shown why it must be so called if anything like coherence is to be preserved in physiological investigations2 and ,i have more than once suggested that the fact of intellectual processes taking place at times with no more consciousness than reflex actions1 is itself sufficient to show that a process does not lapse from the mental to the mechanical sphere simply by passing unconsciously4 ,inasmuch as an organism is a complex of organs1 its total function must be a complex of particular functions1 each of which may analytically be treated apart4 ,vitality is the total of all its physiological functions1 and ,consciousness the total of all its psychological functions4 ,but inasmuch as it is only in its relation to the whole that each part has functional significance1 and cannot therefore be isolated in reality1 as it is in theory--cannot live by itself1 act by itself1 independently of the organism of which it is an organ1 there is strict accuracy in saying that no particular sensation can exist without involving ,consciousness2 for this is only saying that no sensory organ can react without at the same time involving a reaction of the general sensorium4 ,but since this general sensorium is simultaneously affected by various excitations each of which is a force1 every sensation1 perception1 emotion1 or volition is a resultant of the composition of these forces2 and as there can be only one resultant at a time1 to be replaced by another in swift succession1 this one represents the state of ,consciousness1 and this state may or may not be felt under the peculiar mode named 8,consciousness10 in its special meaning4 ,in other words1 the reaction of a sensory organ is always sentient1 but not always consentient4 #b4 ,let us illustrate this by the sensation of musical tone4 ,when we hear a tone we are affected not only by the fundamental tone1 representing the vibrations of the sounding body as a whole1 but also by the harmonics or overtones1 representing the vibrations of the several parts of that whole4 ,it is these latter vibrations which give the tone its timbre1 or peculiar quality2 and as the harmonics are variable with the variable structure of the vibrating parts1 two bodies which have the same fundamental tone may have markedly different qualities4 ,there are some tones which are almost entirely free from harmonics2 that is to say1 their harmonics are too faint for our ear to appreciate them1 though we know that the vibrations must be present4 ,apply this to the excitations of the sensorium4 ,each excitation will have its fundamental feeling1 and more or less accompanying thrills of other feelings3 it is these thrills which are the harmonics1 giving to each excitation its specific quality2 but they may be so faint that no specific quality is discriminated4 ,a fly settles on your hand while you are writing1 the faint thrill which accompanies this excitation of your sensory nerve gives the specific sensation of tickling1 and this causes you to move your hand with a jerk4 ,if your attention is preoccupied1 you are said to be unconscious of the sensation1 and the jerk of your hand is called a reflex action2 but if your attention is not preoccupied1 or if the thrill is vivid1 you are said to be conscious of the sensation1 and the action is no longer reflex1 but volitional4 ,obviously here the difference depends not on the sentient excitation by an impression on the nerve1 but on the state of the general sensorium and its consequent reaction4 ,had not the impression been carried to the sensorium1 no movement would have followed the fly's alighting on your hand1 because no sensation 7sensory reaction7 would have been excited2 the hypothesis of a purely mechanical reflex is quite inadmissible4 #c4 ,or take another case4 ,it sometimes happens that we fall asleep while some one is reading to us aloud4 ,the sounds of the reader's voice at first awaken the familiar thrills which give the tones their quality1 and the words their significance2 but gradually as sleep steals over us1 the organism ceases to react thus2 the words lose more and more of their significance1 the tones lose more and more of their harmonics2 at last we pass into the state of unconsciousness--we cease to hear what is read4 ,but do we cease to feel8 ,we have not heard1 but we have been affected by the sounds4 ,not by distinguishable sensations2 nevertheless a state of the general ,sensibility has been induced4 ,to prove that we have been affected is easy4 ,let the reader suddenly cease1 and if our sleep be not too profound1 we at once awake4 ,now1 unless the sound of his voice had affected us1 it is clear that the cessation of that could not have affected us4 ,or let us suppose our sleep to be unbroken by the cessation of the sound2 even this will not prove that we have been unaffected by the sounds1 it will merely prove that those sounds1 or their cessation1 did not excite a conscious state4 ,for let the reader1 in no louder tone1 ask1 8,are you asleep80 and we start up1 with round eyes1 declaring1 8,not at all40 ,nay1 should even this question fail to awaken us1 the speaker need only utter some phrase likely to excite a thrill--such as1 8,there's the postman60 or1 8,i smell fire60 and we start up4 ,i remember once trying the experiment on a wearied waiter1 who had fallen asleep in one of the unoccupied boxes of a tavern4 ,his arm rested on the table1 and his head rested on his arm3 he snored the snore of the weary1 in spite of the noisy laughter and talk of the guests4 ,i called out 8,johnson10 in a loud tone4 ,it never moved him4 ,i then called 8,wilson10 but he snored on4 ,no sooner did ,i call 8waiter10 than he raised his head with a sleepy 8yessir40 ,now1 to suppose1 in this case1 that he had no sensation when the words 8,johnson0 and 8,wilson0 reached his ears1 but had a sensation when the word 8waiter0 reached his ears1 is to suppose that two similar causes will not produce a similar effect4 ,the dissyllable 8,johnson0 would excite as potent a reaction of his sensory organ as the dissyllable 8waiter02 but the thrills--the reflex feelings--were different1 because the word 8,johnson0 was not associated in his mind with any definite actions1 whereas the word 8waiter0 was so associated as to become an automatic impulse4#bca #d4 ,two sisters are asleep in the same bed1 and a child cries in the next room4 ,the sounds of these cries will give a similar stimulus to the auditory nerve of each sister1 and excite a similar sensory reaction in each4 ,nevertheless1 the one sister sleeps on undisturbed1 and is said not to hear the cry4 ,the other springs out of bed1 and attends to the child1 because she being accustomed to attend on the child and soothe it when crying1 the primary sensation has excited secondary sensations1 thrills which lead to accustomed actions4 ,could we look into the mind of the sleeping sister1 we should doubtless find that the sensation excited by the child's cry had merged itself in the general stream1 and perhaps modified her dreams4 ,let her become a mother1 or take on the tender duties of a mother1 and her vigilance will equal that of her sister2 because the cry will then excite a definite reflex feeling1 and a definite course of action4 ,but this very sister1 who is so sensitive to the cry of a child1 will be undisturbed by a much louder noise2 a dog may bark1 or a heavy wagon thunder along the street1 without causing her to turn in bed4#bcb ,although during sleep the nervous centres have by no means their full activity1 they are always capable of responding to a stimulus1 and sensation will always be produced4 ,when the servant taps at your bedroom door in the morning1 you are said not to hear the tap1 if asleep2 you do not perceive it2 but the sound reaches and rouses you nevertheless1 since when the second tap comes1 although no louder1 you distinctly recognize it4 ,in etherized patients1 sensation is constantly observed returning before any consciousness of what is going on returns4 8,i was called10 says ,mr4 ,potter1 8to give chloroform to a lady for the extraction of ten teeth4 ,the first five were extracted without the slightest movement1 but as the operation proceeded1 sensation returned1 and ,i was obliged to use considerable force to keep her in the chair during the extraction of the last tooth4 ,she came to herself very shortly after1 and was delighted to find she had got over all her troubles without having felt it the least in the world40#bcc #e4 ,we do not see the stars at noonday1 yet they shine4 ,we do not see the sunbeams playing among the leaves on a cloudy day1 yet it is by these beams that the leaves and all other objects are visible4 ,there is a general illumination from the sun and stars1 but of this we are seldom aware1 because our attention falls upon the illumined objects1 brighter or darker than this general tone4 ,there is a sort of analogy to this in the general ,consciousness1 which is composed of the sum of sensations excited by the incessant simultaneous action of internal and external stimuli4 ,this forms1 as it were1 the daylight of our existence4 ,we do not habitually attend to it1 because attention falls on those particular sensations of pleasure or of pain1 of greater or of less intensity1 which usurp a prominence among the objects of the sensitive panorama4 ,but just as we need the daylight to see the brilliant and the sombre forms of things1 we need this living ,consciousness to feel the pleasures and the pains of life4 ,it is therefore as erroneous to imagine that we have no other sensations than those which we distinctly recognize--as to imagine that we see no other light than what is reflected from the shops and equipages1 the colors and splendors which arrest the eye4 ,the amount of light received from the stars may be small1 but it is present4 ,the greater glory of the sunlight may render this starlight inappreciable1 but it does not render it inoperative4 ,in like manner the amount of sensation received from some of the centres may be inappreciable in the presence of more massive influences from other centres2 but though inappreciable it cannot be inoperative--it must form an integer in the sum4 #f4 ,the reader's daily experience will assure him that over and above all the particular sensations capable of being separately recognized1 there is a general stream of ,sensation which constitutes his feeling of existence--the ,consciousness of himself as a sensitive being4 ,the ebullient energy which one day exalts life1 and the mournful depression which the next day renders life a burden almost intolerable1 are feelings not referable to any of the particular sensations1 but arise from the massive yet obscure sensibilities of the viscera1 which form so important a part of the general stream of ,sensation4 ,some of these may emerge into distinct recognition4 ,we may feel the heart beat1 the intestines move1 the glands secrete2 anything unusual in their action will force itself on our attention4 8,what we have been long used to10 says ,whytt1 8we become scarcely sensible of2 while things which are new1 though much more trifling1 and of weaker impression1 affect us remarkably4 ,thus he who is wont to spend his time in the country is surprisingly affected1 upon first coming into a populous city1 with the noise and bustle which prevail there3 of this1 however1 he becomes daily less sensible1 till at length he regards it no more than they who have been used to it all their lifetime4 ,the same seems to be the case also with what passes within our bodies4 ,few persons in health feel the beating of their heart1 though it strikes against their ribs with considerable force every second2 whereas the motion of a fly upon one's face or hands occasions a very sensible and uneasy titillation4 ,the pulsation of the great aorta itself is wholly unobserved by us2 yet the unusual beating of a small artery in any of the fingers becomes very remarkable40 #g4 ,a large amount of sensation is derived from the muscular sense1 yet we are not aware of the nice adjustments of the muscles1 regulated by this sensibility1 when we sit or walk4 ,no sooner are we placed in an exceptional position1 as in walking on a narrow ledge1 than we become distinctly aware of the effort required to preserve equilibrium4 ,it is not the novelty of the position which has increased our sensibility2 that has only caused us to attend to our sensations4 ,in like manner1 the various streams of sensation which make up our general sense of existence1 separately escape notice until one of them becomes obstructed1 or increases in impetuosity4 ,when we are seated at a window1 and look out at the trees and sky1 we are so occupied with the aspects and the voices of external ,nature1 that no attention whatever is given to the fact of our own existence2 yet all this while there has been a massive and diffusive feeling arising from the organic processes2 and of this we become distinctly aware if we close our eyes1 shut off all sounds1 and abstract the sensations of touch and temperature--it is then perceived as a vast and powerful stream of sensation1 belonging to none of the special ,senses1 but to the ,system as a whole4 ,it is on this general stream that depend those well-known but indescribable states named 8feeling well0 and 8feeling ill0--the bien tre and malaise of every day4 ,of two men looking from the same window1 on the same landscape1 one will be moved to unutterable sadness1 yearning for the peace of death2 the other will feel his soul suffused with serenity and content3 the one has a gloomy background1 into which the sensations excited by the landscape are merged2 the other has a happy background1 on which the sensations play like ripples on a sunny lake4 ,the tone of each man's feeling is determined by the state of his general consciousness4 ,except in matters of pure demonstration1 we are all determined towards certain conclusions as much by this general consciousness as by logic4 ,our philosophy1 when not borrowed1 is little more than the expression of our personality4 #h4 ,having thus explained the relation of particular sensations to the general state of ,consciousness considered as the function of the whole organism1 we may henceforward speak of particular sentient states1 as we speak of particular organs and functions1 all the while presupposing that the organs and functions necessarily involve the organism1 since apart from the organism they have no such significance4 ,the reaction of a sensory organ is therefore always a sentient phenomenon4 ,apart from the living organism there can be no such vital reaction1 but only a physical reaction4 ,it is commonly supposed that sensation is simply the molecular excitation of the cerebrum2 yet no one will maintain that if the cerebrum of a corpse be excited1 by a galvanic current sent through the optic nerve1 for instance1 this excitation will be a sensation4 ,whence we may conclude that it is not the physical reaction or stimulus which constitutes sensation1 but the physiological reaction of the living organism4 #i4 ,now this is the point which the advocates of the ,reflex ,theory1 implicitly or explicitly1 always deny4 ,let us trace the origin of the fallacy1 if possible4 ,when we remove the eye from a recently killed animal1 and let a beam of light fall on it1 the pupil contracts4 ,this is a purely mechanical action2 no one would suggest that a sensation determined it4 ,when we remove the leg1 and irritate its nerve1 the leg is jerked out4 ,this is also a purely mechanical action4 ,when we remove the brain from an animal1 and pinch its toes1 the leg is withdrawn or the pincers are pushed aside4 ,is this equally a purely mechanical action8 ,and if not1 why not8 ,the ,reflex ,theory would have us believe that all three cases were mechanical1 at least in so far as they were all destitute of sentient co-operation1 the ground for this conclusion being the hypothesis that the brain is the exclusive seat of sensation4 ,the ,reflex ,theory further concludes that since these1 and analogous actions1 are performed when the brain is removed1 they1 being thus independent of sentience1 may be performed when the brain is present without any co-operation of sentience4 ,the grounds for this conclusion being the facts that in the normal state of the organism there are many actions of which we are sometimes conscious1 and at other times unconscious2 and some actions--such as the dilatation and contraction of the pupil--of which we are never conscious4 ,this observation of parts detached from the organism seems confirmed by observation of actions passing in our own organisms1 both converging to the conclusion that the actions in question are purely mechanical1 involving no sentience whatever4 ,we are taught1 therefore1 that there is besides the sentient mechanism1 to which all conscious actions are referred1 a reflex mechanism1 to which all unconscious actions are referred4 ,the cerebro-spinal axis1 acting as a whole1 constitutes the first2 the spinal axis1 acting without the co-operation of the cerebrum1 constitutes the second4 #aj4 ,before proceeding with our exposition of the theory it may be well to state two considerations which must be constantly in view4 ,if it should appear that there is any reasonable evidence for refusing to limit ,sensibility to the cerebrum--and this evidence ,i shall adduce--the ,reflex ,theory must obviously be remodelled4 ,nor is this all4 ,we might see overwhelming evidence in favor of the hypothesis that the cerebrum is the exclusive seat of ,sensibility1 and still reject as a fallacy the conclusion that because certain actions can be performed in the absence of the cerebrum1 therefore those actions in the normal organism are likewise performed without cerebral co-operation4 ,i mean that it is a fallacy to conclude from the contractions of the pupil1 and the jerking of the leg1 when eye and leg are detached from the organism1 that therefore when eye and leg form integral parts of the organism1 such contractions and jerkings are mechanical reflexes without sentient conditions4 ,and the fallacy is analogous to that which would conclude from the observations of a mechanical automaton1 that similar appearances in a vital organism were equally automatic and mechanical4 ,so long as both sets of phenomena are apprehended simply as they appear to the sense of sight1 they may be indistinguishable2 but no sooner do we apprehend them through other modes1 and examine the modes of production of the phenomena1 than we come upon cardinal differences4 ,a limb detached from the organism is like a phrase detached from a sentence3 it has lost its vital significance1 its functional value1 in losing its connection with the other parts4 ,the whole sentence is necessary for the slightest meaning of its constituent words1 and each word is a language-element only when ideally or verbally connected with the other words required to form a sentence2 without subject1 predicate1 and copula1 no sentence can be formed4 ,so the organic connexus of parts with a living whole is necessary for the simplest function of each organ2 and a limb1 or any other part1 is a physiological element only when 7ideally or really7 an integral of a vital whole4 ,the organism may be truncated by the removal of certain parts1 as the sentence may be abbreviated by the removal of certain phrases2 but so long as subject1 predicate1 and copula remain1 there is a meaning in the sentence2 and so long as the organic connexus needful for vitality remains1 there will be vital function4 ,the eye detached from the organism is no longer a part of the living whole1 it no longer lives1 its phenomena cease to be vital1 its movements cease to have sentient conditions4 ,the movements of the pupil may seem to be the same as those of the living eye2 but when we come to examine their modes of production1 we learn that they are not the same4 ,the stimulus of light falling on the eye in the two cases necessarily has a different effect1 because the effect is the result of the co-operating causes1 and the co-operation in the one case is that of a lifeless organ1 in the other that of a living organism4 ,so long as the eye forms an integral part of the organism1 every stimulus acting on the eye necessarily acts on the organism1 and every reaction of the organ is necessarily conditioned by the state of the organism4 ,further1 every stimulation of a sensory nerve necessarily affects the general sensorium1 since the whole nervous system is structurally continuous and functionally co-operant4 7,see ,prob4 ,,ii4 #af47 ,therefore1 the stimulation of the eye1 although too faint to be discriminated as a conscious sensation1 must enter as a sentient tremor into the general stream of ,sentience2 and although we have no test delicate enough to reveal this operation1 we know the obverse operation of conscious sensation on the movements of the pupil--in surprise1 for example1 the pupil is dilated4 #aa4 ,there are still stronger reasons for asserting that the spinal reflexes are necessarily conditioned by the general state of the sensorium1 so that in the normal organism we cannot legitimately exclude them from ,sentience2 and the ,reflex ,theory is therefore unphysiological1 even on the hypothesis that the cerebrum is the exclusive seat of ,sensibility4 ,this hypothesis1 however1 seems to me untenable2 and all the observed facts which it is invented to explain admit of a far more consistent explanation4 ,it is irrational to suppose that a limb1 detached from the body1 felt the stimulus which caused its muscles to contract4 ,the limb is not a living organism1 having a sentient mechanism in its nervous mechanism4 ,not less irrational is it to suppose that when the limb forms an integral part of a living organism1 with a sentient mechanism of nerves and nerve-centres1 this organism does not react on the stimulus which excites the muscles of the limb to contract2 nor1 pursuing the same train of reasoning1 is it irrational to suppose that when this living organism has been mutilated1 and certain parts destroyed1 which do not in their destruction prevent the connexus of the rest1 but leave intact a sentient mechanism of nerves and nerve-centres1 then also this truncated organism still reacts as a whole1 still feels the stimulus which causes the muscles of the limb to contract4 ,hypothesis for hypothesis1 we may at least say that the one is as reasonable as the other4 ,and ,i shall be disappointed if1 when the reader has gone through all the evidence hereafter to be adduced1 he does not conclude that the hypothesis which assigns ,sensibility to the nervous mechanism as a whole is not the more acceptable of the two4 #ab4 ,let us now pursue our exposition of the ,reflex ,theory4 ,all that we have endeavoured to establish respecting the essential identity of the processes in conscious and unconscious states1 and voluntary and involuntary actions1--an identity which does not exclude differences of degree corresponding with these different terms1--is ignored or denied in the ,reflex ,theory4 ,whereas ,i suppose all processes to be reflex processes1 some of them having the voluntary1 others the involuntary character1 physiologists generally distinguish the involuntary as reflex1 and invent for this class a special mechanism4 ,according to ,marshall ,hall1 who originated the modern form of this theory1 actions are divisible into four distinct classes3 the voluntary1 dependent on the brain2 the involuntary1 dependent on the irritability of the muscular fibre2 the respiratory1 wherein 8the motive influence passes in a direct line from one point of the nervous system to certain muscles02 and the reflex1 dependent on the 8true spinal system0 of incident-excitor nerves1 and of reflex-motor nerves4 ,these last-named actions are produced when an impression on the sensitive surface is conveyed1 by an excitor-nerve1 to the spinal cord1 and is there reflected back on the muscles by a corresponding motor-nerve4 ,in this process no sensation whatever occurs4 ,the action is purely reflex1 purely excito-motor--like the action of an ordinary mechanism4#bcd ,mller1 who shares with ,marshall ,hall the glory of having established this classification1 thinks that although the absence of sensation is a characteristic of the reflex actions1 these actions may be1 and are at times1 accompanied by sensation4 8,the view ,i take of the matter is the following3 ,irritation of sensitive fibres of a spinal nerve excites primarily a centripetal action of the nervous principle conveying the impression to the spinal cord2 if the centripetal action can then be continued to the sensorium commune1 a true sensation is the result2 if1 on account of division of the cord1 it cannot be communicated to the sensorium1 it still exerts its whole influence upon the cord2 in both cases a reflex motor action may be the result40#bce #ac4 ,it is needless nowadays to point out that the existence of a distinct system of excito-motor nerves belongs to ,imaginary ,anatomy2 but it is not needless to point out that the ,imaginary ,physiology founded on it still survives4 ,the hypothetical process seems to me not less at variance with observation and induction1 than the hypothetical structure invented for its basis4 ,we have already seen that what ,anatomy positively teaches is totally unlike the reflex mechanism popularly imagined4 ,the sensory nerve is not seen to enter the spinal cord at one point1 and pass over to a corresponding point of exit2 it is seen to enter the gray substance1 which is continuous throughout the spinal cord2 it is there lost to view1 its course being untraceable4 ,nor does the physiological process present the aspect demanded by the theory3 it is not that of a direct and uniform reflexion1 such as would result from an impression on one spot transmitted across the spinal cord to a corresponding motor-nerve4 ,the impression is sometimes followed by one movement1 sometimes by another very different movement1 each determined by the state of neural tension in the whole central system4 ,even the facts on which the ,reflex ,theory is based are differently interpreted by different physiologists4 ,van ,deen1 for instance1 considers that ,reflexion takes place without ,volition1 but not without ,sensation2 and ,budge1 that it takes place without perception 7,vorstellung74 ,and when it is remembered that most of the reflex actions will be accompanied by distinct consciousness whenever attention is directed to them1 or the vividness of the stimulation is slightly increased1 it becomes evident that the absence of ,consciousness 7discrimination7 is not the differentia of ,reflex action4 #ad4 ,nor can the absence of spontaneity be accepted as a differentia4 ,all actions are excited by stimulation1 internal or external4 ,what are called the spontaneous actions are simply those which are prompted by internal1 or by not recognizable stimuli2 and could we see the process1 we should see a neural change initiated by some stimulation1 whether the change was conscious and volitional1 or unconscious and automatic4 ,the dog rising from sleep and restlessly moving about1 is acting spontaneously1 whether the stimulation which awakens him be a sensation of hunger1 a sensation of sound1 the sharp pain of a prick1 or a dash of cold water4 ,if he wags his tail at the sight of his master1 or wags it when dreaming1 the stimulation is said to be spontaneous2 but if after his spinal cord has been divided the tail wags when his abdomen is tickled1 the action is called reflex4 ,in all three cases there has been a process of excitation and reflexion4 #ae4 ,the advocates of the ,reflex ,theory insist that spontaneity is always absent in brainless animals2 whence the conclusion that the brain is the exclusive organ of sensation4 ,but the fact asserted is contradicted by the evidence4 ,no experimenter can have failed to observe numberless examples of spontaneity in brainless animals4 ,many examples have already been incidentally noticed in previous pages4 ,let me add one more from my notes3 ,i decapitated a toad and a triton1 and divided the spinal cord of another triton and a frog4 ,at first the movements of the decapitated animals were insignificant2 but on the second day the headless toad was quite as lively as the frog2 and the headless triton little less so than his companion with cord divided but brain intact4 ,i have1 at the time of writing this1 a frog whose cord was divided some weeks ago4 ,he remains almost motionless unless when touched2 he is generally found in the same spot1 and in the same attitude to-day as yesterday1 unless touched1 or unless the table be shaken4 ,he occasionally moves one of the forelegs2 occasionally one of the hind-legs2 but without changing his position4 ,if he were brainless1 this quiescence would be cited in proof of the absence of spontaneity in the absence of the brain2 but this conclusion would be fallacious1 and is seen to be so in the spontaneous movements of his companion who has no brain4 #af4 ,with spontaneity is associated the idea of volition1 and with volition choice4 ,now ,i admit that it is complicating the question to ask any one to conceive a headless animal choosing one action rather than another2 but it is equally difficult to reconcile ourselves to the idea of 8choice0 in contemplating the actions of a mollusc4 ,in what sense we can speak of the volition of a mollusc or an insect has already been considered 7p4 #djh74 ,when a man in a fit of coughing seizes a glass of water to allay the tickling in his throat1 we have no hesitation in declaring this to be volitional--and the remedy to be chosen4 ,but when a brainless animal adopts some unusual means1 after the failure of the usual means1 to allay an irritation1 we still hesitate to call the action volitional4 ,i see1 however1 no objection to calling it the adaptation of a sensitive mechanism which is markedly unlike any inorganic mechanism4 ,place a child of two or three years old upon his back1 and tickle his right cheek with a feather4 ,he will probably move his head away4 ,continue tickling1 and he will rub the spot with his right hand1 never using the left hand for the right cheek1 so long as the right hand is free2 but if you hold his right hand1 he will use the left4 ,does any one dispute the voluntary character of these actions8 ,now compare the actions of the sleeping child under similar circumstances1 and their sequence will be precisely similar4 ,this contrast is the more illustrative1 because physiologists generally assume that in sleep consciousness and volition are suspended4 ,they say3 8,the brain sleeps1 the spinal cord never2 volition and sensation may be suspended1 but not reflex action40 ,this proposition is extremely questionable2 yet it is indispensable to the reflex theory2 because unless sensation and volition are suspended during sleep1 we must admit that they