,transcriber's ,notes ,obvious typographical errors have been silently corrected4 ,variations in hyphenation have been standardised but all other spelling and punctuation remains unchanged4 ,italics are represented thus italic1 bold thus bold and superscripts thus yen4 ,the mathematical and chemical formulae accurately represent the original but have not been error checked4 ,there are many mathematical equations where variables are presented as italic letters4 ,for the sake of clarity this has not been shown4 ,,hygiene3 ,a ,,manual ,,of ,personal and ,public ,health ,,by ,,arthur ,,newsholme1 ,m4,d41 ,f4,r4,c4,p41 ,,lond41 ,,university ,,scholar ,,in ,,medicine2 ,,diplomate ,,in ,,public ,,health1 ,,univ4 ,,lond42 ,,medical ,,officer ,,of ,,health ,,of ,,brighton2 ,,member ,,of ,,the ,,council ,,and ,,examiner ,,to ,,the ,,sanitary ,,institute2 ,,examiner ,,in ,,state ,,medicine ,,to ,,the ,,university ,,of ,,london2 ,,late ,,examiner ,,in ,,preventive ,,medicine ,,to ,,the ,,university ,,of ,,oxford1 ,,and ,,president ,,of ,,the ,,incorporated ,,society ,,of ,,medical ,,officers ,,of ,,health4 ,,new ,,edition1 #aijb4 ,,illustrated4 ,,london3 ,,geo4 ,,gill ,,sons1 ,,ld41 ,,minerva ,,house1 ,,warwick ,,lane4 ,,preface4 ,the writing of a preface is perhaps superfluous for a book which has had a large and steady sale for nearly twenty years1 and which has evidently met with the approval of a large constituency4 ,a few words of introduction appear1 however1 desirable in view of the facts that the present edition has been almost entirely re-written2 that a large amount of new matter has been introduced2 and that1 so far as is known1 the comments on each subject represent the most recent and authoritative knowledge upon it4 ,an attempt has been made to meet the requirements of medical students1 as well as of science students and general readers1 for whom former editions were chiefly intended4 ,a large class of medical students and practitioners do not require the detailed statement of the subject contained in the larger text-books4 ,for them1 and1 it is hoped1 also for a large number of candidates for diplomas in public health and in sanitary science1 the present edition will prove to be useful4 ,at the same time1 the subject has been treated as non-technically as is consistent with accuracy1 in order to retain its suitability for non-medical readers4 ,a large number of new illustrations have been introduced4 ,the new chapters dealing with ,dietetics1 ,trade ,nuisances1 ,meteorological ,observations1 ,tuberculosis1 ,disinfection1 and ,vital ,statistics will1 it is believed1 enhance the value of the book4 ,attention is also drawn to the solutions of mathematical problems in the different branches of hygiene1 of which a table of contents is given on page viii4 ,in its new form1 it is hoped that this work will be found to have retained its value as a plain and straightforward account of its subject for the general public and for science students2 and to have become a practical guide to sanitary inspectors and to medical students1 whether preparing for a diploma in public health1 or studying hygiene as an important branch of medicine4 ,the use of smaller type for specially technical matter of less general interest will facilitate discriminative reading4 ,,arthur ,,newsholme4 ,,brighton1 ,february #bhth1 #aijb4 ,,table ,,of ,,contents4 ,,chapter4 ,,page ,i4--,,introductory #a ,,ii4--,,food #d ,,iii4--,,the ,,varieties ,,of ,,food #i ,,iv4--,,diseases ,,due ,,to ,,food #bc ,v4--,,diet #bi ,,vi4--,,the ,,preparation ,,and ,,preservation ,,of ,,food #ch ,,vii4--,,condiments ,,and ,,beverages #de ,,viii4--,,fermented ,,drinks #ee ,,ix4--,,water #fe ,x4--,,the ,,storage ,,and ,,delivery ,,of ,,water #gd ,,xi4--,,impurities ,,of ,,water #gh ,,xii4--,,origin ,,and ,,effects ,,of ,,the ,,impurities ,,of ,,water #hi ,,xiii4--,,the ,,purification ,,of ,,water #id ,,xiv4--,,composition ,,and ,,properties ,,of ,,air #ajj ,,xv4--,,suspended ,,impurities ,,of ,,air #aje ,,xvi4--,,gaseous ,,and ,,other ,,impurities ,,of ,,air #aaa ,,xvii4--,,trade ,,nuisances #abj ,,xviii4--,,the ,,examination ,,of ,,air #abe ,,xix4--,,the ,,purification ,,of ,,air #abi ,,xx4--,,general ,,principles ,,of ,,ventilation #acb ,,xxi4--,,problems ,,as ,,to ,,ventilation #acg ,,xxii4--,,methods ,,of ,,ventilation #adf ,,xxiii4--,,ventilation ,,by ,,the ,,introduction ,,of ,,warmed ,,air #aee ,,xxiv4--,,the ,,warming ,,of ,,houses #aeh ,,xxv4--,,house ,,drainage #afe ,,xxvi4--,,cesspools ,,and ,,main ,,sewers #ahc ,,xxvii4--,,problems ,,as ,,to ,,flow ,,in ,,sewers #ahg ,,xxviii4--,,the ,,disposal ,,of ,,sewage #aij ,,xxix4--,,conservancy ,,methods #aid ,,xxx4--,,position ,,of ,,the ,,house #bja ,,xxxi4--,,the ,,materials ,,used ,,in ,,the ,,construction ,,of ,a ,,house #bje ,,xxxii4--,,construction ,,of ,,the ,,house #bji ,,xxxiii4--,,the ,,soil #bai ,,xxxiv4--,,climate ,,and ,,weather #bbg ,,xxxv4--,,meteorological ,,observations #bcg ,,xxxvi4--,,personal ,,hygiene #bde ,,xxxvii4--,,personal ,,hygiene--,,exercise #bdi ,,xxxviii4--,,personal ,,hygiene--,,rest ,,and ,,sleep #beg ,,xxxix4--,,personal ,,hygiene--,,cleanliness #bfj ,,xl4--,,clothing #bfe ,,xli4--,,parasites #bgc ,,xlii4--,,the ,r,,le ,,of ,,insects ,,in ,,spreading ,,disease #bha ,,xliii4--,,infective ,,diseases #bhd ,,xliv4--,,acute ,,infective ,,diseases #bia ,,xlv4--,,tuberculosis #cji ,,xlvi4--,,notification ,,and ,,isolation #cag ,,xlvii4--,,disinfection #cbd ,,xlviii4--,,vital ,,statistics #cce ,,special ,,table ,,of ,,contents ,,for ,,arithmetical ,,problems ,,in ,,hygiene4 ,,page ,,problems ,,in ,,milk ,,analysis #ab ,,dietetics #ce ,,water ,,analysis #hf ,,air ,,analysis #abf ,,as ,,to ,,ventilation #acg ,,flow ,,in ,,sewers #ahg ,,in ,,meteorology #bdb ,,as ,,to ,,work #bed ,,in ,,vital ,,statistics #ccf ,,hygiene4 ,,chapter ,i4 ,,introductory4 ,in classical mythology1 sculapius was worshipped as the god of ,medicine1 while his daughter ,hygeia had homage done to her as the sweet and smiling goddess of ,health4 ,the temples of these two deities were always placed in close contiguity2 and statues representing ,hygeia were often placed in the temple of sculapius4 ,in these statues she is represented as a beautiful maid1 holding in her hand a bowl1 from which a serpent is drinking--the serpent typifying the art of medicine1 then merely an art1 now establishing its right more and more to the dignity of a science4 ,that considerable attention was paid in very early times to matters relating to health1 is also shewn by the elaborate directions contained in the ,mosaic law as to extreme care in the choice of wholesome foods and drinks1 in isolation of the sick1 and attention to personal and public cleanliness4 ,it is not surprising1 therefore1 to find that the ,jews1 throughout the whole of their history1 have apparently enjoyed a high standard of health4 ,in this country great ignorance of the laws of ,health has prior to the last fifty years prevailed1 and consequently preventible diseases have been rampant1 and have claimed innumerable victims4 ,each century has been marked by great epidemics1 which have swept through the country1 scattering disease and death in their course4 ,in the fourteenth century1 for instance1 there was the ,black ,death1 a disease so fatal that it left scarcely one-fourth part of the people alive2 while ,europe altogether is supposed to have lost about #dj millions of its inhabitants1 and ,china alone #ac millions4 ,a century and a half later came the ,sweating ,sickness 7though there were a score of minor epidemics in between74 ,this was carried by ,henry the ,seventh's army throughout the country1 and so great was the mortality1 that 8if half the population in any town escaped1 it was thought great favour40 ,considerable light is thrown on the rapid spread of this disease after its importation1 when we remember that there were no means of ventilation in the houses2 that the floors were covered with rushes which were constantly put on fresh without removing the old1 thus concealing a mass of filth and exhaling a noisome vapour2 while clothing was immoderately warm and seldom changed2 baths were very seldom indulged in1 and soap hardly used4 ,in the sixteenth and seventeenth centuries there were five or six epidemics of ,the ,plague1 and it was only eradicated from ,london1 when all the houses from ,temple ,bar to the ,tower were burned down in the ,great ,fire of ,september #bnd1 #afff1 which destroyed the insanitary and necessitated the building of new and larger houses4 ,scurvy1 jail-fever1 and small-pox1 are other diseases which were formerly frightfully prevalent4 ,jail-fever1 the same disease as the modern typhus-fever1 has now become practically extinct in its former habitat1 owing largely to the noble work of ,john ,howard1 8whose life was finally brought to an end by the fever1 against the ravages of which his life had been expended40 ,this disease was fostered by overcrowding1 ill-ventilation1 and filth4 ,scurvy formerly produced a very great mortality1 especially among sea-faring men4 ,in ,admiral ,anson's fleet in #agdb1 out of #ifa men1 #fbf died in nine months1 or nearly two out of every three1 and this was no solitary case4 ,captain ,cook1 on the other hand1 conducted an expedition round the world1 consisting of #aah men2 and although absent over three years1 only lost one life4 ,he was practically the first to demonstrate the potency of fresh vegetables in preventing scurvy4 ,the striking facts respecting small-pox will be found on page #bic4 ,the general death-rate has also greatly declined4 ,thus while the annual death-rate in ,london #bjj years ago was #hj per #a1jjj1 it only averaged #ah4h in the four years #ahif-ii2 and the death-rate of ,england and ,wales has declined from #bb4d in #ahda-ej to #ah4g per #a1jjj in #ahia-ie and #ag4f in #ahif-ii4 ,that much still remains to be done is evident on every hand4 ,there is little doubt that the general death-rate might be reduced to #ae per #a1jjj per annum1 instead of the present #ah1 were the laws of health applied in every household and community4 ,it has been estimated that on the average at least #bj cases of sickness occur for every death2 therefore nearly half of the population is ill at least once a year4 ,a simple calculation will show how much loss the community annually suffers from this vast mass of preventible sickness4 ,it amounts to many millions of pounds1 leaving out of the reckoning the suffering and distress which are always associated with sickness4 ,for details relating to special diseases1 see page #big4 ,in the prevention of this mass of sickness1 the knowledge of its causation is half the battle2 when once a disease is traced to its source1 as a rule1 the agency which produces it can be avoided4 ,the reason why even more progress has not been made in the prevention of disease is not far to seek4 ,in order to prevent a disease it is necessary to remove its causes4 ,the causes of disease can only be ascertained by a careful investigation of its phenomena2 and it is only within the last century that these have been studied to any large extent scientifically4 ,such knowledge of morbid processes not only results in improved measures of treatment1 but in more rational and complete measures of prevention4 ,thus1 not only is the number of diseases which are curable becoming gradually augmented1 but the number preventible is even more rapidly on the increase4 ,inasmuch as the preservation of health involves the prevention of disease1 ,hygiene1 the science of health1 is sometimes called ,preventive ,medicine4 ,the subject of ,hygiene naturally divides itself into two parts1 the health of the individual1 and that of the community1 or ,personal and ,public ,health4 ,the former treats of the influence of habits1 cleanliness1 exercise1 clothing1 and food on health2 while the latter is concerned with the interests of the community at large1 as affected by a pure supply of air and water1 the removal of all excreta1 the condition of the soil1 and with the administrative measures required to secure the removal of evil conditions4 ,it is obvious1 however1 that these two divisions are not mutually exclusive4 ,what is important to the health of the community1 is equally so to each individual member of it4 ,the purity of air and water1 for instance1 is of immense importance both personally and collectively4 ,it will be convenient to study first the three main factors in relation to health--food1 water1 and air--subsequently considering other matters of importance to health 7see pages #d-aeg74 ,,chapter ,,ii4 ,,food4 ,,physiological ,,considerations4--,all substances are foods which1 after undergoing preparatory changes in the digestive organs 7rendering them capable of absorption into the circulation71 serve to renew the organs of the body1 and maintain their functions4 ,foods have been classified as tissue producers or energy producers1 the first class renewing the composition of the organs of the body1 and the second class supplying the combustible material1 the oxidation 7or more correctly the metabolism7 of which is the source of the energy manifested in the body4 ,the two main manifestations of energy in the body are heat and mechanical motion1 which are to a large extent interchangeable4 ,all foods come under one of these heads2 they are either tissue or energy producers4 ,they may be both1 and in many cases are so4 ,thus1 all nitrogenous foods 7as meat1 legumens1 etc47 not only help to form the nitrogenous tissues of the body1 but their largest share becomes split up into fats and urea1 and so forms a source of heat to the body4 ,similarly fats may possibly1 after assimilation1 enter into the composition of the various tissues containing fat 7of which the brain is the most important71 though they usually supply an immediate source of heat4 ,proteid foods are1 however1 the tissue producers par excellence1 other foods serving as the immediate sources of energy when metabolised in the body4 ,certain foods do not directly serve either as tissue or energy producers1 but are useful in aiding the assimilation of food4 ,such are the various condiments which may be classed as adjuncts to food4 ,salt is so necessary to the assimilation of food and to the composition of the various tissues1 that it may be ranked as an important food4 ,water1 again1 though already oxidised1 and so not an immediate source of energy1 is absolutely necessary to the assimilation of food1 to the interchange between the various tissues and the blood1 and to the elimination of effete products4 ,,classification ,,of ,,foods4--,inasmuch as milk supplies all the food necessary for health and growth during the first year of life1 it may reasonably be expected to afford some guidance as to the necessary constituents of a diet for the adult2 although the conditions of life being altered in the latter1 we can hardly expect the same proportions of the different materials to hold good4 ,in the infant rapid growth and building up of new tissues and organs are going on1 involving the necessity for a larger proportional amount of nitrogenous food than in the adult4 ,the following is the average composition of #ajj parts of ,,human ,,milk4 ,,cow',s ,,milk4 ,casein #b4d #d4j ,albumin 4#f 4#i ,fat #b4i #c4e ,sugar #e4i #d4j ,salts 4#af 4#g ,total ,solids #aa4if #ac4a ,water #hh4jd #hf4i ,it is evident from this analysis of milk that our food must contain 7at least7 representatives of all the above divisions4 ,we have1 therefore3-- #a4 ,nitrogenous ,foods4 #b4 ,hydrocarbons or ,fats4 #c4 ,carbohydrates or ,amyloids4 #d4 ,salts4 #e4 ,water4 ,condiments and stimulants 7tea1 coffee1 alcohol7 are not foods in the strict sense of the word1 and will be discussed in a later chapter4 ,nitrogenous ,foods include albumin1 casein1 gluten1 legumen1 fibrin1 and gelatin4 ,they all agree in consisting of a complex molecule containing many atoms of carbon1 hydrogen1 oxygen1 and nitrogen1 with the addition of smaller quantities of sulphur1 and in some cases phosphorus4 ,the nitrogenous substances used as food may be divided into two groups1 7a7 those containing gelatin1 and 7b7 numerous bodies which receive the common name of proteids or albuminoids4 ,the percentage composition of gelatin is3-- ,,carbon4 ,,hydrogen4 ,,nitrogen4 ,,oxygen4 #ej4j #f4f #ah4c #be4a ,the percentage composition of all proteids lies within the following limits3- ,,carbon4 ,,hydrogen4 ,,nitrogen4 ,,oxygen4 ,,sulphur4 #eb4g to #f4i to #ae4d to #bj4i to #j4h to #ed4e #g4c #af4e #bc4e #a4f ,proteids also contain a small amount of phosphorus1 chiefly as phosphate of lime1 but also in minute quantity in their essential structure4 ,various proteids are used in food1 e4g4 serum-albumin in the blood and tissues of animals2 egg-albumin in the white of eggs2 myosin in flesh2 casein in milk2 legumin1 or plant-casein1 in the seeds of leguminous plants2 gluten in wheat-flour1 etc4 ,proteid foods are pre-eminently important1 as they construct and keep in repair the tissues of the body4 ,they are not used solely for this purpose4 ,a large share of the energy of the body is derived from the metabolism of proteids4 ,the amount required for these purposes will be discussed on page #cb4 ,meanwhile1 it may be said that it is not found to be compatible with efficient health simply to supply an amount of proteid food which will suffice to replace the wear and tear of the tissues1 leaving fats and carbohydrates to supply the energy of the body4 ,deficiency of proteid food always leads to ill-health2 and it would appear that in all cases proteid food determines1 to a large extent1 the metabolism of non-nitrogenous food1 and so is favourable to all vital action4 ,the action of nitrogenous food in thus increasing metabolism may make it1 when in relative excess1 a tissue waster4 ,banting's cure for corpulence is founded on this principle1 lean meat alone being taken1 all starchy and saccharine foods being carefully avoided4 ,by metabolism is meant the changes undergone by food before it reaches the state in which it is finally eliminated from the body4 ,it is commonly spoken of as oxidation1 but this word less exactly represents the facts4 ,the complexity of the changes undergone by food in the body may be better appreciated by a glance at the following schematic statement1 which only gives an approximation to the truth3- ,,hypothetical ,,typical ,,fat ,,albuminoid4 7,,stearin74 ,,starch4 ,,grape-,,sugar4 ,c,h,n,,so4 ,c,h7,c,h,o74 x7,c,h,o74 7,c,h,o74 ---------------------------------------- ---------------------------------------- ---------------------------------------- ------------- ,various intermediate products1 which are finally broken down into and eliminated as ---------------------------------------- ---------------------------------------- ,urea1 ,,ch,n,o4 ,carbonic acid1 ,,co4 ,water1 ,h,o4 ,hydrocarbons1 or fats1 consist of three elements1 carbon1 hydrogen1 and oxygen1 the amount of oxygen present not being sufficient to oxidise completely either the hydrogen or the carbon4 ,thus the molecule of stearin1 which may be taken as a typical fat1 has the formula ,c,h 7,c#ah;,h#ce,o74 ,in respect to their comparatively unoxidised condition fats compare favourably with starch and sugar1 ,c,h#aj,o and ,c,h#ab,o respectively4 ,it is evident that in starch the ,h#aj,o #e;,h,o1 and that in sugar ,h#ab,o #f;,h,o1 so that in both cases only carbon remains uncombined with oxygen4 ,dried fats produce by their oxidation #b times as much heat as a corresponding amount of sugar or starch2 but the relative advantage of fat is not quite so great as would appear from this comparison1 inasmuch as metabolism within the body is not identical with oxidation4 ,the fat obtained from food is not simply deposited in the body as such1 to form a store of combustible matter1 and to fill up the interstices between the different tissues4 ,if this were so1 the kind of fat deposited would vary with the food1 which is not the case4 ,the fat of the body is probably not formed directly from fatty food1 but as the result of the metabolism of nitrogenous foods when this metabolism is incomplete4 ,in the formation of milk this can be distinctly proved3 the fat cells are formed from the protoplasm of the cells of the mammary gland4 ,possibly carbohydrate food may be a source of fat1 as well as nitrogenous and fatty food4 ,this appears to be the case in the ,strasburg goose1 which is kept penned up in a warm room1 and fed entirely on barley-meal1 in order to produce an enormous fatty liver for the delicacy termed pt de foie gras4 ,but it may be that the large accumulation of fat in the liver is due to the warmth and inaction of the goose diminishing metabolism1 and producing a fatty degeneration of the nitrogenous material of the liver4 ,fats and carbohydrates1 unlike proteids1 do not excite metabolism in the system1 and so1 if in excess of the requirements of the system1 can be stored up with comparative ease4 ,quiet and warmth1 diminishing metabolism1 conduce to the accumulation of fat in animals being fed for the market2 and the same applies to human beings4 ,carbohydrates or amyloids include the various starchy and saccharine foods4 ,they are inferior to fats in nutritive power1 but1 being very digestible1 are in much greater favour4 ,in the process of digestion1 starch is converted into grape sugar1 and starch and sugar are practically equal in nutritive power4 ,even when carbohydrates are entirely absent from the food1 they may be produced in the organism by the breaking up of nitrogenous matter4 ,this certainly happens in diabetes1 in which the nitrogenous food rapidly becomes converted into sugar and urea4 ,the deprivation of carbohydrate food is much better borne than that of fats1 because in the latter the hydrogen is not completely oxidized1 and because fats aid the assimilation of other food4 ,salts1 and especially common salt 7chloride of sodium71 are essential to health4 ,an average adult human body contains about seven pounds of mineral matter1 of which about five-sixths is in the bones4 ,on analysis the whole body yields about five per cent4 of ash4 ,chloride of sodium is necessary for the production of the acid 7hydrochloric7 of gastric juice1 and of the salts of bile2 half the weight of the ash of blood consists of it4 ,an adult requires #aej to #bjj grains of salt per day2 a large part of this is taken in meat1 bread1 etc42 and but little need be taken as a condiment4 ,potassium salts form an important part of milk1 muscle juice1 and the blood corpuscles4 ,they are obtained from bread and fresh vegetables and fruits4 ,it has been maintained that deficiency of potassium salts causes scurvy 7see page #bh72 but this is now discredited1 and probably potash is chiefly useful because of the vegetable acids with which it is associated in fruits and vegetables1 which when oxidised1 help to maintain the alkalinity of the blood1 e4g41 tartrates1 citrates1 and malates1 which become carbonates in the circulation4 ,calcium phosphate 7bone earth7 is essential for the growth of bones1 and is very important for the young4 ,the best source for it is milk4 ,there is more lime in a pint of milk than in a pint of lime water4 ,next to milk1 come eggs1 and then cereals1 especially rice as a source of calcium4 ,lime salts and phosphates as drugs do not benefit like the same substances taken in natural food1 and rickets is not curable by taking such drugs4 ,oxide of iron is always present in the ash of blood and muscles1 and in smaller quantities in milk4 ,fish and veal are usually deficient in it1 while beef and yolk of egg are foods richest in iron4 ,the amount of iron required in food is minute1 and it is amply supplied by ordinary diet4 ,phosphorus is an essential building material for the body4 ,it is contained in foods chiefly in organic combination4 ,the foods richest in it are yolk of egg1 sweetbread 7thymus71 fish-roe1 calves' brains1 and the germ of wheat4 ,milk and cheese are very rich in phosphates4 ,water forms an important article of diet4 ,this is evident from the fact that #hj per cent4 of the blood consists of it1 and #ge per cent4 of the solid tissues2 and from the fact that the daily loss of water from the system averages #ej ounces 7#b pints7 by the kidneys1 and about #dj ounces by the skin and lungs4 ,water is not simply received into the system as a liquid4 ,it forms a large proportion of the solid food taken4 ,thus1 #hg per cent4 of milk1 #gh per cent4 of fish1 #gb per cent4 of lean meat1 #ch per cent4 of bread1 #ac per cent4 of peas1 and #ib per cent4 of cabbage1 consist of water4 ,solid food is dissolved in the alimentary canal by the watery secretions derived from the blood4 ,water swallowed as food1 begins to pass on into the intestine at once4 ,the statement that free consumption of water at meals delays digestion by diluting the gastric juice is therefore not well grounded4 ,in the blood1 water serves to carry nutrient materials to all the tissues2 and1 at the same time being circulated all over the system1 equalises the temperature1 favours chemical changes1 and washes all the tissues4 ,by water again1 the effete matters which have been separated by the kidneys are washed out of its tubes4 ,the ,oxygen of the air1 in a broad sense1 forms one of the foods of the system4 ,this will be considered later4 ,besides the above classification1 foods have also been classified as follows3-- #a4 ,inorganic food--,oxygen1 salts4 ,animal ,nitrogenous4 ,non-nitrogenous4 #b4 ,organic foods ,vegetable ,nitrogenous4 ,non-nitrogenous4 ,or1 as-- ,animal ,nitrogenous4 ,non-nitrogenous4 #a4 ,solid foods ,vegetable ,nitrogenous4 ,non-nitrogenous4 ,water4 #b4 ,liquid foods ,milk and its products4 ,tea and similar beverages4 ,alcoholic beverages4 #c4 ,gaseous foods--,air4 ,,chapter ,,iii4 ,,the ,,varieties ,,of ,,food4 ,,nitrogenous ,,animal ,,foods4--,these are divided into two groups1 the one containing gelatin1 and the other all the proteid or albuminoid substances1 which are taken in the flesh of various animals1 and in milk and eggs4 ,gelatin is obtainable from bones1 and from connective tissue wherever found4 ,being easily digested1 and absorbed1 it has been very popular as an invalid's food2 but the fact that animals cannot sustain life on it without the addition of proteids proves that its value is limited4 ,it is incapable of building tissues1 but is a valuable proteid-saver1 being able to save from metabolism half its weight of proteid1 or twice as much as is spared by an equal weight of carbohydrate4 ,its utility in this direction is1 however1 limited1 because of the dilute form in which it is taken in ordinary foods4 ,it is useful for invalids1 partly because it forms a bulk1 and prevents the evil tendency to give their food in too concentrated a form2 partly because it forms a source of easily metabolised material1 and so prevents tissue-waste2 and partly because it commonly contains phosphate of lime1 derived from the bones forming the source of gelatin4 ,gelatin as prepared for the table contains a considerable proportion of water2 as little as one per cent4 of gelatin in water will cause it to gelatinise on cooling4 ,isinglass obtained from the floating bladder of the sturgeon is an example of the purest kind of gelatin2 glue is an inferior sort1 made from bones1 etc4 ,gelatin is only a cheap food when obtained1 for instance1 from bones which cannot otherwise be utilised4 ,when made from veal it is costly out of proportion to its dietetic value4 ,the ,flesh of various animals is one of the main sources of our nitrogenous and fatty food4 ,meats may be divided into two kinds1 viz41 red meat and white meat4 ,these gradually merge into one another4 ,as common examples of red meats1 we have beef1 mutton1 pork1 game1 wild fowl1 and salmon4 ,the common fowl and turkey1 most fishes1 rabbits1 crustaceans1 and molluscs1 are examples of white meat4 ,as a rule white meats are more digestible than red1 having more delicate fibres1 and containing a smaller proportion of nitrogenous matter4 ,flesh consists almost entirely of muscular tissue1 of which there are two kinds1 striped and unstriped4 ,the striped is the variety most commonly used as food4 ,unstriped muscle has a softer texture1 but is not so easily masticated as striped1 and for this reason may be indigestible4 ,tripe is composed of the unstriped muscle and connective tissue of the stomach of the cow1 and if well cooked forms a cheap and easily digested dish4 ,the influence of feeding on the quality of the meat is great4 ,in ill-fed or old animals1 connective tissue is more abundant1 and the meat is tougher4 ,well-fed and fattened meat contains for equal weights much more nutritious matter than non-fattened meat1 the fat which is deposited in the muscle replacing water and not proteid4 ,hence the gain in nutritive value is an absolute one1 and is not attained at the expense of the proteid part of the meat4 ,young animals1 again1 contain more water and fat and a larger proportion of connective tissue than the full-grown1 and are consequently not so nourishing4 ,meat ought to be eaten either before the onset of rigor mortis1 or near its end1 before putrefaction has commenced4 ,during rigor mortis it is denser1 tougher1 and more difficult to digest than after it4 ,the proportion of fat in meat varies greatly in different individuals of the same species1 in different animals1 and in different parts of the same animal4 ,according to ,dr4 ,ed4 ,smith1 the proportion of fat in fat oxen is 1 in fat sheep 1 in calves 1 lambs 1 and fat pigs 4 ,good meat1 whether beef or mutton1 ought to have a marbled appearance1 a medium colour1 neither pale pink nor deep purple2 its texture should be firm1 and not leave the impress of the finger2 its odour slight and pleasant1 the juice reddish and acid1 the bundles of fibres not coarse1 and free from foreign particles imbedded in them2 and lastly1 it should not be taken from an animal killed near the time of parturition1 nor in consequence of any accident or disease4 ,beef is1 as a rule1 more lean than mutton or pork2 it has a closer texture1 and more nutritive material in a given bulk4 ,it is also fullest of the red-blood juices1 and possesses a richer flavour than the two others4 ,liebig's beef extract contains little if any albumin or gelatin4 ,it is a useful stimulant to the gastric secretion1 as in soups at the beginning of a meal1 but is not a food4 ,its chief constituents are the various extractives of meat1 the most important of which are inosinic acid1 kreatin 7,c,h,n,o1,h,o71 and inosite1 or muscle sugar 7,c,h#ab,o1 #b;,h,o74 ,even in substances like ,bovril1 containing powdered meat fibre mixed with ,liebig's extract1 the amount of nutritive material is very small4 ,the white of one egg contains as much nutritive matter as three teaspoonsful of bovril4 ,none of these substances can be trusted like eggs or milk to keep a patient alive for several weeks4 ,mutton is regarded as being more suitable for people of sedentary occupation than beef4 ,lamb is more watery than mutton1 and less nutritious4 ,veal1 as ordinarily prepared in this country1 is difficult of digestion2 its shreddy1 juiceless fibres eluding the teeth1 and consequently not undergoing proper mastication4 ,pork is not so digestible as beef or mutton1 partly because of the large proportion of fat1 and partly because its fibres are hard and difficult to masticate4 ,its digestibility varies greatly with its age1 breeding1 and proportion of fat4 ,the ,flesh of ,birds contains very little fat1 and that found separate from the meat is rarely nice4 ,most birds are edible1 but fish-eating birds are apt to be nasty4 ,as a rule1 the flavour of the male bird is richer than that of the female4 ,the chief virtues in poultry are their tenderness1 and the large proportion of phosphates they contain4 ,they are deficient in fat and in iron4 ,to compensate for the former1 one commonly takes with them melted butter and fat bacon or pork sausages2 to compensate for the latter1 the addition of ,liebig's extract to the gravy is useful4 ,young1 and consequently tender1 birds are known by their large feet and leg-joints4 ,when a bird appears at table with violet-tinged thighs and a thin neck1 if possible avoid being helped to the leg4 ,wild fowls are harder and less digestible than tame4 ,in ducks and geese fat is more abundant1 and of a stronger flavour2 they are1 consequently1 not so digestible as fowls4 ,fish forms an important article of diet4 ,it is easily cooked1 and usually very digestible2 it possesses a larger bulk in proportion to its nutritive quality1 and hence is very valuable for those who habitually take an excess of meat food1 which is commonly the case with those leading sedentary lives1 and in declining years4 ,there appears to be no foundation for the statement that fish is rich in phosphorus1 and is thus a good brain food4 ,generally1 white-fleshed fish is more digestible than red-fleshed 7such as salmon71 the latter usually containing more fat than the former4 ,when the fat is distributed throughout the flesh1 as in the salmon1 fish is more satisfying than when it is mainly stored up in the liver1 as in the cod-fish4 ,according to ,payen1 the percentage proportion of fat in soles is only #j4bdh1 in whiting #j4chc1 conger eel #e4jba1 mackerel #e4geh1 eels #bc4hfa4 ,the addition of some fatty food1 as melted butter1 is very advisable to such meats as poultry1 rabbits1 soles1 whiting1 plaice1 haddock1 cod1 turbot1 and other fishes2 whereas sprats1 eels14 herrings1 pilchards1 salmon1 etc41 are more or less rich in fat4 ,a ,hen's ,egg usually weighs a little under two ounces4 ,it consists of #gd per cent4 of water and #bf per cent4 of solid matter4 ,the white of the egg is chiefly albumin1 the yolk consists of a very digestible oil1 rich in phosphorus and iron1 each particle of the oil being enveloped in a form of albumin called vitellin4 ,the salts are chiefly contained in the shell4 ,there is no sugar in the egg1 the necessity for such oxidisable material for the chick being obviated by the heat produced by incubation4 ,eggs1 when kept for some time1 lose weight1 owing to evaporation through the porous shell2 similarly1 air entering from without sets up decomposition4 ,in a solution of brine containing an ounce of common salt to half a pint of water1 fresh eggs sink1 stale ones float2 rotten eggs may even float in fresh water4 ,eggs may be preserved by keeping them in brine1 or1 better still in lime water1 or by smearing them over with lard or butter1 as soon as possible after they are laid4 ,cow's ,milk has a specific gravity of #ajbh-cd1 and on allowing it to stand in a long narrow vessel ought to form ten or twelve per cent4 of its volume of cream4 ,the percentage composition of human and cow's milk has been given on page #e4 ,the legal minimum standard for dairy milk1 which is presumably derived from a number of cows1 is now #c per cent4 of fat1 and #h4e per cent4 of 8solids not fat40 ,this standard is unfortunately very low1 and allows a considerable margin of adulteration1 which cannot be prevented by legal means4 ,thus ordinary milk derived from a herd of cows would probably contain #d4e per cent4 of fat2 and it is1 therefore1 practicable to mix pure new milk with a large proportion of separated milk1 and yet keep within the legal standard4 ,this is largely done in towns1 and infants suffer much from the deficiency of cream in their sole food 7see page #bh74 ,the lactometer determines the specific gravity1 which should be taken at a temperature of #fj ,f4 ,in skimmed or separated milk it will be over #ajcd2 watering on the contrary lowers the specific gravity4 ,if the milk has been both watered and skimmed the specific gravity will give an uncertain indication4 ,measurement of the cream in a tall narrow glass will enable one to detect the second possible source of fallacy2 but the composition of milk can only be certainly determined by analysis4 ,this is done 7a7 by evaporating a weighed amount of milk to dryness and then re-weighing4 7b7 ,from a separate amount of dried milk the fat is extracted by ether1 the ether then evaporated1 the remaining fat weighed1 and its percentage calculated4 ,the weight of fat deducted from the total solids i4e4 7b7 from 7a71 gives the 8solids not fat40 ,the following example will make the method then followed clear4 ,the sample gives #g4i per cent4 of 8solids not fat40 ,genuine milk contains at least #h4e per cent4 of 8solids not fat40 ,then the sample contains-- #ajj #g4ih4e #ib4i per cent4 of genuine milk1 i4e4 #g4a per cent4 of water has been added to it4 ,half a pint of milk supplies as much nitrogenous nutriment as two good-sized eggs1 and as three and a half ounces of beef4 ,milk may be deteriorated 7#a7 by skimming or 8separating0 by machinery1 or 7#b7 by the addition of water--the first diminishing the proportion of fats1 and the second the total amount of solids4 ,skim ,milk still contains nearly #a per cent4 of fat1 but ,separated ,milk1 in which the cream has been removed by centrifugal apparatus1 contains less than #ah per cent4 ,skim or separated milk forms a cheap source of nitrogenous food2 but when it is sold mixed with new or alone as new milk1 the public is defrauded1 and infants fed on it are robbed of the fat which is so essential for their growth4 ,condensed ,milk is milk deprived of a large part of its water4 ,it represents three times its volume of fresh milk4 ,there are in the market 7a7 unsweetened and condensed whole milk1 7b7 sweetened and condensed whole milk1 and 7c7 sweetened and condensed skim or separated milk4 ,unfortunately the latter is most largely sold because cheapest2 and infants are thus often robbed of fat1 a most important element in their food4 ,always examine the label of each tin carefully1 to ascertain whether the milk has been deprived of its cream4 ,the law requires that this fact should be stated on the label4 ,tins which have bulged should be rejected4 ,condensed milk is more easily digested by infants than new cow's milk1 but it lacks the anti-scorbutic properties of new milk 7see page #bh74 ,even the condensed whole milk if diluted beyond #a part of milk to #c of water is deficient in fat4 ,sweetened condensed milk has one-third its weight of extraneous sugar added to it1 and on this account it tends in children to produce fatness1 and a distaste for simple food2 in children fed on it alone ossification 7formation of bone7 is retarded1 and resistance to illness is diminished4 ,the only dietetic advantages it possesses over fresh cow's milk are its freedom from possible disease germs and easier digestibility4 ,the digestion of milk is preceded by its clotting in the stomach4 ,the same thing happens when junket is formed by the addition of rennet to milk4 ,this is a different process from the curdling of milk1 which occurs when milk turns sour4 ,the latter is caused by the splitting up of milk sugar and the formation of lactic acid by certain micro-organisms in the milk4 ,when milk is heated1 a skin is formed1 consisting of coagulated albumin1 in which is also a little casein1 fat1 and salts of lime4 ,boiled milk becomes sterilized4 ,cow's milk should always be boiled1 unless it is quite certain that the cows from which it is derived are perfectly healthy1 and that the milk has not been exposed to infection before reaching the house4 ,the disadvantages of boiling which are outweighed by its advantages1 are that the taste of the milk is altered1 some nutritive matter is lost by the formation of the 8skin10 and the casein is not quite so easily digested4 ,pasteurization of milk1 i4e4 keeping it at a temperature of #gj ,c4 7#aeh ,f47 for #bj to #cj minutes has been proposed as an alternative to boiling4 ,this appears to destroy the bacilli causing tuberculosis 7see page #cab74 ,the typhoid bacilli are killed at #fj ,c4 in five minutes when suspended in emulsion4 ,pasteurization is not1 however1 so certainly efficacious for other disease-germs as is boiling1 and is not so easily carried out in domestic life as boiling4 ,by boiling milk in a double saucepan1 i4e4 in a water-bath1 very little change occurs in the taste of the milk1 especially if it be cooled rapidly and strained4 ,cheese is prepared by coagulating milk by 8rennet10 the mucous membrane of the fourth stomach of the calf1 salted and dried before using4 ,by this means the casein is precipitated1 carrying down with it the cream1 and a large proportion of the salts of milk4 ,the whey1 containing the sugar1 soluble albumin1 and remaining salts1 is separated by straining1 while the mixed curd and fat are pressed in moulds4 ,cheese thus consists of casein1 fat in varying proportions1 water and salts1 especially phosphate of lime4 ,it is coloured with annatto1 a vegetable colouring matter4 ,when new1 cheese is tough2 when old1 its oils tend to become rancid2 the best age is from nine to twenty months4 ,it is probable that cheese in small amount helps the digestion of other foods1 though it is itself a highly concentrated and comparatively indigestible food4 ,when toasted it is proverbially indigestible4 ,there are many different kinds of cheese4 ,the following classification gives the more important varieties3-- 7#a7 ,cream cheese is the new curd only slightly pressed1 and is more digestible than ordinary cheese4 7#b7 ,next to these are cheeses made with whole milk rich in cream1 such as ,stilton1 ,gorgonzola1 ,cheshire1 and ,cheddar4 7#c7 ,cheeses made of poor or partially skimmed milk1 such as ,shropshire1 ,single ,gloucester1 and ,gruyre4 7#d7 ,cheeses made of skimmed milk1 such as ,suffolk1 ,parmesan1 and ,dutch4 ,american cheeses may belong to any of these classes2 they are generally pure1 but occasionally are made from separated milk1 margarine being added to take the place of cream4 ,the sale of such cheeses1 except under the name of 8margarine cheese10 is now illegal4 ,,non-,,nitrogenous ,,animal ,,foods4--,these are all fats1 and the most important are the various meat fats and butter4 ,they possess a higher food value than carbohydrates in the proportion of #b to #a4 ,the composition of the various fats differs somewhat2 they usually contain varying proportions of olein1 palmitin1 and stearin1 which are compounds of glycerine with the radicle of a fatty acid 7stearin ,c,h 7,c#ah;,h#ce,o774 ,thus mutton suet consists of stearin1 olein1 and palmitin1 with a preponderance of stearin4 ,beef suet contains less stearin and more olein than mutton suet4 ,the more olein a fat contains the less solid it is4 ,olive oil is composed almost entirely of olein4 ,palmitin1 which melts sooner than stearin1 is the chief solid constituent of butter1 while olein is its chief liquid constituent4 ,butter is specially distinguished by containing #g to #h per cent4 of 8volatile fatty acids10 such as butyric1 caproic1 etc41 combined with glycerine4 ,the presence and amount of these compounds is an important test for the freedom of butter from adulterating fats4 ,cod-liver oil is next to butter the most digestible animal fat known4 ,the best cod-liver oil is frozen at a low temperature1 by which means the stearin is frozen out1 and nearly pure olein is left4 ,traces of iodine have been found in it1 and more commonly a small amount of bile1 which probably increases its digestibility4 ,the temperature at which a fat becomes hard is a fair guide to its digestibility4 ,thus we know that beef1 and still more1 mutton fat1 would become solid1 under conditions in which bacon dripping is still soft4 ,where digestion is weak1 there may be an instinctive loathing of fat meat2 for such persons1 especially for children1 some other fat should always be substituted4 ,thus the addition of butter to the potatoes makes up the deficiency4 ,butter forms #c to #d per cent4 of cow's milk4 ,it is separated from milk by churning1 the oil particles being deprived by this means of their albuminous coats4 ,the more completely the butter-milk is separated the longer the butter keeps4 ,it can be kept longer if salt is added1 or in hot weather by keeping it under frequently-changed water4 ,rancidity indicates the decomposition of traces of the fat of butter into its fatty acid and glycerine4 ,cream contains about #cj per cent4 of butter fat1 ,cheshire cheese #be per cent41 and skim milk cheese #g per cent4 ,butter milk differs from skim milk in the presence of lactic acid4 ,it is more digestible than skim milk1 the casein being in a more flocculent condition4 ,the odour and flavour of butter are not due to olein and palmitin1 the two chief constituents1 but to a smaller quantity of butyrin1 caproin1 and caprylin fats of a much lower series4 ,ordinary butter contains a considerable proportion of water1 and the presence of about #h per cent4 renders it more palatable2 if it is over #ae per cent41 the butter is considered adulterated4 ,an excessive amount of salt is sometimes present4 ,the most frequent adulteration is the substitution of foreign fats for butter fat1 e4g4 lard1 palm oil1 rape seed oil1 or cocoa-nut oil4 ,margarine is most frequently used for this purpose4 ,margarine is prepared from beef-fat by melting1 the stearin becoming solid again at a temperature at which olein and margarine still remain liquid4 ,it forms a wholesome and cheap food1 being nearly as digestible as butter1 for which more expensive food it is often fraudulently sold4 ,when mixed with a small proportion of butter its recognition by smell1 etc41 is almost impossible1 but on careful chemical analysis1 it is found to have a higher melting point and a lower specific gravity than butter1 and a much smaller percentage of soluble fatty acids than the latter4 ,thus3-- ,,melting ,,specific ,,saponification ,,and ,,formation ,,point4 ,,gravity4 ,,of ,,insoluble ,,fatty ,,acid4 ,butter #cb ,c4 4#iac #hh per cent4 insoluble fatty acid ,margarine #ce ,c4#a 4#ijd4ijg #ieb ,,cereal ,,foods4--,gluten is peculiar to plants1 and is chiefly found in plants belonging to the great family of grasses4 ,gluten is to bread what casein is to milk1 and myosin to flesh4 ,if one takes a piece of dough made from wheat flour1 and holds it under a stream of water from the tap1 a large part of it is washed away1 while a sticky adherent mass is left behind4 ,this is gluten1 and it is its tenacity which enables bread to be made4 ,if the fluid with which the dough was washed is collected1 it will be found to contain a large quantity of starch1 a small amount of sugar1 of albumin1 and certain salts4 ,all cereals possess these constituents in various proportions1 as may be seen from the following table3-- ,,water4,,proteid4,,fat4,,carbohydrates4 ,,cellulose4,,mineral ,,matter4 ,wheatmeal #ab4a #ab4i #a4i #gj4c #a4f #a4b ,fine wheat flour #ac4j #i4e #j4h #ge4c #j4g #j4g ,oatmeal #g4b #ad4b #g4c #fe4i #c4e #a4i ,barley meal #aa4i #aj4j #b4b #ga4e #a4h #b4f ,maize meal #aa4d #h4e #d4f #gb4h #a4d #a4c ,rice 7husk removed7 #ab4j #g4b #b4j #gf4h #a4j #a4j ,the proteid varies in character in the different cereals2 wheat flour has the largest proportion of gluten 7#h to #ab per cent47 and therefore makes the best bread4 ,good wheat flour ought to be white1 not gritty or lumpy1 not acid or musty1 forming a coherent stringy dough4 ,examined microscopically1 it should show the absence of any fungi1 or acarus farin1 or of foreign starches1 such as barley1 maize1 rice1 potato1 known by the different shape of their starch granules4 7,see ,fig4 #a47 ,alum has been occasionally added to flour1 to enable the baker to make a white and porous bread from damaged wheat flour4 ,it can be detected as follows3--,pour over the freshly cut surface of a slice of bread some freshly prepared decoction of logwood chips1 and then a solution of carbonate of ammonia4 ,if alum is present1 the bread turns a marked blue to violet colour2 but if the bread is pure1 it is only stained pink4 ,the wheat grain may be used as food in its entirety4 ,thus boiled in milk1 after having been soaked in water1 it forms the chief constituent of frumenty4 ,usually it is converted into flour by grinding or milling4 ,a grain of wheat consists of three parts1 an outer envelope1 the bran1 consisting chiefly of indigestible cellulose1 and composing #ac per cent4 of the grain2 the kernel1 or endosperm1 which makes up #he per cent4 of the grain2 and the germ1 forming #a per cent4 of the grain4 ,in the old method of stone grinding1 the bran was removed1 and the germ left along with the endosperm4 ,in the elaborate processes of modern roller milling1 the bran is removed as in the old grinding1 because it cannot without the greatest difficulty be reduced to powder2 and the germ is also removed1 because the oil abundantly present in it is apt to become rancid and spoil the flour1 and because the soluble proteids in it are apt to change some of the flour into dextrin and sugar1 which become brown in baking and spoil the appearance of the bread4 ,the germ is easily removed1 because its toughness causes it to be flattened out in the milling1 while the endosperm becomes powdery4 ,the central part of the endosperm is the source of #8patents4' ,it is very rich in starch and is used for making fancy breads and pastry4 ,the outer part of the endosperm is #8households4' #8,households flour' is subdivided into 7a7 second patents1 or #8whites'2 7b7 first households2 7c7 second households or #8seconds4' #8,seconds' is richest in gluten1 #8whites' in starch4 ,ordinary bread is normally derived from a blend of these three4 ,some #8strong' wheats1 e4g4 ,australian1 yield a #8patents' which is rich in gluten1 and such flour is used for making ,vienna bread4 #8,strong' wheats take up most water in baking1 and so yield most loaves per sack4 #8,seconds' flour yields a bread which is richer in proteid than most other kinds2 but the dark colour of the loaf makes it unpopular4 ,various schemes have been devised to utilise the germ and the bran1 which are ordinarily discarded4 ,in the preparation of ,hovis flour the separated germ is partially cooked by superheated steam4 ,this kills the ferment contained in the soluble proteids1 and thus prevents it from changing starch into maltose and dextrin4 ,the action thus prevented is represented by the following formula3-- ,,starch4 ,,maltose4 ,,dextrin4 #aj ,c,h,o #f ,h#j #f ,c,h,o #d ,c,h,o4 ,the germ thus treated is ground to a fine meal1 of which one part to three of ordinary flour1 forms ,hovis flour4 ,other #8germ breads' are also in the market4 ,in the making of ,frame food the bran is boiled with water under high pressure4 ,the watery extract1 containing the mineral and part of the nitrogenous constituents of the bran1 is evaporated to dryness1 and forms the basis of various preparations4 ,it is doubtful if this food possesses any great value4 ,brown bread is a somewhat vague expression1 meaning either an admixture of bran or of germ or of both with flour1 or bread made from whole wheat flour4 ,in each of these cases the loaf would be brown4 ,the bran is rich in fat as well as in phosphates4 ,it acts as a mechanical irritant1 ill borne by delicate stomachs1 but very useful where a tendency to constipation exists4 ,the excess of nitrogenous matter in brown bread and its richness in fat1 do not prove its greater nutritiveness1 as it is present in a condition in which only a portion is absorbable from the alimentary canal into the circulation4 ,the harder wheats1 such as ,sicilian wheat1 contain a larger percentage of gluten2 and from them macaroni and vermicelli are obtained1 which are nearly pure gluten4 ,they are very nutritious and useful foods4 ,semolina is prepared from wheat1 the millstones being left sufficiently apart to leave the product in a granular condition4 ,in malted breads1 a syrupy infusion of malted barley 7malt extract7 is added to the flour4 ,malt extract contains in addition to malt sugar 7maltose7 and dextrins1 a ferment 7diastase7 which1 like the saliva1 is able to convert starch into the soluble substances1 maltose and dextrin 7see formul above74 ,the action of this ferment is stopped by the temperature of baking4 ,hence even when the malt extract is allowed a considerable time for its operation on the dough1 only about #aj per cent4 of the starch in the loaf becomes soluble1 as compared with #d per cent4 in an ordinary loaf4 ,oatmeal1 obtained from the common oat1 contains very little gluten1 and so cannot be made into vesiculated bread4 ,it contains a large proportion of other nitrogenous material and of fat4 ,as porridge and oatmeal cake it forms a very nutritious diet4 ,the husk ought to be carefully removed from the meal intended for human food1 as1 although very nitrogenous1 it acts as a mechanical irritant4 ,groats consists of oats from which the husk has been entirely removed4 ,the substitution of rolling for grinding in preparing oats for food and the application of heat during the rolling process1 have made oatmeal more digestible1 as in ,quaker1 ,provost1 and ,waverley oats4 ,barley contains very little gluten2 on this account1 like oatmeal1 it does not admit of being made easily into bread4 ,malt is barley which has been made to germinate by heat and moisture and then dried1 8diastase0 being formed in the process4 ,extract of malt1 containing diastase in an active condition1 is useful in cases of impaired digestion and deficient assimilation of food4 ,rye is rarely used in this country for making bread4 ,in ,germany it is known as 8black bread10 but its colour and acid taste make it disagreeable1 and it is laxative in its action4 ,maize1 or ,indian ,corn1 is deficient in gluten1 and so not suitable for making vesiculated bread4 ,like oatmeal1 it is made into cakes1 called in ,america 8,johnny cake40 ,it contains much fatty matter1 and is largely used for fattening poultry and other animals4 ,oswego flour and corn flour are maize flour deprived by a weak solution of soda1 of its proteids and fat2 hominy contains all its constituents4 ,maize is a cheap and nutritious food4 ,when wheat flour is dear1 it is occasionally adulterated with maize4 ,the adulteration can be detected by the forms of the starch granules1 examined under a low power of the microscope4 ,rice contains less proteids and fat than any other cereal4 ,its chief value as a food depends on the large amount of starch it contains 7table1 page #af74 ,,leguminous ,,foods4--,the chief seeds belonging to this group are peas1 beans1 and lentils4 ,they contain a smaller proportion of starch1 and a larger proportion of nitrogenous materials than cereals4 ,thus while flour contains #i4e and bread #h per cent4 of proteid1 lean meat #ae4ah per cent41 and cheese about #cj per cent41 peas and beans contain #ba to #bf per cent4 7green peas only #d per cent41 dried peas #ba per cent47 of proteid4 ,the nitrogenous material exists chiefly as legumin1 which has been called vegetable casein4 ,although leguminous seeds contain more nutritive material in a given weight than cereals1 dietetically they are inferior1 owing to the fact that they are less digestible1 often causing flatulence and other dyspeptic symptoms4 ,cereals1 again1 are more palatable than leguminous seeds1 and are more prolific1 and consequently cheaper4 ,in the absence of animal food1 legumens form a useful substitute4 ,they are advantageously diluted with oily substances1 or with rice4 ,the farm-labourer's dish of broad beans and fat bacon is founded on strict physiological principles4 ,a mixture of lentil and barley flour is sold under the name of ,revalenta ,arabica4 ,lentil flour costs #b;d41 ,revalenta #cs4 #f;d4 per lb4 ,green peas1 ,french beans1 and scarlet runners are much more easily digested than are dried peas or beans4 ,lentils contain the largest proportion of proteid of any of the pulses4 ,they also contain very little sulphur1 and so do not give rise to the same liberation of sulphuretted hydrogen in the intestine1 as other pulses4 ,the ash of the ,egyptian lentil is particularly rich in iron4 ,,amylaceous ,,foods4 ,amylaceous or starchy substances are contained in many of the preceding foods2 but some other foods consist almost entirely of starch4 ,the chief of these are sago1 tapioca1 and arrowroot4 ,sago is obtained from the pith of the stems of various species of palm2 a single tree may yield several hundred pounds4 ,alone it is easy of digestion4 ,boiled with milk it forms a light1 nutritious1 and non-irritating food4 ,fictitious sagos are frequently sold1 made from potato starch4 ,tapioca and ,cassava are derived from the tubers of more than one species of the poisonous family1 ,euphorbiace4 ,the juices are removed1 and the prussic acid removed by heat4 ,tapioca only differs from cassava in being a purer form of starch2 the latter is more nutritious1 and among the ,indians takes the place of bread4 ,arrowroot is obtained from the tubers of ,maranta ,arundinacea4 ,tous-les-mois is a form of starch obtained from the tubers of a ,west ,indian plant1 the ,canna edulis4 ,illustration3 ,potato4 ,wheat4 ,rice4 ,oats4 ,barley4 ,pea4 ,,fig4 #a4--;,,different ,,forms ,,of ,,starch ,,granules4 ,the detection of the varieties of starch is usually possible owing to their fairly characteristic appearance under the microscope4 ,fig4 #a shows the most important starches4 ,it must be noted that in oats1 maize1 and rice the contour is completely marked by facets or surfaces1 while there are less complete markings in tapioca and sago4 ,in wheat1 rye1 pea1 bean1 barley1 potato1 and arrowroot the contour is even1 though there are minor differences of size and shape4 ,,other ,,vegetable ,,foods4--,green ,vegetables contain comparatively little nutriment1 but form valuable additions to other foods4 ,cellulose1 which forms their main constituent1 although indigestible1 forms a bulk in the alimentary canal1 which is necessary to ensure peristalsis4 ,concentrated nourishment can only be digested in limited quantity1 and is very apt to produce digestive disorder4 ,cabbage contains #ib per cent4 of water1 and #b per cent4 nitrogenous matter4 ,carrots contain #f per cent4 and turnips #b per cent4 of nitrogenous matter2 parsnips are intermediate between these4 ,green vegetables possess valuable anti-scorbutic properties4 ,they may be made an important vehicle for giving fatty food1 by adding butter1 etc4 ,rhubarb and sorrel contain oxalates and tartrates of potash and lime1 to which they owe their tartness4 ,spinach is cooling and laxative1 like rhubarb1 but not tart4 ,sea-kale1 artichoke1 and asparagus are all wholesome vegetables4 ,asparagus is somewhat diuretic1 and gives a peculiar1 disagreeable odour to the urine4 ,salads1 such as mustard and cress1 water-cress1 endive1 and the garden lettuce are very useful as anti-scorbutics4 ,some of them possess a peculiar pungency due to a volatile oil analogous to that contained in horse-radish4 ,the ,potato contains #bf solid parts in #ajj1 of which nearly #bj are starch and #b nitrogenous matter4 ,it forms one of our best-appreciated vegetable foods1 and as it possesses valuable anti-scorbutic properties1 its universal use is1 perhaps1 the chief cause of the present rarity of scurvy4 ,alone1 it possesses too small a proportion of nitrogenous material to support life1 but the addition of butter milk makes up this deficiency2 and these two together form a sufficient diet to maintain life and health for a long time4 ,the ,onion1 ,garlic1 ,leek1 and ,shalot1 all members of the lily family1 are chiefly used as condiments4 ,they contain an acid volatile oil1 which gives them a peculiar odour and flavour4 ,by long boiling1 this is dissipated 7as in the case of the ,spanish onion71 and the onion is then fairly digestible1 as well as nutritious4 ,celery possesses a more delicate flavour and odour than the preceding1 but even the most tender celery is digested with difficulty2 less so1 when boiled or stewed1 or a constituent of soups4 ,only four ,fungi are1 with us1 commonly regarded as safe--mushrooms1 champignons1 morels1 and truffles2 but there are many others which are equally edible4 ,the food value of fungi has been exaggerated4 ,they are difficult of digestion and contain little nutritive material4 ,poisonous fungi usually have an astringent styptic taste and a disagreeable pungent odour4 ,in any doubtful case it is better to abstain4 ,oily ,seeds contain a considerable amount of fixed oil which renders them unfit for persons of weak digestion4 ,the almond1 walnut1 hazel-nut1 and cocoa-nut are common examples4 ,the sweet almond1 when eaten unbleached1 occasionally produces nettlerash1 and its solid texture and large proportion of fixed oils render it difficult of digestion4 ,the chestnut contains less oil1 but a large amount of carbohydrate4 ,it is extensively used as a food in ,italy and some other countries4 ,in the uncooked condition it is very difficult of digestion4 ,fruits are chiefly used as adjuncts to other foods2 but the vegetable salts and the cellulose and sugar which they contain1 make them very valuable4 ,cucurbitaceous fruits are used as vegetables rather than as fruits4 ,vegetable marrow is wholesome and agreeable1 but not very nutritive4 ,cucumber is most digestible when rapidly grown and freshly gathered4 ,stone-fruits or drupes1 such as the peach1 nectarine1 plum1 cherry1 are rather luxuries than foods1 like many other fruits4 ,before ripening they are unfit for food2 when ripening is complete1 the acids and astringent matter largely disappear4 ,the date contains chiefly sugar1 and forms an important food in the ,east4 ,pomaceous ,fruits1 as the apple1 pear1 and quince1 are more digestible when cooked2 and1 speaking generally1 all fruit not perfectly ripe should be cooked before eating4 ,the presence of vegetable acids in fruit soon converts the sucrose of cane sugar into dextrose1 a less sweet variety of sugar4 ,it is therefore more economical to sweeten after than before cooking4 ,the chief ,berries are the grape1 currant1 gooseberry1 cranberry1 and elderberry4 ,the grape is the most important1 and #a1ejj varieties of it have been described4 ,its juice contains a large amount of grape sugar 7dextrose71 and small quantities of glutinous material1 bitartrate of potash1 tartrate of lime1 malic acid1 etc4 ,besides the above fruits1 we have strawberries1 mulberries1 figs1 plantains1 melons1 etc41 which are all refreshing and anti-scorbutic4 ,the orange family furnishes us with the orange1 lemon1 citron1 lime1 shaddock1 and pomelo1 of which the orange is by far the most important1 and possesses most valuable refreshing qualities4 ,sugar exists in two chief forms1 viz4 sucroses and glucoses4 ,sucroses1 known chemically as disaccharids 7,sucrose ,c#ab;,h#bb,o#aa2 compare starch ,c#ab;,h#bj,o#aj7 are exemplified in cane1 beet1 maple1 malt 7maltose71 and milk sugar 7lactose74 ,cane sugar has been gradually displaced by beet sugar4 ,the two are chemically identical1 and equally nutritious4 ,maltose is given in malt extract as a food1 and because of the digestive action of the ferment also contained in the extract on starchy food4 ,thus3-- ,,starch4 ,,maltose4 ,c#ab;,h#bj,o#aj ,h#b,o ,c#ab;,h#bb,o#aa4 ,lactose is comparatively free from sweetness1 and is hardly capable of being fermented by yeasts4 ,of ,glucoses the best example is dextrose ,c#f;,h#ab,o#f1 ,h#b,o1 which can be seen crystallised in dried raisins2 it only possesses one-third the sweetening power of sucrose4 ,starchy food becomes changed into glucose by the action of saliva and pancreatic juice in the alimentary canal4 ,grapes1 cherries1 gooseberries1 figs1 and honey contain lvulose in addition to glucose 7glucose ,c#f;,h#ab,o#f1 ,h#b,o1 lvulose ,c#f;,h#ab,o#f74 ,lvulose resembles dextrose except in being uncrystalline1 and in its effect on polarised light4 ,many ripe fruits1 such as pineapples1 strawberries1 peaches1 citrons1 contain sucrose and lvulose1 the latter being not quite so sweet as sucrose4 ,in the alimentary canal sucroses are inverted into dextrose and lvulose4 ,thus natural foods containing these sugars are more readily assimilated than those containing sucrose4 ,the sweetening power of the varieties of sugar depends on their degree of solubility in water4 ,sucrose is soluble in one-third of its weight of cold1 and in rather more of hot water4 ,dextrose is soluble in its own weight of water2 lvulose is more soluble1 and therefore sweeter than dextrose4 ,lactose requires five to six parts of cold and two of hot water1 and is therefore not so sweet as the other varieties4 ,,chapter ,,iv4 ,,diseases ,,due ,,to ,,food4 ,diseases may arise from the noxious character or from deficiency or excess of some particular food1 or of the food as a whole4 ,,diseases ,,from ,,unwholesome ,,food4--,i4 ,the ,meat of ,diseased ,animals4 7#a7 ,the flesh of animals which have not been slaughtered should be prohibited from sale1 whether death has resulted from accident or disease4 ,the meat from diseased animals is also generally dangerous1 sometimes owing to the drugs with which the animals have been dosed before death1 e4g4 tartar emetic1 or opium4 7#b7 ,meat may be unwholesome from the presence of parasites4 ,of these the most common is-- 7a7 ,the cysticercus cellulos1 which is the undeveloped embryo of the tape-worm2 that from the pig becomes the tnia mediocanellata4 ,the cysticercus of the pig is the most common2 it forms a cyst about the size of a hemp-seed1 commonest on the under surface of the tongue4 ,in hams oval holes are found or opaque white specks1 which are the remains of the cysts converted into calcareous matter4 ,when meat containing the cysticercus alive 7as in under-cooked or raw meat7 is swallowed1 it develops into the tape-worm1 which consists of a number of flat segments1 each capable of producing numerous ova of new cysticerci1 with a minute head at the narrow end surrounded by hooklets4 ,a temperature of #agd ,f4 kills the cysticercus4 ,another kind of tape-worm common on the continent1 called bothriocephalus latus1 is derived from the cysticercus of fish4 ,illustration3 ,,fig4 #b4 ,,cysticercus 78,,measles07 ,,in ,,pork4 7,,natural ,,size47 7b7 ,the trichina spiralis is not a solid worm like the tnia1 but possesses an intestine4 ,in pork it forms a minute white speck1 just visible to the naked eye1 which forms a nest1 and in this one or two coiled up worms can be seen by a magnifying glass in active movement4 ,they are effectually killed by the temperature of boiling water2 but no form of drying1 salting1 or even smoking at a low temperature is sufficient for this purpose4 ,boiling or roasting does not suffice to destroy all the trichin unless the joint is completely cooked in its interior4 ,when trichinous pork is swallowed1 the eggs develop in the alimentary canal in about a week into complete worms1 and in three or four days more each female produces over a hundred young ones4 ,these burrow into every part of the body1 producing great irritation and inflammation4 ,in one case after death upwards of #ej1jjj worms were estimated to exist in a square inch of muscle4 ,most of the cases of trichinosis have occurred in ,germany1 from eating imperfectly cooked sausages4 ,the pig becomes trichinous by eating offal1 and man is infected by eating pork4 ,this disease is rare in ,england4 ,illustration3 ,,fig4 #c4 ,,trichin ,,capsulated ,,in ,,flesh4 7,,magnified47 7#c7 ,tuberculous ,meat1 from animals suffering from tuberculosis1 has been found to cause tuberculosis in small animals experimentally fed on it4 ,koch has recently thrown doubt on the communicability of bovine tuberculosis to man2 but this point must be regarded as still unsettled 7see page #cab74 ,sheep are rarely affected by it1 but it is very common in cattle1 especially in cows1 and it is a serious economical question whether the meat of all such animals should be condemned4 ,the ideal would be to condemn all such animals1 as tuberculosis is an infective disease1 and the bacillus which causes it 7as well as the toxic products of its activity7 may be present in meat which shows no actual signs of disease1 except in the lungs or other internal organs4 ,in practice1 however1 the rules laid down by the ,royal ,commission on ,tuberculosis1 in #ahih1 should be followed for the present4 ,these state that3-- 8,the entire carcase and all the organs may be seized 7a7 when there is miliary tuberculosis of both lungs1 7b7 when tuberculous lesions are present on the pleura and peritoneum1 or 7c7 in the muscular system1 or in the lymphatic glands embedded in or between the muscles1 or 7d7 when tuberculous lesions exist in any part of an emaciated carcase4 ,the carcase1 if otherwise healthy1 shall not be condemned1 but every part of it containing tuberculous lesions shall be seized 7a7 when the lesions are confined to the lungs and the thoracic lymphatic glands1 7b7 when the lesions are confined to the liver1 7c7 or to the pharyngeal lymphatic glands1 or 7d7 to any combination of the foregoing1 but are collectively small in extent40 ,they also add that any degree of tuberculosis in the pig should secure the condemnation of the entire carcase1 owing to the greater tendency to generalisation of tuberculosis in this animal2 and that in foreign meat1 seizure should ensue in every case where the pleura has been 8stripped40 7,see also page #cab47 7#d7 ,other ,infective diseases besides tuberculosis may render meat wholly or partially unfit for food4 ,of these pleuro-pneumonia may not require condemnation of the entire carcase2 but in the following this course should be adopted1 cattle-plague1 pig typhoid 7pneumo-enteritis71 anthrax1 and quarter ill1 as well as in sheep-pox4 ,in puerperal fever1 actinomycosis1 and sheep-rot 7liver flukes7 each case must be decided on its merits4 ,,ii4--,decomposed ,meat4--,putrid meat has often produced diarrha and other severe symptoms4 ,putrid sausages are especially dangerous1 and incipient putridity seems to be more dangerous than advanced4 ,tinned ,meats occasionally produce severe illness1 which has been in several cases fatal4 ,it is important to secure a good brand1 and to eat the meat as early as possible after the tin is opened4 ,tins in which any bulging is present1 showing the presence of putrefactive gases1 must be rejected2 and still more tins which have been pricked and resoldered in a second place4 ,all tinned meats and fruits are stated by ,hehner to contain compounds of tin in solution4 ,these do not seem to be perceptibly injurious1 unlike lead salts1 which are now rarely found4 ,the general subject of ,meat ,poisoning has had much light thrown on it during the last few years4 ,brieger1 about #ahhf1 showed that during the cultivation of bacteria1 alkaloidal bodies known as ptomaines and leucomaines1 were formed1 which were virulently poisonous4 ,it was commonly supposed that the poisoning occasionally produced by eating meat pies1 sausages1 hams1 brawn1 and similar food1 was due to these ptomaines4 ,it is now known1 however1 that there are far more important toxines than the alkaloidal1 which result from bacterial life in meat1 etc4 7see page #bhf74 ,these are more closely related to substances of an albuminous or proteid nature than the ptomaines4 ,these toxines may be fatal when as small a dose as a fraction of a milligramme 7mgm4 about #afd grain7 is given subcutaneously4 ,the evidence now shows that neither ptomaines nor other toxines 7albumoses7 or any other bacterial products besides these1 cause the outbreaks of acute poisoning occasionally traced to food1 but that these are due to bacteria4 ,there is1 in other words1 actual infection1 as well as poisoning4 ,the microbe chiefly found as the cause of these outbreaks is the ,bacillus enteritidis of ,gaertner1 and some allied microbes4 ,in an outbreak at ,oldham1 #afj pies made on a ,thursday1 from the veal of a calf killed on the preceding ,tuesday1 were baked in several batches1 and of the persons eating these pies fifty-four became ill4 ,that the contamination was not introduced after cooking was shown by the fact that several persons were made ill who ate pies still warm from baking4 ,the facts indicated that one batch was imperfectly cooked1 the time allowed being only twenty minutes1 as compared with fifty minutes allowed in corresponding cooking in domestic life4 ,experimentally it has been found that an exposure for one minute to #gj ,c4 kills the ,bacillus enteritidis of ,gaertner4 ,that this bacillus was the cause of the outbreak was subsequently shown by the fact that the serum of blood taken from some of the patients showed characteristic clumping with a pure culture of this bacillus1 just as happens with the blood of a patient suffering from enteric fever when a cultivation of the microbe of this fever is mixed with it 7see page #cja74 ,in this outbreak the symptoms were usually diarrha1 vomiting1 intense thirst1 desquamation of the skin1 and a slow convalescence1 lasting from three to six weeks4 7,see page #bf for poisoning by ,bacillus enteritidis sporogenes47 ,,iii4--,meat injuries from the food eaten before killing4--,pheasants fed on laurel1 hares on rhododendron chrysanthemum1 and other animals fed on the lotus1 wild cucumber1 and wild melon of ,australia1 have caused dangerous symptoms4 ,,iv4--,fish1 especially some kinds1 occasionally produce nettlerash and other disorders1 especially in warm weather4 ,leprosy has been ascribed to the eating of decomposing fish1 but it occurs in countries where a fish diet is impossible4 ,shell-fish and crustaceans 7as lobster1 crab7 are very prone to produce evil results4 ,shell-fish 7mollusca71 such as mussels1 cockles1 and oysters1 are dangerous foods4 ,they are generally grown in estuaries1 to which the sewage of towns has access2 and not infrequently cases of enteric 7typhoid7 fever1 as well as more acute attacks of diarrha and vomiting1 have been traced to them4 ,mussels and cockles are seldom sufficiently cooked to render them safe2 and oysters are eaten raw4 ,they should never be eaten1 unless from personal direct knowledge it is certain that they have been derived from an estuary in which there was no possibility of contamination by sewage4 ,v4--,milk has been a common carrier of disease4 ,cows eating the rhus toxicodendron get the 8trembles10 and their milk produces serious gastric irritation in young children4 ,the milk of goats fed on wild herbs or spurgeworts has produced severe disorders4 ,the milk of animals suffering from foot-and-mouth disease1 although frequently drunk with impunity1 occasionally produces inflammation of the mouth 7aphthous ulceration74 ,the milk derived from cows fed on grass from sewage farms is1 per se1 as wholesome as any other1 and its butter has no more tendency to become putrid than that derived from any other source4 ,the great dangers in respect to milk are of its becoming mixed with contaminated water2 or of its absorbing foul odours4 ,the absorptive power of milk for any vapour in its neighbourhood1 is shewn by exposing it in an atmosphere containing a trace of carbolic acid vapour3 the milk speedily tastes of the acid4 ,milk also tends to undergo rapid fermentative changes1 especially in warm weather1 or when tainted by traces of putrefying animal matter4 ,diarrha in children is frequently due to such a condition1 or to the rapid decomposition of milk in an imperfectly cleaned bottle4 ,milk should always be boiled in warm weather2 and it should never be stored in ill-ventilated larders1 or where there is a possibility of the access of drain effluvia2 nor ought it to be kept in lead or zinc vessels4 ,epidemic diarrha has been ascribed by ,klein to a microbe called the ,bacillus enteritidis sporogenes4 ,this is not killed by heating the liquid containing it to #hj;,c4 for twelve to fifteen minutes1 as is the typhoid bacillus and other non-spore-forming bacilli4 ,in an outbreak of diarrha among the patients in ,st4 ,bartholomew's ,hospital1 ,london1 there was strong evidence that this microbe taken in rice pudding had caused the mischief4 ,eighty-four patients and two nurses were attacked1 and the patients who had eaten rice pudding were almost exclusively attacked4 ,a portion of this pudding after being kept twenty-four hours was found sour and acid4 ,the ,bac4 enteritidis sporog4 was found in it4 ,furthermore it was shewn that the temperature at which the rice puddings were cooked never exceeded #ih;,c41 whereas the spores of this microbe withstand #ajj;,f4 a considerable time4 ,very many epidemics of enteric fever and scarlet fever1 and a smaller number of epidemics of diphtheria have been traced to contaminated milk4 ,usually in enteric fever the contamination of the milk was traced to the use of water 8for washing the milk-cans10 derived from specifically polluted sources1 and doubtless the water was the real source of the disease4 ,in most of the milk outbreaks of scarlet fever1 either there was scarlet fever in the dairy1 or persons employed in the dairy were in attendance on patients suffering from the disease2 but in an outbreak connected with a supply of milk from ,hendon1 it was suspected that a certain eruptive disease of the udders of the cow might have been the cause of scarlet fever in man1 without infection from a previous case of the disease4 ,this point is still sub judice4 ,tubercular disease of the intestines and mesenteric glands may be produced by taking milk derived from tuberculous cows4 ,this was proved in the case of calves 7page #caa71 and there are strong reasons for thinking that the same is true for infants1 though doubt has been thrown by ,koch on the communicability of bovine tuberculosis to the human being4 ,the only safe plan is to sterilise the milk 7page #ac74 ,,vii4--,vegetable ,food 7especially greens7 is indigestible if stale1 and all mouldy vegetables are dangerous4 ,over-ripe and rotten fruit is liable to produce diarrha2 but the diarrha prevalent in summer is due much less to this than to other decomposing foods1 particularly milk4 ,poisonous symptoms have been produced by the admixture of darnel 7lolium temulentum7 with flour4 ,the eating of damaged maize in ,italy is the cause of an endemic skin disease1 called pellagra1 which commonly proves fatal4 ,ergotism is due to the growth on cereals 7and most commonly on the rye7 of a poisonous fungus1 the claviceps purpurea1 which produces a deep purple deposit on the grain4 ,if bread made from such flour is eaten for prolonged periods1 severe symptoms result2 in some cases1 a dry rotting of the limbs4 ,there have been several epidemics on the continent1 due chiefly to eating bad rye bread4 ,starvation ,diseases4--,simple ,starvation causes death in a period varying with the previous state of nutrition4 ,usually death occurs when the body has lost two-fifths of its weight1 whether this be after days1 months1 or years 7,chossat74 ,a supply of water prolongs the duration of life1 to as much as three times what it would otherwise be4 ,good nourishment doubles the power of resisting disease2 while deficient food prepares the way for many diseases4 ,a large share of the decline in the ,english death-rate during the last forty years is due to free trade1 and the great cheapening of wholesome food which has resulted from it4 ,an ill-balanced is more frequent than a deficient diet4 ,deficiency of fat is more serious than deficiency of carbohydrates1 and deficiency of proteid is most serious4 ,scurvy is caused by the absence of fresh vegetables4 ,the use of the potato and the orange1 as well as of lime juice 7the juice of citrus limetta71 has led to its extinction among adults in this country4 ,in former times1 it caused more deaths among seamen than all other causes put together1 including the accidents of war4 ,in infants fed upon tinned foods1 whether condensed milk or patent foods1 a form of scurvy still occurs4 ,infants fed on new-milk never suffer in this way4 ,if1 therefore1 it is necessary to feed an infant on condensed milk for many consecutive months1 potato gruel or raw meat juice or fresh milk must occasionally be given4 ,rickets is chiefly due to improper feeding in childhood4 ,the substitution of artificial foods 7most of them containing starch7 for the natural milk is its chief cause4 ,the lower incisor teeth of an infant appear between the sixth and seventh months4 ,starchy food given before this age is undigested4 ,such food likewise leads to less fat and proteid being given1 which are essential for growth4 ,deficiency of lime salts in the food does not cause it1 and giving them in food or medicine will not cure it4 ,enrichment of the diet by cream or failing this by cod liver oil is the best means of preventing and curing it4 ,abundant fresh air and warm clothing are also necessary4 ,relapsing fever generally follows epidemics of typhus fever1 and is greatly favoured by starvation4 ,ophthalmia has been chiefly prevalent in charity schools in which the children are underfed1 though its essential cause is contagion4 ,diseases ,connected with ,over-,feeding4--,a fire may go out for want of fuel1 or from becoming choked with ashes2 and it is the latter state of things which occurs in ,gout and allied diseases4 ,weakness is commonly complained of1 but this is due to excess of food embarrassing vital action2 and abstinence and exercise are required to restore the balance4 ,excess of nitrogenous food--especially if combined with the use of sweet1 or strong1 or very acid wines1 and beer--is particularly prone to produce gout4 ,in these cases1 animal food should only be taken once a day1 and vegetable food should be allowed to preponderate4 ,obesity is favoured by excess of starchy food and sugar1 and by copious drinking of water or other beverages4 ,the plan of curing obesity by restricting oneself almost entirely to meat food is only advisable1 however1 under certain conditions4 ,gall-stones are favoured by rich foods and excess of sugar2 also by alcoholic indulgence4 ,dyspepsia is commonly due to loading the stomach at too frequent intervals2 but on the other hand1 it not infrequently leads to the taking of insufficient food1 because of the discomfort produced4 ,the result of this is that a chronic starvation results1 with impaired vital powers4 ,dyspeptic patients should abstain from pastry and from tea and coffee1 except in small quantities4 ,alcohol in any form1 as a rule1 does harm4 ,not uncommonly mastication is imperfectly performed1 and a good dentist may cure the indigestion which has resisted all other treatment4 ,,chapter ,v4 ,,diet4 ,the importance of a duly proportioned and sufficient dietary is shown by its great influence on health and constitution4 ,an ill-proportioned or deficient diet is certain to lead to failure of health4 ,the anatomy of an animal may be modified in the course of generations by altered diet1 as well as its character2 thus1 the alimentary canal of the cat has increased in length to adapt it to its omnivorous habits4 ,in the case of the bee we have a still more remarkable instance4 ,if by any accident the queen bee dies1 or is lost1 the working bees 7which are sexually undeveloped7 select two or three eggs1 which they hatch in large cells1 and then feed the maggot on a stimulating jelly1 different from that supplied to the other maggots1 thus producing a queen bee4 ,the food of mankind varies naturally with-- ,i4--,climate4 ,a cold climate leads to increased metabolism1 and consequently a large amount of fatty matter can be eaten without producing nausea4 ,witness the difference between a ,laplander's and a ,hindoo's diet4 ,the season of the year has likewise some influence4 ,vital processes are more active in spring than autumn1 and more food is consequently required in the former season4 ,,ii4--,occupation4 ,although muscular exercise is not associated with an immediate increase of elimination of urea1 yet as a matter of experience more nitrogenous food is required and can be metabolised by hard workers than by idlers4 ,the trappers on the ,north ,american prairies can live for weeks together on meat alone1 accompanied by copious draughts of tea4 ,they are constantly in the open air1 undergoing fatiguing exercises1 in a dry and rare atmosphere4 ,for brain workers no special food is required4 ,foods containing phosphorus have no special value1 so far as is known1 for mental work4 ,such work1 however1 is apt to affect digestion2 consequently the digestibility of food is more important for those engaged in sedentary occupations than its chemical composition4 ,,iii4--,sex4 ,as a rule1 women require about one-tenth less food than men1 but probably this rule hardly holds good in the case of women engaged in laborious work4 ,,iv4--,age4 ,infants require only milk1 and the less they have of any other food before a year old the better4 ,atwater has calculated that---- ,a child under #b requires #caj the food of a man doing moderate work4 of #c to #e #daj of #f to #i #eaj of #aj to #ac #faj ,a girl of #ad to #af #gaj ,a boy of #ad to #af #haj ,vital processes are more active in early life1 and food is required not only to carry on the functions of the body1 but also to furnish the materials for growth4 ,hence1 while the proportion of proteids to carbohydrates and fats should be-- ,as #a3e4c in adults1 it should be about as #a3d4c in children4 ,after the age of thirty-five or forty1 the tendency is to take too much food4 ,all the tissues of the body are established1 and excess of food 7especially nitrogenous food7 is liable to produce tissue degeneration by loading the system with partially metabolised matter1 and may lead to gouty diseases4 ,it is much safer to take what may be regarded as too little than too much food after this period4 ,times for ,eating4--,the best arrangement seems to be to have three meals1 each fairly nutritious1 and containing all the constituents required4 ,the ,romans only had two meals daily1 prandium and cna4 ,this is common among the ,french at present1 but it tends to overloading the digestive organs at these meals4 ,an ordinary full meal has usually passed from the stomach in four hours4 ,fresh food ought never to be introduced before this period2 it is advisable to allow an interval of five hours between meals for the healthy1 so as to give time for the digestive organs to rest1 and for the absorption of food4 ,the practice of taking tea with the chief meal1 or a 8meat tea10 is bad4 ,tea is better taken an hour or two after food4 ,regularity in the time of taking meals is important1 as the digestive organs acquire habits like other parts of the body4 ,work ought not1 if possible1 to be resumed immediately after meals1 nor active exercise of any kind4 ,these tend to abstract blood from the digestive organs1 and so diminish the efficiency of digestion4 ,vegetable and ,animal ,foods4--,the fact that the food we require can be obtained from the vegetable world has led to the proposition that vegetable food should be taken alone4 ,it is urged in favour of this plan1 that a large amount of suffering to animals would be prevented4 ,also that animal food is not so economical as vegetable1 land being more economically employed in producing corn than in feeding cattle4 ,thirdly1 there is the indubitable fact that health can be maintained for prolonged periods on vegetable food 7including nuts1 cereals1 fruits1 etc47 ,on the other hand1 the chief objections to a purely vegetable diet are that the undigested refuse is greater than with an equal quantity of animal food2 that a longer time and more exertion than for animal foods are required in digesting the most nutritious vegetable foods1 such as legumens1 while other vegetable foods do not contain a sufficient proportion of nitrogenous material4 ,also1 if one lived entirely on vegetable food1 a greater bulk would be required1 and owing to the fact that such food is less easily absorbed1 satisfaction to the appetite would not so soon be produced4 ,animal food has a great advantage as regards convenience4 ,man is not an eating machine2 he requires food which is easily converted into the body substance1 and this is supplied by the flesh of animals1 milk and eggs1 with a due proportion of non-nitrogenous food2 sheep and oxen work up indigestible vegetable materials into easily assimilable mutton and beef4 ,the greater convenience of animal food as a supply of proteid is shown by the following examples of foods after the removal of water3-- #ajj parts of rice contain #g parts of proteid4 wheat #af pea flour #bg fat beef #ea dried lean beef #hi ,on the other hand1 vegetable foods are a cheaper source1 not only of carbohydrates and fats1 but also of proteids as well4 ,thus the approximate cost of-- #a lb4 of proteid in beef is #bs4 #h;d4 milk is #bs4 #b;d4 bread is #as4 #f;d4 oatmeal is #g;d4 peas is #g;d4 ,under the ordinary conditions of town life1 there is considerable danger of indulging in an excess of nitrogenous food1 and vegetarians may therefore do good by showing that meat is not absolutely necessary1 and can often with advantage be largely replaced by vegetable food4 ,if we include milk1 cheese1 and eggs in the vegetarian diet1 the objections to it partially disappear2 and it would be well if it were much more widely known1 especially among the poor1 that on these1 together with vegetables1 health can be maintained with the addition of little or no meat4 ,the ,determination of ,diet4--,the first principle in making a dietary is that it must be mixed1 containing all the necessary constituents1 proteids1 hydrocarbons1 carbohydrates1 water1 and salts4 ,no one of these alone will support life for any considerable period4 ,carbohydrates 7sugar and starch7 can be most easily dispensed with2 fats1 on the other hand1 are essential for the maintenance of health4 ,the next point is to ascertain the proportion in which these different foods are required4 ,salts are commonly taken with other foods1 common salt being the only one taken alone4 ,the amount required is given on p4 #g4 ,the amount of water required varies with the season of the year1 the amount of exercise and perspiration1 and other factors4 ,as a rule1 not more than two pints of water are required per day1 and still less if fruit is freely taken4 ,we may therefore confine our attention to the carbonaceous and nitrogenous foods1 and try to ascertain the amount of each of these required4 ,every diet must be subjected to the following tests1 to fully ascertain its value3-- #a4 ,the ,chemical ,test4--,the metabolism undergone by food in the body being essentially a process of oxidation 7though partially modified and incomplete71 the amount of heat yielded on complete combustion of a food may be taken as a measure of its value as a source of energy1 of which heat and work are convertible forms4 ,the standard of heat production is the calorie1 the amount of heat required to raise the temperature of one gramme of water #a ,c4 ,this is the small calorie4 ,the kilo-calorie 7called the ,calorie7 is the amount of heat required to raise #a kilo 7#a litre7 of water #a ,c41 or #a lb4 of water #d ,f4 ,in calculations on this basis1 allowance must be made for foods which are incompletely oxidised in the body4 ,rubner has shown that the heat value of #a gramme 7#ae grains7 of each of the chief food stuffs is as follows3-- ,proteid #d4a ,calories4 ,carbohydrates #d4a ,fat #i4c ,the method of applying this standard to a food is as follows3 the percentage of proteid or carbohydrate given in the following table is multiplied by #d4a1 and the percentage of fat by #i4c3-- ,,in #ajj ,,parts4 ,,water4,,albuminates ,,fats4 ,,carbo ,,salts4 ,,or ,,proteids4 ,,hydrates ,uncooked meat with little fat #gd4d #bj4e #c4e #a4f ,cooked meatwithout loss #ed #bg4f #ae4de #b4ie ,salt beef #di4a #bi4f #j4b #ba4j ,white fish #gh4j #ah4a #b4i #a4j ,bread1 white wheaten #dj4 #h4 #a4e #di4b #a4c ,wheat flour #ae4 #aa4 #b4 #gj4c #a4g ,rice #aj #e 4#h #hc4b #j4e ,oatmeal #ae #ab4f #e4f #fc4j #c4 ,peas 7dry7 #ae #bb #b4 #ec4 #b4d ,potatoes #gd #a4e 4#a #bc4d #a4 ,butter #h #b4 #hh variable ,eggs 7including shell1 for which deduct #aj per cent47 #gc4e #ac4e #aa4f #a ,cheese #cf4h #cc4e #bd4c #e4d ,milk #hg4j #d4 #c4e #d4h 4#g ,thus for bread-- ,proteid #h #d4a #cb4h ,fat #a4e #i4c #ac4ie ,carbohydrate #di4b #d4a #bja4gb ------------ ,total ,caloric value of #ajj grammes of bread #bdh4dg ,the total fuel value in ,calories of one pound of certain typical foods is given by ,hutchison as follows3--,butter #c1egg1 peas #a1dgc1 cheese #a1cjc1 bread #a1abh1 eggs #gci1 beef #fbc1 potatoes #cfi1 milk #cbb1 fish 7cod7 #cae1 apples #bch4 #b4 ,the ,physiological ,test4--,not only is a proper proportion of proteid1 fat1 and carbohydrates required1 but these must be capable of digestion and absorption and of oxidation in the body4 ,cheese is a highly concentrated food1 but its value is less than its percentage composition would indicate1 because of the difficulty of digesting considerable quantities of it4 ,green vegetables consist largely of cellulose1 which is only imperfectly capable of absorption into the blood1 although it can experimentally be oxidised by combustion4 ,the proportion between absorbed food and food rejected in the fces can be ascertained by analysis4 ,many experiments made on these lines show that on a purely animal diet 7meat1 eggs1 milk7 but little nitrogen is lost1 while with vegetable foods 7carrots1 potatoes1 peas1 etc47 the waste of nitrogen is considerable4 ,fats are very completely absorbed from the alimentary canal4 ,the amount remaining unabsorbed is greatest with mutton fat 7#aj per cent471 least with butter 7#b per cent474 ,experimentally it has been found that an amount up to #aej grammes 7about #e oz47 of fat can be absorbed without appreciable loss4 ,carbohydrates are very completely absorbed1 even starchy foods rarely escaping digestion4 ,completeness of absorption from the alimentary canal is not desirable for all foods2 a certain amount of unabsorbed residue is required to stimulate peristalsis4 ,with a purely vegetable diet this amount is excessive1 and there is physiological waste of effort4 #c4 ,in practical dietetics the ,economic test is important4 ,carbohydrate is by far the cheapest food1 and generally vegetable are cheaper than animal foods4 ,thus a shilling's-worth of bread yields #aj1gfd ,calories1 while the same sum spent on milk would only yield #ac1 and on beef #aaj this number of heat units4 ,similarly a shilling's-worth of peas contains #egb grammes of proteid1 about double as much as the same money's-worth of cheese2 while to obtain the same amount of proteid from eggs would cost more than eight1 and from beef more than five times as much as from peas 7,hutchison74 ,the market price of foods is no certain indication of their nutritive value4 ,thus haddock will supply as much nutriment as sole at a fourth of the cost2 ,dutch as much nutriment as ,stilton cheese at less than half the cost4 ,similarly the most economical fats are margarine and dripping4 #d4 ,an ,examination of ,actual ,dietaries under various conditions has strikingly confirmed the results obtained by other methods4 ,it has been found that 7a7 the potential energy required by a healthy man weighing #aa stones1 and doing a moderate amount of muscular work is #c1jjj to #c1ejj ,calories 7#caj grains72 and that 7b7 about #bj grammes of nitrogen and #cbj grammes 7#d1ifj grains7 of carbon are excreted by such a man4 7c7 ,expressing the #c1jjj ,calories required in terms of grammes of food1 it is found that #abe grammes of proteid1 #ejj of carbohydrate and #ej of fat are necessary4 ,these facts are expressed in the following table 7,hutchison73-- ,,standard ,,amount ,,of ,,same ,,amount ,,of ,,food ,,constituents ,,food ,,in ,,terms ,,of ,,yielding ,,energy ,,required ,,in ,,calories4 7,,in ,,grammes74 ,,carbon4 ,,nitrogen4 ,proteid #abe #fb #bj #eabe ,fat #ejj #bjj #bjej ,carbohydrate #ej #ch #dfe #fge #cjj #bj #cjbge ,three of the best known standard dietaries give the amounts in grammes of each food constituent as follows3 ,,playfair4 ,,moleschott4 ,,atwater4 ,,average4 ,proteid #aai #acj #abe #abe ,fat #ea #dj #abe #gb ,carbohydrate #eca #eej #dej #eaj ,calories #cadj #cafj #cebj #cbgc ,expressing the same facts in ,english ounces instead of grammes1 #d-be oz4 of proteid1 #b oz4 of fat1 and #ah oz4 of carbohydrate1 would represent the ounces of each constituent required according to 7#a7 7#b7 ,,average ,,of ,,above ,,hutchison4 ,,three ,,dietaries4 ,proteid #d-be #d-be ,fat #b-ab #a-de ,carbohydrate #ah #ag-ce ,ounces of dry food #bd-iaj #bc-de ,the chief point of divergence in the above standard dietaries is in the relative proportion of carbohydrate and fat4 ,probably the correct proportion between these is as #a to #aj2 but it will vary according to climate and other circumstances4 ,detailed examination of a large number of dietaries shows that the amount of daily proteid should be about #abe grammes1 or #d-be ozs4 ,this is contained in #bj eggs1 or in #ah oz4 i4e4 about #d ordinary platesful of cooked meat4 ,it must be noted that the #bc-bd oz4 of food given above as the standard daily amount represents dry food4 ,this represents #dj oz4 or nearly #c lbs4 of ordinary food4 ,the following example by ,waller1 gives a rather liberal standard ,english diet1 for a man doing a moderate amount of muscular work4 ,,carbon4 ,,nitrogen4 ,foundation3 #a lb4 bread #aag #e4e #ab lb4 meat #cd #g4e #ad lb4 meat #hd -- ,accessories3 #a lb4 potatoes #de #a4c #ab pint milk #bj #a4g #ad lb4 eggs #ae #b4j #ah lb4 cheese #bj #c4j ------ -------- ,total #cce #ba grammes4 ,this divided up into meals works out roughly as follows 7,hutchison73-- ,two slices of thick bread and butter4 ,breakfast ,two eggs4 ,one plateful of potato soup4 ,dinner ,a large helping of meat with some fat4 ,four moderate sized potatoes4 ,one slice of thick bread and butter4 ,tea ,a glass of milk and two slices of thick bread and butter4 ,supper ,two slices of thick bread and butter and #b oz4 of cheese4 ,from the preceding data1 practical problems as to dietaries are easily solved4 ,thus if it be required to find how much oatmeal1 milk1 and butter would be required to give a sufficient quantity of albuminoids1 fats1 and carbohydrates to an adult male1 the calculation may be based on the figures in the table on p4 #cb1 or the following figures may1 for the sake of convenient calculation1 be taken as representing the percentage amount of each of these chief food principles contained in the foods named3-- ,,albuminoids4 ,,fats4 ,,carbohydrates4 ,oatmeal #ab #f #fj ,milk #d #c #e ,butter #b #hh -- ,let o number of ounces of oatmeal required4 m milk b butter ,then 7#abo #dm #b;b7#ajj #d4e ozs4 of albuminoid 7#fo #cm #hh;b7#ajj #c ozs4 of fat 7#fjo #em7_/#ajj #ad4be ozs4 of carbohydrate1 according to ,moleschott's diet4 ,when these equations are worked out by substitution and transference-- o #ai4b ounces4 m #ee4d b #j4bd ,similarly if it is required to find how much meat1 bread1 and butter of the following percentage composition will be required to give a man a sufficient amount of albuminoids1 fats1 and carbohydrates4 ,,albuminoids4 ,,fats4 ,,carbohydrates4 ,meat #be #ae #j ,bread #h #a4e #ej ,butter #b #hh #j ,let m number of ounces of meat required4 b bread ,b butter ,then #abm #h;b #b;,b_/#ajj #d4e ozs4 of albuminoid 7#aem #a4e;b #hh;,b7_/#ajj #c ozs4 of fat #ej;b_/#ajj #ad4be ozs4 of carbohydrates ,when these equations are worked out-- m #f4bh ounces4 b #bh4e ,b #a4ae ,relation of ,food to ,mechanical ,work4--,in the body the movements of every part are constant sources of heat4 ,it is evident therefore that the potential energy of food can be expressed by 7a7 the amount of heat obtained by its complete combustion1 or 7b7 by the amount of work capable of being obtained from it4 ,joule discovered by exact experiment that the mechanical power obtainable from a given amount of fuel is directly proportional to the amount of fuel used1 being in fact due to the oxidation of this fuel1 the heat produced being transformed into mechanical power4 ,the heat unit or calorie has been already given 7p4 #cb74 ,the gram-metre is the work unit4 ,the heat unit corresponds to #dbe4e units of work4 ,thus the same energy required to heat one gramme of water #a ,c4 will raise a weight of #dbe4e grammes to the height of #a metre4 ,conversely a weight of #dbe grammes if allowed to fall from a height of #a metre1 will by its concussion produce heat sufficing to raise the temperature of #a gramme of water #a ,c4 ,in ,england the amount of work done is commonly expressed as foot tons1 i4e4 tons lifted one foot2 while in ,france it is similarly expressed as kilogrammetres4 ,gramme-metres can be converted into foot-pounds by multiplying them by 4#jjgbcc1 and kilogrammetres into foot-tons by dividing by #caa4 ,frankland estimated that-- #a oz4 dry albumin yields #agd foot-tons of potential energy4 #a oz4 fat #cgh #a oz4 starch #ace #a oz4 cane sugar #abi #a oz4 glucose or lactose #abb ,in practical dietetics digestibility of food as well as chemical composition is an important factor4 ,furthermore metabolism in the body is not in every instance so complete as oxidation outside it4 ,hence estimates of potential energy can only be regarded as theoretically correct4 ,examination questions like the following are occasionally asked3-- ,a man does work equal to #agf4h foot-tons in a day4 ,supposing that he eats only bread1 how much will he require to give the amount of energy required1 if bread contains #h per cent4 proteid1 #a4e per cent4 fat1 and #di4b per cent4 carbohydrate8 ,on the above basis1 from #ajj ounces of bread the amount of potential energy obtainable is3-- #h #agd #a1cib foot-tons #a4e #cgh #efg #di4b #ace #f1fdb --------- ,total energy #h1fja obtained from #ajj ozs4 bread4 ,let b number of ounces of bread required to develop #agf4h foot-tons of energy4 ,then #h1fja3 #ajj33 #agf4h3 b4 ,therefore b #b4je ounces4 ,,chapter ,,vi4 ,,the ,,preparation ,,and ,,preservation ,,of ,,food4 ,,objects ,,of ,,cooking4--,food may be taken in its crude condition1 as directly derived from the animal or vegetable world1 or after it has undergone a preparatory process of cooking4 ,man is the only animal who cooks his food4 ,many foods1 in the uncooked condition are almost entirely incapable of digestion by him--such as the proteid and farinaceous materials contained in the seeds of cereal and leguminous plants4 ,but cooking1 as a preparatory help to the digestion of food1 is not equally required by all foods4 ,thus1 fruit is commonly taken uncooked1 and does not undergo any important alteration on cooking4 ,salads are taken uncooked1 but not for their nutritive properties so much as for a relish to other foods1 and for their quasi-medicinal properties4 ,milk1 again1 may be taken cooked or uncooked4 ,the oyster is the only animal which is eaten habitually1 and by preference1 in the uncooked condition2 and there is a physiological reason for this universal custom4 ,the large fawn-coloured liver1 which constitutes the delicacy of the oyster1 is little else than glycogen1 associated with its appropriate ferment diastase1 so that the oyster is almost self-digestive4 ,when cooked1 the ferment is destroyed1 and digestion of the oyster becomes more difficult4 ,cooking is intended--#a4 ,to make the food softer1 and in part to mechanically disintegrate it1 thus rendering it more easily masticated and digested4 ,in fact1 cooking1 in the best sense1 is an artificial help to digestion2 and digestion may well be said to commence in the kitchen4 #b4 ,to produce certain chemical changes4 ,thus1 starch is partially converted into dextrine2 gelatin is formed from connective tissue1 etc4 #c4 ,to destroy any noxious parasites present in the food1 or obviate any ill effects from putrefactive changes4 ,diseased meat chiefly produces bad effects when imperfectly cooked4 #d4 ,to make the food more pleasant to the eye and agreeable to the palate4 ,the improved savour in cooked meat1 for instance1 has a very appetising effect1 and consequently makes digestion easier4 ,,the ,,cooking ,,of ,,flesh4--#a4 ,roasting is1 perhaps1 the most perfect way of cooking meat4 ,it exalts its flavour more than any other method4 ,in roasting1 place the meat at first sufficiently near a brisk fire1 so that the albumin on its surface may be readily coagulated1 and the juices retained in the interior of the joint4 ,after about fifteen minutes1 the joint ought to be removed somewhat further from the fire1 and allowed to cook slowly4 ,frequent basting is desirable to obtain a good result4 ,brown meats1 such as beef1 mutton1 and goose1 require a quarter of an hour per pound weight2 veal and pork require about ten minutes additional1 to ensure the absence of redness4 ,white-fleshed birds require a somewhat shorter time4 ,the time required in roasting will be a little more if the joint is large1 or the fire not very clear4 ,to ascertain if the meat is sufficiently cooked1 press the fleshy part2 if it remains depressed1 it is done2 if not done1 it retains its elasticity4 ,at the first incision1 gravy should flow out of a reddish colour4 ,the changes undergone during roasting are1 that the connective tissues uniting the muscular fibres is converted by the gradual heat into gelatin1 which is soluble and easily digested2 the muscular fibres1 consequently1 become more separable1 and the myosin of which they consist is rendered more digestible4 ,the fat is partly melted out of its fat cells1 and partly combines with the alkali from the blood-serum4 ,empyreumatic oils 7i4e4 fat partially burnt71 developed by charring of the surface of the joint1 are carried off when it is roasted in front of the fire2 and so1 to a large extent1 is acrolein4 ,acrolein 7,c,h,o7 is always produced by the destructive distillation of neutral fats containing glycerine1 and is the cause of the intolerably pungent odour accompanying the process4 ,osmazome1 a peculiar extractive matter1 on which the flavour and odour of meat depend1 is developed better by roasting than by any other method of cooking4 ,it is useful to remember1 in buying beef or mutton1 that #bj per cent4 must be allowed for bone and #bj to #cj per cent4 for the loss during cooking4 ,the following figures are by ,johnston3 ,,in ,,roasting4 ,,in ,,baking4 ,,in ,,boiling4 #d lb4 of mutton lose in weight #a lb4 #f oz4 #a lb4 #d oz4 #ad oz4 beef #a lb4 #e oz4 #a lb4 #c oz4 #a lb4 ,thus roasting is the least economical method of cooking4 ,the chief loss1 however1 is of water2 the dripping and gravy are recoverable4 #b4 ,baking of meat in a closed oven does not produce so agreeable a result as roasting in front of an open fire4 ,the oven ought always to be very hot before the meat is put in1 in order to rapidly coagulate its surface4 ,baked meat may have an unpleasant flavour1 owing to its saturation with empyreumatic oils1 which escape in open roasting4 ,the unpleasant flavour can be prevented by covering the meat with a layer of some non-conducting material1 as a pie-dish or a crust1 no empyreuma being then formed4 ,baked white of egg1 as in the dish of fried ham and eggs1 is one of the most indigestible forms of albumin obtainable4 #c4 ,boiling of meat requires the same time as roasting4 ,if the flavour and juices are to be retained1 the joint ought first to be plunged into soft boiling water1 and then1 after three minutes1 allowed to stand aside in water at #agj ,fahr4 ,the preliminary boiling forms a coating of coagulated albumin over the joint4 ,where there is no thermometer to guide the cooking--after the preliminary boiling for three to five minutes1 add three pints of cold water to each gallon of boiling water1 and retain at the same temperature for the rest of the process1 i4e41 at about #agj ,fahr4 ,if the meat is boiled in an inner vessel surrounded by water 7water-bath71 the temperature of the inner vessel does not rise above #afj-agj ,f4 ,ordinary 8simmering0 means that the meat is kept all the time at a temperature of #bab ,f4 and is thus spoilt4 ,the boiling of an egg is an example of the same point4 ,if an egg is kept in water at a temperature of #agj ,f4 for #aj to #ae minutes1 its contents form a tender jelly1 while an egg kept in water at #bab ,f4 for the same length of time is hard and tough4 ,an egg is more digestible when cooked in water at #agj ,f4 for #aj minutes than when boiled in water for #b minutes4 ,the use of soft water for cooking purposes is always advisable2 otherwise a longer period must be allowed4 ,a preliminary boiling for a few minutes renders hard water softer1 and the addition of a little carbonate of soda has a like effect4 ,when meat is inserted in water at a temperature below its boiling point1 the juices are gradually extracted1 while the meat is left a mass of indigestible fibres4 ,a good soup is produced1 but the meat is almost valueless4 ,in order that the soups and broths may be nutritious1 the less heat is employed in their preparation the better4 ,if a soup is strained to make it clear1 much of the most valuable part is removed4 ,stewing is a process intermediate between boiling and baking4 ,it possesses the great advantage over dry baking that no empyreumatic gases are produced1 and there is no charring4 ,the temperature of the stew-pan ought never to be above #ahj ,fahr42 at this heat the roughest and coarsest kinds of meat are made tender4 ,the only objection to stewing is that the meat becomes saturated with fat and gravy1 and is too rich for weak stomachs4 ,it is advisable to stew lean meats only4 ,hashing is a process of stewing applied to meat which has been previously cooked4 ,the consequence of this double cooking1 is that the meat becomes tough and leathery4 ,a modified hash in which the meat is simply well warmed throughout is preferable4 ,frying1 unless carefully done1 renders meat difficult of digestion1 each fibre becoming coated with fat4 ,the art is to 8fry lightly10 that is1 to burn quickly and evenly1 so that no charring is produced4 ,two methods of frying are described4 ,in the first1 the substance to be fried1 as an omelette or pancake1 is placed with a little fat or oil in a frying-pan4 ,this is really a modified process of roasting1 the fat merely serving to prevent the object from adhering to the shallow pan4 ,in the second1 the substance to be fried is immersed in fat2 for this purpose a frying kettle is required4 ,olive oil or good cotton seed oil is best for use in the frying-kettle4 ,lard is a bad material for frying2 both it and butter are apt to burn unless heated slowly4 ,dripping is a good substance for frying4 ,the fat used must be heated to from #cej to #cij ,f41 and then the substance to be fried1 e4g4 a sole1 plunged into it and left for two or three minutes4 ,in this process the substance of the sole is really being steamed by the steam generated in the substance of the sole4 #f4 ,broiling and ,grilling are really processes of roasting applied to small portions of meat4 ,in grilling1 it is important that the gridiron should be hot before putting anything on it4 ,an external coagulation of albumin is produced1 as in good roasting and boiling4 ,,the ,,cooking ,,of ,,mixed ,,dishes4--,a few instances may be given of common errors in preparing compound dishes4 ,an egg in a custard1 or just coagulated in a poached egg1 is a light and easily-digested food2 baked half an hour in a pudding1 it is much less digestible2 fried with ham1 it is almost as indigestible as leather4 ,spices1 if mixed with a dish before it is boiled1 lose nearly all their flavouring power1 while they remain irritating4 ,they ought to be added near the end of the cooking process4 ,a soup containing vegetables1 as well as meat juices1 should be prepared in two parts4 ,the vegetables require prolonged boiling2 gravy is spoilt by this4 ,similarly1 the jam in a tartlet1 if inserted before baking1 loses its proper fruity flavour2 and oysters baked in a beef-steak pie are indigestible4 ,,the ,,cooking ,,of ,,vegetable ,,foods4--,bread is either vesiculated or unvesiculated2 the latter being what is called unleavened bread4 ,vesiculation of bread has usually been produced by fermentation of some of the sugar of the flour4 ,the starch first becomes sugar 7dextrose7 and then the growth of the yeast plant in the dough splits this up into alcohol and carbonic acid gas4 ,the carbonic acid percolates the substance of the dough1 rendering it porous4 ,when it has 8risen0 sufficiently1 the dough is placed in the oven4 ,the heat of the latter kills the yeast plant1 thus preventing any further fermentation1 but at the same time expands the carbonic acid gas in the bread1 rendering the latter still more porous1 and drives off in a gaseous condition the greater part of the alcohol produced by the previous fermentation4 ,it is objected to this plan of making bread1 that a little of the sugar is wasted in producing alcohol and carbonic acid4 ,to remedy this1 another plan is sometimes adopted1 as first proposed by ,dr4 ,dauglish4 ,in it the dough is charged with carbonic acid dissolved in water under considerable pressure4 ,the gas escapes in the substance of the dough1 and on baking expands as in the ordinary method of making bread4 ,bread made in this manner1 is called 8aerated bread40 ,nevill's bread has a solution of carbonate of ammonia incorporated in the dough1 which is dissipated by heat1 thus causing vesiculation of the bread4 ,on the continent1 a mixture of hydrochloric acid and carbonate of soda is commonly used1 carbonic acid and common salt being formed in the dough4 ,thus ,na,h,c,o ,h,cl ,na,cl ,h,o ,,co4 ,the hydrochloric acid employed should be perfectly pure and free from arsenic4 ,baking powders are also largely used for making cakes4 8,self-raising0 flour is flour with which baking-powder has already been mixed4 ,most baking-powders consist of a mixture of carbonate of soda and tartaric acid or bitartrate of potash1 diluted with starch4 ,when wetted1 carbonic acid gas is evolved4 ,a few contain alum1 which is now an illegal material for this purpose4 ,ten pounds of flour ought to make thirteen to fourteen of bread4 ,the use of stale bread is much more economical than of newly-made bread2 besides this1 it is more digestible4 ,newly-made bread is more palatable than stale1 but it is more cohesive1 and does not crumble into separate particles like stale bread4 ,the consequence is1 that it is less digestible1 being less easily penetrated by the saliva and other digestive juices4 ,the effect of toasting is to render bread more friable1 and consequently more digestible4 ,it ought1 however1 to be thin and eaten soon after it is made2 when thick and kept too long1 it becomes tough and leathery4 ,pastry is less easily digested than ordinary bread4 ,the lard or dripping added renders it more flaky and less easily pulverised2 and1 in addition1 the fat coats over the starch cells2 and thus the action of the digestive juices on the pastry is impeded4 ,potatoes ought to be boiled in their jackets1 or steamed1 to avoid loss of nitrogenous material and salts4 ,moist heat causes the starch granules to swell1 and ultimately softens and bursts the cellulose envelopes in which these are contained4 ,dry heat1 as when potatoes are baked1 converts starch into a soluble form1 and ultimately into dextrine 7 ,c,h,o71 an intermediate stage towards the formation of dextrose 7i4e4 glucose ,c,h,o74 ,peas and ,beans ought to be boiled slowly and for a long time to render them more digestible4 ,if old1 they ought to be soaked in cold water for twenty-four hours1 then crushed1 and stewed4 ,hard water must be avoided in the cooking of peas and beans as well as of other vegetables1 as the lime-salts form insoluble compounds with legumin4 ,green vegetables require thorough and prolonged cooking4 ,this renders their tissues softer and more easily attacked in digestion4 ,the members of the cabbage tribe and carrots can hardly be boiled too long4 ,soft water ought always to be used2 this is one reason why steaming is preferable4 ,before boiling1 all vegetables should be well washed in cold water4 ,a little vinegar will remove any insects present4 ,,cooking ,,apparatus4--,the apparatus required in cooking may be divided into kitchen utensils and cooking ranges4 ,to ensure good cooking1 perfect cleanliness of all apparatus is indispensable4 ,the use of the frying-pan1 gridiron1 spit1 and oven has been sufficiently indicated under the description of the different methods of cooking4 ,the form of stove to be used for cooking meat is gradually being settled against the old open stove4 ,although this secures a somewhat more savoury joint than when meat is baked1 it is extravagant in working4 ,the closed kitchener in which coal is employed is less economical than a gas stove at the present price of gas1 if the latter is carefully used4 ,various appliances for economising fuel have been devised1 and at the same time of allowing of the prolonged action of a moderate degree of heat4 ,these are usually constructed on the principle of an ordinary bath1 consisting of a double pan1 with a layer of water between the two compartments4 ,warren's cooking-pot belongs to this type4 ,the ,aladdin oven consists of an iron box with an opening above to let off superfluous steam4 ,this box is surrounded by another composed of non-conducting material1 while a lamp below furnishes the heat4 ,dr4 ,atkinson has calculated that in an ordinary oven #b lbs4 of fuel must be expended for every pound of food cooked1 while in his ,aladdin oven #b lbs4 of fuel will cook #fj lbs4 of food4 ,time is an important element in cooking4 ,food is most thoroughly cooked and most digestible when subjected to a temperature below that of boiling water for a prolonged period4 ,,the ,,preservation ,,of ,,food4--,all organic foods tend rapidly to decompose and putrefy4 ,putrefaction only occurs when a warm and moist substance is exposed to the air4 ,the problem of preserving any food1 therefore1 may be solved 7#a7 by keeping it at a very low temperature1 7#b7 by desiccating it1 or 7#c7 by boiling or steaming it so as to destroy any microbes in the food which would otherwise start putrefaction1 and then fastening it in an air-tight case4 ,milk is commonly preserved as condensed milk1 and in this condition is very valuable4 ,a pure condensed milk is now supplied1 prepared without the addition of sugar or any antiseptic1 but in which1 as in other condensed milks1 all disease-producing or decomposition-producing microbes have been destroyed during the process of concentration4 ,milk may also be desiccated2 in this condition it is difficult of digestion4 ,in addition to the household methods of preserving fruits1 large quantities of fruits--both moist and dry--are now imported1 protected by syrup or sugar1 in sealed canisters2 and they retain the original flavour almost unchanged4 ,the preservation of meat is effected by-- #a4 ,drying4--,this must be done rapidly4 ,it is a process