,physiology and ,hygiene for ,secondary ,schools by ,francis ,m4 ,walters1 ,a4,m4 ,edition #a1 7,november #ae1 #bjje7 ,d4,c4 ,heath and ,co4 - ,publishers ,original copyright #aiji ,it is quite possible to give instruction in this subject in such a manner as not only to confer knowledge which is useful in itself1 but to serve the purpose of a training in accurate observation1 and in the methods of reasoning of physical science4--,huxley4 ,,preface ,the aim in the preparation of this treatise on the human body has been1 first1 to set forth in a teachable manner the actual science of physiology2 and second1 to present the facts of hygiene largely as applied physiology4 ,the view is held that right living consists in the harmonious adjustment of one's habits to the nature and plan of the body1 and that the best preparation for such living is a correct understanding of the physical self4 ,it is further held that the emphasizing of physiology augments in no small degree the educative value of the subject1 greater opportunity being thus afforded for exercise of the reasoning powers and for drill in the modus operandi of natural forces4 ,in the study of physiology the facts of anatomy have a place1 but in an elementary course these should be restricted to such as are necessary for revealing the general structure of the body4 ,although no effort has been spared to bring this work within the comprehension of the pupil1 its success in the classroom will depend largely upon the method of handling the subject by the teacher4 ,it is recommended1 therefore1 that the relations which the different organs and processes sustain to each other1 and to the body as a whole1 be given special prominence4 ,the pupil should be impressed with the essential unity of the body and should see in the diversity of its activities the serving of a common purpose4 ,in creating such an impression the introductory paragraphs at the beginning of many of the chapters and the summaries throughout the book1 as well as the general arrangement of the subject-matter1 will be found helpful4 ,since the custom largely prevails of teaching physiology in advance of the sciences upon which it rests--biology1 physics1 and chemistry--care should be exercised to develop correct ideas of the principles and processes derived from these sciences4 ,too much latitude has been taken in the past in the use of comparisons and illustrations drawn from everyday life4 ,to teach that the body is a house1 machine1 or city2 that the nerves carry messages2 that the purpose of oxygen is to burn up waste2 that breathing is to purify the blood1 etc41 may give the pupil phrases which he can readily repeat1 but teaching of this kind does not give him correct ideas of his body4 ,the method of teaching1 however1 that uses the pupil's experience as a basis upon which to build has a value not to be overlooked4 ,the fact that such expressions as those quoted above are so easily remembered proves the value of connecting new knowledge with the pupil's experience4 ,but the inadequacy of this experience must be recognized and taken into account4 ,the concepts of the average pupil are entirely too indefinite and limited to supply the necessary foundation for a science such as physiology4 ,herein lies the great value of experiments and observations4 ,they supplement the pupil's experience1 and increase both the number and definiteness of his concepts4 ,no degree of success can be attained if this phase of the study is omitted4 ,the best results in physiology teaching are of course attained where laboratory work is carried on by the pupils1 but where this cannot be arranged1 class experiments and observations must suffice4 ,the ,practical ,work described at the close of most of the chapters is mainly for class purposes4 ,while these serve a necessary part in the development of the subject1 it is not essential that all of the experiments and observations be made1 the intention being to provide for some choice on the part of the teacher4 ,a note-book should be kept by the pupil4 ,to adapt the book to as wide a range of usefulness as possible1 more subject-matter is introduced than is usually included in an elementary course4 ,such portions1 however1 as are unessential to a proper understanding of the body by the pupil are set in small type1 to be used at the discretion of the teacher4 ,the use of books of reference is earnestly recommended4 ,for this purpose the usual high school texts may be employed to good advantage4 ,a few more advanced works should1 however1 be frequently consulted4 ,for this purpose ,martin's ,human ,body 7,advanced ,course71 ,rettger's ,advanced ,lessons in ,physiology1 ,thornton's ,human ,physiology1 ,huxley's ,lessons in ,elementary ,physiology1 ,howell's ,a ,text-book of ,physiology1 ,hough and ,sedgwick's ,hygiene and ,sanitation1 and ,pyle's ,personal ,hygiene will be found serviceable4 ,in the preparation of this work valuable assistance has been rendered by ,dr4 ,c4,n4 ,mc,allister1 ,department of ,psychology1 and by ,professor ,b4,m4 ,stigall1 ,department of ,biology1 along the lines of their respective specialties1 and in a more general way by ,president ,w4,j4 ,hawkins and others of the ,warrensburg1 ,missouri1 ,state ,normal ,school4 ,expert advice from ,professor ,s4,d4 ,magers1 ,instructor in ,physiology and ,bacteriology1 ,state ,normal ,school1 ,ypsilanti1 ,michigan1 has been especially helpful1 and many practical suggestions from the high school teachers of physiology of ,kansas ,city1 ,missouri1 ,professor ,c4,h4 ,nowlin1 ,central ,high ,school1 ,dr4 ,john ,w4 ,scott1 ,westport ,high ,school1 and ,professor ,a4,e4 ,shirling1 ,manual ,training ,high ,school1 all of whom read both manuscript and proofs1 have been incorporated4 ,considerable material for the ,practical ,work1 including the respiration experiment 7page #aja7 and the reaction time experiment 7page #cbc71 were contributed by ,dr4 ,scott4 ,professor ,nowlin's suggestions on subject-matter and methods of presentation deserve special mention4 ,to these and many others the author makes grateful acknowledgment4 ,f4,m4,w4 ,,missouri ,,state ,,normal ,,school1 ,,second ,,district1 ,may #a1 #aiji4 ,,contents ,preface ,contents ,,part ,i3 ,,the ,,vital ,,processes ,,chapter ,i - ,,introduction ,,chapter ,,ii - ,,general ,,view ,,of ,,the ,,body ,,chapter ,,iii - ,,the ,,body ,,organization ,,chapter ,,iv - ,,the ,,blood ,,chapter ,v - ,,the ,,circulation ,,chapter ,,vi - ,,the ,,lymph ,,and ,,its ,,movement ,,through ,,the ,,body ,,chapter ,,vii - ,,respiration ,,chapter ,,viii - ,,passage ,,of ,,oxygen ,,through ,,the ,,body ,,chapter ,,ix - ,,foods ,,and ,,the ,,theory ,,of ,,digestion ,,chapter ,x - ,,organs ,,and ,,processes ,,of ,,digestion ,,chapter ,,xi - ,,absorption1 ,,storage1 ,,and ,,assimilation ,,chapter ,,xii - ,,energy ,,supply ,,of ,,the ,,body ,,chapter ,,xiii - ,,glands ,,and ,,the ,,work ,,of ,,excretion ,,part ,,ii3 ,,motion1 ,,coordination1 ,,and ,,sensation ,,chapter ,,xiv - ,,the ,,skeleton ,,chapter ,,xv - ,,the ,,muscular ,,system ,,chapter ,,xvi - ,,the ,,skin ,,chapter ,,xvii - ,,structure ,,of ,,the ,,nervous ,,system ,,chapter ,,xviii - ,,physiology ,,of ,,the ,,nervous ,,system ,,chapter ,,xix - ,,hygiene ,,of ,,the ,,nervous ,,system ,,chapter ,,xx - ,,production ,,of ,,sensations ,,chapter ,,xxi - ,,the ,,larynx ,,and ,,the ,,ear ,,chapter ,,xxii - ,,the ,,eye ,,chapter ,,xxiii - ,,the ,,general ,,problem ,,of ,,keeping ,,well ,,appendix ,,index ,,physiology ,,and ,,hygiene ,,part ,i3 ,,the ,,vital ,,processes ,,chapter ,i - ,,introduction ,to derive strength equal to the daily task2 to experience the advantages of health and avoid the pain1 inconvenience1 and danger of disease2 to live out contentedly and usefully the natural span of life3 these are problems that concern all people4 ,they are1 however1 but different phases of one great problem--the problem of properly managing or caring for the body4 ,to supply knowledge necessary to the solution of this problem is the chief reason why the body is studied in our public schools4 99,divisions of the ,subject499--,the body is studied from three standpoints3 structure1 use of parts1 and care or management4 ,this causes the main subject to be considered under three heads1 known as anatomy1 physiology1 and hygiene4 ,anatomy treats of the construction of the body--the parts which compose it1 what they are like1 and where located4 ,its main divisions are known as gross anatomy and histology4 ,gross anatomy treats of the larger structures of the body1 while histology treats of the minute structures of which these are composed--parts too small to be seen with the naked eye and which have to be studied with the aid of the microscope4 ,physiology treats of the function1 or use1 of the different parts of the body--the work which the parts do and how they do it--and of their relations to one another and to the body as a whole4 ,hygiene treats of the proper care or management of the body4 ,in a somewhat narrower sense it treats of the laws of health4 ,hygiene is said to be personal1 when applied by the individual to his own body2 domestic1 when applied to a small group of people1 as the family2 and public1 or general1 when applied to the community as a whole or to the race4 99,the ,general ,aim of ,hygiene499--,there are many so-called laws of health1 and for these laws it is essential in the management of the body to find a common basis4 ,this basic law1 suggested by the nature of the body and conditions that affect its well-being1 may be termed the ,law of ,harmony3 ,the mode of living must harmonize with the plan of the body4 ,to live properly one must supply the conditions which his body1 on account of its nature and plan1 requires4 ,on the other hand1 he must avoid those things and conditions which are injurious1 i4e41 out of harmony with the body plan4 ,to secure these results1 it is necessary to determine what is and what is not in harmony with the plan of the body1 and to find the means of applying this knowledge to the everyday problems of living4 ,such is the general aim of hygiene4 ,stated in other words3 ,hygiene has for its general aim the bringing about of an essential harmony between the body and the things and conditions that affect it47#a7 99,relation of ,anatomy and ,physiology to the ,study of ,hygiene499--,if the chief object in studying the body is that of learning how to manage or care for it1 and hygiene supplies this information1 why must we also study anatomy and physiology8 ,the answer to this question has already been in part suggested4 ,in order to determine what things and conditions are in harmony with the plan of the body1 we must know what that plan is4 ,this knowledge is obtained through a study of anatomy and physiology4 ,the knowledge gained through these subjects also renders the study of hygiene more interesting and valuable4 ,one is enabled to see why and how obedience to hygienic laws benefits1 and disobedience to them injures1 the body4 ,this causes the teachings of hygiene to be taken more seriously and renders them more practical4 ,in short1 anatomy and physiology supply a necessary basis for the study of hygiene4 99,advantages of ,properly ,managing the ,body499--,one result following the mismanagement of the body is loss of health4 ,but attending the loss of health are other results which are equally serious and far-reaching4 ,without good health1 people fail to accomplish their aims and ambitions in life2 they miss the joy of living2 they lose their ability to work and become burdens on their friends or society4 ,the proper management of the body means health1 and it also means the capacity for work and for enjoyment4 ,not only should one seek to preserve his health from day to day1 but he should so manage his body as to use his powers to the best advantage and prolong as far as possible the period during which he may be a capable and useful citizen4 ,,chapter ,,ii - ,,general ,,view ,,of ,,the ,,body 99,external ,divisions499--,examined from the outside1 the body presents certain parts1 or divisions1 familiar to all4 ,the main1 or central1 portion is known as the trunk1 and to this are attached the head1 the upper extremities1 and the lower extremities4 ,these in turn present smaller divisions which are also familiar4 ,the upper part of the trunk is known as the thorax1 or chest1 and the lower part as the abdomen4 ,the portions of the trunk to which the arms are attached are the shoulders1 and those to which the legs are joined are the hips1 while the central rear portion between the neck and the hips is the back4 ,the fingers1 the hand1 the wrist1 the forearm1 the elbow1 and the upper arm are the main divisions of each of the upper extremities4 ,the toes1 the foot1 the ankle1 the lower leg1 the knee1 and the thigh are the chief divisions of each of the lower extremities4 ,the head1 which is joined to the trunk by the neck1 has such interesting parts as the eyes1 the ears1 the nose1 the jaws1 the cheeks1 and the mouth4 ,the entire body is inclosed in a double covering1 called the skin1 which protects it in various ways4 99,the ,tissues499--,after examining the external features of the body1 we naturally inquire about its internal structures4 ,these are not so easily investigated1 and much which is of interest to advanced students must be omitted from an elementary course4 ,we may1 however1 as a first step in this study1 determine what kinds of materials enter into the construction of the body4 ,for this purpose the body of some small animal should be dissected and studied4 7,see observation at close of chapter47 ,the different materials found by such a dissection correspond closely to the substances1 called tissues1 which make up the human body4 ,the main tissues of the body1 as ordinarily named1 are the muscular tissue1 the osseous tissue1 the connective tissue1 the nervous tissue1 the adipose tissue1 the cartilaginous tissue1 and the epithelial and glandular tissue4 ,most of these present different varieties1 making all together some fifteen different kinds of tissues that enter into the construction of the body47#b7 99,general ,purposes of the ,tissues499--,the tissues1 first of all1 form the body4 ,as a house is constructed of wood1 stone1 plaster1 iron1 and other building materials1 so is the body made up of its various tissues4 ,for this reason the tissues have been called the building materials of the body4 ,in addition to forming the body1 the tissues supply the means through which its work is carried on4 ,they are thus the working materials of the body4 ,in serving this purpose the tissues play an active rle4 ,all of them must perform the activities of growth and repair1 and certain ones 7the so-called active tissues7 must do work which benefits the body as a whole4 99,purposes of the ,different ,tissues499--,in the construction of the body and also in the work which it carries on1 the different tissues are made to serve different purposes4 ,the osseous tissue is the chief substance in the bony framework1 or skeleton1 while the muscular tissue produces the different movements of the body4 ,the connective tissue1 which is everywhere abundant1 serves the general purpose of connecting the different parts together4 ,cartilaginous tissue forms smooth coverings over the ends of the bones and1 in addition to this1 supplies the necessary stiffness in organs like the larynx and the ear4 ,the nervous tissue controls the body and brings it into proper relations with its surroundings1 while the epithelial tissue 7found upon the body surfaces and in the glands7 supplies it with protective coverings and secretes liquids4 ,the adipose tissue 7fat7 prevents the too rapid escape of heat from the body1 supplies it with nourishment in time of need1 and forms soft pads for delicate organs like the eyeball4 99,properties of the ,tissues499--,if we inquire how the tissues are able to serve such widely different purposes1 we find this answer4 ,the tissues differ from one another both in composition and in structure and1 on this account1 differ in their properties47#c7 ,their different properties enable them to serve different purposes in the body4 ,somewhat as glass is adapted by its transparency1 hardness1 and toughness to the use made of it in windows1 the special properties of the tissues adapt them to the kinds of service which they perform4 ,properties that adapt tissues to their work in the body are called essential properties4 ,the most important of these essential properties are as follows3 #a4 ,of osseous tissue1 hardness1 stiffness1 and toughness4 #b4 ,of muscular tissue1 contractility and irritability4 #c4 ,of nervous tissue1 irritability and conductivity4 #d4 ,of cartilaginous tissue1 stiffness and elasticity4 #e4 ,of connective tissue1 toughness and pliability4 #f4 ,of epithelial tissue1 ability to resist the action of external forces and power to secrete4 ,fig4 #a ,fig4 #a--;,hand and forearm1 showing the grouping of muscular and connective tissues in the organ for grasping4 99,tissue ,groups499--,in the construction of the body the tissues are grouped together to form its various divisions or parts4 ,a group of tissues which serves some special purpose is known as an organ4 ,the hand1 for example1 is an organ for grasping 7,fig4 #a74 ,while the different organs of the body do not always contain the same tissues1 and never contain them in the same proportions1 they do contain such tissues as their work requires and these have a special arrangement--one adapted to the work which the organs perform4 ,in addition to forming the organs1 the tissues are also grouped in such a manner as to provide supports for organs and to form cavities in which organs are placed4 ,the various cavities of the body are of particular interest and importance4 ,the three largest ones are the cranial cavity1 containing the brain2 the thoracic cavity1 containing the heart and the lungs2 and the abdominal cavity1 containing the stomach1 the liver1 the intestines1 and other important organs 7,fig4 #b74 ,smaller cavities serving different purposes are also found4 ,fig4 #b ,fig4 #b--;,diagram of a lengthwise section of the body to show its large cavities and the organs which they contain4 99,organs and ,systems499--,the work of the body is carried on by its various organs4 ,many1 in fact the majority1 of these organs serve more than one purpose4 ,the tongue is used in talking1 in masticating the food1 and in swallowing4 ,the nose serves at least three distinct purposes4 ,the mouth1 the arms1 the hands1 the feet1 the legs1 the liver1 the lungs1 and the stomach are also organs that serve more than one purpose4 ,this introduces the principle of economy into the construction of the body and diminishes the number of organs that would otherwise be required4 ,the various organs also combine with one another in carrying on the work of the body4 ,an illustration of this is seen in the digestion of the food--a process which requires the combined action of the mouth1 stomach1 liver1 intestines1 and other organs4 ,a number of organs working together for the same purpose form a system4 ,the chief systems of the body are the digestive system1 the circulatory system1 the respiratory system1 the muscular system1 and the nervous system4 99,the ,organ and its ,work499--,a most interesting question relating to the work of the organ is this3 ,does the organ work for its own benefit or for the benefit of the body as a whole8 ,does the hand1 for example1 grasp for itself or in order that the entire body may come into possession8 ,only slight study is sufficient to reveal the fact that each organ performs a work which benefits the body as a whole4 ,in other words1 just as the organ itself is a part of the body1 the work which it does is a part of the necessary work which the body has to do4 ,but in working for the general good1 or for the body as a whole1 each organ becomes a sharer in the benefits of the work done by every other organ4 ,while the hand receives only a little of the nourishment contained in the food which it places in the mouth or of the heat from1 fuel which it places on the fire1 it is aided and supported by the work of all the other organs of the body--eyes1 feet1 brain1 heart1 etc4 ,the hand does not and cannot work independently of the other organs4 ,it is one of the partners in a very close combination where1 by doing a particular work1 it1 shares in the profits of all4 ,what is true of the hand is true of every other organ of the body4 99,an ,organization499--,the relations which the different organs sustain to each other and to the body as a whole suggest the possibility of classifying the body as an organization4 ,this term is broadly applied to a variety of combinations4 ,an organization is properly defined as any group of individuals which1 in working together for a common purpose1 practices the division of labor4 ,this definition will be better understood by considering a few familiar examples4 ,a baseball team is an organization4 ,the team is made up of individual players4 ,these work together for the common purpose of winning games4 ,they practice the division of labor in that the different players do different things--one catching1 another pitching1 and so on4 ,a manufacturing establishment which employs several workmen may also be an organization4 ,the article manufactured provides the common purpose toward which all strive2 and1 in the assignment of different kinds of work to the individual workmen1 the principle of division of labor is carried out4 ,for the same reason a school1 a railway system1 an army1 and a political party are organizations4 ,an organization of a lower order of individuals than these human organizations is to be found in a hive of bees4 ,this is made up of the individual bees1 and these1 in carrying on the general work of the hive1 are known to practice the division of labor4 99,is the ,body an ,organization998--,if the body is an organization1 it must fulfill the conditions of the definition4 ,it must be made up of separate or individual parts4 ,these must work together for the same general purpose1 and1 in the accomplishment of this purpose1 must practice the division of labor4 ,that the body practices the division of labor is seen in the related work of the different organs4 ,that it is made up of minute1 but individual1 parts will be shown in the chapter following4 ,that it carries on a general work which is accomplished through the combined action of its individual parts is revealed through an extended study of its various activities4 ,the body is an organization4 ,moreover1 it is one of the most complex and1 at the same time1 most perfect of the organizations of which we have knowledge4 99,summary499--,viewed from the outside1 the body is seen to be made up of divisions which are more or less familiar4 ,viewed internally1 it is found to consist of different kinds of materials1 called tissues4 ,the tissues are adapted1 by their properties1 to different purposes both in the construction of the body and in carrying on its work4 ,the working parts of the body are called organs and these in their work combine to form systems4 ,the entire body1 on account of the method of its construction and the character of its work1 may be classed as an organization4 99,exercises499--#a4 ,name and locate the chief external divisions of the body4 #b4 ,what tissues may be found by dissecting the leg of a chicken8 #c4 ,name the most important properties and the most important uses of muscular tissue1 osseous tissue1 and connective tissue4 #d4 ,define an organ4 ,define a system4 ,name examples of each4 #e4 ,name the chief cavities of the body and the organs which they contain4 #f4 ,what tissues are present in the hand8 ,how does each of these aid in the work of the hand8 #g4 ,define an organization4 ,show that a railway system1 an army1 and a school are organizations4 #h4 ,what is meant by the phrase division of labor8 ,in what manner is the division of labor practiced in a shoe or watch factory8 ,what are the advantages8 #i4 ,what are the proofs that the body is an organization8 ,,practical ,,work 99,observation on the ,tissues499--,examine with care the structures in the entire leg of a chicken1 squirrel1 rabbit1 or other small animal used for food4 ,observe1 first of all1 the external covering1 consisting of cuticle and hair1 claws1 scales1 or feathers1 according to the specimen4 ,these are similar in structure1 and they form the epidermis1 which is one kind of epithelial tissue4 ,with a sharp knife lay open the skin and observe that it is attached to the parts underneath by thin1 but tough1 threads and sheaths4 ,these represent a variety of connective tissue4 ,the reddish material which forms the greater portion of the specimen is a variety of muscular tissue1 and its divisions are called muscles4 ,with a blunt instrument1 separate the muscles1 by tearing apart the connective tissue binding them together1 and find the glistening white strips of connective tissue 7tendons7 which attach them to the bones4 ,find near the central part of the leg a soft1 white cord 7a nerve7 which represents one variety of nervous tissue4 ,the bones1 which may now be examined1 form the osseous tissue4 ,at the ends of the bones will be found a layer of smooth1 white material which represents one kind of cartilaginous tissue4 ,the adipose1 or fatty1 tissue1 which is found under the skin and between the other tissues1 is easily recognized4 99,relation of the ,tissues to the ,organs499--,observe in the specimen just studied the relation of the different tissues to the organ as a whole 7regarding the leg as an organ71 i4e41 show how each of the tissues aids in the work which the organ accomplishes4 ,show in particular how the muscles supply the foot with motion1 by tracing out the tendons that connect them with the toes4 ,pull on the different tendons1 noting the effect upon the different parts of the foot4 ,,chapter ,,iii - ,,the ,,body ,,organization ,what is the nature of the body organization8 ,what are the individual parts1 or units1 that make it up8 ,what general work do these carry on and upon what basis do they practice the division of labor8 ,the answers to these questions will suggest the main problems in the study of the body4 ,fig4 #c ,fig4 #c--;,diagram showing the relation of the cells and the intercellular material4 ,c4 ,cells4 ,i4 ,intercellular material4 99,complex ,nature of the ,tissues499--,to the unaided eye the tissues have the appearance of simple structures4 ,the microscope1 however1 shows just the reverse to be true4 ,when any one of the tissues is suitably prepared and carefully examined with this instrument1 at least two classes of materials can be made out4 ,one of these consists of minute particles1 called cells2 the other is a substance lying between the cells1 known as the intercellular material 7,fig4 #c74 ,the cells and the intercellular material1 though varying in their relative proportions1 are present in all the tissues4 99,the ,body a ,cell ,group499--,the biologist has found that the bodies of all living things1 plants as well as animals1 consist either of single cells or of groups of cells4 ,the single cells live independently of one another1 but the cells that form groups are attached to1 and are more or less dependent upon1 one another4 ,in the first condition are found the very lowest forms of life4 ,in the second1 life reaches its greatest development4 ,the body of man1 which represents the highest type of life1 is recognized as a group of cells4 ,in this group each cell is usually separate and distinct from the others1 but is attached to them1 and is held in place by the intercellular material4 99,protoplasm1 the ,cell ,substance499--,the cell is properly regarded as an organized bit of a peculiar material1 called protoplasm4 ,this is a semi-liquid and somewhat granular substance which resembles in appearance the white of a raw egg4 ,its true nature and composition are unknown1 because any attempt to analyze it kills it1 and dead protoplasm is essentially different from living protoplasm4 ,it is known1 however1 to be a highly complex substance and to undergo chemical change readily4 ,it appears to be the only kind of matter with which life is ever associated1 and for this reason protoplasm is called the physical basis of life4 ,its organization into separate bits1 or cells1 is necessary to the life activities that take place within it4 99,structure of the ,cell499--,though all portions of the cell are formed from the protoplasm1 this essential substance differs both in structure and in function at different places in the cell4 ,for this reason the cell is looked upon as a complex body having several distinct parts4 ,at or near the center is a clear1 rounded body1 called the nucleus4 ,this plays some part in the nourishment of the cell and also in the formation of new cells4 ,if it be absent1 as is sometimes the case1 the cell is short-lived and unable to reproduce itself4 ,the variety of protoplasm contained in the nucleus is called the nucleoplasm4 ,fig4 #d ,fig4 #d--;,diagram of a typical cell 7after ,wilson74 #a4 ,main body4 #b4 ,nucleus4 #c4 ,attraction sphere4 #d4 ,food particles and waste4 #e4 ,cell-wall4 #f4 ,masses of active material found in certain cells1 called plastids4 ,surrounding the nucleus is the main body of the cell1 sometimes referred to as the protoplasm4 ,since the protoplasm forms all parts of the cell1 this substance is more properly called the cytoplasm1 or cell plasm4 ,surrounding and inclosing the cytoplasm1 in many cells1 is a thin outer layer1 or membrane1 which affords more or less protection to the contents of the cell4 ,this is usually referred to as the cell-wall4 ,a fourth part of the cell is also described1 being called the attraction sphere4 ,this is a small body lying near the nucleus and coperating with that body in the formation of new cells4 ,food particles1 wastes1 and other substances may also be present in the cytoplasm4 ,the parts of a typical cell are shown in ,fig4 #d4 99,importance of the ,cells499--,the cells must be regarded as the living1 working parts of the body4 ,they are the active agents in all of the tissues1 enabling them to serve their various purposes4 ,working through the tissues1 they build up the body and carry on its different activities4 ,they are recognized on this account as the units of structure and of function1 and are the individuals in the body organization4 ,among the most important and interesting of the activities of the cells are those by which they build up the body1 or cause it to grow4 99,how the ,cells enable the ,body to ,grow499--,every cell is able to take new material into itself and to add this to the protoplasm4 ,this tends to increase the amount of the protoplasm1 thereby causing the cells to increase in size4 ,a general increase in the size of the cells has the effect of increasing the size of the entire body1 and this is one way by which they cause it to grow4 ,there is1 however1 a fixed limit1 varying with different cells1 to the size which they attain1 and this is quite low4 7,the largest cells are scarcely visible to the naked eye47 ,any marked increase in the size of the body must1 therefore1 be brought about by other means4 ,such a means is found in the formation of new cells1 or cell reproduction4 ,the new cells are always formed by and from the old cells1 the essential process being known as cell-division4 ,fig4 #e ,fig4 #e--,steps in cell-division 7after ,wilson74 ,note that the process begins with the division of the attraction sphere1 then involves the nucleus1 and finally separates the main body4 99,cell-,division499--,by dividing1 a single cell will1 on attaining its growth1 separate into two or more new cells4 ,the process is quite complex and is imperfectly understood4 ,it is known1 however1 that the act of separation is preceded by a series of changes in which the attraction sphere and the nucleus actively participate1 and that1 as a result of these changes1 the contents of the old cell are rearranged to form the new cells4 ,some of the different stages in the process1 as they have been studied under the microscope1 are indicated in ,fig4 #e4 ,gradually1 through the formation of new cells and by the growth of these cells after they have been formed1 the body attains its full size4 ,when growth is complete1 cell reproduction is supposed to cease except where the tissues are injured1 as in the breaking of a bone1 or where cells1 like those at the surface of the skin1 are subject to wear4 ,then new material continues to be added to the protoplasm throughout life1 but in amount only sufficient to replace that lost from the protoplasm as waste4 ,fig4 #f ,fig4 #f--;,a tumbler partly filled with marbles covered with water1 suggesting the relations of the cells to the lymph4 99,cell ,surroundings499--,all cells are said to be aquatic4 ,this means simply that they require water for carrying on their various activities4 ,the cells1 in order to live1 must take in and give out materials1 and water is necessary to both processes4 ,it is also an essential part of the protoplasm4 ,deprived of water1 cells become inactive and usually die4 ,aquatic surroundings are provided for the cells of the body through a liquid known as the lymph1 which is distributed throughout the intercellular material 7,fig4 #f74 ,this consists of water containing oxygen and food substances in solution4 ,besides supplying these to the cells1 the lymph also receives their wastes4 ,through the lymph the necessary conditions for cell life are provided in the body4 99,the ,general ,work of ,cells499--,in handling the materials derived from the lymph1 the cells carry on three well-defined processes1 known as absorption1 assimilation1 and excretion4 ,absorption is the process of taking water1 food1 and oxygen into the cells4 ,assimilation is a complex process which results in the addition of the absorbed materials to the protoplasm4 ,through assimilation the protoplasm is built up or renewed4 ,excretion is the throwing off of such waste materials as have been formed in the cells4 ,these are passed into the lymph and thence to the surface of the body4 ,absorption1 assimilation1 excretion1 and also reproduction are performed by all classes of cells4 ,they are1 on this account1 referred to as the general work of cells4 99,the ,special ,work of ,cells499--,in addition to the general work which all cells do in common1 each class of cells in the body is able to do some particular kind of work--a work which the others cannot do or which they can do only to a limited extent4 ,this is spoken of as the special work of cells4 ,examples of the special work of cells are found in the production of motion by muscle cells and in the secretion of liquids by gland cells4 ,it may be noted that while the general work of cells benefits them individually1 their special work benefits the body as a whole4 ,another example of the special work of cells is found in the ,fig4 #g ,fig4 #g--;,cartilage cells1 surrounded by the intercellular material which they have deposited4 99,production of the ,intercellular ,material499--,though most of the cells of the body deposit to a slight extent this material1 the greater part of it is produced by a single class of cells found in bone1 cartilage1 and connective tissue4 ,cartilage1 bone1 and connective tissue differ greatly from the other tissues in the amount of intercellular material which they contain1 the difference being due to these cells4 ,in the connective tissue they deposit the fibrous material so important in holding the different parts of the body together4 ,in the cartilage they produce the gristly substance which forms by far its larger portion 7,fig4 #g74 ,in the bones they deposit a material similar to that in the cartilage1 except that with it is mixed a mineral substance which gives the bones their hardness and stiffness47#d7 ,the intercellular material1 in addition to connecting the cells1 supplies to certain tissues important properties1 such as the elasticity of cartilage and the stiffness of the bones4 99,nature of the ,body ,organization499--,the division of labor carried on by the different organs1 as shown in the preceding chapter1 is in reality carried on by the cells that form the organs4 ,to see that this is true we have only to observe the relation of cells to tissues and of tissues to organs4 ,the cells form the tissues and the tissues form the organs4 ,this arrangement enables the special work of different kinds of cells to be combined in the work of the organ as a whole4 ,this is seen in the hand which1 in grasping1 uses motion supplied by the muscle cells1 a controlling influence supplied by the nerve cells1 a framework supplied by the bone cells1 and so on4 ,the cells supply the basis for the body organization and1 properly speaking1 the body is an organization of cells7#e7 7,recall the definition of an organization1 page #aj47 ,in this organization there are to be observed3 #a4 ,a definite arrangement of the cells to form the tissues4 ,a tissue is a group of like cells4 #b4 ,a definite arrangement of the tissues in the organ4 ,each organ contains the tissues needed for its work4 #c4 ,in several instances there is a definite arrangement of organs to form systems4 #d4 ,the body as a whole is made up of organs and systems1 together with the structures necessary for their support and protection4 ,there now remains a further question for consideration4 ,what is the one supreme end1 or purpose1 toward which all the activities of the body organization are directed8 ,this purpose will naturally have some relation to the maintenance1 or preservation1 of the cell group which we call the body4 99,the ,maintenance of ,life499--,the preservation of any cell group in its natural condition1 whether it be plant or animal1 is accomplished through keeping it alive4 ,if life ceases1 the group quickly disintegrates and its elements become scattered1 a fact which is verified through everyday observation4 ,though the nature of life is unknown1 it may be looked upon as the organizer and preserver of the protoplasm4 ,but in preserving the protoplasm it also preserves the entire cell group1 or body4 ,life is thus the most essential condition of the body4 ,with life all portions of the body are concerned1 and toward its maintenance all the activities of the body organization are directed4 99,the ,nutrient ,fluid in its ,relations to the ,cells499--,the maintenance of life within the cells requires1 as we have seen1 that they be supplied with water1 food1 and oxygen1 and that they be relieved of such wastes as they form4 ,this double purpose is accomplished through the agency of an internal nutrient fluid1 a portion of which has already been referred to as the lymph4 ,not only does this fluid supply the means for keeping the cells alive1 but1 through the cells1 it is also the means of preserving the life of the body as a whole4 ,the cells1 however1 rapidly exhaust the nutrient fluid4 ,they take from it food and oxygen and they put into it their wastes4 ,to prevent its becoming unfit for supplying their needs1 food and oxygen must be continually added to this fluid1 and waste materials must be continually removed4 ,this is not an easy task4 ,as a matter of fact1 the preparation1 distribution1 and purification of the nutrient fluid requires the direct or indirect aid of practically all parts of the body4 ,it supplies for this reason a broad basis for the division of labor on the part of the cells4 99,relation of the ,body to its ,environment499--,while life is directly dependent upon the internal nutrient fluid1 it is indirectly dependent upon the physical surroundings of the body4 ,herein lies the need of the external organs--the feet and legs for moving about1 the hands for handling things1 the eyes for directing movements1 etc4 ,that the great needs of the body are supplied from its surroundings are facts of common experience4 ,food1 shelter1 air1 clothing1 water1 and the means of protection are external to the body and form a part of its environment4 ,in making the things about him contribute to his needs1 man encounters a problem which taxes all his powers4 ,only by toil and hardship1 by the sweat of his brow1 has he been able to wrest from his surroundings the means of his sustenance4 99,the ,main ,physiological ,problems499--,the study of the body is thus seen to resolve itself naturally into the consideration of two main problems3 #a4 ,that of maintaining in the body a nutrient fluid for the cells4 #b4 ,that of bringing the body into such relations with its surroundings as will enable it to secure materials for the nutrient fluid and satisfy its other needs4 ,the first problem is internal and includes the so-called vital processes1 known as digestion1 circulation1 respiration1 and excretion4 ,the second problem is external1 as it were1 and includes the work of the external organs--the organs of motion and of locomotion and the organs of special sense4 ,these problems are closely related1 since they are the two divisions of the one problem of maintaining life4 ,neither can be considered independently of the other4 ,in the chapter following is taken up the first of these problems4 99,summary499--,the individual parts1 or units1 that form the body organization are known as cells4 ,these consist of minute but definitely arranged portions of protoplasm and are held together by the intercellular material4 ,they build up the body and carry on its different activities4 ,the tissues are groups of like cells4 ,by certain general activities the cells maintain their existence in the tissues and by the exercise of certain special activities they adapt the tissues to their purposes in the body4 ,the body1 as a cell organization1 has its activities directed under normal conditions toward a single purpose--that of maintaining life4 ,in the accomplishment of this purpose a nutrient fluid is provided for the cells and proper relations between the body and its surroundings are established4 99,exercises499--#a4 ,if a tissue be compared to a brick wall1 to what do the separate bricks correspond8 ,to what the mortar between the bricks8 #b4 ,draw an outline of a typical cell1 locating and naming the main divisions4 #c4 ,how do the cells enable the body to grow8 ,describe the process of cell-division4 #d4 ,how does the general work of cells differ from their special work8 ,define absorption1 excretion1 and assimilation as applied to the cells4 #e4 ,compare the conditions surrounding a one-celled animal1 living in water1 to the conditions surrounding the cells in the body4 #f4 ,what is meant by the term environment8 ,how does man's environment differ from that of a fish8 #g4 ,what is the necessity for a nutrient fluid in the body8 #h4 ,why is the maintenance of life necessarily the chief aim of all the activities of the body8 #i4 ,state the two main problems in the study of the body4 ,,practical ,,work 99,observations499--#a4 ,make some scrapings from the inside of the cheek with a dull knife and mix these with a little water on a glass slide4 ,place a cover-glass on the same and examine with a compound microscope4 ,the large pale cells that can be seen in this way are a variety of epithelial cells4 #b4 ,mount in water on a glass slide some thin slices of cartilage and examine first with a low and then with a high power of microscope4 7,suitable slices may be cut1 with a sharp razor1 from the cartilage found at the end of the rib of a young animal47 ,note the small groups of cells surrounded by1 and imbedded in1 the intercellular material4 #c4 ,mount and examine with the microscope thin slices of elder pith1 potato1 and the stems of growing plants4 ,make drawings of the cells thus observed4 #d4 ,examine with the microscope a small piece of the freshly sloughed off epidermis of a frog's skin4 ,examine it first in its natural condition1 and then after soaking for an hour or two in a solution of carmine4 ,make drawings4 #e4 ,mount on a glass slide some of the scum found on stagnant water and examine it with a compound microscope4 ,note the variety and relative size of the different things moving about4 ,the forms most frequently seen by such an examination are one-celled plants4 ,many of these have the power of motion4 #f4 ,examine tissues of the body1 such as nervous1 muscular1 and glandular tissues1 which have been suitably prepared and mounted for microscopic study1 using low and high powers of the microscope4 ,make drawings of the cells in the different tissues thus observed4 ,,chapter ,,iv - ,,the ,,blood ,two liquids of similar nature are found in the body1 known as the blood and the lymph4 ,these are closely related in function and together they form the nutrient fluid referred to in the preceding chapter4 ,the blood is the more familiar of the two liquids1 and the one which can best be considered at this time4 99,the ,blood3 where ,found499--,the blood occupies and moves through a system of closed tubes1 known as the blood vessels4 ,by means of these vessels the blood is made to circulate through all parts of the body1 but from them it does not escape under normal conditions4 ,though provisions exist whereby liquid materials may both enter and leave the blood stream1 it is only when the blood vessels are cut or broken that the blood1 as blood1 is able to escape from its inclosures4 99,physical ,properties of the ,blood499--,experiments such as those described at the close of this chapter reveal the more important physical properties of the blood4 ,it may be shown to be heavier and denser than water2 to have a faint odor and a slightly salty taste2 to have a bright red color when it contains oxygen and a dark red color when oxygen is absent2 and to undergo1 when exposed to certain conditions1 a change called coagulation4 ,these properties are all accounted for through the different materials that enter into the formation of the blood4 ,fig4 #h ,fig4 #h--;,blood corpuscles1 highly magnified4 ,a4 ,red corpuscles as they appear in diluted blood4 ,b4 ,arrangement of red corpuscles in rows between which are white corpuscles1 as may be seen in undiluted blood4 ,c4 ,red corpuscles much enlarged to show the form4 99,composition of the ,blood499--,to the naked eye the blood appears as a thick but simple liquid2 but when examined with a compound microscope1 it is seen to be complex in nature1 consisting of at least two distinct portions4 ,one of these is a clear1 transparent liquid2 while the other is made up of many small1 round bodies that float in the liquid4 ,the liquid portion of the blood is called the plasma2 the small bodies are known as corpuscles4 ,two varieties of corpuscles are described--the red corpuscles and the white corpuscles 7,fig4 #h74 ,other round particles1 smaller than the corpuscles1 may also be seen under favorable conditions4 ,these latter are known as blood platelets4 99,red ,corpuscles499--,the red corpuscles are classed as cells1 although1 as found in the blood of man and the other mammals 7,fig4 #i71 they have no nuclei47#f7 ,each one consists of a little mass of protoplasm1 called the stroma1 which contains a substance having a red color1 known as hemoglobin4 ,the shape of the red corpuscle is that of a circular disk with concave sides4 ,it has a width of about #a_/cbjj of an inch 7#g4i microns7#g77 and a thickness of about #a_/acjjj of an inch 7#a4i microns74 ,the red corpuscles are exceedingly numerous1 there being as many as five millions in a small drop 7one cubic millimeter7 of healthy blood4 ,but the number varies somewhat and is greatly diminished during certain forms of disease4 ,fig4 #i ,fig4 #i--,red corpuscles from various animals4 ,those from mammals are without nuclei1 while those from birds and cold-blooded animals have nuclei4 ,it is the function of the red corpuscles to serve as oxygen carriers for the cells4 ,they take up oxygen at the lungs and release it at the cells in the different tissues47#h7 ,the performance of this function depends upon the hemoglobin4 99,hemoglobin499--,this substance has the remarkable property of forming1 under certain conditions1 a weak chemical union with oxygen and1 when the conditions are reversed1 of separating from it4 ,it forms about nine tenths of the solid matter of the red corpuscles and to it is due the colors of the blood4 ,when united with the oxygen it forms a compound1 called oxyhemoglobin1 which has a bright red color2 the hemoglobin alone has a dark red color4 ,these colors are the same as those of the blood as it takes on and gives off oxygen4 ,the stroma1 which forms only about one tenth of the solid matter of the corpuscles1 serves as a contrivance for holding the hemoglobin4 ,the conditions which cause the hemoglobin to unite with oxygen in the lungs and to separate from it in the tissues1 will be considered later 7,chapter ,,viii74 99,disappearance and ,origin of ,red ,corpuscles499--,the red corpuscles1 being cells without nuclei1 are necessarily short-lived4 ,it has been estimated that during a period of one to two months1 all the red corpuscles in the body at a given time will have disappeared and their places taken by new ones4 ,the origin of new corpuscles1 however1 and the manner of ridding the blood of old ones are problems that are not as yet fully solved4 ,the removal of the products of broken down corpuscles is supposed to take place both in the liver and in the spleen47#i7 ,regarding the origin of the red corpuscles1 the evidence now seems conclusive that large numbers of them are formed in the red marrow of the bones4 ,the red marrow is located in what is known as the spongy substance of the bones 7,chapter ,,xiv7 and consists1 to a large extent1 of cells somewhat like the red corpuscles1 but differing from them in having nuclei4 ,these appear to be constantly in a state of reproduction4 ,the blood1 flowing through the minute cavities containing these cells1 carries those that have been loosened out into the blood stream4 ,nuclei appear in the red corpuscles at the time of their formation1 but these quickly separate and1 according to some authorities1 form the blood platelets4 99,white ,corpuscles499--,the white corpuscles1 or leucocytes1 are cells of a general spherical shape1 each containing one1 two1 or more nuclei4 ,they are much less numerous than the red1 there being on the average only one white corpuscle to about every five hundred of the red ones4 ,on the other hand1 the white corpuscles are larger than the red1 one of the former being equal in volume to about three of the latter4 ,fig4 #aj ,fig4 #aj--99;,escape of white corpuscles from a small blood vessel99 7,hall74 ,at ,a the conditions are normal1 but at ,b some excitation in the surrounding tissue leads to a migration of corpuscles4 #a1 #b1 and #c show different stages of the passage4 ,the white corpuscles are found1 when studied under favorable conditions1 to possess the power of changing their shape and1 by this means1 of moving from place to place4 ,this property enables them to penetrate the walls of capillaries and to pass with the lymph in between the cells of the tissues4 ,the white corpuscles are1 therefore1 not confined to the blood vessels1 as are the red corpuscles1 but migrate through the intercellular spaces 7,fig4 #aj74 ,if any part of the body becomes inflamed1 the white corpuscles collect there in large numbers2 and1 on breaking down1 they form most of the white portion of the sore1 called the pus4 ,new white corpuscles are formed from old ones1 by cell-division4 ,their production may occur in almost any part of the body1 but usually takes place in the lymphatic glands 7,chapter ,,vi7 and in the spleen1 where conditions for their development are especially favorable4 ,in these places they are found in great abundance and in various stages of development4 99,functions of ,white ,corpuscles499--,the main use of the white corpuscles appears to be that of a destroyer of disease germs4 ,these consist of minute organisms that find their way into the body and1 by living upon the tissues and fluids and by depositing toxins 7poisons7 in them1 cause different forms of disease4 ,besides destroying germs that may be present in the blood1 the white corpuscles also leave the blood and attack germs that have invaded the cells4 ,by forming a kind of wall around any foreign substance1 such as a splinter1 that has penetrated the skin1 they are able to prevent the spread of germs through the body4 ,in a similar manner they also prevent the germs from boils1 abscesses1 and sore places in general from getting to and infecting other parts of the body47#aj7 ,another function ascribed to the white corpuscles is that of aiding in the coagulation of the blood 7page #ca72 and still another1 of aiding in the healing of wounds4 99,plasma499--,the plasma is a complex liquid1 being made up of water and of substances dissolved in the water4 ,the dissolved substances consist mainly of foods for the cells and wastes from the cells4 #a4 ,the foods represent the same classes of materials as are taken in the daily fare1 i4e41 proteids1 carbohydrates1 fats1 and salts 7,chapter ,,ix74 ,three kinds of proteids are found in the plasma1 called serum albumin1 serum globulin1 and fibrinogen4 ,these resemble1 in a general way1 the white of raw egg1 but differ from each other in the readiness with which they coagulate4 ,fibrinogen coagulates more readily than the others and is the only one that changes in the ordinary coagulation of the blood4 ,the others remain dissolved during this process1 but are coagulated by chemical agents and by heat4 ,while all of the proteids probably serve as food for the cells1 the fibrinogen1 in addition1 is a necessary factor in the coagulation of the blood 7page #ca74 ,the only representative of the carbohydrates in the plasma is dextrose4 ,this is a variety of sugar1 being derived from starch and the different sugars that are eaten4 ,the fat in the plasma is in minute quantities and appears as fine droplets--the form in which it is found in milk4 ,while several mineral salts are present in small quantities in the plasma1 sodium chloride1 or common salt1 is the only one found in any considerable amount4 ,the mineral salts serve various purposes1 one of which is to cause the proteids to dissolve in the plasma4 #b4 ,the wastes are formed at the cells1 whence they are passed by the lymph into the blood plasma4 ,they are carried by the blood until removed by the organs of excretion4 ,the two waste products found in greatest abundance in the plasma are carbon dioxide and urea4 ,the substances dissolved in the plasma form about #aj per cent of the whole amount4 ,the remaining #ij per cent is water4 ,practically all the constituents of the plasma1 except the wastes1 enter the blood from the digestive organs4 99,purposes of ,water in the ,blood499--,not only is water the most abundant constituent of the blood2 it is1 in some respects1 the most important4 ,it is the liquefying portion of the blood1 holding in solution the constituents of the plasma and floating the corpuscles4 ,deprived of its water1 the blood becomes a solid substance4 ,through the movements of the blood the water also serves the purpose of a transporting agent in the body4 ,the cells in all parts of the body require water and this is supplied to them from the blood4 ,water is present in the corpuscles as well as in the plasma and forms about #hj per cent of the entire volume of the blood4 99,coagulation of the ,blood499--,if the blood is exposed to some unnatural condition1 such as occurs when it escapes from the blood vessels1 it undergoes a peculiar change known as coagulation47#aa7 ,in this change the corpuscles are collected into a solid mass1 known as the clot1 thereby separating from a liquid called the serum4 ,the serum1 which is similar in appearance to the blood plasma1 differs from that liquid in one important respect as explained below4 99,causes of ,coagulation499--,although coagulation affects all parts of the blood1 only one of its constituents is found in reality to coagulate4 ,this is the fibrinogen4 ,the formation of the clot and the separation of the serum is due almost entirely to the action of this substance4 ,fibrinogen is for this reason called the coagulable constituent of the blood4 ,in the plasma the fibrinogen is in a liquid form2 but during coagulation it changes into a white1 stringy solid1 called fibrin4 ,this appears in the clot and is the cause of its formation4 ,forming as a network of exceedingly fine and very delicate threads 7,fig4 #aa7 throughout the mass of blood that is coagulating1 the fibrin first entangles the corpuscles and then1 by contracting1 draws them into the solid mass or clot47#ab7 ,the contracting of the fibrin also squeezes out the serum4 ,this liquid contains all the constituents of the plasma except the fibrinogen4 ,fig4 #aa ,fig4 #aa--99;,fibrin threads99 7after ,ranvier74 ,these by contracting draw the corpuscles together and form the clot4 99,fibrin ,ferment and ,calcium499--,most difficult of all to answer have been the questions3 ,what causes the blood to coagulate outside of the blood vessels and what prevents its coagulation inside of these vessels8 ,the best explanation offered as yet upon this point is as follows3 ,fibrinogen does not of itself change into fibrin1 but is made to undergo this change by the presence of another substance1 called fibrin ferment4 ,this substance is not a regular constituent of the blood1 but is formed as occasion requires4 ,it is supposed to result from the breaking down of the white corpuscles1 and perhaps also from the blood platelets1 when the blood is exposed to unnatural conditions4 ,the formation of the ferment leads in turn to the changing of the fibrinogen into fibrin4 ,another substance which is necessary to the process of coagulation is the element calcium4 ,if compounds of calcium are absent from the blood1 coagulation does not take place4 ,these are1 however1 regular constituents of healthy blood4 ,whether the presence of the calcium is necessary to the formation of the ferment or to the action of the ferment upon the fibrinogen is unknown4 99,purpose of ,coagulation499--,the purpose of coagulation is to check the flow of blood from wounds4 ,the fact that the blood is contained in and kept flowing continuously through a system of connected vessels causes it to escape rapidly from the body whenever openings in these vessels are made4 ,clots form at such openings and close them up1 stopping in this way the flow that would otherwise go on indefinitely4 ,coagulation1 however1 does not stop the flow of blood from the large vessels4 ,from these the blood runs with too great force for the clot to form within the wound4 99,time ,required for ,coagulation499--,the rate at which coagulation takes place varies greatly under different conditions4 ,it is influenced strongly by temperature2 heat hastens and cold retards the process4 ,it may be prevented entirely by lowering the temperature of the blood to near the freezing point4 ,the presence of a foreign substance increases the rapidity of coagulation1 and it has been observed that bleeding from small wounds is more quickly checked by covering them with linen or cotton fibers4 ,the fibers in this case hasten the process of coagulation4 99,quantity of ,blood499--,the quantity of blood is estimated to be about one thirteenth of the entire weight of the body4 ,this for the average individual is an amount weighing nearly twelve pounds and having a volume of nearly one and one half gallons4 ,about #df per cent by volume of this amount is made up of corpuscles and #ed per cent of plasma4 ,of the plasma about #aj per cent consists of solids and #ij per cent of water1 as already stated4 99,functions of the ,blood499--,the blood is the great carrying1 or distributing1 agent in the body4 ,through its movements 7considered in the next chapter7 it carries food and oxygen to the cells and waste materials from the cells4 ,much of the blood may1 therefore1 be regarded as freight in the process of transportation4 ,the blood also carries1 or distributes1 heat4 ,taking up heat in the warm parts of the body1 it gives it off at places having a lower temperature4 ,this enables all parts of the body to keep at about the same temperature4 ,in addition to serving as a carrier1 the blood has antiseptic properties1 i4e41 it destroys disease germs4 ,while this function is mainly due to the white corpuscles1 it is due in part to the plasma47#ac7 ,through its coagulation1 the blood also closes leaks in the small blood vessels4 ,the blood is thus seen to be a liquid of several functions4 ,fig4 #ab ,fig4 #ab--99;,a balanced change99 in water4 ,the level remains constant although the water is continually changing2 suggestive of the changes in the blood4 99,changes in the ,blood499--,in performing its functions in the body the blood must of necessity undergo rapid and continuous change4 ,the red corpuscles1 whose changes have already been noted1 appear to be the most enduring constituents of the blood4 ,the plasma is the portion that changes most rapidly4 ,yet in spite of these changes the quantity and character of the blood remain practically constant47#ad7 ,this is because there is a balancing of the forces that bring about the changes4 ,the addition of various materials to the blood just equals the withdrawal of the same materials from the blood4 ,somewhat as a vessel of water 7,fig4 #ab7 having an inflow and an outflow which are equal in amount may keep always at the same level1 the balancing of the intake and outgo of the blood keeps its composition about the same from time to time4 99,hygiene of the ,blood499--,the blood1 being a changeable liquid1 is easily affected through our habits of living4 ,since it may be affected for ill as well as for good1 one should cultivate those habits that are beneficial and avoid those that are harmful in their effects4 ,most of the hygiene of the blood1 however1 is properly included in the hygiene of the organs that act upon the blood--a fact which makes it unnecessary to treat this subject fully at this time4 ,from a health standpoint1 the most important constituents of the blood are1 perhaps1 the corpuscles4 ,these are usually sufficient in number and vigor in the blood of those who take plenty of physical exercise1 accustom themselves to outdoor air and sunlight1 sleep sufficiently1 and avoid the use of injurious drugs4 ,on the other hand1 they are deficient in quantity and inferior in quality in the bodies of those who pursue an opposite course4 ,impurities not infrequently find their way into the blood through the digestive organs4 ,one should eat wholesome1 well-cooked food1 drink freely of pure water1 and limit the quantity of food to what can be properly digested4 ,the natural purifiers of the blood are the organs of excretion4 ,the skin is one of these and its power to throw off impurities depends upon its being clean and active4 99,effect of ,drugs499--,certain drugs and medicines1 including alcohol and quinine17#ae7 have recently been shown to destroy the white corpuscles4 ,the effect of such substances1 if introduced in considerable amount in the body1 is to render one less able to withstand attacks of disease4 ,many patent medicines are widely advertised for purifying the blood4 ,while these may possibly do good in particular cases1 the habit of doctoring one's self with them is open to serious objection4 ,instead of taking drugs and patent medicines for purifying the blood1 one should study to live more hygienically4 ,we may safely rely upon wholesome food1 pure water1 outdoor exercise and sunlight1 plenty of sleep1 and a clean skin for keeping the blood in good condition4 ,if these natural remedies fail1 a physician should be consulted4 99,summary499--,the blood is the carrying or transporting agent of the body4 ,it consists in part of constituents1 such as the red corpuscles1 that enable it to carry different substances2 and in part of the materials that are being carried4 ,the latter1 which include food and oxygen for the cells and wastes from the cells1 may be classed as freight4 ,certain constituents in the blood destroy disease germs1 and other constituents1 by coagulating1 close small leaks in the blood vessels4 ,although subject to rapid and continuous change1 the blood is able--by reason of the balancing of materials added to and withdrawn from it--to remain about the same in quantity and composition4 ,exercises4--#a4 ,compare blood and water with reference to weight1 density1 color1 odor1 and complexity of composition4 #b4 ,show by an outline the different constituents of the blood4 #c4 ,compare the red and white corpuscles with reference to size1 shape1 number1 origin1 and function4 #d4 ,name some use or purpose for each constituent of the blood4 #e4 ,what constituents of the blood may be regarded as freight and what as agents for carrying this freight8 #f4 ,after coagulation1 what portions of the blood are found in the clot8 ,what portions are found in the serum8 #g4 ,what purposes are served by water in the blood8 #h4 ,show how the blood1 though constantly changing1 is kept about the same in quantity1 density1 and composition4 #i4 ,in the lungs the blood changes from a dark to a bright red color and in the tissues it changes back to dark red4 ,what is the cause of these changes8 #aj4 ,if the oxygen and hemoglobin formed a strong instead of a weak chemical union1 could the hemoglobin then act as an oxygen carrier8 ,why8 #aa4 ,what habits of living favor the development of corpuscles in the blood8 #ab4 ,why will keeping the skin clean and active improve the quality of one's blood8 ,,practical ,,work 99,to demonstrate the ,physical ,properties of ,blood99 7,optional74--,since blood is needed in considerable quantity in the following experiments1 it is best obtained from the butcher4 ,to be sure of securing the blood in the manner desired1 take to the butcher three good-sized bottles bearing labels as follows3 99#a99 ,fill two thirds full4 ,while the blood is cooling1 stir rapidly with the hand or a bunch of switches to remove the clot4 99#b99 ,fill two thirds full and set aside without shaking or stirring4 99#c99 ,fill two thirds full and thoroughly mix with the liquid in the bottle4 ,label #c must be pasted on a bottle1 having a tight-fitting stopper1 which is filled one fifth full of a saturated solution of ,epsom salts4 ,the purpose of the salts is to prevent coagulation until the blood is diluted with water as in the experiments which follow4 99,experiments499--#a4 ,let some of the defibrinated blood 7bottle #a7 flow 7not fall7 on the surface of water in a glass vessel4 ,does it remain on the surface or sink to the bottom8 ,what does the experiment show with reference to the relative weight of blood and water8 #b4 ,fill a large test tube or a small bottle one fourth full of the defibrinated blood and thin it by adding an equal amount of water4 ,then place the hand over the mouth and shake until the blood is thoroughly mixed with the air4 ,compare with a portion of the blood not mixed with the air1 noting any difference in color4 ,what substance in the air has acted on the blood to change its color8 #c4 ,fill three tumblers each two thirds full of water and set them in a warm place4 ,pour into one of the tumblers1 and thoroughly mix with the water1 two tablespoonfuls of the blood containing the ,epsom salts4 ,after an interval of half an hour add blood to the second tumbler in the same manner1 and after another half hour add blood to the third4 ,the water dilutes the salts so that coagulation is no longer prevented4 ,jar the vessel occasionally as coagulation proceeds2 and if the clot is slow in forming1 add a trace of some salt of calcium 7calcium chloride74 ,after the blood has been added to the last tumbler make a comparative study of all4 ,note that coagulation begins in all parts of the liquid at the same time and that1 as the process goes on1 the clot shrinks and is drawn toward the center4 #d4 ,place a clot from one of the tumblers in experiment #c in a large vessel of water4 ,thoroughly wash1 adding fresh water1 until a white1 stringy solid remains4 ,this substance is fibrin4 #e4 ,examine the coagulated blood obtained from the butcher 7bottle #b74 ,observe the dark central mass 7the clot7 surrounded by a clear liquid 7the serum74 ,sketch the vessel and its contents1 showing and naming the parts into which the blood separates by coagulation4 99,to examine the ,red ,corpuscles499--,blood for this purpose is easily obtained from the finger4 ,with a handkerchief1 wrap one of the fingers of the left hand from the knuckle down to the first joint4 ,bend this joint and give it a sharp prick with the point of a sterilized 'needle just above the root of the nail4 ,pressure applied to the under side of the finger will force plenty of blood through a very small opening4 7,to prevent any possibility of blood poisoning the needle should be sterilized4 ,this may be done by dipping it in alcohol or by holding it for an instant in a hot flame4 ,it is well also to wash the finger with soap and water1 or with alcohol1 before the operation47 ,place a small drop of the blood in the middle of a glass slide1 protect the same with a cover glass1 and examine with a compound microscope4 ,at least two specimens should be examined1 one of which should be diluted with a little saliva or a physiological salt solution47#af7 ,in the diluted specimen the red corpuscles appear as amber-colored1 circular1 disk-shaped bodies4 ,in the undiluted specimen they show a decided tendency to arrange themselves in rows1 resembling rows of coins4 7,singly1 the corpuscles do not appear red when highly magnified47 ,a few white corpuscles may generally be found among the red ones in the undiluted specimen4 ,these become separated by the formation of the red corpuscles into rows4 ,they are easily recognized by their larger size and by their silvery appearance1 due to the light shining through them4 99,to examine ,white ,corpuscles499--,obtain from the butcher a small piece of the neck sweetbread of a calf4 ,press it between the fingers to squeeze out a whitish1 semi-liquid substance4 ,dilute with physiological salt solution on a glass slide and examine with a compound microscope4 ,numerous white corpuscles of different kinds and sizes will be found4 ,make sketches4 99,to prepare ,models of ,red ,corpuscles499--,several models of red corpuscles should be prepared for the use of the class4 ,clay and putty may be pressed into the form of red corpuscles and allowed to harden1 and small models may be cut out of blackboard crayon4 ,excellent models can be molded from plaster of ,paris as follows3 ,coat the inside of the lid of a baking powder can with oil or vaseline and fill it even full of a thick mixture of plaster of ,paris and water4 ,after the plaster has set1 remove it from the lid and with a pocket-knife round off the edges and hollow out the sides until the general form of the corpuscle is obtained4 ,the models may be colored red if it is desired to match the color as well as the form of the corpuscle4 ,,chapter ,v - ,,the ,,circulation ,a ,carrier must move4 ,to enable the blood to carry food and oxygen to the cells and waste materials from the cells1 and also to distribute heat1 it is necessary to keep it moving1 or circulating1 in all parts of the body4 ,so closely related to the welfare of the body is the circulation7#ag7 of the blood1 that its stoppage for only a brief interval of time results in death4 99,discovery of the ,circulation499--,the discovery of the circulation of the blood was made about #afaf by an ,english physician named ,harvey4 ,in #afai he announced it in his public lectures and in #afbh he published a treatise in ,latin on the circulation4 ,the chief arguments advanced in support of his views were the presence of valves in the heart and veins1 the continuous movement of the blood in the same direction through the blood vessels1 and the fact that the blood comes from a cut artery in jets1 or spurts1 that correspond to the contractions of the heart4 ,no other single discovery with reference to the human body has proved of such great importance4 ,a knowledge of the nature and purpose of the circulation was the necessary first step in understanding the plan of the body and the method of maintaining life1 and physiology as a science dates from the time of ,harvey's discovery4 99,organs of ,circulation499--,the organs of circulation1 or blood vessels1 are of four kinds1 named the heart1 the arteries1 the capillaries1 and the veins4 ,they serve as contrivances both for holding the blood and for keeping it in motion through the body4 ,the heart1 which is the chief organ for propelling the blood1 acts as a force pump1 while the arteries and veins serve as tubes for conveying the blood from place to place4 ,moreover1 the blood vessels are so connected that the blood moves through them in a regular order1 performing two well-defined circuits4 ,fig4 #ac ,fig4 #ac--99;,heart99 in position in thoracic cavity4 ,dotted lines show positin of diaphragm and of margins of lungs4 99,the ,heart499--,the human heart1 roughly speaking1 is about the size of the clenched fist of the individual owner4 ,it is situated very near the center of the thoracic cavity and is almost completely surrounded by the lungs4 ,it is cone-shaped and is so suspended that the small end hangs downward1 forward1 and a little to the left4 ,when from excitement1 or other cause1 one becomes conscious of the movements of the heart1 these appear to be in the left portion of the chest1 a fact which accounts for the erroneous impression that the heart is on the left side4 ,the position of the heart in the cavity of the chest is shown in ,fig4 #ac4 99,the ,pericardium499--,surrounding the heart is a protective covering1 called the pericardium4 ,this consists of a closed membranous sac so arranged as to form a double covering around the heart4 ,the heart does not lie inside of the pericardial sac1 as seems at first glance to be the case1 but its relation to this space is like that of the hand to the inside of an empty sack which is laid around it 7,fig4 #ad74 ,the inner layer of the pericardium is closely attached to the heart muscle1 forming for it an outside covering4 ,the outer layer hangs loosely around the heart and is continuous with the inner layer at the top4 ,the outer layer also connects at certain places with the membranes surrounding the lungs and is attached below to the diaphragm4 ,between the two layers of the pericardium is secreted a liquid which prevents friction from the movements of the heart4 ,fig4 #ad ,fig4 #ad--99;,diagram of section of the pericardial sac991 heart removed4 ,a4 ,place occupied by the heart4 ,b4 ,space inside of pericardial sac4 a4 ,inner layer of pericardium and outer lining of heart4 b4 ,outer layer of pericardium4 ,c4 ,covering of lung4 ,d4 ,diaphragm4 99,cavities of the ,heart499--,the heart is a hollow1 muscular organ which has its interior divided by partitions into four distinct cavities4 ,the main partition extends from top to bottom and divides the heart into two similar portions1 named from their positions the right side and the left side4 ,on each side are two cavities1 the one being directly above the other4 ,the upper cavities are called auricles and the lower ones ventricles4 ,to distinguish these cavities further1 they are named from their positions the right auricle and the left auricle1 and the right ventricle and the left ventricle 7,fig4 #ae74 ,the auricles on each side communicate with the ventricles below2 but after birth there is no communication between the cavities on the opposite sides of the heart4 ,all the cavities of the heart are lined with a smooth1 delicate membrane1 called the endocardium4 ,fig4 #ae ,fig4 #ae--99;,diagram showing plan of the heart499 #a4 ,semilunar valves4 #b4 ,tricuspid valve4 #c4 ,mitral valve4 #d4 ,right auricle4 #e4 ,left auricle4 #f4 ,right ventricle4 #g4 ,left ventricle4 #h4 ,chord tendine4 #i4 ,inferior vena cava4 #aj4 ,superior vena cava4 #aa4 ,pulmonary artery4 #ab4 ,aorta4 #ac4 ,pulmonary veins4 99,valves of the ,heart499--,located at suitable places in the heart are four gate-like contrivances1 called valves4 ,the purpose of these is to give the blood a definite direction in its movements4 ,they consist of tough1 inelastic sheets of connective tissue1 and are so placed that pressure on one side causes them to come together and shut up the passageway1 while pressure on the opposite side causes them to open4 ,a valve is found at the opening of each auricle into the ventricle1 and at the opening of each ventricle into the artery with which it is connected4 ,the valve between the right auricle and the right ventricle is called the tricuspid valve4 ,it is suspended from a thin ring of connective tissue which surrounds the opening1 and its free margins extend into the ventricle 7,fig4 #af74 ,it consists of three parts1 as its name implies1 which are thrown together in closing the opening4 ,joined to the free edges of this valve are many small1 tendinous cords which connect at their lower ends with muscular pillars in the walls of the ventricle4 ,these are known as the chord tendine1 or heart tendons4 ,their purpose is to serve as valve stops1 to prevent the valve from being thrown1 by the force of the blood stream1 back into the auricle4 ,the mitral1 or bicuspid1 valve is suspended around the opening between the left auricle and the left ventricle1 with the free margins extending into the ventricle4 ,it is exactly similar in structure and arrangement to the tricuspid valve1 except that it is stronger and is composed of two parts instead of three4 ,fig4 #af ,fig4 #af--99,right side of heart99 dissected to show cavities and valves4 ,b4 ,right semilunar valve4 ,the tricuspid valve and the chord tendine shown in the ventricle4 ,the right semilunar valve is situated around the opening of the right ventricle into the pulmonary artery4 ,it consists of three pocket-shaped strips of connective tissue which hang loosely from the walls when there is no pressure from above2 but upon receiving pressure1 the pockets fill and project into the opening1 closing it completely 7,fig4 #af74 ,the left semilunar valve is around the opening of the left ventricle into the aorta1 and is similar in all respects to the right semilunar valve4 99,differences in the ,parts of the ,heart499--,marked differences are found in the walls surrounding the different cavities of the heart4 ,the walls of the ventricles are much thicker and stronger than those of the auricles1 while the walls of the left ventricle are two or three times thicker than those of the right4 ,a less marked but similar difference exists between the auricles and also between the valves on the two sides of the heart4 ,these differences in structure are all accounted for by the work done by the different portions of the heart4 ,the greater the work1 the heavier the structures that perform the work4 ,fig4 #ag ,fig4 #ag--99;,diagram of the circulation991 showing in general the work done by each part of the heart4 ,the right ventricle forces the blood through the lungs and into the left auricle4 ,the left ventricle forces blood through all parts of the body and back to the auricle4 ,the auricles force blood into the ventricles4 99,connection with ,arteries and ,veins499--,though the heart is in communication with all parts of the circulatory system1 it makes actual connection with only a few of the blood tubes4 ,these enter the heart at its upper portion 7,fig4 #ae71 but connect with its different cavities as follows3 #a4 ,with the right auricle1 the superior and the inferior ven cav and the coronary veins4 ,the superior vena cava receives blood from the head and the upper extremities2 the inferior vena cava1 from the trunk and the lower extremities2 and the coronary veins1 from the heart itself4 #b4 ,with the left auricle1 the four pulmonary veins4 ,these receive blood from the lungs and empty it into the left auricle4 #c4 ,with the right ventricle1 the pulmonary artery4 ,this receives blood from the heart and by its branches distributes it to all parts of the lungs4 #d4 ,with the left ventricle1 the aorta4 ,the aorta receives blood from the heart and through its branches delivers it to all parts of the body4 99,how the ,heart does its ,work499--,the heart is a muscular pump7#ah7 and does its work through the contracting and relaxing of its walls4 ,during contraction the cavities are closed and the blood is forced out of them4 ,during relaxation the cavities open and are refilled4 ,the valves direct the flow of the blood1 being so arranged as to keep it moving always in the same direction 7,fig4 #ag74 ,the heart1 however1 is not a single or a simple pump1 but consists in reality of four pumps which correspond to its different cavities4 ,these connect with each other and with the blood vessels over the body in such a manner that each aids in the general movement of the blood4 ,fig4 #ah ,fig4 #ah--;,diagram illustrating the cardiac cycle4 99,work of ,auricles and ,ventricles ,compared499--,in the work of the heart the two auricles contract at the same time--their contraction being followed immediately by the contraction of both ventricles4 ,after the contraction of the ventricles comes a period of rest1 or relaxation1 about equal in time to the period of contraction of both the auricles and the ventricles47#ai7 ,on account of the work which they perform1 the auricles have been called the feed pumps of the heart2 and the ventricles1 the force pumps47#bj7 ,it is the function of the auricles to collect the blood from the veins1 to let this run slowly into the ventricles when both the auricles and ventricles are relaxed1 and finally1 by contracting1 to force an excess of blood into the ventricles1 thereby distending their walls4 ,the ventricles1 having in this way been fully charged by the auricles1 now contract and force their contents into the large arteries4 99,sounds of the ,heart499--,two distinct sounds are given out by the heart as it pumps the blood4 ,one of them is a dull and rather heavy sound1 while the other is a short1 sharp sound4 ,the short sound follows quickly after the dull sound and the two are fairly imitated by the words lbb1 dp4 ,while the cause of the first sound is not fully understood1 most authorities believe it to be due to the contraction of the heart muscle and the sudden tension on the valve flaps4 ,the second sound is due to the closing of the semilunar valves4 ,these sounds are easily heard by placing an ear against the chest wall4 ,they are of great value to the physician in determining the condition of the heart4 99,arteries and ,veins499--,these form two systems of tubes which reach from the heart to all parts of the body4 ,the arteries receive blood from the heart and distribute it to the capillaries4 ,the veins receive the blood from the capillaries and return it to the heart4 ,the arteries and veins are similar in structure1 both having the form of tubes and both having three distinct layers1 or coats1 in their walls4 ,the corresponding coats in the arteries and veins are made up of similar materials1 as follows3 #a4 ,the inner coat consists of a delicate lining of flat cells resting upon a thin layer of connective tissue4 ,the inner coat is continuous with the lining of the heart and provides a smooth surface over which the blood glides with little friction4 #b4 ,the middle coat consists mainly of non-striated1 or involuntary1 muscular fibers4 ,this coat is quite thin in the veins1 but in the arteries it is rather thick and strong4 #c4 ,the outer coat is made up of a variety of connective tissue and is also much thicker and stronger in the arteries than in the veins4 ,fig4 #ai ,fig4 #ai--;,artery dissected to show the coats4 ,marked differences exist between the arteries and the veins1 and these vessels are readily distinguished from each other4 ,the walls of the arteries are much thicker and heavier than those of the veins 7,fig4 #ai74 ,as a result these tubes stand open when empty1 whereas the veins collapse4 ,the arteries also are highly elastic1 while the veins are but slightly elastic4 ,on the other hand1 many of the veins contain valves1 formed by folds in the inner coat 7,fig4 #bj71 while the arteries have no valves4 ,the blood flows more rapidly through the arteries than through the veins1 the difference being due to the fact that the system of veins has a greater capacity than the system of arteries4 ,fig4 #bj ,fig4 #bj--,vein split open to show the valves4 99,why the ,arteries are ,elastic499--,the elasticity of the arteries serves a twofold purpose4 ,it keeps the arteries from bursting when the blood is forced into them from the ventricles1 and it is a means of supplying pressure to the blood while the ventricles are in a condition of relaxation4 ,the latter purpose is accomplished as follows3 ,contraction of the ventricles fills the arteries overfull1 causing them to swell out and make room for the excess of blood4 ,then while the ventricles are resting and filling1 the stretched arteries press upon the blood to keep it flowing into the capillaries4 ,in this way they cause the intermittent flow from1 the heart to become a steady stream in the capillaries4 ,the swelling of the arteries at each contraction of the ventricle is easily felt at certain places in the body1 such as the wrist4 ,this expansion1 known as the pulse1 is the chief means employed by the physician in determining the force and rapidity of the heart's action4 99,purpose of the ,valves in the ,veins499--,the valves in the veins are not used for directing the general flow of the blood1 the valves of the heart being sufficient for this purpose4 ,their presence is necessary because of the pressure to which the veins are subjected in different parts of the body4 ,the contraction of a muscle will1 for example1 close the small veins in its vicinity and diminish the capacity of the larger ones4 ,the natural tendency of such pressure is to empty the veins in two directions--one in the same direction as the regular movement of the blood1 but the other in the opposite direction4 ,the valves by closing cause the contracting muscle to push the blood in one direction only--toward the heart4 ,the valves in the veins are1 therefore1 an economical device for enabling variable pressure in different parts of the body to assist in the circulation4 ,veins like the inferior vena cava and the veins of the brain1 which are not compressed by movements of the body1 do not have valves4 99,purposes of the ,muscular ,coat499--,the muscular coat1 which is thicker in the arteries than in the veins and is more marked in small arteries than in large ones1 serves two important purposes4 ,in the first place it1 together with the elastic tissue1 keeps the capacity of the blood vessels equal to the volume of the blood4 ,since the blood vessels are capable of holding more blood than may be present at a given time in the body1 there is a liability of empty spaces occurring in these tubes4 ,such spaces would seriously interfere with the circulation1 since the heart pressure could not then reach all parts of the blood stream4 ,this is prevented by the contracted state1 or tone1 of the blood vessels1 due to the muscular coat4 ,in the second place1 the muscular coat serves the purpose of regulating the amount of blood which any given organ or part of the body receives4 ,this it does by varying the caliber of the arteries going to the organ in question4 ,to increase the blood supply1 the muscular coat relaxes4 ,the arteries are then dilated by the blood pressure from within so as to let through a larger quantity of blood4 ,to diminish the supply1 the muscle contracts1 making the caliber of the arteries less1 so that less blood can flow to this part of the body4 ,since the need of organs for blood varies with their activity1 the muscular coat serves in this way a very necessary purpose4 ,fig4 #ba ,fig4 #ba--;,diagram of network of capillaries between a very small artery and a very small vein4 ,shading indicates the change of color of the blood as it passes through the capillaries4 ,s4 ,places between capillaries occupied by the cells4 99,capillaries499--,the capillaries consist of a network of minute blood vessels which connect the terminations of the smallest arteries with the beginnings of the smallest veins 7,fig4 #ba74 ,they have an average diameter of less than one two-thousandth of an inch 7#ab 7 and an average length of less than one twenty-fifth of an inch 7#a millimeter74 ,their walls consist of a single coat which is continuous with the lining of the arteries and veins4 ,this coat is formed of a single layer of thin1 flat cells placed edge to edge 7,fig4 #bb74 ,with a few exceptions1 the capillaries are found in great abundance in all parts of the body4 ,fig4 #bb ,fig4 #bb--99,surface of capillary99 highly magnified1 showing its coat of thin cells placed edge to edge4 99,functions of the ,capillaries499--,on account of the thinness of their walls1 the capillaries are able to serve a twofold purpose in the body3 #a4 ,they admit materials into the blood vessels4 #b4 ,they allow materials to pass from the blood vessels to the surrounding tissues4 ,when it is remembered that the blood1 as blood1 does not escape from the blood vessels under normal conditions1 the importance of the work of the capillaries is apparent4 ,to serve its purpose as a carrier1 there must be places where the blood can load up with the materials which it is to carry1 and places also where these can be unloaded4 ,such places are supplied by the capillaries4 ,the capillaries also serve the purpose of spreading the blood out and of bringing it very near the individual cells in all parts of the body 7,fig4 #ba74 99,functions of ,arteries and ,veins499--,while the capillaries provide the means whereby materials may both enter and leave the blood1 the arteries and veins serve the general purpose of passing the blood from one set of capillaries to another4 ,since pressure is necessary for moving the blood1 these tubes must connect with the source of the pressure1 which is the heart4 ,in the arteries and veins the blood neither receives nor gives up material1 but having received or given up material at one set of capillaries1 it is then pushed through these tubes to where it can serve a similar purpose in another set of capillaries 7,fig4 #bc74 99,divisions of the ,circulation499--,man1 in common with all warm-blooded animals1 has a double circulation1 a fact which explains the double structure of his heart4 ,the two divisions are known as the pulmonary and the systemic circulations4 ,by the former the blood passes from the right ventricle through the lungs1 and is then returned to the left auricle2 by the latter it passes from the left ventricle through all parts of the body1 returning to the right auricle4 ,the general plan of the circulation is indicated in ,fig4 #bc4 ,all the blood flows continuously through both circulations and passes the various parts in the following order3 right auricle1 tricuspid valve1 right ventricle1 right semilunar valve1 pulmonary artery and its branches1 capillaries of the lungs1 pulmonary veins1 left auricle1 mitral valve1 left ventricle1 left semilunar valve1 aorta and its branches1 systemic capillaries1 the smaller veins1 superior and inferior ven cav1 and then again into the right auricle4 ,in the pulmonary capillaries the blood gives up carbon dioxide and receives oxygen1 changing from a dark red to a bright red color4 ,in the systemic capillaries it gives up oxygen1 receives carbon dioxide and other impurities1 and changes back to a dark red color4 ,in addition to the two main divisions of the circulation1 special circuits are found in various places4 ,such a circuit in the liver is called the portal circulation1 and another in the kidneys is termed the renal circulation4 ,to some extent the blood supply to the walls of the heart is also outside of the general movement2 it is called the coronary circulation4 ,fig4 #bc ,fig4 #bc--99;,general scheme of the circulation991 showing places where the blood takes on and gives off materials4 #a4 ,body in general4 #b4 ,lungs4 #c4 ,kidneys4 #d4 ,liver4 #e4 ,organs of digestion4 #f4 ,lymph ducts4 #g4 ,pulmonary artery4 #h4 ,aorta4 99,blood ,pressure and ,velocity499--,the blood1 in obedience to physical laws1 passes continuously through the blood vessels1 moving always from a place of greater to one of less pressure4 ,through the contraction of the ventricles1 a relatively high pressure is maintained in the arteries nearest the heart47#ba7 ,this pressure diminishes rapidly in the small arteries1 becomes comparatively slight in the capillaries1 and falls practically to nothing in the veins4 ,near the heart in the superior and inferior ven cav1 the pressure at intervals is said to be negative4 ,this means that the blood from these veins is actually drawn into the right auricle by the expansion of the chest walls in breathing47#bb7 ,the velocity of the blood is greatest in the arteries1 less in the veins1 and much less in the capillaries than in either the arteries or the veins4 ,the slower flow of the blood through the capillaries is accounted for by the fact that their united area is many times greater than that of the arteries which supply1 or the veins which relieve1 them4 ,this allows the same quantity of blood1 flowing through them in a given time1 a wider channel and causes it to move more slowly4 ,the time required for a complete circulation is less than one minute4 99,summary of ,causes of ,circulation499--,the chief factor in the circulation of the blood is1 of course1 the heart4 ,the ventricles keep a pressure on the blood which is sufficient to force it through all the blood tubes and back to the auricles4 ,the heart is aided in its work by the elasticity of the arteries1 which keeps the blood under pressure while the ventricles are in a state of relaxation4 ,it is also aided by the muscles and elastic tissue in all of the blood vessels4 ,these1 by keeping the blood vessels in a state of tone1 or so contracted that their capacity just equals the volume of the blood1 enable pressure from the heart to be transmitted to all parts of the blood stream4 ,a further aid to the circulation is found in the valves in the veins1 which enable muscular contraction within the body1 and variable pressure upon its surface1 to drive the blood toward the heart4 ,the heart is also aided to some extent by the movements of the chest walls in breathing4 ,the organs ,of circulation are under the control of the nervous system 7,chapter ,,xviii74 ,,hygiene ,,of ,,the ,,circulation 99,care of the ,heart499--,the heart1 consisting largely of muscle1 is subject to the laws of muscular exercise4 ,it may be injured by over-exertion1 but is strengthened by a moderate increase in its usual work47#bc7 ,it may even be subjected to great exertion without danger1 if it be trained by gradually increasing its work4 ,such training1 by giving the heart time to gain in size and strength1 prepares it for tasks that could not at first be accomplished4 ,in taking up a new exercise requiring considerable exertion1 precautions should be observed to prevent an overstrain of the heart4 ,the heart of the amateur athlete1 bicyclist1 or mountain climber is frequently injured by attempting more than the previous training warrants4 ,the new work should be taken up gradually1 and feats requiring a large outlay of physical energy should be attempted only after long periods of training4 ,since the heart is controlled by the nervous system1 it frequently becomes irregular in its action through conditions that exhaust the nervous energy4 ,palpitations of the heart1 the missing of beats1 and pains in the heart region frequently arise from this cause4 ,it is through their effect upon the nervous system that worry1 overstudy1 undue excitement1 and dissipation