can act1 without at the same time calling into activity that degree of sensibility which is supposed to constitute consciousness4 ,the child moves in his sleep1 defends himself in his sleep2 but he is not 8aware0 of it4 8,children10 says ,pflger1 8sleep more soundly than adults1 and seem to be more sensitive in sleep4 ,i tickled the right nostril of a three-year-old boy4 ,he at once raised his right hand to push me away1 and then rubbed the place4 ,when ,i tickled the left nostril he raised the left hand4 ,i then softly drew both arms down1 and laid them close to the body1 embedding the left arm in the clothes1 and placing on it a pillow1 by gentle pressure on which ,i could keep the arm down without awakening him4 ,having done this ,i tickled his left nostril4 ,he at once began to move the imprisoned arm1 but could not reach his face with it1 because ,i held it firmly though gently down4 ,he now drew his head aside1 and ,i continued tickling1 whereupon he raised the right hand1 and with it rubbed the left nostril--an action he never performed when the left hand was free40 #ag4 ,this simple but ingenious experiment establishes one important point1 namely1 that the so-called reflex actions observed in sleep are determined by sensation and volition4 ,the sleeping child behaves exactly as the waking child behaved2 the only difference being in the energy and rapidity of the actions4 ,if the waking child felt and willed1 surely the sleeping child1 when it performed precisely similar actions1 cannot be said to have felt nothing1 willed nothing8 ,it is not at one moment a sentient organism1 and at the next an insentient mechanism4 ,it is possible to meet this case by assuming that the child was nearly awake1 and that a dim consciousness was aroused by the tickling1 so that the cerebral activity was in fact awakened4 ,but1 plausible as this explanation may be 7and ,i am the more ready to admit it because ,i believe the brain always co-operates when it is present71 it altogether fails when we come to experiments on decapitated animals4 ,if any one will institute a series of such experiments1 taking care to compare the actions of the animal before and after decapitation1 he will perceive that there is no more difference between them than between those of the sleeping and the waking child4 #ah4 ,even more striking is the following experiment1 devised by ,pflger1 which ,i have verified1 and varied1 many times3 ,a frog is decapitated1 or its brain is removed4#bcf ,when it has recovered from the effect of the ether1 and manifests lively sensibility1 we place it on its back1 and touch1 with acetic acid1 the skin of its thigh just above the condylus internus femoris4 7,let the reader imagine his own shoulder burnt at the point where it can be reached with the thumb of the same arm1 and he will realize the operation47 ,no sooner does the acid begin to burn than the frog stretches out the other leg1 so that its body is somewhat drawn towards it4 ,the leg that has been burnt is now bent1 and the back of the foot is applied to the spot1 rubbing the acid away--just as your thumb might rub your shoulder4 ,this is very like the action of the tickled child1 who always uses the right hand to rub the right cheek1 unless it be held2 but when the child's right hand is prevented from rubbing1 the left will be employed2 and precisely this do we observe with the brainless frog3 prevent it from using its right leg1 and it will use its left6 ,this has been proved by decapitating another frog1 and cutting off the foot of the leg which is to be irritated4 ,no sooner is the acid applied1 than the leg is bent as before1 and the stump is moved to and fro1 as if to rub away the acid4 ,but the acid is not rubbed away1 and the animal becomes restless1 as if trying to hit upon some other plan for freeing himself of the irritation4 ,and it is worthy of remark that he often hits upon plans very similar to those which an intelligent human being adopts under similar circumstances4 ,thus1 the irritation continuing1 he will sometimes cease the vain efforts with his stump1 and stretching that leg straight out1 bends the other leg over towards the irritated spot1 and rubs the acid away4 ,but1 to show how far this action is from one of 8mere mechanism10 how far it is from being a direct reflex of an impression on a group of muscles1 the frog does not always hit even on this plan4 ,sometimes it bends its irritated leg more energetically1 and likewise bends the body towards it1 so as to permit the spot to be rubbed against the flank--just as the child1 when both his hands are held1 will bend his cheek towards his shoulder and rub it there4 #ai4 ,it is difficult to resist such evidence as is here manifested4 ,the brainless frog 8chooses0 a new plan when the old one fails1 just as the waking child chooses4 ,and an illustration of how sensations guide and determine movements1 may be seen in another observation of the brainless frog1 when1 as often happens1 it does not hit upon either of the plans just mentioned1 but remains apparently restless and helpless2 if under these circumstances we perform a part of the action for it1 it will complete what we have begun3 if we rub the irritated leg1 at some distance from the spot where the acid is1 with the foot of the other1 the frog suddenly avails itself of this guiding sensation1 and at once directs its foot to the irritated spot4 ,in these experiments on the triton and the frog1 the evidence of sensation and volition is all the stronger1 because the reactions produced by irritations are not uniform4 ,if when a decapitated animal were stimulated it always reacted in precisely the same way1 and never chose new means on the failure of the old1 it would be conceivable to attribute the results to simple reflex action--i4 e4 the mechanical transference of an impulse along a prescribed path4 ,it is possible so to conceive the breathing1 or the swallowing mechanism3 the impression may be directly reflected on certain groups of muscles4 ,but ,i cannot conceive a machine suddenly striking out new methods1 when the old methods fail4 ,i cannot conceive a machine thrown into disorder when its accustomed actions fail1 and in this disorder suddenly lighting upon an action likely to succeed1 and continuing that2 but ,i can conceive this to be done by an organism1 for my own experience and observation of animals assures me that this is always the way new lines of action are adopted4 ,and this which is observed of the unmutilated animal1 ,i have just shown to be observed of the brainless animal2 wherefore the conclusion is1 that if ever the frog is sentient1 if ever its actions are guided by sensation1 they are so when its brain is removed4 #bj4 ,schrder van der ,kolk thinks that ,pflger was deceived in attributing sensation and volition to the frog1 because the reflex actions are1 he says1 so nicely adapted to their ends1 that they are undistinguishable from voluntary actions4 ,the mechanism is such that1 by means of the communications established between various groups of cells1 all these actions adapted to an end may be excited by every stimulus4 ,but ,i deny the fact4 ,i deny that all the actions are awakened by every stimulus4 ,only some few are awakened1 and those are not always the same1 nor do they follow the same order of succession4 ,one decapitated frog does not behave exactly like another under similar circumstances2 does not behave exactly like himself at different seasons2 unlike a machine1 he manifests spontaneity in his actions1 and volition in the direction of his actions4 #ba4 ,the reader will notice that my illustrations show these actions of the brainless animal to have the same external characters as those of the unmutilated animals4 ,i am therefore not here concerned to prove the psychical nature of these actions1 unless it be granted that the unmutilated animal has sensation and volition4 ,this of course can only be inferred1 not proved4 ,but the inference must not be allowed in the one case and refused in the other4 ,young rabbits and puppies when taken from their mothers manifest discomfort by restless movement and whining4 ,do they feel the discomfort they thus express8 ,if ever rabbits and puppies may be said to feel1 we must answer1 ,yes4 ,well1 if the brain be removed from rabbits and puppies1 precisely similar phenomena are observed when these young animals are taken from their mothers4 8,i observed the motions1 which seemed the result of discomfort1 quickly cease when ,i warmed the young rabbit by breathing on it4 ,after a while it was completely at rest1 and seemed sunk in deep sleep2 occasionally1 however1 it moved one of its legs without any external stimulus having been applied1 and this not spasmodically1 but in the manner of a sleeping animal40#bcg ,is this cessation of the restlessness1 when warmth is restored1 not evidence of sensation8 ,we see an infant restless1 struggling1 and squalling2 and we believe that it is hungry1 or that some other sensations agitate it2 it is put to the breast1 and its squalls subside2 or a finger is placed in its mouth1 and it sucks that1 in a peaceful lull1 for a few moments1 to recommence squalling when the finger yields no satisfaction4 ,if we accept these as signs of sensation1 ,i do not see how we can deny such sensation to the brainless animal which will also cease to cry1 and will suck the delusive finger4 #bb4 ,one of the earliest advocates of the ,reflex ,theory sums up his observations in these words3 8,it is clear that brainless animals1 although without sensation1 because not endowed with mind1 nevertheless1 by means of external impressions which operate incessantly on them1 perform all the acts and manifest all the activity of the sentient animal2 everything that is effected sensationally and volitionally1 they effect by means of the organic forces of the impressions40#bch ,call ,sensibility one of the organic forces1 if you please1 but so long as the acts performed are not only the same as those of a sentient animal1 but are performed by the same mechanism1 they have every claim to the character of sensational acts which can be urged in the case of these animals when the brain is present4 ,and the only reason on which this claim is disputed is the assumed loss of all sensation with the loss of the brain4 ,here1 therefore1 lies the central point to be determined4 ,,chapter ,,ii4 ,,deductions ,,from ,,general ,,laws4 #bc4 ,the evidence is of two kinds3 deductions from the general laws of nervous action1 and inductions from particular manifestations4 ,the former furnish a presumption1 the latter a proof4 ,the central process which initiates a reflex action may be excited by the external stimulation of a peripheral nerve1 by the internal stimulation of a peripheral nerve1 or by the irradiation from some other part of the central tissue4 ,the last-named stimulations are the least intelligible1 because they are so varied and complex1 and so remote from observation2 among them may be placed1 #a1 the organized impulses of ,instinct and ,habit1 with their fixed modes of manifestation2 #b1 the organized impulses of ,emotion1 which are more variable in their manifestations1 because more fluctuating in their conditions2 #c1 the organized impulses of ,intellect1 the most variable of all4 ,whether we shrink on the contact of a cold substance or on hearing a sudden sound1--at the sight of a terrible object1--at the imaginary vision of the object1--or because we feign the terror which is thus expressed1--the reflex mechanism of shrinking is in each case the same1 and the neural process discharged on the muscles is the same2 but the state of ,feeling which originated the change--or1 in strictly physiological terms1 the inciting neural process which preceded this reflex neural process--was in each case somewhat different1 yet in each case was a mode of ,sensibility4 #bd4 ,the property of ,sensibility belongs to the whole central tissue2 and we have every reason to believe that unless it is excited no reflex takes place1 whereas when it is exaggerated--as in epilepsy1 or under strychnine--the reflex discharges are convulsive4 ,when ansthetics are given1 consciousness first disappears1 and then reflexion4 ,when the sensorium is powerfully excited by other stimuli1 the normal stimulus fails to excite either consciousness or reflexion4 ,hence our conclusion is that for consciousness1 on the one hand1 and normal reflexion1 on the other1 the proximate condition is a change in the sensorium2 or--to phrase it more familiarly--,feeling is necessary for reflex action4 ,the difficulty in apprehending this lies in the ambiguity of the term ,feeling4 ,many readers who would find no difficulty in admitting ,sensibility as a necessary element in reflex action1 will resist the idea of identifying ,sensibility with ,feeling4 ,but this repugnance must be overcome if we are to understand the various modes of ,sensibility which represent ,feeling in animals1 and its varieties in ourselves4 ,we understand how the general ,sensibility manifests itself in markedly different sensations--how that of the optic centre differs from that of the auditory centre1 and both from a spinal centre4 ,the tones of a violin are not the same as the tones of a violoncello1 both differ from the tones of a key-bugle3 yet they all come under the same general laws of tonality4 ,so1 as ,i often insist1 the tissues in brain and cord being the same1 their properties must be the same1 their laws of excitation1 irradiation1 and combination the same1 through all the varieties in their manifestations due to varieties of innervation4 ,hence it is that there are reflex cerebral processes no less than reflex spinal processes3 the motor impulse from1 the hemispheres on the corpora striata1 or from posterior gray substance on anterior gray substance1 is similar to that from the anterior gray substance on the motor nerves4 ,the difference in reflexes arises from the terminal organs2 as the difference in sensations arises from the surfaces stimulated4 ,but not only are there reflex processes in the brain1 of the same order as those in the cord1 there are volitional processes in the cord of the same order as those in the brain4 ,and in both the processes are sometimes conscious1 sometimes unconscious4 ,no evidence suggests that in the conscious action there is a sensorial process1 and a purely physical process in the unconscious action--only a different relation of one sensorial process to others4 #be4 ,let us contrast a cerebral and a spinal process1 in respect to the three stages of stimulation1 irradiation1 and discharge4 ,a luminous impression stimulates my retina1 this excites my sensorium1 in which second stage ,i am conscious of the luminous sensation2 the final discharge is a perception1 or a mental articulation of the name of the luminous object4 ,but the irradiation may perhaps not have been such as to cause a conscious sensation1 because the requisite neural elements were already grouped in some other way2 in this case there is an unconscious discharge on some motor group1 and instead of perceiving and naming the luminous object1 ,i move my head1 or my band1 or my whole body1 avoiding the object1 or grasping at it4 ,a third issue is possible3 the irradiation1 instead of exciting a definite perception1 or a definite movement1 may be merged in the stream of simultaneous excitations1 and thus form the component of a group1 and the discharge of this group will be a perception or a movement4 ,it is the same with a spinal process4 ,an impression on the skin is irradiated in the cord1 and the response is a movement1 of which we are conscious1 or unconscious4 ,here also a third issue is possible3 the irradiation may be merged in a stream of simultaneous excitations1 modifying them and modified by them1 thus forming a component in some ulterior discharge4 #bf4 ,the obstacle in the way of recognizing that cerebral processes and spinal processes are of the same order of sensorial phenomena1 and have the same physiological significance when considered irrespective of the group of organs they call into activity1 is similar to the obstacle which has prevented psychologists from recognizing the identity of the logical process in the combinations of ,feeling and the combinations of ,thought1 i4 e4 the ,logic of ,feeling and the ,logic of ,signs4 ,this obstacle is the fixing attention on the diversity of the effects when the same process operates with different elements4 ,because the spinal cord manifests the phenomena of sensation and volition1 we are not to conclude that it also manifests ideation and imagination2 any more than we are to conclude that a mollusc is capable of musical feelings because it is affected by sounds4 #bg4 ,the careless confusion of general properties with special applications of those properties1 and of functions with properties1 has been a serious hindrance to the right understanding of ,sensibility and its operations4 ,instead of recognizing that the nervous system has one general mode of reaction1 which remains the same under every variety of combination with other systems1 physiologists commonly lose sight of this general property1 and fix on one mode of its manifestation as the sole characteristic of ,sensibility4 ,sometimes the mode fixed on is ,pain1 at other times ,attention4 ,thus1 when an animal manifests no evidence of pain under stimulations which ordinarily excite severe pain1 this is often interpreted as a proof that all sensation is absent2 and if with this absence of pain there is--as there often is--clear evidence of the presence of some other mode of sensibility1 the contradiction is evaded by the assumption that what here looks like evidence of sensation is merely mechanical reflexion4 ,one would think that ,physiology and ,pathology had been silent on the facts of analgesia without ansthesia1 and of so much conscious sensation which is unaccompanied by pain4#bci ,who does not know that a patient will lose one kind of sensibility while retaining others--cease to feel pain1 yet feel temperature1 or be insensible to touch1 yet exquisitely alive to pain8#bdj ,inasmuch as ,sensibility depends on the condition of the centres1 an abnormal condition will obviously transform the reaction of the centres into one very unlike the normal reaction4 ,for example1 ,antoine ,cros had a patient who was quite unable to feel the sensation of cold on her left side--every cold object touching her skin on that side was felt as a very hot one2 whereas a hot object produced 8the sort of sensation which followed the application of an intermittent voltaic current40#bda ,thus also the experiments of ,rose#bdb and others have exhibited the effects of a dose of ,santonine in causing all objects to be seen as yellow in one stage1 and violet in another4 #bh4 ,if1 then1 certain alterations in the organic conditions are accompanied by a suppression or perversion of some modes of ,sensibility1 without suppressing the rest1 it is but rational to suppose that profound disturbances of the organic mechanism1 such as must result from the removal of the brain1 will also suppress or pervert several modes of ,sensibility1 and yet leave intact those modes which belong to the intact parts of the mechanism4 ,assuming that the spinal centres with the organs they innervate are capable of reacting under certain modes of sensation1 these will not necessarily be suppressed by removal of the brain--all that will thereby be suppressed is their co-operation with the brain4 ,i know it will be said that precisely this co-operation is necessary for sensation2 and that the spinal reactions are simple reflexions in which sensation has no part4 ,this1 however1 is the position ,i hope to turn4 ,meanwhile my assumption is that sensation necessarily plays a part in the reflex actions of the organism1 and when that organism is truncated1 its actions are proportionately limited1 its sensations less complex4 ,the spinal cord1 separated from encephalic connections1 cannot react in the special forms of ,sensation known as color1 scent1 taste1 sound1 etc41 because it does not innervate the organs of these special senses1 nor co-operate with their centres4 ,but it can1 and does1 react in other modes3 it innervates skin and muscles2 and the sensibilities1 thus excited1 it can also combine and co-ordinate4 ,it has its ,memory1 and its ,logic1 just as the brain has3 both no longer than they are integral parts of an active living organism3 neither when the organism is inactive or dead4 ,we do not expect the retina to respond in sounds1 nor the ear to respond in colors3 we expect each organ to have its special mode of reaction4 ,what is common to both is ,sensibility4 ,what is common to brain and cord is ,sensibility--and the laws of ,grouping4 ,instead of marvelling at the disappearance of so many modes of ,sensibility when the brain is removed1 our surprise should be to find so many evidences of ,sensibility remaining after so profound a mutilation of the mechanism4 #bi4 ,the current hypothesis1 which assumes that the brain is the sole organ of the mind1 the sole seat of sensation1 is a remnant of the ancient hypothesis respecting the ,soul and its seat2 and on the whole ,i think the ancient hypothesis is the more rational of the two4 ,if the ,soul inhabits the organism1 using it as an instrument1 playing on its organs as a musician plays on his instrument1 we are not called upon to explain the mode of operation of this mysterious agent2 but if the ,soul be the subjective side of the ,life1 the spiritual aspect of the material organism1 then since it is a synthesis of all the organic forces1 the consensus of all the sentient phenomena1 no one part can usurp the prerogatives of all1 but all are requisite for each4 ,and this indeed is what few physiologists would nowadays dispute4 ,in spite of their localizing sensation in the cerebral cells1 they would not maintain that the cerebral cells1 nor even the whole brain1 could produce sensation--if detached from the organism2 the cheek of the guillotined victim may have blushed when struck1 but who believes that the brain felt the insult1 or the blow8 ,obviously1 therefore1 when we read that thought is 8a property of the gray substance of the brain1 as gravitation is of matter10 or that the brain is the exclusive organ of ,sensation1 the writers cannot consistently carry out their hypothesis unless they silently reintroduce other organs as co-operating agents2 for a neural process in the cerebrum is in itself no more a sensation than it is a muscular contraction1 or a glandular secretion3 the muscles must co-operate for the contraction1 the gland for the secretion1 the neural process being simply the exciting cause4 ,in like manner the ,sensorium is necessary for the sensation1 the neural process--in cerebrum1 or elsewhere--being simply the exciting cause4 #cj4 ,and what is the ,sensorium8 ,a long chapter would be required to state the various opinions which have been held respecting its seat1 although amid all the disputes as to the organ1 there has been unanimity as to the function1 which is that of converting stimulations into sensations4 ,i cannot pause here to examine the contending arguments1 but must content myself with expounding the opinion ,i hold1 namely1 that the ,sensorium is the whole of the sensitive organism1 and not any one isolated portion of it4 ,when light falls on the optic organ1 or air pulses on the auditory organ1 the reaction of each organ determines the specific character of the sensation1 but no such sensation is possible unless there be a reaction of the organism2 and the nature of the product will of course vary with the varying factors which co-operate--a simple organism1 a truncated organism1 an exhausted or otherwise occupied organism1 will react differently from a complex1 a normal1 or an unoccupied organism4 ,detach the optic organ with its centre from the rest of the organism1 and no normal sensation of ,sight will result from its stimulation2 and in a lesser degree this is equally true of a stimulation of the optic organ when the sensorium is exhausted1 or powerfully affected by other stimuli4 ,because of the great importance of the cerebrum1 and its predominance in the nervous system1 it has been supposed to constitute the whole of the sensorium1 in spite of the evidence of varied ,sensibility after the cerebrum has been removed4 ,i do not wish to understate the cerebral importance 7see p4 #aff71 yet ,i must say that the modern phrase cerebration1 when employed as more than a shorthand expression of the complex processes which a cerebral process initiates1 and when taken as the objective equivalent of ,consciousness or of ,thought1 seems to me not more justifiable than to speak of ,combustion as the equivalent of ,railway ,transport4 ,the railway wagons will not move unless the fuel which supplies the boiler be ignited2 the organism will not think unless the cerebrum excites this peculiar mode of ,sensibility by its action on the organs4 ,it is the man1 and not the brain1 that thinks3 it is the organism as a whole1 and not one organ1 that feels and acts4 #ca4 ,consciousness1 or ,sensation1 is a complex product not to be recognized in any one of its factors4 ,cerebral processes and spinal processes are the elements we analytically separate1 as muscular contractions are the elements of limb-movements4 ,the synthetic unity of these elements is a reflex2 this we analytically decompose into a sensation and a movement2 and then we speak of sensation as the reaction of the sensory organ1 the movement as the reaction of the muscular organ4 ,by a similar procedure we separate the stimulation of a sensory nerve from the reaction of the sensory organ1 and that from the reaction of the sensorium2 and in this way we may come to regard ,cerebration as ,thought4 ,but those who employ this artifice should remember that the organism is not an assemblage of organs1 made up of parts put together like a machine4 ,the organs are differentiations of the organism1 each evolved from those which preceded it1 all sharing in a common activity1 all inter-dependent4 #cb4 ,that co-operation of the ,personality which is conspicuous in conscious actions is also inductively to be inferred in sub-conscious and unconscious actions4 ,we know that a man reacts on an impression according to his physical and mental state at the moment--that through his individuality he feels differently1 and thinks differently from other men1 and from himself at other epochs1 and in other states4 ,because he resembles other men in many and essential points we conclude that he will resemble them in all2 but observation proves this conclusion to be precipitate4 ,other men see a blue color in the sky1 or feel awe at sight of the setting sun2 but he has perhaps not learned to discriminate this sensation1 is not conscious of the blue2 nor has he learned to feel awe at the setting sun4 ,why--having normally constructed eyes--does he not see the blue of the sky8 ,for the same reason that a dog1 or an infant1 fails to see it4 ,the color has no interest for him 7and all cognition is primarily emotion71 nor has this want of personal interest been rectified from an impersonal source3 he has never been taught to distinguish the color of the sky2 and his eye wanders over it with the indifferent gaze with which a savage would regard a ,greek codex4 #cc4 ,the point here insisted on1 namely1 that every reaction on an impression is indirectly the reaction of the whole organism1 and that no organ detached from the organism has more significance than a word detached from a sentence1 is of far-reaching importance1 and peculiarly worthy of attention in considering the ,reflex ,theory1 because almost all the evidence urged in support of that theory presupposes the legitimacy of concluding what takes place in the organism from what is observed in an organ detached from its normal connections4 ,no experimental proof is necessary to show that many actions take place unconsciously2 the fact is undisputed4 ,but does unconsciously mean insentiently8 ,it is certain that the unconscious actions take place in a sentient organism1 and involve organic processes of the same order as the actions which are conscious4 ,it is also certain that many sentient processes take place unconsciously4 ,for thousands of years men used their eyes1 and saw as their descendants see1 yet were unconscious of the blue sky and green of the grass4 ,were their visual reactions not of the same order as our own8 ,so far as the optic apparatus is concerned1 there cannot be a doubt on the point2 yet in them the sensorium having a somewhat different disposition--the neural elements being differently combined--their reactions correspondingly differed4 ,they too had optical ,sensibility1 and visual sensations2 but they did not feel precisely what we feel4 #cd4 ,i have chosen these somewhat remote illustrations for the sake of their psychological interest2 but ,i might have confined myself to more familiar examples4 ,thus the contents of the consciousness of a man born blind cannot be the same as the contents of one who has had visual experiences1 which will enter into the complex of every conscious state1 because the visual organs will have affected his sensorium2 nevertheless in the organism of the blind man there are conditions so similar to those of other men1 and his experiences will have been so similar1 that in spite of the modifications due to the absence of visual experiences1 his consciousness will in the main resemble theirs4 ,but now let us in imagination pursue this kind of modification1 let us take away hearing1 taste1 and smell1 and we shall have proportionately simplified the contents of consciousness--the reactions of the sensorium--in thus simplifying the organism4 ,there still will remain ,touch1 ,temperature1 ,pain1 and the ,systemic ,sensations4 ,there will still remain an organism to react on impressions4 ,so long as there is a living organism1 however truncated1 there is a sentient mechanism4 ,when the brain has been removed1 the removal causes both a disturbance of function and a loss of function2 the mechanism has been seriously interfered with2 yet all those parts of the mechanism which still co-operate manifest their physiological aptitudes4 ,the animal can live without its brain1 ergo it can feel without its brain4 ,observation proves this1 for it discovers the brainless animal manifesting various sensibilities1 and combining various movements4 ,the vision of the brainless animal is greatly impaired1 but it nevertheless persists4 ,the intelligence is greatly impaired1 the spontaneity is reduced to a minimum2 but still both intelligence and spontaneity are manifested4 #ce4 ,the physiologist has only two conclusions open to him4 ,either he holds ,sensation to be a property of nerve-tissue--and in that case he