which is best applicable to fish1 but has been applied also to beef4 ,dried ,hamburg beef is used for making sausages4 ,pemmican1 largely used by ,arctic voyagers1 consists of a mixture of meat and fat1 dried and powdered along with some spices2 it is generally eaten with some kind of meal4 #b4 ,cold4--,frozen meat now forms a very large part of the food of the ,english people4 ,if the meat has been frozen before rigor mortis 7rigidity after death7 has commenced1 it keeps well2 if frozen later1 it rapidly decomposes after being thawed4 ,freezing arrests putrefaction and tends to conceal its odour4 ,hence the bad condition of frozen fish may not be detected until it is cooked4 ,in cooking frozen meat1 time should be allowed for thawing to occur1 before the meat is placed in the oven4 ,much of the ill-founded prejudice against frozen meat arises from inattention to this point4 ,frozen meat is equal in nutritive value to and does not lose more in cooking than fresh meat4 #c4 ,salting may be done with brine or saltpetre 7nitrate of potassium72 the latter does not decolourize the meat like the former4 ,salted meats have lost much of their nutritive material1 in the form of albumin and salts1 and the remaining meat is harder and more difficult of digestion than fresh meat4 #d4 ,immersion in antiseptic liquids or gases1 as sulphite of soda1 is objectionable1 on account of the addition of extraneous1 and not altogether innocuous1 salts4 ,boric acid powder is largely used for sprinkling on meat1 particularly rabbits1 etc41 and for preserving hams and other meats4 ,its use is to be deprecated4 ,all such meats should be thoroughly washed with water1 before being cooked4 ,solutions of boric acid and borax are frequently added to milk4 ,their use is objectionable 7a7 because they tend to conceal incipient decomposition1 but do not prevent its possible evil effects1 and 7b7 because they enable the farmer to palm off dirty milk on the public4 ,were the addition of preservatives to milk forbidden1 the farmer could perfectly well keep his milk sweet until it reached the town-consumer by adopting strict measures of cleanliness1 and by cooling his milk before it leaves the farm4 ,at the least it should be made obligatory on the milk retailer to declare the presence of preservatives in milk sold by him4 ,the presence of borax or boric acid can be detected by evaporating the milk to dryness1 incinerating and then moistening the ash with a drop of strong sulphuric acid4 ,if a little alcohol be now added1 on applying a light1 a green flame indicates boric acid4 ,milk or cream containing boric acid turns blue litmus paper red4 ,formalin is also sometimes used as a preservative for milk in very weak solution4 ,its presence can be determined by diluting the milk with water in a test-tube1 and running strong sulphuric acid down the side of the tube1 taking care to prevent mixing4 ,at the junction of the acid and diluted milk a violet ring is seen if formalin is present4 ,salicylic acid was formerly used as a milk preservative1 but is now seldom used except in beers4 ,all these preservatives are objectionable in milk1 although their injurious action may be difficult to prove4 #e4 ,coating with fat or gelatine has only succeeded in conjunction with the exclusion of air4 ,this process is especially applicable to fishes1 as tinned sardines4 ,in a modified form1 it is useful in coating potted meats1 etc4 #f4 ,heating and ,air-tight ,cases4--,tinned meats prepared according to this method are imported in large quantities4 ,in the process of preparation1 the cases are packed with meat and filled up with gravy1 and then closed with a cover which is hermetically sealed1 except at one point4 ,the case is then heated to #bej ,fahr41 in order to drive out all air1 and destroy any putrefactive germs present4 ,the open point is sealed while the gravy is still boiling1 thus making the case completely air-tight4 ,albumin is coagulated at about #agj ,fahr42 the higher temperature1 which it is found necessary to employ1 overcooks the meat and renders it less digestible 7see also p4 #dj74 ,,chapter ,,vii4 ,,condiments ,,and ,,beverages4 ,,condiments1 ,,etc4--,the name condiment is used in various senses by different writers4 ,in its strictest sense it is a substance containing a volatile oil or ether1 which may be taken with salt1 and the object of which is to excite the senses of taste and smell1 and consequently produce an appetising effect4 ,this definition excludes spices1 substances allied to condiments1 but usually taken with sugar1 as cinnamon1 ginger1 etc42 also flavouring agents1 such as vanilla2 and acids1 such as vinegar and lemon-juice4 ,if we use the word in its widest sense1 to include these various groups of substances1 we find that all condiments are taken with the object of improving the taste or flavour of food1 or of assisting its digestion2 but that they are not foods in the sense of supplying any elements towards building up the body or maintaining its heat4 ,the only partial exception is lemon-juice1 the salts of which have a quasi-medicinal use4 ,taste is usually a compound sensation1 the organs of which are the nerves of taste and smell4 ,true taste is confined to the appreciation of sensations of bitter and sweet2 but the flavour of meats is nearly entirely appreciated by the sense of smell4 ,this is shown by the fact that meats appear tasteless and insipid1 during 8a cold in the head40 ,in the appreciation of acid1 astringent1 and fiery substances1 the sense of touch is also employed4 ,the excitement of these different nerves results in a stimulus which is carried up to the central nervous system1 and causes by reflex action an increased flow of the digestive juices4 ,hot substances1 like cayenne and ginger1 also cause an increased flow of gastric juice1 by directly congesting the mucous membrane4 ,this action is not so desirable as that through the influence of the nervous system4 ,all natural foods are sapid and possessed of flavour1 and thus stimulate secretion2 but any local irritating effect ought to be avoided4 #a4 ,condiments proper comprise chiefly mustard1 pepper1 cayenne1 garlic1 onion1 capers1 mint1 sage1 morels1 mushrooms1 truffles4 ,the last three on the list are also foods1 but are more commonly used as condiments4 ,all these act as stimulants to the digestive organs1 and in small quantities aid digestion4 ,the active principle of mustard and horse-radish is sulphocyanide of allyl4 ,horse-radish is not so wholesome as mustard1 the scraped root being apt to adhere to the stomach like the skins of grapes1 and produce indigestion4 ,pepper contains an acrid resin1 a volatile oil1 and an alkaloidal substance1 called piperine4 ,cayenne contains an analogous substance1 called capsicin4 ,cayenne1 unless in extreme moderation1 is harmful1 as its small particles adhere to the mucous membrane of the stomach1 and may set up considerable irritation4 #b4 ,spices are those condiments which contain an aromatic oil1 and which harmonize with sugar4 ,they are1 as a rule1 less irritating to the stomach than those of the pepper group4 ,cinnamon1 cloves1 camphor1 ginger1 and curry powder are the chief of these4 ,curry powder really belongs to both the first and second divisions4 ,when genuine1 it is said to contain turmeric1 cardamoms1 ginger1 allspice1 cloves1 black pepper1 coriander1 cayenne1 and a few other substances4 #c4 ,flavouring agents1 such as vanilla1 lemon peel1 and fruit essences1 are used to give a pleasant flavour to various dishes4 #d4 ,acidulous substances are taken chiefly because of their sharp and agreeable taste4 ,vinegar is the chief acid employed4 ,it is produced by the action of a fungus 7,mycoderma aceti7 on alcoholic liquids1 as wine1 or beer1 ,c,h,,oh 7alcohol7 becoming ,c,h,o 7acetic acid74 ,it is also produced by the destructive distillation of wood4 ,in small quantities it does not stop digestion1 but1 by exciting the nerves of taste1 may be of actual service4 ,it helps to soften the vegetable fibres in a salad2 and is also useful for the same purpose with hard meats1 as lobster1 etc4 ,in large quantities it diminishes the power to assimilate food4 ,good vinegar ought not to contain less than #c per cent4 of acetic acid2 and sulphuric acid beyond #a in #ajjj in vinegar is to be regarded as an adulteration4 ,a specific gravity below #ajae indicates the addition of water4 ,citric acid and lemon-juice are useful for their refreshing properties1 and the latter also because of its alkaline salts4 ,oils1 such as olive oil1 have been sometimes classed under condiments1 but as they have great nutritive properties1 this is hardly accurate4 ,for the same reason1 salt is not classed under this head4 ,,beverages4 ,water is the universal beverage1 and for healthy persons is preferable to any other4 ,all other beverages necessarily contain it as their basis4 ,it will be convenient to consider first arated and other natural waters2 then tea1 coffee1 and cocoa2 and finally1 alcohol4 #a4 ,aerated ,waters contain carbonic acid 7carbon dioxide7 in solution1 which gives to them their characteristic sharp taste and sparkling character4 ,thus distilled water charged with gas is sold as ,salutaris or ,puralis water4 ,soda water contains three to five grains1 and medicinal soda water fifteen grains of bicarbonate of soda to the bottle4 ,potash water contains fifteen grains of bicarbonate of potash to the pint1 in each case carbonic acid being dissolved under pressure4 ,in lemonade1 ginger-beer1 etc41 the basis is sweetened water1 rendered tart by the addition of an acid1 and finally charged with carbonic acid4 ,lemonade frequently contains acetic or phosphoric acid instead of citric or tartaric1 and ginger-beer the same constituents with some added tincture of ginger4 ,home-made lemonade prepared from fresh lemons is a much more wholesome drink4 ,ginger-beer 7stone ginger7 is produced by the fermentative action of yeast on a solution containing sugar1 bruised ginger1 tartaric acid1 and oil of lemon4 ,it usually contains at least two per cent4 of alcohol4 ,natural ,mineral ,waters usually contain common salt 7chloride of sodium7 and alkaline salts of soda or lime1 and are impregnated with carbonic acid gas4 ,apollinaris1 ,rosbach1 and ,johannis possess these characteristics4 ,the carbonic acid in natural waters is partially combined1 and is given off more gradually than that in artificial mineral waters4 ,in all the preceding waters there is considerable carbonic acid4 ,this acts as a sedative to the mucous membrane of the stomach1 and is useful in indigestion4 ,an arated water added to milk renders it more digestible by diluting it1 and by preventing the formation in the stomach of a heavy clot of casein4 ,in the making of artificial arated waters1 it is essential that the water employed should be pure1 that the acid used in generating the carbonic acid should be free from arsenic or other impurities1 and that the water should not be allowed to come into contact with lead at any stage1 as in pewter fittings4 ,one per cent4 of proof spirit is allowed in temperance beverages by the ,excise4 ,,tea4 ,tea is the leaf of an evergreen shrub1 the ,camellia thea1 which is cultivated in ,china1 ,japan1 ,british ,india1 ,ceylon1 ,java1 and other countries4 ,the tea leaves1 as seen in this country1 uncurl in hot water4 ,they are lanceolated1 with a serrated edge1 and the veins do not extend to the edge of each leaf4 ,by these characteristics they may be distinguished from foreign leaves1 e4g41 the sloe and willow used as adulterants 7,fig4 #d74 ,the use of old and exhausted leaves can be detected by a determination of the percentage of soluble matter dissolved by boiling water from a given weight of tea4 ,this on evaporation to dryness should be #bh to #cj per cent4 of the total weight of the original tea4 ,the presence of clay1 iron dust or other forms of dust is detected by igniting a given amount of tea and determining the amount of ash4 ,this should be only about six per cent4 ,in black tea1 the leaves are dried in the sun1 rolled and allowed to become soft and to ferment4 ,during this process1 some of the tannin appears to be converted into less soluble forms4 ,the leaves are afterwards sun-dried1 and these 8fired0 in a furnace4 ,green tea leaves are dried in the fresh condition over wood fires4 ,indian teas have more 8body0 and astringency than ,china teas4 ,the smallest and topmost leaves of the tea plant give the finest sort of tea 7,orange ,pekoe72 next to this comes ,pekoe2 the next largest leaves producing ,souchong2 after these ,congou2 while the coarser leaves nearer the base used to yield ,bohea1 which is now seldom seen4 ,tea consists of three important constituents--volatile oil1 theine or caffeine1 and tannin--and soluble and insoluble extractive matters4 ,the amount of caffeine varies from #b to #d per cent4 tannin #aj to #ab volatile oil is about #ab 7#a7 ,volatile ,oil gives the aroma and flavour to each particular tea4 ,it is this which causes the headache1 trembling1 wakefulness1 and restlessness1 occasionally produced by tea1 especially by green tea4 ,illustration3 ,,leaves ,,of 7a7 ,,elder4 7b7 ,,tea4 7c7 ,,tea4 7d7 ,,sloe4 7e7 ,,elder4 ,,fig4 #d4 7#b7 ,theine or caffeine1 is an alkaloidal crystalline principle4 ,its composition is represented by the formula ,c,h,n,o1 ,h,o4 ,ceylon tea1 broken leaf contains #djc per cent41 ,assam 7,indian7 tea1 broken leaf #djb per cent41 while ,chinese teas contain from #bhi 7,moyune ,gunpowder7 to #cgd 7,moning1 black leaf7 per cent4 of caffeine 7,allen74 ,theine is the most important constituent of tea and coffee4 ,it is a stimulant1 but unlike alcohol1 acts even more upon the central nervous system than upon the heart4 ,it removes the sense of fatigue1 and may1 especially if taken in excessive doses1 produce sleeplessness4 ,its stimulant action on the heart is followed by increased flow of urine1 and it thus helps in the removal of waste products from the system4 ,the effect on the tissue-changes of the body is somewhat doubtful4 ,it has been stated to arrest or diminish the waste1 i4e41 the metabolism1 constantly going on in the system1 and so diminish the amount of food required to repair this waste4 ,this is highly improbable2 we cannot conceive the likelihood of the development of energy without a corresponding expenditure of material1 and that is what would be the case if theine increased the activity of various organs while retarding their waste4 ,the experiments of ,conty and ,guimars on the action of coffee show that this 7and tea has the same essential constituent7 does not diminish tissue waste4 ,it does not prolong life in starvation1 though it may lessen the feeling of hunger4 ,hence tea and coffee1 which owe their value mainly to the caffeine or theine contained in them1 are in no sense foods4 7#c7 ,the amount of ,tannin varies from #abca in ,ceylon tea 7broken leaf1 ,pekoe7 to #aagf in ,moning1 black leaf1 and #ii per cent4 in ,natal ,pekoe ,souchong 7,allen74 ,the difference in tannin between ,chinese and ,indian teas is not therefore so great as is usually supposed4 ,tannin is a powerful astringent1 and possesses a bitter styptic taste1 and a constipating effect on the bowels4 ,its amount is increased by long 8brewing10 as is shown by the following results 7,hale ,white73-- ,three ,minutes' ,fifteen ,minutes' ,infusion4 ,infusion4 ,finest ,assam #aacj per cent4 #aggc per cent4 ,china #ggg #gig ,common ,congou #icg #aaae ,the ,mode of ,preparation of ,tea is important4 ,it is clear that the percentage of tannin to weight of leaf used in making the infusion increases with the protraction of the infusion4 ,on the other hand caffeine is so soluble that it is nearly completely dissolved as soon as infusion has begun4 ,dittmann found that five minutes infusion of ,indian tea extracted #cfc and ten minutes infusion #cgc per cent4 of caffeine4 ,the ,chinese put the tea leaves in a cup1 and having poured boiling water on them1 drink the resulting infusion after a very short time1 without adding anything4 ,the ,russians drink the infusion with a squeeze of lemon1 and with or without sugar4 ,we add cream or milk and generally sugar1 and so render it more nutritious1 though the delicate flavour is veiled4 ,the ,chinese plan of infusion for a short time is the best1 as it ensures the extraction of the aromatic and stimulant principles of the tea with only a proportion of the tannin4 ,in making tea it is important to use a tea-pot which is quite dry1 in order to avoid mustiness2 to pour a small quantity of boiling water into the tea-pot and then out again1 so that the infusion may be made at the temperature of boiling water2 and to use water which has only freshly come to the boil1 and so has not been rendered flat1 and not to infuse longer than five minutes4 ,for persons of weak digestion1 the best kind of tea is that obtained by pouring boiling water on the leaves1 and then immediately pouring the resulting infusion into another hot tea-pot4 ,in all cases where tea has to be kept a considerable time1 it should be poured into a second tea-pot1 the leaves being left behind4 ,indigestion is not an uncommon consequence of tea-drinking2 caused by the excess of tannin in the tea1 by the other constituents of the tea1 or more commonly by the practice of drinking tea in small sips1 with bread and butter4 ,the tea infusion usurps the place of the saliva1 the secretion of saliva remaining partially in abeyance4 ,the presence of tannin in tea renders it an undesirable part of a substantial meal4 ,tannin coagulates albumin1 and retards its solution by the digestive juices4 ,hence 8high teas0 and 8tea-dinners10 unless the tea is very weak1 are objectionable4 ,the practice of drinking tea with every meal is inexcusable4 ,for quenching thirst during active exercise1 and rendering possible prolonged exertions1 tea is unsurpassed4 ,,coffee4 ,coffee is the seed of the berry of the ,caffea ,arabica4 ,each berry contains two seeds1 or beans as they are sometimes incorrectly called4 ,the coffee is prepared by roasting the seeds until they assume a reddish-brown colour1 in which process they lose #ae per cent4 in weight and gain #cj per cent4 in bulk4 ,during the process of roasting1 a volatile oil having a powerful aromatic smell is developed4 ,this is not produced in such large quantities from fresh seeds2 the best time for roasting varying1 however1 for different varieties of coffee4 ,the amount of ,volatile ,oil in coffee is much less than in tea4 ,as it is elicited during the process of roasting1 this should be done with nicety and care4 ,it is effected in an iron cylinder made to revolve over a fire4 ,after the roasting1 the sooner the seeds are ground the better the coffee4 ,when it cannot be immediately used1 it should be kept in closed canisters1 and not in paper or open jars4 ,in addition to the volatile oil1 which is contained in roasted coffee in the proportion of about #a part in #ej1jjj1 coffee contains caffeine1 of which there is #cd to #a per cent41 and an astringent acid1 called caffeo-tannic or caffeic acid1 which differs from ordinary tannin in that it does not blacken a solution of an iron salt4 ,the chief adulteration of coffee is ,chicory1 which is thought by some to improve the coffee4 ,it is generally harmless1 though in some people it produces heartburn and diarrha4 ,chicory is prepared from the root of the wild endive4 ,it contains a volatile oil and a bitter principle1 but no caffeine4 ,it is1 therefore1 of no utility as a stimulant4 ,its presence can be detected by shaking a little of the suspected coffee on to the surface of the water in a wine-glassful of cold water4 ,coffee swims on the surface1 and gives little or no colouration to the water2 while chicory sinks1 and gives a deep red tint4 ,the aqueous extract of pure coffee 7extracted by boiling water7 is1 when evaporated1 #be to #cj per cent4 of the weight of the original decoction of coffee2 while that of chicory is #fe to #gj per cent42 and on this basis1 as well as on the fact that a filtered decoction of #aj grammes of coffee in #ajj c4c4 of distilled water1 cooled to #fj ,f4 has a specific gravity of #ajji1 while that of a similar solution of chicory would be #ajba1 the proportion of chicory in a mixture of coffee and chicory can be calculated4 ,the microscopical appearances of the two powders differ1 coffee showing hexagonal cells and no laticiferous vessels1 unlike chicory4 ,there is no law against selling mixed coffee and chicory1 if the fact that it is a mixture is stated2 and the proportion of the two unfortunately is not required to be stated4 ,as a pound of coffee costs five times as much as a pound of chicory1 it is obviously to the purchaser's advantage to make his own mixture in the proportions desired4 ,the ,preparation of ,coffee ought to be effected as in the case of tea--by making an infusion and not a decoction1 i4e4 by pouring boiling water on the coffee and allowing it to stand1 but not continuing the boiling4 ,continuance of boiling dissipates the delicate aroma4 ,inasmuch as coffee contains a much smaller percentage of theine than tea1 more of the former must be used to obtain a beverage equally refreshing with tea4 ,two ounces to a pint of boiling water are required4 ,the infusion thus made should be mixed with an equal part of boiled milk4 ,the coffee ought1 if possible1 to be freshly roasted4 ,the colour of coffee is no guide to its strength4 ,many of the black coffees1 especially 8,french coffee10 owe their colour to the caramel 7burnt sugar7 contained in the chicory mixed with them4 ,coffee has similar properties to tea1 with some minor differences4 7#a7 ,like tea1 it is restorative and sustaining in its action1 but seems to act more quickly than tea4 7#b7 ,unlike tea1 it does not tend to produce perspiration1 but rather a dry hot skin4 7#c7 ,with some it is decidedly laxative2 while tea1 especially if badly made1 has an opposite effect2 but this is not always true4 7#d7 ,it seems to have a greater power of antagonising the effects of alcohol than tea2 and is a valuable antidote1 after the action of an emetic1 in poisoning by opium or arsenic or alcohol4 ,as a rule1 coffee is not so prone to disorder the digestion as tea1 but this is not universally true1 and in some persons it always produces 8biliousness40 ,when taken in excess1 it produces--besides indigestion--palpitation1 restlessness1 irritability1 sleeplessness1 and a condition of general nervous prostration2 in fact1 similar symptoms to those produced by a prolonged over-indulgence in tea4 ,while the consumption of tea is rapidly on the increase1 that of coffee is steadily diminishing4 ,this is partly owing to the greater expense of coffee--a larger quantity being required to form a good beverage2 and partly to the greater difficulty in preparing good coffee4 ,,cocoa4 ,cocoa1 or more properly cacao1 is obtained from the seeds of the ,theobroma ,cacao--a native of the ,west ,indies1 ,mexico1 and the central parts of ,america4 ,its name ,theobroma was given it by ,linnus1 and means the 8food of gods40 ,the fruit is a large leathery capsule1 having nearly the form of a cucumber4 ,it contains from #be to #cj seeds1 each about the size of an almond4 ,before using1 these are roasted like coffee berries1 and a peculiar aroma is developed in this process as in the case of coffee4 ,the beans or seeds are then manufactured into three different products4 7#a7 ,they are simply deprived of their husks and broken to pieces2 this forms ,cocoa-,nibs4 7#b7 ,they are ground1 husk and all1 between hot rollers into a paste1 and mixed with starch and sugar2 this forms ,cocoa4 7#c7 ,they are shelled and then ground into a paste1 as in making cocoa2 sugar and some seasoning1 usually vanilla1 being subsequently thoroughly mixed2 this paste is ,chocolate4 ,the purest form is the cocoa-nibs4 ,when these are boiled in water1 a brownish decoction is formed1 with the fat as a scum at the top2 this may be removed1 and the decoction flavoured with milk and sugar4 ,in this form1 cocoa can be taken by invalids with weak digestion1 who would be nauseated by the fat of ordinary cocoa or chocolate4 ,the best cocoa is prepared as above2 but the lowest quality contains the husks of the beans1 with hardly any of the beans in it2 a somewhat better1 though still inferior sort1 is made from the smaller fragments of the nibs1 and a good deal of husk4 ,in some cases the cacao butter is removed during the process of preparation1 and starch or sugar substituted4 ,this form is less likely to disagree with dyspeptics than whole cocoa4 ,the action of the ,volatile ,oil 7not the cacao-butter7 developed during roasting1 is probably similar to that of tea and coffee1 though it is less in amount4 ,the bitterness is greater than that of coffee1 but the astringency less than in either tea or coffee4 ,the ,concrete ,oil1 or fat of cocoa1 forms about half its weight4 ,it is white1 and not apt to turn rancid1 and possesses an agreeable flavour4 ,cocoa also contains a certain amount of starch and cellulose4 ,theobromine is a white crystalline alkaloid1 the exact analogue of caffeine4 ,the latter1 in fact1 is methyl-theobromine--that is1 theobromine plus the theoretical group ,,ch4 ,theobromine possesses similar properties to caffeine4 ,it amounts to #a4e to #b per cent4 of the whole bean4 ,the ordinary preparations of cocoa differ considerably in composition as may be seen from the following table of per centage composition 7,ewell74 ,in each instance other nitrogenous and non-nitrogenous constituents go to make up the total #ajj3 ,,fat4 ,,fibre4,,cane- ,,ash4 ,,added ,,sugar4 ,,starch4 ,fry's ,cocoa ,extract #cji #ci #db ,none4 ,schweitzer's ,cocoatina #caa #cg #fc ,do4 ,rowntree's ,cocoa ,extract #bgf #dd #he ,do4 ,van ,houten's ,cocoa #bih #dd #hf ,do4 ,epps's ,prepared ,cocoa #bei #ae #bf #ca ,much arrowroot4 ,some of the preparations of cocoa 7e4g4 ,van ,houten's7 have added to them alkaline salts to increase their solubility4 ,cocoa is not such a valuable food as might appear from the large amount of fat in it1 because only moderate quantities of this can be taken without deranging digestion4 ,in ,vi-,cocoa a certain amount of kola is added1 which contains a considerable proportion of caffeine4 ,the addition of such a drug to a beverage is distinctly to be deprecated4 ,minor ,stimulants4--,beverages containing theine1 or some analogous principle1 appear to be employed in most countries4 ,in moderate doses1 they may assist the assimilation of other foods1 but their main influence is on the nervous system4 ,theine-containing substances may be described as both sedative and exciting4 ,they are sedative1 in that they allay nervous irritability1 and tend to 8take the edge off0 the disturbance caused by outward circumstances2 and they are exciting1 inasmuch as they are known to form an admirable antidote to the stupefying effects of opium or alcohol4 ,the wakefulness from tea is an instance of the same thing1 while the allaying of sensations of cold and hunger by a cup of tea is an instance of the sedative effect4 ,in ,brazil1 ,guarana 7from ,paullinia sorbilis7 is used as a drink2 it contains theine1 the quantity of which is twice as much as in good black tea1 and five times as much as in coffee4 ,like green tea1 a cup of guarana infusion is sometimes extremely valuable in nervous headaches4 ,in ,peru1 the natives use the leaves of the ,coca plant 7,erythroxylon coca71 which must be carefully distinguished from cocoa4 ,it is chewed somewhat in the same way as the betel-nut4 ,it contains two alkaloids--cocaine and hygrine1 as well as tannin4 ,in its stimulant action it resembles tea and coffee4 ,the active principle of this plant1 ,cocaine1 is a valuable local ansthetic4 ,internally it has been taken as a stimulant and restorative4 ,various wines containing ,coca1 with vaunted restorative powers1 are advertised4 ,they are mischievous when taken frequently4 ,nature's remedy for fatigue1 whether mental or body1 is rest and recreation4 ,stimulants of this class1 even though they enable work to be continued for awhile1 eventually increase the exhaustion for which they are taken4 ,the ,kola-nut is used in some parts of ,western ,africa as a stimulant4 ,it is about the size of a pigeon's egg1 and has a bitter taste4 ,the natives of ,guinea generally take a piece of the seeds before each meal1 and sometimes nibble it throughout the day4 ,kava is prepared from the root of a kind of pepper4 ,the natives of the ,fiji islands commonly indulge in it4 ,its effects resemble those of coffee4 ,in large doses1 it destroys the power of walking1 and may possibly produce impairment of vision4 ,the leaves of the ,ilex ,paraguayense1 ,ilex ,gongorrha1 and ,ilex ,theezans are made into the beverage commonly known as ,paraguay tea or mat4 ,the leaves of the ,hydrangea ,thunbergii are made into a beverage1 which is designated in ,japan 8the tea of heaven40 ,among certain nations of ,asia1 the ,betel-nut 7from a palm called ,areca ,catechu7 is chewed1 after mixing small fragments with pepper and quicklime1 and rolling in a palm leaf4 ,the saliva is tinged blood-red1 and a narcotic effect is said to be produced4 ,the dried flowering tops of the ,indian ,hemp 7,cannabis ,indica7 are smoked by the ,malays and others1 or made into a beverage1 called haschisch1 which produces a kind of intoxication1 in which murder has often been committed 7hence1 assassins equals haschascheens74 ,the ,kamtschatkans drink an infusion made from a fungus1 known as the ,fly ,agaric 7,amanita ,muscaria71 thus producing an intoxication similar to that from haschisch4 ,opium in small doses is a stimulant1 in large doses narcotic4 ,the crude drug is sometimes taken1 and less frequently the active principle1 ,morphia4 ,it is frequently smoked1 as well as taken internally4 ,it is to be feared that secret opium taking is considerably increasing4 ,the taking of morphia1 especially hypodermically1 is too common4 ,generally it has been first prescribed for neuralgia or some other complaint causing acute pain2 and the patient1 having experienced relief by its means1 is tempted to revert to the practice apart from medical advice4 ,such a line of action is most pernicious4 ,eventually both the physical and the moral nature of the victim are shattered by it2 and to break off this insidious habit1 when once thoroughly established1 is most difficult4 ,tobacco may be conveniently mentioned here1 though its usual effects are certainly not stimulant4 ,it is smoked1 chewed1 or taken as snuff2 when indulged in to excess it produces serious depression of the heart's action1 with frequent intermittence4 ,in moderate doses it is sedative as well as slightly laxative4 ,prolonged indulgence in tobacco has produced many cases of incomplete blindness 7tobacco amblyopia71 in some cases it comes on with much smaller doses1 and in all cases is only curable by ceasing to smoke4 ,there is no sufficient ground for the statement that cigarette smoking is more injurious than smoking tobacco in a pipe or cigar1 unless in the former case the smoke is inhaled into the lungs4 ,the practice of smoking is injurious to growing boys1 and should be strictly forbidden4 ,other ,drugs are now not infrequently taken1 apart from medical advice4 ,of these the most commonly used are ,antipyrin and ,phenacetin1 for headaches4 ,their use is injurious1 and should not be entertained as a frequent practice4 ,sleeplessness frequently leads to the practice of taking chloral or sulphonal1 or occasionally the inhalation of chloroform to induce sleep4 7,see also page #bei74 ,remedies to induce sleep should never be taken except under immediate medical advice4 ,they are only justifiable in extreme conditions1 and if frequently taken tend to aggravate the conditions for which they are given4 ,,chapter ,,viii4 ,,fermented ,,drinks4 ,properties of ,alcohol4--,when a saccharine solution is subjected to the influence of warmth and moisture1 and exposed to the air1 it rapidly undergoes a process of fermentation4 ,the most favourable temperature is about #gj ,fahr4 ,the ferment or agent exciting the change in the sugar is derived from the atmosphere2 it is a minute fungus 7torula cerevisi71 the spores of which are constantly floating in the air4 ,when once fermentation has started1 exposure in the air is no longer necessary2 the process continues in closed vessels4 ,the essential change occurring in the vinous fermentation is that grape sugar 7,c,h,o1,h,o7 becomes split up into alcohol 7,c,h,,oh7 and carbonic acid 7,,co74 ,thus-- ,c,h,o ,c,h,o ,two of alcohol ,c,c,h,o ,,co ,,co ,two of carbonic acid4 ,there are other fermentations allied to the vinous4 ,thus the ,acetous fermentation results in the conversion of alcohol into vinegar1 as in the souring of beer or wine4 ,the ,lactic fermentation leads to the conversion of milk-sugar into lactic acid1 with consequent souring of the milk4 ,alcohol1 or more correctly ethylic alcohol1 is a colourless liquid1 having a pleasant vinous odour1 and evaporating rapidly on exposure to air4 ,it burns with a bluish sootless flame1 and is a capital solvent for resins and other substances4 ,rectified spirit is absolute alcohol mixed with #af per cent4 of water4 ,proof-spirit is a mixture of #dbg per cent4 by volume of absolute alcohol1 and #egc per cent4 of water4 ,thus the ratio of alcohol to proof-spirit being as #a3 #agf1 the amount of alcohol in any liquid being given1 the amount of proof-spirit can readily be calculated4 ,the fermented drinks containing alcohol may be classed as 7#a7 malt liquors1 7#b7 wines1 and 7#c7 distilled spirits4 ,the relative properties of these will be considered afterwards2 in the next two sections will be considered the effects of diluted alcohol in whatever form it is taken4 ,effects of ,moderate ,doses of ,alcohol on the ,system4--,in studying the physiological effects of alcohol1 one has to guard against the fallacy that these are the same1 only differing in degree1 whatever the dose may be4 ,the effects of large doses of alcohol are almost exactly the reverse of those produced by small doses4 ,it will be necessary to define1 therefore1 what we mean by a moderate dose4 ,by a moderate dose1 we understand the amount of alcohol which can be taken without any alcohol being eliminated in the urine4 ,dr4 ,anstie found that #a ounces1 that is three tablespoonsful1 of absolute alcohol1 taken in twenty-four hours1 caused its appearance in the urine2 and ,dr4 ,parkes and ,count ,wollowicz obtained almost precisely the same result4 ,anything below some quantity between #a and #a fluid ounces per day can be disposed of in the system1 and is probably oxidised like ordinary foods4 ,the amount of alcohol1 in the form of alcoholic beverages1 corresponding to this maximum dose of absolute alcohol is approximately as follows3-- ,one imperial pint 7#bj fluid ounces7 of bottled beer 7#e per cent4 of alcohol74 ,one tumblerful 7#aj 7of claret1 hock1 and other weaker wines 7#aj 74 #b glasses 7#e 7of port1 sherry1 and other strong wines 7#bj 74 ,one glass 7#b 7of brandy or whiskey 7#ej 74 ,it will be understood1 therefore1 that in describing the effects of a moderate amount of alcohol on the system1 an amount below #a ounces of absolute alcohol per day is meant1 freely diluted1 and taken as a rule with meals4 #a4 ,effect on the ,stomach4--,in very small quantities1 alcohol seems to stimulate digestion in the same way as mustard4 ,but like all other artificial helps to digestion1 it is best avoided in the healthy condition4 #b4 ,the ,effect on the ,liver is similar to that on the stomach--a temporary redness and congestion being produced2 this effect soon disappearing if the dose is small and well diluted4 ,but in all cases where there is a tendency to biliousness1 even small doses of alcohol are injurious4 #c4 ,the ,effect on the ,heart and ,blood-,vessels is first to increase the force of the heart's action and the rapidity of the pulse4 ,the stimulation of the heart is rapidly followed by a universal dilatation of the small arteries of the body1 which diminishes the blood-pressure4 ,parkes and ,wollowicz found that the daily administration of from #a to #g ounces of rectified spirit raised the pulse rate by ten beats per minute1 as compared with other periods2 and that this effect was followed by a period of depression in which the beat was both slower and feebler than usual4 #d4 ,the ,effect on the ,nervous ,system varies4 ,in persons unaccustomed to its effects1 even small doses dull the power of thought and the rapidity of perception1 owing to the paralyzing effect which it exerts on nerve cells4 ,in most cases1 however1 it at first produces increased rapidity of thought and excites the imagination1 though even here it makes it more difficult to keep to one train of thought4 ,this is clearly owing to the more rapid circulation of blood through the brain4 ,dr4 ,e4 ,smith's experiments show that it diminishes the acuteness of the senses4 ,its influence even in dietetic doses1 on the capacity for mental work1 is slightly to diminish it4 #e4 ,the ,effect on the ,muscular ,system is never beneficial4 ,even when only small quantities are taken1 the power of controlling delicate movements is slightly diminished4 ,for persons engaged in laborious occupations1 a small quantity does not produce much apparent effect1 but where the quantity exceeds two fluid ounces per day the capacity for strong and sustained muscular work is manifestly lessened 7,parkes74 ,this effect is probably due partly to the dulling of the nervous system1 rendering the muscles less amenable to the will1 and partly to the over-excitation of the heart causing palpitation and breathlessness4 #f4 ,the ,effect on ,metabolism is to diminish it1 thus favouring the deposit of fat in the tissues4 ,it acts as a poison to the protoplasm of the cells of the body1 diminishing their power to break down the floating nutriment1 especially fat and carbohydrate4 ,the ,effect on the ,temperature is to lower it2 but unless the dose is excessive1 this effect is hardly appreciable4 ,the resistance to excessive cold is diminished by even moderate doses of alcohol1 still more by large doses4 ,in the ,arctic regions1 this has been abundantly proved4 ,this effect is produced1 notwithstanding the fact that alcohol becomes oxidised in the system4 ,the dilatation of the surface blood vessels leads to a greater loss of heat than that produced by the oxidation of the alcohol4 ,,effects ,,of ,,immoderate ,,doses ,,of ,,alcohol ,,on ,,the ,,system4--,bearing in mind the definition given of a moderate dose1 one is bound to admit that a large number of individuals exceed this amount daily1 apparently without any very serious results4 ,the system becomes habituated to large doses1 and if the occupation is a laborious one1 they may in part be oxidised in the system4 ,such1 however1 are exceptional cases4 ,in the majority of cases evil results are by no means confined to those who indulge in very large quantities of alcohol at varying intervals4 ,in fact these very often escape comparatively free1 while others who never take a quantity sufficient to incapacitate them for their work1 are sowing the seeds of chronic and oft incurable disease4 ,the labourer who has a drinking bout at intervals is thoroughly nauseated2 and the condition of liver and stomach induced1 enforces abstinence on him for a time sufficient to bring his organs back to a normal condition2 while the city merchant who indulges more moderately1 but whose organs are almost continuously impregnated with alcohol1 becomes gouty and prematurely old4 ,the ,stomach may become acutely inflamed1 when a large dose of alcohol is taken4 ,the chronic irritation of alcohol1 especially when taken apart from meals1 causes atrophy of the walls of the stomach1 and a change analogous to that in the liver4 ,the ,liver1 when alcohol is daily taken immoderately1 becomes seriously diseased4 ,in some cases it becomes large and fatty2 in others the chronic irritation excites an overgrowth of fibrous tissue between the lobules of the liver1 which1 gradually shrinking1 squeezes the liver cells and causes them to atrophy1 at the same time obstructing the small branches of the portal vein in the substance of the liver4 ,the consequence of this obstruction to the flow of blood through the liver is that all the organs from which the portal vein brings blood become overloaded with blood1 and vomiting of blood and dropsy of the abdomen occur at a later period4 ,the ,lungs are irritated to a less extent by alcohol in large doses4 ,the tendency to chronic bronchitis is increased1 followed by emphysema1 and sometimes an overgrowth of fibrous tissue 7cirrhosis7 like that in the liver occurs4 ,the ,heart and ,blood-vessels tend to become diseased1 owing largely to the gouty condition of system developed4 ,the powers of ,metabolism are diminished4 ,corpulence is1 consequently1 a common result of alcoholism4 ,there may also be fatty deposit in the internal organs1 such as the heart4 ,this must not1 however1 be confounded with a much more serious condition1 fatty degeneration of the heart1 in which the substance of the muscular fibres becomes partially converted into fat1 and which also is sometimes due to alcoholism4 ,the ,nervous ,system is more prone to suffer in chronic alcoholism than any other part of the body1 except perhaps the liver4 ,the first effect of a large dose of alcohol is to stimulate the nervous system1 as already described4 ,this is followed by a dulling of the nervous faculties1 which comes on rapidly in proportion to the amount taken4 ,the phenomena of intoxication are unhappily too familiar to require description1 mental incoherence and muscular incoordination 7lack of control over the muscles7 being the most prominent features4 ,when the dose of alcohol is still larger1 a condition of profound unconsciousness is produced 7coma71 which may be difficult to distinguish from other forms of unconsciousness4 ,delirium ,tremens is another nervous condition1 which may rarely follow a single debauch1 but much more commonly affects the chronic toper4 ,in some cases the immediate exciting cause is a mental shock1 or lack of food1 or a surgical injury4 ,alcoholic subjects suffering from any acute disease are liable to this form of delirium1 and their chance of recovery is greatly diminished4 ,insanity of a more prolonged character than that characterising delirium tremens is an occasional result of alcoholism4 ,besides the nervous diseases already named1 a chronic thickening of the membranes covering the brain and spinal cord1 gradually progressing and finally fatal1 is often the consequence of prolonged alcoholic indulgence4 ,various ,degenerative ,diseases are produced by alcohol4 ,it has been well called by ,dickinson the very 8genius of degeneration40 ,such degenerations are by no means confined to the intemperate2 they are seen in those who are of what would usually be considered moderate habits4 ,the stomach1 liver1 lungs1 and probably the kidneys1 are the main organs to suffer in this way4 ,it is probable that the effect on the kidneys only occurs when a gouty condition is developed4 ,in all these cases there is an overgrowth of fibrous tissue1 with atrophy of the proper gland structures4 ,gout is the common nemesis of those indulging in alcoholic beverages1 more especially wine and beer1 due to the excessive formation or retention of urate of soda in the body4 ,this produces inflammation of the joints1 and other evils--among them the gouty kidney1 named above1 which is always ultimately fatal4 ,rigid arteries are likewise commonly due to alcoholism and gout4 ,if one of these bursts in the brain1 apoplexy results4 ,longevity is diminished by immoderate indulgence in alcohol4 ,the statistics of ,temperance ,insurance ,societies1 show much better results among teetotalers than among moderate drinkers4 ,it is only fair to add that although the latter are supposed to consist of moderate drinkers--and particular enquiries are always made on this point before insurance--it is probable that a large proportion of them exceed #a ounces of alcohol per day4 ,making due allowance for this fact1 the statistics show a great superiority in the expectation of life of teetotalers4 ,factors ,modifying the ,effects of ,alcohol4--#a4 ,age and ,sex4--,until adult life is reached1 total abstinence from alcohol should be enforced4 ,the delicate nervous system of children is easily disturbed by it1 and it appears in some measure to retard growth4 ,another argument against giving alcohol before adult age is reached1 is still more important4 ,it is at this period of life that habits are chiefly formed1 and a craving for alcohol may be insidiously produced1 destined to have most baneful results4 ,old people1 if ordered spirits for medical reasons1 should drink them well diluted4 ,women are much more easily affected by alcohol than men1 and if they acquire the habit of excess1 the hope of reformation is even less than with men4 #b4 ,exercise has a most important influence in modifying the effects of alcohol4 ,those of sedentary occupations and living in towns1 cannot oxidise as much as those engaged in active out-door work1 and are consequently much more prone to suffer4 ,a game-keeper in the ,scotch ,highlands may possibly live to a good old age1 notwithstanding the fact that he consumes an amount of whiskey that would have sent a sedentary man to his grave in the course of a few years4 #c4 ,the ,condition of the ,stomach has also great influence4 ,when the stomach is empty1 alcohol produces at once a powerful reflex stimulation of the heart1 and becomes quickly absorbed into the circulation4 ,thus intoxication may be produced by a quantity that would have had little effect if taken with a meal4 #d4 ,the ,state of ,concentration or ,dilution modifies greatly the action of alcohol1 the local action on the stomach and the reflex stimulation being much greater than when it is concentrated1 and injurious effects being much more likely to occur4 #e4 ,cold and ,heat modify the action of alcohol4 ,a smaller quantity of hot spirits and water will intoxicate than of cold2 the heat stimulating the heart1 and so making the absorption of the alcohol more rapid4 ,a glass of hot spirits and water will often cause sleep1 by drawing the blood towards the abdominal organs4 ,the fact that persons1 who have been drinking spirits in a warm room1 on going out into the cold air become suddenly intoxicated1 seems opposed to what has been already said4 ,but probably this is due to the cold causing contraction of the arteries of the skin1 and so driving more of the blood loaded with alcohol to the internal organs and the brain 7,brunton74 #f4 ,mental ,occupation has some influence in modifying the effects of alcohol4 ,topers have found that if they try to converse during their debauch--the conversation implying increased functional activity of the brain1 and therefore a freer circulation of blood in it--intoxication occurs much more readily1 than when the mind is not active4 #g4 ,disease modifies greatly the effects of alcohol4 ,in some diseases1 as in inflammation of the lungs and in fevers1 it can be given in large quantities without producing intoxication2 and in these conditions it lowers the temperature4 ,in other diseases1 especially gout and kidney disease1 its use is nearly always followed by bad results4 ,the ,advisability of ,alcohol as an ,article of ,diet in ,health4--,in dealing with this difficult point1 two sets of facts require consideration1 those obtained as the result of ,physiological observations 7see page #ef71 and those which are the result of ,experience4 ,there can be no doubt that the former are much more reliable than the latter4 ,experience is very prone to give fallacious results1 especially when questions of appetite are concerned4 ,in making a trial of abstinence1 the mistake has been commonly made of only prolonging the investigation for a few weeks1 and then comparing results4 ,such a method is1 however1 very unfair1 and is certain to lead to an unreliable conclusion4 ,the records of experience under certain conditions have1 however1 been so extensive1 as to lead to trustworthy results4 ,it has been abundantly proved that prolonged muscular work is best undergone during total abstinence from alcohol2 and that the extremes of heat and cold and the exposure and exertions of marching armies1 are best borne under similar conditions4 ,the artificial character of town life is commonly adduced as an argument for the moderate use of alcohol4 ,in the case of healthy workers1 this does not hold good2 many of our hardest workers and thinkers take no alcohol4 ,the universality of the habit of taking stimulants is a curious argument on the same side1 though if the habit be bad1 this can be no more reason for continuing it than can the prevalence of vice be an excuse for indulgence in it4 ,the two chief physiological points bearing on the advisability of alcohol as a part of one's daily diet are--its food properties1 and its effect on the appetite and digestion4 ,it has been already stated that a quantity of alcohol under #a or #a ounces may become oxidised in the system1 and may thus form a source of heat4 ,but in all probability1 although it may be regarded as a food1 it is a most inconvenient one1 inasmuch as it diminishes the oxidation of other foods4 ,it has been aptly compared in this respect to sulphur1 which is an oxidisable material1 but which1 when it is burnt in a chimney1 in which the soot is on fire1 will put an end to the combustion of the latter4 ,its value as a food1 under normal conditions1 is practically nil4 ,its ,effect on the ,digestive ,organs is three-fold4 7a7 ,the contact of alcohol with the mucous membrane of the mouth and stomach1 acts as a reflex nervous stimulus1 which in moderation excites an increased flow of gastric juice4 7b7 ,it also increases the activity of the movements of the stomach4 ,in cases of weak digestion1 therefore1 small doses of alcohol may1 at times1 be useful4 7c7 ,the effect of alcohol on the food taken varies with its degree of dilution4 ,concentrated alcohol coagulates albumin1 and so stops digestion2 largely diluted alcohol has no such effect4 ,the late ,dr4 ,parkes1 the greatest authority on the dietetic use of alcohol1 has summarised the argument as to the dietetic use of alcohol as follows3-- 8,but what1 now1 should be the conclusion as to the use of alcohol in health after growth is completed8 ,admitting the impossibility of proving a small quantity to be hurtful1 and at the same time acknowledging the dangers of excess1 there arises an argument which seems to me somewhat in favour of total abstinence4 ,no man can say when he has passed the boundary which divides safety from harm2 he may call himself temperate1 and yet may be daily taking a little more than his system can bear1 and be gradually causing some tissue to undergo slow degeneration4 ,he may be safe1 but he may be on the verge of danger4 8,this uncertainty1 coupled with the difficulty at present of saying what dietetic advantage is gained by using alcohol1 seems to me rather to turn the scale in favour of total abstinence instead of moderate drinking4 ,but if any one honestly tries1 and finds he is better in health for a little alcohol1 let him take it1 but he should keep within the boundary line1 viz41 that #a ounces of pure or absolute alcohol in twenty-four hours form the limit of moderation4 ,i do not then think he can do himself any harm40 ,the ,varieties of ,fermented ,drinks4--,the three chief kinds of alcoholic beverages are malt liquors1 wines1 and ardent spirits4 ,in addition1 we may mention cider and perry1 which are the fermented juices of apples and pears respectively2 and koumiss1 which the ,tartars prepare by fermenting mare's milk1 though it may also be made from the milk of other animals4 ,all ,beers1 ,ales1 and ,porters are prepared from malt1 which is the germinating grain of barley4 ,the fermentation of the sugar in the barley produces alcohol1 the amount of which varies in different cases4 ,in ,pilsener beer it is #c per cent4 of absolute alcohol2 in stout and porter #e to #f per cent4 ,the hop which is added to the fermenting barley1 gives to beer its characteristic bitterness4 ,london ,porter is coloured with black or roasted malt2 stout is only a stronger form of porter4 ,bottled ales are generally stronger than those on draught1 and being slightly effervescent1 may agree better4 ,the effect of alcohol in beer is modified by the hops1 which help in producing drowsiness4 ,beer has a marked tendency to produce obesity1 more so than any other alcoholic beverage4 ,its influence in the production of gout is also very great4 ,substitutes for ,malt have been largely used4 ,thus by the action of sulphuric acid on starch1 an artificial form of sugar is produced1 which is largely used in place of malt for making beer4 ,many recent cases of poisoning by arsenic have been traced to the use of impure sulphuric acid in manufacturing this form of sugar4 ,the detection of arsenic in organic liquids requires great care1 as so many compounds of arsenic are volatile1 especially in the presence of chlorides1 as in beer4 ,to detect arsenic in beer a pint of the beer is evaporated to dryness1 and treated with #bj c4c4 of strong sulphuric acid1 heated1 and #bj c4c4 of strong nitric acid added drop by drop4 ,violent action occurs3 if possible #bj c4c4 more of nitric acid are worked in4 ,transfer the liquid to a small flask1 and expel the nitric acid by boiling4 ,by this means all chlorine is expelled1 the arsenic is oxidised and the organic matter destroyed4 ,,sh gas is now passed into the acid liquid for some hours1 the precipitated sulphur and any sulphide filtered off and extracted with ammonia1 which dissolves any sulphide of arsenic4 ,the liquid so obtained is subjected to ,marsh's test4 7,see page #baf47 ,in the making of beer from malt1 the first stage is to malt the barley1 i4e4 leave it spread on floors for ten days after soaking4 ,this allows germination to take place1 in which process the insoluble starch is converted into starch1 dextrine1 maltose and glucose4 ,after the dried malt has been screened to break off the sproutings1 the brewer places it in the mash-tub1 with water1 at a temperature of #afj ,f4 ,this completes the transformation of the starch into glucose4 ,the wort is now boiled to stop the process1 and the albumin from the grain is thus coagulated4 ,hops are added at this stage4 ,the boiled liquid is passed into shallow vessels and cooled4 ,the proper temperature for 8top0 yeast is #fj ,f41 for 8bottom10 or ,bavarian yeast1 a much lower temperature is desirable4 ,when the desired temperature is reached1 the liquid is run into the fermenting tun along with yeast4 ,the varieties of beer are due in part to the degree of completeness of fermentation of sugar allowed4 ,if too complete1 the beer does not keep well4 ,wines are produced by the fermentation of the juice of the grape4 ,the wine produced may be bottled before or after fermentation is complete2 in the former case1 an effervescing wine is produced1 such as the sparkling wines of the ,rhine and the ,moselle1 or champagne4 ,when the sugar is nearly all fermented a dry wine is obtained1 of which ,bordeaux and ,burgundy1 ,hock and ,moselle1 are examples4 ,the difference in colour between red and white wines is produced by allowing the juice in the former to ferment in contact with the skins1 from which the colouring matter is extracted by the alcohol4 ,both red and white wines may be obtained from either red or white grapes4 ,from the skins also are extracted a salt of iron1 and a peculiar form of tannin4 ,tartaric and acetic acids1 and tartrate of potass1 are present in varying quantities in wines2 in old wines the tartrate separates as bitartrate of potass1 forming with tannin and colouring matter the 8crust0 of port and other wines4 ,the 8bouquet0 of wines is due chiefly to certain volatile bodies1 such as pelargonic ether4 ,the proportion of alcohol in wines varies from #f to #ad per cent4 ,as fermentation is stopped by the presence of #ad per cent4 of alcohol1 any larger amount of alcohol than this must have been added to the wine4 ,wine1 like beer1 has a strong tendency to produce gout1 especially the sweet and strong wines4 ,it has not1 however1 the same tendency to induce obesity4 ,spirits differ from the two last groups1 to begin with1 in the amount of alcohol they contain4 ,thus1 ,english beers contain from #c to #f per cent41 ,german beers from #b to #e per cent41 wines from #h to #bj1 and all kinds of spirits from #cg to #eh per cent4 of alcohol4 ,they differ in the absence of the bitter principle of beer and much of the salts and sugar and ether of wines4 ,they are all prepared by the distillation of some previously fermented liquor4 ,brandy ought to be made by the distillation of wine2 and then contains1 besides alcohol and water1 small quantities of acetic1 nanthic1 butylic1 and valerianic ethers4 ,but much of the brandy sold is simply made from potato spirit1 by the addition of acetic ether1 burnt sugar1 etc4 ,the starch of potatoes is converted into dextrin and dextrose by dilute acids1 and then fermentation allowed4 ,by the use of patent stills1 all bye-products can be separated1 a fairly pure alcohol known as silent spirit being produced4 ,this is largely employed in manufacturing spirits and in fortifying wines4 ,whiskey is prepared from malted barley1 or from a mixture of grains1 to which a sufficiency of malt to convert their starch into sugar has been added4 ,in grain whiskey the distillation is effected by steam in a patent 7,coffey's7 still1 which separates most of the bye-products 7fusel oil1 etc47 from the spirit4 ,in malt whiskey1 distilled in the old-fashioned pot-still1 these bye-products are not separated4 ,the improvement of whiskey effected by keeping is not due 7,bell7 to the diminution of fusel oil4 ,such a diminution does not occur4 ,the percentage of alcohol diminishes by keeping1 #f to #h per cent4 proof spirit being lost by five years' storage in wood4 8,fusel oil0 is a mixture of alcohols of higher boiling point than ethylic alcohol 7amylic1 propylic1 etc474 ,even in a bad whiskey not more than #aaj per cent4 of fusel oil is present 7about one grain in a glassful74 ,experimentally no marked effects have been produced by fusel oil1 when it is less than #a per cent4 ,possibly the presence of furfurol1 of which there is a trace in malt whiskey1 which disappears on keeping1 may partially explain the disagreeable flavour of new whiskey4 ,but it is fairly clear that those who argue that it is bad whiskey and not good whiskey which does harm are speaking without knowledge4 ,it is not the quality but the quantity of whiskey which is responsible for so much moral and physical evil4 ,gin and ,hollands are obtained from barley1 and flavoured with juniper berries and other materials4 ,the oil of juniper stimulates the urinary excretion4 ,rum is obtained by the distillation of molasses1 and is usually kept for a long time in oak barrels4 ,it is said thus to acquire more astringent matters than other spirits contain4 ,the legal limits of dilution of whiskey1 brandy and rum is down to #be degrees under proof1 and of gin down to #ce degrees under proof4 7,for definition of proof spirit1 see page #ee74 ,the amount of alcohol in an alcoholic liquor is determined by distillation of #ajj c4c41 making up the distillate to #ajj c4c4 by the addition of distilled water1 and then taking the specific gravity of a portion of this liquid by the aid of the specific gravity bottle4 ,the percentage of alcohol corresponding to a given specific gravity is given in tables prepared for this purpose4 ,prolonged indulgence in spirits produces the various organic diseases already described1 and unless well diluted they are more harmful than beers or wines4 ,they differ from wines and beers in not tending to produce gout1 and from beer in not leading to obesity4 ,,chapter ,,ix4 ,,water4 ,uses of ,water4--,water is a prime necessity of life4 ,in its absence life can only exist in lowly organised beings1 and in them only in a dormant state4 ,from a hygienic point of view1 the uses of water are four-fold3--7#a7 ,it is an essential part of our food1 not only serving to build up the tissues of the body1 but also preserving the fluidity of the blood and aiding excretion of effete matters4 7#b7 ,it is necessary for personal cleanliness1 of which the importance can scarcely be exaggerated4 7#c7 ,in the household it is essential for cooking1 as well as for washing the house1 the linen1 and various utensils4 7#d7 ,by the community at large it is required for water-closets and sewers1 for public baths1 for cleansing the streets1 and for horses and other domestic animals1 as well as in many manufacturing processes4 ,it is obvious that the water to be used for domestic and general purposes1 need not be so pure as that for drinking purposes4 ,hence1 a double supply was proposed for ,london in #ahgh1 by the ,metropolitan ,board of ,works--a less pure river supply for general purposes1 and a deep chalk-well supply for drinking purposes4 ,the scheme1 however1 rightly fell through1 because of the expense of a double source of supply1 and the danger that the impure water would1 through carelessness or ignorance1 be often used for drinking purposes1 when it happened to be nearest at hand4 ,quantity of ,water ,required4--,the quantity of water required for all purposes has been variously stated by different authorities4 ,the quantity required for drinking purposes is found to bear a relation to the weight of the individual1 being nearly half an ounce for every pound weight1 or #a gills for every stone weight4 ,thus1 a man weighing #aej lbs4 would require #c-cd pints4 ,of this water1 about one-third is taken in the food2 the remainder1 averaging #b pints1 being required as drink4 ,if we add the water required for other purposes1 according to ,de ,chaumont1 #a gallon is required for drinking and cooking1 #b gallons 7not including a bath7 for personal cleanliness1 #c gallons for a share of utensil and house washing1 #c gallons for clothes washing2 and if a general bath be taken1 #c gallons more2 making a total of about #ab gallons1 to which #e gallons must be added if there is a water closet4 ,in hot summer weather the consumption is about #bj per cent4 above the average of the year2 and frost often increases the amount #cj--dj per cent4 above the average1 owing to the bursting of pipes1 or the loss from taps foolishly left open to prevent bursting4 ,water companies usually reckon #cj-fj gallons for each individual1 to allow for the water required for scavenging and manufactories and for waste4 ,in large houses and hotels where baths are freely used1 often as much as #gj gallons per head is used1 and in hospitals the amount averages from #fj to #ij gallons per head4 ,the following is ,parkes' estimate of the daily allowance for all purposes3-- ,,gallons ,,per ,,head ,,of ,,population4 ,domestic supply #ab ,general baths #d ,water-closets #f ,unavoidable waste #c ,total house supply #be ,municipal purposes #e ,trade purposes #e ,total #ce ,it has been proposed to put a water-meter to each house1 so that the rate may be in proportion to the amount of water used4 ,the plan is objectionable for two reasons3 #ast--,because it tends to restrict the necessary use of water for purposes of cleanliness4 ,a scant supply of water is always followed by uncleanliness of house and person1 with its consequent diseases2 at the same time closets may be imperfectly flushed1 and may become choked4 #bnd--,because of the primary expense of the meter1 and of its maintenance4 ,,sources ,,of ,,water ,,supply4--,all our drinking water is obtained in the first instance1 by a natural process of distillation on a large scale4 ,the sun is constantly causing evaporation from sea and land4 ,the vapour produced1 being condensed by a lower temperature1 returns to the earth as snow1 dew or rain4 ,all these natural products have been at times utilised as sources of drinking water4 #a4 ,dew has on rare occasions been utilised at sea by hanging out fleeces of wool at night and wringing them out in the morning4 ,a much better plan is-- #b4 ,the ,distillation of ,sea-water4 ,this can easily be managed now that steam power is so largely used4 ,it has even been employed on land1 when it was necessary temporarily to continue the use of water derived from an impure source4 ,the first part distilled should always be rejected1 as it is always impure4 ,distilled water is 8flat0 in taste1 owing to its containing no dissolved gases4 ,it can be arated by letting it drop a considerable distance from one cask into another1 through small openings in the upper one1 and by filtration through charcoal4 ,non-arated water is not easily absorbed into the circulation1 and occasionally causes illness4 #c4 ,the utility of ,melted ,snow and ,ice is obviously very limited4 ,moreover1 its use is not free from danger if the ice is derived from contaminated water4 ,outbreaks of enteric fever have been traced in the ,united ,states to the taking of ice obtained from impure water4 #d4 ,rain-water is a much more important source of water supply1 and after passing through the soil it constitutes the chief part of the water we drink4 ,the term1 however1 is properly restricted to the water collected immediately after its descent from roofs1 etc4 ,its purity depends on three conditions--the character of the air it passes through1 the cleanliness of and absence of lead from the channels through which it runs1 and the condition of the water-butts in which it is stored4 ,rain-water is soft2 in fact1 too soft to be pleasant to the palate4 ,in passing through the air1 it carries with it a certain proportion of its constituents2 in towns especially ammonia1 soot1 etc42 near the sea1 it generally contains some salt2 and being soft and having dissolved oxygen from the air1 it dissolves an appreciable amount of lead from roofs or gutters4 ,the ,rivers ,pollution ,commissioners found that out of eight samples of stored rain-water only one was fit to drink4 ,they came to the conclusion that rain-water1 collected from the roofs of houses and stored in underground tanks1 is 8often polluted to a dangerous extent by excrementitious matters1 and is rarely of sufficiently good quality to be used for domestic purposes with safety40 ,also1 that in ,great ,britain1 and more particularly in ,england1 we shall 8look in vain to the atmosphere for a supply of water pure enough for dietetic purposes40 ,the use of rain-water for drinking purposes is only justified in isolated country houses where no better source is available2 and under these circumstances the greatest care should be taken to prevent contamination with lead or organic impurities4 ,the amount of water falling on any impervious material obtainable from rain can easily be estimated1 if the amount of rainfall and the area of the receiving surface are known4 ,the average annual rainfall in this country is #cc inches 7see page #bcf74 ,we may assume the amount practically available to be #bj inches per annum1 and the area of the receiving surface #ejj square feet4 ,multiply the area by #add1 to bring it into square inches1 and this by the rainfall1 and the product gives the number of cubic inches of rain which fall on the receiving area in a year4 ,one cubic foot1 or #a1gbh cubic inches1 of water being equivalent to #fbc gallons1 the number of gallons of water can be easily calculated4 ,to calculate the receiving surface of the roof of a house1 do not take into account the slope of the roof1 but merely ascertain the area of the flat space actually covered by the roof4 ,this may be done roughly by calculating the area of all the rooms on the ground floor1 and allowing an additional amount for the space occupied by the walls4 ,it has been estimated that1 even if a rain-water supply for towns were desirable1 the amount collected from the roofs of houses would scarcely average two gallons per person daily--assuming the average rainfall to be #bj inches1 and that there was a roof area of #fj square feet for each individual4 ,the amount practically available from rain falling on different soils varies with their porosity and slope4 ,thus1 according to ,professor ,rankine1 the proportion of the total rainfall available is as follows3-- ,nearly the whole on steep surfaces of granite1 gneiss1 and slate2 ,from three to four-fifths on moorland hilly pastures2 ,from two-fifths to half on flat cultivated country2 and ,none on chalk4 ,by available rainfall is meant the amount remaining after allowing for percolation1 etc41 which can be stored in reservoirs4 #e4 ,upland ,surface ,water is the water collected in hilly districts1 as on moorlands1 at the head of a river4 ,by its utilisation for drinking purposes1 the sources of water for the river are interfered with1 and any water company or local authority using such a source is1 therefore1 required to run into the stream a quantity of water equal to a third of the available rainfall4 ,the limited and regular supply thus furnished to the stream is found to be advantageous for industrial purposes as its flow is equalised1 and the violence of floods mitigated4 ,in the utilization of upland surface water the water from the surrounding hills is collected at the bottom of a valley1 in an artificial1 strongly-constructed lake2 or in a natural lake1 as in ,loch ,katrine 7from which ,glasgow is now supplied74 ,upland surface water is nearly always soft4 ,its use is much more economical than that of hard water4 ,it may be brownish1 from the presence of peat1 but this is not objectionable1 so far as health is concerned4 ,its occasionally solvent action on lead is a more serious objection4 ,the population of many parts of ,yorkshire and ,lancashire have suffered severely from chronic lead poisoning1 due to the action of certain upland surface water on lead service pipes4 ,only the waters giving an acid reaction possess this plumbo-solvent power4 7,see also page #hb47 #f4 ,springs supply water which1 originally derived from rain-water1 has percolated through the soil until it reaches some impervious stratum1 and has then run along this1 until it arrives at the point at which the impervious stratum reaches the surface of the soil4 ,a spring is thus the outcrop of the underground water4 ,springs are divided into 7#a7 land springs1 and 7#b7 main springs4 ,the former flow from beds of drift or gravel lying on an impervious stratum4 ,they are very subject to seasonal variation1 and may dry up in certain years2 while main springs occurring in chalk1 greensand1 or other regular geological formation1 constantly supply a certain amount of water4 ,springs often occur in connection with 8faults0 in geological strata1 and then may appear on table-lands and high elevations1 unlike springs caused by alternation of strata in valleys of denudation4 ,the two kinds of springs are shewn in ,fig4 #e and #f4 ,in the land spring water crops out at the point where the porous stratum ceases4 ,deep springs may crop out in the same way as land springs1 except that they appear at the bottom of deeper strata4 ,or they may be formed by faults4 ,both these are shown in water having percolated through the chalk beneath the superficial clay1 is stopped at the 8fault0 by the lack of continuity of the chalk stratum1 and is consequently confined under pressure4 ,it therefore makes its way to the surface1 forming a spring4 ,in its passage underground1 water 7owing partly to the carbonic acid it has obtained from the air and soil71 is able to dissolve small quantities of chalk1 sulphate of lime and of magnesium1 and traces of oxide of iron1 aluminium oxide1 and silica4 ,spring-water possesses an equable temperature1 generally about #ej ,fahr41 while impounded or river water is always warm in summer and cold in winter4 ,spring water is well-aerated1 while river water1 and still more rain-water1 are flat4 ,illustration3 ,,fig4 #e4--,,land ,,spring4 ,illustration3 ,,fig4 #f4 ,,main ,,springs ,,formed ,,in ,,valley ,,of ,,denudation ,,and ,,by ,a ,,fault4 #g4 ,wells may form the best or worst sources of water-supply according to their depth and the means of protection against contamination4 ,there are two kinds--,surface wells and deep wells4 ,surface ,wells do not usually descend further than #ae or #bj feet1 and have no impervious stratum between the source of water and the surface of the well4 ,they catch the subsoil or underground-water1 which percolates into them from the surrounding soil1 and the character of the water they receive will therefore vary with the nature of their surroundings4 ,if there is a cesspool near1 this may simply drain into the well4 ,all the soakage from a considerable distance may find its way into the well4 ,in villages and isolated places the water of surface wells is commonly contaminated4 ,one hole may be dug in the garden for a well1 and another for a cesspool1 while there is possibly a farmyard near at hand--the soakage from the cesspool and farmyard soaking into the well4 ,danger may also arise from more distant contamination4 ,the ground water which is tapped by the well is an underground stream flowing towards the nearest brook4 ,heavy rains swelling the ground water may wash impurities from cesspools1 leaky drains1 etc41 at a considerable distance1 and carry these into wells lying between these sources of pollution and the brook into the bed of which the underground water ultimately discharges4 ,the danger of contamination of the water in the well by the contents of the cesspool is much greater in the relative position shown in ,a than in the position shown at ,b1 ,fig4 #g4 ,after heavy rain1 when the underground water is swollen1 the danger of contamination is still further increased4 ,the model bye-laws of the ,local ,government ,board state that a cesspool must be at least #dj feet distant from any well1 spring1 or stream4 ,probably this is insufficient for safety2 cesspools ought to be entirely forbidden4 ,if necessary to retain a surface well1 it should be protected nearly to the bottom with brick1 lined with an impervious layer of cement so as to prevent water from entering the well except near its bottom4 ,in modern wells iron cylinders are employed to line the upper part of the well2 and large glazed earthenware pipes arranged vertically and with water-tight joints are sometimes used for the same purpose4 ,illustration3 ,,fig4 #g4 ,,showing ,,varying ,,danger ,,of ,,contamination ,,of ,a ,,shallow ,,well1 ,,according ,,to ,,level ,,of ,,underground ,,water ,,and ,,relative ,,position ,,of ,,cesspool ,,and ,,well 7after ,galton74 ,deep ,wells are made by digging a surface well1 as above1 except that the ground water is prevented from entering the well by means of impervious steining2 and then boring from the bottom down through the subjacent impervious stratum until a water-bearing stratum is reached4 ,the difference between a surface well and a deep well is shown in ,fig4 #h by ,a and ,b4 ,where the water in this stratum is retained under pressure1 deep wells are known as ,artesian ,wells4 ,such ,artesian wells have been sunk in ,london4 ,rain1 falling on the chalk hills which lie to the south and north of ,london1 percolates through the chalk downwards1 and then laterally1 until it lies in the concave ,london basin4 ,here the clay stratum above it prevents its escape upwards2 and being confined under considerable pressure1 it rises to the surface1 or into a well in the superficial gravel1 when the clay is tapped4 ,in ,fig4 #h1 ,b is an ,artesian well if the pressure is such as to make the water rise through the ,london clay1 when this is cut through and the underlying chalk is reached4 ,c is a well in the chalk1 which does not pass through an impervious stratum1 and therefore comes within the above definition of a surface well2 but as regards depth required to be dug before water is reached it is more like a deep well4 ,illustration3 ,,fig4 #h4 ,,showing ,,difference ,,between ,,deep ,,and ,,superficial ,,well4 ,a4--,,surface ,,well ,,in ,,gravel4 ,b4--,,deep ,,well1 ,,going ,,through ,,gravel ,,and ,,clay ,,to ,,chalk4 ,c4--,,well ,,in ,,chalk ,,district4 ,among the deepest ,artesian wells are ,grenelle 7#a1hjj feet71 and ,kissingen 7#a1hgh feet47 ,the sinking of a deep well and severe pumping of its water may exhaust all the neighbouring wells for two or three miles4 ,there is also danger of contamination from neighbouring cesspools when the upper part of the deep well is not properly constructed4 ,the area exhausted by a deep well undergoing pumping is represented by an inverted cone1 having a very wide base1 and with a convex inner surface pointing towards the well4 ,for country places deep-well water is much preferable to water from streams1 as streams are very liable to be contaminated by the sewage of houses higher up in their course1 or even by that of houses close by4 ,a good well should be at least thirty feet deep--preferably fifty feet and should always be lined with impervious material1 except near its bottom4 ,the absolutely water-tight and impervious condition as well as the distance of all drains or cesspools in the vicinity should be ascertained before deciding whether the drinking water from a given well is above suspicion4 ,the direction of flow of the underground water should also be determined4 ,this may be done by measuring the level of all the wells in the neighbourhood4 ,possible sources of pollution at points from which ground water is flowing towards the well are much more dangerous than those nearer than the well to the river towards which the underground water is flowing 7see ,fig4 #g74 ,steam pumping greatly increases the area from which contamination may be derived4 ,an excellent plan to obtain water for villages1 in a gravelly soil1 is to sink a ,norton's ,abyssinian tube well for fifty or sixty feet4 ,in towns it is preferable to trust to the public water supplied1 rather than to any private well2 and in villages1 a general supply from a pure source should also be provided4 ,the water is obtained from a well by a pump or a draw-well4 ,the former is a safer as well as a less laborious plan4 ,the pump should be fixed some distance from the well1 and the aperture through which the pump pipe passes should be rendered water tight4 ,lead pipes should be avoided1 as well water not infrequently has plumbo-solvent properties4 #h4 ,rivers and running streams originate in upland surface water or springs1 and their water should be of the same quality as these4 ,unfortunately1 they acquire a large amount of impurities in their course4 ,towns commonly pour their more or less clarified sewage into them2 and the discharge of crude sewage from hamlets and single houses on the banks is still far from uncommon4 ,with the more rigid enforcement of the ,rivers ,pollution ,acts1 this pollution of rivers will become less frequent2 but river water previously contaminated by even small amounts of sewage cannot be regarded as an ideal source of water-supply4 ,if no contamination be present in the water of a river1 it forms a good source of water-supply2 being running water1 it is always fairly well arated1 and is not usually so hard as spring-water4 ,even if sewage has entered a river1 it is asserted that it becomes a safe source of water-supply1 after passage through filter beds1 the sewage having been got rid of in four ways4 #ast4--,by subsidence1 the organic matter settling to the bottom4 #bnd4--,by the influence of water-plants1 which assimilate ammonia1 nitrates1 etc41 and give out nascent oxygen4 #crd4--,oxidation4 ,doubtless a large amount of the nitrogenous matter does become oxidised in its course down a river1 and in this condition is harmless4 ,the river ,seine becomes greatly polluted as it passes through ,paris1 but so far as chemical analysis can determine its condition1 it is purer #cj miles below the city than it was before it received the sewage of the city4 #dth4--,it is highly probable that the germs 7or micro-organisms7 of enteric fever and other diseases known to be propagated by polluted water1 are practically or wholly destroyed in the struggle for existence with the natural micro-organisms of river-water4 ,when to this is added the fact that river-water supplied to large communities is carefully filtered through sand1 after having been stored in reservoirs1 in which the chief impurities have time to settle1 it is not surprising that the experience of those communities like ,london1 which are supplied with river-water1 usually shows no evidence of evil ascribable to drinking this water4 ,for over #cj years the inhabitants of ,london have been drinking filtered water from the river ,lea and from the ,thames above ,teddington1 and this gigantic experiment on a population which has increased from #b to #e millions has not been accompanied by any conclusive evidence of evil effect4 ,in regard to the comparative merits of the various waters described1 it will be useful to give here the classification made by the ,rivers ,pollution ,commissioners in their sixth report3-- 4 ,spring ,water ,very palatable4 ,wholesome #b4 ,deep-well ,water #c4 ,upland ,surface ,water ,moderately palatable4 #d4 ,stored ,rain ,water ,suspicious #e4 ,surface ,water from ,cultivated ,land ,palatable4 #f4 ,river ,water to which ,sewage gains ,dangerous access #g4 ,shallow-well ,water ,passage through certain geological strata has a great influence in rendering water palatable1 colourless1 and wholesome by percolation4 ,the following strata are said by the ,commissioners to be the most efficient3--7#a7 ,chalk1 7#b7 oolite1 7#c7 greensand1 7#d7 ,hastings sand1 7#e7 new red and conglomerate sandstone4 ,fissures or cracks in these strata may cause the water to pass through them unpurified by filtration4 ,,chapter ,x4 ,,the ,,storage ,,and ,,delivery ,,of ,,water4 ,the methods of storing and delivering water will vary with its source4 ,in rural districts1 deep wells and springs are the best sources of supply2 but in large towns they are found to be insufficient for the wants of a rapidly-increasing population2 and they can only be multiplied in a given district within certain limits1 as every well drains a large surrounding area4 ,the supply from surface wells in gravel or sand beds or in chalk districts is liable to fail in seasons of drought2 but deep wells in oolite or chalk formations1 and in the new red sandstone1 generally yield a constant and abundant supply4 ,when the water is supplied from upland surfaces1 springs1 or small streams1 a collecting reservoir is required4 ,this is generally a natural valley below the level of the source of supply1 but of sufficient elevation above the place supplied to allow the water to be distributed by gravity1 without any pumping apparatus4 ,the reservoir should be large enough to hold five or six months' supply1 and its embankment should be perfectly water-tight1 and of great strength4 ,when water is collected from upland surfaces1 it is important to know the amount of rainfall to be reckoned on4 ,if we know the area of the surface which drains towards the reservoir1 and the average rainfall1 the total rainfall is easily calculated4 ,this will1 however1 differ greatly from the available rainfall1 owing to the losses from penetration into the ground1 evaporation1 and other causes4 ,the amount lost will vary1 according to the season1 from one-half to seven-eighths of the total rainfall2 and according to the soil 7page #fh74 ,the proportion of percolation in the chief water-bearing strata surrounding ,london varies from #dh to #fj per cent4 7,prestwich74 ,it is less when the ground is steep and the rainfall rapid1 and usually less in winter than in summer4 ,water collected near its actual place of fall1 and from uncultivated districts1 is always purer than that collected further from its source1 and from cultivated land4 ,from the collecting or impounding reservoir1 water is carried by the aqueduct or conduit either directly into the service-pipes1 or when the pressure is too great1 into a second service-reservoir1 resembling the impounding reservoir in general structure1 and capable of holding a few days' supply4 ,this must be high ground1 above the level of the highest houses to which water has to be supplied1 as water cannot rise above its own level4 ,when this cannot be arranged1 the water is pumped into tanks at a higher level1 and distributed from them4 ,the greatest hourly demand for water being double the average hourly demand1 the water-mains supplying a town must have double the discharging power that would be required1 supposing the demand was uniform4 ,the first requisite of a supply of water is that it should be abundant1 and sufficient in amount for any extra strain on its capacities4 ,water ought to be laid on to every house1 and to at least two floors of the house4 ,anything preventing free access to water1 militates against cleanliness4 ,cast-iron is the most serviceable material used in the construction of the main water-pipes2 it is coated with pitch1 or ,dr4 ,angus ,smith's varnish1 or with magnetic oxide of iron 7,barff74 ,the service-pipes to each house are generally made of lead1 and the ease with which this material can be bent and curved1 and carried to the different floors of a house1 makes its use very convenient4 ,lead pipes1 furthermore1 can be easily obliterated in case of bursting1 and so any waste of water and flooding of the house minimised4 ,some kinds of water1 unfortunately1 act on and dissolve lead2 this is especially true of soft waters and those containing organic matter4 ,shallow wells1 being very liable to organic pollution1 ought never to have the supply-pipe of their pumps made of lead4 ,with hard waters1 lead pipes may generally be used safely4 ,when the quality of the water renders lead pipes objectionable1 the use of iron1 tin1 zinc1 tinned copper1 earthenware1 gutta-percha1 and other materials1 has been suggested4 ,of these1 cast and wrought-iron pipes are the most serviceable1 or pipes composed of an inner lining of block-tin and an outer of lead1 a layer of asbestos intervening to prevent galvanic action between the metals4 ,according to ,rawlinson1 8supply-pipes of wrought-iron are cheaper1 stronger1 and more easily fitted than service-pipes of lead20 but it is urged against them by ,perry1 that with soft water they become choked by rust in a few years4 ,if galvanized they are more durable4 ,cast-iron pipes are rusted less easily than wrought-iron4 ,when the water-supply is from a river1 filtering beds are needed1 in addition to the parts of a water-service hitherto described4 ,moreover1 since the river is usually at a low level1 the water1 after passing through the filtering beds1 requires to be pumped into raised tanks1 from which it is delivered4 ,in laying down water-pipes1 in the streets and to houses1 it is very important to make the distance between them and all drains and gas-pipes as great as possible4 ,suction of gases or liquids may occur into leaky pipes1 even though these contain water1 and still more when they are empty2 and disease has occasionally been traced to this source4 ,thus if sewers and water-mains are laid in the same trench1 foul matters which have escaped into the soil from the former may be sucked into the latter4 ,this may happen if the water-mains are leaky1 even when they are running full4 ,experiments have shewn that the flow of water causes a partial vacuum and insuction at the defective points4 ,during intermissions of supply when the mains are partially or entirely empty1 the danger of leakage into them is still greater4 ,coal-gas has been similarly sucked into water-mains4 ,the pipes bringing the water to a house may be kept constantly filled with water1 or only for a limited time once or twice a day4 ,the intermittent system of supply necessitates the provision of cisterns or water-tanks1 in which water can be stored in the intervals of flow of water4 ,with a sufficient and properly-distributed public supply of water1 no cistern ought to be required4 ,cisterns4--,cisterns for the supply of potable water may be made of iron1 slate1 stone1 glass1 glazed earthenware1 or brick lined with ,portland cement4 ,other materials have been used1 as timber1 lead1 and zinc4 ,timber is inadvisable1 as it easily rots2 lead is very objectionable1 owing to the possible solvent action of the water on it4 ,zinc or galvanized iron cisterns are also acted on by soft water2 but they may be used with most waters4 ,galvanized iron is iron coated with a thin layer of zinc4 ,iron cisterns soon rust2 but this may be prevented by giving them a coating of boiled linseed oil before they leave the foundry4 ,stone cisterns are too heavy for use1 except in basements4 ,slate cisterns are good1 but are apt to leak2 the points of leakage have occasionally been stopped with red lead1 which is attacked by the water1 and thus lead poisoning results4 ,if the slate is set in good cement 7not mortar1 as this makes the water hard71 it is a good material for a cistern4 ,every cistern should have a well-fitting lid1 always kept closed1 to avoid the entrance of dust of various kinds1 or even dead cats1 birds1 etc4 ,noxious gases may be absorbed by the stagnant water4 ,the cistern should be easy of access4 ,if it is indoors1 the cistern room should be well ventilated2 and in any case the cistern should be periodically visited and cleaned out4 ,when the cistern is full1 a ball-tap prevents any further flow of water2 and if this does not act properly1 an overflow pipe carries off the excess of water4 ,cisterns badly arranged or neglected have been in the past a common source of disease4 7#a7 ,the overflow pipe should not pass into any part of the water-closet apparatus or the soil-pipe1 or into the supply pipe to the water-closet4 ,where the overflow-pipe discharges into the soil-pipe or closet pan1 foul gases or even solid particles may find their way into the cistern4 7#b7 ,no water-closet ought to be supplied from the same cistern as supplies drinking water1 as the pipe leading down to the closet may when the cistern is accidentally empty carry noxious effluvia into the cistern4 ,a separate flushing cistern capable of discharging two to three gallons of water should be provided for each closet4 ,with a constant supply of water1 cisterns are only required for water-closets and for hot-water apparatus 7see pages #afh and #afd74 ,constant and ,intermittent ,services4--,with an intermittent service of water1 during the intervals of supply1 water is only obtainable from cisterns1 water-butts1 etc4 ,the objections against this system are that--7#a7 ,the cisterns required are expensive1 and liable to get out of order and become foul4 7#b7 ,their overflow pipes may improperly communicate with the soil pipe or with some other part of the drainage1 instead of opening into the external air4 7#c7 ,putrid gases1 from neighbouring ventilating-pipes or other parts of the drainage system1 are liable to be absorbed by the stagnant water in the cistern4 7#d7 ,the chief objection to an intermittent supply is that1 during the intervals in which the water-mains are empty1 foul air and liquids from the contiguous soil and drains are liable to be sucked through imperfect joints into the pipes4 7#e7 ,in case of fire1 the supply of water in the system is insufficient4 ,in certain towns rates of insurance against fire have been reduced on replacing an intermittent by a constant service of water4 ,on the other hand it is urged that more expensive fittings are required for a constant service2 and that1 when taps are left open or pipes burst1 the waste of water is much greater than with a cistern supply4 ,the balance is decidedly in favour of a constant supply without storage cisterns4 ,where storage cisterns are in use1 the taps for drinking-water should be connected with the 8rising-main10 before it supplies the cistern4 ,the ,advantages of the ,constant ,service may be thus summarised3-- 7#a7 ,owing to the absence of cisterns1 the risks connected with stagnant water1 and with improper arrangement of overflow pipes1 are obviated4 7#b7 ,the risk of suction into supply mains of external contaminations is reduced to a minimum1 since the pipes are never empty4 7#c7 ,the pipes are less liable to rust4 ,air in the presence of a little moisture1 causes rapid corrosion4 7#d7 ,there is an abundant supply of water in case of fire4 ,of course1 when there is a temporary stoppage of supply1 as for repairs1 some of the dangers incurred by an intermittent supply will arise4 ,,chapter ,,xi4 ,,impurities ,,of ,,water4 ,properties of ,water4--,when pure1 water is colourless1 or bluish when seen in large quantity4 ,it should be quite inodorous4 ,if1 after keeping it for some time in a perfectly clean vessel1 or if on heating it a smell is developed1 the water is bad4 ,its taste should be pleasant and sparkling from the atmospheric gases dissolved in it4 ,bitterness generally indicates the presence of sulphate of magnesium 7,epsom salts74 ,saltness is always a suspicious property1 except in water obtained in the neighbourhood of salt mines or brine springs1 or near the sea4 ,it should be soft to the touch1 and should dissolve soap easily4 ,it should be bright and clear1 and contain no suspended matters4 ,clear water is not necessarily pure1 but turbid water is always to be rejected2 the only exception being the brownish-tinged water from moors1 which is not hurtful4 ,in all other cases1 printed matter should be legible through at least #ah inches of water in a clear glass cylinder4 ,thoroughly dissolved organic matter is less dangerous than suspended2 the turbidity of water is therefore of great importance4 ,but water may be bright and sparkling and apparently perfectly clear1 and yet highly dangerous4 ,the most important of the physical properties of water in regard to health are the absence of smell and turbidity1 and these can be ascertained by even the most inexperienced4 ,the chemical tests for the more important impurities are given 7pages #he to #hg74 ,the impurities of water may be classed under four heads--gaseous1 mineral1 vegetable1 and animal4 ,the gases ordinarily present in water cannot properly be regarded as impurities1 inasmuch as they are always present1 and greatly increase its palatableness4 ,the dissolved nitrogen and oxygen bear to each other the proportion #adb to #a2 where sewage contamination occurs1 the oxygen will be diminished or disappear1 owing to oxidation of the organic matter4 ,the amount of carbonic acid gas in water varies greatly4 ,it may be considerable in chalk waters1 and in contaminated well-water4 ,mineral ,impurities4--,mineral impurities are dissolved by water in its course through the soil1 and so will vary with the character of the latter4 #a4 ,the water obtained from granitic formations contains very little mineral matter1 often not more than two to six grains per gallon4 ,clay slate water is also generally very pure1 as is the water from hard trap rocks4 #b4 ,the water from millstone grit and hard oolite is very pure1 often containing only four to eight grains per gallon1 chiefly calcium and magnesium sulphate and carbonate4 #c4 ,soft sand-rock waters usually contain thirty to eighty grains per gallon of sodium salts1 with a little lime and magnesia4 #d4 ,loose sand and gravel waters vary greatly4 ,they may be almost free from mineral matter1 or the solids may be more than seventy grains per gallon1 including much organic matter4 #e4 ,waters from the lias clays vary somewhat1 but commonly contain a large quantity of calcium and magnesium sulphates4 #f4 ,chalk waters generally contain from seven to twenty grains of calcium carbonate1 with smaller quantities of other salts4 #g4 ,limestone and magnesian limestone waters differ from the last1 in containing more calcium sulphate and less calcium carbonate1 as well as much magnesium sulphate and carbonate in the dolomite districts4 #h4 ,selenitic waters contain calcium sulphate in considerable quantities4 #i4 ,clay waters usually possess the characters of water from surface wells1 and are objectionable4 #aj4 ,alluvial waters generally contain a large amount of various salts1 including the various calcium1 magnesium1 and sodium salts4 #aa4 ,artesian well water varies greatly in composition4 ,it may contain a large amount of sodium and potassium salts1 or a small quantity of iron1 or calcium salts4 ,the commonest and most important mineral constituent of water is calcium carbonate1 next to this calcium sulphate4 ,these two salts are the chief causes of hardness of water4 ,for practical purposes as regards use in domestic matters and in manufactures1 the most important classification of waters is into hard and soft4 ,the degree of hardness varies within wide limits--from rain-water1 which has no hardness at all1 to the water from new red sandstone rocks which sometimes possesses a hardness of #ij degrees2 or wells in the gravel1 in which it may be as much as #aeb degrees4 ,the following classification of waters1 according to the degree of hardness1 beginning with the least hard and gradually increasing in hardness1 is from the sixth report of the ,rivers ,pollution ,commissioners3--#a4 ,rain-water4 #b4 ,upland surface4 #c4 ,surface from cultivated land4 #d4 ,river4 #e4 ,spring4 #f4 ,deep-well4 #g4 ,shallow-well water4 ,calcium carbonate is the most common cause of hardness1 and the hardness produced by it is remediable by boiling or chemical means4 ,calcium carbonate 7chalk7 is rendered soluble in water1 by the carbonic acid contained in the latter1 a double bicarbonate being thus formed4 ,the air contained in the interstices of the soil through which water passes1 often contains #bej times as much carbonic acid as ordinary air4 ,the water1 in percolating through the soil1 dissolves this carbonic acid1 and thus is able to take up a considerable amount of chalk4 ,the amount of hardness in any given water is expressed in degrees1 one degree being equivalent to a grain of calcium carbonate in a gallon of water4 ,clarke's soap test is employed to detect the amount of hardness4 ,it consists of a solution of soap of a known strength4 ,soft water will form a lather at once with this2 hard water will only form a lather after all the calcium salt is neutralised4 ,the amount of ,clarke's solution required before a lather is produced1 will give an estimate of the amount of hardness4 ,to ,determine the ,total ,hardness take #gj c4c4 of the water and place in a stoppered bottle4 ,from a burette run in a sufficient quantity of the standard soap solution 7of which #a c4c4 equals #a of hardness71 to produce a lather on shaking the water1 which remains unbroken after standing five minutes4 ,thus1 if #ge c4c4 of the soap solution were required1 the hardness is #fe1 as #a c4c4 of the solution is required to produce a lather in soft water4 ,the #fe means #fe milligrammes of calcium carbonate in #gj c4c4 or #fe grains in a gallon of the water4 ,to ,determine the ,permanent ,hardness boil #gj c4c4 of the water in a flask for half-an-hour2 allow the precipitated carbonates of calcium and magnesium to settle4 ,some of the latter will be re-dissolved4 ,carefully decant1 and make up the liquid to the original #gj c4c4 with distilled water4 ,filter through fine filter paper and estimate hardness as above4 ,the amount of soap wasted in consequence of the hardness of water is very great4 ,thus1 in the case of water of one degree of hardness1 as every gallon contains one grain of chalk1 #g1jjj gallons would contain #g1jjj grains--that is1 a pound4 ,but every grain of chalk wastes #h or #i grains of soap2 therefore1 a pound of chalk1 contained in #g1jjj gallons1 would waste about #h pounds of soap4 ,but nearly all waters are harder than this1 and they not uncommonly possess a hardness of #bj or more4 ,if the hardness be #bj1 the waste would be #agj pounds of soap4 ,this quantity would be easily used annually in a family of seven or eight persons1 if we include the washing of clothes4 ,the amount of money thus wasted can be easily estimated4 ,not only does soft water require less soap1 but it is much more suitable for making tea and soup1 and for boiling meat and vegetables--both time and fuel being saved4 ,the reason why better tea is made when a little carbonate of soda is added to the water is that the chalk is by this means precipitated4 ,carbonate of calcium is precipitated from water by boiling it2 carbonic acid being driven off1 the neutral salt falls to the bottom of the vessel4 ,this is the origin of the 8fur0 inside kettles1 which lessens their conductivity to heat1 and renders necessary a greater consumption of fuel4 ,the chalk may also be removed by adding to the water1 while still in the reservoir1 some milk of lime--that is1 quicklime made into a milky solution with water4 ,this is done on a large scale at various waterworks4 ,the reaction may be expressed thus3-- ,calcium bicarbonate calcium oxide calcium carbonate calcium carbonate4 ,the calcium carbonate1 as it is precipitated1 carries down with it organic and other matters1 thus clearing and purifying the water4 ,the hardness due to calcium sulphate is not removable by boiling4 ,it is1 therefore1 called permanent hardness1 to distinguish it from the temporary hardness of chalk waters1 which is removable by boiling4 ,it may1 however1 be partially removed by the addition of washing soda to the water1 as well as the nitrate and chloride of calcium which are also present4 ,the magnesium salts are not removable by boiling or soda4 ,this is shown by the fact that the 8fur0 inside kettles does not usually contain magnesium salts4 ,the amount of hardness varies greatly in different waters4 ,in the deep wells in magnesium limestone1 it varies from #ad-eg2 in the deep wells from chalk beds1 it varies from #ac to #bg and may be higher4 ,in the water from ,bala ,lake1 ,wales1 the temporary hardness is #ja1 the permanent hardness #jc2 in the ,loch ,katrine water there is no temporary hardness1 #ji permanent hardness2 in the water from the new red sandstone 7,nottingham71 the temporary hardness is #if1 permanent #ajb2 in a chalk spring at ,ryde1 temporary hardness #afg1 permanent #ci 7,wanklyn74 ,the total hardness in the metropolitan water supplies from the rivers ,thames and ,lea1 varies from #acb 7,southwark ,company7 to #adf 7,new ,river ,company72 in the ,kent ,deep ,wells #bja2 in deep wells from the chalk at ,brighton it varies from #ab to #ac4 ,in all these1 the hardness is chiefly temporary4 ,the amount of permanent hardness is always great in water from clays1 as the ,london1 ,oxford1 ,kimmeridge1 and ,lower ,lias clays2 or in places where there are large deposits of calcium sulphate1 as at ,montmartre1 near ,paris 7hence the name ,plaster of ,paris1 given to desiccated calcium sulphate74 ,water from fissures in the clay often contains1 also1 a large amount of organic matter4 ,chlorides are always present in small quantities in water4 ,as a rule the presence of more than #a grain per gallon1 i4e4 #g parts per #ajj1jjj of water1 indicates contamination with some animal refuse1 unless the water is derived from new red sandstone1 or brine springs1 or from the neighbourhood of the sea4 ,this rule does not1 however1 hold universally good4 ,the absence or the presence of only a minute quantity of chlorides indicates the probable absence of animal contamination2 but in exceptional cases waters of the highest organic purity may contain more chlorides than the same bulk of sewage4 ,to determine the amount of ,chlorine take #gj c4c4 of the water1 add a few drops of solution of potassium monochromate 7,k,cr,o74 ,from a burette run in gradually a standard solution of silver nitrate 7of such a strength that #a c4c4 of the solution is equivalent to #a milligramme of chlorine74 ,the silver solution forms milky chloride of silver 7,ag,cl7 by combination with the chlorine of the chlorides in the water4 ,when all the chlorine is thus combined1 the next drop of the silver solution forms a deep red tint with the chromate4 ,the number of c4c4's of the silver solution required to produce this effect1 equals the number of milligrammes of chlorine in #gj c4c4 of water1 or the number of grains of chlorine in a gallon of water4 ,to convert this into parts per #ajj1jjj1 divide by #g and multiply by #aj4 ,to express the amount of chlorine in terms of common salt 7,na,cl71 multiply the parts per #ajj1jjj of chlorine by #afe4 ,nitrates in any water are suspicious2 but their import varies with the circumstances under which they occur4 ,a minute quantity of ammonium nitrate is present in nearly all waters2 and the water of deep wells1 especially of wells in the chalk1 which1 as a rule is perfectly free from sewage1 may be highly charged with nitrates4 ,nitrates1 when derived from sewage1 represent a completely oxidised condition of its nitrogenous matter4 ,crude sewage generally contains no nitrates4 ,nitrites as a rule indicate more recent contamination1 and therefore greater danger than nitrates4 ,the presence of more than a trace of phosphates is a strong indication of contamination with sewage matter4 ,to determine the amount of ,nitrites and ,nitrates the best known methods are by the indigo1 the phenol-sulphuric1 the aluminium1 or the zinc-copper couple tests4 ,for nitrites the metaphenylene-diamine test is employed 7page #he74 ,the following qualitative tests will suffice for elementary work4 ,nitrates4 ,an equal amount of a solution of brucine is added to the suspected water in a test-tube1 then a little pure sulphuric acid is poured down the side of the tube4 ,a pink zone is produced if nitrates are present in considerable amount4 ,nitrites4 ,a few drops of each of diluted sulphuric acid and of metaphenylene-diamine solution give a red colour with water after standing for a few minutes1 if nitrites are present4 ,lead is an occasional contamination of slightly acid waters4 ,the purest and most oxygenated waters act most readily on lead2 as also those containing organic matter1 nitrates or nitrites4 ,waters containing chlorides also act on lead1 the chloride of lead being sufficiently soluble to produce poisonous symptoms4 ,upland surface waters derived from moorlands in certain districts1 e4g4 around ,sheffield1 have been found to be capable of dissolving considerable lead from lead service-pipes4 ,the water taken first from the tap in the early morning is the most heavily charged with lead4 ,such waters are very soft2 but other moorland soft waters do not dissolve lead4 ,it is the water having a slightly acid reaction which possesses this property4 ,the source of this acid1 whether sulphuric acid from the products of combustion in a neighbouring town1 or an organic acid1 is uncertain4 ,the plumbo-solvent action of such water is greatest in autumn1 when the amount of acid is at its maximum4 ,the property of dissolving lead is removed by passing the water on a large scale over filters of sand1 spongy iron1 chalk1 or limestone4 ,the addition of a small quantity of carbonate of soda has the same effect4 ,in such districts the use of tin-lined iron pipes for domestic services has been recommended1 but these are liable to fracture when bent4 ,pipes consisting of an outer case of lead and an inner pipe of tin with a layers of asbestos between have also been placed on the market4 7,see also page #fh47 ,hard waters have the least action on lead2 a coating of insoluble carbonate of lead being formed on the interior of the pipe1 which prevents any further action4 ,thus the use of lead pipes for water containing carbonates or sulphate1 or calcium phosphate1 is comparatively safe4 ,hard water containing carbonic acid gas under pressure will dissolve a small amount of carbonate of lead2 this explains the cases of lead poisoning from soda water which was formerly supplied in syphon bottles with lead tubes4 ,lead is dissolved much more easily by water if other metals are in contact with it1 as iron1 zinc1 or tin1 galvanic action being thus set up4 ,zinc pipes containing some lead are very dangerous1 especially with the distilled water used on board ships4 ,to determine the presence of lead in water1 place a given quantity1 say #ajj c4c4 in a white dish1 and stir with a rod dipped in a solution of ammonium sulphide2 if the water becomes coloured1 this is generally due to the presence of iron or lead4 ,if the colour remains after adding a drop or two of hydrochloric acid1 lead is present4 ,to determine the amount of lead1 a standard solution of lead acetate containing #aaj milligrammes of lead in #a c4c41 is made by dissolving #ahc gramme of crystallised lead acetate in a litre of distilled water4 ,place #ajj c4c4 of the water to be examined in a ,nessler glass1 acidify by a few drops of acetic acid2 now add #ab c4c4 of a saturated solution of ammonium sulphide4 ,a brownish-black discoloration is produced if lead is present4 ,to a second ,nessler glass1 containing #ajj c4c4 of distilled water1 the same amounts of acetic acid and ammonium sulphide are added1 and then a sufficient quantity of the standard lead solution is added1 until the tints of the contents of the two ,nessler glasses are identical4 ,the amount of the standard solution added being known1 we know the amount of lead in #ajj c4c41 and the amount per litre 7#a1jjj c4c47 will be tenfold4 ,thus if #b c4c4 of the solution were required for matching colours1 there were #b parts of lead per #ajj1jjj of water1 or #ad grains per gallon4 ,traces of ,iron are sometimes present in water1 giving it an astringent taste4 ,such water is apt to turn brown2 and tea made from it is very dark4 ,organic ,impurities4--,organic impurities may be either vegetable or animal1 the latter being by far the most dangerous4 ,the water from moorlands is often brown1 but this is not noxious4 ,growing plants1 again1 may be beneficial to water1 by absorbing dissolved organic matter1 and aiding its oxidation4 ,decaying vegetable matter is objectionable in water1 and may set up diarrha4 ,the most important organic impurity of water has an animal origin--from sewage2 the liquid or solid excreta 7i4e4 the urine or fces7 gaining accidental access to the water4 ,besides sewage1 the eggs of various intestinal worms have been swallowed with water2 and in a few cases1 even leeches4 ,but whatever the source of the organic matter contained in water1 it contains nitrogen as an essential constituent2 and tends under the influence of warmth1 and therefore especially in summer1 to undergo putrefactive changes1 owing to the action of bacteria4 ,these split up the more complex molecules of organic matter into simpler matter2 ammoniacal compounds and salts1 of which the most important are nitrites and nitrates1 being final products of their activity4 ,the detection of nitrates1 and still more of nitrites1 is important1 as they may indicate the occurrence of previous sewage contamination4 ,these products are quite harmless in water1 except as an indication that the water has been polluted1 and that possibly a certain proportion of the nitrogenous matter in the form of the complex organic matter forming the germs of such diseases as enteric fever1 may still be present4 ,organic matter may be suspended or dissolved1 the former being most dangerous to health4 ,the germs or microbes causing disease consist of suspended1 i4e4 particulate matter4 ,the amount of organic matter is determined by the amount of free ammonia and albuminoid ammonia which are present 7,wanklyn's process71 by ,frankland's combustion process1 or by ,forschammer's oxygen process2 all of which give indications1 rather than an exact estimate of its amount4 ,,methods ,,of ,,water ,,analysis4 ,the following scheme of qualitative examination may be followed1 when an immediate opinion is required as to a water4 ,it can only be trusted when the examination shows pollution4 ,the following results will be obtained1 for instance1 when a minute quantity of urine is added to a gallon of water4 7#a7 ,the water has a faint odour4 7#b7 ,its colour is greenish yellow in bulk4 7#c7 ,on adding a few drops of ,nessler's solution1 a deep yellow colour appears4 7#d7 ,a few drops of an acid solution of permanganate of potassium become yellow when added to it4 7#e7 ,acidify some of the water in a test-tube with nitric acid1 then add silver nitrate solution4 ,distinct cloudiness is produced1 much greater than with pure tap water4 7#f7 ,addition of hydrochloric acid and barium chloride solution shows a much greater quantity of sulphates than the same quantity of tap water4 7#g7 ,a quantity of the water evaporated in a porcelain dish over a ,bunsen's flame gives a white residue1 which speedily turns brown1 with a urinous odour4 7#h7 ,ignite the ash and add some nitric acid to oxidise it more completely4 ,then dissolve in distilled water1 and add acid molybdate solution4 ,a yellow colour1 followed by a precipitate1 indicates high phosphates and sewage pollution4 ,the ,complete ,systematic ,examination is 7a7 physical1 7b7 bacteriological1 and 7c7 chemical4 ,of the physical tests1 colour1 which should never be yellow or brown except for peaty water1 is important4 ,taste is a somewhat uncertain guide1 but any badly-tasting water should be rejected4 ,the odour on heating to #hj ,f4 in a closed flask may indicate pollution4 ,the degree of hardness can be roughly tested by rubbing between the hands4 ,the absence of turbidity is most important1 as suspended impurities are more dangerous than all others4 ,printed matter should be legible through a column of #ah inches of water4 ,microscopally the suspended matter in water which has been allowed to settle should be examined4 ,particles of vegetable matter1 e4g4 fibres of cotton1 linen1 cells of potato1 or spiral cells of cabbage1 are important as indicating domestic impurities4 ,bits of wool1 hair1 wings and legs of insects and epithelium may be discovered4 ,the presence of alg1 diatoms and desmids1 or of water-fleas1 cannot be held to indicate pollution1 as these are found in all running streams and in many wells4 ,the eggs and embryos of worms are much more serious4 ,bacteria are almost invariably present in water4 ,the majority of these micro-organisms are harmless4 ,but as they may number among them the germs producing diseases like enteric fever and cholera1 the estimation of their number and particularly of any deviation from the number usually present in a given water1 and if possible the detection of special disease-producing bacteria1 are very important4 ,this method has been made more practicable since ,koch's method of 8plate cultivation0 of bacteria was discovered4 ,a small quantity of the water to be examined 7kept surrounded by ice until this test is applied1 to prevent multiplication of bacteria in the bottle71 is mixed with sterilised gelatine which has been melted over a water bath4 ,then the mixture is spread in a thin layer on a glass plate and allowed to solidify1 having been covered to prevent atmospheric germs from settling on the gelatine4 ,the bacteria in the water thus become fixed1 each growing and forming 8colonies0 dotted over the plate4 ,these colonies can be recognised by their size and appearance1 and by sub-culturing according to recognised methods4 ,the number of such colonies1 and the number of bacteria1 from which1 presumably1 such colonies sprang in #a c4c4 of filtered ,thames water is usually much below #ajj2 in the water before filtration many thousands are present4 ,it has been suggested that no water should be regarded as wholesome which contains more than #ajj bacteria in each c4c4 ,this standard is1 however1 obviously arbitrary4 ,chalk water ought to have a smaller number than this2 river waters may have more1 and yet be wholesome4 ,everything depends on the character of the bacteria found4 ,the detection of the ,bacillus coli communis1 which is present in sewage1 and normally in the human intestine1 is very suggestive of contamination by sewage4 ,the bacteriological method of examination of water is still in its infancy4 ,,chemical ,,analysis4 7#a7 ,the total solids are ascertained by evaporating a given quantity of the water to dryness1 and weighing4 7#b7 ,determination of ,chlorine 7see page #ha74 7#c7 ,determination of ,hardness 7see page #hj74 7#d7 ,the ,determination of ,nitrites is based on the reddish-brown colouration produced when an acid solution of metaphenylene diamine is brought into contact with a weak solution of nitrous acid4 #ajj c4c4 of the water under examination are placed in a clean glass cylinder4 ,add #a c4c4 of ,h,,so solution 7#a in #c71 then #b c4c4 of metaphenylene diamine solution 7#e grains in #a litre of water with a little ,h,,so added74 ,stir well with a glass rod4 ,if a colouration is produced at once1 a smaller quantity of water must be taken1 and made up to #ajj c4c4 with pure distilled water4 ,the quantity of nitrous acid present is measured by introducing different fractions of a c4c4 of the standard sodium nitrate solution#c into similar glass cylinders4 ,each is then made up to #ajj c4c4 with distilled water1 and the metaphenylene diamine solution and acid added as before4 ,the colour develops slowly2 time must1 therefore1 be allowed in matching4 7#e7 ,the ,determination of ,nitrates can be conveniently made by the following method4 ,when phenyl-hydrogen sulphate solution is poured upon a nitrate1 and sulphuric acid is formed1 picric acid is formed3-- 7,c,h7,,hso #c ,,hno ,c,h7,,no7,,oh ,h,,so #b ,h,o4 ,the addition of free ammonia in excess forms yellow ammonium picrate1 the intensity of the colour of which is an index of the picrate1 and of the nitrate from which it was produced4 7a7 ,evaporate #be c4c4 of the water under examination1 and 7b7 #e c4c4 of standard ,,kno solution 7containing #a part ,n in #ajj1jjj7 to dryness in two porcelain dishes over the water bath4 ,add #a c4c4 of phenyl-sulphate solution to each of these as soon as cool1 stir well with a glass rod1 then add #a c4c4 distilled water to each dish and #c drops of strong ,h,,so4 ,next add #be c4c4 of water to each dish1 and after heating for five minutes over the water bath1 add solution of ammonia to each dish in excess4 ,a yellow colour is produced in proportion to the amount of nitrate present4 ,transfer the liquids to glass cylinders1 and dilute each to #ajj c4c4 ,take #ej c4c4 of the solution showing the least colour1 and dilute the other with distilled water1 until it has the same tint4 ,supposing the #ajj c4c4 of the sample required to be diluted to #aej c4c4-- ,then the amount of ,n will be #aejajj #ebe #c parts per #ajj1jjj4 ,if the two