cause disturbances of the heart4 ,in all such cases the remedy lies in the removal of the cause4 ,the nervous system should also be toned up through rest1 plenty of sleep1 and moderate exercise in the open air4 99,effect of ,drugs499--,a number of substances classed as drugs1 mainly by their action on the nervous system1 produce undesirable effects upon the organs of circulation4 ,unfortunately some of these are extensively used1 alcohol being one of them4 ,if taken in any but small quantities1 alcohol is a disturbing factor in the circulation4 ,it increases the rate of the heart beat and dilates the capillaries4 ,its effect upon the capillaries is shown by the bloodshot eye and the red nose of the hard drinker4 ,another bad effect from the use of much alcohol is the weakening of the heart through the accumulation of fat around this organ and within the heart muscle4 ,the use of alcohol also leads in many cases to a hardening of the walls of the arteries1 such as occurs in old age4 ,this effect makes the use of alcohol especially dangerous for those in advanced years4 ,tobacco contains a drug1 called nicotine1 which has a bad effect upon the heart in at least two ways3 #a4 ,when the use of tobacco is begun in early life1 it interferes with the growth of the heart1 leading to its weakness in the adult4 #b4 ,when used in considerable quantity1 by young or old1 it causes a nervous condition both distressing and dangerous1 known as tobacco heart4 ,tea and coffee contain a drug1 called caffeine1 which acts upon the nervous system and which may1 on this account1 interfere with the proper control of the heart4 ,in some individuals the taking of a very small amount of either tea or coffee is sufficient to cause irregularities in the action of the heart4 ,tea is considered the milder of the two liquids and the one less liable to injure4 99,effect of ,rheumatism499--,the disease which affects the heart more frequently than any other is rheumatism4 ,this attacks the lining membrane1 or endocardium1 and causes1 not infrequently1 a shrinkage of the heart valves4 ,the heart is thus rendered defective and1 to perform its function in the body1 must work harder than if it were in a normal condition4 ,rheumatic attacks of the heart do most harm when they occur in early life--the period when the valves are the most easily affected4 ,any tendency toward rheumatism in children has1 therefore1 a serious significance and should receive the attention of the physician4 ,any one having a defective heart should avoid all forms of exercise that demand great exertion4 99,strengthening of the ,blood ,vessels499--,disturbances of the circulation1 causing too much blood to be sent to certain parts of the body and an insufficient amount to others1 when resulting from slight causes1 are usually due to weakness of the walls of the blood vessels1 particularly of the muscular coat4 ,such weakness is frequently indicated by extreme sensitiveness to heat or cold and by a tendency to catch cold4 ,from a health standpoint the preservation of the normal muscular tone of the blood vessels is a problem of great importance4 ,though the muscles of the blood vessels cannot be exercised in the same manner as the voluntary muscles1 they may be called actively into play through all the conditions that induce changes in the blood supply to different parts of the body4 ,the usual forms of physical exercise necessitate such changes and indirectly exercise the muscular coat4 ,the exposure of the body to cold for short intervals1 because of the changes in the circulation which this induces1 also serves the same purpose4 ,a cold bath taken with proper precautions is beneficial to the circulation of many and so also is a brisk walk on a frosty morning4 ,both indirectly exercise and strengthen the muscular coat of the blood vessels4 ,on the other hand1 too much time spent indoors1 especially in overheated rooms1 leads to a weakening of the muscular coat and should be avoided4 99,checking of ,flow of ,blood from ,wounds499--,the loss of any considerable quantity of blood is such a serious matter that every one should know the simpler methods of checking its flow from wounds4 ,in small wounds the flow is easily checked by binding cotton or linen fiber over the place4 ,the absorbent cotton1 sold in small packages at drug stores1 is excellent for this purpose and should be kept in every home4 ,a simple method of checking nosebleed is that of drawing air through the bleeding nostril1 while the other nostril is compressed with the finger47#bd7 ,another method is to press with the finger 7or insert a small roll of paper7 under the lip against the base of the nose4 7#be7 ,where the bleeding is persistent1 the nostril should be plugged with a small roll of clean cotton or paper4 ,when this is done1 the plug should not be removed too soon because of the likelihood of starting the flow afresh4 ,in dealing with large wounds the services of a physician are indispensable4 ,but in waiting for the physician to arrive temporary aid must be rendered4 ,the one who gives such aid should first decide whether an artery or a vein has been injured4 ,this is easily determined by the nature of the blood stream1 which is in jets1 or spurts1 from an artery1 but flows steadily from a vein4 ,if an artery is injured1 the limb should be tightly bandaged on the side of the wound nearest the heart2 if a vein1 on the side farthest from the heart4 ,in addition to this1 the edges of the wound should be closed and covered with cotton fiber and the limb should be placed on a support above the level of the rest of the body4 ,a large handkerchief makes a convenient bandage if properly applied4 ,this should be folded diagonally and a knot tied in the middle4 ,opposite ends are then tied1 making a loose-fitting loop around the limb4 ,the knot is placed directly over the blood vessel to be compressed and a short stick inserted in the loop4 ,the necessary pressure is then applied by twisting the handkerchief with the stick4 ,time must not be lost1 however1 in the preparation of a suitable bandage4 ,the blood vessel should be compressed with the fingers while the bandage is being prepared4 99,summary499--,the blood1 to serve as a transporting agent1 must be kept continually moving through all parts of the body4 ,the blood vessels hold the blood1 supply the channels and force necessary for its circulation1 and provide conditions which enable materials both to enter and to leave the blood stream4 ,the heart is the chief factor in propelling the blood1 although the muscles and the elastic tissue in the walls of the arteries and the valves in the veins are necessary aids in the process4 ,in the capillaries the blood takes on and gives off materials1 while the arteries and veins serve chiefly as tubes for conveying the blood from one system of capillaries to another4 99,exercises499--#a4 ,of what special value in the study of the body was the discovery of the circulation of the blood8 #b4 ,state the necessity for a circulating liquid in the body4 #c4 ,show by a drawing the general plan of the heart1 locating and naming the essential parts4 ,show also the connection of the large blood vessels with the cavities of the heart4 #d4 ,compare the purpose served by the chord tendine to that served by doorstops 7the strips against which the door strikes in closing74 #e4 ,explain how the heart propels the blood4 ,to what class of pumps does it belong8 ,what special work is performed by each of its divisions8 #f4 ,define a valve4 ,of what use are the valves in the heart8 ,in the veins8 #g4 ,by what means is pressure from contracting muscles in different parts of the body made to assist in the circulation8 #h4 ,of what advantage is the elasticity of the arteries8 #i4 ,how is blood forced from the capillaries back to the heart8 #aj4 ,why should there be a difference in structure between the two sides of the heart8 #aa4 ,following ,fig4 #bc1 trace the blood through a complete circulation1 naming all the divisions of the system in the order of the flow of the blood4 #ab4 ,if the period of rest following the period of contraction of the heart be as long as the period of contraction1 how many hours is the heart able to rest out of every twenty-four8 #ac4 ,state the functions of the capillaries4 ,show how their structure adapts them to their work4 #ad4 ,what kind of physical exercise tends to strengthen the heart8 ,what forms of exercise tend to injure it8 ,state the effects of alcohol and tobacco on the heart4 #ae4 ,how may rheumatism injure the heart8 #af4 ,give directions for checking the flow of blood from small and from large blood vessels4 ,,practical ,,work ,in showing the relations of the different parts of the heart1 a large dissectible model is of great service 7,fig4 #bd74 ,indeed1 where the time of the class is limited1 the practical work may be confined to the study of the heart model1 diagrams of the heart and the circulation1 and a few simple experiments4 ,however1 where the course is more extended1 the dissection of the heart of some animal as described below is strongly advised4 99,observations on the ,heart499--,procure1 by the assistance of a butcher1 the heart of a sheep1 calf1 or hog4 ,to insure the specimen against mutilation1 the lungs and the diaphragm must be left attached to the heart4 ,in studying the different parts1 good results will be obtained by observing the following order3 #a4 ,observe the connection of the heart to the lungs1 diaphragm1 and large blood vessels4 ,inflate the lungs and observe the position of the heart with reference to them4 #b4 ,examine the sac surrounding the heart1 called the pericardium4 ,pierce its lower portion and collect the pericardial fluid4 ,increase the opening thus made until it is large enough to slip the heart out through it4 ,then slide back the pericardium until its connection with the large blood vessels above the heart is found4 ,observe that a thin layer of it continues down from this attachment1 forming the outer covering of the heart4 #c4 ,trace out for a short distance and study the veins and arteries connected with the heart4 ,the arteries are to be distinguished by their thick walls4 ,the heart may now be severed from the lungs by cutting the large blood vessels1 care being taken to leave a considerable length of each one attached to the heart4 ,fig4 #bd ,fig4 #bd--,model for demonstrating the heart4 #d4 ,observe the outside of the heart4 ,the thick1 lower portion contains the cavities called ventricles2 the thin1 upper1 ear-shaped portions are the auricles4 ,the thicker and denser side lies toward the left of the animal's body and is called the left side of the heart2 the other is the right side4 ,locate the right auricle and the right ventricle2 the left auricle and the left ventricle4 #e4 ,lay the heart on the table with the front side up and the apex pointing from the operator4 ,this places the left side of the heart to his left and the right side to his right4 ,notice the groove between the ventricles1 called the inter-ventricular groove4 ,make an incision half an inch to the right of this groove and cut toward the base of the heart until the pulmonary artery is laid open4 ,then1 following within half an inch of the groove1 cut down and around the right side of the heart4 ,the wall of the right ventricle may now be raised and the cavity exposed4 ,observe the extent of the cavity1 its shape1 its lining1 its columns of muscles1 its half columns of muscles1 its tendons 7chord tendine71 the tricuspid valve from the under side1 etc4 ,also notice the valve at the beginning of the pulmonary artery 7the right semilunar7 and the sinuses1 or depressions1 in the artery immediately behind its divisions4 #f4 ,now cut through the middle of the loosened ventricular wall from the apex to the middle of the right auricle1 laying it open for observation4 ,observe the openings into the auricle1 there being one each for the vena cava superior1 the vena cava inferior1 and the coronary vein4 ,compare the walls1 lining1 shape1 size1 etc41 with the ventricle below4 #g4 ,cut off the end of the left ventricle about an inch above the apex4 ,this will show the extension of the cavity to the apex2 it will also show the thickness of the walls and the shape of the cavity4 ,split up the ventricular wall far enough to examine the mitral valve and the chord tendine from the lower side4 #h4 ,make an incision in the left auricle4 ,examine its inner surface and find the places of entrance of the pulmonary veins4 ,examine the mitral valve from above4 ,compare the two sides of the heart1 part for part4 #i4 ,separate the aorta from the other blood vessels and cut it entirely free from the heart1 care being taken to leave enough of the heart attached to the artery to insure the semilunar valve's being left in good condition4 ,after tying or plugging up the holes in the sides of the artery1 pour water into the small end and observe the closing of the semilunar valve4 ,repeat the experiment until the action of the valve is understood4 ,sketch the artery1 showing the valve in a closed condition4 99,to illustrate the ,action of a ,ventricle499--,procure a syringe bulb with an opening at each end4 ,connect a rubber tube with each opening1 letting the tubes reach into two tumblers containing water4 ,by alternately compressing and releasing the bulb1 water is pumped from one vessel into the other4 ,the bulb may be taken to represent one of the ventricles4 ,what action of the ventricle is represented by compressing the bulb8 ,by releasing the pressure8 ,show by a sectional drawing the arrangement of the valves in the syringe bulb4 ,fig4 #be ,fig4 #be--;,illustrating elasticity of arteries4 99,to show the ,advantage of the ,elasticity of ,arteries499--,connect the syringe bulb used in the last experiment with a rubber tube three or four feet in length and having rather thin walls4 ,in the opposite end of the rubber tube insert a short glass tube which has been drawn 7by heating7 to a fine point 7,fig4 #be74 ,pump water into the rubber tube1 observing3 #a4 ,the swelling of the tube 7pulse7 as the water is forced into it4 7,this is best observed by placing the fingers on the tube47 #b4 ,the forcing of water from the pointed tubs during the interval when no pressure is being applied from the bulb4 ,compare with the action of the arteries when blood is forced into them from the ventricles4 ,repeat the experiment1 using a long glass tube terminating in a point instead of the rubber tube4 7,in fitting the glass tube to the bulb use a very short rubber tube47 ,observe and account for the differences in the flow of water through the inelastic tube4 99,to show the ,advantage of ,valves in the ,veins499--,attach an open glass tube one foot in length to each end of the rubber tube used in the preceding experiment and fill with water 7by sucking7 to within about six inches of the end4 ,lay on the table with the glass tubes secured in an upright position 7,fig4 #bf74 ,now compress the tube with the hand1 noting that the water rises in both tubes1 being pushed in both directions4 ,this effect is similar to that produced on the blood when a vein having no valves is compressed4 ,fig4 #bf ,fig4 #bf4--99,simple apparatus99 for showing advantage of valves in veins4 ,now imitate the action of a valve by clamping the tube at one point1 or by closing it by pressure from the finger1 and then compressing with the hand some portion of the tube on the table4 ,observe in this instance that the water is 99all99 pushed in the same direction4 ,the movement of the water is now like the effect produced on the blood in veins having valves when the veins are compressed4 99,to show the ,position of the ,valves in the ,veins499--,exercise the arm and hand for a moment to increase the blood supply4 ,expose the forearm and examine the veins on its surface4 ,with a finger1 stroke one of the veins toward the heart1 noting that1 as the blood is pushed along on one side of the finger the blood follows on the other side4 ,now stroke the vein toward the hand4 ,places are found beyond which the blood does not follow the finger4 ,these mark the positions of valves4 99,to show ,effect of ,exercise upon the ,circulation499--#a4 ,with a finger on the pulse at the wrist or temple1 count the number of heart beats during a period of one minute under the following conditions3 7a7 when sitting2 7b7 when standing2 7c7 after active exercise1 as running4 ,what relation1 if any1 do these observations indicate between the general activity of the body and the work of the heart8 #b4 ,compare the size of the veins on the backs of the hands when they are placed side by side on a table4 ,then exercise briskly the right hand and arm1 clenching and unclenching the fist and flexing the arm at the elbow4 ,place the hands again side by side and1 after waiting a minute1 observe the increase in the size of the veins in the hand exercised4 ,how is this accounted for8 99,to ,show the ,effect of ,gravity on the ,circulation499--,hold one hand high above the head1 at the same time letting the other hand hang loosely by the side4 ,observe the difference in the color of the hands and the degree to which the large veins are filled4 ,repeat the experiment1 reversing the position of the hands4 ,what results are observed8 ,in what parts of the body does gravity aid in the return of the blood to the heart8 ,in what parts does it hinder8 ,where fainting is caused by lack of blood in the brain 7the usual cause71 is it better to let the patient lie down flat or to force him into a sitting posture8 99,to study the ,circulation in a ,frog's ,foot99 7,optional74--,a compound microscope is needed in this study and for extended examination it is best to destroy the frog's brain4 ,this is done by inserting some blunt-pointed instrument into the skull cavity from the neck and moving it about4 ,a small frog1 on account of the thinness of its webs1 gives the best results4 ,it should be attached to a thin board which has an opening in one end over which the web of the foot may be stretched4 ,threads should extend from two of the toes to pins driven into the board to secure the necessary tension of the web1 and the foot and lower leg should be kept moist4 ,using a two-thirds-inch objective1 observe the branching of the small arteries into the capillaries and the union of the capillaries to form the small veins4 ,the appearance is truly wonderful1 but allowance must be made for the fact that the motion of the blood is magnified1 as well as the different structures1 and that it appears to move much faster than it really does4 ,with a still higher power1 the movements of the corpuscles through the capillaries may be studied4 ,,note4--,to perform this experiment without destroying the brain1 the frog is first carefully wrapped with strips of wet cloth and securely tied to the board4 ,the wrapping1 while preventing movements of the frog1 must not interfere with the circulation4 ,,chapter ,,vi - ,,the ,,lymph ,,and ,,its ,,movement ,,through ,,the ,,body ,fig4 #bg ,fig4 #bg--99;,diagram showing position of the lymph99 with reference to the blood and the cells4 ,the central tube is a capillary4 ,the arrows indicate the direction of slight movements in the lymph4 ,the blood1 it will be remembered1 moves everywhere through the body in a system of closed tubes4 ,these keep it from coming in contact with any of the cells of the body except those lining the tubes themselves4 ,the capillaries1 to be sure1 bring the blood very near the cells of the different tissues2 still1 there is need of a liquid to fill the space between the capillaries and the cells and to transfer materials from one to the other4 ,the lymph occupies this position and does this work4 ,the position of the lymph with reference to the capillaries and the cells is shown in ,fig4 #bg4 99,origin of the ,lymph499--,the chief source of the lymph is the plasma of the blood4 ,as before described1 the walls of the capillaries consist of a single layer of flat cells placed edge to edge4 ,partly on account of the pressure upon the blood and partly on account of the natural tendency of liquids to pass through animal membranes1 a considerable portion of the plasma penetrates the thin walls and enters the spaces occupied by the lymph4 ,the cells themselves also help to form the lymph1 since the water and wastes leaving the cells add to its bulk4 ,these mix with the plasma from the blood1 forming the resultant liquid which is the lymph4 ,a considerable amount of the material absorbed from the food canal also enters the lymph tubes1 but this passes into the blood before reaching the cells4 99,composition and ,physical ,properties of the ,lymph4997#bf7--;,as would naturally be expected1 the composition of the lymph is similar to that of the blood4 ,in fact1 nearly all the important constituents of the blood are found in the lymph1 but in different proportions4 ,food materials for the cells are present in smaller amounts than in the blood1 while impurities from the cells are in larger amounts4 ,as a rule the red corpuscles are absent from the lymph1 but the white corpuscles are present and in about the same numbers as in the blood4 ,the physical properties of the lymph are also similar to those of the blood4 ,like the blood1 the lymph is denser than water and also coagulates1 but it coagulates more slowly than does the blood4 ,the most noticeable difference between these liquids is that of color1 the lymph being colorless4 ,this is due to the absence of red corpuscles4 ,the quantity of lymph is estimated to be considerably greater than that of the blood4 99,lymph ,vessels499--,most of the lymph lies in minute cavities surrounding the cells and in close relations with the capillaries 7,figs4 #bg and #cj74 ,these are called lymph spaces4 ,connecting with the lymph spaces on the one hand1 and with certain blood vessels on the other1 is a system of tubes that return the lymph to the blood stream4 ,the smallest of these1 and the ones in greatest abundance1 are called lymphatics4 ,they consist of slender1 thin-walled tubes1 which resemble veins in structure1 and1 like the veins1 have valves4 ,they differ from veins1 however1 in being more uniform in size and in having thinner walls4 ,fig4 #bh ,fig4 #bh--99;,diagram of drainage system for the lymph499 #a4 ,thoracic duct4 #b4 ,right lymphatic duct4 #c4 ,left subclavian vein4 #d4 ,right subclavian vein4 #e4 ,superior vena cava4 #f4 ,lacteals4 #g4 ,lymphatic glands4 ,the small tubes connecting with the lymph spaces in all parts of the body are the lymphatics4 ,the lymphatics in different places gradually converge toward1 and empty into1 the two main lymph tubes of the body4 ,the smaller of these tubes1 called the right lymphatic duct1 receives the lymph from the lymphatics in the right arm1 the right side of the head1 and the region of the right shoulder4 ,it connects with1 and empties its contents into1 the right subclavian vein at the place where it is joined by the right jugular vein 7,fig4 #bh74 ,the larger of the lymph tubes is called the thoracic duct4 ,this receives lymph from all parts of the body not drained by the right lymphatic duct1 and empties it into the left subclavian vein4 ,connection is made with the subclavian vein on the upper side at the place where it is joined by the left jugular vein4 ,the thoracic duct has a length of from sixteen to eighteen inches1 and is about as large around as a goose quill4 ,the lower end terminates in an enlargement in the abdominal cavity1 called the receptacle of the chyle4 ,it is provided with valves throughout its course1 in addition to one of considerable size which guards the opening into the blood vessel4 ,the lymphatics which join the thoracic duct from the small intestine are called the lacteals 7,fig4 #bh74 ,these do not differ in structure from the lymphatics in other parts of the body1 but they perform a special work in absorbing the digested fat 7,chapter ,,xi74 99,lymphatic ,glands499--,the lymphatic glands1 sometimes called lymph nodes1 are small and somewhat rounded bodies situated along the course of the lymphatic tubes4 ,they vary in size1 some of them being an inch or more in length4 ,the lymph vessels generally open into them on one side and leave them on the other 7,figs4 #bh and #cj74 ,they are not glands in function1 but are so called because of their having the general form of glands4 ,they provide favorable conditions for the development of white corpuscles 7page #bi74 ,they also separate harmful germs and poisonous wastes from the lymph1 thereby preventing their entrance into the blood4 99,relations of the ,lymph1 the ,blood1 and the ,cells499--,while the blood is necessary as a carrying1 or transporting1 agent in the body1 the lymph is necessary for transferring materials from the blood to the cells and vice versa4 ,serving as a physiological go between1 or medium of exchange1 the lymph enables the blood to minister to the needs of the cells4 ,but the lymph and the blood1 everything considered1 can hardly be looked upon as two separate and distinct liquids4 ,not only do they supplement each other in their work and possess striking similarities1 but each is made in its movements to pass into the vessels occupied by the other1 so that they are constantly mixing and mingling4 ,for these and other reasons1 they are more properly regarded as two divisions of a single liquid--one which1 by adapting itself to different purposes17#bg7 supplies all the conditions of a nutrient fluid for the cells4 99,movements of the ,lymph499--,as compared with the blood1 the lymph must be classed as a quiet liquid4 ,but1 as already suggested1 it has certain movements which are necessary to the purposes which it serves4 ,a careful study shows it to have three well-defined movements as follows3 #a4 ,a movement from the capillaries toward the cells4 #b4 ,a movement from the cells toward the capillaries4 #c4 ,a movement of the entire body of lymph from the lymph spaces into the lymphatics and along these channels to the ducts through which it enters the blood4 ,by the first movement the cells receive their nourishment4 ,by the second and third movements the lymph1 more or less laden with impurities1 is returned to the blood stream4 7,see ,figs4 #bh and #cj47 99,causes of the ,lymph ,movements499--,let us consider first the movement through the lymph tubes4 ,no pump1 like the heart1 is known to be connected with these tubes and to supply the pressure necessary for moving the lymph4 ,there are1 however1 several forces that indirectly aid in its flow4 ,the most important of these are as follows3 #a4 ,blood ,pressure at the ,capillaries4--,the plasma which is forced through the capillary walls by pressure from the heart makes room for itself by pushing a portion of the lymph out of the lymph spaces4 ,this in turn presses upon the lymph in the tubes which it enters4 ,in this way pressure from the heart is transmitted to the lymph1 forcing it to move4 #b4 ,variable ,pressure on the ,walls of the ,lymph ,vessels4--,pressure exerted on the sides of the lymph tubes by contracting muscles tends to close them up and to push the lymph past the valves1 which1 by closing1 prevent its return 7,fig4 #bi74 ,pressure at the surface of the body1 provided that it is variable1 also forces the lymph along4 ,the valves in the lymph vessels serve the same purpose as those in the veins4 ,fig4 #bi ,fig4 #bi--99;,diagram99 to show how the muscles pump lymph4 ,a4 ,relaxed muscle beside which is a lymphatic tube4 ,b4 ,same muscle in state of contraction4 #c4 ,the ,inspiratory ,force4--,when the thoracic cavity is enlarged in breathing1 the unbalanced atmospheric pressure is exerted from all directions towards the thoracic space4 ,this not only causes the air to flow into the lungs 7,chapter ,,vii71 but also causes a movement of the blood and lymph in such of their tubes as enter this cavity4 ,it will be noted that both of the large lymph ducts terminate where their contents may be influenced by the respiratory movements4 7,see ,practical ,work47 99,where the ,lymph enters the ,blood499--,the fact that the lymph is poured into the blood at but two places1 and these very close to each other1 requires a word of explanation4 ,as a matter of fact1 it is impossible for the lymph to flow into blood vessels at most places on account of the blood pressure4 ,this would force the blood into the lymph vessels1 instead of allowing the lymph to enter the blood4 ,the lymph can enter only at some place where the blood pressure is less than the pressure that moves the lymph4 ,such a place is found in the thoracic cavity4 ,as already pointed out 7page #ed71 the blood pressure in the veins entering this cavity becomes1 with each expansion of the chest1 negative1 i4e41 less than the pressure of the atmosphere on the outside of the body4 ,this1 as we have seen1 aids in the flow of the blood into the right auricle4 ,it also aids in the passage of lymph into the blood vessels4 ,the lymph is said to be sucked in1 which means that it is forced in by the unbalanced pressure of the atmosphere47#bh7 ,some advantage is also gained by the lymph duct's entering the subclavian vein on the upper side and at its union with the jugular vein4 ,everything considered1 it is found that the lymph flows into the blood vessels where it can be drawn in by the movements of breathing and where it meets with no opposition from the blood stream itself 7,fig4 #cj74 ,fig4 #cj ,fig4 #cj--99;,diagram99 showing general movement of lymph from the place of relatively high pressure at the lymph spaces to the place of relatively low pressure in the thoracic cavity4 99,lymph ,movements at the ,cells499--,the double movement of the lymph from the capillaries toward the cells and from the cells toward the capillaries is not entirely understood4 ,blood pressure in the capillaries undoubtedly has much to do in forcing the plasma through the capillary walls1 but this tends to prevent the movement of the lymph in the opposite direction4 ,movements between the blood and the lymph are known to take place in part according to a general principle1 known as osmosis1 or dialysis4 ,fig4 #ca ,fig4 #ca--99,vessel99 with an upright membranous partition for illustrating osmosis4 99,osmosis499--,the term osmosis is used to designate the passage of liquids through some partition which separates them4 ,thus1 if a vessel with an upright membranous partition be filled on the one side with pure water and on the other with water containing salt1 an exchange of materials will take place through the membrane until the same proportion of salt exists on the two sides 7,fig4 #ca74 ,the cause of osmosis is the motion of the molecules1 or minute particles1 that make up the liquid substance4 ,if the partition were not present1 this motion would simply cause a mixing of the liquids4 99,conditions under which ,osmosis occurs499--,osmosis may be shown by suitable experiments 7see ,practical ,work7 to take place under the following conditions3 #a4 ,the liquids on the two sides of the partition must be unlike either in density or in composition4 ,since the effect of the movement is to reduce the liquids to the same condition1 a difference in density causes the flow to be greater from the less dense toward the denser liquid1 than in the opposite direction2 while a difference in composition causes the substances in solution to move from the place of greater abundance toward places of less abundance4 #b4 ,the liquids must be capable of wetting1 or penetrating1 the partition4 ,if but one of the liquids penetrates the partition1 the flow will be in but one direction4 #c4 ,the liquids on the two sides of the partition must readily mix with each other4 99,osmosis at the ,cells499--,in the body osmosis takes place between the blood and the lymph and between the lymph and the cells1 the movements being through the capillary walls and the membranes inclosing the cells 7,fig4 #bg74 ,oxygen and food materials1 which are found in great abundance in the blood1 are less abundant in the lymph and still less abundant in the cells4 ,according to the principle of osmosis1 the main flow of oxygen and food is from the capillaries toward the cells4 ,on the other hand1 the wastes are most abundant in the cells where they are formed1 less abundant in the lymph1 and least abundant in the blood4 ,hence the wastes flow from the cells toward the capillaries4 99,solutions499--,neither the blood plasma nor the lymph1 as already shown1 are simple liquids2 but they consist of water and different substances dissolved in the water4 ,they belong to a class of substances called solutions4 ,the chief point of interest about substances in solution is that they are very finely divided and that their little particles are free to move about in the liquid that contains them4 ,both the motion and the finely divided condition of the dissolved substances are necessary to the process of osmosis4 ,all substances1 however1 that appear to be in solution are not able to penetrate membranes1 or take part in osmosis4 99,kinds of ,solutions in the ,body499--,the substances in solution in the body liquids are of two general kinds known as colloids and crystalloids4 ,the crystalloids are able to pass through membranous partitions1 while the colloids are not4 ,an example of a colloid is found in the albumin of an egg1 which is unable to penetrate the membrane which surrounds it4 ,examples of crystalloids are found in solutions of salt and sugar in water4 ,the inability of a colloid to penetrate a membrane is due to the fact that it does not form a true solution4 ,its particles 7molecules71 instead of being completely separated1 still cling together1 forming little masses that are too large to penetrate the membrane4 ,since1 however1 it has the appearance1 on being mixed with water1 of being dissolved1 it is called a colloidal solution4 ,the crystalloid substance1 on the other hand1 completely separates in the water and forms a true solution--one which is able to penetrate the partition or membrane4 99,osmosis not a ,sufficient ,cause499--,the passage of materials through animal membranes1 according to the principle of osmosis1 is limited to crystalloid substances4 ,but colloid substances are also known to pass through the various partitions of the body4 ,an example of such is found in the proteids of the blood which1 as a colloidal solution1 pass through the capillary walls to become a part of the lymph4 ,perhaps the best explanation offered as yet for this passage is that the colloidal substances are changed by the cells lining the capillaries into substances that form true solutions and that after the passage they are changed back again to the colloidal condition4 99,summary499--,between the cells and the capillaries is a liquid1 known as the lymph1 which is similar in composition and physical properties to the blood4 ,it consists chiefly of escaped plasma4 ,the vessels that contain it are connected with the system for the circulation of the blood4 ,by adding new material to the lymph and withdrawing waste material from it1 the blood keeps this liquid in a suitable condition for supplying the needs of the cells4 ,supplementing each other in all respects1 the blood and the lymph together form the nutrient cell fluid of the body4 ,the interchange of material between the blood and the lymph1 and the lymph and the cells1 takes place in part according to the principle of osmosis4 99,exercises499--#a4 ,explain the necessity for the lymph in the body4 #b4 ,compare lymph and water with reference to density1 color1 and complexity of composition4 #c4 ,compare lymph and blood with reference to color1 composition1 and movement through the body4 #d4 ,show how blood pressure in the capillaries causes a flow of the lymph4 #e4 ,show how contracting muscles cause the lymph to move4 ,compare with the effect of muscular contraction upon the blood in the veins4 #f4 ,trace the lymph in its flow from the right hand to where it enters the blood2 from the feet to where it enters the blood4 #g4 ,what conditions prevail at the cells to cause a movement of food and oxygen in one direction and of waste materials in the opposite direction8 #h4 ,what part does water play in the exchanges at the cells8 #i4 ,show that the blood and the lymph together fulfill all the requirements of a nutrient cell fluid in the body4 ,,practical ,,work 99,to illustrate the ,effect of ,breathing upon the ,flow of ,lymph499--,tightly holding one end of a glass tube between the lips1 let the other end extend into water in a tumbler on a table4 ,in this position quickly inhale air through the nostrils1 noting that with each inhalation there is a slight movement of the water up the tube4 7,no sucking action should be exerted by the mouth47 ,apply to the movements in the large blood and lymph vessels entering the thoracic cavity4 99,to illustrate ,osmosis499--#a4 ,separate the shell from the lining membrane at one end of an egg1 over an area about one inch in diameter4 ,to do this without injuring the membrane1 the shell must first be broken into small pieces and then picked off with a pair of forceps1 or a small knife blade4 ,fit a small glass tube1 eight or ten inches long1 into the other end so that it will penetrate the membrane and pass down into the yolk4 ,securely fasten the tube to the shell by melting beeswax around it1 and set the egg in a small tumbler partly filled with water4 ,examine in the course of half an hour4 ,what evidence now exists that the water has passed through the membrane8 #b4 ,tie over the large end of a thistle tube 7used by chemists7 a thin animal membrane1 such as a piece of the pericardium or a strip of the membrane from around a sausage4 ,then fill the bulb and the lower end of the tube with a concentrated solution of some solid1 such as sugar1 salt1 or copper sulphate4 ,suspend in a vessel of water so that the liquid which it contains is just on a level with the water in the vessel4 ,examine from time to time1 looking for evidence of a movement in each direction through the membrane4 ,why should the movement of the water into the tube be greater than the movement in the opposite direction8 7,if the thistle tube has a very slender stem1 it is better to fill the bulb before tying on the membrane4 ,the opening in the stem may be plugged during the process of filling47 ,fig4 #cb ,fig4 #cb--;,an osmosometer4 ,,note4--,with a special piece of apparatus1 known as an osmosometer1 the principle of osmosis may be more easily illustrated than by the method in either of the above experiments 7,fig4 #cb74 ,this apparatus may be obtained from supply houses4 ,,chapter ,,vii - ,,respiration ,through the movements of the blood and the lymph1 materials entering the body are transported to the cells1 and wastes formed at the cells are carried to the organs which remove them from the body4 ,we are now to consider the passage of materials from outside the body to the cells and vice versa4 ,one substance which the body constantly needs is oxygen1 and one which it is constantly throwing off is carbon dioxide4 ,both of these are constituents of 99,the ,atmosphere499--,the atmosphere1 or air1 completely surrounds the earth as a kind of envelope1 and comes in contact with everything upon its surface4 ,it is composed chiefly of oxygen and nitrogen17#bi7 but it also contains a small per cent of other substances1 such as water-vapor1 carbon dioxide1 and argon4 ,all of the regular constituents of the atmosphere are gases1 and these1 as compared with liquids and solids1 are very light4 ,nevertheless the atmosphere has weight and1 on this account1 exerts pressure upon everything on the earth4 ,at the sea level1 its pressure is nearly fifteen pounds to the square inch4 ,the atmosphere forms an essential part of one's physical environment and serves various purposes4 ,the process by which gaseous materials are made to pass between the body and the atmosphere is known as 99,respiration499--,as usually defined1 respiration1 or breathing1 consists of two simple processes--that of taking air into special contrivances in the body1 called the lungs1 and that of expelling air from the lungs4 ,the first process is known as inspiration2 the second as expiration4 ,we must1 however1 distinguish between respiration by the lungs1 called external respiration1 and respiration by the cells1 called internal respiration4 ,the purpose of respiration is indicated by the changes that take place in the air while it is in the lungs4 ,air entering the lungs in ordinary breathing parts with about five per cent of itself in the form of oxygen and receives about four and one half per cent of carbon dioxide1 considerable water-vapor1 and a small amount of other impurities4 ,these changes suggest a twofold purpose for respiration3 #a4 ,to obtain from the atmosphere the supply of oxygen needed by the body4 #b4 ,to transfer to the atmosphere certain materials 7wastes7 which must be removed from the body4 ,the chief organs concerned in the work of respiration are 99,the ,lungs499--,the lungs consist of two sac-like bodies suspended in the thoracic cavity1 and occupying all the space not taken up by the heart4 ,they are not simple sacs1 however1 but are separated into numerous divisions1 as follows3 #a4 ,the lung on the right side of the thorax1 called the right lung1 is made up of three divisions1 or lobes1 and the left lung is made up of two lobes4 #b4 ,the lobes on either side are separated into smaller divisions1 called lobules 7,fig4 #cc74 ,each lobule receives a distinct division of an air tube and has in itself the structure of a miniature lung4 ,fig4 #cc ,fig4 #cc--99,lungs and air passages99 seen from the front4 ,the right lung shows the lobes and their divisions1 the lobules4 ,the tissue of the left lung has been dissected away to show the air tubes4 #c4 ,in the lobule the air tube divides into a number of smaller tubes1 each ending in a thin-walled sac1 called an infundibulum4 ,the interior of the infundibulum is separated into many small spaces1 known as the alveoli1 or air cells4 ,the lungs are remarkable for their lightness and delicacy of structure47#cj7 ,they consist chiefly of the tissues that form their sacs1 air tubes1 and blood vessels2 the membranes that line their inner and outer surfaces2 and the connective tissue that binds these parts together4 ,all these tissues are more or less elastic4 ,the relation of the different parts of the lungs to each other and to the outside atmosphere will be seen through a study of the 99,air ,passages499--,the air passages consist of a system of tubes which form a continuous passageway between the outside atmosphere and the different divisions of the lungs4 ,the air passes through them as it enters and leaves the lungs1 a fact which accounts for the name4 ,fig4 #cd ,fig4 #cd--99,model of section through the head991 showing upper air passages and other parts4 #a4 ,left nostril4 #b4 ,pharynx4 #c4 ,tongue and cavity of mouth4 #d4 ,larynx4 #e4 ,trachea4 #f4 ,esophagus4 ,the incoming air first enters the nostrils4 ,these consist of two narrow passages lying side by side in the nose1 and connecting with the pharynx behind4 ,the lining of the nostrils1 called mucous membrane is quite thick1 and has its surface much extended by reason of being spread over some thin1 scroll-shaped bones that project into the passage4 ,this membrane is well supplied with blood vessels and secretes a considerable quantity of liquid4 ,because of the nature and arrangement of the membrane1 the nostrils are able to warm and moisten the incoming air1 and to free it from dust particles1 preparing it1 in this way1 for entrance into the lungs 7,fig4 #cd74 ,the nostrils are separated from the mouth by a thin layer of bone1 and back of both the mouth and the nostrils is the pharynx4 ,the pharynx and the mouth serve as parts of the food canal1 as well as air passages1 and are described in connection with the organs of digestion 7,chapter ,x74 ,air entering the pharynx1 either by the nostrils or by the mouth1 passes through it into the larynx4 ,the larynx1 being the special organ for the production of the voice1 is described later 7,chapter ,,xxi74 ,the entrance into the larynx is guarded by a movable lid of cartilage1 called the epiglottis1 which prevents food particles and liquids1 on being swallowed1 from passing into the lower air tubes4 ,the relations of the nostrils1 mouth1 pharynx1 and larynx are shown in ,fig4 #cd4 ,from the larynx the air enters the trachea1 or windpipe4 ,this is a straight and nearly round tube1 slightly less than an inch in diameter and about four and one half inches in length4 ,its walls contain from sixteen to twenty ,c-shaped1 cartilaginous rings1 one above the other and encircling the tube4 ,these incomplete rings1 with their openings directed backward1 are held in place by thin layers of connective and muscular tissue4 ,at the lower end the trachea divides into two branches1 called the bronchi1 each of which closely resembles it in structure4 ,each bronchus separates into a number of smaller divisions1 called the bronchial tubes1 and these in turn divide into still smaller branches1 known as the lesser bronchial tubes 7,fig4 #cc74 ,the lesser bronchial tubes1 and the branches into which they separate1 are the smallest of the air tubes4 ,one of these joins1 or expands into1 each of the minute lung sacs1 or infundibula4 ,mucous membrane lines all of the air passages4 99,general ,condition of the ,air ,passages499--,one necessary condition for the movement of the air into and from the lungs is an unobstructed passageway47#ca7 ,the air passages must be kept open and free from obstructions4 ,they are kept open by special contrivances found in their walls1 which1 by supplying a degree of stiffness1 cause the tubes to keep their form4 ,in the trachea1 bronchi1 and larger bronchial tubes1 the stiffness is supplied by rings of cartilage1 while in the smaller tubes this is replaced by connective and muscular tissue4 ,the walls of the larynx contain strips and plates of cartilage2 while the nostrils and the pharynx are kept open by their bony surroundings4 ,fig4 #ce ,fig4 #ce--99;,ciliated epithelial cells499 ,a4 ,two cells highly magnified4 c4 ,cilia1 n4 ,nucleus4 ,b4 ,diagram of a small air tube showing the lining of cilia4 ,the air passages are kept clean by cells especially adapted to this purpose1 known as the ciliated epithelial cells4 ,these are slender1 wedge-shaped cells which have projecting from a free end many small1 hair-like bodies1 called cilia 7,fig4 #ce74 ,they line the mucous membrane in most of the air passages1 and are so placed that the cilia project into the tubes4 ,here they keep up an inward and outward wave-like movement1 which is quicker and has greater force in the outward direction4 ,by this means the cilia are able to move small pieces of foreign matter1 such as dust particles and bits of partly dried mucus1 called phlegm1 to places where they can be easily expelled from the lungs47#cb7 ,fig4 #cf ,fig4 #cf--99,terminal air sacs499 ,the two large sacs are infundibula2 the small divisions are alveoli4 7,enlarged47 99,the ,alveoli499--,the alveoli1 or air cells1 are the small divisions of the infundibula 7,fig4 #cf74 ,they are each about one one-hundredth of an inch 7#a_/d mm47 in diameter1 being formed by the infolding of the infundibular wall4 ,this wall1 which has for its framework a thin layer of elastic connective tissue1 supports a dense network of capillaries 7,fig4 #cg71 and is lined by a single layer of cells placed edge to edge4 ,by this arrangement the air within the alveoli is brought very near a large surface of blood1 and the exchange of gases between the air and the blood is made possible4 ,it is at the alveoli that the oxygen passes from the air into the blood1 and the carbon dioxide passes from the blood into the air4 ,at no place in the lungs1 however1 do the air and the blood come in direct contact4 ,their exchanges must in all cases take place through the capillary walls and the layer of cells lining the alveoli4 ,fig4 #cg ,fig4 #cg--99;,inner lung surface 7magnified7991 the blood vessels injected with coloring matter4 ,the small pits are alveoli1 and the vessels in their walls are chiefly capillaries4 ,fig4 #ch ,fig4 #ch4--99;,diagram to show the double movement of air and blood through the lungs499 ,the blood leaves the heart by the pulmonary artery and returns by the pulmonary veins4 ,the air enters and leaves the lungs by the same system of tubes4 ,fig4 #ci ,fig4 #ci--99;,diagram to show air and blood movements in a terminal air sac499 ,while the air moves into and from the space within the sac1 the blood circulates through the sac walls4 99,blood ,supply to the ,lungs499--,to accomplish the purposes of respiration1 not only the air1 but the blood also1 must be passed into and from the lungs4 ,the chief artery conveying blood to the lungs is the pulmonary artery4 ,this starts at the right ventricle and by its branches conveys blood to the capillaries surrounding the alveoli in all parts of the lungs4 ,the branches of the pulmonary artery lie alongside of1 and divide similarly to1 the bronchial tubes4 ,at the places where the finest divisions of the air tubes enter the infundibula1 the little arteries branch into the capillaries that penetrate the infundibular walls 7,figs4 #ch and #ci74 ,from these capillaries the blood is conveyed by the pulmonary veins to the left auricle4 ,the lungs also receive blood from two 7in some individuals three7 small arteries branching from the aorta1 known as the bronchial arteries4 ,these convey to the lungs blood that has already been supplied with oxygen1 passing it into the capillaries in the walls of the bronchi1 bronchial tubes1 and large blood vessels1 as well as the connective tissue between the lobes of the lungs4 ,this blood leaves the lungs partly by the bronchial veins and partly by the pulmonary veins4 ,no part of the body is so well supplied with blood as the lungs4 ,fig4 #dj ,fig4 #dj--99,the pleur499 ,diagram showing the general form of the pleural sacs as they surround the lungs and line the inner surfaces of the chest 7other parts removed74 ,a1 ,a'4 ,places occupied by the lungs4 ,b1 ,b'4 ,slight space within the pleural sacs containing the pleural secretion1 a1 a'4 ,outer layer of pleura and lining of chest walls and upper surface of diaphragm4 b1 b'4 ,inner layer of pleura and outer lining of lungs4 ,c4 ,space occupied by the heart4 ,d4 ,diaphragm4 99,the ,pleura499--,the pleura is a thin1 smooth1 elastic1 and tough membrane which covers the outside of the lungs and lines the inside of the chest walls4 ,the covering of each lung is continuous with the lining of the chest wall on its respective side and forms with it a closed sac by which the lung is surrounded1 the arrangement being similar to that of the pericardium4 ,properly speaking1 there are two pleur1 one for each lung1 and these1 besides inclosing the lungs1 partition off a middle space which is occupied by the heart 7,fig4 #dj74 ,they also cover the upper surface of the diaphragm1 from which they deflect upward1 blending with the pericardium4 ,a small amount of liquid is secreted by the pleura1 which prevents friction as the surfaces glide over each other in breathing4 99,the ,thorax499--,the force required for breathing is supplied by the box-like portion of the body in which the lungs are placed4 ,this is known as the thorax1 or chest1 and includes that part of the trunk between the neck and the abdomen4 ,the space which it incloses1 known as the thoracic cavity1 is a variable space and the walls surrounding this space are air-tight4 ,a framework for the thorax is supplied by the ribs which connect with the spinal column behind and with the sternum1 or breast-bone1 in front4 ,they form joints with the spinal column1 but connect with the sternum by strips of cartilage4 ,the ribs do not encircle the cavity in a horizontal direction1 but slope downward from the spinal column both toward the front and toward the sides1 this being necessary to the service which they render in breathing4 99,how ,air is ,brought into and ,expelled from the ,lungs499--,the principle involved in breathing is that air flows from a place of greater to a place of less pressure4 ,the construction of the thorax and the arrangement of the lungs within it provide for the application of this principle in a most practical manner4 ,the lungs are suspended from the upper portion of the thoracic cavity1 and the trachea and the upper air passages provide the only opening to the outside atmosphere4 ,air entering the thorax must on this account pass into the lungs4 ,as the thorax is enlarged the air in the lungs expands1 and there is produced within them a place of slightly less air pressure than that of the atmosphere on the outside of the body4 ,this difference causes the air to flow into the lungs4 ,fig4 #da ,fig4 #da--99;,diagram illustrating the bellows principle in breathing499 ,a4 ,the human bellows4 ,b4 ,the hand bellows4 ,compare part for part4 ,when the thorax is diminished in size1 the air within the lungs is slightly compressed4 ,this causes it to become denser and to exert on this account a pressure slightly greater than that of the atmosphere on the outside4 ,the air now flows out until the equality of the pressure is again restored4 ,thus the thorax1 by making the pressure within the lungs first slightly less and then slightly greater than the atmospheric pressure1 causes the air to move into and out of the lungs4 ,breathing is well illustrated by means of the common hand bellows1 its action being similar to that of the thorax4 ,it will be observed that when the sides are spread apart air flows into the bellows4 ,when they are pressed together the air flows out4 ,if an air-tight sack were hung in the bellows with its mouth attached to the projecting tube1 the arrangement would resemble closely the general plan of the breathing organs 7,fig4 #da74 ,one respect1 however1 in which the bellows differs from the thorax should be noted4 ,the thorax is never sufficiently compressed to drive out all the air4 ,air is always present in the lungs4 ,this keeps them more or less distended and pressed against the thoracic walls4 99,how the ,thoracic ,space is ,varied499--,one means of varying the size of the thoracic cavity is through the movements of the ribs and their resultant effect upon the walls of the thorax4 ,in bringing about these movements the following muscles are employed3 #a4 ,the scaleni muscles1 three in number on each side1 which connect at one end with the vertebr of the neck and at the other with the first and second ribs4 ,their contraction slightly raises the upper portion of the thorax4 #b4 ,the elevators of the ribs1 twelve in number on each side1 which are so distributed that each single muscle is attached1 at one end1 to the back portion of a rib and1 at the other1 to a projection of the vertebra a few inches above4 ,the effect of their contraction is to' elevate the middle portion of the ribs and to turn them outward or spread them apart4 #c4 ,the intercostal muscles1 which form two thin layers between the ribs1 known as the internal and the external intercostal muscles4 ,the external intercostals are attached between the outer lower margin of the rib above and the outer upper margin of the rib below1 and extend obliquely downward and forward4 ,the internal intercostals are attached between the inner margins of adjacent ribs1 and they extend obliquely downward and backward from the front4 ,the contraction of the external intercostal muscles raises the ribs1 and the contraction of the internal intercostals tends to lower them4 ,fig4 #db ,fig4 #db--99,simple apparatus99 for illustrating effect of movements of the ribs upon the thoracic space2 strips of cardboard held together by pins1 the front part being raised or lowered by threads moving through attachments at #a and #b4 ,as the front is raised the space between the uprights is increased4 ,the front upright corresponds to the breastbone1 the back one to the spinal column1 the connecting strips to the ribs1 and the threads to the intercostal muscles4 ,by slightly raising and spreading apart the ribs the thoracic space is increased in two directions--from front to back and from side to side4 ,lowering and converging the ribs has1 of course1 the opposite effect 7,fig4 #db74 ,except in forced expirations the ribs are lowered and converged by their own weight and by the elastic reaction of the surrounding parts4 99,the ,diaphragm499--,another means of varying the thoracic space is found in an organ known as the diaphragm4 ,this is the dome-shaped1 movable partition which separates the thoracic cavity from the cavity of the abdomen4 ,the edges of the diaphragm are firmly attached to the walls of the trunk1 and the center is supported by the pericardium and the pleura4 ,the outer margin is muscular1 but the central portion consists of a strong sheet of connective tissue4 ,by the contraction of its muscles the diaphragm is pulled down1 thereby increasing the thoracic cavity4 ,by raising the diaphragm the thoracic cavity is diminished4 ,the diaphragm1 however1 is not raised by the contraction of its own muscles1 but is pushed up by the organs beneath4 ,by the elastic reaction of the abdominal walls 7after their having been pushed out by the lowering of the diaphragm71 pressure is exerted on the organs of the abdomen and these in turn press against the diaphragm4 ,this crowds it into the thoracic space4 ,in forced expirations the muscles in the abdominal walls contract to push up the diaphragm4 99,interchange of ,gases in the ,lungs499--,during each inspiration the air from the outside fills the entire system of bronchial tubes1 but the alveoli are largely filled1 at the same time1 by the air which the last expiratory effort has left in the passages4 ,by the action of currents and eddies and by the rapid diffusion of gas particles1 the air from the outside mixes with that in the alveoli and comes in contact with the membranous walls4 ,here the oxygen1 after being dissolved by the moisture in the membrane1 diffuses into the blood4 ,the carbon dioxide1 on the other hand1 being in excess in the blood1 diffuses toward the air in the alveoli4 ,the interchange of gases at the lungs1 however1 is not fully understood1 and it is possible that other forces than osmosis play a part4 ,fig4 #dc ,fig4 #dc--99;,diagram99 illustrating lung capacity4 99,capacity of the ,lungs499--,the air which passes into and from the lungs in ordinary breathing1 called the tidal air1 is but a small part of the whole amount of air which the lungs contain4 ,even after a forced expiration the lungs are almost half full2 the air which remains is called the residual air4 ,the air which is expelled from the lungs by a forced expiration1 less the tidal air1 is called the reserve1 or supplemental1 air4 ,these several quantities are easily estimated4 7,see ,practical ,work47 ,in the average individual the total capacity of the lungs 7with the chest in repose7 is about one gallon4 ,in forced inspirations this capacity may be increased about one third1 the excess being known as the complemental air 7,fig4 #dc74 ,fig4 #dd ,fig4 #dd--99;,diagram99 illustrating internal respiration and its dependence on external respiration4 7,modified from ,hall47 7,see text47 99,internal1 or ,cell1 ,respiration499--,the oxygen which enters the blood in the lungs leaves it in the tissues1 passing through the lymph into the cells 7,fig4 #dd74 ,at the same time the carbon dioxide which is being formed at the cells passes into the blood4 ,an exchange of gases is thus taking place between the cells and the blood1 similar to that taking place between the blood and the air4 ,this exchange is known as internal1 or cell1 respiration4 ,by internal respiration the oxygen reaches the place where it is to serve its purpose1 and the carbon dioxide begins its movement toward the exterior of the body4 ,this breathing by the cells is1 therefore1 the final and essential act of respiration4 ,breathing by the lungs is simply the means by which the taking up of oxygen and 99the99 giving off of carbon dioxide by the cells is made possible4 ,,hygiene ,,of ,,respiratory ,,organs ,the liability of the lungs to attacks from such dread diseases as consumption and pneumonia makes questions touching their hygiene of first importance4 ,consumption does not as a rule attack sound lung tissue1 but usually has its beginning in some weak or enfeebled spot in the lungs which has lost its power of resistance4 ,though consumption is not inherited1 as some suppose1 lung weaknesses may be transmitted from parents to children4 ,this1 together with the fact1 now generally recognized1 that consumption is contagious1 accounts for the frequent appearance of this disease in the same family4 ,consumption as well as other respiratory affections can in the majority of cases be prevented1 and in many cases cured1 by an intelligent observation of well-known laws of health4 99,breathe through the ,nostrils499--,pure air and plenty of it is the main condition in the hygiene of the lungs4 ,one necessary provision for obtaining pure air is that of breathing through the nostrils4 ,air is the carrier of dust particles and not infrequently of disease germs47#cc7 ,partly through the small hairs in the nose1 but mainly through the moist membrane that lines the passages1 the nostrils serve as filters for removing the minute solid particles 7,fig4 #de74 ,while it is important that nose breathing be observed at all times1 it is especially important when one is surrounded by a dusty or smoky atmosphere4 ,otherwise the small particles that are breathed in through the mouth may find a lodging place in the lungs4 ,fig4 #de ,fig4 #de--99;,human air filter499 ,diagram of a section through the nostrils2 shows projecting bones covered with moist membrane against which the air is made to strike by the narrow passages4 #a4 ,air passages4 #b4 ,cavities in the bones4 #c4 ,front lower portion of the cranial cavity4 ,in addition to removing dust particles and germs1 other purposes are served by breathing through the nostrils4 ,the warmth and moisture which the air receives in this way1 prepare it for entering the lungs4 ,mouth breathing1 on the other hand1 looks bad and during sleep causes snoring4 ,the habit of nose breathing should be established early in life47#cd7 99,cultivate ,full ,breathing499--,many people1 while apparently taking in sufficient air to supply their need for oxygen1 do not breathe deeply enough to freely ventilate the lungs4 ,shallow breathing1 as this is called1 is objectionable because it fails to keep up a healthy condition of the entire lung surface4 ,portions of the lungs to which air does not easily penetrate fail to get the fresh air and exercise which they need4 ,as a consequence1 they become weak and1 by losing their power of resistance1 become points of attack in diseases of the lungs47#ce7 ,the breathing of each individual should receive attention1 and where from some cause it is not sufficiently full and deep1 the means should be found for remedying the defect4 99,causes of ,shallow ,breathing499--,anything that impedes the free movement of air into the lungs tends to cause shallow breathing ,a drooping of the back or shoulders and a curved condition of the spinal column1 such as is caused by an improper position in sitting1 interfere with the free movements of the ribs and are recognized causes4 ,clothing also may impede the respiratory movements and lead to shallow breathing4 ,if too tight around the chest1 clothing interferes with the elevation of the ribs2 and if too tight around the waist1 it prevents the depression of the diaphragm4 ,other causes of shallow breathing are found in the absence of vigorous exercise1 in the leading of an indoor and inactive life1 in obstructions in the nostrils and upper pharynx1 and in the lack of attention to proper methods of breathing4 ,to prevent shallow breathing one should have the habit of sitting and standing erect4 ,the clothing must not be allowed to interfere with the respiratory movements4 ,the taking of exercise sufficiently vigorous to cause deep and rapid breathing should be a common practice and one should spend considerable time out of doors4 ,if one has a flat chest or round shoulders1 he should strive by suitable exercises to overcome these defects4 ,obstructions in the nostrils or pharynx should be removed4 99,breathing ,exercises499--,in overcoming the habit of shallow breathing and in strengthening the lungs generally1 the practicing of occasional deep breathing has been found most valuable and is widely recommended4 ,with the hands on the hips1 the shoulders drawn back and down1 the chest pushed upward and forward1 and the chin slightly depressed1 draw the air slowly through the nostrils until the lungs are completely full4 ,after holding this long enough to count three slowly1 expel it quickly from the lungs4 ,avoid straining4 ,to get the benefit of pure air1 it is generally better to practice deep breathing out of doors or before an open window4 ,by combining deep breathing with simple exercises of the arms1 shoulders1 and trunk much may be done towards straightening the spine1 squaring the shoulders1 and overcoming flatness of the chest4 ,though such movements are best carried on by the aid of a physical director1 one can do much to help himself4 ,one may safely proceed on the principle that slight deformities of the chest1 spine1 and shoulders are corrected by gaining and keeping the natural positions1 and may employ any movements which will loosen up the parts and bring them where they naturally belong47#cf7 99,serious ,nature of ,colds499--,that many cases of consumption have their beginning in severe colds 7on the lungs7 is not only a matter of popular belief1 but the judgment also of physicians4 ,though the cold is a different affection from that of consumption1 it may so lower the vitality of the body and weaken the lung surfaces that the germs of consumption find it easy to get a start4 ,on this account a cold on the chest which does not disappear in a few days1 but which persists1 causing more or less coughing and pain in the lungs1 must be given serious consideration47#cg7 ,the usual home remedies failing to give relief1 a physician should be consulted4 ,it should also be noted that certain diseases of a serious nature 7pneumonia1 diphtheria1 measles1 etc47 have in their beginning the appearance of colds4 ,on this account it is wise not only to call a physician1 but to call him early1 in severe attacks of the lungs4 ,especially if the attack be attended by difficult breathing1 fever1 and a rapid pulse is the case serious and medical advice necessary4 99,ventilation499--,the process by which the air in a room is kept fresh and pure is known as ventilation4 ,it is a double process--that of bringing fresh air into the room and that of getting rid of air that has been rendered impure by breathing 7#ch7 or by lamps4 ,outdoor air is usually of a different temperature 7colder in winter1 warmer in summer7 from that indoors1 and as a consequence differs from it slightly in weight4 ,on account of this difference1 suitable openings in the walls of buildings induce currents which pass between the rooms and the outside atmosphere even when there is no wind4 ,in winter care must be taken to prevent drafts and to avoid too great a loss of heat from the room4 ,a cold draft may even cause more harm to one in delicate health than the breathing of air which is impure4 ,to ventilate a room successfully the problem of preventing drafts must be considered along with that of admitting the fresh air4 ,fig4 #df ,fig4 #df--,window adjusted for ventilation without drafts4 ,the method of ventilation must also be adapted to the construction of the building1 the plan of heating1 and the condition of the weather4 ,specific directions cannot be given1 but the following suggestions will be found helpful in ventilating rooms where the air is not warmed before being admitted3 #a4 ,introduce1 the air through many small openings rather than a few large ones4 ,if the windows are used for this purpose1 raise the lower sash and drop the upper one slightly for several windows1 varying the width to suit the conditions 7,fig4 #df74 ,by this means sufficient air may be introduced without causing drafts4 #b4 ,introduce the air at the warmest portions of the room4 ,the air should1 if possible1 be warmed before reaching the occupants4 #c4 ,if the wind is blowing1 ventilate principally on the sheltered side of the house4 ,ample provision should be made for fresh air in sleeping rooms1 and here again drafts must be avoided4 ,especially should the bed be so placed that strong air currents do not pass over the sleeper4 ,in schoolhouses and halls for public gatherings the means for efficient ventilation should1 if possible1 be provided in the general plan of construction and method of heating4 ,fig4 #dg ,fig4 #dg--99;,artificial respiration99 as a laboratory experiment4 ,expiration4 ,prone-posture method of ,schaffer4 99,artificial ,respiration499--,when natural breathing is temporarily suspended1 as in partial drowning1 or when one has been overcome by breathing some poisonous gas1 the saving of life often depends upon the prompt application of artificial respiration4 ,this is accomplished by alternately compressing and enlarging the thorax by means of variable pressure on the outside1 imitating the natural process as nearly as possible4 ,following is the method proposed by ,professor ,e4,a4 ,schaffer of ,england1 and called by him the prone-posture method of artificial respiration3 ,the patient is laid face downward with an arm bent under the head1 and intermittent pressure applied vertically over the shortest ribs4 ,the pressure drives the air from the lungs1 both by compressing the lower portions of the chest and by forcing the abdominal contents against the diaphragm1 while the elastic reaction of the parts causes fresh air to enter 7,figs4 #dg and #dh74 ,the operator kneels or squats by the side of1 or across the patient1 places his hands over the lowest ribs and swings his body backward and forward so as to allow his weight to fall vertically on the wrists and then to be removed2 in this way hardly any muscular exertion is required4444 ,the pressure is applied gradually and slowly1 occupying some three seconds2 it is then withdrawn during two seconds and again applied2 and so on some twelve times per minute47#ci7 ,fig4 #dh ,fig4 #dh--;,artificial respiration4 ,inspiration4 ,the special advantages of the prone-posture method over others that have been employed are3 ,i4 ,it may be applied by a single individual and fora long period of time without exhaustion4 #b4 ,it allows the mucus and water 7in case of drowning7 to run out of the mouth1 and causes the tongue to fall forward so as not to obstruct the passageway4 #c4 ,it brings a sufficient amount of air into the lungs47#dj7 ,while applying artificial respiration1 the heat of the body should not be allowed to escape any more than can possibly be helped4 ,in case of drowning1 the patient should be wrapped in dry blankets or clothing1 while bottles of hot water may be placed in contact with the body4 ,the circulation should be stimulated1 as may be done by rubbing the hands1 feet1 or limbs in the direction of the flow of the blood in the veins4 99,tobacco ,smoke and the ,air99 ,passages4--,smoke consists of minute particles of unburnt carbon1 or soot1 such as collect in the chimneys of fireplaces and furnaces4 ,if much smoke is taken into the lungs1 it irritates the delicate linings and tends to clog them up4 ,tobacco smoke also contains the poison nicotine1 which is absorbed into the blood4 ,for these reasons the cigarette user who inhales the smoke does himself great harm1 injuring his nervous system and laying the foundation for diseases of the air passages4 ,the practice of smoking indoors is likewise objectionable1 since every one in a room containing the smoke is compelled to breathe it4 99,alcohol and ,diseases of the ,lungs499--,pneumonia is a serious disease of the lungs caused by germs4 ,the attacks occur as a result of exposure1 especially when the body is in a weakened condition4 ,a noted authority states that alcoholism is perhaps the most potent predisposing cause of pneumonia47#da7 ,a person addicted to the use of alcohol is also less likely to recover from the disease than one who has avoided its use1 a result due in part to the weakening effect of alcohol upon the heart4 ,the congestion of the lungs in pneumonia makes it very difficult for the heart to force the blood through them4 ,the weakened heart of the drunkard gives way under the task4 ,the statement sometimes made that alcohol is beneficial in pulmonary tuberculosis is without foundation in fact4 ,on the other hand1 alcoholism is a recognized cause of consumption4 ,some authorities claim that this disease is more frequent in heavy drinkers than in those of temperate habits1 in the proportion of about three to one1 and that possibly half of the cases of tuberculosis are traceable to alcoholism47#db7 99,the ,outdoor ,cure for ,lung ,diseases99--,among the many remedies proposed for consumption and kindred diseases1 none have proved more beneficial1 according to reports1 than the so-called outdoor cure4 ,the person having consumption is fed plentifully upon the most nourishing food1 and is made to spend practically his entire time1 including the sleeping hours1 out of doors4 ,not only is this done during the pleasant months of summer1 but also during the winter when the temperature is below freezing4 ,severe exposure is prevented by overhead protection at night and by sufficient clothing to keep the body warm4 ,the abundant supply of pure1 cold air toughens the lungs and invigorates the entire body1 thereby enabling it to throw off the disease4 ,the success attending this method of treating consumptives suggests the proper mode of strengthening lungs that are not diseased1 but simply weak4 ,the person having weak lungs should spend as much time as he conveniently can out of doors4 ,he should provide the most ample ventilation at night and have a sleeping room to himself4 ,he should practice deep breathing exercises and partake of a nourishing diet4 ,while avoiding prolonged chilling and other conditions liable to induce colds1 he should take advantage of every opportunity of exposing himself fully and freely to the outside atmosphere4 99,summary499--,the purpose of respiration is to bring about an exchange of gases between the body and the atmosphere4 ,the organs employed for this purpose1 called the respiratory organs1 are adapted to handling materials in the gaseous state1 and are operated in accordance with principles governing the movements of the atmosphere4 ,by alternately increasing and diminishing the thoracic space1 air is made to pass between the outside atmosphere and the interior of the lungs4 ,finding its way into the smallest divisions of the lungs1 called the alveoli1 the air comes very near a large surface of blood4 ,by this means the carbon dioxide diffuses out of the blood1 and the free oxygen enters4 ,through the combined action of the organs of respiration and the organs that move the blood and the lymph1 the cells in all parts of the body are enabled to exchange certain gaseous materials with the outside atmosphere4 ,fig4 #di ,fig4 #di--,model for demonstrating the lungs4 99,exercises4--99#a4 ,how does air entering the lungs differ in composition from air leaving the lungs8 ,what purposes of respiration are indicated by these differences8 #b4 ,name the divisions of the lungs4 #c4 ,trace air from the outside atmosphere into the alveoli4 ,trace the blood from the right ventricle to the alveoli and back again to the left auricle4 #d4 ,how does the movement of air into and from the lungs differ from that of the blood through the lungs with respect to 7a7 the direction of the motion4 7b7 the causes of the motion1 and 7c7 the tubes through which the motion takes place8 #e4 ,how are the air passages kept clean and open8 #f4 ,describe the pleura4 ,into what divisions does it separate the thoracic cavity8 #g4 ,describe and name uses of the diaphragm4 #h4 ,if #cj cubic inches of air are passed into the lungs at each inspiration and 4#je of this is retained as oxygen1 calculate the number of cubic feet of oxygen consumed each day1 if the number of inspirations be #ah per minute4 #i4 ,find the weight of a day's supply of oxygen1 as found in the above problem1 allowing #a4c ounces as the weight of a cubic foot4 #aj4 ,make a study of the hygienic ventilation of the schoolroom4 #aa4 ,give advantages of full breathing over shallow breathing4 #ab4 ,how may a flat chest and round shoulders be a cause of consumption8 ,how may these deformities be corrected8 #ac4 ,give general directions for applying artificial respiration4 ,,practical ,,work ,examine a dissectible model of the chest and its contents 7,fig4 #di74 ,note the relative size of the two lungs and their position with reference to the heart and diaphragm4 ,compare the side to side and vertical diameters of the cavity4 ,trace the air tubes from the trachea to their smallest divisions4 99,observation of ,lungs99 7,optional74--,secure from a butcher the lungs of a sheep1 calf1 or hog4 ,the windpipe and heart should be left attached and the specimen kept in a moist condition until used4 ,demonstrate the trachea1 bronchi1 and the bronchial tubes1 and the general arrangement of pulmonary arteries and veins4 ,examine the pleura and show lightness of lung tissue by floating a piece on water4 99,to show the ,changes that ,air undergoes in the ,lungs499--#a4 ,fill a quart jar even full of water4 ,place a piece of cardboard over its mouth and invert1 without spilling1 in a pan of water4 ,inserting a tube under the jar1 blow into it air that has been held as long as possible in the lungs4 ,when filled with air1 remove the jar from the pan1 keeping the top well covered4 ,slipping the cover slightly to one side1 insert a burning splinter and observe that the flame is extinguished4 ,this proves the absence of sufficient oxygen to support combustion4 ,pour in a little limewater7#dc7 and shake to mix with the air4 ,the change of the limewater to a milky white color proves the presence of carbon dioxide4 ,fig4 #ej ,fig4 #ej--99;,apparatus99 for showing changes which air undergoes while in the lungs4 #b4 ,the effects illustrated in experiment #a may be shown in a somewhat more striking manner as follows3 ,fill two bottles of the same size each one fourth full of limewater and fit each with a two-holed rubber stopper 7,fig4 #ej74 ,fit into each stopper one short and one long glass tube1 the long tube extending below the limewater4 ,connect the short tube of one bottle and the long tube of the other bottle with a ,y-tube4 ,now breathe slowly three or four times through the ,y-tube4 ,it will be found that the inspired air passes through one bottle and the expired air through the other4 ,compare the effect upon the limewater in the two bottles4 ,insert a small burning splinter into the top of each bottle and note result4 ,what differences between inspired and expired air are thus shown8 #c4 ,blow the breath against a cold window pane4 ,note and account for the collection of moisture4 #d4 ,note the temperature of the room as shown by a thermometer4 ,now breathe several times upon the bulb1 noting the rise in the mercury4 ,what does this experiment show the body to be losing through the breath8 99,to show ,changes in the ,thoracic ,cavity499--#a4 ,to a yard- or meter-stick1 attach two vertical strips1 each about eight inches long1 as shown in ,fig4 #ea4 ,the piece at the end should be secured firmly in place by screws or nails4 ,the other should be movable4 ,with this contrivance measure the sideward and forward expansion of a boy's thorax4 ,take the diameter first during a complete inspiration and then during a complete expiration1 reading the difference4 ,compare the forward with the sideward expansion4 ,fig4 #ea ,fig4 #ea--99;,apparatus99 for measuring chest expansion4 #b4 ,with a tape-line take the circumference of the chest when all the air possible has been expelled from the lungs4 ,take it again when the lungs have been fully inflated4 ,the difference is now read as the chest expansion4 ,fig4 #eb ,fig4 #eb--99,simple apparatus99 for illustrating the action of the diaphragm4 99,to illustrate the ,action of the ,diaphragm499--,remove the bottom from a large bottle having a small neck4 7,scratch a deep mark with a file and hold on the end of this mark a hot poker4 ,when the glass cracks1 lead the crack around the bottle by heating about one half inch in advance of it47 ,place the bottle in a large glass jar filled two thirds full of water 7,fig4 #eb74 ,let the space above the water represent the chest cavity and the water surface represent the diaphragm4 ,raise the bottle1 noting that the water falls1 thereby increasing the space and causing air to enter4 ,then lower the bottle1 noting the opposite effect4 ,to show the movement of the air in and out of the bottle1 hold with the hand 7or arrange a support for7 a burning splinter over the mouth of the bottle4 99,to estimate the ,capacity of the ,lungs499--,breathing as naturally as possible1 expel the air into a spirometer 7lung tester7 during a period1 say of ten respirations 7,fig4 #ec74 ,note the total amount of air exhaled and the number of breaths and calculate the amount of air exhaled at each breath4 ,this is called the tidal air4 ,fig4 #ec ,fig4 #ec--99;,apparatus99 7spirometer7 for measuring the capacity of the lungs4 #b4 ,after an ordinary inspiration empty the lungs as completely as possible into the spirometer1 noting the quantity exhaled4 ,this amount1 less the tidal air1 is known as the reserve air4 ,the air which is now left in the lungs is called the residual air4 ,on the theory that this is equal in amount to the reserve air1 calculate the capacity of the lungs in an ordinary inspiration4 #c4 ,now fill the lungs to the full expansion of the chest and empty them as completely as possible into the spirometer1 noting the amount expelled4 ,this1 less the tidal air and the reserve air1 is called the complemental air4 ,now calculate the total capacity of the lungs4 ,,chapter ,,viii - ,,passage ,,of ,,oxygen ,,through ,,the ,,body ,what is the nature of oxygen8 ,what is its purpose in the body and how does it serve this purpose8 ,how is the blood able to take it up at the lungs and give it off at the cells8 ,what becomes of it after being used8 ,these are questions touching the maintenance of life and they deserve careful consideration4 99,nature of ,oxygen499--,to understand the relation which oxygen sustains to the body we must acquaint ourselves with certain of its chemical properties4 ,it is an element7#dd7 of intense affinity1 or combining power1 and is one of the most active of all chemical agents4 ,it is able to combine with most of the other elements to form chemical compounds4 ,a familiar example of its combining action is found in ordinary combustion1 or burning4 ,on account of the part it plays in this process1 oxygen is called the supporter of combustion2 but it supports combustion by the simple method of uniting4 ,the ashes that are left and the invisible gases that escape into the atmosphere are the compounds formed by the uniting process4 ,it thus appears that oxygen1 in common with the other elements1 may exist in either of two forms3 #a4 ,that in which it is in a free1 or uncombined1 condition--the form in which it exists in the atmosphere4 #b4 ,that in which it is a part of compounds1 such as the compounds formed in combustion4 ,oxygen manifests its activity to the best advantage when it is in a free state1 or1 more accurately speaking1 when it is passing from the free state into one of combination4 ,it is separated from its compounds and brought again into a free state by overcoming with heat1 or some other force1 the affinity which causes it to unite4 99,how ,oxygen unites499--,the chemist believes oxygen1 as well as all other substances1 to be made up of exceedingly small particles1 called atoms4 ,the atoms do not exist singly in either elements or compounds1 but are united with each other to form groups of atoms that are called molecules4 ,in an element the molecules are made up of one kind of atoms1 but in a compound the molecules are made up of as many kinds of atoms as there are elements in the compound4 ,changes in the composition of substances 7called chemical changes7 are due to rearrangements of the atoms and the formation of new molecules4 ,the atoms1 therefore1 are the units of chemical combination4 ,in the formation of new compounds they unite1 and in the breaking up of existing compounds they separate4 ,the uniting of oxygen is no exception to this general law4 ,all of its combinations are brought about by the uniting of its atoms4 ,in the burning of carbon1 for example1 the atoms of oxygen and the atoms of carbon unite1 forming molecules of the compound known as carbon dioxide4 ,the chemical formula of this compound1 which is ,,co#b1 shows the proportion in which the atoms unite--one atom of carbon uniting with two atoms of oxygen in each of the molecules4 ,the affinity of oxygen for other elements1 and the affinity of other elements for oxygen1 and for each other1 resides in their atoms4 99,oxidation499--,the uniting of oxygen with other elements is termed oxidation4 ,this may take place slowly or rapidly1 the two rates being designated as slow oxidation and rapid oxidation4 ,examples of slow oxidation are found in certain kinds of decay and in the rusting of iron4 ,combustion is an example of rapid oxidation4 ,slow and rapid oxidation1 while differing widely in their effects upon surrounding objects1 are alike in that both produce heat and form compounds of oxygen4 ,in slow oxidation1 however1 the heat may come off so gradually that it is not observed4 99,movement of ,oxygen through the ,body499--,oxygen has been shown in the preceding chapters to pass from the lungs into the blood and later to leave the blood and1 passing through the lymph1 to enter the cells4 ,that oxygen does not become a permanent constituent of the cells is shown by the constancy of the body weight4 ,nearly two pounds of oxygen per day are known to enter the cells of the average-sized person4 ,if this became a permanent part of the cells1 the body would increase in weight from day to day4 ,since the body weight remains constant1 or nearly so1 we must conclude that oxygen leaves the body about as fast as it enters4 ,oxygen enters the body as a free element4 ,the form in which it leaves the body will be understood when we realize the purpose which it serves and the method by which it serves this purpose4 99,purpose of ,oxygen in the ,body499--,the question may be raised3 ,is it possible for oxygen to serve a purpose in the body without remaining in it8 ,this1 of course1 depends upon what the purpose is4 ,that it is possible for oxygen to serve a purpose and at the same time pass on through the place where it serves that purpose1 is seen by studying the combustion in an ordinary stove 7,fig4 #ed74 ,oxygen enters at the draft and for the most part passes out at the flue1 but in passing through the stove it unites with1 or oxidizes1 the fuel1 causing the combustion which produces the heat4 ,fig4 #ed ,fig4 #ed--99;,coal stove99 illustrating rapid oxidation4 ,now it is found that certain chemical processes1 mainly oxidations1 are taking place in the body4 ,these produce the heat for keeping it warm and also supply other forms of energy17#de7 including motion4 ,it is the purpose of oxygen to keep up these oxidations and1 by so doing1 to aid in supplying the body with energy4 ,it serves this purpose in much the same way that it supports combustion1 i4e41 by uniting with1 or oxidizing1 materials derived from foods that are present in the cells4 99,does ,oxygen serve ,other ,purposes899--,it has been suggested that oxygen may serve the purpose of oxidizing1 or destroying1 substances that are injurious and of acting1 in this way1 as a purifying agent in the body4 ,in support of this view is the natural tendency of oxygen to unite with substances and the well-known fact that oxygen is an important natural agent in purifying water4 ,it seems probable1 therefore1 that it may to a slight extent serve this purpose in the body4 ,it is probable also that oxygen aids through its chemical activity in the formation of compounds which are to become a part of the cells4 ,both of these uses1 however1 are of minor importance when compared with the main use of oxygen1 which is that of an aid in supplying energy to the body4 99,oxygen and the ,maintenance of ,life499--,in the supplying of energy to the body1 one of the conditions necessary to the maintenance of life is provided4 ,because oxygen is necessary to this process1 and because death quickly results when the supply of it is cut off1 oxygen is frequently called the supporter of life4 ,this idea is misleading1 for oxygen has no more to do with the maintenance of life than have the food materials with which it unites4 ,life appears to be more dependent upon oxygen than upon food1 simply because the supply of it in the body at any time is exceedingly small4 ,being continually surrounded by an atmosphere containing free oxygen1 the body depends upon this as a constant source of supply1 and does not store it up4 ,food1 on the other hand1 is taken in excess of the body's needs and stored in the various tissues1 the supply being sufficient to last for several days4 ,when the supply of either oxygen or food is exhausted in the body1 life must cease4 99,the ,oxygen ,movement a ,necessity499--,since free oxygen is required for keeping up the chemical changes in the cells1 and since it ceases to be free as soon as it goes into combination1 its continuous movement through the body is a necessity4 ,the oxygen compounds must be removed as fast as formed in order to make room for more free oxygen4 ,this movement has already been studied in connection with the blood and the organs of respiration1 but the consideration of certain details has been deferred till now4 ,by what means and in what form is the oxygen passed to and from the cells8 99,passage of ,oxygen through the ,blood499--,in serving its purpose at the cells1 the oxygen passes twice through the blood--once as it goes toward the cells and again as it passes from the cells to the exterior of the body3 ,passage toward the ,cells4--,this is effected mainly through the hemoglobin of the red corpuscles4 ,at the lungs the oxygen and the hemoglobin form a weak chemical compound that breaks up and liberates the oxygen when it reaches the capillaries in the tissues4 ,the separation of the oxygen from the hemoglobin at the tissues appears to be due to two causes3 first1 to the weakness of the chemical attraction between the atoms of oxygen and the atoms that make up the hemoglobin molecule2 and second1 to a difference in the so-called oxygen pressure at the lungs and at the tissues47#df7 ,the attraction of the oxygen and the hemoglobin is sufficient to cause them to unite where the oxygen pressure is more than one half pound to the square inch1 but it is not sufficiently strong to cause them to unite or to prevent their separation1 if already united1 where the oxygen pressure is less than one half pound to the square inch4 ,the oxygen pressure at the lungs1 which amounts to nearly three pounds to the square inch1 easily causes the oxygen and the hemoglobin to unite1 while the almost complete absence of any oxygen pressure at the tissues1 permits their separation4 ,the blood in its circulation constantly flows from the place of high oxygen pressure at the lungs to the place of low oxygen pressure at the tissues and1 in so doing1 loads up with oxygen at one place and unloads it at the other 7,fig4 #ee74 ,passage from the ,cells4--,since oxygen leaves the free state at the cells and becomes a part of compounds1 we are able to trace it from the body only by following the course of these compounds4 ,three waste compounds of importance are formed at the cells--carbon dioxide 7,,co#b71 water 7,h#b,o71 and urea 7,n#b;,h#d;,,co74 ,the first is formed by the union of oxygen with carbon1 the second by its union with hydrogen1 and the third by its union with nitrogen1 hydrogen1 and carbon4 ,these compounds are carried by the blood to the organs of excretion1 where they are removed from the body4 ,the water leaves the body chiefly as a liquid1 the urea as a solid dissolved in water1 and the carbon dioxide as a gas4 ,the passage of carbon dioxide through the blood requires special consideration4 ,fig4 #ee ,fig4 #ee--99;,diagram illustrating movement1 of oxygen and carbon dioxide through the body99 7,s4,d4 ,magers74 ,each moves from a place of relatively high to a place of relatively low pressure4 7,see text47 99,passage of ,carbon ,dioxide through the ,blood499--,part of the carbon dioxide is dissolved in the plasma of the blood1 and part of it is in weak chemical combination with substances found in the plasma and in the corpuscles4 ,its passage through the blood is accounted for in the same way as the passage of the oxygen4 ,its ability to dissolve in liquids and to enter into chemical combination varies as the carbon dioxide pressure7#dg7 ,this in turn varies with the amount of the carbon dioxide1 which is greatest at the cells 7where it is formed71 less in the blood1 and still less in the lungs4 ,because of these differences1 the blood is able to take it up at the cells and release it at the lungs 7,fig4 #ee74 ,fig4 #ef ,fig4 #ef--99,soap bubble99 floating in a vessel of carbon dioxide1 illustrating the difference in weight between air and carbon dioxide gas4 99,properties of ,carbon ,dioxide499--,carbon dioxide is a colorless gas with little or no odor4 ,it is classed as a heavy gas1 being about one third heavier than air7#dh7 7,fig4 #ef74 ,it does not support combustion1 but on the contrary is used to some extent to extinguish fires4 ,it is formed by the oxidation of carbon in the body1 and by the combustion of carbon outside of the body4 ,it is also formed by the decay of animal and vegetable matter4 ,from these sources it is continually finding its way into the atmosphere4 ,although not a poisonous gas1 carbon dioxide may1 if it surround the body1 shut out the supply of oxygen and cause death47#di7 99,final ,disposition of ,carbon ,dioxide499--,it is readily seen that the union of carbon and oxygen1 which is continually removing oxygen from the air and replacing it with carbon dioxide1 tends to make the whole atmosphere deficient in the one and to have an excess of the other4 ,this tendency is counteracted through the agency of vegetation4 ,green plants absorb the carbon dioxide from the air1 decompose it1 build the carbon into compounds 7starch1 etc47 that become a part of the plant1 and return the free oxygen to the air 7,fig4 #eg74 ,in doing this1 they not only preserve the necessary proportion of oxygen and carbon dioxide in the atmosphere1 but also put the carbon and oxygen in such a condition that they can again unite4 ,the force which enables the plant cells to decompose the carbon dioxide is supplied by the sunlight 7,chapter ,,xii74 ,fig4 #eg ,fig4 #eg--99,under surface99 of a geranium leaf showing breathing pores1 highly magnified 7,o4,h474 99,summary499--,oxygen1 by uniting with materials at the cells1 keeps up a condition of chemical activity 7oxidation7 in the body4 ,this supplies heat and the other forms of bodily energy4 ,entering as a free element1 oxygen leaves the body as a part of the waste compounds which it helps to form4 ,the free oxygen is transported from the lungs to the cells by means of the hemoglobin of the red corpuscles1 while the combined oxygen in carbon dioxide and other compounds from the cells is carried