I ot Heollh, Education 3nd Welfare. Public Health Sei Bethesda, Md U S Deportment of Health, Education. and Welfare. Public Ht-olih Service DD.A,aS UI]03H 5i|qnd 'ajOjia/vx puo 'uonojnpg 'u,l|03n a: jo iu3ui|joda<] sf| £ pyy 'opsau^sg ■< 0 33IAJ35 U,I|03H I □ * Ln i ui NLM051307389 oicnw jo Aavaan tvnouvn 3Nioia3w do Aavaan ivnouvn o a. 3NOia3w jo Aavaan ivnouvn &JIONAI LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATI o THE ! THEOEY AND PEACTICE OF HYGIENE THE THEORY AND PRACTICE OF HYGIENE / l/Cv J. LANE NOTTER, M.A., M.D. (Dub.), FELLOW OK THE CHEMICAL SOCIETT; ■S'Blj'Eftw AND MEMBER OP COUNCIL OP THE SANITARY INSTITUTE OF GREAT BRITAIN ; HON. MEM. OF THE HUNGARIAN SOCIETY OF PUBLIC HEALTH; EXAMINER IN HYGIENE AND PUBLIC HEALTH IN THE UNIVERSITY OP CAMBRIDGE, AND IN THE VICTORIA UNIVERSITY, MANCHESTER; EXAMINER IN HYGIENE, SCIENCE AND ART DEPARTMENT ; PROFESSOR OF HYGIENE IN THE ARMY MEDICAL SCHOOL, NETLEY ; BRIGADE SURGEON LIEUT.-COLONJIL, ARMY MEDICAL STAFF. \ AND R. H. FIRTH, F.R.C.S., ASSISTANT EXAMINER IN HYOJBtfE, SCIENCE AND ART DEPARTMENT ; ASSISTANT PROFESSOR OF HYGIENE IN THE ARMY MEDICAL SCHOOL, NETLEY; SURGEON MAJOR, ARMY MEDICAL STAFF. PHILADELPHIA P. BLAKISTON, SON & CO. 1012 WALNUT STEEET 1896 WA pcUw#3/^^y *0'/ PREFACE. This volume is founded on the well-known work of the late Dr E. A. Parkes, subsequently enlarged and edited by the late Professor de Chaumont, and latterly re-edited by one of us. The law of progress, to which all science is subject, however, causes any work of a scientific nature to become out of date in a few years, and this applies in a special manner to the very large number of subjects embraced in and closely connected with Hygiene or Public Health. It will readily be conceded that perhaps nowhere has the extra- ordinary activity exhibited in all branches of knowledge during the last twenty years been more marked than in the domain of Sanitation and Preventive Medicine, and this has borne fruit not only in the modification of old ideas as to the causes of disease and methods for their prevention, but also in the introduction of more perfect methods of research and the elaboration of more complete safeguards for the maintenance of the public and individual health. On this account it was at one time deemed advisable to issue a new edition of " Parkes' Hygiene," but an examination of its general scheme of arrangement, combined with a somewhat extensive practical knowledge of the needs of students and others likely to use such a book, soon rendered it apparent that any attempt at mere revision or re-editing would be inadequate for the requirements of the times. We therefore determined to re-write the whole book, and to prepare a new work on the Theory and Practice of Hygiene, in which the historical portions of the original have been retained, but supple- mented by a full statement of our present-day knowledge of the subjects discussed, with accounts of the methods, appliances, and legislative enactments introduced of late years in the application of Science to the Prevention of Disease and the Preservation of Health. As regards the general range of subjects discussed, we have not departed greatly from traditional lines; while, in attempting to discuss each topic, we have endeavoured to explain it both theoreti- cally and practically, in the hope that the book may be found thereby vi PREFACE. useful not only to the sanitary official but also to the student of public health work. The subject of hygienic analysis is so intimately associated with the duties of the Medical Officer of Health, that special efforts have been made in the following pages to render the work in this respect a reliable guide for those who, while not being actually Public Analysts, are frequently called upon to express opinions necessitating an analyst's knowledge. In respect of special analytical methods, it has not been an easy task to decide as to what should be included and what omitted. In all cases'we have given only such processes as experience has indicated to us to be reliable and of practical use for the Medical Officer of Health. The analysis of water and air has necessarily been considered in some detail, not only from the chemical but also from the biological point of view; this latter aspect of the question has been so much developed during recent years as to constitute almost a distinct branch of study. In endeavouring to give explanations of methods for the bacteriological examination of water and air, we have adhered to the principle of advocating only such methods of research as come within the possibilities of the duties of a Medical Officer of Health, and which, in our hands, have been found to be practically useful. The subjects of Ventilation and Heating have been considered at some length, and advisedly so, because experience has indicated to us that these are matters usually imperfectly treated in the majority of text-books, and are subjects, too, upon which students and others are inadequately informed. The accounts of Scurvy and the dietetic value of Alcohol are given, with the exception of some minor verbal alterations, in much of the original language of Dr Parkes. Our knowledge upon these matters has been so little changed during recent years that it was felt that very little improvement could be made upon the original statements. Similarly, the chapters upon Exercise and Clothing have been but slightly altered by us. One matter of great difficulty has been the question of Sanitary Law. While fully recognising the importance of every sanitary officer studying the various legislative enactments bearing upon the Public Health in their original form, and the difficulties in the way of either making a legal chapter interesting or profitable reading, we have endeavoured, in the section which deals with sanitary legislation, to overcome these objections and to construct a chapter which may be not only interesting but useful. Special chapters have also been incorporated upon the subjects of PREFACE. yii Offensive Trades, Disinfection, and the Infective Diseases. The latter has necessarily been somewhat compressed, as the subject is so constantly changing as to be difficult to keep up to date. The general principle adopted in this chapter has been to give merely such an outline of the natural history of each disease as may be readily supplemented by the reader's collateral reading, combined with a brief statement of our present knowledge upon immunity and of the general principles of disease prevention. A chapter is devoted to the consideration of the life-history of Parasites; and for advice and much information on this subject we are indebted to Dr Patrick Manson. To him and to Mr Young J. Pentland we are indebted for the loan of photographic negatives and the use of drawings of certain parasites which illustrate the text. Considerable pains have been taken to render the chapter on Vital Statistics intelligible and useful to the sanitary officer, without at the same time overloading it with redundant matter. The increasing importance attached to vital statistics, and the greater accuracy of our national enumerations, demand a careful study of this subject by all engaged in public health work. We do not profess to have suc- ceeded in writing an exhaustive chapter on this subject, but hope that, if read in conjunction with special treatises and official reports, it may be found equal to the wants of the Medical Officer of Health and others. It is our regret that the delay in the publication of the Registrar General's Summary Report on the census of 1891 has pre- cluded the insertion of the most recent facts and figures respecting occupations; but we think their omission will not materially affect the value of the statement of the general principles of vital statistics herein given. We have, further, not been unmindful of the fact that much of the life-work of our predecessors, the late Drs Parkes and de Chaumont, was devoted to the amelioration of the sanitary conditions of soldiers and sailors, and that their writings, which admittedly form the nucleus of this volume, were primarily intended for the use of the sanitary advisers of the Army and Navy. Bearing this fact in mind, we have incorporated in this work special chapters dealing with the sanitary needs of both the Army and Navy, and have emphasised therein such points as are not in strict accordance with the conditions of civil life. It may be noticed that all foot-notes have been omitted in the following pages. In place of them, we have given at the end of each chapter a Bibliography and References to authors and others quoted ■in the text. It is not claimed that these bibliographies are in any viii PREFACE. way complete, but we hope that they may be found of material use to those desirous of referring to matters in their original form. Throughout the work we have steadily kept in view the importance of freely illustrating the text. To Dr Thresh and to Mr Casella we are indebted for several blocks. To Surgeon-Colonel L. A. Irving, A.M.S., we owe our thanks for the drawings from which Plate I. has been prepared; while to Dr S. Abbott of the Massachusetts State Board of Health we desire to express our acknowledgments for the loan of blocks used in the construction of Plate II. Many of the other illustrations have been drawn for us by Mrs Bruce and by Miss Triscott. It is not without some diffidence we offer this book to the public, as we are aware of its imperfections; but, at the same time, we are conscious of having spared no labour in endeavouring to bring it thoroughly up to date, in order to render it not only a mere text-book for those preparing for examinations in Hygiene, but also a compre- hensive and reliable work of reference and guidance for those engaged in the often difficult but always responsible duty of being the sanitary advisers to local authorities, as well as for those employed in naval and military duties. Woolston, Hants, January 1896. CONTENTS. CHAPTER I. WATER. Properties of water, . . . . . On the quantity and supply of water, Sources of water-supply, . Collection, storage, and distribution of water, Effects of an insufficient or impure supply of water, Purification of water,. Examination of water for hygienic purposes, Bacteriological examination of water, Bibliography and references,. . . . PAGE 1 3 8 15 28 45 52 92 118 CHAPTER II. AIR. The composition and physical properties of air, Impurities in air, .... Effects produced by impurities in air, Examination of air, .... Bibliography and references, . 122 129 148 167 178 CHAPTER III. VENTILATION AND HEATING. Quantity of air required for ventilation, .... Methods by which the necessary quantity of fresh air can be supplied, Methods of heating and cooling, . . Examination of the sufficiency of ventilation, Bibliography and references, ...-•• 181 188 216 238 244 CHAPTER IV. FOOD. Classification of the food-stuffs, The nutritive functions of the food-stuffs, . The nutritive value of the food-stuffs, Quantity of the food-stuffs requisite to preserve health, Diseases connected with food, Meat, ....••• Fish, ...-••• Egg*,....... Milk,...... 246 251 258 263 275 280 297 299 300 X CONTENTS. Food—continued. PAGE Examination of milk, ....... 308 Butter, 322 Cheese, 327 Wheat, 328 Bread, . 334 Examination of bread, 338 Biscuits, 340 Barley, 341 Eye, . 342 Oats, . 344 Eice, . 345 Maize, . 346 Millet and buckwheat, 346 Peas and beans, 347 Potatoes, 349 Arrowroots, tapioca, and sago, 351 Sugar, .... 355 Succulent vegetables and fruits, 356 Prepared concentrated and preserved foods, 357 Bibliography and references, ....... 364 CHAPTER V. BEVERAGES AND CONDIMENTS. Beer,....... .367 Examination of beer, .... 373 Wine, . . . . . 377 Examination of wine, 382 Spirits, ..... 384 The dietetic use of alcohol and alcoholic beverages, 387 Tea, ...... 394 Coffee, ...... 397 Paraguay tea, kola, and coca, . 401 Cocoa and chocolate, .... . 401 Lemon and lime juice, 402 Vinegar, . . . 404 Mustard, ..... . 406 Pepper, ..... . 407 Salt, ...... . 408 Bibliography and references, . : . 409 CHAPTER VI. CI ,OTHIE rG. Materials of clothing,.... Principles of selection and construction of clothing, Bibliography and references, . 410 416 418 CHAPTER VII. EXERCISE. The effects of exercise, Amount of exercise which should be taken, . Bibliography and references, . 419 427 431 CONTENTS. XI CHAPTER VIII. SOIL. The geological origin of soils, Soil features which influence climate and health, The comparison of different soils, Soil in relation to special diseases, The bacteriological examination of soil, The physical and chemical examination of soil, Bibliography and references, . PAGE 432 437 453 456 477 477 483 CHAPTER IX. HABITATIONS. General conditions of health, ....... 484 Sites, .... 486 Construction of dwellings, Artisans' dwellings, . Schools, 488 494 495 General hospitals, Non-infectious special hospitals, Infectious disease hospitals, . Bibliography and references, 498 506 506 510 CHAPTER X. DISPOSAL OF SEWAGE AND REFUSE. Composition of sewage, Removal of excreta by dry methods, Removal of excreta by water, Drains and sewers, Disposal and treatment of sewage, Modifications of wet methods of removing excreta, Comparison of different methods of removing excreta Bibliography and references, . 511 513 517 528 542 551 555 557 CHAPTER XL PARASITES. Classification of parasites, Blastomycetes, or yeasts, Hyphomycetes, or moulds, Protozoa, Insecta, Arachnida, Suctoria, Nematoda, Cestoda, Trematoda, Bibliography and references, 558 559 560 561 563 565 567 567 577 583 585 xii CONTENTS. CHAPTER XII. THE INFECTIVE DISEASES. Nature and origin of the infective diseases, Immunity and protection, Anthrax, Cerebro-spinal fever, Chicken-pox, Cholera, Dengue, Diarrhoea, Diphtheria, Dysentery, Enteric fever, Erysipelas, Glanders, Hydrophobia, Influenza, Leprosy, Malaria, Measles, Mumps, Plague, Pneumonia, Puerperal fever, Relapsing fever, Rotheln, Scarlet fever, . Small-pox, Tetanus, Tuberculosis, . Typhus fever, Whooping-cough, Yellow fever, . Bibliography and references, CHAPTER XIII. DISINFECTION. Disinfectants, antiseptics, and deodorants, Heat as a disinfectant, . Chemical disinfectants, Disinfection of clothing, bedding, and excreta, Disinfection of rooms, Disinfection of ships, Bibliography and references, . CHAPTER XIV. CLIMATE. General effects of climate, Influence of temperature on health, . Influence of atmospheric humidity on health, Influence of winds on health, Influence of atmospheric pressure on health, Acclimatisation, .... Classification of climates, Bibliography and references, . CONTENTS. xiii CHAPTER XV. METEOROLOGY. Temperature, how observed and calculated, Sunshine, Wind, Atmospheric electricity, Ozone,. Clouds, Humidity of the air, . Evaporation, . Rainfall, Atmospheric pressure, Bibliography and references, CHAPTER XVI. VITAL STATISTICS. Population, Marriage-rates, Birth-rates, Death-rates, Occupation in relation to mortality, Sickness-rates, Life-tables, their construction and interpretation, Statistical methods and tabulation of facts, Statistical series and averages, Bibliography and references, . CHAPTER XVII. OFFENSIVE TRADES. Keeping of animals, . Slaughtering of animals, Utilisation of blood, . Boiling of tripe, trotters, flesh, &c, Gut-cleaning, . Fat-melting and candle-making, Soap-making,. Bacon-curing, . . . Felt-mongering and leather-making, Glue-making, . Artificial-manure making, Oil-cloth and linoleum making, India-rubber making, Varnish-making and oil-boiling, Paper-making, . • Manufacture of alkalis, Other trades associated with the generation of irrespirable Trades associated with the use of poisonous metals,. Manufacture of horse-hair, .... Woolsorting, ...••• gases, XIV CONTENTS. CHAPTER XVIII. SANITARY LAW. Local sanitary areas and authorities, . Medical officers, surveyors, and inspectors of nuisances, Definitions, . Bye-laws and regulations, Sewerage and disposal of sewage, House drainage and removal of excreta from houses Cleansing and scavenging, Water-supply, Nuisances, .... Cellar dwellings, Common lodging-houses, Tenement houses, Housing of the working-classes, Unhealthy areas, Unhealthy dwelling-houses, . Lodgings for the working-classes, Canal boats, .... Movable dwellings other than canal boats, New streets and buildings, Offensive trades, Factories, workshops, and bakehouses, Alkali, chemical, and other works, . Slaughter-houses, Unsound food, Horseflesh, .... Adulteration of food, . Dairies, cowsheds, and milkshops, Parks, open places, and commons, Mortuaries and cemeteries, Baths and washhouses, Infectious diseases, Port sanitary authorities, PAGE 820 826 832 834 837 840 844 847 852 857 858 860 863 863 866 869 871 873 874 880 882 887 889 891 892 893 896 899 901 904 905 912 CHAPTER XIX. MILITARY HYGIENE. Selection of recruits, ..... Barracks at home and abroad, Huts, ....... Tents and Camps, ..... Military hospitals at home and abroad, Food of the soldier, ..... Clothing and equipment of the soldier, Work and duties of the soldier in relation to his health, Effects of military service, .... Vital statistics of the soldier,.... 916 918 931 933 938 944 953 962 968 970 CHAPTER XX. MARINE HYGIENE. Nature, extent, and sanitary regulation of the marine population, . . 979 The seaman or sailor, ........ 980 CONTENTS. XV Marine Hygiene—continued. The vessel or ship, Interior economy of ships, Ventilation of ships, . Heating and lighting of ships, Cleansing and disinfection of ships, Water-supply of ships, Food at sea, Disease, accident, and death at sea, Bibliography and references, . PAGE 981 984 991 996 997 998 999 1004 1010 APPENDICES. Appendix I.—Measures of length, ...... 1011 II.—Measures of area, ...... 1011 III.—Solid measures, ...... 1012 IV.—Measures of weight, ...... 1012 V.—Measures of capacity, ...... 1012 VI.—Table of factors for calculating equivalents of weight, volume, length, &c, ...... 1013 ,, VII.—Table showing the daily yield of water from a roof with varying rainfalls, . . . . . 1014 VIII.—The chemical symbols and atomic weights of elementary bodies, ....... 1014 „ IX.—Table showing the amount of oxygen capable of being dis- solved in distilled water, at varying temperatures, under standard pressure, ..... 1015 „ X.—The staining and microscopic examination of micro- organisms, ..%.... 1015 „ XI.—Preparation of ammonia-free distilled water, . . 1018 „ XII.—Statistical Tables A and B required by the Local Govern- ment Board to be appended to the Annual Reports of Medical Officers of Health, .... 1019 Index, ......... 1023 ERRATA. Page 78.—In the third and seventh lines of the Example given on this page, for 1 mgm. of oxygen read 0 8 mgm. of oxygen ; in the eighth line of the same example, for 0-2 mgm. read 0*16 mgm. in two places ; in the tenth line of the same example, for 0*08 part read 0'064 part. DIRECTIONS TO BINDER. Plate I. to face page 288. II. , , 400. III. , 506. IV. , , 508. v. , 510. VI. , 576. VII. 602. VIII. , 614. IX. , 622. X. , 636. THE THEORY AND PRACTICE OF HYGIENE. CHAPTER I. WATER. The supply of wholesome water in sufficient quantity is a fundamental sanitary necessity. Without it injury to health inevitably arises, either simply from deficiency of quantity, or more frequently from the presence of impurities. In all sanitary investigations, the question of the water- supply is one of the first points of inquiry, and of late years much evidence has been obtained of the frequency with which diseases are introduced by the agency of water. There are many industries that cannot be carried on without the use of tolerably pure and soft water, and it has also been found to be the most effectual and economic agent in the removal from our habitations of waste slops and sewage; but paramount to all these is the value of the sanitary results growing out of the maintenance of health and the inducement to cleanliness of person and habitation by the supply of an abundance of water delivered constantly to the householder. PROPERTIES OF WATEE. Water, long believed to be an element or simple substance, is now known to be a chemical compound, consisting of two volumes of hydrogen and one volume of oxygen, and is formed whenever hydrogen gas or a combustible substance containing hydrogen is burnt in oxygen or atmospheric air. At the ordinary temperature of the air it is a clear, transparent, tasteless, and odourless liquid; it appears colourless when seen in small quantities, but that it has a pale blue colour is apparent when a white object is viewed through a column about two feet in depth. At the temperature of 0° C. (32° F.) water becomes solid or freezes; during the act of freezing it expands nearly T]Tth of its volume, a fact which explains the reason why, during frosts, frozen pipes split or burst, and why damp soils and rocks tend to crack during frost. This disintegrating action of water upon rocks and soils is due to the expansive force exerted by water when it solidifies, and the ice formed is practically incompressible—hence the hardest rocks are split and broken up. This solid water or ice has a specific gravity of 0*9168 when compared with water at the same temper- ature, consequently ice always floats on the surface of the water, and, since the density of water is greatest at 4° C. (39°*2 F.), it follows that, when part ■of it is cooled below that point, the colder portion remains at the surface, A 2 WATEK. and when it reaches the freezing point, is then converted into ice, while the water just below remains a few degrees warmer, being protected by this crust of ice from the cooling currents of air. The density of water in the liquid state is about 770 times more than atmospheric air, this density being greatest at a temperature of 4° C. (39°-2 F.). The density of water is always taken as the standard of comparison in reference to which the densities of other solid and liquid substances are expressed. In this country the density of water at the temperature of 15°-5 C. (60° F.) is taken as unity, but on the Continent the tem- perature of its maximum density, namely 4° C. (39°'2 F.), is more usually adopted. The following table gives the weights of certain volumes of water in terms both of the metric system and of the system of weights and measures used in this country :— Grains. Cubic centi- _ . . . , metres at 4' Cent. Cub/^inS,hes as grammes. at bu *■ Pounds. Gallons at 60° .F. Cubic feet at 6 32-98 General average for London, 35-3G Liverpool, . .... 27 Manchester, 24 Edinburgh, 36 Glasgow, 52 Dublin, . 35 Paris, 53 Berlin, . 22 St Petersburg, 49 Rome, . 220 The average supply to 46 English towns in 1888 was 25 gallons per head, of which 20 gallons were for domestic purposes. In Warwick, by careful inspection as regards waste, it has been reduced from 22 to 15 gallons per head daily. The average amount in London for domestic use was 27*12, and in Manchester 15 gallons per head. By decision of the Secretary of State for War, each officer, man, and woman occupying quarters receives 20 gallons, and each child 10 gallons, daily. The gross amount thus taken is used for different purposes, which must now be considered. Amount required for Domestic Purposes (water-closets included).—For drinking purposes the amount varies with age, sex, weight, climate, and occupation; but it may be laid down as a rule that the total daily amount necessary is equal to about half an ounce for each pound weight of the body, or in other words, an adult takes in daily about 70 to 100 ounces (3-J- to 5 pints) of water for nutrition. Now of this water about one-fourth to one- third exists in the so-called solid food, that is, in the meat, bread, &c. and the remainder is taken in some form of liquid. There are, however 'wide ranges from the average. Women drink rather less than' men; children drink, of course, absolutely less, but more in proportion to their bulk than adults. For the cooking of food a certain amount is required, only part of which is actually consumed with the food. This will generally not be less in the case of adults than three-quarters of a gallon daily. Takin^ all sexes and all ages together, we may lay down the minimum necessary for drinkin« and cooking purposes as 1 gallon per head per diem. Parkes measured the water expended in several cases ; the following AMOUNT REQUIRED FOR DOMESTIC PURPOSES. 5 was the amount used by a man in the middle class, who may be taken as a fair type of a cleanly man belonging to a fairly clean household :__ Cooking, ... ... Fluids as drink (water, tea, coffee), .... Ablution, including a daily sponge-bath, which took 2^ to 3 gals., Share of utensil and house-washing, . . Share of clothes (laundry) washing, estimated, 12 These results are tolerably accordant with actual experiments, if we remember that with a large household there is economy of water in washing utensils and clothes, and that the number of wives and children in a regi- ment is not great. In poor families, who draw water from wells, the amount has been found to vary from 2 to 4 gallons per head, but then there was certainly not perfect cleanliness. Bateman states that, in a group of cottages with 82 inmates, the daily average amount was 7| gallons per head, and in another group 5 gallons per head. Letheby found in the poor houses in the city of London the amount to be 5 gallons. In experiments in model lodging- houses, Muir states that 7 gallons daily were used. Easton, in his own house in London, found he used about 12 gallons per head, of which about 5 were for closets, leaving 7 for other uses; but probably the laundry washing was not included. In the convict prison at Portsmouth, where there are water-closets, and each prisoner has a general bath once a week, the amount is 11 gallons. In several of the instances just referred to, it may be questioned whether the amount of cleanliness was equal to what would be expected in the higher ranks. In most instances quoted, no general baths were used ; but it is now becoming so common in England to have bath-rooms that they are often put even in eight-roomed houses. A general bath for an adult requires, with the smallest adult bath (i.e., only 4 feet long and 1 foot 9 inches wide), 38 gallons, and many baths will contain 50 to 60 gallons. A good shower-bath will deliver 3 to 6 gallons. General baths used only once a week will add 5 or 6 gallons per head to the daily con- sumption. We may safely estimate that for personal and domestic use, without baths, 12 gallons per head daily should be given as a usual minimum supply; and with baths and perfect cleanliness, 16 gallons should be allowed. This makes no allowance for water-closets or for unavoidable waste. If from want of supply the amount of water must be limited, 4 gallons daily per head for adults is probably the least amount which ought to be used, and in this case there could not be daily washing of the whole body, and there must be insufficient change of under- clothing. If public baths are used, the amount must be greatly increased. The largest baths the world has seen, those of Ancient Eome, demanded a supply of water so great as, according to Leslie's calculations, to raise the daily average per head to at least 300 gallons. Amount required for Water-Closets.—The old arrangements with cisterns allow any quantity of water to be poured down, and many engineers consider that the chief waste of water is owing to water-closets. In some districts, by attention to this point, the consumption has been Gallons daily per one person. •75 •33 5 3 3 6 WATER. greatly reduced. Small cisterns, termed water-waste preventers, are put up in towns with constant water-supply, which give only a certain limited amount each time the closet is used. The usual size now in use holds about 2 gallons; but even 2 gallons are insufficient to keep the pan and soil-pipe perfectly clean. A committee appointed by the Sanitary Institute to report on the quantity of Avater required to flush water-closets, after making a large number of experiments, recommended that the minimum quantity of flushing water should be fixed at 3 gallons, and that the maximum quantity should not be less than 3| gallons. Con- sidering also that some persons will use the closet twice daily and sometimes oftener, and that occasionally more Avater must be used for thoroughly flushing the pan and soil-pipe, 6 gallons a day per head should probably be allowed for closets. In this particular instance a false economy in the use of water is most undesirable. Water latrines require less ; the amount is not precisely known; the experiments of the Eoyal Engineers at Dublin give an average of 5 gallons per head, but it is considered that this might be reduced. In fixing the above quantities, viz., 12 gallons per head for all domestic purposes, except general baths and closets, 4 gallons additional for general baths, and 6 for Avater-closets, endeavours have been made to base them upon facts, and they are probably not much in error. It is, however, necessary to make some allowance for unavoidable waste within the premises, and for extra supply to closets, and it Avill be a moderate estimate to alloAV 3 gallons daily per head for this purpose. This will make 25 gallons. There is another reason for believing that an amount of about 25 gallons per head should pass from every house daily into sewers, if seAvers are used. It is that in most cases this quantity seems necessary to keep the seAvers perfectly clear, though in some cases, no doubt, Avith a Avell- arranged and constructed seAverage, a less amount may suffice. But the complete cleansing of seAvers is a matter of such fundamental importance, that it is necessary to take the safest course. Hitherto much Avater has run merely to Avaste. Amount required for Animals.—The Queen's Regulations fix the maximum daily supply for each horse in the army at 20 gallons. This amount includes that necessary for the washing of both horses and carriages, and seems ample. Of course the amount that horses drink varies as much as in the case of men, and depends on food, weather, and exertion; but if a horse is alloAved free access to water at all times, and this should be the case, he will drink on an average 6 to 10 gallons, and at times more. In the month of October, Avith cool weather, a horse 16 hands high, doing 8 miles a clay carriage work, and fed on corn and hay, Avas found to drink 1\ gallons. Another carriage horse drank nearly the same amount. In a stable of cavalry horses doing very little work, and at a cool time of the year, the amount per horse was found to be 6^ gallons. Taking a horse as weighing 1000 lb avoir., this is just an ounce of water per pound weight of horse. The amount used for washing Avas 3 gallons daily. In hot or dirty weather the quantity for both purposes Avould be larger. For washing a horse requires at least \\ gallons, and twice this amount if he is washed twice a day. There is a saving, hoAvever, if grooms wash several horses in the same Avater. It is difficult to say hoAv much is used for carriage Avashing. On the Avhole, including carriage Avashing, &c, 20 gallons per horse is not an excessive amount. A cow or an ox, on dry food, will drink 6 or 8 gallons; a sheep or pig, \ to 1 gallon. AMOUNTS REQUIRED FOR MUNICIPAL AND TRADE PURPOSES. 7 25 gallons. 10 „ 6 „ 5 „ 6 „ 5 In the Abyssinian expedition, the folloAving was the calculation for the daily expenditure of Avater per head on ship-board :— Elephants, Camels, Oxen (large draught), . Oxen (small pack animals), Horses, Mules and ponies, For 20 elephants and 100 men, 50,000 gallons were put on board for a voyage of 60 days. For camels on board ship 8 gallons, and on land 15 gallons are required per day (Wolseley). F. Smith found, from experi- ments in India, that a horse in the month of February consumed on an average 8| gallons daily ; this accords Avith Parkes's experiments at home ; of course in hot weather the amount Avould be greater. Amounts required for Municipal and Trade Purposes.—For municipal purposes Avater is taken for Avashing and Avatering streets, for fountains, for extinguishing fires, &c. The amount for these and for trade purposes will vary greatly. Bankine, Avho gives an average allowance of 10 gallons per head for domestic purposes, proposes 10 more for trade and town use in non-manufacturing toAvns, and another 10 gallons in manu- facturing towns. One ton of water (224 gallons or 35*9 cubic feet) is sufficient to lay the dust over a surface of 600 square yards of gravel or macadamised road, or 400 square yards of granite paved streets. The average number of days in which Avatering is required in England is 120. If, now, the total daily amount for all purposes be stated per head of population, it will be as folloAvs :— Gallons. Domestic supply (without baths or closets), .... 12 Add for general baths, ...... 4 Water-closets, ....... 6 Unavoidable waste, ....... 3 Total house supply, ..... Town and trade purposes, animals in non-manufacturing towns, Add for exceptional manufacturing towns, 25 5 5 35 In India and hot countries generally, the amounts now laid doAvn would have to be altered. Much more must be allowed for bathing and for wash- ing generally, while a fresh demand would arise for water to cool mats, punkahs, or air-passages by evaporation. In Calcutta the supply for a population of 433,219 is 37 gallons of filtered, and 5-8 unfiltered Avater, in all 42-8 gallons per head per day. In Madras, in 1887, the consumption was about 18 gallons, and in 1888 about 16 gallons daily per head, the supply being somewhat restricted. Amount required for Hospitals.—In hospitals a much larger quantity must be provided, as there is so much more washing and bathing. From 40 to 50 gallons per head are often used. There are no good experiments as to the items of the consumption, but the following is probably near the truth:— Gallons daily. For drinking and cooking, washing kitchen and utensils, . 2 to 4 For personal washing and general baths, For laundry washing, Washing hospital, utensils, &c. Water-closets, 18 ,; 5,: 3,: 10,, 20 6 15 38 to 51 8 WATER. It Avould be very desirable to have more precise data; possibly the amount for closets is put too high, but not greatly so Avhen all cases are taken into account. At Netley the amount per head per diem is put approximatively at 70 gallons. At Haslar the quantity is the same. At the Cambridge Hospital, Aldershot, the average is 90; Herbert Hospital, Woolwich, 89. These amounts include that used by the hospital attendants and medical staff. In some of the Metropolitan hospitals there is singular diversity in the quantities: University College Hospital, 58 gallons per head; St Thomas's, no less than 106; St Bartholomew's, 57 gallons; whereas at Guy's, Avhere special care is taken to check unnecessary waste, only 35 gallons are used, including Avhat is taken by the resident medical staff. There is no doubt that a considerable quantity of Avater is wasted, and economy might be effected Avithout any detriment to sanitary requirements. In some places it has been found that when the Avater-supply Avas 30 gallons, the actual amount used in the houses was not more than 20 gallons, and in some cases even less. By introducing proper Avaste-detectors economy of water might be accomplished, Avhile the full amount for hygienic requirements might still be given to the consumer. SOURCES OF WATER-SUPPLY. The constant evaporation Avhich takes place from the surface of all masses of water exposed to the atmosphere, the diffusion of Avater-vapour throughout the atmosphere, and its subsequent condensation there to the liquid or solid state, give rise to the incessant circulation of water which is continually taking place. Of this condensed atmospheric vapour, falling on the surface of the various continents and islands, part penetrates into the soil until it reaches a less permeable stratum, above which it accumulates; part flows away and becomes the source of the great rivers and lakes, some is absorbed by the soil itself, while the remainder passes off in vapour to be again condensed. The sources of water-supply are very varied; each class has its own peculiar characteristics, but all are derived from the same source and descend to us in the form of rain, dew, mist, hail and snow. Eain-Water approaches nearer to absolute purity than any other kind of natural water. When collected in clean vessels it contains only such dissolved substances as it can take up from the atmosphere. As it falls through the air it becomes highly aerated, the amount of contained gas averaging 25 c.c. per litre. The ratio of the oxygen to the nitrogen by volume in this gas is greater than in atmospheric air on account of the greater solubihty of oxygen in water. The Rivers Pollution Commissioners in their sixth report (1874) give the following as the gaseous constituents of rain-Avater:— c.c. per litre. Nitrogen, . . . . . . . . 13.08 Oxygen, ........ 6'37 Carbon dioxide, . . . . . . p j-28 Total gases, . . . . . . , 2073 In its passage through the air rain-Avater carries doAvn ammoniacal salts (carbonate, nitrite, and nitrate), • and nitrous and nitric acids in small amount. The total quantity of nitrogen in ammoniacal salts, nitrous and nitric acid, is 0-0985 part per 100,000. Frankland puts the average at 0*032. RAIN-WATER. 