solutions 7a7 and 7b7 when diluted have the same tint1 then the ,amount of ,n in the sample #ebe #b parts per #ajj1jjj4 7#f7 ,determination of ,organic ,matter4 ,frankland's combustion process involves the use of delicate and costly apparatus1 and is seldom employed4 ,in this process the organic carbon is evolved as carbonic acid1 and the nitrogen as such4 ,wanklyn's ammonia process is based on the reduction of organic matter to ammonia4 ,part of this ammonia1 free or saline ammonia1 is simply combined with carbonic1 nitric1 or other acids1 or is easily derived from the urea of urine1 ,,ch,n,o #b;,h,o #b7,,nh7,,co4 ,another part is only set free when the water is boiled with a strongly alkaline solution of permanganate of potassium4 ,this is called the albuminoid ammonia4 ,in carrying out this method1 a retort is taken1 and after having been washed out1 first with a little sulphuric acid1 and then with some of the water to be analysed1 #ejj c4c4 of the latter is put in1 and the retort is connected with a condenser1 and distillation begun2 #ej c4c4 of the distilled water is collected in a cylindrical glass tube called a ,nessler glass4 ,to this #a c4c4 of ,nessler's reagent 7mercuric iodide dissolved in a solution of potassic iodide and made alkaline by potass7 are added4 ,a rich brown colour is produced1 if any ammonia is present in the distillate4 ,the amount of ammonia in the distillate is determined by exactly imitating its colour by adding a known quantity of a standard solution of ammonium-chloride to #ej c4c4 of ammonia-free distilled water1 and then ,nesslerising as before4 ,each c4c4 of the dilute standard ammonium chloride solution is equivalent to #jjjja gramme of ammonia 7,,nh74 ,if the first #ej c4c4 of water distilled over gives only a slight colouration with the ,nessler solution1 no more water needs to be distilled over for free ammonia4 ,if more is present1 two more #ej c4c4's must be distilled over1 and the amounts of the standard solution required for imitating the test in each ,nesslerised #ej c4c4 added together4 ,thus1 if #b c4c4 were needed4 ,this #jjjjb grm4 ,,nh1 which is contained in #ejj c4c4 of the water #jjjjb #bjj #jjd parts saline ,,nh in #ajj1jjj of water4 ,the free ammonia having been distilled over1 #ej c4c4 of an alkaline permanganate solution 7containing #h grammes ,k,mn,o and #bjj grammes of ,na,o,h in #aajj c4c4 of distilled water1 boiled until the bulk is reduced to #a1jjj c4c47 is poured into the retort1 and distillation is begun again4 ,three successive #ej c4c4's of water are collected1 and then the distillation stopped4 ,each of these is ,nesslerised1 and the tint imitated as before with standard ammonia solution4 ,the three amounts of ammonia thus found to be present are added together2 and when multiplied by #bjj1 we obtain the amount of albuminoid ammonia in #ajj1jjj parts of water4 ,this test is universally employed by water analysts along with the next test4 ,the amount of ,oxygen ,absorbed from permanganate of potassium is regarded as an approximate test of the amount of organic matter in water4 ,qualitatively this forms a favourite method of testing the purity of water4 ,two glass cylinders are taken1 one filled with distilled water1 one with the water to be tested4 ,to each is added a given small amount of an acid solution of permanganate of potassium4 ,the distilled water to which permanganate has been added will retain its pink colour2 while1 if the water being tested is very impure1 it will speedily become decolourised4 ,the rapidity and degree of decolourisation are a rough test of the amount of impurity4 ,a rapid decolourisation proves the presence of organic matter having an animal origin1 or of sulphuretted hydrogen1 iron1 or nitrites4 ,sulphuretted hydrogen is rarely present1 and can be easily recognised by its smell2 iron or nitrites are readily distinguished by their appropriate tests4 ,in the absence of these1 the rapid discolouration is an indication of animal contamination4 ,to ,determine the ,amount of ,oxygen ,absorbed1 two glass-stoppered bottles1 each holding about #cej c4c4 are required4 ,into one1 #bej c4c4 distilled water1 and into the other the same amount of the water under examination are placed4 ,to each are then added #aj c4c4 of standard permanganate of potassium solution#d and #aj c4c4 of a standard pure #be per cent sulphuric acid solution4 ,the two bottles1 after being shaken1 are placed in a water-bath at #bg;,c for four hours4 ,at the end of this time add a few drops of potassium iodide solution to each bottle4 ,the pink is now replaced by a yellow colour4#e ,a standard thiosulphate solution 7,na,s,o1 #e;,h,o7#f is placed in a burette4 ,from this the thiosulphate solution is run into the control bottle until the yellow colour almost disappears4 ,now a few drops of starch solution are added1 and a blue colour is produced4 ,the thiosulphate is then added cautiously until all the blue colour disappears4 ,the amount of thiosulphate necessary for this is read off on the burette4 ,the same process is repeated with the bottle containing the sample of water4 ,the starch acts as an indicator4 ,the amount of iodine liberated is an index of the amount of permanganate in the water1 which has not been used up by its impurities4 ,the amount of iodine liberated is measured by the amount of thiosulphate required to decolourise the solution4 ,thus-- #b ,na,s,o ,i #b ,na,i ,na,s,o4 ,suppose that #bj c4c4 of thiosulphate solution were required to decolourise the iodine liberated in #bej c4c4 of a sample of water1 while the distilled water required #be c4c4 ,then #be c4c4 thiosulphate represents #aj c4c4 of the permanganate solution #jja grains of available oxygen4 #be-bj #e ,as #be c4c4 #jja grm4 ,o1 #e c4c4 #ebe of #jja #jjjb grm4 ,this is the amount of ,o absorbed by #bej c4c4 of the sample4 ,therefore #ajj1jjj #jh grm4 ,it is usual to make a similar determination of the amount of oxygen absorbed in fifteen minutes4 ,the ,interpretation of ,results of analysis is more difficult than the analysis4 ,a single analysis may be misleading1 unless the source of the water is known4 ,constancy in composition or analysis is almost as important a criterion of purity as the actual character of the constituents4 ,a knowledge of the source is essential in interpreting results of analysis1 as the chemical composition of water varies with its source4 ,the following rules are only approximately correct1 and are subject to the above general considerations4 ,the total dissolved solids in river-water are usually #aj to #cj parts in #ajj1jjj4 ,shallow well-water may contain from #cj to #bjj parts or even more1 and deep well-water from #bj to #gj parts4 ,saline ,ammonia in water is commonly of animal origin1 ammonia 7,,nh7 being one of the first products of decomposition of nitrogenous animal refuse4 ,upland surface water usually contains about #jjb parts per #ajj1jjj1 but it may reach #jjh or more if the land over which the water passes has been manured4 ,shallow well-water may be free from ammonia1 or this may be very excessive in amount4 ,deep well-water may contain no ammonia or any amount up to #a per #ajj1jjj4 ,its presence is suspicious if the albuminoid ammonia is above a trace1 or if the oxygen absorbed is appreciable in amount4 ,generally water is suspicious if saline ammonia is up to #ja per #ajj1jjj4 ,albuminoid ,ammonia indicates the amount of organic nitrogenous matter present in the water4 ,it should not exceed #jje parts per #ajj1jjj1 while at the same time the saline ammonia should not usually exceed #ja per #ajj1jjj4 ,for ,oxygen consumed the following table of the weight of oxygen required for #ajj1jjj parts of water is given by ,clowes and ,coleman3-- ,,upland ,,surface ,,water4,,water ,,from ,,other ,,sources4 ,water of ,great purity ,not exceeding #a ,not exceeding #je ,medium purity ,from #a to #c ,from #je to #ae ,doubtful purity,from #c to #d ,from #ae to #bj ,impure ,exceeding #d ,exceeding #bj ,the presence of more than #a and still more so of #b grains of ,chlorine per #ajj1jjj of water is most suspicious1 except in saline districts4 ,nitrites if present in an appreciable quantity indicate comparatively recent contamination by sewage4 ,in deep well-water they may be produced by deoxidation of nitrates4 ,nitrates in upland surface waters should not be equivalent to more than #jc of ,n4 per #ajj1jjj2 in shallow well-waters the amount varies greatly2 in deep well-waters it may be excessive4 ,as a rule it ought not to be equivalent to more than #e parts of ,n4 per #ajj1jjj of water2 but the significance of nitrates depends greatly on the source of the water and on the amount of the other constituents present4 ,chemical analysis alone cannot ascertain the safety of a given drinking water4 ,a minute amount of impurity inappreciable to analysis may be competent to produce disease2 while another water may be drunk with impunity1 which contains considerable organic matter4 ,chemical analysis 8can tell us of impurity and hazard1 but not of purity or safety0 7,buchanan74 ,an accurate opinion as to the character of a drinking water can only be expressed when one knows the amount of each chief constituent 7as above71 and whether these amounts deviate from the same water at other times or from other waters in the vicinity4 ,,chapter ,,xii4 ,,origin ,,and ,,effects ,,of ,,the ,,impurities ,,of ,,water4 ,origin of ,impurities of ,water4--,parkes classifies impurities of water as3 #a4 ,those ,received at the ,source4--,the character of water varies with the geological structures through which it has passed2 with its origin from the subsoil or cultivated land1 or deep wells1 or graveyards1 or near the sea1 etc4 ,it is a mistaken policy to commence with an impure water and proceed to purify it2 though communities supplied from rivers may be compelled to submit to this4 ,they must then insist on the most stringent measures of purification 7see p4 #if74 ,inorganic impurities are of much smaller consequence as regards health than organic2 hence the great advantage of deep well-water over river water4 ,it has been suggested1 however1 that when deep well-water becomes polluted1 it is more dangerous than equally polluted river-water1 because in the latter the normal bacteria of water are more abundant1 and possibly interfere with the continued life in water of disease-producing bacteria4 ,this statement is unproved2 and if correct1 is rather an indication for further precautions being taken to prevent access of pollution to deep wells1 than in favour of the continued use of river-water4 #b4 ,impurities of ,transit from ,source to ,reservoir1 acquired during the flow in rivers1 canals1 or other conduits4 ,these impurities have been broadly divided by the ,rivers ,pollution ,commissioners into 8sewage0 and 8manufacturing20 the former including the solid and liquid excreta1 the house and waste water1 etc42 the latter including the refuse from manufacturing processes1 as from dye and bleaching works1 tanneries1 etc4 #c4 ,impurities of ,storage1 whether in wells1 reservoirs1 or cisterns4 ,organic impurities are commonly received at this stage4 ,a well1 for instance1 drains the soil around it in the shape of an inverted cone1 with a very broad base1 unless the entrance of water from its sides is prevented4 #d4 ,impurities of ,distribution4 ,lead1 and occasionally other metals1 are dissolved by certain waters4 ,if the pipes are left empty1 as with an intermittent supply1 sewage may be drawn into them2 in a few cases coal-gas has found its way into the water pipes 7page #gf74 ,effects of ,impure ,water4--#a4 ,effects of ,mineral ,impurities4 ,suspended ,mineral matters in unfiltered water occasionally produce diarrha4 ,the hill diarrha of some parts of ,india has been traced to water containing fine mica particles in suspension4 ,hard water is said by some to be hurtful1 but the salts causing hardness are probably innocuous when not amounting to more than #ab or #af grains per gallon4 ,persons in the habit of drinking hard water find soft water unpalatable4 ,hard water has been thought to favour gout and calculus 7stone71 but this is not so4 ,the salts producing permanent hardness are said to be injurious1 producing indigestion1 but this is doubtful in the amounts ordinarily drunk4 ,goitre1 a swelling of the thyroid gland in the neck1 is often associated with the use of drinking water from magnesian limestone formations2 but that any kind of excessively hard water causes goitre is very doubtful4 ,lead dissolved in water may produce serious and lasting ailments1 and they are often present for a long time before their cause is detected4 ,the amount of lead capable of producing poisonous symptoms has been as little as #aajj grain per gallon of water 7,dr4 ,angus ,smith74 ,according to ,de ,chaumont1 #aaj grain per gallon1 that is #a part in #gjj1jjj is usually required to produce such symptoms4 ,in the well-known case of the poisoning of ,louis ,phillippe's family at ,claremount1 there was #gaj grain of lead in a gallon of water2 and this affected #cd per cent4 of those who drank it4 ,the symptoms produced by lead poisoning are those of indigestion1 accompanied by colic2 a blue line at the junction of the gums with the teeth2 8wrist drop10 a paralysis of the muscles of the forearm1 or some other paralysis2 and if the poisoning is continued1 attacks of gout1 followed by its usual consequences1 chronic kidney disease4 ,the latter affections chiefly occur when the poisoning is continued for a long time1 as in the case of painters or type-setters3 poisoning from water is generally discovered before any other than dyspeptic symptoms and colic are produced4 ,the presence of traces of iron in water may give it a slightly astringent taste2 and such water is liable to cause headache and constipation4 #b4 ,effects of ,vegetable ,impurities4--,living plants are unobjectionable1 but decomposing vegetable matter may produce diarrha and other severe symptoms4 #c4 ,effects of ,animal ,impurities4--,animal impurities of water are by far the most important from a sanitary point of view4 ,they are most commonly derived from leaky drains or cesspools1 or from surface accumulations of filth4 ,the quality of the contamination is more important than its quantity2 and this will explain why water containing a large amount of sewage may be drunk for a prolonged period with impunity1 while at another time the least trace1 if it contain the active germs of disease1 will lead to serious mischief4 ,suspended animal impurities are much more dangerous than those completely dissolved4 ,hence the examination of the colour and turbidity of drinking water is very important4 ,fcal contamination is by far the most dangerous of all1 and chiefly so when it is derived from a patient suffering from some communicable disease1 like enteric fever or cholera4 ,certain ,parasites occasionally are swallowed with water in the form of embryo or egg4 ,the liver fluke1 round worm1 and less frequently other kinds of entozoa have been introduced in this way4 ,the occasional swallowing of small leeches has occasionally given rise to hmorrhage4 ,diarrha may be caused by animal contamination of water4 ,it most often occurs in summer1 when all the circumstances are favourable to active fermentative changes4 ,the summer diarrha of infants is caused by similar changes in milk or other foods4 ,the presence of ftid gases in water may lead to diarrha4 ,this may occur when the overflow pipe of a cistern opens into the soil pipe or into the trap of the ,w4,c4 ,dysentery1 like cholera and enteric fever1 may be propagated by water contaminated with the stools of a patient suffering from the same disease4 ,malaria or ,ague has been stated to be caused by the water of malarious marshes4 ,the evidence on this point requires revision1 in view of the part which the mosquito is now known to play in the propagation of this disease 7pages #bhb and #cjg74 ,enteric 7otherwise called ,typhoid7 fever is most often due to the drinking of water contaminated with sewage4 ,the balance of evidence is in favour of the view that in order to produce enteric fever water must be contaminated with the stools or urine of a patient who has suffered from this disease4 ,numerous instances are on record in which villages1 the inhabitants of which drink sewage-contaminated water1 have remained free from enteric fever1 until a patient suffering from it has come to the village1 when the spread by water has been very rapid4 ,occasionally no known contamination from a case of enteric fever has preceded the outbreak of this disease which has been caused by sewage-contaminated water4 ,it must be remembered on this point that the urine of an enteric fever patient may occasionally contain large numbers of the bacillus causing this disease for several months after the patient is well 7page #cja74 ,the contamination of water with sewage may occur in various ways4 ,in country places surface wells and small streams commonly supply the drinking water1 and these are frequently contaminated4 ,the illustration 7,fig4 #i7 shows the percolation of excretory matters from an out-door closet through the porous gravel1 into a neighbouring well2 the result being an epidemic of enteric fever among those who drank the water of the well4 ,alterations in the level of the subsoil water are sometimes followed by an outbreak of enteric fever 7p4 #gj74 ,a sudden fall of rain occurs1 and the excess of water in the soil absorbs the soakings from country privies or cesspools1 and carries them into the nearest well4 ,the percolation of tainted water through a considerable tract of land1 possibly along fissures1 is sometimes insufficient to purify it1 as proved by a remarkable epidemic in the small village of ,lausen1 in ,switzerland4 ,in other cases sewage gains access into leaky water-pipes4 ,formerly contamination was occasionally due to improper connection between the overflow pipe of the cistern and the soil-pipe1 or to the water-closet being flushed by a pipe directly connected with a water-main 7as in the ,caius ,college outbreak at ,cambridge71 or connected with the drinking-water cistern 7page #gf74 ,milk may1 by the admixture of water1 become contaminated with enteric matter1 and produce widespread epidemics4 ,where the water is very impure1 the small amount used in washing cans may suffice to cause infection4 ,cholera was first proved by ,dr4 ,snow1 in #ahdi1 to be due to the specific contagium of cholera gaining an entrance into drinking water4 ,this contagium is derived as in enteric fever from the intestinal evacuations1 the urine1 and the vomit of patients suffering from the same disease4 ,illustration3 ,,fig4 #i4 ,the close connection of the spread of cholera with an impure water supply has been repeatedly shown in this country4 ,the cholera epidemic of #ahed was very severe in the southern districts of ,london4 ,at that period these districts were supplied with water by the ,southwark and ,vauxhall ,company1 deriving its water from the ,thames at ,battersea1 and by the ,lambeth ,company1 having its intake at ,thames ,ditton1 where the water was purer4 ,the two companies were acting in rivalry1 so that in many streets their mains ran side by side2 and houses in the same street similar in all other respects1 received a different water supply4 ,an investigation of the distribution of cholera in these districts gave the following results3-- ,,population ,,cholera ,,cholera ,,deaths ,,in #ahea4 ,,deaths ,,in ,,per #aj1jjj #ad ,,weeks4 ,,of ,,population4 ,houses supplied by ,southwark ,co4 #bff1eaf #d1jic #aec ,lambeth ,co4 #agc1gdh #dfa #bf ,the facts1 when examined in detail1 brought out still more strikingly the exemption of the houses supplied by the ,lambeth ,company2 the infection picking out in a given street the houses supplied by the ,southwark ,company4 ,the great epidemic of cholera at ,hamburg in #ahib proves the same point4 ,hamburg1 ,wandsbeck and ,altona are three towns adjoining each other1 and really forming one large community2 but while ,hamburg suffered terribly1 the two other towns had no cases of cholera1 except the few that were brought into them4 ,in all respects except water-supply the conditions were alike2 but ,wandsbeck obtained filtered water from a lake1 ,altona obtained filtered water from the ,elbe below the town1 while ,hamburg was supplied1 previous to the epidemic1 by unfiltered water from the ,elbe just above the town4 ,diphtheria and scarlet fever have never been traced to polluted water4 ,effects of an ,insufficient ,supply of ,water4--,the influence on personal health is most baneful4 ,water is used sparingly for purposes of cleanliness1 with the necessary results that cutaneous diseases become more common1 and the whole body suffers2 the linen is imperfectly and infrequently washed2 the house becomes dirty2 drains are imperfectly flushed2 the streets are not cleaned2 and the whole atmosphere becomes loaded with impurities4 ,according to ,parkes1 it is probable that the almost complete disappearance of typhus fever from civilized and cleanly nations1 is not merely owing to better ventilation1 but also to more frequent and thorough washing of clothes4 ,insufficient cleansing of the surfaces of streets and of sewers1 owing to a deficient supply of water1 has a very important influence on the spread of enteric fever and epidemic diarrha4 ,a heavy fall of rain often causes a rapid diminution in the prevalence of the latter disease4 ,,chapter ,,xiii4 ,,the ,,purification ,,of ,,water4 ,when a public water-supply is provided1 it may reasonably be expected to be furnished pure and fit for use2 but this1 occasionally is not so4 ,the reports1 for instance1 of the condition of the ,london ,water ,supply1 occasionally show that it is turbid and contains a slight excess of organic matter4 ,this is especially the case when1 after heavy rainfall1 storm-water is brought into the reservoirs1 and owing to deficient storage1 sufficient time is not allowed for deposit4 ,rain-water always and other waters frequently require to be purified before use4 ,methods of ,purification4--,the only certain way of obtaining pure water is by ,distillation2 but this plan is scarcely applicable to water on a large scale4 ,furthermore distilled water is not so palatable as ordinary water4 ,the distillation of water is more especially required on board ship1 during long voyages4 ,it should be followed by the use of some measure to secure efficient aeration4 #b4 ,boiling water serves to remove the temporary hardness1 and the chalk carries down with it a large proportion of any organic matter that may be present4 ,boiling deprives the water of its dissolved gases1 and renders it flat2 it is desirable1 therefore1 to aerate it by filtration or from a gazogene after boiling4 ,all the microbes which are known to produce disease are destroyed by efficient boiling4 ,certain putrefactive microbes are more persistent of life1 owing to the fact that they form spores1 which are not killed at the temperature of boiling water4 ,tyndall showed that by boiling the liquid containing these spore-forming microbes on three successive days1 thus giving time for the spores to develop into less resistant microbes1 they could be effectually destroyed4 ,boiled water will not cause enteric fever or cholera1 the two chief water-borne diseases4 #c4 ,the exposure of water in divided currents to the air by passing it through a sieve has been proposed as a means of purifying water1 but it is inefficient when trusted to alone4 ,plants in reservoirs help to absorb organic matter2 and fish1 by destroying small crustaceans1 have been found useful4 ,hard waters do not bear exposure to light1 as a thick green growth of chara occurs1 which may block pipes1 and give a bitter taste to the water4 #d4 ,the ,addition of ,chemical ,substances4--7#a7 ,clarke's process consists in adding milk of lime1 i4e4 an emulsion of quicklime with water1 to the water in the reservoir on a large scale4 ,by this means calcium carbonate is precipitated1 but no effect is produced on calcium and magnesium sulphates and chlorides4 ,the hardness of the ,thames water can thus be reduced from #af to #c or #d 7,clarke's scale74 ,the calcium carbonate carries down with it suspended and possibly dissolved organic matter4 ,in the ,porter-,clarke process lime-water1 i4e4 milk of lime diluted1 and the excess of lime separated by settlement or filtration1 is mixed with the water to be purified1 the water being freed from the precipitated calcium carbonate either by subsidence or by being forced through a filter of stretched canvas4 7#b7 ,carbonate of ,soda added to boiling water throws down calcium carbonate1 and possibly lead if present4 ,much less is required when added to boiling than to cold water4 ,maignen's process consists in adding anti-calcaire powder1 containing chiefly carbonate of soda1 lime1 and alum4 7#c7 ,aluminous salts are very effectual in removing suspended organic matter1 if the water contains calcium carbonate4 ,on the addition of alum1 calcium sulphate and aluminium hydrate are formed1 both of which fall to the bottom1 carrying with them other impurities4 ,the amount of alum required is about #f grains per gallon of water4 ,if the water is not hard1 a little calcium chloride and carbonate of soda should be put in before the alum is added1 in order that a precipitable substance may be formed4 7#d7 ,potassium permanganate readily removes the offensive smell of stagnant water1 but it gives a yellow tint to the water4 ,the addition of a little alum will help to carry down the decomposed permanganate4 7#e7 ,perchloride of ,iron1 in the proportion of #b grains to a gallon of water1 has been found to completely purify water from finely suspended organic matters and clay4 7#f7 ,more recently1 other substances1 such as iodine and hyposulphite of soda1 have been recommended4 ,these are supposed to act by sterilizing the water1 and iodine in suitable quantities undoubtedly effects this4 ,chemical processes for the purification of water1 with the exception of the softening process1 are not to be recommended for general use4 ,efficient filtration1 or boiling1 is safer than chemical treatment2 and it would only be justifiable to trust to the latter1 when1 as in a military campaign1 an attempt at purification was necessary1 and no means were available for filtering or boiling water4 #g4 ,filtration4--,the object of filtration is to remove the impurities of water4 ,the most dangerous impurities are suspended in it1 especially the microbes causing infectious diseases4 ,hence the most perfect filter is the one which most completely prevents the passage through it of microbes4 ,if the water supply is pure1 domestic filtration is not only useless1 but likely to do more harm than good4 ,this is true for such upland surface waters as those supplied to ,liverpool1 ,glasgow1 and ,manchester2 for such deep well-water supplies as those of ,brighton 7deep chalk71 of ,nottingham 7new red sandstone71 and others1 when pumped from wells remote from inhabited houses4 ,for upland surface waters known to attack lead pipes1 filtration through charcoal or spongy iron may be advisable2 for river water1 filtration through a germ-proof filter is best4 ,filtration on a large scale is generally carried on as follows3--,a preliminary step consists in collecting the water into settling reservoirs1 wherein the more bulky substances subside4 ,the water is then filtered through beds of gravel and sand1 containing perforated tubular drains below1 into which the filtered water flows4 ,the drains are covered by a bed of gravel about #c feet deep1 over which is spread a layer of sand about #a to #b feet deep4 ,sharp angular particles of sand are the best2 and the gravel should gradually increase in its coarseness as it descends4 ,the effect of this filtration is chiefly mechanical2 it separates any suspended matter1 whether organic or inorganic4 ,a certain amount of biological action possibly also takes place4 ,piefke found that a perfectly cleaned and sterilised filter when first used1 increases the microbes in water1 instead of decreasing them4 ,gradually a gelatinous layer of slimy matter is formed on the top of the sand2 the water now filters through much more slowly1 but it gradually becomes freer from microbes1 these being intercepted by the slimy layer4 ,it is important that this layer should not be disturbed by too rapid or forced filtration1 and that when the surface layer requires to be removed1 because the filter has become impervious1 time should be allowed for another thin film to form before the filtered water is again utilised4 ,koch concluded that the rapidity of filtration should never be allowed to exceed #ajj millimetres 7about #d inches7 per hour2 and that the number of microbes per c4c4 in the filtered water should never exceed #ajj4 ,some oxidation of organic matter1 as well as detention of microbes1 may take place during the filtration of water1 nitrates being formed by the vital activity of certain 8nitrifying0 microbes in the filter4 7,on nitrification1 see pages #aie and #bgd47 ,p4 ,frankland's observations show that the number of microbes in ,thames water is reduced by filtration through sand and gravel beds1 as practised by the ,london ,water ,companies1 so that only #cd per cent4 of those originally present remained4 ,he also concludes that the majority of the microbes present in filtered water are derived from post-filtration sources4 ,thus the number is greater in tap-water than in water derived from near the reservoirs4 ,other materials besides sand have been used for filtration on a large scale1 but none with proved success4 ,domestic ,filtration ought1 as already explained1 not to be needed1 but circumstances often arise in which the public supply is open to suspicion1 and a second domestic line of defence against infection through the water supply is desirable4 ,when this is so1 the form of filter which will best protect the household is one attached to the house-tap1 so that all drinking-water is perforce filtered4 ,when filtering involves the transfer of water from the tap to the interior of the filter1 opportunity is left for carelessness or forgetfulness4 ,the one essential point of a domestic filter is that it will prevent the passage through it of microbes4 ,every filter must be tested from this standpoint4 ,on this point the experiments of ,woodhead and ,cartwright ,wood are conclusive4 ,they first of all experimented on various filters with fine artificial ultramarine containing particles #af to #jf or even less in diameter in suspension2 and milk containing granules and globules of fat #je to #cj or more in diameter1 freely diluted with water4 ,,time ,,in ,,minutes,,presence ,,or ,,presence ,,or ,,required ,,for ,,absence ,,of ,,absence ,,of ,,milk ,,filtration ,,of #a,,ultramarine ,,in,,in ,,filtrate ,,pint ,,of ,,water4 ,,filtrate4 ,silicated carbon filter #fh ,carbon filter #ah ,maignen's ,filtre ,rapide #d #j ,spongy iron filter #ad #j ,pasteur-,chamberland filter #dbj #j #j ,berkefeld filter #adj #j #j ,the number indicates the relative amount of the experimental substances that made their way through the filtering medium4 ,experiments were then made with the actual microbes of certain infectious diseases1 and it was found that certain filters allow these to pass4 ,thus a silicated carbon filter allowed #a1jjj out of #ae1jjj typhoid bacilli suspended in water to pass through its substance2 a manganous carbon filter allowed #fjj to #hjj out of #aj1jjj cholera vibrios to pass through2 ,maignen's filter on the second day of experiment allowed #aej out of #e1jjj cholera vibrios to pass through2 ,lipscombe's charcoal filter experimentally only reduced typhoid bacilli from #bj1jjj to #e1jjj2 the magnetic carbide filter only reduced them from #bj1jjj to #aj1jjj2 the spongy iron filter from #bj1jjj to #c1jjj2 while1 on the contrary1 the ,pasteur-,chamberland and the ,berkefeld filter completely stopped all microbes and produced a sterile water4 7,as to these two1 see page #ih47 ,of the materials enumerated animal charcoal was formerly regarded as an excellent filtering medium4 ,it is capable of oxidising organic matter dissolved in water1 but so far from sterilizing water1 it favours the growth of microbes in it4 ,water filtered through charcoal1 after the first few days of use of the charcoal1 deteriorates1 as the charcoal yields up impurities to it4 ,manganous ,carbon consists of animal charcoal and black oxide of manganese mixed with oil1 and heated strongly together out of contact with the air4 ,the oxidising power of the carbon is said to be thus greatly increased4 ,it shares the objections to carbon4 ,silicated ,carbon consists of #ge per cent4 of charcoal and #bb per cent4 of silica1 with a little oxide of iron and alumina4 ,it is not an efficient filtering medium4 ,spongy iron is prepared by the reduction of hmatite ore with fusion1 so that the iron is obtained in a porous and finely-divided condition4 ,the ,rivers ,pollution ,commissioners found spongy iron to be 8a very active agent1 not only in removing organic matter from water1 but also in materially reducing its hardness1 and otherwise altering its character40 ,it is a powerful oxidising agent1 some of the water being decomposed1 and hydrogen set free1 and the oxygen acting upon any organic matter present4 ,it also removes lead from water4 ,as already seen1 it does not1 however1 fulfil the primary object of water1 by depriving it of any microbes contained in it4 ,magnetic carbide of iron is obtained by heating hmatite ore with sawdust4 ,its action is similar to that of spongy iron4 ,the ,pasteur-,chamberland filter consists of a cylinder of unglazed fine porcelain made from a well-baked ,kaolin of a certain degree of porosity and hardness4 7,fig4 #aj47 ,the water passes through the porcelain from without inwards1 and with the pressure of #a to #b atmospheres which is usually present in the pipes of a water-service1 passes through at the rate of about three quarts per hour4 ,the filter can easily be cleaned by brushing it in a stream of hot water1 or by subjecting to the heat of a ,bunsen burner4 ,the filtration is entirely mechanical1 the filtered water being quite freed of microbes4 ,no chemical action takes place4 ,illustration3 ,,fig4 #aj4 ,,pasteur-,,chamberland ,,filter4 ,a4--,outlet of filtered water4 ,b4--,pasteur tube4 ,c4--,metal tube containing unfiltered water4 ,d4--,unfiltered water delivered through tap4 ,the ,berkefeld filter is cylindrical like the ,pasteur-,chamberland filter1 and is used in the same way4 ,it is made of infusorial earth1 which is soft and friable and liable to break4 ,the cylinder becomes gradually worn thin by cleaning1 and it then ceases to filter efficiently4 ,its sole advantage over the ,pasteur-,chamberland filter is the more rapid rate of filtration2 and against this is to be set the greater liability to fracture and the lack of continuance of efficient filtration4 ,woodhead and ,wood in the report already quoted1 state3 8,the ,berkefeld filter appears to have the largest pores among the efficient filters1 as is evidenced by the fact that the water organisms were not apparently weakened1 that more species of organisms appeared in its filtrate1 and that lowering the temperature to #aa ,c4 did not prevent their appearance4 ,the ,pasteur-,chamberland filter1 on the other hand1 at #aa ,c4 was able to give an apparently sterile filtrate for a prolonged period40 ,more recent experiments have shewn that pathogenic 7disease-producing7 microbes contained in water after awhile grow through the substance of a ,berkefeld filter1 and that this does not happen with a ,pasteur-,chamberland filter4 ,the latter is therefore preferable4 ,in determining the number of bougies required for any filter to secure a given amount of pure water1 it is necessary to calculate on the basis of the output after several weeks' use1 not on the original output4 ,if this is done1 pure water will be secured without disappointment as to the amount supplied4 ,,chapter ,,xiv4 ,,composition ,,and ,,properties ,,of ,,air4 ,an abundant supply of fresh air is necessary at all times4 ,and yet its importance is commonly ignored in practical life4 ,strenuous efforts are made to ensure a supply of food1 and water is commonly filtered or otherwise purified before drinking2 but many are content to live in an impure atmosphere1 which hardly suffices for the preservation of life1 and certainly not of health4 ,deprivation of food1 or even of water1 only kills after several days or weeks2 deprivation of air kills in a few minutes4 ,only about three pints of water are required daily1 while at least #a1ejj gallons of air are necessary every day for carrying on the vital functions4 ,composition of ,air4--,the air constitutes a gaseous ocean in which we live1 as fishes live in water4 ,in virtue of its weight1 it exerts a pressure of about #ae lbs4 on every square inch4 ,this pressure is usually measured by the barometer1 and is equivalent on an average to that of a column of #cj inches of quicksilver4 7,see page #cca74 ,chemically1 air consists of a mixture of various gases and vapours4 ,these are chiefly ,oxygen and ,nitrogen2 but in addition1 there are minute quantities of carbonic acid1 argon1 hydrogen1 water vapour1 ammonia1 ozone1 and suspended matters4 ,the oxygen and nitrogen exist1 in the proportion by volume of #bji of oxygen to #gia of nitrogen1 or of #bcaf grains of oxygen to #gfhd of nitrogen1 by weight4 ,these two gases do not exist in chemical combination1 but mechanically mixed4 ,this is proved by the fact1 that they do not exist in air in the proportion of their combining weights1 or any multiple of these2 that the proportion varies slightly at different parts2 and that the air which is dissolved in water does not contain the nitrogen and oxygen in the proportion #d to #a 7as in the atmosphere71 but in the proportion #ahg to #a4 ,this means that oxygen1 being more soluble in water than nitrogen1 has dissolved in a larger proportion2 as it certainly would not have done1 had the oxygen and nitrogen been chemically combined4 ,the oxygen dissolved in water supplies fishes with the necessary oxygen for their respiratory processes4 ,similarly the oxygen in the atmosphere is its most essential constituent1 being required in all processes of oxidation 7i4e41 combustion71 whether in living organisms or in the inanimate world4 ,nitrogen serves as a diluting agent4 ,it is incapable of supporting life alone2 and many of the fatal accidents which have occurred through men descending deep wells without first testing1 by means of a lit candle held well below them1 the quality of the air near the bottom1 have been due to an accumulation of nitrogen in the well4 ,ozone is a condensed form of oxygen1 which is present in minute quantities in pure air1 and especially during a thunder-storm or after a fall of snow1 and in the air near the sea4 ,in it three volumes of oxygen are condensed so as to occupy two volumes4 ,in this condensed condition it has powerful chemical affinities2 often oxidising substances which oxygen cannot attack4 ,it is generally absent from the close air of towns and dwelling houses1 having been used up to oxidise the organic matter present in these places4 ,air without it is said to be 8devitalised02 and ozone has been described as the scavenger of the air4 ,ozone can be produced by hanging a piece of moist phosphorus in a room2 and it is stated by ,dr4 ,daubeny1 that part of the oxygen given out by plants1 especially by scented flowering plants1 is in the condition of ozone4 ,a small quantity is produced when an electrical machine is worked2 its presence is evidenced by a peculiar smell 7the name ozone is derived from the ,greek word for smell74 ,test of ,ozone in ,air4--,traces of ozone in air are detected by exposing strips of blotting paper moistened with a mixture of a solution of potassic iodide and starch4 ,if ozone is present1 the paper assumes a blue tint1 due to the liberation of iodine1 and its combination with the starch4 ,other acid gases may1 however1 produce the same effect4 ,a second test should1 therefore1 be tried4 ,soak red litmus paper with a very dilute solution of potassic iodide1 and expose as before4 ,potassic oxide is produced if ozone is present1 and this turns the litmus blue4 ,aqueous ,vapour is always present in air1 though the amount varies greatly4 ,it is invisible in the ordinary condition1 but by condensation becomes cloud or fog1 rain1 snow1 or hail4 ,the quantity of moisture present varies with the temperature of the air2 the higher the temperature1 the more water can be vaporised1 without the point of saturation being reached4 ,an increase of #bg ,fahr4 doubles the capacity of air for moisture4 ,the amount of moisture that would saturate air at #ej ,fahr4 only gives #ga per cent4 of the saturation amount at #fj ,fahr4 ,the amount of moisture is estimated by the hygrometer 7page #bdj74 ,air saturated with moisture at #cb ,fahr41 holds vapour equal to #aafj of its weight2 at #ei it holds #ahj1 at #hf #adj1 at #aac #abj1 and at #adj #aaj4 ,ammonia in normal air does not exceed one part in a million of air2 but it is always present--either as free ammonia or as sulphate1 chloride1 carbonate1 or sulphide of ammonia4 ,from this source1 plants derive some of the nitrogen they require as food2 some also from the free nitrogen1 which is fixed by certain microbes1 growing in the nodules connected with the roots of peas1 lentils1 and other plants 7page #bgd74 ,traces of nitrous and nitric acid are also present in the air1 produced by the direct combination of nitrogen and oxygen occurring as the result of the electric spark during lightning4 ,carbonic ,acid or carbon dioxide is always present in air1 in the proportion of #ccf to #d parts in #aj1jjj2 but in impure air may be present in much larger amount4 ,it is a heavy gas1 incapable of supporting combustion1 and therefore of supporting animal life4 ,being a heavy gas1 it tends to accumulate where it is produced1 as about lime-kilns by the heating of chalk4 ,thus ,ca,c,o 7chalk7 7heated7 ,ca,o 7lime7 ,,co 7carbonic acid74 ,tramps have occasionally died of carbonic acid poisoning through sleeping near lime-kilns4 ,it is produced by the oxidation of carbonaceous matters1 hence in all ordinary combustion1 in many cases of putrefaction and fermentation1 and in the respiratory processes of all animals4 ,plants diminish the amount of carbonic acid in the atmosphere4 ,two processes occur in most plants3 a process of respiration1 as in animals2 and a process of assimilation1 by which the leaves and all other green parts of a plant under the influence of sunlight decompose the carbonic acid of the atmosphere1 fixing its carbon and liberating its oxygen4 ,plants such as fungi1 which are destitute of green colouring matter1 cannot decompose carbonic acid2 nor can any plants during the night4 ,during the day green plants are air purifiers2 during the night all plants vitiate the air to a slight extent4 ,the ,air in ,relation to ,respiration4--,the oxygen of air is absolutely essential for the continuance of life4 ,in every organised animal1 lungs or analogous organs are provided1 in order to supply the necessary oxygen to the system1 and to remove the impure air from it4 ,the act of breathing occurs in man about seventeen times per minute4 ,while the inspired air is in contact with the interior of the lungs1 it undergoes important alterations4 ,it comes into contact with the five or six millions air-vesicles which form the minute dilated terminations of the windpipe1 and have an aggregate area of ten to twenty square feet4 ,each of the air-vesicles has extremely thin walls2 and outside these delicate walls lie capillary blood-vessels1 full of impure blood4 ,an active interchange now occurs between the air and the gases dissolved in the blood4 ,oxygen passes through the intervening membrane into the blood1 while carbonic acid and other impurities of the blood pass into the air-vesicle4 ,the consequence of this is that the impure dark-coloured blood becomes bright scarlet and pure4 ,this purification is not confined to any one portion of the blood2 for the heart contracting #fj or #gj times per minute1 pours successive portions of blood into the capillaries surrounding the air-vesicles2 while at the same time1 pure air is brought into the air-vesicles seventeen times per minute1 and so the interchange is constantly kept up4 ,in view of the incessant character of respiration and circulation1 it is clear that all the blood will be purified if the external air is pure2 and that if there is any detrimental matter in the air1 it probably will come into contact with the blood in the lungs4 ,the amount of air taken in with each inspiration is about thirty cubic inches4 ,this is called the tidal air1 as it is constantly ebbing and flowing from and to the lungs4 ,by means of a very forced inspiration1 about #ajj cubic inches of additional air can be inspired2 and similarly after an ordinary inspiration1 one can expire forcibly an additional #ajj cubic inches1 though there will still be left in the lungs another #ajj cubic inches of air4 ,thus3-- ,tidal air #cj cub4 in4 ,complemental air #ajj ,supplemental air #ajj ,residual air #ajj -------- ,total capacity of lungs #ccj ,corresponding to the respiratory changes in the lungs1 there are changes in the tissues throughout the body4 ,the pure and oxygenated blood leaving the lungs1 is carried to all parts of the system4 ,oxidation and allied processes are actively carried on1 the result of which is the formation of urea1 carbonic acid1 and smaller quantities of other effete matters4 ,these are then carried by the blood to the excretory organs1 urea being chiefly eliminated by the kidneys1 and carbonic acid by the lungs4 ,examination of ,expired ,air shows that--#a4 ,it is heated2 in its passage through the nose and deeper respiratory passages it has acquired a temperature approaching that of the blood4 #b4 ,its moisture is increased4 ,by the skin and lungs from #be to #dj ounces of water pass off in the twenty-four hours2 the relative amount varies somewhat4 #c4 ,it contains #d to #e per cent4 less oxygen1 and #d per cent4 more carbonic acid than inspired air4 ,the carbonic acid1 instead of being #d parts in #aj1jjj of air1 becomes over #djj in #aj1jjj1 while the oxygen is diminished in a somewhat larger proportion4 ,thus3-- ,,oxygen4 ,,nitrogen4 ,,carbonic ,,acid4 ,inspired air contains #bjha #giae #jd ,expired #afjcc #gieeg #dch ,the amount of carbonic acid expired varies under different circumstances4 ,it is increased by active work1 by an increase of food1 by a diminution of the external temperature2 it is greater when the surrounding air is pure1 and when it is moist2 and it varies with the season1 being greatest in spring1 and least in autumn4 ,children require more oxygen1 and expire more carbonic acid than adults1 weight for weight4 ,a child six or seven years old requires nearly as much oxygen as one twice that age4 ,boys usually require more air than girls1 as they are more active and exhale a larger amount of carbonic acid and other impurities4 ,the average amount of carbonic acid eliminated by a healthy adult is at least #jf cubic foot per hour1 or #add cubic feet per day4 ,this reckoned as carbon is equivalent to #afj grains per hour1 or half a pound of carbon in the twenty-four hours4 ,liebig gives the amount of carbonic acid expired as #jgi cubic foot per hour1 or #ai cubic feet per day4 #d4 ,it contains organic impurities4 ,these are chiefly gaseous1 solid particles only being expired during coughing1 or possibly during conversation4 ,the danger from the 8breath0 of patients in infectious diseases is really associated rather with the dried discharges on handkerchiefs1 etc41 than from the 8breath0 itself2 unless droplets of saliva discharged during speaking1 or mucus during coughing1 are directly inhaled4 ,,chapter ,,xv4 ,,suspended ,,impurities ,,of ,,air4 ,pure air being essential to life and health1 it is important to ascertain the character and origin of the impurities of air4 ,innumerable substance--in the condition of gases1 vapours1 or solid particles--constantly pass into it1 and deteriorate its quality4 ,to counteract this1 certain purifying agencies are at work1 the mechanism of which will be considered hereafter4 ,impurities are much commoner and more abundant in the air of enclosed spaces than in the external air1 as the natural processes of purification cannot be brought to bear so efficiently in the former case4 ,in sick rooms1 hospitals1 etc41 impurities arise1 which are not present where only healthy people are collected4 ,the most important impurities are derived from the respiration of animals1 and the combustion of gases1 candles1 or lamps in rooms1 from sewage emanations1 from various occupations1 and the air of marshes1 mines1 church-yards1 etc4 ,these may be classed under two heads--solid and gaseous2 the solid being simply suspended in the air in a finely divided condition1 or floated about in a coarser condition by currents of air4 ,they are revealed in an atmosphere in which one did not previously suspect their existence1 by the passage of a beam of sunlight4 ,light itself is invisible1 but its course is rendered visible by the particles from which its rays are reflected4 ,tyndall demonstrated the presence of minute particulate matter in the air of all ordinary situations1 and showed that a large proportion of this matter consists of germs 7microbes74 ,in his experiments with vapours in closed tubes1 floating matter was always revealed by a concentrated beam of light1 even though the air entering the tube had been first drawn through sulphuric acid and through a strong solution of caustic potash4 ,if this air was then passed through a red-hot platinum tube and across folds of red-hot platinum gauze1 it became optically empty2 the floating matter had been burnt1 and disappeared4 ,it was therefore organic4 ,in subsequent experiments1 he took organic solutions1 as of meat1 turnip1 and the like1 and rendered them sterile by repeated boiling4 ,they remained sterile when kept in air-tight vessels or in vessels covered with a thick layer of cotton-wool1 which would efficiently filter any entering air2 but when exposed to the air1 they invariably became turbid1 owing to an enormous multiplication of germs4 ,clearly1 therefore1 air contains organic1 matter1 and much of this organic matter consists of living germs4 ,most of these germs are comparatively harmless under ordinary conditions4 ,they are1 however1 the causes of fermentation1 putrefaction1 and all the processes of decomposition which occur in organic substances4 ,the importance of the exclusion of the dust of air has received an important application in ,lister's antiseptic and in the aseptic system of treatment of wounds4 ,formerly accidents and operations were frequently fatal2 now vast numbers of lives are saved by improved surgical methods4 ,the original antiseptic method acted on the supposition that some germicidal application to the wounds was necessary2 now it is realized that if1 during the operation1 germs are not allowed to remain in the wound1 all that is afterwards necessary to insure rapid recovery is that they shall be prevented from entering the wound from the external air during its process of recovery4 ,by the adoption of such means1 large wounds can be made to heal1 without the formation of a drop of 8pus0 or 8matter40 7,see also page #aaj47 ,suspended ,matters are mineral or organic1 the two being commonly associated together4 ,the mineral matters consist largely of fine particles of common salt1 silica1 clay1 iron rust1 dried mud1 chalk1 coal1 soot1 and similar substances4 ,not uncommonly the mineral particles are coated by1 or mixed with1 organic matter1 the comparative lightness of the organic matter enabling the mineral matter to float about more easily4 ,the objection to dust is thus intensified1 for not only is it irritating to the respiratory passages and generally disagreeable1 but it carries with it putrescent and possibly morbific particles4 ,the prevention of infectious diseases resolves itself largely into means for preventing the inhalation of dust4 ,organic ,suspended ,matters in the open air are1 most commonly1 minute fragments of wood and straw1 dried horse litter1 fragments of insects1 the spores and pollen of plants1 and microscopic plants and animals4 ,in addition1 there is the putrescent organic matter resulting from respiration and other organic functions4 ,indoors1 the air commonly contains1 in addition1 fragments of cotton1 linen1 silk1 or other fibres1 fragments of vegetables1 starch cells1 soot1 charred wood1 splinters from floors1 etc4 ,in ,sick ,rooms1 products of the morbid conditions may be evolved2 thus1 pus-cells1 particles from the expectoration1 blood cells1 fat particles1 epithelium1 or the special germs or microbes to which infectious diseases are due4 ,these are disturbed by the movements of persons1 causing the dust to rise2 and thus the infection of consumption1 and of the acute infectious diseases1 is frequently spread4 ,flies and other winged insects are important auxiliaries in the diffusion of disease-carrying particles4 ,receiving some morbid secretions on their limbs1 or other parts of their bodies1 they have occasionally been the means of spreading erysipelas in hospitals1 and glanders in veterinary stables4 ,the specific contagia of cholera1 enteric fever1 and summer diarrha are occasionally conveyed to food by flies which have previously alighted on latrines or privies or other places where the stools of such patients have been deposited 7page #bha74 ,the excreta of flies1 which are not uncommonly deposited on food1 or on articles of furniture1 have occasionally being found to contain the minute ova of intestinal worms4 ,effects of ,suspended ,matters4--,the inhalation of dust is followed by deleterious effects4 ,we may divide the solid substances inhaled as dust into three kinds3--dead substances1 living substances1 and the contagia 7microbes or germs7 of various diseases4 #a4 ,dead ,substances inhaled for a prolonged period in various occupations are a common cause of premature death4 ,the potter draws into his lungs a fine silicious dust1 which irritates his lungs1 and finally produces a fatal disease1 known as potter's asthma4 ,mill-stone ,cutters and ,stone ,masons inhale the fine particles of stone given off from the material which is being chiselled4 ,these produce serious disease of the lungs4 ,pearl ,cutters inhale fine particles of pearl-dust1 and as they generally work in close rooms1 and the dust is light and tasteless1 serious disease of the lungs results4 ,sand-paper ,makers inhale minute portions of glass and sand2 and needle and knife grinders are exposed to similar dangers1 and at one time the mortality among them was frightful4 ,it has greatly diminished since the introduction of wet grinding1 the use of steam fans1 and wearing of respirators4 ,hemp and ,flax ,dressers inhale a dust which is peculiarly irritating4 ,workers in rags and in wool suffer in like manner from dust4 ,the dust from fleeces of wool1 and especially from the alpaca fleece1 has produced in many cases 7in the neighbourhood of ,bradford and elsewhere7 an acute disease 7anthrax7 proving fatal in a few days4 ,the spores of this disease are very persistent of life 7page #bgd71 and remain active for mischief for months after the death of the animal which had suffered from it4 ,the fleece can be disinfected by steam2 and the use of fans for diverting the dust created during 8sorting0 minimises the danger from it4 ,the miller commonly suffers from a form of asthma1 not so severe as potter's asthma1 as the particles in this case are not equally irritating4 ,the hairdresser is liable to inhale the short fragments of hair cut by the scissors1 and the mortality of this class of workers is high4 ,miners in coal have a surprisingly low mortality1 when accidents are excluded from the calculation2 except in ,south ,wales1 where it is slightly higher than for all males in the same district4 ,coal dust is relatively free from sharp angles1 and is therefore not so irritating to the lungs as metallic dust4 ,consumption is relatively rare among miners4 ,the ,fur-dyer is very prone to suffer from the dust of the dyed furs1 great irritation and disease resulting in many cases4 ,artificial ,flower-makers1 and those engaged in colouring arsenical wall-papers1 suffer from the inhalation of arsenical vapours1 as well as from the irritating effects of its absorption by the skin4 ,these are now seldom seen1 owing to the almost complete abandonment of the use of arsenic for wall-pigments4 ,cigar-makers are liable to have their lungs irritated by inhalation of the dust of the tobacco-leaf2 and may suffer from tobacco-poisoning4 ,workers in ,lead are very liable to be poisoned by the metal1 e4g41 house painters1 potters engaged in the glazing process1 in which the ware is dipped into a solution containing lead1 manufacturers of white lead1 and others4 ,the lead is partly absorbed by the skin2 in some cases it is inhaled as dust2 and more often it is swallowed1 when the workman eats his meals with unwashed hands4 ,of the symptoms 8painter's colic0 and 8drop-wrist0 are the two most important1 though1 in some cases1 lead shews its effects more insidiously1 leading to gout and chronic renal disease4 ,it is now compulsory on employers to provide in the workshop1 complete washing arrangements for the use of workers in lead4 ,every doctor called to attend a case of lead or phosphorus or arsenic poisoning or anthrax1 which has been acquired in an industrial occupation1 must notify the same to ,h4,m4 ,inspector of ,factories4 ,this implies inspection of the factory or workshop and the subsequent adoption of further measures of precaution4 ,brass-founders occasionally inhale the fumes of oxide of zinc2 and diarrha1 cramp1 waterbrash1 and other troubles are the result4 ,those engaged in the manufacture of bichromate of potass1 are liable to partial destruction of the mucous membrane of the nose1 and to irritation of the skin1 with the formation1 in some cases1 of small ulcers4 ,workers with ,phosphorus1 as those engaged in the making of phosphorus matches1 not uncommonly suffer from a gradual necrosis 7death7 of the jaw-bone4 ,those having carious teeth are especially attacked by this disease1 which is due to the fumes of oxide of phosphorus1 attacking the jaw4 ,improved ventilation of workshops1 careful attention to the teeth1 and other measures1 have greatly diminished this disease2 and it has disappeared where safety matches made from red non-volatile phosphorus1 have replaced matches made from the yellow variety4 ,chimney ,sweeps occasionally suffer from irritative skin diseases1 as well as bronchitis4 ,in some cases the chronic irritation of the soot has produced cancer of the skin4 ,the effect of dust on workers can be seen in the mortality returns3 ,among men aged #be to #fe years in #ahha-ij1 the comparative mortality figure in ,england and ,wales was as follows1 all males throughout the country being taken as a standard and given as #a1jjj3-- ,,comparative ,,mortality ,,figures4 ,all males #ajjj ,,occupations ,,with ,,no ,,dust4 ,,dusty ,,occupations4 ,clergyman #ecc ,coal miner 7,derby and ,notts47 #gbg ,gardener #eec ,carpenter #ghc ,farmer #efc ,bricklayer1 mason #a1jja ,teacher #fjd ,coal miner 7,lanc47 #a1jfi ,tool and scissors maker #a1dab ,potter #a1gjf ,file-maker #a1haj ,remedial ,measures4--,means have been taken to diminish the prevalence of the above dust diseases1 in several cases with remarkable success4 ,in the case of steel-grinding1 for instance1 the mortality is greatest with dry grinding1 and least with wet grinding4 ,wet processes have been applied to others of the industries named1 with a like success4 ,where the dust cannot be avoided1 the use of steam or electric fans1 to deflect the dust away from the workman1 has been found successful2 and in many cases1 free ventilation of the workshops has greatly diminished the mortality4 ,where none of the above measures suffice1 the use of respirators ought to be insisted on4 ,breathing through the nostrils ought to be carefully maintained1 as thus the dust is to a large extent stopped before reaching the lungs4 ,the dangers of lead poisoning may be avoided by absolute cleanliness1 the hands being always washed before taking meals1 and the nail-brush used to secure complete cleanliness beneath the nails4 #b4 ,living ,substances4--,the pollen of plants in some persons produces a distressing form of disease1 called hay-asthma1 which is apt to recur each year1 and is sometimes only curable by living in a town or removing to the sea-coast4 ,the amount of pollen floating about in the atmosphere is considerable2 #ie per cent4 of it is grass-pollen1 and this form and the pollen from pine-trees appear to be the most powerful in inducing hay-asthma4 ,according to some authorities1 hay-asthma is rather due to the minute particles constituting the scent of various flowers1 than to the pollen2 but that is probably not the usual mode of origin of the disease1 though it may be in some cases4 ,in some cases1 true asthma results from smelling particular plants4 ,here as in the case of hay-asthma a peculiar idiosyncrasy is involved1 only a very small proportion of those exposed to the minute particles suffering from asthma4 ,the spores of many fungi and of other living organisms are constantly being floated about in the air1 until they find a suitable resting place1 when they settle and proceed to grow and multiply4 ,the souring of milk1 the fermentation of a saccharine solution1 the moulding of bread1 the presence of mildew1 the blighting of corn1 and numerous other phenomena are due to the growth of organisms carried by the atmosphere from one part to another4 #c4 ,the ,contagia 7microbes or germs7 of the acute infectious diseases are minute living organisms1 known as bacteria4 ,hence these diseases may be carried about by currents of air1 some much more easily than others4 ,some of the contagia have a persistent vitality4 ,thus the contagia of scarlet fever1 diphtheria1 or small-pox may infect a room for months1 causing the disease in question1 when infected articles in the room are disturbed4 ,the contagia of typhus fever and of measles1 on the other hand1 are short-lived1 and do not usually resist free ventilation and exposure to sunlight4 ,besides the contagia of the acute fevers1 septic organisms may be carried by the atmosphere4 ,formerly1 blood-poisoning from operation and other wounds was common2 but ,lister1 by insisting on absolute cleanliness of wounds1 and only allowing air to have access to the wound which had been filtered through layers of gauze and deprived of its septic germs1 has secured that wounds can now be kept perfectly 8sweet10 the suppuration in them reduced to a minimum1 and the danger of blood-poisoning almost annihilated 7page #ajf74 ,it had often been noticed that recovery from even very severe injuries was common1 if only the skin remained unbroken2 while the same injuries1 with the addition of a rupture of the skin1 and consequent access of air1 were rapidly fatal4 ,but to ,lister is due the great honour of proving that it was not the air which produced the mischief1 but the germs it contained1 and that filtered air might be admitted with impunity4 ,erysipelas and hospital gangrene have occasionally been carried about in hospital wards by dirty sponges and dressings2 and if the ventilation is not perfect1 particles of epithelium and pus from diseased persons may be carried to other patients at a distance4 ,some forms of purulent disease of the eyes are transferable from patient to patient1 and in children some forms of eczema are also contagious4 ,,chapter ,,xvi4 ,,gaseous ,,and ,,other ,,impurities ,,of ,,air4 ,gaseous impurities of the air are very commonly associated with suspended matters1 and it is often difficult to separate the effects of the two4 ,different gases are also often associated1 and so produce modified results4 ,it will be convenient to consider1 first of all1 certain well-marked gaseous impurities1 and then others in which there is a mixture of several gases1 or of these with suspended solid particles4 ,under the first head the most important impurity is-- 7#a7 ,carbonic ,acid4--,this is reckoned an impurity if amounting to more than #e parts in #aj1jjj of air4 ,owing to the large amount produced in the respiration of animals1 in the combustion of fires1 gas1 lamps1 etc41 and in other natural processes1 it would be much greater in populous parts1 were it not for the rapid diffusion occurring in the air1 and the purifying action of plants4 ,the following analyses 7,angus ,smith7 illustrate the facts that in towns the amount rises1 and is greatest in the most populous parts1 while during fogs it is greatly increased4 ,,volumes ,,of ,,carbonic ,,acid ,,in #aj1jjj ,,volumes ,,of ,,air4 ,on the mountains and moors of ,scotland mean of #eg analyses #ccf ,in the streets of ,glasgow mean of #db analyses #ejb ,london1 ,n41 ,n4,e41 and ,n4,w4 postal districts mean of #cj analyses #dchd ,london1 ,e4 and ,e4,c4mean of #ab analyses #dgde ,manchester streets1 ordinary weather #djc ,during fogs in ,manchester #fgi ,the effects of carbonic acid gas alone must be carefully distinguished from those of the same gas plus the organic impurities from respiration1 with which it is commonly associated4 ,dr4 ,angus ,smith found that air containing #c per cent4 of carbonic acid produced difficulty of breathing1 but he was able to breathe comfortably an atmosphere containing #jb per cent4 carbonic acid4 ,other observers have found they could breathe without discomfort air containing #a per cent4 carbonic acid4 ,when the carbonic acid is derived from respiration1 headache and giddiness are produced in many persons when the carbonic acid amounts to #jae per cent4 ,a fatal result has occasionally occurred from the inhalation of the carbonic acid at the bottom of brewing vats1 or about lime-kilns4 ,the gaseous impurity at the bottom of wells is more commonly nitrogen than carbonic acid 7page #ajb74 ,the presence of an excess of carbonic acid diminishes the elimination of carbonic acid from the lungs1 nutrition and muscular energy being consequently impaired4 ,this is seen in workshops where the air is confined and gaslight is commonly employed2 though the air here also contains carbonic oxide1 sulphurous acid1 and organic impurities1 and these probably have a large share in producing the evil results4 7#b7 ,carbonic ,oxide in the proportion of more than #a per cent4 is rapidly fatal1 and has poisoned when under #ab per cent4 ,poisoning by its means occurs where charcoal stoves are used1 and especially when the charcoal is burnt in rooms with no chimney flue4 ,this is an occasional mode of suicide on the continent4 ,carbonic oxide is a much more deadly poison than the dioxide 7carbonic acid72 it forms a stable compound with the hmoglobin of the red blood-corpuscles1 displacing oxygen from them1 and is got rid of with great difficulty4 ,lace-frame makers place a coke stove under their work1 and thus inhale the invisible gas4 ,headache1 giddiness1 irregular action of the heart1 and depression of the general health result4 ,carbonic oxide is the most poisonous constituent of coal-gas1 and is present in much larger quantity in carburetted water-gas with which coal-gas is now commonly mixed1 than in pure coal-gas 7page #aae74 7#c7 ,the inhalation of ,sulphuretted ,hydrogen produces headache1 nausea1 and diarrha2 but in manufactures involving the inhalation of a small proportion of this gas the symptoms are much slighter4 7#d7 ,sulphurous ,acid is always present in small quantities in the air of towns1 derived from the combustion of coal and coal-gas4 ,straw-bleachers and the bleachers in cotton and worsted manufactories1 often suffer from severe cough and bronchitis due to inhaling its irritating vapours4 7#e7 ,carbon ,disulphide when vaporised and inhaled produces headache1 general muscular pains1 and nervous depression4 ,it is used in the manufacture of waterproof coats1 toy balloons1 etc4 7#f7 ,ammonia produces irritation of the eyes and bronchial irritation4 ,hat-makers commonly suffer from its effects1 being generally pale and feeble4 ,it is difficult to say how much is due to the ammonia1 and how much to the high temperature at which they work4 7#g7 ,acid ,fumes are very irritating to the lungs1 and in the case of alkali manufactures1 they destroy all vegetation for considerable distances4 ,hydrochloric acid produces great irritation1 and chlorine even more so4 ,the fur-dyer is not only subject to the dangers of dust1 but also of the fumes of nitric acid1 used to remove fat and give certain shades of colour to the fur4 7#h7 ,other ,vapours evolved in various processes produce special symptoms4 ,house-painters suffer from the inhalation of turpentine vapour1 headache and loss of appetite commonly resulting4 ,the symptoms from the commonly coexistent lead-poisoning are distinct4 ,brush-makers have a persistent cough1 due to the inhalation of resinous fumes1 evolved in making brushes4 ,workers in paraffin are liable to an irritative disease of the hair-follicles of the body1 followed by the formation of scars1 almost like small-pox marks4 ,workers in quicksilver1 as those engaged in making mirrors or thermometers1 are prone to suffer from mercurial poisoning4 ,the gums become spongy1 and there is profuse salivation1 also generally alimentary disturbance2 and in some cases nervous affections1 resulting in persistent muscular tremblings1 etc4 ,under the second head--cases of inhalation of mixed gaseous and particulate contamination--we must consider 7#a7 ,the ,effects of ,air ,rendered ,impure by ,respiration4--,it has been already stated that an amount of carbonic acid which could easily be borne alone1 is intolerable when other products of respiration are mixed with it4 ,these are chiefly organic gases and solids1 which 7unless removed quickly7 render the atmosphere close and 8stuffy0--an effect which is readily perceptible by the sense of smell of those entering an occupied room immediately from the outer air4 ,when such a room is inhabited for a few hours1 headache1 langour1 drowsiness1 and yawning 7which is really a cry for purer air7 result4 ,the soporific effects so commonly produced in churches1 etc41 are commonly due to the vitiated atmosphere1 rather than as is supposed to the soothing effects of the sermon4 ,when the exposure to foul air is more chronic1 and occurs day after day1 there results a general lowering of strength and vigour--both bodily and mental--even where no actual disease is set up4 ,oxidation processes are retarded2 the consequence is an anmic sallow complexion1 which compares badly with the ruddy complexion of those spending a great part of the day out of doors4 ,the prolonged breathing of air1 foul from the products of respiration1 is perhaps more common in workshops and schools than in private houses2 but in both1 a faint smell is commonly perceptible on entering from the open air1 indicating imperfect ventilation and accumulation of organic putrescible matter4 ,the preceding remarks are left as in the last edition4 ,it must be noted1 however1 that recent research attaches more importance to the particulate matter 7dust7 in the atmosphere than to the amount of gaseous impurity1 though the latter remains a convenient index of impurity4 ,experiments made by ,drs4 ,haldane and ,l4 ,smith on themselves negative the older conclusion that a special organic poison exists in expired air4 ,they were able without any appreciable effect on themselves to breathe air which was vitiated to such an extent as to completely prevent a match from burning2 and they conclude that excess of carbonic acid and deficiency of oxygen are the sole cause of danger from breathing air highly vitiated by respiration4 ,this conclusion may be accepted under the conditions of these experiments4 ,under ordinary conditions1 however1 the evil effects produced by breathing the air of crowded rooms1 are due not only to the excess of carbonic acid and deficiency of oxygen1 but also to the dust which is usually associated with them4 ,this dust1 which may be derived from handkerchiefs of patients suffering from influenza1 consumption1 sore throat1 c41 or from other sources1 is apt to be inhaled by the persons occupying such rooms4 ,the tendency to catarrhs is greatly increased by living in a vitiated atmosphere4 ,in the causation of 8colds0 two elements are concerned1 the infective agent1 and the condition of the patients4 8,colds0 are caused primarily by infection from previous patients4 ,the nasal discharge of a 8cold in the head0 contains the contagium4 ,this is dried on handkerchiefs1 and is subsequently scattered as dust1 and thus conveyed to others4 ,ordinarily there is considerable resisting power against such catarrhs4 ,when1 however1 the general vitality or the local vitality of the mucous membrane of the nose1 throat1 and lungs is impaired by the breathing of impure air or by sitting in wet clothes after exposure to wet and cold1 a catarrh is produced4 ,the close connection of phthisis 7consumption7 with overcrowding and the breathing of a vitiated atmosphere will be discussed hereafter 7page #cac74 ,the polluted air acts in producing consumption by depressing vital functions1 and diminishing the powers of resistance against the actual contagium of the disease1 which is inhaled as dust1 produced by the drying of the expectoration of consumptive patients4 ,the germs of infectious diseases are propagated very rapidly in an impure atmosphere2 and typhus fever occurs almost solely in conditions of overcrowding4 ,in the cattle-plague of #ahff1 it was found that nearly all the cows died when crowded together in unventilated sheds1 while only a third died when there was free ventilation4 ,the effects of air containing the products of respiration in a concentrated condition1 and of a deficient supply of air1 have been shown only too well in the oft-quoted case of the ,black ,hole of ,calcutta4 ,in this case1 #adf persons were confined in a space eighteen feet every way1 with two small windows on one side4 ,next morning #abc were found dead1 and the remaining #bc were very ill4 ,in the experience of this country1 the highest death-rates are in the most densely populated districts4 ,the death-rate from phthisis1 childbirth1 and typhus fever for instance1 is far higher in cities than in country-places4 ,the fact may be explained in various ways4 ,density of population commonly implies insufficient or unwholesome food1 unhealthy work1 and poverty2 but especially impurity of the air1 uncleanliness1 and imperfect removal of excreta4 ,of these factors1 the vitiated air is probably the most powerful for evil4 ,children suffer more than adults from close aggregation of population1 largely owing to the greater ease with which infectious diseases spread in towns4 7#b7 ,coal-gas is obtained by the destructive distillation of coal1 free from access of air4 ,the average composition of ,london coal-gas is hydrogen #ej to #ec1 saturated hydrocarbons #cc to #ff1 unsaturated hydrocarbons #ce to #cf1 carbonic oxide #eg to #ga1 carbonic acid #j to #jf1 nitrogen #be to #da1 and oxygen #jb to #jc per cent4 ,of these the illuminants are olefiant gas 7,c,h7 and the higher hydrocarbons4 ,sulphuretted hydrogen and other sulphur compounds are present in small quantities1 averaging #ab grains of sulphur per #ajj cubic feet of ,london gas4 ,the inhalation of coal-gas1 even in small quantities1 is liable to produce headache1 and may lead to chronic poisoning if allowed to continue4 ,where the escape of gas is more extensive1 as when a tap is left turned on accidentally during the night1 two dangers may arise4 ,if a light is struck in the room an explosion occurs2 or persons may be poisoned in their sleep by inhalation of the gas4 ,the most poisonous gas in coal-gas is the carbonic oxide4 ,the chief product of the combustion of coal-gas is carbonic acid4 ,some sulphurous acid is also produced1 which is irritating to breathe1 and injurious to bookbindings1 picture-frames1 etc4 ,if the flame is imperfect1 as when the pressure of gas is too great1 some carbonic oxide may also escape4 ,in recent years ,carburetted water-gas has been largely mixed with coal-gas in certain districts4 ,this is made by passing steam over heated coke4 ,thus ,c ,h,o ,,co ,h 7coke7 7steam7 7carbonic oxide7 7hydrogen7 ,the product is water-gas which burns with a non-luminous flame and has no smell4 ,for illuminating purposes it is enriched with vaporised paraffin oil1 which gives it a high illuminating power1 and a smell rather like that of coal-gas4 ,in some towns as much as #fj per cent4 of this carburetted water-gas is mixed with #dj per cent4 of coal-gas4 ,now as the former contains about #cj per cent4 of carbonic oxide1 and the latter only #g per cent41 a mixture of equal parts of the two gases would contain #ahe per cent4 of carbonic oxide1 and would therefore be much more dangerous than coal-gas4 ,this has been found to be so in actual experience of escapes of gas4 ,in speaking of these products of different illuminants1 it is necessary to adopt a standard of light4 ,in this country the standard has hitherto been a light known as 8one-candle power0 which is given by a sperm candle burning #abj grains per hour1 or in ,v4 ,harcourt's standard flame by a mixture of air and pentane 7,c,h74 ,a good fish-tail or bat's wing burner for coal-gas gives an illuminating power equal to #af candles1 and burns from #d to #e cubic feet of gas per hour4 ,most flat flame burners known as #d or #e1 and supposed to burn that number of cubic feet of gas per hour1 really consume nearly double this amount of gas4 ,in the following table the amount of various products produced and of vitiation of air caused by various forms of illuminants is compared1 when an illumination equal to #af candles is produced in each instance3-- ,,carbonic ,,amount ,,of ,,amount ,,acid ,,moisture ,,oxygen ,,vitiation ,,burnt4 ,,produced4,,produced4 ,,removed4,,produceda ,sperm candles #agdj grains#ff c4ft4 #ff c4ft#if c4ft4 #aa ,paraffin oil #iib #de #ce #fb #g ,coal gas burned in ,argand burner #dh c4 ft4 #be #fd #eh #d ,flat-flame burner#ee #ce #gd #fe #f a ,stated in terms of the number of adults who would cause an equal vitiation4 ,thus as an adult expires #jf cubic feet of carbonic acid per hour1 it follows that the amount of carbonic acid produced in one hour by the various illuminants named in the above table1 burning so as to give a light equal to #af standard candles1 varies from #d to #aa times the amount produced by the adult4 ,candle and oils possess the advantage over coal-gas that no sulphurous acid is produced in combustion4 ,if the pressure in the mains is excessive1 some gas may escape through the burner unburnt or carbonic oxide may escape4 ,in ,england the flashing-point of mineral oils has been fixed at #gc ,fahr4 ,the material of which the reservoirs of lamps are composed should not be glass or other breakable material1 and the wick should be contained in a small wick chamber extending nearly to the bottom of the reservoir4 ,only a tight fitting wick must be used4 ,the best illuminant for domestic purposes is incandescent electricity1 in which no products of combustion are formed1 and only a comparative small amount of heat is produced4 ,electrical illumination possesses the further advantages that there is no blackening of ceilings and no damaging of other decorations as in illumination by gas4 7#c7 ,air ,rendered ,impure by ,exhalations from the ,sick4 ,in addition to the ordinary impurities of occupied rooms1 special impurities are produced1 varying with the character of the disease4 ,they may include infectious particles from the sick4 ,in wards for consumptives and for diphtheria1 dust in the room has been found to contain the special microbes of these diseases4 ,making beds1 sweeping floors1 c4 may help to scatter infectious dust2 hence the importance of adopting means of cleansing which will not scatter dust1 and of keeping sick-rooms spotlessly clean4 ,in many diseases e4g4 consumption1 a patient may re-infect himself with such infectious dust1 and thus diminish his own chance of recovery 7see page #caa74 ,hospital wards can scarcely be too freely ventilated2 but even more important than ventilation is the strictest cleanliness in every minute detail4 7#d7 ,the ,air of ,sewers1 ,cesspools1 etc41 may contain the products of decomposition of sewage1 such as volatile ftid organic matter1 carbo-ammoniacal substances1 sulphuretted hydrogen1 carbonic acid1 etc4 ,the amount of these various products varies greatly under different circumstances1 such as dilution of the sewage1 ventilation of sewers1 temperature1 etc4 ,the effluvia from cesspools are usually more concentrated than those from sewers4 ,it appears fairly certain that the emanations from sewers or drains may give rise to diarrha and gastric disturbances1 and to certain forms of sore throat1 which favour the production of diphtheria4 ,on the other hand1 there is much evidence showing that the danger from sewer-emanations has been exaggerated4 ,carnelley and ,haldane found that the air of the sewers of the ,houses of ,parliament and of certain sewers of ,dundee was not very impure1 containing a smaller number of bacteria than external air4 ,there is reason to believe that the emanations from well-ventilated sewers1 possessing a good gradient1 so that the contents of the sewers are hurried away to the outfall1 are free from danger4 ,the chief source of possible danger would be the escape of the bacteria of such diseases as enteric fever or diphtheria1 which had been discharged into the sewer from patients suffering from these diseases4 ,but1 in the absence of splashing1 these bacteria could not escape from a liquid medium4 ,their escape could only occur when the sewer became dry1 and the dust was carried up by rapid currents of air1 a very improbable occurrence in sewers4 ,hence in the majority of instances sewer emanations must be freed from the accusation of producing infectious diseases4 ,sewer-men usually enjoy good health1 and there is no excess of infectious diseases among them4 ,the emanations from obstructed drains or sewers may cause serious mischief1 similarly to that occasionally produced by the emanations from cesspools4 ,under such conditions1 sulphuretted hydrogen1 carburetted hydrogen1 and other gases are evolved1 and fatal asphyxia has been caused by these4 ,in other instances acute sewer-gas poisoning1 without pneumonia1 has followed4 ,the exhalations from cesspools or privies while cleaning them out1 may produce severe disorders1 which are sometimes fatal4 ,when a drain is newly opened or sewer gas gets into a house1 a less marked form of poisoning sometimes occurs1 chiefly characterised by languor1 headache1 vomiting1 and diarrha4 ,in some cases there may be febrile attacks lasting a few days4 ,children are especially sensitive to such conditions and quickly fall into ill health4 ,the direct origin of acute infectious diseases from the effluvia from drains or cesspools has occasionally occurred4 ,leaky and choked drains under a house are especially dangerous4 ,the subsoil becomes contaminated more and more as time goes on2 foul gases are aspirated into the house1 owing to its interior being warmer than the subsoil2 and finally infectious matter may find its way into the house1 or carried by insects or vermin1 through cracks in the earth4 ,diphtheria has been ascribed to emanations from drains and sewers4 ,there is reason to believe that a non-specific form of sore throat may originate in this way2 but diphtheria is generally1 if not always1 spread by personal infection4 ,diarrha has been occasionally ascribed to sewer-emanations4 ,it chiefly occurs in hot weather1 and is usually associated with a foul condition of the surface soil1 and speedily ceases after this has been scoured by copious rain4 ,enteric or typhoid fever1 has been frequently ascribed to drain and sewer effluvia4 ,it was formerly thought that putrefactive changes alone1 under certain conditions of temperature1 etc41 would produce it1 and ,dr4 ,murchison1 one of the greatest authorities on the subject1 who adopted this view1 proposed for enteric fever the name 8pythogenic fever0 7i4e4 filth-produced74 ,isolated cases of enteric fever1 occurring where there is no system of drainage1 support the same view1 as does also the fact that1 with the adoption of drainage1 the enteric mortality has steadily diminished4 ,on the other hand1 numerous cases can be quoted to show that emanations from excreta have been breathed1 and sewage-contaminated water drunk1 for years1 without the production of a single case of enteric fever--until a case is accidentally imported4 ,the weight of evidence is clearly on the side of the view that only emanations from the liquid or solid dejecta of previous enteric patients will produce enteric fever1 and that it is the solid particles of the urine or fces1 either inhaled as dust or carried on to food by flies1 c41 or mixed with food by contaminated water1 c41 which cause infection4 ,furthermore1 modern investigation shows that infection by dust is the exception in ,england2 and that the enteric infection is usually swallowed and not inhaled1 being taken in infected water or milk or other food4 7#e7 ,effluvia from ,decomposing ,organic ,matter4--7a7 ,the air of marshes contains an excess of carbonic acid1 marsh gas1 etc41 in addition to other organic matters4 ,malarial diseases are commonly ascribed to the inhalation of the marsh effluvia under certain conditions1 though the recent proof of the part played by the mosquito in spreading malaria1 puts the inhalation of such effluvia in the background as cause of this disease 7page #cjg74 ,some forms of diarrha and dysentery have been ascribed1 with a less degree of probability1 to the same cause4 ,in this case1 as in that of emanations from other organic sources1 the impurities received by the air are both gaseous and particulate4 7b7 ,the ,air of ,graveyards contains an excess of carbonic acid4 ,the older intramural graveyards appear to have been a cause of illness2 but modern graveyards1 kept under good regulations have never been shown to cause illness4 7c7 ,the ,effluvia from ,decomposing ,carcases1 especially of horses on the battle-field1 have led to outbreaks of diarrha and dysentery among the soldiers4 7d7 ,the ,effluvia from ,manure and ,similar ,manufactories do not seem to injure the workmen as a rule1 but attacks of diarrha have been produced in the neighbourhood when the wind has wafted the effluvia towards any particular part4 ,sore throat1 and occasionally diphtheria1 have been ascribed to the inhalation of ,london manure taken into ,essex4 7#f7 ,the ,effluvia from ,certain ,manufacturing ,processes seem to be rather nuisances than actually productive of ill health4 ,the vapours given off by tallow-making and bone-burning processes are most disagreeable1 but there is little or no positive evidence of their direct insalubrity4 ,the air of brickfields and cement works is peculiarly disagreeable4 ,the ,degree of ,moisture and the ,temperature of air are of great importance in relation to health4 ,air which is unduly moist or dry1 hot or cold1 may be injurious apart from any foreign matters it contains4 ,the relative amount of moisture is of greater importance than its actual amount4 ,an atmosphere which contains aqueous vapour up to the point of saturation is very oppressive2 the normal evaporation of insensible perspiration 7and with it of the organic impurities removed from the skin7 is interfered with2 and consequently the 8oppressiveness of the day0 is complained of4 ,an unduly hot air is generally productive of pallor and ill health1 though it is difficult to know how much to ascribe to the high temperature1 and how much to the commonly coexistent vitiated atmosphere4 ,the temperature of living-rooms ought not to be over #fj to #fe ,fahr41 and of bedrooms not over #fj ,fahr4 ,the devitalising influence of extreme cold is well known4 ,its effects are more particularly seen in young children and the very old1 who require to be carefully tended during severe and long-continued cold weather4 ,dry1 cold weather1 with the temperature near the freezing point of water1 and a cutting east wind prevailing1 is not uncommonly described as 8bracing40 ,this is so far from being the case1 that it requires all the vital powers of the strong and healthy to resist its depressing influence1 and the feeble of both extremes of age succumb4 ,,chapter ,,xvii4 ,,trade ,,nuisances4 ,many occupations are the source of considerable danger to the workers engaged in them4 ,they are chiefly injurious by the inhalation into the lungs of some foreign agent1 which produces serious local inconveniences and irritation1 and may be also absorbed into the circulation and produce more remote effects4 ,the injurious agents may be classified under four heads3-- 7#a7 ,insoluble particles or dust4 7#b7 ,soluble or partially soluble substances4 7#c7 ,injurious gases or vapours4 7#d7 ,effluvia from offensive trades4 ,it is evident that1 as regards the effluvia named under 7#d71 they might generally be included under the three previous heads1 though it is convenient for our present purpose to keep them separate4 ,the occupations in which dust and soluble substances are productive of injurious effect have already been described1 pages #ajg to #aji4 ,injurious gases and vapours have received consideration on pages #aaa and #aab4 ,the special offensive trades still require attention4 ,offensive ,trades4--,the legal enactments relating to offensive trades are contained in sect4 #aab of the ,public ,health ,act1 #ahge1 which states1 any person who1 after the passing of this ,act1 establishes within the district of an urban sanitary authority1 without their consent in writing1 any offensive trade1 that is to say1 the trade of-- ,blood boiler1 or ,bone boiler1 or ,fellmonger1 or ,soap boiler1 or ,tallow melter1 or ,tripe boiler1 or any other noxious or offensive trade1 business1 or manufacture1 shall be liable to a penalty not exceeding fifty pounds in respect of the establishment thereof1 and a penalty not exceeding forty shillings for every day on which the offence is continued4 ,these provisions can only be enforced in rural districts with the sanction of the ,local ,government ,board4 ,the 8other noxious or offensive trades10 in order to be brought within the operation of the section1 must be analogous to those which are specially enumerated4 ,the most exhaustive and authoritative report on this subject is by the late ,dr4 ,ballard1 whose report is largely quoted in the following remarks4 ,we may consider 7#a7 the extent to which the public is inconvenienced by various effluvium nuisances4 ,the majority of the nuisances arise from trade processes in which animal matters are chiefly used4 ,among the most disgusting are the effluvia from gut-scraping1 and the preparation of sausage skins and catgut1 the preparation of artificial manures from 8skutch0 7the refuse matter of the manufacture of glue71 the manufacture of some kinds of artificial manures1 and the melting of some kinds of fat4 ,manufacturing businesses dealing with vegetable substances are often offensive1 but rarely give out disgusting effluvia4 ,the most offensive vegetable effluvia are probably those thrown off during the heating of vegetable oils1 as in the boiling of linseed oil1 the manufacture of palmitic acid from cotton oil or palm oil1 the manufacture of some kinds of varnish1 the drying of fabrics coated with such varnishes1 and the burning of painted articles1 such as disused meat-tins4 ,occasionally offensive effluvia arise in connection with industries in which neither vegetable nor animal matters are used2 as in the manufacture of sulphate or chloride of ammonia1 and some other processes in which sulphuretted hydrogen is copiously evolved2 and in the making of gas and the distillation of tar4 ,the fumes from the manufacture of alkali and bleaching powder are acid and irritating1 and produce very injurious effects on vegetation in the neighbourhood4 ,the distances to which nuisances extend vary greatly according to circumstances--as1 for instance1 the elevation at which the effluvia are discharged into the air4 ,discharge from a high chimney may relieve the immediate vicinity of the works at the partial expense of those living at a greater distance4 ,with a damp and comparatively stagnant atmosphere1 effluvia have a much greater tendency to cling about a neighbourhood4 7#b7 ,the industrial processes in which offensive effluvia are produced are classified by ,dr4 ,ballard as follows3-- #a4 ,the keeping of animals4 #b4 ,the slaughtering of animals4 #c4 ,other branches of industry in which animal matters or substances of animal origin are chiefly dealt with4 #d4 ,branches of industry in which vegetable matters are chiefly dealt with4 #e4 ,branches of industry in which mineral matters are chiefly dealt with4 #f4 ,branches of industry in which matters of mixed origin 7animal1 vegetable1 and mineral7 are dealt with4 7#c7 ,it is important to inquire to what extent offensive trade effluvia are injurious to the public health4 ,it is impossible to bring statistics to bear on the inquiry1 as other influences1 apart from occupation1 can scarcely be eliminated4 ,the term 8injurious to health0 is capable of a double interpretation4 ,it might mean either serious damage to health1 or the mere production of bodily discomfort or other functional disturbance by the offensive effluvia1 leading by its continuance to an appreciable impairment of vigour1 though not to any actual disease4 ,in the latter sense offensive effluvia have a deleterious effect on health4 ,such symptoms as loss of appetite1 nausea1 headache1 occasionally diarrha1 and general malaise are produced by effluvia of various kinds1 but agreeing in being all offensive4 8,a condition of dis-ease or mal-aise is produced40 ,there is little difficulty in proving bad effects on the workmen1 though the invariable defence of manufacturers is an appeal to the condition of health of their workmen4 ,the workmen only remain such so long as they are healthy1 and as they become disabled they necessarily cease to rank among workmen4 ,the decomposition of putrefying organic matters is unquestionably dangerous4 ,the general doctrine of sanitation that filth is one of the chief factors in producing disease is certainly applicable to trade effluvia as well as to general sanitation4 ,it has been alleged on behalf of such effluvia as chlorine sulphurous acid and tar vapours that they are useful disinfectants2 but modern research has shown that disinfectants1 in order to be of practical use1 must be in such a concentrated condition that the air containing them is irrespirable4 ,probably such septic diseases as erysipelas are favoured by organic trade effluvia4 7#d7 ,the means available to prevent or minimise the nuisances arising from trade effluvia vary with the character of the processes4 ,the general principles on which treatment must be founded depend1 as ,dr4 ,ballard points out1 on a recognition of the following kinds of effluvia3-- ,effluvia dependent-- #a4 ,on the accumulation of filth on or about business premises1 or on its removal in an offensive condition4 #b4 ,on a generally filthy condition of the interior of buildings and premises and utensils generally4 #c4 ,on an improper mode of disposal of offensive refuse1 liquid or otherwise4 #d4 ,on insufficient or careless arrangements in reception of offensive materials of the trade1 or in removal of offensive products4 #e4 ,on an improper mode of storing offensive materials or products4 #f4 ,on the escape of offensive gases or vapours given off during some part of the trade processes4 ,it is evident that under the first two headings the proper remedy is cleanliness4 ,filth should be removed in impervious covered vessels1 at regular intervals4 ,structural arrangements should be made1 which will facilitate cleansing operations4 ,solid refuse should1 as far as possible1 be separated from liquid refuse1 as thus putrefaction is retarded4 ,under the last head important remedies are applicable4 ,in many cases a careful selection of the materials of manufacture will form an effective remedy4 ,thus much of the nuisance connected with soap or candle works arises from the putrid condition of the fat collected from butchers and marine store dealers1 and might be obviated by more regular and more frequent collection of the materials of manufacture4 ,the offensive vapours arising during processes of manufacture may be intercepted before reaching the external air1 and so treated that they lose their obnoxious character4 ,various methods of interception are adopted1 according to the processes involved4 ,occasionally it is necessary to have the air of the entire workshop drawn by means of artificial ventilation in a special direction2 usually the interception of air from special chambers suffices4 ,when thus collected1 the offensive air may be dealt with by 7#a7 passing it through water or some other liquid capable of absorbing the offensive materials2 or 7#b7 passing it through some powder with which it has chemical affinity2 or 7#c7 if its offensive materials are capable of condensation by cold1 passing them through an appropriate condensing apparatus2 or 7#d7 if the evolved matters are organic in nature1 conducting them through a fire4 7#e7 ,occasionally it is sufficient to discharge the offensive gases into the air from a high chimney2 and this always produces a mitigation of nuisance1 as compared with discharge at a low level4 ,it is usually found that the adoption of one or other of these methods is directly or indirectly profitable to the offender4 ,nuisances from the ,keeping of ,animals4--,the #dgth section of the ,public ,heath ,act prohibits the keeping of pigs in towns so as to be a nuisance1 and1 as a general rule1 it is possible to obtain a magistrate's order1 entirely prohibiting the keeping of pigs in towns4 ,the excreta of the pig have a very offensive and penetrating odour1 and however carefully kept1 pigs in towns form an intolerable nuisance4 ,not only is there nuisance from the accumulation of manure and dirtiness of the piggeries1 but also from the storage and subsequent preparation of food4 ,the boiling of hog-wash is often an even greater nuisance than the filth of the styes4 ,cow-keeping and horse-keeping in towns are still allowed and1 as compared with pig-keeping1 form a small nuisance4 ,mews1 if kept clean and well drained1 need not be offensive1 though it is objectionable for persons to sleep over stables4 ,the removal of manure also constitutes a difficulty4 ,the manure should not be allowed to accumulate in deep wet pits1 but in an iron cage-work over a cement paving at or above the ground-level1 thus allowing free drainage1 and keeping the manure dry1 and reducing ammoniacal decomposition to a minimum4 ,cowsheds are generally very badly ventilated1 as the cowkeeper finds that more milk is produced by the cows when the temperature of the shed is maintained at #fe or higher2 and he does not see the necessity for providing artificial means of warmth4 ,the grains which are used so largely for food are stored in a wet condition1 and speedily give rise to nuisance4 ,cowsheds and stables should be well paved and well drained4 ,at least #hjj cubic feet should be allowed for each cow in the shed4 ,cowsheds are regulated under the ,dairies'1 ,cowsheds'1 and ,milkshops' ,order of the ,local ,government ,board4 ,this order provides for and insists on the registration of cowkeepers1 dairymen1 and purveyors of milk1 by the local authority4 ,it also provides that no cowshed or dairy shall be occupied as such1 unless provision is made to the satisfaction of the local authority1 for the lighting and ventilation1 including air-space1 and the cleansing1 drainage1 and water-supply of the same2 and for the protection of the milk against infection or contamination4 ,with the view of preventing contamination of milk1 no person suffering from an infectious disorder1 or having recently been in contact with a person so suffering1 is allowed to milk cows or take any part in any stage of the business of a milk-seller4 ,the milk of a cow suffering from cattle plague1 pleuro-pneumonia1 or foot and mouth disease must not be mixed with other milk1 must not be sold or used for human food1 nor for food for swine or other animals1 unless it has been boiled4 ,by the order of #ahii this regulation is made to extend to tubercular disease of the udder4 ,slaughtering of ,animals4--,nuisance may arise in slaughter-houses from various causes3--7#a7 the uncleanly way in which animals are kept in the pound or lair before being killed2 7#b7 the insanitary condition1 bad paving1 lack of lime-whiting of walls1 etc41 of the slaughter-house2 7#c7 the accumulation of hides1 blood1 fat1 offal1 dung1 or garbage on the premises2 7#d7 the uncleanly condition of the blood-pits1 or the receptacles for garbage2 7#e7 the flowing of blood or offal into the drains and thence into the public sewer4 ,private slaughter-houses ought to be abolished1 and all animals intended for human food slaughtered in public abattoirs under efficient supervision4 ,when a large number of private slaughter-houses exist in different parts of a large town1 it is impossible for the sanitary officials to properly supervise the slaughtering1 or to ensure that diseased meat shall not enter the market4 ,the inspector may only have the opportunity of examining the flesh1 the internal organs which more particularly show the presence of a diseased condition having been concealed4 ,such concealment and the consequent foisting of diseased meat upon the public1 can only be efficiently prevented by forbidding the slaughtering of any animal intended for food in a private slaughter-house4 ,most local authorities have bye-laws regulating the slaughtering of animals4 ,these provide for a cleanly condition of the lairs1 and prevent keeping the animals longer in the lairs than is necessary for the purpose of preparation for slaughtering4 ,they also insist on the provision of proper covered receptacles of iron or other non-absorbent material for the reception of garbage1 and similar receptacles for blood2 for cleansing of the floor1 etc4 after slaughtering2 for lime-whiting of the walls four times a year2 and for other matters of detail4 ,for knackers' yards similar regulations are applicable4 ,the flesh should not be kept until it becomes putrid before being boiled1 and the boiling of the flesh and fat should be so arranged as to avoid the escape of offensive vapours into the external air4 ,in smoking bacon1 the singeing has formed a serious nuisance4 ,fish-frying in small shops is often a most troublesome nuisance4 ,a hopper over the pan in which the frying is conducted has not been always successful in carrying the fumes up the chimney4 ,the frying should preferably be done in a closed outhouse1 close to a chimney with a good up-draught4 ,the fellmonger prepares skins for the leather-dresser1 the chief operations being taking off the wool1 liming the skins1 etc4 ,the skins deprived of wool are called 8pelts40 ,the pelts are thrown into a pit containing milk of lime1 and thence sent direct to the leather-dresser4 ,nuisance may arise from 7#a7 the odour of the raw skins2 7#b7 the ammoniacal odour from the lime-painted skins hanging in the yard2 7#c7 the emptying and cleansing of the 8poke0 or tank in which the hides are washed2 7#d7 the foul condition of the waste lime taken from the exhausted lime pits2 7#e7 the odour from the dirty unpaved yards4 ,the leather-dresser only deals with 8pelts10 derived from sheep-skins2 the tanner with bullocks'-hides4 ,the skins brought from the fellmonger to the leather-dresser are first deprived of lime1 and then soaked in a solution of dog's dung1 called 8pure10 until they become soft4 ,in winter this 8pure0 solution is warmed for use4 ,the odour is very abominable1 both from the 8pure0 tub1 and from the discharge of the exhausted 8pure0 liquid into the drain4 ,at each stage of tanning nuisance may arise unless great precautions are taken1 as when the hides are soaked in lime and water1 when the hair is being removed1 when the loose inner skin of the hide is being removed1 and especially when the hides are soaked in pits containing pigeons' or other dung4 ,nuisance may arise again during the passage of offensive hides through the street4 ,cleanliness is the great rule4 ,if every process is carried on with due precaution1 including frequent washing out of receptacles and the free use of disinfectants1 little complaint need arise4 ,the manufacturers of glue and size boil out the gelatine from bits of hides and 8fleshings0 from leather dressers and tanners1 from damaged 8pelts10 ox or calves' feet1 horns1 and other similar substances4 ,the raw material is apt to be offensive in collection or while accumulating on the premises4 ,the process of boiling causes offence by the effluvia from the steam4 ,the residue remaining after the process is known as 8scutch10 and this1 unless frequently removed1 is a most serious source of nuisance4 ,prussiate of ,potass is manufactured by heating carbonate of potass with refuse animal matters4 ,in order to avoid nuisance the pot in which the boiling is done should have a pipe to conduct away the steam1 first running horizontally and then vertically down to the back part of the fire4 ,fat-melting and ,dip-candle-making1 as usually carried on1 give rise to nuisance4 ,the fat which is melted down usually comes from butchers and marine-store dealers in a rancid or even putrid condition1 and it may be stored on the premises for some time before it is boiled4 ,the vapours from the melting-vat are very offensive4 ,they should be carried by means of a pipe down until they discharge just under the boiler-fire4 ,the residue from the fat-melting process 7known as 8greaves07 requires frequent removal to avoid nuisance4 ,bone-boiling1 in order to extract the fat and gelatine1 is most offensive1 and most difficult to deal with4 ,after boiling1 the bones are apt to give off offensive smells4 ,the vapours from the closed boiler should be condensed as far as possible in a worm condenser1 and the remainder passed through a furnace fire4 ,in the manufacture of artificial manures nuisance is apt to arise 7#a7 from the reception and accumulation of the raw materials1 as putrid fish1 putrid blood1 scutch 7the residue from the manufacture of glue71 recently boiled bones1 etc42 7#b7 from the preparation of the raw material for use4 ,thus the drying of condemned fish or meat on open kilns is very offensive2 similarly the drying of sewage sludge4 7#c7 ,from the process of mixing the materials of manufacture1 irritant and offensive vapours being evolved1 as for instance in the manufacture of manure by crushing bones1 and converting into super-phosphate by the addition of sulphuric acid4 7#d7 ,from the removal of the manure from the hot den1 after it has been dried4 ,when sulphuric acid is mixed with coprolites or other mineral phosphates1 most irritant and offensive vapours are produced1 which may be perceived in some cases at the distance of a mile4 ,blood-boiling is now almost obsolete1 having been replaced by albumen-making and clot-drying4 ,nuisance may arise from the blood collected from slaughter-houses being in a putrid state2 and from the effluvia evolved during the drying process4 ,gutscraping1 gut-spinning1 and the preparation of sausage-skins are very closely akin4 ,in gut-scraping the putrid intestines are deprived of their interior soft parts by scraping with pieces of wood1 and are then1 after being cleansed1 ready for sausage-skins4 ,in gut-spinning the prepared gut is twisted into a cord4 ,the small intestines of hogs and sheep are used for this purpose4 ,the stench from these establishments is indescribably horrible4 ,extreme cleanliness is desirable4 ,immersion of the guts in common salt is useful2 so also the use of impervious vessels1 early removal of all refuse material1 etc4 ,brick and ballast burning are a frequent source of complaint in the neighbourhood of towns4 ,brick burning is conducted either in kilns or clamps4 ,when bricks are burnt in closed kilns comparatively little nuisance arises2 but when they are burnt in open clamps the effluvia are very irritating1 partly owing to the fact that very commonly house refuse1 containing vegetable and animal matters1 is burnt with the bricks4 ,clamp burning should be absolutely prohibited in the neighbourhood of large towns4 ,in ,ballast burning stiff clay is converted by the agency of heat into a brick-like material1 which is of use in road-making4 ,the clay is usually burnt in heaps1 mixed with ashes and breeze from dust-bins4 ,the process is offensive unless carried on with precautions similar to those for brick-burning4 ,,chapter ,,xviii4 ,,the ,,examination ,,of ,,air4 ,there are various methods of ascertaining the quality of the air in enclosed spaces1 of which not the least useful is the information furnished by the sense of smell1 on entering a room from the external air4 ,besides the evidence given by the senses1 chemical and microscopical examination of the air gives important information1 while the thermometer and hydrometer ascertain the temperature and degree of moisture4 ,examination by the ,senses4--,the dull grey haze hanging over a town1 when it is viewed from a distance1 indicates comparative impurity of its atmosphere1 and the presence of a considerable amount of suspended matter1 including smoke4 ,the smell of a stagnant atmosphere is a good preliminary guide to its condition4 ,the fact that a room has been occupied for some time without efficient ventilation can be at once detected on entering a room from the external air4 ,the sense of smell is extremely delicate2 it has been estimated that the #cajj1jjj1jjj part of a grain of musk can be apprehended by it4 ,but nothing is so soon dulled as the sense of smell4 ,an atmosphere which did not appear to be unpleasant while remaining in a room1 is intolerable when one returns to it after a few minutes in the open air4 ,it is important not to confound the 8closeness0 perceived by the sense of smell1 with the oppression due to the high temperature of a room4 ,the two are easily distinguished 7unless the two co-exist7 by a reference to the thermometer1 which ought always to be placed in rooms inhabited during the evening4 ,the remedy for a close room is to allow free entry of fresh air1 and not allow the fire to go down1 as is so commonly done1 under the impression that the closeness is due to heat4 ,de ,chaumont has made many experiments1 shewing how accurate is the information given by an acute sense of smell4 ,carbonic acid is destitute of odour1 but as its amount is usually proportionate to that of the organic matter producing closeness1 it may be taken as an index of the amount of impurity present in living rooms4 ,de ,chaumont found that the limit of smell is reached when carbonic acid amounts to #f parts in #aj1jjj of air1 or half as much again as in the external air4 ,in the following extracts from his experiments1 there was a close accordance between the evidence of his sense of smell and the amount of carbonic acid3-- ,at #adh per #aj1jjj ,extremely close and unpleasant4 #ajij ,extremely close4 #ifb ,very close4 #iba ,close4 #hdc ,not very foul4 #hjd ,close4 #feh ,not very close4 #efh ,not close4 ,he also found that humidity of the air had marked influence in rendering the smell of organic matter perceptible1 even more than a rise of temperature4 ,the sense of smell is doubtless aided in detecting impurities in the air1 by the besoin de respirer1 a feeling of oppression caused by the deficiency of interchange between the blood and air4 ,the state of cleanliness of the room as well as of the persons in it influences smell2 hence there may not be in particular instances exact correspondence between excess of carbonic acid and of organic matter4 ,chemical ,examination4--,the estimation of nitrogen and oxygen in air is usually unnecessary1 as these vary but little4 ,the oxygen is1 however1 reduced in frequently re-breathed air4 ,the ill effects of an often-breathed atmosphere are due not only to deficiency of oxygen1 but also to the addition of carbonic acid and organic matters1 rendering difficult the interchange between oxygen and the blood4 ,the ,estimation of ,carbonic ,acid is of great importance1 as under ordinary circumstances1 its amount is a fairly exact indication of the amount of contamination in the air4 ,pettenkofer's ,method4--,a carefully dried glass vessel containing a gallon of water is filled with the air to be examined1 by emptying the water in the room1 the air of which is to be examined4 ,fifty cubic centimetres of clear freshly prepared baryta water are then added1 and the stopper of the bottle then replaced4 ,it is then well shaken1 and afterwards allowed to stand for an hour4 ,the carbonic acid combines with part of the baryta to form barium carbonate2 and the baryta water remaining is consequently diminished in alkalinity4 ,given the alkalinity of the baryta water before and after the experiment1 and the difference will give the amount of baryta which has combined with carbonic acid4 ,the alkalinity of the baryta is estimated by a standard solution of oxalic acid1 of such a strength that #a c4c4 is the equivalent of #je c4c4 of ,,co4 ,the indicator used in making this test is phenolphthalein1 which colours baryta water red1 but its colour disappears when neutralization is reached4 ,the following example is taken from 8,pakes' ,laboratory ,text ,book of ,hygiene10 p4 #bib3-- ,the jar is found to contain #c1iej c4c4 ,as #ej c4c4 baryta water were run into the jar1 the air experimented on #c1iej-ej #c1ijj c4c4 ,on titrating #be c4c4 of the original baryta water1 #bbej c4c4 standard acid solution were required to neutralise it4 ,the baryta water in the jar required #aice c4c4 #bbej-aice #cae c4c4 difference of acid used4 ,but #a c4c4 acid #je c4c4 ,,co at #j ,c4 and #gfj mm4 of mercury4 ,therefore ,,co taken up by #be c4c4 of baryta #caeb #aege c4c4 ,as #ej c4c4 were used the ,,co absorbed by the baryta #cae c4c4 ,this was present in #c1ijj c4c4 of air4 ,therefore the ,,co #jhj per cent4 ,correction may be required for variations from the normal pressure of #gfj mm4 and normal temperature of #j ,c41 in accordance with ordinary rules4 ,in ,lunge and ,zeckendorf's ,method1 the air to be examined is pumped through a glass bottle in which is #aj c4c4 of a ,n_/#ejj solution of ,na,,co containing phenolphthalein as an indicator4 ,the air is pumped by a hand pump through this solution until the phenolphthalein is decolourized4 ,the number of times the ball of the pump has been squeezed indicates the amount of ,,co present in accordance with a table prepared from separate experiments by ,pettenkofer's method4 ,dr4 ,angus ,smith's plan for the estimation of carbonic acid in air is similar in principle to the last calculations4 ,it is based on the fact that the amount of carbonic acid in a given volume of air will not render turbid a given amount of lime water1 unless the carbonic acid is in excess4 ,,table4--,to be used when the point of observation is 8,no precipitate40 ,half an ounce of lime water containing #jaie gramme lime4 ,,air ,,at #j ,c4 ,,and #gfj ,m4 ,m4 ,,barometric ,,pressure4 ,,carbonic ,,acid ,,volume ,,of ,,air ,,in,,size ,,of ,,bottle ,,in,,size ,,of ,,bottle ,,in ,,in ,,the ,,air ,,cubic ,,cubic ,,ounces ,,per ,,cent4 ,,centimetres4 ,,centimetres4 ,,avoirdupois4 #jc #ega #ehd #bjfc #jd #dbh #ddc #aefj #je #cdb #cef #abeh #jf #bhe #bii #ajeg #jg #bde #bei #iac #jh #bad #bbh #hje #ji #aij #bjd #gba #aj #aga #ahe #fed #aa #aef #agj #fjj #ab #aec #aeg #eec #ac #acb #adf #eae #ad #abc #acg #dhb #ae #aad #abh #dec #bj #hf #ajj #ceb #be #fi #hc #bib #cj #eg #ga #bea ,the foregoing table shows how to apply this method4 ,the first and second columns state the ratio of carbonic acid in a quantity of air which will give no turbidity or precipitate in half an ounce of lime water2 the third column gives the corresponding size of the bottle in cubic centimetres2 and the fourth column gives the same in ounces4 ,thus different sized bottles1 each containing half an ounce of lime water1 will indicate with a fair degree of accuracy the ratio of carbonic acid in the air containing them1 by giving no precipitate when the bottle is well shaken4 ,for instance1 if a pint bottle is used and there is no precipitate with half an ounce of lime water1 it indicates that the ratio of carbonic acid does not amount to #jc per cent42 if an eight-ounce bottle be used1 and there is no precipitate1 it indicates that the ratio does not amount to #jh per cent41 and so on4 ,the air of a room ought never to contain more than six parts of carbonic acid in #aj1jjj of air1 or #jf per cent41 i4e4 a #aj ounce bottle full of the air shaken up with half an ounce of clear lime water ought to give no precipitate4 ,dr4 ,haldane has recently described 7,journal of ,hygiene1 ,no4 #a1 #aija7 a method of estimating ,,co#b1 which1 although it appears complicated1 is really both simple and convenient4 ,for particulars1 see the above ,journal4 ,the ,estimation of ,organic ,impurities may be accomplished approximately by drawing a definite amount of air by means of an aspirator1 through a dilute solution of permanganate of potassium of known strength4 ,the result is stated by giving the number of cubic feet of air required to decolourise 4#jja gramme of the permanganate in solution4 ,sulphuretted hydrogen1 sulphurous acid1 and other substances in air likewise decolourise the permanganate2 these ought to be separately tested for1 and allowance made4 ,the ,estimation of ,ammonia1 whether free or derived from albuminoid impurities1 is a matter requiring very delicate processes4 ,it is accomplished in the same way as the estimation of ammonia in water1 the air being drawn through perfectly pure distilled water1 and then the analysis proceeded with as a water analysis4 ,the mere presence of free ammonia may be determined by exposing to the air strips of filtering paper dipped in ,nessler's solution1 which become brown if there is any ammonia in the air4 ,microscopical ,examination is required for the detection of suspended matters4 ,these are the most