mainly by the plasma4 ,the limited supply of free oxygen in the body at any time makes necessary its continuous introduction into the body4 99,exercises499--#a4 ,describe the properties of oxygen4 ,how does it unite with other elements8 ,how does it support combustion8 #b4 ,state the purpose of oxygen in the body4 ,what properties enable it to fulfill this purpose8 #c4 ,what is the proof that oxygen does not remain permanently in the body8 ,how does the oxygen entering the body differ from the same oxygen as it leaves the body8 #d4 ,what is the necessity for the continuous introduction of oxygen into the body1 while food is introduced only at intervals8 #e4 ,how are the red corpuscles able to take up and give off oxygen8 ,how is the plasma able to take up and give off carbon dioxide8 #f4 ,if thirty cubic inches of air pass from the lungs at each expiration and #d4e per cent of this is carbon dioxide1 calculate the number of cubic feet of the gas expelled in twenty-four hours1 estimating the number of respirations at eighteen per minute4 #g4 ,what is the weight of this volume of carbon dioxide1 if one cubic foot weigh #a4gi ounces8 #h4 ,what portion of this weight is oxygen and what carbon1 the ratio by weight of carbon to oxygen in carbon dioxide being twelve to thirty-two8 #i4 ,what is the final disposition of carbon dioxide in the atmosphere8 ,,practical ,,work 99,to show the ,difference between ,free ,oxygen and ,oxygen in ,combination499--,examine some crystals of potassium chlorate 7,k,cl,o#c74 ,they contain oxygen in combination with potassium and chlorine4 ,place a few of these in a small test tube and heat strongly in a gas or alcohol flame4 ,the crystals first melt1 and the liquid which they form soon appears to boil4 ,if a splinter1 having a spark on the end1 is now inserted in the tube1 it is kindled into a flame4 ,this shows the presence of free oxygen1 the heat having caused the potassium chlorate to decompose4 ,the difference between free and combined oxygen may also be shown by decomposing other compounds of oxygen1 such as water and mercuric oxide4 99,preparation and ,properties of ,oxygen499--,intimately mix #c grams 7#a_/b teaspoonful7 of potassium chlorate with half its bulk of manganese dioxide1 and place the mixture in a large test tube4 ,close the test tube with a tight-fitting stopper which bears a glass tube of sufficient length and of the right shape to convey the escaping gas to a small trough or pan partly filled with water1 on the table4 ,fill four large-mouthed bottles with water and1 by covering with cardboard1 invert each in the trough of water4 ,arrange the test tube conveniently for heating1 letting the end of the glass tube terminate under the mouth of one of the bottles 7,fig4 #eh74 ,using an alcohol lamp or a ,bunsen burner1 heat over the greater portion of the tube at first1 but gradually concentrate the flame upon the mixture4 ,do not heat too strongly1 and when the gas is coming off rapidly1 remove the flame entirely1 putting it back as the action slows down4 ,after all the bottles have been filled1 remove the end of the glass tube from the water1 but leave the bottles of oxygen inverted in the trough until they are to be used4 ,on removing the bottles from the trough1 keep the tops covered with wet cardboard4 ,fig4 #eh ,fig4 #eh--99;,apparatus99 for generating oxygen4 #a4 ,examine a bottle of oxygen1 noting its lack of color4 ,insert a small burning splinter in the upper part of the bottle and observe the change in the rate of burning4 ,the air contains free oxygen1 but it is diluted with nitrogen4 ,compare this with the undiluted oxygen in the bottle as to effect in causing the splinter to burn4 #b4 ,in a second bottle of oxygen insert a splinter without the flame1 but having a small spark on the end4 ,as soon as the oxygen kindles the spark into a flame1 withdraw from the bottle and blow out the flame1 but again insert the spark4 ,repeat the experiment as long as the spark is kindled by the oxygen into a flame4 ,this experiment is usually performed as a test for undiluted oxygen4 #c4 ,make a hollow cavity in the end of a short piece of crayon4 ,fasten a wire to the crayon1 and fill the cavity with powdered sulphur4 ,ignite the sulphur in the flame of an alcohol lamp or ,bunsen burner1 and lower it into a bottle of oxygen4 ,observe the change in the rate of burning1 the color of the flame1 and the material formed in the bottle by the burning4 ,the gas remaining in the bottle is sulphur dioxide 7,,so#b71 formed by the uniting of the sulphur and the oxygen4 #d4 ,bend a small loop on the end of a piece of picture wire4 ,heat the loop in a flame and insert it in some powdered sulphur4 ,ignite the melted sulphur which adheres1 and insert it quickly in a bottle of oxygen4 ,observe the dark1 brittle material which is formed by the burning of the iron4 ,it is a compound of the iron with oxygen1 similar to iron rust1 and formed by their uniting4 99,preparation and ,properties of ,carbon ,dioxide499--#a4 7a7 ,attach a piece of carbon 7charcoal7 no larger than the end of the thumb to a piece of wire4 ,ignite the charcoal in a hot flame and lower it into a vessel of oxygen4 ,observe its combustion1 letting it remain in the bottle until it ceases to burn4 ,note that the burning has consumed a part of the carbon and has used up the free oxygen4 ,has anything been formed in their stead8 7b7 ,remove the charcoal and add a little limewater4 ,cover the bottle with a piece of cardboard1 and bring the gas and the limewater in contact by shaking4 ,note any change in the color of the limewater4 ,if it turns white1 the presence of carbon dioxide is proved4 #b4 ,burn a splinter in a large vessel of air1 keeping the top covered4 ,add limewater and shake4 ,note and account for the result4 #c4 ,place several pieces of marble 7limestone7 in a jar holding at least half a gallon4 ,barely cover the marble with water1 and then add hydrochloric acid until a gas is rapidly evolved4 ,this gas is carbon dioxide4 7a7 ,does it possess color8 7b7 ,insert a burning splinter to see if it supports combustion4 7c7 ,place a bottle of oxygen by the side of the vessel of carbon dioxide4 ,light a splinter and extinguish the flame by lowering it into the vessel of carbon dioxide4 ,withdraw immediately1 and if a spark remains on the splinter1 thrust it into the bottle of oxygen4 ,then insert the relighted splinter into the carbon dioxide4 ,repeat several times1 kindling the flame in one gas and extinguishing it in the other4 ,finally show that the spark also may be extinguished by holding the splinter a little longer in the carbon dioxide4 7d7 ,tip the jar containing the carbon dioxide over the mouth of a tumbler1 as in pouring water1 though not far enough to spill the acid1 and then insert a burning splinter in the tumbler4 ,account for the result4 ,inference as to the weight of carbon dioxide4 ,fig4 #ei ,fig4 #ei--99,simple apparatus99 for illustrating passage of oxygen through the body4 7e7 ,review experiments 7page #aja7 showing the presence of carbon dioxide in the breath4 99,to illustrate the ,general ,movement of ,oxygen through the ,body499--,into a glass tube1 six inches in length and open at both ends1 place several small lumps of charcoal 7,fig4 #ei74 ,fit into one end of this tube1 by means of a stopper1 a smaller glass tube which is bent at right angles and which is made to pass through a close-fitting stopper to the bottom of a small bottle4 ,another small tube is fitted into a second hole in this stopper1 but terminating near the top of the bottle1 and to this is connected a rubber tube about eighteen inches in length4 ,the arrangement is now such that by sucking air from the top of the bottle1 it is made to enter at the distant end of the tube containing the charcoal4 ,after filling the bottle one third full of limewater1 heat the tube containing the charcoal until it begins to glow4 ,then suck the air through the apparatus 7as in smoking1 without drawing it into the lungs71 observing what happens both in the tube and in the bottle4 ,what are the proofs that the oxygen1 in passing through the tube1 unites with the carbon1 forms carbon dioxide1 and liberates energy8 ,compare the changes which the oxygen undergoes while passing through the tube with the changes which it undergoes in passing through the body4 ,,chapter ,,ix - ,,foods ,,and ,,the ,,theory ,,of ,,digestion ,the body is constantly in need of new material4 ,oxidation1 as shown in the preceding chapter1 rapidly destroys substances at the cells1 and these have to be replaced4 ,upon this renewal depends the supply of energy4 ,moreover1 there is found to be an actual breaking down of the living material1 or protoplasm1 in the body4 ,while this does not destroy the cells1 as is sometimes erroneously stated1 it reduces the quantity of the protoplasm and makes necessary a process of repair1 or rebuilding1 of the tissues4 ,this also requires new material4 ,finally1 substances1 such as water and common salt1 are required for the aid which they render in the general work of the body4 ,since these are constantly being lost in one way or another1 they also must be replaced4 ,these different needs of the body for new materials are supplied through 99,the ,foods499--,foods are substances that1 on being taken into the healthy body1 are of assistance in carrying on its work4 ,this definition properly includes oxygen1 but the term is usually limited to substances introduced through the digestive organs4 ,as suggested above1 foods serve at least three purposes3 #a4 ,they1 with oxygen1 supply the body with energy4 #b4 ,they provide materials for rebuilding the tissues4 #c4 ,they supply materials that aid directly or indirectly in the general work of the body4 99,the ,simple ,foods1 or ,nutrients499--,from the great variety of things that are eaten1 it might appear that many different kinds of substances are suitable for food4 ,when our various animal and vegetable foods are analyzed1 however1 they are found to be similar in composition and to contain only some five or six kinds of materials that are essentially different4 ,while certain foods may contain only a single one of these1 most of the foods are mixtures of two or more4 ,these few common materials which1 in different proportions1 form the different things that are eaten1 are variously referred to as simple foods1 food-stuffs1 and nutrients1 the last name being the one generally preferred4 ,the different classes of nutrients are as follows3 ,nutrients3 ,proteids 7,albuminoids7 ,carbohydrates ,fats ,mineral salts ,water ,it is now necessary to become somewhat familiar with the different nutrients and the purposes which they serve in the body4 99,proteids499--,the proteids are obtained in part from the animal and in part from the plant kingdom1 there being several varieties4 ,a well-known variety1 called albumin1 is found in the white of eggs and in the plasma of the blood1 while the muscles contain an abundance of another variety1 known as myosin4 ,cheese consists largely of a kind of proteid1 called casein1 which is also present in milk1 but in a more diluted form4 ,if a mouthful of wheat is chewed for some time1 most of it is dissolved and swallowed1 but there remains in the mouth a sticky1 gum-like substance4 ,this is gluten1 a form of proteid which occurs in different grains4 ,again1 certain vegetables1 as beans1 peas1 and peanuts1 are rich in a kind of proteid which is called legumen4 ,proteids are compounds of carbon1 hydrogen1 oxygen1 nitrogen1 and a small per cent of sulphur4 ,certain ones 7the nucleo-proteids from grains7 also contain phosphorus4 ,all of the proteids are highly complex compounds and form a most important class of nutrients4 99,purposes of ,proteids499--,the chief purpose of proteids in the body is to rebuild the tissues4 ,not only do they supply all of the main elements in the tissues1 but they are of such a nature chemically that they are readily built into the protoplasm4 ,they are absolutely essential to life1 no other nutrients being able to take their place4 ,an animal deprived of them exhausts the proteids in its body and then dies4 ,in addition to rebuilding the tissues1 proteids may also be oxidized to supply the body with energy4 99,albuminoids99 form a small class of foods1 of minor importance1 which are similar to proteids in composition1 but differ from them in being unable to rebuild the tissues4 ,gelatin1 a constituent of soup and obtained from bones and connective tissue by boiling1 is the best known of the albuminoid foods4 ,on account of the nitrogen which they contain1 proteids and albuminoids are often classed together as nitrogenous foods4 99,carbohydrates499--,while the carbohydrates are not so essential to life as are the proteids1 they are of very great value in the body4 ,they are composed of carbon1 hydrogen1 and oxygen1 and are obtained mainly from plants4 ,there are several varieties of carbohydrates1 but they are similar in composition4 ,all of those used as food to any great extent are starch and certain kinds of sugar4 99,starch99 is the carbohydrate of greatest importance as a food1 and it is also the one found in the greatest abundance4 ,all green plants form more or less starch1 and many of them store it in their leaves1 seeds1 or roots 7,fig4 #fj74 ,from these sources it is obtained as food4 ,glycogen1 a substance closely resembling starch1 is found in the body of the oyster4 ,it is also formed in the liver and muscles of the higher animals1 being prepared from the sugar of the blood1 and is stored by them as reserve food 7,chapter ,,xi74 ,glycogen is1 on this account1 called animal starch4 ,starch on being eaten is first changed to sugar1 after which it may be converted into glycogen in the liver and in the muscles4 ,fig4 #fj ,fig4 #fj--99,starch grains99 in cells of potato as they appear under the microscope4 7,see practical work47 99,sugars499--,there are several varieties of sugar1 but the important ones used as foods fall into one or the other of two classes1 known as double sugars 7disaccharides7 and single sugars 7monosaccharides74 ,to the first class belong cane sugar1 found in sugar cane and beets1 milk sugar1 found in sweet milk1 and maltose1 a kind of sugar which is made from starch by the action of malt4 ,the important members of the second class are grape sugar1 or dextrose1 and fruit sugar1 or levulose1 both of which are found in fruits and in honey4 ,the most important of all sugars1 so far as its use in the body is concerned1 is dextrose4 ,to this form all the other sugars1 and starch also1 are converted before they are finally used in the body4 ,the close chemical relation between the different carbohydrates makes such a conversion easily possible4 99,fats499--,the fats used as foods belong to one or the other of two classes1 known as solid fats and oils4 ,the solid fats are derived chiefly from animals1 and the oils are obtained mostly from plants4 ,butter1 the fat of meats1 olive oil1 and the oil of nuts are the fats of greatest importance as foods4 ,fats1 like the carbohydrates1 are composed of carbon1 hydrogen1 and oxygen4 ,they are rather complex chemical compounds1 though not so complex as proteids4 ,since neither fats nor carbohydrates contain nitrogen1 they are frequently classed together as non-nitrogenous foods4 99,purpose ,served by ,carbohydrates1 ,fats1 and ,albuminoids499--,these classes of nutrients all serve the common purpose of supplying energy4 ,by uniting with oxygen at the cells1 they supply heat and the other forms of bodily force4 ,this is perhaps their only purpose47#ej7 ,proteids also serve this purpose1 but they are not so well adapted to supplying energy as are the carbohydrates and the fats4 ,in the first place they do not completely oxidize and therefore do not supply so much energy2 and1 in the second place1 they form waste products that are removed with difficulty from the body4 99,mineral ,salts and their ,uses499--,mineral salts are found in small quantities in all of the more common food materials1 and1 as a rule1 find their way into the body unnoticed4 ,they supply the elements which are found in the body in small quantities and serve a variety of purposes47#ea7 ,calcium phosphate and calcium carbonate are important constituents of the bones and teeth2 and the salts containing iron renew the hemoglobin of the blood4 ,others perform important functions in the vital processes4 ,the mineral compound of greatest importance perhaps is sodium chloride1 or common salt47#eb7 ,this is a natural constituent of most of our foods1 and is also added to food in its preparation for the table4 ,when it is withheld from animals for a considerable length of time1 they suffer intensely and finally die4 ,it is necessary in the blood and lymph to keep their constituents in solution1 and is thought to play an important rle in the chemical changes of the cells4 ,it is constantly leaving the body as a waste product and must be constantly supplied in small quantities in the foods4 99,importance of ,water499--,water finds its way into the body as a pure liquid1 as a part of such mixtures as coffee1 chocolate1 and milk1 and as a constituent of all our solid foods4 7,see table of foods1 page #abf47 ,it is also formed in the body by the oxidation of hydrogen4 ,it passes through the body unchanged1 and is constantly being removed by all the organs of excretion4 ,though water does not liberate energy in the body nor build up the tissues in the sense that other foods do1 it is as necessary to the maintenance of life as oxygen or proteids4 ,it occurs in all the tissues1 and forms about #gj per cent of the entire weight of the body4 ,its presence is necessary for the interchange of materials at the cells and for keeping the tissues soft and pliable4 ,as it enters the body1 it carries digested food substances with it1 and as it leaves it is loaded with wastes4 ,its chief physiological work1 which is that of a transporter of material1 depends upon its ability to dissolve substances and to flow readily from place to place4 99,relative ,quantity of ,nutrients ,needed499--,proteids1 carbohydrates1 and fats are the nutrients that supply most of the body's nourishment4 ,the most hygienic diet is the one which supplies the proteids in sufficient quantity to rebuild the tissues and the carbohydrates and fats in the right amounts to supply the body with energy4 ,much experimenting has been done with a view to determining these proportions1 but the results so far are not entirely satisfactory4 ,according to some of the older estimates1 a person of average size requires for his daily use five ounces of proteid1 two and one half ounces of fat1 and fifteen ounces of carbohydrate4 ,recent investigations of this problem seem to show that the body is as well1 if not better1 nourished by a much smaller amount of proteid--not more than two and one half ounces 7#fj grams7 daily47#ec7 ,while there is probably no necessity for the healthy individual's taking his proteid1 fat1 and carbohydrate in exact proportions 7if the proportions best suited to his body were known71 the fact needs to be emphasized that proteids1 although absolutely necessary1 should form but a small part 7not over one fifth7 of the daily bill of fare4 ,in recognition of this fact is involved a principle of health and also one of economy4 ,the proteids1 especially those in meats1 are the most expensive of the nutrients1 whereas the carbohydrates1 which should form the greater bulk of one's food1 are the least expensive4 99,effects of a ,one-sided ,diet499--,the plan of the body is such as to require a mixed diet1 and all of the great classes of nutrients are necessary4 ,if one could subsist on any single class1 it would be proteids1 for proteids are able both to rebuild tissue and to supply energy4 ,but if proteids are eaten much in excess of the body's need for rebuilding the tissues1 and this excess is oxidized for supplying energy1 a strain is thrown upon the organs of excretion1 because of the increase in the wastes4 ,not only is there danger of overworking certain of these organs 7the liver and kidneys71 but the wastes may linger too long in the body1 causing disorder and laying the foundation for disease4 ,on the other hand1 if an insufficient amount of proteid is taken1 the tissues are improperly nourished1 and one is unable to exert his usual strength4 ,what is true of the proteids is true1 though in a different way1 of the other great classes of foods4 ,a diet which is lacking in proteid1 carbohydrate1 or fat1 or which has any one of them in excess1 is not adapted to the requirements of the body4 99,composition of the ,food ,materials499--,one who intelligently provides the daily bill of fare must have some knowledge of the nature and quantity of the nutrients present in the different materials used as food4 ,this information is supplied by the chemist1 who has made extensive analyses for this purpose4 ,results of such analyses are shown in ,table #a 7page #abf71 which gives the percentage of proteids1 fats1 carbohydrates1 water1 and mineral salts in the edible portions of the more common of our foods4 ,fig4 #fa ,fig4 #fa--,relative proportions of different nutrients in well-known foods4 99,food ,supply to the ,table499--,the main problem in supplying the daily bill of fare is that of securing through the different food materials the requisite amounts of proteids1 carbohydrates1 and fats4 ,in this matter a table showing the composition of foods can be used to great advantage4 ,consulting the table on page #abf1 it is seen that large per cents of proteids are supplied by lean meat1 eggs1 cheese1 beans1 peas1 peanuts1 and oatmeal1 while fat is in excess in fat meat1 butter1 and nuts 7,fig4 #fa74 ,carbohydrates are supplied in abundance by potatoes1 rice1 corn1 sugar1 and molasses4 ,the different cereals also contain a large percentage of carbohydrates in the form of starch4 ,,table ,i4 ,,the ,,composition ,,of ,,food ,,materials7#ed7 ,food ,water ,solids ,proteid ,fat ,carbohydrates ,mineral ,heat ,materials ,matter ,value of ,one ,pound ,animal ,per cent ,per cent ,per cent ,per cent ,per cent ,per cent ,calories7#ee7 foods1 edible portion ,beef3 #fc4i #cf4a #ai4e #ae4f 444 #a #ajbj ,shoulder ,rib #dh4a #ea4i #ae4d #ce4f 444 4#i #agij ,sirloin #fj #dj #ah4e #bj4e 444 #a #abaj ,round #fh4b #ca4h #bj4e #aj4a 444 #a4b #hje ,veal3 #fh4h #ca4b #bj4b #i4h 444 444 #gij ,shoulder ,mutton3 #fa4h #ch4b #ah4c #ai 444 4#i #aadj ,leg ,loin #di4c #ej4g #ae #ce 444 4#g #agee ,pork3 #ej4c #di4g #af #cb4h 444 4#i #afhj ,shoulder ,ham1 #da4e #eh4e #af4g #ci4a 444 #b4g #aifj salted1 smoked ,fat1 #ab4a #hg4i 4#i #hb4h 444 #d4b #ceaj salted ,sausage3 #da4e #eh4h #ac4h #db4h 444 #b4b #bjfe ,pork ,bologna #fb4d #cg4f #ah4h #db4h 444 #c #ajae ,chicken #gb4b #bg4h #bd4d #a 444 #a4d #edj ,eggs #gc4h #bf4b #ad4i #aj4e 444 4#h #gba ,milk #hg #ac #c4f #d #d4g 4#g #cbe ,butter #aj4e #hi 4#f #he 4#e 4#c #ceae ,cheese3 #cj4b #fi4h #bh4c #ce4e #a4h #d4b #bjgj ,full cream ,skim milk #da4c #eh4g #ch4d #f4h #f4i #d4f #aafe ,fish3 #hb4f #ag4d #ae4h 4#e 444 #a4b #caj ,codfish ,salmon #fc4f #cf4d #ba4f #ac4d 444 #a4d #ife ,oysters #hg4a #ab4i #f #a4b #c4g #b #bcj ,vegetable foods ,wheat #ab4e #hg4e #aa #a4a #gd4i 4#e #afde flour ,graham #ac4a #hf4i #aa4g #a4g #ga4g #a4h #afce flour 7wheat7 ,rye flour #ac4a #hf4i #f4g 4#h #gh4g 4#g #afbe ,buckwheat #ad4f #he4d #f4i #a4d #gf4a #a #afje flour ,oatmeal #g4f #ib4d #ae4a #g4a #fh4b #b #ahej ,cornmeal #ae #he #i4b #c4h #gj4f #a4d #afde ,rice #ab4d #hg4f #g4d 4#d #gi4d 4#d #afcj ,peas #ab4c #hg4g #bf4g #a4g #ef4d #b4i #aefe ,beans #ab4f #hg4d #bc4a #b #ei4b #c4a #afae ,potatoes #gh4i #ba4a #b4a 4#a #ag4i #a #cge ,tomatoes #ie4c #d4g 4#h 4#d #c4b 4#c #hj ,apples #hc4b #af4h 4#b 4#d #ae4i 4#c #cae ,sugar1 #b #ih 444 444 #ig4h 4#c #ahbj granulated ,white #cb4c #fg4g #h4b #a4g #ef4c 4#j #abhj bread 7wheat7 ,peanuts #i4b #ij4h #be4h #bd4d #ch4f #b #befj ,almonds #d4h #ie4b #ba #ag4c #ed4i #b #cjcj ,walnuts #b4e #ig4e #af4f #af4a #fc4d #a4d #cbhe 7,english7 ,variety in the selection of foods for the table is an essential feature1 but this should not increase either the work or the expense of supplying the meals4 ,each single meal can1 and should1 be simple in itself and1 at the same time1 differ sufficiently from the meal preceding and the one following to give the necessary variety in the course of the day4 ,the bill of fare should1 of course1 include fruits 7for their tonic effects7 and very small amounts perhaps of substances which stimulate the appetite1 such as pepper1 mustard1 etc41 known as condiments4 99,purity of ,food499--,the fact that many of the food substances are perishable makes it possible for them to be eaten in a slightly decayed condition4 ,such substances are decidedly unwholesome 7some containing poisons7 and should be promptly rejected4 ,not only do fresh meats1 fruits1 and vegetables need careful inspection1 but canned and preserved goods as well4 ,if canned foods are imperfectly sealed or if not thoroughly cooked in the canning process1 they decay and the acids which they generate act on the metals lining the cans1 forming poisonous compounds4 ,the contents of tin cans should for this reason be transferred to other vessels as soon as opened4 ,foods are also rendered impure or weakened through adulteration1 the watering of milk being a familiar example4 ,the manufacture of jellies1 preserves1 sirups1 and various kinds of pickles and condiments has perhaps afforded the largest field for adulterations1 although it is possible to adulterate nearly all of the leading articles of food4 ,a long step in the prevention of food and drug adulteration was taken in this country by the passage of the ,pure ,food ,law4 ,by forcing manufacturers of foods and medicines to state on printed labels the composition of their products1 this law has made it possible for the consumer to know what he is purchasing and putting into his body4 99,alcohol not a ,food499--,many people in this and other countries drink in different beverages1 such as whisky1 beer1 wine1 etc41 a varying amount of alcohol4 ,this substance has a temporary stimulating or exciting effect1 and the claim has been made that it serves as a food4 ,recently it has been shown that alcohol when introduced into the body in small quantities and in a greatly diluted form1 is nearly all oxidized1 yielding energy as does fat or sugar4 ,if no harmful effects attended the use of alcohol1 it might on this account be classed as a food4 ,but alcohol is known to be harmful to the body4 ,when used in large quantities1 it injures nearly all of the tissues1 and when taken habitually1 even in small doses1 it leads to the formation of the alcohol habit which is now recognized and treated as a disease4 ,this and other facts show that alcohol is not adapted to the body plan of taking on and using new material 7,chapter ,,xi71 and no substance lacking in this respect can properly be classed as a food47#ef7 ,instead of classing alcohol as a food1 it should be placed in that long list of substances which are introduced into the body for special purposes and which are known by the general name of 99,drugs499--,drugs act strongly upon the body and tend to bring about unusual and unnatural results4 ,their use should in no way be confused with that of foods4 ,if taken in health1 they tend to disturb the physiological balance of the body by unduly increasing or diminishing the action of the different organs4 ,in disease where this balance is already disturbed1 they may be administered for their counteractive effects1 but always under the advice and direction of a physician4 ,knowing the nature of the disturbance which the drug produces1 the physician can administer it to advantage1 should the body be out of physiological balance1 or diseased4 ,not only are drugs of no value in health1 but their use is liable to do much harm4 ,,nature ,,of ,,digestion ,before the nutrients can be oxidized at the cells1 or built into the protoplasm1 they undergo a number of changes4 ,these are necessary for their entrance into the body1 for their distribution by the blood and the lymph1 and for the purposes which they finally serve4 ,the first of these changes is preparatory to the entrance of the nutrients and is known as digestion4 ,the organs which bring about this change1 called digestive organs1 have a special construction which adapts them to their work4 ,it will assist materially in understanding these organs if we first learn something of the nature of the work which they have to perform4 99,how the ,nutrients get into the ,body499--,the nature of digestion is determined by the conditions affecting the entrance of nutrients into the body4 ,food in the stomach and air in the lungs1 although surrounded by the body1 are still outside of what is called the body proper4 ,to gain entrance into the body proper1 a substance must pass through the body wall4 ,this consists of the skin on the outside and of the mucous linings of the air passages and other tubes and cavities which are connected with the external surface4 ,to get from the digestive organs into the blood1 the nutrients must pass through the mucous membrane lining these organs and also the walls of blood or lymph vessels4 ,only liquid materials can make this passage4 ,it is necessary1 therefore1 to reduce to the liquid state all nutrients not already in that condition4 ,this reduction to the liquid state constitutes the digestive process4 99,how ,substances are ,liquefied499--,while the reduction of solids to the liquid state is accomplished in some instances by heating them until they melt1 they are more frequently reduced to this state by subjecting them to the action of certain liquids1 called solvents4 ,through the action of the solvent the minute particles of the solid separate from each other and disappear from view4 7,shown in dropping salt in water47 ,at the same time they mix with the solvent1 forming a solution1 from which they separate only with great difficulty4 ,for this reason solids in solution can diffuse through porous partitions along with the solvents in which they are dissolved 7page #gc74 ,by digestion the nutrients are reduced to the form of a solution4 ,the process is1 simply speaking1 one of dissolving4 ,the liquid employed as the digestive solvent is water4 ,the different nutrients dissolve in water1 mixing with it to form a solution which is then passed into the body proper4 99,digestion not a ,simple ,process499--,digestion is by no means a simple process1 such1 for instance1 as the dissolving of salt or sugar in water4 ,these1 being soluble in water1 dissolve at once on being mixed with a sufficient amount of this liquid4 ,the majority of the nutrients1 however1 are insoluble in water and are unaffected by it when acting alone4 ,fats1 starch1 and most of the proteids do not dissolve in water4 ,before these can be dissolved they have to be changed chemically and converted into substances that are soluble in water4 ,this complicates the process and prevents the use of water alone as the digestive solvent4 99,a ,similar ,case499--,if a piece of limestone be placed in water1 it does not dissolve1 because it is insoluble in water4 ,if hydrochloric acid is now added to the water1 the limestone is soon dissolved 7,fig4 #fb74 7,see ,practical ,work47 ,it seems at first thought that the acid dissolves the limestone1 but this is not the case4 ,the acid produces a chemical change in the limestone 7calcium carbonate7 and converts it into a compound 7calcium chloride7 that is soluble in water4 ,as fast as this is formed it is dissolved by the water1 which is the real solvent in the case4 ,the acid simply plays the part of a chemical converter4 ,fig4 #fb ,fig4 #fb--,the dissolving of limestone in water containing acid1 suggesting the double action in the digestion of most foods4 99,the ,digestive ,fluids499--,several fluids--saliva1 gastric juice1 pancreatic juice1 bile1 and intestinal juice--are employed in the digestion of the food4 ,the composition of these fluids is in keeping with the nature of the digestive process4 ,while all of them have water for their most abundant constituent1 there are dissolved in the water small amounts of active chemical agents4 ,it is the work of these agents to convert the insoluble nutrients into substances that are soluble in water4 ,the digestive fluids are thus able to act in a double manner on the nutrients--to change them chemically and to dissolve them4 ,the chemical agents which bring about the changes in the nutrients are called enzymes1 or digestive ferments4 99,foods ,classed with ,reference to ,digestive ,changes499--,with reference to the changes which they undergo during digestion1 foods may be divided into three classes as follows3 #a4 ,substances already in the liquid state and requiring no digestive action4 ,water and solutions of simple foods in water belong to this class4 ,milk and liquid fats1 or oils1 do not belong to this class4 #b4 ,solid foods soluble in water4 ,this class includes common salt and sugar4 ,these require no digestive action other than dissolving in water4 #c4 ,foods that are insoluble in water4 ,these have first to be changed into soluble substances1 after which they are dissolved4 99,summary499--,materials called foods are introduced into the body for rebuilding the tissues1 supplying energy1 and aiding in its general work4 ,only a few classes of substances1 viz41 proteids1 carbohydrates1 fats1 water1 and some mineral compounds have all the qualities of foods and are suitable for introduction into the body4 ,substances known as drugs1 which may be used as medicines in disease1 should be avoided in health4 ,before foods can be passed into the body proper1 they must be converted into the liquid form1 or dissolved4 ,in this process1 known as digestion1 water is the solvent2 and certain chemical agents1 called enzymes1 convert the insoluble nutrients into substances that are soluble in water4 99,exercises499--#a4 ,how does oxidation at the cells make necessary the introduction of new materials into the body8 #b4 ,what different purposes are served by the foods8 #c4 ,what is a nutrient8 ,name the important classes4 #d4 ,what are food materials8 ,from what sources are they obtained8 #e4 ,name the different kinds of proteids2 the different kinds of carbohydrates4 ,why are proteids called nitrogenous foods and fats and carbohydrates non-nitrogenous foods8 #f4 ,show why life cannot be carried on without proteids2 without water4 #g4 ,what per cents of proteid1 fat1 and carbohydrate are found in wheat flour1 oatmeal1 rice1 butter1 potatoes1 round beef1 eggs1 and peanuts8 #h4 ,state the objection to a meal consisting of beef1 eggs1 beans1 bread1 and butter2 to one consisting of potatoes1 rice1 bread1 and butter4 ,which is the more objectionable of these meals and why8 #i4 ,state the general plan of digestion4 #aj4 ,show that digestion is not a simple process like that of dissolving salt in water4 ,,practical ,,work 99,elements supplied by the ,foods499--,the following brief study will enable the pupil to identify most of the elements present in the body and which have1 therefore1 to be supplied by the foods4 ,carbon4--,examine pieces of charred wood1 coke1 or coal1 and also the lead in lead pencils4 ,show that the charred wood and the coal will burn4 ,recall experiment 7page #aad7 showing that carbon in burning forms carbon dioxide4 ,hydrogen4--,fill a test tube one third full of strong hydrochloric acid and drop into it several small scraps of zinc4 ,the gas which is evolved is hydrogen4 ,when the hydrogen is coming off rapidly1 bring a lighted splinter to the mouth of the tube4 ,the gas should burn4 ,hold a cold piece of glass over the flame and observe the deposit of moisture4 ,hydrogen in burning forms water4 ,extinguish the flame by covering the top of the tube with a piece of cardboard4 ,now let the escaping gas collect in a tumbler inverted over the tube4 ,after holding the tumbler in this position for two or three minutes1 remove and1 keeping inverted1 thrust a lighted splinter into it4 7,the gas should either burn or explode47 ,what does this experiment show relative to the weight of hydrogen as compared with that of air8 ,nitrogen4--,nitrogen forms about four fifths of the atmosphere1 where1 like oxygen1 it exists in a free state4 ,it may be separated from the oxygen of an inclosed portion of air by causing that gas to unite with phosphorus4 ,place a piece of phosphorus the size of a pea in a depression in a flat piece of cork4 7,handle phosphorus with wet fingers or with forceps47 ,place the cork on water and have ready a glass fruit jar holding not more than a quart4 ,ignite the phosphorus with a hot wire and invert the jar over it1 pushing the mouth below the surface of the water4 ,the phosphorus uniting with the oxygen fills the jar with white fumes of phosphoric oxide4 ,these soon dissolve in the water1 leaving a clear gas above4 ,this is nitrogen4 ,place a cardboard under the mouth of the jar and turn it right side up1 leaving in the water and keeping the top covered4 ,light a splinter and1 slipping the cover to one side1 thrust the flame into the jar of nitrogen1 noting the effect4 7,flame is extinguished47 ,compare nitrogen with oxygen in its relation to combustion4 ,what purpose is served by each in the atmosphere8 ,oxygen4--,review experiments 7page #aad7 showing the properties of oxygen4 ,phosphorus4--,examine a small piece of phosphorus1 noting that it has to be kept under water4 ,lay a small piece on the table and observe the tiny stream of white smoke rising from it1 formed by slow oxidation4 ,dissolve a piece as large as a pea in a teaspoonful of carbon disulphide in a test tube1 pour this on a piece of porous paper1 and lay the paper on an iron support4 ,when the carbon disulphide evaporates the phosphorus takes fire spontaneously4 7,the heat from the slow oxidation is sufficient to ignite the phosphorus in the finely divided condition47 ,what is the most striking property of phosphorus8 ,what purpose does it serve in the match8 ,sulphur4--,examine some sulphur1 noting its color and the absence of odor or taste4 7,impure sulphur may have an odor and a taste47 ,burn a little sulphur in an iron spoon1 noting that the compound which it forms with oxygen by burning has a decided odor4 ,other ,elements4--,magnesium4 ,examine and burn a piece of magnesium ribbon1 noting the white compound of magnesium oxide which is formed4 ,iron4 ,examine pieces of the metal and also some of its compounds1 as ferrous sulphate1 ferric chloride1 and ferric oxide or iron rust4 ,sodium4 ,drop a piece of the metal on water and observe results4 ,sodium decomposes water4 ,it has to be kept under some liquid1 such as kerosene1 which contains no oxygen4 7,it should not be touched except with the fingers wet with kerosene47 ,chlorine4 ,pour strong hydrochloric acid on a little manganese dioxide in a test tube1 and warm gently over a low flame4 ,the escaping gas is chlorine4 ,avoid breathing much of it4 99,composition of the ,nutrients499--,the simplest way of determining what elements make up the different nutrients is by heating them and studying the products of decomposition1 as follows3 ,to show that ,carbohydrates contain ,carbon1 ,hydrogen1 and ,oxygen4--,place one half teaspoonful of powdered starch in a test tube and heat strongly4 ,observe that water condenses on the sides of the tube and that a black1 charred mass remains behind4 ,the black mass consists mainly of carbon4 ,the water is composed of hydrogen and oxygen4 ,these three elements are thus shown to be present in the starch4 ,the experiment may be repeated1 using sugar instead of starch4 ,to show that ,proteids contain ,carbon1 ,hydrogen1 ,oxygen1 ,nitrogen1 and ,sulphur4--,place in a test tube some finely divided proteid which has been thoroughly dried 7dried beef or the lean of hard cured bacon74 ,heat strongly in the hood of a chemical laboratory or some other place where the odors do not get into the room4 ,first hold in the escaping gases a wet strip of red litmus paper4 ,this will be turned blue1 showing ammonia 7,,nh#c7 to be escaping4 ,next hold in the mouth of the tube a strip of a paper wet with a solution of lead nitrate4 ,this is turned black or brown on account of hydrogen sulphide7,h#b,s7 which is being driven off4 ,observe also that water condenses in the upper part of the tube and that a black1 charred mass remains behind4 ,since the products of decomposition 7,h#b,o1 ,,nh#c1 ,h#b,s1 and the charred mass7 contain hydrogen1 oxygen1 nitrogen1 sulphur1 and carbon1 these elements are of course present in the proteid tested4 ,to show the ,presence of ,mineral ,matter4--,burn a piece of dry bread by holding it in a clear1 hot flame1 and observe the ash that is left behind4 ,this is the mineral matter present in the bread4 99,tests for ,nutrients499 ,proteids4--,cover the substance to be tested with strong nitric acid and heat gradually to boiling4 ,if proteid is present it turns yellow and partly dissolves in the acid1 forming a yellow solution4 ,let cool and then add ammonia4 ,the yellow solid and the solution are turned a deep orange color4 ,apply this test to foods containing proteid such as white of egg1 cheese1 lean meat1 etc4 ,starch4--7a7 ,place a small lump of starch in one fourth of a pint of water and heat gradually to boiling1 stirring well4 ,then add enough water to form a thin liquid and fill a test tube half full4 ,add to this a few drops of a solution of iodine4 7,prepare by dissolving a crystal of iodine in #be cubic centimeters 7#a_/bj pint7 of a solution of potassium iodide in water and add water to this until it is a light amber color47 ,the starch solution is turned blue1 7b7 ,cut with a razor a thin slice from a potato4 ,place this in a weak solution of iodine for a few minutes and then examine with the microscope1 using first a low and then a high power4 ,numerous starch grains inclosed in cellulose walls will be seen 7,fig4 #fj74 ,dextrose1 or ,grape ,sugar4--,place a solution of the substance supposed to contain grape sugar in a test tube and add a few drops of a dilute solution of copper sulphate4 ,then add sodium hydroxide solution until the precipitate which first forms is redissolved and a clear blue liquid obtained4 ,heat the upper portion of the liquid slowly to near the boiling point4 ,a little below the boiling point the blue color disappears and a yellow-red precipitate is formed4 ,if the upper layer of the liquid is now boiled1 the color deepens and this may be contrasted with the blue color below4 ,apply this test to the sugar in raisins and in honey4 ,fat4--,fat is recognized by its effect on paper1 making a greasy stain which does not disappear on heating and which renders the paper translucent4 ,try butter1 lard1 or olive oil4 ,also show the presence of fat in peanuts by crushing them in a mortar and rubbing the powder on thin paper4 ,if the substance to be tested contains but little fat1 this may be dissolved out with ether4 ,if a drop of ether containing the fat is placed on paper1 it evaporates1 leaving the fat1 which then forms the stain4 99,to show the ,effect of ,alcohol upon ,proteid499--,place some of the white of a raw egg in a glass vessel and cover it with a small amount of alcohol4 ,as the albumin 7proteid7 hardens1 or coagulates1 observe that the quantity of clear liquid increases4 ,this is due to the withdrawal of water from the albumin by the alcohol4 ,since the tissues are made up chiefly of proteids1 a piece of muscle or of liver may be used in the experiment1 instead of the egg1 with similar results4 99,to illustrate the ,digestive ,process499--,to a tumbler two thirds full of water add a little salt4 ,stir and observe that the salt is dissolved4 ,taste the solution to see that the salt has not been changed chemically4 ,now add a little powdered limestone to the water and stir as before4 ,observe that the limestone does not dissolve4 ,then add some hydrochloric acid and observe the result4 ,state the part played by the acid and by the water in dissolving the limestone4 ,apply to the digestion of the different classes of foods4 ,,chapter ,x - ,,organs ,,and ,,processes ,,of ,,digestion ,the organs of digestion are adapted to the work of dissolving the foods by both their structure and arrangement4 ,most of them consist either of tubes or cavities and these are so connected1 one with the other1 as to form a continuous passageway entirely through the body4 ,this passageway is known as 99,the ,alimentary ,canal4 99--,the alimentary canal has a length of about thirty feet and1 while it begins at the mouth1 all but about eighteen inches of it is found in the abdominal cavity4 ,on account of its length it lies for the most part in coils1 the two largest ones being known as the small intestine and the large intestine4 ,connected with the alimentary canal are the glands that supply the liquids for acting on the food4 ,the divisions of the canal and most of the glands that empty liquids into it are shown in ,fig4 #fc and named in the table below3 ,table 99,coats of the ,alimentary ,canal499--,the walls of the alimentary canal1 except at the mouth1 are distinct from the surrounding tissues and consist in most places of at least three layers1 or coats1 as follows3 ,fig4 #fc ,fig4 #fc--99;,diagram of the digestive system499 #a4 ,mouth4 #b4 ,soft palate4 #c4 ,pharynx4 #d4 ,parotid gland4 #e4 ,sublingual gland4 #f4 ,submaxillary gland4 #g4 ,esophagus4 #h4 ,stomach4 #i4 ,pancreas4 #aj4 ,vermiform appendix4 #aa4 ,ccum4 #ab4 ,ascending colon4 #ac4 ,transverse colon4 #ad4 ,descending colon4 #ae4 ,sigmoid flexure4 #af4 ,rectum4 #ag4 ,ileo-ccal valve4 #ah4 ,duct from liver and pancreas4 #ai4 ,liver4 ,diagram does not show comparative length of the small intestine4 #a4 ,an inner coat1 or lining1 known as the mucous membrane4 ,this membrane is not confined to the alimentary canal1 but lines1 as we have seen1 the different air passages4 ,it covers1 in fact1 all those internal surfaces of the body that connect with the external surface4 ,it derives its name from the substance which it secretes1 called mucus4 ,in structure it resembles the skin1 being continuous with the skin where cavities open to the surface4 ,it is made up of two layers--a thick underlayer which contains blood vessels1 nerves1 and glands1 and a thin surface layer1 called the epithelium4 ,the epithelium1 like the cuticle1 is without blood vessels1 nerves1 or glands4 #b4 ,a middle coat1 which is muscular and which forms a continuous layer throughout the canal1 except at the mouth4 7,here its place is taken by the strong muscles of mastication which are separate and distinct from each other47 ,as a rule the muscles of this coat are involuntary4 ,they surround the canal as thin sheets and at most places form two distinct layers4 ,in the inner layer the fibers encircle the canal1 but in the outer layer they run longitudinally1 or lengthwise1 along the canal47#eg7 #c4 ,an outer or serous coat1 which is limited to those portions of the canal that occupy the abdominal cavity4 ,this coat is not found above the diaphragm4 ,it is a part of the lining membrane of the cavity of the abdomen1 called ,fig4 #fd ,fig4 #fd--99;,diagram of the peritoneum499 #a4 ,transverse colon4 #b4 ,duodenum4 #c4 ,small intestine4 #d4 ,pancreas4 99,the ,peritoneum499--,the peritoneum is to the abdominal cavity what the pleura is to the thoracic cavity4 ,it forms the outer covering for the alimentary canal and other abdominal organs and supplies the inner lining of the cavity itself4 ,it is also the means of holding these organs in place1 some of them being suspended by it from the abdominal walls 7,fig4 #fd74 ,by the secretion of a small amount of liquid1 it prevents friction of the parts upon one another4 99,digestive ,glands499--,the glands which provide the different fluids for acting on the foods derive their constituents from the blood4 ,they are situated either in the mucous membrane or at convenient places outside of the canal and pass their liquids into it by means of small tubes1 called ducts4 ,in the canal the food and the digestive fluids come in direct contact--a condition which the dissolving processes require4 ,each kind of fluid is secreted by a special kind of gland and is emptied into the canal at the place where it is needed4 99,the ,digestive ,processes499--,digestion is accomplished by acting upon the food in different ways1 as it is passed along the canal1 with the final result of reducing it to the form of a solution4 ,several distinct processes are necessary and they occur in such an order that those preceding are preparatory to those that follow4 ,these processes are known as mastication1 insalivation1 deglutition1 stomach digestion1 and intestinal digestion4 ,as the different materials become liquefied they are transferred to the blood1 and substances not reduced to the liquid state are passed on through the canal as waste4 ,the first two of the digestive processes occur in 99,the ,mouth499--,this is an oval-shaped cavity situated at the very beginning of the canal4 ,it is surrounded by the lips in front1 by the cheeks on the sides1 by the hard palate above and the soft palate behind1 and by the tissues of the lower jaw below4 ,the mucous membrane lining the mouth is1 soft and smooth1 being covered with flat epithelial cells4 ,the external opening of the mouth is guarded by the lips1 and the soft palate forms a movable partition between the mouth and the pharynx4 ,in a condition of repose the mouth space is practically filled by the teeth and the tongue1 but the cavity may be enlarged and room provided for food by depressing the lower jaw4 ,the mouth by its construction is well adapted to carrying on the processes of mastication and insalivation4 ,by the first process the solid food is reduced1 by the cutting and grinding action of the teeth1 to a finely divided condition4 ,by the second1 the saliva becomes mixed with the food and is made to act upon it4 ,fig4 #fe ,fig4 #fe--99,the teeth499 ,a4 ,section of a single molar4 #a4 ,pulp4 #b4 ,dentine4 #c4 ,enamel4 #d4 ,crown4 #e4 ,neck4 #f4 ,root4 ,b4 ,teeth in position in lower jaw4 #a4 ,incisors4 #b4 ,canine4 #c4 ,biscuspids4 #d4 ,molars4 ,c4 ,upper and lower teeth on one side4 #a4 ,incisors4 #b4 ,canines4 #c4 ,biscuspids4 #d4 ,molars4 #e4 ,wisdom4 ,d4 ,upper and lower incisor1 to show gliding contact4 99,accessory ,organs of the ,mouth499--,the work of mastication and insalivation is accomplished through organs situated in and around the mouth cavity4 ,these comprise3 #a4 ,the ,teeth4--,the teeth are set in the upper and lower jaws1 one row directly over the other1 with their hardened surfaces facing4 ,in reducing the food1 the teeth of the lower jaw move against those of the upper1 while the food is held by the tongue and cheeks between the grinding surfaces4 ,the front teeth are thin and chisel-shaped4 ,they do not meet so squarely as do the back ones1 but their edges glide over each other1 like the blades of scissors--a condition that adapts them to cutting off and separating the food 7,d1 ,fig4 #fe74 ,the back teeth are broad and irregular1 having surfaces that are adapted to crushing and grinding4 ,each tooth is composed mainly of a bone-like substance1 called dentine1 which surrounds a central space1 containing blood vessels and nerves1 known as the pulp cavity4 ,it is set in a depression in the jaw where it is held firmly in place by a bony substance1 known as cement4 ,the part of the tooth exposed above the gum is the crown1 the part surrounded by the gum is the neck1 and the part which penetrates into the jaw is the root 7,a1 ,fig4 #fe74 ,a hard1 protective material1 called enamel1 covers the exposed surface of the tooth4 ,the teeth which first appear are known as the temporary1 or milk1 teeth and are twenty in number1 ten in each jaw4 ,they usually begin to appear about the sixth month1 and they disappear from the mouth at intervals from the sixth to the thirteenth year4 ,as they leave1 teeth of the second1 or permanent1 set take their place4 ,this set has thirty-two teeth of four different kinds arranged in the two jaws as follows3 ,in front1 above and below1 are four chisel-shaped teeth1 known as the incisors4 ,next to these on either side is a tooth longer and thicker than the incisors1 called the canine4 ,back of these are two short1 rounded and double pointed teeth1 the bicuspids1 and back of the bicuspids are three heavy teeth with irregular grinding surfaces1 called the molars 7,b and ,c1 ,fig4 #fe74 ,since the molar farthest back in each jaw is usually not cut until maturity1 it is called a wisdom tooth4 ,the molars are known as the superadded permanent teeth because they do not take the place of milk teeth1 but form farther back as the jaw grows in length4 ,fig4 #ff ,fig4 #ff--99;,diagram99 showing directions of muscular fibers in tongue4 #b4 ,the ,tongue4--,the tongue is a muscular organ whose fibers extend through it in several directions 7,fig4 #ff74 ,its structure adapts it to a variety of movements4 ,during mastication the tongue transfers the food from one part of the mouth to another1 and1 with the aid of the cheeks1 holds the food between the rows of teeth4 7,by an outward pressure from the tongue and an inward pressure from the cheek the food is kept between the grinding surfaces47 ,the tongue has functions in addition to these and is a most useful organ4 #c4 ,the ,muscles of ,mastication4--,these are attached to the lower jaw and bring about its different movements4 ,the masseter muscles1 which are the heavy muscles in the cheeks1 and the temporal muscles1 located in the region of the temples1 raise the lower jaw and supply the force for grinding the food4 ,small muscles situated below the chin depress the jaw and open the mouth4 ,fig4 #fg ,fig4 #fg--99,salivary glands99 and the ducts connecting them with the mouth4 #d4 ,the ,salivary ,glands4--,these glands are situated in the tissues surrounding the mouth1 and communicate with it by means of ducts 7,fig4 #fg74 ,they secrete the saliva4 ,the salivary glands are six in number and are arranged in three pairs4 ,the largest1 called the parotid glands1 lie1 one on either side1 in front of and below the ears4 ,a duct from each gland passes forward along the cheek until it opens in the interior of the mouth1 opposite the second molar tooth in the upper jaw4 ,next in size to the parotids are the submaxillary glands4 ,these are located1 one on either side1 just below and in front of the triangular bend in the lower jaw4 ,the smallest of the salivary glands are the sublingual4 ,they are situated in the floor of the mouth1 on either side1 at the front and base of the tongue4 ,ducts from the submaxillary and sublingual glands open into the mouth below the tip of the tongue4 99,the ,saliva and its ,uses499--,the saliva is a transparent and somewhat slimy liquid which is slightly alkaline4 ,it consists chiefly of water 7about #ii per cent71 but in this are dissolved certain salts and an active chemical agent1 or enzyme1 called ptyalin1 which acts on the starch4 ,the ptyalin changes starch into a form of sugar 7maltose71 while the water in the saliva dissolves the soluble portions of the food4 ,in addition to this the saliva moistens and lubricates the food which it does not dissolve1 and prepares it in this way for its passage to the stomach4 ,the last is considered the most important use of the saliva1 and dry substances1 such as crackers1 which require a considerable amount of this liquid1 cannot be eaten rapidly without choking4 ,slow mastication favors the secretion and action of the saliva4 99,deglutition499--,deglutition1 or swallowing1 is the process by which food is transferred from the mouth to the stomach4 ,though this is not1 strictly speaking1 a digestive process1 it is1 nevertheless1 necessary for the further digestion of the food4 ,mastication and insalivation1 which are largely mechanical1 prepare the food for certain chemical processes by which it is dissolved4 ,the first of these occurs in the stomach and to this organ the food is transferred from the mouth4 ,the chief organs concerned in deglutition are the tongue1 the pharynx1 and the esophagus4 99,the ,pharynx99 is a round and somewhat cone-shaped cavity1 about four and one half inches in length1 which lies just back of the nostrils1 mouth1 and larynx4 ,it is remarkable for its openings1 seven in number1 by means of which it communicates with other cavities and tubes of the body4 ,one of these openings is into the mouth1 one into the esophagus1 one into the larynx1 and one into each of the nostrils1 while two small tubes 7the eustachian7 pass from the upper part of the pharynx to the middle ears4 ,the pharynx is the part of the food canal that is crossed by the passageway for the air4 ,to keep the food from passing out of its natural channel1 the openings into the air passages have to be carefully guarded4 ,this is accomplished through the soft palate and epiglottis1 which are operated somewhat as valves4 ,the muscular coat of the pharynx is made up of a series of overlapping muscles which1 by their contractions1 draw the sides together and diminish the cavity4 ,the mucous membrane lining the pharynx is smooth1 like that of the mouth1 being covered with a layer of flat epithelial cells4 99,the ,esophagus991 or gullet1 is a tube eight or nine inches long1 connecting the pharynx with the stomach4 ,it lies for the most part in the thoracic cavity and consists chiefly of a thick mucous lining surrounded by a heavy coat of muscle4 ,the muscular coat is composed of two layers--an inner layer whose fibers encircle the tube and an outer layer whose fibers run lengthwise4 99,steps in ,deglutition499--,the process of deglutition varies with the kind of food4 ,with bulky food it consists of three steps1 or stages1 as follows3 #a4 ,by the contraction of the muscles of the cheeks1 the food ball1 or bolus1 is pressed into the center of the mouth and upon the upper surface of the tongue4 ,then the tongue1 by an upward and backward movement1 pushes the food under the soft palate and into the pharynx4 #b4 ,as the food passes from the mouth1 the pharynx is drawn up to receive it4 ,at the same time the soft palate is pushed upward and backward1 closing the opening into the upper pharynx1 while the epiglottis is made to close the opening into the larynx4 ,by this means all communication between the food canal and the air passages is temporarily closed4 ,the upper muscles of the pharynx now contract upon the food1 forcing it downward and into the esophagus4 #c4 ,in the esophagus the food is forced along by the successive contractions of muscles1 starting at the upper end of the tube1 until the stomach is reached4 ,swallowing is doubtless aided to some extent by the force of gravity4 ,that it is independent of this force1 however1 is shown by the fact that one may swallow with the esophagus in a horizontal position1 as in lying down4 ,fig4 #fh ,fig4 #fh--99;,gastric ,glands499 ,a4 ,single gland showing the two kinds of secreting cells and the duct where the gland opens on to the surface4 ,b4 ,inner surface of stomach magnified4 ,the small pits are the openings from the glands4 99,the ,stomach499--,the stomach is the largest dilatation of the alimentary canal4 ,it is situated in the abdominal cavity1 immediately below the diaphragm1 with the larger portion toward the left side4 ,its connection with the esophagus is known as the cardiac orifice and its opening into the small intestine is called the pyloric orifice4 ,it varies greatly in size in different individuals1 being on the average from ten to twelve inches at its greatest length1 from four to five inches at its greatest width1 and holding from three to five pints4 ,it has the coats common to the canal1 but these are modified somewhat to adapt them to its work4 ,the mucous membrane of the stomach is thick and highly developed4 ,it contains great numbers of minute tube-shaped bodies1 known as the gastric glands 7,fig4 #fh74 ,these are of two general kinds and secrete large quantities of a liquid called the gastric juice4 ,when the stomach is empty1 the mucous membrane is thrown into folds which run lengthwise over the inner surface4 ,these disappear1 however1 when the walls of the stomach are distended with food4 ,the muscular coat consists of three separate layers which are named1 from the direction of the fibers1 the circular layer1 the longitudinal layer1 and the oblique layer 7,fig4 #fi74 ,the circular layer becomes quite thick at the pyloric orifice1 forming a distinct band which serves as a valve4 ,fig4 #fi ,fig4 #fi--99,muscles of the stomach99 7from ,morris' ,human ,anatomy74 ,the layer of ,longitudinal fibers removed4 ,the outer coat of the stomach1 called the serous coat1 is a continuation of the peritoneum1 the membrane lining the abdominal cavity4 99,stomach ,digestion499--,in the stomach begins the definite work of dissolving those foods which are insoluble in water4 ,this1 as already stated1 is a double process4 ,there is first a chemical action in which the insoluble are changed into soluble substances1 and this is followed immediately by the dissolving action of water4 ,the chief substances digested in the stomach are the proteids4 ,these1 in dissolving1 are changed into two soluble substances1 known as peptones and proteoses4 ,the digestion of the proteids is1 of course1 due to the 99,gastric ,juice499--,the gastric juice is a thin1 colorless liquid composed of about #ii per cent of water and about #a per cent of other substances4 ,the latter are dissolved in the water and include1 besides several salts1 three active chemical agents--hydrochloric acid1 pepsin1 and rennin4 ,pepsin is the enzyme which acts upon proteids1 but it is able to act only in an acid medium--a condition which is supplied by the hydrochloric acid4 ,mixed with the hydrochloric acid it converts the proteids into peptones and proteoses4 99,other ,effects of the ,gastric ,juice499--,in addition to digesting proteids1 the gastric juice brings about several minor effects1 as follows3 #a4 ,it checks1 after a time1 the digestion of the starch which was begun in the mouth by the saliva47#eh7 ,this is due to the presence of the hydrochloric acid1 the ptyalin being unable to act in an acid medium4 #b4 ,while there is no appreciable action on the fat itself1 the proteid layers that inclose the fat particles are dissolved away 7,fig4 #gi71 and the fat is set free4 ,by this means the fat is broken up and prepared for a special digestive action in the small intestine4 #c4 ,dissolved albumin1 like that in milk1 is curded1 or coagulated1 in the stomach4 ,this action is due to the rennin4 ,the curded mass is then acted upon by the pepsin and hydrochloric acid in the same manner as the other proteids4 #d4 ,the hydrochloric acid acts on certain of the insoluble mineral salts found in the foods and reduces them to a soluble condition4 #e4 ,it is also the opinion of certain physiologists that cane sugar and maltose 7double sugars7 are converted by the hydrochloric acid into dextrose and levulose 7single sugars74 ,after a variable length of time1 the contents of the stomach is reduced to a rather uniform and pulpy mass which is called chyme4 ,portions of this are now passed at intervals into the small intestine4 99,muscular ,action of the ,stomach499--,the muscles in the walls of the stomach have for one of their functions the mixing of the food with the gastric juice4 ,by alternately contracting and relaxing1 the different layers of muscle keep the form of the stomach changing--a result which agitates and mixes its contents4 ,this action varies in different parts of the organ1 being slight or entirely absent at the cardiac end1 but quite marked at the pyloric end4 ,another purpose of the muscular coat is to empty the stomach into the small intestine4 ,during the greater part of the digestive period the muscular band at the pyloric orifice is contracted4 ,at intervals1 however1 this band relaxes1 permitting a part of the contents of the stomach to be forced into the small intestine4 ,after the discharge the pyloric muscle again contracts1 and so remains until the time arrives for another discharge4 ,in addition to emptying the stomach into the small intestine1 these muscles also aid in emptying the organ upward and through the esophagus and mouth1 should occasion require4 ,vomiting in case of poisoning1 or if the food for some reason fails to digest1 is a necessary though unpleasant operation4 ,it is accomplished by the contraction of all the muscles of the stomach1 together with the contraction of the walls of the abdomen4 ,during these contractions the pyloric valve is closed1 and the muscles of the esophagus and pharynx are in a relaxed condition47#ei7 ,fig4 #gj ,fig4 #gj--99,passage from stomach99 into small intestine4 ,illustration also shows arrangement of mucous membrane in the two organs4 ,d4 ,bile duct4 99,the ,small ,intestine499--,this division of the alimentary canal consists of a coiled tube1 about twenty-two feet in length1 which occupies the central1 lower portion of the abdominal cavity 7,fig4 #ga74 ,at its upper extremity it connects with the pyloric end of the stomach 7,fig4 #gj71 and at its lower end it joins the large intestine4 ,it averages a little over an inch in diameter1 and gradually diminishes in size from the stomach to the large intestine4 ,the first eight or ten inches form a short curve1 known as the duodenum4 ,the upper two fifths of the remainder is called the jejunum1 and the lower three fifths is known as the ileum4 ,the ileum joins that part of the large intestine known as the ccum1 and at their place of union is a marked constriction which prevents material from passing from the large into the small intestine 7,fig4 #gc74 ,this is known as the ileo-ccal valve4 ,the mucous membrane of the small intestine is richly supplied with blood vessels and contains glands that secrete a digestive fluid known as the intestinal juice4 ,the membrane is thrown into many transverse1 or circular1 folds which increase its surface and also prevent materials from passing too rapidly through the intestine4 ,one important respect in which the small intestine differs from all other portions of the food canal is that its surface is covered with great numbers of minute elevations known as the villi4 ,the purpose of these is to aid in the absorption of the nutrients as they become dissolved 7,chapter ,,xi74 ,the muscular coat of the small intestine is made up of two distinct layers--the inner layer consisting of circular fibers and the outer of longitudinal fibers4 ,these muscles keep the food materials mixed with the juices of the small intestine1 but their main purpose is to force the materials undergoing digestion through this long and much-coiled tube4 ,the outer1 or serous1 coat of the small intestine1 like that of the stomach1 is an extension from the general lining of the abdominal cavity1 or peritoneum4 ,in fact1 the intestine lies in a fold of the peritoneum1 somewhat as an arm in a sling1 while the peritoneum1 by connecting with the back wall of the abdominal cavity1 holds this great coil of digestive tubing in place 7,fig4 #fd74 ,the portion of the peritoneum which attaches the intestine to the wall of the abdomen is called the mesentery4 ,most of the liquid acting on the food in the small intestine is supplied by two large glands1 the liver and the pancreas1 that connect with it by ducts4 ,fig4 #ga ,fig4 #ga--99;,abdominal cavity99 with organs of digestion in position4 99,the ,liver99 is situated immediately below the diaphragm1 on the right side 7,figs4 #ga and #gb71 and is the largest gland in the body4 ,it weighs about four pounds and is separated into two main divisions1 or lobes4 ,it is complex in structure and differs from the other glands in several particulars4 ,it receives blood from two distinct sources--the portal vein and the hepatic artery4 ,the portal vein collects the blood from the stomach1 intestines1 and spleen1 and passes it to the liver4 ,this blood is loaded with food materials1 but contains little or no oxygen4 ,the hepatic artery1 which branches from the aorta1 carries to the liver blood rich in oxygen4 ,in the liver the portal vein and the hepatic artery divide and subdivide1 and finally empty their blood into a single system of capillaries surrounding the liver cells4 ,these capillaries in turn empty into a single system of veins which1 uniting to form the hepatic veins 7two or three in number71 pass the blood into the inferior vena cava 7,fig4 #gb74 ,fig4 #gb ,fig4 #gb--99,relations of the liver499 ,diagram showing the connection of the liver with the large blood vessels and the food canal4 ,the liver secretes daily from one to two pounds of a liquid called bile4 ,a reservoir for the bile is provided by a small1 membranous sack1 called the gall bladder1 located on the underside of the liver4 ,the bile passes from the gall bladder1 and from the right and left lobes of the liver1 by three separate ducts4 ,these unite to form a common tube which1 uniting with the duct from the pancreas1 empties into the duodenum4 ,though usually described as a digestive gland1 the liver has other functions of equal or greater importance 7,chapter ,,xiii74 99,the ,bile99 is a golden yellow liquid1 having a slightly alkaline reaction and a very bitter taste4 ,it consists1 on the average1 of about #ig per cent of water and #c per cent of solids47#fj7 ,the solids include bile pigments1 bile salts1 a substance called cholesterine1 and mineral salts4 ,the pigments 7coloring matter7 of the bile are derived from the hemoglobin of broken-down red corpuscles 7page #bg74 ,much about the composition of the bile is not understood4 ,it is known1 however1 to be necessary to digestion1 its chief use being to aid in the digestion and absorption of fats4 ,it is claimed also that the bile aids the digestive processes in some general ways--counteracting the acid of the gastric juice1 preventing the decomposition of food in the intestines1 and stimulating muscular action in the intestinal walls4 ,no enzymes have been discovered in the bile4 99,the ,pancreas99 is a tapering and somewhat wedge-shaped gland1 and is so situated that its larger extremity1 or head1 is encircled by the duodenum4 ,from here the more slender portion extends across the abdominal cavity nearly parallel to and behind the lower part of the stomach4 ,it has a length of six or eight inches and weighs from two to three and one half ounces4 ,its secretion1 the pancreatic juice1 is emptied into the duodenum by a duct which1 as a rule1 unites with the duct from the liver4 99,the ,pancreatic ,juice99 is a colorless and rather viscid liquid1 having an alkaline reaction4 ,it consists of about #ig4f per cent of water and #b4d per cent of solids4 ,the solids include mineral salts 7the chief of which is sodium carbonate7 and four different chemical agents1 or enzymes1--trypsin1 amylopsin1 steapsin1 and a milk-curding enzyme4 ,these active constituents make of the pancreatic juice the most important of the digestive fluids4 ,it acts with vigor on all of the nutrients insoluble in water1 producing the following changes3 #a4 ,it converts the starch into maltose1 completing the work begun by the saliva4 ,this action is due to the amylopsin17#fa7 which is similar to ptyalin but is more vigorous4 #b4 ,it changes proteids into peptones and proteoses1 completing the work begun by the gastric juice4 ,this is accomplished by the trypsin1 which is similar to1 but more active than1 the pepsin4 #c4 ,it digests fat4 ,in this work the active agent is the steapsin4 ,the necessity of a milk-curding enzyme1 somewhat similar to the rennin of the gastric juice1 is not understood4 99,digestion of ,fat499--,several theories have been proposed at different times regarding the digestion and absorption of fat4 ,among these1 what is known as the solution theory seems to have the greatest amount of evidence in its favor4 ,according to this theory1 the fat1 under the influence of the steapsin1 absorbs water and splits into two substances1 recognized as glycerine and fatty acid4 ,this finishes the process so far as the glycerine is concerned1 as this is soluble in water2 but the fatty acid1 which 7from certain fats7 is insoluble in water17#fb7 requires further treatment4 ,the fatty acid is now supposed to be acted on in one1 or both1 of the following ways3 #a4 ,to be dissolved as fatty acid by the action of the bile 7since bile is capable of dissolving it under certain conditions74 #b4 ,to be converted by the sodium carbonate into a form of soap which is soluble in water4 ,the emulsification of fat is known to occur in the small intestine4 ,by this process the fat is separated into minute particles which are suspended in water1 but not changed chemically1 the mixture being known as an emulsion4 ,while this is believed by some to be an actual process of digestion1 the advocates of the solution theory claim that it is a process accompanying and aiding the conversion of fat into fatty acid and glycerine47#fc7 99,the ,intestinal ,juice99 is a clear liquid with an alkaline reaction1 containing water1 mineral salts1 and certain proteid substances that may act as enzymes4 ,it assists in bringing about an alkaline condition in the small intestine and aids in the reduction of cane sugar and maltose to the simple sugars1 dextrose and levulose4 ,since it is difficult to obtain this liquid in sufficient quantities for experimenting1 its uses have not been fully determined4 ,recent investigators1 however1 assign to it an important place in the work of digestion4 99,work of the ,small ,intestine499--,the small intestine is the most important division of the alimentary canal4 ,it serves as a receptacle for holding the food while it is being acted upon2 it secretes the intestinal juice and mixes the food with the digestive fluids2 it propels the food toward the large intestine2 and1 in addition to all this1 serves as an organ of absorption4 ,digestion is practically finished in the small intestine1 and a large portion of the reduced food is here absorbed4 ,there is always present1 however1 a variable amount of material that is not digested4 ,this1 together with a considerable volume of liquid1 is passed into 99,the ,large ,intestine499--,the large intestine is a tube from five to six feet in length and averaging about one and one half inches in diameter4 ,it begins at the lower right side of the abdominal cavity1 forms a coil which almost completely surrounds the coil of small intestine1 and finally terminates at the surface of the body 7,figs4 #b1 #ga and #gc74 ,it has three divisions1 known as the ccum1 the colon1 and the rectum4 ,fig4 #gc ,fig4 #gc--99,passage from small into large intestine499 ,at the ileo-ccal valve is the narrowest constriction of the food canal4 ,the ccum is the pouch-like dilatation of the large intestine which receives the lower end of the small intestine4 ,it measures about two and one half inches in diameter and has extending from one side a short1 slender1 and blind tube1 called the vermiform appendix4 ,this structure serves no purpose in digestion1 but appears to be the rudiment of an organ which may have served a purpose at some remote period in the history of the human race4 ,the ccum gradually blends into the second division of the large intestine1 called the colon4 ,the colon consists of four parts1 described as the ascending colon1 the transverse colon1 the descending colon1 and the sigmoid flexure1 or sigmoid colon4 ,the first three divisions are named from the direction of the movement of materials through them and the last from its shape1 which is similar to that of the ,greek letter sigma 774 ,the rectum is the last division of the large intestine ,it is a nearly straight tube1 from six to eight inches in length1 and connects with the external surface of the body4 ,the general structure of the large intestine is similar to that of the small intestine1 and1 like the small intestine1 it is held in place by the peritoneum4 ,it differs from the small intestine1 however1 in its lining of mucous membrane and in the arrangement of the muscular coat4 ,the mucous membrane presents a smooth appearance and has no villi1 while the longitudinal layer of the muscular coat is limited to three narrow bands that extend along the greater length of the tube 7,fig4 #gd74 ,these bands are shorter than the coats1 and draw the large intestine into a number of shallow pouches1 by which it is readily distinguished from the small intestine 7,fig4 #ga74 ,fig4 #gd ,fig4 #gd--99,section of large intestine991 showing the coats4 #a4 ,serous coat4 #b4 ,circular layer of muscle4 #c4 ,submucous coat4 #d4 ,mucous membrane4 #e4 ,muscular bands extending lengthwise over the intestine4 99,work of the ,large ,intestine499--,the large intestine serves as a receptacle for the materials from the small intestine4 ,the digestive fluids from the small intestine continue their action here1 and the dissolved materials also continue to be absorbed4 ,in these respects the work of the large intestine is similar to that of the small intestine4 ,it does1 however1 a work peculiar to itself in that it collects and retains undigested food particles1 together with other wastes1 and ejects them periodically from the canal4 99,work of the ,alimentary ,muscles499--,the mechanical part of digestion is performed by the muscles that encircle the food canal4 ,their uses1 which have already been mentioned in connection with the different organs of digestion1 may be here summarized3 ,they supply the necessary force for masticating the food4 ,they propel the food through the canal4 ,they mix the food with the different juices4 ,at certain places they partly or completely close the passage until a digestive process is completed4 ,they may even cause a reverse movement of the food1 as in vomiting4 ,all of the alimentary muscles1 except those around the mouth1 are involuntary4 ,their work is of the greatest importance4 99,other ,purposes of the ,digestive ,organs499--,the digestive organs serve other important purposes besides that of dissolving the foods4 ,they provide favorable conditions for passing the dissolved material into the blood4 ,they dispose of such portions of the foods as fail1 in the digestive processes1 to be reduced to a liquid state4 ,a considerable amount of waste material is also separated from the blood by the glands of digestion 7especially the liver71 and this is passed from the body with the undigested portions of food4 ,then the food canal 7stomach in particular7 is a means of holding1 or storing1 food which is awaiting the processes of digestion4 ,considering the number of these purposes1 the digestive organs are remarkably simple1 both in structure and in method of operation4 ,,hygiene ,,of ,,digestion ,many of the ills to which flesh is heir are due to improper methods of taking food and are cured by observing the simple rules of eating4 ,habit plays a large part in the process and children should1 for this reason1 be taught early to eat properly4 ,since the majority of the digestive processes are involuntary and the food1 after being swallowed1 is practically beyond control1 careful attention must be given to the proper mastication of the food and to such other phases of digestion as are under control4 99,necessity for ,thorough ,mastication499--,mastication prepares the food for the digestive processes which follow4 ,unless the food has been properly masticated1 the digestive fluids in the stomach and intestines cannot act upon it to the best advantage4 ,when the food is carefully chewed1 a larger per cent of it is actually digested--a point of importance where economy in the use of food needs to be practiced4 ,a fact not to be overlooked is that one cannot eat hurriedly and practice thorough mastication4 ,the food must not be swallowed in lumps1 but reduced to a finely divided and pulpy mass4 ,this requires time4 ,the one who hurries through the meal is necessarily compelled to bolt his food4 ,thirty minutes is not too long to give to a meal1 and a longer period is even better4 ,perhaps the most important result of giving plenty of time to the taking of food is that of stimulating the digestive glands to a proper degree of activity4 ,that both the salivary and gastric glands are excited by the sight1 smell1 and thought of food and1 through taste1 by the presence of food in the mouth1 has been fully demonstrated4 ,food that is thoroughly masticated and relished will receive more saliva and gastric juice1 and probably more of other juices1 than if hastily chewed and swallowed4 ,this has a most important bearing upon the efficiency of the digestive processes4 99,order of ,taking ,food499--,there has been evolved through experience a rather definite order of taking food1 which our knowledge of the process of digestion seems to justify4 ,the heavy foods 7proteids for the most part7 are eaten first2 after which are taken starchy foods and fats2 and the meal is finished off with sweetmeats and pastry47#fd7 ,the scientific arguments for this order are the following3 #a4 ,by receiving the first of the gastric flow the proteids can begin digesting without delay4 ,since these are the main substances acted on in the stomach1 the time required for their digestion is shortened by eating them first4 #b4 ,sugar1 being of the nature of predigested starch1 quickly gets into the blood and satisfies the relish for food4 ,the result of taking sugar first may be to cause one to eat less than he needs and to diminish the activity of the glands4 #c4 ,fat or grease1 if taken first1 tends to form a coating over the walls of the stomach and around the material to be digested4 ,this prevents the juices from getting to and mixing with the foods upon which they are to act4 #d4 ,starch following the proteids1 for the most part1 does not so quickly come in contact with the gastric juice4 ,this enables the ptyalin of the saliva to continue its action for a longer time than if the starch were eaten first4 99,liquids during the ,meal499--,liquids as ordinarily taken during the meal are objectionable4 ,they tend to diminish the secretion of the saliva and to cause rapid eating4 ,instead of eating slowly and swallowing the food only so fast as the glands can supply the necessary saliva1 the liquid is used to wash the food down4 ,water or other drinks should be taken after the completion of the meal or when the mouth is completely free from food4 ,even then it should be taken in small sips4 ,while the taking of a small amount of water in this way does no harm1 a large volume has the effect of weakening the gastric juice4 ,most of the water needed by the body should be taken between meals4 99,the ,state of ,mind99 has much to do with the proper digestion of the food4 ,worry1 anger1 fear1 and other disturbed mental states are known to check the secretion of fluids and to interfere with the digestive processes4 ,while the cultivation of cheerfulness is important for its general hygienic effects1 it is of especial value in relation to digestion4 ,intense emotions1 either during or following the meal1 should if possible be avoided4 ,the table is no place for settling difficulties or administering rebuke4 ,the conversation1 on the other hand1 should be elevating and joy giving1 thereby inducing a desirable reactionary influence upon the digestive processes4 99,care of the ,teeth499--,the natural teeth are indispensable for the proper mastication of the food4 ,of especial value are the molars--the teeth that grind the food4 ,the development of the profession of dentistry has made possible the preservation of the teeth1 even when naturally poor1 as long as one has need of them4 ,to preserve the teeth they must be kept clean4 ,they should be washed at least once a day with a soft-bristled brush1 and small particles of food1 lodged between them1 should be removed with a wooden pick4 ,the biting of hard substances1 such as nuts1 should be avoided1 on account of the danger of breaking the enamel1 although the chewing of tough substances is considered beneficial4 ,decayed places in the teeth should be promptly filled by the dentist4 ,it is well1 even when decayed places are not known to exist1 to have the teeth examined occasionally in order to detect such places before they become large4 ,on account of the expense1 pain1 and inconvenience there is a tendency to put off dental work which one knows ought to be done4 ,perhaps in no other instance is procrastination so surely punished4 ,the decayed places become larger and new points of decay are started2 and the pain1 inconvenience1 and expense are increased proportionately4 99,the ,natural ,appetite99 should be followed with reference to both the kind and the amount of food eaten4 ,no system of knowledge will ever be devised which can replace the appetite as an aid in the taking of food4 ,it is nature's means of indicating the needs of the body4 ,the natural appetite may be spoiled1 however1 by overeating and by the use of highly seasoned foods1 or by indulging in stimulants during the meal4 ,it is spoiled in children by too free indulgence in sweetmeats4 ,by cultivating the natural appetite and heeding its suggestions1 one has at his command an almost infallible guide in the taking of food4 99,preparation of ,meals499--,the cooking of food serves three important purposes4 ,it renders the food more digestible1 relieving the organs of unnecessary work2 it destroys bacteria that may be present in the food1 diminishing the likelihood of introducing disease germs into the body2 and it makes the food more palatable1 thereby supplying a necessary stimulus to the digestive glands4 ,while the methods employed in the preparation of the different foods have much to do with the ease with which they are digested and with their nourishing qualities1 the scope of our subject does not permit of a consideration of these methods4 99,quantity of ,food499--,overeating and undereating are both objectionable from a hygienic standpoint4 ,overeating1 by introducing an unnecessary amount of food into the body1 overworks the organs of digestion and also the organs of excretion4 ,it may also lead to the accumulation of burdensome fat and of harmful wastes4 ,on the other hand1 the taking of too little food impoverishes the blood and weakens the entire body4 ,as a rule1 however1 more people eat too much than too little1 and to quit eating before the appetite is fully satisfied is with many persons a necessary precaution4 ,the power of self-control1 valuable in all phases of life1 is indispensable in the avoidance of overeating4 99,frequency of ,taking ,food499--,eating between meals is manifestly an unhealthful practice4 ,the question has also been raised as to whether the common habit of eating three times a day is best suited to all classes of people4 ,many people of weak digestive organs have been benefited by the plan of two meals a day1 while others adopt the plan of eating one heavy meal and two light ones4 ,either plan gives the organs of digestion more time to rest and diminishes the liability of overeating4 ,on the other hand1 those doing heavy muscular work can hardly derive the energy which they need from less than three good meals a day4 ,though no definite rule can be laid down1 there is involved a hygienic principle which all should follow3 ,meals should not overlap4 ,the stomach should be free from food taken at a previous meal before more is introduced into it4 ,when this principle is not observed1 material ferments in the stomach1 causing indigestion and other disorders4 ,it should be noted1 however1 that the overlapping may be due to overeating as well as to eating too frequently4 99,dangers from ,impure ,food499--,food is frequently the carrier of disease germs and for this reason requires close inspection 7page #abh74 ,typhoid fever1 a most dangerous disease1 is usually contracted through either impure food or impure water 7,chapter ,,xxiii74 ,one safeguard against disease germs1 as stated above1 is thorough cooking4 ,too much care cannot be exercised with reference to the water for drinking purposes4 ,water which is not perfectly clear1 which smells of decaying material1 or which forms a sediment on standing is usually not fit to drink4 ,it can1 however1 be rendered comparatively harmless by boiling4 ,the objections which many people have to drinking boiled water are removed when it is boiled the day before it is used1 so as to give it time to cool1 settle1 and replace the air driven off by the boiling4 99,care of the ,bowels499--,in considering the hygiene of the alimentary canal1 the fact that it is used as a means of separating the impurities from the body must not be overlooked4 ,frequently1 through lack of exercise1 negligence in evacuating the bowels1 or other causes1 a weakened condition of the canal is induced which results in the retention of impurities beyond the time when they should be discharged4 ,this is a great annoyance and at the same time a menace to the health4 ,in most cases this condition can be relieved1 and prevented from recurring1 by observing the following habits3 #a4 ,have a regular time each day for evacuating the bowels4 ,this is a most important factor in securing the necessary movements4 #b4 ,drink a cup of cold water on rising in the morning and on retiring at night4 #c4 ,eat generously of fruits and other coarse foods1 such as corn bread1 oatmeal1 hominy1 cabbage1 etc4 #d4 ,practice persistently such exercises as bring the abdominal muscles into play4 ,these exercises strengthen indirectly the muscles of the canal4 #e4 ,avoid overwork1 especially of the nervous system4 99,alcohol and ,digestion499--,though exciting temporarily a greater flow of the digestive fluids1 alcoholic drinks taken in any but very small quantities are considered detrimental to the work of digestion4 ,large doses retard the action of enzymes1 inflame the mucous lining of the stomach17#fe7 and bring about a diseased condition of the liver4 ,it may be noted1 however1 that the bad effects of alcoholic beverages upon the stomach1 the liver1 and the body in general are less pronounced when these are taken as a part of the regular meals4 99,effects of ,tea and ,coffee499--,in addition to the stimulating agent caffeine1 tea and coffee contain a bitter1 astringent substance1 known as tannin4 ,on account of the tannin these beverages tend to retard digestion and to irritate the lining of the stomach--effects that may be largely obviated by methods of preparing tea and coffee which dissolve little of the tannin4 7,they should be made without continued boiling or steeping47 ,the caffeine may do harm through its stimulating effect upon the nervous system 7page #ef7 and through the introduction of a special waste into the body4 ,in chemical composition caffeine closely resembles a waste1 called uric acid1 and in the body is converted into this substance4 ,if one is in a weakened condition1 the uric acid may fail to be oxidized to urea1 as occurs normally1 or to be thrown off as uric acid4 ,in this case it accumulates in the body1 causing rheumatism and related diseases4 ,it thus happens that while some people may use tea and coffee without detriment1 others are injured by them4 99,summary499--,the main structure in the digestive system is the alimentary canal4 ,this provides cavities where important dissolving processes take place1 and tubes for joining these cavities1 while glands connecting with the canal supply the necessary liquids for changing and dissolving the foods4 ,the general plan of digestion is that of passing the food through the canal1 beginning with the mouth1 and of acting on it at various places1 with the final result of reducing most of it to the liquid state4 ,the digestive fluids supply water which acts as a solvent and carries the active chemical agents1 or enzymes1 that convert the insoluble foods into substances that are soluble4 ,the muscles in the walls of the canal perform the mechanical work of digestion1 while the nervous system controls and regulates the activity of the various organs concerned in this work4 ,exercises4--#a4 ,state the general purpose of digestion4 ,how does digested food differ from that not digested8 #b4 ,name all the divisions of the alimentary canal in the order in which the food passes through them4 #c4 ,what other work besides digestion is carried on by the alimentary canal8 #d4 ,what is gained by the mastication of the food8 ,why should mastication precede the other processes of digestion8 #e4 ,what is the work of the tongue in digestion8 #f4 ,state the purposes served by the gastric juice4 #g4 ,give reasons for regarding the small intestine as the most important division of the food canal4 #h4 ,at what places1 and by the action of what liquids1 are fats1 proteids1 and starch digested8 #i4 ,what enzymes are found in the pancreatic juice8 ,what is the digestive action of each8 #aj4 ,describe the work performed by the muscles of the stomach1 the mouth1 the esophagus1 and the small intestine4 #aa4 ,what advantages are derived from the use of cooked food8 #ab4 ,state the advantages of drinking pure water4 #ac4 ,if all the food that one needs to take at a single meal can be thoroughly masticated in fifteen minutes1 why is it better to spend a longer time at the table8 #ad4 ,what is meant by the overlapping of meals8 ,what bad results follow8 ,how avoided8 ,,practical ,,work ,examine a dissectible model of the human abdomen 7,fig4 #ge71 noting the form1 location1 and connection of the different organs4 ,find the connection of the esophagus with the stomach1 of the stomach with the small intestine1 and of the small intestine with the large intestine4 ,sketch a general outline of the cavity1 and locate in this outline its chief organs4 ,where it is desirable to learn something of the actual structure of the digestive organs1 the dissection of the abdomen of some small animal is necessary4 ,on account of unpleasant features likely to be associated with such a dissection1 however1 this work is not recommended for immature pupils4 ,fig4 #ge ,fig4 #ge--,model for demonstrating the abdomen and its contents4 99,dissection of the ,abdomen499 7,optional7--,for individual study1 or for a small class1 a half-grown cat is perhaps the best available material4 ,it should be killed with chloroform1 and then stretched1 back downward1 on a board1 the feet being secured to hold it in place4 ,the teacher should make a preliminary examination of the abdomen to see that it is in a fit condition for class study4 ,if the bladder is unnaturally distended1 its contents may be forced out by slight pressure4 ,the following materials will be needed during the dissection1 and should be kept near at hand3 a sharp knife with a good point1 a pair of heavy scissors1 a vessel of water1 some cotton or a damp sponge1 and some fine cord4 ,during the dissection the specimen should be kept as clean as possible1 and any escaping blood should be mopped up with the cotton or the sponge4 ,the dissection is best carried out by observing the following order3 #a4 ,cut through the abdominal wall in the center of the triangular space where the ribs converge4 ,from here cut a slit downward to the lower portion of the abdomen1 and sideward as far as convenient4 ,tack the loosened abdominal walls to the board1 and proceed to study the exposed parts4 ,observe the muscles in the abdominal walls1 and the fold of the peritoneum which forms an apron-like covering over the intestines4 #b4 ,observe the position of the stomach1 liver1 spleen1 and intestines1 and then1 by pushing the intestines to one side1 find the kidneys and the bladder4 #c4 ,study the liver with reference to its location1 size1 shape1 and color4 ,on the under side1 find the gall bladder1 from which a small tube leads to the small intestine4 ,observe the portal vein as it passes into the liver4 ,as the liver is filled with blood1 neither it nor its connecting