must assign it to the spinal cord as to the brain2 or else he holds ,sensation to be a function of an organ--and in that case1 although analytically he may decompose the organism into separate organs1 assigning special sensations to the reactions of each1 he must still admit that in reality these organs only yield sensations as component parts of the organism4 ,the notion of a separate organ1 such as the brain1 being the exclusive seat of sensation is thus seen to be untenable4 ,in popular phrase1 8it is not the eye which sees1 but the mind behind the eye40 ,it is not the stimulus which is the object felt--it is the change in consciousness--the reaction of the sensorium4 ,no one would propound the absurdity that the retinal cells see1 or the auditory cells hear 7although by a conventional ellipsis these cells are said to be 8percipient0 of colors and sounds71 yet many writers have no hesitation in asserting that the cerebral cells are the seats of these and all other sensations4 ,in a hundred treatises may be read the most precise description of the transformation of molecular changes in the retinal cells into molecular changes in the cerebral cells1 where1 it is said1 8we know that the stimulations become sensations40 ,now who knows this8 ,how can it be known8 ,nay1 who1 on reflection1 fails to see that this cannot be so8 ,if a sensation of sight were not much more than a molecular change in the cerebrum stimulated by a molecular change in the optic tract1 three conclusions would follow1 each of which is demonstrably erroneous3-- ,i4 ,the cerebrum in a decapitated animal would respond by a sensation of sight to a retinal stimulation4 ,,ii4 ,the animal deprived of its cerebrum could not respond by a sensation of sight to a retinal stimulation4 ,,iii4 ,the same retinal stimulation would always produce the same cerebral process and the same sensation2 whereas the sensation depends on the condition of the sensorium at the time4 #cf4 ,the difference between the ,reflex ,theory and that here upheld is important in its general relations1 and yet turns on a point which may easily appear insignificant4 ,the ,reflex ,theory asserts that when a sensory nerve is stimulated1 the excitation of the centre may either subdivide into two waves1 one of which passes directly to the brain and there awakens sensation1 the other passes over to the motor-roots and causes muscular contractions2 or1 instead of thus subdividing1 the wave may pass at once to the motor-nerves1 and then there is movement without sensation4 ,this is obviously a restatement in anatomical terms of the observed fact that some reflexes take place consciously and some unconsciously4 ,but what evidence is there for this anatomical statement8 ,we have seen that there is none4 ,according to all we actually know1 and reasonably infer1 the continuity of tissue and the irradiation of excitation are such that the stimulus wave must always affect the whole system1 so that brain and cord being structurally united1 their reactions must co-operate with varying energy dependent on their statical conditions at the time4#bdc #cg4 ,the physiological fact that the irradiation is restricted to certain paths1 and therefore only certain portions of the whole system are excited to discharge--the fact that stimulation takes effect along the lines of least resistance--is that which gives the ,reflex ,theory its plausible aspect4 ,but this fact of restriction is not dependent on an anatomical disposition of structure1 it is1 as we have already seen 7,,problem ,,ii4 #aff71 dependent on a fluctuating physiological disposition--a temporary statical condition of the centres4 ,and it enables us to understand why the reflex action which is at one moment a distinctly conscious or even a volitional action1 is at another sub-conscious or unconscious4 ,when an object is placed in the hand of an infant the fingers close over it by a simple reflex4 ,this having also been observed in the case of an infant born without a brain1#bdd one might interpret it as normally taking place without brain co-operation1 were there not good grounds for concluding that normally the brain must co-operate4 ,thus if the object be placed in the hand of a boy1 or a man1 the fingers will close1 or not close--not according to an anatomical mechanism1 but according to a physiological condition3 if the attention preoccupy his sensorium elsewhere1 his fingers will probably close1 probably not2 if his sensorium be directed towards the object1 either by the urgency of the sensitive impression1 or by some one's pointing to the object1 the fingers will close or not close1 just as he chooses--perhaps the hand will be suddenly drawn away4 ,the centre of innervation for the fingers is in the cord1 and from this comes the final discharge of the sensitive stimulation2 but the neural processes which preceded this discharge1 and were consequent on the stimulation1 were in each case somewhat different4 ,in each case the impression on the skin was carried to the cord1 and thence irradiated throughout the continuous neural axis1 restricted to certain paths by the resistance it met with1 but blending with waves of simultaneous excitations from other sources1 the final discharge being the resultant of these component forces4 ,we may suppose the brain to be the seat of consciousness1 and yet not conclude that the brain was unaffected because the fingers closed unconsciously2 any more than we conclude that the retina of the unoccupied eye is unaffected by light when with the other we are looking through a microscope1 and only see objects with this eye--though directly we attend to the impressions on the other eye we see the objects which before were unseen4 ,we know that the muscles of the back are all involved in walking1 standing1 etc41 but we are seldom conscious of their co-operation till rheumatism or lumbago makes us painfully alive to it4 #ch4 ,the two main positions of the ,reflex ,theory are1 #a1 that reflex actions take place without brain co-operation1--as proved by observation of decapitated animals2 #b1 that they take place without brain co-operation1--as proved by our being unconscious of them4 ,to these the answers are3 #a4 ,the proof drawn from observation of decapitated animals is defective1 because the conditions of the organism are then abnormal--there is a disturbance of the mechanism1 and a loss of some of its components4 ,the fact that a reflex occurs in the absence of the brain is no proof that reflexes when the brain is present occur without its participation4 #b4 ,the absence of consciousness cannot be accepted as proof of the brain not being in action1 because much brain-work is known to pass unconsciously1 and there are cerebral reflexes which have the same characters as spinal reflexes4 #ci4 ,a prick on the great toe traverses the whole length of the spinal axis with effects manifested in various organs--the muscles of the limb1 the heart1 the chest1 the eyes1 etc4 ,the leg is withdrawn1 the heart momently arrested1 the eyes turned towards the source of irritation1 the thoughts directed towards relief4 ,these effects can be observed--there are others which lie beyond our observation1 and can only be revealed by delicate experimental tests4 ,but even the observable effects are very fluctuating1 because they depend on fluctuating conditions4 ,all we can say is1 that so long as there is continuity of structure1 there must be continuity of excitation2 and the brain structurally connected with the centre of a sensory impression1 must necessarily co-operate more or less in the reactions of that centre4 ,in other words1 the brain1 although not the exclusive seat of sensation1 plays a part in every particular sensation1 so long as it forms a part of the stimulated organism4 #dj4 ,this view being so widely opposed to the views current in physiological schools1 ,i was gratified to find ,dr4 ,crichton ,browne led by his researches to a conclusion not unlike it in essential features4 ,in his essay on the ,functions of the ,optic ,thalami#bde 7well worthy of attention on other grounds7 he says3 8,allowing the spinal cord a power of independent action1 it may still be that it generally acts reflexly through1 or in association with1 a superior centre4 ,the sensorial ganglia can undoubtedly act alone in a reflex manner1 but they almost invariably consult the cerebrum before dealing with the impressions which they receive2 so it may be that the spinal cord1 though capable of spontaneous reaction1 may yet commonly refer to some higher seat of compound co-ordination before sending forth an answer to any message brought to it40 ,what is here stated as a possible and occasional process1 ,i consider to be a necessary and universal process4 ,dr4 ,browne acutely remarks that if 8what may be termed the encephalic loop were an integral part of every reflex act1 then the influence of an intracranial lesion in checking reflex action would not be difficult to understand0--and we may add the notorious influence of the brain in arresting reflex actions1 and modifying them by the will1 which is only explicable on the supposition that the cerebral and spinal centres are functionally associated4 ,dr4 ,browne further remarks3 8,in experimenting upon myself ,i have sometimes thought that when the toe is pricked the sensation of pain actually precedes the movement of withdrawal2 and in experimenting upon patients with sluggish nervous systems ,i have certainly noticed that after the pricking of the toe the little cry of pain has anticipated the muscular contractions of the leg4 ,now this cry of pain is a secondary reflex act through the sensorial centre2 it is the result of a discharge from efferent nerves from the summit of what we have spoken of as the encephalic loop line2 and we should certainly not expect that it would be developed earlier than the primary reflexion upon the motor apparatus1 unless indeed what we have regarded as the primary reflexion really itself took place by way of the loop line40 #da4 ,the difference between a voluntary and involuntary act is not1 ,i conceive1 that in the one case the brain co-operates and in the other is inactive1 but that while in both the brain co-operates1 the state of the sensorium known as mental prevision or ideal stimulation1 is present in the one1 and absent or less conspicuous in the other4 ,so likewise the difference between a normal reflex action accompanied1 and the same action unaccompanied by consciousness1 is not that the brain co-operates in the one and is inactive in the other1 but that the state of the sensorium is somewhat different in the two cases4 ,movements which originally were voluntary and difficult of execution--accompanied therefore by brain co-operation--become by frequent repetition automatic1 easy of execution1 and unconscious--they are then said to depend on the direct action of the established mechanism4 ,granted4 ,but what are the components of this mechanism8 ,are they not just those centres and organs which at first effected the movements8 ,in becoming easy and automatic1 the movements do not change their mechanism--the moving organs and the motor conditions remain what they were2 all that is changed is the degree of consciousness1 i4 e4 the state of the sensorium which precedes and succeeds the movement4 ,it is this which constitutes the difficulty of the question4 ,some readers may consider that all is conceded when unconsciousness is admitted4 ,but this is not so4 ,my present argument is the physiological one that the brain co-operates in reflex actions whenever the brain is structurally united with the reflex centres2 the psychological question as to whether consciousness is also involved in this brain co-operation must be debated on other grounds2 and we have already seen that consciousness operates in gradations of infinite delicacy4 ,observe a man performing some automatic action1 such as planing a deal board1 or cutting out a pattern1 which he has done so often that he is now able to do it 8mechanically40 ,it is certain that his brain co-operates1 and that he could not act thus with an injured brain2 yet he is said to act unconsciously1 his brain occupied elsewhere as he whistles1 talks to bystanders1 or thinks of his wife and children4 ,yet the brain is acting as an overseer of his work1 attentive to every stroke of the plane1 every snip of the scissors2 and this becomes evident directly his attention is otherwise absorbed by an interesting question addressed to him1 or an interesting object meeting his eye3 then the work pauses1 his hands are arrested1 and the automatic action will only be resumed when his attention is released--when he has answered your question1 or satisfied himself about the object4 #db4 ,this is a step towards understanding the co-operation of the brain even in those connate reflexes which were not originally voluntary acts1 but were from the first organized tendencies1 and are capable of being realized in the absence of the brain4 ,i admit that it is difficult to find proof of brain co-operation here1 though ,i think the anatomical and physiological evidence render it highly probable4 ,but distinct proof to the contrary would not suffice for the ,reflex ,theory--would not prove that reflex actions were insentient--unless there had previously been proved that which seems to me contradicted by the clearest and most massive evidence1 namely1 that the brain is the sole seat of sentience4 ,this contradictory evidence we will now furnish4 ,,chapter ,,iii4 ,,inductions ,,from ,,particular ,,observations4 #dc4 ,in the last chapter we surveyed the deductive evidence1 from which the conclusion was that ,reflexion necessarily involves ,sensibility1 but not necessarily any one particular mode of ,sensibility1 such as ,consciousness1 ,pain1 ,discomfort1 ,attention1 or the reaction of any one of the special ,senses4 ,although each or all of these modes may be involved in the sensorial process which determines a reflex act1 each or all may be absent4 ,such is the fact of observation4 ,this fact is interpreted on the hypothesis that ,reflexion is the exclusive property of the spinal cord1 as ,sensation is of the brain4 ,when we come to examine the evidence for this hypothesis1 we find it to move in a circle3 the brain is said to be the exclusive seat of sensation1 because reflex actions can be effected after its removal2 and reflex actions are said to be insentient because they take place in the absence of the brain4 ,a gentleman was one day stoutly asserting that there were no gold-fields except in ,mexico and ,peru4 ,a nugget1 dug up in ,california1 was presented to him1 as evidence against his positive assertion4 ,he was not in the least disconcerted4 8,this metal1 sir1 is1 ,i own1 extremely like gold2 and you tell me that it passes as such in the market1 having been declared by the assayers to be undistinguishable from the precious metal4 ,all this ,i will not dispute4 ,nevertheless1 the metal is not gold1 but auruminium2 it cannot be gold1 because gold comes only from ,mexico and ,peru40 ,in vain was he informed that the geological formation was similar in ,california and ,peru1 and the metals similar2 he had fixed in his mind the conclusion that gold existed only in ,mexico and ,peru3 this was a law of nature2 he had no reasons to give why it should be so2 but such had been the admitted fact for many years1 and from it he would not swerve4 ,he was not fond of new-fangled notions1 which1 after all1 would only lead us back to the exploded errors of the past4 ,to accept the statement that gold was to be found elsewhere than in ,mexico and ,peru1 would be to return to the opinion of the ancients1 who thought there was gold in the upper regions of ,tartary6 ,sensation is not tangible1 assayable1 like gold4 ,we can understand1 therefore1 that the very men who would make merry with the auruminium1 would accept easily such a phrase as 8reflex action40 ,the decapitated animal defends itself against injury1 gets out of the way of annoyances1 cleans itself1 performs many of its ordinary actions1 but is said to do these things without that ,sensibility which1 if its head were on1 would guide them4 ,even before the ,reflex ,theory was invented this line of argument was used4 ,gall1 referring to the experiments of ,sue1 previously noticed1 says that 8,sue confounds the effects of ,irritability with those of ,sensibility40#bdf ,not gold1 dear sir1 but auruminium6 #dd4 ,on investigating the phenomena we soon come upon two classes which must cause hesitation4 ,we find that the brain has its reflex processes1 of the same order as those of the cord2 we find that these processes may be conscious or unconscious1 voluntary or involuntary2 so that we can no longer separate brain from cord on the ground of ,reflexion4 ,in this respect1 at least1 the two are mechanisms with similar powers4 ,turning now to the other class of phenomena1 we find that precisely as the brain is an organ of ,reflexion1 the cord is an organ of ,sensation4 ,all the evidence we can have1 from which to infer the presence of sensation1 is furnished by the sensorial processes in the cord4 ,remove the brain1 and the animal still manifests ,sensibility1 and this in degrees of energy and complexity proportional to the mechanisms still intact3 some of these manifestations have the character of volitional actions1 some of automatic actions1 some of ,memory1 ,judgment1 and selective ,adaptation4 ,these we observe not indeed with the energy and variety of such manifestations when the brain co-operates1 since the disturbance of the organism which is the consequence of the brain's removal--or the meagreness of the organism which is the correlative of the brain never having been developed--must of course involve a corresponding difference in the observed phenomena2 but the point here brought forward is that phenomena of the same order are manifested by organisms with or without a brain4 #de4 ,let us go seriatim through the evidence of these two classes3-- ,,cerebral ,,reflexes4 ,while ,theory separated the actions of the cord from those of the brain on the ground of their being at times unconscious and involuntary1 ,observation disclosed that this distinction could not be maintained4 ,this step was taken by ,dr4 ,laycock in #ahdj4 ,in a striking paper#bdg read by him at the ,british ,association in #ahdd1 he brought together the evidence on which his view was founded4 ,the idea has been adopted and illustrated in the writings of ,dr4 ,carpenter1 who now calls the action 8unconscious cerebration40 8,i was led to this opinion10 ,dr4 ,laycock says in announcing his view1 8by the general principle that the ganglia within the cranium1 being a continuation of the spinal cord1 must necessarily be regulated as to their reaction on external agencies by laws identical with those governing the spinal ganglia and their analogues in the lower animals4 ,if1 therefore1 the spinal cord is a centre of reflexion1 the brain must also be one40 ,it is a matter of regret that ,dr4 ,laycock did not extend this principle1 and declare that whatever was true of the properties of the cranial centres must also be true of the spinal centres2 if the brain have ,sensibility1 the spinal cord must also have it4 ,dr4 ,laycock refers to the curious phenomena of ,hydrophobia in proof that reflex actions may be excited by the optic nerves1 or by a mere idea of water4 ,when a mirror was presented to a patient1 the reflexion of the light acting on his retina1 in the manner of a reflexion from the surface of water1 produced a convulsive sobbing1 as in the attempt to swallow water1 and the patient turned aside his head with expressions of terror4 ,money was given him to induce him to look a second time1 but before he had looked a minute the same effect was produced4 ,the idea of water excited similar convulsions4 ,no sooner was it suggested that the patient should swallow a little water than he seemed frightened1 and began to cry out4 ,by kindly encouragements he was brought to express his willingness to drink1 but the sound of the water1 as it was poured out again1 brought on convulsions4 ,in another case1 8on our proposing to him to drink1 he started up1 and recovered his breath by a deep convulsive inspiration4 ,on being urged to try1 he took a cup of water in one hand and a spoon in the other4 ,with as expression of terror1 yet with great resolution1 he filled the spoon and proceeded to carry it to his lips2 but before it reached his mouth his courage forsook him1 and he was forced to desist4 ,he repeatedly renewed the attempt1 but with no more success4 ,his arm became rigid and immovable whenever he tried to raise it to his mouth1 and he struggled in vain against this spasmodic resistance40 ,in #ahdc ,griesinger--who appears to have known nothing of ,dr4 ,laycock's paper--published his remarkably suggestive memoir on ,psychical ,reflexes1#bdh in which he extends the principle of ,reflexion to all the cerebro-spinal centres4 ,the whole course of subsequent research has confirmed this view2 so that we may say with ,landry1 8,l'existence du pouvoir rflexe dans l'encphale ou dans quelques unes de ses parties tablit une nouvelle analogie entre le centre nerveux cranien et la moelle pinire40#bdi ,indeed we have only to consider the ,laughter which follows a ludicrous idea1 or the ,terror which follows a suggestion of danger1--the varying and involuntary expression of ,emotion1--and the curious phenomena of ,imitation and ,contagion1--to see how large a place cerebral reflexion occupies4 #df4 ,the existence of cerebral reflexion having been thus made manifest1 ,dr4 ,carpenter classed all reflex actions under three heads3 #a1 the excito-motor1 determined by the spinal cord2 #b1 the sensori-motor1 determined by the ganglia at the base of the brain2 #c1 ideo-motor1 determined by the brain4 ,from all these ,consciousness is absent4 ,from the first1 he supposes ,sensation to be absent4 ,as an artifice1 such a classification may have its value1 but it is physiologically and psychologically misleading4 ,it sustains the hypothesis of an imaginary excito-motor mechanism4 ,it restricts ,sensibility to one of its many modes4 ,it fails altogether to connect ,sensation with ,thought1 the ,logic of ,feeling with the ,logic of ,signs4 #dg4 ,the view of ,sensibility as common to the whole cerebro-spinal axis is by no means new4 ,robert ,whytt maintained it4 ,prochaska held that the spinal cord formed the greater part of the sensorium commune2 and he adduced1 in proof1 the familiar facts of sensibility manifested by headless animals4 ,the next writer whom ,i can discover to have held this opinion is ,j4 ,j4 ,sue1--the father of the celebrated ,french romance-writer1--who1 in #ahjc1 conceived that his experiments proved the spinal cord to be capable of replacing1 to a certain extent1 the functions of the brain4#bej ,next came ,legallois1#bea who undertook to show1 by a series of experiments1 that the principle of sensation and movement1 in the trunk and extremities1 has its seat in the spinal cord4 ,the mere division of the cord1 he said1 produces 8the astonishing result of an animal1 in which the head and the body enjoy separate vitality1 the head living as if the body did not exist1 and the body living as if the head did not exist4 ,guinea-pigs1 after decapitation1 seem very sensitive to the pain caused by the wound in the neck2 they alternately carry first one hind-leg and then the other1 to the spot1 as if to scratch it4 ,kittens also do the same40 ,a few years afterwards1 #ahag1 ,dr4 ,wilson ,philip concluded that 8the spinal marrow possesses sensorial power1 as appears from very simple experiments02 but he held the brain to be the chief source of sensorial power4#beb ,the following year1 ,lallemand supported this opinion by the very curious phenomena exhibited by infants born without brains3 these infants breathed1 swallowed1 sucked1 squalled1 and gave very unequivocal signs of sensibility4 ,the value of such observations consists in disproving the objection frequently urged against the evidence of decapitated animals1 namely1 that in these animals the spinal cord preserves the remains of a sensibility endowed by the brain4 ,longet here places an observation recorded by ,beyer4 ,a new-born infant1 whose brain1 during the birth1 had been completely extirpated 7to save the mother's life71 was wrapped in a towel1 and placed in the corner of the room1 as a lifeless mass4 ,while the surgeon was giving all his care to the mother1 he heard with horror a kind of murmur proceeding from the spot where the body had been placed4 ,in three minutes a distinct cry was heard4 ,the towel was removed1 and1 to the surprise of all1 this brainless infant was seen struggling with rapid movement of its arms and legs4 ,it cried1 and gave other signs of sensibility for several minutes4#bec ,in #ahbh ,calmeil arrived at the same conclusion as that reached by ,legallois1 ,wilson ,philip1 and ,lallemand4 ,indeed when1 in #ahcc1 the ,reflex ,theory appeared1 this opinion was so firmly rooted1 that we find ,mr4 ,grainger combating it as the established error of the day4 ,he takes as much pains to show that physiologists are wrong in attributing sensation to the spinal cord1 as ,i am here taking to show that they were right4#bed 8,it is1 indeed1 apparent10 he says1 8that the whole question concerning the truth or falsehood of the theory which attributes the reflex power to the spinal cord hinges upon the correctness or incorrectness of the received doctrines respecting the seat of sensation and volition2 so that until those doctrines are proved to be false1 it is impossible to establish the hypothesis of ,dr4 ,hall40#bee ,the reader is requested to take note of this1 because when we come to the evidence which proves the spinal cord to be a centre of sensation1 we shall find that the only ground for rejecting that evidence is the assumed truth of the ,reflex ,theory1 coupled with the assumption of the brain being the exclusive seat of sensation4 ,whereas if the evidence proves that the spinal cord is a sensational centre1 then the ,reflex ,theory is destroyed1 and cannot be urged against such evidence4 #dh4 ,thus many of the facts which prove the sensational function of the spinal cord were known1 and even a vague conception of their real significance was general1 until the ,reflex ,theory came to explain all such facts as the results of mechanical adjustment1 and of a new nervous principle called 8,reflexion40 ,for many years this theory has reigned1 and met with but little opposition4 ,yet the true doctrine has not wanted defenders in ,germany4 ,nasse#bef denied that decapitated animals showed no spontaneity2 he asserted that they exhibited clear signs of mental activity4 ,carus sarcastically pointed out that the word 8reflex0 was replacing 8irritability10 as a key to unlock all puzzles2 and he took up a position which is very similar to the one occupied in these pages1 namely1 that the spinal cord being formed of gray matter as well as of fibres1 it must have sensibility and power of reacting on nervous stimulus1 no less than conductibility2 that1 in fact1 it is a centre1 and must act like all other nerve-centres4#beg ,j4 ,w4 ,arnold opposed the ,reflex ,theory in a very remarkable little work1 in which he vindicates the claim of the spinal cord as a sensory and motor centre1 although denying to its actions any volitional character4#beh ,this was in #ahdd4 ,eleven years elapsed without any further opposition1 when ,edward ,pflger1 in #ahec1 published his work on the ,sensorial ,functions of the spinal cord4#bei ,in this work he recurred to the old views of ,prochaska and ,legallois2 but although he attacked ,marshall ,hall with merciless severity1 he did not point out the fundamental error of the ,reflex ,theory1 which theory he seems to accept4 ,nor did he give his views that philosophical and anatomical basis which could alone render his interpretations acceptable4 ,added to this1 the tone of asperity in which his work was written1 created some prejudice against him2 and thus1 while many admitted his facts1 they rejected his conclusions4#bfj ,in #aheh ,professor ,owen read a paper of mine at the ,leeds meeting of the ,british ,association1 on 8,the spinal cord as a centre of ,sensation and ,volition10 in which a rapid indication of my point of view1 and an account of some experiments to illustrate it1 were given--not1 ,i believe1 conclusive to any of the audience4 ,indeed1 the subject was too vast to be discussed in such a paper2 and my object was rather to excite new inquiry1 than to make converts to a view which could only be embraced after a thorough reinvestigation of the dominant theories4 ,in #ahei appeared ,schiff's work2#bfa and here we find a large space allotted to the discussion of ,pflger's doctrine4 ,schiff1 whose immense experience as an experimentalist1 and whose acuteness and caution every one will highly estimate1 frankly pronounces in favor of the sensational character of spinal actions2 but he denies that they are volitional1 and objects strongly to the introduction of any such idea as that of 8psychical activity40 ,he thinks it utterly untenable to suppose that impressions have reactions in the brain which they have not in the spinal cord3--if one has sensibility1 the other must have it2 and he thinks that1 so far from the actions of the cord being distinguishable from those of the brain by the character of 8reflexion10 and depending on a mechanical arrangement--all actions1 cerebral or spinal1 are reflex2 all depend on a mechanical arrangement4#bfb ,since that time there has been the remarkable work of ,goltz1 so often cited in these pages1#bfc and his subsequent experiments on dogs1 which 7although he does not decisively adopt the views of ,pflger7 furnish ample evidence that sensation and volition cannot be exclusively localised in the brain4 #di4 ,heubel's interesting experiments#bfd show that a frog may be thrown into a state of profound sleep by the withdrawal of all external stimulation1 and in this state will remain lying on its back for hours4 ,now this position is one so very uncomfortable that1 when awake1 the frog will not retain it a moment1 if free to turn round2 and when asleep1 a prick on the toe1 a sudden noise1 or a beam of light will awaken it1 causing it to turn4 ,that is to say1 the withdrawal of the normal stimuli so lowers the sensibility of the frog's nerve-centres1 that he does not feel the effects of the unusual position1 but feels them directly the centres are stimulated into activity4 ,all this is intelligible enough on the supposition of the state of sleep being dependent on a lowering of the cerebral activity4 ,but what shall we say on learning that precisely the same phenomena are manifested by a brainless frog8 ,every one knows that the brainless frog is intolerant of lying on