potent for harm1 containing sometimes the germs of infectious diseases4 ,the suspended matters scattered throughout the air may be collected by ,pouchet's aeroscope4 ,this consists of a small funnel drawn out to a fine point1 under which a slip of glass is placed moistened with glycerine4 ,both funnel and glass are enclosed in an air-tight chamber1 connected by tubing with an aspirator1 by means of which when water is allowed to escape from it1 air is drawn through the funnel and its particles impinging on the glycerine are there arrested4 ,glycerine may be objectionable from the foreign particles previously contained in it4 ,various other plans have been devised1 one of which is to draw the air through a small quantity of pure distilled water and then examine a drop of it4 ,by microscopic examination large particles can be detected4 ,for the detection of bacteria and their spores more delicate methods are required4 ,the ,bacteriological ,examination of air is usually conducted as follows4 ,air is drawn through a wide glass tube 7,hesse's tube71 which has been previously sterilised1 and on the inner side of which liquid gelatine has been allowed to solidify4 ,the air as it passes over the gelatine deposits any germs present in it4 ,the entrance of any further germs is prevented by closing the tube1 and it is then left to stand for two or three days4 ,moulds and colonies of bacteria will develop in the gelatine1 and these can be counted and differentiated by their appearance and by further tests4 ,in closed rooms the number of microbes 7i4e41 bacteria and moulds7 ought not to be more than #bj per litre of air in excess of those in the outside air2 and the ratio of bacteria to moulds ought not to exceed #cj to #a4 ,examination of ,temperature and ,moisture4--,the temperature should be observed at the point most remote from an open fire-place1 and compared with the external temperature4 ,for methods of estimating moisture1 see page #bdj4 ,it may be useful to recapitulate at this point the desiderata in an inhabited room4 ,the temperature should be #fj-fb ,fahr41 the amount of carbonic acid should not exceed #jf per cent4 and the humidity should range between #gc and #ge per cent4 of the amount required to produce saturation4 ,the dry bulb thermometer should read #fc-fe ,fahr41 the wet bulb #eh-fa ,fahr41 and the difference between the two should not be less than #d or more than #h4 ,,chapter ,,xix4 ,,the ,,purification ,,of ,,air4 ,in addition to the artificial measures which will be discussed in the next chapter1 various natural agencies are constantly at work for the removal of the impurities discussed in preceding chapters4 ,of these1 the most important are the action of plants1 the fall of rain1 natural methods of ventilation1 and certain natural constituents of the atmosphere4 #a4 ,plants1 by virtue of the chlorophyll contained in their green parts1 absorb carbonic acid from the atmosphere1 liberating oxygen in an active condition4 ,in addition1 ammonia and nitrous and nitric acids are dissolved from the air by rain-water1 and assimilated by plants4 ,during the night plants only give off carbonic acid4 #b4 ,the ,fall of ,rain clears the atmosphere of any solid particles contained in it1 the impurities being transferred to rain-water which generally contains an appreciable amount of ammonia as well as other impurities4 ,rain not only washes and purifies the air1 but by washing the ground1 diminishes dust1 and prevents its escape into the air4 ,it is the great natural scavenger4 #c4 ,ventilation--that is1 the interchange of pure and impure air1 is constantly being effected4 ,before entering on the details of ventilation1 we must consider the physical causes at work which tend to purify the air1 apart from all artificial contrivances4 ,these are three in number--namely1 diffusion1 winds1 and differences of temperature of masses of air4 7#a7 ,diffusion causes the rapid mixture of gases placed together4 ,every gas diffuses at a certain rate--namely1 inversely as the square root of its density4 ,in any room which is not air-tight1 diffusion is constantly occurring1 air passing in and out at every possible point4 ,through chinks and openings in the carpentry-work of a room1 the air diffuses rapidly4 ,bricks and stone commonly allow air to pass through them2 diffusion occurs to a slight extent even if the wall is plastered1 but very little through paper4 ,diffusion alone is quite insufficient to purify a room under ordinary circumstances2 and solid particles including the organic matter evolved from the skin and lungs1 not being gaseous1 are unaffected by it4 ,to remove these1 the room must be periodically flushed with air1 and washing of all dirty surfaces must be carried out4 ,diffusion sometimes produces evil results1 when the sanitary arrangements of a house are bad4 ,if there is a leakage of sewage under the kitchen floor1 the foul gases from it diffuse upwards2 occasionally foul air diffuses from the dust-bin through the wall into the rooms of a house4 ,these results are helped by the fact that the internal temperature of a house is commonly higher than the external4 7#b7 ,differences of ,temperature cause active movements of air4 ,in fact winds are caused by movements between large masses of air of unequal temperature and consequently of unequal density4 ,light gases ascend1 as familiarly illustrated by the smell of dinner perceived in bedrooms1 or the smell of a cigar lit in the hall perceived in the attic4 ,in rooms differences of temperature of the air are caused by the heat of fire1 gas1 and our own bodies4 ,currents of air result2 the warmer and lighter air ascends up the chimney or towards the ceiling1 while colder and denser air rushes in under the door or through the floor1 etc4 ,the lighter gases carry with them solid particles in suspension and thus tend to remove the most important impurities4 ,assuming that the external air is colder1 if admitted into the lower part of a room1 it produces a draught2 if admitted at the top of a room1 being heavier1 it falls by its own weight on the heads of those in the room4 ,the problem of ventilation is to secure a sufficient interchange of air without the production of perceptible currents4 ,movements of air are constantly occurring1 so long as the temperature of the air is subject to changes4 ,this cause alone will suffice to ventilate all rooms in which the air is hotter than the external air4 ,it may thus happen that a room with windows and doors closed in winter1 may possess purer air than the same room in summer with these thrown widely open4 ,the value of diffusion of air through the walls1 and the influence of temperature on this diffusion are well illustrated by some experiments of ,pettenkofer4 ,when the difference between the outside and inside temperatures was #cd ,fahr4 7#ff inside and #cb outside71 and the doors and windows were shut1 an ordinary room in his house1 of the capacity of #b1fej cubic feet1 which was built of brick1 and furnished with a ,german stove instead of an open fire-place1 had its entire atmosphere changed once in an hour4 ,with the same difference of temperature1 but with the addition of a good fire in the stove1 the change of air rose to #c1cbj cubic feet per hour4 ,on lessening the difference between the external and internal temperature to #g ,fahr4 7#fd and #ga71 the change of air was reduced to only #ghj cubic feet per hour4 ,in these experiments1 all crevices and openings in doors and windows were pasted up4 ,it is instructive to note the greater amount of ventilation effected through the walls1 etc41 than by the draught of the stove4 ,the amount of ventilation through walls varies with the material of which they are built4 ,mortar is exceedingly porous when dry2 sandstones and bricks are easily permeated by both water and air4 ,limestone is almost impervious to air1 but requires much mortar in building1 which effects a partial compensation 7see page #bjf74 ,the rise of temperature caused by the bodily heat and by the combustion of illuminating agents1 is well shown by some figures of ,dr4 ,angus ,smith4 ,he found that the rise of temperature of #agj cubic feet of air in one hour1 produced by the bodily heat of one man was #ef ,fahr42 by the combustion of a candle #ch ,fahr4 ,thus1 in a room #h feet high1 #d feet broad1 and #f feet long1 a man burning a candle would in an hour raise the temperature from #fj to #gj ,fahr4 ,this rise in temperature would not only cause currents of hot air towards the upper part of the room1 but would probably make the room uncomfortable1 and so lead to the opening of a door1 etc4 7#c7 ,winds are of great value in flushing rooms with fresh air4 ,they ought to be utilised as often as possible1 by throwing windows widely open2 without1 however1 taking the place of constant ventilation in the intervals4 ,they are especially valuable in getting rid of organic matters which are unaffected by diffusion4 ,the wind will pass through wood1 and even brick and stone walls4 ,when it is allowed to pass directly through a room1 as from window to door1 it produces a more powerful effect than can be produced in any other way4 ,the average rate of movement of winds in this country is #aj feet per second1 or about #g miles an hour4 ,if the surface which a man exposes to this average wind #f' #a' #i square feet1 then #ij cubic feet of air flows over him in one second1 and #cbd1jjj in an hour4 ,if #c1jjj cubic feet were the allowance for each person indoors--a much greater allowance than is usually given--he only receives #aajh of the air with which he is supplied in the open4 ,winds act as a ventilating agent in two ways--directly by perflation1 driving impure air before them1 or freely mixing with it2 and indirectly by aspiration1 drawing the impure air along with them4 ,in the last case1 the wind causes a partial vacuum on each side of its path1 towards which all the air in its vicinity flows4 ,thus1 the wind blowing over the top of a chimney causes a current at right angles to itself up the chimney4 ,in a spray-producing apparatus we have a familiar instance of the same principle1 the current of air or steam along the horizontal tube causing the fluid to rise in the vertical tube till it is scattered in spray4 ,in ,sylvester's plan of ventilation1 both these forces are used 7see page #aej74 #d4 ,certain ,constituents of the ,atmosphere have an important purifying effect4 ,of these oxygen is by far the most important4 ,by its means organic impurities become oxidised1 and thus rendered harmless4 ,it is probable that much of this oxidation is effected by means of ozone--a peculiarly active and concentrated form of oxygen4 ,a large part of this ozone is probably produced during thunderstorms and similar electrical disturbances of the atmosphere4 ,the ammonia and organic impurities in air become changed into nitrites and nitrates--chiefly of ammonium--and being washed down by rain1 form an important part of the food of plants4 #e4 ,for ,chemical ,measures of purification of the atmosphere see page #cbd4 ,,chapter ,,xx4 ,,general ,,principles ,,of ,,ventilation4 ,the ,amount of ,air required4--,ventilation is chiefly concerned with the removal of the products of respiration1 just as sewage is chiefly concerned with the removal of the solid and liquid excreta4 ,in a less degree it is required for removing the impurities produced by the burning of gas1 candles1 and lamps4 ,the main problem1 however1 is the removal of the respiratory products4 ,the amount of carbonic acid in air is usually fairly proportional to that of the other respiratory products4 ,it may therefore be taken as a measure of the impurity of the air4 ,there are1 however1 certain fallacies in this test4 ,in soda water manufactory1 for instance1 there would be a comparatively harmless excess of carbonic acid4 ,in dirty rooms1 and in hospitals and other institutions where rooms are not vacated for a considerable period1 the amount of organic matter present is often in excess of what would have been anticipated1 judging by an estimation of the carbonic acid4 ,this is strikingly shown by some valuable researches at ,dundee1 which are summarised in the following table4 ,if we take the average amount 7in excess of outside air7 of carbonic acid1 organic matter1 and micro-organisms respectively in houses of four or more rooms as unity1 then in one or two-roomed houses or tenements we have as follows3-- ,,houses ,,of ,,four,,two-,,roomed,,one-,,roomed ,,rooms ,,houses4 ,,houses4 ,,and ,,upwards4 ,carbonic acid #a #ae #bj ,organic matter #a #af #dd ,micro-organisms #a #ea #fg ,it is evident that in these cases the carbonic acid did not increase in the same proportion as the organic matter and micro-organisms1 and that it alone does not form a sufficient test of the impurity of any given atmosphere4 ,the amount of carbonic acid1 however1 is a valuable and convenient test of the condition of the air of a room1 and the problems of ventilation1 of which examples are given on page #acg1 are based on its amount4 ,the ,standard of purity is somewhat difficult to fix4 ,the external air ought only to contain #d parts of carbonic acid to #aj1jjj parts2 but it is almost impossible to maintain this degree of purity in inhabited rooms4 ,the experiments made by ,drs4 ,parkes and ,de ,chaumont showed that when the carbonic acid is #jf per cent41 or in the proportion of #f parts in #aj1jjj of air1 the air begins to be perceptibly stuffy 7page #abe72 this may therefore be taken as the limit of impurity4 ,pettenkofer has adopted the limit of #jg per cent4#g ,the problem then is to discover the amount of pure external air 7containing #jd per cent4 of carbonic acid7 that will be required to pass hourly through a room1 for every person in that room1 in order to keep the carbonic acid at the ratio of #jf per cent4 ,this may be ascertained by actual observation of the air of rooms in which a given number of persons are placed2 or by calculations from physiological data4 ,as the result of numerous experiments on the atmosphere of prisons1 barracks1 etc41 where the amount of fresh air supplied per hour is exactly known1 it is found that in order to keep the carbonic acid at #jf per cent41 #c1jjj cubic feet of pure air are required per head per hour2 #b1jjj cubic feet keep the carbonic acid at #jg per cent42 #a1ejj cubic feet at #jh per cent42 and #a1bjj cubic feet at #ji per cent4 ,for the removal of the products of combustion of gas1 an additional supply of air is required1 for the amount of which1 see page #aaf4 ,where a number of sick persons are collected1 as in hospitals and workhouses1 a much freer supply of air is required4 ,much depends1 however1 on the cleanliness of the wards1 and on whether the ventilation is constant in character4 ,in ,st4 ,thomas's ,hospital1 the space allotted to each ordinary patient is #a1hjj cubic feet1 and to each patient in the fever wards #b1ejj cubic feet4 ,thus1 by changing the air of the wards twice in the hour1 an abundant supply of fresh air is ensured4 ,the mortality after operations1 and in all fevers1 is much diminished by a free supply of air4 ,soldiers are allowed #fjj cubic feet of space per head in their sleeping rooms1 which involves a change of the air five times per hour1 in order that the carbonic acid may be maintained at #jf per cent4 ,the limit of overcrowding for lodging-houses is usually fixed at #cjj to #ejj cubic feet1 but this is too little4 ,the amount of pure air required in order to keep the carbonic acid in a room at #jf per cent41 may also be ascertained from physiological data4 ,an average adult expires #ce 7#f7 cubic foot of carbonic acid per hour4 ,now as the carbonic acid in air to be breathed must not contain more than two parts in #aj1jjj 7#jb per cent47 in excess of what is present in external air 7#jd per cent471 it follows that if x the amount of fresh air required by an adult per hour in order to keep the carbonic acid in the room down to 4#jf per cent41 then3-- #jb 3 #f 33 #ajj 3 x4 x #c1jjj cubic feet4 ,relation of ,air ,required to ,cubic ,space of ,room4--,if we accept #c1jjj cubic feet of air as the amount required per head per hour1 this may clearly be furnished by having a large room with comparatively little circulation of air1 or by having a small room with frequent interchanges4 ,thus1 supposing the cubic space allowed to each individual is #a1jjj cubic feet--that is1 #aj feet in every direction--the atmosphere will require changing three times per hour4 ,now1 it is found that when a current of air1 at the temperature of #ee-fj ,fahr41 is moving at the rate of less than one mile per hour1 it is not perceptible--that is1 produces no draught4 ,the rate of a breeze1 which is just perceptible1 is #ah inches per second1 or one mile per hour4 ,as draughts are objectionable1 ventilation1 in the best sense of the word1 means the supplying of abundant fresh air at a rate of less than one mile per hour1 or warmed air at a higher rate4 ,air moving at the rate of #b miles per hour1 or #c feet per second1 is perceived as a slight draught by all1 at the average temperature of our climate 7about #ej ,fahr47 ,where natural ventilation is employed1 the difficulties of thoroughly ventilating a small space1 without draught1 are very great4 ,a change of air three or four times in an hour is all that can be borne under ordinary conditions in this country1 and this necessitates a supply of #a1jjj or #gej cubic feet of space respectively for each individual4 ,and a change of this frequency is commonly not effected2 the ventilating apparatus may fail temporarily1 or may be wilfully stopped up1 or there may be no means of ventilation2 it is essential therefore to have as large a cubic space as possible4 ,a large cubic space1 does not obviate the necessity for efficient circulation of air4 ,it is1 however1 advantageous1 not only on account of the initial longer time before the air reaches the limit of impurity1 but also because there are less draughts1 and there is a larger wall surface and larger windows for unperceived ventilation4 ,common ,errors as to ,ventilation4--7#a7 ,in relation to the cubic space of a room1 it is most important to note that a lofty ceiling does not compensate for deficiencies in floor-space4 ,one hears1 8lofty0 and 8airy0 rooms spoken of as though the two terms were necessarily synonymous4 ,this is by no means the case4 ,the impurities produced by respiration tend to accumulate about the persons who have evolved them1 although it is true that in rooms heated by gaslight1 a large amount of hot and impure air collects near the ceiling4 ,the necessity of an abundant floor-space is shown by the fact that a space enclosed by four high walls and without a roof1 will1 if crowded1 speedily become offensive4 ,twelve feet is quite high enough for large rooms in schools1 hospital wards1 etc41 and nine feet suffices for the rooms of a private dwelling-house4 ,there is no objection to a greater height1 if it is remembered that in reckoning the practical cubic dimensions of a room1 the height should only be reckoned as twelve feet4 ,supposing #ejj cubic feet is the amount allowed per individual1 then the floor-space should be forty-two square feet1 which would be furnished by a room about #h feet long and #e feet wide4 ,in barracks1 soldiers are allowed fifty square feet of floor-space4 ,in school-rooms the ,education ,code requires that at least ten square feet of floor-space1 and at least #abj cubic feet shall be allowed for each child in average attendance4 7#b7 ,it is commonly supposed that a large room compensates for a deficient circulation of air4 ,the cubic space of a room is really of less importance than the capacity for frequent interchanges of air4 ,even the largest enclosed space can only supply air for a limited period1 after which the same amount of fresh air must be supplied1 whether the space be small or large4 ,thus1 supposing that as large a space as #aj1jjj cubic feet per head were allowed1 the limit of purity would in the absence of ventilation be reached in three hours1 and after that time an hourly supply of #c1jjj cubic feet of air would be just as necessary as if the space were only #bjj cubic feet4 7#c7 ,it must not be overlooked that the furniture in a room must be deducted from the breathing space1 as the amount of air is diminished by the space occupied by the furniture4 ,about #aj cubic feet ought to be allowed for each bed1 and #c to #e cubic feet for each individual in a room2 projecting surfaces must be allowed for by subtraction1 and recesses by addition4 ,the deductions to be made for furniture are not of any great consequence1 if there is a free interchange of air2 as the cubic space is of less importance than free ventilation4 ,general ,rules respecting ,ventilation4--,the two great objects in ventilating being to remove all impurities from the air1 and to avoid draughts1 it is important that-- #a4 ,the entering air should be1 if possible1 of a temperature of #ee to #fj ,fahr4 ,whenever the temperature of a room differs from the external temperature by #aj ,fahr41 a draught is certain to ensue4 ,it is impossible at all times to ensure the incoming air being of the temperature of #fj1 without some artificial means of warming it4 ,in this country it is seldom necessary to cool the incoming air1 but this may be managed in artificial systems of ventilation by passing the incoming air over ice1 or by using compressed air which becomes cooled on expansion1 or by passing the incoming air through subterranean tunnels4 #b4 ,the entering air should be pure4 ,when a room is hotter than the passages and kitchens1 air from the latter1 whatever may be its character1 is drawn into the room4 ,similarly the ground-air under the kitchen-floor or the air from ash-pits may be drawn into the house1 when no other means of ventilation are provided2 and this is often followed by evil results4 #c4 ,no draught or current should be perceptible from the incoming air1 except when it is wished to flush the room with air1 by opening the windows wide4 ,it is a common complaint that a room is draughty1 and1 to remedy this1 keyholes are stopped up1 and mats are placed at the bottom of the door1 etc4 ,the draught can often be remedied by increasing the size and number of the openings through which air is admitted1 so that the current of air is not concentrated and rapid4 ,when this does not remedy it1 the incoming air should be warmed4 ,a feeling of draught is very often due to the radiation to and from a window1 and disappears when a curtain or screen is placed between the radiating surface and the occupant of the room4 #d4 ,the entry of air should be constant1 not intermittent4 ,the occasional opening of a window or door will not compensate for the lack of a constant interchange of air1 although it forms a very valuable adjunct1 especially in the removal of organic particles which do not follow the law of diffusion4 #e4 ,an exit should be provided for impure air1 as well as an entrance for pure air4 ,the chimney furnishes this in most living-rooms1 and diminishes the necessity for other means of exit4 ,if the openings in a room for entrance and exit are properly regulated1 a rate of #e feet per second 7about #c miles per hour7 will provide sufficient air without any unpleasant draught in a room4 ,for instance1 if the opening measure #a square foot1 then a rate of #e feet per second will give five cubic feet of air per second1 that is1 #ah1jjj cubic feet per hour4 ,but as only #c1jjj cubic feet are required1 it follows that an opening one-sixth this size1 i4e4 #bd square inches1 is sufficient for each individual4 ,reckoning the same amount for means of exit1 #dh square inches is the size of the ventilating orifices required by each individual4 #f4 ,a number of small divided openings are not collectively equal in ventilating power to one large one having the same area4 ,thus1 when a ventilating orifice is divided into four parts1 which have the same collective area as the original orifice1 it is found that only half as much air passes through these as through the original orifice4 ,in order to obtain as much air1 therefore1 each opening must be equal in size to half the original opening4 ,this is in accordance with the rule that the friction for air passing through openings is inversely to the diameter of these openings1 i4e4 inversely to the square-root of the area of the openings4 #g4 ,the most important requirements of perfect ventilation may be recapitulated as follows3-- #ast4 ,the maximum impurity of air vitiated by respiration should not exceed #f parts carbonic acid per #aj1jjj volumes4 #bnd4 ,to ensure the maintenance of this standard1 #c1jjj cubic feet of pure air must be supplied per head per hour4 #crd4 ,in order to supply this amount of pure air1 with ordinary means of ventilation1 #a1jjj cubic feet at least must be allowed per head in buildings always occupied4 ,,chapter ,,xxi4 ,,problems ,,as ,,to ,,ventilation4 ,the following formula enables many problems relating to ventilation to be solved4 ,let p the amount of poison 7carbonic acid7 in every cubic foot of fresh air1 viz4 #jjjd cubic foot4 ,let ,a the number of cubic feet of fresh air delivered or available1 ,p the amount of carbonic acid exhaled1 and x the amount of carbonic acid per cubic foot in the room at the end of a given time4 ,then-- x p ,p_/,a1 whence ,a ,p_/7x - p74 ,if the carbonic acid in the air of a room is #ge per #a1jjj volumes 7that in the outer air being #d per #a1jjj volumes71 and there are five persons in the room1 how much air is entering the room per hour8 ,here x #jjjge4 p #jjjd4 ,p #f 7i4e4 number of cubic feet of carbonic acid expired by each person per hour74 ,now x p ,p_/,a4 #jjjge #jjjd #f_/;,a4 ,therefore ,a about #a1gjj4 ,thus #a1gjj cubic feet are required for each individual to keep the air within the given limit1 and five times this amount will be required for five persons #h1ejj cubic feet4 ,a room has been occupied for one hour1 at the end of which the total carbonic acid present was found to be #aa per #a1jjj parts4 ,the carbonic acid in the open air amounting to #jjjd per cubic foot1 find the quantity of air supplied per hour4 ,here x #jjaa4 p #jjjd and ,p #f4 ,hence #jjaa #jjjd #f_/;,a4 ,therefore ,a #heg cubic feet4 ,if six persons are in a room containing #c1jjj cubic feet1 and there is a supply of #b1jjj cubic feet of air per head per hour2 how much carbonic acid is there in the air of the room at the end of #d hours8 ,here p #jjjd4 ,p #f #f #d #add4 ,a #b1jjj #f #d #c1jjj #ea1jjj4 x #jjd #addea1jjj #jjjfhb #fhb parts ,,co in #aj1jjj of air4 ,the air of a room occupied by #f persons and containing #e1jjj cubic feet of space1 yields #ge parts of ,,co per #aj1jjj parts of air4 ,how much air is being supplied per hour8 ,a ,p_/7x - p7 #f x #f_/7jjjge - #jjjd7 #aj1bhj cubic feet4 ,in the same room what would be the condition of the air at the end of #d hours8 x #jjja #f #f #d_/7ajbhj #d #e1jjj7 #jjjd #adddf1abj #jjjgab #gab of ,,co in #aj1jjj of air4 ,given two sleeping rooms1 ,y #aj ft4 by #ae ft4 and #aj ft4 high1 ,z #ae ft4 by #bj ft4 and #ab ft4 high1 with three adults in each2 how much fresh air would you supply in each8 ,what would be the condition of the air of each of the rooms after1 #ad1 #ab1 #a1 and #b hours respectively8 ,amount of fresh air to be supplied in ,y-- ,a ,p_/7x - p7 #f #c_/7jjje - #jjjd7 #i1jjj cubic feet per hour4 ,condition of air in ,y after #ad hour-- ,here p #jjjd4 ,p #f #cd #de4 ,a #i1jjjd #a1ejj #c1gej4 x #jjjd #dec1gej #jjjeb4 ,at the end of #b hours-- x #jjjd #cf_/7ah1jjj #a1ejj7 #jjjehd4 ,and similarly for ,z4 ,suppose two rooms1 one #aj feet cube1 the other #ej feet by #bj feet and #ae feet high1 have continuously admitted into each of them a volume of fresh air containing #jd parts carbonic acid per #ajj parts1 amounting to #b1jjj cubic feet per hour1 so as to replace to that extent the air of the room2 suppose also that an average adult be placed in each room3 show by detailed calculation what would be the condition of impurity of air in each room1 as measured by carbonic acid1 at the end of #d hours and #ab hours respectively4 ,in the case of the first room-- ,p #f #d #bd4 ,a #b1jjj #d #a1jjj #i1jjj4 p #jjjd4 x #jjjd #bdi1jjj #jjjffg4 ,the amount of impurity at the end of #ab hours1 and in the second room may be similarly ascertained4 ,ventilation in relation to ,temperature4--,the temperature of a given atmosphere is a most important factor in determining the ease with which it is replenished from the external air4 ,speaking generally1 the greater the difference between the temperature of two masses of air the more rapidly an interchange occurs4 ,air has weight4 ,a column of it one inch square and extending to the uppermost limit of the atmosphere weighs about #adf lbs41 and exerts this pressure on all substances at the surface of the earth4 ,this pressure is exerted uniformly in all directions2 but for this fact our chests would be crushed in by the external pressure on them1 which amounts to over four tons4 ,if the atmospheric pressure is diminished at any point1 it is evident that the surrounding air will tend to press in this direction4 ,now1 when air is heated it expands1 and consequently the heavier fresh air flows in from all sides and pushes the lighter air upwards4 ,the expansion of air for every increase of #a ,cent4 is #jjcffe 7#abgc71 for every increase of #a ,fahr4 is #jjbjc 7#adib74 ,thus if the air in a room is #bj ,f4 warmer than that outside1 it will be expanded to #abe additional bulk4 ,thus if ,m volume of a given air at #cb1 with the barometer at #cj inches1 and ,m volume at temperature t above #cb1 while a co-efficient of expansion for each degree of elevation of temperature1 then the dilatation effected by heat will be expressed by the formula-- ,m ,m 7#a at74 ,when the temperature is decreasing ,m ,m 7#a -at74 ,if the air in a chimney flue is cooler than the air of the room with which it communicates1 it will flow down into the room4 ,it is the object of an economical fire-place to cause the chimney to act as an outlet for the products of combustion and for the impurities of the air of the room with the smallest possible waste of heat4 ,short of producing a down draught of cold air and smoke1 the smaller the difference between the temperature of the air of a room and of the air escaping near the top of the chimney1 the greater the economy of fuel4 ,the movement of air in flues and other outlets is governed by general laws1 like those governing the general movements of fluids1 but allowances require to be made for friction in the channels of entrance and outlet4 ,the theoretical velocity1 when friction is not taken into account1 may be calculated by a formula based on what is known as the law of ,montgolfier1 or the law of spouting fluids4 ,according to this law1 fluids pass through an opening in a partition with the same velocity as a body would attain in falling through a height equal to the difference in depth of the fluid on the two sides of the partition1 i4e4 to the difference of pressure on the two sides4 ,thus1 if ,,ab equals the height of a column of air at1 say1 #ej ,f41 and ,,ac is the height of the same quantity of air heated to #fj1 then the velocity with which the warmer air ascends will be that which a body would acquire in falling from ,c to ,b4 ,illustration3 ,representing the air column lengths ,now the velocity in feet per second of falling bodies is about eight times the square root of the height from which they have fallen2 and the formula for determining this is-- v c 7#b;gh7 #hb;c h4 ,in this formula v required velocity in feet per second2 g #cbag feet per second2 h distance fallen through by the body2 c a constant determined by experiment1 and expressing the proportion of the actual to the theoretical velocity4 ,adapting this formula to the special circumstances under which ,montgolfier's formula holds1 we find that the force which drives the warm air up the flue is the force of gravity1 i4e4 of the excess of the weight of a column of cold air over the weight of a column of warm air of exactly the same size 7represented by ,,bc in the preceding diagram74 ,the difference of the two weights or pressures is found by multiplying the distance from the point of escape of heated air out of the room 7fire-place or elsewhere7 to the point of escape into the outer air 7top of chimney or other point of exit71 by the difference in temperature inside and outside1 and again multiplying this product by #adib for degrees of ,fahrenheit temperature1 or #abgc for degrees ,centigrade4 ,thus omitting c for the present1 we have-- v 7#b;gh7t - t#a7_/dib7 #hb7;h7t - t#a7_/dib7 ,where t temperature in the chimney1 t#a temperature of the external air1 and h height of chimney4 ,example4--,the chief means of ventilating a given room is by its open fire-place4 ,the temperature in the chimney is #ajj ,f41 that of the external air #dj1 and the height of the chimney #ej feet2 what is the velocity with which air is leaving the room8 v #hb 77#ajj - #dj7 #ejdib7 #bj4 ,this gives the theoretical velocity1 but the real velocity will differ from the theoretical by an amount varying from #bj to #ej per cent4 ,it will be evident1 from what has been said1 that the movements of the air in a confined space are dependent upon 7#a7 the difference between the internal and external temperatures2 7#b7 the area and friction at the apertures through which air enters and leaves the room2 and 7#c7 the height of the column of ascending warm air4 ,the higher the chimney 7assuming it to contain warm air71 the greater the draught and the more efficient the ventilation of the room communicating with it4 ,hence ventilation is more difficult in upper rooms of large houses and in single-storeyed houses than in the lower storeys of large houses4 ,allowance for ,friction4--,practically the friction varies greatly according to the size1 form1 and material of outlet for air4 ,a rough or sooty or angular chimney greatly impedes the outgoing current of air4 ,it is usual to reduce the theoretical velocity by #bj to #ej per cent4 ,apart from the friction which is governed by roughness and length of channels1 that due to bends in the channel may be calculated by the formula #a_/7a-sin#b 71 being the angle at any bend in this channel4 7,it may be convenient to note that-- sin#b #ij #a1 sin#b #fj #cd1 sin#b #de #ab1 sin#b #cj #ad47 ,thus every right angle in a bent shaft reduces the velocity in it by one-half4 ,the loss by friction in two similar tubes of equal sectional area varies 7#a7 directly with the square of the velocity of the air currents2 and 7#b7 directly with the length of the outlet channel4 ,in two similar tubes of unequal size the loss by friction is 7#c7 inversely as the diameter of the cross-section in each4 ,when two tubes are of different shapes1 the loss by friction is inversely as the square roots of the sectional areas4 ,owing to the variable value of the co-efficient of friction 7called c in the first formula given71 it is usually preferable to measure the actual rate of progress of air through a given flue by means of an anemometer 7wind measure74 ,then the velocity of the current of air and the area of the cross section of the flue being given1 the volume of air discharged in a given time is represented by the product of these two and the time which has elapsed4 ,thus1 q a v4 ,where q quantity of air discharged in a given time1 a area of cross section of flue1 v velocity of current4 ,by means of this formula1 the area of chimney required to discharge a given volume of air at a given average velocity can be ascertained4 ,thus-- a q_/v4 ,the application of the preceding principles and formul will be rendered clearer by the following examples4 ,how much inlet and outlet area per head will be required to give #aj persons in a room of #e1jjj cubic feet capacity1 #b1jjj cubic feet of air per head per hour1 supposing that the outside temperature is #dj1 while the internal temperature is #fj1 and the height of the heated column of air #bj feet8 ,first ascertain the velocity of entrance and exit of air4 v #hb7;h7t - t#a7_/dib7 #hb7bj7fj - #dj7_/dib7 #hb #ijb4 #gcifd velocity in feet per second4 ,if we allow one-fourth for friction1 then there remains a velocity of #eedgc feet per second4 #eedgc feet per second #aigjjh feet per hour4 ,now1 a q_/v #b1jjjaigjjh #ajae square feet4 #adf square inches4 ,thus the size of the outlet required per head is #adf square inches4 ,the size of the room and the number occupying it do not enter into the question1 except for a short time at the beginning4 7,see page #ace47 ,the amount of inlet required will also be #adf square inches per head4 ,theoretically it ought to be slightly less than that required for outlet1 as the outgoing air is more expanded than that entering the room2 but practically no allowance need be made for this fact4 ,the total amount of inlet and outlet required per head #bib square inches4 ,if the mean temperature of a room is #fa1 the external temperature #de1 while the heated column of air is #ej feet1 and the required delivery of air #b1jjj cubic feet per hour1 find the size of inlet and outlet4 v #hb7;h7t - t#a7_/dib7 #hb7ej7fa - #de7_/dib7 #ajee feet per second4 #cg1ihj feet per hour4 ,if we make no allowance for friction1 then a q_/v #b1jjjcg1ihj square feet4 #b1jjj #addcg1ihj #geh square inches4 ,this gives the required size of outlet4 ,the size of inlet and outlet together #aeaf square inches4 ,if #c1jjj cubic feet of air are supplied in one hour through an aperture of #ab square inches to a room containing #a1jjj cubic feet of space1 at what rate does the air enter the room8 #ab square inches #aab square foot4 a q_/v #aab #c1jjj_/v ,therefore v #cf1jjj feet per hour4 #aj feet per second4 ,if a room is supplied with #c1jjj cubic feet of air per hour1 through a single opening1 what must be its area1 if the rate of movement of the air is #e feet per second8 #e feet per second #ah1jjj feet per hour4 a #cjjjahjjj #af square foot4 #bd square inches4 ,as already stated1 the difficulties connected with the estimation of amount of friction greatly detract from the practical value of the formul just given4 ,even the results given by anemometers are not always trustworthy1 but by comparing the results given by them with those obtained by the use of ,montgolfier's formula an approximation to the truth can be obtained4 ,the ordinary anemometer consists of four tiny vanes fixed to a spindle1 so that revolutions are caused by the current of air the velocity of which is to be measured4 ,the revolutions are counted by a mechanical arrangement4 ,the value of the revolutions of the vanes has to be first determined by direct experiment2 a known bulk of air being forced through a channel of known size at a uniform rate1 and the instrument graduated accordingly4 ,in ,fletcher's anemometer a modification of the manometer or pressure-gauge has been used for the same purpose4 ,inlets and ,outlets4--,having given the average velocity of the wind1 the size of a room1 and the number of persons occupying it1 the size of inlet opening required can easily be calculated4 ,find the size of inlet for air in a room occupied by one person1 the air moving at the average velocity of #e feet per second1 assuming that #c1jjj cubic feet of air are to be supplied per hour4 ,let x size of inlet4 ,then x #fj #fj #e #c1jjj4 ,therefore x #cjjjahjjj #af square foot4 #bd square inches4 ,given that the air moves at a velocity of #aj feet per second1 and that the area of the inlet aperture into a room is #ab square inches1 find how much air enters the room in an hour4 ,let y amount of air4 ,then #aj #fj #fj #abadd y4 ,therefore y #c1jjj cubic feet of air4 ,calculations as to supply of air in a room founded on the average velocity of air-currents are1 however1 much less trustworthy than when the velocity is determined1 as previously explained1 by means of ,montgolfier's formula1 or1 better still1 by an anemometer4 ,the ,commissioners on ,improving the ,sanitary ,condition of ,barracks and ,hospitals1 in their report 7#ahfa7 recommended for inlets1 one square inch for every #fj cubic feet in the contents of the room2 or one square inch for every #abj cubic feet in the contents1 if warm air is admitted round the fire-grate4 ,for outlet shafts on lower floors1 one square inch to every #fj cubic feet1 slightly increasing for the higher storeys4 ,amount of ,air-space required4--,we may take #c1jjj cubic feet of air as the average amount of air required hourly by each individual1 and inasmuch as the air of a room cannot be changed oftener than three times an hour without producing an unpleasant draught1 it follows that at least #a1jjj cubic feet of space must be allowed per person4 ,this may be compared with the amount actually supplied under various circumstances4 ,in the ,british ,army for each soldier-- ,in permanent barracks #fjj cubic ft4 ,in wooden huts #djj ,in hospital wards at home #a1bjj ,in hospital wards in the tropics #a1ejj ,in general hospitals #a1jjj-a1ejj ,in fever hospitals #b1jjj-c1jjj ,in workhouse hospitals #hej-a1bjj ,in common lodging houses #cjj or #cej ,do41 if occupied night and day #cej or #djj ,in workhouses #cjj ,in schools-- ,london ,school ,board requires per scholar #acj ,english ,educational ,code per scholar 7minimum71 in old schools #hj ,do41 in new schools #abj ,floor-space has an important bearing on ventilation4 ,in calculating the available cubic space of a room1 the height over #ab feet should be disregarded4 ,thus1 if #ejj cubic feet is allowed for each individual1 the floor-space should be #db square feet4 ,in barracks1 soldiers are allowed #ej square feet of floor-space4 ,in the ,government regulations for workhouses it is stated that there must not be more than two rows of beds1 and that the height of rooms above #ab feet must not be reckoned4 ,this gives a minimum floor-space of #be square feet per occupant1 or with dormitories #ag feet wide1 a bed-space of about #c feet4 ,in hospitals1 the question of floor-space is extremely important1 as it regulates the distance between the sick inmates and the convenience of nursing4 ,assuming each bed to be #c feet wide and #f feet long1 the distance between any two beds should be at least #e feet4 ,this makes the wall-space for each bed #h feet long1 and allows from #hj to #if square feet of floor-space per bed4 ,at ,st4 ,thomas's ,hospital1 ,london1 the floor-space is #aab square feet1 and in fever hospitals it is from #aej to #cjj square feet per bed4 ,in regard to the ventilation of hospitals1 it has been well said that nothing less than too much is enough4 ,means of ascertaining ,cubic ,space4--,circumference of a circle ,diameter 7,d7 #c4adaf4 ,area of circle ,d#b 4#ghed4 ,area of square square of one of its sides4 ,area of rectangle product of two adjacent sides4 ,area of triangle base #ab height1 or height #ab base4 ,area of ellipse product of the two diameters #ghed4 ,circumference of ellipse half the sum of the two diameters #cadaf4 ,area of any polygon found by dividing into triangles1 and taking the sum of their areas4 ,cubic capacity of a cube found by multiplying the three dimensions together4 ,cubic capacity of a cylinder area of base height4 ,cubic capacity of a cone or pyramid area of base #ac height4 ,cubic capacity of a dome area of base 7circle7 x #bc height4 ,cubic capacity of a sphere ,d#c x #ebcf4 ,area of segment of a circle found by adding to #bc of product of chord and height1 the cube of the height divided by twice the chord4 7,ch x ,h x #bc7 ,h#cb ,ch ,give the dimensions of a circular ward for #ab patients1 each to have #a1gej cubic feet of available air-space4 ,capacity of ward #a1gej ,x #ab #ba1jjj cubic feet4 ,if we allow #abj square feet floor-space for each patient1 then the total floor-space will be #a1ddj square feet4 ,consequently the height of the ward #bajjjaddj #adge feet4 ,area of circle ,d#b x #ghed4 #a1ddj_/ghed ,d#b4 ,therefore ,d #dcb feet4 ,circumference of circle ,d x #cadaf4 #dcb x #cadaf4 #aceg feet4 ,the dimensions of the circular ward required are therefore a height of #adge feet1 diameter of #dcb feet1 and circumference of #aceg feet4 ,find the cubic capacity of a circular hospital ward #bh feet in diameter1 #aj feet high1 and with a dome-shaped roof #e feet high4 ,area of floor-space ,d#b x #ghed4 #fadh square feet4 ,cubic capacity of the cylinder below the dome is #fadh x #aj #f1adh cubic feet4 ,cubic capacity of dome #fadh x #bc x #e #bjdic cubic feet4 ,total cubic capacity of the ward #haigc cubic feet4 ,in practical measurements of rooms1 deductions must be made from the cubic space for the furniture contained in it and for its inmates4 ,about #aj cubic feet ought to be allowed for each bed and bedding1 and #b to #d cubic feet for each individual4 ,projecting surfaces must be allowed for by subtraction1 and recesses by addition4 ,a circular ward with a diameter of #cf feet has a dome-shaped roof1 the height of whose centre is #ah feet4 ,the height to the dome is #ab feet4 ,find the floor-space and total cubic contents4 ,how many patients ought the ward to accommodate8 ,area of floor-space 7#cf7b x #ghed4 #ajaghghd square feet4 ,cubic capacity of cylinder below dome #ajaghg x #ab #abbade cubic feet4 ,cubic capacity of dome #ajaghg x #bc x #f #djgadh cubic feet4 ,total cubic capacity of the ward #afbheih cubic feet4 ,assuming that #a1ejj cubic feet are required for each patient1 then the ward is large enough for #aj patients4 ,it is well to test this conclusion by calculating whether sufficient floor-space has been allowed for each patient4 ,the floor-space has been found to be about #a1jah square feet1 which would give #ajj feet for each of #aj patients and more than the minimum standard previously stated4 ,what number of people should be allowed to sleep in a dormitory #dj feet long1 of which the accompanying sketch is a section8 ,illustration3 ,outline of rectangular space with triangular roof ,the cubic capacity of the quadrilateral space below the roof #af x #i x #dj #e1gfj cubic feet4 ,area of floor area of base of roof #dj x #aj #fdj square feet4 ,cubic capacity of roof #fdj x #ac7ac - #i74 #hecc cubic feet4 ,total cubic capacity of dormitory #ffacc cubic feet4 ,if we take the low standard of common lodging houses and allow #cej cubic feet of space for each inmate1 then #ah persons may be allowed to sleep in the dormitory4 ,how much space would a man occupy supposing him to weigh #age lbs48 ,how much is usually allowed for a man with his clothes1 bed and bedding8 ,the space occupied by a man is stated by ,parkes to be from #b to #d cubic feet 7say #c for the average74 ,he gives the following rule3 ,the weight of a man in stones divided by #d gives the cubic feet he occupies4 ,thus1 a man weighing #age lbs4 would occupy #c-ah cubic feet of space4 ,about #aj additional cubic feet must be allowed for clothing1 bedding1 and bed for each person4 ,what size of inlet and outlet aperture should be allowed per head8 ,how large should each individual inlet be made8 ,if an inlet aperture #ajj square inches in area is divided into four1 with apertures of #be square inches each1 what is the loss by friction8 ,a size of #bd square inches per head for inlet and the same for outlet meets common conditions4 ,it is desirable to make each individual inlet not larger than #dh to #fj square inches in area1 i4e4 large enough for two or three men2 and each outlet not larger than one square foot1 or enough for six men 7,parkes74 ,this ensures more uniform diffusion of the air throughout a room4 ,on the other hand1 the loss by friction is greatly increased by having a number of small openings instead of one large opening4 ,this loss is inversely to the square roots of the respective areas4 ,thus the square root of #ajj is #aj2 the sum of the square roots of the four apertures of #be square inches each is #bj4 ,the loss by friction is double in the second case what it was in the undivided opening4 ,it is evident1 therefore1 that in order to get as much air through the four openings as through the original large opening1 each must be equal in size to half the original opening4 ,why is ventilation more difficult in upper rooms of large houses and in single-storied houses than in the lower storeys of large houses8 ,cold external air being heavier than the internal warm air presses downwards to the lowest point1 and pushes up the warmer air4 ,if there were a vacuum in the room1 air would rush into it with a velocity which1 as seen before1 is represented by the formula-- v 7#b;gs74 ,where g #cb1 s height of column of air1 which we may take as roughly #e miles4 ,from this formula we obtain v #a1cjf feet per second4 ,it is evident that in such a case the velocity of entry of air into a vacuum on the ground floor would be greater than into a vacuum on any of the higher storeys1 owing to the greater velocity acquired through the increased action of gravity4 ,and the same increased facility of entry of air into lower rooms must hold good under ordinary circumstances1 inasmuch as by ,montgolfier's formula 7which is founded on the fundamental formula v 7#b;gs7 v 7#b;gh7t-t#a7_/dib7 h distance between top of chimney and floor of room in question1 and thus the velocity with which air enters is governed by the difference between the internal and external temperature1 and the height from which the cold air descends in order to take the place of the air which has escaped4 ,,chapter ,,xxii4 ,,methods ,,of ,,ventilation4 ,in most houses no special means of ventilation are provided1 windows1 doors and fire-places being trusted for ensuring a sufficient supply of fresh air4 ,these do not suffice in well-built houses1 unless the inhabitants train themselves into enduring the currents of air necessarily associated with open windows and doors4 ,they are1 however1 aided in the majority of houses by the porosity of walls1 by currents of air through crevices of wood-work1 and so on4 ,it is desirable that adequate special provision for ventilation should be made for every house when it is built1 and that as much care and forethought should be exercised in this respect as in the laying on of a water-supply or sanitary appliances connected with drainage4 ,whatever the system of ventilation adopted1 it is wise to flush rooms frequently with fresh air4 ,this is best effected by throwing the windows wide open whenever a room is left unoccupied4 ,in this way a much more thorough and complete purification is effected than by any other means4 ,this is especially important in the case of bedrooms1 in which organic impurities are most prone to accumulate4 ,not only should rooms be ventilated1 but likewise the furniture they contain4 ,this again is most important for bedrooms4 ,beds should not be 8made0 till sometime after using2 and in the interval1 should be freely exposed to the air4 ,the same applies to night apparel4 ,it is well to allow rooms to lie fallow at intervals4 ,organic matter accumulates about a room1 and devitalises any air which enters4 ,if the room is vacated1 and flushed with air for a continuous period1 it becomes sweeter and purer4 ,the importance of this is now well recognised in the case of hospital wards4 ,such temporary disuse of rooms must not1 however1 be regarded as sufficient without thorough cleansing of every surface in them1 in order effectively to remove all organic and other dust4 ,an ,inlet and ,outlet for air should both be provided4 ,according to some an inlet only is required1 while others would only provide an outlet2 but a perfect system of ventilation requires both4 ,as heated air expands1 the outlets should theoretically be larger than the inlets2 but as the average difference of temperature is only #aj-ae ,fahr41 the expansion is only slight1 and may be practically neglected4 ,the necessity for both inlets and outlets may be illustrated by a single apparatus like that shown in ,fig4 #aa4 ,a taper is burning at the bottom of the jar1 in the stopper of which two tubes1 ,a and ,b1 are placed4 ,so long as both tubes are kept open the candle will keep alight1 but if ,a be blocked1 the candle goes out4 ,illustration3 ,,fig4 #aa4 ,,illustrating ,,necessity ,,of ,,inlet ,,and ,,outlet4 ,inlets should bring air from a pure source1 and should be arranged at intervals in large rooms4 ,externally1 inlets should be protected from the wind2 and the shorter the inlet tubes the better1 as thus a current is ensured1 and they can be easily cleaned4 ,the position of inlets should not be too near the outlets1 otherwise the fresh air may escape immediately4 ,the best position for inlets is at the floor1 but this necessitates warming the entering air1 as otherwise it would be intolerable1 except in summer time4 ,if the air cannot be warmed1 it should he admitted about seven feet above the floor1 and directed upwards4 ,for size of inlets1 see page #adb4 ,outlets1 under ordinary circumstances1 are best placed near the ceiling4 ,they should be enclosed as far as possible within walls1 so as to prevent the outgoing air being cooled2 and should have smooth walls1 reducing friction to a minimum4 ,where artificial warmth increases the temperature of the air1 the discharge of outlets is much more certain and constant4 ,the chimney with an open fire forms one of the best outlets4 ,gas1 again1 may be made to heat an outlet tube1 which carries off the products of combustion4 ,two forms of ventilation are usually described--natural and artificial4 ,the former term is used to describe any plan not requiring heating apparatus or the motive power of steam1 or gas1 or electricity1 while the latter implies the use of some such motive power or source of heat4 ,obviously1 however1 there is no sharp line of demarcation between the two4 ,a lighted fire is strictly an artificial plan of ventilation1 but inasmuch as no apparatus intended for ventilating purposes is required1 it is hardly a means of artificial ventilation4 ,natural ,ventilation4--,the most important means of natural ventilation are the window and the chimney2 but openings in outer walls and over the door may form valuable adjuncts4 ,the ,window is perhaps the most important agent in purifying a room--both the light and air it admits being essential for health4 ,the window is invaluable 7#a7 for flushing the room with fresh air at intervals4 ,where possible1 opposite windows should be opened1 or window and door4 ,cross-ventilation by opposite windows open at the top forms one of the best means of natural ventilation1 in large rooms1 such as school-rooms4 ,this can1 as a rule1 be borne without discomfort1 while the room is occupied1 unless the wind is very high4 7#b7 ,the ,upper ,segment of a window may be made to work inwards on a hinge1 and turned so that the current of air may be upwards4 ,where this plan is adopted1 triangular pieces of glass should be placed at the two sides to prevent cold air from falling directly down at the sides of the opening4 7#c7 ,a ,block of ,wood1 two or three inches wide1 may be inserted at the bottom of the window sash at ,a 7,fig4 #ab71 and then the window pulled down on this4 ,the consequence is that air is admitted between the two sashes at ,b1 its current being necessarily directed upwards 7,fig4 #ab74 ,this plan answers admirably in admitting pure air2 but it possesses a disadvantage common to all the plans in which external air much colder than the internal is admitted into a room4 ,the current of cold air passes upwards for some distance1 but may then fall down on the heads of those occupying the room4 ,illustration3 ,,fig4 #ab4 ,,window ,,ventilation4 7#d7 ,the top sash of the window may be opened1 and some zinc gauze fastened across the open part4 ,this is practically the same as the last arrangement1 except that the air is admitted through the apertures of the zinc1 and the amount admitted is greatly diminished 7page #acf74 7#e7 ,in ,louvre ,ventilators1 a number of parallel pieces of glass1 each directed upwards1 are substituted for a pane of glass4 ,they may be fixed or made movable1 as in ,moore's ventilator4 ,the incoming current of air may be similarly directed upwards1 in an open window1 by arranging ,venetian blinds with the laths inclined upwards4 7#f7 ,in windows that will not open1 ,cooper's ,ventilators are often used4 ,each of these consists of a circular disc of glass1 having five oval apertures in it1 which works on a pivot through its centre1 close in front of one of the panes of a window1 which has five similar holes pierced in it4 ,consequently1 when the disc is turned1 so that its holes are opposite those of the window1 fresh air is admitted4 ,the amount thus admitted is necessarily small4 ,the ,chimney forms the best means of escape of foul air4 ,no room ought to be built without a fire-place1 which should never subsequently be boarded up4 ,in bedrooms the chimney forms a most important means of ventilation4 ,if there is no fire1 the chimney occasionally furnishes an undesirable source of air2 but as a rule the current is upwards1 owing to the aspirating action of winds at the top of the chimney4 ,the downfall of air from a chimney chiefly occurs when there is an insufficient inlet for pure air4 ,this is the explanation of smoky chimneys in nine cases out of ten2 then the cure is easy by laying on a pipe from the outside of the house to the hearth4 ,when the smoky chimney is due to the contiguity of higher buildings1 the chimney must be raised1 or a cowl placed over it4 7#a7 ,the action of the chimney in carrying impure air away from the room may be considerably increased by narrowing the two ends1 so as to produce a more rapid current at the entrance and exit of air4 7#b7 ,the heat of the chimney may be utilised by having a separate smaller flue alongside it1 with openings from the rooms on each floor4 ,the air in this being heated aspirates the air from each room in succession4 ,openings may be made into the chimney-flue at a higher point than the fire-place4 ,these are very valuable for carrying off the heated and impure air resulting from the combustion of gas1 as well as for carrying off the respiratory products1 which1 in their warmed condition1 tend to rise towards the ceiling4 7#c7 ,dr4 ,neil ,arnott first devised a valve for this purpose4 ,an opening being made through the upper part of the wall into the chimney1 an iron box was inserted1 in which was placed a light metal valve capable of swinging towards the chimney flue1 but not towards the room4 ,the objections to this apparatus are that it is apt to make irregular clicking noises1 and to admit blacks from the chimney when out of order4 7#c7 ,in ,boyle's ,valve these objections are partially obviated4 ,it consists of an iron frame1 across which lie iron rods2 and from these are suspended thin talc plates1 only capable of moving in the direction of the chimney 7,fig4 #ac74 ,even this apparatus is rather noisy when there is a strong wind4 ,illustration3 ,view from room4 ,view from chimney4 ,,fig4 #ac4 ,,boyle',s ,,mica ,,flap ,,ventilator4 ,neither of these plans answers so well as a second flue alongside the chimney flue1 communicating with each room near its ceiling2 but the latter can only be arranged for when the house is built1 while the valves may be inserted at any time4 ,the ,ceiling may be utilised for removing foul air2 and thus serve to diminish the draught which is often produced by the currents of air towards the chimney1 when this forms the only means of outlet4 ,in large rooms 7#a7 a sunlight gas-burner forms an important means of ventilation4 ,it causes a strong up-current from every part of the room4 ,if there is a fire in the room1 the burner is apt to become an inlet for air1 or the chimney to smoke1 according to the relative strength of the two currents4 7#b7 ,benham's and other forms of ,ventilating ,gas ,burners serve the same purpose4 ,in each of them the products of combustion are conveyed by special ducts above the ceiling to the outer air4 7#c7 ,mc,kinnell's ,ventilator is useful in single-storied buildings1 like certain barracks4 ,it consists of two tubes encircling one another1 the inner forming an outlet tube1 because the casing of the outer tube maintains the temperature of the air in it4 ,it is made higher than the outer tube1 and is protected by a hood4 ,the outer tube forms the inlet for fresh air4 ,the entering air is thrown up towards the ceiling and then to the walls by a flange placed at the bottom of the inner tube4 ,the air after traversing the room1 and becoming heated1 passes upwards to the inner tube4 ,when doors and windows are open1 both tubes become outlets2 if there is a fire in the room1 they may both become inlets2 but this may be prevented by closing the outlet tube4 ,illustration3 ,,fig4 #ad4 ,,mckinnell',s ,,roof ,,ventilator4 7#d7 ,various other means have been devised for carrying foul air from the ceiling through channels between the ceiling and the floor of the room above4 ,all share the disadvantage that the channels become dirty and are difficult or impossible of access for cleaning4 7#e7 ,various cowls connected by metal tubes with the ceilings of rooms have been placed on roofs1 and their aspirating effect used in ventilating these rooms4 ,when a room is furnished with a chimney such cowls are most undesirable4 ,in large rooms without a fire-place they are helpful1 but much more confidence can be placed in cross-ventilation by hinged windows4 ,it is doubtful if any of the advertised fixed cowls produce materially greater aspiration of air from rooms than a simple open tube of the same size4 ,it is desirable that the tube should be protected at its upper end against the entry of rain1 and that a grating should be provided to prevent birds building their nests in the tube4 ,in the preceding plans of ventilation1 the ceiling serves almost entirely as an outlet for impure air4 ,in the following plan1 it is used as an inlet for pure air4 7#f7 ,in ,sylvester's ,method of ,ventilation1 the perflating force of the wind is employed to produce an abundant entry of fresh air4 ,a cowl is placed1 always turning towards the wind2 the air received is conducted to the basement1 where it is warmed by a stove or hot-water pipes1 and then passed through tubes into the upper rooms4 ,from these it is carried by tubes above the roof1 these tubes being covered with cowls turning from the wind1 so that in this way the aspirating power of the wind is likewise used4 ,ships are often ventilated in a somewhat similar manner4 ,the tube to which a windward cowl is attached above1 ought to be bent at right angles1 so as to lessen the velocity of the entering air4 ,by covering other air-shafts with movable cowls1 turning from the wind1 the aspirating action of the wind is brought into action to aid the escape of foul air4 ,the ,walls of a room1 unless covered with an impervious material1 are constantly traversed by gentle currents of air1 which play an important part in the ventilation of rooms4 ,special apertures may be made to furnish a freer supply1 and these may be in various forms4 7#a7 ,a ,simple ,grating1 may be inserted2 but this is apt to become blocked with dirt1 and does not allow a large amount of air to enter4 ,louvred openings in the walls are objectionable1 except for very large rooms4 7#b7 ,sheringham's ,valve is the most convenient means of ventilating through the wall4 ,an opening in the external wall is made by a ventilating brick or grating2 into the wall is fixed an iron box1 which has in front of it an iron valve hinged along its lower edge1 so that it can open towards the room4 ,on the sides of the valve cheeks are attached1 which fit into the box when the valve is shut4 ,a heavy piece of iron pressing against the valve from within the box1 tends to keep it constantly open4 ,by means of a string and pulley1 the valve can be opened or closed at will1 or fixed in any intermediate position4 ,illustration3 ,,fig #ae4 ,,sheringham',s ,,ventilator4 ,in a very large room1 it is better to have several medium-sized valves1 than a few larger ones1 the air being thus more completely diffused4 ,if there are two valves1 they should not be opposite one another1 as the air may then simply pass from one to the other1 without becoming diffused through the room4 ,if there is only one valve1 it may occasionally serve as an outlet when the wind is to leeward4 ,by means of this form of valve1 the air is projected upwards in a diverging current towards the ceiling4 ,the valve should be placed above the level of one's head1 but not too near the ceiling2 as in the latter case1 the current of air is driven hard against the ceiling1 and falls thence with considerable force towards the floor4 ,a combination of ,sheringham's inlet and ,boyle's mica outlet into the chimney at the opposite side of the room ensures efficient ventilation in a dining-room4 ,better than the outlet into the chimney is an opening into a special flue alongside the chimney-flue1 if this be available4 7#d7 ,ellison's ,inlet consists of a brick pierced with conical holes1 the apex of the cone being towards the external air4 ,by this means any great draught is avoided1 and the air is distributed over a considerable area4 ,in order that this may prove an efficient means of ventilation1 a considerable number of bricks are required4 ,the ,floor of a room is always the source of considerable currents of air1 even when well carpeted4 ,air mounts up through the crevices of the wood-work1 being aspirated into the room when its temperature is higher than that of the rooms below4 ,in the case of rooms on the ground floor1 air is often drawn from the subjacent soil1 or through dust-bins1 etc4 ,theoretically1 in all measures of ventilation1 the floor would be the best point for the entry of cold air4 ,this1 however1 is intolerable when the incoming air is cold1 and the floor must therefore be abandoned as a means of ventilation1 apart from heating apparatus4 ,the floor may be used as a means of entry of fresh air in a modified manner1 by directing the air entering at the floor-level for some distance up a tube at the side of the wall4 ,this apparatus is known as ,tobin's tube4 ,it consists of a rectangular or cylindrical tube from #d to #f feet high1 which communicates at the lowest point with the external air by means of a perforated brick or grating4 ,the air enters the room in an upward direction1 and is consequently sent towards the ceiling1 where it becomes mixed with warmer air1 before diffusing itself throughout the room4 ,but when the incoming air is very cold1 it may fall more rapidly1 causing cold draughts on the heads of those in the room4 ,as the air enters directly from outside the house1 it often carries with it particles of dirt1 soot1 etc4 ,this may be remedied by placing a pan containing a shallow layer of water at the lowest part of the tube1 or by placing cotton wool at the point of entry of the tube into the room4 ,the tray of water soon dries up and is rarely replaced1 while the cotton wool diminishes the amount of entering air4 ,it is very useful however in cold weather1 or when fogs occur4 ,a gauze funnel is sometimes inserted in the tube1 or a sheet of gauze arranged diagonally across the tube from its highest to its lowest point4 ,the gauze does not keep out minuter particles of dust1 and requires occasional cleaning4 ,all ,tobin's tubes1 like other ventilating openings1 should be made to open1 so that their interior can be frequently cleaned4 ,summary as to ,domestic ,ventilation4--,open windows1 doors1 and fire-places may be in most instances trusted4 ,if gas is used as an illuminant1 they should be combined with special arrangements for carrying off the products of combustion from the room4 ,for delicate people1 and especially in small rooms1 outlet ventilation into the chimney breast combined with a ,sheringham's valve on the opposite wall is desirable4 ,artificial ,ventilation4--,artificial ventilation may include two important and very different measures4 ,in one of them currents of air and an exchange of pure for impure air are effected by means of various forms of heating apparatus4 ,in the other mechanical measures are used for the same purpose1--the air being either driven out of the room or drawn out of it4 ,in this chapter we shall consider only the mechanical means of artificial ventilation4 ,there are two kinds1 the first being known as ventilation by aspiration1 or the vacuum system2 and the second as ventilation by propulsion1 or the plenum system4 ,in ,ventilation by ,aspiration the foul air is drawn out of the room by machinery1 its place being supplied by fresh air1 which may be warmed before entry or not4 ,this plan and the next have been employed chiefly in connection with large buildings1 such as hospitals1 etc41 and in mines4 ,the extraction of foul air may be effected by--7#a7 a steam-jet1 which is allowed to pass into a chimney1 and sets in motion a body of air more than #bjj times its own bulk4 ,tubes from each room of the building are connected with this chimney1 and the strong upward current extracts the air from them4 ,this plan is useful in factories1 where there is a superfluous supply of steam4 7#b7 ,a fan or screw may also be used4 ,the vanes of the fan1 when set in motion by electrical or some other motive power1 produce a powerful current of air1 which can be regulated according to requirements4 ,as in the last plan1 the aspirating influence of the fan may be exerted over a system of rooms1 by means of connecting tubes4 ,in ,ventilation by ,propulsion a fan is used as in the last plan1 the air being propelled along conduits leading from it into the room to be ventilated4 ,the size of the conduits being known1 the amount of air to be discharged can be regulated by timing the rapidity of the revolutions of the fan4 ,this plan is suitable for crowded places1 where a large amount of air is required in a short time4 ,it is excellent for large schools1 churches1 and theatres4 ,its superiority for large elementary schools has been proved at ,dundee by the experiments of ,drs4 ,carnelley1 ,haldane1 and ,anderson1 the results of which are summarised in the following table3-- ,column headings3 ,a ,no4 of ,schools4 ,b ,no4 of ,rooms4 ,c ,cubic ft4 allowed per person4 ,d ,carbonic acid in #aj1jjj of air4 ,e ,micro-organisms per litre4 ,f ,bacteria4 ,g ,moulds4 ,a4 ,b4 ,c4 ,d4 ,e4 ,f4 ,g4 ,mechanical ventilation by warmed air #f #cb #afj #abc #age #aj ,natural ventilation and hot pipes #ag #dc #agf #afc #ife #aa ,natural ventilation and open fires #cc #hd #ade #aib #aecb #dh ,the air to be admitted may be warmed by passing it over hot-water or steam-pipes4 ,in large establishments1 as in hospitals1 theatres1 etc41 it has been arranged so that the incoming air is passed through a screen of coarse cloth1 which is kept wet by water trickling down each cord4 ,the air is thus kept moist and freed from dust4 ,the great advantage of the plan of propulsion1 is its certainty4 ,by it the temperature1 moisture1 and freedom from suspended matters of the incoming air can be exactly regulated and controlled4 ,its chief disadvantages are that 7#a7 it is somewhat costly1 and 7#b7 the apparatus requires skilled supervision4 ,on the other hand it maintains the air in crowded rooms in a condition which cannot be secured by any other method4 ,when combined1 as is done in the ,houses of ,parliament1 with the use of a flue for the extraction of foul air1 this plan answers admirably4 ,the ,relative ,value of ,artificial and ,natural ,ventilation scarcely needs to be discussed4 ,they are both valuable1 but under different circumstances4 ,in dwelling-rooms natural ventilation by doors1 windows and chimney usually suffices1 especially if the products of combustion of gas are removed through a special flue4 ,natural ventilation is always occurring1 and only needs a little aid in domestic life4 ,for large rooms occupied by many persons artificial ventilation is necessary to maintain pure air4 ,whatever method of ventilation is adopted1 the atmosphere will remain to some extent polluted1 if the room and its occupants are dirty4 ,in certain experiments made by ,carnelley in schools1 it was found that dirty children increased the number of micro-organisms per litre of air more rapidly than dirty rooms4 ,thus3-- ,,degree ,,of ,,cleanliness ,,of,,clean4,,medium4,,dirty4 ,children #fc #ii #aei ,rooms #he #id #aci ,number of micro-organisms per litre of air4 ,hence cleanliness of rooms and of their occupants is quite as important as a good system of ventilation4 ,,chapter ,,xxiii4 ,,ventilation ,,by ,,the ,,introduction ,,of ,,warmed ,,air4 ,ventilation by the ,burning of ,coal4 ,in winter and at any time of the year when the out-door temperature is below #ej ,fahr41 the warming and ventilation of a room are necessarily combined4 ,if air is admitted unwarmed it will produce draughts1 unless directed upwards by ,tobin's tubes or otherwise4 ,in dwelling-rooms such contrivances may suffice2 but in any larger building1 in order to ensure sufficient ventilation1 it is necessary to warm the incoming air4 ,the ,open ,fire-place forms the most common means of ventilation by heat 7see also page #aei74 ,the ascent of warm air up the chimney1 causes cold air to rush along the floor to the fire-place from all parts of the room1 especially the door4 ,part of the air thus approaching the fire is carried up the chimney with the smoke1 while the remainder1 after having been warmed1 flows upwards towards the ceiling near the chimney-breast4 ,it passes along the ceiling1 and cooling in its progress towards the opposite wall1 descends1 and is again drawn towards the fire-place4 ,thus there is a continuous circulation of the air in a room4 ,in the experiments of the ,barrack ,commissioners 7#ahfa71 it was found that the amount of air passing up the chimney while a fire was lit1 ranged from #e1cjj to #af1jjj cubic feet per hour1 the mean of #be experiments being #i1ijd cubic feet4 ,we may conclude1 then1 that with an ordinary grate1 a chimney provides outlet for impure air sufficient for four or five persons4 ,its lack of economy as a heat-producer will be considered later4 ,its efficiency as a ventilator within the above limits is evident4 ,when a fire is burning in the grate1 all other openings in the room1 except openings into the chimney1 serve as inlets4 ,if the room is insufficiently supplied with openings1 a double current may be established in the chimney1 with the result that occasional down-puffs of smoke occur4 ,as a rule the chimney serves only as an outlet for impure air4 ,it may by appropriate means be made to serve as an inlet for pure and warmed air1 the heat which would otherwise escape up the chimney being utilised for this purpose4 ,galton's stove is one of the best for this purpose4 ,at the back of this stove is an air-chamber1 communicating with the external air1 and in which the fresh air is heated before it enters the room4 ,on the back of the stove broad iron flanges are cast1 in order to present as large a heating surface as possible4 ,they project backwards into the air chamber2 and their heating surface is aided by the iron smoke-flue1 which passes through the air-chamber4 ,the warmed fresh air enters the room by a louvred opening above the mantel-piece1 or by an opening in each side of the chimney breast4 ,by this stove one-third of the total heat of the fire is utilised1 as against one-eighth in an ordinary fire-place4 ,illustration3 ,,fig4 #af4 ,vertical ,section through ,two ,rooms1 showing--,a4 ,currents of cold air with an ordinary fire2 ,b4 ,direction of currents of warmed fresh air with a ,galton's ,ventilating ,stove4 ,shorland's ,manchester and other stoves are constructed on the same principle as ,galton's4 ,the ,ventilation of ,mines is effected by lighting a fire at the bottom of a shaft4 ,the air for the combustion comes down another shaft 7the intake shaft71 or down another half of the same shaft separated by a partition4 ,the consequence is that constant up and down currents of air are produced4 ,the air from the intake shaft is made to traverse the galleries of the mines1 its course being directed by partitions1 before it is allowed to reach the fire and s be carried up out of the mine4 ,in addition to1 or instead of1 an ordinary coal-fire1 the power for extracting impure air may be obtained from ,hot ,water or ,steam ,pipes4 ,there are various plans founded on this principle4 ,when hot-water pipes are used for baths1 etc41 they may also be utilised for ventilation1 in two ways3--#ast4 ,the hot-water pipe may be made to coil round the tube by which fresh air is admitted into a room1 thus warming the air as it enters4 #bnd4 ,the hot-water pipe in its course upwards may be enclosed in a shaft1 which opens into the external air above4 ,the air in this shaft being heated1 the impure air may be collected and removed from the different rooms by tubes connected with it4 ,thus1 a hot-water apparatus1 when well arranged and complete1 may furnish pure warm air1 and carry away impure air4 ,the ventilation by this plan is found in practice to be somewhat irregular4 ,the plan proposed by ,drs4 ,drysdale and ,hayward of ,liverpool is similar in principle3--,fresh air is warmed by a coil of hot-water pipes in the basement1 and is admitted into the staircase and landings1 when it is supplied to the different rooms by openings provided with valves4 ,from the rooms1 special outlets converge to a foul-air chamber under the roof4 ,this is connected with a shaft leading from the kitchen-fire1 the latter1 therefore1 acting as an extraction furnace4 ,lighted ,gas may be employed to produce a current for ventilating purposes1 as well as fire or hot-water4 ,sunlight and ,benham's ,ventilating ,gas-burners1 have already been mentioned in this connection 7page #adi74 ,they are extremely valuable means of ventilation1 producing powerful currents of air from all quarters of the room unless they are specially enclosed4 ,in theatres and similar buildings the ,chandeliers may be made to extract vitiated air4 ,where a number of chandeliers exist1 they may be connected by tubes with a main shaft1 and all made to contribute to the same object4 ,according to the experiments of ,general ,morin1 the discharge of #a1jjj cubic feet of air is produced by the combustion of one cubic foot of gas4 ,various forms of gas-stoves are now sold1 which act as ventilators as well as sources of heat4 ,among these is ,george's ,calorigen ,stove 7,fig4 #ag74 ,it can be obtained in various forms suitable for burning coal-gas1 or coal1 or oil4 ,within its outer case is contained a special iron tube1 which communicates at its lower end with the outer air1 and opens at its upper end into the room4 ,the heat generated in the stove warms the air in the spiral tube1 which accordingly ascends into the room4 ,the ascent of warm air causes a draught from below1 and the consequence is1 that so long as the combustion is going on1 a current of warm air continues to ascend into the room4 ,the products of combustion are carried out of the room by the pipe ,f4 ,this stove is free from most of the objections appertaining to gas-stoves2 it can be fixed into an ordinary fire-place1 and made to keep the temperature of a room uniform4 ,illustration3 ,,fig #ag4 ,,george',s ,,calorigen ,,stove4 ,a--,the interior of the room4 ,b--,exterior of building4 ,c--,wall4 ,d--,the ,calorigen4 ,e--,a cylinder4 ,,ff--,pipes communicating with stove and cylinder to supply air for combustion1 and to carry off the products of combustion4 ,g--,pipe for passage of fresh cold air to ,calorigen4 ,can be carried above the floor between the joists1 as may be more convenient4 ,h--,outlet for air into the apartment after being made warm4 ,bond's ,euthermic ,stove is similarly constructed to the above1 but is open below so that the air needed for the gas combustion is drawn from the interior of the room1 and the continuous change of air is thus favoured4 ,objections to ,ventilation by ,heating ,apparatus4--,when warmed air is admitted into a room1 it is very apt to be dry and irritating4 ,this can be usually avoided by having water standing in the room1 so as to allow evaporation4 ,a more difficult problem is to ensure the complete absence of all products of combustion1 particularly of the products of incomplete combustion4 ,,chapter ,,xxiv4 ,,the ,,warming ,,of ,,houses4 ,physiological and ,physical ,considerations4--,the warmth of our bodies is naturally kept up by the oxidation changes constantly going on in the system4 ,in ,chapter ,,xl41 p4 #bfe1 are discussed the modes in which heat is lost by the system1 and the influence of clothing in controlling the amount of this loss4 ,artificial warming of houses has a similar action to clothing4 ,it diminishes the demand on the system1 and so economises the amount of food required4 ,the degree to which this diminution of loss of heat by clothing and artificial warming of houses may be carried varies with circumstances4 ,there can be no doubt that if food be abundant1 exposure to external cold1 if not too extreme1 is on the whole beneficial1 for vigorous people4 ,but for old people and young children1 means of artificial warmth require to be more carefully provided4 ,severe cold is for them often the harbinger of death4 ,the ,degree of ,temperature at which living-rooms should be kept will vary with circumstances4 ,for healthy adults1 any temperature between #ej and #fj ,fahr41 will be moderately comfortable2 for delicate children and old people it may be #fe with advantage4 ,for sick rooms and hospitals the temperature of #fj is usually adopted1 but this is by no means always necessary4 ,a temperature of the room as low as #ej1 except for such diseases as whooping cough and bronchitis1 suffices if the patient is well covered with warm personal and bed coverings4 ,convalescents from any acute illness bear low temperatures badly4 ,the ,different ,kinds of ,heat4--,heat may be communicated by radiation1 conduction1 and convection4 ,by radiation of heat is meant the process by which heat passes from a fire or other source of heat1 through a vacuum1 dry air or any other medium1 without heating any of the media through which it passes1 but only the bodies against which it finally impinges4 ,the solid bodies 7including ourselves7 which are warmed by radiant heat1 by a process of conduction then warm the surrounding air4 ,this method is the nearest imitation of the natural warmth of the sun4 ,conduction of ,heat is the passage of heat from one particle to another1 whether it be of a gas or solid4 ,it is an extremely slow process when air is concerned1 and may be practically ignored4 ,convection of ,heat is the process by which a gas or liquid actually carries the heat in itself from one part to another4 ,the heated particles are relatively lighter1 and ascend to the higher parts of a room1 while colder and heavier particles descend1 and are subjected to the same process4 ,heat can be carried by convection only by gases and liquids4 ,it is quite possible1 therefore1 for a person to be cold in a room filled with warm air1 if the walls1 etc41 are cold2 and on the other hand1 to feel comparatively warm in a room filled with cold air1 if more heat is radiated from an open fire-place or the warm walls to his body than he radiates to his surroundings4 ,the feeling of 8draught0 when sitting near a wall is sometimes caused by radiation of heat from the body to the colder wall4 ,the ideal arrangement1 were it practicable1 would be to have cool air to breathe1 but to be surrounded by warm walls1 floors1 and furniture4 ,a room warmed by an open fire is more comfortable than a room warmed by hot air from a furnace1 assuming the temperature of the air is the same in both instances1 because the walls of the room are several degrees lower in temperature in the latter than in the former4 ,for warming walls as well as the air high pressure steam pipes are more efficient than hot-water pipes4 ,the great advantages of radiant heat are that--7#a7 it heats the body without appreciably heating the air2 while at the same time 7#b7 there is no possibility of impure gases being added to the air4 ,it has1 however1 considerable disadvantages4 7#a7 ,it is costly1 though its expense may be greatly diminished by a well-constructed fire-place4 7#b7 ,it only acts on bodies near it to any useful extent4 ,its effect lessens as the square of the distance2 thus1 its warming effect at five feet distance1 is twenty-five times less than at a distance of one foot4 ,it is evident1 therefore1 that for long rooms1 and for large assembly-rooms1 a single source of radiant heat is quite inadequate4 ,the immense loss of heat in our ordinary fire-places is slowly leading to their modification2 and although it is probable that radiant heat will always be the favourite source of warmth in dwelling-houses1 it will be used for larger buildings chiefly as an adjunct to convection of heat4 ,the different sources of heat are employed1 either singly or combined1 in the following methods of warming our dwellings and other buildings3-- #a4 ,warming by the open grate4 #b4 ,warming by closed stoves4 #c4 ,warming by hot-water pipes4 #d4 ,warming by steam in pipes4 #e4 ,warming by hot air4 #f4 ,warming by electricity4 ,warming by the open ,grate4--,in the open fire-place radiation is the source of heat chiefly employed4 ,the position of the fire-place is important4 ,it should not be on the external wall of the house1 as thus a large proportion of heat is lost2 but should be placed where the heat from the flue may be utilised in keeping up the temperature of the house4 ,the construction of a fire-place is commonly faulty in several respects4 7#a7 ,the fire-place may be too far included in the wall1 so that the heat at once passes up the chimney4 7#b7 ,it may be composed chiefly of iron1 which rapidly conducts away the heat1 and does not furnish a surface for radiation4 7#c7 ,the bars and bottom of the grate may be so arranged1 that coal and cinders fall out in an incompletely burnt condition4 ,it has been estimated that with an ordinary fire-place1 seven-eighths of the possible heat is lost1 one-half being carried up the chimney with the smoke1 one-quarter carried off in the ascending current of warm air1 and one-eighth of the combustible matter remaining unconsumed1 forming the solid matter of the smoke4 ,the defects which have been indicated may be remedied by bringing the fire-place rather further out into the room2 by substituting fire-brick for iron behind and at the sides of the fire1 and by having a layer of fire-brick at the bottom of the grate1 or the grate lowered1 so that as in ,teale's stove1 it lies on a bed of fire-brick at or below the floor level4 ,the shape of the grate is important4 ,the width of the back of the grate should be about one-third that of the front1 the sides sloping out towards the front of the recess4 ,the depth of the grate from before backwards should be equal to the width of the back4 ,the sides and back of the fire-place must be made of fire-brick1 thus ensuring the heat being retained in the grate4 ,and finally1 the chimney throat must be contracted so as to ensure more complete combustion4 ,the chief objections to an open fire-place are 7#a7 the great waste of fuel involved1 even after the improvements indicated have been carried out4 7#b7 ,the unequal heating at different distances from the fire4 7#c7 ,the smoke and dust always produced to some extent1 from accidental smoking of the fire1 or from the escape of ashes4 7#d7 ,the trouble involved in frequently replenishing the fire4 7#e7 ,the cold draughts produced by the currents of air towards the chimney4 ,these travel chiefly along the floor1 when1 as is commonly the case1 the space between the bottom of the door and the floor forms the chief place for the entry of fresh air4 ,many patents have been brought out for the introduction of the fuel at the lowest part of the fire4 ,the uppermost part of the fuel being first burnt1 and the remainder attacked from above1 the smoke is consumed in passing through the red part of the fire4 ,thus a comparatively smokeless fire is produced1 and the amount of heat evolved is greatly increased4 ,so far none of these have been altogether satisfactory4 ,the production of a comparatively smokeless fire is a great boon4 ,smoke means so much unburnt fuel1 and not only so but the sooty particles float about in the atmosphere1 rendering it impure1 and changing comparatively harmless mists into town fogs1 which are loaded with soot and the products of combustion1 and do incalculable mischief to health and property4 ,the prevention of this smoke nuisance demands more consideration than it has yet received4 ,the ,public ,health ,acts constitute the emission of black smoke from the chimneys of manufacturing premises a nuisance2 and manufacturers can if they use proper boilers1 especially those in which mechanical stokers are employed1 almost completely obviate this nuisance4 ,the great principle is to prevent the escape of smoke before it is completely burnt4 ,this may be accomplished by careful stoking1 by keeping the unburnt coal at the front of the fire1 and by ridges exposing the smoke to red-hot fire-clay before it escapes4 ,in domestic fires1 gas is gradually replacing coal for cooking1 with a corresponding reduction of the smoke-nuisance4 ,the ,utilization of the ,heat ,produced in the fire-place to warm the air on its way into the room1 as in ,galton's and other similar stoves has been already described 7page #aef74 ,a larger amount of heat can be obtained out of a given quantity of fuel by cutting off some of the cold air1 which rushes through the fire1 and carries the half-burnt gases and much of the heat up the chimney4 ,this is effected by having a solid fire-brick bottom to the grate1 or by closing up the front of the open chamber under the grate1 by means of a close-fitting shield or door4 ,these 8,economisers10 as ,mr4 ,teale calls them1 appear to answer better than solid fire-brick bottoms1 as they do not prevent the ashes falling under the grate4 ,the ,fuel burnt in an open fire-place may be either coal or coal-gas4 ,occasionally coke is also employed4 ,coke and coal-gas have the advantage over coal1 that 7#a7 no smoke is produced4 ,coal-gas presents the additional advantages1 that 7#b7 it can be turned on at any moment1 without having to go through a tedious process of lighting the fire2 and that 7#c7 the amount of heat can be exactly graduated by regulating the supply of gas4 ,a gas fire is however1 as a rule1 more expensive than a coal fire4 ,open ,gas-stoves are made in various forms4 ,in the common one1 small jets of gas are lit under the grate1 which is filled with pieces of asbestos4 ,these become red hot1 and radiant heat is emitted4 ,to obtain the greatest value from the heat generated by the combustion of gas1 a stove should be chosen in which the heat generated is brought into contact with a large surface of the grate before the products of combustion are allowed to escape to the flue4 ,gas stoves which are advertised as not needing a flue1 should be avoided4 ,a large amount of carbonic acid is discharged by them into the room1 and the sulphurous acid also produced by the combustion of gas is not completely absorbed in the water of condensation which collects in a tray under such stoves4 ,closed ,stoves form the most economical and efficient warmers for rooms of moderate size1 and coal1 coke1 coal-gas or paraffin may be burnt in them4 ,the advantages rightly claimed for coal stoves of this type are that 7#a7 the amount of fuel consumed is small2 7#b7 by adjusting the damper1 combustion may be rendered as slow as desired1 so that but little heat is lost by the flue or chimney2 and 7#c7 heat radiates from all parts of the stove into the room1 and not simply from a small area of fire-front4 ,the chief objections to closed stoves are1 that 7#a7 they dry the air excessively1 rendering it somewhat unpleasant4 7#b7 ,they produce a peculiar close smell1 apparently caused by the charring of minute particles of organic matter in the air1 coming in contact with the stove4 ,if the air of the room is not heated above #ge ,fahr41 no smell is produced1 and the relative humidity is not lessened to any appreciable extent 7,parkes74 ,but when the heat produced by the stove is excessive1 these results do follow4 ,the unpleasantness may be modified though not entirely removed1 by placing shallow pans of water near the stove4 7#c7 ,portions of the products of combustion may pass through cracks or fissures in the stove1 or even through the joints of the stove4 ,independently of such accidental cracks1 cast-iron stoves1 when red hot1 appear to allow gases to pass through them with comparative ease4 ,thus carbonic oxide and other gases may find their way into the room1 and it is probable that this rather than the dryness of the air1 is the cause of the unpleasant symptoms sometimes complained of in rooms where closed stoves are in use4 ,this escape of carbonic oxide does not occur with earthenware stoves properly encased with fire-clay4 ,many modifications of the older closed stoves are now in common use4 ,in the stove shown in ,fig4 #ah1 excessive heating of the air is prevented by the presence of two air chambers1 only the outer one1 which brings external air to be warmed1 having its air emptied into the room4 ,illustration3 ,,fig4 #ah4 ,,slow ,,combustion ,,stove4 ,warming by open grates or closed stoves is specially applicable to the rooms of private houses2 warming by hot air or steam1 or hot water1 is chiefly used for large buildings4 ,it is quite possible that these methods will be applied at some future time on a large scale to the warming of private houses4 ,in some large towns of the ,united ,states this has been already done1 blocks of a hundred or more houses being warmed from the same centre1 by the same system4 ,but apart from such a central system1 hot air and hot water lend themselves to the heating of houses on what may be called the ,whole ,house ,system 7page #aef74 ,we have mentioned in the last chapter some methods of doing this1 and shall now describe others4 ,hot-water ,pipes are probably the best means of carrying heat to various parts of a large house1 and hot water is more thoroughly under control and less dangerous than either hot air or steam4 ,there are two systems of heating by hot water4 ,in the first1 which we may call the low pressure system1 there is a boiler from which water circulates through pipes to every part of the building1 and as it cools down returns again to the boiler4 ,at the highest points of the pipes1 outlets are provided for air4 ,in this system the water is not heated above #bjj ,fahr41 and there is consequently no great pressure on the pipes4 ,in the high pressure system 7,perkin's patent71 the pipes have an internal diameter of about #ab an inch1 and have thick walls made of two pieces of welded iron4 ,there is no boiler1 but one portion of the tube passes through the fire and the water is heated to #cjj-cej ,fahr41 thus subjecting the pipes to great pressure4 ,in dwelling-houses with the low pressure system1 for every #a1jjj cubic feet of space to be warmed to #ej1 #ab feet of #d-;inch pipe should be given2 with ,perkin's pipes1 probably about two-thirds of this will suffice4 ,steam ,distributed by ,pipes may be employed instead of hot water4 ,this method has been used in factories in which there is a surplus supply of steam4 ,warming by ,hot ,air is only applicable on a large scale1 and should only be used in association with a system of ventilation by propulsion 7page #aec71 in which the temperature1 humidity1 and freedom from dust of the entering air are carefully regulated4 ,warming by ,electricity both for cooking food and for warming rooms has a large future1 but in most districts the supply of electricity is not hitherto sufficiently cheap to be used for these purposes4 ,by its means the atmosphere will be prevented from becoming impure1 labour will be reduced1 and life rendered more pleasant4 ,hot ,water ,supplies4--,nearly every modern house is supplied with a bathroom1 and this may be supplied with hot water either from a geyser or from the kitchen boiler4 ,in a geyser the water is made to flow over a large heating surface furnished by burning coal-gas1 and with the best varieties a bath of #ih ,f4 can be supplied in from five to ten minutes4 ,as the bathroom is usually small and unprovided with an open fire-place1 persons have occasionally been suffocated by remaining in such a room while the gas continues burning4 ,this is due to the production and in-breathing of carbonic oxide4 ,no geyser ought to be allowed to be used which is unprovided with a flue passing into the chimney flue or in its absence through an external wall of the house4 ,short of fatal poisoning1 violent headaches often occur when a warm bath obtained by means of a geyser is taken1 unless such a flue is provided4 ,in ,ewart's lightning geyser1 additional protection is furnished by the fact that a dual valve is so arranged1 that immediately the water is turned off or the supply fails from any cause1 the supply of gas is also cut off4 ,hot water supplies from kitchen boilers1 unless carefully arranged1 may be responsible for serious explosions during severe frosts4 ,four plans are in common use4 7#a7 ,the worm-boiler system4 ,this system is unsafe unless the supply of water to the boiler is attended to2 and as the hot water supply to the kitchen is drawn from the boiler itself and not from the worm1 the hot water supply for the rest of the house may be deficient4 ,usually the small feed cistern for the boiler in this system is too near the boiler to freeze4 7#b7 ,the cylinder system is very effective4 ,in this system a metallic cylinder1 capable of withstanding a pressure of #bj lbs4 to the square inch1 is placed in the kitchen or bathroom between the cold and hot supplies1 its contained water being heated by circulation from the boiler1 hot water ascending and cold descending4 ,on the top floor of a house is a cistern from which cold water is supplied4 ,both the supply pipe and escape pipe for hot water may become frozen during frost4 ,then the supply of water is stopped1 and the boiler and reservoir may boil dry4 ,this would not occur without some indication in unusually vigorous boiling4 ,boilers sometimes explode1 and cylinders sometimes explode4 ,this can be effectually prevented by 7#c7 ,a ,double-cylinder apparatus one within another4 ,in this the water in the outer cylinder supplied from the main cistern can only be heated to #bab ,f41 and the water in the boiler and inner cylinder supplied from a lower feed cistern can only be heated to #bad ,f41 on account of the small head of water4 ,two escape pipes give free communication with the atmosphere4 7#d7 ,in the tank system1 which being cheap1 is usually adopted in poor houses1 the tank is placed high up in the system4 ,the hot water branch pipes are usually taken from the flow-pipe between the boiler and tank4 ,hence when the supply fails1 as during frost1 the tank is drained empty1 the circulation of water ceases1 and the system is changed from a circulation system to a high-pressure one4 ,safety valves cannot always be relied on to prevent explosions4 ,if they lead to the lighting of fires in frosty weather1 when pipes are frozen1 they may cause explosions4 ,explosions from frost only occur when both pipes are blocked4 ,incrustation of the boiler and pipes increases the danger of explosions2 hence the necessity for their periodical cleaning4 ,illustration3 ,cylinder and ,tank systems ,,chapter ,,xxv4 ,,house ,,drainage4 ,the ,removal of ,impurities4--,in order that health may be maintained in any inhabited house1 it is essential that the impurities produced by animal life should be removed4 ,these impurities may be divided into two classes--the first including the gaseous and volatile products evolved from the lungs and skin2 and the second1 the liquid excretion from the kidneys1 and the solid from the bowels4 ,the former are got rid of by efficient ventilation and by cleanliness2 the latter1 ought to be as quickly removed1 but require more elaborate arrangements to ensure this4 ,the average daily amount of solid excreta is about #d ounces1 and of fluid excreta about #ej ounces for each adult male4 ,taking all ages and both sexes into consideration1 the amount per head is about #b-cd ounces of fces and #cb ounces of urine4 ,when dried1 the daily fces amount to #ajd oz41 the daily urine to #agd oz41 so that the manurial value as well as the possible polluting power of urine is much greater than that of the fces4 ,after a variable interval urine and fces begin to decompose1 ammonia and ftid gases being disengaged in large quantities4 ,urea the chief constituent of urine is decomposed into carbonic acid and carbonate of ammonia4 ,thus ,,ch,n,o #b;,h,o 7,,nh7,,co ,in addition to the excreta1 house-slops have to be got rid of1 and 8dust40 ,house-slops vary greatly in quantity1 but probably amount to as much as sixteen gallons per head daily4 ,they consist chiefly of the water used in cooking and washing and for baths4 ,it would be a mistake to suppose that only urine and fces need careful disposal4 ,there are masses of decaying epithelium from lavatories and baths1 organic matters from soiled apparel1 and various organic matters from culinary operations1 all of which may cause serious nuisance unless promptly disposed of4 ,the ,dust consists chiefly of the ashes from fires2 but the dust-bin also forms a favourite refuge for kitchen refuse1 composed of various animal and vegetable matters1 as well as for broken pots and tins4 ,it is dealt with apart from the house-slops and excreta1 except in certain dry methods of disposal of sewage4 ,two chief plans of getting rid of the sewage have been proposed1 though there are many varieties of these4 ,they are-- #a4 ,the ,water ,method1 and #b4 ,the ,dry ,methods4 ,for towns the water carriage of sewage is indispensable1 and in this chapter we shall confine ourselves to the part of this system which relates to the ,drainage of the ,house4 ,the chief sanitary appliances of a house1 which empty their contents into the drain and thence into the street sewer1 are--7#a7 ,rain-water ,pipes2 7#b7 ,bath-room and ,sink-pipes2 7#c7 ,water-closets2 7#d7 ,soil-pipes2 and 7#e7 ,the ,house ,drain4 ,we will consider these in detail4 ,rain-water ,pipes collect the water from the roof by means of gutters1 and carry it down to the house drain1 except in the few cases in which the rain-water is collected for use4 ,the rain-water or stack pipe was formerly joined directly at its base with the underground drain4 ,this was evidently bad1 because the upper end of the pipe was frequently near windows1 and foul gases from the drain might be conducted by it into the house4 ,it is equally objectionable to connect the rain-water pipe with the soil pipe and for the same reasons as above4 ,the general rule with regard to all pipes carrying away water from the house1 with the sole exception of the soil-pipe1 is that they must be disconnected from the underground drain and discharge into the open air over a gulley-trap4 ,this rule applies to rain-water pipes1 and to waste pipes from baths1 lavatories1 sinks4 ,it does not apply to the soil-pipes leading from water-closets and slop-sinks1 which must discharge directly into the drain4 ,overflow or waste-pipes from cisterns for drinking water or from cisterns for flushing w4c4's or to safe trays under the seat of water-closets should all be made to discharge into the open air1 where the leakage can at once be discovered4 ,the form of gully-trap to be used at the junction with the drain is described on page #afg4 ,other ,waste-pipes as from bath1 lavatories1 and sinks1 must be similarly disconnected from the drain1 and made to discharge over gully-traps4 ,when the pipe leading from the bath1 lavatory basin1 or sink1 is long1 it is apt to become foul from the accumulation on its inner surface of slimy matter1 consisting of soap1 dirt1 and other offensive matter4 ,for this reason it is wise to have a syphon bend in the waste-pipe near its junction with the sink or basin4 ,such a trap is shown in ,fig4 #ai4 ,the syphon bend alone in the waste-pipe without disconnection from the drain at its lower end would not suffice to ensure complete absence of nuisance1 especially for sinks and lavatories which may be disused for a considerable period4 ,under these circumstances the water in the syphon trap may become evaporated1 and then foul drain gases be wafted into the house4 ,furthermore1 even if the water in the syphon trap remained1 foul gases may be absorbed from the drain and given out at the end nearest the house 7a1 ,fig #ai74 ,hence it is always best to disconnect all waste-pipes from the drain1 except the soil-pipe which cannot be treated in this way4 ,the waste-pipe from the upstairs lavatory or bath may be made to discharge over a hopper-head and thence into the rain-water pipe1 which is disconnected below from the drain4 ,this plan should only be adopted when the hopper-head is not close to a bedroom window4 ,illustration3 ,,fig4 #ai4 ,,syphon ,,trap ,,under ,,sink1 ,,with ,,screw-,,opening ,,for ,,cleansing4 ,under the bath is usually placed a leaden tray1 called a safe1 to catch any accidental spillings of water4 ,the overflow pipe from this safe should discharge direct into the open air4 ,formerly much evil was caused by allowing waste-pipes from baths1 sinks1 and lavatory-pipes1 or overflow pipes from drinking-water cisterns or from the bath-safe1 to be connected directly either with the trap of the w4c41 or with the soil-pipe beyond it4 ,illustration3 ,,fig4 #bj4 ,a4 ,,stoneware ,,gully-,,trap4 ,b4 ,,section ,,of ,,the ,,same1 ,,showing ,a ,,water-,,seal #c ,,inches ,,in ,,depth4 ,sinks are not uncommonly the source of offensive smells1 when made of wood or stone4 ,a hard glazed sink should be provided2 as this is non-porous and can be kept clean4 ,the sink should be placed against an external wall1 so that the waste pipe can be carried through the wall to a gully-trap outside the house4 ,formerly the sink-pipe was joined below directly into the drain1 the only obstacle to the entry of sewer or drain gases into the kitchen being a bell-trap at the sink4 ,this is quite insufficient for the purpose4 ,the waste-pipe from the sink should have a syphon trap under it1 with an inspection opening at its lowest point 7,fig4 #ai71 and should discharge in the open air over a gully-trap 7,fig4 #bj71 as in the case of rain-water and bath-waste pipes4 ,it is usually stated that the waste-pipes from sinks1 etc41 should discharge at least #ah inches distant from the grating of the gully4 ,this is too far1 because some of the foul water may become dried up in the channel1 and its solid particles be blown about4 ,they may be allowed to discharge directly over the grating of the gully 7,fig4 #bj7 or even into the side of the gully below the grating1 but above and on the house side of the water-seal shown at ,b4 ,fig4 #bj4 ,the gully-trap is connected with the socket of the first drain-pipe1 and the junction is made water-tight by means of a cement joint4 ,on this account1 and because it gives a better water-seal than the bell-trap or ,d trap1 the gully-trap should be always used4 ,the best form of gully-trap1 the ,p trap1 is shown in ,fig4 #bj ,b4 ,this is better than the ,s trap 7,fig #ai71 which involves a bend in the drain at its junction with the trap4 ,water-closets require to be skilfully constructed and well-situated1 if they are not to become a serious nuisance4 ,in building a house1 the position of the closet should be carefully considered4 ,in all cases it should be in an out-standing part of the house1 against an external wall1 and separated from other parts of the house by a passage1 preferably a passage which is cross-ventilated4 ,instead of this1 one commonly finds it in any convenient recess1 abutting on a bedroom1 or where it cannot be properly ventilated4 ,usually the closet is placed at the back of the house2 and as the main-sewer is generally situated in the front street1 it follows that the drain must in terrace houses pass under the house4 ,hence the importance of having it completely water-tight4 ,water-closets in bathrooms are very inadvisable4 ,the ventilation of the closet should be good--if possible1 by two opposite windows2 and where practicable a cross-ventilated lobby should intervene between the closet and the rest of the house4 ,this is now always provided in hospitals4 ,the water-supply to the closet should be abundant4 ,every flush of water should be sufficient to carry the contents of the basin through the soil-pipe and the drain into the sewer4 ,the quantity allowed by the ,water ,companies in ,london is two gallons1 which is barely sufficient for this purpose1 unless the form of closet pan is good1 and the down-pipe to it of sufficient diameter4 ,each closet should have a separate cistern1 the best being the so-called 8water-waste preventer10 by means of which a certain quantity of water1 and no more1 can be discharged each time the handle is pulled4 ,one of the best of these is shown in ,fig #ba4 ,when the handle of this is pulled1 the whole of the water in the cistern is syphoned out by the syphon and carried down to the water-closet1 whether the handle be held down or not4 ,the amount of fall from the cistern to the closet should not be less than four feet1 and the pipe should be free from bends in order to ensure a thorough scouring of the trap and soil-pipe2 and the flushing-pipe should have an internal diameter of not less than #a inches4 ,it is commonly supposed that a small flow of water1 trickling continuously down a closet1 tends to keep it clean1 and prevent smells2 but the water thus used is simply wasted4 ,others fasten up the handle of valve-closets so as to allow a large flow of water4 ,this does not answer the desired end1 and renders the offending person liable to a penalty for wasting water4 ,many different forms of water-closet are in use4 ,in all of them the main requisites are that there should be 7#a7 a good flush of water1 7#b7 a rapid removal of the excreta1 and 7#c7 no possibility of reflux of gases4 ,the chief varieties of closets are the pan1 valve1 wash-out1 and wash-down closets4 ,illustration3 ,,fig4 #ba4 ,,syphon ,,flushing ,,cistern4 ,in ,fig4 #ba a portion of the bell of the syphon is shown cut out1 so as to display the movable plug at the bottom of the cistern4 ,an objectionable feature in most cisterns is their noisiness in use4 ,in the above cistern1 the pipe admitting water is carried down to within an inch of the bottom of the cistern1 thus ensuring noiseless entry of water4 ,pan-closets 7sometimes called double-pan closets7 are essentially bad1 though largely employed in the past4 ,the construction is shown in ,fig #bb4 ,below the conical basin there is a metal pan capable of holding a certain amount of water1 the lower end of the basin dipping into this water4 ,by means of a pull-up apparatus the contents of the pan can be tilted into a second larger pan or container1 and the bottom of the container is connected by means of a short pipe with a leaden bowl-shaped symbol shaped trap1 from the side of which the soil-pipe passes out to be carried down to the drain4 ,the arrangement insures the production of nuisance4 ,the container and bowl-shaped symbol trap always arrest a certain amount of foul matter2 and each time the handle of the closet is pulled up a puff of foul air comes into the operator's face4 ,occasionally the bowl-shaped symbol trap becomes corroded by the filth it contains1 and foul gases from the drain escape into the house4 ,illustration3 ,,fig4 #bb4 ,,insanitary ,,pan ,,closet1 ,,showing ,d ,,trap ,,below4 ,valve ,closets differ from the last in having no container1 but only a small box containing a movable water-tight valve1 exactly fitting the lower edge of the basin 7,fig4 #bc74 ,they are much superior to the pan-closet1 but require an overflow pipe in order to avoid accidental flooding of the closet4 ,the overflow pipe should be made with a syphon bend in it1 and the flushing of the closet should be so arranged that each time it is performed water enters the overflow pipe4 7,see ,fig4 #bc47 ,the trap below the valve should be in the form of a syphon 7see under traps1 page #agi71 as this is not easily fouled4 ,it is preferably made of lead1 securely jointed to the soil-pipe and to the valve box of the closet4 ,a lead tray or 8safe0 is required on the floor beneath a valve closet1 in view of accidental spillings or overflow2 and this should be provided with an overflow pipe discharging into the open air4 ,illustration3 ,,fig4 #bc4 ,,valve ,,closet4 ,a--,pan4 ,b--,overflow pipe with syphon trap4 ,c--,valve shut4 ,c--,valve open4 ,d--,valve box4 ,e--,floorline4 ,f--,water-seal of trap4 ,valveless or ,hopper ,closets1 of which the ,wash-out1 ,wash-down and ,syphonic ,closets1 are the chief forms1 present certain advantages over the valve closet4 ,there is less apparatus to get out of order and no metal to become foul4 ,they do not require an overflow pipe1 as water can escape freely through the trap of the closet4 ,valveless closets need not be encased by wood-work1 thus ensuring freedom from spillings of foul water1 and they are more easily used than valve closets for the discharge of bedroom slops1 thus obviating the necessity for a special housemaid's sink4 ,valveless or hopper closets are cheaper and simpler in use than valve closets1 and when in use are equally sanitary4 ,if a house is left empty for a considerable time1 the water in the trap may1 however1 become evaporated1 an event much less likely to occur with a valve-closet4 ,the latter are furthermore less noisy when flushed4 ,with a valve to hold up the water in the pan1 as in the valve-closet1 a much larger quantity of water can be retained than with a hopper closet4 ,hence the importance of the latter having such a shape as shall prevent fouling of the basin by fces4 ,one of the older hopper closets was the long hopper shewn in ,fig4 #be4 ,in this form the pan is conical in shape1 its sides necessarily becoming fouled by its use1 and the spiral flush1 the point of entry of which is shewn in the figure is quite insufficient for cleansing the pan4 ,of ,short hoppers the best has a nearly vertical back as shewn in ,fig4 #bd1 a rim-flush1 by means of which at least two gallons of water are discharged with the fces1 and the pan is thoroughly cleansed4 ,illustration3 ,,fig4 #bd4 ,,rim ,,flushing ,,wash-,,down ,,basin4 ,the wash-out closet is shewn in ,fig4 #bf4 ,in it a certain amount of water is kept in the upper part of the pan by a ridge over which the fces have to be driven before entering the trap4 ,the force of the flush is thus broken4 ,in this closet a large area is liable to be fouled1 and it is now almost entirely disused4 ,illustration3 ,,fig4 #be4 ,,short ,,hopper ,,closet4 ,,long ,,hopper ,,closet ,,with ,,spiral ,,flush4 ,syphonic water-closets are wash-down closets1 in which the flushing out is aided by syphonic action4 ,they need to be fitted with a flushing cistern1 giving an after-flush as well as a flush2 otherwise the basin is left untrapped4 ,one of the most elaborate closets of this type is ,jennings' ,closet of the ,century4 ,fig4 #bg shows that the flushing cistern has two connections with the closet1 one in the usual manner with the flushing rim of the pan1 the other connected to the long arm of the syphon 7,a ,fig4 #bg74 ,b is a puff pipe allowing the escape of air from this syphon when started4 ,thus while one part of the flush scours the basin1 the other expels the air from ,a through the puff-pipe ,b1 fills both arms of the syphon with water1 and thus starts the syphonic action by which all the contents of the basin are sucked out of it4 ,in this form of w4c41 syphonage is intended to be produced1 and the after-flush prevents the w4c4 from being left untrapped4 ,illustration3 ,,fig4 #bf4 ,,wash-,,out ,,closet4 ,illustration3 ,,fig4 #bg4 ,,syphonic ,,closet4 ,syphonic water-closets appear to me to be unnecessarily elaborate and complicated1 and the only advantage over the wash-down closet is the deeper layer of water in the basin4 ,with a well-shaped wash-down closet this is of little importance4 ,in other forms of wash-down w4c41 unsyphoning may also occur1 for instance1 by pouring the contents of a slop-pail into the pan4 ,this is particularly apt to occur1 when two or three water-closets are on different floors of a house1 one over another4 ,this unsyphoning is prevented in the case of the highest w4c4 by the soil-pipe ventilator1 but not always for the lower w4c4's4 ,for these it may be necessary to carry a pipe from the highest point of the trap of the closet1 where it joins the soil-pipe1 through the wall into the external air4 ,such a pipe is called an anti-syphonage pipe 7,fig4 #bh74 ,it effectually prevents the water being sucked out of the trap of a lower w4c4 when the w4c4 on a higher floor is being flushed4 ,illustration3 ,,fig4 #bh4 ,a--,elevation4 ,b--,section through wall of house1 showing connection of w4c4's on three floors1 with soil-pipe and anti-syphonage pipe4 b--,junction of closet trap with soil-pipe1 a being a ,p and b an ,s trap4 c--,junction of soil-pipe with earthenware drain4 d--,anti-syphonage pipe1 seen best in elevation ,a4 e--,soil-pipe4 f--,anti-syphonage pipe4 g--,underground drain4 h--,soil-pipe ventilator4 i--,cage-work protecting top of h4 j--,point at which anti-syphonage pipe is connected with soil-pipe ventilator1 above the highest w4c4 ,in the forms of w4c4 already described1 clean water is used for flushing1 and we have seen that two gallons1 the quantity usually allowed1 does not suffice for this purpose1 unless the closet pan is of the best possible shape1 and the service pipe sufficiently wide to project the water by means of a rim-flush forcibly over the pan and into and beyond its trap4 ,other forms of w4c4 have been employed of which the most important are slop-water closets1 and trough-closets4 ,in ,slop-,water ,closets the waste water from sinks and baths is utilised for flushing1 and thus a saving of water is effected4 ,this form of closet is used considerably in manufacturing districts1 and is less liable to freeze than an ordinary w4c4 ,the sink discharges on to a gully in the usual manner1 but the outlet of this gully is connected with a tilting vessel or tipper1 holding #c gallons in ,duckett's closet1 which is the best known of this type4 ,the tipper is balanced on brass bearings1 and tips over when full1 discharging its contents into the closet trap1 which is thus flushed4 ,the