blood vessels should be cut at this time4 #d4 ,trace out the continuity of the canal4 ,find the esophagus where it penetrates the diaphragm and joins the stomach4 ,find next the union of the stomach with the small intestine4 ,then1 by carefully following the coils of the small intestine1 discover its union with the large intestine4 #e4 ,within the first coil of the small intestine1 as it leaves the stomach1 find the pancreas4 ,note its color1 size1 and branches4 ,find its connection with the small intestine4 #f4 ,beginning at the cut portion of the abdominal wall1 lift the thin lining of the peritoneum and carefully follow it toward the back and central portion of the abdomen4 ,observe whether it extends back of or in front of the kidneys1 the aorta1 and the inferior vena cava4 ,find where it leaves the wall as a double membrane1 the mesentery1 which surrounds and holds in place the large and small intestines4 ,sketch a coil of the intestine1 showing the mesentery4 #g4 ,find in the center of the coils of small intestine a long1 slender body having the appearance of a gland4 ,this is the beginning of the thoracic duct and is called the receptacle of the chyle4 ,from this the thoracic duct rapidly narrows until it forms a tiny tube difficult to trace in a small animal4 #h4 ,cut away about two inches of the small intestine from the remainder1 having first tied the tube on the two sides of the section removed4 ,split it open for a part of its length1 and wash out its contents4 ,observe its coats4 ,place it in a shallow vessel containing water1 and examine the mucous membrane with a lens to find the villi4 ,make a drawing of this section1 showing the coats4 #i4 ,study the connection of the small intestine with the large4 ,split them open at the place of union1 wash out the contents1 and examine the ileo-ccal valve4 #aj4 ,observe the size1 shape1 and position of the kidneys4 ,do they lie in front of or back of the peritoneum8 ,do they lie exactly opposite each other8 ,note the connection of each kidney with the aorta and the inferior vena cava by the renal artery and the renal vein4 ,find a slender tube1 the ureter1 running from each kidney to the bladder4 ,do the ureters connect with the top or with the base of the bladder8 ,show by a sketch the connection of the kidneys with the large blood vessels and the bladder4 99,to demonstrate the ,teeth499--,procure from the dentist a collection of different kinds of teeth1 both sound and decayed4 7a7 ,examine external surfaces of different kinds of teeth1 noting general shape1 cutting or grinding surfaces1 etc4 ,make a drawing of an incisor and also of a molar4 7b7 ,after soaking some of the teeth for a couple of days in warm water saw one of them in two lengthwise1 and another in two crosswise1 and smooth the cut surfaces with fine emery or sand paper4 ,examine both kinds of sections1 noting arrangement and extent of dentine1 enamel1 and pulp4 ,make drawings4 7c7 ,examine a decayed tooth4 ,which substance of the tooth appears to decay most readily8 ,why is it necessary to cut away a part of the tooth before filling8 7d7 ,test the effect of acids upon the teeth by leaving a tooth over night in a mixture of one part hydrochloric acid to four parts water1 and by leaving a second tooth for a couple of days in strong vinegar4 ,examine the teeth exposed to the action of acids1 noting results4 99,to show the ,importance of ,mastication499--,fill two tumblers each half full of water4 ,into one put a lump of rock salt4 ,into the other place an equal amount of salt that has been finely pulverized4 ,which dissolves first and why8 99,to illustrate ,acid and ,alkaline ,reactions499--,to a tumbler half full of water add a teaspoonful of hydrochloric or other acid1 as vinegar4 ,to a second tumbler half full of water add an equal amount of cooking soda4 ,taste each liquid1 noting the sour taste of the acid1 and the alkaline taste of the soda4 ,hold a piece of red litmus paper in the soda solution1 noting that it is turned blue4 ,then hold a piece of blue litmus paper in the acid solution1 noting that it is turned red4 ,add acid to the soda solution1 and soda to the acid solution1 until the conditions are reversed1 testing with the red and blue litmus papers4 ,hold1 for a minute or longer1 a narrow strip of red litmus paper in the mouth1 noting any change in the color of the paper4 ,repeat1 using blue litmus paper4 ,what effect1 if any1 has the saliva upon the color of the papers8 ,has the mouth an acid or an alkaline reaction8 99,to show the ,action of ,saliva on ,starch499--#a 7,optional74 ,prepare starch paste by mixing half a teaspoonful of starch in half a pint of water and heating the mixture to boiling4 ,place some of this in a test tube and thin it by adding more water4 ,then add a small drop of iodine solution 7page #acf7 to the solution of starch4 ,it should turn a deep blue color4 ,this is the test for starch4 ,now collect from the mouth1 in a clean test tube1 two or three teaspoonfuls of saliva4 ,add portions of this to small amounts of fresh starch solution in two test tubes4 ,let the tubes stand for five or ten minutes surrounded by water having about the temperature of the body4 ,test for changes that have occurred as follows3 7a7 ,to one tube add a little of the iodine solution4 ,if it does not turn blue1 it shows that the starch has been converted into some other substance by the saliva1 7b7 ,to the other tube add a few drops of a very dilute solution of copper sulphate4 ,then add sodium 7or potassium7 hydroxide1 a few drops at a time1 until the precipitate which first forms dissolves and turns a deep blue4 ,then gradually heat the upper portion of the liquid to boiling4 ,if it turns an orange or yellowish red color1 the presence of a form of sugar 7maltose or dextrose7 is proved4 ,see page #acf4 #b4 ,hold some powdered starch in the mouth until it completely dissolves and observe that it gradually acquires a sweetish taste4 ,this shows the change of starch into sugar4 99,to illustrate the ,action of the ,gastric ,juice499--,add to a tumbler two thirds full of water as much scale pepsin 7obtained from a drug store7 as will stay on the end of the large blade of a penknife4 ,then add enough hydrochloric acid to give a slightly sour taste4 ,place in the artificial gastric juice thus prepared some boiled white of egg which has been finely divided by pressing it through a piece of wire gauze4 ,also drop in a single large lump4 ,keep in a warm place 7about the temperature of the body7 for several hours or a day1 examining from time to time4 ,what is the general effect of the artificial gastric juice upon the egg8 99,to illustrate ,effect of ,alcohol upon ,gastric ,digestion499--,prepare a tumbler half full of artificial gastric juice as in the above experiment1 and add #aj cubic centimeters of this to each of six clean test tubes bearing labels4 ,to five of the tubes add alcohol from a burette as follows3 7#a7 4#e c4c41 7#b7 #a c4c41 7#c7 #a4e c4c41 7#d7 #b c4c41 and 7#e7 #c c4c41 leaving one tube without alcohol4 ,now add to each tube about #a_/d gram of finely divided white of egg from the experiment above1 and place all of the tubes in a beaker half full of water4 ,keep the water a little above the temperature of the body for several hours1 examining the tubes at intervals to note the progress of digestion4 ,inferences4 ,,chapter ,,xi - ,,absorption1 ,,storage1 ,,and ,,assimilation ,the dissolved nutrients1 to reach the cells1 must be transferred from the alimentary canal to the blood stream4 ,this process is known as absorption4 ,in general1 absorption means the penetration of a liquid into the pores of a solid1 and takes place according to the simple laws of molecular movements4 ,the absorption of food is1 however1 not a simple process1 and the passage takes place through an active 7living7 membrane4 ,another difference is that certain foods undergo chemical change while being absorbed4 99,small ,intestine as an ,organ of ,absorption499--,while absorption may occur to a greater or less extent along the entire length of the alimentary canal1 most of it takes place at the small intestine4 ,its great length1 its small diameter1 and its numerous blood vessels all adapt the small intestine to the work of absorption4 ,the transverse folds in the mucous membrane1 by retarding the food in its passage and by increasing the absorbing surface1 also aid in the process4 ,but of greatest importance are the minute elevations that cover the surface of the mucous membrane1 known as 99,the ,villi499--,each single elevation1 or villus1 has a length of about one fiftieth of an inch and a diameter about half as great 7,a1 ,fig4 #gf71 and contains the following essential parts3 #a4 ,an outer layer of epithelial cells1 resting upon a connective tissue support4 #b4 ,a small lymph tube1 called a lacteal1 which occupies the center of the villus and connects at the base with other lymph tubes1 also called lacteals 7,b1 ,fig4 #gf74 #c4 ,a network of capillaries4 ,the villi are structures especially adapted to the work of absorption1 and they are found only in the small intestine4 ,the mucous membrane in all parts of the canal1 however1 is capable of taking up some of the digested materials4 ,fig4 #gf ,fig4 #gf--99,the villi499 ,a4 ,diagram of a small section of mucous membrane of small intestine4 #a4 ,villi4 #b4 ,small glands1 called crypts4 ,b4 ,diagram showing structure of villi4 #a4 ,small artery4 #b4 ,lacteal4 #c4 ,villus showing termination of the lacteal4 #d4 ,villus showing capillaries4 #e4 ,villus showing both the lacteal and the capillaries4 #f4 ,small vein4 #g4 ,layer of epithelial cells4 99,work of ,capillaries and ,lacteals499--,the capillaries and lacteals act as receivers of material as it passes through the layer of epithelial cells covering the mucous membrane4 ,the lacteals take up the digested fats17#ff7 and the capillaries receive all the other kinds of nutrients4 ,these vessels do not1 of course1 retain the absorbed materials1 but pass them on4 ,their final destination is the general circulation1 which they reach by two well-defined channels1 or routes4 99,routes to the ,circulation499--,the two routes from the place of absorption to the general circulation are as follows3 #a4 ,route taken by the ,fat4--,the fat is conveyed by the lacteals from the villi to the receptacle of the chyle4 ,at this place it mingles with the lymph from the lower parts of the body1 and with it passes through the thoracic duct to the left subclavian vein4 ,here it enters the general circulation4 ,thus1 to reach the general circulation1 the fat has to pass through the villi1 the lacteals1 the receptacle of the chyle1 and the thoracic duct 7,fig4 #gg74 ,its passage through these places1 like the movements in all lymph vessels1 is slow1 and it is only gradually admitted to the blood stream4 ,fig4 #gg ,fig4 #gg--99;,diagram of routes99 from food canal to general circulation4 ,see text4 #b4 ,route of ,all the ,nutrients except ,fat4--,water and salts and the digested proteids and carbohydrates1 in passing into the capillaries1 mix there with the blood4 ,but this blood1 instead of flowing directly to the heart1 is passed through the portal vein to the liver1 where it enters a second set of capillaries and is brought very near the liver cells4 ,from the liver it is passed through the hepatic veins into the inferior vena cava1 and by these it is emptied into the right auricle4 ,this route then includes the capillaries in the mucous membrane of the stomach and intestines1 the branches of the portal vein1 the portal vein proper1 the liver1 and the hepatic veins 7,fig4 #gg74 ,in passing through the liver1 a large portion of the food material is temporarily retained for a purpose and in a manner to be described later 7page #agg74 99,absorption ,changes499--,during digestion the insoluble foods are converted into certain soluble materials1 such as peptones1 maltose1 and glycerine1--the conversion being necessary to their solution4 ,a natural supposition is that these materials enter and become a part of the blood1 but examination shows them to be absent from this liquid4 7,see ,composition of the ,blood1 page #cj47 ,there are present in the blood1 however1 substances closely related to the peptones1 maltose1 glycerine1 etc42 substances which have in fact been formed from them4 ,during their transfer from the food canal1 the dissolved nutrients undergo changes1 giving rise to the materials in the blood4 ,thus are the serum albumin and serum globulin of the blood derived from the peptones and proteoses2 the dextrose1 from the maltose and other forms of sugar2 and the fat droplets1 from the glycerine1 fatty acid1 and soluble soap4 ,while considerable doubt exists as to the cause of these changes and as to the places also where some of them occur1 their purpose is quite apparent4 ,the materials forming the dissolved foods1 although adapted to absorption1 are not suited to the needs of the body1 and if introduced in this form are likely to interfere with its work47#fg7 ,they are changed1 therefore1 into the forms which the body can use4 99,a ,second ,purpose of ,digestion499--,comparing the digestive changes with those of absorption1 it is found that they are of a directly opposite nature2 that while digestion is a process of tearing down1 or separating1--one which reduces the food to a more finely divided condition--there is in absorption a process of building up4 ,from the comparatively simple compounds formed by digestion1 there are formed during absorption the more complex compounds of the blood4 ,the one exception is dextrose1 which is a simple sugar2 but even this is combined in the liver and the muscles to form the more complex compound known as glycogen4 7,see ,methods of ,storage1 below47 ,these facts have suggested a second purpose of digestion--that of reducing foods to forms sufficiently simple to enable the body to construct out of them the more complex materials that it needs4 ,evidence that digestion serves such a purpose is found in the fact that both proteids and carbohydrates are reduced to a simpler form than is necessary for dissolving them47#fh7 99,the ,storage of ,nutriment499--,for some time after the taking of a meal1 food materials are being absorbed more rapidly than they can be used by the cells4 ,following this is an interval when the body is taking no food1 but during which the cells must be supplied with nourishment4 ,it also happens that the total amount of food absorbed during a long interval may be in excess of the needs of the cells during that time2 and it is always possible1 as in disease1 that the quantity absorbed is not equal to that consumed4 ,to provide against emergencies1 and to keep up a uniform supply of food to the cells1 it is necessary that the body store up nutrients in excess of its needs4 99,methods of ,storage499--,the general plan of storage varies with the different nutrients as follows3 #a4 ,the carbohydrates are stored in the form of glycogen4 ,this1 as already stated 7page #abj71 is a substance closely resembling starch4 ,it is stored in the cells of both the liver and the muscles1 but mainly in the liver 7,fig4 #gh74 ,it is a chief function of the liver to collect the excess of dextrose from the blood passing through it1 and to convert it into glycogen1 which it then stores within its cells4 ,it does not1 however1 separate all of the dextrose from the blood1 a small amount being left for supplying the immediate needs of the tissues4 ,as this is used1 the glycogen in the liver is changed back to dextrose and1 dissolving1 again finds its way into the blood4 ,in this way1 the amount of dextrose in the blood is kept practically constant4 ,the carbohydrates are stored also by converting them into fat4 ,fig4 #gh ,fig4 #gh--99,liver cells99 where is stored the glycogen4 ,c4 ,capillaries4 ,fig4 #gi ,fig4 #gi--99,stored-up fat499 ,the figure shows four connective tissue cells containing small particles of fat4 #a4 ,nucleus4 #b4 ,protoplasm4 #c4 ,fat4 #d4 ,connective tissue fibers4 #b4 ,the fat is stored for the most part in the connective tissue4 ,certain of the connective tissue cells have the property of taking fat from the blood and of depositing it within their inclosing membranes 7,fig4 #gi74 ,when this is done to excess1 and the cells become filled with fat1 they form the so-called adipose tissue4 ,most of this tissue is found under the skin1 between the muscles1 and among the organs occupying the abdominal cavity4 ,if one readily takes on fat1 it may also collect in the connective tissue around the heart4 ,the stored-up fat is redissolved as needed1 and enters the blood1 where it again becomes available to the active cells4 #c4 ,the proteids form a part of all the tissues1 and for this reason are stored in larger quantities than any of the other food substances4 ,the large amount of proteid found in the blood may also be looked upon as storage material4 ,the proteids in the various tissues are spoken of as tissue proteids1 and those in the blood as circulating proteids4 ,the proteids of the tissues serve the double purpose of forming a working part of the cell protoplasm1 and of supplying reserve food material4 ,that they are available for supplying energy1 and are properly regarded as storage material1 is shown by the rapid loss of proteid in starving animals4 ,when the proteids are eaten in excess of the body's need for rebuilding the tissues1 they are supposed to be broken up in such a manner as to form glycogen and fat1 which may then be stored in ways already described4 99,general ,facts ,relating to ,storage499--,the form into which the food is converted for storage in the body is that of solids--the form that takes up the least amount of space4 ,these solids are of such a nature that they can be changed back into their former condition and1 by dissolving1 renter the blood4 ,only energy-yielding foods are stored4 ,water and salts1 though they may be absorbed in excess of the needs of the body1 are not converted into other substances and stored away4 ,oxygen1 as already stated 7page #ajh71 is not stored4 ,the interval of storage may be long or short1 depending upon the needs of the body4 ,in the consumption of stored material the glycogen is used first1 then as a rule the fat1 and last of all the proteids4 99,storage in the ,food ,canal499--,not until three or four hours have elapsed are all the nutrients1 eaten at a single meal1 digested and passed into the body proper4 ,the undigested food is held in reserve1 awaiting digestion1 and is only gradually absorbed as this process takes place4 ,it may properly1 on this account1 be regarded as stored material4 ,that such storage is of advantage is shown by the observed fact that substances which digest quickly 7sugar1 dextrin1 predigested foods1 etc47 do not supply the needs of the body so well as do substances which1 like starch and proteids1 digest slowly4 ,even substances digesting quite slowly 7greasy foods and pastry71 since they can be stored longer in the food canal1 may be of real advantage where1 from hard work or exposure1 the body requires a large supply of energy for some time4 ,these stay by the laborer1 giving him strength after the more easily digested foods have been used up4 ,storage by the food canal is limited chiefly to the stomach4 99,regulation of the ,food ,supply to the ,cells499--,the storage of food materials is made to serve a second purpose in the plan of the body which is even more important than that of supplying nourishment to the cells during the intervals when no food is being taken4 ,it is largely the means whereby the rate of supply of materials to the cells is regulated4 ,the cells obtain their materials from the lymph1 and the lymph is supplied from the blood4 ,should food substances1 such as sugar1 increase in the blood beyond a low per cent1 they are converted into a form1 like glycogen1 in which they are held in reserve1 or1 for the time being1 placed beyond the reach of the cells4 ,when1 however1 the supply is reduced1 the stored-up materials renter the blood and again become available to the cells4 ,by this means their rate of supply to the cells is practically constant4 ,we are now in a position to understand why carbohydrates1 fats1 and proteids are so well adapted to the needs of the body1 while other substances1 like alcohol1 which may also liberate energy1 prove injurious4 ,it is because foods are of such a chemical nature that they are adapted in all respects to the body plan of taking up and using materials1 while the other substances are lacking in some particular4 ,fig4 #hj ,fig4 #hj--99;,diagrams illustrating the relation of nutrients99 and the non-relation of these to alcohol4 ,a4 ,inter-relation and convertibility of proteids1 fats1 and carbohydrates 7after ,hall74 ,b4 ,diagram showing disposition of alcohol if this substance is taken in quantity corresponding to that of the nutrients 7,f4,m4,w474 ,the alcohol thrown off as waste is unoxidized and yields no energy4 99,why ,alcohol is not a ,food499--,if the passage of alcohol through the body is followed1 it is seen1 in the first place1 that it is a simple liquid and undergoes no digestive change2 and in the second place1 that it is rapidly absorbed from the stomach in both weak and concentrated solutions4 ,this introduces it quickly into the blood1 and once there1 it diffuses rapidly into the lymph and then into the cells4 ,since the body cannot store alcohol or convert it into some nutrient that can be stored 7,fig4 #hj71 there is no way of regulating the amount that shall be present in the blood1 or of supplying it to the cells as their needs require4 ,they must take it in excess of their needs1 regardless of the effect1 at least until the organs of excretion can throw off the surplus as waste4 ,compared with proteid1 carbohydrates1 or fats1 alcohol is an unmanageable substance in the body4 ,attempting to use it as a food is as foolish as trying to burn gasolene or kerosene in an ordinary wood stove4 ,it may be done to a limited extent1 but is an exceedingly hazardous experiment4 ,not being adapted to the body method of using materials1 alcohol cannot be classed as a food4 99,assimilation499--,digestion1 absorption1 circulation1 and storage of foods are the processes that finally make them available to the cells in the different parts of the body4 ,there still remains another process for these materials to undergo before they serve their final purposes4 ,this last process1 known as assimilation1 is the appropriation of the food material by the cell protoplasm4 ,in a sense the storage of fat by connective tissue cells and of glycogen by the liver cells is assimilation4 ,the term is limited1 however1 to the disposition of material with reference to its final use4 ,whether all the materials used by the cells actually become a part of the protoplasm is not known4 ,it is known1 however1 that the cells are the places where most of the oxidations of the body occur and that materials taking part in these oxidations must1 at least1 come in close contact with the protoplasm4 ,assimilation1 then1 is the last event in a series of processes by which oxygen1 food materials1 and cell protoplasm are brought into close and active relations4 ,the steps leading up to assimilation are shown in ,table ,,ii4 ,,table ,,ii4 ,,the ,,passage ,,of ,,materials ,,to ,,the ,,cells ,,materials ,,digestion ,,absorption ,,route ,,to ,,storage ,,condition ,,the ,,general ,,in ,,the ,,circulation ,,blood ,proteids ,changed ,in passing ,through the ,become a ,as proteids into into the portal vein part of the in proteoses capillaries1 to the protoplasm colloidal and the liver and of all the solution4 peptones by proteoses from there cells4 the action and through the of the peptones hepatic gastric and change into veins into pancreatic the the juices4 proteids of inferior the blood4 vena cava4 ,fat ,changed ,in passing ,through the ,as fat in ,chiefly as into fatty into the lacteals to the cells minute oil acid1 lacteals1 the of droplets4 glycerine1 the thoracic collective and glycerine duct1 by tissue4 soluable unites with which it is soap by the the soluable emptied bile and soap and into the pancreatic fatty acid left juice4 to form the subclavian oil droplets vein4 of the blood4 ,starch ,reduced to ,enters the ,through the ,as glycogen ,as dextrose some of the capillaries portal chiefly by in different as dextrose4 vein1 the liver1 solution4 forms of liver1 but to some sugar1 as hepatic extent by maltose1 veins1 into muscle dextrose1 inferior cells4 etc4 vena cava4 ,water ,undergoes ,taken up by ,both ,is not ,as the no change4 both the routes1 but stored in water which lacteals and mostly by the sense serves as a capillaries1 way of the that energy carrier of but to the liver4 foods are4 all the greater other extent by constituents the of the capilaries4 blood4 ,common salt ,undergoes ,taken up by ,by way of ,not stored4 ,in solution4 no change4 the portal capillaries vein1 without liver1 and undergoing hepatic apparent veins into change4 inferior vena cava4 ,oxygen ,taken up by ,already in ,is not ,united with the the general stored4 the capillaries circulation4 hemoglobin at the and to a lungs4 small extent in solution in the plasma4 99,tissue ,enzymes499--,the important part played by enzymes in the digestion of the food has suggested other uses for them in the body4 ,it has been recently shown that many of the chemical changes in the tissues are in all probability due to the presence of enzymes4 ,an illustration of what a tissue enzyme may do is seen in the changes which fat undergoes4 ,in order for the body to use up its reserve fat1 it must be transferred from the connective tissue cells1 where it is stored1 to the cells of the active tissues where it is to be used4 ,this requires that it be reduced to the form of a solution and that it renter the blood4 ,in other words1 it must be redigested4 ,for bringing about these changes a substance identical in function with the steapsin of the pancreatic juice has been shown to exist in several of the tissues4 ,although this subject is still under investigation1 it may be stated with certainty that there are present in the tissues1 enzymes that change dextrose to glycogen and vice versa1 that break down and build up the proteids1 and that aid in the oxidations at the cells4 ,the necessity for such enzymes is quite apparent4 99,summary499--,the digested nutrients are taken up by the capillaries and the lymph vessels and transferred by two routes to the circulation4 ,in passing from the alimentary canal into the circulation the more important of the foods undergo changes which adapt them to the needs of the body4 ,since materials are absorbed more rapidly than they are used1 means are provided for storing them and for supplying them to the cells as their needs require4 ,capability of storage is an essential quality of energy-yielding foods2 and substances1 such as alcohol1 which lack this quality are not adapted to the needs of the body4 ,for causing the chemical changes that occur in the storage of foods1 as well as the oxidations at the cells1 the presence of active agents1 or enzymes1 is necessary4 99,exercises499--#a4 ,in what respects does the absorption of food materials from the alimentary canal differ from the absorption of a simple liquid by a solid8 #b4 ,in what different ways is the small intestine especially adapted to the work of absorption8 #c4 ,what are the parts of a villus8 ,what are the lacteals8 ,account for the name4 #d4 ,what part is played by the capillaries and the lacteals in the work of absorption8 ,how does their work differ8 #e4 ,what changes1 if any1 take place in water1 common salt1 fat1 proteids1 and carbohydrates during absorption8 #f4 ,what double purpose is served by the processes of digestion8 #g4 ,trace the passage of proteids1 fats1 and carbohydrates from the small intestine into the general circulation4 #h4 ,what is the necessity for storing nutrients in the body8 ,why is it not also necessary to store up oxygen8 #i4 ,in what form and at what places is each of the principal nutrients stored8 #aj4 ,how is the rate of supply of food to the cells regulated8 ,why is the body unable to regulate the supply of alcohol to the cells when this substance is taken8 #aa4 ,explain ,fig4 #hj1 page #aha4 ,what becomes of the alcohol if this is taken in any but very small quantities8 #ab4 ,state the general purpose of enzymes in the body4 ,name the enzymes found in each of the digestive fluids4 ,what ones are found in the tissues8 ,,practical ,,work ,illustrate the ordinary meaning of the term absorption by bringing the end of a piece of crayon in contact with water1 or a piece of blotting paper in contact with ink1 noting the passage of the liquid into the crayon or the paper4 ,show how absorption from the food canal differs from this kind of absorption4 ,show by a diagram similar to ,fig4 #gg the two routes by which the foods pass from the alimentary canal into the blood stream4 ,,chapter ,,xii - ,,energy ,,supply ,,of ,,the ,,body ,if one stops taking food1 it becomes difficult after a time for him to move about and to keep warm4 ,these results show that food has some relation to the energy of the body1 for motion and heat are forms of energy4 ,the relation of oxygen to the supply of energy has already been discussed 7,chapter ,,viii74 ,we are now to inquire more fully into the energy supply of the body1 and to consider those conditions which make necessary the introduction of both food and oxygen for this purpose4 99,kinds of ,bodily ,energy499--,the healthy body has at any time a considerable amount of potential1 or reserve1 energy1--energy which it is not using at the time1 but which it is able to use as its needs require4 ,when put to use1 this energy is converted into such forms of kinetic energy7#fi7 as are indicated by the different kinds of bodily power4 ,these are as follows3 #a4 ,power of ,motion4--,the body can move itself from place to place and it can give motion to things about it4 #b4 ,heat ,power4--,the body keeps itself warm and is able to communicate warmth to its surroundings4 #c4 ,nervous ,power4--,through the nervous system the body exercises the power of control over its different parts4 ,as motion1 heat1 and nervous power the body uses most of its energy4 99,the ,source of ,bodily ,energy499--,as already indicated1 the energy of the body is supplied through the food and the oxygen4 ,these contain energy in the potential form1 which becomes kinetic 7active7 through their uniting with each other in the body4 ,somewhat as the power of the steam engine is derived from the combustion of fuel in the furnaces1 the energy of the body is supplied through the oxidations at the cells4 ,how the food and oxygen come to possess energy is seen by a study of the general methods by which energy is stored up and used4 ,fig4 #ha ,fig4 #ha--99,simple device99 for storing energy through gravity4 99,simple ,methods of ,storing ,energy499--,energy is stored by converting the kinetic into the potential form4 ,two of the simplest ways of doing this are the following3 #a4 ,storing of ,energy through ,gravity4--,on account of the attraction between the earth and all bodies upon the earth1 the mere lifting of a weight puts it in a position where gravity can cause it to move 7,fig4 #ha74 ,as a consequence the raising of bodies above the earth's surface is a means of storing energy--the energy remaining stored until the bodies fall4 ,as they fall1 the stored-up 7potential7 energy becomes kinetic and can be made to do work4 #b4 ,storing of ,energy through ,elasticity4--,energy is stored also by doing work in opposition to elasticity1 as in bending a bow or in winding a clock spring4 ,the bending1 twisting1 stretching1 or compressing of elastic substances puts them in a condition of strain which causes them to exert a pressure 7called elastic force7 that tends to restore them to their former condition4 ,energy stored by this means becomes active as the distorted or compressed substance returns to its former shape or volume4 ,these simple methods of storing energy will serve to illustrate the general principles upon which such storage depends3 #a4 ,to store energy1 energy must be expended1 or work done4 #b4 ,the work must be against some force1 such as gravity or elasticity1 which can undo the work1 i4e41 bring about an effect opposite to that of the work4 #c4 ,the stored energy becomes active 7kinetic7 as the force through which the energy was stored undoes the work1 or puts the substance upon which the work was done into its former condition 7gravity causing bodies to fall1 etc474 ,these principles are further illustrated by the 99,storing of ,energy through ,chemical ,means499--,a good example of storing energy by chemical means is that of decomposing water with electricity4 ,if a current of electricity is passed through acidulated water in a suitable apparatus 7,fig4 #hb71 the water separates into its component gases1 oxygen and hydrogen4 ,these gases now have power 7energy7 which they did not possess before they were separated4 ,the hydrogen will burn in the oxygen1 giving heat2 and if the two gases are mixed in the right proportions and then ignited1 they explode with violence4 ,this energy was derived from the electricity4 ,it was stored by decomposing the water4 ,fig4 #hb ,fig4 #hb--99,storing energy by chemical means499 ,apparatus for decomposing water with electricity4 ,energy is stored by chemical means by causing it to do work in opposition to the force of chemism1 or chemical affinity4 ,instead of changing the form of bodies or moving them against gravity1 it overcomes the force that causes atoms to unite and to hold together after they have united4 ,since in most cases the atoms on separating from any given combination unite at once to form other combinations1 we may say that energy is stored when strong chemical combinations are broken up and weak ones formed4 ,energy stored by this means becomes active when the atoms of weak combinations unite to form combinations that are strong47#gj7 99,how ,plants store the ,sun's ,energy499--,the earth's supply of energy comes from the sun4 ,while much of this1 after warming and lighting the earth's surface1 is lost by radiation1 a portion of it is stored up and retained4 ,the sun's energy is stored both through the force of gravity7#ga7 and by chemical means1 the latter being the more important of the two methods4 ,plants supply the means for storing it chemically 7,fig4 #hc74 ,attention has already been called to the fact 7page #aab7 that growing plants are continually taking carbon dioxide into their leaves from the air4 ,this they decompose1 adding the carbon to compounds in their tissues and returning the oxygen to the air4 ,it is found1 however1 that this process does not occur unless the plants are exposed to sunlight4 ,the sunlight supplies the energy for overcoming the attraction between the atoms of oxygen and the atoms of carbon1 while the plant itself serves as the instrument through which the sunlight acts4 ,the energy for decomposing the carbon dioxide then comes from the sun1 and through the decomposition of the carbon dioxide the sun's energy is stored--becomes potential4 ,it remains stored until the carbon of the plant again unites with the oxygen of the air1 as in combustion4 ,fig4 #hc ,fig4 #hc--99,nature's device99 for storing energy from the sun4 ,see text4 99,the ,sun's ,energy in ,food and ,oxygen499--,food is derived directly or indirectly from plants and sustains the same relation to the oxygen of the air as do the plants themselves4 7,the elements in the food have an attraction for the oxygen1 but are separated chemically from it47 ,on account of this relation they have potential energy--the energy derived through the plant from the sun4 ,when a person eats the food and breathes the oxygen1 this energy becomes the possession of the body4 ,it is then converted into kinetic energy as the needs of the body require4 ,fig4 #hd ,fig4 #hd--99,simple apparatus99 for illustrating transformation of energy4 ,potential energy is converted into heat and heat into motion4 99,from the ,sun to the ,cells499--,it thus appears that the body comes into possession of energy1 and is able to use it1 through a series of transferences and transformations that can be traced back to the sun47#gb7 ,coming to the earth as kinetic energy1 it is transformed into potential energy and stored in the compounds of plants and in the oxygen of the air4 ,through the food and the oxygen the potential energy is transferred to the cells of the body4 ,then by the uniting of the food and the oxygen at the cells 7oxidation71 the potential becomes kinetic energy and is used by the body in doing its work4 ,the phrase ,child of the ,sun has sometimes been applied to man to express his dependence upon the sun for his supply of energy4 99,why ,oxygen and ,food are ,both ,necessary499--,the necessity for introducing both oxygen and food into the body for the purpose of supplying energy is now apparent4 ,the energy which is used in the body is not the energy of food alone4 ,nor is it the energy of oxygen alone4 ,it belongs to both4 ,it is due to their attraction for each other and their condition of separation4 ,it cannot1 therefore1 become kinetic except through their union4 ,to introduce one of these substances into the body without the other1 would neither introduce the energy nor set it free4 ,they must both be introduced into the body and there caused to unite4 99,bodily ,control of ,energy499--,a fact of importance in the supply of energy to the body is that the rate of transformation 7changing of potential to kinetic7 is just sufficient for its needs4 ,it is easily seen that too rapid or too slow a rate would prove injurious4 ,the oxidations at the cells are1 therefore1 under such control that the quantity of kinetic energy supplied to the body as a whole1 and to the different organs1 is proportional to the work that is done4 ,this is attained1 in part at least1 through the ability of the body to store up the food materials and hold them in reserve until they are to be oxidized 7page #ahj74 99,animal ,heat and ,motion499--,most of the body's energy is expended as heat in keeping warm4 ,it is estimated that as much as five sixths of the whole amount is used in this way4 ,the proportion1 however1 varies with different persons and is not constant in the same individual during different seasons of the year4 ,this heat is used in keeping the body at that temperature which is best suited to carrying on the vital processes4 ,all parts of the body1 through oxidation1 furnish heat4 ,active organs1 however1 such as the muscles1 the brain1 and the glands 7especially the liver71 furnish the larger share4 ,the blood in its circulation serves as a heat distributer for the body and keeps the temperature about the same in all its parts 7page #cc74 ,next to the production of heat1 in the consumption of the body's energy1 is the production of motion4 ,this topic will be considered in the study of the muscular system 7,chapter ,,xv74 99,some ,questions of ,hygiene499--,the heat-producing capacity of the body sustains a very important relation to the general health4 ,a sudden chill may result in a number of derangements and is supposed to be a predisposing cause of colds4 ,one's capacity for producing heat may be so low that he is unable to respond to a sudden demand for heat1 as in going from a warm room into a cold one4 ,as a consequence1 the body is unable to protect itself against unavoidable exposures4 ,impairment of the heat-producing capacity is brought about in many ways4 ,several diseases do this directly1 or indirectly1 to quite an extent4 ,in health too great care in protecting the body from cold is the most potent cause of its impairment4 ,staying in rooms heated above a temperature of #gj ,f41 wearing clothing unnecessarily heavy1 and sleeping under an excess of bed clothes1 all diminish the power of the body to produce heat4 ,they accustom it to producing only a small amount1 so that it does not receive sufficient of what might be called heat-producing exercise4 ,lack of physical exercise in the open air1 as well as too much time spent in poorly lighted and ventilated rooms1 tends also to reduce one's ability to produce heat4 ,moreover1 since most of the heat of the body comes from the union of oxygen and food materials at the cells1 a lack of either of these will interfere with the production of heat4 99,results of ,exhaustion499--,through overwork1 or excesses in pleasurable pursuits1 one may make greater demands upon the energy of his body than it can properly supply4 ,the resulting condition1 known as exhaustion1 is not only a matter of temporary inconvenience1 but may through repetition lead to a serious impairment of the health4 ,it should be noted1 in this connection1 that the energy of the body is spent in two general ways3 first1 in carrying on the vital processes2 and second1 in the performance of voluntary activities4 ,since1 in all cases1 there is a limit to one's energy1 it is easily possible to expend so much in the voluntary activities that the amount left is not sufficient for the vital processes4 ,this leads to various disturbances and1 among other things1 renders the body less able to supply itself with energy4 99,the ,problem of ,increasing ,one's ,energy499--,since the energy supply is kept up through the food and the oxygen1 it might be inferred that the introduction of these substances into the body in larger amounts would increase the energy at one's disposal4 ,this does not necessarily follow4 ,oxidation at the cells is preceded by digestion1 absorption1 circulation1 and assimilation4 ,it is followed and influenced by the removal of wastes from the body4 ,a careful study of the problem leads to the conclusion that while the energy supply to the body does depend upon the introduction of the proper amounts of food and oxygen1 it also depends upon the efficiency of the vital processes4 ,the maximum amount of energy may1 therefore1 be expected when the body is in a condition of perfect health4 ,hence1 one desiring to increase the amount of his energy must give attention to all those conditions that improve the health4 99,effect of ,stimulants on the ,energy ,supply499--,in the effort to get out of the body as much as possible of work or of pleasure1 various stimulants1 such as alcohol1 tobacco1 and strong tea and coffee1 have been used4 ,though these have the effect of giving a temporary feeling of strength and of enabling the individual in some instances to accomplish results which he could not otherwise have brought about1 the general effect of their use is to lessen1 rather than to increase1 the sum total of bodily power4 ,the student1 for example1 who drinks strong coffee in order to study late at night is able to command less energy on the day following4 ,while enabling him to draw upon his reserve of nervous power for the time being1 the coffee deprives him of sleep and needed rest4 ,the danger of stimulants1 so far as energy is concerned1 is this3 they tend to exhaust the bodily reserve so that there is not sufficient left for properly running the vital processes4 ,evidences of their weakening effect are found in the feeling of discomfort and lassitude which result when stimulants to which the body has become accustomed are withdrawn4 ,not until one gets back his bodily reserve is he able to work normally and effectively4 ,increase in bodily energy comes through health and not through the use of stimulants4 99,summary499--,the body requires a continuous supply of energy4 ,to obtain this supply1 materials possessing potential1 or stored-up1 energy are introduced into it4 ,the free oxygen of the air and the substances known as foods1 on account of the chemical relations which they sustain to each other1 contain potential energy and are utilized for supplying the body4 ,so long as the foods are not oxidized1 the energy remains in the potential form1 but in the process of oxidation the potential energy is changed to kinetic energy and made to do the work of the body4 99,exercises499--#a4 ,in what different ways does the body use energy8 #b4 ,show that a stone lying against the earth has no energy1 while the same stone above the earth has energy4 #c4 ,how does potential energy differ from kinetic energy8 #d4 ,what kind of energy is possessed by a bent bow8 ,by a revolving wheel8 ,by a coiled spring8 ,by the wind8 ,by gunpowder8 #e4 ,how does decomposing water with electricity store energy8 #f4 ,account for the energy possessed by the oxygen of the air and food substances4 #g4 ,trace the energy supply of the body back to the sun4 #h4 ,why must both oxygen and food be introduced into the body in order to supply it with energy8 #i4 ,how may overwork and overexercise diminish the energy supply of the body8 #aj4 ,how may one increase the amount of his energy8 ,,practical ,,work 99,suggested ,experiments499--#a4 ,the change of kinetic into potential energy may be shown by stretching a piece of rubber1 by lifting a weight1 and by separating the armature from a magnet4 #b4 ,the change of potential into kinetic energy may be shown by letting weights fall to the ground1 by releasing the end of a piece of stretched rubber1 and by burning substances4 #c4 ,the change of one form of kinetic energy to another may be illustrated by rubbing together two pieces of wood until they are heated1 by ringing a bell1 and by causing motion in air or in water by heating them4 ,if suitable apparatus is at hand1 the transformation of electrical energy into heat1 light1 sound1 and mechanical motion can easily be shown4 #d4 ,a weight connected by a cord with some small machine and made to run it1 will help the pupil to grasp the general principles in the storage of energy through gravity4 ,a vessel of water on a high support from which the water is siphoned on to a small water wheel will serve the same purpose4 #e4 ,the storing of energy by chemical means may be illustrated by decomposing potassium chlorate with heat or by decomposing water by means of a current of electricity4 #f4 ,study the transfer of energy from the body to surrounding objects1 as in moving substances and lifting weights4 ,fill a half gallon jar two thirds full of water and carefully take the temperature with a chemical thermometer4 ,hold the hand in the water for four or five minutes and take the temperature again4 ,inference4 ,,chapter ,,xiii - ,,glands ,,and ,,the ,,work ,,of ,,excretion ,in our study so far we have been concerned mainly with the introduction of materials into the body4 ,we are now to consider the removal of materials from the body4 ,the structures most directly concerned in this work are known as 99,glands499--,as generally understood1 glands are organs that prepare special liquids in the body and pour them out upon free surfaces4 ,these liquids1 known as secretions1 are used for protecting exposed parts1 lubricating surfaces that rub against each other1 digesting food1 and for other purposes4 ,they differ widely in properties as well as in function1 but are all alike in being composed chiefly of water4 ,the water1 in addition to being necessary to the work of particular fluids1 serves in all cases as a carrier of solid substances which are dissolved in it4 99,general ,structure of ,glands499--,while the various glands differ greatly in size1 form1 and purpose1 they present striking similarities in structure4 ,all glands contain the following parts3 #a4 ,gland1 or secreting1 cells4 ,these are specialized cells for the work of secretion and are the active agents in the work of the gland4 ,they are usually cubical in shape4 #b4 ,a basement membrane4 ,this is a thin1 connective tissue support upon which the secreting cells rest4 #c4 ,a network of capillary and lymph vessels4 ,these penetrate the tissues immediately beneath the secreting cells4 #d4 ,a system of nerve fibers which terminate in the secreting cells and in the walls of the blood vessels passing to the glands4 ,these structures--secreting cells1 basement membrane1 capillary and lymph vessels1 and nerve fibers--form the essential parts of all glands4 ,the capillaries and the lymph vessels supply the secreting cells with fluid1 and the nerves control their activities4 99,kinds of ,glands499--,glands differ from one another chiefly in the arrangement of their essential parts47#gc7 ,the most common plan is that of arranging the parts around a central cavity formed by the folding or pitting of an exposed surface4 ,many such glands are found in the mucous membrane1 especially that lining the alimentary canal1 and are most numerous in the stomach1 where they supply the gastric juice4 ,if these glands have the general form of tubes1 they are called tubular glands2 if sac-like in shape1 they are called saccular glands4 ,both the tubular and the saccular glands may1 by branching1 form a great number of similar divisions which are connected with one another1 and which communicate by a common opening with the place where the secretion is used4 ,this forms a compound gland which1 depending on the structure of the minute parts1 may be either a compound tubular or a compound saccular gland4 ,the larger of the compound saccular glands are also called racemose glands1 on account of their having the general form of a cluster1 or raceme1 similar to that of a bunch of grapes4 ,the general structure of the different kinds of glands is shown in ,fig4 #he4 ,fig4 #he ,fig4 #he--99;,diagram illustrating evolution of glands499 ,a4 ,simple secreting surface4 #a4 ,gland cells4 #b4 ,basement membrane4 #c4 ,blood vessel4 #d4 ,nerve4 ,b4 ,simple tubular gland4 ,c4 ,simple saccular gland4 ,d4 ,compound tubular gland4 ,e4 ,compound saccular gland4 ,f4 ,a compound racemose gland with duct passing to a free surface4 ,g4 ,relation of food canal to different forms of glands4 ,the serous coat has a secreting surface4 99,nature of the ,secretory ,process499--,at one time the gland was regarded merely as a kind of filter which separated from the blood the ingredients found in its secretions4 ,recent study1 however1 of several facts relating to secretion has led to important modifications of this view4 ,the secretions of many glands are known to contain substances that are not found in the blood1 or1 if present1 are there in exceedingly small amounts4 ,then again the cells of certain glands have been found to undergo marked changes during the process of secretion4 ,if1 for example1 the cells of the pancreas be examined after a period of rest1 they are found to contain small granular bodies4 ,on the other hand1 if they are examined after a period of activity1 the granules have disappeared and the cells themselves have become smaller 7,fig4 #hf74 ,the granules have no doubt been used up in forming the secretion4 ,these and other facts have led to the conclusion that secretion is1 in part1 the separation of materials without change from the blood1 and1 in part1 a process by which special substances are prepared and added to the secretion4 ,according to this view the gland plays the double rle of a filtering apparatus and of a manufacturing organ4 ,fig4 #hf ,fig4 #hf--99,secreting cells from the pancreas99 7after ,langley74 ,a4 ,after a period of rest4 ,b4 ,after a short period of activity4 ,c4 ,after a period of prolonged activity4 ,in ,a and ,b the nuclei are concealed by the granules that accumulate during the resting period4 99,kinds of ,secretion499--,in a general way all the liquids produced by glands may be considered as belonging to one or the other of two classes1 known as the useful and the useless secretions4 ,to the first class belong all the secretions that serve some purpose in the body1 while the second includes all those liquids that are separated as waste from the blood4 ,the first are usually called true secretions1 or secretions proper1 while the second are called excretions4 ,the most important glands producing liquids of the first class are those of digestion 7,chapter ,x74 99,excretory ,work of ,glands499--,the process of removing wastes from the body is called excretion4 ,while in theory excretion may be regarded as a distinct physiological act1 it is1 in fact1 leaving out the work of the lungs1 but a phase of the work of glands4 ,from the cells where they are formed1 the waste materials pass into the lymph and from the lymph they find their way into the blood4 ,they are removed from the blood by glands and then passed to the exterior of the body4 99,the ,necessity for ,excretion99 is found in the results attending oxidation and other chemical changes at the cells 7page #ajg74 ,through these changes large quantities of materials are produced that can no longer take any part in the vital processes4 ,they correspond to the ashes and gases of ordinary combustion and form wastes that must be removed4 ,the most important of these substances1 as already noted 7page #aaj71 are carbon dioxide1 water1 and urea47#gd7 ,a number of mineral salts are also to be included with the waste materials4 ,some of these are formed in the body1 while others1 like common salt1 enter as a part of the food4 ,they are solids1 but1 like the urea1 leave the body dissolved in water4 ,waste products1 if left in the body1 interfere with its work 7some of1 them being poisons71 and if allowed to accumulate1 cause death4 ,their removal1 therefore1 is as important as the introduction of food and oxygen into the body4 ,the most important of the excretory glands are 99,the ,kidneys499--,the kidneys are two bean-shaped glands1 situated in the back and upper portion of the abdominal cavity1 one on each side of the spinal column4 ,they weigh from four to six ounces each1 and lie between the abdominal wall and the peritoneum4 ,two large arteries from the aorta1 called the renal arteries1 supply them with blood1 and they are connected with the inferior vena cava by the renal veins4 ,they remove from the blood an exceedingly complex liquid1 called the urine1 the principal constituents of which are water1 salts of different kinds1 coloring matter1 and urea4 ,the kidneys pass their secretion by two slender tubes1 the ureters1 to a reservoir called the bladder 7,fig4 #hg74 ,fig4 #hg ,fig4 #hg--99,relations of the kidneys499 7,back view47 #a4 ,the kidneys4 #b4 ,ureters4 #c4 ,bladder4 #d4 ,aorta4 #e4 ,inferior vena cava4 #f4 ,renal arteries4 #g4 ,renal veins4 99,structure of the ,kidneys499--,each kidney is a compound tubular gland and is composed chiefly of the parts concerned in secretion4 ,the ureter serves as a duct for removing the secretion1 while the blood supplies the materials from which the secretion is formed4 ,on making a longitudinal section of the kidney1 the upper end of the ureter is found to expand into a basin-like enlargement which is embedded in the concave side of the kidney4 ,the cavity within this enlargement is called the pelvis of the kidney1 and into it project a number of cone-shaped elevations from the kidney substance1 called the pyramids 7,fig4 #hh74 ,from the summits of the pyramids extend great numbers of very small tubes which1 by branching1 penetrate to all parts of the kidneys4 ,these are the uriniferous tubules1 and they have their beginnings at the outer margin of the kidney in many small1 rounded bodies called the ,malpighian capsules 7,a1 ,fig4 #hh74 ,each capsule incloses a cluster of looped capillaries and connects with a single tubule 7,fig4 #hi74 ,from the capsule the tubule extends toward the concave side of the kidney and1 after uniting with similar tubules from other parts1 finally terminates at the pyramid4 ,between its origin and termination1 however1 are several convolutions and one or more loops or turns4 ,after passing a distance many times greater than from the surface to the center of the kidney1 the tubule empties its contents into the expanded portion of the ureter4 ,fig4 #hh ,fig4 #hh--99,sectional view of kidney499 #a4 ,outer portion or cortex4 #b4 ,medullary portion4 #c4 ,pyramids4 #d4 ,pelvis4 #e4 ,ureter4 ,a4 ,small section enlarged to show the tubules and their connection with the capsules4 ,fig4 #hi ,fig4 #hi--99,malpighian capsule99 highly magnified 7,landois74 a4 ,small artery entering capsule and forming cluster of capillaries within4 e4 ,small vein leaving capsule and branching into c1 a second set of capillaries1 h4 ,beginning of uriniferous tubule4 ,the uriniferous tubules are lined with secreting cells4 ,these differ greatly at different places1 but they all rest upon a basement membrane and are well supplied with capillaries4 ,these cells provide one means of separating wastes from the blood 7,fig4 #ij74 ,fig4 #ij ,fig4 #ij--99;,diagram illustrating renal circulation499 #a4 ,branch from renal artery4 #b4 ,branch from renal vein4 #c4 ,small artery branches1 one of which enters a ,malpighian capsule 7#e74 #f4 ,small vein leaving the capsule and branching into the capillaries 7#g7 which surround the uriniferous tubules4 #d4 ,small veins which receive blood from the second set of capillaries4 #h4 ,tubule showing lining of secreting cells4 99,blood ,supply to the ,kidneys499--,the method by which the kidneys do their work is suggested by the way in which the blood circulates through them4 ,the renal artery entering each kidney divides into four branches and these send smaller divisions to all parts of the kidney4 ,at the outer margin of the kidney1 called the cortex1 the blood is passed through two sets of capillaries4 ,the first forms the clusters in the ,malpighian capsules and receives the blood directly from the smallest arteries4 ,the second forms a network around the uriniferous tubules and receives the blood which has passed from the capillary clusters into a system of small veins 7,fig4 #ij74 ,from the last set of capillaries the blood is passed into veins which leave the kidneys where the artery branches enter1 uniting there to form the main renal veins4 99,work of the ,kidneys499--,why should the blood pass through two systems of capillaries in the kidneys8 ,this is because the separation of waste is done in part by the ,malpighian capsules and in part by the uriniferous tubules4 ,water and salts are removed chiefly at the capsules1 while the remaining solid constituents of the urine pass through the secreting cells that line the tubules4 ,it was formerly believed that the kidneys obtained their secretion by a process of filtration from the blood1 but this belief has been gradually modified4 ,the prevailing view now is that the processes of filtration and secretion are both carried on by the kidneys1--that the capillary clusters in the ,malpighian bodies serve as delicate filters for the separation of water and salts1 while the secreting cells of the tubules separate substances by the process of secretion4 ,on account of the large volume of blood passing through the kidneys this liquid is still a bright red color as it flows into the renal veins 7,fig4 #ij74 ,the kidney cells require oxygen1 but the amount which they remove from the blood is not sufficient to affect its color noticeably4 ,the blood in the renal veins1 having given up most of its impurities and still retaining its oxygen1 is considered the purest blood in the body4 99,urea99 is the most abundant solid constituent of the urine and is the chief waste product arising from the oxidation of nitrogenous substances in the body4 ,although secreted by the cells lining the uriniferous tubules1 it is not formed in the kidneys4 ,the secreting cells simply separate it from the blood where it already exists4 ,the muscles also have been suggested as a likely source of urea1 for here the proteids are broken down in largest quantities2 but the muscles produce little if any urea4 ,its production has been found to be the work of the liver4 ,in the muscular tissue1 and in the other tissues as well1 the proteids are reduced to a lower order of compounds1 such as the compounds of ammonia1 which pass into the blood and are then taken up by the liver4 ,by the action of the liver cells these are converted into urea and this is turned back into the blood4 ,from the blood the urea is separated by the secreting cells of the kidneys4 99,work of the ,liver499--,the liver1 already described as an organ of digestion 7page #aeb71 assists in the work of excretion both by changing waste nitrogenous compounds into urea and by removing from the blood the wastes found in the bile4 ,while the chief work of the liver is perhaps not that of excretion1 its functions may here be summarized4 ,the liver is1 first of all1 a manufacturing organ1 producing1 as we have seen1 three distinct products--bile1 glycogen1 and urea4 ,on account of the nature of the urea and the bile1 the liver is properly classed as an excretory organ2 but in the formation of the glycogen it plays the part of a storage organ4 ,then1 on account of the use made of the bile after it is passed into the food canal1 the liver is also classed as a digestive organ4 ,these different functions make of the liver an organ of the first importance4 99,excretory ,work of the ,food ,canal499--,the glands connected with the food canal1 other than the liver1 while secreting liquids that aid in digestion1 also separate waste materials from the blood4 ,these are passed into the canal1 whence they leave the body with the undigested portions of the food and the waste from the liver4 ,though the nature and quantity of the materials removed by these glands have not been fully determined1 recent investigations have tended to enhance the importance attached to this mode of excretion4 99,the ,perspiratory ,glands499--,the perspiratory1 or sweat1 glands are located in the skin4 ,they belong to the type of simple tubular glands and are very numerous over the entire surface of the body4 ,a typical sweat gland consists of a tube which1 starting at the surface of the cuticle1 penetrates to the under portion of the true skin and there forms a ball-shaped coil4 ,the coiled extremity1 which forms the secreting portion1 is lined with secreting cells and surrounded by a network of capillaries4 ,the portion of the tube passing from the coil to the surface serves as a duct 7,figs4 #ia and #aba74 ,fig4 #ia ,fig4 #ia--99;,diagram of section through a sweat gland499 a4 ,outer layer of skin or cuticle4 b4 ,dermis or true skin4 d1 e4 ,sections of the tube forming the coiled portion of the gland4 c4 ,duct passing to the surface4 ,the other structures of the skin not shown4 ,the sweat glands secrete a thin1 colorless fluid1 called perspiration1 or sweat4 ,this consists chiefly of water1 but contains a small per cent of salts and of urea4 ,the excretory work of these glands seems not to be so great as was formerly supposed1 but they supplement in a practical way the work of the kidneys and1 during diseases of these organs1 show an increase in excretory function to a marked degree4 ,the perspiration also aids in the regulation of the temperature of the body 7,chapter ,,xvi74 99,excretory ,work of the ,lungs499--,while the lungs cannot be regarded as glands1 they do a work in the removal of waste from the body which must be considered in the general process of excretion4 ,they are especially adapted to the removal of gaseous substances from the blood1 and it is through them that most of the carbon dioxide leaves the body4 ,the lungs remove also a considerable quantity of water4 ,this is of course in the gaseous form1 being known as water vapor4 99,ductless ,glands and ,internal ,secretion499--,midway in function between the glands that secrete useful liquids and those that remove waste materials from the blood is a class of bodies1 found at various places1 known as the ductless glands4 ,they are so named from their having the general form of glands and from the fact that they have no external openings or ducts4 ,they prepare special materials which are passed into the blood and which are supposed to exert some beneficial effect either upon the blood or upon the tissues through which the blood circulates4 ,the most important of the ductless glands are the thyroid gland1 located in the neck2 the suprarenal bodies1 situated one just over each kidney2 and the thymus gland1 a temporary gland in the upper part of the chest4 ,the spleen and the lymphatic glands 7page #fh7 are also classed with the ductless glands4 ,the liver1 the pancreas1 and 7according to some authorities7 the kidneys1 in addition to their external secretions1 produce materials that pass into the blood4 ,they perform in this way a function like that of the ductless glands4 ,the work of glands in preparing substances that enter the blood is known as internal secretion4 99,quantity of ,excretory ,products499--,if the weight of the normal body be taken at intervals1 after growth has been attained1 there will be found to be practically no gain or loss from time to time4 ,this shows that materials are leaving the body as fast as they enter and that the tissues are being torn down as fast as they are built up4 ,it also shows that substances do not remain in the body permanently1 but only so long perhaps as is necessary for them to give up their energy1 or serve some additional purpose in the ever changing protoplasm4 ,the excretory organs then remove from the body a quantity of material that is equal in weight to the materials absorbed by the organs of digestion and respiration4 ,this is estimated for the average individual to be about five pounds daily4 ,the passage of waste from the body is summarized in ,table ,,iii4 ,,table ,,iii4 ,,the ,,passage ,,of ,,waste ,,materials ,,from ,,the ,,body ,materials ,state ,how ,formed ,condition in ,how ,removed in the ,body the ,blood from the ,blood ,carbon ,gas ,by the ,dissolved in ,separated dioxide oxidation of the plasma from the the carbon and in loose blood at the of proteids1 combination alveoli of carbohydrates1 with salts the lungs and fats4 in the and then blood4 forced through the air passages into the atmosphere4 ,urea ,solid ,by the ,dissolved in ,removed by oxidation in the plasma4 the the liver of uriniferous nitrogenous tubules of compounds4 the kidneys and to a small extent by the perspiratory glands4 ,water ,liquid ,by the ,as water4 ,removed by oxidation of all the the hydrogen organs of of proteids1 excretion1 carbohydrates1 but in the and fats4 largest ,amount formed quantities in the body is by the small4 kidneys and the skin4 ,salts ,solid ,dissolved in ,by the the plasma4 kidneys1 liver1 and skin4 ,,hygiene ,the separation of wastes from the body has such a close relation to the health that all conditions affecting it should receive the most careful attention4 ,their retention beyond the time when they should be discharged undoubtedly does harm and is the cause of many bodily disorders4 99,value of ,water499--,as a rule the work of excretion is aided by drinking freely of pure water4 ,as water is the natural dissolver and transporter of materials in the body1 it is generally conceded by hygienists and physicians that the taking of plenty of water is a healthful practice4 ,people do not as a rule drink a sufficient amount of water1 about three pints per day being required by the average adult1 in addition to that contained in the food4 ,most of the water should1 of course1 be taken between meals1 although the sipping of a small amount during meals does not interfere with digestion4 ,as stated elsewhere1 the taking of a cup of water on retiring at night and again on rising in the morning is very generally recommended4 99,protection of ,kidneys and ,liver499--,the kidneys and liver are closely related in their work and in many instances are injured or benefited by the same causes4 ,both1 as already stated 7page #abd71 are liable to injury from an excess of proteid food1 especially meats1 and also by a condition of inactivity of the bowels 7page #aff74 ,the free use of alcohol also has an injurious effect on both of these organs47#ge7 ,on the other hand1 increasing the activity of the skin has a beneficial effect upon them1 especially the kidneys4 ,exercise and bathing1 which tend to make the skin more active1 are valuable aids both in ridding the body of impurities and in lessening the work of the other excretory organs4 ,one having a disease of the kidneys1 however1 needs to exercise great care in bathing on account of the bad results which follow getting chilled4 99,special ,care after ,certain ,diseases499--,certain diseases1 as measles1 diphtheria1 scarlet fever1 and typhoid fever1 sometimes have the effect of weakening the kidneys 7and other vital organs7 and of starting disease in them4 ,when this occurs it is usually the result of exposure or of over-exertion while the body is in a weakened condition4 ,severe chilling at such a time1 by driving blood from the surface to the parts within1 often causes inflammation of the kidneys4 ,on recovering from any wasting disease one should exercise great caution both in resuming his regular work and in exposing his body to wet or cold4 99,misunderstood ,symptoms499--,pains in the small of the back1 an increase in the secretions of the kidneys1 and a sediment in the urine very naturally suggest some disorder of the kidneys4 ,it is a fact1 however1 that these symptoms have little or no relation to the state of the kidneys and may occur when the kidneys are in a perfectly healthy condition4 ,the kidneys are not located in the small of the back1 but above this place1 so that pains in this region are evidently not from the kidneys1 while the increase in the flow of the urine may arise from a number of causes1 one of which is an increase of certain waste products passed into the blood4 ,the symptoms referred to are frequently the results of nervous exhaustion1 resulting from overstudy1 worry1 eye strain1 or some other condition that overtaxes the nervous system4 ,when this is the case1 relief is obtained through resting the nerves4 ,actual disease of the kidneys can only be determined through a chemical and microscopic examination of the urine4 ,to resort to some patent medicine for kidney trouble without knowing that such trouble exists1 as is sometimes done1 is both foolish and unhygienic4 99,alcoholic ,beverages and the ,elimination of ,waste499--,causing as it does such serious diseases as cirrhosis of the liver and ,bright's disease of the kidneys 7footnote1 page #baj71 alcohol will greatly interfere in this way with the elimination of waste4 ,there is also evidence to the effect that it interferes with waste elimination before the stage is reached of causing disease of these organs4 ,researches have shown that alcohol increases the amount of uric acid in the body and decreases the amount of urea found in the urine4 ,the conclusion to be drawn is that alcohol interferes in some way with the change of the harmful uric acid into the comparatively harmless urea--an interference which in some instances results in great harm4 ,it has also been shown that malted liquors1 such as beer and ale1 contain substances which1 like the caffein of tea and coffee 7page #afg71 are readily converted into uric acid47#gf7 ,wines contain acids which may also act injuriously4 ,the harm which such substances do is1 of course1 additional to that caused by the alcohol4 99,summary499--,as a result of the oxidations and other changes at the cells1 substances are produced that can no longer serve a purpose in the body4 ,they are of the nature of waste1 and their continuous removal from the body is as necessary to the maintenance of life as the introduction of food and oxygen4 ,the organs whose work it is to remove the waste1 excepting the lungs1 are glands2 and the material which they remove are of the nature of secretions4 ,from the cells1 the waste passes through the lymph in the blood4 ,from the blood it is separated by the excretory organs and passed to the exterior of the body4 99,exercises499--#a4 ,what general purposes are served by the glands in the body8 #b4 ,what are the parts common to all glands8 ,what purpose is served by each of these parts8 #c4 ,how do tubular glands differ in structure from saccular glands8 ,what is a racemose gland8 ,why so called8 #d4 ,describe the nature of the secretory process4 #e4 ,what conditions render necessary the formation of waste materials in the body8 ,why must these be removed8 #f4 ,how do the waste materials get from the cells to the organs of excretion8 #g4 ,show by a drawing the connections of the kidneys with the large blood vessels and the bladder4 ,name parts of drawing4 #h4 ,in what do the uriniferous tubes have their beginning8 ,in what do they terminate8 ,with what are they lined8 #i4 ,why should the blood pass through two sets of capillaries in the kidneys8 #aj4 ,bright's disease of the kidneys affects the uriniferous tubes and interferes with their work4 ,what impurity is then left in the blood8 #aa4 ,trace water and salts from the ,malpighian capsules to the bladder1 naming parts through which they pass4 #ab4 ,trace carbon dioxide from the cells to the outside atmosphere4 #ac4 ,how does the quantity of material introduced into the body compare with that which is removed by the organs of excretion8 #ad4 ,name two ways of lessening the work of the kidneys4 #ae4 ,why is the drinking of plenty of pure water a healthful practice8 ,,practical ,,work 99,to suggest the ,double ,work of ,glands499--,prepare a simple filter by fitting a piece of porous paper into a glass funnel4 ,through this pass pure water and also water having salt dissolved in it and containing some sediment1 as sand4 ,the water and the dissolved salt pass through1 while the sediment remains on the filter4 ,now substitute a fresh piece of paper in the funnel and drop on its surface a little solid coloring matter1 such as cochineal4 ,again pass the liquid through the funnel4 ,this time it comes through colored1 the color being added by the filter4 ,compare the filter and materials filtered to the gland and the materials concerned in secretion 7blood1 the liquid secreted1 substances added by the gland1 etc474 ,fig4 #ib ,fig4 #ib--99,the physiological scheme499 ,diagram suggesting the essential relation of the bodily activities4 ,see ,summary of ,part ,i1 page #bae1 and ,summary of ,part ,,ii1 page #dac4 ,,summary ,,of ,,part ,i ,the body is an organization of different kinds of cells2 it grows through the growth and reproduction of these cells2 and its life as a whole is maintained by providing such conditions as will enable the cells to keep alive4 ,of chief importance in the work of the body is a nutrient fluid which supplies the cells with food and oxygen and relieves them of waste4 ,a moving portion of this fluid1 called the blood1 serves as a transporting agent1 while another portion1 called the lymph1 passes the materials between the blood and the cells4 ,through their effects upon the blood and the lymph1 the organs of circulation1 respiration1 digestion1 and excretion minister in different ways to the cells1 and aid in the maintenance of life4 ,by their combined action two distinct movements are kept up in the body1 as follows3 #a4 ,an inward movement which carries materials from the outside of the body toward the cells4 #b4 ,an outward movement which carries materials from the cells to the outside of the body4 ,passing inward are the oxygen and food materials in a condition to unite with each other and thereby change their potential into kinetic energy4 ,passing outward are the oxygen and the elements that formed the food materials after having united at the cells and liberated their energy4 ,as a final and all-important result1 there is kept up a continuous series of chemical changes in the cells4 ,these liberate the energy1 provide special substances needed by the cells1 and preserve the life of the body 7,fig4 #ib74 ,in the chapters which follow1 we are to consider the problem of adjusting the body to and of bringing it into proper relations with its surroundings4 ,,part ,,ii3 ,,motion1 ,,coordination1 ,,and ,,sensation ,,chapter ,,xiv - ,,the ,,skeleton ,one necessary means of establishing proper relations between the body and its surroundings is motion47#gg7 ,not only can the body move itself from place to place1 but it is able to move surrounding objects as well4 ,in the production of motion three important systems are employed--the muscular system1 the nervous system1 and a system of mechanical devices which are found mainly in the skeleton4 ,the muscular system supplies the energy for operating the mechanical devices1 while the nervous system controls the movements47#gh7 ,although the skeleton serves other purposes1 such as giving shape to the body and protecting certain organs1 its main use is that of an aid in the production of motion4 99,skeleton ,tissues499--,the tissues employed in the construction of the skeleton are the osseous1 the cartilaginous1 and the connective tissues4 ,these are known as the supporting tissues of the body4 ,they form the bones1 supply the elastic pads at the ends of the bones1 and furnish strong bands1 called ligaments1 for fastening the bones together4 ,the skeleton forms about #af per cent of the weight of the body4 ,its tissues1 being of a more durable nature than the rest of the body1 do not so readily decay4 ,especially is this true of the osseous tissue1 which may be preserved indefinitely1 after removal from the body1 by simply keeping it dry4 99,the ,bones499--,the separate units1 or parts1 of which the skeleton is constructed are called bones4 ,they are the hard structures that can be felt in all parts of the body1 and they comprise nearly the entire amount of material found in the prepared skeleton4 ,as usually estimated1 the bones are #bjh in number4 ,they vary greatly in size and shape in different parts of the body4 99,composition and ,properties of ,bones499--,the most noticeable and important properties of the bones are those of hardness1 stiffness1 and toughness4 ,upon these properties the uses of the bones depend4 ,these properties may1 in turn1 be shown to depend upon the presence in osseous tissue of two essentially different kinds of substance1 known as the animal matter and the mineral matter4 ,if a bone is soaked in an acid1 the mineral matter is dissolved out1 and as a result it loses its properties of hardness and stiffness4 7,see ,practical ,work47 ,this is because the mineral matter supplies these properties1 being composed of substances which are hard and closely resemble certain kinds of rock4 ,the chief materials forming the mineral matter are calcium phosphate and calcium carbonate4 ,on the other hand1 burning a bone destroys the animal matter4 ,when this is done the bone loses its toughness1 and becomes quite brittle4 ,the property of toughness is1 therefore1 supplied by the animal matter4 ,this consists mainly of a substance called ossein1 which may be dissolved out of the bones by boiling them4 ,separated from the bones it is known as gelatine4 ,the blood vessels and nerves in the bones1 and the protoplasm of the bone cells1 are also counted in with the animal matter4 ,fig4 #ic ,fig4 #ic--99,section of a long bone99 7tibia71 showing the gross structure4 ,if a dry bone from a full-grown1 but not old1 animal be weighed before and after being burned1 it is found to lose about one third of its weight4 ,from this we may conclude that about one third of the bone by weight is animal matter and two thirds is mineral matter4 ,this proportion1 however1 varies with age1 the mineral matter increasing with advance of years4 99,gross ,structure of ,bones499--,the gross structure of the bones is best learned by studying both dry and fresh specimens4 7,see ,practical ,work47 ,the ends of the bones are capped by a layer of smooth1 elastic cartilage1 while all the remaining surface is covered by a rather dense sheath of connective tissue1 called the periosteum4 ,usually the central part of the long bones is hollow1 being filled with a fatty substance known as the yellow marrow4 ,around the marrow cavity the bone is very dense and compact1 but most of the material forming the ends is porous and spongy4 ,these materials are usually referred to as the compact substance and the cancellous1 or spongy1 substance of the bones 7,fig4 #ic74 ,the arrangement of the compact and spongy substance varies with the different bones4 ,in the short bones 7wrist and ankle bones1 vertebr1 etc47 and also in the flat bones 7skull bones1 ribs1 shoulder blades1 etc47 there is no cavity for the yellow marrow1 all of the interior space being filled with the spongy substance4 ,the red marrow1 relations of which to the red corpuscles of the blood have already been noted 7page #bg71 occupies the minute spaces in the spongy substance4 ,fig4 #id ,fig4 #id--99;,cross section of bone showing minute structure499 ,magnified4 #a4 ,surface layer of bone4 #b4 ,deeper portion4 #c4 ,haversian canals from which pass the canaliculi4 #d4 ,a lacuna4 ,observe arrangement of lacun at surface and in deeper portion4 99,minute ,structure of ,bone499--,a microscopic examination of a thin slice of bone taken from the compact substance shows this to be porous as well as the spongy substance4 ,two kinds of small channels are found running through it in different directions1 known as the ,haversian canals and the canaliculi 7,fig4 #id74 ,these serve the general purpose of distributing nourishment through the bone4 ,the ,haversian canals are larger than the canaliculi and contain small nerves and blood vessels1 chiefly capillaries 7,fig4 #ie74 ,they extend lengthwise through the bone4 ,the canaliculi are channels for conveying lymph4 ,they pass out from the ,haversian canals at right angles1 going to all portions of the compact substance except a thin layer at the surface4 ,in the surface layer of the bone the canaliculi are in communication with the periosteum4 ,fig4 #ie ,fig4 #ie--99,section showing ,haversian canal and contents991 highly magnified 7after ,schfer74 #a4 ,arterial capillary4 #b4 ,venous capillary4 #c4 ,nerve fibers4 #d4 ,lymph vessel4 99,the ,bone ,cells499--,surrounding the ,haversian canals are thin layers of bone substance called the lamin1 and within these are great numbers of irregular bodies1 known as the lacun4 ,the walls of the lacun are hard and dense1 but within each is an open space4 ,in this lies a flattened body1 having a nucleus1 which is recognized as the bone cell1 or the bone corpuscle 7,fig4 #if74 ,it appears to be the work of the bone cells to deposit mineral matter in the walls surrounding them and in this way to supply the properties of hardness and stiffness to the bones4 ,the canaliculi connect with the lacun in all parts of the bone1 causing them to appear under the microscope like so many burs fastened together by their projecting spines 7,fig4 #id74 ,fig4 #if ,fig4 #if--99;,bone cell99 removed from the lacuna and very highly magnified4 7,from ,quain's ,anatomy47 99,how the ,bone ,cells are ,nourished499--,the bone cells1 like all the other cells of the body1 are nourished by the lymph that escapes from the blood4 ,this passes through the canaliculi to the cells in the different parts of the bone1 as follows3 #a4 ,the cells in the surface layer of the bone receive lymph from the capillaries in the periosteum47#gi7 ,it gets to them through the short canaliculi that run out to the surface4 #b4 ,the cells within the interior of the bone receive their nourishment from the small blood vessels in the ,haversian canals4 ,lymph from these vessels is conveyed to the cells through the canaliculi that connect with the ,haversian canals4 99,plan and ,purpose of the ,skeleton499--,the framework of the body is such as to adapt it to a movable structure4 ,obviously the different parts of the body cannot be secured to a foundation1 as are those of a stationary building1 but must be arranged after a plan that is conducive to motion4 ,a moving structure1 as a wagon or a bicycle1 has within it some strong central part to which the remainder is joined4 ,the same is true of the skeleton4 ,that part to which the others are attached is a long1 bony axis1 known as the spinal column4 ,certain parts1 as the ribs and the skull1 are attached directly to the spinal column1 while others are attached indirectly to it4 ,the arrangement of all the parts is such that the spinal column is made the central1 cohering portion of the skeleton and also of the whole body4 ,besides the general arrangement of the parts of the skeleton1 there is such a grouping of the bones in each of its main divisions as will enable them to serve definite purposes4 ,in most places they form mechanical devices for supplying special movements1 and in certain places they provide for the support or protection of important organs4 ,in most cases there is a definite combination of different bones1 forming what is called the bone group4 ,fig4 #ig ,fig4 #ig--,the human skeleton4 99,bone ,groups499--,on account of the close relation between the bones of the same group1 they cannot profitably be studied as individual bones1 but each must be considered as a part of the group to which it belongs4 ,by first making out the relation of a given bone to its group1 its value to the whole body can be determined4 ,the most important of the groups of bones are as follows3 #a4 ,the ,spinal ,column4--,this group consists of twenty-four similarly shaped bones1 placed one above the other1 called the vertebr1 and two bones found below the vertebr1 known as the sacrum and the coccyx 7,fig4 #ih74 ,these twenty-six bones supply the central axis of the body1 support the head and upper extremities1 and inclose and protect the spinal cord4 ,fig4 #ih ,fig4 #ih--,the spinal column4 ,the upper seven vertebr form the neck and are called the cervical vertebr4 ,they are smaller and have greater freedom of motion than the others4 ,the first and second cervical vertebr1 known as the atlas and the axis1 are specially modified to form a support for the head and provide for its movements4 ,the head rests upon the atlas1 forming with it a hinge joint 7used in nodding to indicate yes72 and the atlas turns upon an upward projection of the axis forming a pivot joint 7used in shaking the head to indicate no74 ,the next twelve vertebr1 in order below the cervical1 are known as the thoracic vertebr4 ,they form the back part of the framework of the thorax and have little freedom of motion4 ,the five vertebr below the thoracic are known as the lumbar vertebr4 ,these bones are large and strong and admit of considerable motion4 ,below the last lumbar vertebra is a wedge-shaped bone which has the appearance of five vertebr fused together4 ,this bone1 known as the sacrum1 connects with the large bones which form the pelvic girdle4 ,attached to the lower end of the sacrum is a group of from two to four small vertebr1 more or less fused1 called the coccyx4 ,fig4 #ii ,fig4 #ii--99,two views of a lumbar vertebra499 ,a4 ,from above4 ,b4 ,from the side4 #a4 ,body4 #b1 #c1 #d1 #e4 ,projections from the neural arch4 99,the ,joining of the ,vertebr499--,a typical vertebra consists of a heavy1 disk-shaped portion in front1 called the body1 which is connected with a ring-like portion behind1 called the neural arch4 ,the body and the neural arch together encircle a round opening which is a part of the canal that contains the spinal cord 7,fig4 #ii74 ,from the neural arch are seven bony projections1 or processes1 three of which serve for the attachment of muscles and ligaments1 while the other four1 two above and two below1 are for the interlocking of the vertebr with each other4 ,the separate vertebr are joined together in the spinal column1 as follows3 a4 ,between the bodies of adjacent vertebr are disks of elastic cartilage4 ,each disk is about one fourth of an inch thick and is grown tight onto the face of the vertebra above and also onto the face of the vertebra below4 ,by means of these disks a very close connection is secured between the vertebr on the front side of the column4 b4 ,on the back of the column1 the downward projections from the neural arch of each vertebra above fit into depressions found in the neural arch of the vertebra below4 ,this interlocking of the vertebr1 which is most marked in the lumbar region1 strengthens greatly the back portion of the column4 c4 ,to further secure one bone upon the other1 numerous ligaments pass from vertebra to vertebra on all sides of the column4 #b4 ,the ,skull4--,the skull is formed by the close union of twenty-two irregular bones4 ,these fall naturally into two subgroups--the cranium and the face 7,fig4 #ajj74 ,the cranium consists of eight thin1 curved bones which inclose the space1 called the cranial cavity1 that holds the brain4 ,the face group1 consisting of fourteen bones1 provides cavities and supports for the different organs of the face1 and supplies a movable part 7the inferior maxillary7 which1 with the bones above 7superior maxillary71 forms the machine for masticating the food4 ,fig4 #ajj ,fig4 #ajj--99,the skull 7,huxley7499 ,the illustration shows most of the bones of the skull4 #c4 ,the ,thorax4--,this group contains twenty-four bones of similar form1 called ribs1 and a straight flat bone1 called the sternum1 or breastbone 7,fig4 #aja74 ,the ribs connect with the spinal column behind1 and all but the two lowest ones connect with the sternum in front1 and1 by so doing1 inclose the thoracic cavity4 ,as already stated 7page #he71 the bones of the thorax form a mechanical device1 or machine1 for breathing4 ,the ribs are so arranged that the volume of the thorax is increased by elevating them and diminished by depressing them1 enabling the air to be forced into and out of the lungs4 ,fig4 #aja ,fig4 #aja--99;,bone groups of trunk499 #d4 ,the ,shoulder and ,pelvic ,girdles4--,these groups form two bony supports--one at the upper and the other at the lower portion of the trunk--which serve for the attachment of the arms and legs 7,fig4 #aja74 ,the shoulder girdle is formed by four bones--two clavicles1 or collar bones1 and two scapul1 or shoulder blades4 ,the clavicle on either side connects with the upper end of the sternum and serves as a brace for the shoulder1 while the scapula forms a socket for the humerus 7the large bone of the arm7 and supplies many places for the attachment of muscles4 ,the pelvic girdle consists of two large bones of irregular shape1 called the innominate bones4 ,they connect behind with the sacrum and in front they connect1 through a small pad of cartilage1 with each other4 ,on the inside of the girdle is a smooth1 basin-shaped support for the contents of the abdomen1 but on the outside the bones are rough and irregular and provide many places for the attachment of muscles and ligaments4 ,each innominate bone has a deep1 round socket into which the end of the femur 7the long bone of the leg7 accurately fits4 #e4 ,the ,arm and ,hand ,groups4--,a long bone1 the humerus1 connects the arm with the shoulder and gives form to the upper arm4 ,in the forearm are two bones1 the radius and the ulna1 which connect at one end with the humerus and at the other with the bones of the wrist 7,fig4 #ajb74 ,fig4 #ajb ,fig4 #ajb--99;,bone groups of arm and leg499 ,a group of eight small1 round bones is found in the wrist1 known as the carpal bones4 ,these are arranged in two rows and are movable upon one another4 ,five straight bones1 the metacarpals1 connect with the wrist bones and form the framework for the palm of the hand4 ,attached to the metacarpals are the bones of the fingers and thumb4 ,these form an interesting group of fourteen bones1 called the phalanges of the fingers 7,fig4 #ajb74 ,the bones of the hand provide a mechanical device1 or machine1 for grasping1 and the arm serves as a device for moving this grasping machine from place to place4 ,the work of the arm1 in this respect1 is not unlike that of a revolving crane upon the end of which is a grab-hook4 ,the hand without the arm to move it about would be of little use4 #f4 ,the ,leg and ,foot ,groups4--,these correspond in form and arrangement to the bones of the arm and hand4 ,since1 however1 the leg and foot are used for purposes different from those of the arm and hand1 certain differences in structure are to be found4 ,the patella1 or kneepan1 has no corresponding bone in the arm2 and the carpus1 or ankle1 which corresponds to the wrist1 contains seven instead of eight bones4 ,the bones of the foot and toes are the same in number as those of the hand and fingers1 but they differ greatly in size and form and have less freedom of motion4 ,the femur1 which gives form to the thigh1 is the longest bone of the body4 ,the tibia1 or shin bone1 and the fibula1 the slender bone by its side1 give form to the lower part of the leg 7,fig4 #ajb74 ,the legs are mechanical devices 7walking machines7 for moving the body from place to place4 ,the feet serve both as supports for the body and as levers for pushing the body forward4 ,by their attachment to the legs they may be placed in all necessary positions for supporting and moving the body4 ,the different bone groups are shown in ,fig4 #ig and named in ,table ,,iv4 99,adaptation to ,special ,needs499--,when any single bone is studied in its relation to the other members of the group to which it belongs or with particular reference to its purpose in the body1 its adaptation to some special place or use is at once apparent4 ,each bone serves some special purpose1 and to this purpose it is adapted by its form and structure4 ,long bones1 like the humerus and femur1 are suited to giving strength1 form1 and stiffness to certain parts1 while irregular bones1 like the vertebr and the pelvic bones1 are fitted for supporting and protecting organs4 ,others1 like the wrist and ear bones1 make possible a peculiar kind of motion1 and still others1 like the ribs1 are adapted to more than one purpose4 ,the vast differences in shape1 size1 structure1 and surface among the various bones are but the conditions that adapt them to particular forms of service in the body4 ,,table ,,iv - ,,the ,,principal ,,bones ,,and ,,their ,,grouping ,,in ,,the ,,body ,i4 ,,axial ,,skeleton ,a4 ,skull1 #bh4 #a4 ,cranium1 #h4 a4 ,frontal1 forehead #a b4 ,parietal #b c4 ,temporal1 temple #b d4 ,occipital #a e4 ,sphenoid #a f4 ,ethmoid #a #b4 ,face1 #ad4 a4 ,inferior maxillary #a b4 ,superior maxillary #b c4 ,palatine1 palate #b d4 ,nasal bones #b e4 ,vomer #a f4 ,inferior turbinated #b g4 ,lachrymal #b h4 ,malar1 cheek bones #b #c4 ,bones of the ,ears1 #f4 a4 ,malleus #b b4 ,incus #b c4 ,stapes #b ,b4 ,spinal ,column1 #bf4 #a4 ,cervical1 or neck1 vertebr #g #b4 ,dorsal1 or thoracic1 vertebr #ab #c4 ,lumbar vertebr #e #d4 ,sacrum #a #e4 ,coccyx #a ,c4 ,thorax1 #be4 #a4 ,ribs #bd #b4 ,sternum #a ,d4 ,hyoid1 #a 7at base of tongue74 ,,ii4 ,,appendicular ,,skeleton ,a4 ,shoulder girdle #d4 #a4 ,clavicle1 collarbone4 #b #b4 ,scapula1 shoulder blade #b ,b4 ,upper extremities1 #fj4 #a4 ,humerus #b #b4 ,radius #b #c4 ,ulna #b #d4 ,carpal1 wrist bones #af #e4 ,metacarpal #aj #f4 ,phalanges of fingers #bh ,c4 ,pelvic girdle1 #b4 #a4 ,osinnominatum #b ,d4 ,lower extremities1 #fj4 #a4 ,femur1 thigh bone #b #b4 ,tibia1 shin bone #b #c4 ,fibula #b #d4 ,patella1 kneepan #b #e4 ,tarsal1 ankle bones #ad #f4 ,metatarsal1 instep bones #aj #g4 ,phalanges of toes #bh ,,articulations ,any place in the body where two or more bones meet is called an articulation1 or joint4 ,at the place of meeting the bones are firmly attached to each other1 thereby securing the necessary coherence of the skeleton4 ,the large number of bones1 and consequently of articulations1 are necessary for the different movements of the body and also on account of the manner in which the skeleton develops1 or grows4 ,articulations are classed with reference to their freedom of motion1 as movable1 slightly movable1 and immovable articulations4 ,most of the immovable articulations are found in the skull4 ,here irregular1 tooth-like projections from the different bones enable them to interlock with one another1 while they are held firmly together by