9 At Montsouris, mean of seA-en years, the ammonia amounted to 0*193 per 100,000; mean of all Paris (1881-82), 0-287 per 100,000; the nitric acid (N03), mean of six years, to 0*354 per 100,000. This gives a total nitrogen, from ammonia and nitric acid, of 0'239 per 100,000. The amount is greater just after the commencement of rain than Avhen it has continued for a long time. In toAvns with coal-fires it takes up sulphurous and sulphuric acids, and sometimes hydrogen sulphide. The sulphates in rain increase, according to Angus Smith, as Ave pass inland, and before large towns are reached; they are, according to this author, "the measure of the seAvage in air" Avhen the sulphur derived from the combustion of coal can be excluded, but in this country the exclusion could never be made. Free acids are not found with certainty Avhen combustion and manufactures are not the cause. The acidity taken as sulphuric anhydride (S03) was equal to 0*014 part per 100,000 of rain in a country place in Scotland, and 1*513 in Glasgow; in Manchester in 1870 it Avas 1*202 ; and in London 0*387. The nitric acid in Glasgow was as much as 0*244 part per 100,000, and in London only 0*0884. Albuminoid ammonia Avas no less than 0*0326 part per 100,000 in London rain. Rain also carries doAvn many solid substances, as sodium chloride, in sea air; calcium carbonate, sulphate, and phosphate; ferric oxide; carbon. In the following table are recorded the maximum, minimum, and average1 proportions of each of the several ingredients determined in seventy-one samples of rain, collected in a special rain-gauge (Rivers Pollution Com- mission) :— Total Solid Organic Organic Nitrogen as Hardness. Impurity. Carbon. Nitrogen. Nitrites. Minimum, 0-62 0-021 0-003 0-005 0 0 0 Maximum, 8-58 0-375 0-121 0-155 0-044 1-65 1-7 Average, 3*42 0-095 0-021 0-049 0-007 0-33 0-5 Rain - water from Land's End, 42-80 0-131 0-034 0 0-020 21-80 io-o Rain - water from Hyde Park, London, 2-76 0-385 0-040 0-210 0-008 0-008 1-1 It is thus seen that the composition of rain-water, even in the open country, is liable to very great fluctuations, and that the amount of impurity, both mineral and organic, is occasionally large. Sometimes microscopic plants of the lowest order (as Protococcu* pluviali* and others) are present, and in toAvns the debris arising from street dust. The uncertainty of the rainfall from year to year, the length of the dry season in many countries, and the large size of the reservoirs which are then required, are disadvantages. On the other hand, its general purity and its great aeration make it both healthy and pleasant. The greatest benefits have resulted in many cases from the use of rain instead of spring or well Avater, Avliich is often largely impregnated with earthy salts. In all places Avhere the spring or well water is bad, rain-water should be sub- stituted. So also it has been suggested that in outbreaks of cholera any- Avhere, the rain-Avater is less likely to become contaminated Avith sewage matters than wells or springs, into Avliich organic matters often find their way in an unaccountable manner. Rain-water is very soft, oAving to the absence of salts of lime and magnesia; 10 WATER. it is therefore good for Avashing or cooking purposes, although it is less palatable than other kinds for drinking. Ice and Snow Water.—In freezing, Avater becomes purer, losing a large portion of its saline contents. Even calcium carbonate and sulphate are partially got rid of. The air is at the same time expelled. Ice-water may thus be tolerably pure, but heavy and non-aerated. Snow-water contains the salts of rain-water, Avith the exception of rather less ammonia. The amounts of carbonic acid and air are very small. An analysis of the ice supplies made by the State Board of Health of Massachusetts showed that, taking an average of all the samples examined, the organic impurities of siioav ice, as measured by the ammonias, amounted to 69 per cent, of those of the Avater; that the organic impurities of all the ice, except the snow ice, amounted to 12 per cent., and that clear ice gave only 6 per cent, of the impurities of the Avaters. The salt the Avaters con- tained Avas nearly all removed by the act of freezing. There were 81 per cent, as many bacteria in the siioav ice as in the Avaters; 10 per cent, as many in all other ice, and 2 per cent, as many in the clear ice as in the waters. It is therefore much safer to use for drink- ing water, and for placing in contact with food, that portion of the ice which is clear. Upland Surface Water.—This, of the various kinds of Avater, most nearly approaches rain-Avater. The dissolved solid matters are larger, their amount and nature depending on the kind of soil over which the water rests, and consequently it is usual to subdivide this class according to the geological character of the ground from Avhich the upland surface Avater is obtained. These waters do not contain any considerable amount of dissolved matters, except they are derived from calcareous strata; the organic substances present are chiefly of vegetable and not of animal origin. There is also an absence of ammonia, nitrates and nitrites beyond that in which they occur in rain-Avater. The chlorine is also Ioav and the Avater soft. These upland surface waters are not only valued because of their safety for drinking, but also on account of their fitness for trade purposes. Spring and Well Water.—The rain falling on the ground partly evapor- ates, partly runs off, and partly sinks in. The relative amounts vary with the configuration and density of the ground, and Avith the circumstances imped- ing or favouring evaporation, such as temperature, movement of air, &c. In the magnesian limestone districts, about 20 per cent, penetrates; in the New Red Sandstone (Triassic), 25 per cent.; in the chalk, 42 ; in the loose Tertiary sand, 90 to 96. Evans, from tAventy-nine years' observations in the chalk at Hemel-Hempstead, gives the Avinter average at 60-8 per cent., the summer at 15*5 per cent., and the Avhole year 37*5 per cent. Penetrating into the ground, the Avater absorbs a large proportion of car- bonic acid from the air in the interstices of the soil, Avhich is much richer (250 times) in CO, than the air above. It then passes more or less deeply into the earth, and dissolves everything it meets Avith Avhich can be taken up in the time, at the temperature, and by the aid of carbonic acid. In some sandy soils there is a deficiency of CO,, and then the Avater is also Avanting in this gas, and is not fresh and sparkling. The chemical changes and decompositions Avhich occur in the soil by the action of CO,, and Avhich are probably influenced by diffusion, and perhaps by pressure, as Avell as by temperature, are extremely curious, but cannot be entered upon here. The most common and simple are the solution of calcium carbonate, and the decomposition of calcium and sodium silicate by carbonic acid, or alkaline carbonates. Salts of ammonia, also, when they SPRING AND WELL-WATER. 11 exist, appear from Dietrich's observations to have a considerable dissolving effect on the silicates. Spring-water is almost always clear and bright, in consequence of the great degree of filtration Avhich it naturally undergoes in percolating through the strata Avhich it may have traversed between the gathering ground from which it has penetrated and the point at Avhichit issues again from the earth. For the same reason it is generally cool, unless coming from a depth much above 200 feet; and by reason of the gas it contains, it is sparkling and brisk to the taste. The temperature of the Avater varies, and is chiefly regulated by the depth. The temperature of shalloAV springs alters with the season; that of deeper springs is often that of the yearly mean. In very deep springs, or in some Artesian Avells, the temperature of the Avater is high. Wells are of different kinds—shallow Avells, deep Avells, and Artesian Avells. A well of 50 feet in depth, or less, is generally regarded as a shalloAV Avell; one of 100 feet or more, as a deep Avell. Artesian wells (so called from having been first sunk in the province of Artois in France) are gener- ally of great depth, passing through an upper impermeable stratum, e.g., clay, and penetrating a Avater-bearing stratum, Avhich crops up elsewhere at some higher point, and below Avhich is another impermeable stratum. Ordinary Avells are sometimes supplemented by borings to increase the supply. ShalloAV wells may be contaminated Avith any impurities at or near the surface of the ground, and the Avater from such wells is always to be regarded Avith suspicion. Even when the organic matter is only small in amount, it is generally highly nitrogenous, pointing to its probable animal origin, and in some exceptional cases the organic nitrogen found is actually in excess of the carbon. Deep wells are generally good sources of supply. The great efficiency of the filtration which most of these deep-Avell waters have undergone is attested by their entire freedom from organic matter, and by their almost absolute freedom from every kind of suspended material whether organic or inorganic. Deep-Avell Avaters are, as regards organic matter, amongst the purest to be found in nature, and unless extremely hard, they are of the best for drinking purposes. In shalloAV Avells (10 to 50 feet deep) the soakage Avater from the ground in loose soils of chalk and sand is often very impure. Thus in a town the well-water often shows evidence of nitrites, nitrates, ammonia, and chlorine far in excess of river-water in the neighbourhood, though the strata are the same. Occasionally, by constant passage of the water, a channel is formed, which may suddenly discharge into the Avell; and probably some ■of the cases of sudden poisoning from water have thus arisen. A Avell drains an extent of ground about it nearly in the shape of an inverted cone. The area must depend on the soil; but the experiments at Grenelle and Passy show that the radius of the area drained is equal to four times the depth at least, and that it often exceeds this. Dupuit shows that the curve of the subterranean Avater level rises suddenly near the Avell, and becomes flatter and flatter as it extends under the ground surface, the dis- tance to Avhich it reaches depending upon the loAvering of the level of Avater in the Avell. Thus a shallow well heavily pumped may drain an area Avider than a deeper Avell under moderate pumping. The distance to Avhich the influence of pumping extends is very variable, ranging from 15 to 160 times the depression of the Avater in the well. It is this depression of water in the Avell, that is, the quantity of Avater taken out, that determines the 12 WATER. drainage area, rather than the mere depth of the Avell. Ansted states that the deepest (non-Artesian) Avell will not drain a cone which is more than half a mile in radius. A well which yields a moderate quantity of good water may, if the de- mand on it be increased, draAv in Avater from the surrounding parts to meet the supply, and thus tap sources of impurity Avhich a moderate demand left untouched. A sudden rise in the ground water may also lead to direct communication betAveen a cesspool and a well, by the water tapping the former in its floAv. In some cases a well at a loAver level may receive the drainage of surround- ing hills floAving down to it from great distances. Good coping stones, so as to protect from surface Avashings, and good masonry for several feet below the surface of wells in very loose soils, so as to prevent superficial soakage, are necessary in all shalloAV wells. River-Water.—Fed from a variety of sources, river-Avater is even more complex in its constitution than spring-water; it is also more influenced by the season, and by circumstances connected Avith season, such as the melting of snow or ice, rains and floods, &c. The water taken on opposite sides of the same river has been found to differ slightly in composition. Leffman and Beam state that by admixture of the waters from widely- separated districts, the character and amount of the dissolved matters are much modified, and give the folloAving as an example. The Schuylkill River rises in the anthracite coal region of Pennsylvania, and receiving much refuse mine Avater becomes impregnated with iron salts and free mineral acid, Avhich render it quite unsuitable for drinking or manufacturing pur- poses. In its course of about 100 miles it passes over an extensive lime- stone district, and receives several large streams highly charged with calcium carbonate. The result is a neutralisation of the acid, and a precipitation of the iron and much of the calcium. The river becomes purer, and at its junction with the Delaware at Philadelphia it contains neither free sulphuric nor hydrochloric acid, only traces of iron, and but a small amount of CaS04. Thus there is produced a soft water, superior to that of the river near its source, and to the hard waters of the middle Schuylkill region. The dissolved solids in river-water vary less than in spring-water: they rarely exceed 30 to 40 parts per 100,000. Sometimes the water is almost as pure as rain-water. The amount of dissolved organic substances is gener- ally much greater than in spring-water. This is due to the surface drainage being discharged into the rivers. River-Avater is generally good and palat- able, unless sewage or other impurities are allowed to get into it. The general result of solution and decomposition is, that the water of springs and rivers often contains a great number of constituents—some in very small, others in great amount. Some Avaters are so highly charged as to be termed mineral waters, and to be unfit for drinking, except as medi- cines. The impurities of water are not so much influenced by the depth of the spring as by the strata it passes through. The water of a surface spring, or of the deepest Artesian well, may be pure or impure. The substances which are contained in spring, river, and well waters are noted more fully under the head of " examination of watbb." There may be suspended matters, mineral, vegetable, or animal; dissolved gases, viz.,. nitrogen, oxygen, carbon dioxide, and in some cases hydrogen sulphide and carburetted hydrogen; and dissolved solid matters, consisting of lime, mag- nesia, soda, potash, ammonia, iron, alumina, combined Avith chlorine, and sulphuric, carbonic, phosphoric, nitric, nitrous, and silicic acids. Less fr<- RIVER-WATER—SEA-WATER. 13 quently, or in special cases, certain metals, as arsenic, manganese, lead, zinc, and copper, may be present. The mode of combination of these substances is as yet uncertain; it may be that the acids and bases are equally distributed among each other, or some other modes of combination may be in play. The mode of combina- tion may usually be assumed to be as follows. Each separate substance being determined, the chlorine is combined Avith sodium; if there is an excess it is combined Avith potassium or calcium; if there is an excess of sodium, it is combined with sulphuric acid, or if still in excess, with car- bonic acid. Lime is combined Avith excess of chlorine, or sulphuric acid, or if there be no sulphuric acid, or an excess of lime, with carbonic acid. Magnesia is combined with carbonic acid. So that the most usual combina- tions are sodium chloride, sodium sulphate, sodium carbonate, calcium carbonate (held in solution by carbonic acid), calcium sulphate, calcium chloride and silicate, and magnesium carbonate; but the results of the analysis may render other combinations necessary. Distilled Water.—Distilled water is now largely used, and affords an easy Avay of getting good water. It is the most effectual mode of freeing water from all its impurities. On board ships distillation of sea-water is resorted to in order to render salt water fit for drinking, and although the water thus obtained is pure, yet all the gases having been driven from it by the boiling, it is unpalatable, and by some supposed to be indigestible. It may be aerated by allowing it to trickle sloAvly doAvn through a long column of wood charcoal, or by filtration through animal charcoal or other porous substance. Distilled water is also employed for the manufacture of aerated waters, and for artificial ice. Care should be taken that no lead, zinc, or copper finds its way into the distilled water. Many cases of lead poisoning have occurred on board ships, partly from the use of minium in the apparatus, and partly from the use of zinc pipe* containing lead in their composition. If possible, block tin should always be used. Sea-Water. —While the ocean is constantly receiving waters more or less impure, it is at the same time losing pure Avater in the form of vapour, the mineral salts remaining behind, and imparting to it its saline character. The composition of sea-Avater varies considerably in different places and at different depths. Thus in the vicinity of the poles, the proportion of salt is less than at the equator, Avhilst parts of the Mediterranean are more salt than the great oceans. The average composition of sea-water is given in the following table (Frankland, E.) :— Parts per 100,000. Source. ! Total | Organic Organic Nitrogen. Ammonia. Nitrogen as Nitrites and Nitrates. Total Combined Nitrogen. Chlorine. Hardness. 1 I Total. Fixed. Hastings, two miles from the shore, . 1 3955 1 0-291 0-135 0-005 0-013 0-152 2050 698 646 Comparative Value of the Various Sources of Water-Supply. - This depends on many circumstances. Spring-water is both pure and impure in different cases; and the mere fact of its being a spring is not, as 14 WATER. sometimes imagined, a test of goodness. Frequently, indeed, river-Avater is purer than spring-Avater, especially from the deposit of calcium carbonate ; organic matter is, however, generally in greater quantity, as so much more vegetable matter and animal excreta find their Avay into it. The Avater of a river may have a very different constitution from that of the springs near its banks. A good example is given by the Ouse at York; the Avater of this river is derived chiefly from the millstone grit, Avhich feeds the SAvale, the Ure, and the Nid, tributaries of the Ouse; the Avater contains only 13 parts per 100,000 of salts of calcium, magnesium, sodium, and a little iron. The Avells in the neighbourhood pass down into the soft red sandstone (Yoredale series) which lies below the millstone grit; the Avater contains as much as 92\8 parts, and even, in one case, 137 parts per 100,000 of total solids; in addition to the usual salts there is much calcium chloride, and calcium, sodium, and magnesium nitrates. Shallow-well water is ahvays to be viewed Avith suspicion; it is the natural point to which the drainage of a good deal of surrounding land tends, and heavy rains will often wash many substances into it. Instances are recorded where good and bad water Avas obtained from different levels in the same Avell. The following tables are given by the Rivers Pollution Commissioners :— 1. In respect of Avholesomeness, palatability, and general fitness for drink- ing and cooking:— f 1. Sprine-Avater, . .1 1 , ,. Wholesome J 2. Deep-well water, . [very palatable. I 3. Upland surface water, 1 , , , . , .. Suspicious / 4- Stored rain-water, . | moderately palatable. ™ \ 5. Surface water from cultivated land, . . ^| Dan o ) 6. River-water, to which sewage gains access, . \ palatable. ° ( 7. Shallow-well water,.....J 2. Classified according to softness Avith regard to washing, &c.:— 1. Rain-water. 2. Upland surface water. 3. Surface water from cultivated land. 4. Polluted river Avaters. 5. Spring-water. 6. Deep-well water. 7. Shallow-well water. 3. As regards the influence of geological formation in rendering the water sparkling, colourless, palatable, and wholesome. The following Avater- bearing strata are the most efficient:— 1. Chalk. 2. Oolite. 3. Greensand. 4. Hastings Sand. 5. New Red and Conglomerate Sandstone. Classification of Drinking Waters.—The general characters of good Avater are easily enumerated. Perfect clearness; freedom from odour or taste; coolness; good aeration; and a certain degree of softness, so that cooking operations, and especially of vegetables, can be properly performed, are obvious properties. But when we attempt a more complete description' and assign the amounts of the dissolved matters which it is desirable should not be exceeded, we find considerable difference of opinion, and also a real want of evidence on Avhich to base a satisfactory judgment. Still a hygienic classification or enumeration of potable Avaters, based on COLLECTION OF AVATER. 15 such facts as are generally admitted, will be useful. A division of waters used for drinking into four classes has been adopted in this work :— 1. Pure and Avholesome Avater. 2. Usable 3. Suspicious ,, 4. Impure ,, The waters belonging to the first and second class are generally obtained from upland surface supplies or from spring and deep-Avell Avaters. Upland surface waters may at times receive surface contamination, and it is desirable that such waters should be carefully filtered through sand before delivery. Spring and deep-well Avater undergoes almost perfect filtration in passing through the porous strata of the earth's crust and is a very pure supply. Those of the third and fourth class are usually obtained from rivers and shallow Avells, upon both of Avhich a large portion of the population is dependent for their supply. The danger in the case of both these classes of water lies in the facility with Avhich seAvage matters can gain access to them. When no better source is procurable, every effort must be made to exclude all avoidable sources of contamination and to filter the Avater through sand before distribution. COLLECTION, STORAGE AND DISTRIBUTION OF WATER. Collection of Water.-—In many cases collections of water occur naturally in depressions of the ground surface, or by the commingling of small streams forming rivers. The collection by artificial means consists almost entirely in imitating these natural processes, and in directing to, and finally arrestino- at some point, the rain or the streamlets formed by the rain. The arrange- ments necessarily differ in each case. Rain-A\-ater is collected from roofs, or occasionally from pavements and flags, or cemented ground; in hilly countries, Avith deep ravines, a reservoir is sometimes formed by carrying a Avail across a valley which is well placed for receiving the tributary Avaters of the adjacent hills, or on a flatter surface trenches may be arranged, lead- ing finally to an excavated tank. The collection of the surface water which has not penetrated is usually aimed at, but it was proposed by Bailey-Denton to collect the subsoil Avater by drainage pipes, and thus to accomplish two objects—to dry the land, and to use the Avater taken out of it. Below the surface the Avater is collected by wells—shalloAV, deep, and Artesian—or by boring. Rain.—The amount of Avater given by rain can be easily calculated, if tAvo points are knoAvn, viz., the amount of rainfall and the area of the receiving surface. The rainfall can only be determined by a rain-gauge (the mode of constructing which is given in the chapter on Meteorology) ; the area of the receiving surface must be measured. The following formula is the one generally used :— Area in square feet x 144 x rainfall in inches ,. r , --------*---------^------------------= cubic feet: Cubic feet x 6 "23 = gallons. Cubic inches x -003607=gallons. The calculation may be much simplified by multiplying the area of receiv- ing surface in square feet by half the rainfall in inches, the result is in gallons; here the error is only about 4 per cent. 16 WATER. To calculate the receiving surface of the roof of a house, we must not take into account the slope of the roof, but merely ascertain the area of the flat space actually covered by the roof. The joint areas of the ground-floor rooms Avill be something less than the area of the roof, Avhich also covers the thickness of the Avails and the eaves. In most English towns the amount of roof space for each person cannot be estimated higher than 60 square feet, and in some poor districts is much less. Taking the rainfall in all England at 30 inches, and assuming that all is saved, and that there is no loss from evaporation, the receiving surface for each person Avould give 935 gallons, or 2J gallons a day. But as few toAvn houses have any reservoirs, this quantity runs in great part to waste in urban districts. In the country it is an important source of supply, being stored in cisterns or Avater-butts. If, instead of the roof of a house, the receiving sur- face be a piece of land, the amount may be calculated in the same Avay. It must be understood, however, that this is the total amount reaching the ground; all of this Avill not be available; some Avill sink into the ground, and some Avill evaporate; the quantity lost in this Avay will vary with the soil and the season from the one-half to seven-eighths. (See Appendix.) The proportion borne by the available to the total rainfall varies very much, being affected by rapidity of the rainfall and the compactness or porosity of the soil, the steepness or flatness of the ground, the nature and quantity of the vegetation upon it, the temperature and moisture of the air, the existence of artificial drains, and other circumstances. The folloAving are examples :— Nature of ground and available proportion of total rainfall:— Steep surfaces of granite, gneiss, and slate, nearly ... 1 Moorland and hilly pasture, from . . . . . . 0 "8 to 0*6 Flat cultivated country, from . . . . . . . 0'5 to 0"4 Chalk,........... 0 One inch of rain delivers 4-673 gallons on every square yard, or 22,617 gallons (101 tons by weight) on each square acre. Inches of rainfall x 14,1 — millions of gallons per square mile. In estimating the annual yield of Avater from rainfall, and. the yield at any one time, we ought to know the greatest annual rainfall, the least, the average, the period of the year Avhen it falls, and the length of the rainless season. Hawksley states that the average of tAventy years, less one-third, gives very accurately the amount of rain in the driest year, and the same average, plus one-third, gives very nearly the amount in the wettest year. The average of the three driest years in twenty is a safe basis. It may be assumed that on the average -^ths of the rainfall is available for storage. It must also be remembered that the amount of rainfall differs very greatly even in places near together. Springs and Rivers.—It will often be a matter of great importance to determine the yield of springs and small rivers, as a body of men may have to be placed for some time in a particular spot, and no engineering opinion perhaps, can be obtained. A spring is measured most easily by receiving the Avater into a vessel of known capacity, and timing the rate of filling. The spring should be opened up if necessary, and the vessel should be of large size. The vessel may be measured either by filling it first by means of a knoAvn (pint or gallon) measure, or by gauging it. If it be round or square, its capacity can be at once known, by measuring it, and using the rules laid down in the chapter for measuring the cubic amount of air in rooms. The capacity of the vessel MEASUREMENT OF DISCHARGE OF WATER. 17 in cubic feet may be brought into gallons, if desirable, by multiplying by 6*23. If a tub or cask only be procurable, and if there is no pint or gallon measure at hand, the following rule may be useful:—Find the middle diameter, that is the diameter midway betAveen the bung and the head, and call it M; head diameter H; bung diameter B; length of cask L; then (H2 + B2 + 4M2) x L x 0*0004721 will give the contents in gallons. When it is required to ascertain the yield of any small Avater-course Avith some nicety, it is the practice of engineers to dam up the Avhole stream, and convey the water by some artificial channel of known dimensions. For this purpose one of the folloAving methods may be employed. 1. A wooden trough of a certain length, in Avhich the depth of water and the time Avhich a float takes to pass from one end to the other is measured. 2. A sluice of knoAvn size, in which the difference of level of the Avater above and below the sluice is measured. The discharge of water through a sluice may be found by multiplying the breadth of the opening by the height; this gives the area of the sluice. The discharge equals the area multiplied by five times the square root of the head of water in feet. The head of Avater is the difference of level of the water above and below the dam if the sluice be entirely under the loAver level; or the height of the upper level above the centre of the open- ing, if the sluice be above the loAver level. 3. A weir formed by a plank set on edge in Avhich a rectangular notch is cut, usually 1 foot in Avidth; over this the Avater Aoavs in a thin sheet, and the difference of level is measured by the depth of the water as it Aoavs over the notch. Then by means of a table the amount of Avater delivered per minute is read off. The Aveir must be formed of very thin board and be perfectly level; a plumb-line has generally to be used. If the weir is more or less than a foot, multiply the quantity in the table opposite the given depth by the length of the weir in feet, or decimals of a foot. Thus if the weir measure 1 foot, and the depth of Avater falling over be 2 inches, the delivery is read at once, viz., 13*63 cubic feet, or 84*9 gallons per ininute. Depth falling Discharge per Depth falling Discharge per over, inches. minute. over, inches. minute. i 2 • . 1*70 cubic feet. 21 . 19-70 cubic feet. 1 . 4-82 ,, 3 . 26-62 „ „ H . 8-84 ,, 34 . 33-22 „ 2 . 13-63 ,, 4 • 40-71 „ „ This plan of measuring the yield of Avater-courses is the one noAv most generally adopted by engineers. The same object may, hoAvever, be attained Avith sufficient accuracy for the purposes of the medical officer by selecting a portion of the stream Avhere the channel is pretty uniform, for the length of, say, not less than 12 or 15 yards, and in the course of which there are no eddies. Take the breadth and the average depth in three or four places, to obtain the sectional area. Then, dropping in a chip of wood, or other light object, notice how long it takes to float a certain distance over the portion of channel chosen. From this can be got the surface velocity per second, which is greater of course than the bottom or the mean velocity. Take four-fifths of the surface velocity (being nearly the proportion of mean to surface velocity), and multiply by the sectional area. The result will be the yield of the stream per second. B 18 WATER. It may sometimes be Avorth Avhile, if labour be at hand, to remove some of the irregularities of the channel, or even to dig a neAV one across the neck of a bend in the course of the stream. The yield of a spring or small river should be determined several times, and at different periods of the day. Wells.—The yields of wells can only be knoAvn by pumping out the Avater to a certain level and noticing the length of time required for refilling. In cases of copious Aoav of Avater a steam-engine is necessary to make any impression; but, in other cases, pumping by hand or horse labour may be sufficient perceptibly to depress the Avater, and then, if the quantity taken out be measured, and the time taken for refilling the well be noted, an approximate estimate can be formed of the yield. With respect to wells, if they are situated near a river, and do not pro- duce sufficient water, it has been recommended to lay perforated earthen- ware pipes parallel to the river, and below its fine-Aveather level, in trenches not less than 6 feet deep, and filled up above the pipes Avith fine gravel. The pipes end in the well, and Avater passing from the river and filtered through the gravel passes into them. Tube-Avells, commonly knoAvn as Norton's Abyssinian tube-wells, are used when a temporary supply is required : they are superior to dug Avells, which, from imperfect steining or total absence of it, are liable to become foul from surface pollution. They are constructed by driving tubes into the soil, one length being screwed on to another, the first tube being per- forated at the bottom for about 2 feet, its lower end being furnished Avith a steel point (fig. 3). When the subsoil water is reached, a pump is attached to the tube; the water after pumping a short time is clear ; the tube forms a cavity which corresponds to the ordinary well at the end of the pipe, owing to the removal of the soil by pumping. Koch recommends that iron tubes be placed in dug wells, and the surrounding space filled in with clean gravel and sand, the water to be raised by a pump fixed at the surface. Permanence of Supply.—The importance of the permanence of a supply is obvious. Any available evidence should be obtained, particularly with reference to the amount and period of rain, without which it is impossible to arrive at any safe conclusion. The country which forms the gathering ground for the springs or rivers should be considered. If there be an extensive background of hills, the springs towards the foot of the hills will probably be permanent. In a flat country the permanency is doubtful, unless there be some evidence from the temperature of the spring that the Abater comes from some depth. In lime- stone regions springs are often fed from subterranean reservoirs, caused by the gradual solution of the rocks by the water charged Avith carbonic acid; and such springs are very permanent. In the chalk districts there are feAv springs or streams, on account of the porosity of the soil, unless at the point the level be considerably below that of the country generally. The same may be said of the sandstone formations, both old and new; but deep wells in the sandstone often yield largely, as the permeable rocks form a vast reservoir. In the granitic and trap districts small streams are liable to great variations, unless fed from lakes; springs are more permanent when they exist, being perhaps fed from large collections or lochs. Storage.—The fluctuations of the rainfall, flow of streams and consump- tion of water in the different seasons of the year, require almost invariably that there shall be artificial storage of the surface waters of the seasons of maximum Aoav, to provide for drought during the seasons of minimum Aoav STORAGE OF AVATER. 19 The amount required Avill depend on tAvo circumstances, viz., the quantity used and the ease of replenishing. It is, of course, easy to calculate the space required Avhen these conditions are knoAvn, in this way:—the number of gallons required daily for the whole population must be divided by 6-23 to bring into cubic feet, and multiplied by the number of days Avhich the storage must last; the product is the necessary size of the reservoir in cubic feet. HaAvskley's formula for storage is as foIIoavs :—D = -—=-, where F x/F equals the mean annual rainfall in inches, say - of average annual yield; D is the number of days' supply to be stored. Thus, Avith a rainfall of 20 . , , 1000 1000 nnn 1 , inches, Ave have -jf=- = ^ = 200 days supply. There are losses incidental to artificial storage that must not be overlooked ; for instance, the percolation into the earth and through the embankment, also evaporation from the reservoir and from its saturated borders. Whatever be the size of the reservoir, it should be kept carefully clean, and no possible source of contamination should be permitted. In the large reservoirs for town supply the water is sometimes rendered impure by floods washing surface refuse into them, or by substances being thrown in. In fact, in some cases, Avater pure at its source becomes impure in the reservoirs. As far as possible, all reservoirs, tanks, &c, should be covered in and ventilated; in form they should be deep rather than extended, so as to lessen evaporation and secure coolness. Though they should be periodically and carefully cleaned, it would appear that it is not always wise to disturb water plants which may be growing in them; some plants, as Protococcus, Chara, and others, give out a very large amount of oxygen, and thus oxidise and render innocuous the organic matter which may be dissolved in the water or volatilised from the surface. Chevers mentions that the Avater of some tanks which were ordered to be cleared of water plants by Sir Charles Napier deteriorated in quality. Other plants, however, as some species of duckweed (Lemna at home, Pistia in the tropics), are said to contain an acrid matter which they give off to the Avater. It would be well to remove some of the plant, place it in pure water in a glass vessel, and try by experiment whether the amount of organic matter in the water is increased, or whether any taste is given to the Avater. The presence of some of the Nostoc family gives rise to an offensive pig-pen odour Avhen decaying. Dead vegetable matter should never find its way into, or at any rate remain in, the reservoir. Whenever a reservoir is so large that it cannot be covered in, a second smaller covered tank, capable of holding a few days' supply, might be pro- vided and fitted with a filter, through which the Avater of the larger reservoir might be led as required. When tanks are large they are made of earth, stone, or masonry; if mortar be used it should, as in the case of the smaller reservoirs, be hydraulic, so that it may not be acted on by the water. The materials of small reservoirs and cisterns are stone, cement, brick, slate, tiles, lead, zinc, and iron. Of these, slate is the best, but it is rather liable to leakage, and must be set in good cement or in Spence's metal; common mortar must not be used for stone or cement, as lime is taken up and the water becomes hard. Leaden cisterns, as in the case of leaden pipes, often yield lead to water, and should not be used; they are cor- 20 AVATER. roded by mud or mortar, even Avhen no lead is dissolved in the Avater. Iron cisterns and pipes are often rapidly eaten away; they are sometimes pro- tected by being covered inside Avith Portland cement or Avith a vitreous glaze or with Crease's patent cement. Barff's process of producing the magnetic oxide on the surface of iron has been tried, but seems hardly so successful as it promised. Galvanised iron tanks are also very much used ; they must be covered, and in India be protected from the sun. Zinc has been recommended, but water passing through zinc pipes, or kept in zinc pails, or in badly galvanised iron vessels, may produce symptoms of metallic poisoning, and even taste strongly of zinc salts, especially if the water is rich in nitrates. It Avould certainly be better to abandon lead, zinc, and such like materials for cisterns, as much as possible, unless we are sure that the water contains no substance likely to act upon the metal. Cisterns should always be Avell covered, protected as much as possible from both heat and light, and thoroughly ventilated if they are of any size. Care should always be taken that there is no chance of leakage of pipes into them. A common source of contamination is an overfloAV-pipe passing direct into a sewer, so that the seAver gases pass up, and, being confined by the cover of the cistern, are absorbed by the water; to prevent this, the overAoAV-pipe is curved so as to retain a little Avater and form a trap, but the water often evaporates, or the gases force their way through it; no overAoAV-pipe should therefore open into a seAver, but should end above ground over a trapped grating. A cistern supplying a water-closet should not be used to supply cooking and drinking Avater, as the pipes leading to> the closet often conduct closet air to the cistern. Hence, a small cistern (water-waste preventer) should be used for each closet. Cisterns should be periodically and carefully inspected; and in every new building, if they are placed at the top of the house, convenient means of access should be pro- vided. Tanks to hold rain-water require constant inspection. Distribution.