its back1 and immediately turns round1 if placed on it4 ,yet the brainless frog may be thrown into deep sleep by the same exclusion of external stimuli2 from which he also will be awakened by a prick1 a noise1 or a beam of light2 and no sooner is he awakened than he at once turns round4 ,were the brainless frog incapable of sensation1 a prick on his toe would cause a simple reflex withdrawal of the leg2 but this is not the effect2 on the contrary1 the stimulus excites the whole spinal cord1 and whatever sensation of discomfort may be caused by the abnormal position of the limbs in an uninjured awakened frog1 is excited in the brainless frog4 #ej4 ,i need not swell this chapter with examples of ,sensibility in animals deprived of the brain2 many have already been given1 and any text-book of ,physiology will supply more4 ,no one disputes the observations1 only the inference that these manifestations were sentient3 they are said to have been merely mechanical reflexes4 ,if1 however1 we can detect in them some evidence of what all recognize as peculiarly characteristic of ,mind1 the mechanical interpretation will be less plausible4 ,at the outset the reader must be warned against exaggerating and distorting the bearing of my remarks1 and must not suppose that ,i disregard the vast differences between the ,logic of ,signs which belongs to ,thought1 and the ,logic of ,feeling which belongs to ,sensation1 nor suppose that ,i look upon the spinal cord as a mental organ having the same functions as the brain4 ,all that ,i wish to establish is the common character of spinal and cerebral processes1 modified as each is by the character of the actions initiated by the process4 #ea4 ,this premised1 let us begin with the evidence of ,,discrimination4 ,although this process is usually regarded as purely psychological1 it must obviously have its physiological side2 we find it in ,sensation as in ,ideation1 and may expect to find it in unconscious as in conscious processes--in a word1 in all sensorial processes whatever4 ,place a bit of marble on your tongue1 and it will be touched1 but not tasted3 the sensations of contact and temperature will excite reflexes1 but little or no reflexes from parotid and salivary glands4 ,a difference in sensation has a corresponding difference in reflex action2 which may be made evident by removing the tasteless marble1 and replacing it by a pinch of carbonate of lime1 i4 e4 the marble in another state reduced to a powder3 this will excite a sensation of taste1 and a secretion from the glands4 ,in both cases your sentient organism was affected1 but it reacted differently because the difference of the stimulation was discriminated3 consciously or unconsciously1 you felt differently4 ,again3 touch the back of your mouth with your finger1 or a feather1 and a convulsive contraction of the gullet responds1 followed by vomiting1 if the excitation be renewed4 ,yet these same nerves and muscles respond by the totally opposite action of swallowing1 if instead of the stimulation coming from your finger1 it come from the pressure of food or drink4 ,analogous experiments on animals without their brains yield similar results4#bfe ,the salivary secretion and the ordinary reactions of ,taste are provoked by sapid substances4 ,still more conclusive are the observations made on a dog whose spinal cord has been divided1 and who therefore according to the reigning ideas is incapable of feeling any impression made on parts below the section4 ,a pencil inserted in the rectum causes a reaction of the muscles energetically resisting the entrance of this foreign body2 yet this rectum so sensitive in its reaction on the stimulus of the pencil1 responds by the totally different reaction--the relaxation of the muscles--on the stimulus of fcal matters4 #eb4 8,this is all mechanical10 you say8 ,mechanical1 no doubt1 as all actions are2 but the question here is whether among the conditions of the mechanical action ,sensibility has a place8 ,the answer can only be grounded on induction4 ,the actions of the dog are analogous to the actions which you know were sentient in yourself4 ,there was in both a discrimination1 in both a corresponding reaction4 ,i admit that what is here called 8discrimination0 is the application of a logical term to a mechanical process2 ,i admit that if the spinal mechanism is insentient1 the fact of discrimination may still be manifested2 but ,i conceive that the many and coercive grounds for admitting that the mechanism is sentient gain further support in the evidence of discrimination4 ,every particular sensation has its corresponding reaction2 and although this has been acquired during ancestral or individual experiences1 so that in the majority of cases there is no consciousness accompanying the operation1 this1 as we have seen1 is not a valid argument against the existence of a sensorial process4 ,we have only to lower the ,sensibility of the cord by ansthetics1 or to preoccupy its energies by some other excitation1 and the reaction fails4 ,,memory4 #ec4 8,but discrimination1 if not a purely physical process1 implies ,memory80 ,no doubt4 ,and what is ,memory--on its physiological side--but an organized tendency to react on lines previously traversed8 ,as ,griesinger truly says3 8,there is ,memory in all the functions of the central organs1 including the spinal cord4 ,there is one for reflex actions1 no less than for sense-images1 words1 and ideas40 ,gratiolet makes a similar assertion4#bff ,indeed if1 as we have seen1 reflex actions are partly connate1 and partly acquired1 it is obvious that the second class must involve that very reproduction of experiences1 which in the sphere of ,intellect is called ,memory4 ,there is assuredly something paradoxical at first in this application of the terms of the ,logic of ,signs1 yet the psychologist will find it of great service4 ,but if the terms discrimination and memory be objected to1 they may be replaced by some such phrase as the 8adaptation of the mechanism to varying impulses40 ,on its objective side1 ,discrimination is ,neural ,grouping2 on its subjective side1 it is ,association of experiences4 ,,instinct4 #ed4 ,if we can detect evidences of ,volition and ,instinct in the absence of the brain1 our thesis may be considered less questionable4 ,and such evidence there is4 ,goltz decapitated a male frog 7in the pairing season71 and observed that it not only sought1 grasped1 and energetically embraced a female1 but could always discriminate a female from a male4 ,thus when a male frog closely resembling a female in size and shape was presented to this decapitated animal1 he clasped it1 but rapidly let it go again1 whereas even the dead body of a female was held as in a vice4 ,goltz tried to delude this brainless animal in various ways1 always in vain4 ,only a female would be held in his embrace4 ,goltz then presented a female in a reversed position1 so that the head was grasped by the male4 ,now here1 had there been simply a reflex machine1 incapable of sentient discrimination1 the clutched female would have been held in this position1 just like any other object which excited the reflex2 there would have been no 8sense of incongruity10 such as ,goltz noticed in his frog1 who at once began a series of movements by which he was enabled1 without letting the female escape1 to bring her into the proper position4 ,to render this observation still more significant1 ,i may add that ,goltz did not find all male frogs act thus--many relinquished the female thus improperly presented to them4 ,such phenomena observed in frogs possessing brains1 would be accepted as evidence of sexual instinct and volition4 ,further3 ,goltz removed the brain from a frog1 which he then held under water1 gently pressing the body so as to drive the air out of its lungs2 the body being then heavier than the water sank to the bottom1 where it remained motionless4 ,he repeated this procedure with another frog1 not brainless but blinded4 ,this one sank also1 but in a few minutes rose to the surface to breathe4 ,this difference naturally suggests that the brainless frog was insensible of the condition which in the other caused a movement of relief4 ,the one felt impending suffocation1 the other felt nothing4 ,such was the interpretation of a ,german friend in whose presence ,i repeated the experiment4 ,but ,i had been instructed by ,goltz1 and bade my friend wait awhile4 ,he did so1 and saw the brainless frog slowly rise to the surface and breathe there like his blinded companion4 ,so that the only difference observable was in the lessened sensibility of the brainless frog4 #ee4 ,but ,goltz records a still more conclusive case4 ,in a large vessel of water he inverted a glass jar also containing water1 which could then only be retained in the jar by atmospheric pressure4 ,through the neck of this inverted jar he thrust a blinded frog1 not having pressed the air out of its lungs4 ,it rose at once in the jar1 touching the inverted bottom with its nose1 and when the necessity of fresh air was felt1 the frog began restlessly feeling about the surface of its prison till an issue was found in the neck of the jar1 through which it dashed into the vessel1 and at once rose to the surface of the water to breathe4 ,in this observation are plainly manifested the stimulation of uneasy sensation1 the volition of seeking relief1 and the discrimination of it when found4 ,if this frog was a sentient mechanism1 what shall we say to the fact that a brainless frog was observed to go through precisely the same series of actions8 ,goltz pertinently remarks3 8,so long as physiologists satisfied themselves that the brain was the sole organ of sensation1 it was easy to declare all the actions of the brainless animal to be merely reflex4 ,but now we must ask whether the greater part of these actions are not due to the power of adaptation in the central organs1 and are therefore to be struck out of the class of simple reflexes8 ,if ,i bind one leg of a brainless frog and observe that he not only sees an obstacle1 but crawls aside from it1 ,i must regard these movements as regulated by his central power of adaptation2 but now suppose ,i unbind the leg and remove the obstacle1 then if ,i prick the frog he hops forward4 ,must ,i now declare this hop to have been a simple reflex8 ,not at all4 ,in both cases the physiological processes have been similar40 99 99 99 99 99 #ef4 ,there are no doubt readers who will dismiss all evidence drawn from experiments on frogs1 as irrelevant to mammals and man4 ,let us therefore see how the evidence stands with respect to animals higher in the scale1 endowed with less questionable mental faculties4 ,in a former chapter 7,,problem ,,ii4 #bi7 we recorded the marked results of removing the cerebral hemispheres2 and at the same time suggested that these by no means justified the conclusion usually drawn respecting the hemispheres as the exclusive seat of sensation4 ,and this on two grounds3 ,first1 because the absence of some sensitive phenomena does not prevent the presence of others3 the mutilated organism is still capable of manifesting ,sensibility in those organs which remain intact4 ,secondly1 because were the mutilation followed by total destruction of ,sensibility1 this would not prove ,sensibility in the normal organism to have its seat in the part injured4 ,if the removal of a pin will destroy the chronometric action of a watch1 we do not thence infer that the chronometric action was the function of this pin4 ,and this objection has the greater force when we remember that one hemisphere may be removed without the consequent loss of a single function1 and both may be removed without the loss of several functions usually ascribed to cerebral influence4#bfg #eg4 ,consider the analogous effects of injuries to or removal of the ,cerebellum1 in causing disturbance of locomotion1 whence the conclusion has been drawn that the ,cerebellum is the exclusive organ of muscular co-ordination1 in spite of the unquestionable evidence that very many muscular co-ordinations still persist after this organ is removed4 ,what is the part played by the ,cerebellum ,i do not pause here to examine4#bfh ,i only say that the movements of swimming1 sucking1 swallowing1 breathing1 crying1 micturition1 defecation1 etc41 are co-ordinated as well after removal of the ,cerebellum as they were before1 and that consequently their co-ordination has not its seat in the ,cerebellum4 ,the parallelism is obvious4 ,removal of the ,cerebrum causes a disturbance in the combination of sensations1 and the execution of certain sense-guided actions1 but causes little appreciable disturbance in others4 ,removal of the ,cerebellum causes a disturbance in the combination of certain muscular sensations1 and the execution of certain co-ordinated actions1 with little appreciable disturbance in others4 #eh4 ,so little have the facts been surveyed and estimated in their entirety that there is perhaps no subject on which physiologists are more agreed than on the function of the ,cerebellum being that of co-ordination4 ,yet consider this decisive experiment4 ,i etherized three healthy frogs1 from one ,i removed the entire cranial centres2 from another ,i removed only the cerebellum2 and1 leaving the third in possession of an intact encephalon1 ,i made two sections of the posterior columns of the spinal cord4 ,the two first hopped1 swam1 used their legs in defence1 and exhibited a variety of muscular co-ordinations1 although in both the supposed organ of co-ordination was absent4 ,whereas the third1 which had this organ intact1 and was capable of moving each limb separately1 and each pair of limbs separately1 was utterly incapable of moving all four simultaneously4 ,why was this8 ,obviously because in the first two frogs the motor mechanism remained intact1 and only the cerebral and cerebellar influence was removed2 in the third frog the sensory part of the motor mechanism had been divided1 and no combination of the limbs was possible4 #ei4 ,physiological induction agrees with anatomical induction in assigning to the cerebrum and cerebellum the office of incitation and regulation rather than of innervation2 for1 as we have seen1 no nerve issues directly from them 7,,problem ,,ii4 #g74 ,consequently the effects of injuries to these centres are losses of spontaneity and of complexity in the manifestations4 ,inasmuch as in the intact organism all sensory impressions are propagated throughout the nervous centres1 the reactions of these highest centres will enter into the complex of every adjusted movement2 so the abolition of these centres will be the dropping of a link in the chain1 the abolition of a special element in the complex group4 ,the organs which are still intact will react1 each in its own way1 on being stimulated2 but the reaction will be without the modifying influence of the absent centres4 ,for instance1 the retinal stimulation from a luminous impression normally calls up a cluster of associated feelings derived originally from other senses1 and a perception of the object is associated with emotions of desire1 terror1 etc41 according to the past history of the organism1 and its organized reactions1 due to hereditary or acquired experiences4 ,it is these which form the complex feeling discharged in the particular movement of prehension1 or flight4 ,remove the brain1 and there can be no longer this cluster of associated neural groups excited2 there will be therefore no emotion1 simply the visual sensation1 and such a movement as is directly associated with it4 ,the brainless dog moans when hurt1 it does not bark at the cat which it nevertheless sees1 and avoids as a mere obstacle in its path2 the cat will cry1 it will not mew4 ,the present pain moves the vocal organs1 but does not revive associated experiences4 ,all those combinations by which a series of dependent actions result from a single stimulation are frustrated when the mechanism is disturbed1 so that the mutilated animal can no longer recognize its prey or its enemy1 to feed on the one and fly from the other2 no longer builds its habitation1 or rears its offspring4 ,it can still live1 feed1 sleep1 move1 and defend itself against present discomfort2 it cannot find its food1 or protect itself against prospective discomfort4 ,we must supply the place of its ,intelligence4 ,we must give it the food1 and protect it from injuries4 ,there is therefore ample evidence to show that what is specially known as ,intelligence is very imperfect after the cerebral influence has been abolished2 but this does not prove the ,cerebrum to be the exclusive seat of ,intelligence1 it only proves it to be an indispensable factor in a complex of factors4 ,still less does it prove the ,cerebrum to be the exclusive seat of ,sensation1 ,instinct1 ,volition2 for these may be manifested after its removal1 although of course even these will be impaired by the loss of one factor4 #fj4 ,and here an objection must be anticipated4 ,in spite of the familiar experience that one mode of ,sensibility may be destroyed without involving the destruction of other modes1 there is a general belief--derived from a mistaken conception of what is really represented by the unity of ,consciousness--that ,consciousness disappears altogether when it disappears at all2 and hence1 since ,sensation is supposed to imply ,consciousness1 it also cannot be divisible1 but must vanish altogether if it vanish at all4 ,the first answer is that ,sensation as an abstraction is neither divisible nor indivisible2 but as a generalized expression of concrete sensorial processes it is reducible to these processes1 and divisible as they are4 ,no one doubts that we may lose a whole class of special sensations--sight1 hearing1 pain1 temperature1 etc4--yet retain all the others4 ,no one doubts that we may lose a whole class of registered experiences--forget a language1 or lose memory of places so familiar as the streets of the small town we inhabit1 or of faces so familiar as those of friends and relatives1 while the names of these streets and friends are still remembered when the sounds are heard4 ,yet sensation and intelligence are not wholly lost4 ,the mind is still erect amid these ruins4#bfi #fa4 ,this premised1 let us consider the experimental evidence4 ,flourens declares that when he removed the whole of the ,cerebrum from pigeons and fowls1 they lost all sensation1 all perception1 all instinct1 and all volition4 ,they lived perfectly well for months after the operation1 if the food were placed in their mouths2 but they never sought their food2 they never took it1 even when their beaks were plunged into it3 they could swallow1 and digest the grains2 but they had no instinct to make them seek1 no volition to make them pick up the grains4 ,they saw nothing1 although the iris remained irritable2 they heard nothing2 they could not smell4 ,a state of stupor came on1 resembling that of deep sleep4 ,all voluntary action ceased4 ,if they were thrown into the air1 they flew2 if irritated1 they moved away2 but if left to themselves1 they remained motionless1 with the head under the wing1 as in sleep4 ,now1 inasmuch as these effects always ensue when the ,cerebrum is removed1 and never when only the ,cerebellum is removed1 he concludes that all instincts1 volitions1 and sensations 8belong exclusively to the cerebral lobes40 ,but all experimenters do not agree in other points named by ,flourens2 nor in the conclusions he has drawn4 ,on the contrary1 it is very certain1 and we find evidence even in ,flourens himself1 that all instincts and all sensations are not destroyed by the removal of the cerebral lobes4 #fb4 ,let us hear ,bouillaud on this subject4#bgj ,he repeated the experiment of ,flourens1 removing the whole of the ,cerebrum from the ,brain of a fowl2 and he thus records his observations3 8,this fowl passes the greater part of her time asleep1 but she awakes at intervals1 and spontaneously4 ,when she goes to sleep1 she turns her head on one side and buries it in the feathers of the wing2 when she awakes1 she shakes herself1 flaps her wings1 and opens her eyes4 ,in this respect there is no difference observable between the mutilated and the perfect bird4 ,she does not seem to be moved at all by the noise made round about her1 but a very slight irritation of the skin suffices to awaken her instantaneously4 ,when the irritation ceases1 she relapses into sleep4 ,when awake1 she is often seen to cast stupid glances here and there1 to change her place1 and walk spontaneously4 ,if put into a cage1 she tries to escape2 but she comes and goes without any purpose1 or rational design4 ,when either foot1 wing1 or head is pinched1 she withdraws it2 when she is laid hold of1 she struggles to escape1 and screams2 but no sooner is she liberated than she rests motionless4 ,if severely irritated1 she screams loudly2 but it is not only to express pain that she uses her voice1 for it is by no means rare to hear her cackle and cluck a little spontaneously2 that is to say1 when no external irritation affects her4 ,her stupidity is profound2 she knows neither objects nor places1 nor persons1 and is completely divested of memory in this respect3 not only does she not know how to seek or take food1 she does not even know how to swallow it when placed in her beak--it must be pushed to the throat4 ,nevertheless her indocility1 her movements1 her agitation1 attest that she feels the presence of a strange body4 ,inasmuch as external objects excite in her no idea1 no desire1 she pays no attention to them2 but she is not absolutely deprived of the power of attention1 for if much irritated her attention is awakened4 ,she knows not how to escape an enemy1 nor how to defend herself4 ,all her actions1 in a word1 are blind1 without reflexion1 without knowledge40 ,in this recital1 the evidence both of sensation and instinct is incontestable1 to any unprejudiced mind4 ,bouillaud1 in commenting on his observations1 remarks1 that assuredly all sensation was not destroyed1 since the sensibilities of touch and pain were very manifest4 ,nor is it certain1 he says1 that the fowl heard nothing1 saw nothing4 ,it is true that she stumbled against objects1 and knew not how to avoid them4 ,she opened her eyes on awaking1 looked about1 and showed a sensibility in the pupil to light2 which1 he thinks1 is incompatible with the absence of all sensation of sight #fc4 ,the experiments of ,longet#bga seem decisive on this latter point4 ,having removed the whole of the ,cerebrum from a pigeon1 he observed that whenever he approached a light brusquely to its eyes1 there was contraction of the pupil1 and even winking2 but1 what was still more remarkable1 8when ,i gave a rotatory motion to the candle1 and at such a distance that there could be no sensation of heat1 the pigeon made a similar movement with its head4 ,these observations1 renewed several times in the presence of persons who were at my lectures1 left no doubt of the persistence of sensibility to light after removal of the cerebral lobes40 ,we have only to think of the baby following with its eyes the light moved before it1 to understand the kind of impression produced by the candle on the pigeon4 ,longet also declares that his experiments prove the existence of sensations of sound1 after removal of the whole cerebrum4 #fd4 ,dr4 ,dalton1 giving the results of numerous experiments he performed1 says that removal of the ,cerebrum plunges the animal in 8a profound stupor1 in which he is almost entirely inattentive to surrounding objects4444 ,occasionally the bird opens its eyes with a vacant stare1 stretches his neck1 perhaps shakes his bill once or twice1 or smoothes down the feathers upon his shoulders1 and then relapses into his former apathetic condition4 ,this state of immobility1 however1 is not accompanied by the loss of sight1 of hearing1 or of ordinary sensibility4 ,all these functions remain1 as well as that of voluntary motion4 ,if a pistol be discharged behind the back of the animal1 he at once opens his eyes1 moves his head half round1 and gives evident signs of having heard the report2 but he immediately becomes quiet again1 and pays no further attention to it4 ,sight is also retained1 since the bird will sometimes fix its eye on a particular object1 and watch it for several seconds together40#bgb ,while1 therefore1 ,flourens concludes from his experiments that the ,cerebrum is the seat of all sensation and all volition2 and ,bouillaud concludes that it is most probably the seat of none2 ,dr4 ,dalton concludes that the functions of the ,cerebrum are restricted to those usually classed as intellectual4 8,the animal10 he says1 8is still capable1 after removal of the hemispheres1 of receiving sensations from external objects4 ,but these sensations appear to make upon him no lasting impression4 ,he is incapable of connecting with his perceptions any distinct succession of ideas4 ,he hears1 for example1 the report of a pistol1 but he is not alarmed by it2 for the sound1 although distinctly perceived1 does not suggest any idea of danger or injury4 ,the memory is altogether destroyed1 and the recollection of sensations is not retained from one moment to another4 ,the limbs and muscles are still under the control of the will2 but the will itself is inactive1 because apparently it lacks its usual mental stimulus and direction40#bgc ,dr4 ,dalton reminds us how disturbance of the cerebral functions in human beings recalls these observations on animals4 8,in cases of impending apoplexy1 or of softening of the cerebral substance1 among the earliest and most common phenomena is a loss or impairment of the memory4 ,the patient forgets the names of particular objects1 or particular persons2 or he is unable to calculate numbers with his usual facility4 ,his mental derangement is often shown in the undue estimate which he forms of passing events4 ,he is no longer able to appreciate the true relation between different objects and different phenomena4 ,thus he will show an exaggerated degree of solicitude about a trivial occurrence1 and will pay no attention to other matters of importance4 ,as the difficulty increases1 he becomes careless of the directions and advice of his attendants1 and must be watched and managed like a child or an imbecile4 ,after a certain period he no longer appreciates the lapse of time1 and even loses the distinction between day and night4 ,finally1 when the injury to the hemispheres is complete1 the senses may still remain active and impressible1 while the patient is completely deprived of intelligence and judgment40#bgd #fe4 ,having seen how far other experimenters are from confirming the conclusions of ,flourens1 let us glance at his record of observations1 and we shall find there evidence that all sensation and all volition cannot be localized in the ,cerebrum4 ,speaking of a fowl whose ,cerebrum was removed the day before1 he says3 8,she shakes her head and feathers1 sometimes even she cleans and sharpens them with her beak2 sometimes she changes the leg on which she sleeps1 for1 like other birds1 she sleeps habitually resting upon one leg4 ,in all these cases she seems like a man asleep1 who1 without quite waking1 changes his place1 and reposes in another1 from the fatigue occasioned by the previous posture3 he selects one more comfortable1 stretches himself1 yawns1 shakes himself a little1 and falls asleep again4444 ,on the third day the fowl is no longer so calm2 she comes and goes1 but without motive and without an aim2 and if she encounters an obstacle on her path1 she knows not how to avoid it40#bge ,in his second work he remarks of a ,duck operated on in the same way3 8,as ,i mentioned last year propos of fowls1 the duck walks about oftener1 and for a longer time together1 when it is fasting1 than when it is fed40 ,here he observes the unmistakable evidence of feelings of ,hunger1 ,fatigue1 and ,discomfort in animals which1 according to him1 have lost all sensation4 ,he also observes the operation of instinct 7cleaning the feathers71 and of spontaneous activity 7walking about71 in animals said to have lost all instinct and all volition4 #ff4 ,still more decisive are the observations recorded by other experimenters4 ,leyden removed the hemispheres and the ganglia at their base from a hen2 yet this hen moved about and clucked4 ,meissner noticed that a pigeon whose hemispheres had been removed always uttered its coo1 and showed restlessness at the usual feeding-time4#bgf ,voit carefully extirpated the cerebrum from some pigeons1 and kept them for many months in health4 ,for the first few weeks they exhibited the well-known stupor4 ,then they began to shake this off1 open their eyes1 walk1 and fly about spontaneously4 ,they gave unmistakable signs of seeing and hearing4 ,but the chief defect was in the inability to feed themselves1 and the complete insensibility to danger4 ,they also manifested signs of sexual feeling with lively cooings2 though quite unable to gratify their desires4#bgg ,vulpian having removed the cerebrum1 optic thalami1 and corpora striata from a young rabbit1 found that on pinching its tail it cried out and struggled to escape2 and a rat thus mutilated not only struggled and cried when pinched1 but manifested strong emotion4 8,il est trs craintif1 trs impressionable2 il bondit pour peu qu'on le touche2 le moindre bruit le fait tressaillir4 ,un certain bruit d'appel fait avec les lvres1 ou un soufflet brusque imitant celui qu'emettent les chats en colre excitent chez le rat une vive motion40#bgh #fg4 ,there are several well-authenticated cases on record of children born without a vestige of brain1 and others with only a vestige1 who nevertheless manifested the ordinary signs of sensation4 ,i will cite but one1 and it shall be one for which an illustrious physiologist1 ,panizza1 is the guarantee4 ,a male infant1 one of twins1 who lived but eighteen hours1 during that period manifested such unquestionable signs of ,sensibility as the following3 the pupils contracted under light1 sharp sounds caused flutterings1 and a bitter solution when placed in the mouth was instantly rejected4 ,this infant had not a vestige of cerebrum1 cerebellum1 or cerebral ganglia4 ,the medulla oblongata was normal4 ,there were no olfactory nerves1 and the optic nerves terminated in a little mass of membrane4#bgi #fh4 ,the observations of ,lussana and ,lemoigne are both extensive and precise1 and the conclusion at which they arrive is that the removal of the ,cerebrum is the abolition of ,intelligence and ,instinct1 but is not the abolition of ,sensation4 ,whereas ,rolando1 and after him ,renzi1 consider that only the ,intelligence is abolished1 the supposed loss of ,instinct being really nothing more than the loss of the directive influence which makes the ,instinct to be executed4 #fi4 ,here it becomes needful to understand ,,the ,,mechanism ,,of ,,instinct4 ,were we dealing with an ordinary mechanism1 and the disturbances produced in its actions by the removal of any part1 we should attribute all observed effects to interference with the conditions of dependent sequence3 we should infer that the actions were imperfectly performed1 or wholly abolished1 because their requisite mechanical conditions were disturbed4 ,let us be equally precise in dealing with the physiological mechanism4 ,if we have deprived it of an organ in which certain combinations are effected1 we must expect to find all actions which were dependent on such combinations to be now impossible2 but all the actions which are not directly dependent on these combinations may still be possible4 ,the actions of feeding1 for example1 are determined by certain sensations1 when these are present in a particular sequence1 but not otherwise2 the sensation of sight does not suffice1 because the animal must not only see the food1 he must perceive it4 ,the action of defence and flight are also determined by certain sensations1 but only when these are connected in a certain sequence3 the brainless animal will defend itself1 or move out of the way1 under the stimulus of unpleasant sensation2 but will not be moved by a prospective injury1 because he fails to associate it with the sight of the threatening object4 ,in the same way a blind man shrinks at the actual contact of the heated poker1 but does not shrink at the approach of that poker which he does not see4 ,we do not deny him the possession of the so-called instinct of ,self-preservation on this ground2 why deny it to the brainless animal8 ,the brainless fish or frog swims when placed in the water1 because the sensation from the moving water#bhj sets going the swimming mechanism4 ,to call this a 8swimming instinct0 may seem extravagant2 yet it is as fully entitled to the name as ,self-defence is1 or the ,alimentary ,instinct4 ,in all three cases there is a connate mechanism set going by appropriate feelings4 #gj4 ,since all admit that there is an ,alimentary ,instinct1 let us see what kind of mechanism it implies4 ,there must be a state of feeling called ,hunger1 which--combined with other feelings--determines certain muscular adjustments in the search1 recognition1 capture1 and finally the swallowing of the food3--a very complex series of actions1 which lead to and sustain one another until the desire is gratified4 ,on the mental side there are three constituents1 all indispensable3 the hunger must be felt1 the food must be discriminated1 the desire must be gratified2 on the physical side there are also the indispensable arrangements of the motor mechanism4 ,now it is obvious that the entire mechanism of this instinct cannot be localized in the brain1 even if its mental elements are localized there2 and there is reason to believe that even the mental elements--the feelings of hunger1 discrimination1 and gratification--are not exclusively localized there4 ,the brainless animal manifests if not the feeling of ,hunger1 at any rate that feeling of discomfort which is the basis of ,hunger4 ,the restlessness is that of a hungry animal4 ,now we know that some of the ,systemic ,sensibility is preserved1 for we see the animal breathing1 swallowing1 urinating1 sleeping1 preening its feathers1 changing its attitude1 resting on one leg after the fatigue of the other1 etc4 ,we may therefore infer that other systemic sensations1 such as ,hunger and ,thirst1 arise under the usual conditions4 #ga4 ,we have noted an indication of ,hunger2 but on further observation we discover that although the food is eaten1 if brought within reach of that portion of the feeding mechanism which is still intact1 yet the second step--the feeling of recognition--is wanting4 ,the animal fails to perceive the food brought under his eyes1 or even placed in his mouth2 unless the back part of the mouth be touched1 no swallowing takes place4 ,hence the animal can no longer feed himself1 and is therefore said to have lost his instinct4 ,but although the mechanism of the instinct has been disturbed1 its action is not wholly abolished4 ,the brain is necessary for that combination of adjustments which normally accompany the perception of food through sight and scent2 and its absence of course frustrates such combination2 but we shall presently see that although certain sensible marks by which a perception is guided are absent1 others may still be present1 and suffice4 #gb4 ,before adducing examples let me say that we cannot legitimately attribute the abeyance of an instinct solely to the absence of the brain1 #a1 because we observe a similar abeyance of the instinct and frustration of perception1 even when the brain is present1 and the animal is in its normal state4 #b4 ,on the other hand1 some instincts are unmistakably manifested1 and some perceptions excited1 after the brain has been removed4 ,in fact1 all that is needful is that some of the mental elements of such perception and such instinct be preserved2 and this is the case so long as the leading element is present4 #gc4 ,on the first point consider this unequivocal example4 ,a healthy1 hungry frog may be placed in a vessel in which lie a quantity of dead flies4 ,he sees these flies1 but sight is not enough2 to him they are only so many black spots1 in which he does not recognize his food1 because the flies do not move1 and the leading element in his perception of food is not a colored form1 but a moving form4 ,hence this frog1 in spite of brain and an intact organism1 will starve amidst appropriate food4 ,whereas the frog that will not snap at motionless flies snaps at any other small moving object1 though it be not his food4 ,goltz observed one incessantly snapping at the moving tentacles of a slug which was in the vessel--as if that were possible food6 ,not only the stupid frog1 but the more intelligent carnivora will starve in the presence of appropriate food which is unrecognized1 because the leading element in the recognition is absent4 ,the cat will not eat a dead mouse1 unless she has killed it herself4 ,predatory animals must capture their food--unless the scent of blood excites their alimentary instinct4 ,so intimately is this sensation of a moving object connected with the predatory impulse1 that the cat which is unexcited by the dead mouse cannot resist springing on a moving ball4 ,we need not suppose the cat to mistake this ball for food2 but we must suppose that1 accustomed to pounce upon moving food1 it is unable to resist the impulse of this leading sensation4 #gd4 ,the presence of the brain not sufficing1 in the absence of the leading sensation1 we shall now see that the absence of the brain will not prevent the execution of the instinctive action1 if the leading sensation be present4 ,the brainless bird sees a heap of grain1 or a pan of water1 but no more recognizes them by sight alone than the frog recognizes the dead flies2 yet if the bird's feet be placed in the water1 this sensation will suffice to make him drink2 if placed amid the grain1 this sensation will 7sometimes7 suffice to make him feed4 ,lussana and ,lemoigne state that their brainless pigeons ate and drank with avidity when their feet were placed in grain and water4#bha ,m4 ,krishaber removed the hemispheres from a pigeon1 and observed that when his beak was thrust into a heap of hempseed the head was quickly withdrawn1 whereas when the beak was plunged into water the bird drank eagerly4 ,every day he was forced to feed the bird by pouring the seed into its throat1 but every day it drank when the beak was thrust into the pan of water4#bhb ,brcke noticed that his brainless hen1 which made no attempt to peck at the grain under her very eyes1 began pecking if the grain were thrown on the ground with force1 so as to produce a rattling sound4 ,the sensation of hearing was here more perfect than that of vision1 and sufficed to awaken the state of feeling necessary to initiate the pecking movement4#bhc #ge4 ,somewhat analogous phenomena are observed in ,aphasia4 ,the patient can see printed or written letters1 and even copy them2 but he cannot read1 i4 e4 interpret1 these symbols2 as the birds see the grain1 but cannot connect this sensation with others4 ,these letters and words1 which the patient cannot interpret when seen1 he can interpret when heard2 he can not only understand them when spoken1 but write them if they are dictated to him4 ,the birds recognize the grain and water 7or act as if they did7 when other sensations than those of sight are excited4 ,sound is the leading element in ,language1 both spoken and written4 ,we hear the words even when we see them1 but we do not see them when we hear them4 ,the visible symbols are accessory and subordinate4 ,but to the born deaf the visible symbols dominate4 ,how one sensation will determine a particular group of movements which cannot be effected by any other stimulus is abundantly illustrated in disease no less than in experiment4 ,here is a very luminous example3 ,gratiolet had a patient for six months under his eye incapable of articulating a single word1 owing to the incoherence of her incessant utterance--she babbled sounds1 but could not group the syllables into a recognizable word4 ,yet she could sing the words of any song she knew1 the musical sensations being sufficient to guide her vocal organs4 8,ainsi la mmoire1 infidle dans le cas o les mots taient des ides1 devenait claire et prcise quand les mots taient des chansons40#bhd #gf4 ,these illustrations plainly tell how the brainless animal may starve amid his food1 failing to perceive it because the leading sensation is not excited2 and how the same animal may manifest his feeding instinct if the mechanism be set going by a leading sensation4 ,we are told1 indeed1 that in the absence of the brain the actions are mechanical reflexes from impressions1 and not comparable with the complex processes determined by perception4 ,i think1 however1 that the only difference is in degree of complexity3 a combination of touch1 temperature1 and muscular movement will be simpler than one which also combines sight1 smell1 and the revived images of associated sensations4 ,the sight of a sheep affects the instinctive mechanism of a wolf only when combined with the leading element of smell4 ,place a stuffed sheep in a field1 and no wolf will approach and spring on it1 whereas the blind wolf will find and capture the real sheep2 and ,i believe that were it practicable to remove the brain without injury to the organ of scent and the powers of locomotion1 the wolf would track and capture the living sheep4 #gg4 ,the outcome of this discussion is that the mechanism of each instinct is the adjustment of the organs which effect the instinctive action2 and this adjustment is not simply a cerebral process1 but a complex of many sensorial processes2 consequently the instinct cannot be exclusively localized in the brain1 although the cerebral process may be a very important element in the adjustment4 ,this is true even on the supposition that in speaking of ,instinct we refer only to the state of feeling which originates the action--separating the psychological from the physiological aspect of the phenomenon4 ,for the brain minus the organism is obviously incapable of feelings2 whereas the organism minus the brain is obviously capable of sensibilities adequate to determine the actions4 ,thus the feeling of hunger which prompts the alimentary actions does not arise if the animal is satiated1 nor does the sexual feeling which prompts generative actions arise when the animal is castrated2 but each arises when the organism is in a particular state4 ,in vain will food be placed before the satiated animal1 or a female before the castrated male2 food and female are seen and recognized1 but no desires are excited1 in spite of the brain and its supposed instincts4 ,on the contrary1 when the brain is removed1 the need of the organism for food is felt1 and this need determines restless movements1 which are directed by certain other sensations1 and the instinctive action of feeding is finally effected2 although1 of course1 the removal of the brain has so disturbed the normal mechanism of the instinct that the action is imperfect4 ,renzi says that an animal deprived of its brain has lost the intelligence which enables it to seek and seize its food1 but not the instinct1 since it still has the desire for food4 ,the following experiment may illustrate this4 ,renzi wounded superficially one optic thalamus of a frog without injuring the external margin1 or optic tract4 ,the frog showed no appreciable loss of sight1 but hopped timidly away whenever approached4 ,then both thalami were divided transversely1 the optic tract still being spared4 ,this frog remained motionless under every threat4 ,it manifested no alarm1 and even when directly irritated1 only crawled or hopped away like a brainless frog4 ,sight still so far remained that obstacles were avoided4#bhe ,now since this animal's brain was intact1 and its organs of movement were capable of responding to stimulation1 how are we to explain the loss of its instinct of self-preservation8 ,the frog perceived no danger in a threatening approach1 yet perceived an obstacle and avoided it1 getting under it if there were room enough1 crawling beside it if that was the easier escape4 ,why did one vision prompt the movements of escape1 and another fail8 ,was it not that in the one case the normal pathway was still open1 in the other closed8 ,we know that one injury will destroy the perception of color without destroying that of light and shadow2 so one injury may destroy the combination of neural processes necessary for the perception of a danger1 without destroying those necessary for the perception of a hindrance4 ,if all actions depend on their mechanical conditions1 they must be disturbed according to the disturbance of the conditions4 ,nothnagel found that after removing the nucleus lentiformis on both sides of a rabbit1 leaving all the rest of the encephalon intact1 the rabbit hopped when its tail was pinched2 yet although starting at the sound when hands were loudly clapped1 did not hop as a normal rabbit does2 nor although closing his eyes when a light was brought near them1 did he ever move aside4 ,no feeling of danger was excited by sound or sight4 ,in striking contrast are the phenomena manifested by a rabbit whose corpora striata have been removed3 it is with difficulty made to hop by pinching its skin1 whereas noises and sights cause it to make terrified bounds4#bhf #gh4 ,no sooner do we analyze the conditions of an instinct than we see the error of regarding instincts as localized in the brain4 ,the cerebral process is only one factor in the product--an important factor1 no doubt1 since the cerebrum is the supreme centre of incitation and regulation2 but its absence does not wholly carry away the activity of the mechanism1 sentient and motor1 on which the instincts depend1 it only carries away one source of stimulation and regulation4 #gi4 ,an instinct depends on a connate mechanism4 ,let us glance for a moment at a parallel case of an ordinary reflex action1 also dependent on a connate mechanism1 say that of sneezing4 ,when the inner surface of the nose is stimulated by snuff1 or other irritant1 the nasal branch of the trigeminus is excited1 and the effects are first a deep inspiration1 then a closure of the respiratory orifices by the tongue1 which in turn excites a spasmodic expiration4 ,but the same effects are producible from quite different stimulations--namely1 that of the ciliary nerves on sudden exposure to a glare of sunshine--or of the skin nerves on a sudden draught of cold air4 ,brcke remarks that there is perhaps no spot on the surface of the body from which this reflex may not be excited in very sensitive people4 ,he knew a gentleman who always sneezed when in winter he laid hold of a cold door-bell2 and the fit of sneezing was only arrested by giving him a crust of bread or something hard to gnaw4 ,now just as the connate mechanism of sneezing may be set in action by a variety of stimulations1 so may the connate mechanism of an instinct4 ,,acquisition4 #hj4 ,not only may ,discrimination and ,instinct be manifested in the absence of the brain1 but even the acquisition of new modes of reaction1 such as are classed under ,learning through ,experience4 ,the objection is sometimes urged that animals without their brains only manifest single reactions on stimulation--the pinched foot is withdrawn1 and then remains motionless until again pinched4 ,but although the stimulation does not excite a consecutive series of movements1 because there is no cerebrum to react in successive stimulation1 this does not prove the absence of sensation in the one movement which is excited4 ,if my hand be lying on the table1 and something irritates it1 my hand is withdrawn1 and then remains as motionless as the limb of the brainless animal1 until some fresh stimulation1 external or internal1 moves it4 ,although removal of the brain causes a manifest reduction in the variety and succession of the movements1 all experimenters are agreed that animals acquire a certain dexterity in executing actions which they had previously failed to carry out after removal of their brains4 8,there is10 says ,freusberg1 8a decided improvement acquired in the reactions of the motor centres after division of the spinal cord1 not indeed in vigor1 but in delicacy4 ,removed from the regulating influence of the brain1 the legs acquired through practice a power of self-regulation40 ,nor is this wonderful3 pathways are made easy by repetition of impulses1 and new adaptations form new adjustments4 ,it is thus all learning is effected--intelligent1 and automatic4 ,nor is there any force in the objection that the power thus acquired speedily disappears1 so that if the stimulations are effected at long intervals the reactions do not manifest their acquired dexterity4 ,the spinal centres forget1 as the cerebral centres forget2 but they also remember1 i4 e4 they learn4 ,because an animal shows to-day none of the aptitude it acquired three days ago1 we are not to deny that it had once acquired the aptitude it has now lost4 ,attempt to teach a child to read by giving it spelling lessons of two or three minutes at intervals of two or three months1 and little will the acquisition be6 99 99 99 99 99 #ha4 ,hitherto we have been considering phenomena manifested in the absence of the cerebral hemispheres1 because it is in these that the majority of writers place the sensorium4 ,there are1 indeed1 many authoritative writers who regard the ganglionic masses at the base of the cerebrum1 and even those of the medulla oblongata1 as participating in this sensorial property1 which they refuse to the lower ganglia in the spinal cord4 ,i cannot follow their logic4 ,the cerebrum is by its position as a centre of centres1 and its detachment from all direct innervation of organs1 so different from the rest of the neural axis1 that we can understand how it should be assigned a special function2 although being of the same tissue as the other ganglionic masses1 it must have the same property4 ,and what that special function is ,i shall hereafter endeavor to set forth4 ,but that the upper region of the spinal axis should differ so profoundly from the lower region as to be the seat of psychical processes1 while the lower region is simply the seat of mechanical processes1 is what ,i cannot understand1 so long as the anatomical structure and physiological properties of the two regions are seen to be identical4 ,the various centres innervate various organs1 and have consequently various functions4 ,as each centre is removed1 we observe a corresponding loss of function--the organism is truncated1 but continues to manifest such functions as have still their mechanisms intact4 ,let us suppose the brain or upper regions of the cord detached from the lower regions by a section of the cord2 the animal will still live1 and perform almost all its functions in the normal way1 but there will be little or no consensus between the lower and the upper regions4 ,granting ,sensibility to both1 we must still see that the sensation excited in one will not be felt in the other4 ,and this is the ground on which physiologists deny that the lower regions have ,sensibility4 ,without pausing here to examine this point1 which will occupy us in the next chapter1 ,i assume that the positive evidence of ,sensibility suffices to discredit that argument2 and in furtherance of that assumption will cite an example of sensation and volition manifested by the lower portion of the cord when separated from the brain and upper portion4 #hb4 ,the function of ,urination is one which notoriously belongs to the voluntary class1 in so far as it is initiated or arrested by a voluntary impulse1 and it is one which1 according to the classic teaching1 has its centre in the brain4 ,the grounds on which this cerebral centre is assigned are very similar to those on which other functions are assigned to cerebral centres1 namely1 observation of the suppression of the function when the pathway between certain organs and the brain is interrupted4 ,but the careful experiments of ,goltz#bhg have demonstrated that the 8centre0 of ,urination is not in the brain1 but in the lower region of the cord4 ,when the cord is completely divided1 ,urination is performed in the normal way--not passively1 not irregularly1 but with all the characters of the active regular function4 ,and1 what is also noticeable1 this function is so intimately dependent on ,sensibility that it will be arrested--like any other function--by a sensation excited from the periphery--to be resumed when the irritation ceases4 ,now this arrest from a stimulation of sensory nerves takes place when the brain is cut off from the spinal centre1 just as when the brain is in connection with it4 ,the same is true of ,defecation1 and the still more complex functions of ,generation and ,parturition4 ,i can only refer the reader to the very remarkable case of ,goltz's bitch with the spinal cord divided in the lumbar region1 if evidence be wanted for the performance of complex functions so long as the spinal centres were intact4 ,it is true that ,goltz considers these functions to have been independent of sensation2 but that is because he has not entirely emancipated himself from the traditional views2 for my purpose it is enough that he admits the functions to be dependent on sensorial processes4 99 99 99 99 99 #hc4 ,to sum up the evidence1 we may say that observation discloses a surprising resemblance in the manifestations of the cord and brain4 ,in both there are reflex processes1 and processes of arrest2 in both there are actions referable to conscious and unconscious processes2 in both depression and exaltation are produced by the same drugs2 in both there are manifestations interpretable1 as those of ,discrimination1 ,logic1 ,instinct1 ,volition1 ,acquisition1 ,memory2 in both there is manifestation of ,sensibility--how then can we deny ,sensation to the one if we accord it to the other8 ,,chapter ,,iv4 ,,negative ,,inductions4 #hd4 ,i fancy some reader exclaiming3 8,all your reasoning1 and all your marshalled facts1 are swept away by the irresistible evidence of human patients with injured spinal cords1 whose legs have manifested reflex actions1 and who nevertheless declared they had no sensation whatever in them4 ,we can never be sure of what passes in an animal2 but man can tell us whether he feels an impression1 or does not feel it2 and since he tells us that he does not feel it1 cannot1 however he may try1 we conclude that reflex action may take place without sensation40 ,as this is the one solitary fact which is held to negative the mass of evidence1 anatomical and physiological1 in favor of the ,sensibility of the spinal cord1 it is necessary that we should candidly examine it4 ,no reader will suppose that during the twenty years in which ,i have advocated the doctrine expounded in this volume1 ,i have not been fully alive to the one fact which prevented the general acceptance of the doctrine4 ,from the first it has seemed to me that the fact has been misinterpreted4 #he4 ,certain injuries to the spinal cord destroy the connection of the parts below the injury with the parts above it2 consequently no impression made on the limbs below the injured spot is transmitted to the brain1 nor can any cerebral incitation reach those limbs4 ,the patient has lost all consciousness of these limbs1 and all control over them4 ,hunter's patient on being asked if he felt any pain when the prick caused his leg to kick1 answered1 8,no3 but you see my leg does40 ,this answer has been regarded as a drollery2 ,i think it expressed a physiological truth4 ,for on the assumption that the whole of the cerebro-spinal axis had one uniform property1 corresponding with its uniform structure1 and various functions1 corresponding with the variety of organs it innervates1 a division of this axis would necessarily create two independent seats of ,sensibility1 and interrupt the consensus of their functions4 ,in such a case it would be absurd to expect that the cerebral segment could be affected by1 or co-operate with1 what affected the spinal segment4 ,now1 when a man has a diseased spinal cord1 the seat of injury causes1 for the time at least1 a division of the whole group of centres into two independent groups4 ,for all purposes of sensation and volition it is the same as if he were cut in half2 his nervous mechanism is cut in half4 ,how then can any cerebral control be obeyed by his legs2 how can any impression on his legs be felt by his cerebrum8 ,as well might we expect the man whose arm has been amputated1 to feel the incisions of the scalpel1 when that limb is conveyed to the dissecting-table1 as to feel by his brain impressions made upon parts wholly divorced from organic connection with the brain4 #hf4 ,but1 it may be objected1 this is the very point urged4 ,the man himself does not feel the impressions on his legs when his spine has been injured2 he is as insensible to them as to the dissection of his amputated arm4 ,very true4 ,he does not feel it4 ,but if the amputated arm were to strike the anatomist who began its dissection1 if its fingers were to grasp the scalpel1 and push it away1 or with the thumb to rub off the acid irritating one of the fingers1 ,i do not see how we could refuse to admit that the arm felt although the man did not4 ,and this is the case with the extremities of a man whose spine is injured4 ,they manifest every indication of sensibility4 ,in the frog and pigeon the legs manifest the unmistakable control which we ascribe to volition4 ,it is true that the man himself1 when interrogated1 declares that he feels nothing2 the cerebral segment has attached to it organs of speech and expressive features1 by which its sensations can be communicated to others2 whereas the spinal segment has no such means of communicating its sensations2 but those which it has1 it employs4 ,you can ask the cerebral segment a question1 which can be heard1 understood1 and answered2 this is not the case with the spinal segment3 yet if you test its sensibility1 the result is unequivocal4 ,you cannot ask an animal whether it feels1 but you can test its sensibility1 and that test suffices4 #hg4 ,the question we have to decide1 therefore1 is not whether a patient1 with an injured spine1 can feel impressions on1 or convey voluntary impulses to1 limbs below the seat of injury--for as respects the nervous mechanism these limbs are separated from him1 no less than if actual amputation had taken place--the question is1 whether these separated limbs have any sensibility8 ,and the answer seems to me unequivocally affirmative4 ,i assert1 therefore1 that if there is ample evidence to show that the spinal centres have sensibility1 when separated from the cerebral centres1 such evidence can in no respect be weakened by the fact that a man with an injured spine is unconscious of impressions made below the seat of injury2 since such a fact necessarily follows from the establishment of two centres3 the parts above are then not sensitive to impressions on the parts below2 nor are the parts below sensitive to impressions on the parts above2 but each segment is sensitive to its own affections4 #hh4 ,every one knows that there are animals1 low down in the scale1 which may be cut in two1 each half continuing to live1 and each capable of reproducing its lost segments4 ,would any one1 seeing these separated halves move and manifest ordinary signs of sensibility1 venture to say that the one half was a living1 the other an insentient1 mechanism8 ,and since the one half had eyes1 mouth1 tentacles1 etc41 while the other half had none of these1 would the observer be surprised that the functions of the one differed from those of the other in these respects8 ,why1 then1 should he not conclude the same of the two halves of the human mechanism1 when disease had divided them8 #hi4 ,the man1 you urge1 does not feel the prick on his leg4 ,this is true1 because 8the man0 here designates the seeing1 hearing1 tasting1 smelling1 talking1 thinking group of organs--to the exclusion of the limb or limbs which are no longer in sensitive connection with this group4 ,when a leg is amputated 8the man0 remains--a truncated man1 indeed1 yet still one having all the distinguishing human characters4 ,yet obviously in strict language we can no longer say that the man is the same as he was4 8,man0 or 8animal0 means the complex whole2 and each anatomically separable part forms one constituent of that whole4 ,the medulla oblongata and spinal cord innervate certain parts2 the mesencephalon innervates others2 the cerebrum rises above the whole4 ,if after removing one limb1 then another1 we continued truncating the organism till we left only the head1 should we call that the man8 ,clearly not4 ,should we even suppose that the intact brain--the supposed seat of sensation and volition--still felt1 and willed8 ,clearly not4 ,there is absolutely no evidence1 however faint1 of the isolated head manifesting any sensational and volitional phenomena2 whereas there is ample evidence of the truncated spinal cord manifesting some of these phenomena4 ,and this is intelligible when we understand that the nerve-centres stimulate into action the organs they innervate1 but do not by themselves play any other part4 #ij4 8,the man0 then does not feel the prick on his leg1 but his leg feels it4 ,the man has no consciousness of what takes place outside the sphere of his sensitive mechanism2 and the leg is now outside that sphere4 ,consciousness--as distinguished from ,sentience in general--we have seen to be a resultant of the composition of forces co-operating at the moment2 the ,sensibility of the spinal cord in the regions below the injury cannot