a thin layer of connective tissue4 ,the wavy lines formed by articulations of this kind are called sutures 7,fig4 #ajj74 ,the best examples of joints that are slightly1 but not freely1 movable are found in the front of the spinal column4 ,the cartilaginous pads between the vertebr permit1 by their elasticity1 of a slight bending of the column in different directions4 ,these movements are caused1 not by one bone gliding over another1 but by compressions and extensions of the cartilage4 ,between the vertebr in the back of the spinal column1 however1 there is a slight movement of the bone surfaces upon one another4 99,structure of the ,movable ,joints499--,by far the most numerous and important of the joints are those that are freely movable4 ,such joints are strongly constructed and endure great strain without dislocation1 and yet their parts move over each other easily and without friction4 ,the ends of the bones are usually enlarged and have specially formed projections or depressions which fit into corresponding depressions or elevations on the bones with which they articulate4 ,in addition to this the articular surfaces are quite smooth and dense1 having no ,haversian canals1 and they are covered with a layer of cartilage4 ,strong ligaments pass from one bone to the other to hold each in its place 7,a1 ,fig4 #ajc74 ,some of these consist simply of bands1 connecting the joint on its different sides1 while others form continuous sheaths around the joint4 ,fig4 #ajc ,fig4 #ajc--99,outside and inside view of knee joint499 #a4 ,tendons4 #b4 ,ligaments4 #c4 ,cartilage4 #d4 ,space containing synovial fluid4 ,this space is lined1 except upon the articular surfaces1 by the synovial membrane4 ,the interior of the joint1 except where the bone surfaces rub upon each other1 is covered with a serous lining1 called the synovial membrane 7,b1 ,fig4 #ajc74 ,this secretes a thick1 viscid liquid1 the synovial fluid1 which prevents friction4 ,the synovial membrane does not cover the ends of the bones1 but passes around the joint and connects with the bones at their edges so as to form a closed sac in which the fluid is retained4 99,kinds of ,movable ,joints4--99,the different kinds of movable joints are the ball and socket joint1 the hinge joint1 the pivot joint1 the condyloid joint1 and the gliding joint4 ,these are constructed and admit of motion1 as follows3 #a4 ,in the ball and socket joint the ball-shaped end of one bone fits into a cup-shaped cavity in another bone1 called the socket4 ,the best examples of such joints are found at the hips and shoulders4 ,the ball and socket joint admits of motion in all directions4 #b4 ,in the hinge joint the bones are grooved and fit together after the manner of a hinge4 ,hinge joints are found at the elbows and knees and also in the fingers4 ,the hinge joint gives motion in but two directions--forward and backward4 #c4 ,a pivot joint is formed by the fitting of a pivot-like projection of one bone into a ring-like receptacle of a second bone1 so that one1 or the other1 is free to turn4 ,a good example of the pivot joint is found at the elbow1 where the radius turns upon the humerus4 ,another example is the articulation of the atlas with the axis vertebra as already noted4 ,the pivot joint admits of motion around an axis4 #d4 ,the condyloid joint is formed by the fitting of the ovoid 7egg-shaped7 end of one bone into an elliptical cavity of a second bone4 ,examples of condyloid joints are found at the knuckles and where the wrist bones articulate with the radius and ulna4 ,they move easily in two directions1 like hinge joints1 and slightly in other directions4 #e4 ,gliding joints are formed by the articulation of plain 7almost flat7 surfaces4 ,examples of gliding joints are found in the articulations between the bones of the wrist and those of the ankle4 ,they are the simplest of the movable joints and are formed by one bone gliding1 or slipping1 upon the surface of another4 99,the ,machinery of the ,body499--,a machine is a contrivance for directing energy in doing work4 ,a sewing machine1 for example1 so directs the energy of the foot that it is made to sew4 ,through its construction the machine is able to produce just that form of motion needed for its work1 and no other forms1 so that energy is not wasted in the production of useless motion4 ,the places in machines where parts rub or turn upon each other are called bearings1 and extra precautions are taken in the construction and care of the bearings to prevent friction4 ,the body cannot properly be compared to any single machine1 but must be looked upon as a complex organization which employs a number of different kinds of machines in carrying on its work4 ,the majority of these machines are found in the skeleton4 ,the bones are the parts that are moved1 and the joints serve as bearings4 ,connected with the bones are the muscles that supply energy1 and attached to the muscles are the nerves that control the motion4 ,other parts also are required for rendering the machines of the body effective in doing work4 ,these are supplied by the tissues connected with the bones and the muscles4 ,,hygiene ,,of ,,the ,,skeleton ,of chief concern in the hygiene of the skeleton is the proper adjustment of its parts4 ,the efficiency of any of the body machines is impaired by lack of proper adjustment4 ,not only this1 but because of the fact that the skeleton forms the groundwork of the whole body--muscles1 blood vessels1 nerves1 everything in fact1 being arranged with reference to it--any lack of proper adjustment of the bones interferes generally with the arrangement and work of tissues and organs4 ,the displaced bones may even compress blood vessels and nerves and interfere1 in this way1 with the nourishment and control of organs remote from the places where the displacements occur4 ,for these reasons the proper adjustment of the different parts of the skeleton supplies one of the essential conditions for preserving the health4 99,hygienic ,importance of the ,spinal ,column499--,what has been said about the adjustment of the skeleton in general applies with particular force to the spinal column4 ,the spinal column serves both as the central axis of the body and as the container of the spinal cord4 ,thirty-one pairs of nerves pass between the vertebr to connect the spinal cord with different parts of the body1 and two important arteries 7the vertebral7 pass through a series of small openings in the bones of the neck to reach the brain4 ,unnatural curves of the spine throw different parts of the body out of their natural positions1 diminish the thoracic and abdominal cavities1 and1 according to the belief of certain physicians1 compress the nerves that pass from the cord to other parts of the body4 ,slightly misplaced vertebr in the neck1 by compressing the vertebral arteries1 may also interfere with the supply of blood ,fig4 #ajd ,fig4 #ajd--;,a tendency toward spinal curvature 7after ,mosher7 ,fig4 #aje ,fig4 #aje--;,effect on spinal column of improper position in writing4 7,from ,pyle's ,personal ,hygiene47 99,how the ,skeleton becomes ,deformed99--,we are accustomed to look upon the skeleton as a rigid framework which can get out of its natural form only through severe strain or by violence4 ,this view is far from being correct4 ,on account of their necessary freedom of motion1 the bones1 especially those of the spinal column1 are easily slipped from their normal positions2 and where improper attitudes are frequently assumed1 or continued through long periods of time1 the skeleton gradually becomes deformed 7,fig4 #ajd74 ,for example1 the habit of always sleeping on the same side with a high pillow may develop a bad crook in the neck2 and the ugly curves1 assumed so frequently in writing 7#hj7 7,fig4 #aje71 and also in standing1 when the weight is shifted too much on one foot1 may become permanent4 ,then the habit of reclining in a chair with the hips resting on the front of the seat often deforms the back and causes a drooping of the shoulders4 ,in fact1 slight displacements of the vertebr come about so easily through incorrect positions1 that they may almost be said to occur of themselves where active measures are not taken to preserve the natural form of the body4 ,the very few people who have perfectly formed bodies show to what an extent has been overlooked an essential law of hygiene4 99,prevention of ,skeletal ,deformities499--,those deformities of the skeleton that are acquired through improper positions are prevented by giving sufficient attention to the positions assumed in sitting1 standing1 and sleeping1 and also to the posture in various kinds of work4 ,in sitting the trunk should be erect and the hips should touch the back of the chair4 ,one should not lounge in the ordinary chair4 ,in standing the body should be erect1 the shoulders back and down1 the chest pushed slightly up and forward1 and the chin slightly depressed1 while the weight should1 as a rule1 rest about equally on the two feet4 ,the habit of leaning against some object when standing 7the pupil in reciting often leans on his desk7 should be avoided4 ,in sleeping the pillow should be of the right thickness to support the head on a level with the spinal column and should not be too soft4 ,if one sleeps on his back1 no pillow is required4 ,it is best not to acquire the habit of sleeping always on the same side4 ,where one is compelled by his work to assume harmful positions1 these should be corrected by proper exercises1 and by cultivating opposing positions during the leisure hours4 ,much is to be accomplished through those forms of physical exercise which develop the muscles whose work it is to keep the body in an upright position4 99,school ,furniture499--,it has long been observed that school children are more subject to curvature of the spine and other deformities of the skeleton than the children who do not attend school4 ,while this is due largely to faulty positions assumed by the pupils at their work1 it has been suggested that the school furniture may be in part to blame for these positions4 ,investigations of this problem have shown that most of the school desks and seats in use in our public schools are unhygienically constructed1 in that they force pupils into unnatural positions4 ,school seats should support the pupil in a natural position1 both in the use of his books and in writing1 and there are many arguments in favor of the so-called adjustable school furniture4 ,fig4 #ajf shows the seat and desk designed by the ,boston1 ,mass41 ,schoolhouse ,commission after much study and experimenting and used in the ,boston schools4 ,this furniture1 which provides a seat adjustable for height1 having a back rest also adjustable for height1 and a desk which is likewise provided with a vertical adjustment1 supplies all essential hygienic requirements4 ,it is to be hoped that school furniture of this character may in the near future come into general use4 ,fig4 #ajf ,fig4 #ajf--;,adjustable seat and desk used in schools of ,boston1 ,mass4 99,correction of ,skeletal ,deformities499--,it is1 of course1 easier to prevent deformities of the skeleton by giving attention to proper positions1 than to correct them after they have occurred4 ,it should also be noted that severe deformities cannot be corrected by the individual for himself1 but these must come under the treatment of specialists in this line of medical work4 ,in mild cases of spinal curvature1 drooping of the head1 and round shoulders1 the individual can benefit his condition4 ,by working to substitute a correct attitude for the faulty one17#ha7 he can by persistence bring about marked improvements4 ,it is better1 however1 to have the advice and aid of a physical director1 where this is possible4 ,it should also be borne in mind that the correction of skeletal deformities requires effort through a long period of time1 especially where the deformities are pronounced2 and one lacking the will power to persist will not secure all the results which he seeks4 99,setting ,up ,exercises499--,the splendid carriage of students from military schools shows what may be accomplished in securing erectness of form where proper attention is given to this matter4 ,the military student gets his fine form partly through his exercises in handling arms1 but mainly through his so-called setting up drill4 ,as a suggestion to one desiring to improve the form of his body1 a modification of the usual setting up drill is here given3 #a4 ,standing erect1 with the heels together1 the feet at an angle of #de1 and hands at the sides1 bring the arms to a horizontal position in front1 little fingers touching and nails down4 ,from this position raise the hands straight over the head1 bringing the palms gradually together4 ,then with a backward sweeping movement1 return the hands again to the sides4 ,repeat several times4 #b4 ,with the feet as in the above exercise1 bring the hands and the arms to a level with the shoulders1 palms down1 elbows bent1 middle fingers of the two hands touching1 and the extended thumbs touching the chest4 ,keeping the palms down and the arms on a level with the shoulders1 extend the hands as far sideward and backward as possible1 returning each time to the first position4 ,as the hands move out1 inhale deeply 7through the nose71 and as they are brought back1 exhale quickly 7through the mouth74 ,repeat several times4 #c4 ,with the arms at the sides and the feet side by side and touching1 bring the hands in a circular movement to a vertical position over the head1 and lock the thumbs4 ,keeping the knees straight and the thumbs locked1 bend forward1 letting the hands touch the ground if possible1 and then bring the body and hands again to the vertical position4 ,then by a backward sweeping movement1 return the hands again to the sides4 ,repeat4 ,while these exercises may be practiced whenever convenient1 it is best to set apart some special time each day for them1 as on retiring at night or on rising in the morning4 99,hygienic ,footwear499--,a necessary aid to erectness of position in standing and walking is a properly fitting shoe4 ,heels that are too high tilt the body unnaturally forward1 and shoes that cause any kind of discomfort in walking lead to unnatural positions in order to protect the feet4 ,shoes should fit snugly1 being neither too large nor too small4 ,many shoes1 however1 are unhygienically constructed1 and no attempt should be made to wear them4 ,certainly is this true of styles that approach the ,french heel or the toothpick toe 7,fig4 #ajg74 ,however1 many styles of shoes are manufactured that are both hygienic and neat fitting4 ,rubber heels1 on account of their elasticity1 are to be preferred to those made of leather4 ,fig4 #ajg ,fig4 #ajg--;,heels and toes of unhygienic and of hygienic footwear4 99,the ,skeleton in ,childhood and ,old ,age499--,certain peculiarities are found to exist in the bones of children and of old people which call for special care of the skeleton during the first and last periods of life4 ,the bones of children are soft1 lacking mineral matter1 and are liable to become bent ,for this reason1 children who are encouraged to walk at too early an age may bend the thigh bones1 causing the too familiar bow-legs4 ,these bones may also be bent by having children sit on benches and chairs which are too high for the feet to reach the floor1 and which do not provide supports for the feet4 ,wholesome food1 fresh air1 sunlight1 and exercise are also necessary to the proper development of the bones of children4 ,where these natural conditions are lacking1 as in the crowded districts of cities1 children often suffer from a disease known as rickets1 on account of which their bones are unnaturally soft and easily bent4 ,on account of the accumulation of mineral matter1 the bones of elderly people become brittle and are easily broken1 and from lack of vigor of the bone cells they heal slowly after such injuries occur4 ,this makes the breaking of a bone by an aged person a serious matter4 ,old people should1 as far as possible1 avoid liabilities to falls1 such as going rapidly up and down stairs1 or walking on icy sidewalks1 and should use the utmost care in getting about4 ,in old people also the cartilage between the bones softens1 increasing the liability of getting misshaped4 ,special attention1 therefore1 should be given to erectness of form1 and to such exercises as tend to preserve the natural shape of the body4 99,treatment of ,fractures499--,a fractured bone always requires the aid of a surgeon1 and no time should be lost in securing his services4 ,in the meantime the patient should be put in a comfortable position1 and the broken limb supported above the rest of the body4 ,though the breaking of a bone is not1 as a rule1 a serious mishap1 it is necessary that the very best skill be employed in setting it4 ,any failure to bring the ends of the broken bone into their normal relations permanently deforms the limb and interferes with its use4 99,dislocations and ,sprains499--,dislocations1 if they be of the larger joints1 also require the aid of the surgeon in their reduction and sometimes in their subsequent treatment4 ,simple dislocations of the finger joints1 however1 may be reduced by pulling the parts until the bones can be slipped into position4 ,a sprain1 which is an overstrained condition of the ligaments surrounding a joint1 frequently requires very careful treatment4 ,when the sprain is at all serious1 a physician should be called4 ,because of the limited supply of blood to the ligaments1 they are slow to heal1 and the temptation to use the joint before it is fully recovered is always great4 ,massage7#hb7 judiciously applied to a sprained joint1 by bringing about a more rapid change in the blood and the lymph1 is beneficial both in relieving the pain1 and in hastening recovery4 99,summary499--,the skeleton1 or framework of the body1 is a structure which is movable as a whole and in most of its parts4 ,it preserves the form of the body1 protects important organs1 and supplies the mechanical devices1 or machines1 upon which the muscles act in the production of motion4 ,the skeleton is adapted to its purposes through the number and properties of the bones1 and through the cartilage and connective tissue associated with the bones4 ,the places where the different bones connect one with another are known as joints1 and most of these admit of motion4 ,the preservation of the natural form of the skeleton is necessary1 both for its proper action and for the health of the body4 99,exercises499--#a4 ,state the main purpose of the skeleton4 ,what is the necessity for so many bones in its construction8 #b4 ,how may the per cent of animal and of mineral matter in a bone be determined8 #c4 ,what properties are given the bones by the animal matter8 ,what by the mineral matter8 #d4 ,locate the bone cells4 ,what is their special function8 #e4 ,state the plan by which nourishment is supplied to the bone cells in different parts of the bone4 #f4 ,give the uses of the periosteum4 #g4 ,state the purpose of the ,haversian canals4 ,of the canaliculi4 #h4 ,give functions of the spinal column4 #i4 ,name the different materials used in the construction of a joint and the purpose served by each4 #aj4 ,name four mechanical devices1 or machines1 found in the skeleton and state the purpose served by each4 #aa4 ,name one or more of the body machines not located in the skeleton4 #ab4 ,of what advantage is the peculiar shape of the lower jaw8 ,of the ribs8 ,of the bones of the pelvic girdle8 #ac4 ,state the importance of preserving the natural form of the skeleton4 ,how are unnatural curves produced in the spinal column8 #ad4 ,how may slight deformities of the skeleton be corrected8 #ae4 ,what different systems are employed in the body in the production of motion8 ,what is the special function of each8 ,,practical ,,work ,to obtain clear ideas of the form and functions of the bones1 a careful examination of a prepared and mounted skeleton is necessary4 ,many of the bones1 however1 may be located and their general form made out from the living body4 ,bones of the lower animals may also be studied to advantage4 99,experiments to show the ,composition of ,bone499--#a4 ,examine a slender bone1 like that in a chicken's leg4 ,note that it resists bending and is difficult to break4 ,note also that it is elastic--that1 when slightly bent1 it will spring back4 #b4 ,soak such a bone over night in a mixture of one part hydrochloric acid and four parts water4 ,then ascertain by bending1 stretching1 and twisting what properties the bone has lost4 ,the acid has dissolved out the mineral matter4 #c4 ,burn a small piece of bone in a clear gas flame1 or on a bed of coals1 until it ceases to blaze and turns a white color4 ,can the bone now be bent or twisted8 ,what properties has it lost and what retained8 ,what substance has been removed from the bone by burning8 99,observation on the ,gross ,structure of ,bone499--#a4 ,procure a long1 dry bone4 7,one that has lain out in the field until it has bleached will answer the purpose excellently47 ,test its hardness1 strength1 and stiffness4 ,saw it in two a third of the distance from one end1 and saw the shorter piece in two lengthwise4 ,compare the structure at different places4 ,find rough elevations on the outside for the attachment of muscles1 and small openings into the bone for the entrance of blood vessels and nerves4 ,make drawings to represent the sections4 #b4 ,procure a fresh bone from the butcher shop4 ,note the difference between it and the dry bone4 ,examine the materials surrounding the sides and covering the ends of the bone4 ,saw through the enlarged portion at the end and examine the red marrow4 ,saw through the middle of the bone and observe the yellow marrow4 99,to show the ,minute ,structure of the ,bone499--,prepare a section of bone for microscopic study as follows3 ,with a jeweler's saw cut as thin a slice as possible4 ,place this upon a good-sized whetstone1 not having too much grit1 and keeping it wet rub it under the finger1 or a piece of leather1 until it is thin enough to let the light shine through4 ,the section may then be washed and examined with the microscope4 ,if the specimen is to be preserved for future study1 it may be mounted in the usual way1 but with hard balsam4 ,prepare and study both transverse and longitudinal sections1 making drawings4 ,the sections should be prepared from bones that are thoroughly dry but which have not begun to decay4 99,to show the ,structure of a ,joint499--,procure from a butcher the joint of some small animal 7hog or sheep74 ,cut it open and locate the cartilage1 synovial membrane1 and ligaments4 ,observe the shape and surface of the rubbing parts and the strength of the ligaments4 ,,chapter ,,xv - ,,the ,,muscular ,,system ,as already stated1 the skeleton1 the nervous system1 and the muscular system are concerned in the production of motion4 ,the skeleton and the nervous system1 however1 serve other purposes in the body1 while the muscular system is devoted exclusively to the production of motion4 ,for this reason it is looked upon as the special motor system4 ,the muscular tissue is the most abundant of all the tissues1 forming about #da per cent of the weight of the body4 99,properties of ,muscles499--,the ability of muscular tissue to produce motion depends primarily upon two properties--the property of irritability and the property of contractility4 ,irritability is that property of a substance which enables it to respond to a stimulus1 or to act when acted upon4 ,contractility is the property which enables the muscle when stimulated to draw up1 thereby becoming shorter and thicker 7a condition called contraction71 and when the stimulation ceases1 to return to its former condition 7of relaxation74 ,the property of contractility enables the muscles to produce motion4 ,irritability is a condition necessary to their control in the body4 99,kinds of ,muscular ,tissue499--,three kinds of muscular tissue are found in the body4 ,these are known as the striated1 or striped1 muscular tissue2 the non-striated1 or plain1 muscular tissue2 and the muscular tissue of the heart4 ,these are made up of different kinds of muscle cells and act in different ways to cause motion4 ,the striated muscular tissue far exceeds the others in amount and forms all those muscles that can be felt from the surface of the body4 ,the non-striated muscle is found in the walls of the food canal1 blood vessels1 air passages1 and other tubes of the body2 while the muscular tissue of the heart is confined entirely to that organ4 99,striated ,muscle ,cells499--,the cells of the striated muscles are slender1 thread-like structures1 having an average length of #a-a_/b inches 7#ce millimeters7 and a diameter of about #a_/djj of an inch 7#fj 74 ,because of their great length they are called fibers1 or fiber cells4 ,they are marked by a number of dark1 transverse bands1 or stripes1 called striations17#hc7 which seem to divide them into a number of sections1 or disks 7,fig4 #ajh74 ,a thin sac-like covering1 called the sarcolemma1 surrounds the entire cell and just beneath this are a number of nuclei47#hd7 ,fig4 #ajh ,fig4 #ajh--99;,a striated muscle cell99 highly magnified1 showing striations and nuclei4 ,attached to the cell is the termination of a nerve fiber4 ,within the sarcolemma are minute fibrils and a semiliquid substance1 called the sarcoplasm4 ,at each end the cell tapers to a point from which the sarcolemma appears to continue as a fine thread1 and this1 by attaching itself to the inclosing sheath1 holds the cell in place4 ,most of the muscle cells receive1 at some portion of their length1 the termination of a nerve fiber4 ,this penetrates the sarcolemma and spreads out upon a kind of disk1 having several nuclei1 known as the end plate4 99,the ,muscle-organ499--,we must distinguish between the term muscle as applied to the muscular tissue and the term as applied to a working group of muscular tissue1 which is an organ4 ,in the muscle1 or muscle-organ1 is found a definite grouping of muscle fibers such as will enable a large number of them to act together in the production of the same movement4 ,an examination of one of the striated muscles shows the individual fibers to lie parallel in small bundles1 each bundle being surrounded by a thin layer of connective tissue4 7,see ,practical ,work47 ,these small bundles are bound into larger ones by thicker sheaths and these in turn may be bound into bundles of still larger size 7,fig4 #aji74 ,the sheaths surrounding the fiber bundles are connected with one another and also with the outer covering of the muscle1 known as ,fig4 #aji ,fig4 #aji--99;,diagram99 of a section of a muscle1 showing the perimysium and the bundles of fiber cells4 ,fig4 #aaj ,fig4 #aaj--99;,a muscle-organ in position499 ,the tendons connect at one end with the bones and at the other end with the fiber cells and perimysium4 7,see text47 99,the ,perimysium499--,the plan of the muscle-organ is revealed through a study of the perimysium4 ,this is not limited to the surface of the muscle1 as the name suggests1 but properly includes the sheaths that surround the bundles of fibers4 ,furthermore1 the surface perimysium and that within the muscle are both continuous with the strong1 white cords1 called tendons1 that connect the muscles with the bones4 ,by uniting with the bone at one end and blending with the perimysium and fiber bundles at the other1 the tendon forms a very secure attachment for the muscle4 ,the perimysium and the tendon are thus the means through which the fiber cells in any muscle-organ are made to pull together upon the same part of the body 7,fig4 #aaj74 99,purpose of ,striated ,muscles499--,the striated muscles1 by their attachments to the bones1 supply motion to all the mechanical devices1 or machines1 located in the skeleton4 ,through them the body is moved from place to place and all the external organs are supplied with such motion as they require4 ,because of the attachment of the striated muscles to the skeleton1 and their action upon it1 they are called skeletal muscles4 ,as most of them are under the control of the will1 they are also called voluntary muscles4 ,they are of special value in adapting the body to its surroundings4 99,structure of the ,non-striated ,muscles499--,the cells of the non-striated muscles differ from those of the striated muscles in being decidedly spindle-shaped and in having but a single well-defined nucleus 7,fig4 #aaa74 ,furthermore1 they have no striations1 and their connection with the nerve fibers is less marked4 ,they are also much smaller than the striated cells1 being less than one one-hundredth of an inch in length and one three-thousandth of an inch in diameter4 ,in the formation of the non-striated muscles1 the cells are attached to one another by a kind of muscle cement to form thin sheets or slender bundles4 ,these differ from the striated muscles in several particulars4 ,they are of a pale1 whitish color1 and they have no tendons4 ,instead of being attached to the bones1 they usually form a distinct layer in the walls of small cavities or of tubes 7,fig4 #aaa74 ,since they are controlled by the part of the nervous system which acts independently of the will1 they are said to be involuntary4 ,they contract and relax slowly4 ,fig4 #aaa ,fig4 #aaa--99,non-striated muscle cells499 ,a4 ,cross section of small artery magnified1 showing 7#a7 the layer of non-striated cells4 ,b4 ,three non-striated cells highly magnified4 99,work of the ,non-striated ,muscles499--,the work of the non-striated muscles1 both in purpose and in method1 is radically different from that of the striated4 ,they do not change the position of parts of the body1 as do the striated muscles1 but they alter the size and shape of the parts which they surround4 ,their purpose1 as a rule1 is to move1 or control the movement of1 materials within cavities and tubes1 and they do this by means of the pressure which they exert4 ,examples of their action have already been studied in the propulsion of the food through the alimentary canal and in the regulation of the flow of blood through the arteries 7pages #aei and #di74 ,while they do not contract so quickly1 nor with such great force as the striated muscles1 their work is more closely related to the vital processes4 99,structure of the ,heart ,muscle499--,the cells of the heart combine the structure and properties of the striated and the non-striated muscle cells1 and form an intermediate type between the two4 ,they are cross-striped like the striated cells1 and are nearly as wide1 but are rather short 7,fig4 #aab74 ,each cell has a well-defined nucleus1 but the sarcolemma is absent4 ,they are placed end to end to form fibers1 and many of the cells have branches by which they are united to the cells in neighboring fibers4 ,in this way they interlace more or less with each other1 but are also cemented together4 ,they contract quickly and with great force1 but are not under control of the will4 ,muscular tissue of this variety seems excellently adapted to the work of the heart4 ,fig4 #aab ,fig4 #aab--99,muscle cells from the heart991 highly magnified 7after ,schfer74 99,the ,muscular ,stimulus499--,the inactive1 or resting1 condition of a muscle is that of relaxation4 ,it does work through contracting4 ,it becomes active1 or contracts1 only when it is being acted upon by some force outside of itself1 and it relaxes again when this force is withdrawn4 ,any kind of force which1 by acting on muscles1 causes them to contract1 is called a muscular stimulus4 ,electricity1 chemicals of different kinds1 and mechanical force may be so applied to the muscles as to cause them to contract4 ,these are artificial stimuli4 ,so far as known1 muscles are stimulated naturally in but one way4 ,this is through the nervous system4 ,the nervous system supplies a stimulus called the nervous impulse1 which reaches the muscles by the nerves1 causing them to contract4 ,by means of nervous impulses1 all of the muscles 7both voluntary and involuntary7 are made to contract as the needs of the body for motion require4 99,energy ,transformation in the ,muscle499--,the muscle serves as a kind of engine1 doing work by the transformation of potential into kinetic energy4 ,evidences of this are found in the changes that accompany contraction4 ,careful study shows that during any period of contraction oxygen and food materials are consumed1 waste products1 such as carbon dioxide1 are produced1 and heat is liberated4 ,furthermore1 the blood supply to the muscle is such that the materials for providing energy may be carried rapidly to it and the products of oxidation as rapidly removed4 ,blood vessels penetrate the muscles in all directions and the capillaries lie very near the individual cells 7,fig4 #aac74 ,provision is made also1 through the nervous system1 for increasing the blood supply when the muscle is at work4 ,from these facts1 as well as from the great force with which the muscle contracts1 one must conclude that the muscle is a transformer of energy--that within its protoplasm1 chemical changes take place whereby the potential energy of oxygen and food is converted into the kinetic energy of motion4 ,fig4 #aac ,fig4 #aac--99;,capillaries99 of muscles4 99,plan of ,using ,muscular ,force499--,two difficulties have to be overcome in the using of muscular force in the body4 ,the first of these is due to the fact that the muscles exert their force only when they contract4 ,they can pull but not push4 ,hence1 in order to bring about the opposing movements7#he7 of the body1 each muscle must work against some force that produces a result directly opposite to that which the muscle produces4 ,some of the muscles 7those of breathing7 work against the elasticity of certain parts of the body2 others 7those that hold the body in an upright position71 to some extent against gravity2 and others 7the non-striated muscle in arteries71 against pressure4 ,but in most cases1 muscles work against muscles4 ,fig4 #aad ,fig4 #aad--99,the muscle pair99 that operates the forearm4 ,for names of these muscles1 see ,fig4 #aai4 ,the striated1 or skeletal1 muscles are nearly all arranged after the last-named plan4 ,as a rule a pair of muscles is so placed1 with reference to a joint1 that one moves the part in one direction1 and the other moves it in the opposite direction4 ,from the kinds of motion which the various muscle pairs produce1 they are classified as follows3 #a4 ,flexors and ,extensors4--,the flexor muscles bend and the extensors straighten joints 7,fig4 #aad74 #b4 ,adductors and ,abductors4--,the adductors draw the limbs into positions parallel with the axis of the body and the abductors draw them away4 #c4 ,rotators 7two kinds74--,the rotators are attached about pivot joints and bring about twisting movements4 #d4 ,radiating and ,sphincter ,muscles4 --,the radiating muscles open and the sphincter muscles close the natural openings of the body1 such as the mouth4 ,the pupil should locate examples of the different kinds of muscle pairs in his own body4 99,exchange of ,muscular ,force for ,motion499--,the second difficulty to be overcome in the use of muscular force in the body is due to the fact that the muscles contract through short distances1 while it is necessary for most of them to move portions of the body through long distances4 ,it may be easily shown that the longest muscles of the body do not shorten more than three or four inches during contraction4 ,to bring about the required movements of the body1 which in some instances amount to four or five feet1 requires that a large proportion of the muscular force be exchanged for motion4 ,the machines of the skeleton1 while providing for motion in definite directions1 also provide the means whereby strong forces1 acting through short distances1 are made to produce movements of less force1 through long distances4 ,the mechanical device employed for this purpose is known as 99,the ,lever499--,the lever may be described as a stiff bar which turns about a fixed point of support1 called the fulcrum4 ,the force applied to the bar to make it turn is called the power1 and that which is lifted or moved is termed the weight4 ,the weight1 the power1 and the fulcrum may occupy different positions along the bar and this gives rise to the three kinds of levers1 known as levers of the first class1 the second class1 and the third class 7,fig4 #aae74 ,in levers of the first class the fulcrum occupies a position somewhere between the power and the weight4 ,in the second class the weight is between the fulcrum and the power4 ,in the third class the power is between the fulcrum and the weight4 ,fig4 #aae ,fig4 #aae--99;,classes of levers4 ,i499 ,two levers of first class showing fulcrums in different positions4 ,,ii4 ,lever of second class4 ,,iii4 ,lever of third class4 ,f4 ,fulcrum4 ,p4 ,power4 ,w4 ,weight4 a4 ,power-arm4 b4 ,weight-arm4 99,application to the ,body499--,in the body the bones serve as levers2 the turning points1 or fulcrums1 are found at the joints2 the muscles supply the power2 and parts of the body1 or things to be lifted1 serve as weights4 ,for these levers to increase the motion of the muscles1 it is necessary that the muscles be attached to the bones near the joints1 and that the parts to be moved be located at some distance from the joints4 ,in other words the 7muscle7 power-arm must be shorter than the 7body7 weight-arm47#hf7 ,examining ,fig4 #aaf1 it is seen that the distances moved by the power and weight vary as their respective distances from the fulcrum4 ,that is to say1 if the weight is twice as far from the fulcrum as the power1 it will move through twice the distance1 and if three times as far1 through three times the distance4 ,thus the muscles1 by acting through short distances 7on the short arms of levers71 are able to move portions of the body 7located on the long arms7 through long distances4 ,can all three classes of levers be used in this way in the body8 ,fig4 #aaf ,fig4 #aaf--99,motion producing levers499 ,diagrams show relative distances moved by the power and weight in levers having the power nearer the fulcrum than is the weight4 ,f4 ,fulcrum4 ,p1 ,p'4 ,power4 ,w1 ,w'4 ,weight4 99,classes of ,levers found in the ,body499--,practically all of the levers of the body belong either to the first class or the third class4 ,in both of these the muscle power can be applied to the short arm of the lever1 thereby moving the body weight through a longer distance than the muscle contracts 7,fig4 #aaf74 ,in the levers of the second class1 however1 the weight occupies this position1 being situated between the power and fulcrum 7,fig4 #aag74 ,the weight1 therefore1 cannot move farther than the power in this lever4 ,it must always move a shorter distance4 ,while such a lever is of great advantage in lifting heavy weights outside of the body1 it cannot be used for increasing the motion of the muscles4 ,for this reason no well-defined levers of the second class are present in the body47#hg7 ,fig4 #aag ,fig4 #aag--99,weight lifting levers499 ,diagrams show relative distances moved by the power and weight in levers having the weight nearer the fulcrum than is the power4 ,f4 ,fulcrum4 ,p1 ,p'4 ,power4 ,w1 ,w'4 ,weight4 ,fig4 #aah ,fig4 #aah--99;,diagram of the foot lever499 ,f4 ,fulcrum at ankle joint4 ,w4 ,body weight expressed as pressure against the earth4 ,while the muscle power acts through the distance ab1 the fulcrum support 7body7 is forced through the distance ,,fe4 99,loss of ,muscular ,force499--,using a small spring balance for measuring the power1 a light stick for a lever1 and a small piece of metal for a weight1 and arranging these to represent some lever of the body 7as the forearm71 it is easily shown that the gain in motion causes a corresponding loss in muscular power4 7,see ,practical ,work47 ,if1 for example1 the balance is attached two inches from the fulcrum and the weight twelve inches1 the pull on the balance is found to be six times greater than the weight that is being lifted4 ,if other positions are tried1 it is found that the power exerted in each case is as many times greater than the weight as the weight-arm is times longer than the power-arm4 ,applying this principle to the levers of the body1 it is seen that the gain in motion is at the expense of muscular force1 or1 as we say1 muscular force is exchanged for motion4 ,this exchange is greatly to the advantage of the body2 for while the ability to lift heavy weights is important1 the ability to move portions of the body rapidly and through long distances is much more to be desired4 99,important ,muscles499--,there are about five hundred separate muscles in the body4 ,these vary in size1 shape1 and plan of attachment1 to suit their special work4 ,some of those that are prominent enough to be felt at the surface are as follows3 ,of the head3 ,the temporal1 in the temple1 and the masseter1 in the cheek4 ,these muscles are attached to the lower jaw and are the chief muscles of mastication4 ,of the neck3 ,the sterno-mastoids1 which pass between the mastoid processes1 back of the ears1 and the upper end of the sternum4 ,they assist in turning the head and may be felt at the sides of the neck 7,fig4 #aai74 ,of the upper arm3 ,the biceps on the front side1 the triceps behind1 and the deltoid at the upper part of the arm beyond the projection of the shoulder4 ,fig4 #aai ,fig4 #aai--;,back and front views of important muscles4 ,of the forearm3 ,the flexors of the fingers1 on the front side1 and the extensors of the fingers1 on the back of the forearm 7,fig4 #aai74 ,of the hand3 ,the adductor pollicis between the thumb and the palm4 ,of the trunk3 ,the pectoralis major1 between the upper front part of the thorax and the shoulder2 the trapezius1 between the back of the shoulders and the spine2 the rectus abdominis1 passing over the abdomen from above downward2 and the erector spin1 found in the small of the back4 ,of the hips3 ,the glutens maximus1 fastened between the lower back part of the hips and the upper part of the femur4 ,of the upper part of the leg3 ,the rectus femoris1 the large muscle on the front of the leg which connects at the lower end with the kneepan4 ,of the lower leg3 ,the tibialis anticus on the front side1 exterior to the tibia1 and the gastrocnemius1 the large muscle in the calf of the leg4 ,this is the largest muscle of the body1 and is connected with the heel bone by the tendon of ,achilles 7,fig4 #aai74 ,the use of these muscles is1 in most instances1 easily determined by observing the results of their contraction4 ,,hygiene ,,of ,,the ,,muscles ,the hygiene of the muscles is almost expressed by the one word exercise4 ,it is a matter of everyday knowledge that the muscles are developed and strengthened by use1 and that they become weak1 soft1 and flabby by disuse4 ,the effects of exercise are1 however1 not limited to the large muscles attached to the skeleton1 but are apparent also upon the involuntary muscles1 whose work is so closely related to the vital processes4 ,while it is true that exercise cannot be applied directly to the involuntary muscles1 it is also true that exercise of the voluntary muscles causes a greater activity on the part of those that are involuntary and is indirectly a means of exercising them4 99,exercise and ,health499--,in addition to its effects upon the muscles themselves1 exercise is recognized as one of the most fundamental factors in the preservation of the health4 ,practically every process of the body is stimulated and the body as a whole invigorated by exercise properly taken4 ,on the other hand1 a lack of exercise has an effect upon the entire body somewhat similar to that observed upon a single muscle4 ,it becomes weak1 lacks energy1 and in many instances actually loses weight when exercise is omitted4 ,this shows exercise to supply an actual need and to be in harmony with the nature and plan of the body4 99,how ,exercise benefits the ,body499--,in accounting for the healthful effects of exercise1 it must be borne in mind that the body is essentially a motion-producing structure4 ,furthermore1 its plan is such that the movements of its different parts aid indirectly the vital processes4 ,the student will recall instances of such aid1 as1 for example1 the assistance rendered by muscular contractions in the circulation of the blood and lymph1 due to the valves in veins and lymph vessels1 and the assistance rendered by abdominal movements in the propulsion of materials through the food canal4 ,a fact not as yet brought out1 however1 is that exercise stimulates nutritive changes in the cells1 thereby imparting to them new vigor and vitality4 ,while this effect of exercise cannot be fully accounted for1 two conditions that undoubtedly influence it are the following3 #a4 ,exercise causes the blood to circulate more rapidly4 #b4 ,exercise increases the movement of the lymph through the lymph vessels4 ,the increase in the flow of the blood and the lymph causes changes to take place more rapidly in the liquids around the cells1 thereby increasing the supply of food and oxygen1 and hastening the removal of waste4 99,one should plan for ,exercise499--,since exercise is demanded by the nature and plan of the body1 to neglect it is a serious matter4 ,people do not purposely omit exercise1 but from lack of time or from its interference with the daily routine of duties1 the needed amount is frequently not taken4 ,especially is this true of students and others who follow sedentary occupations4 ,people of this class should plan for exercise as they plan for the other great needs of the body--food1 sleep1 clothing1 etc4 ,it is only by making a sufficient amount of muscular work or play a regular part of the daily program that the needs of the body for exercise are adequately supplied4 99,amount and ,kind of ,exercise499--,the amount of exercise required varies greatly with different individuals1 and definite recommendations cannot be made4 ,for each individual also the amount should vary with the physical condition and the other demands made upon the energy4 ,one in health should exercise sufficiently to keep the muscles firm to the touch and the body in a vigorous condition4 ,of the many forms of exercise from which one may choose1 the question is again one of individual adaptability and convenience4 ,while the different forms of exercise vary in their effects and may be made to serve different purposes1 the consideration of these is beyond the scope of an elementary text4 ,as a rule one will not go far wrong by following his inclinations1 observing of course the conditions under which exercise is taken to the best advantage4 99,general ,rules for ,healthful ,exercise499--,that exercise may secure the best results from the standpoint of health1 a number of conditions should be observed3 #a4 ,it should not be excessive or carried to the point of exhaustion4 ,severe physical exercise is destructive to both muscular and nervous tissues4 #b4 ,it should1 if possible1 be of an interesting nature and taken in the open air4 #c4 ,it should be counter-active1 that is1 calling into play those parts of the body that have not been used during the regular work47#hh7 #d4 ,it should be directed toward the weak rather than toward the strong parts of the body4 #e4 ,when one is already tired from study1 or other work1 it should be taken with moderation or omitted for the time being4 7,for exercise of the heart muscle and the muscular coat of the blood vessels see pages #ee and #eg47 99,massage499--,in lieu of exercise taken in the usual way1 similar effects are sometimes obtained by a systematic rubbing1 pressing1 stroking1 or kneading of the skin and the muscles by one trained in the art4 ,this process1 known as massage1 may be gentle or vigorous and is subject to a variety of modifications4 ,massage is applied when one is unable to take exercise1 on account of disease or accident1 and also in the treatment of certain bodily disorders4 ,a weak ankle1 wrist1 or other part of the body1 or even a bruise1 may be greatly benefited by massage4 ,the flow of blood and lymph is stimulated1 causing new materials to be passed to the affected parts and waste materials to be removed4 ,massage1 however1 should never be applied to a boil1 or other infected sore4 ,the effect in this case would be to spread the infection and increase the trouble4 99,summary499--,motion is provided for in the body mainly through the muscle cells4 ,these are grouped into working parts1 called muscles1 which in turn are attached to the movable parts of the body4 ,the striated muscles1 as a rule1 are attached to the mechanical devices found in the skeleton1 and bring about the voluntary1 movements4 ,the non-striated muscles surround the parts on which they act1 and produce involuntary movements4 ,both1 however1 are under the control of the nervous system4 ,to bring about the opposing movements of the body1 the striated muscles are arranged in pairs2 and to increase their motion1 the bones are used as levers4 ,physical exercise is necessary both for the development of the muscles and for the health and vigor of the entire body4 99,exercises499--#a4 ,compare the striated and non-striated muscles with reference to structure1 location1 and method of work4 #b4 ,in what respects is the muscular tissue of the heart like the striated1 and in what respects like the non-striated1 muscular tissue8 #c4 ,if muscles could push as well as pull1 would so many be needed in the body8 ,why8 #d4 ,locate muscles that work to some extent against elasticity and gravity4 #e4 ,locate five muscles that act as flexors2 five that act as extensors2 two that act as adductors2 and two as abductors4 ,locate sphincter and radiating muscles4 #f4 ,by what means does the nervous system control the muscles8 #g4 ,give proofs of the change of potential into kinetic energy during muscular contraction4 #h4 ,define the essential properties of muscular tissue and state the purpose served by each4 #i4 ,describe a lever4 ,for what general purpose are levers used in the body8 ,what other purpose do they serve outside of the body8 #aj4 ,why are levers of the second class not adapted to the work of the body8 #aa4 ,name the class of lever used in bending the elbow2 in straightening the elbow2 in raising the knee2 in elevating the toes2 and in biting4 ,why is one able to bite harder with the back teeth than with the front ones when the same muscles are used in both cases8 #ab4 ,measure the distance from the middle of the palm of the hand to the center of the elbow joint4 ,find the attachment of the tendon of the biceps muscle to the radius and measure its distance to the center of the elbow joint4 ,from these distances calculate the force with which the biceps contracts in order to support a weight of ten pounds on the palm of the hand4 #ac4 ,how does exercise benefit the health8 ,how does a short walk clear the brain and enable one to study to better advantage8 #ad4 ,when exercisers taken for its effects upon the health1 what conditions should be observed8 ,,practical ,,work ,the reddish muscle found in a piece of beef is a good example of striated muscle4 ,the clear ring surrounding the intestine of a cat 7shown by cross section7 and the outer portion of the preparation from the cow's stomach1 sold at the butcher shop under the name of tripe1 are good examples of non-striated muscular tissue4 ,the heart of any animal1 of course1 shows the heart muscle4 99,to show the ,structure of ,striated ,muscle499--,boil a tough piece of beef1 as a cut from the neck1 until the connective tissue has thoroughly softened4 ,then with some pointed instrument1 separate the main piece into its fiber bundles and these in turn into their smallest divisions4 ,the smallest divisions obtainable are the muscle cells or fibers4 99,to show ,striated ,fibers499--,place a small muscle from the leg of a frog in a fifty-per-cent solution of alcohol and leave it there for half a day or longer4 ,then cover with water on a glass slide1 and with a couple of fine needles tease out the small muscle threads4 ,protect with a cover glass and examine with a microscope1 first with a low and then with a high power4 ,the striations1 sarcolemma1 and sometimes the nuclei and nerve plates1 may be distinguished in such a preparation4 99,to show ,non-striated ,cells499--,place a clean section of the small intestine of a cat in a mixture of one part of nitric acid and four parts of water and leave for four or five hours4 ,thoroughly wash out the acid with water and separate the muscular layer from the mucous membrane4 ,cover a small portion of the muscle with water on a glass slide and tease out1 with needles1 until it is as finely divided as possible4 ,examine with a microscope1 first with a low and then with a high power4 ,the cells appear as very fine1 spindle-shaped bodies4 99,to illustrate ,muscular ,stimulus and ,contraction499--,separate the muscles at the back of the thigh of a frog which has just been killed and draw the large sciatic nerve to the surface4 ,cut this as high up as possible and1 with a sharp knife and a small pair of scissors1 dissect it out to the knee4 ,now cut out entirely the large muscle of the calf of the leg 7the gastrocnemius71 but leave attached to it the nerve1 the lower tendon1 and the bones of the knee4 ,mount on an upright support1 as shown in ,fig4 #abj1 and fasten the tendon to a lever below by a thread or small wire hook3 ,fig4 #abj ,fig4 #abj--99;,apparatus99 for demonstrating properties of muscles4 #a4 ,lay the nerve over the ends of the wires from a small battery which are attached to the support at ,a1 and arrange a second break in the circuit at ,b4 ,at this place the battery circuit is made and broken either by a telegraph key or by simply touching and separating the wires4 ,note that the muscle gives a single contraction1 or twitch1 both when the current is made and when it is broken4 #b4 ,remove the current and pinch the end of the nerve1 noting the result4 ,with very fine wires1 connect the battery directly to the ends of the muscle4 ,stimulate by making and breaking the current as before4 ,in this experiment the muscle cells are stimulated by the direct action of the current and not by the current acting on the nerve4 #c4 ,with the wires attached to either the muscle or the nerve1 make and break the current in rapid succession4 ,this causes the muscle to enter into a second contraction before it has relaxed from the first1 and if the shocks follow in rapid succession1 to continue in the contracted state4 ,this condition1 which represents the method of contraction of the muscles in the body1 is called tetanus4 ,,note4--,in these experiments a twitching of the muscle is frequently observed when no stimulus is being applied4 ,this is due to the drying out of the nerve and is prevented by keeping it wet with a physiological salt solution4 7,see footnote1 page #ch47 99,to show the ,action of ,levers499--,with a light but stiff wooden bar1 a spring balance1 and a wedge-shaped fulcrum1 show3 #a4 ,the position of the weight1 the fulcrum1 and the power in the different classes of levers1 and also the weight-arm and the power-arm in each case4 #b4 ,the direction moved by the power and the weight respectively in the use of the different classes of levers4 #c4 ,that when the power-arm and weight-arm are equal1 the power equals the weight and moves through the same distance4 #d4 ,that when the power-arm is longer than the weight-arm1 the weight is greater1 but moves through a shorter distance than the power4 #e4 ,that when the weight-arm is longer than the power-arm1 the power is greater and moves through a shorter distance than the weight4 99,to show the ,loss of ,power in the ,use of the ,body ,levers499--,construct a frame similar to1 but larger than1 that shown in ,fig4 #abj1 7about #ab inches high71 and hang a small spring balance 7#bej grams capacity7 at the place where the muscle is attached4 ,fasten the end of a lever to the upright piece1 at a point on a level with the end of the balance hook4 7,the nail or screw used for this purpose must pass loosely through the lever1 and serve as a pivot upon which it can turn47 ,the lever should consist of a light piece of wood1 and should have a length at least three times as great as the distance from the hook to the turning point4 ,connect the balance hook with the lever by a thread or string1 and then hang upon it a small body of known weight4 ,note the amount of force exerted at the balance in order to support the weight at different places on the lever4 ,at what point is the force just equal to the weight8 ,where is it twice as great8 ,where three times8 ,show that the force required to support the weight increases proportionally as the weight-arm and as the distance through which the weight may be moved by the lever4 ,apply to the action of the biceps muscle in lifting weights on the forearm4 99,a ,study of the ,action of the ,biceps ,muscle499--,place the fingers upon the tendon of the biceps where it connects with the radius of the forearm4 ,with the forearm resting upon the table1 note that the tendon is somewhat loose and flaccid1 but that with the slightest effort to raise the forearm it quickly tightens4 ,now transfer the fingers to the body of the muscle1 and sweep the forearm through two or three complete movements1 noting the changes in the length and thickness of the muscle4 ,lay the forearm again on the table1 back of hand down1 and place a heavy weight 7a flatiron or a hammer7 upon the hand4 ,note the effort required to raise the weight1 and then shift it along the arm4 ,observe that the nearer it approaches the elbow the lighter it seems4 ,account for the difference in the effort required to raise the weight at different places4 ,does the effort vary as the distance from the tendon8 ,,chapter ,,xvi - ,,the ,,skin ,protective coverings are found at all the exposed surfaces of the body4 ,these vary considerably at different places1 each being adapted to the conditions under which it serves4 ,the most important ones are the skin1 which covers the entire external surface of the body2 the mucous membrane1 which lines all the cavities that communicate by openings with the external surface2 and the serous membrane1 which1 including the synovial membranes1 lines all the closed cavities of the body4 ,in addition to the protection which it affords1 the skin is one of the means by which the body is brought into proper relations with its surroundings4 ,it is because of this function that we take up the study of the skin at this time4 99,the ,skin99 is one of the most complex structures of the body1 and serves several distinct purposes4 ,it is estimated to have an area of from #ad to #af square feet1 and to have a thickness which varies from less than one eighth to more than one fourth of an inch4 ,it is thickest on the palms of the hands and the soles of the feet1 the places where it is most subject to wear4 ,it is made up of two distinct layers--an outer layer called the epidermis1 or cuticle1 and an inner layer called the dermis1 or cutis vera 7,fig4 #aba74 99,the ,dermis499--,this is the thicker and heavier of the two layers1 and is made up chiefly of connective tissue4 ,the network of tough fibers which this tissue supplies1 forms the essential body of the dermis and gives to it its power of resistance4 ,it is on account of the connective tissue that the skins of animals can be converted into leather by tanning4 ,a variety of structures1 including blood and lymph vessels1 oil and perspiratory glands1 hair follicles1 and nerves1 are found embedded in the connective tissue 7,fig4 #abb74 ,these aid in different ways in the work of the skin4 ,fig4 #aba ,fig4 #aba--99,section of skin99 magnified1 a1 b4 ,epidermis1 b4 ,pigment layer4 c4 ,papill1 d4 ,dermis4 e4 ,fatty tissue4 f1 g1 h4 ,sweat gland and duct4 i1 k4 ,hair and follicle4 l4 ,oil gland4 ,on the outer surface of the dermis are numerous elevations1 called papill4 ,these average about one one-hundredth of an inch in height1 and one two hundred and fiftieth of an inch in diameter4 ,they are most numerous on the palms of the hands1 the soles of the feet1 and the under surfaces of the fingers and toes4 ,at these places they are larger than in other parts of the body1 and are closely grouped1 forming the parallel curved ridges which cover the surfaces4 ,each papilla contains a loop of capillaries and a small nerve1 and many of them are crowned with touch corpuscles 7page #cdb74 ,fig4 #abb ,fig4 #abb--99;,diagram99 of section of skin showing its different structures4 99,the ,epidermis99 is much thinner than the dermis4 ,it is made up of several layers of cells which are flat and scale-like at the surface1 but are rounded in form where the epidermis joins the dermis4 ,the epidermis has the appearance of being moulded onto the dermis1 filling up the depressions between the papill and having corresponding irregularities 7,fig4 #aba74 ,no blood vessels are found in the epidermis1 its nourishment being derived from the lymph which reaches it from the dermis4 ,only the part next to the dermis is made up of living cells4 ,these are active1 however1 in the formation of new cells1 which take the place of those that are worn off at the surface4 ,some of the cells belonging to the inner layer of epidermis contain pigment granules1 which give the skin its color 7,fig4 #aba74 ,the epidermis contains no nerves and is therefore non-sensitive4 ,the hair and the nails are important modifications of the epidermis4 99,a ,hair99 is a slender cylinder1 formed by the union of epidermal cells1 which grows from a kind of pit in the dermis1 called the hair follicle4 ,the oval and somewhat enlarged part of the hair within the follicle is called the root1 or bulb1 and the uniform cylinder beyond the follicle is called the shaft4 ,connected with the sides of the follicles are the oil1 or sebaceous1 glands 7,figs4 #aba and #abb74 ,these secrete an oily liquid which keeps the hair and cuticle soft and pliable4 ,attached to the inner ends of the follicles are small1 involuntary muscles whose contractions cause the roughened condition of the skin that occurs on exposure to cold4 99,a ,nail99 is a tough and rather horny plate of epidermal tissue which grows from a depression in the dermis1 called the matrix4 ,the back part of the nail is known as the root1 the middle convex portion as the body1 and the front margin as the free edge 7,fig4 #abc74 ,material for the growth of the nail is derived from the matrix1 which is lined with active epidermal cells and is richly supplied with blood vessels4 ,cells added to the root cause the nail to grow in length 7forward7 and cells added to the under surface cause it to grow in thickness4 ,the cuticle adheres to the nail around its entire circumference so that the covering over the dermis is complete4 ,fig4 #abc ,fig4 #abc--99,section of end of finger99 showing nail in position4 99,functions of the ,skin499--,the chief function of the skin is that of protection4 ,it is able to protect the body on account of the tough connective tissue in the dermis1 the non-sensitive cells of the epidermis1 and also by the touch corpuscles and their connecting nerve fibers4 ,this protection is of at least three kinds1 as follows3 #a4 ,from mechanical injuries such as might result from contact with hard1 rough1 or sharp objects4 ,the main quality needed for resisting mechanical injuries is toughness1 and this is supplied both by the epidermis and by the connective tissue of the dermis4 #b4 ,from chemical injuries caused by contact with various chemical agents1 as acids1 alkalies1 and the oxygen of the air4 ,the epidermis1 being of such a nature as to resist to a considerable extent the action of chemical agents1 affords protection from these substances4 7#hi7 #c4 ,from disease germs which are everywhere present4 ,the epidermis is the main protective agent against attacks of germs1 but should the epidermis be broken1 they meet with further resistance from the fluids of the dermis and the white corpuscles of the blood4 #d4 ,from an excessive evaporation of liquid from the surface of the body4 ,in the performance of this function1 the skin is an important means of keeping the tissues soft and the blood and lymph from becoming too concentrated4 99,other ,functions of the ,skin499--,through the perspiratory glands the skin is an organ of excretion4 ,while the secretion from a single gland is small1 the waste that leaves the body through all of the perspiratory glands is considerable 7#ij7 7page #bjf74 ,by means of the nerves terminating in the touch corpuscles1 the skin serves as the organ of touch1 or feeling 7,chapter ,,xx74 ,to a slight extent also the skin may absorb liquid substances1 these being taken up by the blood and lymph vessels1 and perform a respiratory function1 throwing off carbon dioxide4 ,but the most important function of the skin1 in addition to protection1 is that of serving as 99,an ,organ of ,adaptation499--,forming1 as it does1 the boundary between the body and its physical environment1 the skin is perhaps the most important agent through which the body is adapted to its immediate surroundings4 ,evidence of this is found in the great variety of influences which are able to affect the body through their action upon the nerves in the skin1 and in the changes which the epidermis undergoes on exposure4 ,the latter function is especially marked in the lower animals1 the coverings of epidermal tissue 7hair1 scales1 feathers1 etc47 adapting each species to the physical conditions under which it lives4 ,in man the most striking example of adaptation through the skin is seen in the variations in the quantity of blood circulating through it1 corresponding to the changes in the temperature outside of the body4 ,these variations are of great importance1 having to do with the 99,maintenance of the ,normal ,temperature499--,it is necessary to the continuance of life that the temperature of the body be kept at a nearly uniform degree1 called the normal temperature1 which is about #ih4f ,f4 ,the maintenance of the normal temperature depends mainly upon four conditions3 the chemical changes at the cells1 the circulation of the blood1 the nervous system1 and the skin4 ,the chemical changes produce the heat1 the blood in its circulation distributes the heat over the body1 and the nervous system controls the heat-producing and distributing processes 7page #cbj74 ,the skin is the chief means by which the body gets rid of an excess of heat and1 by so doing1 avoids overheating4 7#ia7 99,how the ,skin cools the ,body499--,the skin is a means of ridding the body of an excess of heat in at least two ways3 #a4 ,by the conduction and radiation of heat from its surface as from a stove4 ,this goes on all the time1 but varies with the amount of heat brought to the surface by the blood4 #b4 ,by the evaporation of the perspiration4 ,it is a well-established and easily demonstrated principle that liquids in evaporating use up heat47,see ,practical ,work47 ,it is also a matter of everyday experience that the perspiration has a cooling effect upon the body and that its flow increases with the amount of heat to be gotten rid of4 ,the quantity of perspiration secreted1 and of heat disposed of through its evaporation1 also varies with the amount of blood circulating through the skin4 99,temperature ,regulation by the ,skin499--,variations in the quantity of blood circulating through the skin enable this organ to throw off just the right amount of heat for keeping the body at the normal temperature4 ,if it is necessary for the body to rid itself of an excess of heat1 the quantity of blood circulating in the skin is increased4 ,this brings the blood near the surface1 where more heat can be radiated and where it may cause an increase in the perspiration4 ,on the other hand1 if the body is in danger of losing too much heat1 the circulation diminishes in the skin and increases in the internal organs4 ,this stops the rapid loss of heat from the surface4 ,the skin in this work is of course made to cooperate with other parts of the body4 ,that it is not the only organ concerned in regulating the escape of heat is seen in the results that follow sensations either of chilliness or of heat at the surface4 99,effects of ,heat and ,cold ,sensations499--,sensations1 or feelings1 of heat and cold are made possible through the nerves which connect the brain with the temperature corpuscles1 found in the skin 7page #cdc74 ,as the warm blood recedes from the skin1 a sensation of cold is felt1 but when the blood returns1 there is again the feeling of warmth4 ,the sensation of cold prompts one to seek a warmer place1 or to put on more clothing2 while the sensation of heat1 if it be oppressive1 leads to activities of an opposite kind4 ,prompted in this way by the sensations from the skin1 one voluntarily supplies the external conditions1 such as clothing and heat1 that affect the body temperature4 99,alcohol and the ,regulation of ,temperature499--,alcohol1 through its effect upon the nervous system1 interferes seriously with the regulation of the body temperature4 ,by dilating the capillaries1 it increases the circulation in the skin and leads to an undue loss of heat4 ,at the same time the excess of blood in the skin causes a feeling of warmth which has led to the erroneous belief that alcohol is a heat producer4 ,if taken on a cold day1 it deceives one about his true condition and leads to a wasting of heat when it should be carefully economized4 ,not only is alcohol of no value in maintaining the body temperature1 but if taken during severe exposure to cold1 it becomes a menace to life itself4 ,arctic1 explorers and others exposed to severe cold have found that they withstand cold far better when no alcohol at all is used47#ib7 ,,hygiene ,,of ,,the ,,skin ,much of the hygiene of the skin is included in the problems of keeping it warm and clean4 ,it is kept warm by clothing2 bathing is the method of keeping it clean4 99,clothing99 should be warm and loose-fitting4 ,woolen fabrics are to be preferred in winter to cotton because1 being poorer conductors of heat1 they afford better protection from the cold4 ,but wool fails to absorb the perspiration rapidly from the skin and to pass it to the outside where it is evaporated4 ,this1 together with its tendency to irritate1 makes woolen clothing somewhat objectionable for wearing next to the skin4 ,this objection1 however1 is obviated by woolen underwear which is lined by a thin weaving of cotton4 99,bathing499--,the solid material from the perspiration1 which is left on the skin1 together with the oil from the oil glands and the dirt from the outside1 tends to close up the pores and develop offensive odors4 ,keeping the skin clean is1 for these reasons1 necessary from both a health and a social standpoint4 ,while one should always keep clean1 the frequency of the bath will depend upon the season1 the occupation of the individual1 and the nature and amount of the perspiration4 ,as to the kind of bath to be taken and the precautions to be observed1 no specific rules can be laid down4 ,these must be determined by the facilities at hand and by the health and natural vigor of the bather4 ,severe chilling of the body should be avoided1 especially by those in delicate health4 ,if a hot bath is taken1 one should dash cold water over the body on finishing4 ,one should then quickly dry and rub the body with a coarse towel4 ,the dash of cold water closes the pores of the skin and lessens the liability of taking cold4 99,the ,tonic ,bath499--,the cold bath has been found to have a beneficial effect upon the general health beyond its effect upon the skin4 ,when taken with care as to the length of time and the degree of cold1 decided tonic effects are observed on the circulation and on the nervous system4 ,the rapid changes of temperature vigorously exercise the non-striated muscles of the blood vessels 7page #eg7 and the nerves controlling them4 ,the irritability of the nervous system in general is also lessened4 ,for this reason the cold bath is one of the best means of keeping both mind and body in good condition during the warm months4 ,sponging off the body with cold or tepid water before retiring is also an excellent aid in securing sound sleep during the hot summer nights4 ,danger from the cold bath arises through the shock to the nervous system and the loss of heat from the body4 ,it is avoided by using water whose temperature is not too low and by limiting the time spent in the bath4 ,a brisk rubbing with a coarse towel should always follow the cold bath4 ,people past middle age are1 as a rule1 not benefited by the cold bath2 and those in delicate health1 especially if inclined toward rheumatism1 are likely to be affected injuriously by it4 99,care of the ,complexion499--,a good complexion is a natural accompaniment of good health and depends primarily upon two conditions--a clear skin and an active circulation of the blood through it4 ,clearness of the skin depends largely upon the elimination of waste material from the body1 and where the solid wastes are not effectively removed through the natural channels 7the liver1 kidneys1 and bowels71 blotches1 sallowness of the skin1 and skin eruptions are likely to result4 ,in seeking to clear the complexion1 attention must be given to all those agencies that favor the elimination of waste1 and especially should there be a free and thorough evacuation of the bowels each day4 ,the general health should also be looked after1 attention being given to exercise1 fresh air1 proper food17#ic7 sufficient sleep1 etc4 ,bathing is the chief means employed for increasing the circulation in the skin1 although exercise which is sufficiently vigorous to cause one to perspire freely is a valuable aid4 ,a daily bath of warm or hot water1 finished off with a dash of cold1 followed by a thorough rubbing of the entire surface1 and this by a kneading of the skin with the thumbs and fingers1 will in most cases bring about the desired results4 ,a little olive oil1 thoroughly worked into the skin during the kneading process1 is beneficial where one lacks flesh or where the skin is dry and thin4 ,the olive oil is also beneficial where the baths are exhausting or render one susceptible to cold4 ,in rubbing and kneading1 the skin should not be bruised or irritated4 ,the much advertised complexion beautifiers which are applied directly to the face frequently have the effect of clogging the pores and of causing eruptions of the skin4 ,on the other hand1 certain authorities state that the cold cream preparations may be of advantage in giving the skin a desired softness1 and that when judiciously used 7the face being cleansed after each application7 they do no harm4 ,of the different kinds of face powder those prepared from rice are considered the least injurious4 99,treatment of ,skin ,wounds499--,skin wounds which may not be serious in themselves frequently become so through getting infected with germs4 ,blood poisoning often results from such infections1 one of the worst forms being tetanus1 or lockjaw4 ,a wound should be kept clean1 and if it shows signs of infection1 it should be washed with some antiseptic solution4 ,or1 it may be cleansed with pure warm water and then covered with some antiseptic ointment17#id7 of which there are a number on the market4 ,a weak solution of carbolic acid 7one part acid to twenty-five parts of water7 makes an excellent antiseptic wash4 ,it may be used not only for cleansing wounds1 but also in counteracting the poisonous effects that follow the bites of insects4 ,a wound resulting from the bite of an animal 7cat or dog71 even though slight1 should receive more serious attention1 and as soon as possible after the occurrence4 ,such wounds should be cauterized1 and for this purpose pure carbolic1 acid 7undiluted with water7 may be used4 ,a wooden toothpick is dipped into the acid and this is worked about in the wound4 ,the acid is then washed out with warm water4 ,a deep wound from a rusty nail or a thorn should be treated in the same manner and should be kept open1 not being allowed to heal at the surface first4 ,if one has reason to believe he has been bitten by a mad dog1 the wound should be cauterized as above1 and a physician should be summoned at once4 ,deep wounds from explosives1 or other causes1 should also receive the attention of the physician4 ,many cases of lockjaw result every year from wounds inflicted by the toy pistols1 firecrackers1 etc41 used in our ,fourth of ,july celebrations4 ,these are due to the embedding in the skin or flesh of small solid particles on which are lockjaw germs4 ,wounds of this nature should1 of course1 receive the attention of the physician4 99,care of the ,nails499--,relief from a blood blister under the nail is secured by boring a small hole through the nail with the sharp point of a sterilized penknife 7page #ch74 ,this simple bit of surgery not only relieves the pain1 but is frequently the only means of saving the nail4 ,ingrown toe nails are relieved by scraping a broad strip in the middle of the nail until very thin4 ,this relieves the pressure1 preventing the sides of the nail from being forced into the toe4 ,while the finger nails should be trimmed in a curve1 corresponding to the end of the finger1 it is recommended that the toe nails be cut straight across 7,fig4 #abd71 as this method diminishes the pressure from the shoe and keeps the nails from ingrowing4 ,shoes that pinch the toes should1 of course1 not be worn 7page #bch74 ,fig4 #abd ,fig4 #abd--,proper method of trimming nails of toes4 99,care of the ,hair499--,occasional washing of the hair is beneficial1 but too much wetting causes decay of the hair roots1 which leads to its falling out4 ,the worst enemy of the hair is dandruff4 ,a method of removing dandruff which is highly recommended is that of rubbing olive oil into the scalp and later of removing this with a cleansing shampoo4 ,the olive oil is placed on the scalp with a medicine dropper and thoroughly rubbed in with the fingers4 ,after three or four hours the hair is washed with soap and water 7any good toilet soap will do7 and rinsed with pure water4 ,the hair is then dried1 the surplus water being removed with a coarse towel4 ,where the dandruff is very troublesome1 this treatment may be given once or twice a week2 but in mild cases once a month is sufficient4 ,massage of the scalp1 by increasing the circulation at the hair roots1 is beneficial1 but irritation by a fine-tooth comb1 a stiff hair brush1 or by other means should be avoided4 ,frequent brushing and combing1 however1 are necessary both for the good appearance of the hair and for spreading the oil secreted by the glands at the hair roots4 99,summary499--,the skin forms the external covering of the body and also serves additional purposes4 ,it is a most important agency in adapting the body to its physical surroundings1 as shown by the part which it plays in the regulation of the body temperature4 ,the skin should be kept clean and active1 and skin wounds1 even though small1 should be guarded against infection4 99,exercises499--#a4 ,name an example of each of the protective coverings of the body4 #b4 ,compare the dermis and the epidermis with reference to thickness1 composition1 and function4 #c4 ,to what is the color of the skin due8 ,how is the color of the skin affected by the sunlight8 #d4 ,what modifications of the epidermis are found on our bodies8 ,what are found on the body of a chicken8 #e4 ,what different kinds of protection are provided by the skin8 #f4 ,how does the perspiration cool the body8 #g4 ,what change occurs in the circulation in the skin when the body is becoming too cold8 ,when becoming too warm8 ,what is the purpose of these changes8 #h4 ,how does alcohol cause one to feel warm when he may be losing too much of his heat8 #i4 ,what precaution should be observed by one in poor health1 in taking a bath8 #aj4 ,how may the cold bath be a means of improving the general health8 ,,practical ,,work 99,observations on the ,skin and its ,appendages499--,examine the palm of the hand with a lens4 ,note the small ridges which correspond to the rows of papill beneath the cuticle4 ,in these find small pits1 which are the openings of the sweat glands4 #b4 ,examine the epidermis on the back of the hand and palm4 ,at which place is it thickest and most resisting8 ,is it of uniform thickness over the palm8 ,try picking it with a pin at the thickest place1 noting if pain is felt4 ,inference8 #c4 ,examine a finger nail4 ,is the free edge or the root the thickest8 ,trim closely the thumb nail and the nail of the middle finger of one hand and try to pick up a pin1 or other minute object1 from a smooth1 hard surface4 ,the result indicates what use of the nails8 ,suggest other uses4 #d4 ,examine with a microscope under a low power hairs from a variety of animals1 as the horse1 dog1 cat1 etc41 noting peculiarities of form and surface4 99,to illustrate ,cooling ,effects of ,evaporation499--#a4 ,wet the back of the hand and move it through the air to hasten evaporation4 ,observe that1 as the hand dries1 a sensation of cold is felt4 ,repeat the experiment1 using ether1 alcohol1 or gasolene instead of the water1 noting the differences in results4 ,these liquids evaporate faster than water4 #b4 ,wet the bulb of a thermometer with alcohol or water4 ,move it through the air to hasten evaporation4 ,note and account for the fall of the mercury4 ,,chapter ,,xvii - ,,structure ,,of ,,the ,,nervous ,,system 99,cordination and ,adjustment499--,if we consider for a moment the movements of the body1 we cannot fail to note the coperation of organs1 one with another4 ,in the simple act of whittling a stick one hand holds the stick and the other the knife1 while the movements of each hand are such as to aid in the whittling process4 ,examples of coperation are also found in the taking of food1 in walking1 and in the performance of different kinds of work4 ,not only is coperation found among the external organs1 but our study of the vital processes has shown that the principle of coperation is carried out by the internal organs as well4 ,the fact that all the activities of the body are directed toward a common purpose makes the coperation of its parts a necessity4 ,the term cordination is employed to express this coperation1 or working together1 of the different parts of the body4 ,a further study of the movements of the body shows that many of them have particular reference to things outside of it4 ,in going about one naturally avoids obstructions1 and if anything is in the way he walks around or steps over it4 ,somewhat as a delicate instrument 7the microscope for example7 is altered or adjusted1 in order to adapt it to its work1 the parts of the body1 and the body as a whole1 have to be adjusted to their surroundings4 ,this is seen in the attitude assumed in sitting and in standing1 in the position of the hands for different kinds of work1 in the variations of the circulation of the blood in the skin1 and in the movements for protecting the body47#ie7 99,work of the ,nervous ,system499--,how are the different activities of the body controlled and cordinated8 ,how is the body adjusted to its surroundings8 ,the answer is found in the study of the nervous system4 ,briefly speaking1 the nervous system controls1 cordinates1 and adjusts the different parts of the body by fulfilling two conditions3 #a4 ,it provides a complete system of connections throughout the body1 thereby bringing all parts into communication4 #b4 ,it supplies a means of controlling action 7the so-called impulse7 which it passes along the nervous connections from one part of the body to another4 ,the present chapter deals with the first of these conditions2 the chapter following1 with the second4 99,the ,nerve ,skeleton499--,if all the other tissues are removed1 leaving only the nervous tissue1 a complete skeleton outline of the body still remains4 ,this nerve skeleton1 as it has been called1 has the general form of the framework of bones1 but differs from it greatly in the fineness of its structures and the extent to which it represents every portion of the body4 ,an examination of a nerve skeleton1 or a diagram of one 7,fig4 #abe71 shows the main structures of the nervous system and their connection with the different parts of the body4 ,corresponding to the skull and the spinal column is a central nervous axis1 made up of two parts1 the brain and the spinal cord4 ,from this central axis white1 cord-like bodies emerge and pass to different parts of the body4 ,these are called nerve trunks1 and the smaller branches into which they divide are called nerves4 ,the nerves also undergo division until they terminate as fine thread-like structures in all parts of the body4 ,the distribution of nerve terminations1 however1 is not uniform1 as might be supposed1 but the skin and important organs like the heart1 stomach1 and muscles are the more abundantly supplied4 ,on many of the nerves are small rounded masses1 called ganglia1 and from many of these small nerves also emerge4 ,at certain places the nerves and ganglia are so numerous as to form a kind of network1 known as a plexus4 ,fig4 #abe ,fig4 #abe--99;,diagram of nerve skeleton499 ,the illustration shows the extent and general arrangement of the nervous tissue4 ,a4 ,brain4 ,b4 ,spinal cord4 ,n4 ,nerve trunks and nerves4 ,g4 ,ganglia4 ,it is through these structures--brain and spinal cord1 nerve trunks and nerves1 ganglia and nerve terminations--that connections are established between all parts of the body1 but more especially between the surface of the body and the organs within4 99,the ,neurons1 or ,nerve ,cells499--,while a hasty examination of the nerve skeleton is sufficient to show the connection of the nervous system with all parts of the body1 no amount of study of its gross structures reveals the nature of its connections or suggests its method of operation4 ,insight into the real nature of the nervous system is obtained only through a study of its minute structural elements4 ,these1 instead of being called cells1 as in the case of the other tissues1 are called neurons4 ,the use of this term1 instead of the simpler one of nerve cell1 is the result of recent advances in our knowledge of the nervous system47#if7 ,fig4 #abf ,fig4 #abf--99;,diagram of a mon-axonic neuron99 7greatly enlarged except as to length74 ,the central thread in the axon is the axis cylinder4 ,the neurons are in all respects cells4 ,they differ widely1 however1 from all the other cells of the body and are1 in some respects1 the most remarkable of all cells4 ,they are characterized by minute extensions1 or prolongations1 which in some instances extend to great distances4 ,though the neurons in certain parts of the body differ greatly in form and size from those in other parts of the body1 most of them may be included in one or the other of two classes1 known as mon-axonic neurons and di-axonic neurons4 99,mon-axonic ,neurons499--,neurons of this class consist of three distinct parts1 known as the cell-body1 the dendrites1 and the axon 7,fig4 #abf74 ,the cell-body has in itself the form of a complete cell and was at one time so described4 ,it consists of a rounded mass of protoplasm1 containing a well-defined nucleus4 ,the protoplasm is similar to that of other cells1 but is characterized by the presence of many small granules and has a slightly grayish color4 ,the dendrites are short extensions from the cell-body4 ,they branch somewhat as the roots of a tree and form in many instances a complex network of tiny rootlets4 ,their protoplasm1 like that of the cell-body1 is more or less granular4 ,the dendrites increase greatly the surface of the cell-body1 to which they are related in function4 ,the axon1 or nerve fiber1 is a long1 slender extension from the cell-body1 which connects with some organ or tissue4 ,it was at one time described as a distinct nervous element1 but later study has shown it to be an outgrowth from the cell-body4 ,the mon-axonic neurons are so called from their having but a single axon4 99,di-axonic ,neurons499--,neurons belonging to this class have each a well-defined cell-body and two axons1 but no parts just like the dendrites of mon-axonic neurons4 ,the cell-body is smooth and rounded1 and its axons extend from it in opposite directions 7,fig4 #abg74 ,fig4 #abg ,fig4 #abg--99;,diagram of a di-axonic neuron499 ,the diagram shows only the conducting portion of the axon1 or axis cylinder4 99,structure of the ,axon499--,the axon1 or nerve fiber1 has practically the same structure in both classes of neurons1 being composed in most cases of three distinct parts4 ,in the center1 and running the entire length of the axon1 is a thread-like body1 called the axis cylinder 7,fig4 #abf74 ,the axis cylinder is present in all axons and is the part essential to their work4 ,it may be considered as an extension of the protoplasm from the cell-body4 ,surrounding the axis cylinder is a thick1 whitish-looking layer1 known as the medullary sheath1 and around this is a thin covering1 called the primitive sheath1 or neurilemma4 ,the medullary sheath and the primitive sheath are not1 strictly speaking1 parts of the nerve cell1 but appear to be growths that have formed around it4 ,certain of the axons have no primitive sheath and others are without a medullary sheath47#ig7 99,form and ,length of ,axons499--,where the axons terminate they usually separate into a number of small divisions1 thereby increasing the number of their connections4 ,certain axons are also observed to give off branches before the place of termination is reached 7,fig4 #aca74 ,these collateral branches1 by distributing themselves in a manner similar to the main fiber1 greatly extend the influence of a single neuron4 ,in the matter of length1 great variation is found among the axons in different parts of the body4 ,in certain parts of the brain1 for example1 are fibers not more than one one-hundredth of an inch in length1 while the axons that pass all the way from the spinal cord to the toes have a length of more than three feet4 ,between these extremes practically all variations in length are found4 99,arrangements of the ,neurons499--,nowhere in the body do the neurons exist singly1 but they are everywhere connected with each other to form the different structures observed in the nerve skeleton4 ,two general plans of connection are to be observed1 known as the anatomical and the physiological1 or1 more simply speaking1 as the side-by-side and end-to-end plans4 ,the side-by-side plan is seen in that disposition of the neurons which enables them to form the nerves and the ganglia1 as well as the brain and spinal cord4 ,the end-to-end connections are necessary to the work which the neurons do4 99,side-by-side ,connections499--,on separating the ganglia and nerves into their finest divisions1 it is found that the nerves consist of axons1 while the ganglia are made up mainly of cell-bodies and dendrites4 ,the axons lie side by side in the nerve1 being surrounded by the same protective coverings1 while the cell-bodies form a rounded mass or cluster1 which is the ganglion 7,fig4 #abh74 ,but the axons1 in order to connect with the cell-bodies1 must terminate within the ganglion1 so that they too form a part of it4 ,to some extent1 also1 axons pass through ganglia with which they make no connection4 ,the neurons in the brain and spinal cord also lie side by side1 but their arrangement is more complex than that in the nerves and ganglia4 ,fig4 #abh ,fig4 #abh--99;,diagrams illustrating arrangement of neurons499 ,a1 ,b4 ,ganglia and short segments of nerves4 #a4 ,ganglion4 #b4 ,nerve4 ,in the ganglion of ,a are end-to-end connections of different neurons2 in the ganglion of ,b are the cell-bodies of di-axonic neurons4 ,c4 ,section of a nerve trunk4 #a4 ,epineurium consisting chiefly of connective tissue4 #b4 ,bundles of nerve fibers4 #c4 ,covering of fiber bundle1 or perineurium4 #d4 ,small artery and vein4 ,the side-by-side arrangement of the neurons shows clearly the structure of the ganglia and nerves4 ,the nerve is seen to be a bundle of axons1 or nerve fibers1 held together by connective tissue1 while the ganglion is little more than a cluster of cell-bodies4 ,their connection is necessarily very close1 for the same group of neurons will form1 with their axons1 the nerve1 and1 with their cell-bodies1 the ganglion 7,fig4 #abh74 99,end-to-end ,connections499--,these consist of loose end-to-end unions of the fiber branches of certain neurons with the dendrites of other neurons4 ,the purpose of such connections is to provide the means of communication between different parts of the body4 ,there appears to be no actual uniting of the fiber branches with the dendrites1 but they come into relations sufficiently close to establish conduction pathways1 and these extend throughout the body 7,fig4 #abi74 ,they connect all parts of the body with the brain and spinal cord1 while connections within the brain and cord bring the parts into communication with each other4 ,fig4 #abi ,fig4 #abi--99;,diagram of a nerve path99 starting at the skin1 extending through the spinal cord1 and passing out to muscles4 ,a division of this path also reaches the brain4 99,nature of the ,nervous ,system499--,the nervous system represents the sum total of the neurons in the body4 ,in some respects it may be compared to the modern telephone system4 ,the neurons1 like the electric wires1 connect different places with a central station 7the brain and spinal cord71 and through the central station connections are established between the different places in the system4 ,as the separate wires are massed together to form cables1 the neurons are massed to form the gross structures of the nervous system4 ,the nervous system1 however1 is so radically different from anything found outside of the animal body that no comparison can give an adequate idea of it4 ,we now pass to a study of the gross structures observed in the nerve skeleton4 99,divisions of the ,nervous ,system499--,while all of the nervous structures are very closely blended1 forming one complete system for the entire body1 this system presents different divisions which may1 for convenience1 be studied separately4 ,as physiologists have become better acquainted with the human nervous system1 different schemes of classification have been proposed4 ,the following outline1 based upon the location of the different parts1 presents perhaps the simplest view of the entire group of nervous structures3 ,table 99,the ,central ,division499--,this division of the nervous system lies within the cranial and spinal cavities1 and consists of the brain and the spinal cord4 ,the brain occupying the cranial cavity and the spinal cord in the spinal cavity connect with each other through the large opening at the base of the skull to form one continuous structure4 ,the brain and cord are the most complicated portions of the nervous system1 and the ones most difficult to understand4 ,fig4 #acj ,fig4 #acj--99;,diagram of divisions of brain499 99,the ,brain499--,the brain1 which is the largest mass of nervous tissue in the body1 weighs in the average sized man about #ej ounces1 and in the average sized woman about #dd ounces47#ih7 ,it may be roughly divided into three parts1 which are named from their positions 7in lower animals7 the forebrain1 the midbrain1 and the hindbrain 7,fig4 #acj74 ,the forebrain consists almost entirely of a single part1 known as 99,the ,cerebrum499--,the cerebrum comprises about seven eighths of the entire brain1 and occupies all the front1 middle1 back1 and upper portions of the cranial cavity1 spreading over and concealing1 to a large extent1 the parts beneath4 ,the surface layer of the cerebrum is called the cortex4 ,this is made up largely of cell-bodies1 and has a grayish