—When houses are removed from sources of water the supply should be by aqueducts and pipes. The distribution by hand is rude and objectionable, for it is impossible to supply the proper quantity, and the risks of contamination are increased. Some of the most extraordinary of the Roman works in both the Eastern and Western Empires Avere under- taken for the supply of water—works whose ruins excite the astonishment and should rouse the emulation of modern nations. The plans for the distribution of Avater should include arrangements for the easy and immediate removal of dirty water. This is an essential point, for in many toAA'ns where houses are not properly arranged for small families, there areno means of getting rid of Avater from the upper rooms, and this inconvenience actually limits the use of water, even Avhen its supply is ample. The supply of water to houses may be on one of tAvo systems, intermittent or constant. The difference betAveen the tAvo plans is, that in the first case there is storage in the houses for from one to three clays ; Avhile in the latter case there is either no storage, or it is only on a very small scale for tAvo purposes, viz., for Avater-closets and for the supply of kitchen boilers. It should, hoAvever, be understood that the constant supply has not ahvays meant in practice an unlimited supply, nor has it been the case that the Avater in the house-pipes Avas always in direct communication Avith the Avater in the reservoirs. On the contrary, the water to the houses has often been cut off, particularly in places where the supply Avas limited, and the fittings not good, and where there Avas great Avaste. The terms used to describe the pipes differ a little apparently ; the mains and district or sub-mains are the large pipes, Avhich are ahvays full of water DISTRIBUTION OF WATER. 21 the latter being, of course, the smaller; the service-pipe is another term for a, district main. The communication-pipe is that which runs from the service-pipe to the house, and in the house it takes the name of house- pipe. The great arguments against storage on the premises (except on a limited scale for closets and boilers) are the chances of contamination in cisterns, and the very imperfect means of storage, which is especially the case in houses occupied by the Avorking-classes. In providing a constant supply, certain precautions are necessary. The fittings must be as perfect as possible. When the fittings are good, there is real economy in the constant system,—as shoAvn in the comparison between Lincoln and Oxford, and by Hawksley's evidence with reference to Norwich. Common taps do not answer, and the best screAv taps and fittings must be used. One important sanitary advantage of the constant system is that, in order to facilitate inspection and detection of waste, no Avaste-pipe is "allowed to open into a seAver, but it is always so placed that any escape of water can be easily seen (the so-called warning-pipe). The great evil of seAver gases being conducted back into houses through overflow-pipes is thus avoided. Careful inspection and good fittings so far lessen the Avaste of the constant system, that in some cases less water is used than under the intermittent plan. Deacon has shown that the loss on the constant system is due to causes over which the consumer has generally little or no control, and that it occurs for the most part before the water reaches him. It arises chiefly from leaks in pipes, draAvn joints, and so on, and up to lately there Avere no means of detecting this in a way practically useful. By the introduction of his water- Avaste meter this is done with the utmost precision and accuracy, so that in Liverpool the expenditure of water has been considerably reduced. Com- paring the_ mean supply of the four years prior to 1874 with that of 1876, when the intermittent system had entirely ceased and a constant service under increased pressure had taken its place, Ave find that in 1876 the loss by leakage had already been so far moderated that a supply Avas given for metered trade purposes, increased by 25 per cent., and, without restriction for domestic and all other purposes to a population already increased by 33,000 persons, Avith 12 per cent, less Avater than in the previous period. The Lambeth Water Company supply part of their district on the constant system and part on the intermittent. The constant supply is checked by Deacon's waste-Avater meters and the results have been very satisfactory, the saving in consumption being about 7 gallons per head as compared with the Company's entire district. At Bradford, during 1887 and 1888, the saving was estimated to be 2,000,000 gallons per diem. The sanitary benefits of the constant supply, causing a constant internal pressure in the Avater-mains ahvays above that of the atmosphere, renders impossible the accession of foul matter to the mains Avhich so commonly occurs—Avhen, during intermissions of supply, the internal pressure falls beloAv that of the atmosphere—scarcely admits of exaggeration. Further improvements in the direction of detecting leakage have been made in Frankfort and other cities in Germany, Avhere the microphone in connection with these Avater- meters has been used. If the constant system is used, a good screw stopcock, available to the tenant, should be placed at the point of entrance of the pipe into the house, so that the Avater may be turned off if pipes burst, or to allow the pipes to be empty, as during frost. Every precaution must be taken that impure 22 WATER. water is not drawn into the pipes by a pipe being emptied and sucking up Avater from a distance. For the supply of a very large city, it might be desirable to divide the city into sections, and to establish a reservoir for each district, holding three or four days' supply. In this Avay the Avaste of one section would not take aAvay the Avater from another. In some instances, people in one part of a toAvn, supplied on the constant system, have used so much water for gardens that other parts have been altogether deprived of supply. The system of secondary reservoirs would not only lessen this chance, but would make it possible to ascertain that every part of the town Avas getting its supply. The number of Avater companies in London has in fact some- what this effect, but the subdivision is not carried far enough. There is no doubt that the constant system is the safer, especially for poor houses, as it leaves no loophole for inattention in the cleansing of cisterns. Only, it requires that the constant system should really fulfil the conditions laid doAvn for it, viz., it should deliver sufficient Avater at all times, and not merely delude us with a phrase. In both plans the Avater is conducted from the reservoirs in pipes. The pipes are composed of iron, stoneAvare, or masonry, for the larger pipes or mains, cast iron being those most generally in use. The length of the pipes is usually about 9 feet, and a hub and spigot joint formed, adapted first to a joint packing of deal Avedges and afterward to a packing of lead. This form of joint admits of their free expansion and contraction Avith varying temperatures of water and earth, and renders them less liable to fracture. For the smaller pipes, galvanised iron, lead, tin, vitreous glazed iron pipes, &c, are used. The action of Avater upon iron pipes appears to be energetic at first, but diminishes after a little time. Several processes have been proposed for the preservation of the pipe surface. Barff's method consists in raising the temperature of the metal to about 1200° F.—a white heat—in a suit- able chamber, into Avliich is passed superheated steam; the metal is exposed to this action for several hours, and becomes coated with a protective oxide. Angus Smith patented a process for coating iron pipes with a varnish of pitch, derived from coal tar; the pipes are heated in a retort or oven to a temperature of about 310° F. and then immersed in a bath of pitch which is maintained at a temperature of not less than 310° F. The pitch is specially prepared, being distilled from coal tar until the naphtha is entirely removed and the material deodorised; to this about 5 or 6 per cent, of linseed oil is added. The pipes should be free from rust and strictly clean when they are immersed in the pitch bath. Sheet iron Avater-pipes lined and coated with hydraulic cement are used in the United States. The sheet iron is formed into pipes about 8 feet long, and riveted. These are then lined with hydraulic cement, and when lined are enclosed in a bed of cement. Iron is the best material for the larger pipes, and it is also necessary (steam-piping) for the smaller pipes under the pressure of the constant service system. Water should be distributed not only to every house, but to every floor in a house. If this is not done, if labour is scarce in the houses of poor people, the water is used seA-eral times; it becomes a question of labour and trouble versus cleanliness and health, and the latter too often give Avay. Means must also be devised for the speedy removal of dirty water from houses for the same reasons. In fact, houses let out in lodgings should be looked upon, not as single houses, but as a collection of dwellings, as they really are. ACTION OF AVATER ON LEAD PIPES. 23 Action of Water on Lead Pipes.—There are more discrepancies of opinion on this subject than might have been anticipated. From an analysis of the statements made, the folloAving points appear to be the most certain :— A. The waters which act most on lead are:— (a) The purest and most highly oxygenated; as rain-water, and the soft waters of lakes and upland streams. (b) Those containing organic matter, nitrites and nitrates; as impure waters contaminated with sewage, &c. (c) Those containing chlorides ; these salts having the power of dissolving the protecting coat of carbonate that may have been formed. (d) Those containing a free acid; as soft peaty waters derived from upland surfaces. Besides the portion dissolved, a film or crust is often formed, especially at the line of contact of water and air; this crust consists usually of two parts of lead carbonate and one part of hydrated oxide. The mud of several rivers, even the Thames, will corrode lead, probably from the organic matter it contains, but it does not necessarily follow that any lead has been dissolved in the water. Bits of mortar will also corrode lead. B. The waters which act least on lead are :— (a) Those that are rich in earthy salts—that is, hard waters, such as are derived from deep wells, &c. Carbonates, phosphates, and sulphates, all have a protecting influence, especially carbonates, and most especially carbonate of lime. According to Lissauer, the presence of 5-8 parts per 100,000 of CaC03 renders a water safe. But when sulphates are in excess, they increase the solvent action of the water. (b) The presence of free carbonic acid exercises a protective influence, a basic carbonate being formed, very sparingly soluble, which is deposited on the pipe. But if the C02 is in excess, or if the water is charged with it under pressure, this coating is dissolved, and the solvent action increased. (c) The presence of silica, according to Crookes, Odling, and Tidy, to the extent of half a grain per gallon, has a protective influence, an insoluble lead silicate being formed. But although most*waters that act markedly on lead contain very little silica, the degree of their activity does not appear proportional to the scarcity of silica present, and some such waters (e.g., Hindhead) contain a considerable amount. (d) It has been said that perfectly pure water containing no gases has no action on lead; this, however, is not strictly correct, as pure distilled water has been known at Netley to take up lead from a leaden pipe. The deposit Avhich frequently coats the lead consists of carbonate, phosphate, and sulphate of lead, calcium and magnesium, if the water have contained these salts. C. There are certain conditions that have a great influence on the solvent action of the water upon lead pipes, irrespective of the composition of the water itself:— (a) NeAv lead pipes always give up more lead than old ones. (b) The length of time the water has been in contact with the lead : the water must not only pass through, but remain in, the pipes for some time : the amount dissolved increases during the first tAventy-four hours, after this some is deposited, and after six days less lead is found in the water. (c) Temperature : hot-water pipes yield more lead than cold-water pipes. (d) Pressure: increased pressure (up to 140 lbs. on the square inch) increases the solvent action. Within the last feAv years numerous extensive outbreaks of lead poison- 24 WATER. ing have been traced to the water supplied as a public service in towns in the north of England, as Sheffield, Huddersfield, Chesterfield, Baeup, &c. These supplies have all been drawn from upland surface-waters, and the outbreaks have occurred either during, or shortly following, periods of drought. The one circumstance common to all the cases appears to have been the presence of a free acid in the water. Sinclair White of Sheffield considers this to be the cause of the solvent action of such waters upon lead. He found that the dissolving poAver Avas proportional to the acidity of the Avater; that filtration through charcoal of an active acid Avater removed both its activity and acidity; and that neutralisation by limestone, lime, or bicarbonate of soda, had the same effect. He believes the acid to be derived from decaying peat, i.e., humic acid. Others believe it to be either sulphuric acid or a derivative of this. Power and Houston have demonstrated that the lead dissolving properties of a water are ahvays associated Avith corresponding variations in the amount of its acidity. This acidity, in the case of moorland Avaters certainly, is dependent upon bacterial activity in moist peat soil. Tavo species of microbes found in peat have Avell-defined powers of producing acidity and of making Avaters plumbo-solvent. D. The lead itself is more easily acted upon if other metals, as iron, zinc, or tin, are in juxtaposition; galvanic action is produced. Bending lead pipes against the grain, and thus exposing the structure of the metal, also increases the risk of solution. Zinc pipes, into the composition of Avhich lead often enters, yield lead in large quantities to Avater, and this has been especially the case with the distilled water on board ships. Amount of Dissolved Lead which xoillproduce Symptoms of Poisoning.— Angus Smith refers to cases of lead paralysis in which as little as T^pth of a grain per gallon was in the water: he states that TV^n °^ a grain Per gallon may affect some persons, while TVth of a grain may be required for others. Adams also speaks of y^oth of a grain causing poisoning. Calvert found that water which had been decidedly injurious in Manchester contained from TVh to ^ths of a grain per gallon. In the celebrated case of*the poisoning of Louis Philippe's family at Claremont, the amount of lead was -^ths of a grain per gallon; this quantity affected 34 per cent, of those who drank the water. On the Avhole, it seems probable that any quantity over -^th. of a grain per gallon ( = 0*07 per 100,000) should be considered dangerous, and that some persons may even be affected by less quantities. The means that have been proposed to prevent injurious effects from lead gaining access to the system through the medium of drinking Avater are :— (1) to treat the water before it enters the pipes, so as to prevent its being capable of acting on the metal, should it come in contact Avith it; and (2) to use for distributing the Avater, pipes Avhich Avill not allow of the Avater coming in contact with the lead. Thus, if the free acid present is neutralised by the addition of lime to the water, its solvent action on lead pipes is avoided. This has been found effectual in the case of the Sheffield water Avhich contains a free acid. It is the safest method of dealing with such waters as are knoAvn to take up lead readily. The alternative plan is to use pipes that do not yield lead to water, such as cast or Avrought iron pipes and if possible they may be glazed internally. Leaden pipes lined Avith tin are very liable to fracture of the lining metal when the pipe is bent, and the waters being exposed to both metals, galvanic action is set up, Avhen the lead as being the more oxidisable metal, is dissolved. Block tin pipes are very expensive, and have the further disadvantage of being eaten through SOURCES OF IMPURITY IN DRINKING WATERS. 25 apparently in consequence of the presence of nitrates in the Avater. Lead, alloyed with 3 per cent, of tin, Avas formerly believed not to yield lead to Avater, but later evidence shows this is not the case if free carbonic acid is present in the Avater. On the Avhole, good iron pipes appear to be the safest. Filtra- tion through sand, charcoal, or spongy iron Avill remove lead from water. Sources of Impurity in Drinking Waters.—The geological formation of a district necessarily influences the composition of the Avater running through it, though it is impossible to tell with absolute certainty Avhat the con- stituents of the water may be. Formations vary greatly, and the broad features laid doAvn by geologists do not always suffice for our purpose. In the middle of a sandy district, yielding usually a soft Avater, a hard selenitic Avater may be found; and, instead of the pure calcium carbonate Avater, a ■ chalk Avell may yield a Avater hard from calcium sulphate and iron. Still it may be useful to give a short summary of the best-known facts. Water from springs in Granite and Gneiss is very pure and of most excellent quality for drinking, cooking, and all domestic purposes: the total solid constituents of these Avatersvary from 1*4 to 9 parts per 100,000 ; the hardness is usually very trifling; the organic matter is in very small amount. The water is bright, clear, and palatable, and has nearly a uniform temperature throughout the year. The Silurian rocks, consisting of shales, slate, sandstones, &c, contain more soluble matter than is met Avith in Granite or Gneiss, and consequently yield to Avater a larger amount of solid material, nearly the Avhole of which consists of innocuous salts. The proportion of organic matter is small, and the Avater is generally soft. The Avater is clear and sparkling, and is Avell adapted for drinking, cooking, and washing purposes. Water from springs in the Devonian rocks and old Red Sandstone is generally of most excellent quality. The average amount of total solids present is 18 parts per 100,000. The organic matter is in very small amount. The Avater is usually soft or of moderate hardness. Of the Carboniferous rocks, the mountain limestone yields water clear, colourless, and palatable; it is rather hard, and therefore not well suited for washing purposes, but it may be effectually softened by Clark's process. The total solid constituents average about 26 parts per 100,000. The waters from the millstone grit are very similar. The hardness varies considerably ; they contain only a trace of organic matter. Unpolluted waters from the Lias clays are clear, colourless, palatable, and Avholesome. They contain only a trace of organic matter, but are rather hard. Some of these Avaters are found to contain a large proportion of solid matters in solution, nearly the Avhole of Avhich consist of mineral matters. Water from Hard Oolite is very pure—nearly the entire composition of these rocks consist of carbonate of lime—and although the Avaters are hard, it is chiefly of a temporary kind. As water-bearing strata, or as a subterranean reservoir for the purification and storage of water, the Oolite rocks are ■ equal, if not superior, to the chalk. Water from the Cretaceous rocks, such as the Hastings Sand and the LoAver Greensands, is pure and wholesome. The hardness varies Avithin Avide limits, but it is usually a very hard Avater, but admits of softening. Water from the Chalk is very sparkling and clear, and is highly charged Avith carbonic acid. The total solid matter averages about 30 parts per 100,000, and consists of mineral salts Avhich are not uiiAvholesome; organic matter is usually in small amount. The Avater is sparkling, colourless, palatable, and Avholesome. Any excess of hardness is of the temporary kind, . and can be easily removed by Clark's process. 26 WATER. Springs in the Drift and Gravel yield water of very variable quality,. owing to the varying character and generally small thickness of the beds through Avhich it percolates. It usually holds in solution a large proportion of organic constituents, although it sometimes contains only a small amount of organic matter. Water from Magnesium Limestone differs from the Chalk Avaters in containing a large amount of permanent hardness. The salts present are chiefly sulphate and carbonate of calcium and magnesium. The Avater is organically A-ery pure, but it is too permanently hard to be a Avholesome drinking Avater. Water from shallow wells in Alluvium and Gravel soils are generally impure,. Avith calcium carbonate and sulphate, magnesium sulphate, sodium chloride and carbonate, iron, silica, and often much organic matter. Occasionally the organic matter oxidises rapidly into nitrites, and if the amount of sodium chloride is large, it might be supposed that the water had been con- taminated with seAvage. The amount of solids per 100,000 varies from 30 to 170 parts or even more. Wells sunk in Gravel on the London Clay yield a bright and palatable water, but are generally polluted, their chief sources of supply being from. sewers and cesspools. The water is unfit for drinking and washing purposes. All surface and subsoil waters are very variable in composition, often very impure, and ahvays to be regarded Avith suspicion. Heaths and moors, on primitive rocks, or on hard millstone grit, may supply a pure water, which may, however, be sometimes slightly coloured with vegetable matter. Cultivated lands, Avith rich manured soils, give a water containing both organic matter and salts in large quantity. Some soils contain potassium, sodium, and magnesium nitrates, and yield these salts in large quantity to> water. In toAvns and among the habitations of men, the surface water and the shalloAr-Avell Avater often contain large quantities of ■ calcium and sodium nitrites, nitrates, sulphates, phosphates, and chlorides. The nitrates in this. case probably arise from ammonia, ammonium nitrite being first formed, which dissolves large quantities of lime. Organic matter generally exists in large amount, and sloAvly oxidises, forming ammonia .and nitric acid. In some cases butyric acid, Avliich unites with lime, is also formed. Marsh water always contains a large amount of vegetable organic matter;. it is not unusual to find of volatile solids from 17 to 57 parts per 100,000, and in some cases even more. Suspended organic matter is also common'. The salts are variable. A little calcium and sodium in combination with carbonic and sulphuric acids and chlorine are the most usual. Of course, if the marsh is a salt one, the mineral constituents of sea-water are present' in varying proportions. Water taken from wells sunk in the vicinity of cemeteries contains ammonium and calcium nitrites and nitrates, and sometimes fatty acids and much organic matter. Lefort found a well of water at St Didier more than 330 feet from a cemetery, to be largely contaminated with ammoniacal salts and an organic matter which was left on evaporation. The water was clear at first, but had a vapid taste, and speedily became putrid The water from old graveyards (disused) may show less organic matter, but it will contain large quantities of nitrates, chlorides, &c. The water derived from deep Artesian wells is'usually of excellent quality and contains only a very minute quantity of organic matter. In some cases however, the water is so highly charged with saline matter as to be un drinkable; the water of the Artesian well at Grenelle contains sufficient sodium and potassium carbonates to make it alkaline ; there is also present in it a con- siderable amount of free ammonia. When not Aery hard, these Avaters are IMPURITIES ADDED DURING TRANSIT, ETC. 27 of good quality, clear and colourless, and, owing to the depth of the well,. are usually of a uniform temperature throughout the year. The water is not Avell aerated, and therefore not so palatable as spring Avater. Some Artesian well waters are Avarm, these are generally used for medicinal pur- poses. Others, again, contain iron or are aperient, these are unfitted for ordinary drinking purposes. The Artesian wells in London are alkaline from the presence of bicarbonate of sodium, and hence are very soft. Water from wells near the sea frequently contains so much saline matter as to taste quite brackish, although the organic matter may not be very large. In some samples from Shoeburyness (analysed at Netley) the total solids ranged from 148 to 312 parts per 100,000, the chlorides being from 31 to 93 : mean of six samples—236 total solids and 50 of chlorides. In one sample, hoAvever, the albuminoid ammonia was only 0-007 per 100,000, and in five the oxygen required for organic matter was under 0*075 per 100,000. Samples from wells at Gibraltar yield in some cases large quantities of solids; in one instance as much as 338 parts of total solids and 244 of chlorides in 100,000. At Landguard Fort, water from a boring 150 feet deep yielded more than 700 parts of solids and 540 parts of chlorides. Rain-water may be contaminated by washing the air it falls through, but more by matters on the surface on which it falls, such as decaying leaves, bird droppings, soot, or other matter on the roofs of houses; it also takes lead from lead coatings and pipes, and zinc from zinc roofs. If stored in underground tanks it may also receive soakings from the soil through leakage. Impurities added during Transit from Source to Reservoir.—Open conduits are liable to be contaminated by surface Avashings carrying in finely divided clay, sand, chalk, and animal matters from cultivated land; and the leaves and branches of trees add their contingent of vegetable matters. These impurities may occur in most cases, but in addition the refuse of houses, trades, and factories is often poured into rivers, and all sorts of matters are thus added. These impurities are broadly divided by the Rivers Pollution Commis- sioners into " sewage " and " manufacturing " : under the former term all solid and liquid excreta, house and waste water, and in fact all impurities coming from dwellings, are included ; under the latter term is placed all manufacturing refuse, such as from dye and bleach works, tanneries, paper- making, woollen, silk, and metal works, &c. The very numerous animal and vegetable substances derived from habita- tions are usually classed under the vague but convenient term of " organic matter," as the separation of the individual substances is impossible. The organic matter is usually nitrogenous, and Frankland has proposed to express its amount in terms of its nitrogen (organic nitrogen), but this view is not yet generally received on account of the difficulty of estimating the very small quantity of nitrogen. The nitrogenous organic matter undergoes gradual transformation, and forms ammonia, and nitrous and nitric acids. On keeping the water the nitrites disappear, and in some cases the nitrates also gradually diminish, both actions resulting from the presence of bacteria. Many of the " organic matters " in water are not actually dissolved, but are so finely suspended that they pass through filtering paper. There is no doubt that among this " suspended organic matter " many minute plants and animals (including bacteria and their spores) are always included. It is probably owing to the variation in the quantity of suspended organic matter (living and dead) that Avater from the same source sometimes gives 28 WATER. different results on analysis, even though the Avater be taken at the same time. During its Aoav in open conduits, purification goes on, by means of sub- sidence, by the action of the ordinary Avater bacteria on pathogenic micro- organisms, should these be present in the Avater, by exposure to direct sunlight, and by the presence of Avater plants. It must be remembered that the natural habitat of pathogenic bacteria is the interior of the human body: Avhen they pass from this into rivers, they are in an unnatural medium, in Avhich they can only maintain their existence and power of multiplication for a limited period and tend rapidly to disappear under the conditions found in ordinary river-Avater. Impurities of Storage.—The chance of substances getting into the Avater of Avells and tanks, and even of cisterns in houses, is very great. Surface Avashings and soakage contaminate Avells and tanks, and leakages from pipes, passage of foul air through pipes, or direct absorption of air by an un- covered surface of Avater, introduce impurities into cisterns. It is singular in Iioav many Avays cisterns and tank Avaters get foul, and Avhat care is necessary not only to place the cistern under safe conditions at first, but to examine it from time to time to detect contamination of the Avater. In India, especially, the tank Avater is often contaminated by clothes washed near, or actually in, the tank; by the passage even of excrement directly into it, as Avell as by surface Avashings, so that in fact in some cases the village tank is one of the chief causes of the sickness of the people. There is, perhaps, no point on Avhich the attention of the sanitary officer should be more constantly fixed than that of the storage of Avater, either on the large or small scale. Impurities of Distribution.—If water is distributed by hand, i.e.,'hy Avater-carts, barrels, or skins, there is necessarily a great chance of its being fouled. In India, where the water is generally carried by Avater-carriers (Bhisties), inspection of the carts or skins should be systematically made, and whenever it be possible, pipes should be substituted for the rude method of hand conveyance. But even pipes may contaminate water; metals (lead, zinc, and iron) may be partly dissolved ; wood rots, and if the pipes are occasionally empty, impure air may be drawn into them, and be after- wards absorbed by the water. Buchanan in his Report on an Outbreak of Fever at Cams College, Cambridge, showed that this was due to foul trap- water sucked in from the closets. In toAvns supplied on the constant system when the pipes are becoming empty the flow of water from a tap has drawn dirty water or air through a pipe at some distance, and in this Avav even the Avater of the mains has been fouled. Coal gas passing into the ground from leaking of gas pipes sometimes ? qU Ti? V™1^' °r even int0 water P^68- In -Berlin, iu 1864, out of 940 public wells, 39 were contaminated by admixture with coal «a<- \ good instance is related by Harvey, Avhere the main pipes were often empty and gas penetrated into them. Having regard to the cases in which gases from the soil (from leaking gas pipes, sewers, &c.) find their way into water pipes, it would seem important not to lay down water pipes near mTetted' "' " ' ^ *U PipGS in SUWayS wliere tne^ can be EFFECTS OF AN INSUFFICIENT OR IMPURE SUPPLY OF WATER. * Insufficient Supply.—The consequences either of a short supply 0f Warpr for domestic purposes, or of difficulty in removing water which has bee EFFECTS OF INSUFFICIENT WATER-SUPPLY. 20 used, are very similar. The Avant of Avater leads to impurities of all kinds : the person and clothes are not Avashed, or are Avashed repeatedly in the same Avater; cooking Avater is used scantily, or more than once ; habitations become dirty, streets are not cleaned, seAvers become clogged ; and in these various Avays a Avant of Avater produces uncleanliness of the very air itself. The result of such a state of things is a general loAvered state of health among the population; it has been thought also that some skin diseases— scabies, and the epiphytic affections especially—and ophthalmia in some cases, are thus propagated. It also appears likely that the remarkable cessation of spotted typhus among the civilised and cleanly nations is in part oAving, not merely to better ventilation, but to more frequent and thorough Avashing of clothes. The deficiency of water leading to insufficient cleansing of sewers has a great effect on the spread of enteric fever and of choleraic diarrhoea; and cases have been known in which outbreaks of the latter disease have been arrested by a heavy fall of rain. Little is known Avith certainty of the effects produced on men by deficiency in the supply of Avater. Under ordinary circumstances, the sensation of thirst, the most delicate and imperative of all our feelings, never permits any great deficiency for a long time, and the water-removing organs eliminate with wonderful rapidity any excess that may be taken, so as to keep the amount in the body Avithin certain hmits. But Avhen circumstances prevent the supply of Avater, it is Avell known that the Avish to drink becomes so great, that men will run any danger, or undergo any pain, in order to satisfy it. The exact bodily condition thus produced is not precisely known, but from experiments on animals and men, it would appear that a lessened amount of Avater in the body diminishes the elimination of the pulmonary carbonic acid, the intestinal excreta, and all the important urinary constituents. The more obvious effects produced on men Avho are deprived for some time of water is, besides the feeling of the most painful thirst, a great loAvering of muscular strength and mental vigour. After a time exertion becomes almost impossible, and it is Avonderful to see what an extraordinary change is produced in an amazingly short time if Avater can be then procured. The supply of Avater becomes, then, a matter of the most urgent necessity Avhen men are undergoing great muscular efforts, and it is very important that the supply should be by small quantities of Avater being frequently taken, and not by a large amount at any one time. The restriction of water by trainers is based on a misapprehension : a little Avater, and often, should be the rule. Effects of Impure Water.—In many cases, very little careful inquiry has been made into the state of health of those using the Avater, and that most fallacious of all evidence, a general impression, Avithout a careful collection of facts, has often been the only ground on Avhich the opinion has been come to. As well observed by Simon, in one of his philosophical Reports, we cannot expect to find the effect of impure Avater always sudden and violent; its results are indeed often gradual, and may elude ordinary observation, yet be not the less real and appreciable by a close inquiry. In fact, it is only Avhen striking and violent effects are produced that public attention is arrested; the minor and more insidious, but not less certain, evils are borne with the indifference and apathy of custom. In some cases it is by no means improbable that the use of the impure Avater, Avhich is supposed to be innocuous, has been really restricted, or that experience has shoAvn the necessity of purification in some way. This much seems to be certain, that as precise investigations proceed, 30 WATER. and, indeed, in proportion to the care of the inquiry and the accuracy of the examination, a continually increasing class of cases is found to be connected Avith the use of impure Avater, and it seems only reasonable to infer that a still more rigid inquiry will further prove the frequency and importance of this mode of origin of some diseases. Recent observations show that epidemics are usually spread by drinking Avater infected by specific germs or spores, and this has been proved by the discovery of the actual bacteria, associated with particular diseases, in the Avater, and further, that these forms are capable of producing in healthy persons the same specific disease. Cholera and enteric fever are the tAvo diseases generally recognised in which the proof of origin from polluted Avater is irrefutable. As regards the presence of these pathogenic micro-organisms in Avater the important points to determine are their capacity to persist and to multi- ply in Avater and the approximate number that are required to be introduced to set up disease in the human body. On these points, as yet, we have no reliable data for arriving at a conclusion. According to the evidence given before the Royal Commission on Metropolitan Water-Supply, it appears to be the general opinion that the presence of saprophytes in water is deleterious to the growth of pathogenic micro-organisms, such as enteric fever bacilli and the comma bacilli of cholera, and the latter is more readily destroyed by sapro- phytic bacteria than the former. This report states that it is the generally received opinion of experts that the pathogenic organisms and the ordinary river bacteria, to Avhich the decomposition of organic matter is due, are naturally antagonistic : and that these latter undoubtedly exert an influence in diminishing the vitality of the typhoid bacillus, either actually consuming it, or, as is more probable, giving rise to products that interfere with its growth. Exposure to direct sunlight destroys these bacteria, while even such diffused daylight as is present in this country injuriously affects their vitality: the influence this can exert largely depends on the depth of the water and whether turbid or otherwise. The influence that the dissolved oxygen in water has upon bacteria is uncertain: it certainly destroys the organic matter present in the Avater,~~~ but probably its action is limited to certain kinds of organic impurity, and indirectly it reduces the number of micro-organisms by limiting the supply of nutriment available for their growth. The most practical way of stating the facts connected Avith the pro- duction of disease by water will be to enumerate the diseases which have been traced to the use of impure water, and to state the nature of the impurities. Cholera.