slop-closet is a great improvement on the privy-middens or pail-closets1 which in some towns it has superseded1 but is not so cleanly as an ordinary w4c4 ,trough ,closets are also known as 8latrines40 ,the best type consists of a glazed earthenware trough under a series of w4c4 seats4 ,the trough is slightly inclined towards the outlet1 at which is a weir1 beyond which is a trap4 ,an automatic flushing tank connected with the upper end of the trough and five to six feet above it1 discharges water at intervals and drives the fcal matter over the weir and through the trap4 ,this form of closet is only suitable for factories4 ,it is to be deprecated for schools1 and even for factories1 unless there are exceptional reasons for its continuance1 as fcal matter possibly of an infectious character may be retained a considerable time in the trough4 ,the domestic ,slop ,closet or 8housemaid's sink0 must not be confused with slop-water closets mentioned above4 ,the slop-closet or sink is used for emptying the contents of bedroom pails4 ,these being necessarily foul and liable to early putrefaction must be treated exactly like other sewage matters4 ,an ordinary pedestal w4c4 with a lift-up seat answers excellently as a slop-closet2 but in large houses and public establishments a separate slop-sink is desirable with a larger surface than most water-closets4 ,the slop-closet must be connected with the soil-pipe1 just in the same way as a w4c4 ,illustration3 ,,fig4 #bi--,,section ,,through ,a ,,house ,,from ,,front ,,to ,,back ,,shewing ,,drainage ,,arrangements4 ,a4--,sewer2 ,b4--,intercepting trap2 ,c4--,cleaning eye for pipes between chamber and sewer2 ,d4--,inspection chamber2 ,e4--,inlet ventilator2 ,f4--,gully-trap for forecourt2 ,g4--,air-bricks for ventilation under floors2 ,h4--,damp-proof course#h2 ,i4--,concrete #f0 thick over site of house2 ,j4--,drain1 fall #a in #bd1 imbedded in concrete2 ,k4--,soil-pipe carried up full size above eaves2 ,l4--,upstairs w4c42 ,m4--,gully-trap receiving water from ,n scullery-sink1 ,o bath and ,p rain-water stack-pipe2 ,s4--,ventilating pipe at upper end of drain2 ,t4--,pipes leading to same4 ,the soil pipe is the vertical pipe carrying the contents of the water-closets in the drain4 ,it must be distinguished from the drain1 which is chiefly1 if not entirely1 underground4 ,the exact position of the soil-pipe and its relation to the drain can be seen in ,fig4 #bh and #bi1 which should be carefully studied4 ,the soil-pipe should be made of drawn lead without seam1 of uniform thickness throughout1 and of at least #g lbs4 or better #h lbs4 weight per superficial foot4 ,any joints in the lead pipe should be of the kind known as 8wiped10 not a 8slip0 joint4 ,the outside of a wiped joint is shewn in ,fig4 #cj;,b4 ,iron pipes if used must be #caf inch thick1 and have sockets sufficiently wide and strong to permit of the joints being caulked with molten i4e4 8blue0 lead1 in the same way as water-mains are laid4 ,the soil-pipe should be throughout its course under observation4 ,it should not be built into a wall1 where it might be accidentally pierced by nails1 nor within the house1 allowing foul gases to escape from weak points in the joints4 ,it should be carried through the wall of the house immediately beyond the closet trap4 ,the soil-pipe should not be more than four inches in diameter4 ,it should be continued from its highest point at the junction with the closet-trap above the roof by a pipe of the same diameter1 with its end wide open 7,fig4 #bi ,k74 ,this ventilation of the soil-pipe is essential 7a7 to prevent the entry of foul effluvia into the house1 especially when the water in the closet-trap is dried up2 7b7 to prevent unsyphoning of the upper by the lower water-closets in a house4 7,on this point see p4 #agb74 ,illustration3 ,,fig4 #cj4 ,a4--,,section ,,showing ,a ,,good ,,method ,,of ,,connecting ,,soil-,,pipe ,,to ,,drain ,,by ,,brass ,,thimble4 ,b4--,,outer ,,view1 ,,showing ,,brass ,,thimble ,,wiped ,,on ,,to ,,soil ,,pipe4 ,the upper end of the ventilating pipe should be made to open remote from any window4 ,it may have a cowl attached to it1 but it is doubtful if this materially aids the aspiration of foul gases4 ,it is wise to cap the upper end of the ventilating shaft with a dome of large meshed wire-netting to prevent birds building their nests in it4 ,the connection of the soil-pipe with the closet-pan is its weakest point1 and the most liable to leak4 ,the main difficulty consists in forming joints between earthenware and metal4 ,socketed connections are not safe4 ,the use of an india-rubber ring inserted between the lead and earthenware flanges and bolted together by means of a brass collar and hooked bolts makes a fairly good connection4 ,various screwed connections are made4 ,in another form the earthenware collar is covered outside with lead1 so that a soldered joint can be made between the earthenware trap and the soil-pipe4 ,in the 8metallo-keramic joint0 the earthenware joint is painted over with a metallic solution and fired4 ,to the metal film thus formed1 lead or other metal can be firmly soldered4 ,the connection of the soil-pipe into the socket of the first pipe of the earthenware drain requires also to be carefully made4 ,this pipe is curved1 and at its upper end has a socket1 into which the soil-pipe enters4 ,a length of brass or copper tubing known as a 8thimble0 7about a foot long7 should be soldered to the bottom of the soil-pipe2 the rim of this thimble rests in the socket of the drain-pipe and the space between the two is filled with ,portland cement 7,fig4 #cj;,a74 ,with the ordinary connection between lead soil-pipe and drain1 the former is apt to become dented by blows1 and the latter is very liable to be partially blocked by the dropping of cement inside the pipe when making the joint4 ,the ,house ,drain under ordinary circumstances receives waste water from sinks and baths1 rain-water1 and the discharge from the closets4 ,illustration3 ,,fig4 #ca4 ,,showing ,,depth ,,of ,,fluid ,,and ,,consequent ,,flushing ,,force ,,of ,,three ,,drains ,,containing ,,an ,,equal ,,quantity ,,of ,,sewage4 ,we may consider drains under the following heads3 material1 form1 joints1 gradient1 ventilation1 trapping4 ,the first essential is that they should be water-tight1 so that their contents do not percolate into the surrounding soil4 ,socketed glazed stoneware pipes and iron pipes best fulfil this condition4 ,the best material for making stoneware pipes is ,devon or ,dorset1 or similar fine clay1 which makes a very strong pipe4 ,tested pipes free from cracks and flaws must alone be used4 ,the pipes should be laid in straight lines1 each pipe being arranged with the spigot and not the socket end directed towards the flow of sewage4 ,the fall should not be less than #a foot in from #dj to #fj4 ,if the fall is less than this amount1 artificial flushing from the upper end of the drain is necessary4 ,usually branch drains are made #d inches in diameter1 the main house-drain having a diameter of #f inches4 ,a larger size than this is seldom necessary4 ,thus if ,a1 ,b1 and ,c be three drains with an equal fall and conveying an equal amount of sewage1 the rate of travel and therefore the flushing force will be greater1 because the depth of the fluid is greater1 in ,a than in ,b1 and in ,b than in ,c4 ,small drains are more completely self-cleansing than large drains4 ,the water-tightness depends on the character of the joints4 ,in this respect iron drains present the great advantage over earthenware that there are fewer joints and that these can be rendered permanently water-tight without difficulty by being run with blue lead and well caulked4 ,to render an earthenware drain water-tight1 7a7 it must be laid on a solid bed of cement concrete at least #f inches thick1 so as to prevent sinking1 and under the house it should be covered with an equal thickness of cement concrete 7,i1 ,fig4 #bi74 7b7 ,the joints must be made with extreme care1 the best ,portland cement being used for the purpose4 ,clay is inadmissible1 as the fibrils of tree-roots easily find their way through it4 ,the inside of the joint must be raked by the workmen1 before the next pipe is laid1 to make sure that no fragments of hard cement are left projecting in its interior4 ,such projections are not uncommon causes of subsequent blockage4 ,various patent joints have been used1 but they are no better than the above when properly laid4 ,just before the drain leaves the curtilage of the house and near its junction with the sewer1 it is trapped1 and on the house-side of the trap 7,e1 ,fig4 #bi7 an inlet ventilator is provided4 ,the general arrangement should be studied in ,fig4 #bi4 ,ventilation of the house drain from end to end is important1 a free escape of foul gases out-of-doors being induced4 ,the exit is provided by carrying the soil-pipe up full bore above the eaves1 and remote from windows4 ,one opening alone would not induce a current of air1 and the other end of the drain being trapped from the sewer 7,b1 ,fig4 #bi7 it is necessary to provide an inlet for fresh air at ,e4 ,this may be placed a few feet above the ground or at the ground-level4 ,usually a mica-flap valve is provided at its upper end1 which closes whenever a puff of foul air attempts to escape from the drain4 ,the necessity for this is doubtful4 ,ordinarily air enters at the inlet and circulates through the drain1 escaping at the upper end of the soil-pipe ventilator4 ,it has been advocated that the soil-pipe ventilator should form a means of ventilating the sewer as well as the house-drain1 the intercepting trap in the latter 7,b1 ,fig4 #bi7 being removed4 ,this is inexpedient1 an element of risk being introduced1 in view of the possibility of the drain or some of the connections of internal sanitary fittings being defective4 ,illustration3 ,,fig4 #cb4 ,,weaver',s ,,intercepting ,,trap4 ,the drain as ordinarily arranged is trapped from the sewer by an intercepting trap4 ,this is not merely a trap1 but a trap provided with ventilation at its end nearest the house4 ,a form commonly employed is shown in ,fig4 #cb4 ,b is the junction with the house-drain1 at ,d is the water-seal1 while at ,c fresh air enters the house-drain4 ,e is a cleaning eye1 through which any chokage can be cleared towards ,a1 leading to the public sewer4 ,it is important that the intercepting trap should be accessible in the event of accidental stopping4 ,this is provided by an inspection chamber or man-hole4 ,this if close to the house is provided with an air-tight cover1 the inlet ventilator being conveyed above ground to a convenient point4 ,the man-hole itself is built with brick set in cement and lined with cement4 ,note that in the man-hole itself half-channel pipes convey the sewage instead of complete pipes4 ,sometimes more than one drain-pipe converges to the same man-hole1 and then a more elaborate arrangement than that shown in ,fig4 #bi is required1 the branch-pipes converging into half-channel pipes in the man-hole4 ,varieties of ,traps4--,traps are placed at various points of the house-drainage system to prevent the admission of currents of foul air into the house4 ,they are all constructed so as to intercept a water-seal between the drain and the house or yard at the upper end of the trap4 ,traps are placed in four positions in connection with the drainage of a house3 7#a7 near the junction of the house-drain with the sewer2 7#b7 under the pan of each w4c42 7#c7 in the open air at the ground level to receive waste water from bath1 sink1 and lavatory basin2 and 7#d7 in the waste-pipe close under the bath1 sink1 or lavatory1 when the waste-pipe is long and apt to become foul2 7#e7 inside sinks at the upper end of their waste-pipes4 ,intercepting traps between the drain and sewer have already been described4 ,they must always be ventilated 7,c1 ,fig4 #cb and ,fig4 #bi74 ,a syphon shape with a water-seal of #c inches is required1 and the trap should be self-cleansing1 that is1 whenever the w4c4 is used1 the fces ought to be carried beyond the intercepting trap into the sewer4 ,other forms of intercepting trap were formerly used1 one of the worst of which is shown in ,fig4 #cc4 ,with such a trap as this1 an accumulation of filth is inevitable4 ,illustration3 ,,fig4 #cc4 ,,deep ,,dipstone ,,trap1 ,,with ,,accumulation ,,of ,,filth ,,in ,,it4 ,a--,drain entering trap4 ,b--,drain leaving trap4 ,c--,dipstone4 ,water-,closet and ,slop-,closet ,traps are of the syphon or anti-,d type4 ,the water-seal in these must be at least #c inches deep1 and the trap must be ventilated by an upright extension of the soil-pipe1 otherwise the water in the trap may be syphoned out when the w4c4 is used4 ,hellyer's 8anti-,d0 trap is a lead syphon trap1 the calibre of which is diminished at its bent portion1 while the portion of the trap nearest the soil-pipe or drain is square instead of circular4 ,the constriction increases the force of the flush of water and thus cleanses the whole trap1 while the square shape impedes the free flow of water1 and thus diminishes the risk of syphonage4 ,various forms of trap are shown in ,fig4 #ai to #cd4 ,the most objectionable of these is the old-fashioned ,d trap 7,fig4 #bb71 the corners and angles of which become fouled1 and consequently the lead becomes corroded4 ,illustration3 ,,fig4 #cd4 ,,bad ,,form ,,of ,,trap3 ,,bell ,,trap4 ,,bad ,,form ,,of ,,trap3 ,,antill ,,trap4 ,gully-traps are placed in the yard1 for the discharge over them of waste-pipes 7,fig4 #bj74 ,a complete disconnection from the drains is thus effected4 ,formerly bell-traps were used for this purpose4 ,in the ,bell-trap not much water can get through1 the space ,a becomes blocked with dirt1 the cover ,b is often taken off and lost1 and then the drain is untrapped2 and even without this1 the water-seal is very slight1 and the water quickly evaporates4 ,traps under sinks1 etc41 have been already described 7page #aff74 ,traps were formerly placed at the upper end of the waste-pipe of the sinks when this was directly connected with the drain4 ,of these the ,bell-trap and ,antill's trap were most common4 ,the ,bell-trap has been described above4 ,in the ,antill-trap the trap is not removable1 and the water-seal is deeper than with a bell-trap4 ,this trap is sometimes used instead of a gully-trap1 but is not so good4 ,efficiency of ,traps4--,eassie has said 8honestly speaking1 traps are dangerous articles to deal with2 they should be treated merely as auxiliaries to a good drainage system40 7#a7 ,the trap may have been imperfectly laid to begin with4 7#b7 ,it may be emptied by evaporation4 7#c7 ,unless the precautions already mentioned 7pages #agb to #agc7 are adopted1 the flushing of one trap may empty another4 7#d7 ,the water of the trap may become impregnated with foul gases1 and these then escape on the house-side of the trap4 ,when a sewer becomes suddenly charged with a large amount of water1 as during heavy rain1 sewer-gases may force their way through the intercepting trap4 ,with a ventilated drain and soil-pipe these dangers are so small that they may be ignored4 ,unsyphoning of traps has been already mentioned4 ,it occurs particularly when there are several water-closets one over another1 connected with the same soil-pipe4 ,the method of preventing it is shown in ,fig4 #bh4 ,the ,examination of ,drains and ,sanitary ,appliances4--,this examination will involve the detection of 7a7 any deviations from the details of construction and ventilation of drain and soil-pipe1 form of w4c41 disconnection of waste-pipes1 already insisted on2 and 7b7 any defect or leakage in any part of these4 #a4 ,testing of ,water-closet4--,the interior of the basin or pan may be painted with a mixture of lamp-black1 size and water4 ,if the usual flush applied immediately afterwards clears this off1 the form of pan and the flushing power are satisfactory4 ,by removing the wood-work around the w4c41 leakage or spillings of slop-water around the w4c4 can be detected4 #b4 ,testing of the soil-pipe may be effected by one of the volatile tests named under the next heading4 ,to give the test a fair trial1 the upper end of the ventilating pipe should be temporarily sealed over4 #c4 ,testing of the drain cannot be efficiently carried out unless access can be obtained to the drain near the sewer4 ,in a properly constructed house-drain a man-hole is provided for this purpose4 ,two chief methods of testing drains and soil-pipes are in use1 by smoke or volatile agents and by water4 ,the smoke-test consists in filling the drains with smoke1 the assumption being that this will find its way through any faulty joint or trap1 thus indicating the site of the defect4 ,various arrangements are employed for pumping the smoke into the drain from the combustion chamber of a pumping apparatus2 or smoke is produced by means of specially prepared rockets4 ,all outlets or ventilating pipes must be carefully stopped during the operation1 and the place where the smoke is smelt will then indicate any leaky point4 ,illustration3 ,,fig4 #ce4 ,,showing ,,stopper ,,for ,,water-,,testing ,,of ,,drains4 ,drain grenades are largely employed for the volatile testing of drains1 the essential constituent being phosphide of calcium4 ,the grenade1 which is attached to a piece of string1 is passed beyond the trap of the w4c41 and as the string unwinds the grenade opens and discharges its contents into the soil-pipe4 ,or a tablespoonful of strong oil of peppermint1 mixed with hot water1 is poured down the highest water-closet in the house4 ,if this is smelt by another person in the lower closets1 it indicates defective traps or soil-pipe4 ,all volatile and smoke tests have but a limited utility4 ,they are useful in detecting defective joints in traps and in the soil-pipe4 ,they may detect defects in an underground drain2 but if no smell or smoke is perceptible when a drain is tested by this means1 the drain may still be seriously defective4 ,the only absolutely trustworthy test for drains is the hydraulic or water test4 ,the lower end of the drain is stopped up by a suitable water-tight stopper4 ,then the drain is filled with water by means of a tap in the yard1 the amount of water used being approximately estimated by the rate of flow from this tap4 ,the drain is filled up to the level of the gully-traps in the yard4 ,if it remains at this level for half an hour1 the drain is sound4 ,more often it leaks so rapidly that it will not fill1 or the level of the water falls quickly after filling1 and it is necessary to strip and repair1 or more generally to relay the drain so as to make it water-tight4 ,rats are an important indication of defective drains4 ,the presence of rats in a house should always lead to a thorough investigation of its drains4 ,,chapter ,,xxvi4 ,,cesspools ,,and ,,main ,,sewers4 ,the terms ,sewer and ,drain are used somewhat confusedly4 ,the term drain should be used to designate the pipes bringing the sewage from the house into the street-sewer1 or any pipes by which the subsoil is drained2 the term sewer being confined to the trunk canals into which the house drains empty their contents4 ,where the water-carriage system of sewerage is adopted1 involving the use of water-closets as described in the last chapter1 the sewage may be carried from the house either into cesspools or into the main sewer4 ,cesspools are only permissible in isolated country-houses supplied with water-closets4 ,they should always be situated a considerable distance from the house1 and should be emptied at regular intervals1 the sewage being placed in shallow trenches on the land4 ,the construction of the cesspool requires careful attention4 ,its walls should be of brickwork set in cement1 lined inside with cement1 and surrounded by clay puddle4 ,the bottom should have a fall towards one side1 where a pump can be fixed1 to remove the more liquid contents4 ,the depth of the cesspool should never exceed #g feet4 ,the drain emptying into the cesspool should be trapped and ventilated1 near its junction with the cesspool2 and the cesspool itself should be ventilated4 ,in connection with many old houses in towns1 cesspools still exist1 sometimes under the basement or near the house1 and so built as to allow soakage in every direction4 ,the surrounding soil becomes contaminated for a considerable distance1 the water in any neighbouring well is tainted1 or leaky water-pipes receive the soakage4 ,the cleansing of cesspools is always a disgusting process1 and even dangerous to the workmen employed4 ,they incur the risk of suffocation1 and are very subject to ophthalmia4 ,to avoid these dangers a pump and hose connected with a partially exhausted barrel is employed1 but even with this provision some nuisance arises4 ,in the ,bexley cart1 which is used for this purpose1 a hose is used to connect the cesspool with an air-tight cylinder in the cart1 into which the contents of the cesspool are pumped4 ,a modification of the cesspool system1 called the ,pneumatic ,system has been proposed by ,captain ,liernur4 ,in it the cesspool is not placed under the house or the courtyard of the house1 but under the street at the angle of junction of several streets4 ,it is made of cast-iron and air-tight1 and is connected with all the houses of several streets by iron pipes4 ,by means of a powerful air-pump worked by steam1 the cesspool is emptied into barrels in which it is sent directly to farms2 and the barrels being placed on ploughs of peculiar construction1 the manure is discharged from the bung-hole of each barrel and covered over with earth in the progress of the plough4 ,the pipes tend in this and similar systems to get clogged with fcal matter1 and large quantities of water are required to keep them clean1 so that the system merges into that of the use of water-closets1 but without the thoroughness of the latter4 ,cesspools have been almost improved out of existence in some continental towns1 by the introduction of movable cesspools1--fosses mobiles1--to which would correspond strictly the tubs and pails used in some of our large towns4 ,such movable receptacles have been still further 8improved0 by the adoption of separators1 by which the liquid parts are allowed to escape into the sewer1 while the solid parts remain comparatively inoffensive4 ,but when this is done1 the cesspool may be as well abolished1 as the foulness of the sewage is not greatly increased by allowing solid as well as liquid excreta to enter it4 ,sewers are built of glazed stoneware or of impervious brick laid on a bed of concrete to prevent sinking of any part1 the parts being most solidly put together with cement4 ,iron and steel pipes are also used especially when extra strength is required1 as when there is some danger of the pipes sinking4 ,for most small streets circular stoneware sewers suffice4 ,oval brick sewers are more suitable for main streets in which the amount of flow varies greatly4 ,the cross-section of these should be an egg-shaped oval with the small end downwards1 as this ensures the most rapid current4 ,sewers should be laid in as straight a line as possible1 and with a fall which will ensure a flow of at least #b feet per second4 ,the following rule gives approximately the fall required for smaller sewers and drains3 ,a #d-;inch pipe requires a fall of #a in #dj4 ,a #f-;inch pipe requires a fall of #a in #fj4 ,a #i-;inch pipe requires a fall of #a in #hj4 ,for further particulars as to the velocity of flow see page #ahg4 ,where a town is very flat1 and a proper fall of sewer impossible1 ,shone's ejectors are sometimes used to raise the sewage4 ,the sewers are laid in sections1 each section falling to a certain point1 from which the sewage is raised by the ejector to a higher level and so carried to the next section of sewers4 ,each section has a separate system of ventilation4 ,the provision of manholes for inspection of an intercepting trap and of ventilation of the house drain near its junction with the sewer has already been considered 7page #agi74 ,as sewers have commonly to carry away the rain-water in addition to the waste matter from houses1 their size must be regulated accordingly4 ,the rainfall being very various1 the sewers may occasionally become overcharged and flood the basements of houses4 ,during heavy rainfall large quantities of road grit are washed into the sewers1 the intercepting gully tanks at the road sides being insufficient to prevent this4 ,in addition to the above disadvantages associated with discharging storm water into sewers1 the sewage owing to its increased bulk is more difficult of disposal1 whatever method of disposal be adopted4 ,the size of the sewers and of storm-outfalls into the nearest river or the sea must be regulated so that they are equal to these sudden strains on them2 or the ,separate system1 by which the rain is carried in special conducts to the nearest river1 must1 in the alternative be adopted4 ,the objections to this plan are that it necessitates a double system of sewerage1 and does not allow of the useful scouring effect of rain on sewers4 ,where it is feasible1 and particularly in small country towns1 its adoption is advisable4 ,in such cases the old brick drains are used for carrying off rain-water1 while new pipe-sewers are employed for carrying the sewage4 ,such pipe sewers are not liable to become fouled1 and on account of the decreased dilution of the sewage can be made smaller than brick-sewers4 ,sewers being closed conduits containing sewage1 it is highly desirable that the gases resulting from decomposition should be freely diluted4 ,such gases in unventilated sewers may find their way through intercepting traps into the house drain4 ,the danger from this source has been considerably exaggerated4 ,ventilation of the sewer is1 however1 desirable4 ,this has been commonly accomplished by gratings opening at intervals directly into the middle of streets4 ,in narrow streets1 the stench from street-grids is occasionally a source of complaint1 and may cause malaise and ill-health4 ,charcoal traps placed below sewer grids to intercept offensive gases have been found to be of little use4 ,the best plan is to do away entirely with surface ventilators1 and carry up iron shafts or brick shafts lined with stoneware pipes above the level of all neighbouring houses4 ,the only difficulty in adopting this plan is the difficulty in securing premises to erect such shafts up houses1 although no danger attaches to the practice4 ,ventilating shafts should be erected at intervals and particularly at the highest points of the sewage system of a town1 the upper end of these shafts being remote from the windows of any dwelling-house4 ,when sewers are laid with too steep a gradient1 they act as chimneys1 the gases mounting to the higher part of the town1 and frustrating attempts at ventilation on lower levels4 ,various attempts have been made to ventilate sewers by artificial means1 as by the aspirating effect of street lamps1 etc41 but these efforts have not been successful1 as the effect of the up-current only influences a short length of sewer4 ,the usual method of combined up-shafts and street grids answers fairly well1 but when any complaint of smell from street-grids occurs they should be replaced by up-shafts4 ,in ,bristol and a few other towns no provision is made for sewer-ventilation1 and no ill effects have apparently resulted4 ,there can be no question that the importance of sewer-ventilation has been exaggerated4 ,if the sewer has a sufficient gradient1 and is properly laid1 and efficiently flushed1 so that no offensive deposits occur1 the provision of up-shafts at favourable points is all that is necessary4 ,sewer effluvia have been credited with causing enteric fever1 diphtheria1 and other diseases4 ,these diseases rarely if ever owe their origin to this cause4 ,the microbes discovered in sewer-air have always been those of the outside atmosphere1 and not derived from the sewage4 ,sewer effluvia might1 however1 predispose to such diseases1 if exposure to them were frequent or protracted1 by lowering the powers of resistance of the constitution4 ,flushing of ,sewers is required at intervals1 in order to remove any deposits of grit or other solid matter4 ,flushing is effected by filling special flushing shafts placed at intervals in the sewers with clean water and then suddenly releasing this4 ,whenever there is stagnation1 a foul odour is certain to be emitted4 ,the cardinal rule with regard to sewage is to keep it in rapid onward motion1 until it has passed the outlet of the sewer4 ,the introduction into a sewer of hot water or waste steam is an occasional cause of nuisance4 ,the ,outfall of a sewer requires to be large and perfectly free in order that the progress of the sewage may not be impeded4 ,when the sewage is discharged into the sea above the low water level1 it becomes backed up in the main sewers when the tide is high4 ,the same condition of things has occurred when the outfall is into a river below the water line1 or into a tank out of which the sewage has to be pumped4 ,in all these cases the ventilation of the sewers requires to be perfect1 and great precautions taken to prevent obstruction of the outflow4 ,in low-lying sewers where the outfall is impeded1 mechanical aids are required to prevent blocking of the sewers4 ,this may be obtained by pumping at the outfall1 to enable sewage to escape at all conditions of the tide1 or to raise the sewage on to land for irrigation4 ,in the ,shone system the sewage is raised to the required height by means of compressed air4 ,in this system the sewage is received into 8ejectors40 ,these are cylindrical reservoirs1 in which is a float on a counterpoised lever4 ,when a certain quantity of sewage has entered1 a valve opens admitting the compressed air1 which forcibly raises the sewage into a higher length of sewer or to the outfall4 ,,chapter ,,xxvii4 ,,problems ,,as ,,to ,,flow ,,in ,,sewers4 ,in order to prevent deposit of solid matter1 sewers should be constructed with a sufficient gradient1 and of a shape which presents the least surface for friction in proportion to the amount of liquid to be conveyed4 ,all brick sewers should be egg-shaped1 with the narrow end downwards4 ,the egg is formed by two circles touching one another1 the diameter of the upper circle being twice that of the lower4 ,this shape possesses the great advantage that when the depth of the stream is diminished the amount of wetted surface of sewer 7wetted perimeter7 is diminished in equal proportion1 whereas in every other form of sewer it is relatively increased4 ,thus the friction1 which depends on the extent of the wetted perimeter1 is kept down to a minimum4 ,where1 as in outfall sewers1 the volume of sewage is large1 and does not vary greatly in amount1 the circular form may be preferable1 as it is cheaper and stronger than the egg-shaped sewer4 ,below #ah inches internal diameter1 sewers should be circular in section1 and made of stoneware1 not brick4 ,the velocity of flow depends upon 7#a7 the hydraulic mean depth of the stream1 and 7#b7 its inclination or fall4 ,the hydraulic mean depth means the depth of a rectangular channel whose sectional area 7and therefore the volume of whose current7 equals that of the curved sewer or pipe1 concerning which the calculation is made1 and whose width equals the entire wetted perimeter of the sewer or pipe4 ,it is thus equal to sectional area_/wetted perimeter4 ,in the case of circular pipes1 if we take the diameter to be #a1 and assume the pipe to be running full1 the sectional area r#b1 where #cadaf and r half diameter4 ,the wetted perimeter #br1 that is1 the circumference of the circle formed by the pipe4 ,therefore hydraulic mean depth h r#bbr #ad ,similarly when the pipe runs half full-- h 7r#bb7_/7br7 #ad ,the solution of problems where a smaller arc of a circle is occupied by fluid requires trigonometrical methods1 and is not usually needed in practice4 ,the quantity of fluid discharged in a given time is represented by the product of the sectional area of the stream into its velocity4 ,the greater the hydraulic mean depth the greater is the velocity1 if the inclination remains the same4 ,the velocity of flow is determined by ,eytelwein's formula1 which states that the mean velocity per second of a stream of water similar in form to those now under consideration is nine-tenths of a mean proportional between the hydraulic mean depth and the fall in two ,english miles1 if the channel were prolonged so far4 ,thus if f the fall 7in feet7 in two miles1 h hydraulic mean depth in feet1 ,v mean velocity per second1 ,then ,v #i7;hf71 or if v velocity per minute1 then v #ee7;hf74 ,it is more convenient to let f fall in one mile4 ,then the formula becomes v #ee7;h #b;f74 ,how much sewage will a circular drain #c feet in diameter running half full convey1 the fall being #a in #djj8 ,here h 7r#bb7_/7br_/#b7 r_/#b #cd4 #a in #djj x in #e1bhj feet 7i4e4 a mile74 f #acb in a mile4 v #ee #dd #bdb feet per minute4 #ee7;h #b;f74 ,s r#bb #cadaf #i_/7d #b7 #cecdc4 v ,s #bdb #cecdc #heeh cubic feet1 discharged per minute4 ,in what way does the size and shape of a sewer affect the velocity of the sewage flowing through it8 ,if a #ab-;inch pipe sewer1 laid at a gradient of #a in #age1 gives a velocity of #c feet per second1 what would be the velocity if the sewer had a gradient of #a in #gjj 7the pipe running half full in each case72 and would this latter velocity suffice to keep the sewer clear of deposit8 ,an elliptical sewer gives greater velocity to flow of small quantities of sewage than a circular one because it exposes a smaller surface for friction4 ,by formula v #ee7;h #b;f74 h #ad h #ab4 f #a in #age #cj feet in one mile4 v 7#eeb7fj #babhe ft4 per min41 i4e4 slightly over #c ft4 per sec4 ,in the second case f #a in #gjj #gef feet in one mile4 v 7#eeb7aeab #ajfig feet per minute4 ,thus in the first case there is a velocity of #cee feet per second1 and in the second case of #agh feet per second4 ,the latter velocity is quite insufficient to keep the sewer free from deposit1 #c feet per second being the minimum velocity required for that purpose4 ,given a sewer #c feet in diameter1 with a fall of #a in #a1gfj1 what would be the relative discharge if the fall were #a in #e1bhj8 ,in the first case1 #a in #a1gfj #c in mile4 #a in #e1bhj #a in mile4 h r_/#b #cd4 v #ee7;h #b;f7 #ee7cd #f7 #afe_/ #aah4 ,in second case v #ee7cd #b7 #ee7cb7 #fgi4 ,thus the velocity of the two streams would be as #aah3 #fgi4 ,supposing a sewer to have a gradient of #a in #cjj1 how much would the velocity and discharge be increased by altering the gradient to #a in #ajj8 #a in #cjj #agf in mile4 #a in #ajj #ebh in mile4 ,as h is not given1 we must assume it #ad1 as it does in circular sewers running full or half full4 v #ee 7h x #b;f7 #ee 7#cebd7 #afc feet per minute4 v#a #ee 7#ajdd7 #bha ,the increase in discharge may be similarly calculated4 ,describe the relation existing in a sewer between gradient1 volume1 velocity1 and size4 ,by the formula v #ee 7h4f47 ,where v velocity in feet per minute4 h hydraulic mean depth 7area of cross section of stream7 7wetted perimeter74 f fall in feet in two miles4 ,in circular sewers h diameter_/#d4 ,thus the velocity varies as the square root of h or f4 ,the volume discharged varies with the value of the factor v s where s sectional area of stream4 ,if h remains constant1 with a varying volume of s1 then the volume discharged may remain constant4 ,thus h and v in a circular sewer are the same1 whether the sewer runs full or half full4 ,in a ,v-shaped channel the velocity remains the same whatever the depth of the stream1 as its bed and area preserve the same proportions4 ,an egg-shaped sewer approximates the ,v shape in form4 ,similar volumes of sewage have velocities which vary not only with the amount of fall1 but the size of the sewer4 ,the friction1 as represented by the wetted perimeter1 would be much less with sewage half filling a circular sewer1 than with the same amount of sewage forming a broad shallow stream on the invert of a large sewer4 ,,chapter ,,xxviii4 ,,the ,,disposal ,,of ,,sewage4 ,the water-carriage system of sewage is1 as the late ,dr4 ,parkes put it1 8the cleanest1 the readiest1 the quickest1 and in many cases the most inexpensive method40 ,but when the sewage is conveyed to the outfall of the sewer1 its ultimate disposal is still one of the most difficult problems of the present day4 ,various plans have been adopted1 of which the following are the chief3-- #a4 ,discharge into running water4 #b4 ,discharge into the sea4 #c4 ,separation of solid and liquid parts ,by settlement4 ,by precipitation4 #d4 ,filtration through various artificial media or through land4 #e4 ,irrigation4 #f4 ,bacterial methods4 ,discharge at once into running water was formerly the favourite plan1 as it was certainly the most convenient4 ,the sewage was turned into the nearest water-course1 regardless of the facts that this might have to supply the drinking water of people at a lower point1 that the mouth of the river tended to become obstructed by sewage mud1 that valuable stocks of fish were destroyed1 and that the river which had practically become a sewer was a source of annoyance and danger to all on it or near it4 ,the enforcement of the ,rivers ,pollution ,prevention ,act of #ahgf has not been followed by as great improvement as is desirable4 ,the sewage entering rivers undergoes considerable purification by subsidence1 by oxidation1 by the influence of water plants1 and still more by the active work of microbes1 causing nitrification of nitrogenous matter4 ,the vitality of the typhoid bacillus and of the cholera vibrio when discharged by sewage into a large river is probably not very protracted2 but water from such a river would form a very dangerous source of domestic supply4 ,discharge into the ,sea is resorted to in seaboard towns4 ,the outfall must be carried well below the lowest low-water mark1 and to such a point that the incoming tide or wind will not bring the sewage back upon the shore1 or on the shore of neighbouring places4 ,discharge into an ,estuary is only justifiable when the flow of the river is rapid1 when the volume of water passing out to sea is very greatly in excess of the volume of sewage1 and when there is no possibility of contaminating oyster-layings or beds of mussels or other molluscs4 ,objection has been taken to the above method on the ground of waste of manure2 but modern sewage is so dilute that its profitable utilization on land still remains a dream4 ,for a single house or small village1 the sewage may be stored in a tank1 with an overflow-pipe1 out of which the liquid parts escape1 and are systematically used to irrigate land1 while the solid parts are removed at intervals4 ,a similar subsidence system has been employed on a larger scale1 the liquid parts being irrigated over land1 while the solid parts are mixed with street sweepings1 and sold as manure4 ,if the liquid parts in any such system as this are turned into a stream1 they are as dangerous as the entire sewage1 and the legal prohibition to discharging sewage into streams applies equally to them4 ,the precipitation of the solid parts of the sewage is rendered much more perfect by the use of chemical agents1 and at the same time the dissolved matters are to some extent removed4 ,milk of lime has been employed1 #f to #ab grains of quicklime being used for each gallon of sewage4 ,secondary decomposition is apt to occur in the effluent1 causing an offensive smell4 ,salts of alumina1 iron salts1 and various combinations of these have also been employed1 but with imperfect results4 ,the ,london sewage for some years has been treated by adding #be grains of sulphate of iron and #cg grains of lime to every gallon of sewage2 a reduction of #ae to #bj per cent4 in the amount of dissolved organic matter being secured4 ,polarite or magnetic spongy carbon is used as a filter in certain places1 the solid and some of the dissolved sewage being first precipitated by magnetic ferrous carbon 7ferrozone74 ,the ,amines process consists in applying a mixture of herring brine and lime to the sewage4 ,the sewage is stated to be sterilized by this means4 ,electrolysis has also been applied to the purification of sewage1 as in the ,hermite process4 ,in this process sea-water is electrolysed1 oxygen-yielding compounds and chlorine being produced4 ,with regard to all the chemical processes hitherto introduced1 the following general statement appears to hold good3 they are expensive and not thoroughly efficient4 ,sewage sludge is deposited in the tanks in chemical processes and needs separate disposal4 ,at ,birmingham the amount of sludge produced daily from the sewage of a thousand persons is nearly a ton4 ,this sludge has been run into rough filter beds and left to dry or carted away for manure1 but in its crude state its manurial value is very slight4 ,at ,ealing it is mixed with house-refuse and burnt in a destructor4 ,the more modern method is to pass it through a filter-press1 thus compressing it into solid cakes which can be sold for manure4 ,filtration of the sewage matter has been accomplished in various ways4 ,intermittent downward filtration through a considerable depth of soil was stated by the ,rivers ,pollution ,commission to be attended with good results4 ,a porous soil is chosen1 and the purified water is received in drains under it4 ,a large part of the organic matter is removed by bacterial agency4 ,frankland's experiments shewed that upward filtration through the same media did not purify4 ,filtration through artificial media has not been successful with crude sewage4 ,precipitation by ferrozone followed by filtration through polarite is said to be satisfactory4 ,broad ,irrigation purifies the sewage efficiently under favourable conditions1 the possible exceptions being during rainstorms and during frosty weather4 ,the effluent into the river cannot1 however1 be regarded as certainly innocuous1 though it is better than the effluent from most other processes4 ,sewage farms are not a commercial success4 ,in such a farm liquid sewage is allowed to flow at intervals over the land1 different fields being irrigated in rotation4 ,immense crops of grass are obtained1 but the grass is coarse and rank4 ,the soil to be irrigated should have a gentle slope1 and the effluent be conveyed by subsoil drains about #e or #f feet deep into the nearest water-course4 ,the sewage should be delivered in as fresh condition as possible1 and should be freed from its coarser portions by settlement or precipitation4 ,the amount of land required is about #a acre for the sewage of #ajj persons4 ,the irrigation must be on the intermittent plan1 in order that the soil may undergo aeration2 as it is only in this way that the best purifying results can be obtained4 ,the sewage farm should be well drained by deep-laid agricultural drains4 ,the chief purification of the sewage occurs in the superficial layers of the soil4 ,nitrification ceases at a depth of about #ah inches4 ,the great point1 therefore1 is to keep the superficial soil in good condition4 ,a similar nitrification occurs in earth-closets 7page #aie74 ,no nuisance need arise in connection with a sewage-farm1 and the supposition that milk and other products from such a farm are less wholesome than the same products from other farms has proved to be unbased4 ,bacterial ,methods of ,treating ,sewage4--,chemical precipitation of sewage is likely to be completely superseded by biological or bacterial methods of sewage disposal4 ,when sewage is treated by filtering through land or by broad irrigation the process is bacterial1 bacteria or microbes in the soil converting injurious organic matter into innocuous mineral products4 ,the typical process is one of nitrification4 ,the novelty of recent methods is in utilising bacteria for the whole process of purification1 and not only for its final stages4 ,the object is1 in fact1 not as in chemical processes to arrest1 but by confining the sewage in tanks to aid and hasten decomposition or putrefaction4 ,two kinds of microbes serve in this process2 those living in air1 known as aerobic1 and those living in other gases than air1 called anaerobic4 ,three biological methods of preliminary treatment of sewage are employed4 7#a7 ,mr4 ,scott ,moncrieff passes the sewage slowly upwards through a filter #ad inches thick1 consisting of successive layers of flint1 coke1 and gravel4 ,this is called a 8cultivation tank40 ,the solid sewage becomes liquefied in passing through this medium1 the microbes in the filter dissolving the sewage4 7#b7 ,in the 8septic tank method10 introduced by ,mr4 ,cameron at ,exeter1 a tank is employed which is covered in to exclude light1 and to a large extent air4 ,the tank is large enough to hold #bd hours' flow of sewage4 ,the microbes in the sewage under these conditions multiply rapidly1 attack1 and liquefy the sewage4 ,as in the first process little or no sludge is left4 ,the ultimate products of the decomposition are water1 ammonia1 and carbonic acid1 and other gases4 ,the effluent from the tank is comparatively clear and inoffensive4 7#c7 ,aerobic biological filters are employed1 as in ,mr4 ,dibdin's installation at ,sutton1 where the filtering material is coke4 ,the sewage slowly passing through the filtering medium becomes liquefied1 the solid matter being peptonised4 ,this action is in part at least due to anaerobic microbes4 ,the filtering beds are used intermittently to allow of aeration1 and the liquefaction of solid organic particles entangled in the filter probably chiefly occurs at this stage4 ,it is desirable to have small subsidence tanks1 for the removal of large suspended matters and of road debris1 etc41 before the sewage is spread over the filtering beds4 ,the material used in the filter varies4 ,most commonly coke-breeze has been employed1 but coal slack and other material have also been utilised4 ,after the preliminary treatment above described1 the sewage requires to be passed over finer filtering beds1 in which aerobic microbes complete the purification by changing the dissolved organic matter into inert inorganic compounds1 by the process known as nitrification4 ,the two processes run into one another1 to some extent going on together4 ,hitherto the ,local ,government ,board have required filtration of sewage through land before any sewage effluent is allowed to pass into a stream4 ,in view of the successful results now obtainable by bacterial processes this requirement will be occasionally waived4 ,it is unsafe to assume1 however1 that the clear effluent obtained is free from all disease-producing microbes2 and drinking water should not be obtained from even a very large river below the point of discharge of such an effluent1 without the most efficient sand filtration4 ,,chapter ,,xxix4 ,,conservancy ,,methods4 ,the refuse to be removed from a house consists of fouled water1 which is at least equal in quantity to the water-supply of the house2 the excreta of the inhabitants2 and 8dust10 which contains1 besides ashes1 considerable kitchen refuse2 consisting of both vegetable and animal matters4 ,in dry methods of removing refuse1 the 8dust0 is often added to the excreta1 and the two removed together2 or the 8dust0 may be separately removed4 ,in either case the foul water1 and to a large extent the urine1 remain to be dealt with1 and require special drains for their removal4 ,thus in large towns1 whether dry or wet methods of removing sewage are adopted1 drains for the removal of foul-water and rain-water will be required1 and it is found that they are practically as foul as if they contained the solid excreta4 ,the dry methods of removing sewage involve a certain amount of retention about the house2 hence the general name of conservancy methods4 ,of these the most important are-- #a4 ,the pail system4 #b4 ,the dry-earth system4 #c4 ,the midden or privy system4 ,the ,pail ,system implies in reality the use of a movable cesspool4 ,the pail may be used alone1 or may contain ashes and house refuse1 or some deodorant4 ,where the pail is used without any admixture of foreign matter1 it should be emptied daily1 and care should be taken that the pails for different houses are not exchanged4 ,in the ,goux ,system the tubs are lined with a composition containing clay and furnished at the lowest part with some absorbent material such as chaff1 straw1 or hay1 which serves to absorb the urine and retard putrefaction4 ,this is1 when well managed1 somewhat less offensive than the ordinary pail system4 ,the pails may be supplied with a deodorant1 such as sulphate of iron1 as at ,birmingham1 ,leeds1 etc42 they may be packed with absorbent material1 as in the ,goux system 7,halifax72 the ashes and house-refuse may be deposited in the same pail 7,edinburgh1 ,nottingham72 or coal ashes may be scattered over the excreta 7,manchester1 ,salford72 but all these systems are rapidly being superseded4 ,although the pail or tub system is an improvement on the midden system1 it is necessarily a cause of considerable nuisance1 and its replacement by water-closets should be recommended in towns4 ,in detached country houses it may be retained without nuisance1 if the pail or tub is emptied daily1 and its contents at once placed in the garden beneath a shallow layer of earth4 ,the pails in large towns are usually collected in specially-constructed closed wagons4 ,in some towns the pail contents have been burnt in a 8,destructor0 7page #bjj7 after having been mixed with ashes4 ,in other towns attempts have been made to utilise the excreta1 either by selling in their crude condition or after drying and deodorising them by heat4 ,none of these methods repays the cost of collection4 ,mixing ashes with the excreta diminishes any possible value they may possess as a manure4 ,the ,dry-earth ,system is an important modification of the pail system4 ,in it dry earth or some other material is added to the excreta1 thus converting them immediately into an inodorous mass4 ,probably the best contrivances for thus deodorising the excreta1 as soon as they fall into the receptacle1 are ,moule's or ,moser's ,earth-,closets4 ,it is found that #a lbs4 of dry earth completely deodorise the closet each time it is used4 ,loamy earth is the most valuable material2 a mixture of peat and earth or ashes is very good2 sand1 gravel1 and chalk are practically useless4 ,it is necessary that the earth should be very dry1 and that it should be finely sifted4 ,if the earth is damp1 decomposition of the excreta speedily occurs4 ,the act of sitting and rising works a hopper which scatters a supply of earth4 ,charcoal and sawdust have also been used in connection with ,moule's or ,moser's closet1 and with good results4 ,charcoal has been obtained cheaply for the purpose from street sweepings1 and from seaweed1 as in ,stanford's closet1 in which #ab lb4 of charcoal from seaweed is used each time4 ,mr4 ,stanford found that while dry clay absorbs only #d to #e per cent4 of water1 dry charcoal prepared from seaweed absorbs #adg per cent4 ,the best material1 however1 is dry earth1 but it must be thoroughly dry4 ,the microbes in the earth disintegrate the excreta1 converting them into mineral compounds1 such as nitrates4 ,even the paper used disappears4 ,hence the same earth may be used over again after being stored dry for six weeks4 ,whether the excreta of an infectious patient are freed from infection by this process is doubtful2 if not1 the infection might be scattered by means of dust4 ,the dry earth system is more expensive in use than the pail system1 and although applicable to villages and isolated houses1 is quite unsuited to large towns1 owing to the practical difficulties connected with the procuring and storing of dry earth4 ,the dry earth closet requires frequent attention1 in addition to not being so convenient as the pail closet2 and there is much less manurial value in the contents of earth closets than in those of pail closets4 ,the advantages of the earth-closet as compared with the water-closet have been thus summarised by the late ,sir ,geo4 ,buchanan4 8,it is cheaper in the original cost1 it is not injured by frost1 it is not damaged by improper substances driven down it1 and it very greatly diminishes the quantity of water required by each household40 ,these advantages only accrue when the system is perfectly worked1 and do not counterbalance the immense advantage and greater safety of the water-carriage system in towns4 ,the ,privy or ,midden ,system1 involving the use of a fixed receptacle1 is still prevalent in many towns as well as in innumerable villages4 ,in its worst form1 the receptacle consists of a pit with sides of porous materials1 allowing percolation of filth in every direction2 and in this pit the excreta of whole households are allowed to collect for months4 ,it has been improved by providing a cover to keep out the rain1 and thus retard decomposition2 still more by providing a drain for the excess of liquid2 and by making the sides and bottom of the pit impervious to moisture4 ,the addition of dry ashes to the excreta tends still further to prevent any smell2 and the greatest improvement of all consists in raising the receptacle above the ground level1 and providing for easy cleaning from the back4 ,the raising of the receptacle involves a diminution in its size1 and so prevents the retention of putrefying matters near a house for a long time4 ,the model ,bye-laws of the ,local ,government ,board recommend a capacity for the privy not exceeding #h cubic-feet1 the provision of means for the frequent application of ashes1 dust1 or dry refuse2 they forbid any connection between the privy and the drain2 insist on its being at least #f feet from a dwelling-house 7too low a limit72 and require a flagged or asphalted floor at least #c inches above the level of the surrounding ground4 ,the ,nottingham tub-closet forms a link between the pail and midden system4 ,it is really a small movable middenstead1 used for receiving excreta1 vegetables and ashes4 ,even when carefully supervised1 middens are almost certain to be productive of evil4 ,they possess two great disadvantages as compared with pails or dry closets4 7#a7 ,the time between collections of excreta by the scavengers is much longer2 and 7#b7 the receptacle for the refuse is part of the structure of the building1 and cannot easily be renewed when it has become saturated with excreta4 ,the use of pails or dry-earth closets is a great improvement on the old middens1 but even these compare very unfavourably with water-closets in two respects4 7#a7 ,the excreta require to be retained about the house for a longer or shorter period1 whereas with an efficient water-carriage system1 they are at once projected into the sewer4 7#b7 ,in removing the excreta1 the weight of the receptacle has to be added to that of the excreta1 while in the water-carriage system1 the water serves as the means of transport4 ,in villages and isolated houses1 where no drains are provided for waste water1 and the dry system of closets is adopted1 the disposal of waste water requires special provision4 ,very commonly the slops are thrown out of the door1 and soak into the ground about the house4 ,they should be carried by means of a waste-pipe into a water-tight cesspool1 remote from the house1 whence they can be pumped into a field1 or carried away by special conduits4 ,relative ,merits of ,dry and ,wet ,methods4 ,no absolute answer can be given in exclusive favour of either plan4 ,each is the best under different circumstances2 the dry method being chiefly suitable for small villages1 and for temporary collections of people1 as in camps2 and the wet method for towns4 ,the question of value of manure does not enter into the problem1 as it seldom repays for carriage4 ,the objections to the water-carriage system are really due to its not being carried out in an efficient manner4 ,when sewers are properly laid2 when they1 as well as house-drains1 are freely ventilated2 when house-drains are efficiently trapped and ventilated near their junction with the sewer2 when the drains are efficiently flushed1 and the outflow from the sewer is unimpeded1 the objections disappear4 ,these objections are that--7#a7 the sewers1 as underground channels1 transfer effluvia and the germs of disease from one place to another2 7#b7 pipes become disjointed owing to being badly laid1 and the ground is contaminated2 7#c7 the water supply is in danger of receiving impurities from the sewers4 ,these objections do not hold good in practice4 ,the contamination of water-mains or of wells from sewers implies gross carelessness in the method of laying of sewers or pipes4 ,the only objections which are of any force1 are 7#d7 that water-closets require a large amount of water1 and the sewage obtained is greatly diluted1 and consequently diminished in value2 while 7#e7 the disposal of such an amount of water1 in the case of a large inland town1 is a problem of the utmost difficulty4 ,modern engineering enterprise by bringing water from a greater distance1 and by aiding the discharge of sewage when necessary by pumping1 has overcome these difficulties4 ,there are many objections to the dry methods of removing excreta4 7#a7 ,whatever dry method be adopted1 the excreta are retained for some time in or about the house1 instead of being immediately removed4 7#b7 ,although the initial outlay in closets and sewers is less than with the water-carriage system1 there is the constantly recurring expense of removing the excreta1 as well as of cleansing the pails1 etc4 7#c7 ,in the dry-earth closets1 the provision of dry earth or other material involves some expense4 7#d7 ,whatever dry method be adopted1 sewers are always required to carry off the foul water1 as well as liquid trade products1 and a certain proportion at least of the urine4 ,it is impossible to supply sufficient dry earth to absorb all the urine and slops of the population4 ,thus1 as the ,indian ,army ,sanitary ,commission said1 speaking of barracks1 8to have two systems of cleansing stations--a foul-water system1 and a dry-earth system--would simply be paying double where one payment would answer2 or1 if all the excreta1 solid and liquid1 are to be carried away1 this must be done at a cost ten times greater than that which would be necessary1 if all the excreta were removed by drains40 ,with some of the dry methods1 as where middens or cesspits are drained into the sewers1 the sewer-water is more offensive than in towns supplied with water-closets4 ,when a midden or cesspool is drained1 the principle of conservation1 which distinguishes the dry system from the wet1 is practically abandoned2 and not only so1 but the solid matters still remain to be disposed of1 by a tedious process4 7#e7 ,the dry systems1 involving the retention of excreta about the house1 poison the atmosphere4 ,in all towns where the refuse matters are not removed immediately1 there is a high mortality1 especially among children4 ,on the other hand1 the introduction of the water-carriage system into large towns1 with the abolition of midden-heaps and cesspools1 has been followed in nearly every case by a diminution in the death-rate1 and especially a considerable diminution in that from such diseases as enteric fever4 ,it has furthermore increased the comfort of life1 and removed those serious nuisances which are inevitably associated with privies and pail closets1 and to a less extent1 when care is not exercised1 with earth closets4 ,,house ,,refuse4 ,in an ordinary household the disposal of ashes from fires1 of broken pots and cans1 of waste-paper1 and of vegetable and animal debris form a serious difficulty4 ,the difficulty is one that can be minimised by the careful housekeeper4 ,old newspapers1 etc41 may be sold1 though their value is very small2 other waste-paper should be burnt4 ,all vegetable and animal debris should be burnt4 ,this may be effected without nuisance if coal-fires are in use1 by placing potato-peelings1 cabbage leaves and similar substances under the fire until thoroughly dried1 and then burning them4 ,the careful housewife will not waste bones1 but utilise them for soup4 ,after being boiled they are much less liable to putrefy in the dust-bin2 but should even now be burnt in the fire4 ,if this plan be pursued1 the contents of the dust-bin will be simply ashes1 broken pots and cans1 and a few cinders--here again a sifter is desirable--and no nuisance can arise4 ,it is only organic refuse that smells4 ,if only gas or paraffin stoves are in use1 as during the summer months1 any possible nuisance in connection with the dust-bin is minimised by allowing all refuse to dry before it is placed in the dust-bin1 or by wrapping all putrefiable substance inside several layers of newspaper4 ,in emptying the dust-bin or ash pit1 care must be taken that the bottom is thoroughly scraped out4 ,it is well to keep some quicklime 7thoroughly dry7 for sprinkling on the bottom and sides of the receptacle each time after it is emptied4 ,this greatly helps in keeping it dry and diminishing nuisance during summer4 ,in many households a separate receptacle is kept for what is known as 8hog-wash10 containing waste-food1 often in a foul and putrefying condition4 ,in well-ordered households1 except in hotels and similar establishments1 there is no necessity for a 8hog-wash0 tub1 and its presence argues wastefulness and carelessness4 ,food which cannot be eaten because it has 8gone bad0 should be burnt4 ,two forms of receptacle are used for house-refuse1 an ash-pit or a dust-bin4 ,an ash-pit is a fixed receptacle for the reception of house-refuse4 ,in many towns the same receptacle is used for excreta4 ,then we have a privy or privy midden1 according to size 7see page #aif74 ,ash-pits for household refuse alone should be small1 so as not to hold more than a week's refuse4 ,no part should be below the ground level4 ,the floor and walls should be lined with impervious smooth cement1 and the ash-pit should have a hinged cover to keep out rain1 and a door on one side to facilitate emptying4 ,the ash-pit should be at least six feet distant from any wall of the house4 ,even the best constructed ash-pit is as much worse than a dust-bin1 as a privy is worse than a pail closet4 ,a fixed is always less easily cleansed than a movable receptacle4 ,a dust-bin is usually made of galvanized iron with a tight-fitting lid4 ,this receptacle can be kept clean1 and can be carried without any transference to another tub direct to the cart4 ,the removal of house refuse constitutes an important part of municipal work4 ,in most towns it is carried out weekly1 sometimes less frequently1 while in some towns removal twice or three times a week is secured4 ,a daily removal is carried out in a few towns1 and this is by far the best plan1 as decomposition and the dangers associated with it have then no chance of becoming serious4 ,the house refuse should always be conveyed through the streets in covered carts4 ,the disposal of house refuse constitutes a problem of increasing difficulty4 ,unfortunately in the suburbs of many towns it is deposited on low-lying land in disused quarries and brickfields4 ,when land has been thus levelled1 it often next appears as 8an eligible building site40 ,a very common practice has been to excavate gravel and sand upon the site of proposed dwellings1 and allow the excavation to be filled with dust-bin refuse4 ,before building on such a soil it is necessary to excavate down to the virgin earth1 and to render it impervious by a layer of cement concrete4 ,a second method is to sift and sort the refuse1 separating by means of sieves the finer ash and dust from the coarser parts4 ,this is usually carried out in a large dust-yard adjoining a river or railway-siding4 ,the 8breeze10 consisting of cinders and coals1 along with the fine ash1 are sold to brickmakers2 the 8hard core10 consisting of clinkers1 broken crockery1 etc41 is used for road making2 and the 8soft core10 consisting of animal and vegetable refuse1 to which is often added stable manure1 is sold for manure4 ,iron1 tin1 paper1 rags1 bottles1 and corks are separately collected and sold4 ,this disgusting process1 often carried on by women1 is now gradually being disused4 ,a third method is to cremate the house refuse4 ,this has been done to a large extent by burning the house refuse for making bricks 7page #abd74 ,this method of slow and imperfect combustion necessarily involves a nuisance4 ,a more elaborate means of securing the same end is by the modern ,destructor1 which has been gradually brought towards perfection4 ,a destructor is a large furnace1 in which1 after the fire has been first lit1 the combustible matter in the house refuse suffices to keep it alight4 ,various mechanical devices are in use for emptying the trucks of house refuse on to the fires without handling it1 for clearing out of the fire the inorganic refuse1 and for ensuring sufficiency of draught4 ,the amount of draught has in the older destructors been dependent upon the height of the chimney4 ,in some more recent destructors the same end has been more efficiently secured by injecting a steam blast into the furnaces4 ,a temperature of about #b1jjj ,f4 is reached in certain parts of the destructor1 the rapid draught ensuring enormous heat4 ,in view of the possibility of a portion of the smoke not being completely burnt1 a second 8fume cremator0 is often provided1 through which the products of combustion in the furnace are passed4 ,the fuel in the 8fume cremator0 is coke4 ,besides incomplete combustion of combustible material1 which is rare when the fume cremator is provided1 the escape of fine dust up the chimney requires to be guarded against4 ,this is partially prevented by ledges near the bottom of the chimney4 ,in a destructor the house refuse is reduced to about one-third of its original bulk1 the residue being innocuous clinker1 metallic refuse1 and dust4 ,this material can be utilised for making roads1 and in the manufacture of mortar4 ,the waste heat of the destructor has been partially utilised for various purposes4 ,this method of disposal of house refuse is usually the best available for large towns1 and offers the additional advantage that no nuisance is caused by the deposit of offensive material in neighbouring districts4 ,,chapter ,,xxx4 ,,position ,,of ,,the ,,house4 ,lord ,bacon said3 ,he who builds a fair house upon an ill seat committeth himself to prison40 ,the first considerations1 therefore1 in choosing a house are those of aspect1 surrounding objects1 and soil4 ,on the first of these considerations1 that of aspect1 ,thomas ,fuller's quaint remarks give the essential points4 ,he says3 8,light 7,god's eldest daughter7 is a principal beauty in a building2 yet it shines not alike from all parts of heaven4 ,an east window welcomes the beams of the sun before they are of strength to do any harm1 and is offensive to none but a sluggard4 ,a south window in summer is a chimney with a fire in it1 and needs the screen of a curtain4 ,in a west window in summer towards night the sun grows low and even familiar1 with more light than delight4 ,a north window is best for butteries and cellars1 where the beer will not be sour from the sun shining on it40 ,a workroom or study requiring steady light1 should point north or some point between north-east and north-west4 ,a breakfast room should face north-east to south2 while one aspect of a drawing-room should be south-east to north-east4 ,store-rooms1 dairies1 larders1 should have a northerly aspect4 ,it is preferable1 as a rule1 for the house not to face in the direction of the four points of the compass1 but diagonally to these4 ,surrounding ,objects of an objectionable character1 as factories1 noisy or offensive trades are to be avoided4 ,the possibility of neighbouring cesspools contaminating the water supply must be considered4 ,trees close to a house are objectionable1 rendering it damp1 and preventing the free access of sun and air4 ,more remote from the house they form a useful shelter1 especially when to the north or east4 ,the banks of water courses are to be avoided for similar reasons4 ,if there is a choice1 the slope of a hill should be selected2 and it is essential that no part of the dwelling should rest against sloping ground at a higher level4 ,rank vegetation indicates a damp clayey soil4 ,the main point is to secure that the house shall receive ample light and ventilation4 ,in calculating the amount and intensity of sunshine which a house built on a given site will secure the variations according to season must be remembered4 ,the direction 7orientation7 of the sun is the same all the year through2 but the altitude of the sun varies with the latitude4 ,thus in a house facing directly south in the latitude of the south of ,england the sun's altitude at noon on the #bast of ,december is #ae #d1 on the #bast of ,june #fb #d4 ,a ray of light entering the highest point of a window facing south at each of these seasons will illuminate a much larger part of the room in summer than in winter4 ,not only so1 but inasmuch as it enters the room more nearly vertically it is more powerful than when entering at an angle more nearly approximating a horizontal direction1 in accordance with the general law that the intensity of illumination falling on a horizontal surface 7as the floor of a room7 is inversely as the square of the width of the area embraced within the same angle of incidence of light4 ,in houses in a street the angular aperture through which light enters is greatest in the upper stories4 ,it may be increased 7a7 by increasing the height of rooms2 7b7 by carrying the window heads nearly to the level of the ceiling2 and 7c7 by avoiding the proximity of other buildings which would impede the access of light4 ,fig4 #cf shows the importance of the last consideration4 ,this represents a three-storied house in a street1 of which the opposite house ,l is of the same height4 ,it will be observed that each room is divided into two regions of different degrees of illumination by a plane ,lm1 formed by a line connecting the ridge of the roofs of the houses on the opposite side of the street with the interior surface of the rooms and touching the uppermost point of the window in transit4 ,below this line there is 8sky-light0 sufficient in quantity2 above this line light is insufficient in amount and is diffused and reflected4 ,the area receiving sufficient light increases from the ground floor upwards4 ,we have already seen that its intensity similarly increases in the higher stories1 the rays of light being more nearly vertical in these4 ,illustration3 ,,fig4 #cf4 ,,showing ,,variations ,,of ,,illumination ,,in ,,different ,,stories4 ,the amount of sky-light visible can be expressed in terms of the angle of aperture1 i4e4 the arc of sky visible at any given point a in the room4 ,thus in ,fig4 #cf the triangle of aperture bac is greater than bac1 and this greater than bac4 ,the sides of the angle of aperture1 it will be seen1 are formed by drawing one line from the point a to c1 which1 if prolonged1 would touch ,l1 and another line to b1 which passes through the highest point of the window4 ,the amount of light received in a dwelling-house is largely determined by the width of the street and the distance between the backs of the houses in adjacent streets4 ,the model ,bye-laws of the ,local ,government ,board insist that no new street shall be less than #cf feet wide if it exceeds #ajj yards in length or is intended to be a carriage road1 not less than #bd feet in any case4 ,furthermore1 a new house must have in the rear an open space exclusively belonging to the house1 at least #aej square feet in area1 and free from any erection above the ground level4 ,this must extend along the entire width of the house1 and must never measure less than #aj feet from every part of the back wall of the house2 the distance must be at least #ae feet1 if the house is #ae feet high2 #bj feet if #be feet high1 and #be feet if #ce feet high or more4 ,illustration3 ,,fig4 #cg4 ,,diagram ,,illustrating ,,the ,,necessary ,,requirements ,,as ,,to ,,open ,,space ,,in ,,front ,,of ,,and ,,at ,,the ,,rear ,,of ,,dwelling-,,houses4 ,streets should never be less in width than the height of the houses in them2 and a line drawn from the ridge of the roof to the foot of the wall of the opposite houses 7,fig4 #cg7 or in the rear to the foot of the wall or fence dividing the back yards of contiguous houses1 should not make an angle of more than #de with the ground 7,fig4 #cg74 ,this is the angle required for new buildings in the residential parts of ,liverpool1 and was proposed for ,london1 but unfortunately not made obligatory4 ,the size of windows is discussed on page #baf4 ,the light received in a given house is often diminished at corners of streets by contiguous houses4 ,the ,soil has an important influence on the healthiness of a site4 ,the relative merits of the different kinds of soil are discussed on page #bai4 ,undrained soils of whatever kind are bad1 and made-soils are always to be regarded with profound distrust4 ,the planning of a house should be carefully considered4 ,the principle is that the sun should enter every living room at some time of the day4 ,the relative positions of fire-place1 window1 and door in each room are important4 ,with the sole window of a room in the same wall as the fire-place the area ventilated is the least1 with it situated on the opposite wall the area ventilated is the greatest4 ,the door should be as remote from the window as possible1 in order to secure occasional perflation of air2 the two being preferably on opposite walls4 ,staircase windows are indispensable to secure through ventilation of a dwelling4 ,houses constructed 8back to back0 cannot be properly ventilated as no through current of air is possible4 ,hence the necessity for open yards at the area1 as well as air-space in front of the house4 7,fig4 #cg74 ,in the construction of a house1 apart from access of light and air1 the main problems are to secure dryness and equability of temperature4 ,we shall consider in this connection the materials used in the construction of walls1 floors1 and roofs4 ,,chapter ,,xxxi4 ,,the ,,materials ,,used ,,in ,,the ,,construction ,,of ,a ,,house4 ,in this country walls of houses are usually built of brick1 stone1 timber1 or concrete1 of which the first two are the most important4 ,timber is1 owing to its inflammability1 only allowed to be used in towns under special restrictions4 ,bricks and stones are bonded together and imbedded in mortar or cement4 ,there are several kinds of bonds in brickwork1 of which the strongest is the ,english4 ,this consists of alternate courses of 8headers0 and 8stretchers10 the former being bricks carried through the wall from face to back1 the short end showing on the face1 and the latter bricks laid lengthwise along the face of the wall4 ,hence the wall is held together in every direction4 ,a ,flemish bond consists of alternate headers and stretchers in the same course4 ,it is used where a specially smooth wall is desired1 but is not so strong as the ,english bond4 ,bricks are generally of a uniform size1 of #i inches in length by #d in width and #b-cd inches in thickness4 ,those bricks which are heaviest and hardest are generally the most durable2 bricks of good quality when knocked together give a clear ringing sound4 ,the relative conductivity for heat of brick as compared with other materials1 is shown in the following table1 from ,galton1 which gives the units of heat transmitted per square foot per hour by a plate #a inch thick1 the two surfaces differing in temperature #a ,fahr43-- ,stone--ordinary free stone #acfh ,glass #ff ,brickwork #dhc ,plaster #chf ,fir planks #acg ,brick dust #acc ,it is evident that in this respect1 brick walls compare very favourably with stone walls1 and are much more economical of heat4 ,increased conductivity of a material may be counteracted by increased thickness4 ,brick is very porous1 as shewn by its power to absorb moisture4 ,a good brick can absorb from #aj to #bj per cent4 of its weight of water2 while good granite only takes up #ab per cent41 sandstone usually from #h to #aj per cent41 marble only a trace1 and ,portland limestone #ac per cent4 ,being porous1 brick allows the passage of a considerable amount of air1 unless its pores are occupied by moisture4 ,the following table1 from ,galton1 shews the number of cubic feet of air which every hour pass through a square yard of wall-surface of equal thicknesses1 built of the following materials1 there being a temperature of #gb ,fahr4 on one side the wall1 and of #dj on the other3-- ,wall built of brick #gi cubic feet4 quarried limestone #fe 8 sandstone #dg 8 limestone #aja 8 mud #add 8 ,mortar should consist of clean sharp sand and slaked lime1 usually in the proportion of three of the former to one of the latter4 ,grouting1 or liquid mortar1 is merely ordinary mortar to which a larger quantity of water has been added4 ,it is used for filling up the crevices between the brickwork about every fourth course1 and is required to a greater extent in stone work1 owing to the difficulty in filling up spaces left by inequalities in the stone4 ,the sand used in mortar should be free from small stones4 ,it should not contain any earthy or clayey matters1 as these greatly diminish the adhesive quality of the mortar1 which depends on the combination of the sand and lime4 ,all the sand used in a building should be washed1 unless it is perfectly clean1 in order to remove impurities4 ,many builders use an inferior mortar1 in which other materials1 such as 8road scrapings10 are substituted for sand4 ,sand taken from the sea-shore is unfit for making mortar1 as the salt contained in it is apt to deliquesce and weaken the mortar4 ,lime is obtained by burning chalk or limestone in a kiln4 ,thus ,ca,c,o ,ca,o ,,co4 ,there are three kinds of lime3 7#a7 ,fat or quicklime1 used for internal plastering1 7#b7 stone lime1 used for ordinary building work1 and 7#c7 hydraulic lime1 used for building in damp situations4 ,the last named contains a quantity of silicates1 and sets under water4 ,common mortar crumbles away1 if laid under water before it has had time to harden4 ,portland cement is an artificial cement1 of a dark grey colour4 ,it is made by grinding chalk1 mixing it with blue clay or river-mud in certain proportions1 and then burning it in a kiln and afterwards grinding it to a fine powder4 ,it is used1 mixed with sand1 for external plastering 78compoing07 of walls1 for making concrete1 or instead of lime for making mortar if extra strength is required4 ,compo consists of ,portland cement and sand1 and is used for covering walls when an impervious smooth surface is required1 and for keeping out rain4 ,it is laid on in two coats4 ,the first or rough coat #cd inch thick1 is composed of one part cement to #e parts compo sand1 i4e4 coarse sand mixed with fine beach4 ,the outer or fine coat is composed of two parts fine or washed sand to one part cement4 ,to 8render0 or 8compo0 a wall is to cover it with this material4 ,the internal plastering of a chimney flue is called 8pargetting40 ,concrete is of two kinds1 lime or cement concrete4 ,it is composed of three parts broken ballast or large beach1 two parts of sand1 and one part of lime or cement4 ,lime concrete has no resisting strength1 and is only used for surrounding drain-pipes1 or where no great strength is required4 ,stone varies very greatly in character4 ,it is uncommon for the whole thickness of the walls of a house to be built of stone2 usually there is merely a facing of stone and a backing of brickwork4 ,if good stone is not available1 the less it is used the better4 ,the stone chosen should be durable1 and able to resist the action of the sulphuric1 sulphurous1 and carbonic acids absorbed from the atmosphere1 and brought in contact with it by means of rain4 ,the stone of which a considerable part of the ,houses of ,parliament consists is dolomite1 a double carbonate of lime and magnesia4 ,the acid fumes in the air produce on its surface sulphate of magnesium1 which is washed away in successive layers4 ,if the stone presents any stratification1 it should be laid in the wall in the same position as that in which it was originally deposited in the quarry4 ,thus1 any planes of stratification will be horizontal1 and the scaling off by the action of frost and rain is minimised4 ,comparatively homogeneous stones1 such as granite and millstone-grit1 can be laid in any position4 ,in testing the character of any stone1 the least porous1 densest1 and most resistent to crushing1 will as a rule be the most durable4 ,the chief difficulty in the use of stone for the walls of houses1 is that of keeping out the wet4 ,to obviate this1 stone-houses are often built of great thickness1 and are consequently cooler in summer and warmer in winter4 ,in and near large towns brick is chiefly used for walls of houses1 and stone employed only for window-sills1 columns1 steps1 etc4 ,it is even more important in these cases to carefully select the stone1 as the parts where it is placed are those most exposed to the weather4 ,if a soft1 friable freestone is used1 after a sharp frost large scales are seen falling off in flakes1 owing to the freezing and subsequent thawing of the moisture in the stone4 ,portland stone is the best-wearing stone to be had in the neighbourhood of ,london4 ,bath stone is also considerably used1 but it varies greatly in quality1 and should be very carefully selected4 ,for landing-steps and paving1 ,yorkshire stone is extensively used1 but artificial cement pavings are replacing it to some extent4 ,most kinds of stone can only be economically used near the quarries from which they are derived4 ,the ,slate used for roofs is an altered form of clay1 possessing a laminated structure4 ,the ease with which it splits along the planes1 renders it peculiarly suitable for this purpose4 ,the ,welsh slates are considered the best4 ,terra-cotta is made from certain kinds of clay1 mixed with glass1 pottery or sand2 then ground up1 strained1 and kneaded2 and lastly thrown into moulds and baked in a kiln4 ,iron and ,wood have occasionally been employed alone in building houses4 ,the former1 owing to its good conducting powers for heat1 is cold in winter and hot in summer2 while the latter becomes rotten from exposure to wet1 and is also very combustible4 ,corrugated iron buildings lined with wood are also employed1 but are not very satisfactory4 ,for roofs1 slates or tiles are the materials most frequently employed2 but occasionally lead and corrugated iron are used1 also thatch in country places1 and tarred felt for temporary buildings4 ,lead is the most suitable metallic covering for roofs1 as it is durable and easily worked4 ,it is1 however1 heavy and demands considerable strength in the timbers by which it is supported4 ,galvanized iron has also been largely used4 ,it is cheaper and lighter than lead4 ,both lead and zinc require very careful laying if they are to be weather-tight4 ,thatch protects the interior of a house well from extremes of heat and cold4 ,,chapter ,,xxxii4 ,,construction ,,of ,,the ,,house4 ,in preparing to build a house1 or in entering into a house already built1 the following requisites should each receive careful attention3-- #a4 ,the site of the house should be healthy1 and its relation to surrounding objects in accordance with the laws of health4 7,see page #bja74 #b4 ,the house should be warm in winter1 and cool in summer4 #c4 ,it should be always dry4 #d4 ,there should be an abundant and uninterrupted supply of air4 #e4 ,the water supply should be abundant1 conveniently arranged1 and pure4 #f4 ,the excreta and waste-water should be immediately removed from the house and its annexa4 ,the three last requisites have already received consideration4 ,of those still to be considered1 dryness is the most important4 ,a damp house is certain to be an unhealthy one4 ,it is this for two reasons3--#ast1 it is a cold house1 as damp walls1 like damp clothes1 conduct the heat of the body away much more rapidly than dry walls2 #bnd1 if the pores of the bricks are occupied by water1 air cannot pass through1 and thus the ventilation and purification of the house are greatly impeded4 ,damp may arise from the ground on which a house stands1 or from the rain beating against the walls1 or from a defective roof4 ,unless special means are taken to prevent it1 moisture rises by capillary attraction through brick after brick4 ,the ,foundation requires to be solid and substantial1 otherwise sinking occurs1 with cracking of the walls1 resulting in an unsafe condition1 and an exposure to rain and wind4 ,in making the foundation for a house1 the ground should be excavated1 so as to secure a solid bed of earth or rock not liable to be affected by the weather4 ,a continuous bed of the best cement concrete should then be laid1 not only under the walls1 but covering the entire site of the house1 and extending on every side at least #f inches beyond the footings of the wall2 and for footings it should never be less than #ah inches thick4 ,the concrete serves two purposes3 it1 to a large extent1 cuts off the entrance of the ground-air through the basement floor into the house2 and prevents the entrance of damp into the house from below4 ,to further ensure dryness where the floor is below the level of the adjacent ground1 a dry area is frequently provided1 that is1 a closed chamber lined with stone or cement below the ground level of the house1 and surrounding the underground part of its four walls1 or a hollow wall is built below the ground-level1 as shown in ,fig4 #ch4 ,neither a dry area nor a hollow wall constitutes the best arrangement1 as the cavity is usually inaccessible1 and rather aids than hinders the entry of the ground air into the house4 ,the best plan is to provide a solid wall1 impervious to both moisture and air4 ,a vertical layer of roofing slates is sometimes used for this purpose2 or1 still better1 a narrow cavity about #ab to #cd-;inch wide is provided in the body of the wall1 and this is run full with molten asphalte4 ,the ,walls of the house must be provided with a 8damp-proof course0 carried through their whole thickness1 slightly above the highest point at which the ground is touched4 ,it may be formed by 7#a7 sheet lead1 which possesses the disadvantage of being costly2 7#b7 two layers of ordinary roofing slate1 set in cement1 with broken joints10 i4e4 the joints of the upper layer over the centre of the slates below them2 7#c7 a layer of good asphalte1 about -inch thick2 7#d7 perforated glazed stoneware slabs2 or 7#e7 two or three courses of hard blue ,staffordshire bricks1 laid without mortar4 ,the use of asphalte is an excellent plan1 and is now commonly adopted in good buildings4 ,illustration3 ,,fig4 #ch4 ,,double ,,damp-,,proof ,,course ,,and ,,hollow ,,wall4 a1 a--,damp-proof courses4 b--,level of neighbouring ground4 c--,floor-boards4 d--,floor joist4 f--,vertical space in wall4 g--,concrete under foundation and over site of house4 ,this suffices when there is no basement4 ,if there is a basement an open area around the house is desirable4 ,where for a given wall this cannot be secured1 the vertical damp-proof course already described must be made to extend from the foundations well above the ground level4 ,the open area1 however1 should be insisted on whenever practicable4 ,the damp-proof course protects the walls from damp proceeding from the soil around or beneath the house4 ,it is necessary also that the walls above the level of the ground should1 as far as possible1 be kept free from damp4 ,damp walls1 not due to ascent of moisture1 may be caused by 7#a7 ,rain falling on window-sills which do not project beyond the walls1 and consequently do not throw the water clear of them4 ,this is remedied by constructing the window-sills so as to project beyond the walls1 and 8throating0 them to prevent rain from running along the bottom of the sill4 ,the throat is shown at a1 ,fig4 #ci4 7#b7 ,rain falling on cornices and other projecting portions of the wall itself4 ,the evil from this source may be diminished by sloping the top of the projection1 downwards from the face of the wall4 7#c7 ,parapet walls1 gables1 etc41 not being properly covered with coping4 ,all such walls should be topped with a projecting slab of stone1 or with a damp-proof course under the top course of bricks1 which should be laid on edge4 7#d7 ,overflow from defective roof-gutters or rain-water pipes4 ,in this case1 either clearing out1 repairing1 or renewing is required4 7#e7 ,rain beating against the walls4 ,this as a rule produces no great harm1 if the walls are well constructed4 ,most of the water runs off as it falls on the surface4 ,it is advisable1 however1 to protect a much exposed wall by a coating of ,portland cement1 or in extreme cases with slate4 ,various impervious paints have also been employed4 ,illustration3 ,,fig4 #ci4 ,,section ,,through ,,window4 ,showing stone sill 8weathered0 at i1 and 8throated0 at a4 b--,wall4 c--,inside plaster of room4 d--,window-board4 e--,oak sill4 f--,beading and g--bottom rail of window-sash4 h--,window4 j--,iron tongue let into slot in i and e to prevent rain driving in4 ,if it is not proposed to coat exposed surfaces of brickwork1 the wall may be formed of two parallel walls1 two inches apart1 and tied together by a sufficient number of bonding-ties of iron or glazed stoneware1 or some other non-absorbent material4 ,this arrangement is shown in ,fig4 #dj4 ,an excellent plan is to fill in the narrow space between two such walls1 as the building proceeds1 with asphalte or slab slate1 thus forming a vertical damp course1 in the same way as below the ground level4 ,the evils arising from damp can be avoided in every new house by proper methods of construction4 ,in an old house1 however1 they are much more difficult to remove4 ,the dampness is indicated on entering1 by a peculiar mouldy smell1 and by the discolouration and destruction of wall-papers1 and dry rotting of floor timbers4 ,in such a case a damp course may1 with care and patience1 be inserted in the wall1 and the soil under the basement may be covered with concrete1 and a dry-area excavated around the basement4 ,free ventilation under the floor-boards of the lower floors also helps in keeping the house dry4 ,illustration3 ,,fig4 #dj4 ,,showing ,,hollow ,,wall ,,and ,,bonding-,,ties ,,of ,,glazed ,,stoneware4 a--,cavity4 b--,tie4 c--,floor-joist4 d--,wall-plate4 e--,concrete foundation of wall4 ,the thickness of the walls of a house requires to be sufficient to ensure stability1 to keep out the damp1 and to prevent a too rapid loss of heat from the walls4 ,the relative merits of the different materials employed for these purposes have been already considered4 ,a thin-walled house is hot in summer1 and cold in winter4 ,the upper stories of houses are often built with too thin walls1 the result being chilly bedrooms4 ,a single-brick wall 7#i inches thick7 will rarely keep out the weather effectually1 and frequently a brick-and-a-half wall 7#ad inches thick7 is insufficient for this purpose4 ,the bricks should be so interlaced as to 8bond0 or tie the wall together in all directions4 ,the strength of walls may be increased by the introduction of hoop-iron between the courses of brickwork4 ,in the construction of fire-places and chimneys1 it is important to avoid the proximity of timber and wood-work to the inside of flues1 as this is a common cause of fires4 ,inside ,coverings of ,walls4 ,plaster is made of lime mortar1 or cement mortar2 the former is generally preferred for domestic dwellings because it remains porous and moisture does not condense on it4 ,in houses built by speculative builders1 the plaster commonly used consists of a mixture of lime with road scrapings4 ,the result is a composition which unless supported by the wall-papering1 is soon damaged4 ,ordinary plaster consists usually of three layers4 ,the first is laid on with a mixture of about equal parts of lime and sand with long ox-hairs if required for ceilings4 ,the second coat consists of slaked lime1 mixed to the consistency of cream4 ,the last or setting coat consists of a thin layer of slaked lime called plasterers' putty4 ,some plaster of ,paris 7gypsum7 may be added1 to ensure rapid setting1 but it should only be used in small quantities4 ,for the internal plastering of rooms serapite 7a form of cement7 is now commonly employed4 ,this is not so absorbent as mortar1 but is sufficiently so to prevent condensation of moisture on the walls4 ,its chief advantage over plaster is that it hardens quicker and is smoother1 and can be used in a single thin layer4 ,this1 however1 diminishes the impermeability of ceilings for sound4 ,keene's cement and ,parian cement are mixtures of calcined gypsum and other substances2 ,keene's cement being the hardest1 and capable of receiving a high polish4 ,selenitic cement contains a small proportion of plaster of ,paris ground along with lime4 ,lime may also be selenised by the addition of any other sulphate1 or of sulphuric acid4 ,the presence of the sulphate causes the lime to set rapidly4 ,selenitic cement is useful in plastering1 as a backing of cements1 such as ,parian4 ,the treatment of the internal wall-surface of a room differs according to circumstances4 ,lime-washing is suitable only for stables and other outbuildings4 ,it is made by the addition of water to quicklime1 no size being added4 ,it is an excellent germicide and insecticide4 ,whitewashing is quite different from limewashing4 8,whiting10 i4e4 finely-ground chalk1 to which a certain proportion of size and alum had been added is mixed with water4 ,the size and alum are added to prevent the whitewash from being rubbed off4 ,distempering is identical with whitewashing1 except that pigments are added4 ,it is distinguished from painting in oils1 by the fact that the pigments are mixed with size1 instead of with linseed-oil and turpentine4 ,painting in distemper is practically limited to plaster1 which should first receive a coat of whitewash to diminish its porosity4 ,oil-paints are impervious1 distemper is as absorbent as plaster or whitewash4 ,various washable distempers1 as duresco1 are made1 which are more durable and non-absorbent4 ,water-glass consists of silicate of potash1 which in the gelatinous form is soluble like size in hot-water1 but when allowed to dry forms an impervious film4 ,it can be used for protecting porous stone from the effects of weather2 and renders internal surfaces of walls non-absorbent and washable4 ,oil-painting renders wall-surfaces impervious1 and enables them to be easily washed4 ,the importance of this in the event of any infectious disease occurring1 is obvious4 ,the question arises whether distempered or papered walls1 which are porous1 or painted walls1 which are non-porous1 are preferable from the standpoint of health4 ,the difference between the two is seen during damp weather1 when moisture condenses and runs down the latter and is invisible in the former4 ,in practice in domestic dwellings the former are preferred2 but although some advantage is thus secured in ventilation through the wall-substance1 there is the serious disadvantage that particles of dirt accumulate and may seriously interfere with the purity of the air of a room4 ,hence the importance of rubbing down the internal surface of a room1 whether distempered or papered1 at intervals with bread crumb or dough 7see page #ccb74 ,this effectually removes all accumulations of dirt4 ,a painted wall presents the enormous advantage that it can be frequently washed2 while the loss of ventilation may be ignored1 if windows and doors be properly utilised for this purpose4 ,the presence of poisonous pigments in oil-paints is of importance to the workman1 but not to the householder except during the painting1 as paint1 unlike distemper1 does not rub off the wall4 ,lead is the chief poison present1 as white lead 7carbonate of lead74 ,various substitutes for lead paints have been introduced4 ,painting wood or iron-work is valuable1 not only as a preservative from the effects of the weather and the oxidising action of the air1 but also because it tends1 to a large extent1 to prevent the absorption of organic matters2 and its surface can be frequently cleansed4 ,paper is the material most commonly employed for covering walls4 ,it is more absorbent and retentive of moisture than distemper4 ,light-coloured papers should be chosen1 as they are more cheerful1 and are not so likely to harbour dust4 ,glaring patterns are objectionable1 as they tire the eyes4 ,the paper should not present any surface-projection for the lodgment of dust4 ,in bathrooms and water-closets1 the wall-surface should be non-absorbent4 ,paper1 unless varnished1 should therefore be avoided4 ,the best covering for these places is glazed tiling1 or painted cement4 ,not uncommonly1 a new paper is pasted over an old one2 and this may be repeated several times4 ,under these circumstances dangerous dirt accumulates4 ,before new papering is put on1 the walls should be cleared of all vestiges of the old1 thoroughly washed down1 and subsequently coated with size 7that is1 8clear coloured074 ,the sizing diminishes the absorptive power of the wall1 and gives a good surface for applying the paper4 ,bed-room papers require to be more frequently changed than those of other rooms4 ,bed-rooms in regular use should be re-papered at least every two years4 ,it is still better to use distemper for such rooms1 as this can be washed off in a few hours with comparatively little expense1 and can be made of any tint desired4 ,rooms in the basement should not be papered1 as the walls require frequent washing down and cleaning4 ,here also a washable distemper colour can be used4 ,various kinds of sanitary paper are now sold which are washable1 and relatively non-absorbent4 ,some of them require varnishing2 others do not4 ,such papers are certainly cleaner than ordinary paper2 but it would not be safe to trust to their non-absorptive character4 ,lincrusta ,walton is non-absorbent1 and can be scrubbed with soap and water2 but it is expensive4 ,other cheaper materials possessing the same properties can now be bought4 ,arsenic in ,wall-,papers and ,paints has until a few years ago been a not uncommon source of prolonged ill-health--the cause of which has possibly not been detected until the illness disappears1 when the offending room is vacated for a period4 ,arsenical pigments are now only rarely used for wall-papers4 ,the symptoms produced vary greatly1 and may closely simulate those of different diseases4 ,in some cases repeated attacks of diarrha and abdominal pain occur4 ,or there may be nausea1 headache1 frequent griping pains1 and loss of appetite4 ,in other cases restlessness1 loss of sleep1 and general malaise are the chief symptoms1 with the occasional addition of conjunctivitis 7superficial inflammation of the eye74 ,out of #ajj cases collected and reported on by a ,committee of the ,medical ,society of ,london1 diarrha1 nausea1 and intestinal mischief occurred in #he2 severe depression in #af2 conjunctivitis in #ai2 and cough1 asthma1 etc41 in #i4 ,the severity of the symptoms produced will vary with the amount of arsenic contained in the paper1 and the length of time daily that the patient is exposed to the fumes4 ,some persons again are much less susceptible to the influence of arsenic than others4 ,this will explain why some escape while occupying the same room in which others suffer severely4 ,more commonly1 however1 the exemption is due to shorter exposure4 ,the most dangerous preparation occasionally employed in wall paper printing is ,scheele's green 7arsenite of copper74 ,emerald-green--an aceto-arsenite of copper--is sometimes used to produce more delicate tints4 ,aniline dyes1 especially the red1 may contain much arsenious acid 7white arsenic74 ,the arsenic compound is made to adhere to the paper by size or some other material4 ,when dry1 it cracks and peels off1 and minute particles get into the air as dust4 ,in addition1 arsenic compounds easily volatilise1 and become diffused in a gaseous condition throughout the atmosphere of a room1 even when its temperature is not greatly raised4 ,the virulence of the arsenical colouring is in proportion to its volatility4 ,arsenic seems to be much more dangerous when associated with size4 ,it has been shown that a mixture of white arsenic and starch paste1 or other organic substance1 leads to the formation of gaseous arseniuretted hydrogen1 while this does not occur when no organic matter is present 7,dr4 ,fleck74 ,distemper frequently contains arsenic1 and as it also contains size1 arseniurretted hydrogen is liable to be given off at any time4 ,size is largely used for fixing colour2 thus1 the proper conditions for the development of arseniurretted hydrogen--the most dangerous compound of arsenic--are present4 ,as much as #ag grains of arsenic have been discovered in each square foot of a wall-paper4 ,now1 arsenic is sometimes given internally for certain skin and other diseases1 but the dose is only from #afj to #aab grain2 the capacity for poisoning of such a paper as the above will therefore be evident4 ,papers of other colours than green have been found to contain dangerous quantities of arsenic2 thus blue1 mauve1 red1 and brown may contain large quantities2 the delicate greys often yield a considerable amount1 and some white papers are heavily loaded with it4 ,arsenic is occasionally present in stockings and other wearing apparel1 artificial flowers1 toys1 etc4 ,in these cases1 it may produce irritation of the skin1 and even eczema4 ,the presence of arsenic may be detected by the following tests3-- 7a7 ,reinsch's test4 ,a portion of the suspected paper 7two or three inches square7 is cut into small pieces1 and placed in a good-sized test tube2 water is added until the tube is about a third full and then one or two teaspoonfuls of pure hydrochloric acid1 and a small piece of pure copper foil4 ,if the test tube is now heated for a few minutes over a spirit lamp1 arsenic1 if present1 will be deposited as a black or dark steel-coloured coating on the copper4 ,a mere tarnish of the copper must not be accepted as evidence of the presence of arsenic1 but an almost complete obliteration of the colour of the copper4 7b7 ,take the copper covered with arsenic1 dry it1 and then heat it in a perfectly dry test tube4 ,crystals of white arsenic1 which may be identified under the microscope1 will be deposited higher up in the tube4 7c7 ,marsh's test4 ,the ordinary apparatus for developing hydrogen by the action of diluted sulphuric acid on zinc is employed1 the suspected paper being inserted in the bottle4 ,the hydrogen coming off is burnt1 and a clean porcelain surface is applied to the flame4 ,if there is arsenic in it1 it is deposited on the porcelain in a black patch4 ,windows are required to open directly into the external air in every habitable room4 ,the window area according to the model bye-laws of the ,local ,government ,board and the ,london ,buildings ,act of #ahid1 must be at least one-tenth of the floor area1 and half of this at least must be made to open4 ,the following rules have also been given4 7,b breadth1 ,l length and ,h height of room47 ,area of window 7,b ,l7_/#aj ,london ,building ,act 7,b ,l ,h7_/#ajj ,gwilt 7,b ,l ,h7 ,morris ,in a room measuring #ae #bj #ab feet1 the preceding rules would give a superficial area of window space of #cj1 #cf1 and #fj square feet respectively4 ,plate glass dissipates heat less quickly than sheet glass4 ,objection may be taken to plate glass windows1 in passing1 especially for shops1 banks1 etc41 in view of the fact that they are commonly made without any arrangement for ventilation 7see also page #adh74 ,the hygienic necessities of ,floors are that they shall be impervious to moisture and to dust4 ,on the ground floor the ordinary arrangement is to provide a joisted and boarded floor raised about a foot above the ground4 ,dry rot is one of the dangers in connection with such boarded floors on the ground floor4 ,the chief causes which tend to induce rotting1 are damp walls1 lack of ventilation1 contact with mortar1 damp earth1 or vegetable mould1 and worst of all1 alternations of damp and dryness1 or wet along with heat4 ,in order to avoid these dangers in connection with boarded floors1 the ends of all timbers resting on walls should have a clear air-space around them1 and communicate with the external air by means of perforated bricks4 ,the larger timbers1 girders1 etc41 should rest on stone templates1 and the smaller joists on hoop-iron bonds4 ,in all cases1 the timber used should be well seasoned1 and properly ventilated4 ,the ends of oak posts1 which are to be driven into the ground1 should be charred1 if the timber is old1 or steeped in a solution of chloride of zinc4 ,the ends of the joists should be trimmed1 so as not to come too near to chimney flues4 ,the best plan for flooring is to place an impervious flooring resting on the solid ground4 ,this is more secure against rot than the boarded floor1 and affords no space for dirt and vermin to lodge4 ,such an impervious floor may be formed of concrete over a layer of asphalte1 as in the well-known terrazzo flooring4 ,this is very suitable for corridors1 pantries1 etc4 ,for living-rooms wood-block flooring is placed over the cement1 molten pitch connecting the two4 ,the blocks are #b to #c inches thick4 ,if the wood is soft1 as deal1 it must be kept clean by washing2 if hard1 as oak or teak1 it can be wax-polished4 ,parquetry consists of small pieces of hard woods carefully fixed and polished4 ,for upper floors the ordinary flooring is of floor-boards supported on wood joists1 beneath which are wood laths and plaster4 ,the floor-boards should be thoroughly seasoned1 otherwise they will shrink1 and the joints be filled with dirt4 ,this dirt may accumulate for years between the floor and the ceiling of the room below1 vitiating the air and helping to increase the stuffiness characteristic of dirty houses4 ,various plans are adopted for uniting the edges of floor-boards and preventing dust from dropping between the boards4 ,illustration3 ,,fig4 #da4 ,,tongued ,,floor4 ,the one most commonly employed is the ploughed and tongued floor 7,fig4 #da74 ,in this1 both edges of the floor are grooved so as to receive strips or tongues of iron or wood1 an equal half of each strip being in the groove of each of two boards when they are in place4 ,a less expensive method than the above is to splay the ends of the boards so that they slightly overlap each other4 ,this is not so efficient as the above1 but is much better than simply placing the boards side to side as is commonly done4 ,solid wood floors resting on a bed of concrete are free from the risk of harbouring dust1 and are relatively fire-proof4 ,oak or teak in narrow boards1 made with close joints1 and then oiled and beeswaxed and rubbed to a polish1 makes a good and almost non-absorptive floor4 ,one of the best floors is made of concrete1 with iron joists1 and oak boards laid above this4 ,carpets are commonly made to cover the entire floor of rooms4 ,this cannot be too much deprecated4 ,carpets1 like curtains1 are mere dirt-traps1 which become loaded with filth of every description4 ,this is abundantly proved when a carpet is swept1 and the dust allowed to settle on all the articles in the room4 ,such dust1 if examined1 will be found to consist not only of mineral matter1 but also of every description of vegetable and animal impurities4 ,the inhalation of such dust1 which may contain particles of fcal matter1 as well as the dried expectoration from consumptive or other infectious patients1 is a not infrequent cause of infection to healthy persons4 ,the substitution of a central carpet1 for one covering the entire floor1 is a great improvement4 ,the carpet should be easily removable1 in order that it and the floor may be thoroughly cleaned at intervals4 ,in bedrooms1 the less carpet the better4 ,good ,chinese or ,indian matting is serviceable1 as it does not retain the dust and other impurities which are apt to become fixed in the woolly texture of the carpet4 ,oil-cloth1 linoleum1 and similar materials are in common use for covering halls1 passages1 etc4 ,they are particularly useful in preventing dust from gaining access to the spaces between floor-boards4 ,the prevention of dust should be the great aim of the householder1 as dirt frequently carries infection4 ,sweeping as ordinarily done scatters dirt over the room1 and dusting with a dry cloth fails to remove it4 ,mechanical sweepers1 in which the dirt is collected in a box are valuable4 ,the best plan is to have movable carpets1 roll them up for shaking or beating at a distance from any house1 and wipe the boards with damp cloths4 ,all wooden and leather furniture1 picture frames1 etc41 should be wiped down with cloths rung out of water so as to be just damp4 ,,chapter ,,xxxiii4 ,,the ,,soil4 ,the ,varieties of ,soil4--,the following facts summarise what is regarded as the relative healthiness of various sites for dwellings4 ,the differences between different sites may1 however1 be reduced to a minimum by having the dwelling well above the ground-level and by protecting it from dampness4 #a4 ,granitic1 ,metamorphic1 and ,trap ,rocks usually form healthy sites for houses4 ,the slope is generally great1 and the ground consequently dry4 #b4 ,clay ,slate resembles the last in its effects on health4 ,water is1 however1 often scarce1 owing to the impermeability of the rocks1 and for the same reason occasional floods occur4 #c4 ,limestone and ,magnesian ,limestone ,rocks resemble the last in possessing considerable slope1 so that the water passes away quickly4 ,the hard oolite is the best formation under this head1 and magnesian limestone the worst4 #d4 ,chalk is a healthy soil when unmixed with clay1 and permeable4 ,goitre is not so common as in limestone districts4 ,if the chalk be mixed with clay1 it is often damp and cold4 #e4 ,the ,sandstones are healthy1 soil and air being dry4 ,if mixed with clay1 or if clay lie under a shallow layer of sand-rock1 the site may be damp4 ,the hard millstone grit is a healthy formation4 #f4 ,gravels of any depth are healthy1 unless they are water-logged1 as near rivers4 ,then a house on impervious clay may be drier than one on gravel4 #g4 ,sands are healthy when of considerable depth2 they may be unhealthy when shallow1 and lying on a clay basis2 or when the ground water rises through them from ground at a higher level4 #h4 ,clay1 ,dense ,marls1 and ,alluvial ,soils generally1 are apt to be cold and damp4 ,water is retained in them1 and is often very impure4 ,thorough drainage improves a clay soil1 and a house on a clay soil may be so constructed1 as not to be damp4 #i4 ,cultivated ,soils are not necessarily unhealthy2 but #aj4 ,made ,soils are always to be carefully avoided1 as sites for houses4 ,the materials with which inequalities have been filled up are commonly the contents of dust-bins1 or some other refuse4 ,the gradual putrefaction of organic matters renders the air about the houses impure4 ,such soils require free subsoil drainage1 in order to keep them dry4 ,it appears that the organic matters in soil are gradually removed by oxidation and bacterial purification4 ,at least three years should be allowed before any such site is built on4 ,the following table places different geological formations in their order of healthiness for the purposes of a site 7,parkes73-- ,,permeability ,,emanations ,,of ,,water4 ,,into ,,air4 #a4 ,primitive rocks1 clay slate1 millstone grit ,slight4 ,none4 #b4 ,gravel and loose sands1 with permeable subsoils ,great4 ,slight4 #c4 ,sandstones ,variable4 ,slight4 #d4 ,limestones ,moderate4 #e4 ,sands with impermeable subsoil ,arrested by ,considerable4 subsoils4 #f4 ,clays1 marls1 alluvial soils ,slight4 ,considerable4 #g4 ,marshes1 when not peaty ,slight4 ,considerable4 ,the general geological conditions have an important bearing on the choice of a site for a house in so far as they affect the local climate1 and the difficulty of keeping the house warm and dry4 ,pettenkofer expressed this in his dictum1 that we take holiday for change of soil1 rather than for change of air4 ,the character of a soil has an important influence on humidity1 radiation1 evaporation1 and in fact most of the factors going to make up 8climate40 ,the immediate local surroundings of a house 7page #bja7 have an even greater influence on its salubrity than the underlying geological formation4 ,the soil consists of mineral and organic matters4 ,on the amount and character of the animal and vegetable matters 7along with the condition of moisture and aeration71 the healthiness of a given soil depends4 ,the presence of vegetable matter1 subject to alternate wettings and dryings1 and to heat1 has until recently been regarded as the condition on which malaria depends2 but it is now known that malarial places owe their character to their being favourable to the growth of the larv of certain mosquitoes 7page #cjg72 and that drainage of the soil cures malaria by removing the ponds in which these develop4 ,the two chief agencies at work to rid the soil of organic impurities1 are nitrification and the influence of growing plants4 ,the organic matters become oxidised into ammonia1 nitrites1 and nitrates1 and these are eagerly assimilated by vegetation4 ,nitrification is effected by micro-organisms in the soil4 ,ordinary garden mould and agricultural humus contain large numbers of micro-organisms4 ,their number diminishes with the depth of the soil1 and below #ab to #ae feet there are few4 ,apart from the occasional presence of pathogenic 7disease-producing7 micro-organisms1 the most important are those producing oxidation of organic matter1 especially nitrification4 ,this occurs at a less depth than #d feet from the surface of the ground4 ,the operation of these micro-organisms is necessary to convert sewage and other impurities into harmless nitrites and nitrates1 and it is regularly going on in all normal soils4 ,that the power of purification of sewage by soil is due to the micro-organisms in the latter1 can be proved by the fact that when the soil is baked1 it loses for a time its purifying power4 ,the ,air contained in the ,soil varies greatly in amount with the character of the soil1 and with the level of the ground-water4 ,as the ground-water rises1 the ground-air is driven out4 ,thus1 after a heavy rainfall a large proportion of this air will be displaced4 ,variations in barometric pressure1 and a rise or fall of temperature1 cause movements in ground-air4 ,a house artificially warmed is liable to receive air from underground1 unless means are adopted to make the floors impervious4 ,the warmth of the house acts as an air-pump1 aspirating the colder air into its interior4 ,the air from cesspools or defective drains may be similarly aspirated into the house2 and the same cause particularly explains the unhealthiness of houses built on 8made soils04 ,coal gas has occasionally made its way into houses when not laid on to them1 by the gas escaping from leaky pipes in the street often following the track of water or drain-pipes until it is aspirated from beneath the house into its interior4 ,this has resulted in one instance in an explosion1 and in others in poisoning by the gas4 ,illustration3 ,,fig4 #db4 ,the occurrence of currents of air in soil may be illustrated by a simple experiment4 ,in ,fig4 #db ,b is filled with fine sand in which is imbedded the tube ,a with its open end ,f at the bottom of the sand ,c4 ,the upper end of ,a is connected by the rubber tubing ,d with the ,u-shaped tube ,e1 in which is inserted some coloured water4 ,when the experimenter blows on the surface of the sand at ,a1 the impulse passes through the sand up the tube from ,f1 and deflects the water in the syphon bend at ,e4 ,the amount of ground-air varies greatly4 ,loose sands often contain #dj to #ej per cent41 soft sandstone #bj to #dj per cent41 and loose surface-soil many times its own volume4 ,the nature of the air is not accurately known4 ,it is1 however1 extremely rich in carbonic acid1 of which it contains from #a to #aj per cent4 or even more4 ,the carbonic acid is derived from the organic matter in the soil1 by the action of bacteria1 in a manner analogous to nitrification4 ,the ,water contained in the ,soil is divided into moisture and ground or subsoil-water4 ,when air is present in the soil as well as water1 the soil is merely moist4 ,pettenkofer defines the ground-water as that condition in which all the interstices are filled with water1 so that1 except in so far as its particles are separated by solid portions of soil1 there is a continuous sheet of water4 ,the ,moisture in the soil varies in amount4 ,open gravel will absorb from #i to #ac per cent4 by weight of water2 gravelly surface soil #dh per cent42 light sandy soils from #bc to #cf per cent42 loamy soil #dc per cent42 stiff land and clay soils from #dcc to #egf per cent42 sandy and peaty soils from #fae to #hj per cent42 peat #ajc per cent4 7,b4 ,latham74 ,the moisture being derived from the rainfall on one side1 and the ground-water on the other1 will vary with the amount of these4 ,some soils are practically impermeable to water1 such as trap or metamorphic rocks1 unweathered granite1 hard limestone1 and dense clay2 while others1 such as chalk1 sand1 sandstone1 vegetable soils are permeable4 ,commonly the metamorphic rocks and hard limestones present fissures1 which render them pervious4 ,the rainfall which does not penetrate the soil flows into the streams and rivers at once1 or is re-evaporated4 ,the amount of percolation of rainfall is estimated by an artificial soil-gauge4 ,most percolation and least evaporation of rainfall occurs from ,october to ,march inclusive4 ,the difference between the percolation and rainfall is the loss caused by evaporation and vegetation4 ,the ,ground-water forms a subterranean sheet of water1 which is in constant motion4 ,there is first of all1 an irregular rise and fall of the water1 according as it receives new additions from the rainfall1 or loses a certain amount of its substance by percolation and evaporation2 and there is1 secondly1 a constant movement towards the nearest water-course or the sea4 ,many towns derive their drinking-water from the ground-water1 especially that in the chalk4 ,thus in ,brighton there are no streams2 but wells are dug in the ,south ,downs about #aej to #ahj feet deep down to the level of the subterranean