appearance47#ii7 ,the cortex is greatly increased in area by the presence everywhere of ridge-like convolutions1 between which are deep but narrow depressions1 called fissures4 ,the interior of the cerebrum consists mainly of nerve fibers1 or axons1 which give it a whitish appearance4 ,these fibers connect with the cell-bodies in the cortex 7,fig4 #aca74 ,the cerebrum is a double organ1 consisting of two similar divisions1 called the cerebral hemispheres4 ,these are separated by a deep groove1 extending from the front to the back of the brain1 known as the median fissure4 ,the hemispheres1 however1 are closely connected by a great band of underlying nerve fibers1 called the corpus callosum4 ,fig4 #aca ,fig4 #aca--99,microscope drawing99 of a neuron from cerebral cortex4 a4 ,short segment of the axis cylinder with collateral branches4 ,at the base of the cerebrum three large masses of cell-bodies are to be found4 ,one of these1 a double mass1 occupies a central position between the hemispheres1 and is called the optic thalami4 ,the other two occupy front central positions at the base of either hemisphere1 and are known as the corpora striata1 or the striate bodies4 99,the ,midbrain99 is a short1 rounded1 and compact body that lies immediately beneath the cerebrum1 and connects it with the hindbrain4 ,on account of the great size of the cerebrum1 the midbrain is entirely concealed from view when the other parts occupy their normal positions4 ,however1 if the cerebrum is pulled away from the hindbrain1 it is brought into view somewhat as in ,fig4 #acj4 ,the midbrain carries upon its back and upper surface four small rounded masses of cell-bodies1 called the corpora quadrigemina4 ,the upper two of these bodies are connected with the eyes2 the lower two appear to have some connection with the organs of hearing4 ,on the front and under surface1 the midbrain separates slightly as if to form two pillars1 which are called the crura cerebri1 or cerebral peduncles4 ,these contain the great bundles of nerve fibers that connect the cerebrum with the parts of the nervous system below4 99,the ,hindbrain99 lies beneath the back portion of the cerebrum1 and occupies the enlargement at the base of the skull4 ,it forms about one eighth of the entire brain1 and is composed of three parts--the cerebellum1 the pons1 and the bulb4 99,the ,cerebellum99 is a flat and somewhat triangular structure with its upper surface fitting into the triangular under surface of the back of the cerebrum4 ,it is divided into three lobes--a central lobe and two lateral lobes--and weighs about two and one half ounces4 ,in its general form and appearance1 as well as in the arrangement of its cell-bodies and axons1 the cerebellum resembles the cerebrum4 ,it differs from the cerebrum1 however1 in being more compact1 and in having its surface covered with narrow1 transverse ridges instead of the irregular and broader convolutions 7,fig4 #acb74 99,the ,pons991 or pons ,varolii1 named from its supposed resemblance to a bridge1 is situated in front of the cerebellum1 and is readily recognized as a circular expansion which extends forward from that body4 ,it consists largely of bands of nerve fibers1 between which are several small masses of cell-bodies4 ,the fibers connect with different parts of the cerebellum and with parts above4 ,fig4 #acb ,fig4 #acb--99;,human brain99 viewed from below4 ,c4 ,cerebrum4 ,cb4 ,cerebellum4 ,m4 ,midbrain4 ,p4 ,pons4 ,b4 ,bulb4 ,i-,,xii4 ,cranial nerves4 99,the ,bulb991 or medulla oblongata1 is1 properly speaking1 an enlargement of the spinal cord within the cranial cavity4 ,it is somewhat triangular in shape1 and lies immediately below the cerebellum4 ,it contains important clusters of cell-bodies1 as well as the nerve fibers that pass from the spinal cord to the brain4 99,the ,spinal ,cord499--,this division of the central nervous system is about seventeen inches in length and two thirds of an inch in diameter4 ,it does not extend the entire length of the spinal cavity1 as might be supposed1 but terminates at the lower margin of the first lumbar vertebra47#ajj7 ,it connects at the upper end with the bulb1 and terminates at the lower extremity in a number of large nerve roots1 which are continuous with the nerves of the hips and legs 7,fig4 #acc74 ,two deep fissures1 one in front and the other at the back1 extend the entire length of the cord1 and separate it into two similar divisions4 ,these are connected1 however1 along their entire length by a central band consisting of both gray and white matter4 ,fig4 #acc ,fig4 #acc--99,spinal cord991 showing on one side the nerves and ganglia with which it is closely related in function4 ,a4 ,bulb4 ,b4 ,cervical enlargement4 ,c4 ,lumbar enlargement4 ,d4 ,termination of cord4 ,e4 ,nerve roots that occupy the spinal cavity below the cord4 ,p4 ,pons4 ,d4,g4 ,dorsal root ganglia4 ,s4,g4 ,sympathetic ganglia4 ,n4 ,nerve trunks to upper and lower extremities4 ,the arrangement of the neurons of the spinal cord is just the reverse of that in the cerebrum--the center being occupied by a double column of cell-bodies1 which give it a grayish appearance1 while the fibers occupy the outer portion of the cord1 giving it a whitish appearance4 ,the spinal cord is not uniform in thickness1 but tapers slightly1 though not uniformly1 from the upper toward the lower end4 ,at the places where the nerves from the arms and legs enter the cord two enlargements are to be found1 the upper being called the cervical and the lower the lumbar enlargement4 ,these1 on account of the difference in length between the cord and the spinal cavity1 are above--the lower one considerably above--the places where the limbs which they supply join the trunk 7,fig4 #acc74 99,arrangement of the ,neurons of the ,brain and ,cord499--,the cell-bodies in the brain and spinal cord are collected into groups1 and their fibers extend from these groups to places that may be near or remote4 ,guided by the white and gray colors of the nervous tissue1 and also by the structures revealed by the microscope1 physiologists have made out three general schemes in the grouping of cell-bodies1 as follows3 #a4 ,that of surface distribution1 the cell-bodies forming a thin but continuous layer over a given surface4 ,this is the plan in the cerebrum and cerebellum1 and here are found devices for increasing the surface3 the cerebrum having convolutions1 the cerebellum transverse ridges4 #b4 ,that of collections of cell-bodies into rounded masses4 ,such masses are found in the bulb1 the pons1 the midbrain1 and the base of the cerebrum4 #c4 ,that of arrangement in a continuous column4 ,this is the plan in the spinal cord4 ,it matters not at what place the spinal cord be cut1 a central area of gray matter1 resembling in form the capital letter ,h1 is always found4 ,the fibers connecting with the cell-bodies in the brain and spinal cord are gathered into bundles or tracts1 and these pass through different parts somewhat as follows3 #a4 ,in the cerebrum they extend in three general directions1 forming three classes of fibers4 ,the first connect different localities in the same hemisphere1 and are known as association fibers 7,a1 ,fig4 #acd74 ,the second make connection between the two hemispheres1 and form the corpus callosum4 ,these are known as commissural fibers 7,c1 ,fig4 #acd74 ,the third connect the cerebrum with the parts of the nervous system below1 and are called projection fibers 7,p1 ,fig4 #acd74 #b4 ,in the cerebellum both association and commissural fibers are found4 ,bands of fibers1 passing upward toward the cerebrum and downward toward the cord1 connect this part of the brain with other parts of the nervous system4 ,fig4 #acd ,fig4 #acd--99,semi-diagrammatic representation of a section through the right cerebral hemisphere991 showing fiber tracts4 ,a4 ,association fibers4 ,c4 ,commissural fibers4 ,p4 ,projection fibers4 ,the cell-bodies with which the fiber bundles connect are in the surface layer or cortex4 #c4 ,in the midbrain1 bulb1 and spinal cord fibers are found3 first1 that connect these parts with the cerebrum7#aja7 and cerebellum above2 second1 that pass into and become a part of the nerves of the body2 and third1 that connect the opposite sides of these parts together4 99,the ,peripheral ,division499--,the peripheral division of the nervous system includes all the nervous structures found outside of the brain and spinal cord4 ,these consist of the cranial1 spinal1 and sympathetic nerves1 and of various small ganglia1 all of which are closely connected with the central system4 99,spinal ,nerves and ,dorsal-root ,ganglia499--,the spinal nerves comprise a group of thirty-one pairs1 which connect the spinal cord with different parts of the trunk1 with the upper1 and with the lower extremities4 ,each nerve joins the cord by two roots1 these being named from their positions the ventral1 or anterior1 root and the dorsal1 or posterior1 root4 ,the two roots blend together within the spinal cavity to form a single nerve trunk1 which passes out between the vertebr4 ,on the dorsal root of each spinal nerve is a small ganglion which is named1 from its position1 the dorsal-root ganglion4 7,consult ,figs4 #acc and #ace1 and also ,fig4 #abe47 99,double ,nature of ,spinal ,nerves499--,charles ,bell1 in #ahaa1 made the remarkable discovery that each spinal nerve is double in function4 ,he found the portion connecting with the cord by the dorsal root to be concerned in the production of feeling and the portion connecting by the ventral root to be concerned in the production of motion4 ,in keeping with these functions1 the two divisions of the nerve are made up of different kinds of fibers1 as follows3 #a4 ,the dorsal-root divisions1 of the fibers of di-axonic neurons1 the cell-bodies of which form the dorsal-root ganglia 7,fig4 #ace74 #b4 ,the ventral-root divisions1 of the fibers of mon-axonic neurons1 the cell-bodies of which are in the gray matter of the cord4 ,the first convey impulses to the cord and are called afferent neurons27#ajb7 the second convey impulses from the cord and are known as efferent neurons4 ,thus1 by forming a part of the nerve pathways between the skin and the brain1 the dorsal divisions of these nerves aid in the production of feeling2 and by completing pathways to the muscles1 the ventral divisions aid in the production of motion 7,figs4 #abi1 #ace1 and #ada74 ,fig4 #ace ,fig4 #ace--99;,connection of spinal nerves with the cord499 ,on the right is shown a nerve pathway from the skin to the muscle4 ,a division of this pathway reaches the brain4 99,the ,cranial ,nerves499--,from the under front surface of the brain1 twelve pairs of nerves emerge and pass to the head1 neck1 and upper portions of the trunk4 ,these1 the cranial nerves1 have names suggestive of their function or distribution and1 in addition1 are given numbers which indicate the order in which they leave the brain 7,fig4 #acf74 ,unlike the spinal nerves1 the cranial nerves present great variety among themselves1 scarcely any two of them being alike in function or in their connection with different parts of the body4 ,several of them have to do with the special senses1 and are for this reason very important4 ,they connect the brain with the different parts of the head1 neck1 and trunk1 as follows3 #a4 ,the first pair 7olfactory nerves2 nerves of smell2 afferent7 connect with the mucous membrane of the nostrils 7,fig4 #acf74 #b4 ,the second pair 7optic nerves2 nerves of sight2 afferent7 connect with the retina of the eyes4 #c4 ,the third1 fourth1 and sixth pairs 7motores oculi2 control muscles of the eyes2 efferent7 connect with the internal and external muscles of the eyeballs 7,fig4 #acf74 ,fig4 #acf ,fig4 #acf--99;,diagram suggesting the distribution and functions of the cranial nerves99 7,colton74 ,see also ,fig4 #acb4 #d4 ,the fifth pair 7trigeminal nerves2 nerves of feeling to the face1 of taste to the front of the tongue1 and of control of muscles of mastication2 afferent and efferent7 connect with the skin of the face1 the mucous membrane of the mouth1 the teeth1 and the muscles of mastication4 #e4 ,the seventh pair 7facial nerves2 control muscles that give the facial expressions2 efferent7 connect with the muscles just beneath the skin of the face4 #f4 ,the eighth pair 7auditory nerves2 nerves of hearing2 afferent7 connect with the internal ear4 #g4 ,the ninth pair 7glossopharyngeal nerves2 nerves of taste to back of tongue and of muscular control of pharynx2 afferent and efferent7 connect with the back surface of the tongue and with the muscles of the pharynx4 #h4 ,the tenth pair 7vagus1 or pneumogastric1 nerves2 nerves of feeling and of muscular control2 afferent and efferent7 connect with the heart1 larynx1 lungs1 and stomach4 ,they have the widest distribution of any of the cranial nerves4 #i4 ,the eleventh pair 7spinal accessory nerves2 control muscles of neck2 efferent7 connect with the muscles of the neck4 #aj4 ,the twelfth pair 7hypoglossal nerves2 control muscles of the tongue2 efferent7 connect with the muscles of the tongue4 99,sympathetic ,ganglia and ,nerves499--,the sympathetic ganglia are found in different parts of the body1 and vary in size from those which are half an inch in diameter to those that are smaller than the heads of pins4 ,the largest and most important ones are found in two chains which lie in front1 and a little to either side1 of the spinal column1 and extend from the neck to the region of the pelvis 7,figs4 #abe and #acc74 ,the number of ganglia in each of these chains is about twenty-four4 ,they are connected on either side by the right and left sympathetic nerves which extend vertically from ganglion to ganglion4 ,in addition to the ganglia forming these chains1 important ones are found in the head 7outside of the cranial cavity7 and in the plexuses of the thorax and the abdomen4 ,the sympathetic ganglia receive nerves from the central division of the nervous system1 but connect with glands1 blood vessels1 and the intestinal walls through fibers from their own cell-bodies4 ,some of these latter fibers join the spinal nerves1 and some blend with each other to form small sympathetic nerves4 99,protection of ,brain and ,spinal ,cord499--,on account of their delicate structure1 the brain and spinal cord require the most complete protection4 ,in the first place1 they are surrounded by the bones of the head and spinal column2 these not only shield them from the direct effects of physical force1 but by their peculiar construction prevent1 to a large degree1 the passage of jars and shocks to the parts within4 ,in the second place1 they are surrounded by three separate membranes1 as follows3 #a4 ,the dura1 or dura mater1 a thick1 dense1 and tough membrane which lines the bony cavities and forms supporting partitions4 #b4 ,the pia1 or pia mater1 a thin1 delicate membrane1 containing numerous blood vessels1 that covers the surface of the brain and cord4 #c4 ,the arachnoid1 a membrane of loose texture1 that lies between the dura and the pin4 ,finally1 within the spaces of the arachnoid is a lymph-like liquid which completely envelops the brain and the cord1 and which1 by serving as a watery cushion1 protects them from jars and shocks4 ,thus the brain and cord are directly shielded by bones1 by membranes1 and by the liquid which surrounds them4 ,they are also protected from jars resulting from the movements of the body by the general elasticity of the skeleton4 99,summary499--,the nervous system establishes connections between all parts of the body1 and provides a stimulus by means of which they are controlled4 ,it is made up of a special form of cells1 called neurons4 ,the neurons form the different divisions of the nervous system1 and also serve as the active agents in carrying on its work4 ,through a side-by-side method of joining they form the nerves1 ganglia1 spinal cord1 and brain2 and by a method of end-to-end joining they connect places remote from each other1 and provide for nervous movements through the body4 ,the nervous system1 may in some respects be compared to a complicated system of telephony1 in which the chains of neurons correspond to the wires1 and the brain and spinal cord to the central station4 ,exercises4--#a4 ,give the meaning of the term cordination4 ,supply illustrations4 #b4 ,what two general conditions are supplied in the body by the nervous system8 #c4 ,compare the skeleton outline of the nervous system with the bony skeleton4 #d4 ,sketch outlines of mon-axonic and di-axonic neurons4 #e4 ,give two differences between the neurons and the other cells of the body4 #f4 ,describe the two general methods of connecting neurons in the body4 ,what purpose is accomplished by each method8 #g4 ,name and locate the principal divisions of the nervous system4 #h4 ,draw an outline of the brain 7side view71 locating each of its principal divisions4 #i4 ,if a pencil were placed over the ear1 what portions of the brain would be above it and what below8 #aj4 ,describe briefly the cerebrum1 the cerebellum1 the midbrain1 the pons1 and the bulb4 #aa4 ,locate and describe the cortex4 ,state purpose of the convolutions4 #ab4 ,state the general differences between the cranial and the spinal nerves4 #ac4 ,locate and give the number of the dorsal-root ganglia4 ,locate and give the approximate number of the sympathetic ganglia4 #ad4 ,show how the two portions of the spinal nerves are formed--the one from the mon-axonic and the other from the di-axonic neurons4 #ae4 ,enumerate the different agencies through which the brain and spinal cord are protected4 #af4 ,what cranial nerves contain afferent fibers8 ,what ones contain efferent fibers8 ,what ones contain both afferent and efferent fibers8 #ag4 ,in what respects is the nervous system similar to a system of telephony8 ,in what respects is it different8 ,,practical ,,work ,examine a model of the brain1 identifying the different divisions and noting the position and relative size of the different parts 7,fig4 #acg74 ,observe the convolutions of the cerebrum and compare these with the parallel ridges of the cerebellum4 ,if the model is dissectible1 study the arrangement of the cell-bodies 7gray matter7 and the distribution of the fiber bundles 7white matter74 ,note the connection of the cranial nerves with the under side4 ,fig4 #acg ,fig4 #acg--,model for demonstrating the brain 7dissectible74 ,a prepared nervous system of a frog 7such as may be obtained from supply houses7 should also be examined4 ,observe the appearance and general distribution of the nerves and their connection with the brain and spinal cord4 ,if such a preparation is not at hand1 some small animal may be dissected to show the main divisions of the nervous system1 as follows3 99,dissection of the ,nervous ,system99 7by the teacher74--,for this purpose a half-grown cat is generally the best available material4 ,this should be killed with chloroform and secured to a board as in the dissection of the abdomen 7page #afi74 ,open the abdominal cavity and remove the contents1 tying the alimentary canal where it is cut1 and washing out any blood which may escape4 ,dissect for the nervous system in the following order3 #a4 ,cut away the front of the chest1 exposing the heart and lungs4 ,find on each side of the heart a nerve which passes by the side of the pericardium to the diaphragm4 ,these nerves assist in controlling respiration and are called the phrenic nerves4 ,find other nerves going to different parts of the thorax4 #b4 ,remove the heart and lungs4 ,find in the back part of the thoracic cavity1 on each side of the spinal column1 a number of small knots of nervous matter joined together by a single nerve4 ,these are sympathetic ganglia4 ,where the neck joins the thorax1 find two sympathetic ganglia much larger than the others4 #c4 ,cut away the skin from the shoulder and upper side of the fore leg4 ,by separating the muscles and connective tissue where the leg joins the thorax1 find several nerves of considerable size4 ,these connect with each other1 forming a network called the brachial plexus4 ,from here nerves pass to the thorax and to the fore leg4 #d4 ,from the brachial plexus trace out the nerves which pass to different parts of the fore leg4 ,in doing this separate the muscles with the fingers and use the knife only where it is necessary to expose the nerves4 ,note that some of the branches pass into the muscles1 while others connect with the skin4 #e4 ,remove the skin from the upper portion of one of the hind legs and separate the muscles carefully until a large nerve is found4 ,this is one of the divisions of the sciatic nerve4 ,carefully trace it to the spinal cord1 cutting away the bone where necessary1 and find the connections of its branches with the cord4 ,then trace it toward the foot1 discovering its branches to different muscles and to the skin4 #f4 ,unjoint the neck and remove the head4 ,examine the spinal cord where exposed4 ,cut away the bone sufficiently to show the connection between the cord and one of the spinal nerves4 ,on the dorsal root of one of the nerves find a small ganglion4 ,what is it called8 #g4 ,fasten the head to a small board and remove the scalp4 ,saw through the skull bones in several directions4 ,pry off the small pieces of bones1 exposing the upper surface of the brain4 ,study its membranes1 convolutions1 and divisions4 #h4 ,with a pair of bone forceps1 or nippers1 break away the skull until the entire brain can be removed from the cavity4 ,examine the different divisions1 noting the relative position and size of the parts4 #i4 ,with a sharp knife cut sections through the different parts1 showing the positions of the gray matter and of the white matter4 ,,note4--,if the entire class is to examine one specimen1 it is generally better to have the dissecting done beforehand and the parts separated and tacked to small boards4 ,this will permit of individual examination4 ,sketches of the sciatic nerve1 brachial plexus1 and of sections through the brain and spinal cord should be made4 99,location of ,nerves in the ,body499--,several of the nerves of the body lie sufficiently near the surface to be located by pressure and are easily recognized as sensitive cords4 ,slight pressure from the fingers reveals the presence of nerves in the grooves of the elbow 7the crazy bone71 between the muscles on the inner side of the arm near the shoulder1 and in the hollow part of the leg back of the knee4 ,these are all large nerves4 ,small nerves may be located in the same manner in the face and neck4 ,,chapter ,,xviii - ,,physiology ,,of ,,the ,,nervous ,,system ,in the preceding chapter was pointed out the method by which the different parts of the body are brought into communication by the neurons or nerve cells4 ,we are now to study the means whereby the neurons are made to control and cordinate the different parts of the body and bring about the necessary adjustment of the body to its surroundings4 ,this work of the neurons naturally has some relation to their properties4 99,properties of ,neurons499--,the work of the neurons seems to depend mainly upon two properties--the property of irritability and the property of conductivity4 ,irritability was explained1 in the study of the muscles 7page #bdc71 as the ability to respond to a stimulus4 ,it has the same meaning here4 ,the neurons1 however1 respond more readily to stimuli than do the muscles and are therefore more irritable4 ,moreover1 they are stimulated by all the forces that induce muscular contraction and by many others besides4 ,they are by far the most irritable portions of the body4 ,conductivity is the property which enables the effect of a stimulus to be transferred from one part of a neuron to another4 ,on account of this property1 an excitation1 or disturbance1 in any part of a neuron is conducted or carried to all the other parts4 ,thus a disturbance at the distant ends of the dendrites causes a movement toward the cell-body and1 reaching the cell-body1 the disturbance is passed through it into the axon4 ,this movement through the neuron is called the nervous impulse4 99,purpose of the ,impulse4 99--,though the nature of the nervous impulse is not understood1 7#ajc7 its purpose is quite apparent4 ,it is the means employed by the nervous system for controlling and cordinating the different parts of the body4 ,the arrangement of the neurons enables impulses to be started in certain parts of the nervous system1 and the property of conductivity causes them to be passed as stimuli to other parts4 ,this enables excitation at one place to bring about action at another place4 ,acting as stimuli1 the impulses seem able to produce two distinct effects3 first1 to throw resting organs into action and to increase the activity of organs already at work2 and second1 to diminish the rate1 or check entirely1 the activity of organs4 ,impulses producing the first effect are called excitant impulses2 those producing the second effect1 inhibitory impulses4 99,functions of the ,parts of ,neurons499--,the cell-body serves as a nutritive center from which the other parts derive nourishment4 ,proof of this is found in the fact that when any part of the neuron is separated from the cell-body1 it dies1 while the cell-body and the parts attached to the cell-body may continue to live4 ,in addition to this the cell-body probably renforces the nervous impulse4 ,the dendrites serve two purposes3 first1 they extend the surface of the cell-body1 thereby enabling it to absorb a greater amount of nourishment from the surrounding lymph2 second1 they act as receivers of stimuli from other neurons4 ,the same impulse does not pass from one neuron to another4 ,an impulse in one neuron1 however1 is able to excite the neuron with which it makes an end-to-end connection1 so that a series of impulses is produced along a given nerve path 7,fig4 #abi74 ,the special function of the axon is to transmit the impulse4 ,by its length1 structure1 and property of conductivity it is especially adapted to this purpose4 ,the axis cylinder1 however1 is the only part of the axon concerned in the transmission4 ,the primitive sheath and the medullary layer protect the axis cylinder1 and1 according to some authorities1 serve to insulate it4 ,the medullary sheath may also aid in the nourishment of the axis cylinder4 99,nerve ,stimuli499--,while the properties of irritability and conductivity supply a necessary cause for the production and transmission of nervous impulses1 these alone are not sufficient to account for their origin4 ,an additional cause is necessary--a force not found in the nerve protoplasm1 but one which1 by its action on the protoplasm1 makes it produce the impulse4 ,in this respect1 the neuron does not differ essentially from the cell of a muscle4 ,just as the muscle cell requires a stimulus to make it contract1 so does the neuron require a stimulus to start the impulse4 ,hence1 in accounting for the activities of the body1 it is not sufficient to say they are caused by nervous impulses4 ,we must also investigate the nerve stimuli--the means through which the nervous impulses are started4 ,most of these are found outside of the body and are known as external stimuli4 99,action of ,external ,stimuli499--,in the arrangement of the nervous system the most favorable conditions are provided for the reception of external stimuli4 ,not only do vast numbers of neurons terminate at the surface of the body17#ajd7 but they connect there with delicate structures1 called sense organs4 ,the purpose of the sense organs is to sensitize 7make sensitive7 the terminations of the neurons4 ,this they do by supplying special structures through which the stimuli can act to the best advantage upon the nerve endings4 ,moreover1 there are different kinds of sense organs1 and these cause the neurons to be sensitive to different kinds of stimuli4 ,acting through the sense organs adapted for receiving them1 light1 sound1 heat1 cold1 and odors all act as stimuli for starting impulses4 ,indeed1 the arrangement is so complete that the nervous system is subjected to the action of external stimuli in some form practically all the time4 ,the work of the sense organs is further considered in ,chapters ,,xx1 ,,xxi1 and ,,xxii4 99,how ,external ,stimuli act on ,internal ,organs499--,for stimulating the neurons not connected with the body surface we are dependent1 so far as known1 upon the nervous impulses4 ,an impulse started by the external stimulus goes only so far as its neuron extends4 ,but it serves as a stimulus for the neuron with which the first connects and starts an impulse in this connecting neuron1 the point of stimulation being where the fiber terminations of the first neuron make connection with the dendrites of the second4 ,this impulse in turn stimulates the next neuron1 and so on1 producing a series of impulses along a given nerve path4 ,in this way the effect of an external stimulus may reach and bring about action in any part of the body4 ,this is in brief the general plan of inducing action in the various organs of the body4 ,this plan1 however1 is varied according to circumstances1 and at least three well-defined forms of action are easily made out4 ,these are known as reflex action1 voluntary action1 and secondary reflex action4 99,reflex ,action499--,when some sudden or strong stimulus acts upon the nerve terminations at the surface of the body1 an immediate response is frequently observed in some quick movement4 ,the jerking away of the hand on accidentally touching a hot stove1 the winking of the eyes on sudden exposure to danger1 and the quick movements from slight electrical shocks are familiar examples4 ,the explanation of reflex action is that external stimuli start impulses in neurons terminating at the surface of the body and these1 in turn1 excite impulses in neurons which pass from the spinal cord or brain to the muscles 7,fig4 #ach74 ,since there is an apparent turning back of the impulses by the cord or brain1 the resulting movements are termed reflex47#aje7 ,fig4 #ach ,fig4 #ach--99;,diagram illustrating reflex action of an external organ499 99,reflex ,action and the ,mind499--,if one carefully studies the reflex actions of his own body1 he will find that they occur at the time1 or even a little before the time1 that he realizes what has happened4 ,if a feather is brought in contact with the more sensitive parts of the face of a sleeping person1 there is a twitching of the skin and sometimes a movement of the hand to remove the offending substance4 ,surgeons operating upon patients completely under the influence of chloroform1 and therefore completely unconscious1 have observed strong reflex actions4 ,these and other similar cases indicate clearly that reflex action occurs independently of the mind--that the mind neither causes nor controls it4 ,if a further proof of this fact were needed1 it is supplied by experiments upon certain of the lower animals17#ajf7 which live for a while after the removal of the brain4 ,these experiments show that the nervous impulses that produce reflex action need only pass through the spinal cord and do not reach the cerebrum1 the organ of the mind4 99,the ,reflex ,action ,pathway499--,by study of the impulses that produce any reflex action1 a rather definite pathway may be made out1 having the following divisions3 #a4 ,from the surface of the body to the central nervous system 7usually the spinal cord74 ,this1 the afferent division1 is made up of di-axonic neurons1 and these have 7in the case of the spinal nerves7 their cell-bodies in the dorsal root ganglia 7page #bie74 ,they are acted upon by external stimuli1 while their impulses in turn act on the neurons in the spinal cord4 #b4 ,through the central system 7spinal cord or base of brain74 ,this1 the intermediate division1 may be composed of mon-axonic neurons1 or it may consist of branches from the afferent neurons4 ,in the case of separate neurons1 these are acted upon by impulses from the afferent neurons1 while their impulses serve in turn as stimuli to other neurons within the cord 7,fig4 #abi74 #c4 ,from the central nervous system to the muscles4 ,this1 the efferent division1 is made up of mon-axonic neurons4 ,most of these have their cell-bodies in the gray matter of the cord1 while their fibers pass into the spinal nerves by the ventral roots47#ajg7 ,they may be stimulated by impulses either from the intermediate neurons1 or from branches of the afferent neurons4 ,their impulses reach and stimulate the muscles4 99,reflex ,action in ,digestion499--,the flowing of the saliva1 when food is present in the mouth1 is an example of reflex action4 ,in this case1 however1 the organ excited to activity is a gland instead of a muscle4 ,the food starts the impulses1 and these1 acting through the bulb1 reach and stimulate the salivary glands4 ,in a similar manner food excites the glands that empty their fluids into the stomach and intestines1 and stimulates the muscular coats of these organs to do their part in the digestive process4 ,to a considerable extent1 neurons having their cell-bodies in the sympathetic ganglia are concerned in these actions 7,fig4 #aci74 ,fig4 #aci ,fig4 #aci--;,diagram illustrating reflex action in its relation to the food canal4 ,the nerve path in this case includes sympathetic neurons4 99,reflex ,action in the ,circulation of the ,blood499--,on sudden exposure to cold1 the small arteries going to the skin quickly diminish in size1 check the flow of blood to the surface1 and prevent too great a loss of heat4 ,in this case1 impulses starting at the surface of the body are transmitted to the bulb and then through the efferent neurons to the muscles in the walls of the arteries4 ,in a somewhat similar manner1 heat leads to a relaxation of the arterial walls and an increase in the blood supply to the skin4 ,other changes in the blood supply to different parts of the body are also of the nature of reflex actions4 ,as in the work of digestion1 neurons having their cell-bodies in the sympathetic ganglia aid in the control of the circulation4 99,purposes of ,reflex ,action499--,the examples of reflex action so far considered illustrate its two main purposes--7#a7 protection1 and 7#b7 a means of controlling important processes4 ,the pupil has but to study carefully the reflex actions of his own body for a period1 say of two or three weeks1 in order to be convinced of their protective value4 ,he will observe that portions of his body have1 on exposure to danger1 been moved to places of safety1 while in some instances1 like falling1 his entire body has been adjusted to new conditions4 ,he will also find that reflex action is quicker1 and for that reason offers in some cases better protection1 than movements directed by the mind4 ,in digestion and circulation are found the best examples of the control of important processes through reflex action4 99,voluntary ,action499--,it is observed that reflex action1 in the sense that it has so far been considered1 is not the usual mode of action of the external organs1 but is1 instead1 a kind of emergency action1 due to unusual conditions and excitation by strong stimuli4 ,voluntary actions1 on the other hand1 represent the ordinary1 or normal1 action of these organs4 ,they comprise the movements of the body of which we are conscious and which are controlled by the mind4 ,but while they are of a higher order than reflex actions and are under intelligent direction1 they are brought about in much the same manner4 99,voluntary ,action ,pathways99 differ in but one essential respect from those of reflex action4 ,they pass through the cerebrum1 the organ of the mind 7,fig4 #adj74 ,this is necessary in order that the mind may control the action4 ,from all portions of the body surface1 afferent pathways may be traced to the cerebrum2 and from the cerebrum efferent pathways extend to all the voluntary organs4 ,a complex system of intermediate neurons1 found mostly in the brain1 join the afferent with the efferent pathways4 ,the voluntary pathways are not distinct from1 but include1 reflex pathways1 a fact which explains why the same external stimulus may excite both reflex and voluntary action 7,fig4 #ada74 ,fig4 #adj ,fig4 #adj--99;,diagram of a voluntary action pathway499 99,choice in ,voluntary ,action499--,in reflex action a given stimulus1 acting in a certain way2 produces each time the same result4 ,this is not the case with voluntary action1 the difference being due to the mind4 ,in these actions the external stimulus first excites the mind1 and the resulting mental processes--perhaps as memory of previous experiences--supply a variety of facts1 any of which may act as stimuli to action4 ,before the action takes place1 however1 some one fact must be singled out from among the mental processes excited4 ,this fact becomes the exciting stimulus and leads to action4 ,it follows1 therefore1 that the action which finally occurs is not necessarily the result of an immediate external stimulus1 but of a selected stimulus--one which is the result of choice4 ,fig4 #ada ,fig4 #ada--99;,diagram of voluntary action pathways99 including reflex pathways4 ,not only does the element of choice enter into the selection of the proper stimulus1 but it also enters into the time1 nature1 and intensity of the action4 ,for these reasons it is frequently impossible to trace voluntary actions back to their actual stimuli4 ,the pupil will recognize the element of choice in such simple acts as picking up some object from the street1 complying with a request1 and purchasing some article from a store4 99,reflex and ,voluntary ,action ,compared499--,certain likenesses and differences1 already suggested in these two forms of action1 may now be more fully pointed out4 ,reflex and voluntary action are alike in that the primary cause of each is some outside force or condition which has impressed itself upon the nervous system4 ,they are also alike in the general direction taken by the impulses in producing the action4 ,the impulses are1 first1 from the surface of the body to the central nervous system2 second1 through the central system2 and third1 from the central nervous system to the active tissues of the body4 ,their chief differences are to be found1 first1 in the pathways followed by the impulses1 which are through the cerebrum 7the organ of the mind7 in voluntary action1 but in reflex action are only through the spinal cord or the lower parts of the brain2 and second1 in the fact that voluntary action is under the direction of the mind1 while reflex action is not4 ,it would seem1 therefore1 that the statement sometimes made that voluntary action is reflex action plus the mind is not far from correct4 ,mind1 however1 is the important factor in this kind of action4 99,secondary ,reflex ,action499--,everyday experience teaches that any voluntary action becomes easier by repetition4 ,a given act performed a number of times under conscious direction establishes a condition in the nervous system that enables it to occur without that direction and very much as reflex actions occur4 ,actions of this kind are known as secondary reflex actions1 or as acquired reflexes4 ,walking1 writing1 and numerous other movements pertaining to the occupation which one follows are examples of such reflexes4 ,these activities are at first entirely voluntary1 but by repetition they gradually become reflex1 requiring only the stimulus to start them4 ,the advantages to the body of its acquired reflexes are quite apparent4 ,the mind does not have to attend to the selection and direction of stimuli and1 to that extent1 is left free for other work4 ,a good example of this is found in writing1 where the mind apparently gives no heed to the movements of the hand and is only concerned in what is being written4 ,the student will easily supply other illustrations of the advantages of secondary reflex action4 ,the development of secondary reflexes probably consists in the establishment of fixed pathways for impulses through the nervous system4 ,through the branching of the nerve fibers many pathways are open to the impulses4 ,but in repeating the same kind of action the impulses are guided into particular paths1 or channels4 ,in time these paths become so well established that the impulses flow along them without conscious direction and it is then simply necessary that some stimulus starts the impulses4 ,by following the established pathways1 these reach the right destination and produce the desired result4 ,according to this view1 secondary reflex action is but a higher phase of ordinary reflex action--a kind of reflex action1 the conditions of which have been established by the mind through repetition4 7,see functions of the cerebellum1 page #cag47 99,habits499--,people are observed to act differently when exposed to the same conditions1 or when acted upon by the same stimuli4 ,this is explained by saying they have different habits4 ,by habits are meant certain general modes of action that have been acquired by repetition4 ,certain acts repeated again and again have established conditions in the nervous system which enable definite forms of action to be excited1 somewhat after the manner of reflex action4 ,on account of habits1 therefore1 the actions of the individual are more or less predisposed4 ,what he will do under certain conditions may be foretold from his habits4 ,habits simply represent1 a higher order of secondary reflexes--those more closely associated with the mental life and character than are the lower forms4 ,habits1 in common with other forms of secondary reflex action1 serve the important purpose of economizing the nervous energy4 ,however1 if pernicious habits are formed instead of those that are useful1 they are detrimental from both a moral and physical standpoint4 ,youth is recognized as the period in which fundamental habits are formed and character is largely determined4 ,therefore parents and teachers do wisely when they insist upon the formation of right habits by the young4 99,functions of ,divisions of the ,nervous ,system499--,the relationship between the different parts of the nervous system is very close and one part does not work independently of other parts4 ,at the same time the general work of the nervous system requires that its different divisions serve different purposes3 #a4 ,the peripheral divisions of the nervous system are concerned in the transmission of impulses between the surface of the body and the central system and between the central system and the active tissues4 ,the nerves are the carriers of the impulses4 ,the ganglia contain the cell-bodies which serve as nutritive centers2 and1 in the case of the sympathetic ganglia1 these cell-bodies are the places where the fiber terminations of one neuron connect with1 and stimulate1 other neurons4 #b4 ,the gray matter in the spinal cord1 bulb1 pons1 and midbrain 7through the cell-bodies1 fiber terminations1 and short neurons which they contain7 completes the reflex action pathways between the surface of the body and the voluntary muscles1 and also between the surface of the body and the organs of circulation and digestion4 #c4 ,the white matter of the spinal cord1 bulb1 pons1 and midbrain 7by means of the fibers of which they are largely composed7 forms connections with1 and passes impulses between1 the various parts of the central nervous system4 #d4 ,the bulb1 because of certain special reflex-action pathways completed through it1 is the portion of the central nervous system concerned in the control of respiration1 circulation1 and the secretion of liquids4 99,work of the ,sympathetic ,ganglia and ,nerves499--,the neurons which form these ganglia aid in controlling the vital processes1 especially digestion and circulation4 ,these neurons are controlled for the most part by fibers from the bulb and spinal cord1 and cannot for this reason be looked upon as forming an independent system4 ,their chief purpose seems to be that of spreading the influence of neurons from the central system over a wider area than they would otherwise reach4 ,for example1 a single neuron passing out from the spinal cord may1 by terminating in a sympathetic ganglion1 stimulate a large number of neurons1 each of which will in turn stimulate the cells of muscles or of glands4 ,because of this function1 the sympathetic neurons are sometimes called distributing neurons4 99,functions of the ,cerebellum499--,efforts to discover some special function of the cerebellum have been in the main unsuccessful4 ,its removal from animals1 instead of producing definite results1 usually interferes in a mild way with a number of activities4 ,the most noticeable results are a general weakness of the muscles and an inability on the part of the animal to balance itself4 ,this and other facts1 including the manner of its connection with other parts of the nervous system1 have led to the belief that the cerebellum is the chief organ for the reflex cordination of muscular movements1 especially those having to do with the balancing of the body4 ,in this connection it is subordinate to and under the control of the cerebrum4 ,of the relations which the cerebellum sustains to the cerebrum and to the different parts of the body1 the following view is quite generally held3 ,in the development of secondary reflexes1 as already described1 conditions are established in the cerebellum1 such that given stimuli may act reflexively through it and produce definite results in the way of muscular contraction4 ,after the establishment of these conditions1 afferent impulses from the eyes1 ears1 skin1 and other places1 under the general direction of the cerebrum1 may cause such actions as the balancing of the body1 walking1 etc41 as well as the delicate and varied movements of the hand4 ,this view of its functions makes of the cerebellum the great center of secondary reflex action4 99,functions of the ,cerebrum499--,while the work of the cerebrum is closely related to that of the general nervous system1 it1 more than any other part1 exercises functions peculiar to itself4 ,the cerebrum is the part of the nervous system upon which our varied experiences leave their impressions and through which these impressions are made to influence the movements of the body4 ,but the power to alter1 postpone1 or entirely inhibit1 nervous movements is but a part of the general work ascribed to the cerebrum as the organ of the mind4 ,numerous experiments performed upon the lower animals1 together with observations on man1 show the cerebrum to be the seat of the mental activities1 and to make possible1 in some way1 the processes of consciousness1 memory1 volition1 imagination1 emotion1 thought1 and sensation4 99,localization of ,cerebral ,functions499--,many experiments have been performed with a view to determining whether the entire cerebrum is concerned in each of its several activities or whether special functions belong to its different parts4 ,these experiments have been made upon the lower animals and the results thus obtained compared with observations made upon injured and imperfectly developed brains in man4 ,the results have led to the conclusion that certain forms of the work of the cerebrum are localized and that some of its parts are concerned in processes different from those of others4 ,fig4 #adb ,fig4 #adb--99,location of cerebral functions499 ,diagram of cerebrum1 showing most of the areas whose functions are known4 ,the work of locating the functions of different parts of the cerebrum forms one of the most interesting chapters in the history of brain physiology4 ,the portions having to do with sight1 voluntary motion1 speech1 and hearing have been rather accurately determined1 while considerable evidence as to the location of other functions has been secured4 ,much of the cerebral surface1 however1 is still undetermined 7,fig4 #adb74 ,,nervous ,,control ,,of ,,important ,,processes 99,circulation of the ,blood499--#a4 ,control of the ,heart4--,the ability to contract at regular intervals has been shown to reside in the heart muscle4 ,among other proofs is that furnished by cold-blooded animals1 like the frog1 whose heart remains active for quite a while after its removal from the body4 ,these automatic contractions1 however1 are not sufficient to meet all the demands made upon the circulation4 ,the needs of the tissues for the constituents of the blood vary with their activity1 and it is therefore necessary to vary frequently the force and rapidity of the heart's contractions4 ,such changes the heart itself is unable to bring about4 ,for the purpose of controlling the rate and force of its contractions1 the heart is connected with the central nervous system by two kinds of fibers3 a4 ,fibers that convey excitant impulses to the heart to quicken its movements4 b4 ,fibers that convey inhibitory impulses to the heart to retard its movements4 ,the cell-bodies of the excitant fibers are found in the sympathetic ganglia1 but fibers from the bulb connect with and control them4 ,the cell-bodies of the inhibitory fibers are located in the bulb1 from where their fibers pass to the heart as a part of the vagus nerve4 ,in addition to the fibers above mentioned1 are those that convey impulses from the heart to the bulb4 ,these connect with neurons that in turn connect with blood vessels and with them act reflexively1 when the heart is likely to be overstrained1 to cause a dilation of the blood vessels4 ,this lessens the pressure which the heart must exert to empty itself of blood4 ,these fibers serve1 in this way1 as a kind of safety valve for the heart4 #b4 ,control of ,arteries4--,changes in the rate and force of the heart's contractions can be made to correspond only to the general needs of the body4 ,when the blood supply to a particular organ is to be increased or diminished1 this is accomplished through the muscular coat in the arteries4 ,the connection of the arterial muscle with the sympathetic ganglia and the method by which they vary the flow of blood to different organs has already been explained 7pages #caa and #di71 so that only the location of the controlling neurons need be noted here4 ,these1 like the controlling neurons of the heart1 have their cell-bodies in the bulb4 ,it thus appears that the entire control of the circulation is effected in a reflex manner through the nerve centers in the bulb4 ,these centers are stimulated by conditions that relate to the movement of the blood through the body4 99,respiration499--,efferent fibers connect the different muscles of respiration with a cluster of cell-bodies in the bulb1 called the respiratory center4 ,this center together with the nerves and muscles in question form an automatic1 or self-acting1 mechanism similar in some respects to that of the heart4 ,through the impulses passing from the respiratory center to the muscles1 a rhythmic action is maintained sufficient to satisfy the usual needs of the body for oxygen4 ,the demand of the body for oxygen1 however1 varies with its activities1 and to such variations the respiratory center alone is unable to respond4 ,the regulating factor in the respiratory movements has been found to be the condition of the blood with reference to the presence of oxygen and carbon dioxide4 ,if the blood contains much carbon dioxide and little oxygen1 it acts as a strong stimulus to the respiratory center1 causing it1 in turn1 to stimulate the respiratory muscles with greater intensity and frequency4 ,on the other hand1 if the blood contains much oxygen and little carbon dioxide1 it acts only as a mild stimulus4 ,this explains how physical exercise increases the breathing1 since the muscles at work consume more oxygen than when resting and give more carbon dioxide and other wastes to the blood4 ,the respiratory center is also connected by afferent nerves with the mucous membrane of the air passages4 ,irritation of the nerve endings in this membrane causes impulses to pass to the center1 and this leads1 by reflex action1 to such modifications of the respiratory acts as sneezing and coughing4 ,there is also a connection between the cerebrum and the respiratory center4 ,this is shown by the fact that one can voluntarily change the rate and force of the respiratory movements1 and further by the fact that emotions affect the breathing4 99,regulation of the ,body ,temperature499--,as explained in the study of the skin 7page #bgj71 the nervous system regulates the body temperature by controlling the circulation of the blood through the skin and the internal organs4 ,this is accomplished by stimulating in a reflex manner the muscles in the walls of certain arteries4 ,to prevent the body from getting too hot1 muscles in the arteries going to the skin relax1 thereby allowing more blood to flow to the surface1 where the heat can be disposed of through radiation and through the evaporation of the perspiration4 ,on the other hand1 if the body is in danger of losing too much heat1 the muscles in the walls of arteries going to the skin are made to contract and those to internal organs relax1 so that less blood flows to the skin and more to the internal organs4 ,in this way the nervous system adjusts the circulation to suit the conditions of temperature outside of and within the body and1 in so doing1 maintains the normal body temperature4 99,summary499--,the nervous system is able to control1 cordinate1 and adjust the different organs of the body through its intimate connection with all parts and through a stimulus 7the nervous impulse7 which it supplies and transmits4 ,nervous impulses1 excited by external stimuli1 follow definite paths and cause activity in the different parts of the body4 ,all such pathways are through the central nervous system4 ,in reflex action the impulses are mainly through the spinal cord1 but to some extent through the bulb1 pons1 and midbrain4 ,in voluntary action they pass through the cerebrum--a condition that leads to important modifications in the results4 ,the cerebrum1 in addition to controlling the voluntary movements1 is able to establish the necessary conditions for secondary reflex actions1 such as walking1 writing1 etc4 ,although certain of the divisions of the nervous system exercise special functions1 all parts of it are closely related4 ,exercises4--#a4 ,give the function of each of the parts of a neuron4 #b4 ,state the purpose of the nervous impulse4 #c4 ,show that the exciting cause of bodily action is outside of the nervous system and1 to a large extent1 outside of the body4 #d4 ,describe the arrangement that enables stimuli outside of the body to cause action within the body4 #e4 ,describe a reflex action and show how it is brought about4 #f4 ,distinguish between afferent1 efferent1 and intermediate neurons4 #g4 ,draw diagrams showing the impulse pathways in voluntary and in reflex action4 #h4 ,what purposes are served by the sympathetic neurons8 #i4 ,describe the method of control of the circulatory and digestive processes4 ,how do reflex actions protect the body8 #aj4 ,compare voluntary and reflex action4 ,in what sense are all the activities of the body reflex8 #aa4 ,in what sense is walking voluntary8 ,in what sense is it reflex8 #ab4 ,how does secondary reflex action lessen the work of the nervous system8 #ac4 ,state the special functions of the nerves1 ganglia1 spinal cord1 bulb1 cerebellum1 and cerebrum4 #ad4 ,state the importance of the formation of correct habits4 ,fig4 #adc ,fig4 #adc--,nerve board for demonstrating nerve pathways4 ,,practical ,,work 99,to demonstrate ,nerve ,pathways499--,a smooth board1 #bx#f ft41 is painted black1 and upon this is drawn in white a life-size outline of the body4 ,pieces of cord of different colors and lengths are knotted to represent mon-axonic and di-axonic neurons4 ,these are then pinned or tacked to the board in such a manner as to represent the connections in the different kinds of nerve pathways4 ,fig4 #adc shows such a board with connections for a reflex action and a voluntary action of the same muscle4 99,study of the ,knee ,jerk ,reflex499--,a boy is seated on a chair with the legs crossed4 ,with a small pointer he is given a light1 quick blow on the upper margin of the patella at the point of connection of the tendon4 ,the stroke will usually be followed by a reflex movement of the foot4 ,does this take place independently of the mind8 7,the one upon whom the experiment is being performed should assume a relaxed condition and make no effort either to cause or prevent the movement47 ,can the movement be inhibited 7prevented78 ,repeat the experiment1 effort being made to prevent the movement1 but not by contracting opposing muscles4 ,other reflex actions adapted to class study are those of the eyes1 such as the closing of the lids on moving objects near them and the dilating of the pupils when the eyes are shaded4 ,the involuntary jerking of the head on bringing the prongs of a vibrating tuning fork in contact with the end of the nose is also a reflex action which can be studied to advantage4 99,to determine the ,reaction ,time499--,have several pupils join hands1 facing outwards1 making a complete circle1 excepting one gap4 ,give a signal by touching the hand of one pupil at the end of the line4 ,let this pupil communicate the signal1 by pressure of the other hand1 to the next pupil and so on around1 having the last pupil raise the free hand at close of the experiment4 ,note carefully the time1 preferably with a stop watch1 required to complete the experiment and divide this by the number of pupils1 to get the average reaction time4 ,the experiment may be repeated with boys only and then with girls1 comparing their average reaction time4 99,reflex ,action of the ,salivary ,glands499--,place a small pinch of salt upon the tongue and note the flow of saliva into the mouth4 ,try other substances1 as starch1 bits of wood1 and sugar4 ,what appears to be the natural stimulus for these glands8 ,compare with reflex actions of the muscles4 ,,chapter ,,xix - ,,hygiene ,,of ,,the ,,nervous ,,system ,the far-reaching effects and serious nature of disorders of the nervous system are sufficient reasons for considering carefully those conditions that make or mar its efficiency4 ,controlling all the activities of the body and affecting through its own condition the welfare of all the organs1 the hygiene of the nervous system is1 in a large measure1 the hygiene of the entire body4 ,moreover1 it is known that some of our worst diseases1 including paralysis and insanity1 are disorders of the nervous system and are prevented in many instances by a proper mode of living4 99,the ,main ,problem499--,many of our nervous disorders are undoubtedly due to the age in which we live4 ,our modern civilization1 with all its facilities for human advancement and enjoyment1 throws an extra strain upon the nervous system4 ,educational and social standards are higher than ever before and life in all its phases is more complex4 ,since we can hardly change the conditions under which we live1 and probably would not if we could1 we must learn to adapt or adjust ourselves to them so as to secure for the nervous system such relief as it requires4 ,this adjustment is sometimes difficult1 even when the actual needs of the nervous system are known4 ,the healthful action of the nervous system requires1 on the one hand1 exercise1 but on the other hand1 a certain condition of quietude1 or poise--a state which is directly opposed to that of restlessness4 ,the conditions of modern life seem able to force upon the nervous system all the exercise that it needs1 and more 7whether it be of the right kind or not71 so that the main problem of to-day seems to be that of conserving1 or economizing1 the nervous energy and of preventing nervous waste4 99,wasteful ,forms of ,nervous ,activity499--,there are without doubt many forms of activity that waste the vital forces of the body and lead to nervous exhaustion4 ,take1 for example1 the rather common habit of worrying over the trivial things of life4 ,certainly the nervous energy spent in this way cannot be used in doing useful work1 but must be counted as so much loss to the body4 ,one who would use his nervous system to the best advantage must find some way of preventing waste of this kind47#ajh7 ,undue excitement1 as well as pleasurable dissipations1 also tend toward nervous exhaustion4 ,and while the fact is recognized that pleasurable activities supply a necessary mental exercise1 the limit of healthful endurance must be watched and excesses of all kinds avoided4 ,intense emotional states are found to be exhausting in the extreme2 and the suppression of such undesirable feelings as anger1 fear1 jealousy1 and resentment are of immense value in the hygiene of the nervous system4 99,the ,habit of ,self-control499--,much of the needless waste of nervous energy1 including that of worrying over trivial matters1 may be prevented through the exercise of self-control4 ,from the standpoint of the nervous system1 the present age differs from the past mainly in supplying a greater number and variety of nerve stimuli4 ,self-control means the ability to suppress activities that would result from undesirable stimuli and to direct the bodily activities into channels that are profitable4 ,self-control1 therefore1 is not only to be exercised on occasions of great emergency1 but in the everyday affairs of life as well4 ,it is even more important that the daily toiler at his task be able to keep the petty annoyances of life from acting as irritants to his nervous system than that he keep cool during some great calamity4 ,the habit of self-control is acquired mainly through the persistent effort to prevent any and all kinds of petty annoyances from affecting the nerves or the temper4 99,nervousness499--,self-control is much more easily practiced by some than by others4 ,this is due partly to habit1 but is also due to an actual difference in the degree of sensitiveness1 or irritability1 of the nervous systems of different people4 ,one whose nervous system tends to respond too readily to any and all kinds of stimuli is said to be nervous4 ,this condition is in some instances inherited1 but is in most cases due to the wasteful expenditure of nervous energy or to the action of some drug upon the body4 ,excess of mental work1 too much reading1 long-continued anxiety1 eye strain1 and the use of tea1 coffee1 alcohol1 tobacco1 or other drugs1 including many of those taken as medicines1 are known to cause nervousness4 ,nervousness is not only a source of great annoyance1 both to one's self and to others1 but is a menace to the general health4 ,the first step toward securing relief from such a condition is the removal of the cause4 ,the habits should be inquired into and excesses of all kinds discontinued4 ,in some instances it may be necessary to have the eyes examined and glasses fitted by a competent oculist47#aji7 ,the nervous energy should be carefully economized and the habit of self-control diligently cultivated4 ,special exercises that have for their purpose the equalizing of the circulation and the strengthening of the blood vessels of the neck and the brain also have beneficial effects4 99,nervous ,overstrain499--,both mental and physical overwork tends to weaken the nervous system and to produce nervousness4 ,where hard mental work is long continued1 or where it is carried on under excitement1 a tense nervous condition is developed which is decidedly weakening in its effects4 ,the causes which lead to such a condition1 and in fact overwork of all kinds1 should if possible be avoided4 ,where this is not possible1 and in many cases it is not1 the period of overwork should be followed by one of rest1 recreation1 and plenty of sleep4 ,to the overworked in body or in mind1 nothing is more important from a hygienic1 as well as moral1 standpoint1 than the right use of the one rest day in seven4 ,the best interests of our modern civilization require that the ,sabbath be kept as a quiet1 rest-giving day4 99,disturbed ,circulation of the ,brain499--,nervousness not infrequently is accompanied by an increase in the circulation of the brain and disappears when this condition is relieved4 ,though mental work and excitement tend naturally to increase the circulation in the brain1 this should subside with rest and relief from excitement4 ,when there is a tendency for this condition to become permanent1 effort should be made looking for relief4 ,increasing the circulation in the lower extremities by hot or cold foot baths1 or by much walking1 is found to be most beneficial4 ,special exercises of the muscles of the neck are also recommended as a means of relieving this condition47#aaj7 99,hygienic ,value of ,work499--,within reasonable limits1 both mental and physical work are conducive to the vigor of the nervous system4 ,through work the energies of the body find their natural outlet1 and this prevents dissipation and the formation of bad habits4 ,even hard work does not injure the nervous system1 and severe mental exertion may be undergone1 provided the proper hygienic conditions are observed4 ,the nervous disorders suffered by brain workers are not1 as a rule1 due to the work which the brain does1 but to violation of the laws of health1 especially the law of exercise4 ,such persons should observe the general laws of hygiene and especially should they practice daily those forms of physical exercise that tend to counteract the effects of mental work4 99,physical ,exercise99 properly taken is beneficial to the nervous system through both direct and indirect effects4 ,a large proportion of the nerve cells have for their function the production of motion1 and these are called into play only through muscular activity4 ,then1 as already suggested1 physical exercise counteracts the unpleasant effects of mental work4 ,hard study causes an excess of blood to be sent to the brain and a diminished amount to the arms and to the legs4 ,physical exercise redistributes the blood and equalizes the circulation4 ,light exercise should1 therefore1 follow hard study4 ,the student before retiring at night is greatly aided in getting to sleep and is put in a better condition for the next day's work by ten to fifteen minutes of light gymnastics4 ,a daily walk of two or three miles is also an excellent means of counteracting the effects of mental work4 ,the brain worker should1 however1 avoid violent exercise or the carrying of any kind of exercise to exhaustion4 99,sleep991 and plenty of it1 is one of the first requirements of the nervous system4 ,it is during sleep that the exhausted brain cells are replenished4 ,to shorten the time for sleep is to weaken the brain and to lessen its working force4 ,no one should attempt to get along with less than eight hours of sleep each day and most people require more4 ,children require more sleep than adults4 ,those under six years should have from eleven to twelve hours of sleep per day4 ,children between six and ten years should have at least ten hours4 99,insomnia991 or sleeplessness1 on account of its effects upon the nervous system1 is to be regarded as a serious condition1 and hygienic means for relieving it should be diligently sought4 ,having its cause in nervousness1 a disturbed circulation of the brain1 or some form of nervous exhaustion1 it is benefited through relieving these conditions and in the manner already described4 ,of course the external conditions for aiding sleep should not be overlooked4 ,the bed should be comfortable1 and the room should be cool1 well ventilated1 dark1 and quiet4 ,the inducing of sleep by means of drugs is a dangerous practice and should never be resorted to except under the direction of the physician4 99,effects of ,heat and ,cold499--,heat and cold both have their effects upon the nervous system4 ,heat increases the nervous irritability1 while cold acts as a natural sedative to the nerves4 ,a nervous person is made more nervous by an overheated atmosphere1 but derives beneficial effects from exposing the body freely to cold air and water4 ,the tonic cold bath 7page #bgc71 if taken with the usual precautions1 can be used to good advantage in diminishing nervousness4 ,the taking of outdoor exercise in cold weather is1 for the same reason1 an excellent practice4 99,effect of ,emotional ,states499--,we have already noted the effect of certain emotional states upon the digestion of the food 7page #afb74 ,emotional states are also known to interfere with breathing and with the action of the heart4 ,such effects are explained through the close relation of the mind to the work of the nervous system in general4 ,while certain emotional states1 such as fear1 anger1 melancholia1 and the impulse to worry1 interfere seriously with the normal action of the nervous system1 others1 such as contentment1 cheerfulness1 and joy1 are decidedly beneficial in their effects4 ,how important1 then1 is the habit of suppressing the states that are harmful and of cultivating those that are beneficial4 ,from a hygienic1 as well as social1 standpoint a cheerful1 happy disposition is worth all the effort necessary for its attainment4 99,the ,nervous ,condition of ,children99 should be a matter of deep concern on the part of both parents and teachers4 ,in the home1 as well as in the school1 the child may be pushed until the nervous system receives permanent injury4 ,exhaustion of nerve cells is produced through too many and too vivid impressions being made upon the immature brain4 ,the child should be protected from undue excitement4 ,he should have the benefit of outdoor exercise and should be early inured to cold4 ,he should be shielded from the poisoning effects of tea1 coffee1 tobacco1 alcohol1 and other drugs4 ,he should have impressed upon him the habit of self-control4 ,he should not be indulged in foolish caprices or whims1 but should be taught to be content with plain1 wholesome food and with the simple forms of enjoyment4 99,influences at ,school499--,school life is necessarily a great strain upon the child4 ,night study added to the work of the day makes a heavy burden for elementary pupils to bear4 ,though the legal school age is usually fixed at six years1 delicate children should be kept out of school until they are seven or eight years old1 provided they have good homes4 ,in addition to the excitation incident to studying and reciting lessons1 conditions frequently arise both in the schoolroom and upon the playground that create a feeling of fear or dread in the minds of children4 ,quarrels and feuds among the children and the bullying of big boys on the playground may work untold harm4 ,all conditions tending to develop fear1 uneasiness1 or undue excitement on the part of children should receive the attention of those in authority4 99,excessive ,reading99 is a frequent cause of injury to the nervous systems of children4 ,this has a bad effect1 both on account of too many impressions being made upon the mind and also on account of the strain to the eyes4 ,then if the reading consists mostly of light fiction1 the mind is directed away from the really important things of life4 ,the reading of children should be thoughtfully controlled1 both as to quality and quantity4 ,exciting stories should1 as a rule1 be excluded1 but a taste for biography1 historical and scientific writings1 and for the great works of literature should be cultivated4 ,simple fairy tales which have a recognized value in developing the imagination of the child need not be omitted1 but it is of vital importance that the story-reading habit be not formed4 99,effects of ,drugs499--,because of its delicacy of structure a number of chemical compounds1 or drugs1 are able to produce injurious effects upon the nervous system4 ,some of these are violent poisons1 while others1 in small quantities1 are mild in their action4 ,certain drugs1 in addition to their immediate effects1 bring about changes in the nervous system which cause an unnatural appetite1 or craving1 that leads to their continued use4 ,this is the case with alcohol1 the intoxicating substance in the usual saloon drinks1 and with nicotine1 the stimulating drug in tobacco4 ,the same is also true of morphine1 chloral1 and several other drugs used as medicines4 ,the danger of becoming a slave to some useless and pernicious habit should dissuade one from the use of drugs except in cases of positive emergency4 99,alcohol and the ,nervous ,system499--,alcohol1 as already shown1 injures practically all portions of the body2 but it has its worst effects upon the nervous system4 ,through its action on this system1 it interferes with the circulation of the blood1 produces a condition of temporary insanity called intoxication1 weakens the will1 and eventually dethrones the reason4 ,worst of all1 it produces a condition of chronic poisoning which manifests itself in an unnatural craving1 and this causes it to be used by the victim even when he knows he is drinking to his own destruction4 ,though its use in small quantities does not1 as a rule1 produce such marked effects upon the nervous system1 it develops the craving1 and this is apt in time to lead to its use in larger quantities4 ,but even if this does not occur1 the practice is objectionable for its unhygienic effects in general47#aaa7 ,tippling with such mild solutions of alcohol as light wine1 beer1 and hard cider is1 for these reasons1 a dangerous pastime4 99,alcohol and ,crime499--,it is sometimes stated that no one who leaves alcohol alone will be injured by it4 ,this is true only of its direct effects2 not of its indirect effects4 ,whenever a crime is committed somebody is injured1 and alcohol is known to be a chief cause of crime4 ,alcohol causes crime through the loss of self-control1 seen especially in intoxication1 and also because of the moroseness and quarrelsomeness which it developes in certain individuals4 ,indirectly it causes crime through the poverty which it engenders and through its influence in bringing about social conditions out of which crime develops4 ,everything considered1 the free use of alcohol is incompatible with the nervous health and moral tone of a community4 99,nicotine and the ,nervous ,system499--,nicotine is an oily substance which is extracted from the tobacco plant4 ,its action on the nervous system is in general that of a poison4 ,taken in small quantities1 it is a mild stimulant and1 if the doses are repeated1 a habit is formed which is difficult to break4 ,tobacco is used mainly for the stimulating effect of this drug4 ,while not so serious in its results as the alcohol and other drug habits1 the use of tobacco is of no benefit1 is a continual and useless expense1 and1 in many instances1 causes a derangement of the healthy action of the body47#aab7 ,with the bad effects of the nicotine must be included those of questionable substances added to the tobacco by the manufacturer1 either for their agreeable flavor or for adulteration4 99,relation of ,age to the ,effects of ,nicotine499--,the use of tobacco by the young is especially to be deplored4 ,in addition to the harmful effects observed in those of mature years1 nicotine interferes with the normal development of the body and lays1 in many instances1 the foundation for physical and mental weakness in later life4 ,the cigarette is decidedly harmful1 especially when inhalation is practiced1 its deadening effects being in part due to the wrappers1 some of which have been shown to contain arsenic and other poisonous drugs4 ,while dulling the intellect and weakening the body1 cigarette smoking also tends to make criminals of boys47#aac7 ,parents1 teachers1 school officers1 and all who have the good of mankind at heart should take every precaution1 including that of setting a good example1 to prevent the formation of the tobacco habit by those of immature years4 99,habit versus ,self-control499--,the power of self-control1 already emphasized for its importance in the economical expenditure of the nervous energy1 is of vital importance in its relation to the habits of the body4 ,self-control is the chief safeguard against the formation of bad habits and is the only means of redemption from such habits after they have once been formed4 ,the persistent cultivation of the power to control the appetites and the passions1 as well as all forms of activity which tend to injure the body or debase the character1 gives a tone to the nervous system which increases the self-respect and raises the individual to a higher plane of life4 ,the worst habits can be broken and good ones formed in their stead1 if only there is sufficient determination to accomplish these results4 ,failure comes from not having the mind thoroughly made up and from not having1 back of the desire to do better1 the strong will of a righteous determination4 99,effects of ,external ,conditions499--,while the inner life and habits have most to do with the hygiene of the nervous system1 a certain amount of attention may properly be given to those conditions outside of the body which affect directly or indirectly the state of this system4 ,noise1 disorder1 and confusion act as nervous irritants1 but quiet1 order1 and system have the opposite effect4 ,there is1 therefore1 much in the management of the office1 factory1 schoolroom1 or home that has to do with the real hygiene of the nerves as well as with the efficiency of the work that is being done4 ,the suppression of distracting influences not only enables the mind to be given fully to the work in hand1 but actually prevents waste of nervous energy4 ,although the responsibility for securing the best conditions for work rests primarily with those in charge1 it is also true that each individual in every organization may contribute to the order or disorder that prevails4 99,social ,relations499--,in considering the external conditions that affect the nervous system1 the fact must not be overlooked that man is a social being and has to adjust himself to an established social order4 ,his relations to his fellow-men1 therefore1 affect strongly his nervous condition and theirs also4 ,for this reason the best hygiene of the nervous system is based upon moral as well as physical right living4 ,along with the power of self-control and the maintenance of a correct nervous poise1 there should be a proper regard for the welfare of others4 ,on account of the ease with which one individual may disturb the nervous state of another1 those social forms and customs which tend to establish harmonious relations among men are truly hygienic in their effects1 and may well be carried out in spirit as well as in letter4 ,it is also a fact that a given mental state in one person tends to excite a like state in those with whom he associates4 ,how important1 then1 that each and all cultivate1 as habits1 the qualities of cheerfulness1 kindness1 and good-will1 instead of the opposite states of mind4 ,especially in the family1 and other groups of closely associated individuals1 should the nervous effect of one member upon the others be considered and every effort made to secure and maintain harmonious relations4 99,the ,high ,ideal499--,everything considered1 the conditions most favorable to the healthfulness of the nervous system are in harmony with what our greatest teachers have pointed to as the higher plane of living4 ,on this account a true conception of the value and meaning of life is of the greatest importance4 ,an ever present1 strong desire to live a vigorous1 but simple and noble1 life will suggest the proper course to pursue when in doubt and will stimulate the power of self-control4 ,it will lead to the stopping of nerve leaks and to the maintenance of harmonious relations with one's fellows4 ,it will cause one to recoil from the use of alcohol and other nerve poisons1 as from a deadly serpent1 seeing the end in the beginning1 and will be the means eventually of leading the body into its greatest accomplishments4 99,summary499--,the nervous system1 on account of its delicate structure1 is liable to injury through wrong methods of using it and also through the introduction of drugs1 or poisons1 into the body4 ,there are also found in our methods of living and systems of education conditions that tend to waste the nervous energy4 ,to protect the nervous system from all these threatened dangers requires1 among other things1 the power of self-control4 ,this enables the individual to direct his life according to his highest ideals and to free himself from habits known to be injurious4 ,children must have their nervous systems safeguarded by parents and teachers4 ,especially must they be kept from becoming enslaved to some drug1 such as alcohol or the nicotine of tobacco4 99,exercises499--#a4 ,in what respect is the hygiene of the nervous system the hygiene of the entire body8 #b4 ,of what value in the hygiene of the nervous system is the power of self-control8 ,how is the habit of self-control formed8 #c4 ,name several forms of activity that waste the nervous energy4 #d4 ,name several influences that react unfavorably on the nervous systems of children4 #e4 ,how may too much reading prove injurious to the nervous system8 #f4 ,what forms of physical exercise are beneficial to the brain worker8 #g4 ,why is the use of alcohol even in small quantities to be regarded as a dangerous practice8 #h4 ,name several causes of nervousness4 #i4 ,what are the unanswerable arguments for preventing the use of tobacco by the young8 #aj4 ,why do cigarettes have a more harmful effect upon the body than other forms of tobacco8 #aa4 ,enumerate conditions in the schoolroom that dissipate the nervous energy of pupils2 that economize it4 ,,chapter ,,xx - ,,production ,,of ,,sensations ,our study of the nervous system has shown that impulses arising at the surface of the body are able1 through connecting neurons1 to bring about various activities4 ,moving along definite pathways1 they induce motion in the muscles1 and in the glands the secretion of liquids4 ,it is now our purpose to consider the effect produced by afferent impulses upon the brain and1 through the brain1 upon the mind47#aad7 ,this effect is manifested in a variety of similar forms1 known as 99,the ,sensations499--,sensations constitute the lowest forms of mental activity4 ,roughly speaking1 they are the states of mind experienced as the direct result of impulses reaching the brain4 ,in a sense1 just as impulses passing to the muscles cause motion1 impulses passing to the brain cause sensations4 ,the feeling which results from the hand's touching a table is a sensation and so also is the pain which is caused by an injury to the body4 ,the mental action in each case is due to impulses passing to the brain4 ,care must be exercised by the beginner1 however1 not to confuse sensations with the nervous impulses1 on the one hand1 or with secondary mental effects1 such as emotion or imagination1 on the other4 ,sensations are properly regarded as the first conscious effects of the afferent impulses and as the beginning stage in the series of mental processes that may take place on account of them4 ,in some way1 not understood1 the mind associates the sensation with the part of the body from which the impulses come4 ,pain1 for example1 is not felt at the brain where the sensation is produced1 but at the place where the injury occurs4 ,this association1 by the mind1 of the sensations with different parts of the body1 is known as localizing the sensation4 99,sensation ,stimuli499--,while the sensations are dependent upon the afferent impulses1 the afferent impulses are in turn dependent upon causes outside of the nervous system4 ,if these are removed1 the sensations cease and they do not start up again unless the exciting influences are again applied4 ,any agency1 such as heat or pressure1 which1 by acting on the neurons of the body1 is able to produce a sensation1 may be called a sensation stimulus4 ,it has perhaps already been observed that the stimuli that lead to voluntary action1 as well as those that produce reflex action of the muscles1 cause sensations at the same time4 ,from this we may conclude that sensation stimuli are the same in character as those that excite motion4 ,on the other hand1 it should be noted that sensations are constantly resulting from stimuli that are of too mild a nature to cause motion4 99,classes of ,sensations499--,perhaps as many as twenty distinct sensations1 such as pain1 hunger1 touch1 etc41 are recognized4 ,if these are studied with reference to their origin1 it will be seen that some of them result from the action of definite forms of stimuli upon the neurons terminating in sense organs2 while the others1 as a rule1 arise from the action of indefinite stimuli upon neurons in parts of the body that do not possess sense organs4 ,the members of the first class--and these include the sensations of touch1 temperature1 taste1 smell1 hearing1 and sight--are known as the special sensations4 ,the others1 including the sensations of pain1 hunger1 thirst1 nausea1 fatigue1 comfort1 discomfort1 and those of disease1 are known as organic1 or general1 sensations4 ,these two classes of sensations differ in their purpose in the body as well as in the manner of their origin4 99,purposes of ,sensations499--,any given sensation is related to the stimulus which excites it as an effect to a cause4 ,it starts up or stops1 increases in intensity or diminishes1 according to the action of the exciting stimulus4 ,as the stimuli are outside of the nervous system1 and in the majority of cases outside of the body1 the sensations indicate to the mind what is taking place either in the body itself or in its surroundings4 ,they supply1 in other words1 the means through which the mind acquires information4 ,by means of the special sensations1 a knowledge of the physical surroundings of the body is gained1 and through the organic sensations the needs of the body and the state of the various organs are indicated4 ,in general1 sensations are made to serve two great purposes in the body1 as follows3 #a4 ,they provide the necessary conditions for intelligent and purposeful action on the part of the body4 #b4 ,they supply the basis for the higher mental activities1 as perception1 memory1 thought1 imagination1 and emotion4 ,intelligent action is impossible without a knowledge both of the bodily organs and of the body's surroundings4 ,protection and the regulation of the work of an organ necessitate a knowledge of its condition1 while the adapting and adjusting of the body to its surroundings require a knowledge of what those surroundings are4 ,the dependence of all the higher forms of mental activity upon sensations is recognized by psychologists and is easily demonstrated by a study of the manner in which we acquire knowledge4 ,without sensation there can be no thought4 99,steps in the ,production of ,sensations499--,the steps in the production of sensations are not essentially different from those in the production of reflex action4 ,first of all1 external stimuli act upon the fiber terminations in the sense organs1 or elsewhere1 starting impulses in the neurons4 ,these pass into the central nervous system and there excite neurons which in turn discharge impulses into the cerebrum4 ,the result is to arouse an activity of the mind--a sensation4 ,the steps in the production of any special sensation naturally involve the following parts3 #a4 ,a sense organ where the terminations of the neurons are acted upon by the stimulus4 #b4 ,a chain of neurons which connect the sense organ with the brain4 #c4 ,the part of the cerebrum which produces the sensation4 99,sense ,organs499--,the sense organs are not parts of the afferent neurons1 but are structures of various kinds1 in which the neurons terminate4 ,their function is to enable the sensation stimuli to start the impulses4 ,by directing1 concentrating1 or controlling the stimuli1 the sense organs enable them to act to the best advantage upon the neurons4 ,when it is recognized that such widely different forces as light waves1 sound waves1 heat1 pressure1 and odors are enabled by them to stimulate neurons1 the importance of these organs becomes apparent4 ,as would naturally be inferred1 the construction of any sense organ has particular reference to the nature of the stimulus which it is to receive4 ,this is most apparent in the sense organs of sight and hearing4 99,simple ,forms of ,sense ,organs499--,the simplest form of a sense organ 7if such it may be called7 is one found among the various tissues4 ,it consists of the terminal branches of nerve fibers which spread over a small area of cells1 as a network or plexus4 ,such endings are numerous in the skin and muscles4 ,next in order of complexity are the so-called end-bulbs4 ,these consist of rounded1 or elongated1 connective tissue capsules1 within which the nerve fibers terminate4 ,on the inside the fibers lose their sheaths and divide into branches1 which wind through the capsule4 ,end-bulbs are abundant in the lining membrane of the eye1 and are found also in the skin of the lips and in the tissues around the joints4 ,slightly more complex than the end-bulbs are the touch corpuscles4 ,these are elongated bulb-like bodies1 having a length of about one three-hundredth of an inch1 and occupying the papill of the skin 7,fig4 #add74 ,they are composed mainly of connective tissue4 ,each corpuscle receives the termination of one or more nerve fibers4 ,these1 on entering1 lose the medullary sheath and separate into a number of branches that penetrate the corpuscle in different directions4 ,fig4 #add ,fig4 #add--99;,a touch corpuscle99 highly magnified4 7,see text47 ,the largest of the simple forms of sense organs are bodies visible to the naked eye and called1 from their discoverer ,pacini1 the ,pacinian corpuscles4 ,they lie along the course of nerves in many parts of the body1 and have the general form of grains of wheat4 7,see ,practical ,work47 ,the ,pacinian corpuscles are composed of connective tissue arranged in separate layers around a narrow central cavity called the core 7,fig4 #ade74 ,within the core is the termination of a large nerve fiber4 ,these corpuscles are found in the connective tissue beneath the skin1 along tendons1 around joints1 and among the organs of the abdominal cavity4 ,fig4 #ade ,fig4 #ade--99,pacinian corpuscle991 magnified4 ,a4 ,medullated nerve fiber4 ,b4 ,axis cylinder terminating in small bulb at ,c4 ,d4 ,concentric layers of connective tissue4 ,e4 ,inner bulb4 ,the simple forms of sense organs have a more or less general distribution over the body1 and are concerned in the production of at least three special sensations4 ,these are touch1 temperature1 and the muscular sensation4 99,touch991 or feeling1 is perhaps the simplest of the sensations4 ,the sense organs employed are the touch corpuscles1 and the external stimulus is some form of pressure or impact4 ,pressure applied to the skin1 by acting on the fiber terminations in the corpuscles1 starts the impulses that give rise to the sensation4 ,the touch corpuscles render the fiber terminations so sensitive that the slightest pressure is able to arouse sensations of touch4 ,it is found that a change of pressure1 rather than pressure that is constant1 is the active stimulus4 ,that all parts of the skin are not equally sensitive to pressure1 and that the mind does not interpret equally well the sensations from different parts1 are facts easily demonstrated by experiment4 7,see ,practical ,work47 99,the ,temperature ,sensation499--,temperature sensations1 like those of touch1 are limited almost entirely to the skin4 ,they are of two kinds1 and are designated as heat sensations and as cold sensations4 ,whether the sense organs for temperature are different from those of touch is not known4 ,it is known1 however1 that the same corpuscles do not respond alike to heat1 cold1 and pressure4 ,a ,change of ,temperature1 rather than any specific degree of heat or cold1 is the active temperature stimulus4 ,the sensation of warmth is obtained when the temperature of the skin is being raised1 and of cold when it is being lowered4 ,this explains why in going into a hallway from a heated room one receives a sensation of cold1 while in coming into the same hallway from the outside air he receives a sensation of warmth4 ,it is for the same reason that we are able to distinguish only the relative1 not the actual1 temperature of bodies4 99,muscular ,sensations499--,these are sensations produced by impulses arising at the muscles4 ,such impulses originate at the fiber terminations which are found in both the muscles and their tendons4 ,by muscular sensations one is conscious of the location of a contracting muscle and of the degree of its tension4 ,they also make it possible to judge of the weight of objects4 ,fig4 #adf ,fig4 #adf--99,sense organs of taste499 ,a4 ,map of upper surface of tongue1 showing on the left the different kinds of papill1 and on the right the areas of taste 7after ,hall74 ,area sensitive to bitter 7----72 to acid 7444472 to salt 7--4--4--4--72 to sweet 7--------74 ,b4 ,section through a papilla4 n4 ,small nerve connecting with taste buds at d4 e4 ,epithelium4 ,c4 ,single taste bud magnified4 n4 ,nerve1 the fibers of which terminate between the spindle-shaped cells a4 e4 ,epithelial cells4 99,the ,sensation of ,taste499--,the sense organs of taste are found chiefly in the mucous membrane covering the upper surface of the tongue4 ,scattered over this surface are a number of rounded elevations1 or large papill 7,a1 ,fig4 #adf74 ,toward the back of the tongue two rows of these1 larger than the others1 converge to meet at an angle1 where is located a papilla of exceptional size4 ,surrounding each papilla is a narrow depression1 within which are found the sense organs of taste 7,b1 ,fig4 #adf74 ,these are called1 from their shape1 taste buds1 and each bud contains a central cavity which communicates with the surface by a small opening--the gustatory pore4 ,within this cavity are many slender1 spindle-shaped cells which terminate in hair-like projections at the end nearest the pore1 but in short fibers at the other end4 ,nerve fibers enter at the inner ends of the buds and spread out between the cells 7,c1 ,fig4 #adf74 ,these fibers pass to the brain as parts of two pairs of nerves--those from the front of the tongue joining the trigeminal nerve1 and those from the back of the tongue1 the glossopharyngeal nerve4 ,the gustatary1 or taste stimulus1 is some chemical or physical condition of substances which is manifested only when they are in a liquid state4 ,for this reason only liquid substances can be tasted4 ,solids to be tasted must first be dissolved4 ,the different taste sensations are described as bitter1 sweet1 sour1 and saline1 and in the order named are recognized as the tastes of quinine1 sugar1 vinegar1 and salt4 ,as to how these different tastes are produced1 little is known4 ,flavors such as vanilla and lemon1 and the flavors of meats and fruits1 are really smelled and not tasted4 ,taste serves two main purposes3 it is an aid in the selection of food and it is a means of stimulating the digestive glands 7page #afa74 ,fig4 #adg ,fig4 #adg--99,sense organ of smell499 ,a4 ,distribution of nerves in outer wall of nasal cavity4 #a4 ,turbinated bones4 #b4 ,branch of fifth pair of nerves4 #c4 ,branches of olfactory nerve4 #d4 ,olfactory bulb4 ,b4 ,diagram showing connection of neurons concerned in smell4 99,the ,sensation of ,smell499--,the sense organs of smell are found in the mucous membrane lining the upper divisions of the nasal cavities4 ,here are found two kinds of cells in great abundance--column-shaped epithelial cells and the cells which are recognized as the sense organs of smell4 ,these olfactory cells are spindle-shaped1 having at one end a slender1 thread-like projection which reaches the surface1 and at the other end a fiber which joins an olfactory nerve 7,b1 ,fig4 #adg74 ,in fact1 the olfactory cells resemble closely the cell-bodies of neurons1 and are thought to be such4 ,the divisions of the olfactory nerve