—This disease is endemic in India, in the delta of the Ganges. In other parts of the world it only occasionally appears, but no place is safe from its ravages, as it does not seem to be limited in its spread by either climate or geographical position. There is ample evidence to show that Avater plays a most important part in its diffusion, and to Snow must certainly be attributed the very great merit of discovering this most important fact. In 1849, in investigating some circumscribed outbreaks of cholera in Horsleydown, Wandsworth, and other places, Siioav came to the conclusion that in these instances the disease arose from cholera evacuations finding their way into the drinking water. In 1854 occurred the celebrated instance of the Broad Street pump in London, Avhich was investigated by a committee, Avhose report contains the most convincing evidence that in DIFFUSION OF CHOLERA BY AVATER. 31 that instance, the poison of cholera found its Avay into the body through drinking water. ° In 1865 occurred the important outbreak at Newcastle-on-Tyne, when all the circumstances pointed very strongly to the influence of the impure Tyne water. In 1865 also was the remarkable and undoubted case of water-poisoning at Theydon Bois, recorded by Radcliffe, and in the following year the violent outbreak in the east of London was shown to be connected Avith the circulation of impure AA-ater by the East London Water Works Company. The Company distributed foul and unfiltered water, excessively polluted_ with sewage from their uncovered reservoir at Old Ford, and which, in Radcliffe's opinion, was specifically contaminated with the excrement of the first tAvo patients avIio died in that year of cholera in the east district of London. The district supplied with Avater from this source was the sole area of intense cholera in London; the disease limiting itself " almost exactly to the area of this particular Avater-supply, nearly, if not absolutely, filling it, and scarcely at all reaching beyond it." In further confirmation of the view that Avater is a fertile agent in spread- ing the disease, the folloAving instances may be adduced. The epidemic of cholera in Hamburg in 1892 was a remarkable instance in which this disease may be spread through the agency of Avater. ""Hamburg, Altona, and Wandsbeck are three towns which adjoin each other and really form a single community; they do not differ except in so far as each has a separate and different kind of water-supply. Wandsbeck obtains filtered water from a lake, Hamburg until recently obtained its Avater in an unfiltered condition from the Elbe just above the town and Altona obtains filtered Avater from the Elbe below the toAvn. Whereas Hamburg was visited with a severe epidemic of cholera, Wandsbeck and Altona, if one excepts the cases brought thither from Hamburg, were nearly quite free from the disease. On both sides of the boundary the conditions of soil, buildings, sewerage, population, everything of importance were the same, and yet the cholera in Hamburg went right up to the boundary of Altona and there stopped." In this large population on each side of the boundary nearly all the factors Avere the same except the water-supply. The population supplied with the unfiltered Avater from the Elbe suffered. severely from cholera, while the population supplied with carefully filtered water from the same source escaped. Clemow quotes the following instance of the spread of cholera by water, from the Report of the First Conference of Caucasian Physicians:__"One of a number of Persian labourers, fleeing in panic from the infected govern- ments (Baku and others) and passing through this district, died of cholera during the night's halt close to the village of Dashkesaw. His companions, thinking that if the local authorities knew of the cause of their comrade's death, they would not be alloAved to enter Persia, decided to throAv the corpse into one of the wells Avhich provided the whole population of Dashkesaw Avith drinking water. On the following day cholera broke out in the village. There were seventeen deaths from cholera on the first day of the epidemic, and the village suffered incomparably more severely from cholera than any other village in the province." In the cholera epidemic in Warsaw in 1892 the majority of cases occurred in people living on the banks of the river, every one of whom had drunk unboiled water taken directly from the river. When the practice of taking Avater from the river Avas put a stop to and boiled water was generally provided, cases of cholera ceased. The whole history of cholera in 1892 sIioavs that it Avas by means of 32 WATER. Avater in almost every instance that cholera Avas spread; the A\ast rivers Avliich Aoav through Russia, and upon Avhich the inhabitants largely rely for their drinking Avater, affording an easy means for the dissemination of the specific poison. Considering the vast size of many of these rivers, such as the Volga, the Vistula, the Don, and many others, the degree of dilution in Avhich the virus of cholera may be spread seems to be very great; information on this point is, however, extremely hard to obtain. Clemow gives a good example of the distance to Avhich the cholera poison maybe carried by Avater and yet maintain its activity; he shows that in one case the infection must have been taken 6|- miles and possibly to another village 13 miles loAver doAvn the river. India furnishes many instances of cholera being conveyed by Avater. In 1867 the appearance of cholera and its rapid spread among the vast crowd of pilgrims after the great bathing day at HurdAvar was a case of Avater- poisoning on a gigantic scale. In 1879 a similar outbreak occurred, and again in 1892, from whence it spread to Russia. A remarkable case occurred at Yerrauda jail. Out of 1279 prisoners there Avere 24 cases of cholera in 5 days, Avith 8 deaths. Of those, 22 cases occurred among 134 prisoners employed as a road-gang, and only 2 among all the others variously employed. It Avas sIioavii that the road-gang alone drank of Avater from the Mootla River, a little beloAv the spot Avhere the clothes of tAvo cholera patients from the village had been Avashed and their bodies burned a feAv days before. The rest of the prisoners drank the usual water-supply laid on from a lake near Poonah. In the tAvo cases among those otherwise employed direct infection AAras undoubted in one, as he attended on cholera patients, and, contrary to orders, took his meals in the cholera ward, and drank Avater that had been standing there; the other man slept near one of the first cases, the patient vomiting in his immediate vicinity. If we look at the remarkable residts which have folloAved on the supply of pure Avater to the European troops who are quartered at Fort-William, Calcutta, within the endemic area of cholera, the evidence is even stronger. From 1826 to 1861 the average mortality among them for this disease Avas 20 per 1000. From 1863 to the present time it has been 1 per 1000. In 1863 Fort-William Avas for the first time supplied with pure drinking water, and with the result referred to. Another example of a similar kind is afforded in the case of Madras. Since the introduction of the neAv water-supply from the Red Hills, cholera has almost ceased to exist there, and the same immunity extends to the other districts using the Avater, Avhereas places which do not use it still suffer from the disease (Furnell). Gunter always suffered from cholera up to 1868, since which time it has been practically free, folloAving the neater care for the water-supply (Tyrrell). Calcutta showed a greatly diminished cholera mortality Avhen the neAv Avater-supply was furnished in 1870. The subsequent increase in cholera was due to the scarcity of the neAv supply necessitating the use of "tank" Avater. In evidence of this kind, Ave must remember that each successive instance adds more and more Aveight to the instances previously observed, until, from the mere accumulation of cases, the cogency of the argument becomes irresistible. The evidence derived from such local outbreaks is supported by that draAvn from the history of more general attacks, in which districts supplied with impure water by a water company have suffered greatly, while other DIFFUSION OF CHOLERA BY AVATER. 33 districts in the same locality, and presenting otherwise the same conditions, were supplied Avith pure water, and suffered very little. Thus, Sir J. Simon showed that in the district supplied in 1853, part by the Lambeth Company Avith a pure water, and part by the SoutliAvark Company Avith an impure Avater, the population drinking the Lambeth supply furnished 370 cases per 100,000, while those using the Southwark Co.'s water furnished 1300 cases per 100,000; all other circumstances except the water-supply being identical. Schiefferdecker, in Konigsberg, has also given evidence to show the different extent to which districts in the same city supplied Avith pure and impure Avater suffer. In Berlin, in 1866, in the houses supplied with good water, the number of houses in which cholera occurred was 36'6 per cent.; in the houses with bad water, 52-3 per cent. Additional arguments can be drawn from instances in which toAvns which could not have had water contaminated with sewage have escaped, and instances in which towns which have suffered severely in one epidemic have escaped a later one, the only difference being that, in the interval, the supply of water was improved. Exeter, Hull, Newcastle-on-Tyne, Glasgow, and Moscow are instances of this. Two very good cases are related by Sir H. Acland. The parish of St Clement was supplied in 1832 with filthy water from a sewer-receiving stream. In 1849 and 1854 the water was from a purer source. In the first year, the cholera mortality was great; in the last years, insignificant. In Copenhagen a fresh Avater-supply was introduced in 1859. Although cholera had prevailed very severely there previously, in 1865 and 1866 there were only a few cases. In Haarlem, in Holland, cholera prevailed in great intensity in 1849. In 1866 it returned, and again prevailed as severely in all parts of the toAvn except one. The part entirely exempted in the second epidemic was inhabited by bleachers, who, between 1849 and 1866, had obtained a fresh source of pure water. In the epidemic in Spain in 1885, Malaga, Seville, and Toledo drew water from pure sources, and had little cholera; on the other hand, Granada, Zaragoza, and Aranjuez derived water from open canals, and suffered severely. The prevalence of cholera in Russia, with an outdoor temperature below zero of Fahr., has always seemed an extraordinary circumstance, which it appeared only possible to explain by supposing that, in the houses, the foul air and the artificial temperature must have given the poison its necessary conditions of development. But Routh has pointed out that, in the poorer Russian houses, everything is thrown out round the dwellings; then, owing to the cold and the expense of bringing drinking water from a distance, the inhabitants content themselves with taking the snow near their houses and melting it. It is thus easy to conceive that, if cholera evacuations are thus thrown out, they may be again taken into the body. This is all the more likely, as cholera stools have little smell or taste, and when mixed even in large quantity with Avater, cannot be detected by the senses. We may therefore conclude that cholera evacuations which obtain access to drinking water contaminate it and render it immediately capable of producing the disease. If it is taken into the mouth and swallowed, the micro-organism may be destroyed by the acid secretions in the healthy stomach during the process of food digestion; but if, on the contrary, this does not take place, and the specific organism reaches the intestines, then the disease which almost invariably follows is cholera. The relative frequency of such immunity, the incubation period, and the severity of the disease produced, are points still uncertain. C 34 WATER. Assuming that the comma bacillus described by Koch, and found by him to be present in the drinking-water tanks in Calcutta, is the actual cause of cholera, the objection that this bacillus Avould probably be destroyed m a short time by the putrefactive organisms present in such Avater, loses its force when it is considered that, owing to the habits of the people, the infectious matter has every chance of being imbibed by other persons almost imme- diately after it reaches the Avater. There are some who even still deny that cholera is a water-b :>rne disease, though their number is rapidly diminishing. Pettenkofer of Munich adheres to this opinion. He states that the etiology of cholera appears to him as an equation with three unknown quantities—x, y, and z. x is the specific germ disseminated by human intercourse; y something that depends on the place or time, the " local disposition"; and z the individual pre- disposition met Avith in all infectious diseases. These conditions are essential for an epidemic of cholera to take place. These views have not borne the test of time. As he has himself stated, " the contagionists have eliminated the y, finding sufficient explanation in Koch's discovery of the x and seeing in the individual tendency or absence of immunity the factor x." In addition to the production of cholera from drinking water containing the cholera poison, it has been supposed that the use of impure Avater of any kind predisposes to cholera, though it cannot produce the disease. If the Avater acts in this way, it may be by causing a constant tendency to diarrhoea, or by lowering the resistance of the body, and rendering it more favourable as a nidus for the poison. Enteric Fever.—It is now generally accepted that the poison of enteric fever exists in the excretal discharges, e^pjeciallxtfie_urine, of those suffering from the disease, and if these gain access to water, it becomes one of the chief agents in the distribution of the disease. The micro-organism associated with enteric fever is a rod-shaped bacillus described by Eberth and Gaffky. That water may be the means of propagating this disease has long been admitted by those who have made the subject their special study, and is borne out by the researches of Jenner, Budd, Simon, and Hirsch, who consider that few points in the etiology of enteric are so certainly proved as the conveyance of the morbid poison by drinking water or by food contaminated with infected water. Many instances are recorded showing the connection between this disease and an impure water-supply long before the specific organism which is associated with it was recognised. In Mill- bank Prison enteric fever prevailed constantly until 1854, the water-supply being derived from the polluted Thames. After this it Avas taken from an Artesian well in Trafalgar Square : only three deaths occurred from 1854 to 1872 and no case at all since 1865. At Guildford, in 1867, an outbreak occurred almost exclusively amongst the dwellers in a particular area of water-supply. This particular area of 330 houses had been exceptionally supplied on one day in August with water from a new well; the epidemic broke out ten or eleven days afterwards. On examination the water Avas found to be polluted Avith organic matter; the well was situated in porous and fissured chalk, dangerously near a sewer, and this was found to be leaking. An interesting outbreak is that of Lausen in Switzerland, which occurred in 1872. The cases were confined to those who drank water from a certain spring. On the other side of a hill, 300 feet high, was a brook contami- nated with enteric excreta: when this Fiirler brook was dammed up to water the meadows, it was noticed that the spring at Lausen became turbid and bad tasting. Shortly afterwards 10 persons were attacked in one day DIFFUSION OF ENTERIC FEVER BY WATER. 35 and 57 more in the nine days following. Salt Avas put into the Fiirler brook, and its presence detected in the water at Lausen, clearly showing a direct connection. A destructive outbreak took place at Caterham and Redhill during 1878. This Avas traced to contamination of the Avater-supply by the stools of a workman suffering from mild enteric fever, avIio Avas employed in the Company's wells. The disease Avas confined to those avIio consumed the water, and ceased after the Avells were pumped out and cleansed. The inmates of the Lunatic Asylum and the detachment of troops at Caterham barracks used the Avater from the asylum Avell, and did not suffer. An outbreak of enteric fever at the Hampshire Lunatic Asylum at Fareham in 1886 Avas traced to the use of Avater originally pure, which had become polluted by spreading sewage on a portion of the land, also by percolation from the cemetery; the underground Aoav from the neighbour- hood of the cemetery and the sewage Avorks was in the direction of the well. An epidemic occurred at NeAv Herrington, Durham, in April 1889 : 275 cases were reported between 1st April and 7th June, Avhen the epidemic may be said to have ceased. The cause Avas traced to the pollution of a deep well (330 feet) by the overfloAv from a tank containing farm seAvage, situated three-quarters of a mile above this well. The overflow escaped and disappeared down a fissure in the ground, Avhich entered the Avell through a crack in the steining 45 feet beloAV the surface. Two tons of salt were throAvn down this fissure, and the chlorine entering the well through the " feeder," rose from 4 to a maximum of 24 grains per gallon. Specific contamination, hoAvever, of the farm-house sewage could not be made out, no illness resembling enteric fever having been known there for some years. One of the most remarkable and extensive epidemics of enteric fever was that which prevailed in 1890-91 in the Lower Tees Valley. Enteric fever attacks occasioning the first outburst were most marked during a six-weeks' period, 7th September to 18th October 1890; that occasioning the second outburst during a six-Aveeks' period, 28th December 1890 to 7th February 1891. The total number of enteric cases in the ten Registration Districts, form- ing the area under consideration, in the tAvo six-weeks' periods referred to, were 1463. Of these 1334, or 91 per cent., occurred in three out of the ten districts, namely, those of Darlington, Stockton, and Middlesbrough, all of which Avere supplied Avith water taken from the River Tees. The estimated population in the ten Registration Districts receiving their supply of water from the River Tees amounted to 219,435, whereas the estimated population receiving their water from other sources than the Tees reached 284,181. Calculating the attack rates upon these figures, it was found that the rate of attack from enteric fever per 10,000 living during the first six-weeks' epidemic had been 33 amongst persons supplied with the Tees Avater and 3 amongst persons supplied with other water; whereas in the second six- weeks' epidemic the rates were 28 and 1 respectively. Above the intakes of the water company the Tees receives either directly or indirectly the drain- age of tAventy villages and hamlets as well as that of the town of Barnard Castle. " Seldom, if ever, has the proof of the relation of the use of a water so befouled to the wholesale occurrence of enteric fever been more obvious and patent" (Thome Thorne). Worthing Avas visited with a severe outbreak of enteric fever in 1893. Between May 3rd and November 30th 1315 attacks are knoAvn to have occurred in the borough, with 168 deaths. After the first three weeks the 36 WATER. epidemic abated considerably, only to recur in the month of July with an outbreak of remarkable intensity. On investigating into the circumstances Avhich led to the epidemic of this disease, it Avas shown that it Avas intimately related in point of time to the admission to the Worthing Service Supply of water from a neAv source of supply, undertaken in order to obtain an in- crease of water for the borough; that thereafter the disease became general throughout the areas supplied by this service, and that Avithin the limits of these areas the incidence of fever Avas almost wholly on houses supplied with this water. It Avas further sIioavii that not only was this neAv source of supply open to dangerous contamination, but that also, on bacteriological examination, subcultures presented, morphologically as well as culturally, all the characters of the enteric fever bacillus. In this case the water Avas contaminated by seAvage Avhich flowed through a fissure communicating Avith the new well; the seAvers being jointed with clay and permitting leakage into the soil. It Avas also noted that there was comparative immunity from enteric fever of persons avIio habitually consumed water from local wells; and that there was heavy incidence of the disease on those who used the Avater delivered by the Public Service Supply. Moreover the Avater Avas not filtered. Experiments made in New York show that the enteric bacillus survives in river-Avater longer during the cold half of the year than the warm. Ordinary bacteria in the water Avere found to decrease from 10,500 in December to 300 per cubic centimetre in July. Hence water purifies itself most rapidly in Avarm Aveather, and enteric outbreaks are usually in the spring or fall. The spread of the disease through the medium of milk has now been abundantly proved, the poison having gained access to the milk no doubt through water. Budd was of opinion that in the cases in which the poison is conveyed by water, infection seems to be much more certain and the incubation period materially shortened, but this latter statement is not borne out by the history of more recent epidemics. In the attack at Guildford the in- cubation period was 11 days (Buchanan). Quincke, of Berne, published some cases due to drinking contaminated Avater, Avhere the incubation period Avas very accurately determined: the shortest was 8 days, and the longest betAveen 16 and 18 days. From 10 to 15 days is the usual period in enteric fever hoAvever pro- pagated. There has been some difference of opinion as to whether seAvage per se Avill produce enteric fever, or must the evacuations from an enteric fever patient pass into the Avater. This is part of the larger question of the origin and propagation of specific poisons. Those who believe in the evolution of species have perhaps good grounds for considering that any sewage, receiving faecal matters, may give rise to this specific form of fever; but as yet the weight of evidence is against such taking place. Diarrhoea.—There is ample evidence to prove that diarrhoea may result from drinking impure Avater, and when thus produced may be due to a variety of causes. Suspended mineral matters, such as clay and marl, found chiefly in the Avaters of rivers, such as the Mississippi, the Maas, Rio Grande, Kansas, and the Ganges, Avill at certain times of the year produce diarrhoea, especi- ally in persons unaccustomed to the Avater. The hill diarrhoea at Dhurmsala is said to be produced by very fine scales of mica suspended in the Avater. RELATION OF DIARRHCEA TO WATER-SUPPLY. 37 Suspended matters, animal (faecal) and vegetable, have produced diarrhoea in many cases; such water always contains dissolved organic matters to which the effect may be partly oAving. In cases in Avhich the water is largely contaminated Avith sewage, its use may produce symptoms resembling cholera. An instance is recorded Avhere seven persons in one house were attacked with violent gastro-intestinal derangement (vomiting, diarrhoea &c.) produced by water contaminated by seAvage which had passed into a cistern (Gibb). In St Petersburg the Avater of the Neva, Avhich is rich in organic substances, gives diarrhoea to strangers. Gore has recorded a violent outbreak of diarrhoea at Bulama, on the west coast of Africa, produced by Avater taken from a Avell: the water was good, but was milky from suspended matters, consisting of the debris of plants, chlorophyll, minute cellular and branched algce, monads, polygastrica, &c. When filtered the Avater was quite harmless. Wanklyn states that in the Leek Workhouse there has been for years past a general tendency to diarrhoea, which could not be accounted for until the Avater was examined and sIioavii to be loaded Avith vegetable matter. The water Avas almost free from chlorine, containing only 0*5 grain per gallon. He also instances the case of a well on Biddulph Moor, a few miles from Leek, Avhich on analysis yielded 0*5 grain per gallon of chlorine and 0'03 free and 0*14 albuminoid ammonia parts per million. The persons who were in the habit of drinking this Avater suffered from diarrhoea. An excess of dissolved nitrogenous organic matter may produce diarrhoea, but it is difficult to estimate its exact influence, on account of the presence of other impurities. The animal organic matter derived from graveyards appears to be especially hurtful; here also ammonium and calcium nitrites and nitrates may be present. Water containing much hydrogen sulphide Avill give rise to diarrhoea, especially if organic matter be also present. In the Mexican War (1861— 62) the French troops suffered at Orizaba from a peculiar dyspepsia and diarrhoea, attended with immense disengagement of gas and enormous eruc- tations after meals. The eructed gas had a strong smell of hydrogen sul- phide. This was traced to the use of water from sulphurous and alkaline springs; even the best waters of Orizaba contained organic matter and ammonia in some quantity. Medicinal sulphuretted waters are well known to have a purgative action. The absorption of sewer gases by water, as when the overfloAv-pipe of a cistern opens into the sewers, will cause diarrhoea. Dissolved mineral matters, Avhen in excess, may produce diarrhoea. Sulphates of magnesia and lime are the most usual as pro- ducing this effect, as is seen in the case of many purgative medicinal Avaters. Calcium nitrate Avaters also produce diarrhoea. A case is on record, in Avhich a Avell water Avas obliged to be disused, in consequence of its impreg- nation with butyrate of calcium (150 parts per 100,000), which Avas derived from a trench filled with decomposing animal and vegetable matters. The effect of calcium and potassium nitrate in causing a tendency to diarrhoea Avas also observed in Berlin. Brackish Avater (whether rendered so by the sea, or derived from loose sands) produces diarrhoea in a large percentage of persons, and at some of the Cape frontier stations water of this character formerly caused much disease of this kind. In a Avater examined at Netley, which became brackish from sea-Avater and produced diarrhoea in almost all persons, the amount of chloride of sodium Avas found to be 361 parts per 100,000. 38 WATER. But, doubtless, a much less quantity than this, especially if chloride of magnesium be present, will act in this way. Sometimes organic matter in Avater, by producing nitrates and nitrites, which act on metals (lead), may produce illness of a specific character. Dysentery.—This disease is decidedly produced by impure water, and the substitution of a pure for an impure supply has been frequently followed by a decrease in the prevalence of dysentery in an affected community. The instances in Avhich outbreaks of dysentery have been traced to the use of water contaminated with faecal impurities are very numerous. We shall simply notice a few of the most conclusive instances of this nature. On the west coast of Africa (Cape Coast Castle), an attack of dysentery was traced to the passage of seAvage from a cesspool into one of the tanks. This Avas remedied, and the result Avas the almost total disappearance of the disease. That in the East Indies a great deal of dysentery has been produced by impure water, is a matter too familiar almost to be mentioned. Its constant prevalence at Secunderabad, in the Deccan, appears to have been partly OAving to the water, which percolated through a large graveyard. The great effect produced by the impure Avater of Calcutta in this Avay has been pointed out by Chevers. In time of Avar this cause has often been present; and the great loss by dysentery in the Peninsula, at Ciudad Rodrigo, was partly attributed by Sir J. M'Grigor to the use of Avater passing through a cemetery where nearly 20,000 bodies had been hastily interred. At Metz, during the summer of 1870, there Avas a severe epidemic of dysentery in two regiments, the rest of the troops escaping the disease. Inquiry showed that the former had drunk well-water greatly contaminated with faecal soakage from latrines placed opposite and close to them. When the wells Avere closed the disease suddenly ceased. In 1881, the troops occupying the same barrack Avere supplied with drinking water from the same wells, Avhereupon cases of dysentery reappeared, and the closing of the wells had once more the desired effect. In a large number of these instances, the water Avhich gave rise to dysentery was polluted with faecal and possibly Avith dysenteric discharges. But the disease has also been ascribed to the use of marsh and brackish water, of water contaminated Avith decaying animal matters, and of Avaters containing an excess of mineral salts in solution. It is easy to understand that water may not only serve as a vehicle by means of which the specific cause of dysentery may be introduced into the system, but it may also serve as an irritant, and thus act as a predisposing cause of infection. Yellow Fever.—As, like dysentery, enteric fever and cholera, the ali- mentary mucous membrane is primarily affected in yellow fever, there is an a priori probabihty thatfthe cause is SAvallowed also in this case, and that it may possibly enter with the drinking water. But no good evidence has been yet brought forward. Dyspepsia.—Symptoms which may be referred to the convenient term dyspepsia, and which consist in some loss of appetite, vague uneasiness or actual pain at the epigastrium, and slight nausea and constipation, with occasional diarrhoea, are caused by water containing a large quantity of calcium sulphate and chloride, and the magnesian salts. Sutherland found the hard water of the red sandstone rocks, which Avas formerly much used in Liverpool, to have a decided effect in producing constipation, lessening the secretions, and causing visceral obstructions; and in GlasgoAv the substitution of soft for hard Avater lessened the prevalence of dyspeptic RELATION OF MALARIAL FEVERS TO WATER-SUPPLY. 39 complaints (Leech). It is a well-knoAvn fact that grooms object to wive hard water to their horses, on the ground that it makes the coat staring and rough—a result which has been attributed to some derangement of diges- tion. The exact amount which will produce these symptoms has not been determined, but water containing more than 11 parts per 100,000 of each substance individually or collectively appears to be injurious to many persons. A much less degree than this will affect some persons. In a well- water at Chatham, which Avas found to disagree Avith so many persons that no one would use the water, the main ingredients Avere 27 parts of calcium carbonate, 16 parts of calcium sulphate, and 18'5 parts of sodium chloride in 100,000. The total solids Avere 71-4 parts in 100,000. In another case of the same kind, the total solids Avere 83 parts in 100,000 ; the calcium carbonate Avas 31, the calcium sulphate 16, and the sodium chloride 20 parts per 100,000. Iron, in quantities sufficient to give a slight chalybeate taste, often pro- duces slight dyspepsia, constipation, headache, and general malaise. Custom sometimes partly removes these effects. Malarial Fevers.—Water from marshes has been long considered to produce fever in those Avho drink it, and the same belief exists now among the inhabitants of marshy countries, avIio assert that marsh waters can produce fever. Even Hippocrates in his time noticed that the spleens of those who drank water of this kind became enlarged and hard. It is difficult to state exactly the role water plays in disseminating the poison of malaria, as those who suffer are otherwise exposed to malarious influences: still there is evidence to show that cases have occurred which can only be accounted for by using Avater derived from marsh lands and malarious soils. On making some inquiries of the inhabitants of the highly malarious plains of Troy during the Crimean war, Parkes found the villagers univer- sally stated, that those who drank marsh water had fever at all times of the year, while those avIio drank pure water only got ague during the late summer and autumnal months. The same belief is prevalent in India. In the Wynaad district in Madras it is notorious that the water produces fever and affections of the spleen. Instances are knoAvn Avhere villages are placed under the same conditions as to marsh air, yet in some of them fevers are prevalent, in others not; the only difference being, that the latter are supplied with pure water, the former Avith marsh or nullah water full of vegetable debris. In one village there were two sources of supply—a tank fed by surface and marsh water, and a spring; those only who drank the tank water got fever. In a village (Tulliwaree) no one used to escape the fever; a well was dug, the fever disappeared, and, during fourteen years, had not returned. Another village (Tambatz) was also " notoriously unhealthy " ; here also a well was dug, and the inhabitants became healthy. Nothing can well be stronger than the positive and negative evidence here given. Moore also noted his opinion of malarious disease being thus produced; and Commaille has since stated, that in Marseilles paroxysmal fevers, formerly unknown, have made their appearance, since the supply to the city has been taken from the canal of Marseilles. In reference also to this point, Townsend, the Sanitary Commissioner for the Central Provinces in India, states in one of his reports that the natives have a current opinion that the use of river and tank water in the rainy season (Avhen the water always contains much vegetable matter) will almost certainly produce fever (i.e., ague), and he believes that there are many circumstances supporting 40 AVATER. this vieAv. In this Avay the prevalence of ague in dry elevated spots is often, he thinks, to be explained. He mentions also that the people who use the water of streams draining forest lands and rice fields " sutler more severely from fever (ague) than the inhabitants of the open plain drawing their water from a soil on which wheat grows." In the former case there is far more vegetable matter in the Avater. The Upper Godavery tract is said to be the most aguish in the province, yet there is not an acre of marshy ground; the people use the water of the Godavery, Avhich drains more dense forest land than any river in India. In the belt of marshy land and forest stretching along the base of the Himalayas, and known as the Terai, it has always been the belief that the transmission of malarial fever was caused by drinking water. Whalley states that a party of workmen, sent to repair a bridge over the Chuka, and Avho Avere dependent on this stream for their drinking water, suffered severely from fever, only three escaping out of thirty, and many dying. Since then a deep masonry Avell has been constructed a few hundred yards from the bridge, and the forest guards who are located there, and drink only the well-water, find the station as healthy as any other. The folloAving instructive case bears on this question. The artillery quartered at Tilbury Fort formerly suffered more or less from ague, whilst the people at the raihvay station, and the coastguard and their families in the ship lying just outside the fort, never suffer from malarious poisoning. The troops had been supplied Avith drinking water from two underground tanks Avhich received rain-Avater from the roof of the barracks, Avhilst the other persons above mentioned draw their drinking water from a spring near the railway station. In the six months, from January to June 1873, there were amongst the troops 12 admis- sions for ague out of a strength of 102. From December 1873 to July 1874 they Avere supplied from the spring near the railway station, on account of the barrack tanks being out of repair. From December 1873 to July 1874 there was only one case out of a strength of 90 men; Avhile from November 1874, when the Avater from the tanks was brought into use again, until March 1875, there were four cases out of a strength of 53 men. An analysis of the waters showed that the tanks Avere exposed to soakage from the surrounding salt marsh; for the so-called rain-Avater yielded 59 parts per 100,000 of total solids in the one case and 207*5 in the other; the chlorine being respectively 18 and 47 parts per 100,000. Another case of importance is that recounted by Smart. In the Rocky Mountain district of North America a fever prevails, which is popularly knoAvn as the Maintain fever ; it is of a remittent type, and is amenable to quinine. _ There is, however, no malarious district in the neighbourhood, and cases of intermittent fever from the plains recover rapidly there; the disease occurs sometimes when the thermometer is at times below zero, and always below the freezing point, but most frequently at times when fever does not occur in the plains, but which coincide with the melting of the snoAvs, viz., May, June, and July. On analysis it was found that all the water in the rivers contained a large excess of organic matter, the purest showing from 0*019 to 0*028 per 100,000 of albuminoid ammonia, Avhilst the springs showed only 0*010. The amount Avas much increased after heavy snowfall and on analysing the snow he was surprised to find it contained a large excess of organic matter, especially that which fell in large heavy flakes (as high sometimes as 0*058 of albuminoid ammonia). Smart concludes that vege- table organic matter is bloAvn up from the plains and precipitated with the RELATION OF MALARIAL FEVERS TO WATER-SUPPLY. 