water4 ,then long adits are tunnelled1 parallel to the coast at or near the level of this water1 which is thus intercepted on its way towards the sea1 and pumped up to supply the town4 ,in ,munich1 ,pettenkofer reckoned the rate of movement of the ground water towards the outlet as #ae feet daily4 ,it is impeded by impermeability1 or a deficient slope of the soil4 ,the roots of trees also greatly impede its flow4 ,the level of the ground-water is constantly changing 7see ,fig4 #g74 ,the alteration in level may be only a few inches either way1 while in some parts of ,india it is as much as #af feet4 ,the level is generally lowest in ,october and ,november1 highest in ,february and ,march4 ,a fall in the level of the ground-water may be due to a dry season1 or to improved subsoil drainage4 ,a rise in its level is due to an increase in the rainfall1 or some obstruction in the outflow1 as from a swollen river4 ,the tide may influence the level of the ground-water at a great distance4 ,a sudden alteration in the level of the ground-water is a common cause of floods in mines4 ,the distance of the ground-water from the surface may be only two or three feet1 or several hundred feet1 the difference being due to the varying level of the nearest impervious stratum of soil4 ,its distance below the surface of the soil can easily be measured by ascertaining that of the water of a shallow well in the neighbourhood4 ,it should preferably not be nearer the surface than five or six feet4 ,sudden changes in the level of the ground-water from inundations render any soil unhealthy1 and are even more objectionable than a persistently high level4 ,this is especially true in the case of permeable soils4 ,a sudden rising of ground-water expels the air in the soil1 together possibly with particles which may comprise infectious material2 it also washes similar impurities out of the subsoil1 and carries them into neighbouring wells4 ,numerous epidemics have been traced to this source4 ,the ,temperature of the ,soil varies greatly with its geological character1 as well as with the temperature of the atmosphere4 ,the daily changes in the temperature of the atmosphere do not affect the soil beyond a depth of about three feet4 ,the annual changes in the atmosphere will affect the soil in a varying degree1 the amount being dependent on the character of the soil as regards conductivity and retentiveness for heat4 ,such annual variations do not penetrate below forty feet1 and are very small below twenty-four feet4 ,the temperature of the earth increases with its depth1 the rate of increase in ,england being stated to be about #a ,fahr4 for every #ed feet4 ,in ,england the water of permanent springs has a fairly constant temperature of #di to #ea ,fahr41 which is the temperature of the deeper part of the subsoil4 ,the method of taking the daily temperature of the subsoil at a depth of #d feet is described on page #bdj4 ,although the average temperature of any soil depends on the climate1 soils conduct heat in a very varying degree1 and therefore absorb unequal quantities4 ,this has an important bearing on the comfort of those living on a particular soil4 ,schbler's experiments give the absorbing power of the chief kinds of soil1 #ajj being taken as the standard4 ,sand1 with some lime #ajjj ,pure sand #ief ,light clay #gfi ,gypsum #gcb ,heavy clay #gaa ,clayey earth #fhd ,pure clay #ffg ,fine chalk #fah ,humus #dij ,it is evident from this table that sand is very retentive of heat1 while clays and humus are very cold4 ,green vegetation lessens the absorbing power of the soil1 and radiation of heat is more rapid1 evaporation occurring constantly from the herbage4 ,the influence of trees on the temperature of the soil is considered on page #bbh4 ,damp soils are colder than dry soils because of the evaporation going on4 ,buchan finds as the result of drainage of the soil1 that 7#a7 the mean temperature of arable land is raised #jh ,fahr42 7#b7 cold is propagated more quickly through undrained land2 7#c7 drained land loses less heat by evaporation2 7#d7 the temperature of drained land is more equable1 and 7#e7 in summer is often #ae to #c above that of undrained land4 ,,diseases ,,arising ,,from ,,the ,,soil4--,the soil may be a cause of disease3 7a7 indirectly and 7b7 directly4 ,indirectly a damp soil may cause disease by acting as a means of lowering the vitality of man and diminishing his resistance to disease4 ,it is in this way that it has been credited with causing such diseases as neuralgia1 catarrhs1 and rheumatism4 ,it is one of the elements in producing a climate unfavourable to health4 ,as to rheumatism1 see page #bbe4 ,directly the soil may transmit the actual contagia 7micro-organisms7 of disease either by means of the subsoil water or its air4 ,in the former case the disease-causing material gains access to the drinking water of wells1 springs1 or rivers2 in the latter case it may be borne to the surface of the soil by currents of the ground-air or by insects1 and then inhaled as dust1 or gain access to food4 ,certain disease-producing micro-organisms have been proved to be capable of living for some time in the soil4 ,the chief of these found in the soil are the bacilli of tetanus 7lockjaw71 of anthrax1 of malignant oedema1 and of enteric 7typhoid7 fever4 ,there are reasons for thinking also that the micro-organisms causing diphtheria1 rheumatic fever1 and epidemic diarrha1 and possibly some other diseases1 may occasionally live in the soil4 ,in some diseases as enteric fever1 cholera1 dysentery and anthrax1 the contamination of the soil can be shown to be derived from a patient suffering from the same diseases4 ,in others1 and particularly in tetanus1 the same chain of evidence is obtainable4 7#a7 ,the conditions favourable to the production of malarial diseases have been generally considered to be the presence of a certain proportion of dead organic matter1 the exposure of the soil to alternations of heat and moisture1 with a limited access of air1 and a temperature of at least #fe;,f4 ,though most common in marshy districts1 and in recent alluvial soils1 malaria may develop in connection with any geological formation4 ,that it may be removed by drainage of the subsoil1 is well known4 ,the true nature of the connection between soil and malaria is stated on page #bbj4 7#b7 ,according to observations made by ,pettenkofer in ,munich1 attacks of enteric 7typhoid7 fever are connected with fluctuations of the subsoil-water4 ,he states his conclusions as follows3-- 8,between the fluctuations of subsoil water and the amount and severity of enteric fever there is an unmistakable connection in this wise1 that the total number of cases of and deaths from enteric fever falls with a rise of the subsoil water1 and rises with fall of it2 that the level reached by the disease is not in proportion1 however1 to the then level of the subsoil water1 but only to the variation in it on each occasion2 or in other words1 that it is not the high or low level of the subsoil water that is decisive1 but only the range of fluctuation40 ,his observations have not been confirmed in this country2 and the coincidence between excess of enteric fever and lowness of ground-water has been explained by the fact that under these circumstances the water in wells is low1 and the area of drainage and the consequent risk of contamination are proportionately increased4 ,there can be no doubt that the most common origin of enteric fever is from the infection of water or milk by infective matter from a recent case of the disease4 ,this does not exclude the fact that enteric fever in this country is more prevalent in hot dry autumns1 in which the ground-water is low4 ,probably under such conditions the contagium of the disease multiples more rapidly in the soil1 in privies and other polluted places1 and consequently the risks of infection of water and food as well of infection by dust carried from the contaminated spot are greatly increased4 7#c7 ,in regard to cholera1 ,pettenkofer holds similar views4 ,he believes that the contagium of cholera can only be developed when there is a damp porous subsoil to receive the infected stools from a cholera patient2 the damp porous subsoil forming a second host in which the poison of cholera must pass through one stage of its existence1 before it is again capable of producing the disease4 ,such an essential relationship of the soil is not borne out by observations in ,india2 and in ,england cholera has been repeatedly shown to be due to contamination of food 7e4g4 oysters7 or water by the stools of preceding cholera patients1 without the intervention of any agency of the soil4 7#d7 ,it has been repeatedly stated that a damp soil favours the prevalence of diphtheria4 ,i have shown elsewhere1 however1 that this is not true1 and that the greatest epidemics of diphtheria have occurred in exceptionally dry years1 especially when several years of exceptionally small rainfall have succeeded each other2 and have suggested that this may be associated with an intermediate stage in the life-history of the diphtheria-bacillus in the soil4 ,a low ground-water and a comparatively high temperature of the soil go along with deficient rainfall1 and would probably favour the multiplication of this bacillus in the soil4 7#e7 ,in rheumatic fever ,i have similarly shown that the supposed connection between damp soil and this disease is erroneous1 the disease being most prevalent1 both in this and other countries1 in years of exceptional drought4 7#f7 ,epidemic or ,summer ,diarrha has been supposed to have a special relationship with soil-temperature1 ,ballard having found that the summer rise in the mortality from this disease does not commence until the mean temperature recorded by the four-foot earth thermometer has attained somewhere about #ef;,f4 ,the soil-temperature may be accepted as a convenient index of the conditions causing this disease4 ,the disease ,i have elsewhere shown occurs most severely with a high temperature of the air and a deficient rainfall1 and its fundamental cause is an unclean soil1 the particulate poison from which infects the air1 and is swallowed most commonly with food1 especially milk4 7#g7 ,the close connection of consumption 7phthisis7 with a damp soil has been independently stated by ,drs4 ,buchanan and ,bowditch4 ,buchanan found that in the districts where improved sanitary arrangements had led to a drying of the soil1 the death-rate from phthisis diminished2 but where with sanitary improvements the soil was not dried1 the death-rate from phthisis remained in one or two instances almost stationary4 ,in ,salisbury1 ,ely1 ,rugby1 and ,banbury1 the death-rate from phthisis fell from #ada to #di per cent4 ,the amount of reduction in the death-rate from phthisis did not appear to be consistently proportional to the amount of drying of the subsoil4 ,in a later investigation into the incidence of deaths from phthisis in the south-east of ,england1 ,buchanan came to the further conclusions that 7a7 there was less phthisis among populations living on pervious soils than among populations living in impervious soils2 7b7 less phthisis among populations living on high-lying pervious soils than among populations living on low-lying pervious soils2 and 7c7 less phthisis among populations living on sloping impervious soils than among populations living on flat impervious soils4 ,he1 therefore1 concluded that wetness of soil is a cause of phthisis to the population living upon it4 7,see also page #cac74 ,drainage of the ,soil4--,there are two chief plans for rendering the soil drier--deep drainage and opening the outflow4 ,subsoil ,drainage should always be carried out by drains1 separate from those for sewage4 ,if the sewers are utilised for this purpose1 their contents when full contaminate the surrounding soil4 ,the subsoil drains should be composed of agricultural1 i4e4 unglazed1 drain-pipes laid in towns in the same trench1 but above the sewers1 and they should discharge into the nearest water-course4 ,if it is necessary to join them with a sewer1 they should not pass directly into it1 but into a disconnecting man-hole4 ,opening the ,outflow1 in order that water may not remain stagnant in the soil1 is occasionally required4 ,this may be done by clearing water-courses1 removing obstructions1 and forming fresh channels4 ,the provision of sufficient surface-drains to carry off ordinary water and storm-water helps in drying the soil of urban districts4 ,vegetation tends to diminish dampness of soil by causing rapid evaporation1 and at the same time uses up the organic matter in the soil4 ,certain plants are more active in producing these effects than others3 the ,eucalyptus genus1 including many species1 and represented by the well-known blue-gum tree of ,australia1 is noted for its power in this respect2 and the common sun-flower1 which is very easy of cultivation1 has a powerful influence in the same direction4 ,,chapter ,,xxxiv4 ,,climate ,,and ,,weather4 ,the ,climate of a country has an important influence on the health and character of its inhabitants4 ,the character of a climate depends on four main conditions3-- #a4 ,the distance from the equator4 #b4 ,the height above the sea4 #c4 ,the distance from the sea4 #d4 ,the prevailing winds4 ,there are other conditions which are of subsidiary importance1 but which have great influence in modifying the climate of any given locality4 ,thus3-- #e4 ,the nature of a surface--its aspect1 shelter1 slope2 the colour of the soil or rock1 the reflection from rocks or sheets of water1 and the influence of vegetation4 #f4 ,the cultivation of the soil4 #g4 ,the drainage of marshes and damp soils4 #h4 ,the planting and clearing away of forests4 ,the ,distance from the ,equator is the most important factor in relation to climate4 ,the sun's rays become less powerful as they fall more obliquely1 in travelling from the equator4 ,this primary factor in producing climate is largely modified1 however1 by the relative distribution of land and water1 and by the character of the prevailing winds of a district4 ,the ,elevation of a locality affects the temperature and the barometric pressure1 both falling as the height is increased4 ,the amount of fall varies with the latitude of the place1 with its situation in regard to surrounding districts1 the degree of moisture of the air1 the presence of winds1 the hour of day1 and the season of the year4 ,it is usual to allow #a ,fahr4 for every #cjj feet of ascent above the level of the sea1 and one-thousandth part of an inch depression of the barometer for every increase of one foot in height4 ,hills1 ,plain and ,valley4--,the law of decrease of temperature with increase of altitude1 is liable to great modifications1 and even subversions1 from various causes4 ,the chief cause producing such modification of the law is the elevation in relation to the surrounding district4 ,thus1 in the case of rising ground1 the higher parts become rapidly cooled by radiation4 ,the air here is likewise cooled by contact1 and becoming heavier in consequence1 flows down to low-lying ground4 ,hence places on rising ground are not so fully exposed to the intensity of frosts at night as places in the valley4 ,valleys surrounded by hills and high grounds1 not only retain their own cold and heavy air1 but serve as reservoirs for the cold air falling from neighbouring heights4 ,one finds1 in consequence1 mists in low situations1 while adjoining eminences are quite clear4 ,the air of mountains is 7#a7 cooler than that of lower districts with the exception already named4 7#b7 ,it is less dense in proportion to the altitude2 its pressure at the height of #af1jjj feet being only half that at the sea level4 7#c7 ,its absolute humidity is decidedly diminished2 there is some difference of opinion as to the relative humidity4 7#d7 ,the air is as a rule purer4 ,it is generally free from dust1 and to a large extent aseptic 7that is1 free from microbes74 7#e7 ,the amount of ozone is commonly greater than in lower regions4 ,in addition to these characters1 7#f7 the light is intense1 and 7#g7 the direct heat of the sun is greater1 and the difference between sun and shade greater than in lower regions4 ,owing to these peculiarities of mountain air1 it is of great value as a restorative4 ,the circulation of blood is increased1 nutrition is improved1 the chest expands1 and the increase in its size may be permanent4 ,the presence of forests and sheets of water counteracts the effects of radiation from the earth4 ,thus if a deep lake fills the basin of a valley1 the cold air descending from higher levels cools the surface water1 which sinks and is replaced by warmer water from below4 ,in this way deep lakes are sources of heat in winter1 and places on their shores are free from the severe frosts which are peculiar to other low-lying situations4 ,if the slopes of a hill are covered with trees the temperature of its sides and base are considerably increased1 as the trees obstruct the descending currents of cold air4 ,the frosts of winter are felt most severely in localities where the slopes above them are destitute of vegetation1 and especially of trees4 ,it follows that in any given locality1 the best protection against the winter cold is ensured by a dwelling situated on a slope a little above the plain or valley from which it rises1 with a southern exposure1 and sheltered by trees planted above it4 ,such local conditions should always be carefully enquired into1 when a choice of site is possible1 as the temperature of one part of a neighbourhood may differ by several degrees from that of another part near at hand4 ,this is particularly important in the case of invalids4 ,forests tend to modify a climate1 and mitigate its extremes1 whether situated on the slopes of mountains or on plains4 ,in ,america1 as elsewhere1 the effect of destruction of forests has been to produce greater variation in the annual rainfall1 to lengthen periods of drought1 and to increase the power of floods and cloud bursts4 ,trees are heated and cooled by radiation like other bodies1 but from their slow conducting power1 the periods of their maximum and minimum temperatures are not reached for some hours after the same phases of the temperature of the air1 and the effects of radiation are not confined to a small surface on the soil1 but distributed to the level of the tree-tops4 ,for these reasons1 trees make night warmer and day cooler1 thus giving to forest districts something of the character of an island climate4 ,evaporation occurs slowly from the damp soil beneath trees1 as it is screened from the sun1 and the trees prevent a free circulation of wind4 ,hence the relative humidity and rainfall are increased4 ,at the same time forests mitigate the disintegrating effect of the rainfall on the soil4 ,ground covered with ,vegetation has a more uniform temperature than bare soil1 the effect being much the same as that of forests1 though on a smaller scale4 ,all growing vegetation evaporates a large quantity of water4 ,a plant evaporates #bjj pounds of water while it forms one pound of woody fibre2 the effect of a forest must1 therefore1 be enormous4 ,at the same time1 vegetation1 and especially trees1 retain moisture in the soil4 ,the water-supply of barren regions may be greatly increased by planting trees4 ,the absence of vegetation leads to extreme fluctuations of temperature4 ,an extent of sand1 for instance1 raises the temperature of the air greatly during the day1 as it is a bad conductor2 but at night1 radiation is very great1 and the temperature falls accordingly4 ,relation of ,sea to ,climate4--,water has the greatest specific heat of any known substance1 being four times greater than that of the earth's crust4 ,on this account it takes longer to heat and to cool than the earth4 ,unlike the earth1 likewise1 it allows free penetration of the sun's rays1--in clear water probably to a depth of at least #fjj feet2 consequently1 the surface of the water becomes less rapidly heated4 ,the freezing point of fresh water is #cb1 while that of sea-water is #bge-bhd4 ,thus1 the sea remains open at a temperature at which inland lakes freeze1 and has1 therefore1 a greater influence in moderating winter cold and summer heat4 ,another factor rendering it more competent to mitigate extremes of temperature than lakes1 is the presence of currents1 causing admixture of the water of different climates4 ,of these currents the most important for this country is the ,gulf ,stream1 an immense stream of water which1 when it leaves the ,gulf of ,mexico1 is travelling at the rate of four to five miles an hour1 and has a surface temperature of #hh ,f4 ,it is important to distinguish between the surface temperature and the deep-sea temperature1 the latter being fairly constant4 ,the whole of the depths of the sea is filled with water at or near #cb ,fahr41 which in the tropics is #dj-ej below the temperature of the surface-water4 ,the influence of seas on climate is so great as to lead to a classification of climates into oceanic1 insular1 and continental4 ,an oceanic climate is least liable to violent changes of temperature4 ,it can only be obtained by a sea-voyage4 ,an insular climate presents smaller differences between the temperature of summer and winter than the interior of great continents1 especially when the island is small and in the midst of the ocean4 ,in the ,british ,islands1 the prevailing winds being westerly1 places on the east coast are less truly insular than similarly situated ones on the west coast2 and their climate approaches more nearly that of inland countries4 ,a continental climate is drier and more subject to extreme alternations of temperature than insular and oceanic climates4 ,isothermal lines 7lines of equal mean temperature7 around the world bend up and down1 the bendings being determined by the relative position of continents and oceans4 ,new ,york has the same mean temperature as ,london1 though ,new ,york is as far south of ,london as ,madrid4 ,this fact illustrates the fallacy in judging of the climate of a locality by the annual mean temperature4 ,means1 it has been well said1 are general truths but particular fallacies4 ,one should know the extremes of temperature1 and the extremes for each month of the year1 as well as the amount and distribution of the rainfall1 and the amount of sunshine1 before judging of a local climate4 ,winds are due to differences in atmospheric pressure caused by changes in temperature and moisture4 ,inasmuch as the temperature and degree of moisture of air vary with the prevailing winds1 their consideration becomes very important4 ,winds bring with them the temperature of the air they have traversed3 thus1 in ,england1 south winds are warm1 while north winds are cold4 ,winds coming over an ocean cause less variation in temperature than those which have passed over an extensive tract of country4 ,thus1 moist ocean winds are accompanied by a mild winter and cool summer1 while dry continental winds cause the reverse conditions4 ,the amount of moisture capable of being carried by a current of air increases with its temperature2 therefore1 equatorial winds become moister as they proceed1 while north winds become drier4 ,the south-west winds1 in the ,british ,isles1 being both oceanic and equatorial1 are very moist1 while the north-east winds1 being both northerly and continental1 are peculiarly dry and parching4 ,owing to the atmospheric pressure diminishing from the south of ,europe northwards to ,iceland1 south-west winds are the most prevalent in ,great ,britain2 and as this diminution of atmospheric pressure is greatest in the winter months1 south-west winds are most common at this season4 ,the result is that the temperature of these islands is higher than that due to mere latitude1 and the temperature on the west coast is fairly uniform from ,shetland to ,wales4 ,mountain ranges have an important bearing in determining the character of the prevailing winds4 ,if the range is perpendicular to the direction of the winds1 the latter lose the greater part of their moisture1 and the places to leeward being exposed more completely to solar and terrestrial radiation 7from comparative absence of aqueous vapour71 winter becomes colder and summer hotter4 ,the difference between the climates of the west and east parts of ,great ,britain is largely due to this cause4 ,in ,ireland1 the mountains are not grouped in ranges running north and south1 but in isolated masses1 and the difference in climate between the east and west coasts is consequently less marked4 ,the prevailing winds have a great influence on the rainfall4 7#a7 ,thus if the wind has traversed a considerable extent of ocean1 the rainfall is moderately large4 7#b7 ,if a wind reaches into a colder region1 its saturation point is lowered1 and the rainfall is greatly increased2 and if a range of mountains lies across its path1 the rainfall on the side facing the wind is greatly increased1 but diminished on the opposite side of the range4 7#c7 ,if a wind after reaching land proceeds into lower latitudes or warmer regions1 the rainfall is small1 or absent4 ,this accounts for the rainless summers of ,california1 ,north ,africa1 and ,south ,europe4 ,the ,barometric ,pressure varies daily1 being at its maximum at about #i a4m4 and #i p4m4 ,the average range in the tropics amounts to #ja inch1 but in this country does not usually exceed #jjb inches4 ,during the year the minimum barometric pressure usually occurs about the end of ,october1 while the maximum is usually at the end of ,may or early in ,june4 ,the ordinary variations in barometric pressure with changes of weather have little apparent effect on health2 but more extreme changes produce marked effect4 ,in mountain-climbing faintness and nausea may be caused at great altitudes4 ,at the opposite extreme1 in pier-driving and laying the foundations of bridges1 men have to work in air-chambers at a pressure of from three to four atmospheres4 ,then what is known as 8caisson disease0 may be produced4 ,the usual symptoms are discomfort or pain in the ears1 giddiness1 bleeding at the nose1 vomiting1 or even temporary paralysis4 ,in such occupations it is most important that on leaving the air-chambers the atmospheric pressure should be gradually lowered4 ,the use of the barometer as a weather indicator is based on the fact that moist air is lighter than dry air4 ,hence1 if the air is moist and rain imminent1 the barometer falls rapidly4 ,the maximum daily range in this country is rarely greater than #c inches4 ,weather observations can be based on records kept at one spot4 ,their value is greatly enhanced1 when such observations are compared with others distributed over a wide area4 ,the wider the area from which such observations are collated1 the more accurate the deductions that can be secured4 ,if observations of places at which the barometrical pressure is identical be recorded on a map1 we have a synoptic map1 and the lines of equal barometrical pressure connecting these points are called isobars4 ,the modern development of meteorology1 enabling forecasts of weather to be made with approximate accuracy1 is based chiefly on telegraphic communication of information1 enabling isobars to be constructed4 ,it is found that isobars arrange themselves into seven chief forms 7#a7 ,cyclones4 7#b7 ,secondary cyclones4 7#c7 ,v-shaped depressions4 7#d7 ,anti-cyclones4 7#e7 ,wedge-shaped isobars4 7#f7 ,cols4 7#g7 ,straight isobars4 ,each of these varieties is shown in ,fig4 #dc1 which embraces the conditions in ,europe1 the eastern part of the ,united ,states1 and over the ,north ,atlantic on a certain day4 ,the closeness of the isobars1 i4e4 the rapidity of changes in atmospheric pressure determines the barometric gradient4 ,the steeper this gradient1 the greater the velocity of the wind in any given place4 ,the distance between two isobars is equal to a change of a tenth of an inch in the mercury in the barometer4 ,the direction of the wind in a given place is from the higher to the lower isobars4 ,this is expressed in ,buys ,ballot's law1 which states that in the northern hemisphere1 if you stand with your back to the wind1 the lowest pressure is to your left and in front4 ,illustration3 ,,fig4 #dc4 ,,the ,,seven ,,fundamental ,,shapes ,,of ,,isobars 7after ,abercrombie74 ,cyclones or depressions are areas of low barometric pressure4 ,a cyclonic system 7,fig4 #dc7 is formed by circles of concentric isobars4 ,the differences between cyclones and anti-cyclones are as follows3-- ,cyclones4 ,anti-cyclones4 ,wind moves in the opposite ,wind moves in same direction as direction to the hands of a watch4 the hands of a watch4 ,barometer is lowest in the centre4 ,barometer is highest in the centre4 ,area comparatively small4 ,area comparatively large4 ,gradient from centre to ,gradient not steep4 circumference steep4 ,short duration4 ,long duration4 ,velocity of wind great4 ,air comparatively quiet4 ,weather bad2 much rainfall4 ,weather fine4 ,cool in summer2 warm in winter4 ,hot in summer2 cold and frosty in winter4 ,cyclones usually travel from west to east1 and are always associated with bad weather4 ,the essential point in determining the character of the weather1 both in cyclones and anti-cyclones1 is the barometric gradient4 ,thus1 according to the gradient1 a cyclone may mean mild wet weather1 a gale1 or a hurricane4 ,the turning point of a cyclone1 just before the barometer begins to rise again1 is called the trough4 ,cyclones are usually oval in shape1 except in the tropics1 where they are smaller and circular4 ,the ordinary course of events in a cyclone is shown in ,fig4 #dd1 reading it from left to right4 ,in ,secondary ,cyclones1 bad weather is usually associated with a stationary barometer and no wind4 ,they are incompletely circular looped concentric isobars1 with the lowest pressure in the centre4 ,they frequently follow primary cyclones4 ,v-shaped ,depressions are angular areas1 with the lowest pressure in the centre1 frequently forming between adjoining anti-cyclones 7,fig4 #dc74 ,in the northern hemisphere the tip usually points south4 ,they usually move with great rapidity from east to west1 and are always associated with squalls or thunderstorms4 ,their movement is very uncertain1 and their forecast therefore more difficult than that of cyclones and anti-cyclones4 ,illustration3 ,,fig4 #dd4 ,,weather ,,sequence ,,in ,a ,,cyclone 7after ,abercrombie74 ,the tracing indicates the line which a self-recording barometer would have marked4 ,the arrows mark the shift of the wind1 and the number of barbs denote the varying force of the wind4 ,anti-cyclones are associated with calm and cold in the centre1 while on the borders the wind blows around the centre1 spirally outwards in the direction of the hands of a clock4 ,an anti-cyclone is usually accompanied by a blue sky1 dry cold air1 a hot sun1 a hazy horizon1 and little or no wind4 ,wedge-shaped ,isobars1 unlike ,v's1 usually point north4 ,they are areas of high pressure moving along between two cyclones1 being really projecting parts of an anti-cyclone4 ,the fine weather accompanying them is only temporary1 because they are never stationary1 and are generally followed by cyclonic disturbances4 ,at the narrow end of the wedge thunderstorms or showers often occur1 and at the wide end fog is common4 ,cols or necks of relatively low barometric pressure occur between two anticyclonic areas4 ,like straight isobars they are intermediate systems4 ,over cols the weather is dull and gloomy2 in summer they may be associated with thunderstorms4 ,straight ,isobars obviously do not enclose any area of high or low pressure4 ,they form an intermediate condition1 preceding the formation of a cyclone2 and are usually associated with a blustering wind and hard sky4 ,weather forecasting is necessarily somewhat difficult and uncertain4 ,if one is dependent on observations at a single point the following rules are useful3-- 7a7 ,if the barometer falls slowly and steadily bad weather will follow4 7b7 ,the barometer falls for rain with ,s4,w41 ,s4,e41 and ,w4 winds4 7c7 ,when the barometer falls rapidly1 heavy storms may be expected4 7d7 ,the barometer rises rapidly for unsettled weather4 7e7 ,the barometer rises gradually for fine1 settled weather4 ,the ,thermometer also is of great value as a weather indicator1 especially if one knows what is the average temperature at the place of observation for each day of the year4 ,thus3-- 7a7 ,a temperature continued for some time above or below the average1 indicates a probable change4 7b7 ,electric storms follow unusual warmth in summer4 7c7 ,a low thermometer and almost steady barometer are succeeded in winter by gales from ,n4,n4,w4 or ,n4,e4 ,the veering of the wind in ,england is also useful as an indicator4 ,thus3-- 7a7 ,when the wind1 in shifting1 goes round in the same direction as the hands of a clock--i4e41 from ,n4 by ,e4 to ,s41 or from ,s4 by ,w4 to ,n41--favourable changes of weather may be looked for4 7b7 ,when the wind backs--that is1 veers round in the opposite direction--bad weather generally follows4 ,the direction of the wind is an important factor4 ,thus3 7a7 ,settled ,n4,w4 winds bring cold and fine weather4 7b7 ,continued ,w4 and ,s4,w4 winds are followed by rain4 ,clouds give useful indications4 ,thus3-- ,a mackerel sky1 that is1 one covered with lines of cirrus clouds1 causing halos around the sun and moon1 presages rain in summer and thaw in winter4 ,by degrees the light clouds descend and pass into either masses of cumulus1 or into dense1 horizontal stratus1 which form at sunset and disappear at sunrise4 ,both these kinds pass into the grey1 shapeless nimbus1 which soon covers the entire sky and is followed by rain4 ,when numerous observations can be synoptically studied1 forecasting becomes much more nearly certain4 ,for this purpose telegraphic communications are indispensable4 ,the continent of ,europe is better placed than ,england for accurate forecasting4 ,areas of high pressure coincide usually with large areas of land1 of low pressure with large surfaces of water4 ,thus ,england is placed near the boundary of the usual anticyclonic and cyclonic systems1 and its chief disturbances come from the ,atlantic from which early communication is impracticable4 ,furthermore cyclonic disturbances may be diverted from their course by a coastline or mountains or by the formation of an anticyclonic area4 ,in view of these uncertainties1 the large proportion of correct forecasts is somewhat surprising4 ,the ,moisture of the ,air depends upon the amount of vapour present in it1 and the ratio of this to the amount which would saturate the air at the actual temperature4 ,the former is called the absolute humidity1 the latter the relative humidity4 ,the dew point is the point at which condensation of some of the vapour in the atmosphere occurs1 either as dew1 rain1 snow1 or hoar-frost4 ,the amount of moisture which the atmosphere can retain before such condensation occurs1 varies with the temperature 7see page #aja74 ,thus the air is drier at noon than at midnight1 though the amount of vapour present in the two cases be the same2 and it is for the most part drier in summer than in winter4 ,this refers to the relative humidity1 which is highest in cold weather4 ,the absolute humidity is higher in summer than in winter2 it varies more in continental than in maritime and insular climates2 and there are daily variations according to the state of the sky1 the movements of air1 etc4 ,the relative humidity is expressed as a percentage of what would be required to produce saturation at the given temperature4 ,the usual relative humidity is #ej to #ge per cent4 ,a moist air prevents excessive changes of temperature due to radiation4 ,it protects the earth from too great intensity of the solar rays by day and from too rapid loss of heat by radiation at night4 ,the inhalation of a dry air plays an important part in the cure of consumption4 ,when the air is almost saturated with moisture1 evaporation from the skin and lungs is diminished1 and there is a feeling of oppression and disinclination to work caused by the interference with the tissue changes of the system4 ,rainfall is caused by over-saturation of a column of moist air4 ,this may be due to the contact of the air with a cold surface1 as the ridge of a mountain or a large surface of water1 or to the impact of a colder wind4 ,the amount of rainfall varies greatly4 ,in some parts there is no rain1 as in the desert of ,sahara2 while on the south-east slopes of the ,himalayas1 which are exposed to winds laden with moisture1 it may be several hundred inches4 ,the latitude of a place has a great influence4 ,as a rule the rainfall decreases with increasing distance from the equator2 but local conditions may produce great modification1 or even alterations of this law4 ,the elevation above the sea-level has a varying influence4 ,in the ,swiss ,alps it is said that the rainfall increases with the elevation2 but this rule does not hold good in ,america4 ,the nearness of large surfaces of water in summer tends to increase the rainfall1 when water is colder than its surroundings1 while in winter it has the opposite effect4 ,the neighbourhood of the sea is for the west of ,england and islands adjacent1 a cause of increased rainfall4 ,the influence of winds on the rainfall has been already considered4 ,in ,great ,britain south-west winds more especially increase the rainfall4 ,in their course they have travelled over the ,gulf ,stream and the general equatorial current1 and have thus received warmth and moisture4 ,the condensation of their moisture liberates a large amount of latent heat1 thus raising the temperature of this country4 ,in summer1 however1 south-west winds are cool and moist1 as the ,atlantic is not so hot as the continents of ,asia and ,europe over which other winds have travelled4 ,in ,england the average rainfall is about #cc inches1 in ,scotland #df1 and in ,ireland #ch inches4 ,in the east of ,great ,britain1 the rainfall is from twenty to twenty-eight inches4 ,on the west coasts of ,scotland and ,ireland it is from #fj to #hj inches2 and in some parts of ,cumberland may be about #aej inches per annum4 ,the annual rainfall varies greatly from the average for a number of years4 ,in this country it has been estimated that the maximum annual rainfall exceeds by one-third1 and the minimum annual rainfall is less by one-third than the average rainfall of a series of years4 ,the number of rainy days by no means corresponds with the amount of rainfall4 ,there are fewest rainy days at the equator1 where the rainfall is greatest4 ,the rain diminishes the relative humidity of the air1 and purifies it from dust4 ,,chapter ,,xxxv4 ,,meteorological ,,observations4 ,the ,royal ,meteorological ,society recognises stations for the making and recording of observations of three kinds3 7#a7 ,second ,order ,stations1 at which observations are taken twice daily at #i a4m4 and #i p4m42 7#b7 ,climatological ,stations1 at which the observations are taken once daily1 at #i a4m42 7#c7 ,stations at which one or more elements only1 e4g4 rainfall1 are observed4 ,all instruments used should have been previously verified at ,kew ,observatory1 so that the corrections for index error may be known4 ,the ,barometer used should be of a standard kind4 ,five chief kinds of barometer are in use1 only the last two of which are sufficiently accurate for scientific purposes4 #a4 ,the ,dial or wheel barometer consists of a bent tube ,a ,b1 the open end of which supports an ivory float ,b4 ,this1 as it rises and falls with the mercury1 by means of the rack ,c turns a wheel1 in the axle of which a needle is fixed4 ,the needle turns in one direction1 or the other as the mercury rises or falls 7,fig4 #de72 the dial is divided by comparing it with a standard barometer4 ,as the ordinary variations of the barometer are from #bh to #ca inches1 the circumference of the wheel is made exactly #a inches1 and thus the float ,b will rise or fall #a inches for a rise or fall of #c inches in the barometer4 ,illustration3 ,,fig4 #de4 #b4 ,the ordinary syphon barometer 7,fig4 #df7 consists of a bent tube attached to a piece of wood1 and furnished with a screw v4 ,the atmospheric pressure acts on the mercury at d1 and the difference between the level of the mercury in the two arms of the syphon is the height of the barometer4 ,to find the true height of the barometer the screw is turned till the shorter column stands at a opposite zero4 #c4 ,the aneroid barometer is made by exhausting the air from a small round metal box4 ,this box is closed by a flexible lid of metal which1 being elastic1 yields to changes in the atmospheric pressure4 ,to the lower end of the lid a spring is attached which runs downwards to the floor of the box and resists the atmospheric pressure4 ,the movements thus produced by variations in pressure are magnified by a rack and pinion1 and so communicated to a long index which moves over a graduated scale4 ,illustration3 ,,fig4 #df4 ,the standard ,kew and ,fortin barometers are both cistern barometers1 the mercury in the inverted tube communicating with the mercury in a cistern below4 #d4 ,the ,kew pattern barometer has a closed cistern below1 the area of which being accurately known1 the inches on the scale are not real inches1 but inches of pressure1 i4e4 inches so shortened as to compensate for the rise of the mercury in the cistern4 ,this compensation is necessary inasmuch as changes in atmospheric pressure affect the level of the mercury in the cistern as well as of that in the tube4 #e4 ,in the ,fortin barometer 7,fig4 #dg7 the cistern has a pliable base of leather1 which can be raised or lowered by means of a screw4 ,the upper part of the cistern is made of glass1 a piece of ivory indicating the zero of the scale4 ,before taking a reading1 the level of the mercury must always be set exactly to this point by means of the screw4 ,the ,fortin is the most sensitive form of barometer1 and the adjustment required in order to take a reading is easily performed4 ,to ensure more accurate reading of the barometer1 a secondary scale or vernier is used1 which slides upon the principal scale4 ,this vernier is so graduated that #be of its divisions correspond to #bd of the divisions on the fixed scale4 ,the fixed scale is divided into inches1 tenths 7#a71 and half-tenths 7#je74 ,each division of the movable scale or vernier is therefore shorter than each division of the scale by #abe of #je1 i4e4 #jjb inch4 ,consequently the vernier shows differences of two thousands of an inch4 ,illustration3 ,,fig4 #dg4 ,,fortin ,,barometer4 a--,attached thermometer4 b--,screw of vernier4 c--,screw for setting level of cistern4 ,method of reading ,fortin's ,barometer4--,first note the reading of the attached thermometer2 next turn the screw at the bottom of the cistern1 so that the ivory point just touches the surface of the mercury4 ,next adjust the vernier by means of the rack and pinion at the side of the barometer 7,fig4 #dg7 so as to bring its two lower edges exactly on a level with the convex surface of the mercury4 ,in reading the barometer1 first read off the division next below the lower edge of the vernier4 ,in ,fig4 #dh this is #bije4 ,then the true reading is #bije plus the vernier indication4 ,next look along the vernier until one of its lines is found to agree with a line on the scale4 ,in ,fig4 #dh this is at the fourth division on the vernier4 ,but each of the figures marked on the vernier counts as #aajj 7#ja71 and each intermediate division as #bajjj 7#jjb72 hence the reading of the vernier will be #jjh inch1 and the reading of the barometer #bije #jjh #bijeh inch4 ,if two lines on the vernier are in equally near agreement with two on the scale1 the intermediate value should be adopted4 ,certain corrections are required in the actual reading for 7#a7 index error2 7#b7 temperature2 and 7#c7 height above sea-level4 ,the index error is found by comparison with a recognised standard at ,kew4 ,correction for temperature is required4 ,every barometer has a thermometer attached1 and the reading is reduced to the standard temperature of #cb ,f1 by means of tables such as are given on page #cb of ,marriott's ,hints to ,meteorological ,observers4 ,the height of the cistern of the barometer above sea-level should always be exactly obtained4 ,the correction necessary to reduce observations to sea-level 7i4e4 mean half-tide level at ,liverpool71 depends on the temperature and pressure of the air1 as well as on the altitude4 ,the data for this correction are given in ,table ,,iii4 of ,marriott's ,hints4 ,illustration3 ,,fig4 #dh4 ,,scale ,,of ,,barometer 7,,to ,,right7 ,,and ,,of ,,vernier 7,,to ,,left74 ,thermometers4--,the maximum thermometer may be on ,negretti and ,zambra's1 or on ,phillips' principle4 ,in the former 7,fig4 #di7 the bore of the tube is reduced in section near the bulb 7,a7 in such a way that while the expanding mercury forces its way into the tube1 the column of mercury breaks off on contraction1 so that its upper limit shows the highest temperature that has been reached4 ,the thermometer is set by holding it bulb downwards and shaking to make the mercurial column continuous4 ,it is mounted in the screen horizontally 7,fig4 #ea74 ,illustration3 ,,fig4 #di4 ,,negretti ,,and ,,zambra',s ,,maximum ,,thermometer4 ,the minimum thermometer chiefly used is ,rutherford's4 ,it contains spirit in which is an immersed index 7,a1 ,fig4 #ej74 ,with a falling temperature the spirit draws the index along with it2 but on rising again1 the spirit passes the index1 leaving it at the lowest point to which it has been drawn4 ,thus the end farthest from the bulb registers the minimum temperature4 ,the instrument is set by raising the bulb and allowing the index to slide to the end of the column of spirit4 ,the thermometer must be firmly fixed and mounted quite horizontally4 ,illustration3 ,,fig4 #ej4 ,,minimum ,,thermometer4 ,thermometer ,screen4--,the above thermometers1 as well as the dry and wet bulb thermometers are mounted in a ,stevenson's screen 7,fig4 #ea74 ,this is a doubled-louvred box through which the air can pass freely1 but the sun cannot enter4 ,the horizontal position of the maximum and minimum and the vertical position of the dry and wet bulb thermometers are shown in ,fig4 #ea4 ,three additional thermometers are usually included in a well-organised meteorological station4 ,a minimum thermometer placed on the grass gives the lowest temperature on the grass1 which is often considerably lower than that of the neighbouring gravel walk4 ,this record is chiefly useful for agricultural purposes4 ,the earth thermometer chiefly used is shown in ,fig4 #eb4 ,it consists of a sluggish thermometer mounted in a short weighted stick attached to a strong chain1 and of a stout iron pipe which is drawn out at the bottom to a point and driven into the earth1 usually to a depth of #d feet4 ,solar radiation is measured by black-bulb and light-bulb thermometers in vacuo1 which are mounted on a post #d feet above the ground and record the maximum temperature4 ,humidity in the air is measured by direct or indirect hygrometers4 ,of the former ,dines'1 ,daniell's1 and ,regnault's are the best known1 but as they are not used in observations acknowledged by the ,royal ,meteorological ,society1 the reader may be referred to their description in books on physics4 ,the indirect hygrometer which is universally employed in this country is that furnished by the dry and wet bulb thermometers4 ,in frosty weather they require much attention1 and then a ,saussure's hair hygrometer may be used as supplementary4 ,the general arrangement of the dry and wet bulb thermometers is shown in ,fig4 #ec4 ,illustration3 ,,fig4 #ea4 ,,stevenson',s ,,thermometer ,,screen4 ,the wet bulb is covered with a single layer of soft muslin1 while a noose of six to eight strands of darning cotton connects the neck of the wet bulb with a covered water receptacle #b to #c inches distant1 below and at its side4 ,this receptacle is kept filled with rain-water4 ,illustration3 ,,fig4 #eb4 ,,symons' ,,earth ,,thermometer4 ,illustration3 ,,fig4 #ec4 ,,dry ,,and ,,wet ,,bulb ,,thermometers4 ,from the readings of the dry and wet bulb thermometers three deductions can be made3 #a4 ,the temperature of the dew point4 #b4 ,the elastic force of aqueous vapour4 #c4 ,the relative humidity4 ,the dew point temperature is that temperature at which the outside air at the time the observation is taken will deposit the moisture contained in it4 ,it is the temperature at which the air is saturated with moisture4 ,it is calculated from the readings of the wet and dry bulb thermometers 7a7 by ,glaisher's tables2 7b7 by ,apjohn's formula4 ,glaisher's tables are based on a series of numbers called ,greenwich or ,glaisher's factors1 which he determined by comparison between observations made with the dry and wet bulb thermometers and with ,daniell's hygrometer4 ,the formula for using the factors is as follows3-- d ,d - 7,d - ,w7 f where d dew point1 ,d dry bulb temperatures1 ,w wet bulb temperature1 and f factor4 ,the following examples are from ,glaisher's table of factors4 ,,reading ,,of ,,dry ,,bulb,,factor4 ,,thermometer ,,fahr4 #ee #aif #ef #aid #eg #aib #eh #aij #ei #ahi #fj #ahh ,thus1 if ,d #fj1 ,w #ee1 then dew point #fj - 7#fj - #ee7 #aif #ejb4 ,the dew-point may also be obtained by ,apjohn's formula2 which for a pressure of about #cj inches is ,f f-7,d-,w7_/#hg ,d being dry and ,w wet bulb temperature1 ,f elastic force of vapour corresponding to dew-point1 and f1 elastic force corresponding to wet bulb temperature 7ascertained from a table of tensions74 ,the elastic force of aqueous vapour1 i4e4 the amount of barometric pressure due to the vapour present in the air is dependent upon the temperature of the dew-point4 ,it is given for every tenth of a degree of temperature in ,table ,,vi4 7p4 #db7 of ,marriott's ,hints4 ,the relative humidity is a term expressing the percentage of saturation of the air with water vapour4 ,it is obtained from ,table ,,vi4 7above7 as follows3-- ,elastic force of water vapour at the temperature of the ,relative dew-point ---------------------------------------- ---------------------------------------- ------------------------------------ ,humidity ,elastic force of water vapour at the temperature of the air 7i4e4 the dry-bulb reading47 ,thus elastic force with dry bulb #ee is #dcc in4 in the table4 dew-point #dfe is #cag in4 #cag_/dcc #gc4 ,if saturation #ajj1 relative humidity is #gc4 ,in ,table ,,vii4 of ,marriott's ,hints1 a table is given which enables the relative humidity to be found by mere inspection4 ,thus if the dry bulb temperature is #ehe1 wet-bulb #eag1 and the difference #fh1 the relative humidity given in the table is #fb4 ,the ,rain-,gauge is best made of copper in the shape of a circular funnel1 usually #e or #h inches in diameter1 leading into a bottle underneath4 ,it must always be set in an open situation away from trees1 walls1 and buildings4 ,according to ,scott no object ought to subtend a greater angle with the horizon than #bj in any direction from the gauge4 ,the rain is measured by pouring the contents of the bottle into a glass measure1 which is graduated to represent tenths and hundredths of an inch on the area of the gauge1 the measure holding half an inch of rain on this area4 ,snow is melted before being measured4 ,illustration3 ,,fig4 #ed4 ,,snowdon ,,pattern ,,rain-,,gauge4 ,a4 ,copper ,upper ,part of ,gauge4 ,b4 ,funnel4 ,c4 ,bottle4 ,to the right is shown the glass measure inverted4 ,observations of wind should include its direction and force4 ,the direction is observed by means of a well-oiled and freely exposed vane4 ,there are #cb points to the compass1 but a reading to eight points suffices4 ,the force of the wind should be estimated by ,beaufort's scale1 from #j to #ab4 ,thus3-- ,,force4 ,,miles ,,per ,,hour4 #j4 ,calm #c #a4 ,light air #h #b4 ,light breeze #ac #c4 ,gentle #ah #d4 ,moderate #bc #e4 ,fresh #bh #f4 ,strong #cd #g4 ,moderate gale #dj #h4 ,fresh #dh #i4 ,strong #ef #aj4 ,whole #fe #aa4 ,storm #eg #ab4 ,hurricane #ij ,robinson's anemometer is also employed1 but it is not altogether trustworthy4 ,sunshine is recorded by the ,campbell-,stokes burning recorder1 and the ,jordan photographic recorder4 ,of these the former is the more easily worked and gives more uniform results4 ,it consists of a sphere of glass #d inches in diameter1 supported on a pedestal in a metal zodiacal frame 7,fig4 #ee74 ,the setting of the recorder should be due south1 level from east to west1 and with the axis of the ring inclined to the horizon at an angle equal to the latitude of the place1 and so that the image of the sun1 when the sun is due south1 shall fall on the meridian line marked on the ring4 ,the sun burns away or chars the surface of the cards inserted in the proper groove1 and so gives a record of the duration of bright sunshine4 ,illustration3 ,,fig4 #ee4 ,,campbell-,,stokes ,,sunshine ,,recorder4 ,the amount of ,cloud should be estimated daily1 according to a scale ranging from #j to #aj1 i4e4 clear sky up to completely overcast4 ,the form of cloud should also be stated1 as cirrus1 cirro-cumulus1 cirro-stratus1 cumulus1 cumulo-stratus1 stratus1 and nimbus4 ,,chapter ,,xxxvi4 ,,personal ,,hygiene4 ,certain personal factors are very important in relation to health4 ,the chief of these are constitution1 temperament1 heredity1 idiosyncrasy1 age1 sex1 and habits4 ,constitution4--,health may vary in degree without the presence of actual disease4 ,this fact is expressed by the use of such terms as 8perfect10 8strong10 8feeble10 8delicate10 in speaking of the health of the same person at different times1 and also as distinguishing one person from another4 ,the constitution is an important factor in resisting disease1 and a robust constitution may determine recovery from a severe illness1 while the patient with a feeble constitution falls a victim to it4 ,the constitution of an individual is partly acquired1 partly inherited4 ,a feeble or delicate constitution may be acquired by unhygienic conditions1 such as deficient exercise1 the prolonged breathing of impure air1 unhealthy occupations1 some imperfection in diet1 or dissipation4 ,but while many a robust constitution is enfeebled by such conditions1 a weak constitution may happily be strengthened by careful and prolonged attention to the laws of health4 ,this is especially well seen in the case of those who strengthen their muscular system by carefully-graduated and not excessive exercise4 ,heredity has a great influence on health4 ,as a rule the children of healthy parents are robust1 and on the contrary1 any 8weak point0 in the parents' constitutions is liable to be participated in by their children4 ,both mental and physical conditions may be inherited4 ,a peculiar habit of mind1 as well as the same expression of features1 may be inherited4 ,as regards physical diseases1 the influence of parents is not less remarkable4 ,the son of a gouty father requires to be particularly abstemious in order to avoid his father's disease4 ,certain specific febrile diseases1 e4g41 enteric fever1 diphtheria1 and still more rheumatic fever1 are hereditary in the sense that the members of certain families are more prone to them than others4 ,insanity1 epilepsy1 asthma1 neuralgia1 and hysteria are also hereditary in the same sense1 and it is noticed that they occasionally alternate in different generations4 ,cancer1 consumption1 certain skin diseases1 and a tendency to the early onset of degenerative diseases1 appear also to occur more often in certain families than in others4 ,in most cases it is the tendency to disease which is transmitted1 and not the disease itself4 ,when an actual disease is inherited1 as happens very rarely in tuberculosis and often in syphilis1 the actual infection is transmitted before birth from the parent4 ,a peculiarity of form1 character1 or tendency to disease has been known to disappear in one generation and re-appear in the next2 this variety of heredity is termed atavism4 ,the evidence showing the inheritance of acquired characters1 i4e4 those which arise in consequence of the effect of external forces on the organism is not conclusive4 ,weismann believes that only those forces that influence the germ-plasm are inherited4 ,it must be admitted that the instances of inheritance of acquired characters can be better explained otherwise4 ,thus the long neck of the giraffe was formerly explained on the supposition that the neck became gradually lengthened owing to the efforts made generation after generation in reaching food2 but is better explained by ,weismann on the supposition that those giraffes which1 during times of famine were able to reach higher and obtain food from the twigs of trees would survive and pass on their characteristics to their young1 while shorter necked giraffes would be exterminated4 ,the inheritance of proclivity to or immunity from attacks of infectious diseases is a problem of great difficulty2 but there is no substantial reason for thinking that the efforts being made to diminish the prevalence of these diseases 7including consumption7 are likely to produce a weaker race or one more likely to suffer with excessive severity from these diseases should they be introduced after a long absence4 7,see also page #cji74 ,temperament indicates a peculiarity in constitution1 causing a liability to particular diseases1 or to a special character in any disease to which a person becomes subject4 ,four temperaments are usually recognized--the sanguine1 phlegmatic1 bilious1 and nervous1 but unmixed specimens of these temperaments are rarely seen4 ,by idiosyncrasy is understood a peculiarity limited to a comparatively small number of individuals4 ,four varieties of idiosyncrasy may be described4 ,the first consists in an extreme susceptibility to the action of certain things1 or an extreme lack of susceptibility4 ,thus most people at some time or other inhale the pollen of grasses1 but only in a few cases does it produce that troublesome and distressing complaint--hay asthma4 ,in certain persons a very minute dose of iodide of potassium produces distressing symptoms2 in most cases these symptoms arise if the drug is taken for a prolonged period2 but in a few cases it may be taken for an indefinite period without troublesome result4 ,the case of a physician at ,bath is very curious4 ,the smell of hyacinths in bloom always made him faint away2 so constant was this result1 that before entering a room during the hyacinth season1 he always asked the servant if there were any hyacinths in it4 ,the second form of idiosyncrasy consists in the production of poisonous results by common articles of diet4 ,thus some people cannot partake of shell-fish or lobsters without having severe nettlerash4 ,in rare instances the smallest amount of egg1 or in other cases mutton1 or pepper1 or some other substance will produce severe indigestion or nettlerash4 ,the third form consists in an inversion of the usual effects of certain substances1 especially drugs4 ,thus opium in rare cases produces convulsions2 while the aperient ,epsom salts have been known to produce constipation4 ,a fourth form1 that of mental idiosyncrasies1 may be added1 as where there is a strange preference or aversion for objects usually regarded as indifferent4 ,many cases of mental peculiarity1 short of actual insanity1 will come under this head2 as will instances of depraved appetite for food1 etc4 ,age and ,sex4--,according to the period of life1 danger arises from different sources4 ,in infancy and old age extreme changes of temperature are especially dangerous1 and additional protection is required 7see also page #bga74 ,thousands of deaths occur in the first year of life1 from substituting starchy foods for milk1 the natural food for infancy and childhood 7see page #cjc74 ,in childhood the danger from bad feeding is still present1 and is evidenced by the frequency of rickets 7page #bh72 infectious diseases claim their thousands2 and the disorders associated with dentition are common4 ,in youth rapid growth is proceeding1 and so the food must be abundant and nutritious4 ,a proportionately larger amount is required than by an adult1 as the functions of the body not only require to be carried on1 but material is necessary to build up the growing tissues4 ,manhood is the period of greatest stability of health4 ,the health now depends on the use made of the previous periods of life1 and on the habits acquired4 ,with the onset of old age come various degenerative diseases4 ,the tendency is to death by gradual decay--a euthanasia or easy death1 which is too seldom seen4 ,commonly1 bronchitis or apoplexy or kidney diseases bring the scene to a somewhat premature end4 ,the mortality of man is greater than that of woman at all ages except #e--bj4 ,habits4--,the immense power of habits in the formation of character is perhaps duly appreciated2 but their influence on physical health is not so well appreciated2 though it would be difficult to exaggerate it4 ,the laws of health are as inexorable and unaltering as all other laws of nature2 and whether broken through carelessness or ignorance1 the ,nemesis of disease inevitably follows4 ,whatever a man sows he reaps1 in health as in other matters4 ,habits are easily formed2 but1 when once formed1 not so easily broken4 ,they ought to be our servants2 very commonly they become our masters4 ,in reference to eating and drinking1 habits regular as to time and moderate as to quantity are especially important4 ,the habit of eating hastily and masticating the food imperfectly1 is certain1 sooner or later1 to produce disease4 ,over-eating1 again1 is a fertile source of disease1 especially when the excess is in animal food4 ,the amount of stimulation produced by a given dose of alcohol1 gradually diminishes with its repetition2 the consequence is1 that in order to produce the amount of stimulation to which the system has become habituated1 the stimulant requires to be gradually increased4 ,the craving for stimulants is often a sign of ill-health1 owing to disregard of hygienic laws or actual disease4 ,not infrequently it is due to badly-ventilated rooms or long hours of work without food1 producing a sense of depression which food does not immediately allay4 ,when the cause is unknown1 recourse should be had to competent medical advice1 and not to the brandy bottle4 ,attention to the ,action of the ,bowels is a matter which is commonly neglected4 ,the importance of a regular habit in this respect cannot be exaggerated2 the bowels should always be relieved at a particular time each day4 ,where this does not occur the condition of constipation results4 ,owing to the retention of the fces in the intestines beyond the normal period1 the stomach and higher parts of the intestines do not perform their functions normally2 indigestion and 8dyspepsia10 accompanied by headache1 flatulence1 and other symptoms follow4 ,hmorrhoids 7piles7 are another frequent consequence4 ,at the junction of the small and large intestines is a dilated sac 7in the ccum74 ,this becomes distended when constipation occurs2 inflammation may be set up1 and an operation required1 or the condition is fatal4 ,powerful purgative medicines are injurious to the bowels1 and they tend afterwards to increase constipation4 ,it is better to take slow-acting aperient remedies1 and better still not to take any at all1 but relieve the condition by means of such articles of diet as stewed fruit1 pears1 figs1 olive oil1 or brown bread4 ,as a rule more exercise is required in this condition1 and always a prompt attention to the calls of nature4 ,,chapter ,,xxxvii4 ,,personal ,,hygiene--,,exercise4 ,physiological ,considerations4--,in the strict sense of the word1 exercise signifies the performance of its functions by any part of the body2 thus1 digestion is exercise of the stomach1 respiration is exercise of the lungs1 thinking is an exercise of the brain4 ,but the term is usually applied chiefly to muscular contraction1 and restricted to contraction of voluntary muscles4 ,involuntary muscles1 which are concerned in the carrying on of the unconscious organic functions of life1 are not directly controllable1 and so their growth and state of nutrition cannot be regulated4 ,there are two sets of involuntary muscle1 which are of special importance--the heart and the muscles of respiration4 ,the heart contracts at least sixty times per minute2 the respiratory muscles contract about seventeen times per minute2 and this amount of exercise goes on throughout the whole day4 ,but although we cannot make our hearts beat quicker by a direct volition1 and cannot breathe more rapidly than usual beyond a few seconds1 yet a brisk walk will cause increased action of the heart and respiratory muscles1 as well as a vigorous contraction of the muscles directly concerned in walking4 ,going uphill is a valuable exercise for the heart4 ,the vermicular contractions of the intestines are to some extent also increased by voluntary exercise1 through the indirect excitation of the whole system2 thus1 exercise is an important element in the treatment of constipation4 ,the muscles contain about a fourth of the whole blood of the body1 and a very large share of the metabolism 7page #d7 of the body occurs in them4 ,hence the importance of keeping them in a healthy condition by exercise4 ,the great danger is of not equilibrating the muscular and nervous functions4 ,the ideal condition is where neither mental nor muscular culture is neglected1 but both are co-ordinated to the production of a healthy man4 ,effects of ,healthy ,exercise4--#a4 ,the ,nutrition of the ,muscles is improved4 ,the volume1 density1 and energy of the muscles are increased4 #b4 ,the action of the lungs is increased4 ,dr4 ,e4 ,smith found that if the air inspired while lying down be represented by unity1 the amount inspired when erect is #acc2 when walking at the rate of one mile per hour1 #ai2 at four miles per hour1 #e2 at six miles per hour1 #g2 riding on horseback1 #dje2 swimming1 #dcc4 ,or1 putting it in another way1 under ordinary circumstances a man inspires #dhj cubic inches per minute2 if he walks four miles per hour1 he inspires #b1djj cubic inches2 if six miles an hour1 #c1bfj cubic inches4 ,at the same time the amount of carbonic acid expired is increased4 ,its amount bears a nearly constant relation to the amount of muscular exercise1 and consequently the amount of carbonic acid eliminated in various forms of exercise affords a just estimate of their relative value4 ,the increased elimination of carbonic acid1 the corresponding increased absorption of oxygen1 and the absence of increase of elimination of urea are shown in the following summary of observations by ,pettenkofer and ,voit3-- ,,absorption ,,of ,,elimination ,,in ,,grammes ,,of ,,oxygen ,,in ,,grammes4,,carbonic ,,acid4,,water4,,urea4 ,work day #iee #abhd #bjdb #cgj ,rest day #gji #iab #hbh #cgb ,the above amounts are for the entire day4 ,during actual exercise the excess of elimination of carbonic acid is much greater4 ,thus1 ,dr4 ,e4 ,smith experimentally found that if the amount of carbonic acid eliminated during rest be represented by one1 the amount walking at two miles an hour and carrying #g lbs #ahe1 the amount walking at three miles an hour #bfd4 ,alcohol diminishes the excretion of carbonic acid1 and should therefore be avoided during muscular training4 ,by muscular exercise the size of the lungs is increased1 and their vital capacity1 that is1 the amount of air capable of being expired after a forced inspiration1 is considerably increased4 ,corresponding with this increase of vital capacity1 exercise1 especially that in which the arm and chest muscles are systematically developed1 increases the size of the chest4 ,a perceptible difference in the circumference of the chest may be noticed after only a few weeks' methodical exercise4 #c4 ,the action of the skin is increased4--,sensible perspiration is commonly induced1 but less readily in those habituated to hard work4 ,insensible perspiration is always increased4 #d4 ,the temperature of the body is not increased1 so long as perspiration occurs4 ,every muscular contraction involves the production of heat2 but this is counteracted by increased evaporation from the skin1 and by the circulatory current carrying the hotter blood to every part of the body1 and so rapidly equalising its temperature4 ,chilblains are due to the defective circulation of the blood1 and can in most cases be cured by active exercise aided by warmer clothing and an abundant supply of oxidisable food4 #e4 ,the ,heart and ,blood-vessels4--,by exercise the heart's action is increased in frequency and force4 ,the pulse usually increases from ten to thirty beats per minute above the rate while at rest4 ,after prolonged exercise it may temporarily fall below the normal standard4 #f4 ,the ,digestion and assimilation of food are aided by exercise1 especially when taken in the open air4 #g4 ,the nervous system is improved in nutrition and power by a moderate amount of exercise4 ,in fact1 a certain amount of muscular exercise is essential for a healthy mind4 #h4 ,the elimination of urea is not increased by exercise4 ,evidently then it is not the metabolism of the nitrogenous substance of the muscles which supplies the energy for muscular contraction2 but of the other oxidisable and non-nitrogenous substances 7such as glycogen and sugar7 contained in them4 ,in practice it is found that with exercise more nitrogenous and non-nitrogenous food are both required4 ,effects of ,excessive ,exercise4--,after prolonged exertion muscles become exhausted4 ,this is associated with an accumulation in the muscles of the products of their action 7especially sarcolactic acid74 ,then rest becomes necessary1 in order that the effete products may be removed1 and the nutrition of the muscles restored4 ,long-continued over-exertion produces chronic exhaustion1 which may1 if excessive1 cause wasting of muscles4 ,exhaustion is much more liable to occur when a small group of muscles are exercised out of all proportion to others4 ,thus1 in clerks1 we have what is known as the writer's or scrivener's palsy4 ,the muscles of the hand1 and especially of the thumb1 cease to respond to the volition of the writer1 but are seized with spasm every time writing is attempted2 and the muscles of the thumb tend to waste4 ,a similar condition sometimes arises in violinists1 tailors1 etc4 ,the practical inference from these facts is1 that one group of muscles should not be exercised disproportionately to the muscles of the rest of the body1 and that proper intervals of rest should be allowed4 ,excessive exercise of the whole muscular system is very apt to harm those of previously sedentary habits4 ,a walking tour entered on with more zeal than discretion1 and not taken by easy stages for the first few days1 is often productive of more harm than good4 ,in the intervals of great mental labour1 as with students1 the amount of exercise should not be suddenly increased1 but should be regular and moderate in amount4 ,competitive exercise should be strictly regulated4 ,the ,oxford and ,cambridge crews have been said to acquire heart-disease more commonly than the average1 but this is not correct4 ,hypertrophy of the heart may occur as the result of severe exercise1 and this within certain limits is not an abnormal condition4 ,occasionally dilatation of the heart has been produced in weakly lads4 ,amount of ,exercise ,desirable4--,according to ,parkes1 the average daily work of a man engaged in manual labour in the open air is equivalent to the work involved in lifting #bej to #cej tons one foot high2 this is a moderate amount1 #djj tons being a heavy day's work4 ,the amount of muscular exercise involved in this may be easily known by remembering that a walk of #bj miles on a level road is equivalent to about #cec-bc tons lifted #a foot2 and that a walk of #aj miles while carrying #fj lbs4 is equivalent to #bdg tons lifted #a foot4 7,haughton74 ,the amount of work done by a healthy adult per diem is stated by ,m4 ,foster to be about #aej1jjj metre-kilogrammes 7i4e41 #aej1jjj kilogrammes lifted #a metre74 ,metre-kilogrammes can be converted into foot-pounds by multiplying by #gbcc2 into foot-tons by multiplying by #jjcbbi2 #aej1jjj metre-kilogrammes therefore equal #dhdce foot-tons4 ,this is considerably in excess of ,parkes' estimate1 but in certain laborious occupations this high amount is reached4 ,in addition to this amount of external work1 there is the internal work of the heart1 muscles of respiration1 digestion1 etc4 ,this is estimated by ,parkes at about #bfj foot-tons4 ,the internal and external muscular work of the body together amount to about #agth to #ahth of the total force obtainable from the food4 ,every healthy man probably ought to take an amount of exercise represented by #aej tons raised #a foot1 which is equal to the work done in walking #h to #i miles on a level road4 ,a certain amount of this exercise is taken in performing one's daily work2 but apart from this1 out-door exercise should be taken equivalent in amount to a walk of five or six miles4 ,it is impossible to lay down rules to suit all cases1 but a less amount of exercise than that named is probably incompatible with perfect health4 ,effects of ,deficient ,exercise4--,the muscles themselves become enfeebled and wasted4 ,some wasting of muscle occurs after a few days' confinement to bed2 and a limb confined in a splint speedily loses its healthy1 rounded contour4 ,oxidation processes are diminished2 less carbonic acid is eliminated1 and it tends to accumulate in the system1 owing to the diminished activity of respiration4 ,in consequence of the diminished oxidation1 the temperature of the body is not well maintained1 and the heat is not uniformly distributed4 ,cold feet are a common complaint of those who lead sedentary lives1 though seldom complained of by others4 ,along with the other muscles1 the heart becomes enfeebled and the circulation less perfect4 ,digestion is enfeebled2 the appetite is poor4 ,the nervous system also suffers2 nervous irritability is a common result1 while sleeplessness--a thing almost unknown among those who live by the sweat of their brow--is becoming much more common among the worried and ill-exercised inhabitants of our towns4 ,many diseases are favoured by deficient exercise1 and can be averted by systematic exercises and the concomitant increased supply of pure air4 ,it is often difficult to appraise the relative merits of exercise and pure air2 but there can be no doubt that both are of extreme importance4 ,the prevention of consumption1 even in those with a strong hereditary tendency1 is greatly helped by systematic exercises1 especially those directed to the expansion of the chest cavity4 ,in cases of consumption there is commonly a history of deficient exercise or an occupation involving a cramped position1 as well as of living in an impure air4 ,various deformities are induced by defective exercise of particular groups of muscles4 ,thus drooping shoulders may be caused by shoulder-straps confining the action of the shoulder-muscles in the earlier years of life4 ,stooping is favoured by sitting in cramped positions in school1 and by the use of desks not inclined at the proper angle4 ,lateral curvature of the spine is due to weakness of the muscles of the back1 and is best treated in its earlier stages by gymnastic exercises specially directed to strengthening these muscles4 ,the tendency to such curvatures is greatly increased in girls by the fact that their trunks are imprisoned in corsets as if in splints1 and so exercise of the trunk muscles is reduced to a minimum4 ,rules respecting ,exercise4 #a4 ,the clothing during exercise should not be excessive1 and should not interfere with the free play of the limbs1 nor with full expansion of the chest4 ,flannel is the best material to wear next the skin1 as it absorbs perspiration without becoming non-porous4 #b4 ,avoid chill after exercise4 ,it is well1 if there has been any perspiration during exercise1 to strip and scrub the skin1 particularly about the chest and arm-pits1 with a rough towel4 #c4 ,exercise should be systematic and regular4 ,it is important to avoid sudden1 violent1 and competitive exercise4 ,no severe exercise ought to be undertaken without a gradual training4 #d4 ,the amount of exercise must be regulated by individual fitness4 ,a chain is no stronger than its weakest link4 ,the muscles may be stronger than the heart or lungs1 and the latter may be fatally injured by an amount of exercise which the muscles can well bear4 ,hence the importance of ascertaining the condition of the vital organs before entering on a course of training4 ,another important bearing of this rule is in relation to the exercise of growing boys and girls4 ,when we remember that a boy at school will sometimes grow six to eight inches in a year1 it is evident that much energy is being expended in this direction1 and that excessive gymnastic exercise can only do harm4 ,between the ages of fifteen and seventeen there is usually the greatest amount of physical development1 and if there is great muscular strain at this period1 growth is interfered with1 and the power of resistance to disease may be seriously lowered4 #e4 ,every part of the body ought to be exercised4 ,this is done spontaneously by the infant4 ,every muscle of his body acts in sheer delight4 ,the evils of exercise confined to particular groups of muscles have been already described4 ,lawn tennis is very valuable as affording exercise for both limb and trunk muscles4 #f4 ,exercise should not be taken immediately after meals1 as thus digestion is interfered with4 #g4 ,exercise should be taken1 as far as possible1 in the open air4 ,a small amount of exercise out of doors is much more invigorating than a large amount indoors4 ,the ,forms of ,exercise taken may be divided into recreative and educational1 though both of course may be recreative under many circumstances4 ,the primarily recreative exercises1 such as rowing1 cricket1 football1 tennis1 hockey1 will1 it may be hoped1 be never replaced by educational gymnastics1 though the latter possess a high value4 ,the recreative influence as well as the influence on the power of self-control of such games as cricket and football render them of national importance4 ,educational gymnastics can be applied to exercise the muscles of any part of the body1 and can be exactly graduated to individual requirements4 ,singing1 speaking1 and reading aloud1 are forms of muscular exercise very much neglected1 and they are particularly important1 as the lungs and voice are by these means greatly strengthened1 and rendered much less liable to the inroads of disease4 ,professor ,haughton has shown that the work done by a man walking on a level surface at the rate of three miles an hour is equivalent to raising his own weight1 plus the weight he carries through #abj of the distance walked4 ,thus1 if ,w weight of the man1 ,w#a weight carried by him1 ,d distance walked in feet1 ,c co-efficient of traction 7#abj1 at three miles an hour71 then we obtain by the following formula the amount of work done1 the co-efficient of traction being multiplied by #b1bdj 7the number of pounds in a ton7 to obtain the result in foot-tons4 7,w ,w#a7 ,d_/7,c #b1bdj7 ,in ascending a height1 a man raises his whole weight through the height ascended4 ,a regiment of soldiers marches ten miles1 each carrying a weight of #fj lbs4 ,what amount of work is performed by each soldier8 ,if we assume the average weight of each soldier to be #aej lbs41 and that the march was at the rate of three miles an hour1 then-- 7#aej #fj7 #aj #e1bhj_/7bj #b1bdj7 #bdge foot-tons4 ,in this example it is assumed that the march is on entirely level ground that all weights are carried in the most convenient manner1 and that the rate of travel is three miles an hour4 ,velocity is gained at the expense of carrying power4 ,it has been found that the amount of work is generally inversely as the square of the velocity4 ,haughton has determined from ,weber's calculations the co-efficient of resistance for three velocities4 ,,velocity4 ,,co-,,efficient ,,of ,,traction ,,or ,,resistance4 #ahah miles per hour #abhbg #dcec #aacgj #ajegg #agea ,parkes has extended these calculations to show the distance in miles required to be travelled at various velocities to do work equal to #cjj foot-tons1 and the time required in each instance4 ,,distance ,,for ,,men ,,of ,,time ,,required ,,velocity ,,in ,,co-,,efficient ,,of #aef ,,lbs4 ,,to ,,equal ,,in ,,hours ,,miles ,,per ,,hour4 ,,resistance4 #cjj ,,foot-,,tons4 ,,and ,,minutes4 hrs4 mins4 #b #abfgd #abb #aj #cf #c #abjei #afc #e #bd #d #aafgd #acc #c #ah #f #aabah #if #a #cf #h #aifj #gf #j #eg #aj #aghi #fc #j #ch ,the co-efficient #abj1 corresponds very nearly to #ca miles per hour1 and it appears that at this rate of travel the greatest amount of work can be done with the least expenditure of energy4 ,how much work is done by a man weighing #aej lbs4 who walks #ae miles up an incline #a in #bjj8 ,the number of feet ascended in #ae miles #e1bhj #aebjj #cif4 ,the amount of work done by the man in raising his own weight #cif feet high #cif #aejb1bdj #bfe foot-tons4 ,the amount of work done in walking #ae horizontal miles at the rate of #c miles an hour #aej #ae #e1bhj_/7bj #b1bdj7 #bfe4b foot-tons4 ,total amount of work done #bfe4b #bf4e #bia4g foot-tons4 ,eight palanquin bearers carry an officer weighing #ahj lbs4 and a palanquin weighing #bej lbs41 a distance of #be miles4 ,assuming that each man weighs #aej lbs41 what amount of work was done by each man8 7,parkes47 #bej #ahj #dcj #aej #h #a1bjj --------- ,w ,w#a #a1fcj #a1fcj #be #e1bhj_/7bj #b1bdj7 #d1hjbg foot-tons4 ,this being the total work done1 the work per man nearly #fjj4c foot-tons4 ,a hill-coolie weighing #aej lbs4 goes #cj miles with an ascent of #e1ejj feet in three days1 carrying #hj lbs4 in weight4 ,what is the work per day8 7,parkes47 ,work of the ascent 7#aej #hj7 #e1ejjb1bdj #efdg foot-tons4 ,work of #cj miles walk #bcj #cj #e1bhj_/7bj #b1bdj7 #hacb foot-tons4 ,total work #efdg #hacb #a1cggi4 ,total work per day #a1cggic #deic foot-tons4 ,suppose a man weighing #aej lbs4 in his clothes1 carries a load of bricks weighing #ce lbs4 up a perpendicular ladder #cj feet high1 #ajj times daily1 what amount of work does he do2 and what will it equal in miles walked upon a flat road at the rate of #c miles an hour8 77#aej #ce7 #cj #ajj7 _/ #b1bdj #bdgh foot-tons 7#ahe ,d7 _/ 7#bj #b1bdj7 #bdgh4 ,therefore ,d #fj1jef feet about #aad miles4 ,suppose a man strikes #ab1jjj strokes in #e hours with a #ad-lb4 hammer1 raising it at each stroke #d feet1 how much work does he do8 ,compare this with a walk of #ae miles on a level ground at #c miles an hour1 the weight of the man and what he carries being #ahj lbs4 7a7 #ab1jjj #ad #d #fgb1jjj foot-lbs4 of work #cjj foot-tons4 7b7 7#ahj #ae #e1bhj7 _/ 7#bj #b1bdj7 #cahb foot-tons4 ,the two amounts of work are related as #cjj3 #cahb4 ,,chapter ,,xxxviii4 ,,personal ,,hygiene 7continued7--,,rest ,,and ,,sleep4 ,physiological ,considerations4--,life is made up of alternations of rest and action4 ,the exercise of any organ is followed by a necessary period of repose1 during which the oxidised materials produced by functional activity are removed by the blood1 and carried to the excretory organs2 while at the same time fresh nutritive material is supplied by the blood to make good the losses thus sustained4 ,the only apparent exceptions to this rule of alternation of rest and exercise are the heart and lungs1 and some less important organs acting out of the control of personal volition4 ,but even these organs obey the universal law4 ,the difference is that their rest is very frequent and momentary2 the heart having to contract sixty or seventy times per minute1 rests #faa of a second each second1 or more than thirteen hours in the twenty-four4 ,the lungs and respiratory muscles rest a shorter time than this1 but probably about three hours per day4 ,the necessity for rest is well shown by the sense of taste4 ,if salt is kept in the mouth for a considerable time1 the power of tasting it disappears1 and only returns in its original strength after several hours4 ,the gustatory nerve has been exhausted4 ,the other sense-organs illustrate the same principle4 ,persons are not uncommonly made deaf by the sounds of machinery4 ,after looking at a particular colour for some time1 the nerves receiving impressions from this colour are exhausted1 and only its complementary colour is visible4 ,rest may be either partial or general4 ,the principle of partial rest has very useful practical bearings4 ,such rest is illustrated by the student who takes a walk1 or uses methodical gymnastic exercises2 a concert may provide agreeable exercise for the auditory nerves and the part of the brain connected with them1 while allowing the over-tired intellectual part of the brain to rest in peace2 similarly1 light literature may prove a pleasing rest after severer studies4 ,walking is more especially the exercise of the brain-worker4 ,partial rest is the same thing as change of occupation1 and by a careful regulation of the relative amount of cerebral and muscular work1 energy can be largely economised4 ,the horse1 which exercises chiefly his muscles1 requires only five or six hours to recuperate his energy2 and our muscles require less sleep than our brain4 ,sleep is the only form of complete and general rest4 ,in attaining this condition1 the muscles sleep first1 then the eyes close 7owing to muscular rest71 and the thoughts wander2 hearing is the last sense to lose cognizance of the surrounding world2 dreaming succeeds wandering thoughts1 and even dreaming may cease if the brain repose is complete4 ,during sleep the brain diminishes in size1 and becomes paler2 the amount of blood in the brain being diminished4 ,probably the cerebral anmia is rather a consequence of the functional inactivity of the brain during sleep than a cause of the sleep4 ,during sleep the heart and lungs continue their work2 the blood is circulated and purified1 the intestines continue their vermicular contractions1 and absorb food from the alimentary canal1 and the organs nourish themselves at leisure4 ,two facts relating to sleep have important practical bearings4 ,first1 during sleep metabolism is less active1 and so the temperature of the body tends to be somewhat lowered4 ,secondly1 assimilation is more energetic2 this favours the absorption of noxious vapours1 if any are present4 ,there is probably1 therefore1 slightly less danger of remaining in a stuffy1 impure atmosphere during the day than at night4 ,practical ,rules ,concerning ,sleep4--#a4 ,amount of sleep required4 ,it is impossible to lay down any fixed rule applicable to all persons and circumstances4 ,the amount of sleep required1 like the amount of food1 varies greatly4 ,habitual deficiency of sleep produces a condition of wretchedness and prostration1 with great restlessness4 ,prolonged watching inevitably breaks down the constitution4 ,not the least evil consequence of irregular and deficient sleep is1 that sleep1 when desired1 is often courted in vain4 ,habitual excess of sleep produces a condition of brain less active than usual1 and less favourable for thought and action4 ,impressions are received less readily1 and the power of will is correspondingly diminished4 ,the amount of sleep required varies with-- 7#a7 ,age4--,the infant1 if healthy1 spends the larger part of his existence in sleep2 gradually the amount required diminishes until1 for the adult1 seven or eight hours suffice4 ,children over two or three years old require sleep only during the night4 ,in advanced life there is a tendency to revert to infantile habits1 sleep occurring in frequent short snatches4 7#b7 ,sex4--,women have been stated to require rather more sleep than men1 but this is doubtful4 ,the hours of sleep required have in accordance with this view been stated to be1 8,six for a man1 seven for a woman1 and eight for a fool40 ,a reversal of this order would more nearly approximate to the requirements of town life4 7#c7 ,temperament4--,those of a cold lymphatic temperament require more sleep than sanguine or nervous people1 though the latter sleep more deeply4 ,frederick the ,great1 ,john ,hunter1 and ,napoleon ,i4 are said to have required only five hours' sleep per day2 but the last of these had the faculty of taking short naps at a few moments' notice4 7#d7 ,the sick and convalescent require much more sleep than those who are healthy4 7#e7 ,habit has a very important influence4 ,many people appear to sleep too much1 and thus dull to some extent their mental faculties2 but on the other hand1 modern life1 with its nervous strain1 keen competition1 and constant hurry and worry may make a larger amount of sleep necessary than that required by our forefathers1 who invented the foregoing proverb4 7#f7 ,occupation4--,mental work requires more repose than physical4 #b4 ,relation of sleep to food4--,the molecular life of the tissues--that is1 the processes of nutrition--ought to be undisturbed4 ,these go on most perfectly when no active function1 such as that of digestion1 is being performed4 ,but while the stomach carries on the digestive functions to only a small extent during sleep1 the intestines continue still to digest and absorb food4 ,in accordance with these facts1 it is advisable to allow at least two hours between the last meal of the day and sleep1 especially if animal food has been taken4 #c4 ,as absorption is increased and the temperature is lowered during sleep1 it is important to sleep in pure air1 and to have warm coverings1 especially about the shoulders and arms4 ,many an obstinate cough might be cured by the simple expedient of wearing a flannel jacket at night4 #d4 ,sleep during the night and not during the day4 ,it should hardly be necessary to say this1 as the universal instinct of animals shows its advisability2 but1 unfortunately1 the habits of mankind have commonly led to a partial reversal of the natural arrangement4 #e4 ,the room should be dark2 light1 like sound1 is inimical to sleep4 ,the head should be moderately raised4 ,the temperature of the room for robust persons need not be artificially raised4 ,sleeplessness1 as a rule1 occurs only when some physiological law has been broken4 ,to relieve it1 it is essential to equilibrate muscular and mental functions4 ,increase of muscular exercise is an important element in its treatment4 ,in addition it is advisable not to have any severe mental work during the evening1 nor to indulge in late suppers4 ,sleeplessness is the bane of many men of a nervous temperament1 and chiefly attacks those of sedentary habits4 ,it is apt to recur1 and for this reason1 if for no other1 narcotics ought to be scrupulously avoided4 ,the habit of taking such soporifics is unfortunately becoming much more common1 and is productive of many evils4 ,death from accidental overdose is a frequent calamity2 and1 apart from this possibility1 the invalid's nervous system is completely ruined by persistence in the habit1 his power of will is annihilated1 and he becomes the miserable slave of an evil habit1 whose end is death 7see also page #ed74 ,,chapter ,,xxxix4 ,,personal ,,hygiene 7continued7--,,cleanliness4 ,physiological ,considerations4--,the skin consists of a superficial part or epidermis1 and a deeper part called the dermis or cutis4 ,tubes of two kinds open on the surface of the skin1 penetrating at their deeper ends into the cutis1 viz4 sweat or sudoriparous glands and sebaceous glands4 ,the sudoriparous glands are simple tubes1 the lower ends of which lie coiled up in the dermis4 ,each tube when straightened out is about a quarter of an inch long4 ,it has been estimated that in the palm of the hand there are #c1ebh orifices of sudoriparous and sebaceous glands on a square inch of surface2 reckoning each gland at #ad inch long1 this means #gc feet of tubes in this small space4 ,assuming that there are #b1hjj tubes to every square inch1 and that the amount of surface in a man of ordinary height and bulk is #b1ejj square inches1 it follows that there are seven million pores in a man--that is1 #a1gej1jjj inches1 or nearly twenty-eight miles4 ,the perspiration secreted by the sudoriparous glands is constantly evaporating from the surface of the body4 ,it is very important that the orifices of these glands should be kept open in order that the secretion may not be interfered with4 ,animals have been killed by covering their skin with gelatine1 and so preventing the escape of perspiration4 ,the sebaceous glands are shorter than the sudoriparous1 and commonly end alongside the hairs before the latter issue from the skin4 ,they secrete an oily material which serves the purpose of a natural pomade4 ,the sebaceous secretion also keeps the general surface of the skin unctuous and supple4 ,the smell of the sebaceous secretion may be unpleasant1 especially in the arm-pits and some other parts4 ,frequent washing is therefore desirable4 ,the ,conditions ,due to ,uncleanliness are due to obstruction of the excretory ducts1 to accumulation of dbris on the general surface of the skin1 and to the consequent interference with the circulation4 #a4 ,the obstruction of the sudoriparous pores of the skin interferes with the elimination of waste products by the perspiration2 these are re-absorbed or retained in the system2 consequently more work is thrown on the lungs and kidneys1 and the equilibrium of health is destroyed4 ,sebaceous obstruction causes an accumulation of oily secretion in the ducts4 ,the black spots so commonly seen about the nose1 are the blocked up orifices of sebaceous glands1 and by squeezing the nose tiny threads of fatty matter are forced out from the interior of these glands4 ,pimples on the face are usually due to obstruction of the sebaceous glands2 sometimes the obstruction leads to inflammation around the sebaceous gland 7acne7 which often permanently injures the skin4 #b4 ,accumulation of effete matter on the skin occurs1 unless frequent ablutions are performed4 ,the epidermis is constantly shedding its older and more superficial parts1 in the form of minute scales or 8scurf40 ,in the absence of frequent washing1 the scales of epithelium tend to accumulate1 the sebaceous secretion matting the scales together1 and rendering them more adhesive4 ,the saline matters of the perspiration also accumulate along with the scales and sebaceous secretion1 and in virtue of their hygroscopic properties tend to keep the skin clammy and cold4 ,the obstruction of excretions and the accumulation of dbris lead to other consequences4 ,thus3--#c4 ,the sensibility of the skin is dulled when the sensory papill are covered with dirt4 ,the sensations received by the skin are important in regulating the temperature of the body4 ,a cold external temperature should cause a reflex contraction of the small arteries bringing blood to the skin1 thus diminishing the flow of blood and preventing undue loss of heat4 ,similarly1 if the external temperature is high1 or the internal development of heat is too great1 these arteries dilate1 and sending more blood to the skin1 cause a greater loss of heat by radiation and conduction4 ,impaired sensibility of the skin leads to imperfect action of the reflex nervous mechanism to which the above effects are due1 and consequently the dangers resulting from sudden alterations of temperature are greatly increased4 #d4 ,the tendency to chills is increased1 not only by deficiency of the nervous tone of the skin1 but also by obstruction of the pores of the skin1 and by the hygrometric action of the saline matter collected on it4 #e4 ,cutaneous diseases are due to1 or favoured by1 uncleanliness4 ,these are of two kinds--parasitic and non-parasitic4 ,acne1 which is the chief non-parasitic disease favoured by uncleanliness1 has been already mentioned4 ,parasitic skin diseases are greatly favoured by the presence of a dirty skin1 which affords a suitable soil for the development of the parasites4 7,see also page #bge74 ,uses of ,soap4--,soap is produced by an action of an alkali on an oil4 ,the alkali displaces glycerine from the oil1 and forms an alkaline stearate1 which is soap4 ,soft soap is chiefly stearate of potassium2 hard soap is stearate of sodium4 ,there may also be present the alkaline salts of oleic and palmitic acid4 ,soft soap is not used for washing the skin1 as it is too irritating4 ,all soaps contain a slight excess of soda2 the greater this excess1 the more irritating is the soap to delicate skins4 ,hard soaps may be also made with potash1 if the fat employed be a solid one2 but such soaps are rather softer than ordinary hard soaps1 and more caustic4 ,cocoa-nut oil is used in making marine soaps1 because1 unlike all other kinds1 it is not rendered insoluble by brine1 and so will form a lather with sea-water4 ,normal soaps contain from #ae to #ce per cent4 of water4 8,liquoring0 a soap consists in adding #e to #be per cent4 of soluble silicates4 ,by this means the soap may be made to hold #gj per cent4 of water1 which is obviously very wasteful4 ,in washing the skin1 the water washes away a considerable amount of epidermis1 and the saline matters which have collected4 ,for the oily sebaceous secretion soap is required4 ,the alkali in soap combines with the oily matter1 forming an emulsion which carries away with it a quantity of the dirt which previously blocked the orifices of the sebaceous and sweat ducts4 ,when the skin is rubbed by the towel after washing1 the softened epithelium1 and with it any remaining dirt1 are rubbed off1 leaving the skin clean1 and able to perform its normal functions4 ,the ,use of ,baths4--,the primary object of bathing is cleanliness4 ,a secondary consideration is the pleasure derived from bathing4 ,baths are especially necessary for those persons who lead sedentary lives4 ,when the skin is kept in an active condition by exercise1 it to some extent cleanses itself4 ,thus1 a farm labourer who has a weekly bath1 may be really cleaner than a person of sedentary habits1 who has two baths per week4 ,baths are classified according to temperature as follows3--,below #gj ,fahr4 they are described as cold2 tepid up to #he2 warm up to #ig2 and hot over this temperature4 ,it is important in deciding the temperature of a bath not to trust to one's sensations2 the only accurate measure is by the thermometer4 ,a cold morning tub in the summer will commonly contain water at #ee to #fj2 while the same in winter will be down to #dj1 or occasionally to #cb4 ,for purposes of cleanliness the warm bath is the most efficient1 combined with the free use of soap4 ,the chief objection to it is that it produces an increased flow of blood to the skin1 by relaxing the cutaneous blood-vessels1 thus increasing the danger of chills if there is subsequent exposure4 ,the increased sensibility to cold resulting from a warm bath may be obviated by afterwards rapidly sponging the body all over with cold water1 and then drying the body quickly1 and using the friction of a moderately rough towel4 ,it is desirable for both cold and warm baths to have a 8bath-sheet10 in which the person may be completely enclosed on coming out of the bath4 ,drying is thus much more quickly accomplished1 and the danger of chill is minimised4 ,a daily morning cold bath is a most important agent in the maintenance of robust health4 ,the first sensation on entering a cold bath is of shock1 due to the cooling of the surface of the body4 ,this is followed in a few seconds by a glow1 due to the blood returning with considerable force to the skin4 ,a cold bath ought to be taken as rapidly as possible4 ,if soaping the body is desired1 it should be done before entering the bath1 and the stay in the latter should be little more than momentary4 ,in this way the best reaction or 8glow0 is obtained4 ,if a feeling of cold and chilliness remains after a cold bath1 it has done more harm than good4 ,this condition may often be avoided by quick drying and brisk friction2 if after this a good reaction is not obtained1 the temperature of the water should be increased4 ,for those who are not very robust1 the 8cold tub0 in winter is to be deprecated4 ,if the water be raised to #fj by the addition of warm water1 or in some cases even to #gj1 a good reaction may be obtained4 ,in other cases1 in which a reaction is not experienced even after a bath of the latter temperature1 a tepid bath may be taken1 and then the body rapidly sponged with colder water4 ,cold baths increase the tone of the skin1 rendering it less susceptible to changes of temperature4 ,the tendency to 8catch cold0 is diminished1 the blood-vessels and nerves of the skin both responding more readily to any stimuli4 ,swimming is a valuable combination of bathing and exercise4 ,a sudden plunge into cold water for swimming purposes is dangerous to those who are not hardened to it1 and especially so in the case of running water1 as in rivers or the sea4 ,here the water around the swimmer is constantly being changed1 and each layer of water coming in contact with him abstracts a considerable amount of heat4 ,many of the cases of so-called death from 8cramp0 are really due to the benumbing and depressing influence of continued cold on the vital organs4 ,swimming1 under proper superintendence1 ought to be universally enforced4 ,the exercise accompanying it serves in most cases to counteract the depressing action of the cold water2 but it is important in all cases to attend to certain rules4 ,the immersion should not be prolonged2 the body should be warm at the time of entering the water2 and the bath should not be taken until about two hours after a meal2 nor after prolonged fasting1 as before breakfast4 ,personal ,cleanliness4--,personal cleanliness involves not only attention to the skin1 which we have already considered1 but to the hair1 nails1 mouth1 and other parts of the body4 ,the hair ought to be carefully brushed and combed1 but it is not desirable to use soap to it as often as to the skin4 ,soap removes the sebaceous secretion from the hairs1 and renders them dry and brittle4 ,artificial pomades are1 as a rule1 unnecessary4 ,the nails should be cut square1 and not down at the sides4 ,it is hardly necessary to say that they should be kept clean3 they may convey serious infection4 ,the mouth and all mucous orifices should be kept scrupulously clean4 ,a ftid breath is not uncommonly due to the discharges from carious teeth1 or to the decomposition of food which has been allowed to accumulate in the cavities of teeth4 ,such decomposing matters when swallowed1 are apt to produce indigestion2 and this also occurs from imperfect mastication of food by the bad teeth4 ,it is important that the teeth should be frequently cleansed1 and that all carious teeth should be 8stopped0 at an early period1 and tartar and other accumulations removed4 ,whether bad teeth1 which are so extremely common1 are due to the drinking of very hot liquids1 or to the fact that the more perfect cooking of food gives less healthy friction to the teeth1 is doubtful4 ,whatever the cause1 by keeping the mouth thoroughly sweet and clean1 and by having the carious teeth stopped as soon as discovered1 their vitality may be greatly prolonged4 ,teeth should be periodically inspected by a competent dentist4 ,irregularities of the teeth may be corrected1 if they receive early attention4 ,carious 8milk-teeth0 should receive attention from a dentist1 as well as the permanent teeth4 ,general ,cleanliness4--,next to cleanliness of the skin1 that of the apparel is most important4 ,there is a general preference for colours 8that do not show the dirt02 the fact that it is still there1 though not seen1 being partially ignored4 ,changing of apparel is commonly confined to underclothing4 ,it is forgotten that vests1 trousers1 dresses1 etc41 acquire a large amount of dirt and organic matter1 and ought to be changed and well aired at intervals4 ,cleanliness in respect to bedclothes is very important4 ,organic matters evolved from the skin1 lungs1 etc41 hang about the bed-linen1 and give the bedroom the 8close smell0 which can be perceived on entering it in the morning straight from the fresh air4 ,the beds should not be made directly after being evacuated1 but the clothes should be thrown over the bottom of the bed1 the bolsters and mattress well shaken1 and every part exposed to a free current of air during the greater part of the morning1 before re-arranging the clothes4 ,eider-down quilts1 unless frequently ventilated by exposure to outside air1 are unwholesome4 ,superfluous bedroom furniture should be avoided1 as it all takes away from the breathing-space4 ,bed-hangings should be reduced to a minimum1 and all excretory matters covered up during their stay in the room1 and removed as early as possible4 ,cleanliness of the house is also very important as a means of health4 ,dust1 in however obscure a corner it rests1 attracts to itself organic matters1 and forms a soil in which disease germs may grow4 ,besides this1 it devitalises the air1 depriving it of its active oxygen4 7,see also page #aja74 ,dust in the streets serves to carry about various diseases1 besides mechanically irritating any part it comes in contact with1 producing bronchitis1 etc4 ,,chapter ,,xl4 ,,clothing4 ,physiological ,considerations4--,the average temperature of the surface of the body in man is #ihd to #ihf4 ,the maintenance of a tolerably uniform temperature is an essential condition of life4 ,the factors governing the temperature of the body are the amount of heat produced and the amount lost4 ,if more heat escapes1 more has to be generated2 and the source of all the heat produced in the body is the food taken4 ,this becomes changed by the metabolic processes occurring in the body which produce heat4 ,heat is lost1 7#a7 by the skin2 7#b7 in respiration1 the expired air having been heated during its stay in the lungs2 7#c7 with the food and drink taken1 if not at the temperature of the body2 7#d7 with the excreta2 and 7#e7 by transformation of heat into mechanical energy4 ,of the whole loss by these different channels1 probably eighty to ninety per cent4 is through the skin4 ,the ,loss of ,heat by the ,skin is in three different ways4 ,first1 by conduction1 when the skin comes in contact with anything cooler than itself2 secondly1 by radiation into space2 and thirdly1 by evaporation of the perspiration4 ,the last cause produces a considerable reduction of temperature1 even when the perspiration is not so abundant as to be visible1 but is in the form of insensible perspiration4 ,the losses by these different sources vary in amount2 when one is increased1 another is diminished1 by way of compensation4 ,thus1 in very cold weather1 the amount of radiation and conduction of heat are increased2 but evaporation greatly decreases1 and the diminished loss of heat in this respect counter-balances in some degree the increased loss by radiation and conduction4 ,when the external warmth is considerable1 increased evaporation occurs2 while when the weather is cold1 the cutaneous arteries contract1 and less blood goes to the skin1 and so the loss of heat is diminished4 ,in most climates1 however1 this action of the skin requires to be supplemented by some kind of clothing4 ,requisites of ,dress4--#a4 ,the first and most important requirement is that clothing should maintain a uniform and equable temperature in all parts of the body4 ,in hot climates clothes are required in order to protect the body from external heat4 ,in this country1 they are required to prevent the too rapid escape of heat from the body4 ,for both these purposes1 dress must be of a non-conducting material1 in order not to encourage transfer of heat into or from the surrounding atmosphere4 ,the loss of heat by the skin may be prevented by interfering with radiation or conduction of heat1 or with evaporation from its surface4 ,radiation of heat from the skin is prevented by clothing1 the dress taking the place of the skin as a radiating surface4 ,the amount of radiation from the dress will depend on the rapidity of conduction of heat from the skin4 ,the amount of conduction and of radiation of heat will vary considerably with the material and colour of the dress4 ,as regards conductivity1 the two extremes are represented by linen and fur4 ,it is found that if the conducting power for heat of linen #ajj1 then that of wool #ej to #gj4 ,this partly explains why woollen goods are so much warmer than linen4 ,we shall find that there is another explanation in the relative hygroscopic properties of the two materials4 ,as regards radiation of heat1 in one experiment it was found that while a piece of linen took #aj minutes to cool1 a corresponding piece of flannel took #aa minutes4 ,apart from the material1 the colour of dress has some influence in regulating the loss of heat4 ,dark-coloured materials absorb more light and heat than lighter coloured materials2 they may be good or bad conductors of heat1 according to the nature of the material4 ,white reflects the rays of light and heat2 hence it is a poor absorber4 ,in summer it prevents the passage of heat inwards1 and1 in winter1 may prevent its passage from the body4 ,it is thus well adapted for both winter and summer clothing1 and has the additional advantage of being the cleanest colour4 ,franklin placed a number of squares of different coloured cloths of the same material on snow1 and found after a time that the snow covered by the black piece was most1 and by the white piece least melted4 ,in another set of experiments1 shirting materials dyed various colours were taken1 and it was found that if the rays of heat received by white were represented as #ajj1 pale straw received #ajb1 dark yellow #adj1 light green #aee1 ,turkey red #afe1 dark green #afh1 light blue #aih1 black #bjh4 ,the influence of colour is antagonised to a large extent by the nature of the material2 the increased heat absorbed by a dark material may be counterbalanced by the material being a good conductor4 ,also the influence of colour is only exerted superficially2 hence1 although it produces considerable effect in thin textures1 as gauze1 it has little influence on thick materials4 #b4 ,the dress should not interfere with perspiration4 ,in order that it may not do this1 it should be competent to absorb moisture easily1 without its surface becoming wetted4 ,materials like linen which lose their porosity and rapidly become wetted by perspiration1 cause rapid loss of heat from the body1 inasmuch as water is a better conductor of heat than air4 ,pettenkofer found that while the maximum hygroscopic power of wool 7flannel7 is #agd and the minimum #aaa2 the maximum of linen is #ge and the minimum #da4 ,hence1 with a flannel vest next the skin1 the liability to chill is much less than with a linen one4 ,there is one slightly counterbalancing drawback2 hygroscopic materials absorb moisture from the air1 as well as from the skin4 ,a woollen coat during a damp day1 without rain1 increases considerably in weight4 ,waterproof clothing is injurious when worn beyond a short period1 on account of its being non-porous and consequently keeping the body enveloped in a vapour bath composed of its own perspiration4 ,for a similar reason ,india-rubber boots are objectionable1 except for short periods2 they make the feet damp1 and even sodden4 ,sealskin jackets are objectionable for walking1 not only because of their weight1 but because they are not porous4 #c4 ,the warmth of clothing should be uniformly distributed throughout the body4 ,this principle is very frequently departed from2 and consequently one part may be chilled while another is over-heated4 ,this is seen especially in female apparel4 ,the same evil is seen in the short sleeves1 and short and low-necked dresses of young children4 8,combination0 garments for women1 and sleeves and leggings for young children are happily becoming more generally adopted1 and will diminish the diseases due to exposure to cold4 #d4 ,the clothing should not be tight2 and this for three reasons4 ,first1 because loose clothing is warmer than tight2 this everyone has experienced in the case of gloves4 ,the retention of air in the meshes of clothing is one of the main causes of its warmth1 air being a bad conductor of heat4 ,the imprisonment of air in the meshes of the material largely explains the warmth of eider-down quilts1 furs1 and flannels as contrasted with linen4 ,secondly1 clothing should not be tight1 in order to avoid interference with the action of the muscles4 ,tight sleeves prevent the muscles of the arms and chest from being exercised4 ,tightly laced corsets imprison the trunk muscles1 prevent their contractions1 and so lead to muscular weakness and occasionally spinal curvature4 ,tight skirts similarly prevent free play of the lower limbs1 leading to a halting gait1 a diminished amount of exercise1 with all the evils following deficient exercise4 ,tight clothing is not confined to one sex1 and in all cases leads to hampered movements and deficient muscularity4 ,thirdly1 tight clothing tends to impede the functions of circulation1 respiration1 and digestion4 ,the fashion which more than any other interferes with important functions is tight-lacing4 ,this produces 7#a7 compression and displacement of the viscera2 the liver and the stomach especially suffer4 7#b7 ,respiration and circulation are impeded1 the action of the diaphragm being impeded4 7#c7 ,the muscles of the trunk being tightly encased1 are incapable of movement1 and consequently tend to waste and atrophy4 ,the general outline of the body is altered4 ,instead of the waist being elliptical1 as it naturally is1 it becomes nearly circular2 and instead of its circumference averaging twenty-six to twenty-seven inches1 it may be eighteen to twenty-one inches4 ,tight garters tend to produce varicose veins4 ,tight boots are injurious1 as they tend to destroy the natural elasticity of the movements1 and confine them within narrow limits4 ,they act to some extent the part of splints4 ,by interfering with the circulation of blood through the feet1 they cause cold feet1 and not uncommonly chilblains4 ,high-heeled boots do not allow the natural elasticity of the foot to come into action4 ,they distort the movements of the body and cause corns and bunions4 ,similar effects are produced by boots which are too narrow and have pointed toes1 thus not allowing free movement of the toes4 #e4 ,the weight of the clothing should be the smallest amount consistent with warmth1 and it should be evenly distributed4 ,the chief weight should not be suspended from the waist1 as here the parts are not well supported by bones4 ,the shoulders and hips should share in the suspension of clothing1 thus diminishing the danger of compression and displacement of internal organs4 ,in order that garments may be as light as possible1 they should be made to fit to each limb separately1 thus diminishing the amount of material required4 #f4 ,the materials of dress should be as far as possible non-inflammable4 ,this may sometimes be disregarded1 but is often important1 as in the nursery4 ,in this respect1 as in many others1 wool possesses great advantages4 ,woollen fabrics smoulder rather than burst into flames1 and thus the injury resulting from any accident is limited4 ,cotton is more inflammable than linen1 linen than silk1 and silk than wool4 ,a closely woven cloth is less inflammable than one with open meshes4 ,dress materials1 and more particularly muslin1 have been rendered non-inflammable by treating with a solution of ammonic phosphate1 or ammonic phosphate and ammonic chloride mixed4 ,the best material1 however1 is sodic tungstate1 which1 unlike the others1 is not affected by ironing4 ,sodic molybdate is used in arsenals to render the workmen's clothing non-inflammable4 ,all the above plans are objectionable1 as the weight of the material is increased #ah to #bi per cent41 and they all wash out4 ,to remedy this1 a 8fire-proof starch10 containing sodic tungstate has been devised4 ,perfect non-inflammability is only required in certain dangerous occupations4 ,the plans hitherto mentioned simply prevent the fabric breaking out into flame4 ,the only cloth absolutely unaffected by fire is asbestos cloth4 #g4 ,elegance of dress1 although not so important as utility1 is not to be neglected1 and the two are perfectly compatible4 ,in fact1 elegance is indirectly associated with utility1 for nothing which is awkward1 or leads to obstructed movements or distortions of the body1 is really elegant4 ,a sudden constriction1 as in a very tight waist1 is not only bad from a hygienic point of view1 but is also ugly4 ,materials for ,clothing4--,the materials used are derived partly from the vegetable world1 as hemp1 flax1 cotton2 and partly from the animal world1 as silk1 wool1 hair1 feathers4 ,the most important materials are wool1 silk1 cotton1 and flax4 #a4 ,wool varies somewhat in character1 according to the animal from which it is derived4 ,in all its varieties1 however1 it preserves the character of a bad conducting and porous substance1 the two most important requisites in a dress material4 7#a7 ,wool from the sheep is really a soft and elastic hair1 composed of fibres three to eight inches long1 and about #aajjj inch thick4 ,the finer and shorter wools are used for fine cloth1 the longer and coarser for 8poplins10 8worsted pieces10 etc4 ,flannel is a woollen stuff of rather open and slight fabric4 ,wool is irritating to delicate skins1 and may be so much so1 that it cannot be worn next the skin1 whether as flannel1 worsted1 or merino4 ,in these cases1 it may be worn outside a linen or gauze vest1 and so all its advantages secured4 ,it is one of the worst conductors of heat1 and ought always to be worn in winter2 while even in summer1 it ensures a greater immunity from chill after perspiration than any other material4 7#b7 ,cashmere is made from the down found about the roots of the hair of the ,thibet goat4 ,imitation cashmere is made of various materials mixed together4 ,illustration3 ,,fig4 #ef4 ,,microscopical ,,appearance ,,of ,,fibres ,,of ,a--,,cotton4 ,b--,,silk4 ,c--,,linen4 ,d--,,wool4 7#c7 ,alpaca is obtained from the fleece of the llama1 alpaca1 and vicuna4 ,it is longer than the fleece of the sheep1 the fibres1 which are soft and strong1 averaging six inches in length4 ,it is commonly made up with cotton or silk4 7#d7 ,mohair is the hair of a