now enter into that composition4 ,it is detached from the upper organs4 ,but inasmuch as the organs it innervates are still living and active1 the functions of this detached portion are still displayed4 ,we have seen the dog with divided cord capable of ,urination1 ,defecation1 ,generation1 etc42 its hinder legs1 though not moving in a consensus with the forelegs1 yet moved independently2 and all the normal reflexes of the parts followed on stimulations4 ,to say that 8the dog0 showed no signs of ,sensibility when its hinder limbs were irritated1 is identifying 8the dog0 with the anterior half of the organism which was not in connection with the posterior half4 ,it is equally true that the posterior half showed no signs of ,sensibility when the anterior was irritated4 ,the two halves were united by the circulation1 nutrition1 etc41 but disunited as to sensation and volition4 #ia4 ,do ,i then suppose the separated half of an animal to feel pain and pleasure1 hope and terror8 ,the reader who has attentively followed the exposition will be at no loss to answer4 ,pain1 pleasure1 hope1 and terror1 are special modes of ,sensibility1 dependent on particular neural combinations4 ,the organs comprised in the anterior half of the animal furnish the main conditions for these special modes1 whereas the organs comprised in the posterior half furnish few or none of those--they contain none of the special ,senses1 and they are without the chief combining centre1 the brain4 ,but since we know that a large amount of normal ,sensation is wholly without the special characters of pain1 pleasure1 hope1 or terror1 we need not hesitate to assign ,sensation to the spinal cord because these characters are absent4 #ib4 ,all ,i contend for is that the spinal centres have ,sensibility of the same order as the cerebral centres2 and that in the normal organism this ,sensibility enters as a factor into the general ,consciousness--no one portion of the nervous system being really independent of all the others1 all co-operating in every result4 ,over and over again ,i have had to insist that the property of ,sensibility is only the general condition of ,sensation2 and that each particular sensation receives its character from the organs innervated1 plus the reaction of the whole organism4 ,obviously1 therefore1 the peculiar character of a sensation1 or 8state of consciousness10 must vary with the variations in either of these factors4 ,to say that every segment of the spinal cord has ,sensibility1 is not saying that an excitation of that segment will produce a particular sensation of definite character2 because for this definite character there is needed the co-operation of all those parts of the mechanism which enter into the complex product4 99 99 99 99 99 #ic4 ,and here attention must be called to a double fallacy pervading the arguments on the other side4 ,it is always assumed that the reactions of an organ1 or part of the organism1 when separated from the rest1 are typical of their reactions when forming constituents of the normal organism4 ,nothing of the kind4 ,the movement of a muscle or a limb separated from the body may resemble that movement when normally effected--but only as the movements of a mechanical bird resemble those of a living bird3 the modes of production are different4 ,so that were we to grant the postulate of the brain being the exclusive seat of sensation1 we should still deny that an action which was effected after removal of the brain was typical of the action effected when the brain was present4 ,the leg of ,hunter's patient jerked when the skin was irritated2 but this action could not be altogether the same as the similar action in a leg united with the rest of the sensitive mechanism4 ,nor is this all4 ,the leg may have been insensible1 the spinal segment which innervated it may have been wholly without ,sensibility1 and still we should have to question the logic which extended such an inference to the very different and far more complex actions of decapitated animals4 ,on this ground3--,the leg is1 by the hypothesis1 insensible because cut off from all connection with the sensitive mechanism4 ,but this is not the case with the decapitated animal3 there still remain the essential parts of a sensitive mechanism--all the chief organs are still in activity1 still manifesting their functions4 ,decapitation has produced a great disturbance in the mechanism1 and has removed an important centre2 but nevertheless every impression excites a connected group of centres1 and this group responds4 99 99 99 99 99 #id4 ,in conclusion1 unless we adopt the opinion that ,sensation--,consciousness--,sensibility 1 is something not belonging to the physiological properties of the nervous system in a vital organism 7the opinion held by spiritualists71 there seems no alternative but to adopt the opinion advocated in this volume1 namely1 that the physiological properties of the nervous system are inseparable from every segment of that system2 and the functions are the manifestation of those properties as determined by the special organs with the co-operation of all4 ,,footnotes #a ,,wordsworth4 #b ,crystals not only grow by assimilation1 but even repair injuries1 with a certain superficial resemblance to the repair of animal tissues4 ,thus1 according to the experiments of ,,jordan cited by ,sir ,,james ,,paget 7,lectures on ,surgical ,pathology1 ,i4 #aec1 and #b;d ed4 p4 #aae71 an octohedral crystal of alum1 if fractured and replaced in a motherlye will in a few days exhibit a complete restoration of the original form4 ,the whole crystal increases1 but the increase is greatest on the broken edge1 and the octohedral form is completely renewed4 7,comp4 #aac47 #c ,cited by ,,drysdale1 ,life and the ,equivalence of ,force1 ,part ,,ii4 p4 #adi4 #d ,,ranke1 ,die ,lebensbedingungen der ,nerven1 #ahfh1 p4 #hj4 #e 8,il n'y a peut tre pas un seul phnomne chimique dans l'organisme qui se fasse par les procds de la chimie de laboratoire2 en particulier il n'y a peut tre pas une oxydation qui s'accomplisse par fixation directe d'oxygne40--,,claude ,,bernard4 #f ,dr4 ,,madden1 in his essay ,on the ,relation of ,therapeutics to ,medicine1 #ahga1 p4 #e1 gives a remarkable illustration of what may be called the frustration of chemical affinity effected by mechanical conditions4 8,before calico can be printed1 every loose particle of cotton must be removed from the surface in order that the colored inks may not run4 ,this removal is effected by passing the calico over and in contact with a red-hot iron cylinder1 and by regulating the rapidity with which the cylinder revolves1 the intense heat burns off the loose fibres1 yet does no injury to the woven cloth4 ,in other words1 the changes in the relation of the high temperature and the cotton are too rapid to admit of the fibre combining with the oxygen4 ,let the rate of revolution be reduced but very little1 and the calico would burst into flames40 ,any one who has snuffed a candle with his fingers will understand this4 ,dr4 ,madden further instances certain fulminates which can be detonated in contact with gun-cotton without causing it to explode--the extreme rapidity with which the fulminates expand is too great to enable the gun-cotton to adjust its movements to this new motion4 ,precisely the same kind of thing occurs in organized matter4 ,if the rate of its changes be reduced below a certain point1 the ordinary chemical affinities will assert themselves4 #g ,i am often reminded of the surprising movements of particles of carbonate of lime in water which my friend ,professor ,,preyer showed me during a visit to ,bonn4 ,he had removed one of the concretions1 usually found in connection with nerves along the spine of old frogs1 and crushed it in water2 under the microscope the seeming spontaneity and variety of the movements of the particles was such that had we not known their origin we should certainly have attributed them to vitality3 no infusoria could have moved with more seeming spontaneity4 ,it is hardly physiological to conclude that because fragments of tissue manifest ambbiform movements therefore they are alive 7,,stricker1 art4 ,die ,zelle in his ,handbuch der ,lehre von den ,geweben1 #ahfh1 p4 #g71 or that the heart removed from the body is alive because it still beats4 ,,lieberk,,hn1 ,ueber ,bewegungserschsinungen der ,zellen1 #ahgj1 pp4 #ceg-cei1 cites examples of such movements in undeniably dead substances4 ,for ,life1 we demand not only ,movement1 but ,functional ,activity4 #h ,,telesius1 ,de ,natura ,rerum1 #aehf1 ,v4 #ahd4 ,,telesio might have been saved from the mistake had he attended to what ,,niphus had said on the point in his ,expositio subtilissima1 #aeei1 p4 #bde4 ,comp4 also ,,philelphus1 ,epist4 ,familiarum1 #aejb1 p4 #bec1 verso4 #i ,the authorities just cited are ,,aristotle1 ,de ,anima1 ,lib4 ,,ii4 c4 ,i4 ,,kant1 ,kritik der ,urtheilskraft4 ,m,,ller1 ,physiology4 ,,beale1 ,bioplasm1 and ,introduction to ,todd and ,bowman's ,anatomy4 ,,schelling1 ,erster ,entwurf1 and ,transcendent4 ,idealismus4 ,,bichat1 ,recherches sur la ,vie et la ,mort4 ,,stahl1 ,theoria ,vera ,medica4 ,,dug,s1 ,physiologie ,compare4 ,b,,clard1 ,anatomie ,gnrale4 ,,lamarck1 ,philosophie ,zoologique4 ,,comte1 ,cours de ,philosophie ,positive4 ,,owen',s ,hunterian ,lectures1 #ahed4 ,,herbert ,,spencer1 ,principles of ,biology4 #aj ,,fletcher1 as quoted by ,,drysdale1 ,life and the ,equivalence of ,force1 ,part ,,ii4 p4 #abj4 #aa ,,robin et ,,verdeil1 ,trait de ,chimie ,anatomique1 #ahec4 #ab ,,paget1 ,lectures on ,surgical ,pathology1 p4 #ad4 #ac ,comp4 ,,haeckel1 in ,siebold und ,klliker's ,zeitschrift1 #ahfe1 p4 #cdb1 and his ,generelle ,morphologie1 #ahff1 ,i1 #ace1 #ccf4 #ad ,in the ,archiv fr mikros4 ,anatomie1 #ahfe1 p4 #baa4 #ae ,here organization is the simplest form of all--molecular organized structure1 which in the higher forms becomes tissue structure1 and organ structure4 ,the word structure properly means orderly arrangement of different materials2 and molecular structure refers to the different proximate principles which constitute the organized substance4 ,usually1 however1 the word structureless indicates the absence of visible arrangement of the parts2 a cell has structure since it has nucleus and protoplasm4 #af ,in the cell-theory established by ,,schleiden and ,,schwann1 in #ahch1 and which has formed the basis of modern histology1 the cell-wall was endowed with an importance which can no longer be upheld now that the existence of independent organisms1 and of cells1 without a trace of enveloping membrane has been abundantly observed4 ,cells without walls were first described by ,,coste in the ,comptes ,rendus1 #ahde1 p4 #acgb4 ,they were also described by ,,charles ,,robin in #ahee1 ,dict4 de la ,mdicine1 art4 ,cellule4 ,but little notice was taken until ,,max ,,schultze1 in his famous essay1 ,ueber ,muskelkrperchen und was man eine ,zelle zu nennen habe1 which appeared in ,reichert und ,du ,bois ,reymond's ,archiv1 #ahfa1--;,,bruecke1 in his memoir1 ,die ,elementarorganismen1 #ahfa1--;and ,,lionel ,,beale1 in his ,structure of the ,simple ,tissues1 #ahfa1--;all about the same time began the reform in the cell-theory which has effected a decisive change in the classical teaching4 ,,leydig claims1 and with justice1 to have furnished important data in this direction 7,vom ,bau des thierischen ,krpers1 #ahfd1 ,i4 p4 #aa74 ,the student interested in this discussion should consult ,,max ,,schultze1 ,das ,protoplasma der ,rhizopoden und der ,pflanzenzellen1 #ahfc2 ,,haeckel1 ,die ,radiolarien1 #ahfb2 the controversial papers by ,,reichert1 in his ,archiv 7beginning with the ,report of #ahfc71 and ,,max ,,schultze1 in his ,archiv fr mikros4 ,anat41 with ,,henle',s judgment in his ,jahresberichte1 and ,k,,lliker',s summing-up in the last edition of his ,gewebelehre4 ,for a full yet brief history of the cell-theory see ,,drysdale1 ,the ,protoplasmic ,theory of ,life1 #ahgd1 pp4 #if-ajf4 #ag ,at the time this was written1 ,i had some fish ova in the course of development4 ,out of the same mass1 and in the same vessel1 all those which were supported by weed at a depth of half an inch from the surface1 lived and developed2 all those1 without exception1 that were at a depth of two to four inches1 perished4 ,in ordinary parlance1 surely1 nothing would be objected to in the phrase1 8these ova were all in the same ,medium02 the water was the same1 the weed the same1 the vessel the same2 yet some difference of temperature and carbonic acid made all the difference between life and death4 ,another curious fact was observed2 ,i removed eight of these ova with active embryos1 and placed them in a large watch-glass containing a solution 7one half per cent7 of bichromate of ammonia4 ,in this acid the embryos lived and were active fifty-seven hours1 although other embryos placed in a similar watch-glass containing pond-water1 survived only forty hours4 ,the non-effect of the acid was probably due to the non-absorption which nullifies the effect of certain virulent poisons when they are swallowed2 but why the fish should live longer in the acid than in the simple water1 ,i do not at all comprehend4 #ah ,,agassiz1 ,essay on ,classification1 #ahei1 p4 #ae4 #ai ,,haeckel1 ,generelle ,morphologie1 ,,ii4 #baa4 #bj ,see on this last point ,,ranke1 ,die ,lebensbedingungen der ,nerven1 #ahfh1 p4 #cd4 #ba ,see ,,waldeyer1 art4 ,eierstock1 in ,,stricker',s ,handbuch der ,lehre von den ,geweben1 #ahgj1 p4 #egj4 8,i found in a ftus1 which1 in a case of extra-uterine pregnancy1 had lain thirty years in the body of its mother1 the structure of the muscles as intact as if it had been born at its full time40--,,virchow1 ,cellular ,pathologie1 ,lect4 ,,xiv4 #bb ,see ,,beale1 ,the ,structure of the ,simple ,tissues1 #ahfa2 the ,introd4 to his edition of ,todd and ,bowman's ,physiological ,anatomy1 #ahff2 and ,how to ,work with the ,microscope1 #dth ed41 #ahfh2 also ,bioplasm1 #ahgb4 #bc 8,the physical property of the tissue does not depend upon this matter1 nor is its function due to it40--,beale1 ,introduction to ,todd and ,bowman1 p4 #aa4 ,that is to say1 he regards even contractility and neurility as physical1 not vital facts4 #bd ,in turning over the pages of a work which was celebrated some half-century ago--,,rudolphi',s ,grundriss der ,physiologie--,i was interested to find a clear recognition of this biological principle3 8,alle ,theile aller ,organismen10 he says1 ,i4 #bcc1 8sie mgen noch so verschieden in ihrem ,bau1 in ihrer ,mischung1 und in ihrer ,thtigkeit seyn1 sind ohne ,ausnahme als organisch und mithin als lebend zu betrachten40 ,in a note he adds that physiologists have considered certain solid parts--epidermis1 nail1 hair1 and bones--to be dead2 8but all these are organically developed1 and are in direct connection with the other parts40 #be ,,virchow1 ,die ,cellular ,pathologie1 #ahfj1 ,lect4 ,i4 #bf ,,beale1 ,bioplasm1 #ajd4 #bg ,k,,lliker1 ,gewebelehre1 #eth ed41 #ahfg1 p4 #ab4 #bh ,nevertheless there are some facts directly contradicting his conclusions4 ,for example1 he considers the axis cylinder of the nerve to be formed material1 and agrees with ,,max ,,schultze and others as to its fibrillated structure2 yet according to ,,lister and ,,turner1 ,,gerlach and ,,frey1 the axis cylinder is deeply stained by carmine1 and in this respect resembles the nucleus of protoplasm4 #bi ,from the quite recent experiments ,m4 ,,baillon has submitted to the ,acadmie des ,sciences 7#aeth ,february1 #ahge71 it appears that although cut flowers absorb colored fluids1 the roots when intact only absorb the fluid1 and reject the coloring matters1 by a veritable dialysis4 #cj ,,gerlach cited by ,,ranke1 op4 cit41 p4 #gf4 #ca ,,stein1 ,der ,organismus der ,infusionsthierchen1 #ahei1 p4 #gf4 #cb ,,stahl had a profound conviction of the radical difference1 though he was not able to point out the conditions involved4 ,see his ,disquisitio de mechanismi et organismi vera diversitate4 #cc ,m4 ,,fernand ,,papillon has shown that animals may be fed with food deprived of phosphates of lime if its place is supplied with magnesia1 strontia1 or alumina2 they make their bones out of these as out of lime4 ,but no such substitution is possible in muscle1 nerve1 or gland2 we cannot replace the phosphate of magnesia in muscles by the phosphate of iron1 lime1 or potash1 as we can replace the iron of a wheel by steel1 copper1 or brass4 #cd ,anatomy resolves the ,tissues into ,organites 7cells1 fibres1 tubes72 here its province ends1 and that of ,chemistry begins by pointing out the molecular composition of the ,organites4 #ce ,this luminous conception1 though vaguely seized by ,,pinel1 was first definitely wrought out by ,,bichat4 ,see his ,recherches sur la ,vie et la ,mort--and especially his ,anatomie ,gnrale1 #ahab1 ,i4 p4 lxx4 ,it was one of the most germinal conceptions of modern times4 #cf ,just as there go other materials besides canvas to make a sail1 and others besides iron to make a windlass1 so there go other tissues besides the muscular to form a muscle--there is the membranous envelope1 the nerve1 the blood-vessels1 the lymphatics1 the tendon1 and the fat4 ,even in ,contraction there is another property involved besides the ,contractility of the muscular element1 namely1 the ,elasticity of the fibrous wall of the muscular tube2 but ,contractility is the dominant property1 and determines the speciality of the function4 #cg 8,l'lment musculaire peut tre annex une foule de mcanismes divers2 tantt un os1 tantt un intestin1 tantt une vessie1 tantt un vaisseau1 tantt un conduit excrteur1 tantt enfin des appareils tout fait spciaux certaines espces d'animaux40--,,claude ,,bernard1 ,rapport sur les ,progrs de la ,physiologie gnrale1 #ahfg1 p4 #ch4 #ch ,,vulpian1 ,leons sur la ,physiologie du ,systme ,nerveux1 #ahff1 p4 #eha4 ,in a work just published ,i find ,m4 ,,luys hesitating at the consistent application of this law4 ,after pointing out the identity of the tissue in cerebrum and spinal cord1 he is only prepared to say that we cannot deny that there is no impossibility in admitting physiological equivalence where there is morphological equivalence4--,,luys1 ,actions ,reflexes du ,cerveau1 #ahgd1 p4 #ad4 #ci ,it is because men converted the result into a principle1 and supposed that ,life preceded the ,organism1 that they were led to puzzle themselves over such facts as the continuance of vitality in divided organisms4 ,,aristotle felt the force of the objection3 8,plants when divided are seen to live1 and so are certain insects1 as if still possessing the same ,vital ,principle 77 considered specifically 7 7 though not the same numerically 7 74 ,each of these parts has sensation and locomotion for a time2 and there is no room for surprise at their not continuing to manifest these properties1 seeing that the organs necessary for their preservation are absent40--,de ,anima1 ,lib4 ,i4 ,ch4 ,,iv4 ,compare ,,basso1 ,philos4 ,naturalis adversus ,aristotelem1 ,amsterdam1 #afdi1 p4 #bfj2 and ,,taurellus1 ,contra ,csalpinum1 #afej1 p4 #hej2 neither of them grappling with the difficulty so firmly as ,,aristotle4 #dj ,,spencer1 ,principles of ,biology1 #ahfd1 ,i4 #aec4 #da ,comp4 ,,lamarck1 ,philos4 ,zool41 ,,ii4 #aad4 #db ,comp4 ,,spencer1 op4 cit41 ,,ii4 #cfb1 #cfc1 for good illustrations of this4 #dc ,,agassiz1 ,essay on ,classification1 p4 #ia4 #dd 8,nulla in corpore animali para ante aliam facta est1 et omnes simul creat exiatunt40--,,haller1 ,elementa ,physiologi1 ,,viii4 #adh4 #de ,,quatrefages1 ,metamorphoses de l',homme et des ,animaux1 #ahfb1 p4 #db4 #df ,,von ,,baer1 ,ueber ,entwickelungageschichte1 #ahbh1 ,i4 #bba4 #dg ,curiously enough1 while the ,nudibranch1 which is without a shell1 possesses one during its embryonic life1 there is another mollusc1 ,neritina fluviatilis1 which possessing a shell in its subsequent life is without one during the early periods1 and according to ,,clapar,,de begins an independent existence1 capable of feeding itself before it acquires one4 ,see his admirable memoir on the ,neritina1 in ,mller's ,archiv1 #aheg4 #dh ,has any advocate of the hypothesis that animals were created as we see them now1 fully formed and wondrously adapted in all their parts to the conditions in which they live1 ever considered the hind legs of the seal1 which he may have watched in the ,zologial ,gardens8 ,here is an animal which habitually swims like a fish1 and cannot use his hind limbs except as a rudder to propel him through the water2 but instead of having a fish-like tail he has two legs flattened together1 and nails on the toes--toes and nails being obvious superfluities4 ,now which is the more rational interpretation1 that these limbs1 in spite of their non-adaptation1 were retained in rigid adherence to a ,plan1 or that the limbs were inherited from an ancestor who used them as legs1 and that these legs have gradually become modified by the fish-like habits of the seal8 #di ,,milne ,,edwards1 ,intro4 la ,zoologie ,gnrale1 #ahea1 p4 #i4 #ej ,,von ,,baer1 op4 cit41 ,i4 #bjc4 #ea ,,wolff1 ,theorie der ,generation1 #agfd1 #fg4 ,the reader will find abundant and valuable corroboration of this biological principle in ,,sir ,,james ,,paget',s ,lectures on ,surgical ,pathology4 #eb ,,von ,,baer1 ,selbstbiographie1 #ahff1 p4 #cai4 #ec ,,milne ,,edwards1 ,intro4 la ,zoologie ,gnrale1 #agf4 #ed ,,von ,,baer1 ,ueber ,entwickelungsgeschichte1 ,i4 #adg4 #ee ,,lotze1 art4 ,lebenskraft1 in ,wagner's ,handwrterbuch der ,physiologie1 p4 ,,xxvi4 #ef ,i had kept these tritons four years in the hope that they would breed2 but in spite of their being subjected to great varieties of treatment--for months well supplied with food1 and for months reduced almost to starvation--they never showed the slightest tendency to breed2 another among the many illustrations of the readiness with which the generative system is affected even in very hardy and not very impressionable animals4 ,,clapar,,de observed the still more surprising fact that the ,neritina fluviatilis 7a river snail7 not only will not lay eggs1 but will not even feed in captivity4 ,he attributes it to the stillness of the water in the aquarium1 so unlike that of the running streams in which the mollusc lives4 ,see ,mller's ,archiv1 #aheg4 #eg ,,bronn1 ,morphologische ,studien ber die ,gestaltungs-,gesetze1 #aheh4 ,compare the note on #aa4 #eh ,,darwin1 ,on ,domestication1 ,,ii4 #cdj4 ,in the ,annales des ,sciences1 #ahfb1 p4 #ceh1 ,m4 ,,malm describes a fish in his collection1 the tail of which had been broken1 and the bone which grew out at the injured spot had formed a second tail with terminal fin4 #ei ,in the memoir on the ,anatomy and ,physiology of the ,nematoids1 by ,dr4 ,,charlton ,,bastian1 which appeared in the ,philosophical ,transactions for #ahff1 we read that even these lowly organized worms have little power of repair4 ,speaking of the 8paste eels0 7,anguilulid71 he says1 8,i may state as the result of many experiments with these that the power they possess of repairing injuries seems very low4 ,i have cut off portions of the posterior extremity1 and though ,i watched the animal for days after1 could never recognize any attempt at repair40 ,perhaps1 however1 the season may have some influence2 and ,dr4 ,,williams',s denial respecting the ,nas may be thus explained4 ,what is said above was written in #ahfh1 and published in the ,june number of the ,fortnightly ,review4 ,in the ,august of that year the question of reproduction of lost limbs was treated by ,prof4 ,,rolleston in his ,address to the ,british ,medical ,association1 in which he showed cogent evidence for the conclusion that the reproduction of limbs only exists is animals that have feeble respiration1 and consequently slow vital processes4 #fj ,this beautiful and transparent larva reminds one in many respects of the ,pike as it poises itself in the water awaiting its prey4 ,it is enabled to do so without the slightest exertion by the air-bladders which it possesses in the two kidney-shaped rudiments of trache1 and which in the gnat become developed into the respiratory apparatus4 ,the resemblance to the air-bladder of fishes is not simply that it serves a similar purpose of sustaining the body in the water1 it is in both cases a rudiment of the respiratory apparatus1 which in the fish never becomes developed4 ,,weismann calls attention to an organ in the larv of certain insects 7the ,culicid71 which have what he calls a tracheal gill1 which gill has this striking analogy with the fish-gill that it separates the air from the water1 and not1 as a trachea1 direct from the atmosphere4 ,see his remarkable memoir ,die nachembryonale ,entwickelung des ,muscidens1 in ,siebold und ,klliker's ,zeitschrift1 #ahfd1 p4 #bbc4 #fa ,the ,variation of ,animals and ,plants1 #ahfh1 ,,ii4 p4 #bgb4 #fb ,origin of ,species1 #eth ed4 p4 #if4 #fc ,mr4 ,darwin has himself1 in the following passage1 stated a somewhat similar view1 and rejected it3 8,in one sense the conditions of life may be said not only to cause variability1 but likewise to include ,natural ,selection1 for the conditions determine whether this or that variety shall survive4 ,but when man is the selecting agent1 we clearly see that the two elements of change are distinct2 the conditions cause the variability1 the will of man acting either consciously or unconsciously accumulates the variations in certain directions1 and this answers to the survival of the fittest under nature40 7p4 #afh47 #fd ,even in the nerve-sheaths of some ,annelids there are muscles4 #fe ,,spencer1 ,principles of ,biology1 ,,ii4 #gb #ff ,,faivre1 ,variabilit de l',espce1 p4 #ae4 #fg ,these luminous organs would furnish an interesting digression if space permitted it4 ,the student is referred to the chapter in ,,milne ,,edwards',s ,leons sur la ,physiologie et l',anatomie ,compare1 #ahfc1 ,,viii4 #id1 sq4 ,,leydig1 ,histologie1 #aheg1 p4 #cdc4 ,k,,lliker1 ,microscopical ,journal1 #aheh1 ,,viii4 #aff1 and ,,max ,,schultze1 ,archiv fr mikros4 ,anat41 #ahfe1 p4 #abd4 ,my friend ,,schultze was kind enough to show me some of his preparations of the organs of ,lempyris splendidula1 from which the drawings in his memoir were made4 ,they reminded me of the electric organs in fishes by a certain faint analogy1 the trachea in the one holding the position of nerves in the other4 ,i may remark1 in passing1 that it is not every phosphorescent animal that has distinct luminous organs4 ,there is a lizard 7,pterodactylus ,gecko7 which occasionally becomes luminous4 8,a singular circumstance occurred to the colonial surgeon1 who related it to me4 ,he was lying awake in bed when a lizard fell from the ceiling upon the top of his mosquito-curtain2 at the moment of touching it the lizard became brilliantly luminous1 illuminating the objects in the neighborhood1 much to the astonishment of the doctor40 ,,collingwood1 ,rambles of a ,naturalist1 #ahfh1 p4 #afi4 #fh ,,max ,,schultze1 ,zur ,kenntniss der electrischen ,organe der ,fische1 #aheh-i4 #fi ,,leydig1 ,histologie1 #aheg1 p4 #de4 #gj ,,owen1 ,anatomy of ,the ,vertebrates1 #ahff1 ,i4 #ceh4 #ga ,,davy1 ,researches1 ,physiological and ,anatomical1 #aci1 ,i4 #cc4 #gb 8,if it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous successive slight modifications1 my theory would absolutely break down40--,,darwin1 ,origin of ,species1 #eth ed4 p4 #bbg4 ,in several passages insistence is made on this4 8,natura non facit saltum0 may be perfectly true2 but without impugning the ,law of ,continuity we may urge that the ,law of ,discontinuity is equally true4 ,the one is an abstract ideal conception2 the other is a concrete ideal conception4 ,according to the one1 every change from rest to motion1 or from one state to another1 must pass through infinites2 according to the other every change is abrupt4 ,in my ,first ,series1 ,vol4 ,i4 p4 #cbg1 ,i have shown how1 on mechanical principles1 every change in an organism must be abrupt4 ,a glance at the metamorphoses of the embryo1 or the stages of insect-development1 will show very sudden and abrupt changes4 ,let me also cite ,mr4 ,darwin against himself3 8,when we remember such cases as the formation of the more complex galls1 and certain monstrosities1 which cannot be accounted for by reversion1 cohesion1 etc41 and sudden1 strongly marked deviations of structure1 such as the appearance of a moss-rose on a common rose1 we must admit that the organization of the individual is capable through its own laws of growth1 under certain conditions1 of undergoing great modifications1 independent of the gradual accumulation of slight inherited modifications40--,origin1 p4 #aea4 ,see also note to #acj1 further on1 p4 #adb4 #gc ,on the ,nutrition of ,monads1 see the remarkable memoir by ,,cienkowski1 in the ,archiv fr mikros4 ,anatomie1 ,i4 #bba1 sq4 #gd ,,paget1 ,lectures on ,surgical ,pathology1 edited by ,,turner1 #ahfe1 p4 #ai4 #ge ,it has recently been shown that certain ,crustacea vary not only from species to species1 but from genus to genus1 when living in water of different degrees of saltness4 ,by continued dilution of the salt water an ,artemia was developed into another species1 and this again into a ,branchipus--a genus of large dimensions1 with an extra abdominal segment1 and a different tail2 a genus1 moreover1 which is propagated sexually1 whereas the ,artemia is parthenogenetic1 as a rule4 ,see ,nature1 #ahgf1 ,june #h1 p4 #acc4 ,the exceeding importance of this fact is1 that it proves specific and even generic differences to originate simply through the gradual changes of the medium and the adaptation of the organism to these new conditions4 ,it also disproves the very common notion--adopted even by ,mr4 ,,darwin himself--that 8organic beings must be exposed during several generations to new conditions to cause any appreciable amount of variation40 ,again1 8,natural ,selection1 if it be a true principle1 will banish the belief of any great and sudden modification of structure40--,comp4 note to #aba1 p4 #acb4 #gf ,compare ,,leydig1 ,vom ,bau des thierischeu ,krpers1 #ahfd1 p4 #bg4 #gg ,,ferdinand ,,cohn1 ,die contractile ,gewebe im ,pflanzenreich1 #ahfb4 ,by a series of numerous well-devised experiments1 ,cohn found that in the stamen of the centauria a tissue exists which is excitable by the same stimula as muscle is1 and which reacts like muscle1 describing a similar curve when excited1 and1 after reaching its maximum1 relaxing4 ,like the muscle it becomes fatigued by repeated contraction1 and recovers its powers by repose4 ,like the muscle it may be rendered tetanic4 7,the researches of ,dr4 ,,burdon ,,sanderson and ,mr4 ,,darwin have since placed beyond a doubt the ,contractility and ,sensibility of certain plants47 #gh ,,mivart1 ,the ,genesis of ,species1 #ahga1 p4 #bc4 #gi ,,dohrn1 ,der ,ursprung der ,wirbelthiere und das ,princip des ,functionswechsels1 #ahge1 p #gd4 #hj ,,sigmund ,,mayer1 ,die peripherische ,nervenzelle und die sympathische ,nervensystem1 #ahgf4 #ha ,on these cells see note to #adj4 #hb ,these terms designate the surface aspect of a transverse section1 of what more correctly should be called the gray columna4 ,see ,figs4 #c to #f4 #hc ,but this only in the higher animals4 ,in reptiles and amphibia the medulla descends into the cervical region1 as far as the second and third cervical vertebr4 ,this should be remembered in experimenting4 #hd ,,foster and ,,balfour1 ,elements of ,embryology1 ,part ,i41 #ahgd4 ,comp4 ,,schwalbe1 art4 ,die ,retina1 in the ,handbuch der ,augenheilkunde of ,,graefe and ,s,,misch1 #ahgd1 ,i4 #cfc4 #he ,the development of the olfactory lobe and bulb is similar2 it need not be followed here4 #hf ,german anatomists divide this axis into trunk and crown 7,hirnstamm and ,hirnmantel74 ,there is convenience in this division4 ,if we remove all the gray matter of the cerebrum1 with all the white matter radiating from it1 until we again come upon gray matter--and if we then cut the cerebellum from its descending strands of white matter--we shall have removed the crown1 and leave the trunk remaining4 ,this trunk is constituted by the corpora striata1 nucleus lentiformis1 optic thalami1 corpora quadrigemina1 crura cerebri1 pons1 medulla oblongata1 and medulla spinalis4 ,from this trunk all the organs of the body are directly innervated 7except those innervated from the sympathetic874 #hg 8,on s'est proccup du rle spcial que pouvaient jouer les ganglions priphriques situs dans le voisinage de certaines organes2 et on a prtendu que les nerfs ne jouissaient de leur proprit d'agir sur ces organes qu'aprs avoir travers ces ganglions4 ,on avait admis que l'excitation porte sur le filet nerveux avant son entr dans le ganglion restait sans effet2 que pour obtenir l'action excitatrice des fonctions de l'organe il fallait exciter le nerf entre lui et le ganglion voisin40--,,claude ,,bernard1 ,systme ,nerveux1 ,,ii4 #afi4 ,but on proceeding to verify these statements by experiment1 ,,bernard is led to the conclusion1 8que le ganglion n'a pas d'influence propre sur le mode de l'excitation transmise l'organe40 ,i was delighted to find my opposition to the current teaching respecting the central functions of ganglionic cells thoroughly borne out by the elaborate researches of ,,sigmund ,,mayer 7,archiv fr ,psychiatrie1 ,bd4 ,,vi4 ,heft #b74 ,having artificially produced such cells1 he pertinently asks1 ,how can we attribute central functions to cells which appear in the process of regeneration of a divided nerve6 ,the error has its origin in the confusion of functions with properties4 #hh ,it is often1 though incorrectly1 stated that every segment of an annulose animal has its separate ganglion4 ,the fact is1 that while the ganglia are usually fewer than the segments1 they are sometimes more numerous4 #hi ,it has been proved that the cells of the cornea and the pigment cells of the skin contract under nervous excitation4 ,we cannot suppose that although these are the only cells which have hitherto been brought under experimental observation1 they are the only cells subject to nerve-influence4 ,we may safely assume that wherever a nerve-fibre terminates1 its action will be transformed into an excitation of the part4 ,habitually1 however1 motor-nerves are spoken of as muscle-nerves4 #ij ,on ,deduction1 see ,problems3 ,first ,series1 ,vol4 ,,ii4 p4 #aei #ia ,i do not here touch upon the question as to whether these actions of the senses are sensations1 because that question demands that we should first settle what is ,sensation4 ,i may at once1 however1 say that what is ordinarily understood as a sensation of color1 or a sensation of sound1 is1 in my opinion1 not possible without the cerebrum4 ,but the sensibility of the eye and ear is manifestly preserved4 #ib ,it has been observed that removal of the cerebellum affects the pigment cells of the skin4 ,no doubt other parts are also affected1 but the changes have hitherto escaped observation4 #ic ,,owsjannikow describes the results of removing carefully the cranial ganglia of the crayfish2 and these effects ,,meyer observes to be identical with those which follow removal of the large claw of the crayfish6 ,a4 ,b4 ,,meyer1 ,das ,hemmungsnerven-system des ,herzens1 #ahfi1 p4 #bc4 ,let me add that the phenomena described by ,m4 ,,faivre as following the destruction of one subsophageal ganglion in the ,dytiscus1 are so little to be referred to the mere absence of the ganglion1 that ,i find them not to occur when the whole head is removed4 #id ,,pfl,,ger1 ,die ,sensorischen ,funktionen des ,rckenmarks1#aheh4 ,,auerbach1 ,gnzburg's ,zeitschrift4 ,jahrgang ,,iv4 p4 #dhf4 ,,lewes1 ,leeds ,meeting of ,british ,association1 #aheh1 and ,physiology of ,common ,life1 #ahfj4 ,this recognition of sensation1 and even of volition1 in spinal actions may be found in the writings of ,,whytt1 ,,unzer1 ,,prochaska1 ,,legallois1 and ,,mayo2 but the establishment of the ,reflex ,theory had displaced it1 and its revival dates from ,,pfl,,ger4 #ie ,,friedl,,nder 7,versuch ber die innern ,sinne1 #ahbf1 ,i4 #gg7 declares it to be a rational necessity3 8,die ,annahme eines ,nervenfluidums ist ,nothwendigkeit der ,vernunft40 #if ,these terms and the conception they embody were proposed by me in #ahei in a paper 8,on the necessity of a reform in ,nerve-physiology10 read at the ,aberdeen meeting of the ,british ,association1 and were reproduced in the ,physiology of ,common ,life4 7,prof4 ,,owen1 probably in forgetfulness of my suggestion1 proposed 8neuricity40 ,lectures on the ,comp4 ,anat4 of ,vertebrates1 #ahff1 ,i4 p4 #cah47 ,the terms were fortunate enough to meet with acceptance from some physiologists both in ,england and ,france2 and the conception has been more widely accepted than the terms4 ,the most distinguished approver was ,prof4 ,,vulpian4 8,faute d'une meilleure dtermination on peut1 avec ,m4 ,lewes1 donner la proprit physiologique des fibres nerveuses le nom de neurilit2 c'est l ce qui correspondra la oontractilit des fibres musculaires40 ,leons sur la physiologie du systme nerveux1 #ahff1 p4 #bbj4 ,he also adopted my suggestion 7since modified7 of ,sensibility as the property of ganglionic cells4 ,compare also ,,gavarret1 ,phnomnes physiques de la ,vie1 #ahfi1 pp4 #bac and #bbb4 ,,taule1 ,notions sur la nature de la matire organise1 #ahff1 p4 #aca4 ,,charles ,,robin1 ,anatomie et physiologie cellulaires1 #ahgc1 p4 #aff4 ,by these channels1 and by the ,german1 ,italian1 ,russian1 ,polish1 and ,hungarian translations of my work1 the suggestions were carried over ,europe1 crept into scientific journals1 and became known to writers who never heard of me4 ,i only mention these facts lest the reader should suppose that my views had been anticipated by certain continental writers4 #ig 8,la force nerveuse n'existe pas comme puissance independant des proprits de tissu4 ,elle consiste en l'action des parties excits1 sur les parties excitables1 l'tat de l'excitation des premires agissant comme impression ou stimulation sur les secondes40--,,landry1 ,trait des ,paralysies1 #ahei1 ,i4 #adb4 #ih 8,le systme nerveux est tout la fois l'origine des sensations et l'origine des mouvements4 ,mais est-ce par une proprit unique1 ou par deux proprits diverses qu'il dtermine deux phnomnes aussi distincts60 ,,flourens1 ,recherches sur les proprits et les fonctions du ,systme ,nerveux1 #ahbd1 p4 #a4 ,he concludes that 8la puissance nerveuse n'est pas unique2 il n'y a pas une seule proprit1 il y en a deux10 p4 #bd4 ,in this he has been generally followed4 #ii 8,i have raised and stretched the thick orbital nerve of horses on the handle of a scalpel1 like a string on the bridge of a violin1 without exciting the least sensation2 but as soon as mechanical or chemical irritation had given rise to inflammation of the nerve a gentle touch caused violent pain40--,,romberg1 ,nervous ,diseases 7translated for the ,sydenham ,society71 ,i4 #aj4 #ajj ,the experiments of ,,haller1 ,sur la nature sensible et irritable des parties1 ,i4 #bde2 and the remarks of ,,prochaska1 ,,de ,,functionibus ,,systematis ,,nervosi 7translated by ,,laycock in the volume published by the ,sydenham ,society1 p4 #cif71 ought to have sufficed4 ,see further on1 ,chap4 ,v4 #aja ,in mammals about three days1 in birds four days1 in frogs fourteen to twenty days4 #ajb ,,rutherford1 in ,journal of ,anatomy1 #ahgc1 ,no4 ,,viii4 p4 #cca4 7,,fleischl denies that the nerve in situ has different degrees of reaction4 ,sitzungsberichte der ,wiener ,akad41 ,december1 #ahgf47 #ajc ,,munk1 in the ,archiv fr ,anat41 #ahfj1 p4 #gih4 #ajd ,,haller1 ,mmoires sur la nature sensible et irritable des parties4 #aje ,comptes ,rendus1 #ahfb1 ,,liv4 p4 #ife4 #ajf 8,j'espre vous convaincre que tous les lments anatomiques des nerfs sensitifs1 moteurs1 vasomoteurs1 et autres1 ont les mmes proprits1 et ne sont distincts que par leurs fonctions4 ,cette question est de la plus haute importance pour la physiologie gnrale4 ,c'est celle qui domine toute la physiologie des fibres nerveuses40--,,vulpian1 ,leons sur la ,physiologie du ,systme ,nerveux1 p4 #aa4 #ajg ,mr4 ,,james ,,andrews4 #ajh ,in the second number of ,la ,revue ,philosophique1 ,paris1 #ahgf1 ,i have treated this question of specific energies more at length than ,i could find space for in the present volume4 #aji ,in #ahei ,i mentioned that if the nerves of a frog's back be exposed by raising the skin1 they may be pricked or even cut without sensible effect1 although a slight prick on the skin will excite the nerves1 and cause a reflex action4 ,in #ahgj1 ,prof4 ,,fick expressed his astonishment at finding that after he had cut out a piece of the skin1 leaving it attached to the body by a single nerve1 electrical stimulation of this excised skin caused the frog to make the reflex movement of rubbing the irritated surface2 whereas electrical stimulation of the nerve-trunk itself produced no reflex effect1 only a twitching of a muscle4 ,pflger's ,archiv1 #ahgj1 p4 #cbg4 ,,brown ,s,,quard tries to establish a distinct species of nerves as conductors of sensitive impressions1 from those which are impressionable4 ,the facts on which he founds these two properties simply show that nerves are so disposed that the stimulus which excites them in one place fails in another4 ,he could hardly maintain that a skin nerve contained impressionable fibres at its periphery1 and only conducting fibres in its trunk6 ,see his communication to the ,royal ,society1 ,proceedings1 #ahef2 and ,lectures in the ,lancet1 #ajth ,july1 #aheh4 #aaj ,in consequence of this observation some physiologists have maintained that ,feeling or ,consciousness never arises in cerebral activity1 unless the thalami and the connected tracts are at the same time in action4 ,i go further1 and maintain that there is no ,consciousness 7in the restricted meaning of the term7 unless the whole organism is involved4 ,cerebral or spinal activity will be activity of ,sensibility2 but this is only the basis of ,consciousness4 #aaa 8,an unconscious sensation1 which ,lewes distinguishes from perception1 is to me an inconceivable 7ist fr mich ein ,unding740--,,schr,,der ,,van ,,der ,,kolk1 ,die ,pathologie des ,geistes-,krankheiten1 p4 #bb4 #aab ,by selective adaptation is meant the varying combination of motor impulses to suit the varying requirements of the effect to be produced4 ,physical mechanisms are limited to the performance of definite actions2 sensitive mechanisms employ fluctuating combinations of elements in response to fluctuations of stimuli4 ,the wheels1 levers1 springs1 and valves of a machine cannot be differently combined according to varying degrees of the motor-force1 as the nerves and muscles of an organism are differently combined by varying sensations4 ,an automaton may be constructed to play on the violin1 but it will only play the air to which it is set2 it cannot vary the performance1--cannot play a false note1 or throw in a crescendo here1 a largo there1 according to a caprice of feeling4 ,we must admit that violinist has his delicate and changing movements guided by sensations1 auditory and muscular2 any interruption in the sensations would arrest the movements1 which in truth incorporate them4 ,and yet it is well known that the violinist may perform while completely 8unconscious40 ,i do not simply refer to the fact that his thoughts and attention may be elsewhere2 ,i refer to such facts as are recorded in ,pathology4 ,,trousseau1 for example1 had an epileptic patient who was occasionally seized with attacks of complete unconsciousness while he was performing in the orchestra2 yet1 on reawakening to consciousness1 he found that he had continued to play1 had kept proper time1 and played the proper notes4 #aac ,,claude ,,bernard1 ,systme ,nerveux1 #aheh1 ,i4 #cdi4 #aad ,,wordsworth1 ,the ,prelude4 #aae 8,on peut dire que toujours un phnomne de mouvement reconnait pour point de dpart une impression sensitive40--,,claude ,,bernard1 ,i4 #bfg4 #aaf ,since this was written ,prof4 ,,michael ,,foster and ,mr4 ,,dew ,,smith have published their very important researches on the motions of the heart1 which establish beyond a doubt that1 in the molluscs at least1 there is no co-operation of either centre or nerve4--,proceedings of the ,royal ,society1 #ahth ,march1 #ahge4 7,see also ,studies from the ,physiological ,laboratory of ,cambridge1 ,part ,,ii41 #ahgf47 ,mr4 ,foster knows that ,i had independently1 and from a totally different line of research1 arrived at the same conclusion respecting the heart's movement4 #aag ,comptes ,rendus de la ,soct de ,biologie1 #ahdg1 ,i4 #dj4 ,in #ahef he showed that not only were the muscles of the iris directly stimulated by light 7and this not by its calorific or chemical rays71 but that sixteen days after removal of the eye from the orbit1 this effect was observable in the eel4 ,yet a very few days after extirpation of the eye the nerves are disintegrated4--,proceedings of the ,royal ,society1 #ahef1 p4 #bcd4 ,,donders has the following observations3 8,the movements of the iris are of two kinds--reflex and voluntary4 ,reflex action is exhibited as constriction of the pupil in consequence of the stimulus of incident light upon the retina4 ,fontana has shown that the light falling upon the iris produces no remarkable contraction4 ,we have confirmed this result by causing the image of a small distant light to fall1 by means of a convex lens1 upon the iris1 whereby1 during slight perception of light1 a doubtful contraction occurred1 which gave way to a strong contraction so soon as the light entering the pupil excited a vivid perception4 ,nevertheless1 the experiments of ,harless and ,budge have shown that even after death1 so long as irritability remains1 the pupil still contracts upon the continued action of light4 ,of the correctness of this we have satisfied ourselves4 ,in a dog killed by loss of blood the one eye was closed1 the other opened and turned to the light3 after the lapse of an hour1 the pupil of the opened eye was perceptibly smaller than that of the closed eye4 ,the latter now remained also exposed to the light1 and on the following day the diameter of both eyes was equal4 ,the upper jaw1 alone with the eyes1 was taken out of some frogs2 one eye was exposed to the light1 while the other was covered with a closely folded piece of black paper3 after the lapse of half an hour the pupil turned to the light was narrow1 the other wide4 ,but the latter also contracted almost immediately after the removal of the paper40--,,donders1 ,on the ,anomalies of ,accommodation and ,refraction of the ,eye4 ,trans4 of the ,new ,sydenham ,society1 p4 #egb4 #aah ,the experiment often fails1 but ,i have seen it several times succeed4 #aai ,pflger's ,archiv1 #ahgb1 p4 #fah4 #abj ,see his ,researches in ,pflger's ,archiv1 ,bde4 ,,ii4 and ,,iv4 #aba ,d',,orbigny1 ,des ,mollusques ,vvants et fossils1 p4 #aac4 #abb ,seaside ,studies1 #b;d ed41 p4 #aja4 #abc ,cited by ,,brown ,s,,quard1 ,journal de la ,physiologie1 #aheh1 p4 #cei4 #abd ,dr4 ,,norris has recorded some striking observations in his paper on 8,muscular ,irritability0 in the ,journal of ,anatomy1 #ahfg1 ,no4 ,,ii4 p4 #bag4 ,here is the only one ,i can find room for3 8,on taking up the dead frog and touching the limb 7which during life had been paralysed by section of its nerve7 with my finger1 it was suddenly shot out as if alive4 ,i placed the body down1 and one or two apparently spontaneous movements of small extent afterwards occurred4 ,on touching the skin gently with the point of a needle1 by the slight pressure upon the muscle beneath1 movements of the limb were also induced1 but this high degree of exaltation very rapidly disappeared40 #abe ,see their papers in the ,archiv fr ,psychiatrie1 #ahge1 ,bd4 ,v4 ,heft #c4 #abf ,this latter statement will be justified when ,i come to expound the ,triple ,process1 which ,i have named the ,psychological ,spectrum4 #abg ,,foster and ,,balfour1 ,elements of ,embryology1 #ahgd1 ,part ,i4 p4 #eb4 ,,his1 ,untersuchungen ber die erste ,anlage des ,wirbelthierleibes1 #ahfh1 p4 #aig4 #abh ,they state that the cells of the epiblast are the results of direct segmentation1 whereas the cells of the other layers are formed at a subsequent period1 and are only indirectly results of segmentation4 ,but if the observations of ,,kowalewsky are exact1 this is not the case with the hypoblast of the ,amphioxus1 which is from the first identical with the epiblast4 #abi ,k,,lliker1 ,entwicklungsgeschichte des ,menschen und der hheren ,thiere1 #ahfa1 p4 #ga4 #acj ,according to ,,balfour',s recent observations1 a large part of the muscular tissue is derived from the layer of the mesoblast belonging to the hypoblast4 #aca ,,his1 ,untersuchungen1 pp4 #ci1 #dj4 #acb ,quite recently ,,owsjannikow has pointed out the termination of fibres in the phosphorescent cells of the ,lampyris ,noctiluca4 ,see his paper in the ,mmoires de l',acad4 de ,st4 ,petersbourg1 #ahfh1 ,,xi4 #ag4 ,these phosphorescent cells are said to be ganglion-cells by ,,panceri1 ,intorno della luce che emana dalle celleule nervose 7,rendiconto della ,accad4 delle ,scienze1 ,april1 #ahgb72 and by ,,eimer1 ,archiv fr mikros4 ,anatomie1 #ahgb1 p4 #fec4 ,k,,lliker also calls the phosphorescent organ a nervous organ4 ,this is not to be interpreted as meaning that neurility is phosphorescence1 but simply that in some nerve-cells there is phosphorescent matter1 which is called into activity by stimulus of the nerves4 #acc ,,bidder und ,,kupffer1 ,textur des ,rckenmarks1 #aheg1 p4 #ajh4 ,what is said in the text has been rendered doubtful by the recent researches of ,mr4 ,f4 ,,balfour1 ,on the ,development of the ,spinal ,nerves in ,elasmobranch ,fishes 7,philos4 ,trans41 ,vol4 ,,clxvi4 ,part ,i471 which show that in these fishes the ganglion has its origin in the spinal cord4 #acd ,comp4 ,,problem ,i4 #acj1 with the remarks of ,,charles ,,robin1 ,anatomie et ,physiologie ,cellulaires1 #ahgc1 p4 #bj4 #ace ,,kleinenberg1 ,hydra2 ,eine ,anatomisch-,entwickelungs-,untersuchung 1 #ahgb1 p4 #aa4 ,,eimer1 ,zoologische ,studien auf ,capri1 #ahgc1 p4 #ff4 ,a similar formation is described by ,dr4 ,,allman in the ,myriothela2 he says1 however1 that he has never been able to trace a direct continuity of the caudal processes of the cells with muscular fibrils4 ,he believes that the processes make their way to the muscular layer through undifferentiated protoplasm4--,philos4 ,transactions1 ,vol4 ,,clxv4 ,part ,,ii4 p4 #eed4 ,an intermediate stage between this neuro-muscular tissue and the two differentiated tissues seems presented in the ,nematoid worms which have muscles that send off processes into which the nerves pass4 ,,gegenbaur declares his inability to decide whether these processes are muscles or nerves4 ,b,,tschli thinks the nerve-process blends with the muscle-process4--,archiv fr mikros4 ,anatomie1 #ahgc1 p4 #hi4 #acf 8,the gray matter of the cord seems undoubtedly to be formed by a metamorphosis of the external cells of the epiblast of the neural tube1 and is directly continuous with the epithelium2 there being no strong line of demarcation between them40--,op4 cit41 p4 #ahe4 #acg ,,robin1 ,anat4 et ,physiol4 ,cellulaires1 p4 #ccb4 #ach ,,stilling1 ,bau der ,nervenprimitiv-,fasern1 #ahef1 p4 #af4 #aci 8,there was a time10 says ,k,,lliker1 8when ,i confidently believed that an hypothetical explanation of the arrangement of elements in the spinal cord could be grounded on a basis of fact2 but the deeper my insight into the minute anatomy1 the less my confidence became2 and now ,i am persuaded that the time is not yet come to frame such an hypothesis40--,gewebelehre1 #ete ,auf4 #ahfg4 #adj ,in the ,gasteropoda the cells range from #bbj to #c 7 #j1jja millimtre74 #ada ,,haeckel1 ,mller's ,archiv1 #aheg4 ,,leydig1 ,vom ,bau des thierischen ,krpers1 #ahfd1 ,i4 #hd4 ,,robin1 ,anat4 et ,physiol4 ,cellulaires1 p4 #hi4 ,should the observations of ,,heitzmann be confirmed1 there would be ground for believing that neurine is normally fibrillated4 ,he says that the living protoplasm in the ,amba1 white blood-corpuscle1 etc41 is an excessively fine network1 which condenses into granules at each contraction4 7,cited in the ,jahresberichte ber ,anat4 und ,physiol41 #ahgc1 ,bd4 ,,ii47 ,,walther1 who examined frozen brains1 describes the cells as quite transparent at first1 with very rare granules1 but gradually while under observation the granules became more numerous4 ,centralblatt1 #ahfh1 p4 #dei4 ,according to ,,mauthner1 ,beitrge zur ,kenntniss der morphologischen ,elemente des ,nervensystems1 #ahfb1 p4 #da1 neurine has three cardinal forms--transparent1 finely granular1 and coarsely granular4 #adb ,,trinchese1 ,struttura del sistema nervoso dei ,cefalopodi1 ,florence1 #ahfh1 p4 #g4 #adc ,an eminent friend of mine was one day insisting to me that the physiological postulate made it impossible for a nerve-cell to be without its ingoing and outgoing fibres2 and he was not a little astounded when ,i replied1 8,come into my workroom and ,i will show you a thousand40 #add ,,eichhorst in ,virchow's ,archiv1 #ahge1 ,,lxiv4 p4 #dcb4 #ade ,,auerbach 7,ueber einen ,plexus ,myentericus1 #ahfb7 describes the ganglia as filled with apolar cells1 among which only a few are unipolar4 ,,stieda 7,centralnervensystem der ,vgel1 #ahfh7 finds both apolar and unipolar cells in the spinal ganglia of birds4 ,,axmann 7,de ,gangliorum ,systematis ,structura penitiori1 #ahdg7 says the spinal cells are all unipolar4 ,,schwalbe 7,archiv fr mikros4 ,anat41 #ahfh7 and ,,courvoisier 7ibid41 #ahfi7 say the same4 ,so also ,,ranvier1 ,comptes ,rendus1 #ahge4 ,k,,lliker 7,gewebelehre7 speaks decidedly in favor of both apolar and unipolar cells1 but thinks the apolar are embryonic4 ,,pagliani 7,saggio sullo ,stato attuale delle ,cognizioni della ,fisiologia intorno al ,sistema nervoso1 #ahgc71 who represents the views of ,,moleschott1 admits the existence of apolar and unipolar cells4 ,the authors just cited are those ,i happen to have before me during the rewriting of this chapter1 and the list might easily be extended if needful4 ,,auerbach1 ,,bidder1 and ,,schweigger-,,seidel describe unipolar cells which in some places present the aspect of bipolar cells simply because two cells lie together1 their single poles having opposite directions4 ,i will add that the bipolar cells do not really render the physiological interpretation a whit more easy than the unipolar1 for they are simply cells which form enlargements in the course of the nerve-fibres4 #adf ,when ,dr4 ,,beale says 8that it is probable no nerve-cell exists which has only one single fibre connected with it0 7,bioplasm1 p4 #ahf71 he has no doubt this in his mind2 since he would not1 ,i presume1 deny that there are cells each with a single process4 #adg ,,deiters1 ,untersuchungen ber ,gehirn und ,rckenmark1 #ahfe4 #adh ,archiv fr mikros4 ,anat41 #ahfi1 p4 #bag4 ,compere also ,,butzke1 ,archiv fr ,psychiatrie1 #ahgb1 p4 #ehd4 #adi ,,henle1 ,nervenlehre1 #ahga1 p4 #eh1 ,fig4 #ba4 #aej ,when men of such experience and skill as ,k,,lliker1 ,,bidder1 ,,goll1 and ,,lockhart ,,clarke declare that they have never seen a cell-process pass directly into a dark-bordered fibre in the anterior root1 what are we to say to such figures and descriptions as those given in the works of ,,schr,,der ,,van ,,der ,,kolk1 ,,gratiolet1 and ,,luys8 ,even did such arrangements exist1 no transverse nor longitudinal section could display them1 owing to the different planes at which the fibres enter1 and the length and irregularity of their course4 #aea ,long after the text was written1 ,,willigk published in ,virchow's ,archiv1 #ahge1 ,,lxiv4 p4 #afc1 observations of anastomoses which even ,k,,lliker admitted to be undeniable4 ,yet out of sixty-four preparations1 amid hundreds of cells1 he could only reckon seven cases of conjunction4 #aeb ,see the history given in ,,stilling',s learned work1 ,ueber den ,bau der ,nervenprimitiv-,faser1 p4 #cd2 and compare ,,max ,,shultze1 ,de ,retin ,structura1 p4 #h1 and ,bau der ,nasenschleimhaut1 p4 #ff2 ,,waldeyer1 in the ,zeitschrift fr rat4 ,med41 #ahfc2 ,,lister and ,,turner1 ,observations on the ,structure of ,nerve-,fibres1 in ,quarterly ,micros4 ,journal1 #ahei2 ,,ranvier1 in the ,archives de ,physiologie1 #ahgb4 #aec ,virchow's ,archiv1 ,bd4 ,,lxxii4 p4 #aic4 #aed ,monthly ,journal of ,micros4 ,science1 #ahgd1 ,,xi4 p4 #bad4 #aee ,,babuchin1 ,centralblatt1 #ahfh1 p4 #gef4 #aef ,even so eminent an authority as ,w4 ,,krause holds this both with regard to the varicose aspect and the double contour3 ,handbuch der menschlichen ,anatomie1 #ahgf1 ,i4 #cfg4 ,,butschli1 however1 describes the nerves in a living ,nematode as varicose3 ,archiv fr ,anat41 #ahgc1 p4 #gh2 and ,i have somewhere met with an observation of the double contour being visible in the living animal4 #aeg ,,butzke1 ,archiv fr ,psychiatrie1 #ahgb1 p4 #eid1 states that the granular substance has the chemical composition of myeline4 ,if this be so1 we may suppose the 8fibrils of crystallization0 to represent the coagulation of the substance which is in solution amid the myeline granules1 and corresponds with the axis cylinder of a fibre4 ,i may remark that in almost every good preparation nerve-cells will be found in which1 while one process is distinctly granular1 another is striated or even fibrillated4 #aeh ,,boll1 ,die ,histiologie und ,histiogenese der nervsen ,centralorgane1 in the ,archiv fr ,psychiatrie1 #ahgc1 p4 #dg4 #aei ,,stieda1 ,studien ber das ,centralnervensystem der ,vgel1 #ahfh1 p4 #fe4 ,,mauthner1 ,op4 cit41 p4 #d4 #afj ,,turner and ,,lister1 ,op4 cit41 p4 #h4 #afa ,,blessig1 ,de ,retin ,structura1 #aheg4 #afb ,,luys1 ,recherches sur le ,systme nerveux1 #ahfe1 p4 #bfg4 ,in a recent and remarkable treatise the student is informed that 8plus une cellule est charge d'un rle purement mcanique plus elle est volumineuse2 plus l'acte qu'elle produit tend revtir un caractre psychique plus elle est petite02 to move a limb the agitation of the cerebral cells must materialize itself more and more1 8,il a besoin de passer par des cellules1 de moins en moins spirituelles et de plus en plus matrielles4444 ,de mme pour les cellules sensitives4 ,l'impression extrieure va en se modifiant1 en se spiritualisant1 de la priphrie au centre4444 ,un phnomne de l'ordre spirituel ne sanrait devenir sans transition un phnomne d'ordre physique40 ,and what is this marvellous transition between spiritual and physical8 ,it is the action of medium-sized cells which 8travaillent la vibration reue1 la modifient de faon lui ter de son spiritualisme et la rapprocher davantage des branlements physiques40 ,i will not name the estimable author1 because he is simply restating what many others implicitly or explicitly teach2 but ,i will only ask the reader to try and realize in thought the process thus described4 #afc ,,schr,,der ,,van ,,der ,,kolk1 ,pathologie der ,geisteskrankheiten1 #ahfc1 p4 #fi4 #afd ,,wundt1 ,physiologische ,psychologie1 p4 #bfa4 ,in his ,mechanik der ,nerven1 #b ,abth4 7published just as this sheet is going to press71 he shows that a stimulus is both retarded and weakened in its passage through a ganglion4 #afe ,,trinchese also says that the fibres 8provengono dalle cellule e non son altro che i loro prolungamenti o poli40--,op4 cit41 p4 #ac4 ,an unequivocal example is seen in the ,torpedo1 where the large cells have each their prolongation continuing without interruption into the electrical organ4 ,see the figure given by ,,reichenheim in the ,archiv fr ,anat41 #ahgc1 ,heft ,,vi4 #aff ,,golgi1 ,sulla struttura della sostanza grizia del ,cervello4 ,,arndt1 ,archiv fr mikros4 ,anat4 #ahgj1 p4 #agf4 ,,rindfleisch also traces these processes into the neuroglia 7ibid41 #ahgb1 p4 #dec74 8,deiters1 ,boddaert1 and other observers have stated that one dark-bordered nerve-fibre enters each cell4444 ,my own observations lead me to conclude that all the fibres are composed of the same material1 but that one fibre does not divide until it has passed some distance from the cell1 while others give off branches much closer to it40--,,beale1 ,bioplasm1 p4 #ahi4 #afg ,,beale1 ,bioplasm1 p4 #agg4 ,,max ,,schultze1 in ,stricker's ,handbuch1 p4 #acd4 ,comp4 ,,stilling1 ,nervenprimitiv-,faser1 p4 #acc4 ,,arndt1 ,archiv fr mikros4 ,anat41 #ahfh1 p4 #eab2 and #ahfi1 p4 #bcg4 ,weighty as these authorities are1 their view is questionable--firstly1 because the forms of these cells are too constant and definite in particular places to result from the union of fibrils coming from various origins2 but secondly1 and mainly1 because the teaching of ,development is opposed to it4 #afh ,,robin1 ,anat4 et ,physiol4 ,cellulaires1 p4 #cce4 #afi ,archives de ,physiologie1 #ahgb1 p4 #bfh4 #agj ,the fact of the existence of cells in the white substance is one which is very difficult of interpretation on the current hypotheses4 ,the cells are found in regular columns and irregularly scattered4 ,,boll thinks that while in the white substance of both cerebrum and cerebellum there are true nerve-cells as well as connective corpuscles1 in the cord there are only the latter4 ,but hitherto there has been no decisive test by which a nerve-cell can be distinguished from a connective corpuscle4 #aga ,monthly ,journal of ,micros4 ,science1 ,,xi4 #bai4 ,this accords with what ,,kupffer says respecting the entire absence of cells in the earliest stages observed by him in the sheep4 ,the white substance of the spinal cord he describes as soft1 transparent1 and gelatinous1 in which dark points are visible2 these dark points are seen in longitudinal sections to arise from the fibrillation of the substance4--,,bidder und ,,kupffer1 ,op4 cit41 p4 #aaa4 #agb ,,weismann1 ,die nachembryonale ,entwick4 der ,musciden1 in