41 snow, and, when the latter melts, carried into the streams. The exclusion of the snoAV-Avaters and heavy rainfalls, by erecting storage reservoirs, gave the place a comparatively pure spring-Avater at all times, and this fever occurred afterwards but slightly. One very important circumstance is the rapidity of development of the malarious disease and its fatality when introduced in Avater. It is the same thing as in the case of diarrhoea and dysentery. Either the fever-making cause must be in larger quantity in the water, or, Avhat is equally probable, must be more readily taken up into the circulation and carried to the spleen, than AAdien the cause enters by the lungs. In opposition, however, to all these statements must be placed a remark of Finke's, that in Hungary and Holland marsh water is daily taken with- out injury; but in Hungary, Grosz states that, to avoid the injurious effects of the marsh Avater, it is customary to mix brandy Avith it. Colin, of the Val de Grace, who is so well knoAvn for his researches on intermittent fever, questions the production of paroxysmal fevers by marsh water. He cites numerous cases in Algiers and Italy, where impure marsh water gave rise to indigestion, diarrhoea, and dysentery, but in no case to intermittent fever, and in all his observations he has never met with an instance of such an origin of ague. Hirsch considers that the observations, which have been adduced to prove the diffusion of malaria by means of drinking Avater, do not bear the con- structions that the writers put upon them; and he believes that there is no proof of the propagation of the disease by this means. W. North adduces the fact that " the healthiest parts of the city of Rome are supplied by Avater admitted to be the best in the Avorld, and Avhich rises—to take the Acqua di Trevi or Acqua Vergine as an example—on unenclosed land, in springs which bubble up and cover the surface in a locality so unhealthy, that to pass several nights there in August might involve risk to hfe, and certainly to health." He thinks that "proof that the malarial affection can be conveyed by Avater is Avanting, though very largely credited by the natives of countries Avhere the disease prevails." Although it has been alleged that malarial diseases may be introduced on board ship by means of drinking water, the records of the Royal Navy do not support this view. The statistical returns for the last thirty years do not shoAV a diminution in the proportion of cases of malarial fever, although very great improvements have been made during that time in regard to supplies of drinking water and the more extended use of distilled water. Other Zymotic Diseases.—Scarlet fever appears to be the only other zymotic disease likely to be propagated by water. The evidence for such propagation was formerly very slight, but numerous cases have occurred Avhich have been attributed to water mixed with milk. Later researches go to shoAV that it is the milk which is the medium of infection and not the water. Although there seems no primd facie reason against water being a channel of infection, evidence that it is so is wanting : this disease certainly is not disseminated by Avater as a rule. It has been suggested that diphtheria may be disseminated by the agency of drinking water, but the evidence at present is against such being the case. In no single instance has Avater been identified as the probable cause of diphtheria in the investigations undertaken by the Local Government Board. As a matter of fact, the diphtheria organism finds it very difficult to live in Avater. It can apparently only maintain existence in very polluted Avater, ■ but average Avater is to a large extent destructive to its vitality (Thorne). Oriental Sore.—Under this term are included those specific forms of sores 42 AVATEK. spoken of as Aleppo, Bagdad, or Delhi boil. Various Avriters have attri- buted its spread to the use of impure water. It is certain that the disease can be conveyed by inoculation, and therefore that it depends on an organised virus. The disease is probably conveyed in the course ^ of washing with infected water: this possibly being only one means by which it is disseminated. Goitre.—The opinion that impure drinking Avater is the cause of goitre is as old as Hippocrates and Aristotle, and has been held by the majority of physicians. The opinion may be said actually to have been put to ^ the test of experiment, since both in France and Italy the drinking of certain Avaters has been resorted to, and apparently Avith success, for the purpose of produc- ing goitre, and thereby gaining exemption from military conscription. And this is supported by the evidence of Bally, Coindet, and by many of the French army surgeons, Avho have seen goitre produced even in a feAv days (8 or 10) by the use of certain Avaters. Apart from this, the evidence for the causation by water is extremely strong, many cases being recorded where in the same village,- and under the same conditions of locality and social life, those who drank a particular water suffered, while those avIio did not do so escaped. Another author who has written on this subject, and avIio has accumulated an immense amount of evidence, Saint-Lager, expresses himself very confidently on the point. In the report of the French Commission (1873) Ave find the folloAving case : —At Bozel (Tarentaise) there were, in 1848, about 900 goitrous persons, and 109 cretins in a population of 1472, while the village of St Bon, standing 800 metres higher, was quite free from both diseases : a water-pipe having been carried from this village to Bozel, and this Avater having come into general use, the endemic decreased so remarkably, that in 1864 there were only 39 goitres and 58 cretins, and no fresh cases occurring. The impurity in the Avater which causes goitre is not yet precisely known. It is certainly not owing to the want of iodine, as stated by Chatin, and there is little probability of its being caused by a deficiency of chlorides, by fluorine, or by silica. On the other hand, the coincidence of goitre with sedimentous Avater is very frequent. Since the elaborate geological inquiries of Grange and the analysis of the waters of the Isere, magnesian salts in some form have often been considered to be the cause, to Avhich many add lime salts also; and certainly the evidence that the Avater of goitrous places is derived from limestone and dolomitic rocks, or from serpentine in the granitic and metamorphic regions, is very strong. The investigations now include the Alps, Pyrenees, Dauphine, some parts of Russia, Brazil, and districts in Oude in North-West India. A table compiled from M'Clellan's Avork is very striking : — Goitre and Cretinism in Kumaon (Oude). Water derived from Granite and gneiss, . Mica, slate, and hornblende, Clay slate, Green sandstone, Limestone rocks, Percentage of Population affected. With Goitre. With Cretinism. 0*2 0 0 0 0-54 0 0 0 •JO 3 0 RELATION OF PARASITIC DISEASES TO WATER-SUPPLY. 43 There are, hoAvever, not wanting analyses of Avater of goitrous regions which show that magnesia may be absent (in Rheims, according to Maumene ; in Auvergne, according to Bertrand; in Lombardy, according to Demortain; and Saint-Lager enumerates other cases), Avhile it has been also denied that there need be any excess of lime. Goitre does not appear to be a prevalent disease in Sunderland or in Bristol, towns Avhich have water-supplies which are hard, calcareous, and rich in magnesium salts. In the jail at Durham, Johnston states that Avhen the water contained 110 parts per 100,000 (chiefly of lime and magnesium salts) all the prisoners had swellings of the neck; these disappeared Avhen a purer water, contain- ing 26 parts per 100,000, was obtained. Wilson carried out some inquiries at Bhagsu, Dhurmsala, where goitre prevails extensively. He analysed specimens of the drinking water Avithin a radius of ten miles, and found them exceptionally pure, only three shoAving traces of lime, and none giving any evidence of magnesia or iron. Macnamara, basing his opinion on personal observation and inquiry, does not believe that there is any relation betAveen the lime and magnesium hardness in Avater and goitre. In the Brahmapootra and Chenab valleys, are certain spots on the river bank' where goitre is prevalent, while in neighbouring villages similarly situated, where the same water, that of the river, is used, there is none. He further states that in all goitrous localities, it is during and after the rains, Avhen the water, so far as their mineral ingredients are concerned, must be in the state of greatest dilution, that the disease most commonly commences and most rapidly develops. It seems, therefore, that the question is still undecided, and it is much to be desired that more extended inquiry should be made, with careful analyses, as well as records of local and other conditions, which probably contribute more or less to the production of the disease. Parasitic Diseases.—Whereas the Taenia solium and the Ttenia medio- canellata, and many entozoa, find their way into the body with the food, the two forms of the Bothriocephalus lotus (T. lata) may pass in Avith the drinking water. Both embryo and eggs (but principally, or perhaps entirely, the former) exist in river-water. The ciliated embryo moves for several days very actively in water; it may after a time lose its ciliary covering, and then, not being able to move further, perishes; or it may find its way into the body of some animal, and there develop into the Bothriocephalus lotus. It is mostly indigenous to the sea coast and to the shores of lakes and other inland water. It is most common in the interior of Russia, Sweden, in part of Poland, and in Switzerland. Distonia hepaticum (Fasciola hepatica).—The eggs are developed in water, and the embryos swim about and live, so that introduction in this way for sheep is probable, and for men is possible. The Ascaris lumbricoidvs (Round-Avorm) appears also sometimes to enter the body by the drinking water. At Moulmein, in Burmah, during the wet season, and especially at its commencement, natives and Europeans, both sexes and all ages, Avere, in former years, so affected by lumbrici that it was almost an epidemic. The only circumstance common to all classes Avas that the drinking Avater, draAvn chiefly from shallow wells, Avas greatly contaminated by the substances washed in by the floods of the excessive monsoon which prevails there. Similar facts have also been noticed in England. Leuckart has no doubt of the passage of the Ascarides' eggs into drinking Avater; and, indeed, they have been actually seen in the Avater by Mosler. 44 AVATER. But it seems yet doubtful (as all experiments have failed in producing from the drinking water the worms in animals) Avhether the eggs alone Avill suffice, and it seems possible that they must pass through some other host before developing in the human intestine. This Avas also the opinion of Cobbold. Mosler attributed in his case much influence to the large amount of vegetable food taken by the persons affected. The Dochmius duodenalis (Strongylus duodenalis, Anch ylostomum seu Sclerostoma duodenale) Avould appear from Leuckart's statement to be introduced by impure Avater. It is especially prevalent in Brazil and in Egypt, where it causes the so-called "Egyptian chlorosis" (Griesinger). During the construction of the St Gothard Tunnel, the Avorkmen were much affected by a severe, and often fatal, form of anaemia, due to the presence of this parasite. The disease is propagated mainly, if not altogether, by drinking water containing the ova or embryos. The Beri-beri of Ceylon is said by Kynsey to be due to the presence of Anchylostomum duodenale in the intestinal canal; "to be, in fact, Anchylostomiasis." The cause is the presence of the ova of the parasite in drinking water. Oxyuris vermicular is, very common in children, but occasionally also found in adults, is probably sometimes taken through Avater. Filaria Dracunculus (Guinea-Avorm).—The introduction by Avater of Filaria has long been a favourite opinion. It has been a matter of debate whether it is taken into the stomach as drink, and thence finds its Avay (like Trichina, to the muscles) into the subcutaneous cellular tissue, or whether it penetrates the skin during bathing or Avading in streams. The latter opinion seems to be the more probable in the majority of cases. Fedschenko, hoAvever, has shown that the embryo enters the body of a cyclops, which acts as its host, and that it undergoes development there, and is thus taken in Avith drinking water. Boiling the Avater before drinking appears to have a preservative effect. Filaria sanguinis hominis appears to find its Avay into the blood of man through water in a curious way. Manson has found that the mosquito is an active agent in the propagation of Filaria. The embryos are taken into the mosquito's stomach with the blood of persons infected by the haamatozoon. Arrived there, the parasite penetrates the walls of the stomach, and works its Avay to the thoracic tissues of the insect, where further development takes place. Thence they are transferred to the water, whence it is assumed that it again finds entrance into the body of man. It produces Elephantiasis and chyluria. Bilharzia hosmatobia.—From the observations of Griesinger, John Harley, and Cobbold, there seems no doubt that the embryos of this entozoon live in water, and the animal may be thus introduced probably by the medium of some other animal. Batho doubts, hoAvever, this introduction by water, since the entozoon occurred in persons using rain-Avater and pure mountain stream water. It causes endemic hematuria in Egypt, the Cape, and elsewhere. Leeches.—Small leeches may be present in water, Avhich fix on the pharynx, or in the posterior nares, after drinking. Cleghorn noticed that coughs, nausea, and spitting of blood Avere thus caused. In a march of the French near Oran, in Algiers, more than 400 men were at one time in hospital from this cause. In some cases the repeated bleedings from the larynx have simulated haemoptysis and phthisis, and have produced anaemia. A leech, once fixed, seldom falls off spontaneously. Lead, Arsenic, Copper, Zinc, &c, in Water.—The question of lead poisoning by drinking water has already been considered. It is only PURIFICATION OF AVATER. 45 necessary to mention the fact of metals passing into the drinking water, either by trade refuse being poured into streams, or by the water dis- solving the metal as it flows through pipes or over metallic surfaces. The amount of copper required to produce poisonous symptoms appears to be doubtful. In 1864 a factory at Basle discharged Avater containing arsenic into a pond, from Avliich the ground and adjacent Avells were contaminated, and severe illness in the persons Avho drank the Avell-Avater Avas produced. Water, impregnated with sulphurous acid, gives rise in cattle to a number of serious symptoms, among others to diseases of the bones. The sulphur dioxide evolved from the copper Avorks at Swansea has caused numerous actions on account of the loss of herbage and cattle. Rossignol states that Avater highly charged with calcium carbonate and sulphate Avas found to give rise to exostoses in horses ; pure water being given, the bones ceased to be diseased. General Conclusions.—An endemic of diarrhoea, in a community, is almost ahvays owing either to impure air, impure water, or bad food. If it affects a number of persons suddenly, it is probably owing to one of the two last causes; and if it extends over many families, almost certainly to Avater. But as the cause of impurity may be transient, it is not easy to find experi- mental proof. Diarrhoea or dysentery, constantly affecting a community, or returning periodically at certain times of the year, is far more likely to be produced by bad water than by any other cause. A very sudden and localised out- break of either enteric fever or cholera is almost certainly owing to the introduction of the poison by Avater, and the same fact holds good in cases of malarious fever and especially if the cases are very grave. The introduc- tion of the ova of certain entozoa by means of Avater is proved in some cases and is probable in others. Although it is not at present possible to assign to every impurity in water its exact share in the production of disease, or to prove the precise influence on the public health of water which is not extremely impure, it appears certain that the health of a community always improves Avhen an abundant and pure water-supply is given; and, apart from this actual evidence, we are entitled to conclude, from other considerations, that abundant and good water is a primary sanitary necessity. PURIFICATION OF WATER. The purification of Avater may be necessary to remove excessive hardness, suspended matters, dissolved organic matter, or the micro-organisms usually associated with specific diseases. Distillation.—This is undoubtedly the best plan, for if properly carried out all danger is removed. Unless, however, the water is taken from a clean source it may produce illness even if distilled. An outbreak of diarrhoea on board H.M. ships in the harbour of Valetta Avas attributed to impurities in the Avater distilled from the not over-clean water of the Grand Harbour. The distilled water Avas also complained of as " going bad " very quickly in the Soudan campaign; but there the dirty water of the harbour of Suakim was used, and in such a case there may have been an excessive quantity of free ammonia in the water which passed over into the distillate; this shows the necessity of seeking a pure supply to distil the water from. All distilled Avater should be tested Avith a few drops of dilute nitric acid 46 WATER. and silver nitrate; if no haze appears, then the Avater may be considered safe: all other Avaters "will give evidence of the presence of chlorine, by the formation of a precipitate, turbidity, or haze according to the amount; and so Avill distilled Avater (so-called), if it has been contaminated during the process of distillation, or by being received in vessels not perfectly clean. Boiling.—This plan is next best to distillation: it gets rid of calcium carbonate, iron in part, and hydrogen sulphide, and lessens, it is said, organic matter. Tyndall's experiments have shown that there are stages in the life of bacteria during which they can resist almost any moist heat. But as they soften before propagation a solution can be successfully sterilised by repeated boilings, so as to attack the several crops of bacteria in their vulnerable condition. Most fungus spores are killed by boiling. On the whole Ave may take it that water, even only once boiled, is in all likelihood safe, and, if repeatedly boiled at intervals, quite safe. Chemical Processes.—Alum has been used to purify water from suspended matters. It does this very effectually if there be calcium carbonate in the water; calcium sulphate is formed, and this and a bulky aluminum hydrate entangle the floating particles and sink to the bottom. The quantity of crystallised alum to be used should be about 6 grains per gallon. If a sedimentous water is extremely soft, a little calcium chloride and sodium carbonate should be put in before the alum is added. Clark's process for the softening of water really combines chemical Avith mechanical action. This plan has been carried out with great success on a large scale in the form known as the Porter-Clark process. Lime water is mixed, by means of rakes or fans, with the water to be purified, and by entering into combination with the C02 in the water, the calcic carbonate is rendered insoluble, and thrown down as a precipitate : this acts mechani- cally in removing a large portion of the organic matter, and, it is said, iron. The water is subsequently clarified either by subsidence or by being forced through a filter of stretched canvas, by which all solid impurities are removed : it does not touch calcium and magnesium sulphate or chloride. The folloAving equation explains this action :— CaC03 + C02 + CaH202 = 2CaC03 + H20. Sodium carbonate, with boiling throws down lime, and a little lead, if present. Maignen's process consists in adding to the Avater a powder, called anti- calcaire, containing chiefly lime, sodic carbonate, and alum. The alum precipitates organic matter, whilst the sodic carbonate attacks the lime and magnesia. Addition of Potassium or Sodium Permanganate.—Pure Condy's fluid readily removes the smell of hydrogen sulphide and the peculiar offensive odour of impure water which has been kept in casks or tanks. If it forms a precipitate of manganic oxide, it also carries down suspended matters • but the formation of this precipitate is very uncertain. The action on the dissolved organic matters will,, of course, vary with the nature of the substance; some of the organic matters, both animal and vegetable will be oxidised; but in the cold it will not act upon the whole of these substances, and some organic matters are not touched. One objection to the use of the permanganate is that it often communi- cates a yellow tint to the Avater, arising from suspended finely divided peroxide of manganese. This is probably of no moment as far as health is concerned, but it is unpleasant. Sometimes the addition of a little alum FILTRATION OF AVATER. 47 will carry doAvn this suspended matter; boiling may be used, but often has no effect. Sometimes nothing removes it but filtration. The indications for the use of permanganate are these. In the case of any foul-smelling or suspected Avater, add good Condy's fluid, teaspoonful by teaspoonful, to 3 or 4 gallons of the Avater, stirring constantly. When the least permanent pink tint is perceptible, stop for five minutes; if the tint is gone, add 36 drops, and then, if necessary, 30 more, and then allow to stand for six hours; then add for each gallon 6 grains of a solution of crystallised alum, and if the Avater is very soft, a little calcium chloride and sodium carbonate, and allow to stand for twelve or eighteen hours. Filtration.—One of the chief, if not the chief, objects of water filtration for domestic purposes is a removal of disease-producing germs. It is there- fore of primary importance to learn the bacterial efficacy of filters, as well as to ascertain what amount of chemical purification the water has undergone by the action of the filtering media. The knowledge which later methods of investigation have afforded concerning the nature of the infective matter, teaches us that AArater, by the process of filtration, must not only be rendered clear and free from sedimentary deposits, but that, Avhen taken from any doubtful source, it must be freed from the infectious material which may gain access to it. The chemical examination of Avater affords useful information and is not too hastily to be disregarded or given up for bacteriological tests. It distinctly, in the present instance when dealing Avith the principles of filtration, indicates the quantity of food material in the Avater and Avhether it is present in sufficient amount to support a vigorous growth of bacteria : it also shows whether the organic nitrogen remains the same in the filtering medium, or if it is increased by the organic matter stored in it. While, therefore, we must necessarily rely on bacteriological tests for direct information as regards specific diseases and their dissemina- tion by water, chemical analysis affords us a guide as to the general characters of potable water and whether it is likely to produce disease. One method of investigation assists the other : both taken together afford the best basis from which to draw safe conclusions. It is necessary, therefore, to consider filtration on a large scale as carried out with large water-supplies by public companies, and domestic filtration as applied to relatively small quantities of water in habitations. Filtration through Sand and Gravel.—On a large scale, Avater is received into settling reservoirs, where the most bulky substances subside, and is then filtered through gravel and sand, either by descent or ascent, or both. The New River Company's filter beds are constructed from above downwards of a layer of sand, 30 inches in thickness, followed by 6 inches of gravel placed on a similar thickness of bricks. The water passes through at the rate of 6 inches per hour : half a cubic foot of water ( = 3*11 gallons) percolates dowmvards through each square foot of surface per hour : this is equal to nearly 136,000 gallons per acre per hour. The action of a sand filter bed is partly mechanical, partly vital: the mechanical action consists in holding back the grosser suspended substances in the Avater, and this, which Avas until recently supposed to be the only operation in a filter, is noAV held to be of secondary importance: the vital action takes place in the deposit from the unpurified water; a gelatinous layer is formed on the surface of the filter, and it is on the activity of the living matter in this surface layer that real filtration takes place. A new filter has no effect in producing bacteriological purification untU this deposit, 48 WATER. charged with living micro-organisms, is formed on the surface, and it is to these organisms, Avhich rest on the surface and penetrate the sand to a slight distance, that both the nitrification of organic matter and the arrest of other microbes is effected. This surface layer should not be disturbed during the process of filtration until it becomes so thick as to be imperme- able to water. Cleansing, by which the superficial layer is removed, should only be carried out Avhen the filter ceases to act. The thickness of the layer of sand, and the rate the water percolates, are two points requiring careful attention. The former should never be alloAved to get below 30 cm. (=11*8 inches), and the rate of filtration should not exceed 100 mm. ( = 3'94 inches) in an hour, in order to obtain the most perfect filtration. If the filter Avorks satisfactorily in every respect, there should be found less than 100 germs capable of develop- ment in 1 c.c. of filtered Avater. The small number of germs remain- ing in the filtered Avater are due to the filtering media in process of time being covered with vegetable micro-organisms; these are naturally Moveable covering stone Paving Level of ground Animal charcoal is far too expensive for use in large filters, and this DOMESTIC FILTERS. 49 medium is noAV almost entirely restricted to small filters used for domestic purposes. Spongy iron is a substance obtained by roasting haematite ore : it is a porous metallic iron, not unlike animal charcoal in appearance, and occupies :about tAventy cubic feet to the ton. It yields a little iron to Avater, which, however, can be removed by further filtration through pyrolusite or black oxide of manganese and fine gravel and sand. It acts upon the Avater itself, decomposing it and setting free hydrogen, the oxygen being given up to the organic matter. Its action on water is both mechanical and chemical, for it arrests suspended matters and also oxidises organic matter in solution. It is said, however, not to sterilise water, and water cannot be stored after filtration without undergoing signs of deterioration. Unless kept covered Avith Avater, spongy iron dries rapidly and cakes, when it loses its^poAver of effecting any change, and water ceases to pass through it. This material has been used in the water works at Antwerp, and is said to give satisfaction. It possesses no advantages over sand, while there are -certain disadvantages connected with its use, notably its tendency to cake, and the addition of iron salts to the Avater which have subsequently to be removed. Moreover, it permits the free passage of bacteria. Polarite, or magnetic spongy carbon, consists of magnetic oxide of iron with some alumina, magnesia, silica, lime, and a trace of carbon. Its action is very similar to that of spongy iron, over which it possesses no special advantages. All these substances have been abandoned, more or less, in this country as giving less satisfactory results than clean sand. If a fairly pure water- supply be adopted, the best results will be obtained by filtration through clean sand. It is hopeless to attempt to make a polluted water safe for drinking purposes by any process of simple filtration, and any attempt to do .so should be deprecated. Domestic Filters.—When water is supplied by a public company for -domestic purposes it should be sufficiently purified, before distribution, so as not to require filtration. Circumstances exist, however, in Avhich domestic filtration is often a necessity. A number of substances have been suggested or used for this purpose. Among the more important of these are, animal and vegetable charcoal, in granules or powder or made into blocks, or fine silica impregnated with charcoal (silicated carbon filters), haematite and magnetic iron ores, the so-called magnetic carbide, spongy iron, manganic -oxide, flannel, wool, sponges, porous sandstones (natural and artificial), &c. Animal charcoal was formerly considered to be one of the best filtering materials. Later experiments, however, show that, although it possesses considerable oxidising powers on organic impurities present in Avater, it does not sterilise it, but, on the contrary, favours the development of micro- organisms in the water. It adds both phosphates and nitrogen to water, which form a nutritive medium for bacteria. Water filtered through animal charcoal rapidly deteriorates as the charcoal yields up impurities to water, so that in many cases the water is more impure after it has passed through the filter than it was originally. While the charcoal attacks and oxidises the putrefactive organic matters in solution, it permits fresh or vital organic matter to pass through unchanged. On the whole, there is perhaps no material more unsuited or unsafe to use as a filtering medium for potable waters than animal charcoal. This cannot be too widely knoAvn, -as it is still advocated in many standard works as being the best filtering material, notwithstanding the fact that recent methods of investigation liave shoAvn it to be the very reverse. D 50 WATER. Doulton's Manganous Carbon is a mixture of animal charcoal and black oxide of manganese : the manganese dioxide is intended to act as an oxidiser. Carbalite is used in the Royal Navy. It is said that, Avhile having all the purifying powers of animal charcoal, from the absence of any phosphate or nitrogenous animal matter, it in no way favours the groAvth of Ioav forms of life. It is used in Crease's filters. Spencer's Magnetic Carbide is prepared by roasting equal parts of red haematite ore and saAvdust in a retort; the resulting carbide of iron is crushed and mixed Avith sand: it is said to ansAver Avell for filtering. purposes. Spongy iron and polarite have also been used in domestic filtration. Beyond a little iron, spongy iron yields nothing to Avater, and in this respect is preferable to any form of animal charcoal. Sponge has a considerable effect in mechanically arresting suspended particles; it is apt to get foul, and being itself an organic substance ought not- to be used. Asbestos is a much better material and can be easily reburnt. The Chamberland-Pasteur is the best of all domestic filters. Its con- struction is very simple, for it merely consists of a cylinder of unglazed porcelain made from a well-baked kaolin of a certain degree of porosity and hardness, closed above and terminating beloAv in an open nozzle. This cylinder is inclosed in a metal or glass jacket, a space intervening between the two above and at the sides, while beloAv they are fixed together by a screAv tap, with an opening in the centre for the passage of the nozzle. The outer cylinder is closed above except where it joins the water- pipe (fig. 2). The water passes through the porcelain from without inAvards and under a pressure of from li to 1\ atmos- pheres, such as is usually present in the pipes of a Avater service, at the rate of about three quarts per hour. These filters can be easily cleaned by brushing under a stream of hot Avater, and afterwards, if deemed desirable, by submitting them to the action of steam, or by heat applied direct from a spirit lamp or Bunsen burner. This filter acts mechanically, and is most efficacious in removing the finest suspended matters, and even micro-organisms are stopped by it. The Berkefeld filter is on the same principle as the Chamberland-Pasteur: it is made of infusorial earth, Avhich is someAvhat soft and friable and liable to fracture. This filter, hoAvever, possesses distinct sterilising action, inasmuch as it is capable of remov- ing bacteria from samples of water and other impure liquids passed through it. Its action is practi- cally similar to the Chamberland-Pasteur filters, but whether it possesses any superiority over them is doubtful. On the contrary the bougies are brittle and liable to fracture Avhen moist, and further experi- mental proof is required to shoAV whether or not the frequent cleansing of the filter by brushing Avill not wear aAvay the bougie too rapidly; a contingency which we know in the case of the Chamber- land-Pasteur filter does not exist. Summing up our present knowledge of this subject, we find that Charcoal filters are entirely inoperative: recent experiments prove that the bacilli from enteric and cholera cultures pass freely into the filtrate ; Spongy iron permits the free passage of bacteria, filtration only removing about 40 per SEARCH AFTER AVATER. 51 cent.; and that none of the more common filtering materials are capable of removing micro-organisms from water. The Earthemuare filters on the Chamberland-Pasteur and Berkefeld principle give, in nearly every instance, a filtrate practically free from germs. The question, therefore, of the efficient filtration of water is a practical one which closely concerns the daily duties of every sanitary officer. In this connection, it is of the greatest importance that medical officers of health should thoroughly realise that the conversion of a suspicious into a wholesome Avater depends not upon the mere diminution of organic matter, chemically demonstrable as being present, but upon the removal of the actual sources of danger present in it, that is, micro-organisms. But the evidence is overwhelm- ing that practically few filters, in common use, are long capable of efficiently removing bacteria and other micro-organisms from water. These defects, in this respect, may be and are commonly due to the folloAving causes : (1) Imperfect fittings, particularly of taps and plugs; (2) the employment of a filtering material whose pores are initially too large to exert any specific influence in arresting micro-organisms; (3) structural imperfections in the filtering medium which have been induced during its use or purification by heat, such as cracks or faults in its substance; (4) the gradual growth of bacteria originally present in the water through the substance of the filter, so that they actually appear in the filtrate. It is the duty, therefore, of every sanitary officer to critically examine every filter coming under his notice in respect of these possible sources of inefficiency. As the rapidity Avith Avhich any particular filtering medium allows the growth of microbes through it depends upon (a) temperature, (b) original foulness of the water, (c) its quantity, depth, or thickness, (d) fineness of its pores, (e) pressure or head of water under Avhich filtration proceeds, special attention needs to be directed to seeing that the filters in use do not present any of these conditions. Every medical officer should be in a position to test the efficiency of any filters he may be called upon to examine, by seeing whether they yield a filtrate which is free from micro-organisms. The application of this bacteriological test is the only adequate safe- guard against the continued use of foul and dangerous filters. Search after Water.—Occasionally a medi- cal officer may be in a position in which he has to search for water. FeAV precise rules can be laid down. On a plain, the depth at Avhich water will be found Avill depend on the permeability of the soil and the depth at which hard rock or clay will hold up water. The plain should be well surveyed; and, if any part seems below the general level, a well should be sunk, or trials made with Norton's tube-wells (fig. 3). The part most covered with herbage is likely to have the water nearest the surface. On a dry sandy plain° morning mists or swarms of insects are said sometimes to mark JUbte^ '&W&L:~. Fig. 3. 