goat inhabiting the mountains near ,angora4 ,it is woven into an almost waterproof cloth1 and used in making plush1 braid1 etc4 #b4 ,hair derived from the horse or cow differs from the hair usually called wool1 in the greater solidity of its structure1 which makes it ill adapted for clothing4 ,its chief use is in the manufacture of felts1 of which hats are made4 #c4 ,leather is a kind of natural felt1 very close and firm in its texture4 ,it is used in this country chiefly for boots1 but in some colder climates also for coats1 etc4 ,it is impervious to moisture1 like sealskin1 and is consequently not very healthy4 ,the same objection applies to chamois-leather underclothing1 which is non-porous1 and consequently keeps the skin hot and clammy2 also1 it cannot be washed without becoming stiff on drying4 ,this necessitates wearing the material after it has become impregnated with perspiration4 #d4 ,silk4 ,the thread spun by the silk-worm is composed of filaments #abjjj inch wide1 and is the strongest and most tenacious of textile fabrics4 ,its thread is three times as strong as a thread of flax of the same thickness1 and twice as strong as a thread of hemp4 ,its fibres are round like those of linen1 but softer and smaller2 it gives an agreeable sensation of freshness to the skin even more than linen4 ,it is a worse conductor of heat than cotton or linen4 ,its great disadvantage for wearing next the skin1 apart from its expense1 is that it irritates delicate skins4 ,satin is silk so prepared as to form a smooth1 polished surface4 ,velvet is a silk fabric of which the pile is due to the insertion of short pieces of silk thread under the weft or cross-thread4 ,cheaper kinds are made1 containing a certain proportion of cotton4 ,crape is made of raw silk gummed and twisted to form a gauze-like fabric4 ,taffety1 moire1 brocade1 and plush are made of silk alone or combined with cotton4 #e4 ,cotton consists of the downy hairs investing the seeds of the gossypium plant4 ,the threads of which it is composed are flat1 ribbon-like1 and twisted1 about #ahjj to #abjjj inch wide4 ,owing to its flat fibres with sharp edges1 it is apt to irritate delicate skins2 linen is preferable for dressing wounds for a similar reason4 ,cotton is warmer than linen1 being a worse conductor of heat4 ,it also absorbs moisture better1 not becoming wet so soon2 but it lacks the 8freshness0 which makes linen materials pleasant to wear4 ,calico1 fustian1 jean1 velveteen1 and muslin are the chief cotton fabrics4 #f4 ,flax is formed from the fibres of the flax plant4 ,linen is made from it4 ,cambric and lawn are very fine and thin linen materials4 ,the fibres of linen are round and pliable2 thus it is smooth and soft1 and peculiarly agreeable to the skin4 ,it is1 however1 a good conductor of heat1 and consequently 8it feels cold0 to the skin4 ,furthermore its pores quickly become filled with perspiration1 which escapes rapidly1 thus chilling the body4 #g4 ,mackintoshes are valuable as a temporary protection against external wet4 ,worn for more than a short period1 they produce great heat and a sense of closeness1 owing to retention of the perspiration4 ,the best form of mackintosh is one having a cape1 with a space for evaporation between it and the rest of the garment4 ,the ,amount of ,clothing required varies with circumstances4 #a4 ,health2 those of robust constitution require less than the feeble4 ,the more active are digestion and assimilation1 the less is the amount of clothing required4 ,if heat is preserved by clothing1 less food is required4 ,thus a distinct saving of food is effected by warm clothes4 ,warm clothes are the equivalent of so much food that would have been required to keep up the temperature of the body1 if the clothes had not been worn4 ,thinly clad persons under conditions of starvation die more quickly than those who are better protected4 #b4 ,clothing requires to be adapted to climate and season4 ,in winter and in cold climates the amount of clothing must be increased1 and warmer materials chosen4 ,in the changeable climate of ,great ,britain1 it is difficult to adapt the character of one's dress to the requirements of the weather4 ,clothing ought1 however1 not to be changed according to the calendar1 but according to the weather4 ,the tendency is to assume summer clothing too early in the spring1 and to continue it too far into the autumn4 ,according to ,borhave1 winter clothing should be put off on ,midsummer day1 and resumed the day after4 ,this1 although rather exaggerated1 may serve to impress the caution required4 ,the same authority says that only fools and beggars suffer from cold1 the latter not being able to procure sufficient clothes1 the former not having the sense to wear them4 #c4 ,age4 ,those at the two extremes of life are specially susceptible to cold4 ,the mortality of infants during the first three months of life is nearly doubled in winter4 ,bronchitis and pneumonia prove fatal chiefly at the two extremes of age4 ,the younger a child the larger is its surface as compared with its bulk1 inasmuch as the area of a body varies as the square of its dimensions1 while its mass varies as their cube4 ,thus a cube #a inch each side has #f square inches of surface to #a cubic inch of bulk1 while a cube #aj inches each side has #fjj square inches of surface to #ajjj cubic inches in bulk4 ,similarly a child #aaj the size of its mother1 besides its feebler powers of producing heat1 has ten times as much surface in proportion to its size by which heat is lost4 ,after the age of thirty-five1 it is better to exceed than to be deficient in clothing4 ,a degree of cold that would act as a useful tonic to the robust and middle-aged1 produces serious and even fatal depression of the vital powers in children or aged people4 ,for the same reason it is advisable to discontinue cold baths as age advances4 ,a very pernicious delusion is prevalent1 that children ought to be 8hardened0 to the influences of cold1 and that too much clothing 8makes them tender40 ,excessive clothing may possibly increase the tendency to 8catch cold10 owing to its exciting perspiration1 or owing to the fact that the extra clothing is commonly thrown off at irregular intervals--witness the effects of wearing a scarf round the neck occasionally4 ,but to suppose that children can be hardened by exposure of arms and legs1 and other parts of their bodies1 is irrational4 ,a large amount of heat is lost from these bare surfaces1 and apart altogether from the danger of chill1 more food must be taken to compensate for this loss of heat1 and keep up an equable temperature4 ,also if the food taken is expended in preserving the warmth of the unprotected body1 less material is left for the purpose of growth4 ,from these causes it frequently happens that children remain stunted in growth1 even if latent disease is not actually developed by the extra strain on their resources4 ,the children of the very poor are often pointed to as demonstrating the power of hardening4 ,it is forgotten how many of these poor children have perished under the hardening system1 and that the good health of those remaining is in spite of the hardening4 ,poisonous ,dyes in ,clothing4--,these1 like poisonous wall-papers1 were formerly much more common than at present1 and1 as in wall-papers1 the poisonous agent has most frequently been arsenic1 large quantities of which were formerly used in the preparation of certain dyes4 ,occasionally such poisonous pigments are still employed4 ,the means of detecting arsenic in any fabric or wall-paper are given on page #baf4 ,,chapter ,,xli4 ,,parasites4 ,parasites 7,greek1 para1 upon1 and siteo1 ,i feed71 in the broadest sense of the word1 are living organisms1 which derive their nourishment from other living organisms4 ,they may belong to the vegetable or animal kingdoms1 and may live on the skin1 in the alimentary canal1 or in some one of the internal organs4 ,some1 like the fungus causing ringworm1 feed on the living tissues of the animal infested2 others1 like tape-worms1 on the partly digested food2 while other parasites1 like fleas1 only pay temporary visits to the surface of the body1 for the purpose of obtaining food4 ,vegetable ,parasites4--,vegetable parasites all belong to the class of fungi1 and more accurately to the two lowest divisions of this class which have been provisionally formed1 viz4--,schizophyta1 and ,zygophyta4 ,the ,schizophyta include two orders1 ,schizomycetes and ,saccharomycetes4 ,,bacteria4 ,bacterium is the generic name given to the micro-organisms belonging to the schizomycetes1 whether a bacillus 7rod-shaped71 coccus 7rounded71 spiral-formed 7spirillum or vibrio71 or filamentous 7leptothrix and spirochta74 ,all these are destitute of chlorophyll and multiply by fission4#i ,they are all extremely small1 the width usually not exceeding #a #abejjj inch4 ,various names are given to them1 which are synonymous1 thus3 germs1 microbes1 micro-organisms1 microzymes1 bacteria 7singular bacterium74 ,when they cause disease they are called contagia4 ,they multiply rapidly1 and may reach maturity in #bj to #cj minutes4 ,one bacterium may1 under favourable conditions1 become #af1jjj1jjj in #bd hours4 ,methods of ,examination4--,until ,koch discovered the method of cultivating bacteria on solid media1 the science of bacteriology remained in its infancy1 as it was impracticable to obtain pure1 i4e4 unmixed cultures of a given bacterium4 ,koch hit on the idea of mixing minute portions of cultivations of bacteria which were growing in liquid broth with liquefied gelatine1 and then spreading the mixture on glass plates1 and allowing it to solidify under cover1 so that no atmospheric bacteria could contaminate the growth4 ,when this was done1 individual bacteria formed individual 8colonies0 scattered over the gelatine1 and these could be identified by sub-culturing and other methods1 for the details of which books on bacteriology must be consulted4 ,the food supply of most bacteria is vegetable or animal refuse4 ,some of them have a most useful purpose in nature1 that of breaking down complex organic substances and reducing them to a simpler form4 ,thus bacteria play an essential part in purifying the soil1 and in the operations in sewage tanks and on sewage farms 7pages #aib1 #aie and #bbj74 ,a thimbleful of ordinary garden soil which has received a periodical manurial dressing contains one to three million bacteria4 ,certain bacteria have been found to be capable of exercising an opposite effect1 i4e4 fixing the atmospheric nitrogen and building it up into the nitrogenous tissues of plants4 ,thus the nodules on the roots of leguminous plants consist of bacteria living in symbiosis with the protoplasm of the plant and supplying it with nitrogen in an assimilable condition4 ,pure cultures of these bacteria have been put on the market as nitragin1 for enriching land poor in nitrogen4 ,thus a fairly complete cycle of nature is secured1 and by rotation of plants 7legumes alternating with other seeds71 manures1 especially nitrogenous manures1 may be partially saved4 ,the souring of milk is caused by the bacillus lactis4 ,this souring is an indispensable preliminary to the making of cheese1 and the bacillus can now be used in pure culture to hasten the natural process4 ,the peculiar aroma of good butter is due to a bacterium which has been isolated2 and it can now be supplied in pure culture for butter-making1 thus obviating bad butter4 ,certain bacteria are disease-producing or pathogenic4 ,the largest of these is the ,bacillus of ,anthrax1 a disease common in sheep and oxen1 and sometimes communicated to man4 ,this bacillus is #ab thick and #f to #h long4 ,when an animal dies of this disease it should be buried without cutting the skin4 ,when exposed to the air this bacillus forms minute spores1 very difficult to destroy4 ,they may live for several years in pits in which animals dying from anthrax have been buried4 ,butchers have died when inoculated through cracked fingers when dressing the carcase of a cow which has had anthrax4 ,similarly men handling the hides of such animals may be inoculated1 either with a form of disease in which rapid blood-poisoning is produced1 or with a malignant carbuncle1 from which recovery is possible if it be treated promptly4 ,wool sorters of mohair wool are very liable to suffer from a fatal form of pneumonia due to the dust from wool derived from animals which have died from anthrax 7page #ajg74 ,this disease gives a good instance of possible attenuation of virus1 of which another example is seen in small pox 7page #bic74 ,pasteur grew anthrax bacilli in broth at a temperature of #aaj ,fahr4 ,at this temperature the bacilli multiplied by division1 and no spores were formed4 ,by repeatedly sub-culturing after the bacilli had become old 7i4e4 by putting minute quantities of the growth into fresh broth7 and exposing to air1 he obtained anthrax bacilli which were only slightly virulent1 only producing slight constitutional disturbance when inoculated1 i4e4 injected under the skin of sheep1 and yet protected them against ordinary infection by anthrax4 ,other methods of attenuation of virus have been discovered4 ,for instance the growth of the bacillus in the presence of a feeble antiseptic1 or passing it through the circulation of an animal which is relatively insusceptible to the particular bacillus has this effect4 ,other important pathogenic bacteria will be considered later 7pages #bih to #cih74 ,it is only necessary here to mention that suppuration1 erysipelas1 puerperal fever1 and a number of forms of blood-poisoning are due to the invasion of the system by cocci4 ,a single round cell 7commonly not more than #abejjj inch in diameter7 is called a micrococcus4 ,when in pairs as in the micro-organism causing pneumonia they are called diplococci2 when in chains1 streptococci 7i4e4 twisted72 when in masses1 staphylococci4 ,when cocci and other micro-organisms are kept out of wounds1 healing occurs without suppuration2 this is the principle of the antiseptic and aseptic methods of treating wounds 7pages #ajf and #aaj74 ,the question of immunity is discussed on page #bhh4 ,saccharomycetes occur in fermenting substances1 as in the fermentation of saccharine solutions4 ,the only organism belonging to this order1 which is associated with diseased conditions1 is the ,sarcina ,ventriculi4 ,this is found occasionally in the vomit or even in the urine of some persons4 ,the ,zygophyta occur as thread-like growths1 forming a mycelium4 ,this is composed of jointed branching tubular cells1 in which minute spores are produced4 ,each spore1 when liberated from its tube1 is capable of producing another mycelium1 and thus the growth spreads4 ,the spores may be carried through the atmosphere1 thus producing infection at a distance4 ,they have an average diameter of #f about #adjjj inch4 ,the following are the chief ,zygophytous parasitic diseases3--,thrush is associated with the growth of a minute filamentous fungus1 the oidium albicans4 ,it is common in babies1 who are improperly fed1 and in old people1 or in persons exhausted by any chronic disease4 ,small white patches collect on the tongue and neighbouring parts1 and these are often followed by the formation of minute ulcers4 ,when it occurs in children1 the food must be carefully attended to1 and feeding bottles frequently scalded1 etc4 ,ringworm is due to the growth of a large spored or a small spored fungus 7known under the names of ,microsporon ,audouini2 ,trichophyton megalosporon endothrix1 ,trichophyton megalosporon ectothrix7 which attacks the skin4 ,it is most difficult to eradicate when it occurs in hairy parts1 as the growth penetrates to the roots of the hairs1 and continues to live here long after it has been destroyed on the general surface of the skin4 ,the fungus spreads on the skin in gradually enlarging circles1 forming rings with a slightly raised margin4 ,it is extremely contagious1 being especially apt to spread in schools4 ,the spores may be carried about by means of hats or bonnets1 by gloves1 towels1 razors1 and other means4 ,the disease often remains undetected for some time2 and many cases1 especially where the scalp is affected1 remain contagious after they have been apparently cured4 ,the removal of ringworm1 as of all other skin parasites1 is effected by some local parasiticide4 ,prolonged treatment1 including the pulling out of diseased hairs1 is required for ringworm of the scalp4 ,a special cap should be worn1 when the patient mixes with others4 ,favus1 or 8scald-head10 is due to the growth in the skin of a minute fungus called the ,achorion ,schnleinii1 which invades the same parts as those affected by ringworm1 but differs in its mode of formation of spores2 yellow cupped discs from #ad to #ac inch in diameter being produced4 ,it is very rare in ,england1 and almost confined to persons 7especially children7 who are kept in a filthy condition4 ,it is a common and fatal disease in mice4 ,the treatment is similar to that of ringworm4 ,tinea versicolor is caused by the growth in the epithelial cells of the skin1 of a fungus called the microsporon furfur1 which1 unlike the two last1 does not invade the hair or nails4 ,it forms light brown patches covered with a horny scurf1 which gradually spread1 until nearly the whole trunk may be covered4 ,it does not attack children1 and never affects uncovered parts of the body4 ,it chiefly occurs in those who do not take frequent baths1 and who perspire freely4 ,it can be removed by daily washing with soap and water and rubbing with a rough towel1 followed by the application of a weak carbolic lotion4 ,animal ,parasites4--,animal parasites are found on the skin or in internal organs or in the blood or lymphatic vessels4 ,the following are the most common3-- ,the ,acarus ,scabiei is a minute animal not unlike a cheese mite1 which causes the disease known as scabies or the itch4 ,it is probably never more than #agg of an inch in length4 ,the female has eight legs1 with terminal suckers on the four front legs and hairs on the hind legs4 ,the male is smaller than the female1 and in the adult condition the two hindmost legs have suckers1 as well as the four anterior4 ,it remains on the surface of the skin1 while the female burrows deeply in the substance of the epidermis4 ,at the bottom of the oblique burrow it deposits ten to fifteen or more eggs1 which hatch in a fortnight and then commence similar operations on their own account4 ,scabies generally starts between the fingers1 whence it rapidly spreads4 ,the disease is acquired from some patient suffering from the disease1 or by contact with his apparel4 ,it may become very severe when suspicion as to its parasitic character has not been entertained4 ,formerly it was called 8the seven years' itch10 from the great difficulty in curing it before its true cause was discovered4 ,the irritation caused by the insect produces eczema1 and this may be thought to be the only disease present1 unless careful examination is made for the burrows of the insect4 ,to remove this parasite1 first the skin is softened1 the superficial epidermis is removed1 and the burrows are laid bare1 by the daily use of hot baths with soft soap1 and subsequent rubbing with flesh towels4 ,then some parasiticide1 such as the well known sulphur ointment1 is rubbed into all the affected parts of the skin4 ,a few days' perseverance in this treatment usually suffices for a cure4 ,the patient's clothes and bed clothes ought also to be thoroughly purified by boiling or by steam disinfection or by baking in an oven2 otherwise he may become re-infected4 ,the ,larv of several insects have been found embedded in the skin4 ,in the ox1 the larva or bot of the gadfly produces a troublesome disease1 a large boil being formed under the skin as the larva grows4 ,this larva has1 on rare occasions1 attacked human beings4 ,rare cases are recorded where other larv have become developed in men1 in all upwards of twenty separate kinds of insects having been recognized4 ,the treatment consists in removing the parasite4 ,the ,chigoe1 commonly known as the jigger or sand-flea1 is a minute parasitic insect1 found in the ,west ,indies and northern parts of ,south ,america4 ,it is so small as to be scarcely visible2 but the impregnated female possesses a proboscis1 by means of which it penetrates the skin generally near the nails and there develops a bladder the size of a pea1 which sets up severe inflammation4 ,to get rid of the intruder1 the orifice by which it entered must be dilated with a needle1 until large enough to admit of its extraction1 without rupturing the cyst4 ,several species of ,fleas infest the human frame4 ,they are propagated by means of eggs1 the worms from which enclose themselves in a tiny cocoon before assuming the adult form4 ,three varieties of ,lice occur on the human skin4 ,the first 7pediculus capitis7 infests the head1 especially of children1 and multiplies with astonishing rapidity1 the female laying altogether about fifty eggs4 ,the other two varieties are the body louse 7pediculus corporis7 and the crab louse 7pediculus pubis74 ,strict attention to cleanliness is the best means of getting rid of fleas and bugs4 ,a wash made of carbolic acid and vinegar painted over bed crevices is very efficient4 ,lice may be removed from the head by cutting the hair short1 and carefully cutting out any hairs to which nits are attached4 ,the nits are cemented to the shafts of hairs4 ,washing the hair with methylated spirit or paraffin is also helpful in removing them4 ,afterwards the use of white precipitate ointment will prevent their re-appearance4 ,the ,trematoda or ,flukes furnish two human parasites1 viz4 the liver-fluke 7,distoma hepatis71 and the ,bilharzia hmatobia4 ,the liver-fluke occasionally produces jaundice in man4 ,in sheep it is the cause of the disease known as the 8rot40 ,the ,bilharzia hmatobia is chiefly found in ,egypt1 and the ,cape ,colony4 ,it is about a quarter of an inch long1 and infests the blood vessels1 more particularly of the kidneys2 setting up severe irritation and the discharge of blood4 ,it is probable that the eggs of this parasite are received in drinking water or on salads1 though occasionally inoculation may occur through the skin when bathing4 ,the family of ,nematoda possesses numerous parasitic members4 ,the common thread worm 7,oxyuris ,vermicularis7 is one of the most common of these4 ,the female is #ac to #ab inch in length1 and inhabits chiefly the lower bowel4 ,the ova1 which are from #adij to #aaajj inch in diameter1 often gain access to drinking water1 or are carried by flies1 or received on salads1 etc4 ,the injection of salt and water into the bowel1 and treatment tending to improve the general health1 are the proper remedies4 ,the round worm 7,ascaris ,lumbricoides7 inhabits chiefly the small intestine2 hence medicines for its removal require to be given by the mouth4 ,the female is from #aj to #ad inches long2 the ova1 of which each female discharges on an average #afj1jjj daily1 are from #acdj to #addj inch in diameter4 ,the whip-worm 7,trichocephalus ,dispar7 is a smaller nematode1 which is rarely met with in this country4 ,the ,dochmius ,duodenalis is met with chiefly in ,italy and ,egypt4 ,it sucks the blood in the intestine1 causing dangerous anmia4 ,the ,strongylus ,gigas is chiefly found in the kidneys of the ox1 dog1 etc41 and is very rare in man4 ,it resembles a very large round worm4 ,in the kidney it produces severe disorders4 ,how it gets there is not known4 ,the ,trichina ,spiralis has been already described 7page #bc74 ,the ,filaria ,dracunculus 7,guinea ,worm7 seems to gain access into the stomach along with water1 or possibly in some cases1 by perforating the skin4 ,it burrows among the tissues1 especially of the legs1 and attains a length of several feet4 ,it causes large boils and sores1 and through these the eggs escape and pass into water4 ,here the embryo which has escaped from the egg meets with a fresh water crustacean 7cyclops71 enters its body1 undergoes larval growth1 and is swallowed with its host by a man1 in whom it burrows and undergoes its next stage of life4 ,the embryos of three species of ,filaria infest the blood of man1 chiefly in the tropics4 ,one embryonic species is found in the blood of infested patients by day1 one by night1 and one during both day and night4 ,the length of the embryos varies from #age to #aabe inch1 and its width from #acjjj to #acejj inch4 ,the night embryo1 which is the most common1 is produced by the ,filaria ,bancrofti4 ,this adult worm infests the lymphatic system of man1 sometimes reaching a length of three to four inches4 ,its embryos may obstruct lymphatic vessels1 causing obstruction of the flow of chyle 7hence originates chyluria71 and elephantiasis1 in which enormous swelling of the legs and other parts ensues4 ,the nocturnal migration into the lymphatic vessels1 and thence into the blood of the embryo of the ,f4 ,bancrofti1 is an adaptation to the nocturnal habits of a particular mosquito 7culex pipiens or ciliaris74 ,when the mosquito bites an infested person1 his proboscis removes some embryo filari1 which are quickly transferred to its stomach4 ,some of these escape digestion1 develop within the mosquito1 and when the mosquito dies in water they bore their way out1 and are subsequently swallowed by man4 ,it is essential1 therefore1 in order to prevent this disease to boil or efficiently filter all drinking water1 and to prevent the access of mosquitoes to water4 ,persons infested with filari should sleep inside mosquito nets1 in order that they may not1 when bitten by mosquitoes1 spread the disease4 ,tape-worms are found infesting the alimentary canal of man4 ,each has a double phase of existence4 ,in the first1 the characteristic head1 or scolex1 along with a bladder-like body1 lies embedded in the solid tissues of an animal2 in the second1 the strobilus or tape-worm1 occupies the alimentary canal of another animal4 ,the tape-worm consists of a number of flat segments1 each of which is capable of producing a large number of eggs1 from each of which a six-hooked embryo is developed4 ,the segments escape from the alimentary canal1 and their ova are discharged and scattered broad-cast4 ,these eggs are swallowed by another animal1 the hooked embryo escapes from its case1 migrates into the solid tissues1 and there produces a scolex4 ,when the host is eaten by another animal or by man1 the scolex enters the alimentary canal1 loses its bladder-like body1 and developes a chain of segments4 ,it follows from the above that two distinct hosts are necessary to complete the cycle of existence of these creatures1 one being commonly a herbivorous1 and the other a carnivorous animal4 ,thus3-- ,cystic ,form4 ,tape-worm ,form4 ,cysticercus ,cellulos in becomes ,tnia ,soluim in the alimentary the muscles of the pig canal of man4 ,cysticercus ,bovis in the ,tnia ,mediocanellata in the muscles of the ox alimentary canal of man4 ,cnurus ,cerebralis of the ,tnia ,cnurus in the alimentary sheep's brain canal of the dog4 ,echinococcus of man1 etc4 ,tnia ,echinococcus in the alimentary canal of the dog4 ,the cysticercus cellulos has been already described 7page #bc74 ,the cystic form of the dog's tape-worm 7echinococcus7 is a most dangerous parasite for man4 ,when the egg of the dog's tape-worm is swallowed by man1 the embryo escaping from this egg burrows from the alimentary canal1 and forms large cysts1 chiefly in the liver1 but occasionally in the lungs1 brain1 and other organs4 ,for the removal of these1 surgical interference is required4 ,this form of cyst is commonly known as a hydatid4 ,it is most frequently seen in ,iceland and ,australia1 though not uncommon in this country4 ,its frequency depends largely on the number of dogs1 and on the facility with which the ova of their tape-worms can gain access to water4 ,the adult ,tape-worms are usually derived in man from eating meat containing the cystic form4 ,the cysticercus of the pig produces ,tnia ,solium2 that of the ox1 the ,tnia ,mediocanellata4 ,these are the two most common forms of tape-worm in man4 ,the minute head of ,t4 ,solium has four suckers and a double row of hooklets1 #bh in number2 while the head of ,t4 ,mediocanellata has four suckers but no hooklets4 ,the segments of ,t4 ,solium are smaller than of ,t4 ,medioc41 and the structure of the segments of the two is somewhat different4 ,preventive ,measures4--,in avoiding the various ,entozoa described1 it is important 7#a7 to carefully avoid all underdone meat4 ,the eating of smoked sausages1 or of meat which is not cooked throughout1 is a common source of tape-worm and of trichinosis4 7#b7 ,all vegetables should be thoroughly washed3 this is especially important in the case of water-cress1 lettuce1 etc41 which are eaten raw4 7#c7 ,if the purity of the water is not ensured1 it should be boiled or filtered through a ,pasteur-,chamberland filter 7page #ih71 especially in tropical climates1 and where many dogs are kept4 ,dogs should be kept out of the kitchen1 lest ova accidentally gain access to articles of food4 7#d7 ,the possibility of flies and mosquitoes acting as carriers of parasitic disease must be remembered1 and precautions taken4 ,,chapter ,,xlii4 ,,the ,r,,le ,,of ,,insects ,,in ,,spreading ,,disease4 ,insects are now known to be important agents1 7a7 as carriers and 7b7 as intermediate hosts of disease-agents4 ,the common domestic fly 7,musca domestica7 is the unwelcome companion of man in nearly every country4 ,the eggs are usually laid and the larv undergo their development in excrement1 but the female sometimes selects meal1 bread1 or fruit for the purpose4 ,in practice1 however1 one of the best means of diminishing the number of domestic flies is to insist on the daily removal of all manure1 especially horse manure1 and to sprinkle the manure receptacle in the interval with lime4 ,the fly may obviously be the means of conveying infected material from place to place4 ,anthrax has been ascribed to this cause4 ,nuttall has proved experimentally that flies are able to carry the infection of plague1 and that they die of the disease4 ,the presence of enormous numbers of flies in cholera times has been noted4 ,experimentally1 flies caught in cholera wards have been found to harbour the cholera spirillum4 ,it is probable that they play a serious rle in spreading the infection of cholera4 ,hence all infectious dejecta 7stools and urine7 should be covered until finally disposed of1 and food should be protected against flies4 ,the same remarks apply for enteric fever4 ,flies fed with pure cultures of the bacillus of enteric fever pass these bacilli in their dejecta in a still virulent condition4 ,in camps1 especially in connection with large armies1 there is the strongest reason for believing that flies carry infection from latrines to food4 ,flies have been known to feed on the expectoration of consumptive patients and it is possible therefore that they may thus infect food4 ,the bed bug 7,cimex lectularius7 has been stated to be capable of conveying by its bite the infection of plague and other diseases from an infected to a healthy person2 but ,nuttall's experimental results were entirely negative4 ,fleas 7pulex7 probably do not play any part in spreading anthrax4 ,experimentally1 anthrax bacilli die off rapidly in fleas4 ,in ,india1 persons who had handled rats dead of plague frequently acquired the disease4 ,this was explained by ,simond on the supposition that the fleas abandoned the dead rat for the human subject4 ,the rats which appeared to have caused plague in man were stated to have died but a short time before2 and the handling on the day after their death of rats dead of plague was stated to be safe because the rats' fleas had then deserted the dead rat4 ,it is assumed that the flea injects the poison of plague under the skin4 ,on the contrary it is to be remembered that the fleas infesting rats and mice belong to a different family from that which attacks man4 ,whether this is a usual means of conveying plague may therefore be regarded as still doubtful4 ,that rats convey plague to man is certain2 whether fleas act as an intermediary remains somewhat uncertain4 ,the ,mosquito family 7,culicid7 has been found to be an important if not the sole means of spreading certain serious diseases to man4 ,to this family belong all true gnats or mosquitoes2 but the only two genera which have been proved to be able to cause disease are ,culex and ,anopheles4 ,the culex may usually be distinguished by the fact that when alive and at rest its head is below the level of the thorax and abdomen1 thus giving the insect a hump-backed appearance1 while the body of the anopheles under the same circumstances is all in a line4#aj ,the anopheles is more slender and its head smaller than that of the culex4 ,the anopheles usually confines its blood-sucking operations to the evening and night4 ,during the day it remains in dark corners4 ,it lays its eggs usually in a natural pool or pond on the ground1 on the surface of the water4 ,in about two days a minute larva is hatched out4 ,this grows rapidly1 assumes the pupa form1 from which the perfect insect emerges4 ,the female insect alone is blood-sucking4 ,in about #bj days after birth1 it lays from #aej to #bjj eggs4 ,its relation to malaria may be gathered from the following historical sketch4 ,in #ahhj ,laveran found in the red blood corpuscles of malarious patients minute bodies which he regarded as not bacteria1 but a very low form of animal life1 possessing amboid movements4 ,these grew at the expense of the blood corpuscles1 deposited a dark pigment1 and often assumed the appearance of a 8rosace10 a rounded body with little spherules at its circumference4 ,golgi in #ahhi observed differences between the rosaces of tertian and quartan fever1 and found that the periods of occurrences of the fever corresponded with the times of maturation of the rosaces4 ,it was concluded therefore1 that the rosaces caused the fever by shedding their sporules into the blood4 ,these sporules when thus shed were found to attach themselves to1 and grow in1 other red blood corpuscles4 ,it is now known that there are three species of the parasite1 in one of which the parasites are crescentic in shape4 ,the examination of a drop of blood from a patient now enables a doctor to recognise which of these three forms of malaria he is dealing with4 ,laveran observed that certain forms of the parasite presented 8flagella10 i4e4 filaments exhibiting very active movements4 ,manson having observed that flagella were not found in blood first drawn1 but only appeared after a little time had elapsed1 conceived the idea that the function of these must be that of spores4 ,having previously observed that a microscopic worm1 filaria1 is drawn with the blood into the stomach of a kind of mosquito 7page #bgh71 and finds in the latter a secondary host1 he concluded that a similar cycle of events might occur in malaria4 ,ross tested this theory1 and by causing mosquitoes bred in bottles from the larva to bite persons affected with the crescent form of malaria1 after repeated unsuccessful attempts1 was eventually able to find in comparatively rare mosquitoes which had thus bitten a malarious patient1 small rounded bodies embedded in the wall of the stomach4 ,these were watched and found to present appearances identical with those of the parasite of malaria4 ,similar pigmented bodies were subsequently found in other mosquitoes4 ,the malarial parasite belongs to the ,protozoa1 of which it is one of the smallest members4 ,man is its intermediate host1 and the anopheles its definitive or final host4 ,in the red blood corpuscle of man it is a unicellar organism1 from #a to #h in diameter4 ,it has two methods of reproduction1 endogenous by spore formation and exogenous or sexual4 ,the former occurs in man2 the latter in the mosquito4 ,without the latter1 the parasite being unable to pass from man to man1 would die with its host4 ,in endogenous multiplication spores are formed which separate from the original parasite and gain access to other red blood corpuscles4 ,the large pigmented spheres and the crescent bodies require to enter the stomach of the anopheles to attain full development4 ,in the anopheles the crescents become spherical1 flagella are shot out1 having a length of #d to #e times the diameter of a red blood corpuscle4 ,these represent the male element1 while other spheres without flagella are the females4 ,by the fusion of these two a fertilised cell is produced 7the travelling vermicule71 which now assumes the shape of a spear-head and is actively mobile4 ,the travelling vermicule pierces the stomach wall of the mosquito and develops into a zygote4 ,if an infected mosquito is examined on a succession of days under the microscope1 the following stages can be traced4 ,the zygote consists of pigmented spheres #g to #h in diameter1 lying in the muscular fibres of the mosquito4 ,these grow1 and become surrounded by a capsule4 ,smaller spheres form and subdivide1 bud-like processes develop on their surfaces2 these gradually become sickle-shaped and protrude into the body cavity4 ,they increase in size4 until they attain dimensions of from #dj1 to #fj 4 ,eventually they rupture1 and the sickle-shaped bodies 7sporozooites7 escape and are carried in the body fluid of the mosquito to its salivary glands4 ,these sporozooites are about #ad long1 and human infection is caused by them4 ,they have been traced as far as the end of the proboscis of the mosquito4 7,see also page #cjg74 ,,chapter ,,xliii4 ,,infective ,,diseases4 ,the prevention of disease depends largely on a knowledge of its causes4 ,disease may be due to a personal life not in accordance with physiological laws2 or to some cause or causes acting ab extra4 ,with advance of knowledge the number of diseases which can be proved to be caused by a contagium vivum introduced from without is steadily increasing4 ,we have already discussed the influence of habits1 of clothing1 exercise1 sleep1 and food on health1 and have shown how errors in these respects may lead to disease4 ,it now remains to consider more particularly the prevention of diseases1 due to the introduction into the system of contagia4 ,in the study of such diseases three chief factors require consideration3 7#a7 the contagium itself2 7#b7 conditions of environment1 as climate1 soil1 season1 weather1 etc41 which may favour or impede its spread2 and 7#c7 personal conditions which similarly influence it4 ,of these age1 heredity1 fatigue1 injury1 diet1 and race are specially important4 ,the first two groups of diseases given in the ,registrar-,general's classification of causes of death are 7#a7 ,specific ,febrile or ,zymotic ,diseases1 and 7#b7 ,parasitic ,diseases4 ,the objection to the word 8specific0 is that1 although in most instances diseases in this group are 8specific0 in the sense that they are caused by a particular microbe1 e4g4 tetanus1 anthrax1 tuberculosis1 in a few instances the same lesions may be caused by several microbes1 e4g4 septicaemia 7blood-poisoning71 pneumonia4 8,zymotic0 was the name given by ,farr1 in view of the analogy of the febrile process to that of alcoholic fermentation4 ,in both there is the introduction of a living germ or germs2 in both a period of 8incubation0 in which nothing can be observed2 then follows the active disturbance2 and in the disease1 as well as in the fermenting liquid1 the process is stopped1 when the microbes have multiplied to a certain extent1 a temporary or permanent protection being the result4 ,the best name for the diseases in this group is 8,infective40 ,parasitic diseases1 like ringworm1 scabies1 or trichinosis1 are also infective2 but for convenience may be described separately as 8parasitic40 ,the relation between the words 8infectious0 and 8contagious0 requires explanation4 ,a disease like measles or small-pox1 which can be transmitted from person to person1 without immediate contact between the two1 is termed infectious4 ,in these cases the infection is conveyed by mucus expectorated or by dust blown about1 or carried in apparel1 etc41 from the first patient4 ,such diseases may also1 of course1 be communicated by direct contact4 ,if direct contact between the sick and well is indispensable for the transmission of a disease it is called contagious4 ,there is no such hard line in nature1 although some diseases can be more easily communicated than others4 ,the term contagious is usually applied to parasitic diseases like ringworm and scabies1 but even these can be communicated by means of infected articles as well as persons4 ,the word contagious should be abandoned for all the acute febrile diseases4 ,the word infective is used to include all specific febrile diseases1 however spread4 ,this word1 therefore1 includes not only infectious and contagious diseases1 but also diseases spread by inoculation1 i4e4 injection of the infection under the skin4 ,thus malaria is not infectious from patient to patient2 but can be inoculated by the mosquito4 ,infective ,diseases are either acute or chronic4 ,of acute infective diseases small-pox and enteric fever are typical examples2 of chronic1 tuberculosis and syphilis4 ,it was formerly supposed that in certain diseases the contagium or infective agent grew in external noxious matter1 a miasm being produced2 while in other diseases contagion was only produced direct from patient to patient2 and others originated in either way4 ,hence the classification of infective diseases into 7a7 miasmatic1 7b7 contagious1 and 7c7 miasmatico-contagious diseases4 ,this classification has now been abandoned4 ,thus influenza and ague were formerly thought to be miasmatic2 but the former is spread by personal infection2 the latter by inoculation of the contagium by an infected mosquito4 ,bacteriology has thrown an immense light on the causation of infective diseases4 ,a large number of these have been proved to be caused by bacteria1 and by analogy we infer the same thing for many others4 ,koch has laid down the following postulates as necessary before it can be stated that a particular disease is directly caused by a given microbe3-- 7#a7 ,the microbe shall be demonstrated in the diseased tissues or blood of man or an animal suffering or dead from the disease4 7#b7 ,the microbes shall be isolated from these and cultivated in suitable media until obtained in pure culture4 ,that is to say1 matter containing the microbe1 taken from the infected source1 must be cultivated in artificial media outside the animal body1 under conditions excluding the possibility of the introduction of other microbes1 until pure cultures of these microbes are obtained1 and these microbes must be transplanted from generation to generation1 until it is certain that no trace of non-living matter derived from the original animal body remains in the culture4 7#c7 ,a pure culture of the microbe1 thus obtained1 shall1 when introduced into the body of a healthy susceptible animal1 reproduce the disease in question4 7#d7 ,the microbe in question shall be found in the animal so affected4 ,kanthack adds a further condition1 that 7#e7 ,the toxins and poisonous substances obtained from the artificial cultivations shall agree chemically and physiologically with those obtained from the diseased animal4 ,all the preceding conditions have been fulfilled for anthrax1 diphtheria1 and tetanus2 and the first four conditions have been fulfilled in regard to tuberculosis1 glanders1 gonorrha1 malignant dema1 and actinomycosis4 ,in enteric fever and influenza the first two conditions have been met2 but inoculation experiments 7#c7 have failed4 ,in leprosy and relapsing fever the first condition is met1 but 7#b7 has failed4 ,in the following diseases the specific microbe has not been isolated1 though from analogy it is believed that each of them is caused by such a microbe3-- ,measles4 ,rubella 7,german measles74 ,typhus fever4 ,scarlet fever4 ,varicella 7chicken pox74 ,variola 7small-pox74 ,whooping ,cough4 ,mumps4 ,hydrophobia1 etc4 ,erysipelas occupies a special position4 ,it is a specific disease due to a microbe1 which1 when it attacks other parts than the skin1 may produce abscesses1 boils1 or blood-poisoning4 ,bacteria are either saprophytes1 i4e4 they can grow on dead organic or even inorganic matter2 or parasites1 i4e4 they are dependent for their existence on a living plant or animal which they invade4 ,there are two varieties of each of these1 obligate and facultative4 ,an obligate parasite can develop only within a living host2 while a facultative parasite can1 according to circumstances1 lead either a parasitic or saprophytic form of existence4 ,the fact that certain contagia are completely1 and others only partially1 parasitic brings out important differences in their life-history4 ,thus1 so far as we know1 the contagia of scarlet fever1 measles1 small-pox and hydrophobia do not multiply outside the body4 ,hence there is a reasonable prospect of annihilating them by measures of disinfection and isolation4 ,the position of diphtheria is doubtful4 ,it may have a saprophytic phase of life4 ,the contagium of tuberculosis1 as well as of erysipelas1 may have a life outside the host1 though to what extent is doubtful4 ,cholera and enteric fever1 although generally communicated by infection1 appear sometimes to be communicated by contagia grown in saprophytic life1 remote from preceding cases4 ,the infection caused by bacteria may be local or general4 ,thus in tetanus and in diphtheria the invading bacteria usually remain at their original point of invasion 7under the skin in tetanus1 in the throat in diphtheria74 ,in anthrax always1 and often in enteric fever1 they are present in the general circulation4 ,in both instances the symptoms of disease are due chiefly to the toxic products or toxins formed by the bacteria4 ,these toxins are enzymes1 ptomaines1 tox-albumins1 etc4 ,the specific toxins of anthrax1 diphtheria1 and tetanus have been identified2 and by this means the possibility of neutralising them is created4 ,the channels of infection1 i4e4 of invasion of contagia1 are the skin and the mucous membranes1 particularly of the digestive and respiratory tracts4 ,the ,incubation ,period of an infectious disease is the interval elapsing between the receipt of infection and the earliest development of symptoms4 ,the period of incubation of the chief infectious diseases is shown in the following table3-- ,,disease4 ,,begins ,,usually ,,but ,,may ,,possibly ,,be ,,at ,,on ,,the ,,any ,,period ,,between ,scarlet fever #dth day4 #a and #g days4 ,diphtheria #bnd #b #e ,small-pox #abth #a #ad ,chicken pox #adth #aj #ah ,typhus fever #abth #a #ba ,enteric fever #adth-#bast #a #bh ,cholera #ast-#crd ,a few hours and #aj days4 ,measles #abth-#adth #aj and #ad days4 ,rtheln 7,german measles7 #adth #ab #ah ,mumps #aith #af #bd ,whooping cough #adth #g #ad ,influenza #bnd #b #f ,the period of incubation is several weeks in hydrophobia and syphilis1 and may be several years in leprosy4 ,following the period of incubation1 come the premonitory symptoms1 which usually are somewhat sudden in onset4 ,for the chief symptoms of onset see page #cah4 ,persons vary in susceptibility to attack by different infective diseases4 ,the intensity of an attack depends on the condition of the patient1 and on the number and the virulence of the particular microbes infecting the patient4 ,in certain families attacks of particular diseases are more severe1 and attacks are more liable to occur than in others4 ,it has been shown in certain diseases that the cells and the fluids of the body have a protective effect against infection4 ,this protective action varies in different persons1 and in the same person at different times4 ,the cells of the body 7phagocytes7 swallow up and destroy a certain number of bacteria4 ,this action is called phagocytosis4 ,it is overcome when the dose of contagium is excessive1 or when the vitality of the individual is lowered1 especially the local vitality at the part attacked4 ,thus children with 8weak throats0 are particularly prone to scarlet fever and diphtheria4 ,the protection afforded by one attack of an infective disease against its recurrence varies greatly4 ,a second attack of small-pox is very rare1 of scarlet fever less uncommon1 of diphtheria common4 ,in erysipelas1 influenza1 pneumonia1 and rheumatic fever1 second or even more numerous attacks are common4 ,immunity against an infective disease may be natural1 but is more often acquired by an attack of the disease in question4 ,this latter immunity is active1 and is due to the formation in the tissues of the immunised person or animal of substances produced by the reaction of these tissues to the stimulus of the contagium4 ,thus a pig when it has recovered from an attack of swine-plague has produced what are called in ,german antikrpers1 and its tissues are now a medium unfavourable to the growth of the bacillus of swine-plague4 ,if the serum of the protected pig is injected under the skin of another pig1 the latter acquires passive immunity against swine-plague1 which is not so persistent as active immunity4 ,active ,immunity can be produced 7#a7 by an attack of an infective disease1 or 7#b7 by artificial inoculation 7under the skin7 of the contagium of the disease1 producing a milder attack of the disease4 ,this may be done 7a7 by inoculating small doses of a virulent contagium1 as in the inoculation of small-pox from a previous patient2 or 7b7 by inoculating an attenuated virus1 as in vaccination4 ,inoculation of small-pox virus usually produced a milder attack than infection by ordinary means2 but patients thus inoculated were a great source of danger to other persons4 ,in vaccination the virus of small-pox is employed1 which has become attenuated by passing through the calf4 ,in its passage1 it has lost the power of producing anything beyond a vesicle at the point of inoculation4 ,the principle of protecting by attenuated virus was extended by ,pasteur1 who was able to render animals resistant against anthrax1 swine-fever1 and quarter-evil1 and hens against fowl-cholera1 by inoculating them with attenuated cultures of the contagia of these diseases4 ,haffkine has applied the same method on a large scale for cholera4 ,the above are methods of bacterial vaccination4 ,salmon and ,smith have shown that artificial active immunity can be produced also by 7#c7 toxin-injection4 ,they artificially cultivated the hog-cholera bacillus in broth4 ,this broth was then sterilized1 the bacilli being killed1 but their products remaining4 ,by injecting pigeons with this sterilized broth they made them resistant to subsequent infection by the bacillus itself1 thus proving that immunity can be produced by chemical as well as by biological means4 ,the immunity was proportional to the dose of the toxin absorbed4 ,by gradually increasing the dose1 it was found practicable to confer immunity1 not only against doses of toxin that would otherwise have been fatal1 but also against bacterial infection by the particular bacillus used in manufacturing the toxin4 ,passive ,immunity4--,behring and ,kitasato found that if the toxin 7free from the bacilli7 of tetanus be injected into an animal in increasing doses until it becomes immune against infection by the bacilli of tetanus1 the blood serum of the animal in question injected into white mice confers the same immunity on them4 ,the protection thus conferred is only temporary4 ,exactly the same procedure has been adopted for diphtheria1 and it is now found that by injecting anti-diphtheritic serum into children who are exposed to the infection of diphtheria1 they can for several weeks be prevented from developing the disease4 ,this is of great practical importance1 as meanwhile the source of infection can have been removed4 ,furthermore1 the protective serum is also curative1 and by its means diphtheria1 if early treated1 can be reduced from a dangerous to an insignificant disease4 ,various theories have been propounded to explain immunity4 ,pasteur supposed that the special pabulum or food of the bacillus of the given disease became exhausted2 but this does not fit in with the immunity that can be produced by toxins and anti-toxins4 ,chauveau supposed that certain bacterial products are retained in the body1 rendering it unsuitable for further growth of the particular bacillus2 just as more than #ad per cent4 of alcohol in a saccharine solution prevents further fermentation4 ,this does not explain all the facts4 ,metschnikoff concluded that the fight of the leucocytes and phagocytes of the body against weaker bacilli1 gave the power of fighting and overcoming a more virulent bacilli1 and that these properties of the cells were transmitted to later generations of body cells4 ,this theory fails to explain the acquired immunity against toxins as well as against bacteria which occurs4 ,the discovery that the blood and other normal tissue fluids possess some power of destroying bacilli has relegated the phagocytal theory to a secondary position4 ,natural ,immunity varies in different animals4 ,thus enteric fever1 scarlet fever1 and measles are not known to occur except in man4 ,tuberculosis1 anthrax1 hydrophobia 7called rabies in the dog71 glanders and tetanus are common to man and certain other animals4 ,man1 cattle and pigs frequently suffer from tuberculosis2 goats1 sheep1 horses1 and dogs are practically immune to it4 ,epidemic and ,endemic ,diseases4--,infective diseases may occur sporadically1 in epidemics1 or in pandemics1 i4e4 epidemics spread over a number of countries4 ,the word epidemic is used here to mean specially prevalent1 and not to apply only to infective diseases4 ,thus there may be an epidemic of arsenical poisoning from contaminated beer4 ,certain infective diseases are endemic or topical1 i4e4 they have special homes or centres1 from which they occasionally spread as epidemics4 ,yellow fever1 cholera1 and malaria belong to this group4 ,in a minor degree enteric fever1 epidemic diarrha1 and tuberculosis may be described as endemic4 ,each infective disease has a special seasonal incidence4 ,of these the most important are the autumnal group1 viz4 ,epidemic ,diarrha1 maximum prevalence in ,july and ,august4 ,enteric ,fever ,november1 but excessive1 ,aug4 to ,dec4 ,erysipelas ,nov4 to ,dec4 ,diphtheria ,nov4 and ,dec41 excessive1 ,sept4 to ,dec4 ,scarlet ,fever ,oct41 excessive in ,aug4 to ,dec4 ,of other infective diseases ,small-pox has its maximum prevalence in ,may1 but is excessive ,jan4 to ,june4 ,whooping ,cough ,dec4 to ,may4 ,measles commonly has two seasonal maxima1 in ,june and ,december with intervening minima4 ,causes of ,epidemics4--,measles recurs in the large towns of ,england every alternate year4 ,other infective diseases occur at less regular intervals4 ,the recurrence of epidemics is not solely due to personal infection and the accumulation of a population at susceptible ages4 ,there are longer cycles of the causes of which but little is known4 ,thus scarlet fever has been shown by ,longstaff and ,gresswell to become epidemic chiefly in dry years2 and ,i have shown that diphtheria and rheumatic fever become widely epidemic under the same conditions1 diphtheria becoming so only when a series of dry years occur in immediate succession4 ,,chapter ,,xliv4 ,,acute ,,infective ,,diseases4 ,acute ,infectious ,diseases are characterised by certain definite characters4 #a4--,they are usually infectious or contagious4 ,it is preferable to use these two terms as interchangeable4 ,the modes in which infection is received vary greatly with different fevers4 7#a7 ,some can only be propagated by inoculation--the introduction through an abraded surface of a minute quantity of the poison2 as in glanders and hydrophobia4 ,others1 again1 may be introduced in this way1 but are usually acquired in another manner1 as scarlet fever1 small-pox4 7#b7 ,some are carried through the atmosphere4 ,the contagium of small-pox can be carried as far as any1 while that of typhus fever only traverses a few feet4 ,the atmosphere acts as a conveyer of infection1 and the infectious matter must necessarily1 in most instances1 be in the condition of dust to enable it to be wafted by currents of air or disturbed by the movements of persons in an infected room4 7#c7 ,clothes1 books1 and furniture are not uncommonly carriers of infection4 ,an old letter1 or a lock of hair1 has even after many years' concealment in an enclosed space produced infection on being brought to light4 ,woollen articles convey infection more easily than calico1 and dark clothes better than light coloured4 ,a fever nurse's clothes should never be woollen1 but some washable material4 7#d7 ,drinking water and food often form a vehicle for infection4 ,milk and water are the two usual sources of infection2 but uncooked food1 especially oysters and mussels1 fed in sewage-polluted estuaries1 may produce the same effect4 ,cholera1 enteric fever1 dysentery1 and summer diarrha are the chief diseases from this source2 but scarlet fever and diphtheria occasionally have a similar origin4 ,milk may be infected from having been handed by an infectious patient2 or it may possibly convey infection of the disease from which the cow at the time is suffering1 e4g41 tuberculosis 7see also page #cab74 ,water may be contaminated with sewage or the excreta of a single infectious patient4 #b4 ,they retain their specific character and origin4 ,small-pox never produces scarlet fever1 nor vice vers2 and it is found universally that all the specific fevers 8breed true10 each one retaining its identity4 ,more than this1 a previous case of the same fever can nearly always be detected on careful examination4 ,overcrowding and other insanitary conditions diminish the resistance to infection1 and may increase its virulence4 #c4 ,the behaviour of contagia1 when received into the system1 is characteristic of these diseases4 ,there is first of all a period of latency or incubation1 during which no symptoms are manifested 7see page #bhg47 ,the incubation period is followed by the characteristic symptoms of the particular fever1 which disappear in a variable period1 leaving the patient1 as a rule1 more or less insusceptible to a second attack 7see page #bhh74 ,throughout the progress of the disease1 except in the period of incubation1 the patient is able to communicate his disease to persons about him who have not been rendered safe by a previous attack4 ,the way in which he thus communicates his disease varies in different cases4 ,in scarlet fever1 the throat and skin are the chief sources of contagion2 in influenza1 whooping-cough1 and measles1 the secretions from the respiratory passages2 in hydrophobia1 the saliva2 in enteric fever and cholera1 the vomit and stools4 ,prevention of the ,spread of the ,chief ,acute ,infectious ,diseases4--,we may divide these into three classes4 7#a7 ,those which are infectious by contact with the patient or by the atmosphere around him4 7#b7 ,those in which the intestinal and renal evacuations are almost alone infectious2 as enteric fever and cholera4 7#c7 ,those in which inoculation through an abraded surface is generally if not always necessary to produce infection4 ,,small-,,pox ,,or ,,variola4 ,the contagium of small-pox is very tenacious of life4 ,all parts of the body1 and all secretions and excretions contain it4 ,as in typhus it adheres to every article in the room1 but unlike typhus is possessed of great vitality1 and if not exposed to the air may be active after many years4 ,there is considerable evidence indicating that the contagion of small-pox may occasionally be conveyed aerially for a considerable distance1 for even a quarter or half a mile from hospitals in which small-pox patients are isolated4 ,whether this is the aerial convection of infection1 or in part at least due to carelessness of persons connected with the hospital in their movements to and fro1 may remain an open question2 but such hospitals in the midst of towns are in practice a mistake2 and in ,london small-pox has been found to be more manageable since its small-pox patients were all conveyed to extra-urban hospitals4 ,the means for the prevention of small-pox are 7#a7 ,isolation of infectious patients4 7#b7 ,disinfection of all infected articles4 ,for particulars under these two heads1 see pages #cai and #cbd4 ,they must be carried out most rigidly in this disease4 7#c7 ,vaccination and re-vaccination4 ,inoculation of small-pox virus was largely practised as a means of ensuring a comparatively mild attack1 until it was made illegal in #ahdj4 ,sometimes1 however1 the attack thus produced was fatal1 and every case of inoculated small-pox became a new focus of infection1 and a source of high mortality1 especially among young children4 ,vaccination4 ,about the year #agie ,dr4 ,edward ,jenner was informed by a milk-maid that she could not take small-pox1 as she had already contracted the natural cow-pox during milking4 ,many had previously heard this same statement made2 but ,jenner was the first to put the matter to the test4 ,he took the lymph or virus from a woman who had accidentally acquired cow-pox 7vaccinia7 from a cow1 and inoculated a boy with it4 ,some months later he inoculated the same boy with small-pox1 and a second time five years afterwards1 without producing small-pox on either occasion4 ,many other experiments were made1 all confirming these results2 and in #agih ,jenner published his results4 ,the practice of vaccination gradually became more general1 and was followed by a progressive decrease in the mortality from small-pox4 ,cow-pox or vaccinia is small-pox modified and mitigated by its passage through the system of the cow1 and not a spontaneous disease of the cow4 ,by its passage through the cow it has become attenuated and altered4 ,instead of a general eruption all over the body1 there are vesicles only at the point of inoculation2 and vaccinia1 unlike small-pox1 is not communicable from person to person except by inoculation4 ,furthermore it is in the vast majority of instances an extremely mild ailment1 not involving more than a few days discomfort4 ,objection is taken to vaccination for small-pox on the ground that serious diseases such as syphilis1 erysipelas1 and tuberculosis may be inoculated at the same time4 ,with lymph obtained from healthy children this is impossible4 ,most of the cases of infection described have been in reality hereditary disease1 the local irritation of vaccination serving to call into activity the morbid tendencies of the child4 ,the risk of such infection is infinitesimal2 it may be reduced to zero by moderate care and attention to detail4 ,with modern antiseptic methods1 it is very rare for a vaccination sore to 8go wrong40 ,erysipelas may be inoculated from dirt getting into a vaccination sore1 as it may be into any other sore2 but with cleanliness this need not occur2 and in fact very seldom does occur4 ,the risks are so small as to be negligible2 and if the protection afforded is one tithe of what is claimed for it1 no parent is justified in withholding this protection from his infant4 ,the law as to vaccination requires that every infant shall be vaccinated within six months of its birth1 domiciliary visits for this purpose being made by the public vaccinator4 ,the obligation can only be avoided by a statement on oath before a magistrate by the parent of conscientious objection to vaccination4 ,does ,vaccination protect against ,small-,pox8 ,the registration of deaths for the whole country only began in #ahcg1 and before this period death-rates from small-pox in terms of the population cannot be accurately stated4 ,since that time there has been less or more vaccination1 so that it is difficult to obtain a true comparison between periods with and without vaccination4 ,some indication of the facts in ,london prior to #ahja1 when the first ,english census was taken1 may be obtained from the fact that in #agif 7two years before the date of ,jenner's 8,inquiry107 small-pox reached its highest point1 causing #ah deaths out of every #ajj total deaths from all causes4 ,in the pr-vaccination period small-pox was #i times as fatal as measles1 and #g times as fatal as whooping-cough 7,mc,vail71 while since vaccination has been practised it has sunk to an insignificant position1 when compared with these diseases4 ,dr4 ,guy found that in ,london there were in #dh years of the seventeenth century ten epidemics1 in the whole of the eighteenth century #ai epidemics1 and in the nineteenth century no epidemic during which the deaths from small-pox caused one-tenth or more than one-tenth of the total deaths from all causes in any year4 ,the worst year under obligatory vaccination in ,london was #ahga1 in which barely #d per cent4 of the total deaths was due to small-pox1 a proportion which was exceeded in the eighteenth century ninety-three times4 ,in ,sweden1 the highest death-rate before vaccination 7#aggd-ahjj7 was #gbc per #a1jjj inhabitants1 the lowest #jca2 under permissive vaccination 7#ahja-ahae7 the highest #beg per #a1jjj inhabitants1 the lowest #jab2 under compulsory vaccination 7#ahaf-he7 the highest #jid per #a1jjj inhabitants1 the lowest #jjjje4 ,it has been stated that these results1 which might be extended by quotations from the statistics of other countries1 have been obtained not by vaccination1 but by improved sanitation1 including in this term not only improved housing and better water and food supply but also increased means of isolating the infectious sick4 ,improved housing may by diminishing overcrowding aid in diminishing the spread of this disease4 ,whether in view of the immense increase in the proportion of the population which lives in towns1 it can be said that this has occurred is doubtful4 ,hospital isolation undoubtedly prevents the spread of infection when promptly effected4 ,but a large share of the improvement in small-pox mortality occurred before either hospital or home-isolation of small-pox patients was generally enforced4 ,there is no reason for supposing that impure water or food1 or nuisances about houses have any connection with the origin or spread of small-pox1 any more than they have with the origin or spread of measles or whooping-cough2 which still remain as prevalent as in the past4 ,further light can be thrown on the subject by an examination of the age-incidence of small-pox1 and of its attack-rate and severity in vaccinated and unvaccinated respectively4 ,the age incidence of deaths from small-pox has1 since #ahdg1 when returns classified according to age became available1 undergone a remarkable alteration4 ,prior to #ahgj the small-pox deaths in infants nearly always formed #bj per cent4 or more of the total mortality from this disease1 between #ahgj and #ahij they did not greatly exceed #aj per cent4 of the total1 while since #ahij they have again begun to form an increasing proportion of the total small-pox mortality4 ,at ages #a-e the change is even more remarkable4 ,before #ahgj deaths at these ages nearly always exceeded #cj per cent4 of the total2 since #ahgj they have varied between #e and #ad per cent4 of the total2 and since #ahij they have1 like the proportion of deaths under one1 again increased4 ,at the higher ages the proportion of deaths has correspondingly increased1 so that the curves of age incidence have become curiously inverted4 ,the lowered birth-rate can only account for a small portion of this transference of the chief mortality due to small-pox from childhood to adult life4 ,furthermore it must not be supposed that the only change which has occurred is that the deaths which formerly occurred in childhood now occur in adult life4 ,the death-rate at all ages has greatly declined4 ,the only explanation which in my judgment satisfactorily explains this remarkable change in age-incidence of small-pox mortality is the fact that vaccination protects children from small-pox and that the protection diminishes1 though it never entirely disappears1 with advancing years4 ,this conclusion is confirmed by the evidence obtained as to the proportion of vaccinated and unvaccinated attacked1 and as to the severity of the attacks occurring when a community is invaded by small-pox4 ,attack-rate among ,vaccinated4--,if the protective effect of vaccination1 like that of a preceding attack of small-pox1 wears off1 it will not be expected that no attacks of small-pox will occur among the vaccinated4 ,for evidence of immunity from attacks we must examine the records as to revaccinated persons exposed to infection4 ,during the six years #ahij-ie1 out of a staff in the ,london small-pox hospitals varying from #fd to #cbj1 the percentage attacked by small-pox was nil1 except in #ahib when it was #ad1 and in #ahic when it was #ai4 ,taking the experience of towns in which during recent years epidemics of small-pox have occurred1 the following attack-rates have occurred4 ,by attack-rate is meant the percentage number of attacks occurring among persons living in infected houses4 ,by fatality is meant the number dying out of #ajj attacked4 ,,attack ,,rate ,,under ,,attack ,,rate ,,over #aj ,,years ,,of ,,age4 #aj ,,years ,,of ,,age4 ,,vaccinated4 ,,unvaccinated4 ,,vaccinated4 ,,unvaccinated4 ,dewsbury #ajb #ejh #bgg #ecd ,leicester #be #cec #bbb #dgf ,gloucester #hh #dfc #cbb #ejj ,severity 7,fatality7 among ,vaccinated4--,the experience of the same three towns comes out as follows3-- ,,attack ,,rate ,,under ,,attack ,,rate ,,over #aj ,,years ,,of ,,age4 #aj ,,years ,,of ,,age4 ,,vaccinated4 ,,unvaccinated4 ,,vaccinated4 ,,unvaccinated4 ,dewsbury #bb #cba #b4f #ahg ,leicester #j4j #adj #a4j #gh ,gloucester #ch #daj #ajj #cig ,in view of such results as the above it is not surprising that the ,royal ,commission1 in their majority report1 summed up the advantages of vaccination as follows3 87#a7 ,that it diminishes the liability to be attacked by the disease4 87#b7 ,that it modifies the character of the disease1 and renders it 7a7 less fatal1 and 7b7 of a milder or less severe type4 87#c7 ,that the protection it affords against attacks of the disease is greatest during the years immediately succeeding the operation of vaccination4 ,it is impossible to fix with precision the length of this period of highest protection4 ,though not in all cases the same1 if a period is to be fixed1 it might1 we think1 fairly be said to cover in general a period of nine or ten years4 87#d7 ,that after the lapse of the period of highest protective potency1 the efficacy of vaccination to protect against attack rapidly diminishes1 but that it is still considerable in the next quinquennium1 and possibly never altogether ceases4 87#e7 ,that its power to modify the character of the disease is also greatest in the period in which its power to protect from attack is greatest1 but that its power thus to modify the disease does not diminish as rapidly as its protective influence against attacks1 and its efficacy during the later periods of life to modify the disease is still very considerable4 87#f7 ,that re-vaccination restores the protection which lapse of time has diminished1 but the evidence shows that this protection again diminishes1 and that1 to ensure the highest degree of protection which vaccination can give1 the operation should be at intervals repeated4 87#g7 ,that the beneficial effects of vaccination are most experienced by those in whose case it has been most thorough4 ,we think it may fairly be concluded that where the vaccine matter is inserted in three or four places1 it is more effectual than when introduced into one or two places only--and that if the vaccination marks are of an area of half a square inch1 they indicate a better state of protection than if their area be at all considerably below this40 ,,scarlet ,,fever4 ,scarlet ,fever and ,scarlatina are the same disease4 ,it is extremely infectious1 the contagium retaining its virulence for protracted periods4 ,it occurs in epidemics at irregular intervals4 ,during recent years the type of scarlet fever has become greatly attenuated1 and this constitutes one of the difficulties of prevention1 as the mild form of the disease is apt to be overlooked4 ,the fatality per #ajj persons attacked varies greatly with age4 ,it is highest in children under four1 rapidly declining with increasing age4 ,hence the importance of protecting children from attack in early life4 ,two results follow from the wise precautions taken to prevent attack early in life4 7a7 ,with each successive year of life the liability to attack1 when exposed to infection1 diminishes2 7b7 the danger of the attack if it occurs and its liability to be fatal becomes rapidly less with greater age4 ,the most common mode of infection is by contact with a previous patient4 ,outbreaks due to milk infected by a scarlatinal patient also occur4 ,infected cream has also been known to convey infection4 ,in a milk outbreak the patients would be found chiefly among the customers of a special dairyman1 the cases occur almost simultaneously1 except secondary cases which may be infected from the first4 ,the simultaneous occurrence of two or more attacks in one house1 especially if the same thing happens in a number of houses should throw suspicion on the milk supply4 ,it has been suggested that scarlet fever may originate apart from human infection1 from a special disease of the cow1 but the evidence on this point is inconclusive4 ,the duration of infection is usually reckoned until the desquamation of the skin is complete1 i4e4 about six or seven weeks from the onset of the attack4 ,occasionally it is more protracted even though desquamation is complete1 infection appearing to persist in discharges from the nose and ear and in sore places inside the nostril and possibly in other parts4 ,the period of greatest infectivity is in the earlier part of the disease1 when the throat is inflamed4 ,the common notion that the disease is most infectious during the later period1 that of desquamation1 is erroneous4 ,the micro-organism causing scarlet fever has not certainly been identified4 ,the measures of prevention are those common to infectious diseases 7page #cag74 ,,measles4 ,measles is an extremely infectious disease1 before as well as after the rash appears on the fourth day of the disease4 ,the infectivity of the catarrhal stage constitutes one of the main difficulties in preventing its spread1 as measles may be unrecognisable at this stage4 ,the common notion that measles and whooping-cough are comparatively harmless infantile complaints will be dissipated by a study of the comparative death-rate for the five years #ahia-e per million persons living in ,england and ,wales3-- ,,england ,,and ,,wales4--,,death ,,rates ,,per ,,million ,,of ,,population4 ,small-pox #bj ,measles #djh ,scarlet fever #ahc ,typhus fever #d ,enteric fever #agd ,whooping-cough #cih ,diphtheria #bec ,diarrha #fcj ,it is a mistake also to suppose that measles and whooping-cough are only serious when neglected4 ,such neglect greatly increases the likelihood of death from bronchitis or pneumonia2 but the diseases themselves1 especially measles1 are frequently fatal during the acute early stage4 ,more children are attacked with measles under the age of five than at any other age1 and the greatest number between two and four years of age4 ,the greatest fatality is in the second year of life1 when it may be #bd per cent4 of those attacked1 as compared with between two and three per cent4 in the fourth year of life1 and a trifling amount at higher ages4 ,these facts explain the folly of allowing children to have an infectious complaint when another child in the house is attacked1 8to have it over at one trouble40 ,such action is pregnant with evil results4 7#ast7 ,severe cases occur1 in which a fatal result ensues2 and even where death does not occur1 the child may be left weakly and very prone to become tuberculous4 7#bnd7 ,every additional case forms a new centre of infection4 ,it is like the old practice of inoculation for small-pox2 the individual is protected1 but becomes a source of danger to all around him4 ,if there is only one case of measles in a family the risk to neighbouring households is much smaller than where several children are infected4 7#crd7 ,every year that a child's attack can be delayed1 increases his chance of recovery if he is subsequently attacked1 and diminishes the likelihood of his being attacked4 ,the duration of infection should be reckoned as at least three weeks4 ,the contagium of measles does not appear to hang about rooms with the persistence of that of scarlet fever1 and less stringent disinfection is required4 ,,whooping ,,cough4 ,very few people have reached adult life without having suffered from this disease1 as well as measles4 ,this is chiefly due to the carelessness in mixing infected with healthy children4 ,one frequently hears the peculiar and characteristic cough of a child with whooping-cough1 in public assemblies1 in railway trains1 or in the out-patient rooms of hospitals4 ,the contagium of whooping-cough is conveyed chiefly by the expectoration1 which becoming dry1 may be scattered like that of phthisis1 as dust4 ,clothing conveys infection easily2 visits to infected children should1 therefore1 be prohibited to all who have to mix with susceptible children4 ,the duration of infection should be reckoned as at least six weeks from the first recognisable symptoms4 ,it may be longer than this4 ,,diphtheria4 ,this disease has become increasingly prevalent in the last ten years after a period of only slight prevalence for about twenty-five years4 ,i have shown that epidemics of diphtheria occur during a succession of years of protracted drought4 ,diphtheria is more common in girls than boys1 possibly owing to their more affectionate habits2 and occurs chiefly under ten years of age1 the fifth year of life being that of greatest prevalence4 ,unlike the acute infections hitherto considered1 the bacillus causing diphtheria has been identified and cultivated in the laboratory 7called the ,klebs-,loeffler bacillus or diphtheria bacillus74 ,direct infection from patient to patient is probably more common than indirect infection by clothes1 etc41 though the latter occurs4 ,the infection may hang persistently about a house and its belongings1 in the absence of complete purification4 ,when diphtheria is prevalent slighter sore throats occur1 sometimes before true diphtheria is detected4 ,this led to the theory that under conditions of overcrowding1 especially in schools1 there occurred in the micro-organisms causing these sore-throats 8the progressive development of the property of infectiveness40 ,possibly these were slight non-typical attacks of diphtheria4 ,such attacks occur also during epidemics of diphtheria1 and unless specimens 78throat swabs07 from these sore-throats are examined bacteriologically1 are likely to spread diphtheria by attendance at school1 etc4 ,aggregation in schools seems to intensify the contagium of diphtheria4 ,the practices of kissing1 of transferring sweetmeats from mouth to mouth1 of cleaning slates with saliva1 are common means of spreading it4 ,effluvia from foul drains and sewers have been commonly held to cause diphtheria4 ,if they aid in producing it1 it is rather by lowering the vitality and causing ordinary sore throat4 ,sore throats and catarrhs make the subjects of them much more prone to diphtheria 7see also page #aag74 ,damp houses have been stated to favour the development of diphtheria4 ,probably they do so in the same way as effluvia from drains4 ,it is likely that the diphtheria bacillus has a saprophytic stage of existence in the soil1 as indicated by its excessive prevalence in dry warm years4 ,besides direct infection from patient to patient and indirect infection by fomites 7i4e4 in clothing1 etc471 milk occasionally causes epidemics of diphtheria4 ,the infection has been usually caused by the handling of the milk by an infectious person4 ,in certain outbreaks no human contamination of the milk could be discovered2 and it has been surmised that an analogous disease in the cow may cause diphtheria in man4 ,this is still a moot point4 ,fowls1 cats1 and other animals are the occasional victims of diphtheria1 and may convey it to man4 ,the duration of infection in diphtheria is usually less than six weeks2 but it may be much more protracted4 ,in some instances long after all naked-eye evidences of diphtheria has disappeared1 bacteriological examination may still show the presence of the diphtheria bacillus for two or three months2 in rare cases even longer4 ,the protection afforded by one attack of diphtheria against a second is slight and only temporary4 ,the means of prevention are isolation and disinfection as for other infectious diseases4 ,two additional means are available 7a7 bacteriological diagnosis2 7b7 prophylactic injection of antitoxic serum4 ,many sore throats without membrane on the throat are due to the diphtheria bacillus4 ,even if membrane be present there may be doubt as to whether the case is true diphtheria4 ,hence the importance of bacteriological examination4 ,the patient's throat is swabbed with cotton-wool which has been rolled around a metal probe and sterilised4 ,the wool is then smeared over sterilised and solified blood serum in a test tube4 ,it is then incubated over night at a temperature of #cg ,c4 ,next morning the minute growth that has occurred on the surface of the blood serum is spread on a microscopic cover-glass1 appropriately stained1 and examined microscopically4 ,if diphtheria bacilli are present1 they can be recognised by their form and arrangement4 ,the same means enable us to ascertain when a patient has recovered1 whether he is fit to be released from isolation4 ,antitoxic serum has been found to be a valuable prophylactic and curative agent4 ,the serum is obtained as follows3 ,sterilised broth is inoculated with virulent diphtheria bacilli1 and grown at #cg ,c4 for a week or more4 ,the broth is then filtered through a ,pasteur filter4 ,the filtrate contains toxine free from bacilli4 ,some of this toxine is injected under the skin of a horse4 ,a few days later the dose is repeated1 gradually increasing amounts being injected until injection of further quantities of the toxine is found experimentally not to increase the antitoxic value of the horse's blood serum4 ,next the horse is bled4 ,its serum is found to have acquired the power of protecting a guinea-pig against doses of the toxine of diphtheria which would otherwise be fatal4 ,ten times the quantity of the horse's serum which will protect a guinea-pig 7of #bej grammes weight7 against ten times the minimum fatal dose of the toxine is called an antitoxic unit4 ,the treatment of diphtheria in man by the antitoxic serum thus obtained has proved to be remarkably successful4 ,furthermore1 if a susceptible person who has been exposed to the infection of diphtheria1 is injected with a small dose of antitoxic serum1 he becomes temporarily immune1 and does not fall a victim to diphtheria4 ,this is a most important point especially for young children1 who may already be incubating a disease which but for this prophylactic injection might occur and prove fatal4 ,,typhus ,,fever4 ,this disease was formerly known as spotted or jail-fever1 and for many ages has been the scourge of prisons and armies1 and all collections of people living in overcrowded and insanitary districts4 ,the history of typhus is the history of human misery4 ,it is essentially associated with filth1 overcrowding1 and destitution2 but when once established by these conditions1 it can be carried by infection to others who live amidst healthy surroundings4 ,it generally occurs in winter1 when overcrowding is greatest4 ,with free ventilation1 the disease cannot be carried more than a few feet4 ,it can be transmitted by clothing4 ,the micro-organism causing it has not been discovered4 ,with the clearance of the rookeries of our great towns1 it is rapidly decreasing1 and appears likely to become extinct4 ,the means of prevention1 in addition to the abatement of nuisances1 including overcrowding1 are isolation and disinfection 7pages #cai and #cbe74 ,,relapsing ,,fever4 ,this disease was formerly common in this country1 but except in some parts of ,ireland has entirely died out4 ,it is caused by a micro-organism 7,spirillum ,obermeieri7 which can be detected in the blood4 ,inoculation of this will produce the disease in man or in monkeys4 ,epidemics of relapsing fever commonly follow in the track of typhus fever2 overcrowding and filth being especially associated with typhus1 and starvation with relapsing fever1 hence its name of 8famine fever40 ,,enteric ,,or ,,typhoid ,,fever4 ,enteric fever causes its highest death-rate in early adult life1 though it is not peculiar to any age4 ,eberth in #ahhj discovered the ,bacillus typhosus in the spleen and other organs of enteric fever patients4 ,this is commonly known as ,eberth's bacillus1 and is the cause of enteric fever4 ,a few years later it was isolated and can now be grown on agar or gelatine in laboratories4 ,it closely resembles other bacilli which are normal inhabitants of the human intestine2 but can be distinguished by certain tests4 ,it is a small rod1 rounded at its ends1 and from #b to #d long and three times as long as broad4 ,in the living state it is freely motile1 and possesses a number of minute cilia or flagella4 ,apart from other means of distinction between it and other bacilli1 ,grber's serum reaction enables its identity to be ascertained4 ,the bacillus suspected to be the ,bac4-typhosus is cultivated in broth in the bacteriological laboratory4 ,a small quantity of blood is taken from the finger of a patient known to be suffering from enteric fever4 ,the serum is separated from the blood corpuscles of this blood by a centrifugalising machine4 ,a drop of the blood serum is diluted with #ajj drops of broth culture of the suspected bacillus4 ,if the latter is not the ,bac4-typhosus1 the individual bacilli when a drop of the mixture is examined under the microscope1 will continue to move about freely2 if it is the ,bac4-typhosus1 the bacilli will adhere together in 8clumps0 and become immobile4 ,conversely a valuable means of ascertaining whether a suspected case is really suffering from enteric fever is secured1 as this blood added to #cj times the amount of a pure culture of the ,bac4-typhosus in broth will cause the latter to 8clump0 within half-an-hour 7,widal reaction74 ,higher dilutions are usually unnecessary4 ,the chief means of spread of enteric fever is by the urine and fces2 and nurses who have to empty bed-pans unless very careful to wash their hands afterwards1 using the nail-brush1 are very liable to become infected1 probably when eating food afterwards4 ,the urine in a considerable proportion of cases1 contains the typhoid bacilli1 and it is therefore most important that care should be exercised in the cleansing of all chamber utensils1 and that the urine as well as the fces should be rigidly disinfected 7see page #cca74 ,the infectivity of enteric fever has been underrated in the past4 ,when patients with this disease are nursed at home by relatives who do not appreciate the full importance of the necessary precautions1 it is rather the rule than the exception for them to fall victims to its infection4 ,probably1 sometimes the infection has been scattered as dust1 owing to small particles of fces or of urine having become dried on bed linen4 ,the most absolute cleanliness is essential in nursing this disease4 ,in hot climates there is reason to believe that infective dust may be blown about from privies4 ,insanitary local circumstances are an important means of spreading enteric fever4 ,it is more prevalent where there are privies than where there are pail-closets2 and more prevalent where there are pail-closets1 than where water-closets are the rule4 ,defective drains or soil-pipes are frequently found in houses in which enteric fever originates1 and there can be little doubt that the former are at least partially responsible for the latter4 ,the exact link is doubtful4 ,probably infective dust is blown or aspirated into the room and is inhaled4 ,the most common cause of enteric fever is infected food or water4 ,of foods milk not infrequently has been the means of spread of enteric fever4 ,large epidemics have been traced to this source4 ,usually this has arisen by washing the milk cans with or wilfully adding contaminated water to the milk4 ,water1 whether added to milk or taken independently1 must have contained the specific contagium 7the ,bac4-typhosus7 of enteric fever1 to enable it to cause enteric fever4 ,hence water from a contaminated stream is more likely to have produced this effect than well-water1 unless a patient has had enteric fever in the house to which the well is attached1 and his dejecta have contaminated the water4 ,surface waters or spring waters may be contaminated with sewage 7as at ,maidstone7 or deep well waters through fissures 7as at ,worthing7 and thus widespread epidemics be produced4 ,after floods1 rivers and wells are most likely to contain the specific contagium of enteric fever1 as at such times surface impurities from middens1 etc41 are apt to be washed into the water4 7,see also pages #ia and #bbd74 ,the means of prevention of enteric fever are the discovery and removal of the cause of an outbreak1 and the isolation of each patient and disinfection of all discharges4 ,an early means of diagnosis is secured by ,widal's reaction4 ,this is especially useful in cases not presenting characteristic clinical symptoms4 ,the recognition of a disease or at least the suspicion of its presence is an indispensable first step for the taking of precautionary measures4 ,,cholera4 ,cholera1 which was formerly so prevalent1 now seldom occurs in this country1 and at each successive visit to ,england its inroads have become less serious4 ,at its last visit in #ahic it scarcely obtained a footing in the country4 ,thus in the epidemic of #ahed in ,england it caused #ajhj1 in that of #ahff it caused #fgb1 and in that of #ahic only #de deaths per million of population4 ,in this country at least it is chiefly spread by infected water and foods1 especially by infected water2 and the preceding figures form an excellent testimony to our improvement in this respect4 ,for particulars of the ,hamburg outbreak1 see page #ic4 ,in its mode of prevalence and propagation it is very similar to enteric fever1 being infectious by means of the evacuations4 ,the means of prevention are the same as for enteric fever4 ,cholera was shown by ,koch to be caused by what is known as the comma bacillus or spirillum of ,asiatic cholera1 so called because of its curved shape4 ,it is from #ae to #bf long and #e broad4 ,for the supposed connection of enteric fever and cholera with movements of the ground-water1 see page #bbe4 ,,summer ,,or ,,epidemic ,,diarrh,a is a most fatal disease among infants in the third quarter of each year4 ,it is chiefly a disease of urban life1 and occurs to a preponderant extent among the children of the artisan and still more of the unskilled labouring classes4 ,it is much less abundant in towns which have adopted the water-carriage system of sewage than in those retaining the conservancy methods of removal of excrement 7page #aih74 ,towns with the most perfect domestic and street scavenging arrangements have the least epidemic diarrha4 ,an impervious soil favours a low diarrhal mortality2 while persons living on porous soils usually have much diarrha4 ,i have shewn elsewhere that given two towns equally placed so far as social and sanitary conditions are concerned1 their relative diarrhal mortality is proportional to the height of the temperature and the deficiency of rainfall of each town1 particularly the temperature and rainfall of the third quarter of each year4 ,in other words there is a general inverse relationship between rainfall and diarrha and a direct relationship between temperature and diarrha4 ,thus wet and cool summers are adverse to diarrha4 ,ballard concluded that the summer rise of diarrhal mortality does not commence until the mean temperature recorded by the #d-;foot earth thermometer has attained somewhere about #ef ,f41 no matter what may have been the temperature previously attained by the atmosphere4 ,this is a convenient index1 as the summer warmth does not immediately cause diarrha4 ,all the above facts point to the conclusion that the fundamental condition favouring epidemic diarrha is an unclean soil1 the particulate poison from which infects the air1 and is swallowed most commonly with food1 especially milk4 ,thus1 diarrha1 like enteric fever1 is a 8filth-disease40 ,as the contagium appears to gain entrance by food1 the following card of precautions which is distributed each year in the poorer districts of ,brighton may be reproduced here3 ,,how ,,to ,,prevent ,,diarrh,a4 ,during the summer a large number of infants die from diarrha4 ,scarcely a single baby who was being suckled dies from this cause4 ,it is evident1 therefore1 that in the prevention of this very fatal summer disease1 precautions as to food are most important4 ,attention to the following points would save many infants' lives3-- #a4 ,do not wean your infant during the hot months of ,july1 ,august and ,september4 ,to begin artificial feeding during hot weather is very dangerous4 #b4 ,if feeding by hand is absolutely necessary1 carefully follow these directions3 7a7 ,all milk should be boiled before being given to the infant4 7b7 ,the infants' food must be prepared fresh each time4 7,for particulars see below47 ,milk and water1 and still more 8pap0 or patent foods1 if left two or three hours1 8go bad10 and are then very highly dangerous to the infant4 7c7 ,all jugs or other utensils used for storing milk must be scalded out and kept absolutely clean4 ,they should be covered to prevent access of dust4 7d7 ,the feeding bottle must be thoroughly scalded after each meal1 and the tube thoroughly cleansed4 ,it is best to use alternately two boat-shaped bottles without tubes4 ,if the bottle smells sour1 something is not clean1 and the infant will suffer4 #c4 ,decomposing refuse1 such as decaying vegetables1 bones1 fish-heads1 c41 is a fertile source of ,diarrha4 ,it should be burnt1 and not placed in the dust-bin4 #d4 ,scrupulous cleanliness of the house1 especially of the rooms where food is stored1 is most important4 ,dust in every form is dangerous to health1 and for removing it wet cleansing is preferable to dry4 ,thus washing and scrubbing are safer means of cleansing floors1 c41 than sweeping4 #e4 ,report to the ,sanitary ,office1 ,town ,hall1 any smells or choked closet or drain4 ,,directions ,,for ,,preparations ,,of ,,infants' ,,food4 ,for a ,child aged ,mix and then boil ,for each ,meal 7#a part fresh milk 7 ,under #f weeks #b parts water #d tablespoonsful4 7#a teaspoonful cream 7 ,mix and then boil 7#a part fresh milk 7 #f weeks old #a part water #h tablespoonsful4 7#b teaspoonsful cream7 ,mix and then boil 7#b parts fresh milk 7 ,from #c to six months old #a part water #h tablespoonsful4 7#b or #c teaspoonsful 7 cream4 ,the infant should be fed at regular intervals only1 at first every two hours1 the interval being gradually increased4 ,the infant should be fed slowly4 ,if the milk as prepared above disagrees1 freshly boiled barley water should be used instead of water4 ,the addition of cream is necessary because cows' milk is poorer in cream than mothers' milk1 and because it is very often made poorer still by mixing with separated milk before sale4 ,deficiency of cream causes rickets4 ,a little sugar may also be added to the milk1 but this must not be regarded as a substitute for the cream4 ,,tetanus4 ,tetanus or lockjaw is not infectious1 but is conveyed to man by the inoculation of a wound by dirt or earth which contains the tetanus bacillus4 ,for this reason it is more apt to follow injuries to the hands or feet4 ,extreme cleanliness of wounds is the only practicable preventive means4 ,little is known of the history of the tetanus bacillus outside the body2 and as to what soils contain it most abundantly4 ,wounds contaminated by horse manure appear to be especially dangerous4 ,,glanders4 ,glanders is common in horses4 ,it attacks the mucous membrane of the nose1 causing ulceration4 ,it is extremely infectious4 ,farcy is a more chronic form of the same disease1 in which the so-called 8farcy-buds0 are produced4 ,its prevention can best be ensured by killing both actually diseased and suspected animals1 if the latter give a reaction to mallein4 ,mallein is a product allied to tuberculin1 obtained from cultivations of the bacillus of glanders4 ,it sets up febrile reaction in glandered1 but not in healthy horses4 ,further preventive measures are the temporary closing of public drinking fountains for horses1 and the thorough cleansing and disinfection of stables4 ,men1 especially grooms1 are sometimes infected by the horse1 and the disease is commonly fatal4 ,,hydrophobia4 ,hydrophobia is the disease in man which is caused by the bite of a dog or other animal suffering from rabies4 ,it is seldom if ever communicated otherwise than by inoculation4 ,the incubation period in the dog varies from three to six weeks1 and in man is usually about the same2 but occasionally it is much longer1 occasionally even more than a year4 ,at the ,pasteur ,institute1 ,paris1 patients who have been bitten by rabid dogs are treated by the inoculation of an attenuated virus of rabies derived from rabbits1 with promising results4 ,dogs only acquire rabies from dogs or other animals already rabid4 ,so far as is known1 it does not arise de novo4 ,hence the necessity for an extensive area of muzzling when cases of rabies occur4 ,the enforcement of this plan has greatly reduced the amount of hydrophobia in this country in recent years4 ,there has been much misplaced sympathy with dogs on this score4 ,in the dog the symptoms of rabies occur in three stages3 a premonitory stage1 in which the dog's habits change1 he becomes morose and quiet1 and dribbles2 a second stage1 in which he has paroxysms of fury1 his voice is high-toned and croupy1 and he cannot swallow water2 and a third or paralytic stage1 in which his jaws drop1 he drags his hind legs and soon dies4 ,,erysipelas4 ,erysipelas occurs on various parts of the skin4 ,it is caused by the inoculation through an abraded surface of a virulent form of the same streptococcus that commonly causes suppuration4 ,it occurs chiefly in debilitated subjects4 ,some persons are specially prone to it1 and may have many attacks4 ,erysipelas1 like scarlet fever1 occurs most in years in which there is deficient rainfall2 and is probably conveyed by dust4 ,it may spread1 though exceptionally1 from case to case4 ,,yellow ,,fever4 ,yellow fever never occurs in ,england1 except when imported from the ,west ,indies or other countries in which it is endemic4 ,it clings to seaport towns in hot countries2 and as a permanent disease is only found when the mean winter temperature is at least #fh-gb ,f4 ,a frost always stops an epidemic of this disease4 ,the germs of this disease are communicated by mosquitoes1 which act as an intermediate host4 ,dr4 ,j4 ,w4 ,lazear1 although isolated from yellow fever cases1 died of it seven days after submitting to the puncture of an infected mosquito1 thus proving the communicability of this disease1 and entitling himself to an honoured position among scientific martyrs4 ,,plague4 ,plague is an ,eastern disease1 which occasionally shows a tendency to become widely epidemic4 ,it is due to a rod-shaped bacterium1 averaging #h to #af in length1 which does not form spores4 ,in its characteristic form patients suffering from this disease have inflammatary swellings 7buboes7 of various glands3 hence the name ,bubonic ,plague4 ,in other cases it simulates ordinary pneumonia1 typhus or septicaemia2 or the patient may be so slightly ill as to be able to walk about4 ,it appears probable that the bacillus enters the body through cracks or other lesions of the skin1 possibly also by inhaling infective dust4 ,the rat is an important factor in the spread of plague4 ,very commonly plague has been widely prevalent and fatal among them before it attacks human beings4 ,rats also bring it in ships from infected ports4 ,hence one of the most important preventive measures is to kill all rats on board ship1 before the cargo is unloaded4 ,this has been done by sulphurous acid fumigation in the holds4 ,the use of carbonic oxide gas will probably be found practicable for the same purpose4 ,manson has put the importance of this point tersely as follows3 8,to prevent cholera the tea-kettle1 malaria the mosquito net1 and plague the rat-trap40 ,flies may carry the infection 7page #bha74 ,it has been suggested that the fleas of rats carry the infection 7page #bha74 ,,anthrax4 ,anthrax is a very fatal disease in cattle and sheep1 occasionally in pigs4 ,butchers may inoculate themselves with it when dressing a diseased carcase2 the tanners similarly when handling the hide2 and woolsorters may inhale it when sorting wool derived from a diseased animal 7page #ajg74 ,to prevent the latter1 suspected wool must be disinfected by steam1 and special arrangements made for carrying off the dust produced during sorting4 ,,puerperal ,,fever occurs after childbirth4 ,it is caused like erysipelas by the inoculation of septic material4 ,this may be conveyed by dirty instruments 7syringes1 etc471 or by dirty hands4 ,hence the importance of extreme cleanliness of hands1 finger-nails1 and all articles used during and after childbirth4 ,,rheumatic ,,fever has been commonly attributed to a damp condition of the atmosphere and soil4 ,i have elsewhere shown that this is a mistake1 probably arising from the fact that these conditions produce what are called 8rheumatic0 pains1 though they have no true relationship with acute rheumatism 7rheumatic fever74 ,i have shown that rheumatic fever occurs chiefly in very dry years1 the excess of prevalence in such years being sufficient to justify the use of the term 8epidemic40 ,there is strong reason to believe that rheumatic fever is an infective disease1 derived1 not from other patients suffering from the same disease1 but from some outside micro-organism which is ordinarily saprophytic4 ,it follows the rule that when the lesion produced by an infective disease is deepseated 7in the joints in this instance71 no infection can be communicated to other persons4 ,some families are much more prone to rheumatic fever than others4 ,,influenza is1 like diphtheria1 a somewhat mysterious infectious disease4 ,like the latter it almost disappeared for a series of years1 and then again became epidemic in #ahhi4 ,the previous epidemics of influenza in the #aith century had occurred in #ahjc1 #ahcc1 #ahcg-h1 and #ahdg-h4 ,the causes of this recurrence of influenza are unknown4 ,it is spread from person to person by direct infection1 the infection being conveyed by the mucous discharge from the nose1 throat1 and lungs4 ,pocket-handkerchiefs probably are largely responsible for conveying the infection as dust4 ,the disease is particularly fatal to the old2 and these should not expose themselves to possible sources of infection1 as in public places of assembly1 during an epidemic4 ,every patient attacked with the disease should remain indoors for at least ten days4 ,this is in his own interest1 as he thus minimises the risk of such dangerous complications as pneumonia2 and it is his duty in the interest of the rest of the community4 ,many lives might have been saved1 had not influenzal patients 8struggled about0 during the early stages of the disease4 ,,malaria4 ,malaria1 or ,ague1 is a generic name given to a disease caused by the invasion of the body by the plasmodium malari1 discovered by ,laveran in #ahhj4 ,it occurs in two chief types1 remittent fever and intermittent fever4 ,for many generations it has been regarded as due to a marshy condition of the soil1 associated with decaying vegetable matter1 and a moderately high temperature4 ,it is now clear that these conditions are necessary1 only because they are necessary for the life of the mosquito4 ,the well-known danger of being out of doors at night in a malarious country is explained by the nocturnal habits of the mosquito4 ,the higher salubrity of the upper stories of houses is explained by the fact that the mosquito does not rise high from the ground2 and of high-lying localities by their greater dryness4 ,the value of the mosquito net1 of smoke1 and of fire as protections from malaria are due to their keeping mosquitos at a distance4 ,the mosquito clings to the puddle or swamp where she was born1 and where she will deposit her eggs4 ,hence the special danger of the immediate vicinity of such collections of water4 ,thus the prevention of malaria resolves itself chiefly into means for preventing the development of certain species of ,anopheles 7page #bhb74 ,the conditions necessary for the multiplication of these are 7#a71 an atmospheric temperature from #ge to #ajd ,f42 7#b7 collections of fresh or slightly brackish water2 and 7#c7 the presence in these of low forms of animal and vegetable life4 ,we have already described the cycle of life of the plasmodium malari 7page #bhb74 ,man is the chief1 if not the only source1 from which the mosquito derives this parasite4 ,in native communities the young children1 even when apparently not ill with malaria1 nearly always harbour these parasites in their blood corpuscles4 ,hence the importance of ,europeans having their dwellings as remote as possible from native houses4 ,mosquitos do not travel far4 ,instances of the prevalence of malaria in the absence of mosquitos are not substantiated4 ,the outbreaks of malaria where the soil has been disturbed after long lying uncultivated1 probably mean the formation of puddles favourable to the breeding of the larv of mosquitos4 ,the necessary preventive measures are classified by ,manson as3 #a4 ,suppression of mosquitos4 #b4 ,prevention of infection of mosquitos4 #c4 ,prevention of infection by mosquitos4 ,the suppression of mosquitos involves the draining or filling in of swamps and ponds1 the cleansing and canalisation of sluggish streams1 and the afforestation of hills to prevent floods4 ,cultivation of rice and other plants entailing the prolonged flooding of land should be restricted to fields remote from dwellings4 ,subsoil drainage is helpful4 ,the 8painting0 of stagnant waters with petroleum1 which should be renewed every week or two1 frees water for a considerable time from the larv of mosquitos4 ,eucalyptus and other balsamic trees may help to dry up pools1 c4 ,the prevention of infection of mosquitos is secured by insisting on all malarial patients using mosquito nets4 ,this prevents the access of mosquitos4 ,at the same time patients should vigorously and persistently take quinine1 which kills the malarial parasites in the blood1 and thus diminishes and finally removes the danger to other persons produced by the intermediation of the mosquito4 ,the prevention of mosquito bites is secured by rendering the house mosquito-proof by filling in all openings by fine wire gauze1 and by having mosquito curtains to all beds2 also by fumigating the rooms occasionally with the dried flowers of the chrysanthemum1 by strict cleanliness of rooms1 and by flushing them with sunlight4 ,the proof of the mosquito theory as to the causation of malaria has been recently supplied by two test experiments4 7a7 ,in the first1 a number of mosquitos which had been fed on the blood of malarious patients were sent to ,london from ,rome4 ,these were allowed to bite ,dr4 ,manson's son1 who had never previously had malaria4 ,a few days later he had a characteristic attack of fever4 ,malarial parasites were found in his blood4 ,he recovered in a week's time after free dosage with quinine1 and the parasites disappeared from his blood4 ,he suffered from a slight relapse about a year later4 7b7 ,on a fever-haunted spot in the ,roman ,campagna a wooden hut was built1 and ,drs4 ,sambon and ,low1 and three others took up their abode here during the malarious season1 the only precautions taken being the use of mosquito nets and wire screens in doors and windows4 ,they went about the country daily1 but were always home before sunset4 ,they all remained at the end of the season free from malaria4 ,,chapter ,,xlv4 ,,tuberculosis4 ,,consumption ,,and ,,other ,,tubercular ,,diseases4 ,consumption 7also called phthisis or phthisis pulmonalis7 in the year #ahii caused a recorded death-rate of #a1ccf1 and tubercular diseases of other parts of the body a death-rate of #ege per million of the population4 ,in the same year the chief infectious diseases1 including small-pox1 measles1 scarlet fever1 whooping cough1 typhus1 and enteric fever1 and diphtheria1 were together responsible for a death-rate of #a1bdh per million4 ,in the five years1 #ahfa-fe1 the mean death-rate from consumption was #b1ebg per million1 so that a reduction of nearly #ej per cent4 has apparently occurred4 ,notwithstanding this great decline1 consumption and other consumptive diseases1 which may together be classed under the name tuberculosis1 still cause more deaths than all the acute infectious diseases put together4 ,its importance is emphasised by the fact that between the ages of #bj and #de1 one-third of all the deaths of males1 and between one-third and one-fourth of all the deaths of females occurring at these ages are due to consumption of the lungs4 ,formerly great stress was laid on the hereditary character of consumption4 ,it would appear1 however1 that what is inherited is simply an increased vulnerability of tissues4 ,judging by the analogy of other animals it may be said that infants are rarely1 if ever1 born tuberculous4 ,bang examined #f1jjj head of cattle with the tuberculin test 7see page #caa71 and found that in calves under #f months old only #ajg per cent4 reacted1 i4e4 showed evidence of tuberculosis1 between #f and #ab months old #ahg per cent41 #a to #b years #bcb per cent41 and over this age #cac per cent4 reacted2 from which it may be inferred that the infection is nearly always received after birth4 ,the real cause of tuberculosis was shewn by ,koch1 in #ahha1 to be the tubercle bacillus4 ,this is a minute bacillus1 the length of which is from a quarter to half the size of a blood corpuscle4 ,these bacilli1 obtained from tuberculous growths in the body1 ,koch was able to cultivate on glycerine agar at blood-heat outside the body4 ,by sub-culturing he obtained pure cultures1 and after growing the bacilli for as long as fifty-four days1 he inoculated various animals1 producing tuberculosis in every case1 while in similar check experiments in which all the conditions were the same1 barring the absence of bacilli1 no tuberculosis resulted4 ,the tubercle bacilli are easily distinguished from most other bacilli by the fact that after being stained by aniline dyes1 such as carbol-fuchsin1 the colouration is not removed when the preparation is soaked in dilute acid4 ,by this means the presence of tubercle bacilli in the sputum 7expectoration7 of a phthisical patient is easily discovered1 and a valuable means of early recognition of the disease secured4 ,this is most important1 as in its early stages consumption is an easily curable disease4 ,tubercle bacilli are discharged from the lungs in consumption of the lungs1 from the bowels in consumption of the bowels1 and so on4 ,hence the essential necessity for disinfecting these discharges4 ,such discharges while in a moist condition have1 unless they are actually swallowed1 little or no capacity for evil4 ,it is when they become dry that they become dangerous4 ,thus the expectoration of a consumptive patient spat on to the floor or deposited in a pocket handkerchief is1 so long as it remains moist1 perfectly innocuous4 ,what is evaporated from the wet surface is simply steam1 harmless as the steam escaping from the domestic tea-kettle4 ,but when it becomes dry1 then comes danger4 ,dust is formed1 which contains the living tubercle bacilli1 and with the mere shaking of the handkerchief or the disturbance of the dust on the floor these are inhaled1 and often cause consumption4 ,the person thus infected may be a new patient4 ,often also it is the consumptive patient who is thus re-infected4 ,consumptive patients tend to recover4 ,but if the patient's disease is daily recruited by fresh doses of the tubercle bacilli inhaled with the dust of previous expectoration1 fresh centres of disease are produced1 and thus the patient is unwittingly helping to cause his own death4 ,the infectious character of tuberculosis has been long suspected4 ,in the #ahth century1 in ,naples1 there were enactments insisting on the isolation of consumptive patients and disinfection of their furniture1 books1 etc4 ,we now know1 however1 that these were counsels of panic1 and that for practical purposes the infection may be regarded as confined to the sputum4 ,the expired breath is free from infection except during coughing4 ,that the sputum is infectious can be easily proved by feeding guinea-pigs or the domestic fowl on it4 ,these rapidly become affected by generalised tuberculosis4 ,the simple character of the precautions against infection which are required may be gathered from the following copy of a card which is given to consumptive patients in ,brighton3-- ,precautions for ,consumptive ,persons4 ,consumption is1 to a limited extent1 an infectious disease4 ,it is spread chiefly by inhaling the expectoration 7spit7 of patients which has been allowed to become dry and float about the room as dust4 ,do not spit except into receptacles1 the contents of which are to be destroyed before they become dry4 ,if this simple precaution is taken1 there is practically no danger of infection4 ,the breath of consumptive persons is free from infection4 ,the following detailed rules will be found useful1 both to the consumptive and to his friends3-- #a4--;,expectoration indoors should be received into small paper bags and afterwards burnt4 #b4--;,expectoration out of doors should be received into a suitable bottle1 to be afterwards washed out with boiling water2 or into a small paper handkerchief1 which is afterwards burnt4 #c4--;,if ordinary handkerchiefs are ever used for expectoration1 they should be put into boiling water before they have time to become dry2 or into a solution of a disinfectant1 as directed by the doctor4 #d4--,wet cleansing of rooms1 particularly of bedrooms occupied by sick persons1 should be substituted for 8dusting0 and sweeping4 #e4--,sunlight and fresh air are the greatest enemies of infection4 ,every patient should sleep with his bedroom window open top and bottom1 a screen being arranged1 if necessary1 to prevent direct draught2 and1 if possible1 occupy a separate bedroom4 ,the patient need not fear going out of doors in any weather1 if warmly clad4 ,n4,b4--,the patient himself is the greatest gainer by the above precautions1 as his recovery is retarded and frequently prevented by renewed infection derived from his own expectoration4 #f4--,persons in good health have little reason to fear the infection of consumption4 ,over-fatigue1 intemperance1 bad air1 dusty occupations1 and dirty rooms favour consumption4 ,the most common source of infection is undoubtedly the dried expectoration4 ,infection may1 however1 probably be derived from infected food1 as milk or meat4 ,the danger from meat is much less than that from milk1 because the former is more generally cooked than the latter1 and because the diseased portions of the former would be at least partially removed before it was sold4 ,the conditions under which the meat derived from tuberculous cattle should be destroyed are given on page #bd4 ,the abolition of private slaughter-houses1 the general establishment of public abattoirs1 and efficient meat inspection would do much towards aiding in eliminating tuberculous cattle from herds2 because it would no longer be found remunerative to keep tuberculous cows until they become seriously diseased4 ,the danger from infected milk is probably very great4 ,this has been repeatedly proved experimentally for bovine tuberculosis by experimenting on calves and pigs4 ,a cow may suffer from tuberculosis of its udder1 and yet go on freely secreting milk4 ,the milk from such an udder readily produces tuberculosis in calves or pigs drinking it2 but if another animal be fed during the same period with boiled milk obtained from the same udder1 it remains well4 ,the presence of tuberculosis in cattle can be determined with almost complete certainty by the tuberculin test4 ,a glycerine extract of pure cultivations of tubercle bacilli 7filtered so as to be free from bacilli7 was found by ,koch to contain substances which1 when injected into guinea-pigs suffering from tuberculosis1 produced a febrile reaction1 and appeared likely to cure the disease4 ,so far as man and larger animals are concerned the hope of cure by this means has not been realised2 but as a means of diagnosis1 i4e4 detection of tuberculosis1 injection of a small quantity of tuberculin under the skin1 has been found most valuable4 ,if the cow thus injected is suffering from the slightest tuberculosis1 it becomes feverish for a few days2 if it is healthy no 8febrile reaction0 occurs4 ,by using this test tuberculous cattle can be detected1 they can then be kept in separate sheds1 the former sheds cleansed and disinfected2 the milk of these cattle kept separate from that of the rest of the herd1 and boiled before being drunk1 or the infected cattle sent to the butcher4 ,if the disease is strictly localised the carcases can be utilised for food1 after careful destruction of all diseased portions4 ,if these means were generally adopted1 tuberculosis might gradually be eliminated from the cattle of the entire country1 and a serious source of loss to farmers1 as well as of danger to children drinking the infected milk1 removed4 ,the presence of tubercle bacilli in cow's milk is detected by microscopic examination and by injection of small quantities of the suspected milk into guinea-pigs4 ,the proportion of infected samples found when examinations of milk supplies have been made in different towns has varied from #aj to over #ej per cent4 ,it is probable that tuberculosis is conveyed by cow's milk only when the tuberculous disease affects the udder4 ,but inasmuch as the udder of a tuberculous animal may become tuberculous very rapidly and without being detected for a considerable time1 it is evident that no tuberculous animal of