the ,zeitschrift fr ,wissen4 ,zoologie1 #ahfd1 ,bd4 ,,xiv4 ,heft ,,iii4 #agc ,the suggestion in the text has since received a striking confirmation in the observations of ,,sigmund ,,mayer on the regeneration of nerves4 ,the nerve when divided rapidly undergoes fatty degeneration1 which is succeeded by a transformation of the myeline and axis cylinder into a homogeneous mass2 in this resolved pulp new longitudinal lines of division appear1 which subsequently become new fibres1 and new nuclei are developed in the remains of the untransformed substance4--,archiv fr ,psychiatrie1 ,bd4 ,,vi4 ,heft ,,ii4 #agd ,strong confirmation of various statements in the text1 since they were written1 has been furnished by the researches of ,,eichhorst1 published in ,virchow's ,archiv1 ,,lxiv4 ,our knowledge of the development of nerve-tissue in human embryos is so scanty that these researches have a great value4 ,,eichhorst describes the striation of the cells in the cord to begin only at the fourth month2 up to this time they are1 what ,i find most invertebrate cells to be1 granular1 not fibrillar4 ,there is very slight branching of the cell processes until the ninth or tenth month1 when the multipolar aspect first appears2 the cells are unipolar up to the end of the fourth month4 ,the connection between the white columns and the gray columns is very loose up to the fifth month2 and the two are easily separated4 ,subsequently the union is closer4 ,the substance of the white columns readily separates into bundles and fibres1 but that of the gray columns falls into a granular detritus if attempted to be teased out with needles4 ,but after the fifth month this is no longer so4 ,instead of a granular detritus there appears a network of fine fibres and fibrils4 ,although the white posterior columns are developed before the fifth month1 not a single cell can be seen in the posterior gray columns until the second half of the ninth month4 7,yet the fibres are imagined to arise in the cells67 ,the passage from the granular to the fibrillar state is the same in the cell substance and the neuroglia4 ,the nerve-fibre1 as distinguished from a naked axis cylinder1 does not appear till the fourth month4 ,it is at first a bipolar prolongation of the nucleus4 ,as it elongates1 the nucleus seems to sit on it1 and so loosely that it is easily shifted away by pressure on the covering glass4 ,finally the fibre separates entirely from the nucleus1 and then begins to clothe itself with the medullary sheath4 ,very curious is the observation that so long as the axis cylinder is naked it is never varicose1 but with the development of the medulla the primitive axis becomes fluid4 #age ,,mayer1 ,op4 cit41 #cic4 ,i cannot1 however1 agree with ,,mayer when he says that the continuity of a nerve-fibre with a cell has never been distinctly shown 7p4 #cie72 in the ,invertebrata and in the ,electric fishes such a continuity is undeniable2 and it has occasionally been seen in ,vertebrata4 #agf ,,ranvier1 in the ,comptes ,rendus1 #ahge1 ,vol4 ,,lxxxi4 p4 #abgf4 ,this observation throws light on the fact that cell processes are sometimes seen entering nerve-roots 7 #abd74 ,the very remarkable observations of ,mr4 ,f4 ,,balfour1 ,on the ,development of the ,spinal ,nerves in ,elasmobranch ,fishes 7,philos4 ,trans41 ,vol4 ,,clxvi4 p4 #a71 show that the spinal root1 ganglion1 and nerve-trunk arise from histological changes in a mass of cells at first all alike2 not that ganglion-cells are formed and from their processes elongate into fibres4 ,the nerve1 he says1 forms a continuation of its root rather than of its ganglion 7p4 #aha72 which accords with ,,ranvier',s view4 #agg ,in the ,handbuch der menschlichen ,anatomie of ,w4 ,,krause1 which has just appeared1 ,i am pleased to find a similar view1 p4 #cgf4 #agh ,on this point consult ,,axel ,,key and ,,retzius1 in the ,archiv fr mikros4 ,anat41 #ahgc1 p4 #cjh1 where the nutritive disturbance is assigned to the fact that the lymph can no longer take its normal course4 ,,waller',s observations on the degeneration of the optic nerves1 with preservation of the integrity of the retina1 after division of the nerves 7,proceedings of ,royal ,society1 #ahef1 p4 #aj71 cannot be urged in support of his view1 because ,,berlin and ,,lebert',s observations are directly contradictory of his4 ,,saemisch und ,,graefe1 ,handbuch der ,augenheilkunde1 ,,ii4 #cdf4 ,it is said by ,,krenchel that if the nerves be divided1 so as to prevent disturbances in the circulation1 no peripheral degeneration takes place 7cited by ,,engelmann in ,pflger's ,archiv1 #ahge1 p4 #dgg74 #agi ,,schiff1 ,lehrbuch der ,physiologie1 pp4 #abj1 #aba4 #ahj ,k,,lliker1 ,gewebelehre1 #cag4 ,,schwalbe1 ,archiv fr mikros4 ,anat41 #ahfh1 p4 #ea4 #aha ,i was first shown this in #aheh by the late ,prof4 ,,harless in ,munich1 who at the same time showed me that the nerve thus bared of its sheath1 if left some hours in gastric juice1 split up into regular discs1 like the sarcous elements of muscles4 #ahb ,,stieda1 ,bau des centralen ,nervensystem der ,amphibien und ,reptilien1 #ahge1 p4 #da4 #ahc ,,butzke1 in ,archiv fr mikroskopische ,anatomie1 ,bd4 ,,iii4 ,heft #c1 p4 #eif4 #ahd ,except in the rare cases where there is anastomosis of the muscle-fibres2 as1 for example1 in the heart4 ,according to ,,engelmann',s remarkable researches1 the muscles of the heart form a continuum1 so that irritation is propagated from one to the other3 ,pflger's ,archiv1 #ahge1 p4 #dfe4 ,this is indubitably the case in the embryonic heart1 as ,,eckhard pointed out4 ,this ,i hold to be the main cause of its rhythmic pulsation after removal from the body4 ,whatever influence the ganglia may have in exciting this pulsation1 such influence would be powerless were not the muscles so connected2 as may be seen in the other organs which are richly supplied with ganglia1 yet do not move spontaneously2 and in organs 7such as the ureter or the embryonic heart1 and the hearts of invertebrata7 which move spontaneously1 yet have no ganglia4 #ahe ,,schr,,der ,,van ,,der ,,kolk1 ,bau und ,funktionen der ,med4 ,spinalis1 p4 #fg4 #ahf ,it is very instructive to learn that for some six months or so the rat is quite incapable of correctly localizing the pain4 #ahg ,,vulpian1 ,leons sur le ,systme ,nerveux1 p4 #bhh4 ,the experiment has been confirmed by ,,rosenthal1 and by ,,bidder 7,archiv fr ,anatomie1 #ahfe1 p4 #bdf71 who first 7in #ahdb7 attempted this union of different nerves1 but arrived at negative results2 as did ,,schiff 7,lehrbuch der ,physiol1 #ahei1 p4 #acd7 and ,,gluge et ,,thiernesse 7,annales des ,sciences ,naturelles1 #ahei1 p4 #aha74 #ahh ,,sachs1 in the ,archiv fr ,anat41 #ahgd1 pp4 #aie1 sq4 #ahi ,,laplace1 ,essai ,philos4 sur les ,probabilits1 p4 #bci4 #aij ,the mode of termination of nerves in muscles is still a point on which histologists disagree2 probably because there is no abrupt termination1 but a blending of the one tissue with the other4 ,in the ,tardigrades1 for example1 there is actually no appreciable distinction between nerve and muscle at the point of insertion of the nerve2 and if in the higher animals there is an appreciable difference between nerve and muscle1 there is an inseparable blending of undifferentiated substance at their point of junction4 ,according to ,,engelmann',s recent researches1 there seems good reason to suppose that muscles are composed of contractile substance and a substance which is a modification of axis-cylinder substance2 the first being doubly refracting1 the second isotropic3 ,pflger's ,archiv1 #ahge1 p4 #dcb4 #aia ,,schiff1 ,lehrbuch1 p4 #gc4 #aib ,,freusberg observed that the reflex movements in the legs of a dog whose spine had been divided were considerably lessened after food or drink4 ,they fell from #ie to #df pendulum-beats in a minute after a litre of water had been drunk4 ,see his instructive memoir1 ,reflex-,lhmungen beim ,hunde1 in ,pflger's ,archiv1 #ahgd1 p4 #cfi4 #aic ,m4 ,,herzen thus describes the effects of stimulating the vagus with varying intensities3 8,si l'on se sert de l'appareil de ,dubois ,raymond1 on commence par appliquer une irritation tellement faible qu'elle ne produit aucun effet2 on rapproche alors peu peu lea deux bobines de l'appareil avec le plus grand soin1 par fractions de centimtres1 par millimtres s'il le faut1 et l'on trouve ainsi le degr d'irritation qui accelre les battements du cur et qui produit le maximum de pulsations dans l'unit de temps admise pour l'exprience4 ,quand on est l il suffit d'un millimtre de plus pour faire disparatre l'augmentation1 un autre millimtre peut produire une diminution1 et un troisime peut arrter le cur compltement4 ,en reculant alors1 en loignant peu peu les deux bobines1 on rtourne la force qui produit l'augmentation des battements40 ,,herzen1 ,expriences sur les ,centres ,modrateurs de l',action ,rflexe1 #ahfd1 p4 #fh4 ,there have been serious doubts thrown on these experiments2 but several experimenters have confirmed their exactness4 ,quite recently they have been confirmed by ,,bulgheri1 ,il ,morgagni1 ,,viii42 and by ,,arloing and ,,tripier1 ,archives de ,physiologie1 #ahgb1 ,,iv4 p4 #dah4 ,it must be confessed1 however1 that the whole subject of the heart's innervation is at present very imperfectly understood4 #aid ,,cayrade1 ,recherches sur les ,mouvements ,rflexes1 #ahfd1 p4 #eh4 #aie ,a frog's brain is removed1 and the body then suspended by the lower jaw1 the legs are allowed to dip into a slightly acidulated liquid1 the chemical action of which stimulates the skin4 #aif ,i saw a patient in the ,berlin ,charit whose face and left hand were in a constant state of convulsive twitching1 but no sooner was a scar on the left hand 7where the nerve had been divided7 firmly pressed than the twitchings ceased1 and pain was felt2 on removal of the pressure1 pain ceased and the twitchings returned4 #aig ,pflger's ,archiv1 #ahge4 ,no one interested in the ,reflex ,theory should omit a careful study of the papers by ,,freusberg and ,,goltz4 ,i have drawn freely from them4 #aih ,sir ,,james ,,paget has an interesting collection of facts which illustrate this ,law of ,arrest1 in his paper on 8,stammering with other ,organs than those of ,speech10 ,british ,medical ,journal1 #ahfh1 ,vol4 ,,ii4 p4 #dcg1 reprinted in his ,clinical ,lectures and ,essays1 #ahge1 p4 #gg4 #aii ,archives de ,physiol41 #ahfh1 p4 #aeg4 #bjj ,west ,riding ,lunatic ,asylum ,reports1 #ahgd1 p4 #bjj4 #bja ,,claude ,,bernard1 ,systme ,nerveux1 ,i4 #chc4 #bjb ,see the excellent remarks of ,dr4 ,,lauder ,,brunton on this point in his paper on ,inhibition in the ,west ,riding ,lunatic ,asylum ,reports1 #ahgd1 p4 #ahj4 #bjc ,the interesting question of interference has been experimentally treated by ,,wundt in his recently published ,mechanik der ,nerven1 #ahgf1 and theoretically as wave-movement by ,,medem1 ,grundzge einer exakten ,psychologie1 #ahgf4 #bjd ,on the distinction between first notions and theoretic conceptions1 see ,problems of ,life and ,mind1 ,vol4 ,,ii4 p4 #bgg4 #bje ,not transcendental and a priori1 as ,kant teaches2 but immanent in ,feeling4 #bjf ,the reader will understand that although mechanical relations are modes of ,feeling1 as all other relations are1 yet their aspect is exclusively objective1 referring to objects ideally detached from subjects4 #bjg ,,antoine ,,cros1 ,les ,fonctions suprieures du ,systme nerveux1 #ahge1 p4 #he4 #bjh ,the solution offered in the present chapter was first offered in ,problems of ,life and ,mind1 #ahge1 ,,ii4 #dfe1 sq4 ,i mention this because since the publication of that volume other writers have expressed the same ideas1 sometimes using my language and illustrations3 e4 g4 ,m4 ,,taine in the ,revue ,philosophique1 ,january1 #ahgg1 art41 ,les ,vibrations crbrales et la ,pense4 #bji ,problems of ,life and ,mind1 ,vol4 ,,ii4 pp4 #ddc and #dhb4 #baj 8,the retinal image is the last effect known of the action of objects on us2 what happens beyond the retina we know not2 our knowledge of the objective process has at present here its limit40--,,ewald ,,hering1 ,beitrge zur ,physiologie1 #ahfb1 p4 #aff4 ,that is to say1 we have a definite translation of the process in geometric terms as far as the retina1 and thence onwards ,geometry fails us1 and ,neurology and ,psychology are invoked4 #baa ,compare ,,problem ,,ii4 ,chap4 ,,iv4 #bab 8,das ,bewusstwerden ist nichts ,anderes als ein weiter fortgeschrittenes ,erinnern oder ,neuwerden des von aussen aufgenommenen ,wissens1 ein innerliches ,wissen dieses ,wissens oder ein in sich reflectirtes ,wissen40--,,jessen1 ,versuch einer ,wissenschaftlichen ,begrndung der ,psychologie1 #ahee1 p4 #dgg4 #bac ,in common language a stone or a tree is said to be unconscious2 but this is an anthropomorphic extension of the term4 ,in strictness we should no more speak of unconsciousness outside the sphere of ,sentience than of darkness outside the sphere of ,vision4 #bad ,the contraction may be effected in the eye out of the organism4 ,see p4 #bbi4 ,it is then no reflex4 #bae ,glasgow ,medical ,journal1 #aheg1 p4 #dea4 ,see also further on1 note to p4 #dbf4 #baf ,,mayer1 ,die ,elementarorganisation des ,seelenorgans1 p4 #ab1 is the authority for the last statement4 #bag ,allgemeine ,zeitschrift fr ,psychiatrie1 ,bd4 #ca1 p4 #gaa4 #bah ,,aubert1 ,grundrge der physiol4 ,optik1 #ahgf1 p4 #fcc4 8,the accommodative movement of the eye is to be considered voluntary4 ,it is true we contract the pupil without being conscious of the contraction of muscular fibres1 but this holds good for every voluntary movement4 ,when a person raises the tone of his voice he is not conscious that by muscular contraction he makes his chord vocales more tense2 he attains his object without being aware of the means by which he does so4 ,the same is applicable to accommodation for near objects and to the contraction of the pupil accompanying it4 ,the fact that this last is only an associated movement does not deprive it of its voluntary character1 for there is perhaps no single muscle which can contract entirely by itself40 ,,donders1 ,on the ,anomalies of ,accommodation1 #ahfd1 p4 #egd4 ,professor ,,beer of ,bonn has the rare power of contracting or dilating the pupils of his eye at will2 here ideas act as motors4 ,when he thinks of a very dark space the pupil dilates1 when of a very bright spot the pupil contracts4 7,,noble1 ,the ,human ,mind1 #aheh1 p4 #abd47 ,i believe this to be only an exaggerated form of the normal tendency4 ,in all of us the mechanism is so disposed that the feelings of dilatation are associated with feelings 7and consequently ideas7 of darkness2 and by this association a reversal of the process obtains1 so that the idea of darkness calls up the feeling it symbolizes4 #bai ,,spencer1 ,principles of ,psychology1 ,i4 #dii4 #bbj ,,descartes expressly calls them sensitive machines4 ,he refuses them ,thought1 but neither 8la vie ou le sentiment40 ,he adds1 8,mon opinion n'est pas que les btes voient comme nous lorsque nous sentons que nous voyons40--uvres1 ,,iv4 p4 #cci4 ,this example is cited by him in proof of human automatism3 8,que ce n'est point par l'entremise de notre me que les yeux se ferment1 puisque c'est contre notre volont1 laquelle est sa seule ou du moins sa principale action2 mais c'est cause que la machine de notre corps est tellement compose que le mouvement de cette main vers nos yeux excite un autre mouvement en notre cerveau qui conduit les esprits animaux dans les muscles qui font abaisser les paupires40 ,all indeed that we assign to ,sensibility1 he assigns to these hypothetical animal spirits1 and thence he concludes1 8,qu'il ne reste rien en nous que nous devions attribuer notre me sinon nos penses40--,les ,passions de l'me1 art4 #ac and #ag4 ,comp4 ,discours de la ,mthode1 partie iv4 #bba ,,descartes compares the animal mechanism to that of the grottos and fountains at ,versailles1 the nerves to the water-tubes3--8,les objets extrieurs qui par leur seul prsence1 agissent contre les organes des sens1 et qui par ce moyen1 la dterminent se mouvoir en plusieurs diverses faons1 selon comme les parties du cerveau sont disposes1 sont comme les trangers1 qui entrant dans quelques unes des grottes de ces fontaines causent euxmmes sans y penser les mouvements qui s'y font en leur prsence3 car ils n'y peuvent entrer qu'en marchant sur certains carreaux tellement disposs1 que s'ils approchent d'une ,diane qui se baigne1 ils la font cacher dans les roseaux2 et s'ils passent outre pour la poursuivre1 ils feront venir vers eux un ,neptune qui les menacera de son trident2 ou s'ils vont de quelque autre cost1 ils en feront sortir un monstre marin qui leur vomira de l'eau contre la face40--,trait de l',homme1 #affd1 p4 #ab4 ,ingenious as the comparison is1 it only illustrates how machines may be constructed to imitate animal actions4 ,diana always hides herself when a certain spot is trodden upon2 and ,neptune always appears when another spot is trodden upon4 ,there is no fluctuation1 no sensibility discerning differences and determining variations4 ,compare the following experiment3 ,a monkey was placed on the table and a shrill whistle made close to its ear3 8,immediately the ear was pricked and the animal turned with an air of intense surprise1 with eyes widely opened and pupils dilated1 to the direction whence the sound proceeded4 ,on repetition of the experiment several times1 though the pricking of the ear and the turning of the head and eyes constantly occurred1 the look of surprise and dilatation of the pupils ceased to be manifested40--,,ferrier1 ,the ,functions of the ,brain1 #ahgf1 p4 #aga4 ,a mechanical monkey would always have reacted in precisely the same way on each stimulus4 #bbb ,printed in the ,fortnightly ,review1 ,november1 #ahgd1 from which all my citations are made4 #bbc ,,schiff1 ,lehrbuch der ,physiol41 #aheh1 p4 #bab4 ,,hermann1 ,physiology1 translated by ,,gamgee1 #ahge1 p4 #eaa4 #bbd ,meanwhile the reader is referred to ,,schr,,der ,,van ,,der ,,kolk1 ,pathologie der ,geisteskrankheiten1 #ahfc1 p4 #ea2 or ,,jessen1 ,physiologie des menschlichen ,denkens1 #ahgb1 p4 #ff4 #bbe ,,griesinger1 ,les ,maladies ,mentales1 p4 #if4 #bbf ,m4 ,,luys cites the case of a patient who conversed quite rationally with a visitor 8sans en avoir conscience1 et ne se souvenait de rien02 and he draws the extraordinary conclusion that the conversation 8s'oprait en vertu des forces rflexes40--tudes de ,physiologie et de ,pathologie ,crbrales1 #ahgd1 p4 #aag4 ,is it not obvious that the patient must have been conscious at the time1 though the consciousness vanished like that in a dream8 ,the persistent consciousness is the continuous linking on of one state with previous states--the apperception of the past4 #bbg ,,abercrombie1 ,inquiries concerning the ,intellectual ,powers1 #ahdj1 p4 #aea4 ,,wigan1 ,the ,duality of the ,mind1 #ahdd1 p4 #bgj4 ,,despine1 ,la ,psychologie ,naturelle1 #ahfh1 ,i4 #ed4 #bbh ,dr4 ,,hughlings ,,jackson has quite recently cited some curious examples in his own practice4 ,see ,west ,riding ,lunatic ,asylum ,reports for #ahge4 #bbi ,,problems1 ,vol4 ,,ii4 p4 #dgh1 sq4 #bcj 8,le sentiment fait natre le mouvement1 et le mouvement donne naissance au sentiment40--,,van ,,deen1 ,traits et ,dcouvertes sur la ,molle pinire1 #ahda1 p4 #ajb4 #bca ,dr4 ,,carpenter tells a similar story of ,admiral ,,codrington1 who1 when a midshipman1 could always be awakened from the profoundest slumber if the word 8signal0 were uttered2 whereas no other word disturbed him4 #bcb ,compare an interesting personal example given by ,,jouffroy1 quoted in ,sir ,w4 ,,hamilton',s ,lectures1 ,i4 #cca4 #bcc ,lancet1 #ajth ,july1 #aheh4 #bcd ,,marshall ,,hall in ,philos4 ,trans41 #ahcc4 ,lectures on the ,nervous ,system and its ,diseases1 #ahcf4 ,new ,memoir on the ,nervous ,system1 #ahdc4 #bce ,m,,ller1 ,physiology1 ,i4 #gba4 #bcf ,it is better simply to remove the brain1 than to remove the whole head1 which causes a serious loss of blood4 ,an etherized animal may be operated on with ease and accuracy4 ,for many experiments1 mere division of the spinal cord is better than decapitation4 ,great variations in the results must be expected1 because the condition of the animal1 its age and sex--whether fasting or digesting--whether the season be spring or summer--and a hundred other causes1 complicate the experiment4 #bcg ,,volkmann1 quoted by ,,pfl,,ger4 #bch ,,unzer1 ,the ,principles of ,physiology 7translated for the ,sydenham ,society71 p4 #bce4 #bci ,even so eminent an investigator as ,,goltz has fallen into this confusion4 ,he introduces an experiment to prove that the brainless frog is insensible to pain by the words 8when an animal1 placed under circumstances which would be very painful1 makes no movement1 although quite capable of moving1 the least we can say is that it is improbable that the animal has sensation0 7,nervencentren des ,frosches1 p4 #abg74 ,i need not discuss the proof itself1 having already done so in ,nature1 ,vol4 ,,ix4 p4 #hd4 ,the point to which ,i wish to call attention is the confusion of insensibility in general with insensibility to pain4 #bdj ,see ,,duchenne1 ,de lectrisation localise1 p4 #cih4 ,,griesinger cites various examples of insane patients who have burned the flesh off their bones while manifesting a total indifference to these injuries4 ,maladies ,mentales1 p4 #id4 ,,falret says1 8,nous avons vu plusieurs fois des alins s'inciser1 s'amputer eux-mmes diverses parties du corps sans paratre ressentir aucune souffrance40 ,leons cliniques de ,mdicine ,mentale1 #ahed1 ,i4 #ahi4 ,patients incapable of feeling the contact of a hot iron with their skin have felt subjective burnings in the skin thus objectively insensible4 #bda ,,cros1 ,les ,fonctions suprieures du ,syst4 nerveux1 #ahge1 p4 #bg4 #bdb ,virchow's ,archiv1 ,bd4 ,,xxviii4 p4 #cj4 #bdc ,the idea of a fixed anatomical mechanism for reflexion1 such as that of an excito-motory system1 is completely refuted by the fact that the gray substance may anywhere be cut sway1 and yet so long as a small bridge of gray substance remains the stimulation will be propagated through it4 ,the idea of a fixed pathway is also refuted by the fact of the variations in the reflex responses1 and the necessary irradiation even for very simple reflexes4 ,take1 for example1 that of breathing4 ,an irritation of the bronchial filaments is transmitted by the pneumogastric to its centre in the medulla oblongata2 from this1 however1 it is immediately irradiated downwards to the cervical and dorsal regions1 which innervate the muscles of chest and diaphragm1 and upwards to the brain1 whether the stimulation awaken consciousness or not4 ,one may say1 indeed1 that inasmuch as under normal conditions the bronchial irritation always causes a movement of a particular group of muscles1 there is to this extent a fixed pathway of discharge2 but1 as ,i have formerly explained1 this is only an expression of the particular tension of particular centres1 and is variable with that tension2 the other centres are also affected1 even when they are not excited to discharge4 #bdd ,,lallemand1 ,recherches sur ,l',encphale1 ,,iii4 #caj4 #bde ,west ,riding ,lunatic ,asylum ,reports1 #ahge1 ,vol4 ,v4 pp4 #beb1 sq4 #bdf ,,gall et ,,spurzheim1 ,anat4 et ,physiol4 du ,systme ,nerveux1 ,i4 #hc4 #bdg ,printed in the ,british and ,foreign ,medical ,review1 ,jan4 #ahde4 #bdh ,,griesinger1 ,abhandlungen1 #ahgb4 ,the first volume contains a reprint of this memoir4 #bdi ,,landry1 ,trait des ,paralysies1 ,i4 #ee4 ,conf4 ,,ziemssen1 ,chorea in the ,handbuch der speciellen ,pathologie1 ,bd4 ,,xii4 #b1 p4 #djh4 ,and ,,luys1 tudes de physiol4 et pathol4 crbrales1 #ahgd1 pp4 #hi-id4 #bej ,,sue1 ,recherches ,philosophiques sur la ,vitalit et le ,galvanisme1 p4 #i4 ,he was not consistent1 however1 but adopted ,bichat's opinion respecting the sensibility of the viscera1 p4 #fh4 #bea ,,legallois1 ,expriences sur le principe de la vie4 ,published1 ,i conclude1 in #ahaa2 the edition ,i use is the one printed in the ,encyclopdie des ,sciences ,medicales1 ,,iv4 #beb ,,wilson ,,philip1 ,experimental ,inquiry into the ,laws of the ,vital ,functions1 pp4 #bji1 #baj4 #bec ,,longet1 ,trait de ,physiologie1 ,,ii4 #aje4 #bed ,he cites ,cuvier1 ,majendie1 ,deamoulins1 and ,mayo as maintaining this error4 #bee ,,grainger1 ,structure and ,functions of the ,spinal ,cord1 p4 #ff4 #bef ,,nasse1 ,unters4 zur ,physiologie und ,pathologie1 ,vol4 ,,ii4 ,part #b4 #beg ,,carus1 ,system der ,physiologie1 ,,iii4 #aja4 #beh ,j4 ,w4 ,,arnold1 ,die ,lehre von der ,reflex-,function1 #hf4 #bei ,,pfl,,ger1 ,die sensorischen ,functionen des ,rckenmarks der ,wirbelthiere4 #bfj ,except ,,auerbach1 who repeated and varied the experiments2 and ,,funke1 who partially adopted the conclusions in his systematic treatise on ,physiology4 #bfa ,,schiff1 ,lehrbuch der ,physiologie1 #bjh4 #bfb ,,landry1 ,trait des ,paralysies1 #ahei1 maintains that the cord is a centre of sensation1 and that there is in it a faculty analogous to the perception and judgment of the brain4 ,compare pp4 #afc et sq4 and #cje4 ,he also cites an essay by ,dr4 ,,paton of ,edinburgh 7,edinburgh ,medical ,journal1 #ahdf71 in which the sensational and volitional claims of the spinal cord are advanced4 #bfc ,,goltz1 ,beitrge zur ,lehre von den ,functionen der ,nervencentren des ,froeches1 #ahfi4 #bfd ,pflger's ,archiv1 ,bd4 ,,xiv4 p4 #aeh4 #bfe ,see ,prob4 ,,ii4 #ahc4 #bff 8,il y a donc une mmoire par le cerveau et une mmoire par l'automate4 ,tous les organes ont une mmoire propre1 c'est dire une tendance reproduire les sries d'actes qu'ils ont plusieurs fois executs40--,,gratiolet1 ,anat4 du ,systme ,nerveux1 #aheg1 p4 #dfd4 #bfg ,to obviate misunderstanding let me say that1 unless the contrary is specified1 ,i use the term ,brain throughout this argument as equivalent to the cerebral hemispheres1 because it is in these that sensation1 volition1 and consciousness are localized by the generality of writers1 many of whom1 indeed1 regard the cells of the gray matter of the convolutions as the exclusive seat of these phenomena1 dividing these cells into sensational1 emotional1 and intellectual4 ,there are physiologists who extend sensation to the cerebral ganglia and gray masses of the medulla oblongata2 but the medulla spinalis is so clearly continuous with the medulla oblongata that there is a glaring inconsistency in excluding sensation from the one if it is accorded to the other2 and the grounds on which sensitive phenomena are admitted in the absence of the hemispheres1 force us to admit analogous phenomena in the absence of the ganglia and medulla oblongata3 in each case the phenomena are less complex and varied as the mechanisms become less complex4 #bfh ,compare ,,lussana e ,,lemoigne1 ,fisiologia dei centri encefalici1 #ahga1 ,,ii4 #bci1 #bdj1 #ccj4 #bfi ,see a very interesting case of this special loss of memory in a priest who still occupied himself reading classic authors and performing his official duties many months after an injury to the brain4 ,,lussana e ,,lemoigne1 ,fisiologia dei centri encefalici1 ,i4 #bja4 #bgj ,,bouillaud1 ,recherches ,exprimentales sur les ,fonctions du ,cerveau en gnral1 #ahcj1 p4 #e1 sq4 #bga ,,longet1 ,trait de ,physiologie1 ,,ii4 #bdj4 #bgb ,,dalton1 ,human ,physiology1 ,philadelphia1 #ahei1 p4 #cfb4 #bgc ,,dalton1 p4 #cfb4 #bgd ,,dalton1 p4 #cfc4 #bge ,,flourens1 p4 #hi4 #bgf ,,leyden in the ,berliner klinische ,wochenschrift1 #ahfg1 ,no4 #g4 ,,meissner1 ,jahresbericht ber ,physiol41 #ahfg1 p4 #daj4 #bgg ,,voit in the ,sitzungsberichte der ,mnchener ,academie1 #ahfh1 p4 #aje4 ,comp4 also ,,goltz in ,pflger's ,archiv1 ,bd4 ,,xiv4 #dce4 #bgh ,,vulpian1 ,systme ,nerveux1 #edb-dh4 #bgi ,for other examples see ,,gintrac1 ,pathologie ,interne1 #ahfh1 ,,vi4 #ea-eg4 #bhj ,if the water is perfectly still the fish sinks to the bottom and remains motionless until the water be stirred4 ,mere contact does not suffice2 there must be intermittent pulses from the moving water4 #bha ,,lussana e ,,lemoigne1 ,op4 cit41 ,i4 #ae4 #bhb ,archives de ,physiologie1 #ahfi1 p4 #eci4 #bhc ,,br,,cke1 ,physiologie1 ,,ii4 p4 #ec4 ,while these sheets are passing through the press1 ,,goltz has published his second series of experiments on the brain4 ,the following detail is a good illustration of what is said in the text3 ,a dog deprived of a portion of both hemispheres displayed a marked imperfection in the execution of ordinary instincts4 ,although sight was impaired he could see1 and recognize men and certain objects3 the sight of a whip made him cower1 but the sight of meat did not suffice to set the feeding mechanism in action4 ,when meat was suspended above his head1 the scent caused him to sniff about in search1 but he failed to find it1 and even when he was so placed that he could see the suspended meat1 the unusual impression failed to guide him4 ,if the meat were held towards him1 or placed before him in a dish1 he took it at once--this being the customary stimulation4 ,so also1 if the hand were held up1 in the usual way when dogs are made to leap for food1 this dog sprang vigorously up and caught the food2 but he would spring up in the same way when the hand was held empty1 and continue fruitlessly springing1 whereas an uninjured dog ceases to spring when he sees the hand is empty4--,pflger's ,archiv1 ,bd4 ,,xiv4 p4 #dai4 #bhd ,,gratiolet1 ,anat4 ,compare du ,systme ,nerveux1 #aheg1 p4 #dei4 #bhe ,,lussana e ,,lemoigne1 ,op4 cit41 ,i4 #cfc4 #bhf ,virchow's ,archiv1 ,bd4 ,,lx4 pp4 #acj-cc4 ,yet there are many physiologists who persist in placing the motorium commune in the corpora strata6 ,and they place the sensorium commune in the optic thalami1 although1 not to mention the ambiguous evidence of ,pathology1 the experiments of ,,nothengel and ,,veyssi,,re show that destruction of the thalami does not destroy sensation4 ,see ,,veyssi,,re1 ,recherches sur l'hmianesthsie de cause crbrale1 #ahgd1 pp4 #hc1 #hd4 ,i may observe1 in passing1 that the notion of the corpora striata being the necessary channel for volitional impulses1 and the optic thalami for reflex actions1 is utterly disproved by the experimental evidence recorded in the text1 as well as in #ff4 #bhg ,pflger's ,archiv1 ,bde4 ,,viii4 and ,,ix4 ,transcriber's ,notes ,punctuation1 hyphenation1 and spelling were made consistent when a predominant preference was found in the original book2 otherwise they were not changed4 ,simple typographical errors were corrected2 unbalanced quotation marks were remedied when the change was obvious1 and otherwise left unbalanced4 ,illustrations in this e,book have been positioned between paragraphs and nearer to the text that references them4 ,footnotes in this e,book have been collected and moved to the end of the book4 ,the ,table of ,contents entry for ,problem ,,ii1 ,chapter ,,ii1 referenced the wrong page2 corrected here4