52 WATER. water below. Near the sea, Avater is generally found; even close to the sea it may be fresh, if a large body of fresh Avater floAving from higher ground holds back the salt Avater. But usually Avells sunk near the sea are brackish; and it is necessary to sink several, passing farther and farther inland, till the point is reached Avhere the fresh Avater has the predominance. Among the hills the search for Avater is easier. The hills store up Avater, Avhich runs off into plains at their feet. Wells should be sunk at the foot of hills, not on a spur, but, if possible, at the loAvest point; and if there are any indications of a Avater-course, as near there as possible. In the valleys among hills the junction of two long valleys will, especially if there is any narrowing, generally give Avater. The outlet of the longest valleys should be chosen, and if there is any trace of the junction of two water- courses, the well should be sunk at their union. In a long valley with a contraction, Avater should be sought for on the mountain side of the contraction. In digging at the side of a valley, the side Avith the highest hill should be chosen. Before commencing to dig, the country should be as carefully looked over as time and opportunity permit, and the dip of the strata made out if possible. A little search Avill sometimes show which is the direction of fall from high grounds or a watershed. " ■> —■•—! If moist ground only is reached, the insertion of a tube, pierced Avith holes, deep in the moist ground, will sometimes cause a good deal of water to be collected. The Norton tube-well gave satisfaction in Abyssinia, although it did not succeed so well in Ashantee. It was also used with some success in the Soudan, 1884. This pump Avill yield about 7 gallons per minute. A common pump will raise the water in it if the depth be not more than 24 or 26 feet; if deeper, a special force pump has to be used. EXAMINATION OF WATER FOR HYGIENIC PURPOSES. The analysis of water for hygienic purposes has for its object to ascertain whether the Avater contains any substances, either suspended or dissolved, Avhich are likely to be hurtful. There are some substances which we knoAv are not likely to do any harm, such as carbonate of sodium, calcium, and magnesium in small quantities. Others are at once viewed with suspicion as indicating an animal origin, and therefore being probably derived from habitations or resorts of men or animals, or from decaying bodies. In other cases, substances in themselves harmless, such as nitrates, nitrites, and am- monia, are suspicious from implying the coexistence of, or the previous contamination of the water by, nitrogenous substances. In addition to these purely chemical bodies, all Avaters contain a greater or less number of micro-organisms. The greater number of these are absolutely innocuous, while some others may be the essential causative agents of disease. Unfortunately the chemical conditions of a water sample are not ahvays indicative of the extent and nature of its contained bacteria • for, at times, a Avater may be found to be chemically free from organic pollution, and yet contain a sufficient number of pathogenic micro-organisms to give rise to distinct disease processes in those consuming it; on the other hand, a water sample may, from chemical evidence, be deemed organically impure, and yet, by virtue of not containing any but non-pathogenic micro- organisms, be incapable of disease production. The difficulties, therefore in the hygienic examination of a water sample are not inconsiderable and a judgment will be only correctly arrived at from a collation of all the COLLECTION OF WATER SAMPLES. 53 evidence, rather than from the results of one or two tests. The purely chemical evidence must be considered, as a rule, in conjunction Avith the bacteriological; for Avhile the former, by informing us of the amount of organic matter present in Avater, places in our hands evidence of its dangerous or suspicious nature, in that it is either open to sources of infective disease (microbes), or that the presence of organic matter may perhaps render the water a most suitable medium for the growth of patho- genic organisms, should these gain access to it, it is only the bacteriological evidence Avhich can actually say whether these sources of danger are truly absent or not. This statement of the case must not be taken to imply that mere chemical data are valueless as a means of forming a hygienic opinion; on the contrary, they constitute in the majority of cases practically the only facts upon which an opinion can be based, as, in the present state of our knowledge, exact bacteriological examinations of water occupy days or Aveeks, while a chemical analysis is rapidly performed. As, in the greater number of instances, a definite opinion is Avanted Avithout delay, a chemical analysis is still an important procedure, though necessarily incomplete unless supported by a biological investigation. The examination of Avater, for hygienic purposes, may be conveniently considered under the general headings of (1) its physical characters, (2) its qualitative chemical examination, (3) its quantitative chemical analysis, (4) the microscopical examination of its suspended matters, and (5) its bacterio- logical examination. Preliminary to these discussions may be considered the proper precautions to be taken Avith regard to collection of samples, while as a necessary corollary and conclusion to them Avill folloAv a statement as to the interpretation of results. CoUection of Samples.—Great care must be taken that a fair sample of the Avater is collected in perfectly clean glass vessels (not in earthenware jars)—Winchester quarts, Avhich hold about half a gallon, and can be obtained of most chemists, are most convenient; they should be repeatedly AArashed out with some of the Avater to be examined. In taking water from a stream or lake, the bottle ought to be plunged below the surface before it is filled. In draAving from a pipe a portion ought to be allowed to run away first, to get rid of any impurity in the pipe. In judging of a town supply, samples should be obtained direct from the mains, as well as from the houses. The bottle should be stoppered; a cork should be avoided, except in great emergency, but if used it should be quite neAv, well tied down, and sealed. No luting of any kind (such as linseed meal and the like) should be used. For a complete sanitary investigation half a gallon is necessary, but Avith a litre or a couple of pints a pretty good examination can be made if more cannot be obtained. If a detailed mineral analysis is required (which will only be seldom) a gallon ought to be provided. It is always advisable to have a good supply in case of breakage or accident; two Winchester quarts of each sample Avill generally be found sufficient. The examination ought to be undertaken immediately after collection, if possible. If this cannot be done, then as short a time as may be should be allowed to elapse, for changes in the most important constituents take place Avith great rapidity. Pending examination, it ought to be kept in a dark cool place. The fullest information ought ahvays to be furnished Avith the sample, the following being the most important particulars :— (a) Source of the Avater, viz., from tanks or cisterns, main or house pipe, spring, river, stream, lake, or Avell. (b) Position of source, strata so far as they are known. 54 AVATER. (c) If a Avell; depth, diameter, strata through Avhich sunk, Avhether im- perviously steined in the upper part, and Iioav far doAvn. Total depth of well and depth of Avater to be both given. If the well be open, furnished with cover, or Avith a pump attached. (d) Possibility of impurities reaching the Avater: distance of well from cesspools, drains, middens, manure heaps, stables, etc. ; if drains or seAvers discharge into streams or lakes; proximity of cultivated land. (e) If a surface-Avater or rain-Avater, nature of collecting surface and con- ditions of storage. (/) Meteorological conditions, Avith reference to recent drought or excessive rainfall. (g) A statement of the existence of any disease supposed to be connected with the Avater-supply, or any other special reason for requiring analysis. Any further information that can be obtained Avill ahvays be useful. Each bottle should also be distinctly labelled, so as to correspond Avith the official letter or invoice. When it is possible, it is most desirable that the medical officer or analyst should visit the locality itself Avhence the Avater is obtained; in this Avay he may obtain information Avhich might otherAvise escape him. If the analysis can be made immediately on the spot, it Avill be all the more valuable. Physical Examination.—This Avill have reference to the following points, and affords, at times, valuable preliminary information as to any given sample. Colour.—This may be judged of by alloAving any sediment to settle, and then pouring off the supernatant water into a tall glass placed upon a piece of Avhite paper. Or a horizontal tube of colourless glass with glass ends may be used. The stratum should be of sufficient thickness, if possible two or three feet, but a fair idea of the colour may be obtained Avith 18 inches or even a foot. The Society of Public Analysts recommends 24 inches. If a tube be used, it may either be half full, and the tint com- pared with the colour of the air in the upper half Avhen directed against a Avell illuminated white surface; or, better still, it may be filled, and the comparison made with a second tube placed alongside, containing pure distilled Avater. Perfectly pure water has a bluish tint, but most ordinary Avaters have either a greyish, greenish, yellow, or brown appearance. The best samples are those coloured bluish or greyish. Green Avaters OAve their colour to vegetable matter, chiefly unicellular algce, and are usually harmless. Yellow or broAvn waters are most to be feared, as their colour is often due to animal organic matter, chiefly sewage. It is sometimes, however, oAving to vegetable matter, such as peat, and under these circumstances it is not generally hurtful. It may also be caused by salts of iron, although in most cases the iron is precipitated as ferric oxide in the sediment. Clearness.—The presence or absence of turbidity may be judged of in the same way as the colour, only the Avater should be shaken up, so as to distribute the suspended matter and simulate its condition Avhen drawn. The depth necessary to obscure printed matter may be used as a measure. Occasionally Avater remains hazy or turbid even after standing for some time; in such a case the suspended matter is in very fine division, such as is sometimes found Avith sulphate of calcium, minute scales of mica, &c. Sediment.—The nature of the sediment may be roughly judged of by the eye, as to Avhether it is mineral or vegetable, or stained Avith iron or the like. The larger living forms, such as Anguillulos, Avater-fleas, leeches, &c. may also be detected. But the only satisfactory examination is to be made with the microscope. LUSTRE, TASTE, AND SMELL OF WATER. 55 Lustre.—The lustre or brilliancy (eclat) has been recommended as a good physical indication of the amount of aeration (Gerardin). The different de- grees may be noted in any convenient Avay, such as nil, dull, vitreous, adaman- tine, which is an ascending scale from zero to the maximum brightness. Taste.—Taste is an uncertain indication. Any badly tasting water should be rejected or purified before use. Suspended animal organic matters often give a peculiar taste, so also vegetable matters in stagnant waters. Some growing plants, as lemna and pistia, give a bitter taste ; but most growing plants have no taste. Dissolved animal matter is frequently quite tasteless. As regards dissolved mineral matters, taste is of little use, and differs much in different persons. On an average— Grains Parts per gallon. per 100,000 Sodium chloride is tasted when it reaches 75 107 Potassium ,, 20 29 Magnesium ,, : > 50 to 55 71 to 79 Calcium sulphate >> ,, 25 to 30 36 to 43 ,, carbonate ,, 10 to 12 14 to 17 ,, niti-ate > j 15 to 20 21 to 29 Sodium carbonate 60 to 65 86 to 93 Iron ,, ,, ,, 0*2 0-28 Iron is thus the only substance Avhich can be tasted in very small quantities. A permanently hard Avater has sometimes a peculiar fade, or slightly saline taste, if the total salts amount to 35 or 40 grains per gallon (50 to 57 parts per 100,000), and the calcium sulphate amounts to 6 or 8 grains (8'6 to 11'4 per 100,000). The taste of good drinking water is due entirely to the gases dissolved; Avater nearly free from carbonic acid hard- ness, such as distilled Avater, is not so pleasant as the brisk, Avell-carbonated Avaters; it may be called flat, but it is difficult to define the kind of taste or absence of it. Smell.—The Avater may be Avarmed or distilled, Avhen the odour of faecal matter is often brought out clearly both in the distillate and residue. If the water is put in a stoppered bottle, which it half fills, and is exposed to light, and then opened and smelt after a feAV days, commencing putre- faction, or the formation of butyric acid, or something similar, can some- times be detected. Tiemann recommends that the Avater should be heated to 110° or 120° F. (42° to 49° C.); if hydrogen sulphide be present, add a little copper sulphate, Avhich precipitates it, and permits any putrid smell to be perceived. The Society of Public Analysts recommends heating the Avater in a wide-mouthed stoppered bottle to 100° F. (38° C). This may be done by immersing it in Avarm water. Any particular smell should be recorded, if distinctly recognised,—Avith its degree of intensity, such as nil, very slight, slight, marked, &c, as the case may be. Sometimes an offensive smell is detected on boiling, Avhich is not otherwise perceived. Although the physical characters give only an imperfect idea of the value of a water, they are yet important Avhen no further examination can be made. If a Avater be colourless, clear, free from suspended matter, of a hrilliant (or adamantine) lustre, devoid of smell or taste, except such as is recognised to be the characteristic of good potable Avater, Ave shall in the large majority of cases be justified in pronouncing it a good and wholesome Avater; Avhilst, according as it deviates from these characters, Ave shall be proportionately justified in regarding it Avith suspicion. Suspended matter is probably the most dangerous, and, Avhen in the form of disease-causing micro-organisms, exists Avithout revealing itself by any visible turbidity, or 56 AA'ATER. even to any ordinary microscopic examination. Bacteria can only be detected! by biological examination: nor must Ave shut our eyes to the possibility of hurtful dissolved substances, so that Avhen our opinion of a Avater is based only on its physical characters, the fact ought to be duly recorded. Qualitative Chemical Examination of Water.—The sample may be either at once treated, or, in the case of some constituents, a portion of it should be concentrated by evaporation. Water not Concentrated. Substance sought for. Reagents to be used, and effects. Reaction. Lime. Chlorine. Sulphuric Acid. Nitric Acid. Nitrous Acid. Litmus and turmeric papers; usual red or brown re- actions. Usually neutral. If acid, and acidity disappears on boiling, it is due to car- bonic acid. If alkaline, and alkalinity disappears on boiling, to ammonia (rare). If permanently alkaline, to sodium carbonate. i Six grains per gallon (9 per 100,000) give turbidity; sixteen grains (23 per 100,000) considerable precipitate. Nitrate of Silver and dilute One grain per gallon (1*4 per 100,000) nitric acid. gives a haze ; four grains per gallon (6 White precipitate, becoming , per 100,000) give a marked turbidity; lead colour. j ten grains (14 per 100,000) a consider- able precipitate. Oxalate of Ammonium. White precipitate. Chloride of Barium dilute hydrochloric ac White precipitate. and | One-and-half grain (2 per 100,000) of d. i sulphate give no precipitate until after | standing ; three grains (4 per 100,000) give an immediate haze, and, after a time, a slight precipitate. Brucine solution and pure , The sulphuric acid should be poured sulphuric acid. i gently down to form a layer under A pink and yellow zone. the mixed water and brucine solu- I tion ; half a grain of nitric acid per gallon ( = 0-7 per 100,000) gives a marked pink and yellow zone ; or, as recommended by Nicholson, 2 c.c. of the water may be evaporated to dryness; a drop of pure sulphuric acid and a minute crystal of brucine be dropped in; 0*01 grain per gallon ( = 0*0143 per 100,000) can be easily detected. Add the solution of iodide of potassium and starch, and then the acid ; the blue colour should be immediate; make a comparative experiment Avith distilled water. This is a very delicate test; a yellow colour will appear in the water in half an hour, if there be only one part of nitrous acid in 10,000,000 of water. Iodide of Potassium and starch in solution and di- lute sulphuric acid. An immediate blue colour. Solution of meta-phenylene- diamine and dilute sul- phuric ae fulfilled :— 1. The substance under examination must exist in clear solution in a liquid miscible Avith the liquid reagent: for this purpose aqueous solutions are the best. 2. The operator must thoroughly understand the relationship betAveen measures of weight and volume. 3. The apparatus employed must be accurately graduated. 4. The titrating reagent must be a solution of known strength, that is, ■a so-called standard solution. 5. We need a special reagent (indicator) in order to ascertain Avhen sufficient quantity of the standard solution c has been added to effect the required reaction, or the complete transformation of a into b. To carry out any quantitative analysis, the first essential is the thorough •comprehension of the simple relationship between liquids and solids. In the following pages of this Avork, oAving to its uniformity and simplicity in -all analytical methods, the metric system of weights and measures will, as far as possible, be employed. Although tables of the various metric weights and measures are given in the Appendix, it may not be out of place here to emphasise the fact that a cube of distilled water, at its temperature of greatest density, namely at 4° C. or 39°*2 F., whose side measures 1 decimetre, has exactly the weight of 1 kilogramme, or 1000 grammes, and occupies the volume of 1 litre or 1000 cubic centimetres. In other words, 1 cubic •centimetre, as a measure of volume, equals or corresponds to 1 gramme as a measure of weight, and that:— x Grammes of a substance dissolved in 10 cubic centimetres of water are x parts in x „ „ „ 100 x „ „ „ 1000 a; Decigrammes ,, ,, ,, „ a; Centigrammes ,, ,, ,, ,, a; Milligrammes ,, ,, ,, ,, x „ „ „ 100 x „ ,, „ 10 x >> >> i< ii It is most usual in this country and on the Continent to express the Tesults of a quantitative analysis of Avater as parts per 100,000, or centi- grammes per litre, or mdligrammes per 100 cubic centimetres. Some analysts express their results as parts per million, or milligrammes per litre. The statement of a ratio in parts per 100,000 will be adopted in the folloAV- ing analytical processes, while, for the sake of brevity, the term "cubic ■centimetre " Avill be written as c.c. Occasionally, the expression " grains per gallon " is met with in English analysis. This is equivalent to parts per 70,000, as one gallon of water at 39°'2 F. or 4° C. weighs 10 lb., or 70,000 grains. The conversion of parts per 100,000 to grains per gallon is, of course, readily performed by multi- plying by seven-tenths, or by 0*7, and from grains per gallon to parts per 100,000 by multiplying by 10 and dividing by 7. The apparatus specially needed for making an ordinary quantitative analysis of Avater includes :— A pair of balances and weights, according to the metric system. In these sets of weights, the larger ones represent grammes, the next in size deci- grammes, and the next centigrammes. Small forceps are used for picking up and applying these weights to the pans of the balance. The milli- grammes are added by shifting a little piece of bent Avire along the cross- beam of the balance, which has on it ten markings, numbered from 1 to 10, on either side of the pivot. of water are x pa rts in 10 ,, X 100 (1 litre) X 1,000 ,, X ,, 10,000 ,, X 100,000 ,, X 1,000,000 of water X 100,000 ,, X „ 10,000 n X ,, 1,000 62 AVATER. A platinum dish, capable of holding 200 c.c. of Avater. One or more shallow porcelain evaporating dishes, capable of holding 300 c.c. A small porcelain crucible, with lid, for igniting residues. 4 .pestfe and mortar, for powdering reagents previous to solution. One or more retorts, or boiling flasks. A Graham's, or Liebig's condenser. Six Nessler glasses, each capable of holding 150 c.c. Glass stiiring-rods. Tavo glass-stoppered bottles, capable of holding 250 c.c. Glass funnels for filtering. A packet of Swedish filter papers. A dozen test tubes, Avith stand, cleaner, and holder. A measuring flask, to hold at least 1 litre and graduated in c.c. Glass burettes, or graduated tubes, holding 20 c.c, and graduated in c.c. and tenths of a c.c. One of these should be mounted on a wooden stand, and be provided Avith a stopper at the top, and fitted with a stop-cock at the bottom. A glass pipette, graduated to deliver 10, 20, 50, or 100 c.c. An iron tripod. One or more triangles of iron wire, covered Avith pipe clay. A pair of small crucible tongs. A long thermometer, graduated in either Centigrade or Fahrenheit degrees. The " Standard Solutions " required in a volumetric quantitative analysis are solutions of definite strength, made by dissolving a given weight of a reagent, in grammes, in a definite volume of distilled water in cubic centi- metres (or in grains or fluid grains). These solutions are usually made by dissolving either a molecular Aveight of a reagent in grammes, or some decimal part of such Aveight in 1000 c.c. (1 litre) of distilled water. The following abbreviations are often used to express the strength of standard solutions:— N = a normal solution having 1 molecular weight in grammes per litre. N • , - = a semi-normal ,, a > > »> — = a deci-normal ,, rV ,, ,, -- = a viginti-normal ,, -^ ,, ,, —— =a centi-normal ,, rl^ >> >> ■—— = a milli-normal ,, T1J\ju ,, ,, Occasionally, in making standard solutions the equivalent hydrogen weio-ht, or molecular weight of a reagent, cannot be taken, but its particular Aveight'in a particular reaction in a given analysis has to be regarded. For instance, when using a solution of potassic permanganate, as an oxidising agent, having the chemical formula KMn04, and the molecular weight of 158, and yielding five volumes of oxygen in a particular reaction, its normal solution is made by dissolving one-fifth of its molecular weight, iss or 3P5 grammes, in a litre of water. In other instances, when the equivalent or combining weights of a substance are not identical with the atomic or molecular weights, the amounts taken are those of their equivalent weights. Thus oxalic acid, C2Ho04.2H20, with an atomic weight of 126, DETERMINATION OF DISSOLVED SOLIDS. 63- is a bivalent substance, and its equivalent Aveight is one-half of its atomic Aveight; consequently, a normal solution of oxalic acid would be made by dissolving 63 grammes of the crystallised acid in 1 litre of distilled water. Similarly, phosphoric acid, which is a trivalent substance, would require, for the preparation of a normal solution of sodic phosphate, Xa.JHP0412II00, one-third of its molecular Aveight *~, or 119*3 grammes, being dissolved in 1 litre of distilled water. In some other cases, standard solutions cannot be prepared directly, because the substance to be dissolved cannot be obtained sufficiently pure to make an accurate solution. Hence Ave must have recourse to an indirect method. Thus, if it were Avanted to make a solution of potash-lye, contain- ing 56 grammes of potassium hydroxide to the litre, we could not make it by simply Aveighing out 56 grammes of potassium hydroxide and dissolving it in a litre of water, because the alkali can never be procured absolutely pure. But if, say, 65 grammes be dissolved and sloAvly diluted down until 10 c.c. exactly neutralise 10 c.c. of an oxalic acid solution made by dissolv- ing 63 grammes of CoHo04.2H20 in a litre, we then get a solution of the potassium hydroxide of the strength of 56 grammes per litre, because from their molecular weights we knoAv 63 grammes oxalic acid exactly neutralise 56 grammes of potassium hydroxide. An "indicator" is a substance added to enable us to ascertain by a change of colour, or other equally marked effect, the exact point at Avhich a given reaction is complete. The chief indicators employed are as follows:— (a) Solution of litmus, Avhich turns red with acids and blue with alkalies.. This solution needs to be made from the best litmus, by boiling in water for eight minutes, then neutralising the alkaline carbonate which it usually contains with HC1, until the wine-red colour remains even on further boiling. The solution is then cooled and an equal volume of strong alcohol added. The stock solution should be kept in a bottle Avith a delivery pipette inserted through the cork. (6) Alcoholic solution of phenol-phthalein, made by dissolving 5 grammes, with the aid of 25 c.c. of spirit of Avine, in 500 c.c. of distilled water. This solution is colourless with acids, but becomes red with alkalies. (c) Starch mucilage, which turns blue in the presence of free iodine. (d) Saturated solution of potassium chromate, which gives a red colour with nitrate of silver, but not until all the halogen present has entirely com- bined with the silver. (e) Saturated solution of potassium ferricyanide, which ceases to give a blue colour when any iron present has been fully raised to the ferric state. Determination of the Dissolved Solids.—The remark already made about suspended matters must be attended to; if possible, obtain a clear Avater by subsidence rather than by filtering through paper. The solids are determined by evaporation, and are generally spoken of as the total, fixed, and volatile solids. Total Solids.—If very good balances are available, 200 c.c. of the Avater are sufficient, if the balances are inferior, 500 or 1000 c.c. of the Avater sample must be taken, then evaporate to dryness with a moderate heat, taking care that the Avater does not boil, else there may be loss from spurting. If the smaller quantity be taken, the whole evaporation may be conducted in one vessel (of platinum, if possible); but if the larger amount must be used the evaporation should be commenced in a large evaporating dish, and the concentrated water and deposit, if any, transferred into a small weighed crucible. The transference demands great care, so that none of the solids •64 WATER. -shall remain encrusted in the evaporating dish. All the contents of the large dish being transferred, evaporate to complete dryness in air, Avater, or steam bath, at 212° F. (100° C). Weigh as soon as the crucible is •cold, as the dried mass may be hygroscopic. It may be necessary to replace it in the bath and Aveigh again after an interval of half an hour. If there is no material difference the drying is completed. Wanklyn advises a very simple form of steam bath. A common tAvo- gallon tin can is taken, a perforated cork fitted in the mouth, and a funnel passed through the perforation; the crucible is placed in the funnel, a little roll of paper being placed between the funnel and crucible to let the steam pass. Water is boiled in the tin can. The determination of the total solids is an important point, and should be carefully done. It gives a control over the other quantitative deter- minations, and if erroneous may make the other conclusions wrong. Fixed Solids.—Incinerate the dried solids at as low a heat as possible; watch the process, and note if there be much blackening, or if any fumes can be seen, or any smell be perceived as of burnt horn. A piece of filter- ing paper dipped in solution of potassium iodide and starch, and then dried, or a piece of ozone paper, should be held over the crucible to detect any nitric oxide which may be given off. Volatile Solids.—The loss on ignition may be stated as " volatile substances." It consists of destructible organic matters, nitrates, nitrites, ammoniacal salts, combined water, combined carbonic acid, and sometimes chlorides. The variableness of the composition of the " volatile substances " has led to the disuse of the process by ignition as too uncertain. Combined Avith other evidence it gives, however, some useful indications. The in- cinerated solids may be examined for silica and iron, as hereafter noted. The combined C02 can be partly restored after incineration by adding a few drops of a saturated solution of carbonate of ammonia, then drying and driving off the excess of ammonia. Example.—1. Total solids.—200 c.c. dried as described :— Weight of dish and residue, . . . 19*27 grammes. ,, of dish alone .... 19*23 Difference, . . . . 0 04 being grammes of total solids in 200 c.c. of water. To bring to centigrammes per litre, or parts per 100,000 : 0"04 x 500 = 20= centigrammes per litre, or parts per 100,000. To bring to grains per gallon : 20 x 0-7 = 14-0 grains per gallon. 2. Fixed solids.—-The above residue is incinerated, and the CO., restored to the earthy •carbonates if required. Weight of incinerated residue and dish, . 19'26 ,, of dish alone, . . . , 19-23 Difference, . . . . o*03 being grammes of fixed solids in 200 c.c. of water. 0-03x500 = 15 parts per 100,000. 15x0-7 = 10*5 grains per gallon. 3. Volatile solids:— Parts per 100,000. Grains per gallon. Total solids, = 20-0 14#0 Fixed „ = 15-0 10-5 Difference, being volatile solids, 5-0 3'5 DETERMINATION OF CHLORINE AND HARDNESS. 65 The amounts of total solids in ordinary Avater samples vary from 3 or 4 to 50 or 60 parts per 100,000. Of these not more than 15 per 100,000 should be volatile or lost on ignition. Determination of the Chlorine.—For this purpose two solutions are required. (1) A solution of Potassium Manockrornate, made by dissolving 50 grammes of the salt in a litre of distilled Avater. Xitrate of silver is added until a permanent red precipitate is formed, Avhich is allowed to settle and the clear liquid decanted off. (2) A deci-normal standard solution of Silver Nitrate, made by dissolving 17 grammes of AgX03 (molecular weight being 170) in a litre of distilled water. This will be equivalent to one-tenth of the atomic weight of chlorine (35*5) or 3-55 grammes of chlorine and 1 c.c. of this solution will equal 3'55 mgms. of chlorine. The process consists in taking 250 c.c. of the water sample, placing them in a white porcelain dish, and rendering them of a distinct yellow colour by means of two or more drops of the potassium chromate solution. From a burette, run in drop by drop some of the — silver nitrate solution, stirring after each addition. The red silver chromate which is at first formed will disappear as long as any chlorine is present. Stop directly the least red tint is permanent. As each c.c. of the silver solution equals 3*55 mgms. of chlorine, the number of c.c. used indicates the mgms. of chlorine in 250 c.c. of the water, that is, parts per 250,000, and that divided by 2"5 or multi- plied by 0-4 will give parts of chlorine per 100,000. Example.—In 2E0 c.c. of water, rendered yellow with potassium chromate, 1'5 c.c, of silver solution gave a permanent red tint; then— 1*5 x 3-55 — 9—— = 2-13 parts of chlorine per 100,000. The purest water, as a rule, contains less than l-5 parts of chlorine per 100,000. An increase may be due to sea-water, percolation through salt bearing strata, to sewage, or other impurities. Some deep wells often con- tain large quantities of chlorides; but generally an excessive presence of chlorine is a reason for suspicion unless a satisfactory explanation of its presence is obtainable. Determination of the Hardness.—Clark's very useful soap test offers a ready mode of determining this in a manner quite sufficient for hygienic and economic purposes. Soap is an alkaline oleate, resulting from the combination of an alkali with one or more of the fatty acids, i.e., oleic, stearic, or palmitic acids. When an alkaline oleate is mixed with pure water, a lather is given almost immediately; but if lime, magnesia, iron, baryta, alumina, or other substances of this kind be present, oleates of these bases are formed, and no lather is given until the earthy bases are thrown down or used up. The hardness of a water depends upon the presence in it of more or less of these earthy bases, and the more they are present the greater will be the expenditure of soap to make a lather. Free carbonic acid has a similar effect. The soap combines in equivalent proportions with these bases, so that if the soap solution be graduated by a solution of known strength of any kind, it will be of equivalent strength for corresponding solutions of other bases. There are, however, one or two points which render the method less certain. One of these is that, in the case of magnesia, there is a tendency to form double salts, so that the determination of magnesia is never so accurate as in the cases of lime or baryta. Carbonic E 66 WATER. acid appears to unite in equivalent proportions Avhen it is passed through the soap solution; but if it be diffused in Avater, and then shaken up Avith the soap solution, tAvo equivalents of the acid unite Avith one of soap. A certain amount of the hardness of a Avater is removed by boiling, hence it is usual to speak of the hardness present before boiling as total hardness, that remaining after boiling as fixed or permanent hardness, and that which has been dissipated by the boiling as the temporary hardness. The total hardness in most drinking waters is caused by salts of calcium and magnesium Avith some free carbonic acid. Hence waters from the chalk, oohte, limestone, dolomite, and iicav red sandstone are apt to furnish the greatest degrees of hardness. Bain-water, being free from these salts, is usually very soft. Many of the salts contributing to the total hardness are held in solution by carbonic acid, which Avhen the Avater is boiled is dissipated, causing these salts to fall to the bottom or form incrustations on the sides of the containing vessel as insoluble salts. The chief of these are carbonates and sulphates of lime and magnesium Avith salts of silica, alumina, and iron when these are present. The permanent hardness, or Avhat still remains in solution, consists mainly of some sulphates, chlorides, and nitrates of calcium and magnesium, with a little iron and alumina. The amount of hardness is, for convenience, usually expressed either in degrees of the metrical scale (parts per 100,000) or in grains per gallon of calcium carbonate, each grain representing 1 degree of hardness on the scale proposed by Clark. Of course it is understood that the hardness depends on various constituents, but in England is equivalent to so much calcium carbonate. In France, the hardness is also expressed as calcium carbonate, but only on the metrical scale, that is, in parts per 100,000. In Germany, the hardness is always expressed as so much lime, CaO, per 100,000. In cases of comparative analysis, therefore, 1 metrical French or English degree of hardness equals 0'56 German degree, and 1 degree of hardness on Clark's scale equals 0*39 German degree and 0-7 French or English metrical degree. The Soap solution for the estimation of hardness is best made by thoroughly dissolving by stirring and warming some soft soap in a mixture of 4 parts methylated spirits to 6 of distilled water and then filtering. This solution of soap should be standardised, that is, diluted or strengthened as the case may be, so that 2-2 c.c. of it exactly give a permanent lather Avhen shaken up with 50 c.c. of a solution of nitrate of barium. Barium nitrate, Ba(X03).2, has a molecular weight ratio to calcium carbonate, CaC03, of as 261 is to 100, and if 0-261 gramme of barium nitrate be dis- solved in a litre of distilled water, that solution equals O'l gramme of calcium carbonate, and 50 c.c. of the same solution equals 5 mgms. of calcium carbonate. Xow, if the soap solution be so made that 2-2 c.c. of it give a lather with 50 c.c. of the above barium nitrate solution, after deducting 0-2 c.c. for the amount of soap solution necessary to give a lather with 50 c.c. of distilled water, we get 2 c.c. of the soap solution to equal 50 c.c. of a barium nitrate solution, Avhich again is equivalent to 5 mgms. of calcium carbonate, hence each c.c. of the soap solution equals 2-5 mgms. of calcium carbonate. Say, for instance, 35 c.c. of soap solution of unknown strength have been made, and, on being standardised Avith 50 c.c. of the barium nitrate solution, it is found that 1 c.c. gives a lather in place of 2*2 c.c. being so required. Then as 1 : 2*2 : : 30 : x= 66; that is, 30 c.c. of it must be diluted up to 66 c.c. to give a soap solution, of which 1 c.c. shall exactly equal 2-5 mgms. of calcium carbonate. Of course, if the soap DETERMINATION OF HARDNESS. 67 solution be found too Aveak it must be proportionately fortified with more soap until 2*2 c.c. exactly give a lather with 50 c.c. of the 0*261 barium nitrate solution. In some analytical statements the term "measure" is used to avoid the repetition of the expression "tenth of a cubic centimetre." If so employed, one measure of soap solution may be taken, therefore, as precipitating 0'25 of a milligramme of calcium carbonate. Total Hardness.—Take 50 c.c. of the sample and place in a stoppered shaking bottle. From a burette run in sufficient of the soap solution until, on being briskly shaken, the contents of the bottle give only a faint dull sound with the formation of a quarter inch of fine uniform lather. This lather should sIioav an unbroken surface after standing five minutes. Example.—Suppose the addition of 2*4 c.c. of the soap solution have produced the necessary sound and lather. Deducting 0'2 c.c. as being necessary for the production of a lather in 50 c.c. of the purest water, we get 2'2 c.c. of the soap solution required by 50 c.c. of the water sample or 4"4 necessary for 100 c.c. Each of these c.c. equals 2-5 mgms. of calcium carbonate: hence4'4 x 2*5 = 11 mgms. of calcium carbonate in 100 c.c. of the water, representing a total hardness of 11 parts per 100,000, that is 11 degrees of hardness on the metrical scale. Expressed as grains of calcium carbonate per gallon, or degrees of hardness on Clark's scale, we get 11 x 0'7 = 7'7 grains per gallon of CaC03. When the total hardness exceeds 4 c.c. of the soap solution, an over- estimation may be made as the excess of calcium and magnesium salts interfere with the formation of the characteristic lather. In these cases, it is better to dilute 25 c.c. of the sample with 25 c.c. of distilled water, proceed as explained, Avhen the net amount of soap solution used will indicate the hardness in parts per 100,000. The Permanent or Fixed Hardness.