pass through many small openings in the ethmoid bone to connect with the olfactory bulbs1 which in turn connect with the cerebrum 7,a1 ,fig4 #adg74 99,the ,olfactory ,stimulus499--,only substances in the gaseous state can be smelled4 ,from this it is inferred that the stimulus is supplied by gas particles4 ,solids and liquids are smelled because of the gas particles which separate from them4 ,the substance which is smelled must be kept moving through the nostrils and made to come in direct contact with the olfactory cells4 ,there is practically no limit to the number of distinct odors that may be recognized4 99,value of ,smell499--,although the sense of smell is not so acute in man as in some of the lower animals1 it is1 nevertheless1 a most important and useful gift4 ,it is the only sense that responds to matter in the gaseous state1 and is1 for this reason1 the only natural means of detecting harmful constituents of the atmosphere4 ,in this connection it has been likened to a sentinel standing guard over the air passages4 ,many gases are1 however1 without odor1 and for this reason cannot be detected by the nostrils4 ,it is of especial importance that gases which are likely to become mixed with the air supply to the body have odor1 even though the odor be disagreeable4 ,the bad odors of illuminating gas and of various compounds of the chemical laboratory1 since they serve as danger signals to put one exposed to them on his guard1 are of great protective value4 99,sight and ,hearing499--,the sense organs of sight and hearing are highly complicated structures1 and will be considered in the chapters following4 99,summary499--,sensations are certain activities of the mind that result from excitations within the body or at its surface4 ,these cause the neurons to discharge impulses which on reaching the cerebrum cause the sensations4 ,sensations are necessary for intelligent and purposeful action and for acquiring all kinds of knowledge4 ,to enable the stimuli to act to the best advantage in starting the impulses1 special devices1 called sense organs1 are employed4 ,these receive the terminations of the neurons1 and by their special structure enable the most delicate stimuli to start impulses4 ,the simpler forms of sense organs are those of touch1 temperature1 taste1 and smell4 99,exercises499--#a4 ,compare sensations and reflex actions with reference to their nature and cause4 ,give steps in the production of each4 #b4 ,give examples of sensation stimuli4 ,state the purpose of sense organs4 #c4 ,how do general sensations differ from special sensations8 #d4 ,of what value is pain in the protection of the body8 #e4 ,show that sensations lead to the higher forms of mental activity1 such as emotion and imagination4 #f4 ,of what value to the body is the localizing of the sensation8 #g4 ,what kinds of sense organs are found in the skin8 ,state the purpose of each4 #h4 ,through what sense avenues is one made aware of solids1 of liquids1 and of gases8 #i4 ,of what special protective value is the sense of smell8 ,,practical ,,work 99,to demonstrate the ,pacinian ,corpuscles499--,spread out the mesentery from the intestine of a cat and hold it between the eye and the light3 ,pacinian corpuscles will appear as small translucent bodies having the general form of grains of wheat4 ,secure a portion of the mesentery over a circular opening in a thin piece of cork and examine it with a microscope of low power4 ,follow the course of the nerve fiber to the nerve from which it branches4 99,to show ,relative ,sensitiveness of ,different ,parts of the ,skin499--,holding a bristle between the fingers1 bring the end in contact with the skin1 noting the amount of pressure necessary to cause a sensation of touch4 ,test the lips1 tongue1 tips of fingers1 and palm and back of hand1 trying different sizes of bristles4 ,has the degree of sensitiveness any relation to the thickness of the cuticle8 99,to show ,perceptive ,differences of ,different ,portions of the ,skin499--,place the points of a pair of dividers on the back of the hand of one who looks in the opposite direction4 ,is one point felt or two8 ,repeat several times1 changing the distance between the points until it is fully determined how near the two points must be placed in order to be felt as one4 ,in like manner test other parts of the body1 as the tips of the fingers and the back of the neck4 ,compare results obtained at different places4 99,to locate ,warm and ,cold ,sensation ,spots499--,slowly and evenly draw a blunt-pointed piece of metal over the back of the neck4 ,if it be of the same temperature as the skin1 only touch sensations will be experienced4 ,if it be a little colder 7the temperature of the room7 sensations of cold will be felt at certain spots4 ,if slightly warmer than the body1 heat sensation spots will be found on other parts of the skin4 ,if the heat and cold sensation spots be marked and tested from day to day they will be found to remain constant as to position4 ,inference4 ,,chapter ,,xxi - ,,the ,,larynx ,,and ,,the ,,ear ,man is a social being4 ,his inclinations are not to live alone1 but to be a part of that great human organization known as society4 ,for men to work together1 to be mutually helpful one to another1 requires the ability to exchange ideas and this in turn requires some means of communication47#aae7 ,one means of communication is found in certain movements of the atmosphere1 known as sound waves4 ,in the exchange of ideas by this means there are employed two of the most interesting divisions of the body--the larynx and the ear4 ,the first is an instrument for the production of sound waves2 the second is the sense organ which enables the sound waves to act as stimuli to the nervous system4 99,nature of ,sound ,waves499--,if some sonorous body1 as a bell1 be struck1 it is given a quivering1 or vibratory1 motion4 ,this is not confined to the bell1 but is imparted to the air and other substances with which the bell comes in contact4 ,these take up the movements and pass them to objects more remote1 and they in turn give them to others1 until a very considerable distance is reached4 ,such progressive vibrations are known as waves1 and1 since they act as stimuli to the organs of hearing1 they are called sound waves4 ,sound waves always originate in vibrating bodies47#aaf7 ,they are transmitted chiefly by the air1 which1 because of its lightness1 elasticity1 and abundance1 readily takes up the vibrations and spreads them in all directions 7,fig4 #adh74 ,while these vibratory movements of the atmosphere are correctly classified as waves1 they bear little resemblance to the waves on water4 ,instead of being made of crests and troughs1 as are the water waves1 the sound waves consist of alternating successions of slightly condensed and rarefied layers of air4 ,then1 while the general movement of the water waves is that of ever widening circles over a surface1 the sound waves spread as enlarging spherical shells through the air4 ,in sound waves1 as in all other waves1 however1 it is only the form of the wave that moves forward4 ,the individual particles of air that make up the wave simply vibrate back and forth4 ,fig4 #adh ,fig4 #adh--;,diagram illustrating the spreading of sound waves through air4 99,how ,sound ,waves act as ,stimuli499--,any sound wave represents a small but definite amount of energy1 this being a part of the original force that acted on the vibrating body to set it in motion4 ,the hammer1 for instance1 in striking a bell imparts to it a measurable quantity of energy1 which the bell in turn imparts to the air4 ,this energy is in the sound waves and is communicated to the bodies against which they strike47#aag7 ,though the force exerted by most sound waves is1 indeed1 very slight1 it is sufficient to enable them to act as stimuli to the nervous system4 99,how ,sounds ,differ499--,three distinct effects are produced by sound waves upon the nerves of hearing1 and through them upon the mind4 ,these are known as pitch1 intensity1 and quality1 and they are dependent upon the vibrations of the sound-producing bodies4 ,pitch1 which has reference to the height1 or degree of sharpness1 of tones1 is determined by the rapidity of the vibrations of the vibrating body4 ,the more rapid the vibrations1 the higher the pitch1 the number of vibrations doubling for each musical interval known as the octave4 ,intensity is the energy1 or force1 of the sound waves4 ,this is recognized by the strength of the sensation and is expressed by the term loudness4 ,intensity is governed mainly by the width of the vibrations of the vibrating body1 and the width depends upon the force applied to the body to make it vibrate4 ,quality is that peculiarity of sound that enables tones from different instruments to sound differently1 although they may have the same pitch and intensity4 ,quality depends upon the fact that most tones are complex in nature and result from the blending together of simple tones of different pitch4 99,renforcement of ,sound ,waves499--,the sound vibrations from small bodies are not infrequently renforced by surrounding conditions so that their outgoing waves reach farther and are more effective than waves from larger bodies4 ,this is true of the sound waves produced by most musical instruments and also those produced by the human larynx4 ,such renforcement is effected in two general ways--by sounding boards and by inclosed columns of air4 ,stringed instruments--violin1 guitar1 piano1 etc4--employ sounding boards1 while wind instruments1 as the flute1 pipe organ1 and the various kinds of horns1 employ air columns for renforcing their vibrations4 ,in the use of the sounding board1 the vibrations are communicated to a larger surface1 and in the use of the air column the vibrations are communicated to the inclosed air4 7,see ,practical ,work47 99,value of ,sound ,waves to the ,body499--,from a physiological standpoint1 the value of sound waves is not easily overestimated4 ,in addition to the use made of them in the communication of ideas1 they serve the purpose of protecting the body1 and in the sphere of music provide one of the most elevating forms of entertainment4 ,sounds from different animals1 as well as from inanimate objects1 may also be the means of supplying needed information4 ,the existence of two kinds of sound instruments in the body--the one for the production1 the other for the detection1 of sound--is certainly suggestive of the ability of the body to adjust itself to1 and to make use of1 its physical environment4 ,both the larynx and the ear are constructed with special reference to the nature and properties of sound waves4 ,,the ,,larynx 99,the ,sound-producing ,mechanism of the ,body99 consists of the following parts3 #a4 ,delicately arranged bodies that are easily set in vibration4 #b4 ,an arrangement for supplying the necessary force for making these bodies vibrate4 #c4 ,contrivances for modifying the vibrating parts so as to produce changes in pitch and intensity4 #d4 ,parts that renforce the vibrations4 #e4 ,organs by means of which the sounds are converted into the forms of speech4 ,the central organ in this complex mechanism is 99,the ,larynx499--,the larynx forms a part of the air passages1 being a short tube at the upper end of the trachea4 ,mucous membrane lines the inside of it and muscles cover most of the outer surface4 ,the framework is made of cartilage4 ,at the top it is partly encircled by a small bone 7the hyoid71 and its opening into the pharynx is guarded by a flexible lid1 called the epiglottis4 ,the cartilage in its walls is in eight separate pieces1 but the greater portion of the structure is formed of two pieces only4 ,these are known as the thyroid cartilage and the cricoid cartilage 7,fig4 #adi74 ,both can be felt in the throat--the thyroid as the projection known as ,adam's apple1 and the cricoid as a broad ring just below4 ,fig4 #adi ,fig4 #adi--,the larynx4--,a4 ,outside view4 ,b4 ,vertical section through larynx1 showing inside4 #a4 ,thyroid cartilage4 #b4 ,cricoid cartilage4 #c4 ,trachea4 #d4 ,hyoid bone4 #e4 ,epiglottis4 #f4 ,vocal cord4 #g4 ,false vocal cord4 #h4 ,lining of mucous membrane4 ,the thyroid cartilage consists of two ,v-shaped pieces1 one on either side of the larynx1 meeting at their points in front1 and each terminating at the back in an upward and a downward projection4 ,between the back portions of the thyroid is a space equal to about one third of the circumference of the larynx4 ,this is occupied by the greater portion of the cricoid cartilage4 ,this cartilage has the general shape of a signet ring and is so placed that the part corresponding to the signet fits into the thyroid space1 while the ring portion encircles the larynx just below the thyroid4 ,muscles and connective tissue pass from the thyroid to the cricoid cartilage at all places1 save one on each side1 where the downward projections of the thyroid form hinge joints with the cricoid4 ,these joints permit of motion of either cartilage upon the other4 ,at the summit of the cricoid cartilage1 on each side1 is a small piece of triangular shape1 called the arytenoid cartilage4 ,each arytenoid is movable on the cricoid and is connected with one end of a vocal cord4 ,fig4 #aej ,fig4 #aej--99,vocal cords99 as seen from above4 ,a4 ,in producing sound1 ,b4 ,during quiet breathing4 99,the ,vocal ,cords99 are formed by two narrow strips of tissue which1 connecting with the thyroid cartilage in front and the arytenoid cartilages behind1 lie in folds of the mucous membrane4 ,they have the general appearance of ridge-like projections from the sides of the larynx1 but at their edges they are sharp and smooth4 ,the open space between the cords is called the glottis4 ,when sound is not being produced1 the glottis is open and has a triangular form1 due to the spreading apart of the arytenoid cartilages and the attached cords4 ,but when sound is being produced1 the glottis is almost completely closed by the cords4 ,above the vocal cords1 and resembling them in appearance1 are two other folds of membrane1 called the false vocal cords 7,b1 ,fig4 #adi74 ,the false cords do not produce sound1 but they aid in the closing of the glottis4 99,how the ,voice is ,produced499--,the voice is produced through the vibrations of the vocal cords4 ,a special set of muscles draws the arytenoid cartilages toward each other1 thereby bringing their edges very near and parallel to each other in the passage4 ,at the same time other muscles act on the thyroid and cricoid cartilages to separate them at the top and give the cords the necessary tension4 ,with the glottis now almost closed1 blasts of air from the lungs strike the sharp edges of the cords and set them in vibration 7,fig4 #aej74 ,the vocal cords do not vibrate as strings1 like the strings of a violin1 but somewhat as reeds1 similar to the reeds of a ,french harp or reed organ4 ,the location of the vocal cords in the air passages enables the lungs and the muscles of respiration to aid in the production of the voice4 ,it is their function to supply the necessary force for setting the cords in vibration4 ,the upper air passages 7mouth1 nostrils1 and pharynx7 supply resonance chambers for renforcing the vibrations from the vocal cords1 thereby greatly increasing their intensity4 ,in ordinary breathing the vocal cords are in a relaxed condition against the sides of the larynx and are not acted upon by the air as it enters or leaves the lungs4 99,pitch and ,intensity of the ,voice499--,changes in the pitch of the voice are caused mainly by variations in the tension of the cords1 due to the movements of the thyroid and cricoid cartilages upon each other47#aah7 ,in the production of tones of very high pitch1 the vibrating portions of the cords are thought to be actually shortened by their margins being drawn into contact at the back4 ,this raises the pitch in the same manner as does the shortening of the vibrating portion of a violin string4 ,the intensity1 or loudness1 of the voice is governed by the force with which the air is expelled from the lungs4 ,the vibrations of the cords1 however1 are greatly renforced by the peculiar structure of the upper air passages1 as stated above4 99,production of ,speech499--,the sounds that form our speech or language are produced by modifying the vibrations from the vocal cords4 ,this is accomplished by mouthing the sounds from the larynx4 ,the distinct sounds1 or words1 are usually complex in nature1 being made up of two or more elementary sounds4 ,these are classed either as vowels or consonants and are represented by the different letters of the alphabet4 ,the vowel sounds are made with the mouth open and are more nearly the pure vibrations of the vocal cords4 ,the consonants are modifications of the vocal cord vibrations produced by the tongue1 teeth1 lips1 and throat4 99,words and their ,significance499--,in the development of language certain ideas have become associated with certain sounds so that the hearing of these sounds suggests the ideas4 ,our words1 therefore1 consist of so many sound signals1 each capable of arousing a definite idea in the mind4 ,to talk is to express ideas through these signals1 and to listen is to assume an attitude of mind such that the signals may be interpreted4 ,in learning a language1 both the sounds of the words and their associated ideas are mastered1 this being necessary to their practical use in exchanging ideas4 ,from spoken language man has advanced to written language1 so that the sight of the written or printed word also arouses in the mind the associated idea4 ,,the ,,ear 99,the ,ear99 is the sense organ which enables sound waves to so act upon afferent neurons as to excite impulses in them4 ,the effect upon the mind which these impulses produce is known as the sensation of hearing4 ,in the performance of its function the ear receives and transmits sound waves and also concentrates them upon a suitable exposure of nerve cells4 ,it includes three parts--the external ear1 the middle ear1 and the internal ear4 99,external ,ear499--,the external ear consists of the part on the outside of the head called the pinna1 or auricle1 and the tube leading into the middle ear1 called the auditory canal 7,fig4 #aea74 ,the pinna by its peculiar shape aids to some extent the entrance of sound waves into the auditory canal47#aai7 ,it consists chiefly of cartilage4 ,the auditory canal is a little more than an inch in length and one fourth of an inch in diameter1 and is closed at its inner end by a thin1 but important membrane1 called 99,the ,membrana ,tympani499--,this membrane consists of three thin layers4 ,the outer layer is continuous with the lining of the auditory canal2 the inner is a part of the lining of the middle ear2 and the middle is a fine layer of connective tissue4 ,being thin and delicately poised1 the membrana tympani is easily made to vibrate by the sound waves that enter the auditory canal4 ,in this way it serves as a receiver of sound waves from the air4 ,it also protects ,fig4 #aea ,fig4 #aea--99;,diagram of section through the ear991 showing relations of its various parts4 7,see text47 99,the ,middle ,ear499--,the middle ear1 or tympanum17#abj7 consists of an irregular cavity in the temporal bone which is lined with mucous membrane and filled with air4 ,it is connected with the pharynx by a slender canal called the ,eustachian tube4 ,extending across the middle ear and connecting with the membrana tympani on one side1 and with a membrane closing a small passage to the internal ear on the other1 is a tiny bridge formed of three small bones4 ,these bones1 named in their order from the membrana tympani1 are the malleus1 the incus1 and the stapes 7,fig4 #aea74 ,where the malleus joins the membrane is a small muscle whose contraction has the effect of tightening the membrane4 ,the ,eustachian tube admits air freely to the middle ear1 providing in this way for an equality of atmospheric pressure on the two sides of the drum membrane4 ,the bridge of bones and the air in the middle ear receive vibrations from the membrana tympani and communicate them to the membrane of the internal ear4 99,purposes of the ,middle ,ear4 99--,the middle ear serves two important purposes4 ,in the first place1 it makes it possible for sound waves to set the membrana tympani in vibration4 ,this membrane could not be made to vibrate by the more delicate of the sound waves if it were stretched over a bone1 or over some of the softer tissues1 or over a liquid4 ,its vibration is made possible by the presence of air on both sides1 and this condition is supplied1 on the inner side1 by the middle ear4 ,the ,eustachian tube1 by providing for an equality of pressure on the two sides of the membrane1 also aids in this purpose4 ,in the second place1 the middle ear provides a means for concentrating the force of the sound waves as they pass from the membrana tympani to the internal ear4 ,this concentration is effected in the following manner3 #a4 ,the bridge of bones1 being pivoted at one point to the walls of the middle ear1 forms a lever in which the malleus is the long arm1 and the incus and stapes the short arm1 their ratio being about that of three to two4 ,this causes the incus to move through a shorter distance1 but with greater force than the end of the malleus4 #b4 ,the area of the membrana tympani is about twenty times as great as the membrane of the internal ear which is acted upon by the stapes4 ,the force from the larger surface is1 therefore1 concentrated by the bridge of bones upon the smaller surface4 ,by the combination of these two devices1 the waves striking upon the membrane of the internal ear are rendered some thirty times more effective than are the same waves entering the auditory canal4 99,the ,internal ,ear991 or labyrinth1 occupies a series of irregular channels in the petrous process of the temporal bone47#aba7 ,it is very complicated in structure1 and at the same time is very small4 ,its greatest length is not more than three fourths of an inch and its greatest diameter not more than one half of an inch4 ,it is filled with a liquid which at one place is called the perilymph1 and at another place the endolymph4 ,it is a double organ1 being made up of an outer portion which lies next to the bone1 and which surrounds an inner portion of the same general form4 ,the outer portion is surrounded by a membrane which serves as periosteum to the bone and1 at the same time1 holds the liquid belonging to this part1 called the perilymph4 ,the inner portion1 called the membranous labyrinth1 consists essentially of a closed membranous sac1 which is filled with the endolymph4 ,the auditory nerve terminates in this portion of the internal ear4 ,three distinct divisions of the labyrinth have been made out1 known as the vestibule1 the semicircular canals1 and the cochlea 7,fig4 #aeb74 ,fig4 #aeb ,fig4 #aeb--99;,general form1 of internal ear499 ,the illustration represents the structures of the internal ear surrounded by a thin layer of bone4 #a4 ,vestibule4 #b4 ,cochlea4 #c4 ,semicircular canals4 #d4 ,fenestra ovalis4 #e4 ,fenestra rotunda4 99,the ,vestibule99 forms the central portion of the internal ear and is somewhat oval in shape4 ,it is in communication with the middle ear through a small opening in the bone1 called the fenestra ovalis1 at which place it is separated from the middle ear only by a thin membrane4 ,sound waves enter the liquids of the internal ear at this point1 the foot of the stapes being attached to the membrane4 ,six other openings lead off from the vestibule at different places4 ,one of these enters the cochlea4 ,the other five open into 99,the ,semicircular ,canals499--,these canals1 three in number1 pass through the bone in three different planes4 ,one extends in a horizontal direction and the other two vertically1 but each plane is at right angles to the other two4 ,both ends of each canal connect with the vestibule1 though two of them join by a common opening4 ,the inner membranous labyrinth is continuous through each canal1 and is held in position by small strips of connective tissue4 ,the purpose of the semicircular canals is not understood4 ,it is known1 however1 that they are not used in hearing4 ,on the other hand1 there is evidence to the effect that they act as equilibrium sense organs1 exciting sensations necessary for balancing the body4 ,their removal or injury1 while having no effect upon the hearing1 does interfere with the ability to keep the body in an upright position4 ,fig4 #aec ,fig4 #aec--;,diagram showing the divisions of cochlear canal4 99,the ,cochlea99 is the part of the internal ear directly concerned in hearing4 ,it consists of a coiled tube which makes two and one half turns around a central axis and bears a close resemblance to a snail shell 7,figs4 #aea and #aeb74 ,it differs in plan from a snail shell1 however1 in that its interior space is divided into three distinct channels1 or canals4 ,these lie side by side and are named1 from their relations to other parts1 the scala vestibula1 the scala tympani1 and the scala media4 ,any vertical section of the cochlea shows all three of these channels 7,fig4 #aec74 99,the ,scala ,vestibula and the ,scala ,tympani99 appear in cross section as the larger of the canals4 ,the former1 so named from its connection with the vestibule1 occupies the upper position in all parts of the coil4 ,the latter lies below at all places1 and is separated from the channels above partly by a margin of bone and partly by a membrane4 ,it receives its name from its termination at the tympanum1 or middle ear1 from which it is separated only by a thin membrane47#abb7 ,both the scala vestibula and the scala tympani belong to the outer portion of the internal ear and are1 for this reason1 filled with the perilymph4 ,at their upper ends they communicate with each other by a small opening1 making by this means one continuous canal through the cochlea4 ,this canal passes from the vestibule to the tympanum and1 in so doing1 goes entirely around 99,the ,scala ,media499--,this division of the cochlea lies parallel to and between the other two divisions4 ,it is above the scala tympani and below the scala vestibula1 and is separated from each by a membrane4 ,the scala media belongs to the membranous portion of the internal ear and is1 therefore1 filled with the endolymph4 ,it receives the terminations of fibers from the auditory nerve and may be regarded as the true sense organ of hearing4 ,the nerve fibers terminate upon the membrane known as the basilar membrane1 which separates it from the scala tympani4 ,this membrane extends the length of the cochlear canals1 and is stretched between a projecting shelf of bone on one side and the outer wall of the cochlea on the other4 ,it is covered with a layer of epithelial cells1 some of which have small1 hair-like projections and are known as the hair cells4 ,above the membrane1 and resting partly upon it1 are two rows of rod-like bodies1 called the rods of ,corti4 ,these1 by leaning toward each other1 form a kind of tunnel beneath4 ,they are exceedingly numerous1 numbering more than #fjjj1 and form a continuous series along the margin of the membrane4 ,fig4 #aed ,fig4 #aed--99;,diagram99 illustrating passage of sound waves through the ear4 99,how ,we ,hear499--,the sound waves which originate in vibrating bodies are transmitted by the air to the external ear4 ,passing through the auditory canal1 the waves strike against the membrana tympani1 setting it into vibration4 ,by the bridge of bones and the air within the middle ear the vibrations are carried to and concentrated upon the liquid in the internal ear 7,fig4 #aed74 ,from here the vibrations pass through the channels of the cochlea and set into vibration the contents of the scala media and different portions of the basilar membrane4 ,this serves as a stimulus to the fibers of the auditory nerve1 causing them to transmit impulses which1 on passing to the brain1 produce the sensation of hearing4 ,much of the peculiar structure of the cochlea is not understood4 ,its minute size and its location in the temporal bone make its study extremely difficult4 ,the connection of the scala vestibula with the scala tympani1 and this with the middle ear1 is necessary for the passage of vibrations through the internal ear4 ,its liquids1 being practically incompressible and surrounded on all sides by bones1 could not otherwise yield to the movements of the stapes4 7,see ,practical ,work47 ,the rods of ,corti are thought to act as dampers on the basilar membrane1 to prevent the continuance of vibrations when once they are started4 99,detection of ,pitch499--,the method of detecting tones of different pitch is not understood4 ,several theories have been advanced with reference to its explanation1 one of the most interesting being that proposed by ,helmholtz4 ,this theory is based on our knowledge of sympathetic vibrations4 ,the basilar membrane1 while continuous throughout1 may be regarded as made up of many separate cords of different lengths stretched side by side4 ,a tone of a given pitch will set into vibration only certain of these cords1 while tones of different pitch will set others into vibration4 ,another theory is that the basilar membrane responds to all kinds of vibrations and the analysis of sound takes place in the brain4 ,a third view is that the filaments from the hair cells1 rather than the basilar membrane1 respond to the vibrations and in turn stimulate the terminations of the nerve fibers4 ,fig4 #aee ,fig4 #aee--99;,diagram99 showing how wax may plug the auditory canal and cause deafness4 99,hygiene of the ,ear499--,the ear1 being a delicate organ1 is frequently injured by careless or rough treatment4 ,the removal of the ear wax by the insertion of pointed instruments has been found to interfere with the natural method of discharge and to irritate the membrane4 ,it should never be practiced4 ,it is unnecessary in the healthy ear thus to cleanse the auditory canal1 as the wax is passed by a natural process to where it is easily removed by a damp cloth4 ,if the natural process is obstructed1 clean warm water and a soft linen cloth may be employed in cleansing the canal1 without likelihood of injury4 ,clean warm water may also be introduced into the auditory canal as a harmless remedy in relieving inflammation of the auditory canal and of the middle ear4 ,children's ears are easily injured1 and it goes without saying that they should never be pulled nor boxed4 ,it frequently happens that a mass of wax collects in the auditory canal and closes the passage so completely as to cause deafness 7,fig4 #aee74 ,this may come about without pain and so gradually that one does not think of seeking medical aid4 ,such masses are easily removed by the physician1 the hearing being then restored4 ,both for painful disturbances of the ear and for the gradual loss of hearing1 the physician should be consulted4 99,the ,hearing of ,school ,children499--,school children not infrequently have defective hearing and for this reason are slow to learn4 ,the hearing is easily tested with a watch1 the normal ear being able to hear the watch tick at a distance of at least two feet4 ,pupils with defective hearing should1 of course1 have medical attention1 and in the classroom should be seated where they can hear to the best advantage4 99,summary499--,sound waves constitute the external stimuli for the sensation of hearing4 ,they consist of progressive vibratory movements of the air that originate in vibrating bodies4 ,through the larynx and the ear1 sound waves are utilized by the body in different ways1 but chiefly as a means of communication4 ,the larynx produces sound waves which are renforced and modified by the air passages4 ,the ear supplies suitable conditions for the action of sound waves upon nerve cells4 ,both the ear and the larynx are constructed with special reference to the nature and properties of sound waves1 and they illustrate the body's ability to adjust itself to1 and to make use of1 its physical environment4 99,exercises499--#a4 ,for what different purposes are sound waves employed in the body8 #b4 ,how do sound waves originate8 ,how are they transmitted8 ,how do they differ from the waves on water8 #c4 ,how are sound waves able to act as nerve stimuli8 #d4 ,describe two methods of renforcing sound waves4 ,which method is employed in the body8 #e4 ,name all the parts of the body that are directly or indirectly concerned in the production of sound4 #f4 ,describe the larynx4 #g4 ,describe the condition of the vocal cords in speaking and in ordinary breathing4 #h4 ,how are sounds differing in pitch and intensity produced by the larynx8 #i4 ,how is the sound produced by the vocal cords changed into speech8 #aj4 ,what parts of the ear are concerned in transmitting sound waves8 #aa4 ,give the purposes of the middle ear4 #ab4 ,trace a sound wave from a bell to the basilar membrane1 and trace the impulse that it causes from there to the brain4 #ac4 ,give the purpose of the ,eustachian tubes2 of the rods of ,corti2 of the semicircular canals4 #ad4 ,give directions for the proper care of the ear4 ,,practical ,,work 99,to illustrate the ,origin of ,sound499--#a4 ,strike a bell an easy blow and hold some light substance1 as a pith ball attached to a thread1 against the side1 noting the result4 #b4 ,sound a tuning fork by striking it against the table4 ,test it for vibrations as above1 or by letting the vibrating prongs touch the surface of water4 #c4 ,pluck a string of a guitar or violin1 and find proof that it is vibrating while giving out sound4 99,to show the ,transmission of ,sound499--#a4 ,vibrate a tuning fork and press the stem against a table or desk4 ,the vibrations which are renforced in this way will be heard in all parts of the room4 ,now press one end of a wooden rod1 as a broom handle1 against the table1 and bring the stem of the vibrating fork against the other end4 ,the vibrations now move down the stick to the table1 from whence they are communicated to the air4 ,observe that the sound waves1 to reach the ear1 must pass through the rod1 the table1 and the air4 #b4 ,fasten the tuning fork to a flat piece of cork by pressing the stem into a small hole in the center4 ,vibrate the fork and let the cork rest on the surface of water in a half-filled tumbler on the table4 ,the sound will1 as before1 pass to the table and then to the air4 ,observe that in this case the vibrations are transmitted by a liquid1 a solid1 and by the air4 ,compare this action with the transmission of sound waves by different portions of the ear4 99,to show ,effects of ,sound ,waves499--#a4 ,place two large tuning forks of the same pitch1 and mounted on thin boxes for renforcing their vibrations1 near each other on a table4 ,vibrate one of the forks for a moment and then stop it by means of the hand4 ,observe that the other fork has been set in vibration4 7,this experiment does not work with forks of different pitch47 #b4 ,while holding a thin piece of paper against a comb with the open lips1 produce musical tones with the vocal cords4 ,these will set the paper in vibration1 producing the so-called comb music4 #c4 ,examine the disk in a telephone which is set in vibration by the voice4 ,observe that it is a thin disk and1 like the membrane of the ear1 has air on both sides of it4 99,to show the ,renforcement of ,sound499--#a4 ,vibrate a tuning fork in the air1 noting the feebleness of the tone produced4 ,then hold the stem against a door or the top of a table1 noting the difference4 #b4 ,hold a vibrating tuning fork over a tall jar1 or bottle1 and gradually add water4 ,if the vessel is sufficiently tall1 a depth will be reached where the air in the vessel renforces the sound from the fork4 #c4 ,hold a vibrating fork over the mouth of a small fruit jar1 partly covered with a piece of cardboard4 ,by varying the size of the opening1 a position will be found where the sound is renforced4 ,if not successful at first1 try bottles and jars of different sizes4 99,to illustrate the ,manner of ,vibration of the ,liquid in the ,internal ,ear499--,tie a piece of dental rubber over the end of a glass or wooden tube about half an inch in diameter and six inches in length4 ,fill the tube entirely full of water and1 without spilling1 tie a piece of thin rubber tightly over the other end4 ,holding the tube horizontally1 press the rubber in at one end and note that it is pushed out at the other end4 ,make an imitation of a vibration with the finger against the rubber at one end of the tube and note the effect at the other end4 ,to what do the tube and the rubber on the ends of the tube correspond in the internal ear8 ,fig4 #aef ,fig4 #aef--99,simple apparatus99 for demonstrating the larynx4 99,to show the ,plan of the ,larynx499--,cut from stiff paper four pieces of different shapes as indicated in ,fig4 #aef4 7,the piece to the left should have a length of about six inches1 the others proportionally large47 ,the largest represents the thyroid cartilage1 the next in size the cricoid1 and the two smallest the arytenoid cartilages4 ,by means of pins1 or threads1 connect these with each other according to the description of the larynx on page #bec4 ,with this simple model the movements of the different cartilages and their effect upon the vocal cords may be illustrated4 99,to show the ,relation of the ,movements of the ,vocal ,organs to the ,production of ,different ,sounds499--#a4 ,lightly grasp the larynx with the fingers while talking4 ,observe the changes1 both in the position and shape of the larynx1 in the production of sounds of different pitch4 #b4 ,observe the difference in the action of the muscles of respiration in the production of loud and faint sounds4 #c4 ,pronounce slowly the vowels1 ,a1 ,e1 ,i1 ,o1 ,u1 and the consonants ,c1 ,f1 ,k1 ,m1 ,r1 ,s1 ,t1 and ,v1 noting the shape of the mouth1 the position of the tongue1 and the action of the lips in each case4 99,to demonstrate the ,ear499--,examine a dissectible model of the ear1 locating and naming the different parts4 ,trace as far as possible the path of the sound waves and find the termination of the auditory nerve4 ,note also the relative size of the parts1 and calculate the number of times the model is larger than the natural ear4 ,suggestion3 ,the greatest diameter of the internal ear is about three fourths of an inch4 ,in an extended course it is a profitable exercise to dissect the ear of a sheep or calf1 observing the auditory canal1 middle ear1 bridge of bones1 and the tympanic membrane with attached malleus and tensor tympanic muscle4 ,pass a probe from the nasal pharynx through the ,eustachian tube into the middle ear4 ,with bone forceps or a fine saw1 split open the petrous portion of the temporal bone and observe the cochlea and the semicircular canals4 ,by a careful dissection other parts of interest may also be shown4 ,,chapter ,,xxii - ,,the ,,eye ,sight is considered the most important of the sensations4 ,it is the chief means of bringing the body into proper relations with its surroundings and1 even more than the sensation of hearing1 is an avenue for the reception of ideas4 ,the sense organs for the production of sight are the eyes2 the external stimulus is 99,light499--,light1 like sound1 consists of certain vibrating movements1 or waves4 ,they differ from sound waves1 however1 in form1 velocity1 and in method of origin and transmission4 ,light waves are able to pass through a vacuum1 thus showing that they are not dependent upon air for their transmission4 ,they are supposed to be transmitted by what the physicist calls ether--a highly elastic and exceedingly thin substance which fills all space and penetrates all matter4 ,as a rule1 light waves originate in bodies that are highly heated1 being started by the vibrations of the minute particles of matter4 ,light is influenced in its movements by various conditions4 ,in a substance of uniform density it moves with an unchanging velocity and in a straight line4 ,if it enters a less dense1 or rarer1 substance1 its velocity increases2 if one more dense1 its velocity diminishes2 and if it enters either the rarer or denser substance in any direction other than perpendicularly1 it is bent out of its course1 or refracted4 ,if it strikes against a body lying in its course1 it may be thrown off 7reflected71 or it may enter the body and either be passed on through 7transmitted7 or absorbed 7,fig4 #aeg74 ,light which is absorbed is transformed into heat4 99,kinds of ,reflection499--,waves of light striking against the smooth surface of a mirror are thrown off in definite directions1 depending on the angle at which they strike4 7,illustrate by holding a mirror in the direct rays of the sun47 ,but light waves that strike rough surfaces are reflected in practically all directions and apparently without reference to the angle at which they strike4 7,illustrate by placing a piece of white paper in the direct rays of the sun4 ,it matters not from what direction it is viewed1 waves of light strike the eye47 ,this kind of reflection is called diffusion1 and it serves the important purpose of making objects visible4 ,the light waves passing out in all directions from objects which have received light from the sun1 or some other luminous body1 enable them to be seen4 ,fig4 #aeg ,fig4 #aeg--99;,diagram illustrating passage of light waves499,on the right the light is transmitted by the glass1 reflected by the mirror1 refracted by the prism1 and absorbed by the black cloth4 ,on the left the light from the candle forms an image by passing through a small hole in a cardboard and falling upon a screen4 99,formation of ,images499--,another principle necessary to seeing is that of refraction4 ,refraction means the bending1 or turning1 of light from a straight course4 ,one of the most interesting effects of refraction is the formation of images of objects1 such as may be accomplished by light from them passing in a certain manner through convex lenses4 ,if1 for example1 a convex lens be moved back and forth between a candle and a screen in a dimly lighted room1 a position will be found where a picture of the candle falls upon the screen4 ,this picture1 called the image1 results from the refraction of the candle light in passing through the lens4 ,fig4 #aeh ,fig4 #aeh--99;,diagram illustrating formation of images499 ,on the right the image is formed by a double convex lens2 on the left by the lenses of the eye4 ,the candle flame represents a luminous1 or light-giving1 body2 but light passes from the large arrow by reflection4 7,see text47 ,in order to form an image1 the light waves spreading out from the object must be brought together1 or focused4 ,focusing means literally the bringing of light to a point1 but it is evident in the formation of an image that all the waves are not brought to a single point4 ,if they were1 there would be no image4 ,in the example of the candle given above1 the explanation is as follows3 ,the light from the candle comes from a great number of separate and distinct points in the candle flame4 ,the lens1 by its peculiar shape1 bends the waves coming from any single point so that they are brought to a corresponding point on the screen4 ,furthermore1 the points of focused light are made to occupy the same relative positions on the screen as the points from which they emanate in the candle flame 7,fig4 #aeh74 ,this is why the area of light on the screen has the same form as the candle1 or makes an image of it4 ,the same explanation applies if1 instead of the luminous candle1 a body that simply reflects light1 as a book1 is used4 99,the ,problem of ,seeing499--,what we call seeing is vastly more than the stimulation of the brain through the action of light upon afferent neurons4 ,it is the perceiving of all the different things that make up our surroundings4 ,if one looks toward the clear sky1 he receives a sensation of light1 but sees no object4 ,he may also get a sensation of light with the eyelids closed1 if he turn the eyes toward the window or some bright light4 ,but how different when the light from various objects enters the eyes4 ,there is apparently no consciousness of light1 but instead a consciousness of the size1 form1 color1 and position of the objects4 ,seeing is perceiving objects4 ,stimulation by the light waves is only the means toward this end4 ,the chief problem in the study of sight is that of determining how light waves enable us to become conscious of objects4 99,sense ,organs of ,sight499--,the sense organs of sight consist mainly of the two eyeballs4 ,each of these is located in a cavity of the skull bones1 called the orbit1 where it is held in position by suitable tissues and turned in different directions by a special set of muscles4 ,a cup-shaped receptacle is provided within the orbit1 by layers of fat1 and a smooth surface is supplied by a double membrane that lies between the fat and the eyeball4 ,in front the eyeballs are provided with movable coverings1 called the eyelids4 ,these are composed of dense layers of connective tissue1 covered on the outside by the skin and lined within by a sensitive membrane1 called the conjunctiva4 ,at the base of the lids the conjunctiva passes to the eyeball and forms a firmly attached covering over its front surface4 ,this membrane prevents the passage of foreign materials back of the eyeball1 and by its sensitiveness stimulates effort for the removal of irritating substances from beneath the lids4 ,the eyelashes and the eyebrows are also a means of protecting the eyeballs4 99,the ,eyeball991 or globe of the eye1 is a device for focusing light upon a sensitized nervous surface which it incloses and protects4 ,in shape it is nearly spherical1 being about an inch in diameter from right to left and nine tenths of an inch both in its vertical diameter and from front to back4 ,it has the appearance of having been formed by the union of two spherical segments of different size4 ,the smaller segment1 which forms about one sixth of the whole1 is set upon the larger and forms the projecting transparent portion in front4 ,the walls of the eyeballs are made up of three separate layers1 or coats--an outer coat1 a middle coat1 and an inner coat 7,fig4 #aei74 ,fig4 #aei ,fig4 #aei--99;,diagram of the eyeball in position499 #a4 ,yellow spot4 #b4 ,blind spot4 #c4 ,retina4 #d4 ,choroid coat4 #e4 ,sclerotic coat4 #f4 ,crystalline lens4 #g4 ,suspensory ligament4 #h4 ,ciliary processes and ciliary muscle4 #i4 ,iris containing the pupil4 #aj4 ,cornea4 #aa4 ,lymph duct4 #ab4 ,conjunctiva4 #ac4 ,inferior and superior recti muscles4 #ad4 ,optic nerve4 #ae4 ,elevator muscle of eyelid4 #af4 ,bone4 ,a4 ,posterior chamber containing the vitreous humor4 ,b4 ,anterior chamber containing the aqueous humor4 99,the ,outer ,coat99 surrounds the entire globe of the eye and consists of two parts--the sclerotic coat and the cornea4 ,the sclerotic coat covers the greater portion of the larger spherical segment and is recognized in front as the white of the eye4 ,it is composed mainly of fibrous connective tissue and is dense1 opaque1 and tough4 ,it preserves the form of the eyeball and protects the portions within4 ,it is pierced at the back by a small opening which admits the optic nerve1 and in front it becomes changed into the peculiar tissue that makes up the cornea4 ,the cornea forms the transparent covering over the lesser spherical segment of the eyeball1 shading into the sclerotic coat at its edges4 ,it has a complex structure1 consisting in the main of a transparent form of connective tissue4 ,it serves the purpose of admitting light into the eyeball4 99,the ,middle ,coat99 consists of three connected portions--the choroid coat1 the ciliary processes1 and the iris4 ,these surround the larger spherical segment4 ,all three parts are rich in blood vessels1 containing the blood supply to the greater portion of the eyeball4 ,the choroid coat lies immediately beneath the sclerotic coat at all places except a small margin toward the front of the eyeball4 ,it is composed chiefly of blood vessels and a delicate form of connective tissue that holds them in place4 ,it contains numerous pigment cells which give it a dark appearance and serve to absorb surplus light4 ,near where the sclerotic coat joins the cornea1 the choroid coat separates from the outer wall and1 by folding1 forms many slight projections into the interior space4 ,these are known as the ciliary processes4 ,the effect of these folds is to collect a large number of capillaries into a small space and to give this part of the eyeball an extra supply of blood4 ,between the ciliary processes and the sclerotic coat is a small muscle1 containing both circular and longitudinal fibers1 called the ciliary muscle4 ,the iris is a continuation of the choroid coat across the front of the eyeball4 ,it forms a dividing curtain between the two spherical segments and gives the color to the eye4 ,at its center is a circular opening1 called the pupil1 which admits light to the back of the eyeball4 ,by varying the size of the pupil1 the iris is able to regulate the amount of light which passes through and it employs for this purpose two sets of muscular fibers4 ,one set of fibers forms a thin band which encircles the pupil and serves as a sphincter to diminish the opening4 ,opposing this are radiating fibers which are attached between the inner and outer margins of the iris4 ,by their contraction the size of the opening is increased4 ,both sets of fibers act reflexively and are stimulated by variations in the light falling upon the retina4 ,fig4 #afj ,fig4 #afj--99;,diagram showing main nervous elements in the retina499 ,light waves stimulate the rods and cones at back surface of the retina1 starting impulses which excite the ganglion cells at the front surface4 ,fibers from the ganglion cells pass into the optic nerve4 99,the ,inner ,coat1 or ,retina499--,this is a delicate membrane containing the expanded termination of the optic nerve4 ,it rests upon the choroid coat and spreads over about two thirds of the back surface of the eyeball4 ,although not more than one fiftieth of an inch in thickness1 it presents a very complex structure1 essentially nervous1 and is made up of several distinct layers4 ,of chief importance in the outer layer are the cells which are acted upon directly by the light and are named1 from their shape1 the rods and cones4 ,in contact with these1 but occupying a separate layer1 are the ends of small afferent nerve cells4 ,these in turn communicate with nerve cells in a third layer1 known as the ganglion cells1 that send their fibers into the optic nerve 7,fig4 #afj74 ,in the center of the retina is a slight oval depression having a faint yellowish color1 and called1 on that account1 the yellow spot4 ,this is the part of the retina which is most sensitive to light4 ,directly over the place of entrance of the optic nerve is a small area from which the rods and cones are absent and which1 therefore1 is not sensitive to light4 ,this is called the blind spot4 7,see ,practical ,work47 99,the ,crystalline ,lens499--,immediately back of the iris and touching it is a transparent1 rounded body1 called the crystalline lens4 ,this is about one fourth of an inch thick and one third of an inch through its long diameter1 and is more curved on the back than on the front surface4 ,it is inclosed in a thin sheath1 called the membranous capsule1 which connects with a divided sheath from the sides of the eyeball1 called the suspensory ligament 7,fig4 #aei74 ,both the lens and the capsule are highly elastic4 99,chambers and ,humors of the ,eyeball499--,the crystalline lens together with the suspensory ligament and the ciliary processes form a partition across the eyeball4 ,this divides the eye space into two separate compartments1 which are filled with the so-called humors of the eye4 ,the front cavity of the eyeball1 which is again divided in part by the iris1 is filled with the aqueous humor4 ,this is a clear1 lymph-like liquid which contains an occasional white corpuscle4 ,it has a feeble motion and is slowly added to and withdrawn from the eye4 ,it is supplied mainly by the blood vessels in the ciliary processes and finds a place of exit through a small lymph duct at the edge of the cornea 7,fig4 #aei74 ,the back portion of the eyeball is filled with a soft1 transparent1 jelly-like substance1 called the vitreous humor4 ,it is in contact with the surface of the retina at the back and with the attachments of the lens in front1 being surrounded by a thin covering of its own1 called the hyaloid membrane4 ,the aqueous and vitreous humors aid in keeping the eyeball in shape and also in focusing4 99,how we see ,objects499--,to see an object at least four things must happen3 #a4 ,light must pass from the object into the eye4 ,objects cannot be seen where there is no light or where1 for some reason1 it is kept from entering the eye4 #b4 ,the light from the object must be focused 7made to form an image7 on the retina4 ,in forming the image1 an area of the retina is stimulated which corresponds to the form of the object4 #c4 ,impulses must pass from the retina to the brain1 stimulating it to produce the sensations4 #d4 ,the sensations must be so interpreted by the mind as to give an impression of the object4 99,focusing ,power of the ,eyeball499--,the eyeball is essentially a device for focusing light4 ,all of its transparent portions are directly concerned in this work1 and the portions that are not transparent serve to protect and operate these parts and hold them in place4 ,of chief importance are the crystalline lens and the cornea4 ,both of these are lenses4 ,the cornea with its inclosed liquid is a plano-convex lens1 while the crystalline lens is double convex47#abc7 ,because of the great difference in density between the air on the outside and the aqueous humor within1 the cornea is the more powerful of the two4 ,the crystalline lens1 however1 performs a special work in focusing which is of great importance4 ,the iris also aids in focusing since it1 through the pupil1 regulates the amount of light entering the back chamber of the eyeball and causes it to fall in the center of the crystalline lens1 the part which focuses most accurately4 ,fig4 #afa ,fig4 #afa--99;,diagram showing changes in shape of crystalline lens99 to adapt it to near and distant vision4 99,accommodation499--,a difficulty in focusing arises from the fact that the degree of divergence of the light waves entering the eye from different objects1 varies according to their distance4 ,since the waves from any given point on an object pass out in straight lines in all directions1 the waves that enter the eye from distant objects are at a different angle from those that enter from near objects4 ,in reality waves from distant objects are practically parallel1 while those from very near objects diverge to a considerable degree4 ,to adjust the eye to different distances requires some change in the focusing parts that corresponds to the differences in the divergence of the light4 ,this change1 called accommodation1 occurs in the crystalline lens47#abd7 ,in the process of accommodation1 changes occur in the shape of the crystalline lens1 as follows3 #a4 ,in looking from a distant to a near object1 the lens becomes more convex1 i4e41 rounder and thicker 7,fig4 #afa74 ,this change is necessary because the greater divergence of the light from the near objects requires a greater converging power on the part of the lens47#abe7 #b4 ,in looking from near to distant objects1 the lens becomes flatter and thinner 7,fig4 #afa74 ,this change is necessary because the less divergent waves from the distant objects require less converging power on the part of the lens4 ,the method employed in changing the shape of the lens is difficult to determine and different theories have been advanced to account for it4 ,the following1 proposed by ,helmholtz1 is the theory most generally accepted3 ,the lens is held in place back of the pupil by the suspensory ligament4 ,this is attached at its inner margin to the membranous capsule1 and at its outer margin to the sides of the eyeball1 and entirely surrounds the lens4 ,it is drawn perfectly tight so that the sides of the eyeball exert a continuous tension1 or pull1 on the membranous capsule1 which1 in its turn1 exerts pressure on the sides of the lens1 tending to flatten it4 ,this arrangement brings the elastic force of the eyeball into opposition to the elastic force of the lens4 ,the ciliary muscle plays between these opposing forces in the following manner3 ,to thicken the lens1 the ciliary muscle contracts1 pulling forward the suspensory ligament and releasing its tension on the membranous capsule4 ,this enables the lens to thicken on account of its own elastic force4 ,to flatten the lens1 the ciliary muscle relaxes1 the elastic force of the eyeball resumes its tension on the suspensory ligament1 and the membranous capsule resumes its pressure on the sides of the lens4 ,this pressure1 overcoming the elastic force of the lens1 flattens it4 99,movements of the ,eyeballs499--,in order that the light may enter the eyeballs to the best advantage1 they must be moved in various directions4 ,these movements are brought about through the action of six small muscles attached to each eyeball4 ,four of these1 named1 from their positions1 the superior1 inferior1 internal1 and external recti muscles1 are attached at one end to the sides of the eyeball and at the other end to the back of the orbit 7,fig4 #afb74 ,these1 in the order named1 turn the eyes upward1 downward1 inward1 and outward4 ,the other two1 the superior and inferior oblique muscles1 aid in certain movements of the recti muscles and1 in addition1 serve to rotate the eyes slightly4 ,the movements of the eyeballs are similar to those of ball and socket joints4 ,fig4 #afb ,fig4 #afb--99;,exterior muscles of eyeball499 99,binocular ,vision499--,in addition to directing the eyeballs so that light may enter them to the best advantage from different objects1 the muscles also enable two eyes to be used as one4 ,whenever the eyes are directed toward the same object1 an image of this object is formed on the retina of each4 ,double vision is prevented only by having the images fall on corresponding places in the two eyes4 ,this is accomplished by the muscles4 ,in each act of seeing1 it becomes the task of the superior and inferior recti muscles to keep the eyes in the same plane1 and of the external and internal recti muscles to give just the right amount of convergence4 ,if slight pressure is exerted against one of the eyes1 the action of the muscles is interfered with and1 as a consequence1 one sees double4 ,the advantages of two eyes over one in seeing lie in the greater distinctness and broader range of vision and in the greater correctness of judgments of distance4 99,visual ,sensations499--,the visual sensations include those of color and those of a general sensibility to light4 ,proof of the existence of these types of sensation is found in color blindness1 a defect which renders the individual unable to distinguish certain colors when he is still able to see objects4 ,color sensations are the results of light waves of different lengths acting on the retina4 ,while the method by which waves of one length produce one kind of sensation and those of another length a different sensation is not understood1 the cones appear to be the portions of the retina acted on to produce the color4 ,on the other hand1 the rods are sensitive to all wave lengths and give general sensibility to light4 99,visual ,perceptions499--,seeing is very largely the mental interpretation of the primary sensations and the conditions under which they occur4 ,for example1 our ability to see objects in their natural positions when their images are inverted on the retina is explained by the fact that we are not conscious of the retinal image1 but of the mind's interpretation of it through experience4 ,experience has also taught us to locate objects in the direction toward which it is necessary to turn the eyes in order to see them4 ,in other words1 we see objects in the direction from which the light enters the eyes4 ,that the object is not always in that direction is shown by the image in the mirror4 ,the apparent size and form of objects are inferences1 and they are based in part upon the size and form of the area of the retina stimulated4 ,we judge of distance by the effort required to converge the eyes upon the objects1 by the amount of divergence of the waves entering the pupil1 and also by the apparent size of the object4 99,the ,lachrymal ,apparatus499--,seeing requires that the light penetrate to the retina4 ,for this reason all the structures in front of the retina are transparent4 ,one of these structures1 the cornea1 on account of its exposure to the air1 is liable to become dry1 like the skin1 and to lose its transparency4 ,to preserve the transparency of the cornea1 and also to lubricate the eyelids and aid in the removal of foreign bodies1 a secretion1 called tears1 is constantly supplied4 ,fig4 #afc ,fig4 #afc--99;,diagram of irrigating system of the eye499 ,after wetting the eyeball the tears may also moisten the air entering the lungs4 ,the lachrymal1 or tear1 glands are situated at the upper and outer margins of the orbits4 ,they have the general structure of the salivary glands and discharge their liquid by small ducts beneath the upper lids4 ,from here the tears spread over the surfaces of the eyeballs and find their way in each eye to two small canals whose openings may be seen on the edges of the lids near the inner corner 7,fig4 #afc74 ,these canals unite to form the nasal duct1 which conveys the tears to the nasal cavity on the same side of the nose4 ,when by evaporation the eyeball becomes too dry1 the lids close reflexively and spread a fresh layer of tears over the surface4 ,any excess is passed into the nostrils1 where it aids in moistening the air entering the lungs4 ,,hygiene ,,of ,,the ,,eye 99,defects in ,focusing499--,the delicacy and complexity of the sense organs of sight render them liable to a number of imperfections1 or defects1 the most frequent and important being those of focusing4 ,such defects not only result in the imperfect vision of objects1 but they throw an extra strain upon the nervous system and may render the process of seeing exceedingly painful4 ,a normal eye is able1 when relaxed1 to focus light accurately from objects which are twenty feet or more away and to accommodate itself to objects as near as five inches4 ,an eye is said to be myopic1 or short-sighted1 when it is unable to focus light waves from distant objects1 but can only distinguish the objects which are near at hand4 ,in such an eye the ball is too long for the converging power of the lenses1 and the image is formed in front of the retina 7,c1 ,fig4 #afd74 ,fig4 #afd ,fig4 #afd--99;,diagrams illustrating long-sightedness and short-sightedness991 and method of remedying these defects by lenses4 ,a4 ,normal eye4 ,b4 ,long-sighted eye4 ,c4 ,short-sighted eye4 ,a long-sighted1 or hypermetropic1 eye is one which can focus light from distant objects1 but not from near objects4 ,in such an eye the ball is too short for the converging power of the lenses and the image tends to form back of the retina 7,b1 ,fig4 #afd74 ,these defects in focusing are remedied by wearing glasses with lenses so shaped as to counteract them4 ,short-sightedness is corrected by concave lenses and long-sightedness by convex lenses1 as shown in diagrams above4 ,astigmatism is another defect in the focusing power of the eye4 ,in astigmatism the parts of the eye fail to form the image in the same plane1 so that all portions of the object do not appear equally distinct4 ,certain parts of it are indistinct1 or blurred4 ,the cause is found in some difference in curvature of the surfaces of the cornea or crystalline lens4 ,it is corrected by lenses so ground as to correct the particular defects present in a given eye4 ,whenever defects in focusing are present1 particularly in astigmatism1 extra work is thrown on the ciliary muscle as well as the muscles that move the eyeballs4 ,the result is frequently to induce a condition1 known as muscle weakness1 which renders it difficult to use the eyes4 ,even after the defect in focusing has been remedied1 the muscles recover slowly and must be used with care4 ,for this reason glasses should be fitted by a competent oculist7#abf7 as soon as a defect is known to exist4 ,when one is unduly nervous1 or suffers from headache1 the eyes should be examined for defects in focusing 7page #cbf74 99,eye ,strain and ,disease499--,the extra work thrown upon the nervous system through seeing with defective eyes1 especially in reading and other close work1 is now recognized as an important cause of disease4 ,through the tax made upon the nervous system by the eyes1 there may be left an insufficient amount of nervous energy for the proper running of the vital processes4 ,as a result there is a decline of the health4 ,ample proof that eye strain interferes with the vital processes and causes ill health1 is found in the improvements that result when1 by means of glasses1 this is relieved4 99,the ,eyes of ,school ,children499--,school children often suffer from defects of vision which render close work burdensome1 and cause headache1 general nervousness1 and disease4 ,furthermore1 the visual defects may be unknown both to themselves and to their parents4 ,pupils showing indications of eye-strain should be examined by an oculist1 and fitted with glasses should defects be discovered47#abg7 ,the precaution1 adopted by many schools1 of having the eyes of all children examined by a competent physician employed for the purpose1 is most excellent and worthy of imitation4 99,reading ,glasses499--,many people whose eyes are weak1 because slightly defective1 find great relief in the use of special glasses for reading and other close work4 ,by using such glasses they may postpone the time when they are compelled to wear glasses constantly4 ,it is in the close work that the extra strain comes upon the eyes1 and if this is relieved1 one can much better withstand the work of distant vision4 ,the reading glasses should be fitted by a competent oculist1 and used only for the purpose for which they are intended4 99,general ,precautions in the ,use of the ,eyes499--,if proper care is exercised in the use of the eyes1 many of their common ailments and defects may be avoided4 ,any one1 whether his eyes are weak or strong1 will do well to observe the following precautions3 #a4 ,never read in light that is very intense or very dim4 #b4 ,when the eyes hurt from reading1 stop using them4 #c4 ,never hold a book so that the smooth page reflects light into the eyes4 ,the best way is to sit or stand so that the light passes over the shoulder to the book4 #d4 ,never study by a lamp that is not shaded4 #e4 ,practice cleanliness in the care of the eyes4 ,avoid rubbing the eyes with the fingers unless sure the fingers are clean4 ,if the eyes are weak1 use them less and avoid1 if possible1 reading by artificial light4 ,weak eyes are sometimes benefited by bathing them in warm water1 or with water containing enough salt to make them smart slightly4 ,boracic acid dissolved in water 7#dj grains to #d ounces of distilled water7 is also highly recommended as a wash for weak eyes4 ,fig4 #afe ,fig4 #afe--99,method of procedure in lifting the eyelid99 7,pyle74 99,removal of ,foreign ,bodies from the ,eyes499--,foreign bodies embedded in the eyeball should be removed by the oculist or physician4 ,small particles of dust or cinder may be removed without the aid of the physician1 by exercising proper care4 ,first let the tears1 if possible1 wash the offending substance to the corner of the eye1 or edge of the lid1 where it can be removed with a soft cloth4 ,if it sticks to the ball or the under surface of the lid1 it will be necessary to find where it is located1 and then dislodge it from its position4 ,begin by examining the lower lid4 ,pull it down sufficiently to expose the inner surface1 and1 if the foreign substance be there1 wipe it off with the hem of a clean handkerchief4 ,if it is not under the lower lid1 it will be necessary to fold back the upper lid4 ,the patient is told to look down1 the edge of the lid and the lashes are seized with the forefinger and thumb of the right hand 7,fig4 #afe71 and the lid is drawn at first downward and forward away from the globe2 then upward and backward over the point of the thumb or forefinger of the left hand1 which is held stationary on the lid1 and acts as a fulcrum47#abh7 ,the foreign body is now removed in the same manner as from the lower lid4 ,a large lens may be used to good advantage in finding the irritating substance4 99,strong ,chemicals in the ,eyes499--,students in the laboratory frequently1 through accident1 get strong chemicals1 as acids and bases1 in the eyes4 ,the first thing to do in such cases is quickly and thoroughly to flood the eyes with water4 ,any of the chemical which remains may then be counteracted by the proper reagent1 care being taken to use a very dilute solution4 ,to counteract an acid1 use sodium bicarbonate 7cooking soda71 and for bases use a very dilute solution of acetic acid 7vinegar74 ,to guard against getting the counteractive agent too strong for the inflamed eye1 it should first be tried on an eye that has not been injured4 99,summary499--,the nervous impulses that cause the sensation of sight are started by light waves falling upon a sensitized nervous surface1 called the retina4 ,by means of refractive agents1 forming a part of the eyeball in front of the retina1 light from different objects is focused and made to form images of the objects upon the surface4 ,in this way the light is made to stimulate a portion of the retina corresponding to the form of the object4 ,this1 the image method of stimulation1 enables the mind to recognize objects and to locate them in their various positions4 ,while the greater portion of the eyeball is concerned in the focusing of light1 the crystalline lens1 operated by the ciliary muscle1 serves as the special instrument of accommodation4 ,muscles attached to the eyeballs turn them in different directions1 and so adjust them with reference to each other that double vision is avoided4 99,exercises499--#a4 ,under what conditions are light waves reflected1 refracted1 and absorbed8 #b4 ,why does the body not need a light-producing apparatus1 corresponding to the larynx in the production of sound8 #c4 ,how is the light from a candle made to form an image8 #d4 ,what different things must happen in order that one may see an object8 #e4 ,make a sectional drawing of the eyeball1 locating and naming all the parts4 #f4 ,of what parts are the outer1 middle1 and inner coats of the eyeball made up8 #g4 ,what portions of the eyeball reflect light8 ,what absorb light8 ,what transmit light8 ,what refract light8 #h4 ,show how the iris1 the crystalline lens1 the retina1 the ciliary muscle1 and the cornea aid in seeing4 #i4 ,trace a wave of light from a visible object to the retina4 #aj4 ,why does not the inverted image on the retina cause us to see objects upside down8 #aa4 ,what change occurs in the shape of the crystalline lens when we look from distant to near objects8 ,from near to distant objects8 ,why are these changes necessary8 ,how are they brought about8 #ab4 ,how does the method of adjustment1 or accommodation1 of the eyeball differ from that of a telescope or a photographer's camera8 #ac4 ,with two eyes how are we kept from seeing double8 #ad4 ,what different purposes are served by the tears4 ,trace them from the lachrymal glands to the nostrils4 #ae4 ,show how the proper lenses remedy short- and long-sightedness4 #af4 ,describe the conjunctiva and give its functions4 ,why should it be so sensitive8 #ag4 ,how may eye strain cause disease in parts of the body remote from the eyes8 #ah4 ,how does image stimulation differ from light stimulation in general8 ,,practical ,,work 99,to illustrate ,simple ,properties of ,light499--#a4 ,heat an iron or platinum wire in a clear gas flame4 ,observe that when a high temperature is reached it gives out light or becomes luminous4 #b4 ,cover one hand with a white and the other with a black piece of cloth1 and hold both for a short time in the direct rays of the sun4 ,note and account for the difference in temperature which is felt4 #c4 ,stand a book or a block of wood by the side of an empty pan in the sunlight1 so that the end of the shadow falls on the bottom of the pan4 ,mark the place where the shadow terminates and fill the pan with water4 ,account for the shadow's becoming shorter4 #d4 ,place a coin in the center of an empty pan and let the members of the class stand where the coin is barely out of sight over the edges of the pan4 ,fill the pan with water and account for the coin's coming into view4 ,show by a drawing how light1 in passing from the water into the air1 is so bent as to enter the eye4 #e4 ,with a convex lens1 in a darkened room1 focus the light from a candle flame so that it falls on a white screen and forms an image of the candle4 ,observe that the image is inverted4 ,in a well-lighted room focus the light from a window upon a white screen4 ,show that1 as the distance from the window to the screen is changed1 the position of the lens must also be changed4 7,accommodation47 #f4 ,hold a piece of cardboard1 about eight inches square and having a smooth1 round hole an eighth of an inch in diameter in the center1 in front of a lighted candle in a darkened room4 ,back of the opening place a muslin or paper screen 7,fig4 #aeg74 ,observe that a dim image is formed4 ,account for the fact that it is inverted4 ,hold a lens between the cardboard and the screen so that the light passes through it also4 ,the image should now appear smaller and more distinct4 ,fig4 #aff ,fig4 #aff--99;,diagram99 for proving presence of the blind spot4 99,to prove the ,presence of the ,blind ,spot499--,close the left eye and with the right gaze steadily at the spot on the left side of this page 7,fig4 #aff74 ,then starting with the book a foot or more from the face1 move it slowly toward the eye4 ,a place will be found where the spot on the right entirely disappears4 ,on bringing it nearer1 however1 it is again seen4 ,as the book is moved forward or backward1 the position of the image of this spot changes on the retina4 ,when the spot cannot be seen1 it is because the image falls on the blind spot4 99,dissection of the ,eyeball499--,procure from the butcher two or three eyeballs obtained from cattle4 ,after separating the fat1 connective tissue1 and muscle1 place them in a shallow vessel and cover with water4 ,insert the blade of a pair of sharp scissors at the junction of the sclerotic rotic coat with the cornea and cut from this point nearly around the entire circumference of the eyeball1 passing near the optic nerve4 ,spread open in the water and identify the different parts from the description in the text4 ,open the second eyeball in water by cutting away the cornea4 ,examine the parts in front of the lens4 ,fig4 #afg ,fig4 #afg--99,model99 for demonstrating the eyeball4 99,to illustrate ,accommodation499--,paste together the ends of a strip of stiff writing paper 7two by five inches7 making a ring a little less than three inches in diameter4 ,this is to represent the crystalline lens4 ,now paste a piece of thin paper 7two by seven inches7 upon a second strip of the same size1 leaving an open place in the middle for the insertion of the paper lens4 ,a flexible piece of cardboard 7three by twelve inches7 is now bent into the form of a half circle and to its ends are fastened the strips of paper containing the ring4 ,make a small hole in each of the four corners of the bent cardboard4 ,through these holes pass two loops of thread1 or fine string1 in opposite directions1 letting the ends hang loose from the cardboard4 ,when everything is in position1 the tension from the cardboard flattens the paper lens1 while pulling the strings releases this tension and permits the lens to become more rounded4 ,with this simple device the changes in the curvature of the lens for near and distant vision are easily shown4 ,,chapter ,,xxiii - ,,the ,,general ,,problem ,,of ,,keeping ,,well ,to cure was the voice of the ,past3 to prevent is the divine whispering of ,to-day4 ,as stated in the introduction to our study1 the fundamental law of hygiene is the law of harmony3 ,habits of living must harmonize with the plan of the body4 ,having acquainted ourselves with the plan of the body1 we may now review briefly those conditions that help or hinder its various activities4 ,the hygiene already presented in connection with the study of the various organs may be condensed into general rules1 or laws1 as follows3 #a4 ,of exercise3 ,exercise daily the important groups of muscles4 #b4 ,of form3 ,preserve the natural form of the body4 #c4 ,of energy3 ,observe regular periods of rest and exercise and avoid exhaustion4 #d4 ,of nutriment3 ,eat moderately of a well-cooked and well-balanced diet and drink freely of pure water4 #e4 ,of respiration3 ,breathe freely and deeply of pure air and spend a part of each day out of doors4 #f4 ,of nervous poise3 ,suppress wasteful and useless forms of nervous activity1 avoid nervous strain1 and practice cheerfulness4 #g4 ,of cleanliness3 ,keep the body and its immediate surroundings clean4 #h4 ,of restraint3 ,abstain from the unnecessary use of drugs as well as from the practice of any form of activity known to be harmful to the body4 #i4 ,of elimination3 ,observe all the conditions that favor the regular discharge of waste materials from the body4 ,obedience to these laws is of vast importance in the proper management of the body4 ,they should1 indeed1 be so thoroughly impressed upon the mind as to become fixed habits4 ,there are1 however1 other conditions that relate to this problem1 and it is to these that we now turn4 ,these conditions have reference more specifically to 99,the ,prevention of ,disease499--,while the average length of life is not far from thirty-five years1 the length of time which the average individual is capable of living is1 according to some of the lowest estimates1 not less than seventy years4 ,this difference is due to disease4 ,people do not1 as a rule1 die on account of the wearing out of the body as seen in extreme old age1 but on account of the various ills to which flesh is heir4 ,it is true that many people meet death by accident and not a few are killed in wars1 but these numbers are small in comparison with those that die of bodily disorders4 ,the prevention of disease is the greatest of all human problems4 ,though the fighting of disease is left largely to the physician1 much is to be gained through a more general knowledge of its causes and the methods of its prevention4 99,causes of ,disease499--,disease1 which is some derangement of the vital functions1 may be due to a variety of causes4 ,some of these causes1 such as hereditary defects1 are remote and beyond the control of the individual4 ,others are the result of negligence in the observance of well-recognized hygienic laws4 ,others still are of the nature of influences1 such as climate1 the house in which one lives1 or one's method of gaining a livelihood1 that produce changes in the body1 imperceptible at the time1 but1 in the long run1 laying the foundations of disease4 ,and last1 and most potent1 are the minute living organisms1 called microbes or germs1 that find their way into the body4 ,although there are two general kinds of germs1 known as bacteria 7one-celled plants7 and protozoa 7one-celled animals71 most of our germ diseases are caused by bacteria4 99,effects of ,germs499--,while there are many kinds of germs that have no ill effect upon the body and others that are thought to aid it in its work1 there are many well-known varieties that produce effects decidedly harmful4 ,they gain an entrance through the lungs1 food canal1 or skin1 and1 living upon the fluids and tissues1 multiply with great rapidity until they permeate the entire body4 ,not only do they destroy the protoplasm1 but they form waste products1 called toxins1 which act as poisons4 ,diseases caused by germs are known as infectious1 or contagious1 diseases47#abi7 ,the list is a long one and includes smallpox1 measles1 diphtheria1 scarlet fever1 typhoid fever1 tuberculosis1 la grippe1 malaria1 yellow fever1 and others of common occurrence4 ,in addition to the diseases that are well pronounced1 it is probable that germs are responsible also for certain bodily ailments of a milder character47#acj7 99,avoidance of ,germ ,diseases499--,the problem of preventing diseases caused by germs is an exceedingly difficult one and no solution for all diseases has yet been found4 ,one's chances of avoiding such diseases1 however1 may be greatly enhanced3 #a4 ,by strengthening the body through hygienic living so that it offers greater resistance to the invasions of germs4 #b4 ,by living as far as possible under conditions that are unfavorable to germ life4 #c4 ,by understanding the agencies through which disease germs are spread from person to person4 99,conditions ,favorable and ,unfavorable for ,germs499--,conditions favorable for germ life are supplied by animal and vegetable matter1 moisture1 and a moderate degree of warmth4 ,hence disease germs may be kept alive in damp cellars and places of filth4 ,even living rooms that are poorly lighted or ventilated may harbor them4 ,water may1 if it contain a small per cent of organic matter1 support such dangerous germs as those of typhoid fever4 ,fresh air1 sunlight1 dryness1 cleanliness1 and a high temperature1 on the other hand1 are destructive of germs4 ,the germs in impure water1 as already noted 7page #afe71 are destroyed by boiling4 99,how ,germs are ,spread499--,some of the more common methods by which the germs of disease are spread1 and by so doing find new victims1 are as follows3 #a4 ,by ,means of ,foods4--,foods1 on account of the locality in which they are produced or the method of gathering or of handling-them1 may become contaminated with germs1 which are then transported with the foods to the consumer4 #b4 ,by ,means of ,dust4--,material containing germs1 e4g41 discharges from the throat and lungs1 will on drying form dust4 ,this is lifted with other fine particles by the air and may be carried quite a distance4 ,the dust from public halls and other places where people congregate is the kind most likely to contain disease germs4 ,dust should be breathed as little as possible and only through the nostrils4 ,where one is compelled1 as in sweeping1 to breathe dust-laden air for some time1 he should inhale through a moistened sponge1 or cloth1 tied in front of the nostrils4 #c4 ,by ,means of ,domestic ,pets and ,different ,kinds of ,household ,vermin4--,germs sticking to the bodies of small animals are carried about and may be easily communicated to people4 ,by this means1 rats1 mice1 bedbugs1 etc41 where such exist1 are frequently the means of spreading disease2 and particularly dangerous1 on this account1 is the common house fly4 ,feeding as it does on filth of all kinds1 it is easy for it to transfer the bacteria that may stick to its body to the food which is supplied to the table4 ,the proper screening of houses and the destruction of material in which flies may develop1 such as the refuse from stables1 are necessary precautions4 ,germs are spread also by the clothing of people1 by railroad and steamship lines1 by the mails1 and by the natural elements4 ,in fact1 any kind of carrier1 in or upon which germs can live1 may serve as a means of spreading those of certain kinds4 99,public ,sanitation499--,the general conditions under which germs may thrive and some of the means by which they are scattered1 emphasize the practical value of measures which have for their purpose the making of one's surroundings more wholesome and hygienic4 ,such measures may be directed both toward one's immediate surroundings--the home--and toward the neighborhood1 town1 or city in which one lives4 ,the hygienic conditions of primary importance in every city or town are as follows3 #a4 ,an adequate public supply of pure water4 #b4 ,an efficient system of underground pipes for the removal of sewage4 #c4 ,an efficient system for removing from the streets and alleys everything of the nature of waste4 #d4 ,prevention1 by enforcement of ordinances1 of spitting upon sidewalks and the floors of public halls and conveyances4 #e4 ,a hospital or sanitarium in which people can be cared for when sick with infectious diseases4 ,in the larger cities other hygienic measures demand attention1 such as provisions for parks and playgrounds1 the proper housing of the poor of the city1 and the suppression of the smoke and dust nuisances4 ,crowded together as people are in the cities1 the welfare of each individual depends in a large measure upon the welfare of all4 ,hence the problems of public sanitation are matters in which all are vitally concerned4 99,sanitary ,conditions of the ,home499--,the home1 being the feeding and resting place for the entire family1 is the most important factor in one's physical1 as well as moral1 environment4 ,for this reason there is no place where careful attention to hygienic requirements will yield better results4 ,much of the danger from germs may be prevented by instituting and maintaining proper sanitary conditions in and about the home4 ,one of the first requisites of the home is a suitable location for the house4 ,the house should be built upon ground that is well drained1 and if natural drainage be lacking1 artificial drainage must be supplied4 ,it should not be situated nearer than a quarter of a mile to any marsh or swamp and1 if so near as that1 it ought to be on the side from which the wind usually blows4 ,a stone foundation should be provided1 and at least eighteen inches of ventilated air space should be left between the ground and the floor4 ,ample provisions must be made for pure air and sunlight in all the rooms4 ,the cellar1 if one is desired1 needs to be constructed with special care4 ,it should be perfectly dry and provided with windows for light and ventilation4 ,adequate means must also be provided1 by sewage pipes and other methods1 for the disposal of all waste4 ,where drainage pipes are provided1 care must be taken to prevent the entrance of sewer gas into the house and also the passage of material from these pipes into the water supply4 ,the placing and connecting of sewer pipes should1 of course1 be under the direction of a plumber4 99,the ,water ,supply499--,since water readily takes up and holds the impurities with which it comes in contact1 it should be exposed as little as possible in the process of collecting4 ,where cistern water is used1 care must be taken to prevent filth from the roof 7,fig4 #afh71 water pipes1 or soil from getting into the reservoir4 ,water should be collected from the roof only after it has rained long enough for the roof and pipes to have been thoroughly cleaned4 ,the cistern should have no leaks 7,fig4 #afi71 and the top should be tightly closed to prevent the entrance of small animals and rubbish4 ,fig4 #afh ,fig4 #afh--99;,contamination of cistern water99 by birds nesting in the gutter trough4 ,shallow wells are to be condemned1 as a rule1 because of the likelihood of surface drainage 7,fig4 #afi71 and water from springs should1 for the same reason1 be used with caution4 ,deep wells that are kept clean usually may be relied on to furnish water free from organic impurities1 but such water often holds in solution so much of mineral impurities as to render it unfit for drinking4 ,the presence in water of any considerable quantity of the compounds of iron or calcium makes it objectionable for regular use4 ,fig4 #afi ,fig4 #afi--99,sources of contamination of cistern and well water499 ,illustration shows liability of contamination from surface drainage and from entrance of filth at top4 99,hygienic ,housekeeping499--,however carefully a house has been constructed from a sanitary standpoint1 the constant care of an intelligent housekeeper is required to keep it a healthful place in which to live4 ,daily cleaning and airing of all living rooms are necessary1 while such places as the kitchen1 the cellar1 and the closets need extra thoughtfulness and1 at times1 hard work4 ,moreover1 the problem is not all indoors4 ,the immediate premises must be kept clean and sightly1 and all decaying vegetable and animal matter should be removed4 ,home sanitation consists1 not of one1 but of many1 problems1 all more or less complex4 ,none of these can be slighted or turned over to a novice4 99,destruction of ,infectious ,material499--,at times the housekeeping has to be directed especially toward hygienic requirements1 such an occasion being the sickness of one of the inmates with some contagious disease4 ,unless special precautions are taken1 the disease will spread to other members of the household and may reach people in the neighborhood4 ,not only must great care be exercised that nothing used in connection with the sick shall serve as a carrier of disease1 but germs passing from the patient should1 as far as possible1 be actually destroyed4 ,all discharges from the body likely to contain bacteria1 should be burned or treated with disinfectants and buried deeply at a remote distance from the water supply to the house4 ,after recovery all clothing1 bedding1 and furniture used in connection with the sick should be disinfected or burned4 ,the room also in which the sick was cared for should be thoroughly disinfected and cleaned2 in some instances the woodwork ought to be repainted and the walls repapered or calcimined4 ,the purpose is1 of course1 to destroy all germs and prevent1 by this means1 a recurrence of the disease4 99,fumigation499--,to destroy germs in the air or adhering to the walls of rooms1 furniture1 clothing1 etc41 fumigation is employed4 ,this is accomplished by saturating the air of rooms with some vapor or gas which will destroy the germs4 ,fumigation is quite generally employed in the general cleaning after the patient leaves his room4 ,this1 to be effective1 must be thorough4 ,formaldehyde is considered the best disinfectant for this purpose1 and it should be evaporated with heat in the proportion of one half pint of the #dj per cent solution to #ajjj cu4 ft4 of space4 ,since formaldehyde is inflammable and easily boils over1 it has to be evaporated with care4 ,it should be boiled in a tall vessel 7a tin or copper vessel which holds about four times the quantity to be evaporated7 over a quick fire1 the room being tightly closed 7openings around windows and doors plugged with cotton or cloth74 ,after three or four hours the room may be opened and thoroughly aired4 ,since formaldehyde is most disagreeable to breathe1 one should not attempt to occupy the room until it is free from the gas4 ,this will require a day or more of thorough ventilation4 99,facts ,relating to the ,spread of ,certain ,diseases499--,the problem of preventing disease in general often resolves itself into the problem of preventing the spread of some particular disease4 ,it is then of vital importance to know the special method by which the germs of this disease leave the body of the patient and are conveyed to the bodies of others4 ,some of these methods are novel in the extreme1 and are not at all in accord with prevailing notions4 ,particularly is this true of that disease known as 99,malaria1 or ,malarial ,fever499--,this disease1 so common in warm climates and also prevalent to a large extent in the temperate zones1 is due to animal germs 7protozoa71 which attack and destroy the red corpuscles of the blood4 ,these germs1 it is found1 pass from malarial patients to others through the agency of a variety of mosquitoes known as ,anopheles4 ,in sucking the blood of a malarial patient1 the mosquito first infects her own body47#aca7 ,in the body of the mosquito the germs undergo an essential stage of their development1 after which they are injected beneath the skin of whomsoever the mosquito feeds upon4 ,for the spreading of malaria1 then1 two conditions are necessary3 first1 there must be people who have the disease2 and second1 there must be in the neighborhood the special variety of mosquito that spreads the disease4 ,if either condition be lacking1 the disease is not spread4 ,the malarial mosquito 7,anopheles7 may be distinguished from the harmless variety 7,culex7 by the position which it assumes in resting1 as shown in ,fig4 #agj4 ,fig4 #agj ,fig4 #agj--99,mosquitoes99 in resting position4 7,from ,howard's ,mosquitoes47 ,on left the malarial mosquito 7,anopheles72 on the right the harmless mosquito 7,culex74 99,remedies against ,mosquitoes499--,the natural method of preventing the spread of malaria is1 of course1 the destruction of mosquitoes4 ,this is accomplished by draining pools of water where they are likely to breed1 and by covering pools of water that cannot be drained with crude petroleum or kerosene4 ,the kerosene1 by destroying the larvae1 prevents the development of the young4 ,in communities where such measures have been diligently carried out1 the mosquito pest has been practically eliminated4 ,other methods are also under investigation1 such as the stocking of shallow bodies of water with varieties of fish that feed upon the mosquito larvae4 ,fig4 #aga ,fig4 #aga--99,stegomyia991 the yellow-fever mosquito 7after ,howard74 99,yellow ,fever499--,this scourge of the tropics is1 like malaria1 caused by animal germs4 ,it is also propagated in the same manner as malaria1 but by a different variety of mosquito 7,stegomyia1 ,fig4 #aga74 ,the stamping out of yellow fever in ,havana1 the ,panama ,canal ,zone1 and other places1 through the destruction of this variety of mosquito1 affords ample proof of the correctness of the mosquito theory4 ,fig4 #agb ,fig4 #agb--99;,consumption germs99 from the spit of one having the disease4 ,highly magnified and stained4 7,huber's ,consumption and ,civilization47 99,consumption991 or tuberculosis of the lungs1 spoken of as the white plague1 was among the first diseases shown to be due to bacteria4 ,consumption is now recognized as an infectious disease1 though not so readily communicated as some other diseases4 ,several methods are recognized by which the germs are passed from the sick to the well1 the most important being as follows3 #a4 ,by personal contact of the sick with the well1 especially in kissing4 #b4 ,by the sputum1 or spit1 which1 if allowed to dry1 is blown about as dust and breathed into the lungs7#acb7 7,fig4 #agb74 #c4 ,by means of objects 7drinking cups1 tableware1 etc47 that have been handled by consumptives4 #d4 ,by infectious material associated with houses or rooms in which consumptives have lived4 ,these methods of spreading consumption suggest the necessity for the greatest care1 on the part of both the patient and those having him in charge47#acc7 ,the material coughed up from the lungs and throat should be collected on cloths or paper handkerchiefs and afterwards burned4 ,the house where a consumptive has lived should be disinfected1 repapered or calcimined1 and thoroughly cleaned before it is again occupied4 ,the inside woodwork should also be repainted4 ,the approaches to the house where the patient may have expectorated should be disinfected and cleaned4 ,since the germs are able to live in the soil1 fresh lime or wood ashes should be spread around the doorsteps and along the walks4 99,typhoid ,fever991 one of our most dangerous diseases1 is caused by germs 7bacteria7 that enter the body through the food canal4 ,they attack certain glands in the walls of the small intestine1 where they produce toxins that pass with the germs to all parts of the body4 ,typhoid fever germs spread from those having the disease