any kind should be allowed to remain in any cowshed where milch cows are kept4 ,recently 7,july1 #aija7 ,koch has thrown doubt on the identity of bovine and human tuberculosis1 which was previously accepted1 because 7unlike some other observers7 he has been unable to produce in #ai cattle1 on which he experimented1 tuberculosis by mixing with their food expectoration of consumptive persons1 or inoculating under their skins similar material4 ,even if these negative results should subsequently be confirmed1 the converse proposition does not follow1 that bovine tuberculosis cannot be communicated to man2 and apart from this possibility milk containing the bacilli of bovine tuberculosis cannot be regarded as wholesome4 ,the boiling of milk destroys tubercle bacilli4 ,so does a temperature considerably below #bab ,f4 ,in ,denmark1 where butter and cheese are manufactured on a large scale1 and the raw milk is collected in central dairies1 a law was passed in #ahih1 obliging every proprietor of a dairy to heat all skimmed milk1 or butter milk1 to a temperature of #he ,c4 7#ahe ,f47 before returning it to the farms4 ,pasteurization1 i4e4 the heating of milk in a special apparatus to a temperature of #gj ,c4 7#aeh ,f471 and keeping it at this temperature for #cj minutes kills tubercle bacilli4 ,if it is rapidly cooled1 the nutritive value and taste of the milk are not spoilt4 ,it is safer1 however1 to go beyond this point1 and the use of an apparatus like the ,aylmer or ,sentinel ,sterilizer can be recommended4 ,more recent experiments have made it doubtful whether tubercle bacilli in milk are always killed in milk at a temperature of #gj ,c41 the pellicle formed on milk when it is heated appearing to shield the bacilli from the effect of the heat4 ,hence it is desirable that 8no sterilizer should be looked upon as thoroughly efficient for the purpose in which a temperature of at least #he ,c4 7#ahe ,f47 is not attained40 ,the following test may be used to determine whether milk has been efficiently pasteurized3-- ,natural milk contains a ferment or enzyme1 which is destroyed at a temperature of #agf ,f4 ,this enzyme splits up hydrogen peroxide 7,h,o7 into water and oxygen1 but this effect is not produced in milk heated above #agf ,f4 ,take one drop of a dilute aqueous solution of hydrogen peroxide1 add it to one teaspoonful of the milk4 ,next add two drops of a watery solution of paraphenyldiamine4 ,a dark indigo colour is produced with uncooked milk1 no change of colour if the milk has been pasteurized4 ,the same test can be used for determining whether butter has been made with pasteurized milk4 ,infection is not the sole determining cause of tuberculosis4 ,certain conditions of environment may determine whether the infection will succeed in 8taking root0 or not4 ,of these the following are important3 ,the nutrition of the individual if defective favours infection4 ,probably one chief reason why consumption has declined nearly #ej per cent4 in the last #ej years is the better1 more varied and more abundant food of the population4 ,improved housing of the population has greatly helped in the same direction4 ,tubercular diseases increase with density of population1 and are most prevalent in overcrowded tenements4 ,probably overcrowding chiefly acts by favouring direct infection1 but it must also lower the health and power of resistance of the individual against infection4 ,the drying of the subsoil has been regarded as a chief cause of the reduction of consumption 7page #bbf74 ,it is probable1 however1 that the wet soil merely predisposed to consumption1 because it was commonly associated with cold and wet houses1 which would favour catarrhs1 and open the way for the infection of consumption4 ,the dryness of the house is a most important matter4 ,if a damp soil means also a damp house it must favour consumption and other chest affections4 ,damp air1 like water1 rapidly abstracts heat from the body4 ,compare1 for instance1 the discomfort of sitting clad in water at a temperature of #fe ,f4 with the comfort of sitting clad in a dry room at the same temperature6 ,the domestic fowl is naturally immune to anthrax2 but by being kept for a few hours with its feet in cold water1 it can be rendered susceptible to inoculation with this disease4 ,the effects of breathing foul air are clearly shewn by the varying death-rate from phthisis in different occupations4 ,thus1 if the comparative mortality figures of agriculturists be represented as #ajj1 that of a commercial clerk #agf1 of a draper #bjj1 of a tailor #baa1 of a printer #bdd1 of a bookbinder #bdf4 ,the effects of breathing dust-laden air are even more marked4 ,thus1 if the comparative mortality figures from phthisis of agriculturists #ajj1 that of a coal-miner #aff1 of a mason #bae1 of a chimney-sweep #bdi1 of a file-maker #cgc1 of a cutler #djg1 of a potter #dec4 ,the last figure probably also shows the influence of alcoholism1 which greatly favours tuberculosis4 ,means for ,preventing ,tuberculosis4--,the means for preventing tuberculosis from infected milk and meat have been already indicated4 ,they comprise-- 7a7 ,means of eradicating tuberculosis from cattle2 7b7 ,means of preventing harm from tubercle bacilli in milk or meat2 ,under the first head improved conditions of housing of cattle1 greater air-space1 improved ventilation1 a larger proportion of out-door life are important4 ,the use of the tuberculin test1 the separation of healthy from diseased cattle2 the disinfection of sheds occupied by infected cattle are also essential4 ,under the second head come efficient sterilization of suspected food 7see p4 #ac71 and the rejection of diseased meat4 7,see p4 #bd74 ,the most important measure against tuberculosis is the prevention of infection from patients with consumption4 ,under this head are comprised the following steps3-- ,a4 ,means of ascertaining the existence of the disease-- #a4 ,bacteriological diagnosis4 #b4 ,notification of cases1 voluntary or compulsory4 ,b4 ,direct preventive measures-- #a4 ,law against expectoration in places of public resort4 #b4 ,disinfection and cleanliness4 #c4 ,isolation4 #d4 ,general sanitary improvement4 ,c4 ,education of the public and of patients as to the importance of the preceding measures4 ,the gratuitous examination of suspected sputum is now being undertaken in certain towns4 ,the earlier the infectious condition of expectoration is detected1 the sooner can the necessary precautions be taken4 ,the notification to the medical officer of health of all cases of consumption ,i have repeatedly advocated4 ,this is already carried out for the chief acute infectious diseases1 and although the difficulties of acting on the information received in regard to a chronic disease like consumption are considerable1 they can be overcome with tact and discretion4 ,voluntary notification is already practised in ,brighton1 ,manchester1 and a few other towns4 ,notification gives increased and more exact opportunities of preventing phthisis by--#a4 ,enabling disinfection and cleansing of affected rooms to be effected2 #b4 ,enabling instructions to be given to the patient and his relatives as to the exact precautions required2 and by #c4 ,facilitating the removal of the insanitary conditions of home and work which may have caused the case or favoured its untoward progress4 ,the following scheme of measures of disinfection was prepared by ,drs4 ,niven and ,newman and myself for the ,national ,association for the ,prevention of ,consumption1 and is issued by them in pamphlet form3-- ,in preventing a consumptive person from spreading the disease1 two sets of preventive measures are required3--#ast1 ,the removal or destruction of the infective matter already disseminated by the patient's discharges1 especially by his phlegm2 and1 #bnd1 the prevention of future dissemination4 ,for the latter purpose the main object is not to permit any discharge to become dry before being destroyed4 ,before the consumptive person has learned the personal precautions which must be taken1 and up to the time when he has been trained to carry them out carefully1 he has probably distributed a considerable amount of infective matter4 ,this is especially liable to accumulate in a dangerous form at home1 where the space is small1 and light and ventilation are defective4 ,infective particles will be found in greater abundance on and near the floors1 on ledges1 and in room-hangings4 ,but the personal clothing and bedclothes will also have become infected4 ,hence it is necessary to disinfect the floor1 walls1 and ceiling of the rooms occupied by the patient1 as well as the furniture1 carpet1 bedclothes1 c4 ,when this has been done1 if the personal precautions advised are carried out by the consumptive1 further disinfection should not be needed4 ,it is1 however1 difficult to make sure that personal precautions are fully carried out1 and rooms should therefore be subsequently cleaned at least once in six months1 the floors being scrubbed with soft soap1 the furniture washed1 the walls cleaned down with dough1 and the ceiling whitewashed4 ,confined workshops in which a consumptive has worked for some time should be cleansed1 and a notice in reference to spitting should be suspended in all workshops4 ,the latter precaution should also be observed in all public-houses and common lodging houses1 both of which require special attention to cleansing4 ,disinfection of rooms which have been occupied by consumptive patients may be secured in various ways1 but the following are the practical rules which must underlie any methods adopted3-- #a4 ,gaseous ,disinfection of ,rooms1 or 8,fumigation10 as it is termed1 by whatever method it is practised1 is inefficient in such cases4 #b4 ,in order to remove and destroy the dried infective discharges1 the ,disinfectant must be applied directly to the infected surfaces of the room4 #c4 ,the ,disinfectant may be applied by washing1 brushing1 or spraying4 #d4 ,amongst other chemical solutions used for this purpose a solution of ,chloride of ,lime 7#a to #b per cent47 has proved satisfactory and efficient4 #e4 ,in view of the well-established fact that it is the dust from dried discharges which is chiefly infective1 emphasis must be laid upon the importance of thorough and wet cleansing of infected rooms4 #f4 ,bedding1 carpets1 curtains1 wearing apparel1 and all similar articles belonging to or used by the patient1 which cannot be thoroughly washed1 should be disinfected in an efficient steam disinfector4 #g4 ,after all necessary measures of ,disinfection have been carried out1 the essential principle governing the subsequent control of a case of consumption is that all discharges1 of whatever kind 7especially expectoration from the lungs71 should under no circumstances be allowed to become dry4 _/ ,besides measures of disinfection and cleanliness1 the patient must be placed under the best conditions for overcoming the disease4 ,the same measures tend to prevent infection4 ,thus abundant food1 an open-air life1 sleeping with bedroom windows widely open1 avoidance of dust1 abundance of sunshine1 are all important4 ,the importance of sunlight in the prevention of consumption can scarcely be exaggerated4 ,koch found that tubercle bacilli were killed in from a few minutes to some hours1 according to the thickness of the layer in which they were exposed to the sunlight4 ,he found that even ordinary daylight produced the same effect1 if it lasted long enough2 cultures of tubercle bacilli dying in from five to seven days if exposed at the window in compact masses4 ,these experimental facts emphasise the importance of abundant open space about dwelling-houses 7see p4 #bjc71 the provision of a large window-area 7see pages #bjb and #baf71 of staircase ventilation1 and lighting1 c4 ,scrofula means a tubercular affection of the lymphatic glands4 ,it occurs most commonly in the neck4 ,the infection is usually received from some neighbouring mucous surface1 as from the throat1 being derived from dried expectoration or diseased milk4 ,the same indications as for the prevention of phthisis hold good for scrofula4 ,,chapter ,,xlvi4 ,,notification ,,and ,,isolation4 ,we are confident from the actual discovery of the micro-organisms causing certain infective diseases1 that the other diseases of an analogous nature are similarly caused by living contagia4 ,on this supposition1 action is taken for the prevention of these diseases4 ,this action comes under a number of different heads1 which may be classified as follows3-- #a4 ,means for the early recognition of the infectious character of a disease4 ,the bacteriological aids to recognition in diphtheria 7page #bii71 enteric fever 7page #cja71 and phthisis 7page #caj7 have been already mentioned4 ,it is important to call in medical aid when any suspicious symptoms arise1 even when these symptoms do not appear to be urgent4 ,if an infectious disease is not recognised in its early stage1 it may be easily overlooked1 and the patient cause a serious epidemic4 ,the following hints for teachers are in ,brighton sent with each circular letter as to excluding infected children from school4 ,the list is not exhaustive1 but may aid in drawing attention to suspicious symptoms4 ,the only safe rule when in doubt is to act as though a case is infectious until a skilled opinion can be obtained4 ,,hints ,,as ,,to ,,infectious ,,diseases4 ,as infection is sometimes spread by means of children attending school while suffering from undetected infectious diseases1 the following hints may be useful to the teacher3-- #a4 ,any scholar having a sore throat should be sent home and regarded as infectious until the throat has been examined by a doctor4 ,if a scholar has enlarged glands in the neck1 and especially if he or she is very pallid1 the suspicion of possible diphtheria should be entertained4 ,many slight cases of diphtheria escape detection4 #b4 ,any scholar suffering from a severe cold1 with sneezing1 redness of the eyes and running at the nose1 should be sent home4 ,it may mean an influenza cold or the commencement of measles1 and both are infectious4 ,this recommendation is particularly important when measles is known to be prevalent4 #c4 ,a child with a violent cough1 especially if it is severe enough to cause vomiting or nose-bleeding1 should be suspected of whooping-cough1 and sent home1 even if the characteristic 8whoop0 is not heard4 #d4 ,slight cases of scarlet fever sometimes escape notice1 and the patients are sent to school with the skin on the hands1 etc41 freely 8peeling40 #e4 ,in any of the above instances1 or any other case of suspicion1 the ,medical ,officer of ,health1 on receiving a confidential intimation1 will be glad to make an investigation4 ,,symptoms ,,of ,,onset ,,of ,,scarlet ,,fever4 ,sudden onset4 ,usually vomiting4 ,always headache4 ,feverish1 with dry1 hot skin4 ,sore throat4 ,red rash on chest in a few hours4 ,,measles4 ,severe 8cold in the head0 for #gb hours before the blotchy rash appears4 ,measles is extremely infectious in this preliminary stage4 ,consider every severe influenza cold as possibly measles4 ,,diphtheria may be very indistinct4 ,languor and sore throat4 ,glands under and behind jaw are enlarged4 ,patient very pallid4 ,white or yellow patches seen on examining inside throat4 ,whenever doubtful1 send the scholar home4 ,,whooping ,,cough4 ,in a child under seven1 a severe cough should always be regarded as possibly whooping-cough1 although no 8whoop0 has yet been heard4 #b4 ,the notification of all cases of infectious diseases to the medical officer of health1 is clearly a means to an end1 that of securing that the preventive measures to be next named are effectively carried out4 #c4 ,means for the production of an artificial immunity4 ,this is only practicable at present for two diseases of this country1 small-pox by means of vaccination 7page #bic71 and a temporary immunity against diphtheria by a dose of antitoxic serum 7page #bii74 ,apart from these means1 any measures for improving the health of a child tend in the same direction4 ,enlarged tonsils1 8adenoids0 at the back of the nose 7causing the child to snore at night and to breathe through his mouth71 discharges from nostrils or ear1 and similar conditions should receive early medical attention4 #d4 ,isolation3 preventing the conveyance of the contagium from the sick to the healthy4 #e4 ,disinfection1 i4e4 destruction of the contagium of the disease4 ,the ,infectious ,disease 7,notification7 ,act1 #ahhi1 and the corresponding ,london ,act of #ahia1 impose a dual duty of notification 7a7 on every medical practitioner attending on or called in to visit an infectious patient1 as soon as he becomes aware of its nature2 and 7b7 on the head of the family to which the patient belongs or the nearest relative4 ,the intimation must be sent by each of these to the local medical officer of health1 the practitioner being paid a small fee for his trouble4 ,usually notification by the householder is only enforced when no doctor is in attendance4 ,the diseases to which this ,act applies are small-pox1 cholera1 diphtheria1 membranous croup#aa1 scarlet fever1 erysipelas1 and the fevers known by any of the following names3 typhus1 typhoid1 enteric1 relapsing1 continued or puerperal4 ,the list of notifiable diseases may be extended by resolution of the ,local ,authority4 ,the enforcement of notification is most important for the public health4 7a7 ,it enables the medical officer of health to take immediate steps to prevent the spread of infection1 by enforcing proper isolation of the patient1 efficient disinfection1 and by preventing the attendance of children from infected houses1 at school1 etc4 7b7 ,it enables the links of evidence connecting a series of cases to be identified1 e4g4 cases due to a common milk supply1 or attendance at a particular school4 7c7 ,it has a valuable educational effect on all concerned in the cases4 ,,isolation4 ,both the patient and his attendant need to be isolated in diseases like scarlet fever1 diphtheria and small-pox4 ,the rule is less absolute in enteric fever4 ,in the following description the standard of requirements taken is that of the most dangerous infectious disease1 small-pox4 ,the first point to decide is whether the patient may be safely isolated at home4 ,for small-pox this ought never to be allowed in a town4 ,for other diseases1 this may be permitted1 if the following conditions can be fulfilled4 ,for ,isolation at ,home a couple of rooms are required1 preferably on a higher floor or in a detached wing of the house4 ,the w4c4 used for the dejecta of the patient must not be used by any other members of the household4 ,all linen1 towels1 handkerchiefs1 etc41 should be immersed in actually boiling water containing some washing soda1 before leaving the sick-room4 ,other articles to be washed1 if they will be deteriorated by soaking in boiling water or a chemical disinfectant1 must be tightly wrapped in bundles1 and covered with a clean wet sheet saturated with a strong disinfectant solution 7page #cca74 ,solid and liquid excreta1 expectoration and other discharges must be treated as described on page #cca4 ,the nurse should not eat her meals in the patient's room4 ,she should wear a cotton dress to be changed before going out for a walk4 ,her hands must be thoroughly washed and brushed after handling or helping the patient1 particularly in enteric fever4 ,it is advantageous if the nurse has previously had the patient's complaint4 ,attention on the part of the nurse to minute detail is essential1 especially in view of the possibility of receiving infection from infected articles as well as directly from the patient4 ,the measures required for the subsequent disinfection of the sick-rooms and of clothing1 bedding1 books1 etc41 are given on page #ccb4 ,the use of hospital isolation has rapidly increased in recent years1 thus releasing private families from a serious burden4 ,the number of beds which a ,local ,authority should supply for their district is usually stated as one for every #a1jjj inhabitants1 but in poorer districts this does not suffice4 ,the site of the hospital should be well removed from houses4 ,there must be a minimum zone of #dj feet between all infected buildings and the boundary walls1 and the same distance between neighbouring buildings4 ,a wall at least #f ft4 #f in4 high should enclose the hospital site4 ,the hospital is divided into separate detached pavilions for the treatment of different infectious diseases4 ,a floor space of #aef square feet should be allowed for each bed4 ,the height of the ward should be about #ac feet1 its width from #bd to #bf feet1 and the total cubic space for each patient should be #b1jjj cubic feet for scarlet fever1 #b1ejj for diphtheria4 ,the lavatories and water-closets are separated from the main ward by a cross-ventilated lobby4 ,in an isolation hospital every surface should be washable2 all corners should be rounded off1 and all projections on which dust can lodge avoided4 ,the proportion of window space should be about #a square foot to every #gj cubic feet4 ,special isolation pavilions are required for cases of doubtful diagnosis4 ,the ventilation and warming of wards must be carefully regulated4 ,cross-ventilation by windows open on opposite sides of the ward can be maintained in nearly all weathers4 ,the temperature of the ward should be maintained at #ee-fj ,f4 ,ambulances are usually provided by the ,local ,authority for the removal of infectious patients4 ,the ambulance should be cleansed and disinfected after each journey4 ,the use of private conveyances for infectious patients is forbidden1 except under special limitations4 ,the hospital isolation of small-pox is beset with special difficulties4 ,there is a considerable body of evidence indicating that small-pox may be aerially carried from patients in hospitals to people living within a zone of half a mile1 or possibly further4 ,without accepting the view that aerial dissemination of small-pox to considerable distances from the patient frequently occurs1 it still remains true that1 either by this means or by errors in the administration of small-pox hospitals1 they do frequently constitute a source of danger to persons living in the vicinity4 ,the ,local ,government ,board recommended that a ,local ,authority should not contemplate the erection of a small-pox hospital4 7a7 ,on any site where it would have within a quarter of a mile of it as a centre either a hospital1 whether for infectious diseases or not1 or a workhouse1 or any similar establishment1 or a population of #aej-bjj persons2 7b7 on any site where it would have within half a mile of it as a centre a population of #ejj-fjj persons1 whether in one or more institutions or in dwelling-houses4 ,,quarantine4 ,this term has been chiefly employed to denote the limitation of the movements of vessels coming from infected ports1 for a term which1 as the name indicates1 was formerly forty days1 but is now shorter4 ,it may be conveniently employed1 however1 to signify the restriction of the movements of all persons who have been apparently exposed to infection1 or who continue to live in infected dwellings4 ,in this sense we may speak of3 #a4 ,domestic ,quarantine4 #b4 ,scholastic ,quarantine4 #c4 ,national and ,international ,quarantine4 ,domestic ,quarantine1 to a varying extent1 is desirable for the members of a family of which one member has been attacked by an infectious disease4 ,for small-pox every member of a household should be kept under strict watch until sixteen days have elapsed since the last contact with the case of small-pox1 or until successful vaccination has been secured4 ,for enteric fever this strict watch would be unnecessary1 but the remaining members of the household should be warned to call in a doctor on the first symptom of malaise4 ,quarantine is specially indicated for certain occupations4 ,thus if the child of an out-door labourer had been removed to a hospital with scarlet fever1 it would be unnecessary to keep the latter away from work during the following week4 ,if1 however1 he were a milk-carrier1 or a tailor1 or an assistant in a sweet-stuff shop this would be a desirable measure4 ,the ,quarantine of ,school ,children is more necessary than that of adults1 because the former are more susceptible to infection4 ,children are kept from school3 7a7 ,because the infectious patient still remains in the house4 ,in this case the healthy children must be kept from school until the patient has ceased to be infectious and disinfection has been thoroughly carried out2 and for a further period longer than the longest known period of incubation of the disease in question 7page #bhg71 a margin being left for contingencies4 ,it would probably be #h plus #b weeks for scarlet fever4 7b7 ,children are kept from school for a period exceeding the longest period of incubation when the patient has been removed to hospital4 ,the table on page #cbb1 modified from the ,author's ,school ,hygiene1 is introduced as furnishing a convenient summary of the subject4 ,objection is sometimes taken to the exclusion of children under the above circumstances from school1 on the ground that they continue to mix with others in the street or in neighbouring houses4 ,clearly1 however1 in a school-room1 a suspected child may communicate infection to children coming from widely scattered streets1 while out-of-doors the danger is comparatively slight1 and among neighbours the danger is very limited in area4 ,it is assumed in the following table that all infected articles have been disinfected before the termination of the period of quarantine4 ,,duration ,,of ,,date ,,at ,,which ,,quarantine ,,school ,,of ,,children ,,duration ,,of ,,attendance ,,may ,,exposed ,,to ,,disease4 ,,infection4 ,,be ,,resumed4 ,,infection4 ,scarlet ,from #e to #h weeks2 ,not less than #h weeks#ad days4 fever ceases when all from the beginning peeling of the skin of the rash1 and has been completed1 then only if no sore and when the child throat or sore is free from places4 discharge from the nose or ear or sore places4 ,diphtheria ,at least #ba days2 ,not less than #b #ab days4 often much longer4 months1 and not ,absence of infection then if strength not should be confirmed recovered1 or if any by bacteriological sore throat or any tests4 discharge from nose1 eyes1 ears1 etc4 ,small-pox ,about #d to #e weeks ,when every scab has #ah days4 and ,chicken fallen off4 pox ,measles ,from #c to #d weeks2 ,not less than #d weeks#ba days4 when all cough and from beginning of branny shedding of rash4 skin has ceased4 ,rtheln #b to #c weeks ,from #c to #d weeks #ba days4 7,german from beginning of measles7 rash4 ,mumps ,about #ba days from #d weeks from the #bd days4 the beginning4 beginning4 ,whooping #f weeks from the ,in about #h weeks #ba days4 cough beginning of whooping1 or when the cough has quite ceased4 ,typhus and #d to #e weeks ,when strength #bh days4 enteric sufficient4 fevers ,influenza #b to #c weeks #a month #aj days4 ,school ,closure is occasionally required to prevent the further spread of an infectious disease4 ,this can be enforced on the order of any two members of the ,local ,sanitary ,authority acting on the advice of the medical officer of health4 ,this ought to be only occasionally necessary if notification of infectious diseases is strictly enforced1 and if suspicious individual children are excluded from attendance at school4 ,in diphtheria school closure may occasionally be rendered unnecessary by systematic bacteriological examination of the throats of children who had been exposed to infection 7see page #bii74 ,school closure is more useful for country than for town schools1 as in the former the homes of children are more remote from each other1 but it is occasionally necessary for both4 ,for measles school closure is specially indicated in ,infants' ,schools4 ,we have already seen that this disease is chiefly fatal when caught at a tender age 7page #big74 ,the early closure of ,infants' ,schools1 and particularly of the ,babies' ,class is therefore indicated4 ,it is unfortunate that the attendance at school of children under six years of age is encouraged4 ,such children have more severe and more frequently fatal attacks of diphtheria1 scarlet fever1 measles1 and whooping-cough2 and these are frequently acquired at school4 ,international ,quarantine was originally enforced against plague2 but in many countries has been extended to other diseases1 as cholera1 yellow fever1 typhus fever1 small-pox and leprosy4 ,in ,england cholera is the only disease in connection with which it has been in the past enforced4 ,it has now been entirely abandoned4 ,it consists in the compulsory isolation at the port of entry of all persons who have come from an infected district1 or have been in contact with a case of the infectious disease against which quarantine is enforced1 for a length of time which will enable it to be determined whether the persons detained are or are not incubating the disease4 ,if this measure could be strictly enforced1 and if infectious diseases were conveyed only by infectious persons1 quarantine would undoubtedly be effective4 ,but in practice quarantine cannot be enforced in ,europe2 and as it cannot be efficiently enforced it forms an ineffective and irrational derangement of commerce4 ,thus if plague prevailed in ,france it would be impracticable to detain for ten or twelve days every person entering ,england4 ,furthermore1 in this instance1 infection is brought by rats as well as persons2 and measures effective for the latter do not prevent the former from importing infection4 ,because of its impracticability and of the disorganization of commerce which would be associated with any attempt to enforce it1 ,england has abandoned quarantine and other countries are gradually following its example4 ,england bases its action on the ground that 7a7 sanitation is the true chief means of defence1 especially against cholera4 ,it does not trust to this alone but to this along with 7b7 medical inspection at the ports1 7c7 and subsequent medical supervision of persons landed from suspected vessels4 ,by these means a watch can be kept over persons who have been in contact with infection4 ,regulations are issued at intervals by the ,local ,government ,board requiring the disinfection by steam of all rags and similar materials imported from towns in which small-pox1 cholera1 etc41 are prevalent4 ,,chapter ,,xlvii4 ,,disinfection4 ,by disinfection is meant the destruction of the active cause of each infectious disease4 ,a disinfectant is therefore synonymous with a germicide4 ,disinfectants must be distinguished from deodorants or deodorisers1 such as charcoal1 and from antiseptics1 which are antagonistic to the growth of bacteria1 without necessarily killing them1 e4g4 common salt4 ,disinfection may be effected by chemical or physical means4 ,,chemical ,,disinfectants4 ,a chemical disinfectant should fulfil the following conditions3 #a4 ,it must be an efficient germicide4 #b4 ,its germicidal power should not be destroyed by the fcal or other polluting matter1 with which the bacteria of infection are associated4 #c4 ,for many purposes1 it must not be destructive to or liable to stain the skin1 or fabrics1 or other articles to which it is applied4 #d4 ,it should preferably not be a virulent poison2 and should be moderately cheap4 ,the search for a completely non-poisonous disinfectant is a chimera4 ,there are three great classes of chemical disinfectants4 #a4 ,oxidising agents1 as the halogens 7chlorine1 etc47 and permanganates4 #b4 ,deoxidising agents1 as sulphurous acid 7,,so7 and formic aldehyde 7,,ch,o74 #c4 ,other disinfectants1 which act by coagulating protoplasm or otherwise1 as carbolic acid1 corrosive sublimate4 ,the number of disinfectants is legion4 ,only the chief ones can be mentioned and their chief properties described4 ,it is a good rule to eschew the use of all disinfectants of which the exact composition is not given2 and all disinfectants which are described by 8fancy0 names1 which are not descriptive of their composition4 ,a4 ,,oxidising ,,agents4 ,chlorine has been most commonly used as chloride of lime 7,ca,cl1 ,ca7,cl,o774 ,this is somewhat unstable in composition4 ,a solution of sodium hypochlorite containing #aj per cent4 of available chloride is preferable4 ,chloride of lime for sprinkling on decomposing matter should contain at least #aj to #ae per cent4 of available chlorine4 ,sulphuretted hydrogen and other offensive gases are decomposed by it4 ,thus ,,sh ,cl ,s #b;,h,cl4 ,its chief action is as an oxidising agent4 ,thus ,h,o ,cl #b;,h,cl ,o4 ,a large excess must be used in disinfecting1 otherwise the chlorine may simply oxidise fcal or other organic matter1 and not effectually destroy contagia4 ,methods of ,use--7a7 ,as a gas1 by the action of hydrochloric acid on strong chloride of lime4 ,the molecular density of chlorine is #cee1 of formic aldehyde #ae1 of sulphurous acid #cb2 and the rate of diffusion of gases being inversely to the square-root of their densities1 clearly chlorine does not compare favourably as a gas with formic aldehyde4 ,the bleaching effect of chlorine on coloured articles of apparel is a disadvantage4 7b7 ,as a liquid3 used thus chlorine is very efficient1 applied either as a spray or brushed on walls and other surfaces4 ,delpine found that a solution of one part of chloride of lime in #ajj parts of water applied to wall paper impregnated with tubercular matter1 disinfected it in a few hours1 or in a few minutes if the layer of infected matter was not thick4 ,bromine1 ,iodine1 and ,euchlorine 7a mixture of chlorine and ,cl,o7 are efficient disinfectants4 ,iodine ,trichloride 7,i,cl7 was found by ,behring to share with corrosive sublimate 7,hg,cl7 carbolic acid and cresol mixed with acids 7see page #cbg71 the halogens 7,cl1 ,br1 and ,i71 and chloride of lime a superiority over other disinfectants in their power of killing anthrax spores in a short time4 ,permanganates have been largely used as disinfectants1 but their value is small4 ,impure sodium manganate 7,na,mn,o7 with much common salt 7,na,cl7 containing some permanganate is known as 8,condy's ,green ,fluid40 8,condy's ,red ,fluid0 consists of permanganate and sulphate of soda4 ,to be of any use it must be employed in #e per cent4 solution4 ,it stains fabrics brown1 and it exhausts its feeble disinfecting power in first oxidising decomposing organic matter4 ,b4 ,,deoxidising ,,agents4 ,sulphurous ,acid 7,,so7 acts chiefly as a reducing agent on organic matter4 ,it is used chiefly as a gaseous disinfectant1 and for this purpose is generated 7a7 by burning #a lb4 of sulphur for every #a1jjj cubic feet of space in the room 7which will equal #aab per cent4 of ,,so74 ,the windows and chimney of the room are first closed2 the sulphur is placed in a saucepan supported over a bucket of water1 and its ignition is aided by a small quantity of methylated spirit4 ,the door of the room is then sealed1 and the room left until the next morning4 7b7 ,carbon disulphide may be burned in a benzoline lamp4 7c7 ,,so liquefied under pressure is supplied in cylinders available for convenient use4 ,the experimental results of the action of ,,so on various bacteria are somewhat discrepant4 ,it probably is fairly efficient for some diseases1 but not in tuberculosis4 ,formaldehyde or ,formic ,aldehyde 7,,ch,o7 is produced by the slow and incomplete oxidation of methyl alcohol 7,,ch,,oh7 under access of air4 ,a saturated solution in water containing #dj per cent4 of the formaldehyde gas is known as formalin4 ,the simple evaporation or heating of formalin is liable to produce the polymeric paraform which is solid and inert4 ,to prevent the formation of paraform when formalin is evaporated1 ,trillat adds to it a solution of calcium chloride 7,ca,cl71 the mixture being known as formochloral4 ,it is stated that when the air of a room is charged with less than one per cent4 of the vapour1 rapid and complete disinfection of surfaces occurs1 and that it possesses a certain amount of penetrating power into loose fabrics4 ,no damage is done to textile fabrics2 and disinfection by this means possesses the advantage over disinfection by sulphurous acid or chlorine that the room can be entered without serious discomfort soon after the disinfection is carried out4 ,in solution formalin is undoubtedly a powerful disinfectant1 and in the gaseous condition it is at least equal in value to ,,so1 probably better4 ,formaldehyde is used as a disinfectant4 7a7 ,by evaporating a #fj per cent4 solution of ,,ch,o in methyl alcohol 7trade name holzine7 over pieces of glowing coke placed under an asbestos plate 7,opperman-,rosenberg apparatus74 7b7 ,by subliming tabloids of paraform by the heat of a lamp4 ,a methylated spirit lamp is employed1 and the moisture from the combustion in this causes the transformation of a considerable proportion of paraform into ,,ch,o vapour4 ,it is doubtful if the quantity of the latter evolved is sufficient for efficiency4 7c7 ,in ,trillat's apparatus formalin 7i4e4 the #dj per cent4 solution in water of ,,ch,o7 with ,ca,cl solution is heated in an autoclave worked at a pressure of #dj lbs41 provided with a pressure gauge and thermometer4 ,in all these methods the room must be carefully sealed1 as the tendency for the disinfectant to escape is greater than with ,,so or ,cl4 7d7 ,the best method is to spray a solution of formalin #d oz4 to one gallon of water on all the surfaces of the room 7see page #ccc74 ,this is equal to a strength of #a in #dj of formalin1 or #a in #ajj of formic aldehyde4 ,c4 ,,other ,,disinfectants4 ,,tar ,,acids4--,when coal tar is treated by acids and alkalies in succession1 it becomes separated into 7#a7 hydrocarbons1 7#b7 phenols or tar acids1 carbolic1 cresylic1 etc41 7#c7 aniline and other basic substances4 ,the hydrocarbons are known in commerce as 8neutral tar oils40 ,they are brown and syrupy1 turning milky with water1 and feebly disinfectant4 ,the two most important 8tar acids0 are phenol or carbolic acid 7,c,h,,oh7 and methyl-phenol1 also called cresol or cresylic acid 7,c,h7,,ch7,,oh74 ,the higher members of this same group yield milky emulsions with water1 and are less poisonous than phenol4 ,various mixtures of them are used as disinfectants1 and sold as creolin1 ,jeye's and ,lawes' fluids4 ,izal belongs to the same series4 ,carbolic ,acid 7phenol7 did not kill anthrax spores until a #c per cent4 strength of its solution was used for #g days 7,koch71 but sporeless anthrax bacilli were destroyed in a few minutes by a #a to #b per cent4 solution4 ,the disinfecting power of carbolic acid is greatly increased by adding mineral acids4 ,carbolic acid and lysol are superior to creolin for disinfecting stools4 ,a #e per cent4 solution of carbolic acid destroys tubercle bacilli in sputum in #bd hours4 ,carbolic acid powders are in common use4 ,in my opinion quicklime is more valuable4 ,cresol is obtained from 8crude carbolic acid0 by fractional distillation at a temperature between #ahe and #bje ,c4 ,a one-half per cent4 solution has equal disinfecting power to a #b or #c or sometimes a #e per cent4 of phenol 7carbolic acid74 ,creolin consists of cresol emulsified in a solution of hard soap4 ,behring classifies the comparative germicidal power of phenol1 cresol1 and creolin on bacteria in broth as #a1 #d1 and #aj respectively4 ,when albumen is present1 creolin loses a part of its disinfectant power4 ,lysol contains #ej per cent4 of cresol1 dissolved by means of neutral potash soap4 ,it is completely soluble in water and does not turn milky as creolin does when water is added4 ,it is more effective than creolin1 and still more than ,hg,cl in albuminous liquids4 ,soap has1 owing to its alkalinity1 disinfectant as well as cleansing action4 ,a temperature of #ee-ge ,c4 greatly aids its action4 ,antiseptic soaps possess no special value as germicides1 but carbolic soap is a useful insecticide4 ,lime in a one-tenth per cent4 solution destroys typhoid and cholera microbes4 ,mercuric ,chloride 7,hg,cl1 corrosive sublimate7 was found by ,koch to destroy anthrax bacilli in a dilution of #a in #bj1jjj4 ,others have obtained less favourable results1 but it is certainly a powerful germicide4 ,the germicidal effect is greatly diminished by contact with organic matter1 an insoluble albuminate of mercury being produced4 ,for this reason ,hg,cl is not the best disinfectant for fces unless mixed with acid1 as in the following solution3 ,hg,cl oz41 ,h,cl #a oz41 aniline blue #e grains to three gallons of water4 ,this gives a solution of #a in #ifj4 ,the colouring is added to avoid accidental poisoning4 ,hg,cl is not a good disinfectant for linen4 ,stains are apt to be fixed by it1 and if linen soaked in it is subsequently washed with soap1 without first carefully washing out the ,hg,cl1 it is darkened in colour4 ,it attacks metals1 and must not therefore be placed in metal receptacles4 ,chloride of ,zinc in a solution containing #be grains to the fluid drachm is known as 8,sir ,william ,burnett's solution40 ,it is a good deodorant1 but an inefficient disinfectant4 ,chinosol 7,c,h,,nkso7 belongs to the quinoline group4 ,it is an almost inodorous powder1 very soluble in water1 noncorrosive1 and does not stain4 ,a solution of #a in #abjj forms an efficient germicide4 ,,disinfection ,,by ,,physical ,,means4 ,natural processes tend to the destruction of pathogenic microbes after their elimination from the patient4 ,of these desiccation1 sunlight1 and fresh air are the most potent4 ,heat and cold have a similar effect4 ,filtration or mechanical separation deprives a contaminated liquid of its microbes4 ,desiccation attenuates the virulence of and finally kills most microbes4 ,in laboratory experiments the vibrio of ,asiatic cholera when dried dies in from three hours to two days1 according to the degree of desiccation4 ,the bacilli of enteric fever1 tuberculosis1 and diphtheria only die after drying for a few weeks or even months4 ,the anthrax bacillus may retain its vitality for several years in a desiccated state4 ,clearly1 therefore1 desiccation has no administrative value in the prevention of disease1 and on the contrary it aids the dissemination of the microbes of tuberculosis1 small-pox1 scarlet fever1 etc4 ,direct ,sunlight kills a large proportion of the sporeless pathogenic microbes4 ,diffuse is less energetic in its action than direct sunlight4 ,the bacillus of diphtheria is destroyed by a half to one hour's exposure to sunlight4 ,as to tubercle bacilli1 see page #caf4 ,downes and ,blunt showed that diffused sunlight retards the putrefaction of organic infusions1 and that direct sunlight inhibits putrefaction4 ,sunlight cannot1 however1 be trusted as an efficient disinfectant4 ,it only secures surface disinfection1 and could not be relied upon for pillows1 mattresses1 etc4 ,m4 ,ward's experiments showed that the actinic rays of the sun are germicidal1 independent of the heat4 ,fresh ,air1 like sunlight1 should be employed as a valuable auxiliary1 not as an agent to be depended upon apart from systematic disinfection4 ,the experiments of ,downes and ,blunt showed that light and oxygen together accomplished what neither alone could do4 ,the presence of air in anthrax increases danger4 ,the anthrax bacillus does not form spores in an animal suffering from this disease1 and does not do so post mortem1 unless the animal is dissected4 ,hence the importance of keeping the skin unbroken in this disease1 only examining a drop of blood to establish the diagnosis4 ,filtration is a means of separating microbes from the gases or liquids containing them4 ,for the filtration of water see page #if4 ,the carbolic sheet outside a sick-room is supposed to filter the air leaving the room from microbes4 ,it is probably useless except as a reminder to the nurse to change her dress and adopt other precautions on leaving the sick-room4 ,settlement of dust also acts as an aerial disinfectant4 ,if a room be locked up1 its air next day is almost free from particles1 and all that is then required is disinfection of the surfaces of the room and of the articles in it4 ,whatever method of disinfection is employed1 it is not disinfection of the air1 but of the surfaces of a room which is the end in view4 ,washing is the most efficacious means of removing infection4 ,it is a mechanical means of removing the particular matter of which the contagium consists from the person or article to which it adheres into the water1 which subsequently enters the drain1 in the same way as do urine and fces4 ,washing is an absolutely efficient means of purifying articles that can be completely submitted to it4 ,a consideration of the physical laws governing the spread of infection will make this clear4 ,the contagia are passive4 ,when contained in a liquid they cannot escape from it under ordinary circumstances4 ,thus foul smelling gases may escape from sewage1 but bacteria do not escape1 except rarely during bubbling1 or from dried portions of the invert of the sewer4 ,barring rare accidents 8microbes submerged are imprisoned40 ,contagia are harmless until they become dust4 ,hence the danger associated with the use of pocket handkerchiefs in such diseases as influenza and phthisis2 and the importance of keeping all infectious discharges wet1 until they can be finally disposed of4 ,,disinfection ,,by ,,heat4 ,heat may be applied in various ways3 7#a7 ,prolonged boiling in water of materials which are not spoilt by this means4 7#b7 ,destruction by fire of infected articles4 7#c7 ,dry hot air4 7#d7 ,steam4 ,boiling kills most pathogenic microbes4 ,the cholera vibrio is killed in four minutes at a temperature of #eb ,c4 7#abf ,f472 the typhoid bacillus at #ei4d ,c4 7#ach4h ,f47 in ten minutes4 ,if boiling be continued for five minutes1 the spores of pathogenic microbes are killed4 ,the addition of one to two per cent4 of washing soda to the water hastens this effect4 ,for infected linen nothing beyond this is required4 ,destruction by ,fire is to be recommended for comparatively worthless articles1 such as toys1 straw from beds1 rags1 old clothing and bedding4 ,dry ,hot ,air has been largely used in the past in ovens1 for the disinfection of bulky bedding4 ,it is now entirely superseded by steam4 ,its disadvantages are that 7a7 heat penetrates very slowly into the interior of bedding4 ,disinfection in test experiments was not accomplished in the interior of small bundles of clothes in three or four hours4 7b7 ,scorching of articles often occurs4 ,the sole advantage of this method is that bound books and leather goods are less liable to be damaged by it than by steam4 ,if no other apparatus is available a baker's oven will serve to kill the non-sporiferous microbes of cholera1 enteric fever1 and diphtheria1 as well as animal vermin4 ,if1 however1 we accept the proper test proposed by ,buchanan of the efficacy of disinfection1 the 8destruction of the most stable known infective matter10 dry heat is unsatisfactory4 ,steam may be employed as a disinfectant either 7a7 superheated1 or 7b7 saturated1 i4e4 close to the temperature at which condensation occurs4 ,this temperature depends upon the pressure under which the water has been boiled4 ,at ordinary atmospheric pressure it is #ajj ,c4 7#bab ,f474 ,the temperature of boiling is raised by subjecting the water to pressure4 ,consequently boiling water and the steam produced from it may be at any temperature4 ,thus steam may be 7a7 ,under pressure1 with a temperature above #bab ,f4 7b7 ,not under pressure1 at a temperature of #bab ,f4 ,illustration3 ,,fig4 #eg4 ,,equifex ,,saturated ,,steam ,,disinfector4 ,a--,disinfection chamber4 ,b--,partition wall separating infected from disinfected side4 ,c--,door on disinfected side4 ,d--,door on infected side4 ,,ee--,safety-locking bolt for securing door4 ,,ff--,stiffening rings on doors4 ,g--,steam inlet from boiler4 ,h--,steam separator for arresting water condensed in ,g4 ,i--,valve controlling admission of steam to disinfecting chamber4 ,k--,valve controlling admission of steam to coils4 ,,lm--,safety valves regulating steam pressure in chamber and coils respectively4 ,,nu--,pressure guages indicating steam pressure in chambers and coils respectively4 ,,oo--,objects after disinfection4 ,p--,wheeled carriage and cradle for ,,oo4 ,q--,hinged rails on which ,p runs4 ,r--,exhaust pipe for steam and air on first admission4 ,s--,thermometer showing rise of temperature 7to control complete air evacuation74 ,t--,valve for closing exhaust pipe ,r when air is completely evacuated4 ,v--,sluice valve to cause sudden escape of steam4 ,w--,cock to admit steam to ejector4 ,x--,exhaust pipe fitted with ejector for escape of steam before and of air during drying4 ,y--,valve for admission of air for drying under suction of ejector4 ,in some types of this machine this valve is placed on the lower part of ,c4 ,steam when admitted into a disinfecting stove comes into contact with cold objects4 ,if the steam is saturated1 immediate condensation to #aafjj part of its original volume occurs4 ,its latent heat is at the same time evolved4 ,the condensation causes enormous shrinkage in bulk4 ,more steam is thus insucked into the partial vacuum produced1 and this is repeated1 until in every part of the mattress or other material undergoing disinfection equality of temperature is reached1 when condensation of steam will cease1 and disinfection is complete4 ,if the steam is superheated and no condensation allowed1 disinfection occurs by the relatively slow method occurring with dry heat4 ,in practice at the early stage cooling causes some conversion of superheated into saturated steam1 though subsequently the much slower process of disinfection by conduction of heat goes on4 ,hence superheated steam is a less efficient disinfecting agent than saturated steam4 ,superheating is produced in disinfecting stores in two ways3 7#a7 ,by a jacket around the stove1 which is kept at about double the pressure and about #bj to #cj ,f4 hotter than the interior of the stove2 as in the older patterns of the ,washington ,lyon stove4 7#b7 ,by having a jacket containing a solution of calcium chloride1 which is heated by a furnace under the stove4 ,this solution is kept at a constant strength by an automatic supply from a cistern4 ,the temperature of the boiling water is thus raised without pressure to #bbe ,f4 ,this is the principle of ,thresh's stove4 ,the object of superheating steam is to assist in rapidly drying materials2 but this object can equally well be secured by periodically allowing the sudden escape of the steam confined under pressure1 in pressure disinfectors4 ,this last method is the best1 as it can not only be utilised at the last stage of the disinfection for drying the articles2 but at the earlier stage for sweeping the air out of the stove1 and thus removing what1 owing to its low conductivity for heat is one of the most serious obstacles to rapid and efficient disinfection4 ,in the above description it has been assumed that the steam1 whether saturated or superheated1 is confined1 except when the exhaust is employed for drying purposes4 ,steam may also be employed as current steam4 ,current steam disinfectors are initially cheap1 but more steam1 and therefore more fuel1 is required in their use2 and unless pressure is used by impeding the escape of the steam a temperature of only #bab ,f4 can be secured4 ,accepting ,buchanan's dictum1 a stove supplying saturated steam under pressure at a temperature in the interior of the stove of #bcd ,f4 is to be preferred4 ,this temperature with saturated steam destroys the spores of the most resistant known microbe 7that of symptomatic anthrax74 ,with superheated steam or hot air stoves on the same basis a temperature of #bhj ,f4 would be required1 which is damaging to most textiles1 except horsehair4 ,,the ,,practice ,,of ,,disinfection4 ,the ,management of the ,sick-room and ,patient requires careful and conscientious attention to detail4 ,certain details are given on page #cai4 ,all unnecessary furniture1 carpets1 and hangings should be removed as soon as the nature of the illness is known2 but unless these articles have been contained in close trunks or drawers1 and not opened since before the onset of the illness1 they must be disinfected4 ,food left over from the patient's meals must be burnt1 if solid1 in the patient's room2 if liquid1 emptied down the water-closet4 ,dry sweeping of the floors is to be avoided1 only wet brushing or cloths being used4 ,volatile aerial disinfectants during the sickness are valueless4 ,the ,treatment of ,discharges from the ,patient is the most important point in the management of infection4 ,the stools should be received into a bed-pan containing a #e per cent4 solution of carbolic acid1 a #c per cent4 solution of cresol or lysol1 or a #e per cent4 solution of chloride of lime4 ,milk of lime 7#bj per cent4 strength7 is very reliable1 when added like the preceding solutions in bulk equal to that of the stool to be disinfected4 ,the urine and vomit1 if any1 should be treated in exactly the same way4 ,the infection of enteric fever is often spread by undisinfected urine4 ,discharges from the throat1 nose and mouth of patients should be received into a solution of lysol #e oz4 to #a gallon of water1 or carbolic acid #g oz4 ,the efficacy of the carbolic acid solution is increased by adding #b oz4 of ,na,cl1 or #ab-ad oz4 of ,na,cl to each gallon4 ,pocket-handkerchiefs must be avoided1 linen rags being employed instead1 and placed at once in one of the above solutions or burnt4 ,the skin may scatter infection1 especially in small-pox and scarlet fever4 ,frequent baths and inunction with vaseline or oil are useful4 ,the disinfection of hands is most important for all attendants on the infectious sick4 ,a solution of corrosive sublimate #a-ajjj1 or one of the above solutions may be used for this purpose2 but this is to be supplemented by the free use of the nail-brush and soap and water4 ,the treatment of linen has been described 7page #cbi74 ,woollen articles of underclothing1 and blankets can be disinfected by steam1 which shrinks them less than boiling water4 ,the ordinary laundry processes appear1 however1 to suffice to rid them of infection1 without boiling4 ,bedding1 curtains1 and carpets should be disinfected by steam4 ,certain precautions are required in removing these to the disinfecting station4 ,surface disinfection of the room must have been first effected 7see below72 and the infected bedding should be encased in canvas bags or sheets4 ,when a steam disinfector is inaccessible1 the mattress and pillows should be taken to pieces1 the covers washed1 and their contents disinfected by spraying with formalin solution 7#a in #dj7 or ,hg,cl solution 7#a in #a1jjj71 and subsequently exposing to sun and air4 ,for disinfection of suits of clothes1 current steam may be improvised as follows3--,over two bricks at the bottom of the kitchen 8copper0 thin floor-boards are placed1 above the level of #b or #c inches of water previously placed at the bottom of the copper4 ,the cover of the copper is put on1 and by means of a brisk fire steam is kept streaming through the clothes4 ,this is continued for an hour1 and the clothes then hung out to dry4 ,furniture1 when wooden1 can be washed4 ,if upholstered it can be disinfected by spraying 7see p4 #ccc71 and then beating and dusting in the open air4 ,furs1 ,boots1 and ,shoes are spoilt by steam4 ,for the first1 spraying freely with formalin 7#a in #dj71 or exposure over a formalin lamp 7page #cbf7 is recommended4 ,boots and shoes should be filled and washed with a solution of ,hg,cl1 chinosol1 or formalin4 ,illustration3 ,,fig4 #eh4 ,,equifex ,,spray ,,disinfector ,,in ,,use4 ,the sick-room can only be efficiently disinfected after the patient has left it4 ,the aim is surface disinfection4 ,aerial disinfection is sufficiently effected by open windows4 ,four chief methods of surface disinfection are practised4 7a7 ,fumigation by ,,so1 formalin1 cresol1 or other vapours 7see page #cbf74 7b7 ,spraying the ceiling1 walls1 floor1 and furniture with a disinfectant solution is probably the most convenient method of disinfection4 ,it is more effectual than fumigation1 less laborious than rubbing down walls1 etc41 by bread or wet cloth1 and less likely to damage wall-papers than brushing a disinfectant solution on them4 ,solutions of ,hg,cl #a in #a1jjj1 or chinosol #a in #a1bjj1 or formalin #a in #dj are efficient4 ,a special spray apparatus 7,fig4 #eh7 is usually employed4 ,a practical point is to spray the wall from below upwards1 to prevent the solution running down the wall and producing streaks of discolouration4 7c7 ,washing ceiling and walls with the disinfectant solution may be substituted4 ,a one per cent4 solution of hypochlorite of lime is largely used for this purpose1 applied by a long-handled whitewash brush4 7d7 ,attrition of walls1 etc41 by means of bread or dough sterilises them by mechanically removing microbes4 ,the bread is cut into pieces suitable for grasping in the hand1 the cut surface being applied to the wall4 ,the crumbs must afterwards be burnt in the room4 ,this is the official method in ,germany4 ,floors may be treated like walls and ceiling after the patient has left the room4 ,during his occupancy of the room1 tea-leaves or sawdust thoroughly impregnated with lysol or cresol should be sprinkled on the floor before it is swept1 or washing substituted for sweeping4 ,scrubbing with soap and water constitutes the best disinfectant for floors and all other washable surfaces4 ,books are difficult of disinfection4 ,steam damages leather4 ,the penetrating power of dry heat is doubtful4 ,cheap books should be burnt4 ,abel discovered virulent diphtheria bacilli on toys six months after the patient1 to whom they belonged1 had diphtheria4 ,formalin and phenol vapours have been used to disinfect books in closed chambers1 the books being stood on end4 ,letters can be rendered safe by steam disinfection4 ,corpses of infectious patients should be placed in the coffin and buried as early as possible4 ,a thick layer of sawdust saturated with lysol or cresol should be placed at the bottom of the coffin1 and the corpse enveloped in cotton wool4 ,cremation is better than burial4 ,,chapter ,,xlviii4 ,,vital ,,statistics4 ,vital ,statistics is the science of numbers applied to the life-history of communities4 ,its significance is similar to that of the more recently coined word--,demography--though the latter does not necessarily confine itself strictly to study of life by statistical means4 ,another term has been frequently used in recent years--8,vital and ,mortal ,statistics40 ,the continued use of the word 8mortal0 in this connection is undesirable and objectionable4 ,the term 8,vital ,statistics0 is comprehensive and complete1 as death is but the last act of life4 ,of the problems of life with which the science of ,vital ,statistics is concerned1 population1 births1 marriages1 sickness1 and deaths1 possess the chief importance2 and in the following sketch of the subject ,i shall concern myself chiefly with these4 ,the subject naturally divides itself into two sections3 the sources of information1 and the information derived from these sources1 and both of these will require consideration4 ,the importance of numerical standards of comparison in science increases with every increase of knowledge4 ,the value of experience1 founded on an accumulation of individual facts1 varies greatly according to the character of the observer4 ,as ,dr4 ,guy has put it3 8,the sometimes of the cautious is the often of the sanguine1 the always of the empiric1 and the never of the sceptic2 while the numbers #a1 #aj1 #ajj1 and #ajj1jjj have but one meaning for all mankind40 ,hence the importance of an exact numerical statement of facts4 ,the sneering statement that statistics cannot be made to prove anything can only be made by one ignorant of science4 ,in fact1 nothing can be proved without their aid1 though they may be so ignorantly or unscrupulously manipulated as to appear to prove what is untrue4 ,instances of fallacious use of figures will be given as we proceed4 ,an accurate statement of population forms the natural basis of all vital statistics4 ,thus the comparison of the number of deaths in one with the number of deaths in a second community has no significance unless we know also the number living out of which these deaths occurred4 ,even then our knowledge would be defective1 without further particulars as to the proportion in each population living at different ages1 and the number dying at the corresponding ages4 ,for other purposes we should require to know the number married and unmarried1 the number engaged in different industries1 and so on2 in order that the influence of marital conditions1 of occupation1 etc41 on the prospects of life may be calculated4 ,the first desideratum of accurate vital statistics is a census enumeration of the population at such intervals as will not cause the intervening estimates of population to be very wide of the mark4 ,in this country a decennial census is taken1 the last occurring in #aija4 ,in the intervals the population of the entire country1 and of each town or district is estimated4 ,various methods of estimating the population have been adopted4 7#a7 ,if a strict record of emigration and immigration is kept1 then in a country in which a complete registration of births and deaths is enforced1 the population can be easily ascertained by balancing the natural increase by excess of births over deaths1 and the increase or decrease due to migration4 ,this is done in ,new ,zealand1 but is impracticable in ,england1 as no complete account of migration can be kept4 7#b7 ,the increase of inhabited houses in a district being known year by year1 the increase of population may be estimated on the assumption that the number of persons per house is the same as at the last census4 ,this may not be strictly accurate4 ,in #aija it was found that in ,england and ,wales the average number of persons per house was fractionally less than in #ahia4 7#c7 ,it may be assumed that the annual increase during the present decennium will be #aaj of the increase during the last decennium #ahia-aija4 ,if so1 the population1 e4g4 in #aije1 is the enumerated population in #aija plus #d times the annual increase occurring during #ahha-ia4 7,the fourth is required because the census is taken early in ,april1 and the population is estimated to the middle of the year74 ,this method is fallacious1 because it makes no allowances for the steadily increasing numbers who year by year attain marriageable age and become parents4 ,it assumes1 in other words1 simple interest1 when compound interest is in operation4 7#d7 ,the ,registrar-,general's method1 the one generally adopted1 assumes that the same rate of increase will hold good as in the preceding intercensal period1 i4e4 that the population increases in geometrical progression1 and not in arithmetical progression as under 7#c74 ,the application of this method will be best understood by an example4 ,if the census population of a town is #cb1jjj in #ahia1 and #cf1jjj in #aija1 what is the mean population in #aije8 7a7 ,find the rate of increase in #ahia-aija4 ,if ,p population at census #ahia1 and if ,p#a #aija1 and if ,r rate of increase of population1 then ,p#a ,p - ,rn in the nth year4 log ,p#a log ,p #aj log ,r4 #aaj7log ,p#a - log ,p7 log ,r4 7#deefcjc - #dejeaej7aj #jjeaaec log ,r4 7b7 ,apply this to the increase in the next #d years4 ,here ,p#aije ,p#aija ,r7#agd7 log ,p#aije #deefcjc 7#agd7 7#jjeaaec7 #deghjdc4 ,by consulting the table of logs1 the population corresponding to this number will be found to be #cg1hdh population at the middle of #aije4 ,estimates made by the last-named 8official0 method are liable to error1 even for the entire country1 and still more when applied to special districts4 ,thus the decennial rate of increase of the population of ,england and ,wales in the #ajj years has varied from #aeh per cent4 in #ahba-ca to #aaf per cent4 in #ahia-aija4 ,the anomalies are even greater when the official method is applied to great towns4 ,in one decennium such a town may1 owing to brisk trade1 have a rapid increase of working population with many children1 and in the next decennium in consequence of emigration or transmigration there may be little or no increase4 ,the declining birth-rate1 which is having a greater effect on the number of population than the declining death-rate1 is another cause of disturbance which increases the difficulty in forming a correct estimate of the population in intercensal periods4 ,a quinquennial census is highly desirable1 in order to avoid the doubts necessarily associated with estimates of population in the later years of a decennium1 and with the birth and death-rates which are based on these estimates4 ,the ,registration of ,births and ,deaths4--,civil registration of births and deaths began in #ahcg1 but was not compulsory till #ahgj4 ,it will be going beyond the scope of this chapter to give details of the enactments as to registration4 ,it suffices to state that it is the duty of the practitioner to give a certificate stating the cause of death of his patient to the best of his knowledge and belief4 ,there is no registration of still-births in this country4 ,many deaths are registered of which the cause of death is not medically certified1 and the value of our national vital statistics is considerably diminished on this account4 ,much improvement is desirable in the medical certification of causes of death4 ,every medical student ought to receive instruction on this subject before the completion of his studies4 ,names of symptoms as dropsy1 hmorrhage1 convulsions2 and obscure names1 as abdominal disease1 should be avoided4 ,if the patient has recently suffered from injury1 or recently passed through childbirth1 or had a specific febrile disease1 this must not be omitted from the certificate4 ,the ,registration and ,notification of ,sickness forms another valuable source of information4 ,various attempts have been made to secure a general registration of disabling sickness1 but with only partial success4 ,district and workhouse medical officers appointed since ,february1 #ahgi1 are required to furnish the medical officer of health with returns of pauper sickness and deaths4 ,this source of information might with advantage be more fully utilised by medical officers of health4 ,sec4 #bi of the ,factory and ,workshops ,act1 #ahie1 requires that every medical practitioner attending on or called in to visit a patient whom he believes to be suffering from lead1 phosphorus1 or arsenical poisoning1 or anthrax1 contracted in any factory or workshop1 shall send to the ,chief ,inspector of ,factories at the ,home ,office1 ,london1 a notice stating the name and full postal address of the patient1 and the disease from which he is suffering2 a fee of #bs4 #f;d4 being payable for each notification1 and a fine not exceeding #djs4 being incurred for failure to notify4 ,the ,compulsory ,notification of ,infectious ,diseases is enforced by the ,act of #ahhi1 which now applies to the whole country4 ,the list of diseases to be notified is as follows3 8,small-pox1 cholera1 diphtheria1 membranous croup1 erysipelas1 the disease known as scarlatina or scarlet fever1 and the fevers known by any of the following names3 typhus1 typhoid1 enteric1 relapsing1 continued1 or puerperal1 and also any infectious disease to which the ,act has been applied by the ,local ,authority in manner provided by the ,act40 ,it is the duty of the medical practitioner to ascertain whether in his own district1 such diseases as whooping cough and measles have been added to the schedule of notifiable diseases4 ,it is the duty of 7a7 the head of the family to which the patient belongs2 in his default1 of 7b71 the nearest relatives in the house2 in their default1 of 7c71 every person in attendance upon the patient2 and in default of any such person1 of 7d7 the occupier of the building1 as soon as they become aware that the patient is suffering from an infectious disease to which this ,act applies1 to send notice thereof to the ,medical ,officer of the ,district4 7e7 ,the more formal duty of sending to the ,medical ,officer of ,health a certificate stating the name of the patient1 the situation of the building1 and the infectious disease from which in his opinion the patient is suffering1 is imposed on every medical practitioner attending on1 or called in1 to visit the patient1 on becoming aware that the patient is suffering from an infectious disease to which this ,act applies4 ,he is entitled to a fee of #bs4 #f;d4 if the case occurs in his private practice1 and of #as4 if the case occurs in his practice as medical officer of any public body or institution4 ,he is subject to a fine not exceeding #djs4 if convicted of failure to notify4 ,the value of returns of infectious diseases as enabling preventive measures to be taken is increased by interchange of notification returns of different districts4 ,this is now undertaken weekly for a large number of districts by the ,local ,government ,board1 and the ,registrar-,general publishes quarterly summaries of such returns1 as well as weekly returns of infectious diseases for the metropolis4 ,marriages are usually stated in proportion to the total population1 or the number per thousand of population2 but a more accurate method would be to base the marriage-rate for comparative purposes on the number of unmarried persons living at marriageable ages4 ,in ,england the marriage-rate is always higher in large towns than in rural districts4 ,thus in #aijj the marriage-rate in ,london was #agf as compared with an average marriage-rate in #ahia-ie of #aeb per thousand of the estimated population in ,england and ,wales4 ,the higher marriage-rate in towns is chiefly owing to the fact that higher wages and greater scope for remunerative work attract young country people of marriageable ages to towns4 ,births are usually reckoned as a rate per thousand of population4 ,clearly1 however1 if one population had a larger proportion than another of women of child-bearing years this method of comparison would not be free from possible error4 ,even were the proportion of women of child-bearing ages equal1 the comparison might be fallacious if in one population the proportion of single women was much higher than in the other4 ,illegitimate births do not materially vitiate this conclusion1 as such births do not constitute more than #d per cent4 of the total births1 and this number is not excessive in the districts in which there is the greatest excess of single women1 viz4 in districts in which a large number of domestic servants are employed4 ,the only strictly accurate method is to subdivide the births into legitimate and illegitimate1 stating the former per #a1jjj married women of child-bearing years1 and the latter per #a1jjj unmarried women of child-bearing years4 ,i append an example of the relative accuracy of the three methods above indicated#ab3-- ,,birth-,,rate ,,per #a1jjj ,,per #a1jjj ,,per #a1jjj ,,married ,,inhabitants4 ,,women ,,women ,,aged ,,aged #ae-de4ae-de ,,years4 ,kensington #ba4h #fa4f #bae4d ,whitechapel #ci4i #agb4a #cbh4c ,percentage excess #hc #agi #ec of birth-rate in ,whitechapel over ,a ,b ,c that in ,kensington ,thus1 according to the ordinary method 7,a7 of stating the legitimate birth-rate1 it is #hc higher in ,whitechapel than in ,kensington1 whereas it is really only #ec higher4 ,similarly a statement of the illegitimate birth-rate in the two districts 8per #a1jjj inhabitants10 shows an excess of only #f in ,whitechapel1 while a statement 8per #a1jjj unmarried women aged #ae-de years0 shows the real excess of #add4 ,both in this and other civilised countries there has been in the last #be years a steady decline in the birth-rate4 ,in ,england the maximum birth-rate was #cfc per #a1jjj of population in #ahgf1 and the minimum #bic in #ahii4 ,this diminution is only caused to a minor degree by postponement of marriage to more mature years1 and by a larger proportion of celibacy4 ,nor is there any reasonable ground for the view that a diminished power of either sex to produce children has been produced by alcohol1 syphilis1 tobacco1 or other causes4 ,the main cause of the diminution of the birth-rate is 8the deliberate and voluntary avoidance of child-bearing on1 the part of a steadily increasing number of married persons40 ,deaths are calculated in proportion to every #a1jjj of the population1 the unit of time being a year4 ,this unit is preserved even when death-rates for shorter periods1 e4g4 a week1 are stated4 ,thus the death-rates for the #cc great towns published weekly in the chief newspapers are annual death-rates2 they represent the number who would die per #a1jjj of the population1 supposing the same proportion of deaths to population held good throughout the year4 ,the best plan to obtain the weekly annual death-rate is as follows3 the correct number of weeks in a year being #ebaggdg1 if the population of a town be #adc1ief1 and the number of deaths in a given week are #ce1 then the death-rate is #abfhg4 ,thus3-- #adc1iefebaggdg #bgeh4 #a1jjjb1geh #jcfbe4 ,this is the factor by which the weekly number of deaths must be multiplied4 #ce #jcfbe #abfhge or #abg4 ,the above is the crude death-rate4 ,various corrections are required1 which must now be considered4 ,the most important of these are for public institutions1 for visitors1 and for age and sex4 ,a public institution1 e4g4 a workhouse1 infirmary1 or asylum1 in a given district may consist almost entirely of persons belonging to another district4 ,the rule is to relegate to the district to which they belong all deaths of inmates of an institution1 i4e4 subtract all deaths of outsiders occurring in inside institutions1 and add all deaths of inhabitants occurring in outside institutions4 ,the population as well as the deaths of these institutions should be excluded1 in so far as they are derived from the outside district1 in order to make the net death-rate approximately correct4 ,theoretically the correction ought to be extended so as to apply to visitors who do not die in public institutions4 ,in practice1 however1 this cannot be effected1 until a central 8clearing house0 is established4 ,the exclusion of deaths of visitors from the district in which they occur is easy2 their inclusion in the returns of the district from which they come is more difficult to secure4 ,for the present1 they should be included in the death-rate of the district in which they occur4 ,death-rate according to ,age and ,sex4--,to obtain a true conception of the death-rate in a community1 it is necessary to state the number of deaths in each sex in proportion to the number living at different ages4 ,the importance of this is shown by the following extract from the ,registrar-,general's report for #ahii4 ,england and ,wales4--,deaths to #a1jjj living at each of #ab groups of ages4 ,,all ,,aged ,,ages4 #j #e #aj #ae #bj #be #ce ,males #aie #fjd #ch #bb #cf #ec #ga #abc ,females #agc #ejg #ci #bc #cc #dc #fa #ajj #he ,,and #de- #ee- #fe- #ge- ,,upwards4 #bjj #cgb #fih #aebf #cjjc #aed #bih #fae #adbf #bgbj ,thus at ages over #e and under #de for males1 and under #ee for females1 the death-rate is lower than is the total death-rate for all ages4 ,for females at all ages except from #e to #ae1 the death-rate is lower than for males4 ,from the above statement it will be clear that a considerable excess of women 7as in a residential district with a large number of domestic servants7 or a considerable excess of either sex at the ages of #ae to #de 7as in most large towns7 in proportion to the number living at other ages1 would produce a lower total or crude death-rate1 which does not imply any truly more healthy condition than that of another district1 which is less favourably constituted so far as the proportion of the sexes and the numbers living at different ages are concerned4 ,by a means of correction now to be described this source of error can be eliminated4 ,the method of obtaining the factor for correction can be best understood by an example4 ,the annual death-rate of ,england and ,wales in #ahha-ij was #ai4ae1 and the death-rate at each age-group is given in the following table3 ,,ages4 ,,mean ,,annual ,,death,,rate ,,in ,,england ,,and ,,wales #ahhaij1 ,,per #a1jjj ,,living ,,at ,,each ,,group ,,of ,,ages4 ,males4 ,females4 ,under #e #fa4ei #ea4ie #e #ece #ebg #aj #bif #caa #ae #dcc #ddb #bj #egc #eed #be #ggh #gda #ce #abda #ajfa #de #aicf #aeji #ee #cdfi #bhde #fe #gjci #fjcf #ge and upwards #afb4fb #adg4ih ,,population ,,calculated ,,of ,,huddersfield ,,in ,,number ,,of ,,deaths #ahia4 ,,in ,,huddersfield4 ,males4 ,females4 ,males4 ,females4 #d1eea #d1ghe #bhj #bdi #d1fia #e1jha #be #bg #e1aac #e1afe #ae #af #d1ije #e1edi #ba #be #d1eda #e1dfa #bf #cj #g1dff #h1hcd #eh #fe #e1egf #f1bfe #fi #ff #c1idd #d1fdi #gf #gj #b1cic #c1jag #hc #hf #a1abh #a1eij #gi #if #bej #dff #da #fi ,totals #dd1eeh #ej1hfb #ggc #gii _/ _/ #ie1dbj #a1egb ,the population of ,huddersfield at each of the corresponding periods as given by the census of #ahia1 is also shown in this table1 and in the last column the number of male and female deaths that would occur by applying the death-rates for ,england and ,wales to the population of ,huddersfield are shewn4 ,the total number of deaths thus calculated is #aegb in a population of #ie1dbj1 and the total death-rate #afdg per #ajjj4 ,this is the standard death-rate1 i4e41 the death-rate at all ages calculated on the hypothesis that the rates at each of #ab age-periods in ,huddersfield were the same as in ,england and ,wales during the ten years of the last intercensal period1 viz4 #aiae in #ahha-ij4ac ,but the standard death-rate of ,huddersfield would have been #aiae instead of #afdg1 were it not for the fact that the distribution of age and sex in the ,huddersfield population is more favourable than in the country as a whole4 ,hence it must be increased in the ratio of #aiae3 #afdg1 i4e41 multiplied by the factor #aiaeafdg #aafbg4 ,when the crude or recorded death-rate for #aijj of #afgh is multiplied by this factor we obtain the corrected death-rate of #afgh #aafbg #aiea per #ajjj1 which is the correct figure to compare with the death-rate of #ah4ca for ,england and ,wales in that year4 ,if the death-rate of ,england and ,wales be stated as #ajjj1 then #ajjj #aieaahca #ajff1 is the comparative mortality figure for ,huddersfield4 ,similarly in the year #aijj the comparative mortality figure of ,london was #ajic1 of ,croydon #hca1 of ,norwich #iai1 while that of ,liverpool was #aeci1 of ,salford #aeda4 ,in all the towns except ,plymouth and ,norwich the corrected death-rate is higher than the crude or recorded death-rate4 ,this implies that1 in all except these two towns1 the factor of correction is greater than unity4 ,this is a convenient point for briefly discussing the relationship between the birth-rate and death-rate4 ,the opinion is commonly held that a high birth-rate is a direct cause of a high death-rate1 owing to the great mortality amongst infants4 ,the table on page #cdj shows that the death-rate at ages under five is three times as high as at all ages together1 and it is therefore natural to suppose that a high birth-rate by producing an excessive proportion of persons of tender years will cause a high general death-rate4 ,this might be so1 if the birth-rate were to remain high for only five years4 ,but if the high birth-rate continued longer1 the proportion of the total population at ages of low mortality would be increased1 and the general death-rate would be lowered4 ,we have already seen that in nearly all the great towns1 in which the birth-rate is higher than in rural districts1 the age distribution of the population is more favourable to a low death-rate than in rural districts2 and their higher crude death-rate is made still higher than that of rural districts when the necessary factor of correction is applied4 ,the ,infantile ,mortality should be stated in terms of the infantile population4 ,this is more accurately assumed to be equal to the number of births in the given year1 than estimated from the number stated to be under one year of age at the last census4 ,the number of deaths under one year of age per #ajjj births was #afc for ,england and ,wales in #ahii1 being lowest in the agricultural counties and highest in manufacturing counties4 ,in the #cc great towns it averaged #agb in the year #aijj1 ranging from #acb in ,croydon1 ,huddersfield and ,halifax to #bcf per #ajjj births in ,preston4 ,of #ajjj male children born in ,england and ,wales in #ahha-ij1 the number surviving at the age of three months was #iba1 at the age of six months #hhi1 twelve months #hci1 while the number of female children surviving one year of #ajjj born was #hfi4 ,in towns a smaller number survive4 ,of the conditions causing this high infantile mortality1 ignorance and inexperience on the part of parents bear a considerable part1 especially as influencing the food and mode of feeding4 ,the death-rates at other age-groups beyond infancy are given in the table on page #cdj4 ,season influences the death-rate4 ,the third quarter of the year has the lowest death-rate1 unless the amount of ,epidemic ,diarrha has been excessive4 ,in the first quarter of the year1 the highest death-rate usually occurs4 ,mild winters and cool summers both lower the mortality4 ,the seasonal incidence of infectious diseases need only be mentioned in passing4 ,density of ,population has important bearings on the death-rate4 ,thus the urban districts in #ahii had a death-rate of #aib and the rural of #afc per #ajjj of population4 ,farr found that the death-rate increased with the density of populations1 not in direct proportion1 but in proportion to the #fth roots of the contrasted populations4 ,this rule does not now hold generally good4 ,it is only after the density has reached a certain degree of intensity that it begins to exert an appreciable effect4 ,even then it is what is implied in aggregation rather than the aggregation itself that is pernicious4 ,in particular1 poverty is usually greater in densely populated districts than elsewhere1 with its accompaniments of deficient food and clothing and bad housing4 ,hence the excess of phthisis in tenemented houses1 especially in houses with only three rooms4 ,i have shown that the true density that should be considered is the number of persons to each room1 not the number of persons on a given area 78,the ,vital ,statistics of the ,peabody ,buildings10 ,roy4 ,statist4 ,soc41 ,feb41 #ahia74 ,occupation and ,mortality4--,to obtain correct statistics showing the influence of occupation on vitality1 one must know the number and age of those engaged in each industry1 and the corresponding number of deaths4 ,a statement of the mean age at death of those engaged in different occupations would be most fallacious 7page #cdd74 ,the best plan is to restrict the statistics to men aged #be-fe1 and calculate for these death-rates in a standard population1 after the fashion already described 7page #cdj74 ,by this means a 8comparative mortality figure0 can be obtained4 ,for all males it is #ajjj1 for farmers #efc1 teachers #fjc1 lawyers #hba1 doctors #iff1 butchers #ajif1 plumbers #aabj1 brewers #adbg1 innkeepers #afei1 potters #agjf1 file-makers #ahaj4 ,speaking generally1 the occupations are most unhealthy in which there is most exposure to dust1 to the breathing of foul air1 and to excessive indulgence in alcoholic drinks 7for further details see the author's ,elements of ,vital ,statistics1 page #afi et seq474 ,deaths from ,various ,causes4--,these may be stated in proportion to total deaths from all causes1 or in terms of the population4 ,the first plan must be adopted only when it is desired to ascertain the proportional share of a given cause of death in the total mortality4 ,in #ahii1 in ,england and ,wales the diseases named in the first column of the table 7page #cdd71 were the most prolific causes of deaths4 ,,england ,,and ,,wales1 #ahii4 ,,deaths ,,from ,,various ,,causes ,,to #aj1jjj ,,deaths ,,from ,,all ,,causes4 ,bronchitis #hhj ,phthisis #gbi ,pneumonia #fhe ,old age #eda ,diarrha1 ,dysentery #eaa ,cancer #deb ,apoplexy #cbg ,influenza #bac ,whooping cough #agd ,measles #agb ,diphtheria #afj ,enteric fever #ajh ,scarlet fever #fd ,small-pox #c ,the diseases in the second column are given in order to indicate their proportional share of the total number of deaths4 ,the proper plan of stating the death-rate from a given disease is in terms of the population1 or better still subdivided into death-rates from the disease for different age-groups as in the table on page #cdj1 if the number of deaths is not too small to admit of this4 ,the importance of stating the death-rate for different age-groups is greatest for such diseases as diarrha1 whooping cough1 and measles1 in which most of the deaths occur at ages under five4 ,in the following table are given the death-rates from the causes of death which are most important1 either from their magnitude1 or because of their preventible character3-- ,,england ,,and ,,wales1 #ahii4--;,,death-,,rate ,,per #a1jjj ,,persons ,,living4 ,small-pox #jje ,measles #cb ,scarlet fever #ab ,influenza #ci ,whooping cough #cb ,diphtheria #bi ,enteric fever #bj ,typhus fever #jja ,cholera #jd ,diarrha1 ,dysentery #id ,intemperance #jiad ,cancer #hc ,phthisis #acd ,other tubercular diseases #eh ,premature birth #eh ,old age #ii ,apoplexy #fj ,convulsions #eg ,valvular disease of heart #ch ,bronchitis #afa ,pneumonia #abf ,gastro-enteritis #fa ,bright's disease #bi ,accidents #ei ,ill defined and not specified causes #gc ---- ,all causes #ahcc ,determination of ,longevity4 ,we have hitherto considered only death-rates1 i4e4 the number dying each year out of each #a1jjj of population4 ,the mean duration of life involves another aspect of the same problem4 ,although nothing is more uncertain than the duration of individual life1 the duration of life for the entire community is subject to so little variation that annuities and life assurance can be made the subject of exact calculations4 ,of the tests employed to measure the duration of human life the most commonly employed is the mean age at death4#ae sum of ages at death4 ,mean age at death ---------------------------------------- --4 number of deaths4 ,this is a fair method of stating the average longevity of a particular group of persons1 if the group is sufficiently large to avoid the possible error caused by paucity of data 7page #cdi74 ,but it would be entirely unsafe to assume that by this means a safe standard of comparison between two groups can be formed4 ,thus in #ahij it was stated that the mean age at death of workmen was #bi-cj years1 of the well-to-do classes #ee-fj years4 ,this statement throws no light on the relative vitality of the two classes under comparison4 ,the well-to-do classes consist largely of those whose working days are past2 and it is as untrustworthy to compare their mean age at death with that of workmen1 as it would be to base any conclusion on the fact that mean age at death of bishops is much higher than that of curates4 ,the mean age at death is lowest in countries with a high birth-rate4 ,hence it would be very fallacious to compare the mean age at death in ,england and ,france4 ,the probable duration of life 7vie probable7 is a term sometimes employed to denote the age at which any number of children born into the world will be reduced to one half4 ,in practice it can only be ascertained from a life-table4 ,the true mean duration of life or expectation of life can only be ascertained from a ,life ,table1 and this must therefore be briefly described4 ,this is the true biometer1 of equal importance in all inquiries connected with human life with the barometer or thermometer and similar instruments employed in physical research4 ,the ,life ,table represents 8a generation of individuals passing through time40 ,the data required for its construction are the number and ages of the living1 and the number and ages of the dying1 i4e4 the data required for ascertaining the death-rate for each year of life4 ,theoretically the best plan for forming a ,life ,table would be to observe a million children1 all born on the same day1 through life1 entering in a column 7headed lx7 the number who remain alive at the end of each successive year until all have died2 and in a second column 7headed dx7 the number dying before the completion of each year of life4 ,this method is impracticable1 and were it otherwise1 the experience would be obsolete before it could be utilised4 ,the method employed in constructing the national ,life ,tables for ,england is1 without tracing the history of individuals through life1 to assume that the population being given by the census returns and the death-rate for each age for a given decennium being known1 that the same death-rate will continue during the remainder of the lives of the population included in the census returns4 ,the total mean number living and the total number dying for a given age-period are known4 ,the mean chance 7px7 of living one year during this age-period is found by the fraction ,population - ,deaths ---------------------------------------- ------ px ,population ,deaths ,it is usual to start with a million or #ajj1jjj children at birth1 and to make a separate table for the proportionate number of males and females at birth4 ,thus in ,brighton in #ahha-ij these were in the proportion of #ea1aie and #dh1hje4 ,starting with #ea1aie male infants at birth1 and multiplying this number by #hdfjh1 the probability of surviving for one year1 we obtain #ea1aie #hdfjh #dc1cae4 ,for the second year of life1 the probability of surviving was #iccih2 hence the number of survivors is #dc1cae #iccih #dj1deb1 and so on4 ,the general arrangement is shewn in the following example of a ,life ,table1 which only gives the data at or near the two extremes of life1 the intermediate figures having been omitted from considerations of space4 ,,brighton ,,life ,,table4--,,males4 7,based on the mortality of the #aj years #ahha-ij47 ,,age4 ,,dying ,,in ,,born ,,and ,,sum ,,of ,,the ,,number ,,mean ,,after ,,each ,,year ,,surviving ,,living1 ,,or ,,years ,,of ,,life-,,time ,,of ,,life4 ,,at ,,each ,,life ,,lived ,,at ,,each 7,,expectation ,,of ,,age4 ,,age1 x #a1 ,,and ,,life7 ,,at ,,each ,,upwards1 ,,to ,,the ,,last ,,age4 ,,age ,,in ,,the ,,table4 x dx lx lx#a ex #j #g1hhj #ea1aie #b1bjf1agd #dcei #a #b1hfc #dc1cae #b1afb1hei #ejdc #b #iif #dj1deb #b1abb1djg #ebif #c #gcc #ci1def #b1jhb1iea #ecbi #d #ddj #ch1gbc #b1jdd1bbh #ecbi #ig #ab #bi #dc #afj #ih #g #ag #bf #aec #ii #d #aj #af #adh ,the #dc1cae males surviving to the end of the first year of life out of #ea1aie born will each have lived a complete year in the first year1 or among them #dc1cae years4 ,similarly the #dj1deb males will live among them #dj1deb further complete years1 and so on1 until all the males started with become extinct at the age of #aje4 ,evidently1 therefore1 the total number of complete years lived by the #ea1aie males started with at birth will be #dc1cae #dj1deb #ci1def #ch1gbc 444 #aj #f #d #c #b #a #b1bjf1agd years1 this sum being obtained by adding together the numbers living at each age beyond 7i4e4 below on this table7 the age in question right down to its last item4 ,this number of years is lived by #ea1aie males4 ,hence the number of complete years lived by1 i4e4 the expectation of life of1 each male #b1bjf1agd ------------------ #dcji years4 #ea1aie ,this is the curtate expectation of life4 ,it deals only with the complete years of life1 not taking into account that portion of life-time lived by each person in the year of his death1 which may be assumed to be on an average half a year4 ,hence the complete expectation of life according to the above table is #dcei years4 ,in the following table the expectation of life 7complete7 for various towns and for ,england is given3-- ,,life ,,table4--,,expectation ,,of ,,life ,,at ,,birth4 ,male4 ,female4 ,english ,life ,table1 #ahch-ed 7,farr7 #ciia #dahe #ahga-hj 7,ogle7 #dace #ddfb #ahha-ij 7,tatham7 #dcff #dgah ,london1 #ahha-ij 7,murphy7 #djff #ddia ,brighton1 #ahha-ij 7,newsholme7 #dcei #dibe ,manchester ,city1 #ahha-ij 7,tatham7 #cdga #chdd ,glasgow1 #ahha-ij 7,chambers7 #ceah #cggj ,formul of varying degrees of accuracy have been devised for giving in the absence of a ,life ,table an approximation to the expectation of life4 ,willich's ,formula is as follows3--,if x expectation of life1 and a present age1 then x #bc 7#hj-;a74 ,thus1 at the age of #ej years the expectation of life1 according to this formula1 is #bj years4 ,by the ,english life-table for #ahha-ij it was #ah4hb for males1 and #bjef for females4 ,farr's formula is based on the birth and death-rates4 ,if b birth-rate and d death-rate per unit of population1 then ,expectation of life 7#bc #a;d7 7#ac #a;b74 ,thus b for ,england and ,wales1 #ahhi-ih #cjca1jjj #jcjc4 and d #ahda1jjj #jahd4 7#bc #ajcjc7 7#ac #ajahd7 #dg4b years1 as compared with the expectation of life for #ahha-ij shown in the above table4 ,in a life-table the number out of which one dies annually are the mean age at death identical and the expectation of life in value when the whole duration of life from birth to death is included in the calculation4 ,this is only true for a stationary or life-table population1 in which the number dying is assumed to be regularly replaced by a corresponding number of persons of the same age4 ,life ,capital4--,the life-tables now in use are those based on the experience of #ahha-ij4 ,the gain in any subsequent year1 as in #aijj1 may be ascertained as follows3 the mean population and the death-rate for each age-group as #j-e1 #e-aj1 etc41 are calculated4 ,then the mean death-rate of the same community for #ahha-ij is applied to this population4 ,by this means the 8calculated number0 of deaths in #aijj is obtained4 ,the difference between these numbers and the 8actual number0 obtained from the death-registers1 gives the gain or loss during the year4 ,next multiply these differences by the mean expectation of life for the corresponding groups of years4 ,by adding the gains thus ascertained and subtracting any losses1 we obtain the net gain in 8life-capital0 7,tatham7 during the year #aijj4 ,tests of the ,health of a ,community4 #a4 ,the general death-rate is the test most commonly applied1 and generally trusted4 ,it has its limitations in this respect4 ,it may usually be trusted in comparing a town or district for a single year with preceding years1 as the age and sex distribution of a given population only changes slowly4 ,but when comparison with other towns or districts is made1 the possibility that erroneous conclusions may be drawn becomes considerable4 7a7 ,before the death-rates of two districts can be compared1 either this comparison must be made by means of death-rates for age-groups 7#j-e1 #e-aj1 444 #fe-ge1 etc47 or the factors of correction1 the method of obtaining which is described on page #cda1 must be applied4 7b7 ,it must be ensured that in the two compared districts1 an equal amount of correction has been made for deaths occurring in public institutions and among visitors 7page #cdj74 7c7 ,even when the above precautions are taken1 it is conceivable that a town with a death-rate of #ae per #a1jjj may really be as healthy as another with a death-rate of #ab per #a1jjj1 though a statistical justification of this statement is a difficult task4 ,social conditions quite irrespective of the sanitary condition or the natural salubrity of a district have an important influence on the death-rate4 ,poverty and all that it connotes1 necessarily involves a higher death-rate than occurs among the well-to-do4 ,furthermore1 the domestic servants employed by the latter frequently die in districts other than those in which they are employed1 without any possibility of the requisite correction being made4 #b4 ,the zymotic death-rate is frequently quoted as a test of sanitary condition4 ,this is a death-rate based on the deaths from the 8seven chief zymotic diseases10 small-pox1 measles1 whooping-cough1 diphtheria1 scarlet fever1 fever 7chiefly enteric71 and diarrha4 ,this death-rate should be entirely discarded1 the death-rate from each infectious disease being separately stated4 ,a high death-rate from enteric fever would be a much more serious reflection on the health of a town than a high death-rate for whooping-cough4 ,the death-rate from each of these diseases in ,london and in ,england in #ahii was as follows3-- ,,death-,,rate ,,in #ahii ,,per #a1jjj ,,living4 ,england and ,wales4 ,london4 ,small-pox #jje nil ,measles #cb #dg ,scarlet fever #ab #jh ,diphtheria #bi #dc ,typhus #jja nil ,enteric fever #bj #ah ,whooping cough #cb #ch ,diarrha #id #ib ,a statement of the death-rate from each of these diseases for a series of years is a much more trustworthy test than a similar statement for a single year1 in which accidental causes may have caused a temporary increase1 or than a statement of the average result for a series of years1 which tends to conceal the epidemic variations of the disease in question4 ,the danger of such averages has been well exposed by ,chadwick in the remark that 8a mean between the condition of ,dives and ,lazarus tends to make it appear that after all ,lazarus has not so much to complain of40 #c4 ,the infantile mortality 7page #cdb7 is a delicate test of mixed sanitary and social conditions1 and stress may always be laid on it from these standpoints4 ,the importance of comparing death-rates at other age-groups has already been explained4 #d4 ,the most delicate and exact method1 if all the data are accurate and complete1 is to construct a ,life ,table1 and ascertain the expectation of life in comparison with that of other communities4 ,the preceding statistical tests of the salubrity of a community1 and any others that may be available1 should all1 when practicable1 be utilised2 and it should always be remembered that these tests1 especially the general death-rate1 are most trustworthy when contrasting the experience of a community with its past experience1 and least trustworthy when contrasting its experience with that of others2 owing to the difficulty in the latter case of ensuring the avoidance of error arising from non ceteris paribus4 ,statistical ,fallacies4--,if 8fallacies0 be regarded as synonymous with 8errors10 clearly they may occur at every step4 ,they may be classified as errors of data1 and errors of methods4 ,the most important errors of data are erroneous estimates of population1 and erroneous returns of deaths1 especially in the direction of exclusion of certain deaths 7page #cdj74 ,death-rates for short periods are relatively untrustworthy4 ,the erroneous use of the mean age at death as a test of longevity has been mentioned 7page #cdd74 ,these are in part also errors of methods1 and numerous mixed examples are given below4 ,errors from ,paucity of ,data frequently arise1 the 8fallacy of small numbers10 a too hasty generalization1 being the most common fault in medical writings1 especially in therapeutics4 ,the degree of approximation to the truth of a varying number of observations is estimated by means of ,poisson's formula4 total number of cases recorded in two groups4 m number in one group4 n number in the other group1 so that m n4 ,the extent of variation in the proportion of each group to the whole will vary within the proportions represented by-- m #b7bmn#c71 and n - #b7bmn#c7 ,the larger the number of the total observations 771 the less will be the value of #b7bmn#c71 and the less will be the limits of error in the simple proportion m4 ,thus1 of #adg cases of enteric fever1 #ag died1 a fatality of #aad per cent4 ,the possible error is determined by the second half of the above formula-- #b7b #ag #acjadgc7 #b7d1dbjc1agf1ebc7 #jgdf4 i4e4 the possibility of error #jgdf to unity or #gdf per cent4 ,in other words1 in a second series of cases of enteric fever under the same conditions as the above1 the fatality may vary from #cid to #ahhf per cent41 a vague result which indicates that the first series cannot be regarded as establishing more than a prim facie case in favour of any special method of treatment that may have been adopted4 ,non ceteris paribus4--,the necessity that data to be compared shall be collected on a uniform plan1 and be of a strictly comparable nature1 is very frequently ignored4 ,the conclusion that the administration of a given antiseptic is a valuable means of treating enteric fever is not demonstrated by the fact that the fatality in the series of cases thus treated is #g per cent41 while in another series treated without antiseptics it is #ad per cent41 unless it is shown that the age and other previous conditions of the patients in the two cases were not widely different1 and unless the series are sufficiently long to avoid the fallacy due to paucity of data4 ,errors from the ,composition of ,rates4--,if the death-rate of ,a having a population of #aj1jjj is #aj per #ajjj1 and of ,b having a population of #bj1jjj is #ae per #ajjj1 the combined death-rate is not 7#aj #ae7b #abe4 ,to obtain the correct combined death-rate1 the number of deaths in ,a 7#ajj7 and in ,b 7#cjj7 must first be ascertained1 and the death-rate on a population of #cj1jjj in which #djj deaths occurred will then be found to be #acc per #ajjj4 ,errors from ,stating ,deaths in proportion to ,total ,deaths4--,there is nothing erroneous per se in stating the proportion of deaths at one age as a ratio of the total deaths at all ages1 or the deaths from one cause as a ratio of the total deaths from all causes4 ,it is a useful and in fact the only method practicable when it is required to give the proportion of one of these to the other4 ,but beyond this1 such a ratio cannot be trusted4 ,for instance1 the proportion of fatal accidents among male infants is #abb1 and among female infants #bea per cent4 of the total fatal accidents in the male and female sex respectively4 ,but it would be erroneous1 if it were concluded from these figures that female are more subject to fatal accidents than male infants4 ,the only conclusion that they justify is that at higher ages females are much less subject to fatal accidents than males4 ,in actual facts1 for every #ajjj infants born1 only #bi female as against #ca males die under one year of age as the result of accident4 ,again1 suppose the case of two towns1 ,a and ,b4 ,a with a population of #aj1jjj has #aej annual deaths1 of which #bj are caused by cancer2 the general death-rate therefore being #ae1 and the death-rate from cancer #bj per #ajjj1 while the deaths from cancer form #bae of the total deaths4 ,b1 with the same population as ,a1 has #cjj deaths1 its death-rate being #cj per #ajjj1 and #dj deaths from cancer1 its cancer death-rate being #dj per #ajjj2 while the proportion of the deaths from cancer to the total deaths is #bae as before4 ,it is useful to know in regard to each of these individual communities that cancer causes #bae of its total mortality1 but no comparison between the two is practicable on this basis4 ,the only proper comparison is between the death-rate from cancer per #ajjj of population in ,a and ,b1 which shows that it is twice as high in ,b as in ,a4 ,a still more accurate method is to ascertain the number of deaths from cancer1 and the number living at different age-groups1 thus avoiding any errors due to variations in age and sex distribution of population4 ,errors as to ,averages4--,the most common of these results from paucity of data 7page #cdi74 ,note that the results obtained from an average cannot be applied to a particular case4 ,the mean duration or expectation of life1 obtained from a life-table1 expresses with almost mathematical certainty1 the number of years of life of the members of a community taken one with another1 but is often not accurate when applied to a single individual4 ,in ,army statistics errors have arisen by failure to comprehend what is meant by the average strength of a force4 ,the statistics must comprise the lives of a given number of persons as well as the deaths occurring among them for an entire year1 or allowance must be made in this respect when required4 ,hospital statistics for similar reasons are frequently fallacious4 ,thus death-rates have been frequently given per #ajj occupied beds1 which are most misleading1 as the frequency of succession of patients as well as the nature of the patients' complaints will vary greatly in different hospitals4 ,the only proper method of stating hospital-returns is on the basis of the aggregate annual number of cases treated to a termination4 ,the cases should be further subdivided according to age and sex and disease4 ,average death-rates for epidemic diseases when used to compare one community with another may give rise to erroneous conclusions4 ,this is inseparable from the nature of such diseases4 ,during the period under comparison1 one town may happen to have1 say1 three epidemics1 and the other four2 possibly if two or three additional years had been added to the series1 the place of the two towns would have been reversed as regards their average death-rate from the disease in question4 ,the proper plan is to give the death-rates from the epidemic disease for every year recorded1 to draw a curve of these death-rates for the two towns on the same scale1 and to compare the height1 the variations of height1 and the trend of the curve in each instance4 ,,index4 ,a ,acarus ,scabiei1 #bgf ,achorion ,schnleinii1 #bgf ,acne1 #afa ,aerated ,waters1 #df ,ague 7see ,malaria7 ,air--,bacteria in1 #aji1 #aba ,composition1 ,properties of1 #ajj ,contagia and1 #aji1 #aad ,degree of ,moisture of1 #aai1 #abh ,gaseous and ,other ,impurities of1 #aaa ,examination of1 #abf ,moisture of1 #bcd ,in ,soil1 #bba ,suspended ,impurities of1 #aje ,temperature of1 #aai1 #abh of ,mountains1 #bbh ,purification of1 #abi ,air-space1 amount required1 #adb ,alcohol1 #ee ,amines process1 #aia ,ammonia--in ,air1 #aja in ,water1 #hf ,amyloids1 #g ,amylaceous ,foods1 #ai ,anopheles 7see ,mosquito7 ,anthrax1 #bgd1 #cjf ,anti-cyclones1 #bcc ,antidiphtheritic ,serum1 #bfh1 #bii ,anti-syphonage1 #agd ,antill ,trap1 #ahj ,apjohn's ,formula1 #bdb ,arnott's ,valve1 #adi ,arrowroot1 #ai ,arsenic--in ,beer1 #fb in ,wall ,papers1 #bad in ,clothing1 #bgb ,artesian ,wells1 #ga ,artificial ,ventilation1 #aeb ,relative ,value1 #aed ,ascaris1 #bgh ,ash-pits1 #aii ,aspect1 #bja ,atavism1 #bdf ,b ,bacteria1 #bgc ,bacterial ,methods1 ,sewage ,treatment1 #aib ,ballard's ,researches1 #cjc ,barley1 #ah ,barometers1 #bcg ,barometric ,pressure1 #bca ,baths1 #bfb ,beaufort's ,scale1 #bdc ,beef1 #aj ,beer1 #fa ,bell-trap1 #ahj ,benham's ,gas ,burners1 #aeg ,berkefeld ,filter1 #ih ,beverages1 #df ,bilharzia ,hmatobia1 #bgg ,birds1 ,flesh of1 #aa ,birth-rate1 #cci ,black ,death1 #a ,bonds1 ,english1 ,flemish1 #bje ,borax and ,boric ,acid1 #dd ,boyle's ,mica ,valve1 #adi ,bowels1 ,attention to1 #bdh ,brandy1 #fc ,bread1 brown and white1 #ag1 #da ,bricks1 #bje ,broad ,irrigation1 #aib ,burnett's ,solution1 #cbg ,butter1 #ad ,buys ,ballot's ,law1 #bcb ,c ,caffeine1 #dh ,calorigen ,stove1 #aeg ,carbohydrates1 #f ,carbolic ,acid as ,disinfectant1 #cbg ,carbon ,filters1 #ig ,carbonic ,acid--in ,air1 #ajb1 #aaa estimation of1 #abf ,carbonic ,oxide1 #aab ,calorie1 #cb ,carpets1 #bah ,cement1 #bac ,cereal ,foods1 #ae ,cesspools1 #ahc ,cheese1 #ac ,chicory1 #ej ,chigoe1 #bgg ,chlorides in ,water1 #ha ,chlorine as ,disinfectant1 #cbd ,cholera1 #ib1 #bbe1 #cjb ,cisterns1 #gf ,clarke's ,process1 #id ,soap ,test1 #gi ,climate1 #bbg ,closets1 #afh ,clothing1 #bfe ,coal ,gas1 #aae ,cocoa1 #ea ,cod ,liver ,oil1 #ad ,coffee1 #ej ,cols1 #bcc ,comparative ,mortality ,figures1 #cdb ,concrete1 #bjg ,condiments1 #de ,condy's ,fluid1 #cbe ,conservancy ,methods1 #aid ,constipation1 #bdh ,constitution1 #bde ,consumption 7see ,tuberculosis7 ,container1 #afi ,cooking1 #cci ,cooper's ,ventilators1 #adi ,corrosive ,sublimate as ,disinfectant1 #cbg ,cotton1 #bgj ,cream1 #ae ,cyclones1 #bcb ,cysticercus ,cellulos1 #bc1 #bgi ,d ,d-,trap1 #afi ,damp1 ,cause of1 #baa ,damp-proof ,course1 #baj ,death-rate1 #b ,crude1 #cdj ,corrected1 #cdb ,zymotic1 #big1 #cdh ,decomposed ,meat1 #bd ,demography1 #cce ,density of ,population1 #cdc ,destructors1 #bjj ,dew ,point1 #bda ,diarrha1 ,epidemic1 #cjb ,diet1 #bi ,dietaries1 #cc ,diffusion1 #abi ,diphtheria1 #bbe1 #bih ,diseased ,animals1 ,meat of1 #bc ,disinfection1 #cbd ,distillation1 #id ,drainage1 #aff of ,soil1 #bbf ,drains1 #agg ,examination of1 #ahj ,drugs1 #ed ,dust in ,air1 #aje ,dust-bins1 #aii ,dyspepsia1 #bh1 #bdh ,e ,earth-closets1 #aie ,eggs1 #aa ,ellison's ,bricks1 #aea ,endemic ,diseases1 #bhi ,enteric ,fever1 #ia1 #bbd1 #cjj ,epidemic ,diarrha1 #bf1 #bbe1 #cjb ,epidemic ,diseases1 #bhi ,erysipelas1 #aaj1 #cje ,excreta1 #afe ,exercise1 #bdi ,expectation of ,life1 #cdf ,f ,farcy 7see ,glanders7 ,farr's ,formula1 #cdg ,fats1 #f ,favus1 #bgf ,fermented ,drinks1 #ee ,filaria1 #bgh ,filters1 #ig ,filtration1 #ie ,fire ,grates1 #aei ,fish1 #aa ,dangers of1 #bf ,flax1 #bgj ,fleas1 #bgg ,flesh ,food1 #i ,floors1 #bag ,flour1 #af ,flukes 7see ,trematoda7 ,fomites1 #bii ,food1 #d ,diseases due to1 #bc ,heat value of1 #cb ,preparation and ,preservation of1 #ch1 #dc ,relation of1 to ,mechanical ,work1 #cf ,variations from ,climate1 ,age1 c1 #bi ,vegetable and ,animal1 #ca ,forests and ,climate1 #bbi ,formalin41 #dd and ,formaldehyde as disinfectants1 #cbf ,fortin's ,barometer1 #bch ,fruits1 #ba ,fuel1 #afa ,fungi1 #bj ,g ,gaertner's ,bacillus1 #be ,galton's ,stove1 #aee ,gas ,stoves1 #aeg1 #afa ,gelatin1 #i ,gin1 #fc ,glanders1 #cjd ,glaisher's ,tables1 #bda ,glucose1 #ba ,gluten1 #ae ,gout1 #bh1 #ei ,goux ,system1 #aid ,graveyards1 ,air of1 #aah ,green ,vegetables1 #bj1 #db ,ground-water1 #bbb ,gully-trap1 #afg1 #ahj ,h ,habits1 #bdg ,haffkine's ,cholera ,vaccine1 #bbh ,hardness of ,water1 #gi1 #ij ,heat1 kinds of1 #aei ,hendon ,disease1 #bg ,heredity1 #bde ,hermite ,process1 #aia ,hopper-closets1 #agj ,hot ,water ,supplies1 #afc ,pipes1 #afb ,house ,construction1 #bji ,drainage1 #afe ,materials of ,construction of1 #bje ,position of1 #bja ,refuse1 #aih ,slops1 #afe ,humidity1 absolute and relative #bce ,measurement of1 #bdj ,hydatids1 #bgi ,hydrocarbons1 #f ,hydrophobia1 #cje ,hygrometers1 #aja1 #bdj ,i ,idiosyncrasy1 #bdf ,illuminants1 #aae ,immunity1 #bhg ,incubation ,periods1 #bhg ,infantile ,mortality1 #cdb ,infective ,diseases1 #bhd of ,animals1 #bd ,infectious ,diseases1 ,hospitals for1 #cbj ,notification of1 #cch ,influenza1 #cji ,insects and ,disease1 #bha ,intermittent ,downward ,filtration1 #aib ,iron in ,water1 #hc ,isobars1 #bca ,isolation1 #cai ,isothermal ,lines1 #bcj ,j ,jenner's ,discoveries1 #bic ,k ,koch's ,postulates1 #bhe ,l ,latrines1 #agd ,laveran1 #bhb ,lead in ,water1 #hb1 #ij ,workers in1 #ajh ,lice 7see ,pediculi7 ,liebig's ,extract of ,meat1 #aj ,life ,capital1 #cdg ,tables1 #cde ,linen1 #bgj ,lysol as ,disinfectant1 #cbg ,m ,macaroni1 #ag ,main ,sewers1 #ahc ,maize1 #ah ,malaria1 #ia1 #bbd1 #cjg ,mallein1 #cjd ,malt1 #ah1 #fb ,malted ,bread1 #ag ,margarine1 #ae ,mc,kinnell's ,ventilator1 #adi ,metabolism1 #f ,measles1 #big ,meat1 #i ,diseased1 #bd ,tinned1 #be ,parasites in1 #bc ,meat ,poisoning1 #be ,metchnikoff's ,theory1 #bhi ,meteorological ,observations1 #bcg ,metallo-keramic ,joint1 #agg ,miasm1 #bhe ,microbes 7see ,bacteria7 ,microscoporon ,audouini1 #bge ,milk1 #ab and ,disease1 #bf1 #bif1 #bii1 #cja ,boric ,acid in1 #dd ,souring of1 #bgd and ,tuberculosis1 #caa ,mineral ,waters1 #dg ,mortar1 #bjf ,mosquito1 #bhb1 #cjh ,moule's ,closet1 #aie ,mountain ,climate1 #bbh ,mutton1 #aj ,n ,natural ,ventilation1 #adg ,relative value1 #aed ,nematoda1 #bgh ,nitrogen1 #bgd ,nitrates in ,water1 #ha ,nitrification1 #aib1 #bbj ,nitrogenous ,foods1 #e ,notification of ,consumption1 #cad ,infectious ,diseases1 #cah1 #cch ,trade ,diseases1 #ccg ,o ,oatmeal1 #ag ,obesity1 #bh ,occupation and ,mortality1 #cdc ,offensive ,trades1 #abj ,oidium albicans1 #bge ,oils1 #df ,onion1 #bj ,over-feeding1 #bh ,oxygen in ,air1 #ajj ,oxygen ,absorbed1 #hf ,oxyuris1 #bgh ,oysters and ,disease1 #bia ,ozone1 #aja ,p ,pan-closets1 #afi ,pandemics1 #bhi ,parasites1 #bgf in ,meat1 #bc ,pasteur-,chamberland ,filter1 #ih ,pasteurization of ,milk1 #ac1 #cab ,pediculi1 #bgg ,personal ,hygiene1 #bde1 #beg1 #bfj ,pettenkofer's ,method1 #abf ,phagocytosis1 #bhg ,phosphorus1 in ,food1 #e ,workers with1 #ajh ,phthisis1 #bbe1 #caj ,piles1 #bdh ,plaster1 #bab ,plague1 #bha1 #cje ,pneumatic ,system1 ,liernur1 #ahc ,poisson's ,formula1 #cdi ,population1 ,density of1 #cdc ,estimation of1 #ccf ,pork1 #aa ,porter-,clarke ,process1 #ie ,portland ,cement1 #bjf ,potato1 #bj ,privy or ,midden ,system1 #aif ,proof ,spirit1 #fd ,proteids1 #e ,propulsion1 ,ventilation by1 #aec ,puerperal ,fever1 #cjf ,q ,quarantine1 #cbj ,r ,rabies 7see ,hydrophobia7 ,rainfall1 #bce ,rain ,gauge1 #bdb ,water1 #fg ,pipes1 #aff ,rats and ,plague1 #cjf ,registration of ,births and ,deaths1 #ccg ,relapsing ,fever1 #bh1 #cjj ,respiration1 #ajb1 #aac ,rest1 #beg ,rheumatic ,fever1 #bbe1 #cjf ,rickets1 #bh ,ringworm1 #bge ,rivers1 #gb ,roasting1 #ch ,roofs1 #bjh ,rum1 #fc ,rye1 #ah ,s ,saccharomycetes1 #bge ,sago1 #ai ,salts as ,food1 #g ,saprophytes1 #bhf ,scarlatina or ,scarlet ,fever1 #bif ,schools1 ,closure of1 #cbb ,scott ,moncrieff ,process1 #aib ,scrofula1 #caf ,scurvy1 #b1 #bg ,seasonal ,incidence of ,diseases1 #bhi ,sea ,relation to ,climate1 #bbi ,sebaceous ,glands1 #bfj ,semolina1 #ag ,septic-tank1 #aic ,sewage--,disposal of1 #aij ,dry and ,wet ,methods of ,removal of1 #aig ,sewers1 #ahc1 #ahd ,air of1 #aag ,problems as to flow in1 #ahg ,shell-fish and ,disease1 #bia ,sheringham's ,valve1 #aea ,shone ,system1 #ahf ,sinks1 #afg ,silk1 #bgj ,sleep1 #beh ,slop-closets1 #agd ,small-pox1 #b1 #bib ,smoke ,nuisance1 #afj ,test1 #aha ,soap1 #bfa ,soil1 #bai ,diseases in ,relation to1 #bbd ,drainage of1 #bbf ,soil-pipe1 #agd ,spices1 #df ,spirits1 #fc ,springs1 #fh ,starch1 ,detection of1 #ai ,starvation1 #bg ,statistical ,fallacies1 #cdi ,steam as ,disinfectant1 #cbi ,stoves1 #aeg1 #afa ,streets1 ,width of1 #bjc ,sugar1 #ba ,sulphuretted ,hydrogen1 #aab ,sulphurous ,acid 7,disinfectant71 #cbe ,summer ,diarrha1 #bbe ,sunshine ,recorders1 #bdc ,sweat ,glands1 #bfj ,sweating ,sickness1 #a ,sylvester's ,method1 #aej ,synoptic ,map1 #bca ,syphonic ,closet1 #agb ,t ,tannin1 #di ,tape-worms1 #bgi ,tapioca1 #ai ,tea1 #cj1 #dg ,temperature of ,rooms1 #aeh ,tetanus1 #cjd ,thermometers1 ,maximum and ,minimum1 #bci ,thermometers1 ,dry and ,wet ,bulb1 #bdj ,thrush1 #bge ,tight ,lacing1 #bfg ,tinea1 #bgf ,tobacco1 #ed ,tobin's ,tubes1 #aeb ,toxins1 #bhf ,trades and ,disease1 #ajg1 #aah ,offensive1 #abj ,traps1 #agi ,trematoda1 #bgg ,trichina ,spiralis1 #bc ,trichophyton1 #bge ,trough-closets1 #agd ,tuberculin ,test1 #caa ,tuberculosis1 #cji ,prevention of1 #cad ,tuberculous ,meat1 #bd ,typhoid ,fever 7see ,enteric ,fever7 ,typhus ,fever1 #cjj ,v ,v-shaped ,depressions1 #bcc ,vaccination1 #bic ,valve-closets1 #agj ,variola 7see ,small-pox7 ,veal1 #aj ,vegetables1 #bj ,ventilation1 #acb ,methods of1 #adf ,problems as to1 #acg ,by ,propulsion1 #aec ,ventilation by ,introduction of ,warmed ,air1 #aee ,of ,mines1 #aef ,of ,drains1 #agh ,vermicelli1 #ag ,vernier1 #bch ,vinegar1 #df ,vital ,statistics1 #cce ,w ,wall-paper1 #bad ,walls of ,house1 #baj ,wanklyn's ,ammonia ,process1 #hf ,warming of ,houses1 #aei ,wash-out and ,wash-down ,closets1 #agb ,waste-pipes1 #aff ,water1 #fe ,as food1 #h ,analysis of1 #hd ,classification of supplies of1 #gc ,constant and ,intermittent ,services1 #gf ,enteric ,fever and1 #gb ,hardness of1 #gi ,impurities of1 #gh1 #hi1 #ij ,sources of1 #ff ,storage and ,delivery of1 #gd in ,soil1 #bbb ,purification of1 #id ,water-closets1 #afh ,water-gas1 ,carburetted1 #aae ,water-test of ,drains1 #ahb ,weather ,forecasting1 #bcd ,weissman on ,heredity1 #bdf ,wells1 #fi ,whiskey1 #fc ,whooping ,cough1 #bih ,widal ,reaction1 #cja ,willich's ,formula1 #cdg ,windows1 #baf ,winds1 #aca1 #bcj1 #bdc ,wines1 #fb ,wool1 #bfi ,wool-sorters' ,disease1 #bgd ,work1 ,amount done1 #beb ,relation of ,food to1 #cf ,wort1 #fb ,writers' ,palsy1 #beb ,y ,yellow ,fever1 #cje ,z ,zygophyta1 #bge ,,footnotes3 ,footnote #a3 ,while the addition of animal fat like margarine raises the melting point1 rape-seed oil and other vegetable oils lower it4 ,footnote #b3 ,the fat to be analysed is saponified with soda or potash1 and then the fatty acid set free by hydrochloric acid4 ,if water be now added1 #aa or #ab per cent4 of the fatty acid will be dissolved1 if the fat is butter2 less than this if it is a mixture2 and not more than #e per cent4 if no butter is present in the fat4 ,footnote #c3 ,freshly made2 of which #a c4c4 #jjjja grm4 of ,n,o ,footnote #d3 ,made by dissolving #cie grm4 of ,k,mn,o in #a1jjj c4c4 of water4 ,each c4c4 of this solution #jjja grm4 of oxygen available for oxidation4 ,footnote #e3 ,caused by the liberation of iodine4 ,thus-- ,k,mn,o #h ,h,,so #aj ,,ki #f ,k,,so #b ,mn,s,o #h ,h,o #e ,i4 ,footnote #f3 ,of the strength of #a grm4 of crystalline sodium thiosulphate to #a litre of water4 ,footnote #g3 ,in practice one has frequently to be contented if the ,,co does not exceed #a part per #ajjj of air2 and if the room is clean and free from dust1 this higher limit may be accepted4 ,footnote #h3 ,the damp-proof course should have been shown close under the plate carrying the floor joists4 ,footnote #i3 ,some bacteria form in their interior minute spores1 by means of which they are able to resist ordinary destructive agents4 ,these spores again develope into bacteria4 ,footnote #aj3 ,furthermore1 it is stated that when at rest on a plane surface the ,culex assumes a position with the axis of the body more or less parallel to the surface2 while the ,anopheles1 under the same circumstances1 has the axis of its body more or less at right angles to the surface4 ,footnote #aa3 ,this is diphtheria attacking the larynx ,footnote #ab3 ,from 8,elements of ,vital ,statistics10 by ,a ,newsholme4 ,footnote #ac3 ,this was written before the figures for the period #ahia-aijj were available2 but the method adopted is the same1 substituting the death-rates1 etc41 for the later period4 ,footnote #ad3 ,the death-returns greatly understate the actual death-rate from this cause4 ,footnote #ae3 ,there is no general agreement as to the exact sense in which the words average and mean should be used4 ,they are used here interchangeably4