—Take 100 c.c. of the water and 100 c.c. of distilled water ; boil in a flask briskly for half an hour, allow it to cool down to 60° F. (15°-5 C.) in the vessel, Avhich should be corked, and then make up the bulk to exactly 100 c.c. Avith distilled water; determine the hardness in 50 c.c. If distilled water is not procurable, then boil 200 c.c. down to 100; take half the remainder (=100 of unboiled water) and determine the hardness. By boiling, all carbonic acid is driven off; all calcium carbonate, except a small quantity, is thrown doAvn; the calcium sulphate and chloride are not affected if the evaporation is not carried too far; the magnesium carbonate at first thrown doAvn is redissolved as the water cools. Example.—Say 50 c.c. of the water thus treated required 1*6 c.c. of soap solution. Deducting 0'2 c.c. for lather, we get 1*4 c.c, and 1*4 x 2'5 x 2 = 7 mgms. of calcium carbonate present in 100 c.c. of the water, and these 7 mgms. CaC03 represent the permanent hardness of 100 c.c. (100,000 mgms.) of the water sample, or, in other words, 7 parts per 100,000 of permanent hardness, or 4 "9 grains per gallon. Removable Hardness.—The difference between the total and permanent hardness is the temporary or removable hardness, which in the example Avould be 11-7 = 4 degrees of the metrical scale, and 7*7 - 4*9 = 2*8 degrees of Clark's scale. The total hardness of a water should not exceed 30 parts per 100,000, otherAvise it is unsuitable for domestic purposes. What are called hard waters vary from 20 to 30 degrees on the metrical scale; a soft water from 8 to 15 ; while a very soft water may contain up to 6 or 8. The amount of permanent hardness is very important, as it chiefly repre- sents the most objectionable earthy salts—viz., calcium sulphate and chloride, and the magnesian salts. The greater the permanent hardness, the more objectionable is the water. The permanent hardness of a good water should 68 WATER. not, if possible, be greater than about 5 degrees of the metrical scale, equal to 3 degrees or 4 degrees of Clark's scale. Determination of Organic Matter in a Water Sample.—It has already been explained Iioav organic matter is constantly gaining access to water by many channels, and that folloAving in the Avake of this organic pollution of drinking waters come Avidespread evil consequences in the form of various kinds of disease. By organic pollution is meant the fouling of Avater by both animal and vegetable material, together with the products of their decomposition; and although the relative significance of, and danger from, animal contamination is usually greater than that from vegetable impurities, still the recognition of either or both forms of organic matter constitutes an important procedure in the analysis of Avater for health purposes. Unfortu- nately there is no single analytical process Avhich, by itself, can give us any closely proximate estimation of this organic matter. Recognising the fact that all organic matter, Avhether of animal or vegetable origin, exhibits a natural tendency to resolve itself, under suitable conditions of temperature and moisture, into simple parts, such as carbonic acid, ammonia, and oxidised salts of nitrogen, such as nitrites and nitrates, the most reliable processes for the determination of organic matter in Avater are only indirect ones, being practically estimations of either carbonic acid, ammonia, or nitrogen produced by the decomposition of organic matter. In addition to these, the chemical processes for the determination of organic matter in Avater include others Avhose object is essentially to detect the presence of other chemical constituents which, by entering into the composition of organic bodies, gain access to Avater along Avith it, that is, chlorides, sulphates, and phosphates. To these may be added estimations of the affinity of the particular sample for oxygen. Possibly one of the most ingenious processes proposed to determine the organic matter in water, is that devised by Frankland; but, owing to the need of special apparatus and of great technical skill to avoid errors in its conduction, it is quite unsuited for the requirements of the greater number of those engaged in public health work. By this method, a measured volume of water is evaporated to a solid residue, and this, after collection in a hard glass combustion tube, is mixed with oxide of copper, and burnt in a furnace. The oxide of copper parts with its oxygen to the organic matter, which is completely burnt, and the resulting carbonic acid and nitrogen collected, measured, and returned in terms of "organic carbon" and "organic nitrogen." By this process the purity of water is judged from a consideration of the actual amounts of organic carbon and organic nitrogen present, and their relative proportions to each other. A low quantity of each and a small relative amount of organic nitrogen is deemed favourable to the water. Much carbon and little nitrogen is indicative of vegetable pollution, whereas, on the other hand, the nearer the amount of nitrogen approximates to that of carbon the greater is the indication of the pollution being of animal origin. Speaking of this particular process of Frankland's, the Rivers Pollution Com- mission held that " a good drinking water should not yield more than 0*2 part of organic carbon or 0*02 of organic nitrogen in 100,000 parts ": on this dictum, one might condemn a water containing as much as 0-1 part of the former and 0*03 part of the latter. More practical than, if not actually superior to, Frankland's is the method proposed by Wanklyn, Chapman and Smith, in which two kinds of ammonia are recognised, namely, the free or saline ammonia and the albuminoid ammonia. The former is held to have its origin mainly in DETERMINATION OF THE FREE AMMONIA. 69 organic pollution, being virtually an early stage in the decomposition of such matter, while the latter, being derived from nitrogenous organic matter as the result of its breaking up by the addition of a solution of strongly alkaline potassium permanganate, is taken as the indication of pollution actually present as organic matter. Although no better clue to the presence of organic matter can be well imagined than an estimation based upon the nitrogen resulting from its decomposition, still the difficulty exists in the fact that all hurtful organic matter is not necessarily nitrogenous. In the case of water pollution, this objection is largely theoretical, but it nevertheless suggests the fact that, as regards organic matter, much has yet to be learnt of its chemical constitution and detection. It is further obvious that no chemical process can decide whether any organic matter is living or dead, or whether, if living, it is injurious or not. Remembering how small the germs of disease are, it will be seen at once that even considerable numbers of them in a water cannot by themselves materially increase the organic ammonia: but as they are nearly always associated with an organic nutritive medium, the excessive presence of organic pollution, which analysis Avould necessarily indicate, at once suggests doubt and suspicion as to the purity of the Avater under examination. Besides the combustion process, commonly known as Frankland's, and the ammonia determinations of Wanklyn, a new method, that of Kjeldahl, has been introduced for the determination of the total combined nitrogen, except nitrates, in natural Avaters. Although it cannot be claimed for them that they Avill estimate the absolute quantity of organic matter present, the Wanklyn and Kjeldahl processes constitute the two best methods of estimating its relative quantities in different Avaters, and, being readdy per- formed by any medical officer of health, will be now described. Determination of the Free Ammonia.—For this estimation it is necessary to have the following solutions:— (1) Nessler's Reagent.—This is a saturated solution of mercuric iodide in potassic iodide. It gives a yellowish tinge, with the faintest trace of ammonia, passing, if much ammonia is present, to the formation of a yellow- brown precipitate of the di-mercuric-ammonium iodide. Xessler's solution is made by dissolving 35 grammes of potassic iodide in 100 c.c. of distilled water. Also dissolve 17 grammes of mercuric chloride in 300 c.c. of distilled water. Add the mercury solution to that of the iodide gradually untd a precipitate of the red periodide of mercury just begins to be per- manent. Then dflute up to a litre with a 20 per cent, solution of caustic soda: add more mercuric chloride, to render the solution "sharp," until a permanent red precipitate again forms : allow this to settle, and then decant off the clear solution. (2) A milli-normal Standard Solution of Ammonium Chloride.— Ammonium chloride, represented by the formula XH4C1, bears a ratio to ammonia, as represented by XH3, of as 53-5 is to 17. Therefore, if 00535 gramme of ammonium chloride be dissolved in 1 litre of distilled water, that solution will be a milli-normal one and equal 0-017 gramme of ammonia : and X 1 c.c. of this j7jwa solution will equal 0*017 mgm, of ammonia. To perform the process, place 250 c.c. of the water sample in a retort, then attach the retort to the Liebig's condenser, and distil off about 130 c.c.; collect 1 c.c. more of the distillate, and test it with a feAv drops of Xessler, to see if any ammonia is still coming over; if so, the distillation must be continued longer. Carefully measure the amount of distillate ; test a little with Xessler's solution in a test-tube; and, if the colour be not 70 AVATER. too dark, take 100 c.c. of the distfllate and put it into a cylindrical glass vessel, placed upon a piece of Avhite paper. Add to it 1-5 c.c. of Xessler. Pour into another similar cylinder as many c.c of the standard ammonium chloride solution as may be thought necessary (practice soon shows the amount), and fill up to 100 c.c. Avith pure distilled Avater; drop in 1*5 c.c. of Xessler. If the colours correspond after three to five minutes, the process is finished, and the amount of ammonium chloride used is read off. If the colours are not the same, add a little more ammonium chloride so long as no haze shoAvs itself ; if it does, then a fresh glass must be taken, and another trial made. When the process is completed, read off the number of c.c. of ammonium chloride used, allow for the portion of distillate not used, multiply by 0*017 to give mgms. of XH3; by 4 to bring to the litre; and by 0*1 to bring from mgms. to centigrammes; or shortly, multiply by 0-0068 : the result is centigrammes of free ammonia per litre, or parts per 100,000. Example.—From 250 c.c. of Avater, 140 were distilled: 100 c.c. were taken for the experiment, and 2*3 c.c. of ammonium chloride solution were required to give the proper colour : then, 2*3 x — x 0*017 x 0'4 = 0*02189 per 100,000 of free ammonia. if 100 ±- > Should the colour of the distillate, after the addition of Xessler's reagent, prove too dark, a smaller quantity may be used, and made up to 100 c.c. Avith distilled Avater. Wanklyn recommends distilling only 50 c.c, Xessler- ising it, and then adding one-third to the result, on the ground that (as he says) two-thirds of the ammonia come off* in the first 50 c.c. He also states that with smaller sized apparatus 100 c.c. of Avater gives satisfactory results. The Society of Public Analysts recommend successive portions being distilled over, and Xesslerised until ammonia ceases to appear. Practically we have found at Xetley that the whole of the ammonia comes over in the first 130 c.c, or nearly so; but it is necessary to continue the distillation until ammonia has entirely ceased to come over. When a Liebig's condenser cannot be obtained, a flask may be used instead of a retort, and the distillate conveyed to the receiver by a tube of glass (or block tin) passing through a vessel of cold Avater, which must be renewed from time to time. The tube may be bent in any convenient Avay, so as to expose it to the cooling Avater as much as possible. Every part of the apparatus must be scrupulously clean and well washed Avith distilled Avater previous to commencing the experiment. It is Avell to wash the retort, flask, and glass tubes Avith dilute sulphuric acid, and then rinse them out clean with distilled water. In distilhng, the retort should be thrust well into the flame, and the distillation carried on rapidly. If the Avater is very soft, the addition of a little pure or recently heated sodium carbonate may be made, but in ordinary circumstances it is not necessary, and is not advisable. The typical yellow or brownish colour produced, when Xessler's solution is placed in the presence of minute quantities of ammonia, is due to the precipitation of the di-mercuric-ammonium iodide (XHg2I), that is, am- monium iodide (XH4I), from Avhich the four atoms of the monad hydrogen have been displaced bytAvo atoms of the dyad mercury: thus XH + 2HgI2 = XHg2I + 3HI. The " free " or " saline ammonia " represents the ammonia combined Avith carbonic, nitric, or other acids, and also what may be derived from urea, or other easily decomposable substances, if they are present. The limit in pure waters is taken at 0*002 centigramme per litre ; in bad waters it often reaches 100 times this and more : in usable waters it should not exceed 0*005. DETERMINATION OF THE ORGANIC NITROGEN. 71 After the distillation of the free ammonia, the residue of the Avater in the retort is used for determining the albuminoid ammonia, to be now described. Determination of the Albuminoid Ammonia.—In addition to the Xessler's solution and the standard ammonium chloride solution used in the last process, the following is required :■— An alkaline Permanganate of Potash solution made by dissolving 200 grammes of caustic potash and 8 grammes of potassium permanganate in 1100 c.c. of distilled water, and then rapidly boiling the solution down to 1 litre or 1000 c.c To make this determination, add to the residue left in the retort employed in the last process 25 c.c. of the alkaline permanganate solution and 25 c.c. of ammonia-free distilled Avater. Proceed to distil over as before, and continue to do so until no more ammonia comes over; this it Avill generally cease to clo after some 110 or 120 c.c. have been distilled. This ammonia is the so-called albuminoid, due to the breaking up of any organic matter present in the water under the influence of an oxidising agent in the presence of a caustic alkali. The determination of the ammonia in this case is conducted in precisely similar fashion as for the free ammonia. Example.—Suppose 120 c.c. were distilled over ; 100 c.c. were taken for the experi- ment ; 4"5 c.c of ammonium chloride solution Avere required to give the proper colour : 120 then 4-5 x _ x 0-017 x 0*4 = 0-03672 of albuminoid ammonia per 100,000. 100 In this process, before adding the alkaline permanganate solution to the residue in the retort, it is as well to boil it (the permanganate) for five minutes in order to get rid of any traces of ammonia which may be in it. The object of this process is to get a measure of the nitrogenous organic matter in Avater, by breaking it up and converting the nitrogen into ammonia by means of potassium permanganate in presence of an alkali: the ammonia can be distilled off and estimated as above. It is to be under- stood that this does not deal Avith all the nitrogenous matter, but the results are sufficiently uniform to be useful. As so calculated out, the albuminoid ammonia is approximately one-tenth of the nitrogenous matter in water. In drinking Avaters of good quality, the albuminoid ammonia should not exceed 0'01 per 100,000. Much albuminoid ammonia, Avith a small amount of free ammonia, indicates usually vegetable contamination, particularly so if the chlorides, nitrites, and nitrates are Ioav. Peaty waters commonly yield large quantities of albuminoid ammonia, which is evolved slowly and some- what persistently; badly polluted Avaters, on the other hand, generally yield their high proportion of albuminoid ammonia promptly and sharply. Determination of the Organic Nitrogen.—The application of Kjeldahl's nitrogen process affords a very convenient method for making this deter- mination in natural waters. The process practically consists of concentrating half a litre of the Avater doAvn to 300 c.c. : the residual Avater is then operated upon with sulphuric acid, and after all the Avater has been driven off, the organic residue is broken up Avith permanganate of potash in the presence of a caustic alkali, from which, on further distillation, the organic nitrogen is determined from the resulting ammonia. The actual process is as follows :— Place 500 c.c. of the Avater in a round-bottomed flask, of about 900 c.c. capacity, and boil until 200 c.c. have been distilled off. The free ammonia which is thus expelled may, if desired, be determined by connecting the flask 72 AVATER. with a condenser, and its eqihvalent nitrogen expressed as the ammoniacal nitrogen. To the remaining 300 c.c. of water in the flask, after cooling, add 10 c.c. of nitrogen-free sulphuric acid, agitating the whole gently, so that the acid may thoroughly mix Avith the water. The flask is then placed at an inclination, on Avire gauze, on an appropriate support, and the liquid boiled down till the oily residue is colourless or pale yellow in tint. The flask is removed from the flame, and a very little powdered permanganate of potas- sium added until the green colour of the liquid shows that an excess of the permanganate has been added. Should the liquid become purple and not green, all the water has not been driven off. After cooling, 200 c.c. of ammonia-free distilled Avater are added, the neck of the flask being washed free from acid by so doing, and then 100 c.c. of the alkaline permanganate solution as used for albuminoid ammonia also added. So soon as these additions have been made, the flask is at once connected Avith a condenser, well shaken, and the distillation commenced and continued until the whole of the ammonia has come over. This Avill usually do so Avhen some 200 c.c. have been distilled. The distillate is collected, measured, and Xesslerised in the usual way for ammonia. This ammonia is now expressed in terms X 14 of nitrogen, by multiplying by Mff" = T7 = 0*8235, the product being or- ganic nitrogen, exclusive of that nitrogen existing in the form of either nitrites or nitrates. It is not found that, Avith the extreme dilution of natural waters, the determination of the organic nitrogen by this process is vitiated by the presence of nitrites and nitrates. In carrying out the operation, the most scrupulous care must be taken in preventing access of ammonia from any source. The acid solutions will absorb ammonia from the air, if alloAved to remain uncovered for any length of time. The process should, therefore, be carried out without interruption, in a place free from dust, and if any doubt exist as to the freedom from ammonia of the reagents, a blank analysis with ammonia-free water should be made. Practically, the organic nitrogen by the Kjeldahl process is about twice the nitrogen of the albuminoid ammonia, and in usable drinking- waters does not usually exceed 0*016 part per 100,000. Any water, unless peaty, containing more than this may be regarded with suspicion. Example.— From 500 c.c. of water, after the first distillation, 200 c.c. were distilled, and its ammonia found to be equal to 2 c.c. of the ammonium chloride solution : then 2 x 0-017 x 0-2 x 0-8235 = 0-0056 of ammoniacal nitrogen per 100,000. The second dis- tillation, after breaking up of the residual water and residue, gave a distillate of 215 c.c.; of this, 20 c.c. were found to require, on Nesslerising, 2-2 c.c. of the ammonium chloride solution : then 2-2 x ^_ x 0*017 x 0-2 x 0-8235 = 0-05621 of organic nitrogen per 100,000. Determination of the Nitrites.—When organic matter putrefies or de- composes it becomes reduced to its absolute elements. Of these, nitrogen is the chief, and this combining with hydrogen forms first ammonia, hence the presence, more or less, of free or saline ammonia in a water when at all polluted Avith organic matter, such as raw sewage. In the course of time or as it percolates through the soil, the ammonia in the Avater acquires oxygen and gradually becomes partially oxidised to nitrous acid, HXO or to nitric acid, HX03, Avhich acids, by combining with bases like calcium sodium, or potassium, form nitrites and nitrates. The oxidation of organic matter cannot go beyond the formation of nitric acid and nitrates, while the nitrous acid and nitrites mark an intermediate stage of imperfect oxidation The determination, therefore, of nitrites and nitrates in a Avater is DETERMINATION OF NITRITES. 73 important, as indicating either a, pollution at some remote period with possibly dangerous matter, or more recently Avith a partially or completely oxidised sewage. Waters fouled by vegetable matter yield, as a rule, little nitrite or nitrate, chiefly because not only does vegetable decomposition yield rela- tively little nitrogen, but also because the natural tendency of all plant life is to remove both nitrites and nitrates from a Avater. For the direct determination of nitrites, in terms of nitrous acid (X02), two processes are available, namely, Griess's by means of meta-phenylenediamine and ddute sulphuric acid: and Ilosvays modification of Griess's test by means of sulphanilic acid and naphthylamine. Both are extremely sensitive, and require for their conduction one or more of the following solutions. (1) Dilute Sulphuric acid, consisting of one volume of strong acid to two of distilled water. (2) A solution of Meta-phenylenediamine, made by dissolving 5 grammes of meta-phenylenediamine in a litre of distdled Avater, rendered acid with sulphuric acid. This should be decolourised, if necessary, by filtering through animal charcoal. (3) A milli-normal Standard solution of Potassium Nitrite.—OAving to the unstable nature of this salt, it is necessary to prepare it specially for making up this solution. By the folloAving chemical equation, AgX0o + KC1 = AgCl + KXO,, 154 " 71*5 143-5 85 ■" it is seen that 154 parts of pure silver nitrite, in the presence of 74*5 parts of potassium chloride, are decomposed, with the formation of 143*5 parts of sdver chloride and 85 parts of potassium nitrite, or 46 of nitrous acid, as re- presented by X02. Hence, if 1*54 grammes of pure silver nitrite be dissolved in hot water, decomposed Avith a slight excess of potassium chloride, allowed X to cool, made up to a litre, Ave obtain a f~ solution of potassic nitrite equal- ling 0*46 gramme of nitrous acid as X09. If each 100 c.c. of this solution, after standing and subsidence of the silver chloride, be again diluted up to X a litre with distilled water, Ave get a j^kk s°hition of KN02, equalling 0*046 gramme of X02, and each c.c. of which equals 0*046 of a milligramme of X0.2. (4) A solution of Sulphanilic acid, made by dissolving 0*5 gramme in 150 c.c. of diluted acetic acid (sp. gr. 1*04). (5) A solution of Naphthylamine, made by dissolving 0*1 gramme in 20 c.c. of distilled water, then filtering and mixing the filtrate Avith 180 c.c. of dilute acetic acid. Griess's test is thus performed. One c.c. of the dilute sulphuric acid and 1 c.c. of the meta-phenylenediamine solution are added to 100 c.c. of the water to be examined, Avhich is put in a Xossler glass; an orange colour is produced, eventually deepening to a reddish tint. Another glass is placed alongside, and into it is put as much of a standard solution of potassium nitrite as may be necessary, making up the bulk to 100 c.c. with distilled water; then add 1 c.c. each of the sulphuric acid and the meta-phenylene- diamine. The remainder of the process is carried on much in the same way as ordinary Xesslerising for ammonia. Care must be exercised that the water originally taken is not too strong; so if the red colour be too deep, smaller portions diluted up to 100 c.c. must be used, until the faintest tint distinctly recognisable is obtained. The standard potassium nitrite, being of the strength of 1 c.c. = 0*046 milligramme of X02, or nitrogen tetroxide, 74 WATER. the number of c.c. used gives the milligrammes of X02 present in the sample of water. Example.—A sample of water containing a good deal of nitrous acid is taken, and 25 c.c, made up to 100 c.c. with pure distilled water, putinaNesslerglass. One c.c. of the sulphuric acid and 1 c.c. of the solution of meta-phenylenediamine added : a distinct orange colour is obtained. Into another Nessler glass 2 c.c. of the standard potassium nitrite are put, made up to 100 c.c. Avith distilled water, and the same shade of tint obtained with the solution as above. Then, 2x0-046x4 = 0*368 mgms. N02 in 100 c.c. of water or parts per 100,000. Multiplying this by -=- =-— = 0*304 gives the equivalent in terms of nitrogen. The above is a very accurate method of determining nitrites, but some care is required, for both the Avater and the colouring solution must be either colourless or decolourised. The chief objections to Griess's test are that the colour reaction only develops after some five minutes, and the solutions are liable to change. It may be Avell to mention here that the method of stating the results varies, as in the case of nitric acid, some reckoning as HX02, some as X203, and others as X02. The last is the best, as it corresponds to CI. In the same way X03 is to be preferred for the nitric acid, S04 for the sulphuric acid, and P04 for the phosphoric acid. Ilosvay's test is performed by placing 100 c.c. of the Avater sample in a colour comparison or Xessler glass, and then, by means of a pipette or burette, adding 2 c.c. each of the solutions of sulphanilic acid and naphthylamine. If nitrites are present, a pink colour is produced. Into another clean glass 1 c.c. of the standard nitrite solution is placed, made up Avith nitrite-free Avater to 100 c.c, and treated Avith the reagents as above. At the end of five minutes the colour of the tAvo solutions are compared, and the colours equalised by diluting the darker. Example.—Suppose the 100 c.c. of Avater sample is darker than the distilled water, containing 1 c.c. of the standard nitrite solution. It is necessary to dilute the water sample down to the tint given by the other : 60 c.c. of the 100 c.c. are taken and made up to 100 with distilled water : on comparison, suppose the colour to be still too deep : 70 c.c. of this diluted water is then taken and compared with the other. Presuming that the colours or tints now coincide, we get 100 x—. x — = 42 of the original 100 6 100 100 ° c.c. equal to 1 c.c. of the standard potassium nitrite solution, which again equals 0-046 f>T^ x.x. r 100x0-046 „ „„„ ,T^ . mgm. of N02: therefore ----—----= x = 0-085 mgm. N02 in 100 c.c, or 0*085 part per 100,000. Had the glass containing the 1 c.c. of standard solution been the darker, that could have been dduted doAvn in a similar Avay, and the various fractions calculated as parts of 1 c.c. or equivalents of 1 c.c. in terms of X02. The reactions in this process consist in the conversion of the sulphanilic acid into diazo-benzene sulphonic anhydride, by the nitrites present: this compound is in turn then converted by the naphthylamine into azo-«-amido- naphthalene-parazobenzene sulphonic acid. It is this last named compound which gives the pink colour to the liquid. Thus, Sulphanilic Nitrous Diazo-benzene acid. acid. sulphonic acid. C6H7NS03 + HN02 = C6H4N2S03 + 2H20 Diazo-benzene Naphthylamine Azo-alpha-amido-naphthalene sulphonic acid. parazo-benzene sulphonic acid C6H4N2S03 + C10H7NH3C1 = C10Ht/NH,)NNC,H4HSO3 + HC1. DETERMINATION OF THE NITRATES. 75 It may be accepted as a good rule that no Avater Avhich shows the presence of nitrites is fitted for domestic use. Determination of the Nitrates.—For this estimation Ave have tAvo convenient processes, either of Avliich can be readily performed : they are (1) the phenol-sulphuric acid method, and (2) the aluminium process. Phenol-Sulphuric Acid Method.—This method is simple in its applica- tion, and yields good results : for it the folloAving solutions are required :— (1) Phenol-sulphuric acid, made by adding 6 grammes of pure phenol and 3 c.c. of distilled Avater to 37 c.c. of strong sulphuric acid free from nitrates. (2) Standard solution of Potassium Nitrate, made by dissolving 0*722 gramme of recently fused nitrate of potassium in Avater, and the solution subsequently made up to a litre. One c.c. of this solution Avill contain 0*1 milligramme of nitrogen. The process is thus performed: 10 c.c. of the Avater under examination and 10 c.c. of the standard potassium nitrate solution are evaporated separately just to dryness in tAvo porcelain or platinum dishes. To each of the residues, 1 c.c. of the phenol-sulphuric acid is added and thoroughly mixed by means of a glass rod. If the Avater under examination contains a large amount of nitrates, the liquid wdl quickly turn red; if it contain but a small quantity, this colour will not appear for about ten minutes. After the dishes have stood for from ten to fifteen minutes, their contents are Avashed out successively with 25 c.c. of distilled Avater into tAvo clean Xessler glasses, about 20 c.c. of liquor ammonia added (sp. gr. 0*96), and both made up to 100 c.c. Avith more distflled Avater. Any nitrate present in the solutions converts the phenol-sulphuric acid into picric acid, Avliich, by the action of the ammonium, forms ammonium picrate : this gives a yellow colour to the solution, the intensity of which is proportional to the amount present. The colours of the tAvo solutions are uoav compared, and the darker one diluted until the tints are adjusted, the calculation being made as explained in the description of Ilosvay's test for nitrites. The comparative volumes of the liquids furnish the necessary data for determining the amount of nitrate, as the following example Avill sIioav. Example.—Say 10 c.c. of the water sample and 10 c.c. of the standard nitrate solution have, after treatment and dilution each to 100 cc, given two shades of yellow, of which that from the standard solution is the darker. This, on being diluted to 200 c.c, is still found to be too dark, but this again, on being further diluted to 900 c.c, giA^es the required match in colour. As the 10 c.c. of standard solution originally treated equal 1 milligramme of nitrogen, then, 900 : 100 : : 1 : a:=0*ll mgm. of nitrogen in 10 c.c. of the water sample, or 1*1 parts of nitrogen from nitrates per 100,000. If expressed as N03, this equals 4'3 per 100,000. In the case of very good Avaters, it is better to evaporate doAvn 20, 50, or more c.c. of the sample and only 5 c.c. of the standard nitrate of potassium : if the water under examination be very rich in nitrates, 10 c.c. of the sample should be pipetted into a 100 c.c. measuring flask, and made up to the mark with distilled Avater, then 10 c.c. of this Avell mixed and diluted liquid (=1 c.c. of original Avater) AvithdraAvn, evaporated, and treated as above. Aluminium Process.—If to a strongly alkaline Avater some aluminium foil be added, decomposition of the Avater ensues Avith the evolution of hydrogen. If nitrites or nitrates be present in the Avater, these salts are reduced by the hydrogen Avith the result that, on being boiled, their nitrogen is given off as ammonia. The reagents required for the determination of the nitrates are (1) some 76 WATER. thin aluminium foil, and (2) a solution of sodium hydrate. This is best made by dissolving 100 grammes of solid sodium hydrate in 1 litre of distilled Avater. When cold, introduce a strip of aluminium foil, previously heated to just short of redness, wrapped round a glass rod. When the aluminium is dissolved, boil the solution briskly in a porcelain basin until about one-third of its volume has evaporated : alloAv it to cool and make it up to its original volume Avith ammonia-free distilled Avater. The solution should be tested to prove the absence of nitrates. 100 c.c. of the Avater sample with 100 c.c. of the sodium hydrate solution and a strip of the aluminium foil are placed in a retort, corked, and left for six or more hours. At the termination of this time, heat must be applied, after connecting the retort with a condenser, and the ammonia present in the flask contents distilled over in precisely the same way as described for estimating the free and albuminoid ammonias. The ammonia Avhich will come over in the distillate will consist partly of any free ammonia which may be present in the sample, partly of ammonia due to reduction of nitrites, if any be present, and partly of ammonia due to reduction of nitrates, if they be present. After elimination of the two former, the remaining ammonia will represent nitrates, and from it the quantity of nitric acid as nitrates can be readily estimated. The principle of this process consists in the deoxidation of nitric acid or nitrates, and consequent formation of ammonia by evolution of hydrogen. Thus, 4A1 + IXaHO + 4H20 = 2 Al2Xa904 + 6H., 12H2 + 3KX03 = 31vHO + 6H20 + 3XH,. Example.—Presume that the whole of the ammonia has come over in 120 c.c. Ten c.c. of this distillate are taken for experiment, and diluted to 100 c.c. : on Nesslerising, 4 c.c of the ammonium chloride solution are found to give the required colour. Then 120 4 x —— x 0*017 = 0'816 mgm. of ammonia in 100 c.c. of water or parts per 100,000. This 0-816 part of ammonia in 100,000 is the total ammonia yielded by the 100 c.c. of water sample, and includes not only free ammonia (if any), but also ammonia due to nitrites (if any) and nitrates. Suppose this particular water sample to have already yielded 0'005 of free ammonia and 0'52 of nitrites as N02, both in parts per 100,000. The 0*52 of N0.2 is convertible 17 x 0'52 into NH3 in the ratio of as 46 is to 17, or - r— =0*192 of NH3, and this added to^ the 0'005 of free NH3 = 0-197 of ammonia per 100,000 to be deducted from the total ammonia before we get the NH3 due solely to the reduction of any nitrates present. This meansO-816 - 0-197 = 0'619 per 100.000 of NH:J representing nitrates as N03. Convert- ing this NH3 into terms of N03, we get 62 x °_619 = 2*257 mgms. of N03in 100 c.c. of the sample or parts per 100,000. Expressed as nitrogen, this equals 0-509 part per 100,000. Speaking generally, no water, used for drinking purposes, should contain more than 0*35 part per 100,000 of nitrogen in the form of nitrates: this equals about 1 grain per gallon of X205 or P5 parts of XO. per 100,000. Determination of the Oxygen Consuming Power.—Although, by itself, of little value as a measure of the organic impurity of a water sample, this determination of its affinity for oxygen, when taken in conjunction with other analytical facts, is often a material aid in forming an opinion as to the quality of any particular water. Much of the organic matter present in water is capable of oxidation, but since the ease of oxidation bears no constant ratio to the nature of the organic matter, its estimation affords no very reliable index to the real pollution present. In all the efforts to judge the oxidisable organic matter, advantage is taken of the fact that, in the DETERMINATION OF THE OXYGEN CONSUMING POWER. 77 presence of most organic substances, permanganate of potassium freely parts with its oxygen until all the permanganate has been reduced to hydrated manganese dioxide: thus, 2KMn04 = Iv2Mn04 + Mn02 + 02. Unfortunately, different substances reduce different proportions of permanganate, and slight variations in temperature and acidity or alkalinity materially influence the readiness with Avhich the permanganate parts with its oxygen. To determine the oxidisable organic matter, use is best made of what is knoAvn as Tidy's process. This process is based upon the chemical fact that, in the presence of an acid and heat, the following decomposition of perman- ganate takes place:—4KMn04 + 6H2S04 = 2K2S04 + 4MnS04 + 6H20 + 500, or in other words, 632 parts of potassium permanganate yield in the presence of sulphuric acid 160 parts of oxygen. For Tidy's process, the following solutions are necessary :— 1. Standard Potassium Permanganate Solution. — Since 632 parts of the salt with an acid yield 160 parts of oxygen, then 0-316 gramme of potassium permanganate, if dissolved in a litre of water, will be equivalent to 0*08 gramme of oxygen. This constitutes the standard solution; 1 c.c. of it used with acid yields 0*08 mgm. of oxygen. 2. Potassium Iodide Solution.—A 10 per cent, solution in distilled Avater. 3. Sodium Thiosulphate Solution.—One gramme dissolved in a litre of distilled water. 4. Starch Solution.—One gramme of starch, mixed with half a litre of distilled water, boiled for five minutes, and filtered. 5. Dilute Sulphuric Acid, consisting of one volume of strong acid to three of distilled Avater. In performing this process, Tidy recommended two determinations to be made, namely, one of the oxygen absorbed after fifteen minutes' exposure at a temperature of 80° F., and one after four hours' exposure at the same heat. He considered that during the first quarter of an hour, the more or less putrescent easily-oxidised animal organic matters Avere oxidised, while the oxidation of the vegetable organic material did not take place till after four hours or so. Practically, as much information as can be gained is obtained at the end of fifteen minutes; therefore, except in special cases, the second observation after four hours is hardly necessary. If re- quired, it is performed exactly in the same manner as the shorter exposure. Into a stoppered bottle, capable of holding from 300 to 400 c.c, place 250 c.c. of the water sample, and heat in a water bath to 80° F. (26*7 C.); Avhen the required temperature is reached, run in 10 c.c. of the sulphuric acid and 10 c.c. of the permanganate solution. A pink colour will result. Maintain the bottle contents at 80° F., carefully noting whether the pink tint is discharged; if the tint disappear add more permanganate. At the end of fifteen minutes, add to the water three drops of the iodide of potassium solution. OAving to there being a certain amount of oxygen available from the permanganate, as previously explained, this will liberate iodine from the iodide, with the result that the pink-coloured bottle contents will now become yellow: thus, 502 + 20KI + 10H2O = 20KHO + 10I2. The quantity of iodine set free will, of course, be dependent on the amount of potassium permanganate remaining unreduced in the water. If the iodine set free is absolutely dependent upon the amount of permanganate left unreduced by the organic matter in the Avater, it is obvious that any estimation of the iodine liberated will be a measure of the unused oxygen, and this, deducted from what was rendered available by the original quantity of permanganate added, Avill give a measure of the oxidisable organic matter in the 250 c.c. of water. 