to others1 chiefly through the discharges from the bowels and the kidneys4 ,the germs contained in these1 if not destroyed by disinfectants1 find their way into the soil1 or into sewage1 where they may be picked up by water and widely distributed4 ,finding suitable places1 such as those containing decaying material1 the germs may rapidly increase in number1 and from these sources find their way into the bodies of new victims4 ,they are likely1 on account of manures1 to get on vegetables2 on account of uncleanly methods of milking1 to get into the milk supply2 and from sewerage outlets1 to get into the oysters that grow in bays and harbors near seaboard cities2 but they are most frequently introduced into the body through the drinking of impure water4 99,diphtheria991 also known as membranous croup1 is caused by germs that attack the membranes of the throat4 ,this most dangerous of children's diseases is spread chiefly by discharges from the mouth and throat4 ,these should be collected on cloths and burned1 or rendered harmless with disinfectants4 ,the disease may be spread also by objects brought into contact with the mouth1 such as cups1 toys1 pencils1 etc4 ,children are known to have diphtheria germs in the mouth for some time after recovering from the disease1 and should1 for this reason1 be kept away from other children until pronounced safe by the physician4 ,the antitoxin method of treating diphtheria has robbed this disease of much of its terror1 yet it not infrequently happens that the physician is called too late to administer this remedy to the best advantage4 ,since certain cases of diphtheria are likely to be mistaken for croup1 the parent frequently does not realize the serious condition of the child4 ,a croupy cough that lasts through the day1 or a sore throat which shows small white patches1 are indications of diphtheria4 99,scarlet ,fever1 ,measles1 ,chicken ,pox1 and ,smallpox991 on account of the eruptions of the skin which attend them1 are classed as eruptive diseases4 ,as the eruptions heal1 scales separate from the skin1 and these are supposed to be the chief means of spreading the germs4 ,attention must be given to the destruction of these scales by burning or thoroughly disinfecting all objects1 such as clothing1 bedding1 etc41 that may serve as carriers of them4 ,those having eruptive diseases should be confined to their rooms as long as the scales continue to separate from the body4 99,vaccination499--,the method of preventing smallpox known as vaccination1 which has been practiced since its discovery in #agif by ,jenner1 has always proved effective4 ,in some instances the sore arm causes considerable inconvenience1 but this generally results from neglect to cleanse the arm thoroughly before applying the virus1 or from contact of the sore with the clothing later4 ,the virus should be applied by a physician and the wound should be protected after the operation4 ,if discomfort is felt when it takes1 medical advice should be sought4 99,isolation991 or quarantining1 is a most important method of combating contagious diseases4 ,by removing the sick from the well many outbreaks of disease are quickly checked4 ,isolation of individual patients1 and sometimes of infected neighborhoods1 is absolutely necessary2 and while this works a hardship to the few1 it is frequently the only safeguard of the many4 ,the community1 on the other hand1 should make ample provision for the care of the afflicted in the way of hospitals1 or sanitaria1 and if it is deemed necessary to remove people from their homes1 they should not be subjected to unnecessary hardship4 ,where one is sick from some contagious disease in the home and there is liability of communicating it to the other members of the family1 room isolation should be practiced4 ,infection cannot spread through solid walls1 and where the doors1 and the cracks around the doors1 are kept completely closed and the usual precautions are observed by those attending the patient1 the other inmates of the house can be protected from the disease4 99,the ,physician and ,his ,work499--,in combating disease the services of the physician are a prime necessity4 ,the special knowledge which he has at his command enables the conflict to be carried on according to scientific requirements and vastly increases the chances for recovery4 ,he should be called early and his directions should be carefully followed4 ,everything1 however1 must not be left to the physician1 for recovery depends as much upon proper nursing and feeding as upon the drugs that are administered4 ,of great importance is the saving of the energy of the patient1 and to accomplish this visitors should1 as a rule1 be excluded from the sick room4 99,precautions in ,recovery from ,disease499--,many diseases1 if severe1 not only leave the body in a weakened condition1 but may1 through the toxins which the germs deposit1 cause untold harm if the patient leaves his bed or resumes his usual activities too soon4 ,especially is this true of typhoid fever17#acd7 diphtheria1 scarlet fever1 and measles4 ,rheumatism and affections of the heart1 lungs1 kidneys1 and other bodily organs frequently follow these diseases1 as the result of slight exposure or exertion before the body has sufficiently recovered from the effects of the toxins4 ,to guard against such results1 certain physicians require their patients to keep their beds for a week1 or longer1 after apparent recovery from diseases like typhoid fever1 diphtheria1 and scarlet fever4 99,relation of ,vocation to ,disease499--,with a few exceptions1 the pursuit of one's vocation1 or calling in life1 does not supply either the quantity or the kind of activity that is most in harmony with the plan of the body4 ,especially is this true of work that requires most of the time to be spent indoors1 or which exercises but a small portion of the body4 ,the effect of such vocations1 if not counteracted1 is to weaken certain organs1 thereby disturbing the functional equilibrium of the body--a result that may be brought about either by the overwork of particular organs or by lack of exercise of others4 ,herein lies the explanation of the observed fact that people of the same calling in life have similar diseases4 99,a ,special ,problem for the ,brain ,worker499--,farthest removed from those forms of activity which harmonize with the plan of the body1 and which therefore are most hygienic1 is that class of workers known as the professional class1 or the brain workers4 ,this class includes not only the members of the learned professions--law1 medicine1 and the ministry--but a vast army of business men1 engineers1 teachers1 stenographers1 office clerks1 etc41 a class that is ever increasing as our civilization advances4 ,it is this class in particular that must give attention to those conditions that indirectly1 but profoundly1 influence the bodily well-being and must seek to obviate if possible such weaknesses as the occupation induces4 99,the ,remedy99 lies in two directions--that of spending sufficient time away from one's work to allow the body to recover its normal condition1 and that of counteracting the effect of the work by special exercise or other means4 ,in many cases the first symptoms of weakness indicate a suitable remedy4 ,thus exhaustion from overwork suggests rest and recreation4 ,the diverting of too much blood from other parts of the body to the brain suggests some form of exercise which will equalize the circulation4 ,if feebleness of the digestive organs is being induced1 some natural method of increasing the blood supply to these organs is to be looked for4 ,and effects arising from lack of fresh air and sunlight are counteracted by spending more time out of doors4 99,exercise as a ,counteractive ,agent499--,in counteracting tendencies to disease and in the maintenance of the functional equilibrium of the body1 no agent has yet been discovered of greater importance than physical exercise1 when applied systematically and persistently4 ,this may consist of exercises that call into play all the muscles of the body1 or which are concentrated upon special parts4 ,when general tonic effects are desired1 the exercise should be well distributed2 but when counteractive or remedial effects are wanted1 it must be applied chiefly to the parts that are weak or that have not been called into action by the regular work4 ,unfortunately1 health is sometimes confused with physical strength and exercise is directed toward the stronger parts of the body with the effect of making them still stronger4 ,not only is health not to be measured by the pounds that one can lift or by some gymnastic feat that one can perform1 but the possession of great muscular power may1 if the heart and other vital organs be not proportionally strong1 prove a menace to the health4 ,this being true1 one having his health primarily in view will use physical exercise1 in part at least1 as a means of building up organs that are weak4 ,since the body1 like a chain1 can be no stronger than its weakest part1 this is clearly the logical method of fortifying it against disease4 99,value of ,work499--,although there may exist in one's vocation certain tendencies to disease1 it must not be inferred that work in itself is detrimental to health4 ,health demands activity1 and those forms of activity that provide a regular and systematic outlet for one's surplus energy and compel the formation of correct habits of eating1 sleeping1 and recreating best serve the purpose4 ,work furnishes activity of this kind and serves also as a safeguard against the unhealthful and immoral habits contracted so often from idleness4 ,even physical exercise which has for its purpose the renforcement of the body against disease may frequently consist of useful work without diminishing its hygienic effects4 99,the ,mental ,attitude499--,while a proper thoughtfulness and care for the body is both desirable and necessary1 it is also true that over-anxiety about1 or an unnatural attention to1 the needs of the body reacts unfavorably upon the nervous system4 ,observance of the laws of health1 therefore1 should be natural and without special effort--a matter of habit4 ,the attention should never be turned with anxiety upon any organ or process1 but the mental attitude should at all times be that of confidence in the power of the body organization to do its work4 ,fear and morbidity1 which are disturbing and paralyzing factors1 should be supplanted by courage1 cheerfulness1 and hopefulness4 ,let it be borne in mind that hygienic living requires nothing more than the application of the same intelligence and practical common sense to the care of the body that the skillful mechanic applies to an efficient1 but delicate1 machine4 ,and1 just as in the case of the machine1 care of the body keeps its efficiency at the maximum and lengthens the period that it may be used4 ,this end and aim of hygienic living is best attained by cultivating that attitude of mind toward the body that avoids interference in the vital processes and permits the natural appetites1 sensations1 and desires to indicate very largely the body's needs4 99,attitude toward ,habit-forming ,drugs499--,among the different substances introduced into the body1 either as foods or as medicines1 are a number which have the effect of developing an artificial appetite or craving which leads to their continued use4 ,since the effect of such substances is usually harmful and since they tend to engraft themselves upon communities as social customs1 they present a twofold relation to the general problem of keeping well4 ,the individual may be injured through the personal use which he makes of them1 or he may be injured through the effect which they have upon relatives or friends or upon society at large4 ,since our social environment is a factor in health little less important than our physical environment1 the conditions that make for their continuance should be more generally understood4 99,how ,social ,agencies perpetuate the ,use of ,habit-forming ,drugs499--,when the use of some habit-forming drug has risen to the importance of a general custom1 a number of conditions arise which tend to continue its use1 even though the fact may be quite generally known that the substance does harm4 ,in the first place1 those who have formed the habit suffer inconvenience and distress when deprived of its use4 ,in the second place1 a number of people will have become interested in the production and sale of the substance1 and these will lose financially if it is discontinued4 ,in the third place1 those of the rising generation will1 from imitation or persuasion1 be constantly acquiring the habit before they are sufficiently mature to decide what is best for them4 ,thus may the use of a substance most harmful1 such as the opium of the ,chinese1 be indefinitely continued--a species of slavery from which the individual finds it hard to escape4 ,such is human nature and such are the forces and influences of human society1 that the freeing of a people from the bondage of some habit-forming drug cannot be accomplished without strenuous and persistent effort4 ,education1 persuasion1 the good example of abstainers1 and legal restrictions must be pitted against the forces that make for its continuance4 ,such a struggle is now in progress in all civilized countries relative to the use of alcoholic beverages47#ace7 99,how the ,use of ,alcohol became a ,social ,custom499--,the general use of alcohol as a beverage may be accounted for by three facts4 ,alcohol is a habit-forming drug2 it has a stimulating effect which many have found agreeable2 and being a product of the fermentation of fruit juices and other liquids containing sugar1 it is easily obtained4 ,through the operation of these causes the human family became habituated very early to the use of alcohol4 ,the wine of primitive man1 however1 did little harm as compared with the alcoholic liquors of modern times4 ,it was a weak solution and on account of the crude methods of manufacture and storage could only be produced in limited quantities4 ,perhaps the worst effect of its early use was the establishment of a general belief in its power to benefit1 since this laid the foundation for excess in its use when the developments of a later period made it possible4 ,during the eleventh century the method of making alcoholic drinks from starch-producing substances1 such as wheat1 barley1 and potatoes1 became quite generally known1 and also the method of concentrating them by distillation4 ,this knowledge made possible the manufacture of alcoholic drinks in large quantities and in considerable variety4 ,alcoholic indulgence was now no longer the pastime of the few1 but the privilege of all4 ,its evil effects followed as a matter of course2 and as these became more and more apparent1 there began the struggle to restrict the consumption of alcohol which has continued with varying success to the present time4 99,counts against ,alcohol499--,the statements found in different parts of this book relative to the effects of alcohol upon the body may here be summarized as follows3-- #a4 ,alcohol has an injurious effect upon the white corpuscles of the blood and lessens the power of the body to resist attacks of disease 7pages #ce1 #ih74 #b4 ,alcohol injures the heart and the blood vessels 7page #ef74 #c4 ,alcohol causes diseases of the liver and kidneys and interferes with the discharge of waste through these organs 7pages #baj1 #bab74 #d4 ,alcohol interferes seriously with the regulation of the body temperature 7page #bga74 #e4 ,alcohol is one of the worst enemies to the nervous system 7pages #cbf1 #ccb-ccd4 #ccf1 #ccg74 #f4 ,through its effect upon the nervous system and through its interference with the production of bodily energy 7page #aie71 alcohol greatly diminishes the efficiency of the individual4 #g4 ,the taking of alcohol in amounts that apparently do not harm the tissues is1 nevertheless1 liable to produce a habit which leads to its use in amounts that are decidedly harmful4 99,alcohol and the ,social ,environment499--,our social environment includes the people with whom we are directly or indirectly associated4 ,the presence in any community of those who are immoral1 inefficient1 or defective1 places a burden upon those who are mentally and physically capable and renders them liable to results which are the outgrowth of weakness or viciousness4 ,the fact that alcohol causes pauperism1 crime1 and general inefficiency1 thereby rendering the social environment less conducive to what is best in life1 is plainly evident4 ,to realize how alcohol harms the individual through its effects upon society in general1 one has only to take into account his dependence upon society for intellectual and moral stimuli1 for industrial and economic opportunity1 for protection1 and for general conditions that make for health and happiness4 ,as we strive to improve our physical environment1 so should we also strive for the betterment of social conditions4 99,industrial ,use of ,alcohol499--,interesting and instructive in this connection is the fact that alcohol is1 after all1 a substance capable of rendering great service to humanity4 ,the injury which it causes is the result of its misuse4 ,though unfit for introduction into the human body1 except in the most guarded manner1 it is adapted to a great variety of uses outside of the body4 ,a combustible substance which is readily convertible into a gas1 it may be substituted for gasoline in the cooking of food1 lighting of dwellings1 and the running of machinery4 ,as a solvent for gums1 resins1 essential oils1 etc41 it is used in the preparation of varnishes1 extracts1 perfumes1 medicines1 and numerous other substances of everyday use4 ,through its chemical interactions1 it is used in the manufacture of ether1 chloroform1 explosives1 collodion1 celluloid1 dyestuffs1 and artificial silk4 ,in fact1 alcohol is stated by one authority to be1 next to water1 the most valuable liquid known47#acf7 ,opposed to an extensive use of alcohol for industrial purposes is the guard which the government must keep over its manufacture on account of its use in beverages4 ,though alcohol may be profitably manufactured and sold at thirty cents per gallon1 the government revenue stamp of #b4jh per gallon practically prohibits its use for many purposes4 ,a step toward a wider application to industrial purposes has been taken by the law permitting the sale of so-called denatured7#acg7 alcohol without the tax for revenue4 ,this law has proved beneficial to some extent1 though the practical solution of the problem is still remote4 99,nicotine and ,social ,custom499--,the influences which brought about a general use of tobacco are similar to1 though not identical with1 those that engrafted alcohol upon society4 ,the drug nicotine is a habit-forming substance and the plant producing it is easily cultivated47#ach7 ,its immediate effect upon the user is generally agreeable1 acting as a stimulant to some1 but having a soothing effect upon the nerves of others4 ,moreover1 a strong deterring factor in its use is lacking1 since its harmful effects are not readily discernible and by many are avoided through moderation in its use4 ,as with alcohol1 tobacco is conveniently used to promote sociability among men1 a fact which has much to do with its very general use4 ,if it could be limited to social purposes1 it would likely do little harm1 but the habit1 once started1 is continued without reference to sociability--a matter of selfish indulgence4 ,in fact1 one effect of tobacco is to cause the user to become less sensitive to the rights of others1 this being evidenced by smokers who do not hesitate to make rooms and public halls almost unbearable to those unaccustomed to tobacco4 99,counts against ,nicotine499--,the physiological objections to the use of tobacco1 as already stated 7pages #ef1 #ib1 #cbf1 #ccc1 #ccf71 are the following3-- #a4 ,the use of tobacco before one reaches maturity stunts the growth4 ,the boy who uses it cannot develop into so strong and capable a man as he would by leaving it alone4 #b4 ,tobacco injures the heart4 #c4 ,tobacco injures the air passages1 especially when inhalation is practiced4 #d4 ,tobacco injures the nervous system and by this means interferes in a general way with the bodily processes4 ,for the same reason it interferes with mental and moral development1 the cigarette being a chief cause of criminal tendencies in boys4 #e4 ,in some cases tobacco injures the vision4 #f4 ,the tobacco habit is expensive and is productive of no good results4 99,tobacco and the ,rising ,generation499--,the problem of limiting the use of tobacco to the point where it would do slight harm1 in comparison to what it now does1 would be solved if those under twenty years of age could be kept from using it4 ,but few would then acquire the habit1 and those who did would not be so seriously injured4 ,in our own country it lies within the province of the home and the school to bring about this result4 ,the fact that parents use tobacco is no reason why the boys should also indulge4 ,the decided difference in effects upon the young and upon the mature makes this point very clear4 ,laws protecting boys from the evil effects of tobacco1 not only cigarettes1 but other forms as well1 are both just and necessary4 99,social ,custom and the ,caffeine ,habit499--,by suitable processes a white1 crystalline solid1 easily soluble in water1 can be separated from the leaves of tea1 and from the berry of the coffee plant4 ,this is the drug caffeine1 the substance which gives to tea and coffee their stimulating properties1 but not their agreeable flavors4 ,less injurious1 on the whole1 than either alcohol or tobacco1 caffeine has come into general use in much the same way as these substances4 ,in a sense1 however1 caffeine is more deceptive than either alcohol or nicotine1 because the usual mode of preparing tea and coffee gives them the appearance of real foods4 ,the housewife who would feel condemned in purchasing caffeine put up as a drug somehow feels justified when she extracts it from plant products in the regular preparation of the meal4 99,counts against ,caffeine499--,people of vigorous constitutions and of active outdoor habits are injured but slightly1 if at all1 by either tea or coffee when these are used in moderation4 ,as already stated 7pages #ef1 #afg1 #cbf1 #cbi71 they do harm when used to excess and1 in special cases1 in very small amounts1 in one of the following ways3-- #a4 ,by stimulating the nervous system1 thereby causing nervousness and insomnia and interfering with vital organs4 #b4 ,by introducing a waste which forms uric acid into the body1 thereby throwing an extra burden upon the organs of elimination4 ,in this connection it may also be stated that there appears to be little1 if any1 real advantage to the healthy body from the use of either tea or coffee1 beyond that of temporary stimulation and the gratification of an appetite artificially acquired4 ,hence the large sums of money expended for these substances in this country yield no adequate returns4 99,caffeine ,restrictions ,necessary499--,though with many the cup of tea or coffee at breakfast does no harm1 but gives an added pleasure to the meal1 there is no question but that the use of caffeine beverages should be greatly curtailed4 ,children should not be permitted to drink either tea or coffee4 ,brain workers and indoor dwellers generally should use these substances very sparingly1 and people having a tendency to indigestion1 nervousness1 constipation1 rheumatism1 or diseases of the heart1 kidneys1 or liver frequently find it best to omit them altogether4 99,caffeine and ,soft ,drinks499--,recently the practice has sprung up of using caffeine as a constituent of certain drinks supplied at the soda-water fountains4 ,such drinks usually purport to be made from the kola nut1 which contains caffeine1 or to consist of extracts from the plants which yield cocoa and chocolate1 when in reality they consist of artificial mixtures to which caffeine has been added4 ,those using these beverages are stimulated as they would be by tea or coffee and soon acquire the habit which makes them regular customers4 ,chief harm comes to the children who frequent the soda fountains and to those who1 on account of constitutional tendencies1 should avoid caffeine in all of its forms4 ,it is generally understood that the so-called soft drinks are harmless4 ,if this reputation is to be maintained1 those containing caffeine must be excluded4 99,danger from ,certain ,medicinal ,agents499--,among the most valuable drugs used by the physician in the treatment of disease are several1 such as morphine1 chloral1 and cocaine1 which possess the habit-forming characteristic4 ,sad indeed are the cases in which some pernicious drug habit has been formed through the reckless administration of such medicines4 ,even the taking of such a drug as quinine as a tonic tends to develop a dependence upon stimulation which is equivalent to a habit4 ,in the same list come also the drugs that are taken to relieve a frequently recurring indisposition1 such as headache4 ,the so-called headache powders are most harmful in their effects upon the nervous system and should be carefully avoided47#aci7 99,stimulants in ,health ,unnecessary499--,stimulants have been aptly styled the whips of the nervous system4 ,the healthy nervous system1 however1 like the well-disposed and well-fed horse1 needs no whip1 but is irritated and harmed through its use4 ,even in periods of weakness and depression1 stimulants are usually not called for1 but a more perfect provision for hygienic needs4 ,rest1 relaxation1 sleep1 proper food1 and avoidance of irritation1 not stimulants1 are the great restorers of the nervous system4 ,a surplus of nervous energy gained through natural means is more conducive to health and effective work than any result that can possibly be secured through drugs4 ,then withal comes the satisfaction of knowing that one has the expression of his real self in the way in which he feels and in what he accomplishes--not a whipped-up condition that must be paid for by weakness or suffering later on4 99,summary499--,to solve the problem of keeping well1 one must live the life which is in closest harmony with the plan of the body4 ,such a life1 because of differences in physical organization1 as well as differences in environment and occupation1 cannot be the same for all4 ,all1 however1 may observe the conditions under which the body can be used without injuring it and the special hygienic laws relative to the care of different organs4 ,causes of disease1 whether they be in one's environment1 vocation1 in his use of foods or drugs1 or in his mode of recreation1 must either be avoided or counteracted4 ,while the problem is beset with such difficulties as lack of sufficient knowledge1 inherited weakness1 and time and opportunity for doing what is known to be best for the body1 yet study and work that have for their aim the preservation or improvement of the health are always worth while4 ,health is its own reward4 ,the expression of the poet1 ,each morn to feel a fresh delight to wake to life1 ,to rise with bounding pulse to meet whate'er of work1 of care1 of strife1 day brings to me1 suggests the joy of being well4 ,but the ultimate realization of one's aims and ambitions in life and the actual prolongation of one's period of usefulness are higher and more enduring rewards4 99,exercises499--#a4 ,summarize the different laws of hygiene4 ,upon what one fundamental law are these based8 #b4 ,state the important differences between a condition of health and one of disease4 #c4 ,in what general ways may disease originate in the body8 #d4 ,describe a model sanitary home4 ,with what special hygienic problems has the housekeeper to deal8 #e4 ,describe a method of collecting a wholesome supply of cistern water4 ,state possible objections to well and spring water4 #f4 ,what means may be employed in preventing the spread of contagious diseases8 #g4 ,by what means are malaria1 typhoid fever1 diphtheria1 and tuberculosis spread from one individual to another8 #h4 ,why are extra precautions necessary in the recovery from certain diseases1 as typhoid fever1 diphtheria1 and scarlet fever8 #i4 ,how may one's vocation become a cause of disease8 ,what conditions in the life of a student may1 if uncounteracted1 lead to poor health8 #aj4 ,of what special value are the parks and pleasure grounds in a city to the health of its inhabitants8 #aa4 ,discuss the hygienic value of work4 #ab4 ,what conditions lead to the continuance of habit-forming substances after their use has become general8 #ac4 ,how is it possible for one not using alcohol to be injured by this substance8 #ad4 ,discuss the effect of alcoholic abuse upon social environment4 #ae4 ,summarize the rewards of hygienic living4 ,,summary ,,of ,,part ,,ii ,for the maintenance of life the needs of the cells must be supplied and the body as a whole must be brought into proper relations with its surroundings4 ,the last-named condition requires that the body be moved from place to place2 that its parts be controlled and cordinated2 and that it be adjusted in its various activities to external physical conditions4 ,to accomplish these results there are employed3 #a4 ,the skeleton1 or bony framework1 which preserves the form of the body and supplies a number of mechanical devices1 or machines1 for causing a variety of special movements4 #b4 ,the muscular system1 which supplies the energy necessary for executing the movements of the body4 #c4 ,the nervous system1 which 7a7 controls and cordinates the various activities and 7b7 provides for the intelligent adjustment of the body to its environment4 7,review ,summary of ,part ,i1 page #bae1 and consult ,fig4 #ib1 page #bad47 ,,appendix 99,equipment499--,nearly all of the apparatus and materials called for in this book may be found in the physical1 chemical1 and biological laboratories of the average high school4 ,there should be ready1 however1 for frequent and convenient use1 the following3 ,one or more compound microscopes with two-thirds and one-fifth inch objectives2 a set of prepared and mounted slides of the various tissues of the body2 a set of dissecting instruments1 including bone forceps2 a mounted human skeleton and a manikin or a set of physiological charts2 a set of simple chemical apparatus including bottles1 flasks1 test tubes1 and evaporating dishes2 and a ,bunsen burner or some other means of supplying heat4 ,the few chemicals required may be obtained from a drug store or from the chemical laboratory4 ,access to a work bench having a set of carpenter's tools will enable one to prepare many simple pieces of apparatus as they are needed4 99,physiological ,charts99 are easily prepared by teachers or pupils by carefully enlarging the more important illustrations found in text-books or by working out original sketches and diagrams4 ,these1 if drawn on heavy ,manila paper1 may be hung on the wall as needed and preserved indefinitely4 ,by the use of colors1 necessary contrasts are drawn and emphasis placed on parts as desired4 ,the author has for a number of years used such home-made charts in his teaching and has found them quite satisfactory4 ,his plan has been to draw on heavy ,manila paper1 cut in sizes of two by three feet1 the general outline in pencil and then to mark over this with the desired colors4 ,there is of course an opportunity for producing results that are artistic as well as practical1 and if one has time and artistic skill1 better results can be obtained4 ,many of the cuts in this book are excellently suited to enlargement and1 if properly executed1 will provide a good set for general class purposes4 99,models499--,the use of prepared models of the different bodily organs is strongly urged4 ,these may be so used in elementary courses as to obviate much of the dissections upon lower animals4 ,although the actual tissues cannot be so well portrayed1 the general form and construction of organs are much better shown4 ,models well adapted to class or laboratory work are easily obtained through supply houses4 ,illustrations of several of these are shown in connection with the ,practical ,work4 ,,index ,abdomen2 dissection of1 #afi4 ,abdominal cavity1 #g1 #ach1 #aeb4 ,absorption1 #agc-ahf4 ,defined1 #ah1 #agc4 ,accommodation1 #cgi4 ,to illustrate1 #cia4 ,acid reactions1 #aga4 ,acquired reflexes1 #cad4 ,adipose tissue1 #e1 #agh4 ,afferent neurons1 #bif4 ,air1 #gf4 ,changes it undergoes in lungs1 #aja4 ,complemental1 #hi1 #ajc4 ,reserve1 #hi1 #ajc4 ,residual1 #hi1 #ajc4 ,tidal1 #hh1 #ajc4 ,air passages1 #hj4 ,albuminoids1 #aai4 ,purpose served by1 #aba4 ,alcohol1 ,a cause of crime1 #ccc4 ,effects on circulation1 #ee1 #ef4 ,effects on digestion1 #afg4 ,effects on energy supply1 #aie4 ,effects on respiratory organs1 #ih4 ,effects on social environment1 #dac4 ,effect on temperature regulation1 #bga4 ,effects on waste elimination1 #bab4 ,general considerations1 #dab-dae4 ,alimentary canal1 coats of1 #ach4 ,alimentary muscles1 work of1 #aei4 ,alkaline reactions1 #aga4 ,alveoli1 #hb4 ,amylopsin1 #aee1 #aef4 ,anatomy1 defined1 #a4 ,animal heat1 #aib4 ,anopheles1 #dja4 ,antiseptic ointment1 #bge4 ,antitoxin1 #dje4 ,appetite1 natural1 #afc4 ,aqueous humor1 #cgg4 ,arachnoid1 #bii4 ,arteries1 #dg4 ,bronchial1 #hd4 ,functions of1 #ea4 ,pulmonary1 #hd4 ,renal1 #bjb4 ,to illustrate elasticity of1 #fb4 ,why elastic1 #dh4 ,articulations1 #bcj-bcb4 ,kinds of1 #bcj4 ,assimilation1 #ah1 #ahb4 ,astigmatism1 #chd4 ,atlas1 #bbc4 ,atoms1 defined1 #aje4 ,attraction sphere1 #ae4 ,auditory canal1 #ceh4 ,auricles1 #db4 ,axis1 #bbc4 ,axis cylinder1 #bhd4 ,axon1 #bhc4 ,form and length of1 #bhd4 ,function of1 #cjf4 ,structure of1 #bhd4 ,bacteria1 #cid4 ,ball-and-socket joint1 #bca4 ,basement membrane1 #aig4 ,basilar membrane1 #cfc4 ,bathing1 #bgb1 #bgd4 ,biceps muscle1 action of1 #bfc4 ,bicuspids1 #adc4 ,bile1 #aed1 #aee4 ,binocular vision1 #cha4 ,blind spot1 #cgg4 ,to prove presence of1 #cij4 ,blood1 #bd-ci4 ,changes in1 #cd4 ,checking flow from wounds1 #eh4 ,coagulation of1 #ca4 ,experiments with1 #cg-ci4 ,flow of1 how regulated1 #ej4 ,functions of1 #cc4 ,hygiene of1 #cd-cf4 ,physical properties of1 #bd4 ,quantity of1 #cc4 ,supply to lungs1 #hb4 ,velocity of1 #ed4 ,where found1 #bd4 ,blood platelets1 #be4 ,blood pressure1 #eb1 #gj4 ,blood pressure and velocity1 #eb4 ,blood vessels1 to strengthen1 #eg4 ,body1 organization of1 #ai4 ,bone groups1 #bbc-bbi4 ,bones1 #baf-bdb4 ,adaptation of1 #bbh4 ,composition1 #bag4 ,gross structure of1 #bah4 ,minute structure of1 #bai4 ,observation on gross structure1 #bda4 ,properties of1 #bag4 ,table of1 #bbi4 ,to show composition of1 #bda4 ,to show minute structure of1 #bdb4 ,bowels1 rules for care of1 #aff4 ,brachial plexus1 #cjb4 ,brain1 #bhj1 #bhh-bia4 ,disturbed circulation1 #cbg4 ,protection of1 #bii4 ,brain workers1 #djh4 ,breathing1 see ,respiration4 ,causes of shallow1 #ib4 ,illustrated1 #hg4 ,to prevent shallow1 #ib4 ,breathing exercises1 #ic4 ,bronchus1 #hj4 ,bulb1 #bia4 ,ccum1 #aea1 #aeh4 ,calcium carbonate1 #abb4 ,calcium phosphate1 #abb4 ,calorie1 defined1 #abf4 ,cane sugar1 #abj4 ,canines1 #adc4 ,capillaries1 #ej1 #fd1 #bdi4 ,blood pressure at1 #gj4 ,functions of1 #ea4 ,work of1 #agd4 ,carbohydrates1 #aai1 #abe4 ,purpose served by1 #aba4 ,storage of1 #agg4 ,tests for1 #ace4 ,carbon1 #acd4 ,carbon dioxide1 ,final disposition of1 #aaa4 ,preparation1 #aae4 ,pressure1 #aaj4 ,properties1 #aaj1 #aae4 ,cardiac cycle1 #df4 ,cardiac orifice1 #adg4 ,carpals1 #bbg4 ,carpus1 #bbh4 ,cell body1 #bhc4 ,functions of1 #cje4 ,cell-division1 #af4 ,cell nucleus1 #ad4 ,cell reproduction1 #af4 ,cell structure1 #ad4 ,cell surroundings1 #ag4 ,cell wall1 #ae4 ,cells1 #ac-bc4 ,bone1 how nourished1 #bbj4 ,ciliated epithelial1 #ha4 ,food supply to1 #ahj4 ,general work of1 #ag4 ,importance of1 #ae4 ,passage of materials to1 #ahc4 ,relation to nutrient fluid1 #bj4 ,specialized1 #aig4 ,special work of1 #ah4 ,striated muscle1 #bdd4 ,cerebellum1 #bij4 ,functions of1 #cag4 ,cerebral functions1 localization of1 #cah4 ,cerebral hemispheres1 #bhi4 ,cerebral peduncles1 #bij4 ,cerebrum1 #bhh4 ,functions of1 #cag4 ,chlorine1 #ace4 ,cholesterine1 #aee4 ,chord tendine1 #dc4 ,choroid coat1 #cge4 ,chyme1 #aej4 ,cigarettes1 #ccc4 ,cilia1 #ha4 ,to observe1 #aja4 ,ciliary muscle1 #cge4 ,ciliary processes1 #cge4 ,circulation of blood1 #dj-fd4 ,causes of1 #ed4 ,discovery of1 by ,harvey1 #dj4 ,divisions of1 #ea1 #eb4 ,effects of exercise upon1 #fc4 ,effects of gravity upon1 #fd4 ,in a frog's foot1 #fd4 ,organs of1 #dj-ed4 ,routes to1 #agd4 ,coagulation1 ,causes of1 #ca4 ,purpose of1 #cb4 ,time required for1 #cc4 ,cochlea1 #cfb4 ,coffee1 ,effects on complexion1 #bgd4 ,effects on digestion1 #afg4 ,effects on heart1 #ef4 ,colds1 #aic4 ,serious nature of1 #id4 ,to cure1 #id4 ,colon1 parts of1 #aeh4 ,complexion1 care of1 #bgc4 ,compound1 defined1 #ajd4 ,conduction pathways1 #bhf4 ,conductivity1 #cjd4 ,condyloid joint1 #bcb4 ,conjunctiva1 #cgc4 ,consumption1 see ,tuberculosis4 ,control of arteries1 #cai4 ,convolutions1 #bhi4 ,cordination1 defined1 #bgi4 ,cornea1 #cge4 ,corpora quadrigemina1 #bij4 ,corpora striata1 #bhi4 ,corpus callosum1 #bhi1 #bic4 ,cortex1 #bhh1 #bid4 ,coughing1 #ha4 ,cranial cavity1 #g1 #bbe4 ,cranial nerves1 #bif4 ,crura cerebri1 #bij4 ,crystalline lens1 #chj4 ,culex1 #djb4 ,cytoplasm1 #ae4 ,defects in focusing1 #chc4 ,deformities of skeleton1 #bcc-bcf4 ,correction of1 #bcf4 ,prevention of1 #bce4 ,deglutition1 #ade4 ,steps in1 #adf4 ,dendrites1 #bhc1 #cjf4 ,dentine1 #adc4 ,dermis1 #bfd4 ,dextrose1 #cj1 #abj1 #aej4 ,diaphragm1 #hh4 ,to illustrate action of1 #ajb4 ,diastole1 #df4 ,diaxonic neuron1 #bhc4 ,diet1 one-sided1 #abd4 ,diffusion1 #cga4 ,digestion1 #acj-agb4 ,hygiene of1 #afj4 ,nature of1 #acj4 ,not a simple process1 #aca4 ,of fat1 #aef4 ,purpose of1 #agg4 ,stomach1 #adh4 ,digestive fluids1 #acb4 ,digestive organs1 #afj4 ,table of1 #ach4 ,digestive processes1 #acj1 #ada4 ,illustrated1 #acg4 ,diphtheria1 #id1 #dje4 ,care after1 #baa4 ,disaccharides1 #abj4 ,disease1 #cib-dab4 ,causes of1 #cic4 ,eruptive1 #dje4 ,precautions in recovery from1 #djg4 ,prevention of1 #cic4 ,dislocations1 #bci4 ,dorsal-root ganglia1 #bie4 ,drill1 setting up1 #bcg4 ,drugs1 effects of1 #ce1 #ee1 #abi1 #ccb4 ,duodenum1 #aea4 ,dura1 #bii4 ,ear1 #ceh4 ,hygiene of1 #cfe4 ,to demonstrate1 #cfi4 ,ear drum1 #cei4 ,efferent neurons1 #bif4 ,element1 defined1 #ajd4 ,elevators of the ribs1 #hg4 ,emetics1 #aea4 ,emotional states1 effects of1 #ccj4 ,end bulbs1 #cdb4 ,endocardium1 #db4 ,endolymph1 #cfa4 ,end-plate1 #bdd4 ,end-to-end connections1 #bhf4 ,energy1 #ajg1 #ahf-aif4 ,bodily control of1 #aib4 ,from sun to cells1 #aia4 ,how plants store sun's1 #ahi4 ,increasing one's bodily1 #aid4 ,in food and oxygen1 #aij4 ,kinds of1 #ahf4 ,methods of storing1 #ahg1 #ahh4 ,transformation of1 in muscle1 #bdh1 #bdi4 ,enzymes1 #acb1 #aee4 ,of the tissues1 #ahd4 ,epidermis1 #bfd1 #bff4 ,epiglottis1 #hj1 #ced4 ,epithelium1 #aci4 ,eruptive diseases1 #dje4 ,esophagus1 #adf4 ,eustachian tube1 #cei4 ,excessive reading1 #cca4 ,excitant impulse1 #cje4 ,excretion1 #aig-bac4 ,defined1 #ah4 ,necessity for1 #bja4 ,exercise1 #bef1 #beg1 #cbh1 #dji4 ,general rules for1 #bei4 ,results of1 #beg4 ,exhaustion1 nervous1 #baa4 ,results of1 #aie4 ,external ear1 #ceh4 ,external stimuli1 action of1 #cjg4 ,eye1 #cgj-cia4 ,eyeball1 #cgc4 ,chambers of1 #cgg4 ,focusing power of1 #cgh4 ,movements of1 #cha4 ,eyelids1 #cgc4 ,eyes1 ,care of1 #chf4 ,removal of foreign bodies from1 #chg1 ,strong chemicals in1 #chh4 ,eye strain1 #baa4 ,and disease1 #che4 ,fat1 #cj1 #adi1 #afb4 ,digestion of1 #aef4 ,emulsification of1 #aeg4 ,purpose served by1 #aba4 ,route taken by1 #age4 ,tests for1 #acg4 ,where stored1 #agh4 ,fatty acid1 #aef4 ,fenestra ovalis1 #cfa4 ,fenestra rotunda1 #cfc4 ,ferments1 see ,enzymes4 ,fibrin1 #ca4 ,fibrin ferment1 #cb4 ,fibrinogen1 #cj1 #ca4 ,fissures1 #bhi4 ,food1 #aag-acg4 ,advantages of coarse1 #afg4 ,classes of1 #aah1 #aai4 ,composition of1 #abd4 ,dangers from impure1 #afe4 ,defined1 #aag4 ,elements supplied by1 #acd4 ,excess of proteid1 #bjh4 ,frequency of taking1 #afe4 ,materials1 table of1 #abf1 #abf4 ,nitrogenous1 #aai4 ,order of taking1 #afa4 ,preparation of1 #afd4 ,purity of1 #abh4 ,quantity of1 #afd4 ,simple1 #aah4 ,variety1 #abh4 ,with reference to digestive changes1 #acb4 ,foot lever1 diagram of1 #bec4 ,foot-pound1 #aif4 ,foot-wear1 hygienic1 #bch4 ,fractures1 treatment of1 #bci4 ,fumigation1 #djj4 ,furniture1 school1 #bcf4 ,gall bladder1 #aed4 ,ganglia1 #bha4 ,dorsal-root1 #bie4 ,sympathetic1 #bih4 ,gastric glands1 #adg4 ,gastric juice1 to illustrate action of1 #agb4 ,gelatine1 #bah4 ,germ diseases1 avoidance of1 #cid4 ,germs1 #bi1 #cid1 #cie4 ,how spread1 #cie4 ,glands1 #aig-bac4 ,digestive1 #adj4 ,ductless1 #bjh4 ,excretory1 work of1 #bja4 ,gastric1 #adg4 ,kinds of1 #aig1 #aih4 ,lymphatic1 #fh1 #bjh4 ,perspiratory1 #bjf4 ,salivary1 #add4 ,structure of1 #aig4 ,thymus1 #bjh4 ,thyroid1 #bjh4 ,gliding joint1 #bcb4 ,glottis1 #cee4 ,glycogen1 #abj1 #agg4 ,grape sugar1 tests for1 #abj1 #acf4 ,gross anatomy1 defined1 #a4 ,gullet1 #adf4 ,gustatory pore1 #cde4 ,gustatory stimulus1 #cde4 ,habits1 #cae1 #ccd4 ,hair1 #bfg4 ,care of1 #bgf4 ,hair cells1 #cfc4 ,hair follicle1 #bfg4 ,haversian canals1 #bai4 ,hearing1 defective1 #cff4 ,heart1 #da4 ,care of1 #ee4 ,connection with arteries and veins1 #de4 ,difference in parts of1 #dd4 ,how it does its work1 #de4 ,observations on1 #fj1 #fa1 #fb4 ,sounds of the1 #dg4 ,valves of1 #dc4 ,heart muscle1 structure of1 #bdg4 ,heat and cold1 effects of1 #ccj4 ,hemoglobin1 #bf4 ,hepatic artery1 #aed4 ,hepatic veins1 #aed4 ,hindbrain1 #bij4 ,hinge joint1 #bca4 ,histology1 defined1 #a4 ,humerus1 #bbg4 ,hyaloid membrane1 #cgh4 ,hydrochloric acid1 #adi1 #aej4 ,hydrogen1 #acd4 ,hygiene1 ,defined1 #b4 ,general aim of1 #b4 ,general laws of1 #b1 #cib4 ,of digestion1 #afj4 ,of skeleton1 #bch4 ,relation of physiology and anatomy to1 #c4 ,hygienic housekeeping1 #cii4 ,hypoglossal nerves1 #bih4 ,ileo-ccal valve1 #aea4 ,ileum1 #aea4 ,images1 ,diagram illustrating1 #cgb4 ,formation of1 #cga4 ,incisors1 #adc4 ,incus1 #cei4 ,infectious diseases1 #cid4 ,infundibula1 #hj1 #hd4 ,inhibitory impulse1 #cje4 ,insomnia1 #cbi4 ,inspiratory force1 #gj4 ,intercellular material1 production of1 #ac1 #ah4 ,internal ear1 #cfj4 ,intestinal juice1 #aeb1 #aeg4 ,iris1 #cge4 ,iron1 #ace4 ,irritability1 #f1 #bdc1 #cjd4 ,isolation1 #djf4 ,jejunum1 #aea4 ,joints1 #bcj-bcb1 #bdb4 ,kidneys1 #bja4 ,blood supply to1 #bjd4 ,cortex of1 #bjd4 ,inflammation of1 #baa4 ,pelvis of1 #bjb4 ,structure1 #bjb4 ,symptoms of diseased1 #baa4 ,work of1 #bje4 ,knee jerk reflex1 #cbb4 ,lachrymal glands1 #chc4 ,lacteals1 work of1 #agd4 ,lacun1 #bbj4 ,lamin1 #bbj4 ,large intestine1 #aeg4 ,division of1 #aeh4 ,work of1 #aei4 ,larynx1 #hj1 #cec-ceg4 ,to show plan of1 #cfh4 ,lever1 #bea4 ,application to the body1 #bea4 ,classes of1 in body1 #bea4 ,producing motion1 diagram of1 #beb4 ,to show action of1 #beb4 ,leucocytes1 #bg4 ,levulose1 #abj1 #aej4 ,life1 maintenance of1 #bj4 ,light1 #cgj1 #cga4 ,simple properties1 illustrated1 #chi4 ,light waves1 diagram illustrating passage of1 #cgj4 ,lime water1 to prepare1 #aja4 ,liver1 #eb1 #aeb-aee1 #agh4 ,protection of1 #baj4 ,work of1 #bjf4 ,lockjaw1 #bgf4 ,longsightedness1 #chd4 ,lung capacity1 diagram illustrating1 #hi4 ,lung diseases1 out-door cure for1 #ih4 ,lungs1 #gg-ajc4 ,capacity of1 #hh4 ,changes air undergoes in1 #aja4 ,excretory work of1 #bjg4 ,interchange of gases in1 #hh4 ,observations of1 #ajj4 ,supply of blood to1 #hb4 ,to estimate capacity of1 #ajc4 ,weakest portions of1 #ib4 ,lymph1 #fe-ge4 ,composition1 #ff4 ,movements at the cells1 #ga4 ,origin of1 #fe4 ,physical properties1 #ff4 ,where it enters the blood1 #gj4 ,lymph movements1 causes of1 #fi4 ,lymph spaces1 #ff4 ,lymph vessels1 #ff4 ,variable pressure on the walls of1 #gj4 ,magnesium1 #ace4 ,malarial fever1 #dja4 ,malleus1 #cei4 ,malpighian capsules1 #bjc4 ,maltose1 #abj4 ,massage1 #bei4 ,mastication1 ,muscles of1 #add4 ,slow1 #ade4 ,thorough1 #afj4 ,to show importance of1 #aga4 ,matrix1 #bfg4 ,measles1 #id4 ,care after1 #baa4 ,median fissures1 #bhi4 ,medulla oblongata1 #bia4 ,medullary sheath1 #bhd4 ,membrana tympani1 #ceh4 ,membrane1 ,active1 #agc4 ,basement1 #aig4 ,basilar1 #cfc4 ,membranous capsule1 #cgg4 ,membranous labyrinth1 #cfa4 ,mesentery1 #aeb4 ,metacarpals1 #bbg4 ,midbrain1 #bhi4 ,middle ear1 #cei4 ,purposes of1 #cfj4 ,milk sugar1 #abj4 ,mineral salts1 #cj4 ,uses1 #aba4 ,moderate drinkers1 #ccc4 ,molars1 #adc4 ,molecules1 defined1 #aje4 ,mon-axonic neuron1 diagram of1 #bhb4 ,mono-saccharides1 #abj4 ,mosquitoes1 #dja-djc4 ,remedies against1 #djb4 ,mouth1 #ada4 ,movable joints1 ,kinds of1 #bca4 ,structure of1 #bcj4 ,mucous membrane1 #hj1 #bfd4 ,mucus1 #aci4 ,muscle organ1 #bde4 ,muscles1 #bdc-bfc4 ,alimentary1 #ahi4 ,important1 #bed-bef4 ,intercostal1 #hg4 ,of mastication1 #add4 ,properties of1 #bdc4 ,muscular force1 plan of using1 #bdi4 ,muscular sensations1 #cdd4 ,muscular stimulus1 #bdh4 ,muscular stimulus and contraction1 to illustrate1 #bfa4 ,muscular tissue1 kinds of1 #bdc1 #bdd4 ,nails1 #bfg4 ,care of1 #bgf4 ,nasal duct1 #chc4 ,neck exercise1 #cbh4 ,nerve cells1 #bha1 #bhb4 ,nerve fibers1 #bhb1 #bic1 #bid4 ,nerve path1 diagram of1 #bhf4 ,nerve pathways1 to demonstrate1 #cbb4 ,nerves1 #bha4 ,nerve skeleton1 #bhj4 ,diagram of1 #bha4 ,nerve stimuli1 #cjf4 ,nerve trunks1 #bha4 ,nervous activity1 wasteful forms of1 #cbe4 ,nervous control of1 ,body temperature1 #cbj4 ,circulation of blood1 #cah4 ,respiration1 #cbj4 ,nervous energy1 economizing of1 #cae4 ,nervous impulse1 #bdh1 #cje4 ,nervousness1 #cbf4 ,nervous system1 #bgi-ccg4 ,diagram of1 #bhg4 ,dissection of1 #cjb4 ,divisions of1 #bhg4 ,hygiene of1 #cbd-ccg4 ,nature of1 #bhg4 ,physiology of1 #cjd-cbc4 ,work of1 #bhj4 ,neural arch1 #bbd4 ,neurilemma1 #bhd4 ,neurons1 #bha1 #bhb4 ,arrangement of1 #bhd1 #bic4 ,diagram1 illustrating1 #bhe4 ,properties of1 #cjd4 ,nicotine1 ,effects of1 #ccc4 ,relation of age to effects1 #ccc4 ,nitrogen1 #acd4 ,non-striated cells1 to show1 #bfa4 ,non-striated muscles1 ,purpose of1 #bdf4 ,structure of1 #bdf4 ,work of1 #bdg4 ,normal temperature1 #bfi4 ,nosebleed1 #eh4 ,nucleoplasm1 #ad4 ,nutrients 7see ,foods71 ,composition of1 #ace4 ,relative quantity needed1 #abc4 ,routes taken by1 #age4 ,tests for1 #acf4 ,nutriment1 storage of1 #agg-ahj4 ,olfactory stimulus1 #cdg4 ,opsonins1 #cd4 ,optic thalami1 #bhi4 ,orbit1 #cgc4 ,organ1 defined1 #g4 ,organism1 defined1 #ai4 ,organization1 defined1 #aj4 ,osmosis1 #gb4 ,at the cells1 #gb4 ,to illustrate1 #ge4 ,ossein1 #bah4 ,overstudy1 #baa4 ,oxidation1 defined1 #ajf4 ,oxygen1 #ajd-aag4 ,combined1 #aje1 #aac4 ,free1 #aje1 #aac4 ,how it unites1 #aje4 ,main uses of1 #ajh4 ,movement a necessity1 #ajf1 #ajh1 #aae4 ,movement in body1 #ajf1 #ajh1 #aae4 ,nature of1 #ajd4 ,passage of1 from cells1 #aaj4 ,passage of1 through blood1 #aji4 ,passage of1 toward cells1 #aji4 ,preparation of1 #aac4 ,pressure1 #aji4 ,properties of1 #aac4 ,purpose of1 in the body1 #ajf4 ,oxyhemoglobin1 #bg4 ,pacinian corpuscles1 #cdb1 #cdc4 ,to demonstrate1 #cdh4 ,pancreas1 #aee4 ,pancreatic juice1 #aee4 ,papill1 #bff4 ,patent medicines1 #aff4 ,pelvic girdle1 #bbf4 ,pepsin1 #adi4 ,peptones1 #adi1 #agf4 ,pericardium1 #da4 ,perilymph1 #cfa4 ,perimysium1 #bde4 ,periosteum1 #bah4 ,peritoneum1 #ahj4 ,perspiration1 #bjg4 ,pharynx1 #ade4 ,openings into1 #ade1 #adf4 ,phosphorus1 #ace4 ,phrenic nerve1 #cjb4 ,physiological salt solution1 #ch4 ,physiology1 defined1 #b4 ,pia1 #bii4 ,pigment granules1 #bff4 ,pinna1 #ceh4 ,pitch1 detection of1 #cfe4 ,pivot joint1 #bcb4 ,plasma1 #be1 #bi4 ,pleura1 #hd4 ,plexus1 #bha4 ,pneumonia1 #id4 ,pons1 #bij4 ,pons ,varolii1 #bij4 ,portal vein1 #aed4 ,primitive sheath1 #bhd4 ,proteids1 #afa4 ,circulating1 #agi4 ,kinds of1 #aah4 ,purposes of1 #aai4 ,supplied by1 #abe4 ,tests for1 #ace1 #acf4 ,tissue1 #agi4 ,proteoses1 #adi1 #agf4 ,protoplasm1 #ad4 ,protozoa1 #cid4 ,ptyalin1 #ade4 ,public sanitation1 #cif4 ,pulp cavity1 #adc4 ,pupil1 #cge4 ,pure food law1 #abh4 ,pus1 #bh1 #bi4 ,pyloric orifice1 #adg4 ,pyramids1 #bjb4 ,quarantine1 #djf4 ,radius1 #bbg4 ,reaction time1 to determine1 #cbc4 ,reading glasses1 #chf4 ,receptacle of the chyle1 #fh1 #agj4 ,rectum1 #aeh4 ,red corpuscles1 #be4 ,disappearance of1 #bg4 ,function of1 #bf4 ,origin of1 #bg4 ,to examine1 #ch4 ,to prepare models of1 #ci4 ,red marrow1 #bai4 ,renforcement of sound1 #ceb1 #cef1 #cfh4 ,reflection1 kinds of1 #cga4 ,reflex action1 #cjh4 ,diagram illustrating1 #caj4 ,in circulation of blood1 #caa4 ,in digestion1 #caj4 ,purposes of1 #caa4 ,reflex action and mind1 #cjh4 ,reflex action pathway1 #cji4 ,refraction1 #cga4 ,rennin1 #adi4 ,respiration1 #gf-ajc4 ,artificial1 #ig4 ,internal1 #hi4 ,lung1 #gf4 ,retina1 #cgf4 ,retinitis1 #ccc4 ,rheumatism1 ,effects on the heart1 #ef4 ,sequel to other diseases1 #djg4 ,right lymphatic duct1 #fg4 ,rods and cones1 #cgg4 ,rods of ,corti1 #cfd4 ,sacrum1 #bbd4 ,saliva1 #ade4 ,composition of1 #ade4 ,uses of1 #ade4 ,to show action on starch1 #aga4 ,salivary glands1 #add4 ,kinds of1 #add4 ,reflex action of1 #cbc4 ,sanitation1 defined1 #b4 ,sarcolemma1 #bdd4 ,sarcoplasm1 #bdd4 ,scala media1 #cfc4 ,scala tympani1 #cfc4 ,scala vestibula1 #cfc4 ,scarlet fever1 care after1 #baa4 ,sciatic nerve1 #cjb4 ,sclerotic coat1 #cgd4 ,secondary reflex action1 #cad4 ,secretions1 #aig4 ,kinds of1 #bjj4 ,secretory process1 nature of1 #aii4 ,seeing1 problem of1 #cgb4 ,self-control1 #cbf1 #ccd4 ,habit of1 #cbe4 ,semicircular canals1 #cfb4 ,semilunar valves1 #dd4 ,sensations1 #cch-cdi4 ,classes of1 #cci4 ,production of1 #cch1 #cdi4 ,purposes of1 #cdj4 ,special1 #cdj4 ,sensations 7continued74 ,steps in production of1 #cda4 ,sensation stimuli1 #cci4 ,sense organs1 simple forms of1 #cda1 #cdb ,serous coat1 #adj1 #adh4 ,serous membrane1 #bfd4 ,serum albumin1 #cj4 ,serum globulin1 #cj4 ,shortsightedness1 #chd4 ,shoulder girdle1 #bbf4 ,sight1 organs of1 #cgc4 ,sigmoid flexure1 #aeh4 ,simple life1 #daj4 ,skeleton1 #baf-bdc4 ,how deformed1 #bcd4 ,hygiene of1 #bcc4 ,plan of1 #bba4 ,purpose of1 #bba4 ,skin1 #bfd-bgg4 ,as regulator of temperature1 #bgj4 ,experiments on1 #cdi4 ,functions of1 #bfg1 #bfh4 ,observations on skin1 #bgh4 ,skin wounds1 treatment of1 #bge4 ,skull1 #bbe4 ,sleep1 #cbi4 ,small intestine1 #aea4 ,mucous membrane of1 #aea4 ,muscular coat of1 #aeb4 ,as organ of absorption1 #agc4 ,parts of1 #aea4 ,serous coat of1 #aeb4 ,work of1 #aeg4 ,smell1 ,sensation of1 #cdf4 ,value of1 #cdg4 ,sneezing1 #ha4 ,sodium1 #ace4 ,sodium carbonate1 #aee4 ,sodium chloride1 #abb4 ,soft palate1 #ada4 ,solution1 #aca4 ,kinds of1 #gc4 ,solution theory1 #aef4 ,solvents1 #aca4 ,sound1 ,to illustrate origin of1 #cfg4 ,to show transmission of1 #cfg4 ,sound waves1 ,as stimuli1 #cca4 ,nature of1 #cej4 ,renforcement of1 #ceb4 ,to show effects of1 #cfh4 ,value of1 #cec4 ,speech1 production of1 #ceg4 ,spinal column1 #bbc-bbe4 ,hygiene of1 #bcc4 ,spinal cord1 #bhj4 ,protection of1 #bii4 ,spinal nerves1 #bie4 ,double nature of1 #bie4 ,spitting1 #djc4 ,spleen1 #bjh4 ,sprains1 #bci1 #bdj4 ,stapes1 #cei4 ,starch1 #afb4 ,action of1 on saliva1 #aga4 ,animal1 #abj4 ,tests for1 #acf4 ,steapsin1 #aee1 #aef4 ,stegomyia1 #djc4 ,sternum1 #bbe4 ,stomach1 #adg4 ,mucous membrane of1 #adg4 ,muscular action of1 #aej4 ,muscular coat1 #adh4 ,serous coat1 #adh4 ,storage of nutriment1 #agg-agi4 ,strenuous life1 #daj4 ,striated fibers1 to show1 #bfa4 ,striated muscles1 to show1 #bfa4 ,stroma1 #be4 ,sugars1 kinds1 #abj4 ,sulphur1 #ace4 ,supra-renal bodies1 #bjh4 ,suspensory ligament1 #cgg4 ,sutures1 #bcj4 ,sympathetic ganglia and nerves1 #bih4 ,work of1 #caf4 ,synovial fluid1 #bca4 ,synovial membrane1 #bca4 ,system1 defined1 #bj4 ,systole1 #df4 ,taste buds1 #cde4 ,tea1 ,effects on digestion1 #afg4 ,effects on heart1 #ef4 ,tears1 #chc4 ,teeth1 #adb4 ,care of #afc4 ,kinds of1 #adc4 ,temperature1 ,body1 #bjg4 ,corpuscles1 #bga1 #cde4 ,sensation1 #cdc4 ,tendon of ,achilles1 #bef4 ,tendons1 #bdf4 ,tests for foods1 #acf1 #acg4 ,tetanus1 #bfb1 #bge4 ,thoracic cavity1 #g1 #he1 #ajj1 #ajb4 ,thoracic duct1 #fg1 #agj4 ,thorax1 #he4 ,bones of1 #bbe4 ,tissue enzymes1 #ahb4 ,tissues1 #d4 ,complex nature of1 #ac4 ,defined1 #bj4 ,general purposes of1 #e4 ,kinds of1 #e1 #f4 ,observations on1 #ab4 ,properties of1 #f4 ,tobacco1 effect on heart1 #ef4 ,tobacco heart1 #ef1 #ccc4 ,tongue1 #adc4 ,tonic bath1 #bgc4 ,touch1 #cdc4 ,touch corpuscles1 #cdb4 ,toxins1 #cid4 ,trachea1 #hj4 ,trypsin1 #aee1 #aef4 ,tuberculosis1 #ij1 #ib1 #id1 #ih4 ,how communicated1 #djc4 ,outdoor treatment1 #ih4 ,to prevent1 #djd4 ,tympanum1 #cei4 ,typhoid fever1 #djd1 #djg4 ,ulna1 #bbg4 ,urea1 #aaj1 #bje1 #bjg1 #baj4 ,ureters1 #agj4 ,uriniferous tubules1 #bjc4 ,vaccination1 #djf4 ,valves1 ,advantages of1 in veins1 #di1 #fc4 ,mitral1 #dc4 ,position of1 in veins1 #fc4 ,purposes of1 #di1 #fc4 ,tricuspid1 #dc4 ,veins1 #dg4 ,functions of1 #ea4 ,renal1 #bjb4 ,ventilation1 #id4 ,rules for1 #ie1 #if4 ,ventricles1 #db4 ,to illustrate action of1 #fb4 ,vermiform appendix1 #aeh4 ,vertebr1 #bbc-bbe4 ,interlocking of1 #bbe4 ,joining of1 #bbd4 ,kinds1 #bbc4 ,vestibule1 #cfa4 ,villi1 #aeb4 ,parts of1 #agc1 #agd4 ,visual perceptions1 #chb4 ,visual sensations1 #chb4 ,vitreous humor1 #cgh4 ,vocal cords1 #cee4 ,voice1 #cec-ceg4 ,how produced1 #cef4 ,pitch and intensity1 #cef4 ,voluntary action1 #caa1 #cab4 ,voluntary action pathways1 #cab4 ,vomiting1 #aea1 #aeb4 ,waste material1 passage from body1 #baj4 ,wastes1 #cj4 ,water1 ,importance of1 #abc4 ,supply of1 #cih4 ,value of1 #baj4 ,water-vapor1 #bjh4 ,white corpuscles1 #bg1 #bh4 ,functions of1 #bi4 ,to examine1 #ci4 ,work1 ,hygienic value of1 #cbh1 #dji4 ,worry1 #baa4 ,yellow fever1 #djc4 ,yellow marrow1 #bah4 ,yellow spot1 #cgg4 ,,footnotes #a ,the body is affected by what it does 7exercise1 work1 sleep71 by things taken into it 7food1 air1 drugs71 and by things outside of it 7the house in which one lives1 climate1 etc474 ,that phase of hygiene which has for its object the making of the surroundings of the body healthful is known as sanitation4 #b ,when classified according to their essential structure1 the tissues fall into four main groups3 epithelial and glandular tissue1 muscular tissue1 nervous tissue1 and connective tissue4 ,according to this system the osseous1 cartilaginous1 and adipose tissues are classed as varieties of connective tissue4 ,see page #ah4 #c ,the properties of substances are the qualities or characteristics 7color1 weight1 etc47 by means of which they are recognized4 #d ,certain of these cells also form deposits of fat1 giving rise to the adipose1 or fatty1 tissue4 #e ,any organized structure1 such as the body1 whose parts are pervaded by a common life1 is known as an organism4 ,the term organism is frequently applied to the body4 #f ,in birds1 reptiles1 amphibians1 and fishes the red corpuscles have nuclei 7,fig4 #i74 #g ,the micron is the unit of microscopical measurements4 ,it is equal to #a_/ajjj of a millimeter and is indicated by the symbol 4 #h ,the peculiar shape of the red corpuscle has no doubt some relation to its work4 ,its circular form is of advantage in getting through the small blood vessels1 while its extreme thinness brings all of its contents very near the surface--a condition which aids the hemoglobin in taking up oxygen4 ,if the corpuscles were spherical in shape1 some of the hemoglobin could not1 on account of the distance from the surface1 so readily unite with the oxygen4 #i ,the coloring matter of the bile consists of compounds formed by the breaking down of the hemoglobin2 the spleen contains many large cells that seem to have the power first of engulfing and later of decomposing red corpuscles4 ,a further evidence that the spleen aids in the removal of worn-out corpuscles is found in the fact that during diseases that cause a destruction of the red corpuscles1 such as the different forms of malaria1 the spleen becomes enlarged4 #aj ,an infected part of the body1 such as a boil or abscess1 should never be bruised or squeezed until the time of opening4 ,pressure tends to break down the wall of white corpuscles and to spread the infection4 ,pus from a sore contains germs and should not1 on this account1 come in contact with any part of the skin4 7,see treatment of skin wounds1 ,chapter ,,xvi47 #aa ,coagulation is not confined to the blood4 ,the white of an egg coagulates when heated and when acted upon by certain chemicals1 and the clabbering of milk also is a coagulation4 #ab ,if the blood be stirred or whipped while it is coagulating1 the clot may be broken up and the fibrin separated as fast as it forms4 ,the blood which then remains consists of serum and corpuscles and will not coagulate4 ,it is known as defibrinated blood4 #ac ,certain substances1 called opsonins1 have recently been shown to exist in the plasma1 that aid the white corpuscles in their work of destroying germs4 ,the opsonins appear to act in such a manner as to weaken the germs and make them more susceptible to the attacks of the white corpuscles4 #ad ,some of the changes in the blood are very closely related to our everyday habits and inclinations4 ,for example1 a lack of nourishment in the blood causes hunger and this leads to the taking of food4 ,if the fluids of the body become too dense1 a feeling of thirst is aroused which prompts one to drink water4 #ae ,metchnikoff1 ,the ,new ,hygiene4 #af ,a physiological salt solution is prepared by dissolving 4#f of a gram of common salt in #ajj cc4 of distilled water or pure cistern water4 ,this solution1 having the same density as the plasma of the blood1 does not act injuriously upon the corpuscles4 #ag ,the term circulation literally means moving in a circle4 ,while the blood does not move through the body in a circle1 the term is justified by the fact that the blood flows out continually from a single point1 the heart1 and to this point is continually returning4 #ah ,the heart at first glance seems to bear little resemblance to the pumps in common use4 ,when it is remembered1 however1 that any contrivance which moves a fluid by varying the size of a cavity is a pump1 it is seen that not only the heart1 but the chest in breathing and also the mouth in sucking a liquid through a tube1 are pumps in principle4 ,the ordinary syringe bulb illustrates the class of pumps to which the heart belongs4 7,see ,practical ,work47 #ai ,the contraction of the heart is known as the systole and its relaxation as the diastole4 ,the systole plus the diastole forms the so-called cardiac cycle 7,fig4 #ah74 ,this consists of 7#a7 the contraction of the auricles1 7#b7 the contraction of the ventricles1 and 7#c7 the period of rest4 ,the heart systole includes the contraction of both the auricles and the ventricles4 #bj ,martin1 ,the ,human ,body4 #ba ,the pressure maintained by the left ventricle has been estimated to be nearly three and one half pounds to the square inch--a pressure sufficient to sustain a column of water eight feet high4 ,the pressure maintained by the right ventricle is about one third as great4 ,in maintaining this pressure the heart does a work equal to about one two-hundredth of a horse power4 #bb ,the location of the heart in the thoracic cavity causes movements of the chest walls to draw blood into the right auricle for the same reason that they draw air into the lungs4 #bc ,active exercise through short intervals1 followed by periods of rest1 such as the exercise furnished by climbing stairs1 or by short runs1 is considered the best means of strengthening the heart4 #bd ,nosebleed in connection with any kind of severe sickness should receive prompt attention1 since a considerable loss of blood when the body is already weak may seriously delay recovery4 #be ,newton1 ,practical ,hygiene4 #bf ,on account of its position in the body1 the lymph is not easily collected for examination4 ,still1 nearly every one will recall some experience that has enabled him to see lymph4 ,the liquid in a water blister is lymph1 and so also is the liquid which oozes from the skin when it is scraped or slightly scratched4 ,swelling in any part of the body is due to the accumulation of lymph at that place4 #bg ,in certain small animals of the lowest types a single liquid1 serving as a medium of exchange between the cells and the body surface1 supplies all the needs of the organism4 ,in larger animals1 however1 where materials have to be moved from one part of the cell group to another1 a portion of the nutrient fluid is used for purposes of transportation4 ,this is confined in channels where it is set in motion by suitable organs4 ,the portion which remains outside of the channels then transfers material between the cells1 on the one hand1 and the moving liquid1 on the other4 #bh ,surgeons in opening veins near the thoracic cavity have to be on their guard to prevent air from being sucked into them1 thereby causing death4 #bi ,oxygen forms about #ba per cent of the atmosphere1 nitrogen about #gh per cent1 carbon dioxide about 4#jc per cent1 and the recently discovered element argon about #a per cent4 ,the oxygen is in a free1 or uncombined1 condition--the form in which it can be used in the body4 #cj ,the peculiar work devolving upon the organs of respiration necessitates a special plan of construction--one adapted to the properties of the atmosphere4 ,being concerned in the movement of air1 a gaseous substance1 they will naturally have a structure different from the organs of circulation which move a liquid 7the blood74 ,all the organs of the body are adapted by their structure to the work which they perform4 #ca ,in ordinary inspirations the force that causes the air to move through the passages is scarcely an ounce to the square inch1 while in forced inspirations it does not exceed half a pound4 ,on this account the closing of any of the air passages by pressure1 or by the presence of foreign substances1 would keep the air from reaching some part of the lungs4 #cb ,coughing1 which is a forceful expulsion of air1 has for its purpose the ejection of foreign substances from the throat and lungs4 ,sneezing1 on the other hand1 has for its purpose the cleansing of the nostrils4 ,in coughing1 the air is expelled through the mouth1 while in sneezing it is expelled through the nostrils4 #cc ,the amount of dust suspended in what we ordinarily think of as pure air is shown when a beam of direct sunlight enters an otherwise darkened room4 #cd ,some children find it difficult to breathe through the nostrils on account of growths 7called adenoids7 in the upper pharynx4 ,such children should have medical attention4 ,the removal of these growths not only improves the method of breathing1 but in many instances causes a marked improvement in the general health and personal appearance4 #ce ,the weakest portions of the lungs appear to be the tiny lobes at the top4 ,as they occupy the part of the thorax most difficult to expand1 air penetrates them much less freely than it does the lobes below4 ,in most cases of consumption 7some authorities give as high as eighty per cent71 the upper lobes are the first to be affected4 ,flat chests and round shoulders1 by increasing this natural difficulty in breathing1 have long been recognized as causes which predispose to consumption4 #cf ,the following exercise1 from ,dudley ,a4 ,sargent's ,health1 ,strength1 and ,power1 will be found most beneficial3 ,stand with the feet together1 face downward1 arms extended downward1 and backs of the hands touching4 ,raise the hands1 arms1 and elbows1 keeping the backs of the hands together until they pass the chest and face4 ,then continue the movement upward1 until the hands separate above the head with the face turned upward1 when they should be brought downward and outward in a large circle to the starting point4 ,begin to inhale as the arms are raised and take in as much air as possible by the time the hands are above the head1 then allow the breath to go out slowly as the arms descend4 #cg ,colds may frequently be broken up at their beginning by taking a prolonged hot bath and going to bed4 ,after getting a start1 however1 they run a course of a few days1 a week1 or longer1 depending upon the natural vigor of the individual and the care which he gives his body during the time4 ,in throwing off a cold1 the following suggestions will be found helpful3 #a4 ,dress warmly 7without overdoing it7 and avoid getting chilled4 #b4 ,diminish the usual amount of work and increase the period for sleep4 ,if very weak1 stay in bed4 ,save the energy for throwing off the cold4 #c4 ,if able to be about1 spend considerable time in light exercise out of doors1 but avoid getting chilled4 #d4 ,keep the bowels active1 taking a cathartic if necessary4 #e4 ,to relieve pain in the chest1 apply a mustard plaster or a flannel cloth moistened with some irritating substance1 such as turpentine or a mixture of equal parts of kerosene and lard4 ,keep up a mild irritation until the pain is relieved1 but avoid blistering4 #ch ,not only do the lungs remove oxygen from the air and add carbon dioxide to it1 but they separate from the body considerable moisture and1 according to some authorities1 a small amount of an impurity referred to as animal matter4 ,odors also arise from the skin1 teeth1 and clothing which1 if not dangerous to the health1 are offensive to the nostrils4 ,if on going into a room such odors are detected1 the ventilation is not sufficient4 ,this is said to be a reliable test4 #ci ,e4,a4 ,schaffer1 ,artificial ,respiration in its ,physiologic ,aspects1 ,the ,journal of the ,american ,medical ,association1 ,september1 #aijh4 #dj ,testing the prone-posture method by suitable apparatus1 ,professor ,schaffer has found it capable of introducing more air per minute into the lungs than any of the other methods of artificial respiration1 and more even than is introduced by ordinary breathing4 #da ,osier1 ,the ,principles and ,practice of ,medicine4 #db ,huber1 ,consumption and ,civilization4 #dc ,to prepare limewater some small lumps of fresh lime 7either slacked or unslacked7 are added to a large bottle of water and thoroughly shaken4 ,this is put aside until the lime all settles to the bottom and the water above is perfectly clear4 ,this is now ready for use and may be poured off as needed4 ,when the supply is exhausted add more water and shake again4 #dd ,an element is a single kind of matter4 ,those substances are classed as elements which cannot be separated into different kinds of matter4 ,two or more elements combined in definite proportions by weight form a compound4 ,the elements are few in number1 only about eighty being known4 ,compounds1 on the other hand1 are exceedingly numerous4 #de ,the term energy1 as used here1 has the same general meaning as the word power4 ,see ,chapter ,,xii4 #df ,the oxygen pressure of the atmosphere is that portion of the total atmospheric pressure which is due to the weight of the oxygen4 ,since oxygen comprises about one fifth of the atmosphere1 the pressure which it exerts is about one fifth of the total atmospheric pressure1 or1 at the sea level1 about three pounds to the square inch 7#ae x #a_/e #c74 ,this is the oxygen pressure of the atmosphere4 ,the low oxygen pressure in the tissues is due to its scarcity1 and this scarcity is due to its entering into combination at the cells4 #dg ,see footnote on oxygen pressure1 page #aji4 #dh ,the impression prevails to some extent that carbon dioxide1 on account of its weight1 settles out of the atmosphere1 collecting in old wells and at the floor in crowded rooms4 ,any such settling of the carbon dioxide is prevented by the rapid motion of its molecules4 ,this motion not only prevents a separation of carbon dioxide and air after they are mixed1 but causes them to mix rapidly when they are separated1 if they still have surface contact4 ,the carbon dioxide found in old wells is formed there by decaying vegetable or animal matter4 ,in rooms it is no more abundant at the floor than in other parts4 #di ,on account of the formation of carbon dioxide in places containing decaying material1 the descent into an old well or other opening into the earth is often a hazardous undertaking4 ,before making such a descent the air should always be tested by lowering a lighted lantern or candle4 ,artificial respiration is the only means of restoring one who has been overcome by this gas 7page #ig74 #ej ,while awaiting oxidation at the cells1 the carbohydrates and fats are stored up by the body1 the carbohydrates as glycogen and the fats as some form of fat4 ,in this sense they are sometimes looked upon as serving to build up certain of the tissues4 #ea ,the following table shows the main elements in the body and their relation to the different nutrients3 ,nutrient ,table #eb ,the recently advanced theory that the molecules of the mineral salts1 by dissolving in water1 separate into smaller divisions1 part of which are charged with positive electricity and part with negative electricity1 has suggested several possible uses for sodium chloride and other mineral salts in the body4 ,the sodium chloride in the tissues is in such concentration as to be practically all separated into its sodium and chlorine particles1 or ions4 ,it has recently been shown that the sodium ions are necessary for the contraction of the muscles1 including the muscles of the heart4 ,there is also reason for believing that the different ions may enter into temporary combination with food particles1 and in this way assist in the processes of nutrition4 #ec ,chittenden1 ,the ,nutrition of ,man4 #ed ,compiled from different sources1 but mainly from ,atwater's ,foods3 ,nutritive ,value and ,cost1 published by the ,u4,s4 ,department of ,agriculture4 #ee ,the calorie is the adopted heat unit4 ,as used in this table it may be defined as the quantity of heat required to raise #a kilogram 7#b4b pounds7 of water1 #a degree centigrade4 ,the calories also show the relative amount of energy supplied by the different foods4 #ef ,while alcohol cannot be classed as a food1 it is believed by some authorities to contain food value and1 in the hands of the physician1 to be a substance capable of rendering an actual service in the treatment of certain diseases4 ,it might1 for example1 be used where one's power of digestion is greatly impaired1 since alcohol requires no digestion4 ,but upon this point there is a decided difference of opinion4 ,certain it is that no one should attempt to use alcohol as food or medicine except under the advice and direction of his physician4 #eg ,a layer of connective tissue between the mucous membrane and the muscular coat is usually referred to as the submucous coat4 ,this contains numerous blood vessels and nerves and binds the muscular coat to the mucous membrane4 #eh ,the saliva may continue to act for a considerable time after the food enters the stomach4 ,careful examination of the contents of the fundus 7large end of the stomach7 by ,cannon and ,day has shown that no inconsiderable amount of salivary digestion occurs in the stomach4--,,fischer1 ,the ,physiology of ,alimentation4 #ei ,perhaps the simplest method of inducing vomiting is that of thrusting a finger down the throat4 ,to make this method effective the finger should be held in the throat until the vomiting begins4 ,an emetic1 such as a glass of lukewarm salt water containing a teaspoonful of mustard1 should also be taken1 and1 in the case of having swallowed poison1 the vomiting should be repeated several times4 ,it may even be advantageous to drink water and then vomit it up in order to wash out the stomach4 #fj ,hammerstein1 ,text-book of ,physiological ,chemistry4 #fa ,amylopsin is absent from the pancreatic juice of infants1 a condition which shows that milk and not starch is their natural food4 #fb ,the fact that butter is more easily digested than other fatty substances is probably due to its consisting largely of a kind of fat which1 on splitting1 forms a fatty acid 7butyric7 which is soluble in water4 #fc ,fischer1 ,physiology of ,alimentation4 #fd ,beginning the meal with a little soup1 as is frequently done1 may be of slight advantage in stimulating the digestive glands4 ,to serve this purpose1 however1 and not interfere with the meal proper1 it should contain little greasy or starchy material and should be taken in small amount4 #fe ,dr4 ,william ,beaumont1 an ,american surgeon of the last century1 made a series of observations upon a human stomach 7that of ,alexis ,st4 ,martin7 having an artificial opening1 the result of a gunshot wound4 ,much of our knowledge of the digestion of different foods was obtained through these observations4 ,in spite of the protests of his physician1 ,st4 ,martin would occasionally indulge in strong drink and always with the same result--the lining of the stomach became much inflamed and very sensitive1 and the natural processes of digestion were temporarily suspended4 #ff ,the lacteals 7from the ,latin lacteus1 milky7 are so called on account of their appearance1 which is white1 or milk-like1 due to the fat droplets4 #fg ,peptones and proteoses1 when injected directly into the blood1 are found to act as poisons4 #fh ,the soluble double sugars 7maltose1 milk sugar1 and cane sugar7 are reduced to the simple sugars 7dextrose and levulose74 ,furthermore the action on the proteids does not stop with the production of peptones and proteoses1 but these in turn are still further reduced4 #fi ,energy1 which is defined as the ability to do work1 or to cause motion1 exists in two general types1 or forms1 known as kinetic energy and as potential energy4 ,kinetic energy is energy at work1 or energy in the act of producing motion2 while potential energy is reserve1 or stored1 energy4 ,all moving bodies have kinetic energy1 and all stationary bodies which have within them the capability of causing motion possess potential energy4 ,a bent bow1 a piece of stretched rubber1 a suspended weight1 the water above a mill dam1 all have the capability of causing motion and all have potential energy4 ,examples of kinetic energy are found in the movements of machinery1 in steam and electricity1 in winds1 and in currents of water4 ,kinetic is the active1 and potential the inactive1 form of energy4 #gj ,as the atoms of hydrogen and oxygen that make up the molecules of water separate1 they unite with atoms of their own kind--the hydrogen with hydrogen and the oxygen with oxygen atoms4 ,since these combinations are weaker than those of the water molecules1 energy is required to bring about the change4 ,but when hydrogen burns in the oxygen1 the change is from a weaker to a stronger combination4 ,the stored-up energy is then given up or becomes active4 #ga ,in the evaporation of water1 the energy of the sun is stored with reference to the force of gravity4 ,in evaporating1 water rises as a gas1 or vapor1 above the earth's surface1 but on condensing into a liquid1 it falls as rain4 ,it then finds its way through streams back to the ocean4 ,all water above the sea level is in such a position that gravity can act on it to cause motion1 and it possesses1 on this account1 potential or stored-up energy4 ,it is because of this energy that rapids and waterfalls are such important sources of power4 #gb ,energy1 like matter1 can neither be created nor destroyed4 ,it can1 however1 be transferred from one body to another and transformed from one form to another form4 ,whenever work is done1 energy is transferred from the body doing the work1 to the body upon which the work is done4 ,during this process there may1 or may not1 be a transformation of energy4 ,in turning a grindstone1 kinetic energy is passed to the stone and used without transformation1 but in winding a clock1 the kinetic energy from the hand is transformed into potential energy in the clock spring4 ,then as the clock runs down this is retransformed into kinetic energy1 causing the movements of the wheels4 ,not only is kinetic transformed into potential energy and vice versa1 but the different forms of kinetic energy 7heat1 light1 electricity1 sound1 and mechanical motion7 are readily transformed the one into the other4 ,with suitable devices1 mechanical motion can be changed into heat1 sound1 or electricity2 heat into motion and light2 and electricity into all the other forms of energy4 ,these transformations are readily explained by the fact that the different varieties of kinetic energy are but different forms of motion 7,fig4 #hd74 #gc ,the simplest arrangement of the parts of a gland is that where they are spread over a plain surface4 ,this arrangement is found in serous membranes1 such as the pleura and peritoneum4 ,these membranes1 however1 are not called glands1 but secreting surfaces4 #gd ,in the oxidations that occur in the body it is not supposed that the nutrients are immediately converted to carbon dioxide1 water1 and urea4 ,on the other hand1 it is held that their reduction takes place gradually1 as the reduction of sugar by fermentation1 and that the wastes leaving the body are but the end products and show only the final results4 #ge ,alcohol1 if used in considerable quantity1 leads to cirrhosis of the liver and ,bright's disease of the kidneys1 both very dangerous diseases4 ,dr4 ,william ,osler in his treatise1 ,the ,practice of ,medicine1 states that alcohol is the chief cause of cirrhosis of the liver4 ,dr4 ,t4,n4 ,bogart1 specialist in kidney diseases1 asserts that one third of all the cases of ,bright's disease coming under his observation are caused by alcohol4 #gf ,hall1 ,the ,purin ,bodies4 #gg ,review ,main ,physiological ,problems1 page #ba4 #gh ,in the production of motion in the body1 as well as in the production of any kind of purposeful motion outside of the body1 three conditions must be fulfilled4 ,there is required1 in the first place1 a mechanical device or machine which is so constructed as to produce a certain kind of motion4 ,in the second place1 energy is needed to operate this device4 ,and1 finally1 there must be some controlling force1 by means of which the motion is made to accomplish definite results4 ,the driving of a horse hitched to a wagon will illustrate these conditions4 ,the wagon is the mechanical device1 the horse furnishes the energy1 and the driver supplies the controlling force4 ,in this1 as in most cases1 the machinery1 the source of energy1 and the controlling force are disconnected except when at work2 but in the body all three occur together in the same structure4 #gi ,the dependence of the outer layers of bone cells upon the periosteum for nourishment causes a destruction of this membrane to affect seriously the bone beneath1 producing in many instances a decay of the bone substance4 #hj ,it has been claimed that the introduction of vertical writing has reduced the number of cases of spinal curvature originating in the schoolroom1 and statistics appear to prove the claim4 ,it is shown1 on the other hand1 that unnatural positions also are unnecessary in the slanting system of writing1 and that in either system the pupil who is permitted to do so is liable to assume an improper position4 #ha ,lovett1 ,lateral ,curvature of the ,spine and ,round ,shoulders4 #hb ,see ,hygiene of ,muscles1 ,chapter ,,xv4 #hc ,on account of the striations of these cells the muscles which they form are called striated muscles4 #hd ,the striated muscle cells1 having many nuclei1 are said to be multi-nucleated4 #he ,every movement in the body has its opposing movement4 ,this is necessary both on account of the work to be accomplished and for preserving the natural form of the body4 #hf ,the distance from the fulcrum to the power is called the power-arm and the distance from the fulcrum to the weight is called the weight-arm 7,fig4 #aae74 #hg ,the foot in lifting the body on tiptoe appears at first thought to be a lever of the second class1 the body being the weight and the toe serving as the fulcrum4 ,however1 if the distance which the body is raised is compared with the distance which the muscle shortens1 it is found that the supposed weight has moved farther than the power 7,fig4 #aah74 ,it will also be noted that the muscle which furnishes the power is attached at its upper end to the weight4 ,these facts show clearly that we are not here dealing with a lever of the second class4 ,the foot in this instance acts as a lever of the first class with the fulcrum at the ankle joint and the toe pressing against the earth1 which is the actual weight4 ,since the earth is immovable1 the body is lifted or pushed upward1 somewhat as a fulcrum support is made to move when it is too weak to hold up the weight that is being lifted4 ,in other words1 we have the same lever action in the foot in lifting the body as we have when one lies face downward1 and1 bending the knee1 lifts some object on the toes4 #hh ,walking is considered one of the very best forms of counter-active exercise for the brain worker 7page #cbh74 #hi ,the epidermis does not afford complete protection against chemicals1 many of them being able to destroy it quickly4 ,the rule of washing the skin immediately after contact with strong chemical agents should always be followed4 #ij ,rough calculations have placed the number of sweat glands on the entire body at about #b1jjj1jjj4 ,rettger1 ,studies in ,advanced ,physiology4 #ia ,heat also leaves the body by the lungs1 partly by the respired air and partly through the evaporation of moisture from the lung surfaces4 ,respiration in some animals1 as the dog1 is the chief means of cooling the body4 #ib ,the story is told of some woodsmen who were overtaken by a severe snowstorm and had to spend the night away from camp2 they had a bottle of whisky1 and1 chilled to the bone1 some imbibed freely while others refused to drink4 ,those who drank soon felt comfortable and went to sleep in their improvised shelter2 those who did not drink felt very uncomfortable throughout the night and could get no sleep1 but in the morning they were alive and able to struggle back to camp1 while their companions who had used alcohol were frozen to death4444 ,this1 if true1 was of course an extreme case2 but it accords with the universal experience of arctic travelers and of lumbermen and hunters in the northern woods1 that the use of alcohol during exposure to cold1 although contributing greatly to one's comfort for the time being1 is generally followed by undesirable or dangerous results4--,,hough ,,and ,,sedgwick3 ,the ,elements of ,hygiene and ,sanitation4 #ic ,foods that are difficult to digest1 or which cause disturbances of the digestive organs 7a coated tongue being one indication71 have a bad effect upon the skin4 ,it is in this way that the use of tea and coffee by some people induces a sallow or muddy condition of the complexion4 #id ,a most valuable antiseptic ointment is prepared by the druggist from the following formula3 ,lanolin1 #be grams4 ,ichthyol1 #f grams4 ,yellow vaseline1 #bj grams4 ,this is applied as a thin layer on the surface1 except in the case of boils or abscesses4 ,in treating these a heavy layer is spread over the affected part and then covered with absorbent cotton or a thin piece of clean cotton cloth4 #ie ,in a larger sense adjustment includes all those activities by means of which the body is brought into proper relations with its environment1 including the changes which the body makes in its surroundings to adapt them to its purposes4 #if ,almost to the present time1 physiologists have described the nervous system as being made up of two kinds of structural elements which were called nerve cells and nerve fibers4 ,the nerve cells were supposed to form the ganglia and the fibers to form the nerves4 ,recent investigators1 however1 employing new methods of microscopic study1 have established the fact that the so-called nerve cell and nerve fiber are but two divisions of the same thing and that the nervous system is made up of1 not two1 but one kind of structural element4 ,the term neuron is used to denote this structural element1 or complete nerve cell4 #ig ,many of the axons in the brain and spinal cord have no primitive sheath4 ,axons without the medullary sheath are found in the sympathetic nerves4 ,these are known as non-medullated axons and they have a gray instead of a white color4 #ih ,the difference in weight between the brain of man and that of woman is due mainly to the fact that man's body is1 as a rule1 considerably larger than that of woman's4 #ii ,the nervous tissues present1 at different places1 two colors--one white1 and the other a light gray4 ,great significance was formerly attached to these colors1 because it was supposed that they represented two essentially different kinds of nervous matter4 ,it is now known that the protoplasm in all parts of the neuron proper--cell-body1 axis cylinder1 and dendrites--has a grayish color1 while the coverings of most of the fibers are white4 ,hence gray matter in any part of the nervous system indicates the presence of cell-bodies1 and white matter the presence of nerve fibers4 #ajj ,in very early life the spinal cord entirely fills the spinal cavity1 but as the body develops the cord grows less rapidly than the spinal column1 and1 as a consequence1 separates at the lower end from the inclosing bony column4 #aja ,fibers passing between the spinal cord and the cerebrum cross to opposite sides--most of them at the bulb1 but many within the cord--so that the right side of the cerebrum is connected with the left side of the body1 and vice versa4 ,this accounts for the observed fact that disease or accidental injury of one side of the cerebrum causes loss of motion or of feeling in the opposite side of the body4 #ajb ,in general1 afferent neurons or fibers are those that convey impulses toward the central nervous system 7brain and cord71 while efferent neurons or fibers are those that convey impulses from the central system4 #ajc ,at different times the nervous impulse has been regarded as a current of electricity2 as a progressive chemical change1 likened to that in a burning fuse2 as a mechanical vibration1 such as may be passed over a stretched rope2 and as a molecular disturbance accompanied by an electrical discharge4 ,the velocity of the nervous impulse1 which is only about one hundred feet per second1 proves that it is not a current of electricity4 ,it takes place with little or no exhaustion of the cell protoplasm and consequently is not due to chemical action4 ,and the loose1 relaxed condition of the nerves prevents their transmission of physical vibrations1 like those on a stretched rope4 ,the view that the impulse is a progressive molecular disturbance1 accompanied by an electrical discharge1 has much evidence in its favor1 but it has only recently been proposed and is likely to be modified upon fuller investigation4 #ajd ,the surface of the body includes the linings of the air passages1 food canal1 and certain cavities1 as well as the external covering or skin4 #aje ,derived from the ,latin re1 back1 and flectere1 to turn or bend4 #ajf ,a frog from which the brain has been removed is suspended with its feet downward and free to move4 ,if a toe is pinched1 the foot is drawn away1 and if dilute acid1 or a strong solution of salt1 is placed on the tender skin1 the feet are moved as if to take away the irritating substance4 ,this of course shows that reflex action can take place independently of the brain4 ,now if the spinal cord is also destroyed1 there is no response when the irritation of the skin is repeated4 ,the animal remains perfectly quiet1 because the destruction of the cord has interrupted the reflex action pathway4 ,this shows that some part of the central nervous system is necessary to reflex action4 #ajg ,review description of the spinal nerves1 page #bie4 #ajh ,where a deep-seated cause for worry exists1 there may be occasion for grave concern4 ,many people have become insane through continued worry about some one thing4 ,in cases of this kind the sufferer needs the aid of sympathetic friends1 and sometimes of the physician1 in getting the mind away from the exciting cause4 ,a change of scene1 a visit1 or some new employment is frequently recommended1 where the actual cause for the worry cannot be removed4 #aji ,any part of the body which is overworked or which works at a disadvantage tends to disturb1 more or less1 the entire nervous system and to produce nervousness4 ,especially is this true of such delicate and highly sensitive structures as the eyes4 ,if the eyes do not focus properly or if the muscles that move the eyeballs are out of their natural adjustment1 extra work is thrown upon these delicate parts4 ,one of the first and sometimes the only indication of eye strain is that of some disturbance of the nervous system4 ,for this reason it is important to carefully test the eyes in determining the cause of nervousness 7page #che74 #aaj ,one form of neck exercise recommended for this purpose is easily taken on retiring at night4 ,lying flat on the back1 without a pillow1 lift the head slowly from the bed and let it as slowly settle back to the level of the body4 ,repeat several times1 lying on the back1 and then again on the face and again on each side4 ,practice these exercises every night during an interval of a month or until relief is secured4 #aaa ,insurance statistics show that habitual moderate drinkers do not live so long as abstainers4 #aab ,organs very frequently affected by tobacco are the heart and the eyes4 ,it induces1 as already stated 7page #ef71 a dangerous nervous derangement called tobacco heart1 and it causes a serious disorder of the retina 7retinitis7 which leads in some instances to loss of vision4 ,tobacco smoke also acts as an irritant to the delicate lining of the eyes1 especially when the tobacco is smoked indoors4 #aac ,of #daag boys in the ,illinois ,state ,reformatory1 #djjj used tobacco1 and over #cjjj were cigarette smokers4 ,dr4 ,hutchison1 of the ,kansas ,state ,reformatory1 says3 ,using cigarettes is the cause of the downfall of more of the inmates of this institution than all other vicious habits combined4 #aad ,the term mind is used in this and preceding chapters in its popular1 not technical1 sense4 #aae ,the problem of social adjustment is but a phase of the general problem of establishing proper relations between the body and its surroundings4 #aaf ,a vibrating body is one having a to-and-fro movement1 like that of a clock pendulum or the string of a violin on sounding4 ,bodies to give out sound waves must vibrate rapidly1 making not less than sixteen vibrations per second4 ,the upper limit of hearing being about #dj1jjj vibrations per second1 certain bodies may even vibrate too rapidly to be heard4 #aag ,somewhat as the waves on a body of water impart motion to the sticks and weeds along the shore1 sound waves are able to cause bodies that are small or that are delicately poised to vibrate4 #aah ,some idea of how the movements of the cartilages change the tension of the cords may be obtained by holding the fingers on the larynx1 between the thyroid and cricoid cartilages1 and making tones first of low and then of high pitch4 ,for the high tones the cartilages are pulled together in front1 and for the low tones they separate4 ,as they pull together in front1 they of course separate behind and above1 where the cords are attached4 #aai ,it is only the central portion of the pinna that aids the entrance of sound into the auditory canal4 ,if by accident the outer portion of the pinna is removed1 there is no impairment of the hearing4 #abj ,the middle ear is also called the ear drum1 and1 by the same system of naming1 the membrana tympani is referred to as the drum membrane4 #aba ,the inner projection of the temporal bone is known as the petrous process4 #abb ,a small opening in the bone at this place is called the fenestra rotunda4 #abc ,consult some work on physics on the different kinds of lenses and their uses4 #abd ,with respect to its adjustments the eye does not differ in principle from various other optical instruments1 such as the microscope1 telescope1 photographer's camera1 etc41 which1 in their use1 form images of objects4 ,these all require some adjustment of their parts1 called focusing1 which adapts them to the distance4 ,the eye's method of focusing1 however1 differs from that of most optical instruments1 in that the adjustment is brought about through changes in the curvature of a lens4 #abe ,the converging power of convex lenses varies as the curvature--the greater the curvature1 the greater the converging power4 #abf ,an oculist is a physician who specializes in diseases of the eye4 #abg ,some of the more common symptoms of eye strain are nervousness1 headache1 insomnia1 irritations of the eyelids1 sensitiveness to bright light1 and pain in the use of the eyes4 #abh ,pyle1 ,personal ,hygiene4 #abi ,an infectious disease is one in which disease germs infect 7that is1 invade7 the body from without4 ,among the infectious diseases are some that are quite directly and quickly conveyed from person to person and to these the term contagious is applied4 ,formerly a sharp line was drawn between infection and contagion1 but to-day it is recognized that no such line exists4--,,hough ,,and ,,sedgwick1 ,the ,elements of ,hygiene and ,sanitation4 #acj ,the arctic explorer1 ,nansen1 states that during all the time that his party was exposed to the low temperature of the arctic region1 no one was attacked by a cold1 but on returning to a warmer climate they were subject to colds as usual4 ,the difference he attributes to the absence of germs in the severe arctic climate4 ,there seems to be no doubt but that most of our common colds are due to attacks of germs4 #aca ,an interesting biological fact is that the female ,anopheles1 and not the male1 sucks the blood of animals and is the cause of the spreading of malaria4 #acb ,the habit of spitting upon the floors of public buildings and street cars1 and also upon sidewalks1 is now recognized as a most dangerous practice4 ,not only consumptives1 but people with throat affections1 may do no end of harm in the spreading of disease by carelessness in this respect4 #acc ,for further information on the care of consumptives1 consult ,huber's ,consumption and ,civilization4 #acd ,as typhoid fever is a disease of the small intestine1 great care must be exercised in taking food and in the bodily movements4 ,solids greatly irritate the diseased lining of the intestine1 and the weakened walls may actually be broken through by pressure resulting from moving about4 #ace ,alcoholic beverages include all the various kinds of drinks that owe their stimulating properties to a substance1 ethyl alcohol 7,c#b;,h#e,,oh71 which is made from sugar by the process of fermentation4 ,they include malt liquors1 such as beer and ale1 which contain from three to eight per cent of alcohol2 wines1 such as claret1 hock1 sherry1 and champagne1 which contain from five to twenty per cent of alcohol2 and distilled liquors1 such as brandy1 whisky1 rum1 and gin1 which contain from thirty to sixty-five per cent of alcohol4 ,alcoholic beverages all contain constituents other than alcohol1 these varying with the materials from which they are made and with the processes of manufacture4 ,the distilled liquors are so called from the fact that their alcohol has been separated from the fermenting substances by distillation4 #acf ,duncan1 ,the ,chemistry of ,commerce4 #acg ,alcohol is denatured by adding substances to it such as wood alcohol1 which render its use as a beverage impossible4 #ach ,the tobacco plant1 ,nicotiana tobacum1 is a native of ,america1 and the use of tobacco began with the ,american ,indians4 ,it was taken back to ,europe by the early explorers1 ,sir ,walter ,raleigh being credited with introducing it to the nobility of ,england4 #aci ,most headaches are the result either of eye strain or of digestive disturbances1 such as indigestion and constipation1 and are to be relieved through the work of the oculist or through attention to the hygiene of the digestive system4