78 WATER. We proceed to make these estimations in the folloAving manner. To the iodine-tinted water, the thiosulphate solution is gradually added Avith the object of reducing it: thus, I2 + 2Xa2S203 = 2XaI + Xa.2S40(i. In order to knoAv exactly when all the free iodine has been removed from the Avater, an indicator in the form of 1 c.c. of the starch solution is added ; this, so long as any free iodine is present, Avill give a blue tint. Therefore, con- tinuing the addition of the thiosulphate, Ave stop the moment all the blue colour has gone, and read off the actual amount of thiosulphate used. Unfortunately, thiosulphate of soda is a very unstable salt, and its particular value as a reducing agent needs to be judged, at the time of each experiment, by means of a control observation of its poAver upon an identical quantity of permanganate in distilled water, as was used for the unknoAvn sample. Accordingly, into a similar bottle, 250 c.c. of distilled Avater are placed, heated to 80° F., 10 c.c. of the sulphuric acid, and exactly the same amount of permanganate as Avas used for the water sample added, and the Avhole kept at 80° F. for fifteen minutes. In this bottle, OAving to there being no organic matter, practically the Avhole of the oxygen liberated from the permanganate under the circumstances Avill be unconsumed, and con- sequently, on the addition of three drops of potassium iodide, more iodine Avill be liberated, and more of the thiosulphate Avill be required to reduce it. The iodide, the starch, and the thiosulphate are added precisely as in the other experiment. So soon as all the iodine has been removed, as shown by the disappear- ance of the blue colour, the amount of thiosulphate used is read off; its volume Avill represent, for the time being, the actual reducing value of the thiosulphate for the precise amount of permanganate used or added in the experiment. And the difference betAveen the amount of thiosulphate solution needed to reduce the x amount of potassium permanganate in this pure distilled Avater, and that required for the same amount/ Avhich has been more or less decomposed or reduced by oxidisable organic matter in the Avater sample, Avill represent the quantity of oxygen consumed by such oxidisable matter. Example.—Say 10 c.c of KMn04 in the distilled water have used up 40 c.c. of the thiosulphate solution: therefore, 40 c.c. of the thiosulphate may be considered as equivalent to 10 c.c. of KMn04 or 1 mgm. of oxygen. Another 10 c.c. of KMn04, in the unknown sample, have used up, say, 32 c.c. of thiosulphate solution : therefore, an amount of oxygen equivalent to the difference be- tween 40 and 32 c.c. of thiosulphate solution has been taken up by the organic matter. But if 40 c.c. of thiosulphate equal 1 mgm. of oxygen, then 8 c.c, or the difference be- tween 40 and 32, equal 0 *2 mgm. of oxygen. This means that 0*2 mgm. of oxygen is taken up by 250 c.c. of the water sample, or parts per 250,000 : ttes multiplied by 0*4 equals 0*08 part of oxygen consumed by the oxidisable organic matter per 100,000. In performing this process, the permanganate added must be sufficient to create a pink colour, which remains distinctly permanent at the end of the heating. If the four hours test be applied, it may be necessary to make repeated additions of the permanganate solution. The total quantity actually used must be carefully noted, and the same amount, of course, employed in the distilled Avater experiment. In endeavouring to interpret the results of this oxygen consuming process, it must be borne in mind that besides organic matter, iron salts, nitrites, and sulphuretted hydrogen wdl reduce permanganate of potassium; and these latter, if present, must be duly allowed for. It is difficult to distinguish between the oxygen consumed by the nitrogenous and the non- nitrogenous matter. Roughly speaking, the four hours experiment gives DETERMINATION OF THE PHOSPHATES AND IRON. 79 information as to the total amount of oxidisable organic matter, while the fifteen minutes reaction is valuable as indicating the proportion of putrescent or readily oxidisable, and presumably dangerous material. Peaty Avaters consume large quantities of oxygen: hence, as in all other attempts to measure the organic matter in a Avater sample, the results of the oxygen process must be considered in conjunction Avith the other analytical data and the source of the Avater. In a general Avay, it may be said that Avaters of great organic purity Avill not consume more than 0*05 of oxygen per 100,000 in fifteen minutes at 80° F., and that, when the oxygen consumed exceeds 0-1 per 100,000, the sample may be considered of doubtful purity. If, after four hours' exposure, more than 0-3 part of oxygen are consumed per 100,000 of Avater, the sample must be regarded Avith suspicion. Determination of the Phosphates.—For this estimation, Ave require a solution of Ammonium Molybdate, made by dissolving 10 grammes of molybdic anhydride in 41*7 c.c. of liquor ammonia (sp. gr. 0*96), the solu- tion being then slowly poured, Avith constant stirring, into 125 c.c. of nitric acid (sp. gr. 1*20), and alloAved to stand in a Avarm place for several days until clear. The process is carried out by evaporating 500 c.c. of the Avater, slightly acidified with nitric acid, doAvn to 50 c.c. A feAv drops of a dilute solution of ferric chloride are added, and then strong ammonia in slight excess. A precipitate of all the phosphates is formed; this is filtered off and dissolved on the filter by the smallest possible quantity of hot dilute nitric acid. At this stage the filtrate and Avashings should not exceed 5 c.c. in volume : if more, they must be evaporated doAvn to this bulk. The liquid should noAV be heated to nearly boiling, 2 c.c. of the ammonium molybdate solution added, and the liquid kept Avarm for half an hour. If there is any appreciable precipitate, this must be collected on a small tared filter, Avashed Avith distdled Avater, dried and weighed. The weight of the precipitate multiplied by 0*035 gives the amount of P205, or multiplied by 0*0467 gives that of P04. If the quantity is too small to collect and weigh, it is usually reported, according to circumstances, as "traces," "heavy traces," or " very heavy traces." Determination of Iron.—This quantitative process as originally elaborated by Thompson Avas first described by Sutton in his Volumetric Analysis. It is very delicate and presents no difficulties in procedure ; for it the f oIIoav- ing solutions are required :— A Standard Solution of Ferric Sulphate.—Dissolve 0*7 gramme of ferrous sulphate in distilled Avater acidified with sulphuric acid, and add potassium permanganate solution until a faint pink colour is produced. The solution is then diluted to a litre. One c.c. of this solution contains 0*1 milligramme of iron. Dilute Nitric Acid.—Dilute 30 c.c. of pure concentrated nitric acid Avith distilled water to about 100 c.c. A Solution of Potassium Sulphocyanate.—Five grammes dissolved in 100 c.c. of water. To make a quantitative estimation of iron, acidify 100 c.c. of the water sample Avith pure hydrochloric acid and add just sufficient dilute potassium permanganate solution to convert any iron which may be present to the ferric state. Xext evaporate this pink-tinted solution nearly to dryness, in order to drive off excess of acid, then dilute to its original volume of 100 c.c. with distilled water. Into each of two Xessler glasses place 5 c.c. of the dilute nitric acid and 15 c.c. of the potassium sulphocyanate solution. To 80 AVATER. one of these a measured volume of the treated water is added and both glasses filled up to 100 c.c. with distilled water. If any iron be present in the treated water, a blood-red colour Avill be produced in the glass to Avhich a measured volume was added. Into the other glass some of the standard iron solution is added until the colour agrees. The precise amount of the treated water to be added to the first glass will depend upon the quantity of iron present; but as a rule not more should be used than will require 2 or 3 c.c. of the standard iron solution to match it, otherwise the colour produced will be too deep for accurate comparison. Example.—Say, after treating 100 c.c. of the water sample in the manner explained, 10 c.c. of it are added to a Nessler glass, containing 5 c.c. of dilute nitric acid and 15 c.c. of the sulphocyanate solution, and made up to 100 c.c with water. A red tint is produced. The addition of 2 c.c. of the standard iron solution to the other glass is found to give the same colour. Then 10 c.c. of the original water equal 2 c.c. of the standard iron solution or contain 0 '2 milligramme of iron : this is equivalent to 2 parts of iron per 100,000, or 1*4 grains per gallon. Determination of Lead.—As drinking waters very rarely contain copper, the amount of lead present can be conveniently determined by the following method. A standard solution of Lead Acetate is prepared by dissolving 0*183 gramme of the crystallised salt in a litre of distilled water. One c.c. of this solution contains 0*1 milligramme of metallic lead. 100 c.c. of the water to be examined are placed in a Xessler glass and acidified by the addition of a feAV drops of acetic acid : to this is now added 0*5 c.c. of a saturated solution of ammonium sulphide. If any lead be present a brownish-black colouration will be produced. Into another similar vessel 100 c.c. of distilled water are placed, together with the same quantities of acetic acid and ammonium sulphide, and sufficient of the standard lead solution added to match the tint in the other glass. From the amount of lead solution used, the quantity of lead in the water under examination is readily calculated. The result should be expressed both in parts per 100,000 and in grains per gallon. Many Avaters, especially those that are soft and peaty, and therefore liable to act on lead, possess sufficient colouration to equal 0*5 or even 1 c.c. of the lead solution: if this is the case, a proportionate reduction should be made before calculating out the amount of lead present. By this method 0*05 per 100,000 or ^ grain per gallon may be easily detected. Copper, Arsenic, and Zinc—The mere presence of these metals in appreciable quantity is enough to condemn a water, therefore it will seldom be necessary to determine their amount quantitatively. Silica may be determined from the incinerated residue by treating it with strong nitric or hydrochloric acid, evaporating to dryness, and again treating with acid; distdled water (about 50 c.c.) is then added, and a little heat applied till everything soluble is dissolved ; the residue is silica, which may be collected on a small filter, ignited, and weighed. A number of Indian waters contain considerable quantities of silica, either combined or in the suspended matter. Determination of the Dissolved Oxygen.—This estimation in connection with water analysis has hitherto been much neglected. For hygienic purposes, a method of estimating dissolved oxygen must be simple, speedy, and accurate, and must not require large quantities of water. A further condition is that the water must not be subjected to a diminished oxygen pressure, i.e., must not be operated upon in an atmosphere of inert gas DETERMINATION OF THE DISSOLVED OXYGEN. 81 otherAvise there might be, according to the experiments of Eoscoe and Lunt, a rapid loss by diffusion. Several methods for determining the dissolved oxygen in water have been proposed: the more notable being those of Winkler, Dibdin, Thresh and Mohr. The chief objection to them all has been the necessity of special apparatus. As being perhaps the most simple and readily applied, we here describe Thresh's method. This process is based primarily upon the fact that 16 parts by Aveight of oxygen Avill liberate 254 parts of iodine, and as the latter element admits of being accurately estimated, therefore the oxygen is capable of precise determination. We have simply to add to a known volume of the water a definite quantity of sodium nitrite, together Avith an excess of potassium iodide and acid, avoiding access of air, and then to determine volumetrically the amount of iodine liberated. After deducting the proportion due to the nitrite used, the remainder represents the oxygen which was dissolved in the water and in the volumetric solution used. The solutions required for the process are :— Solution of Sodium Nitrite and Potassium Iodide, containing 0*5 gramme of the nitrite and 20 grammes of the iodide, in 100 c.c. of distilled Avater. Dilute Sulphuric Acid, containing one part of pure acid to three of distilled Avater. A clear or fresh Solution of Starch. Solution of Sodium Thiosulphate, containing 7*75 grammes of thiosulphate of soda, in a litre of distilled Avater. 1 c.c. of this solution corresponds to 0*25 milligramme of oxygen. The apparatus used consists of a wide-mouthed bottle A (see fig. 4), of 500 c.c. capacity, closed with a caoutchouc stopper having four per- forations. Through one passes the tube B, connected by a rubber tubing at its upper end Avith the burette C containing the thiosul- phate. Through another opening passes the neck of the " separator " D, of known capacity, and pro- vided with a stopper and stopcock. Through a third opening passes the tube E, Avhich can, by means of rubber tubing, be attached to the ordinary gas supply. Through the fourth aperture is the tube for the gas exit, and to the end of this is sufficient tubing to allow the cork G- at its end to be placed in the neck of the separator D when the stopper is removed. A small piece of glass tube projects through this cork to allow of the escaping gas to be ignited. The separator D is filled with the water to be examined, and 1 c.c. of the nitrite iodide and 1 c.c. of the acid solution are added, and the stopper instantly fixed in its place, displacing a Uttle of the Avater, and including no F Fig. 4. 82 WATER. air. By inverting the separator a feAV times, a uniform admixture of these reagents Avith the water is secured; then its nozzle is pushed through the bottle cover, and the whole alloAved to stand for 15 minutes to enable the reaction to become complete. A rapid current of coal gas is iioav passed through the bottle A, untd all the air is displaced, and the gas burns at G with a bright flame. The flame is noAV extinguished, the stopper of D removed, and the cork G rapidly inserted in its place. On turning the stopcock of D, the water flows into A. The stopcock is turned off, the cork G removed from D, and the gas relighted at G, being so regulated that only a small flame is produced. Thiosulphate is noAV run in from C into the Avater in A until the yellow colour of the iodine is nearly discharged. A little solution of starch is then poured into D, and about 1 c.c. alloAved to Aoav into the water in A by opening the stopcock. The titration Avith the thiosulphate is continued until the blue colour is discharged. Frequently, the blue tint returns after a few seconds, due to the oxygen dissolved in the thiosulphate solution; if so, the further addition of a few drops of thiosulphate, hoAvever, effects the final discharge. The amount of thiosulphate solution used is now read off and recorded. Call this e. This will represent a, or the oxygen dissolved in the water examined, plus b, or the oxygen in the 1 c.c. of the nitrite-iodide solution and the oxygen in the acid and starch solution added, plus c, or the oxygen dissolved in the thiosulphate solution added. To find the value of a, it is obvious that b and c must be ascertained. Once this is known, they do not require redetermination, unless the conditions are changed. To find the Value of b.—Having completed a determination as above described, then, by means of D, introduce into A, in succession, 5 c.c. each of nitrite-iodide solution, dilute acid, and starch solution. Then titrate with the thiosulphate. One-fifth of the quantity of this used will obviously represent the value of 1 c.c. of each of these solutions as originally used. To find the Value of c.—This correction is a comparatively small one, and is sufficiently accurately stated if we assume that the thiosulphate solution normally contains as much dissolved oxygen as distilled water at the same temperature. Complete a determination as above described, then remove the stoppered bottle D, and insert a tube similar to that attached to the burette C, and drop in from it 10 to 20 c.c. of oxygen saturated distilled water exactly as the thiosulphate is dropped in. AHoav to stand for a few minutes and titrate. One-tenth or one-twentieth of thiosulphate, used according as to whether 10 or 20 c.c. of Avater were added, gives the cor- rection for each c.c. of volumetric solution used. Call this d. Practically, for temperatures between 40° F. and 60° F., the value of d may be taken to be 0*031. In Appendix IX. is given a table showing the amount of oxygen dissolved by distilled water, per litre, at various temperatures. The actual calculation of milligrammes of oxygen, dissolved in 1 litre of the water under examination, is conveniently made from the following statement:— 1000 . _ 7, . x= ~±f (e-b-ed): in which / is the capacity of the separator D, less 2 c.c. for volume of reagents added: e is the number of c.c. of thiosulphate solution used: b is, as already explained, the oxygen in the 1 c.c. of nitrite iodide, acid and starch solution added. For strict accuracy, when the water sample contains nitrites, as determined independently by either Griess' or Ilosvay's tests, a deduction of oxygen for them must be made in the proportion of 0*017 milligramme of oxygen per htre for every part of nitrite per 100,000 found, as they may act as oxygen carriers. DETERMINATION OF THE DISSOLVED OXYGEN. 83 Example. —Say 322 c.c. of water were capable of being placed in the separator D, this, less 2 c.c. for reagents added, gives 320 c.c. of Avater operated upon =/. After being treated as already explained, presume that 15"2 c.c. of thiosulphate were used = e. Say b Avas found to be 3-l c.c. and that d is taken as being 0*031: then, sc= (15'2 - 3*1 - (15-2 x 0-031)) = 9-085 milligrammes 0„ per litre. Presuming further that the Avater contained 0*02 of nitrites per 100,000, then the dissolved oxygen per million will be 9-085 -(0*02 x 0-017) = 9'08466. The presence of nitrates, even in large quantities, does not interfere Avith the accuracy of this process. Our knoAvledge at present is small concerning the amount of dissolved oxygen in various Avaters : but the following table gives some results obtained :— /• e. X. Source or Kind of AA'ater. Amount of Thiosulphate e-b-ed. Alilligrammes AA'ater employed. required. of 02 per Litre. Distilled water shaken with air at 60° F., . 232-5 11-90 9-43 10*14 Rain-water, 250-0 11-10 8-65 8-65 Do. ... 3160 13-00 10-49 8 30 Shallow-well water, 250-0 10-22 7-80 7*80 Deep-well water, 250-0 9-50 7-11 7*11 Dupre has endeavoured to employ the determination of dissolved oxygen in Avater as a means of estimating the proportion of oxygen-consuming micro- organisms present. The principle of his method is that pure water, if kept in a closed vessel, will neither gain nor lose oxygen in any length of time; but if organisms capable of causing absorption of oxygen are present, the quantity will decrease. The experiment is earned out by placing a sample of the Avater in a clean bottle, and vigorously shaking it to saturate with air. A clean 250 c.c. bottle is completely filled with the water, tightly stoppered, and maintained at a temperature of 68° F. (20° C.) for ten days : the oxygen remaining is then determined, and compared Avith that which was originally dissolved in the water. The amount of dissolved oxygen in surface waters follows the average temperature of the air. This is proved by graphically plotting the average monthly temperature and the average temperature of saturation of surface Avaters during that month. The curves follow each other pretty closely, rising steadily from a minimum about January to a maximum about August, and decreasing suddenly in September or October. Underground Avaters, as a general rule, are characterised by low dissolved oxygen, the amount bearing no obvious relation to the temperature of the season. In some of the deepest wells only traces of oxygen are found. Usually, as the oxygen is found to be deficient, so is the free C02 found to be in excess, but there is no absolute rule for this. What interpretation is to be put upon it is a matter for further experiment. In a Avater, shown by the presence of free C02 and little organic matter to be a ground Avater, a small amount of dissolved oxygen will be a good rather than a bad sign, as it indicates that the water has come from a depth. Determination of the Carbonic Acid.—As carbon dioxide is always being absorbed from the atmospheric air, and especially from the ground air, Avater Avithout carbonic acid does not occur. Carbonic acid may exist in Avater in three states, namely, as carbonates, bicarbonates, and free acid. The usual •German expressions are " combined or fixed " for that existing as simple car- 84 WATER. bonates, " half-bound " for that necessary to convert the carbonates into bicarbonates, and " free " for that remaining in excess. As practically all the so-called free and half bound C02 is expelled from a Avater on boiling, the sum of these tAvo constitutes Avhat may be called the volatile carbonic acid. The- combination of C02 is effected chiefly in the form of acid salts of the alkaline earths, especially acid calcium carbonate. If an aqueous solution of this salt is boiled, or even alloAved to stand exposed to the air, it is split up into car- bonic acid and neutral calcium carbonate. This neutral CaC03 is almost insoluble in water, and is stable : the so-called acid calcium carbonate (calcium bicarbonate) has a distinctly alkaline reaction. Thus Ave have the folloAving scheme :— ( Fixed. Total C09 -J ,r , ,., \ Half-bound. 2 (Yolatlle{Free. Any attempt to estimate the C02 volumetrically is based upon the folloAAr- ing facts:— 1. An indicator, like methyl orange, is unaffected by CO.,, hence the earthy bases present as carbonates or bicarbonates can be at once titrated by a standard acid, whether an excess of (free) C02 be present or not. 2. Carbonates are alkaline to phenolphthalein; bicarbonates neutral, free C02 acid. Hence (a) a carbonate titrated Avith an acid, in dilute solution or under conditions Avhich prevent loss of COL>, becomes neutral Avhen all the car- bonate is converted into bicarbonate : thus, Xa2C03 + HC1 = XaHC03 + XaCl. (b) Free carbonic acid, in dilute solutions, can be titrated Avith sodic car- bonate, neutrality arriving when the alkali is converted into bicarbonate. Seyler's experiments have shoAvn that, if a Avater is neutral or acid to phenolphthalein, and this is generally the case, the half-bound C02 is equal to the fixed, and the volatile C02 is equal to the sum of the fixed and free. If a Avater is alkaline to phenolphthalein, it contains no free CO.,, and the volatile C02 is less than the fixed by an amount capable of being determined by titration with an acid until neutral to phenolphthalein. The Free Carbonic Acid may be best titrated, according to Trillich, by taking 100 c.c. of the water, after the addition of phenolphthalein, and dropping in a — solution of Xa2C03 (2*19 grammes to the htre), until a faint • pink colour appears. The consumption of each cubic centimetre of the soda solution represents the presence of 1*1 milligramme of free carbonic acid. The titration must, for any accurate results, be repeated, running in nearly the right amount at once and then finishing drop by drop. The Fixed Carbonic Acid may be determined, as suggested by Lunge, by taking 100 c.c. of the Avater, after adding some methyl orange, and X dropping ina- mineral acid, such, for instance, as sulphuric acid (2*45 grammes to the litre), 1 c.c of which equals 1*1 milligramme of C02. The principle involved in this titration is that, if sulphuric acid is added to a carbonate or bicarbonate, along Avith an aqueous yellow solution of methyl orange, metallic sulphate and free carbonic acid are formed, and the pale yellow colour remains unchanged until the carbonates are completely decom- posed, and a trace of free sulphuric acid is present Avhen a red colour appears. The presence of other salts has no importance. This method determines the combined carbonic acid, a molecule of the acid salt consuming exactly as much acid as a molecule of the neutral salt: thus, CaC03 + HSO = CaS04 + C02 + H20, and Ca(HC03)2 + H2S04 = CaS04 + 2C02 + 2U.6. * DETERMINATION OF THE CARBONIC ACID. 85 In any case in Avhich both free and fixed C02 have to be determined, this may be done upon the same 100 c.c; titrating first Avith the alkali, and then adding methyl orange and titrating Avith the acid. The number of c.c of soda used is of course subtracted, and the results will be quite accurate, unless the combined C02 be very small. Thus, taking 100 c.c. of aAvater, neutral or acid to phenolphthalein, and in which the half-bound C02 may be taken, from Seyler's experiments, to be X equal to the fixed, and the volatile equal to their sum, say 9 c.c. of — soda •carbonates Avere used, and 12 c.c. of acid Avere required, then Ave have— Free CO., =1*1 x 9 = 9*9 parts per 100,000. Fixed COo =1*1x12 =13-2 „ ,, „ Volatile CO., =1*1(9 + 12) =23*1 ,, Total C02 =1*1(2x12 + 9) =36*3 ,, ,, ,, In another case, if the Avater is alkaline to phenolphthalein, 100 c.c. may be titrated Avith acid until the pink vanishes, and then finished Avith methyl orange. If m be the number of c.c. of acid required Avith methyl orange andp that required Avith phenolphthalein, then Ave have— Fixed CO., =lTm parts per 100,000. Volatile CO., = l*l(m- 2p) ,, ,, Total C0.2 =l-l(2m-2p) „ ,, „ We have 2 p here because the same acid corresponds to tAvice as much *C02 Avhen phenolphthalein is used as when methyl orange is used. Thus, tAvo simple titrations will in a few minutes give a fairly complete information as to the nature and amount of C02 existing in a Avater sample. The presence of free carbonic acid is an almost constant characteristic of ground water. The amount varies, but may be as high as 13 parts per 100,000; it appears to be in inverse ratio to the dissolved oxygen. The source of the free CO., in ground Avater is apparently the ground air, in- creasing with the depth and decreasing with the porosity of the soil. When ground water is exposed to the air it may rapidly lose its free C02, and even become alkaline to phenolphthalein. Such waters generally contain magnesic carbonate, and betray their exposure to the air by becoming saturated Avith dissolved oxygen. The estimation of free and combined C02 is further of interest in regard to the reaction of a Avater, and also in connection with its action on lead. Waters Avhich contain both free and combined C02 are often distinctly amphioteric: that is, they turn red litmus paper blue, and blue paper red. These reactions are probably explicable as the result of a competition for the base betAveen the free C02 and the red litmus, which is itself a Aveak acid, having blue salts. If some of the red paper is placed in a solution con- taining carbonates and free C02, it seizes a portion of the base until ■equilibrium is established. If the blue paper be placed in the solution, the free C02 attacks it for part of the base, and liberates red litmus until the same •condition of equilibrium is reached. Practically, testing the reaction of a Avater Avith litmus paper is much better replaced by an estimation of the free and combined C02. In its connection with the action of Avater upon lead, the relative amounts of free and combined C02 are often important factors. Frequently, waters Avhich act upon lead contain more free than combined carbonic acid, and yet are distinctly alkaline to red litmus paper. In testing the action on lead, it ia 86 AVATER. of importance to conduct the experiments in closed vessels, as Avell as in open beakers, to prevent the loss of C02, as the results will be sometimes found positive in the former and negative in the latter. Inferences from the Quantitative Tests.—The conclusions to be draAvn from the qualitative tests hold good for the quantitative, only greater pre- cision is given. It must, however, be understood that such conclusions are still only approximative, and they are only of a certain value Avhen all the circumstances of the case are taken into consideration. Some chemists have gone so far as to say that they Avould rather knoAv nothing about the sample, and merely Avish it marked with some distinctive mark, such as A or B, or 1 or 2, their confidence being so great in the indications of their analyses that they feel convinced they can give a perfectly trustAvorthy opinion on the wholesomeness or otherAvise from these alone. There is no doubt that a practised chemist may make a fairly good guess under such circumstances, but as a rule an opinion so formed is worth very little. It is,_ of course, desirable that an analyst should come to his inquiry perfectly unbiassed; but before adopting a conclusion as regards a Avater, the medical officer will ahvays do well to obtain every item of information about it that it is possible to get— otherwise he is sure to fall sooner or later into error. Thus, constituents may be present in a deep-well water and have no particular significance, Avhilst in a shalloAV-well Avater they would be sufficient to condemn it. At present Ave have little or no means of positively distinguishing vegetable from animal organic matter ; yet it is obvious that an amount of the former Avould be admissible Avhich could not be alloAved of the latter. The analysis should ahvays be as careful and complete as possible, but let the results ahvays be interpreted in the light afforded by a searching exami- nation of the source of the sample. Want of attention to this point is liable to lead to errors fraught Avith most disastrous consequences. Subjoined is a critical survey of the more important data, as yielded by a chemical analysis. 1. Chlorine in Chlorides.—The purest Avaters contain small quantities of chlorides, generally less than 1*5 per 100,000. Rain-Avater generally contains 0*22 to 0*5 per 100,000. An increase in ordinary drinking Avater may be due to sea-Avater, salt-bearing strata, or sewage, or other impurities. In the tAvo former cases it is comparatively innocent, but in the last it may be an indication of dangerous contamination, in Avhich case it is usually connected Avith an increase in the ammonias, the oxidisable matter, and the nitrogen acids. SeAvage contamination can never take place Avithout some increase in the chlorides, unless it be through gaseous emanations. Some deep wells contain large quantities of chlorides, but the other details of the analysis Avill show that this is not due to any recent contamination. Generally speaking, hoAvever, an excess of chlorine is a reason for suspicion, until a satisfactory explanation of its presence is obtained. In most cases, however, a correct judgment can only be formed by comparison Avith the average character of the Avaters of the district. 2. Solids, Total and Volatile.—The amount of solids varies very greatly with the source of the water. Pure upland surface Avaters contain very little, sometimes not more than 3 to 4 parts per 100,000. The Loch Katrine Avater, supplied to Glasgow, yields only 2*4 per 100,000 ; Thirlmere Lake, supplied to Manchester, almost the same, and the River Vyrmvy, which supplies Liverpool, 3*4 per 100,000. On the other hand, Avaters from pure sources other than upland surface shoAV much more than this. On the Avhole, Ave may lay it doAvn that the purest upland surface Avaters seldom contain more than about 7 parts per INFERENCES FROM QUANTITATIVE ANALYSIS. 87 100,000, but that considerable latitude may be admitted in Avaters from deep wells, chalk strata, and the like. Of the solids not more than about 1*5 per 100,000 ought to be volatile, or capable of being driven off by a red heat. The solids should blacken but very slightly on ignition. A little deviation from this rule is admissible in water from peat land. 3. Ammonia, Free and Albuminoid.—Pure Avaters yield from nil to 0*002 per 100,000 of free ammonia, and from nil to 0*005 per 100,000 of albu- minoid ammonia. Usable Avater may contain up to 0*005 per 100,000 of freehand 0*01 per 100,000 of albuminoid ammonia. These numbers, Iioav- ever, require qualification, for they may be exceeded in cases where water is thoroughly good for dietetic purposes. Rain-Avater often contains a large amount of free ammonia, probably derived from soot, and it appears to be harmless. Deep Avells often show a large amount of free ammonia and chlorides with- out necessarily indicating pollution; but the same amounts in a shahW Avell would point to probable sewage pollution, or at least to the presence of urine. The presence of a considerable amount of albuminoid ammonia, Avith little free ammonia and chlorides, is generally indicative of vegetable organic matter, often peaty. This is the character of the greater part of the water- supply of Ireland. If the chlorine be high, that is, in excess of the average of the district, it may be inferred that the material Avhich yields the ammonia is in great part of animal origin. The real significance of the albuminoid ammonia has been much discussed, but the results obtained are sufficiently uniform to give us a convenient measure of purity, provided Ave are careful not to draw the line too close. All the nitrogen of the organic matter is certainly not obtained by this method, but this is immaterial so long as the proportion is fairly maintained. The results correspond to a certain extent Avith the organic nitrogen of Frank- land, and the process is much more feasible for medical officers generally. Practically, 0*615 part of albuminoid ammonia per 100,000 equals 1 part of Frankland's organic nitrogen per 100,000; and double the nitrogen from the albuminoid ammonia equals the organic nitrogen as determined by Kjeldald's process. 4. Nitric and Nitrous Acids in Nitrates and Nitrites.—The significance of these is very important. Xitric acid is the ultimate stage of oxidation of nitrogenous organic matter, and Avhen present in Avater it is almost ahvays the result of previous pollution, either of the Avater itself or of the strata through Avhich it Aoavs. It gives us no information, however, as to the exact time Avhen the pollution took place. In some samples from deep wells it is evident that the pollution must have been very ancient. It has been distinctly shown by Schloesing and Muntz and by R. Warington that nitrification is a fermentative process, excited and carried on through the agency of a minute organism, just as ordinary fermentation is carried on through the medium of torula. Xitrous acid indicates the presence of organic matter undergoing change: it is either a stage in the direct oxidation of such matter, progressive or arrested, or a retrogression from nitric acid in consequence of the latter having yielded up a part of its oxygen. In this Avay nitrous acid might retrograde still further and become converted again into ammonia, or be dissipated as nitrogen. Xitrous acid is a much more important substance than nitric, as indicating present danger, and a very small amount of it is sufficient to remove a Avater into the sus- picious class. It is rare to find any of the higher forms of life in a water rich in nitrites, although bacteria may be found. Pure Avater ought 88 AVATER. to be quite free from nitrites, and ought to show only traces at most of nitrates. FeAV drinking Avaters, hoAvever, come up to this standard : a more practical statement of a permissible limit Avould be that in cases Avhere the strata may be excluded as the source from which a Avater derives such salts, the nitrogen in nitrates and nitrites should not exceed 0*1 per 100,000. In other cases, the nitrogen from nitrates alone should not be in excess of 0*35 per 100,000, or the total combined nitrogen (including that in the free and albuminoid ammonias) should in no case exceed 0*4 per 100,000, or one- third of a grain per gallon. On these points it is extremely difficult to lay doAvn any hard and fast rules, as every individual sample of water needs to be judged upon its own analytical facts. The merest traces of nitrites is always suspicious, and in most cases should condemn the water; while the marked presence of nitrates ought to be ground for careful inquiry. In some soils, especially sands and gravels, and in ferruginous soils, the process of nitrification goes on extremely rapidly, and the existence of organic im- purity may escape notice if the examination for nitrates be omitted. 5. Oxygen absorbed.—This ought not to exceed 0*1 per 100,000 within fifteen minutes for organic matter alone, that is, after deducting any that may be absorbed by nitrous acid if present. This latter, hoAvever, should not be present in a Avater of the first class. Opinions differ as to the significance of the oxygen-consuming poAver of a water. Attempts have been made to fix limits for the various types of Avater, and also to gauge the character and condition of the organic matter by observing the rate at Avhich the oxidation takes place, but no positive conclusion can be given. In general, it may be said that a sample which has a high oxygen-consuming poAver will be more likely to be unAvholesome than one which is Ioav in this respect; but the interferences are so numerous, and the susceptibility to oxidation of different organic matters, even if of the same kind, is so different, that the method is, at best, only of accessory value. It is, hoAvever, the only one that is practicable for many medical officers, or gives us any measure of the oxidis- able organic matter in water, and is, in the present state of our knoAvledge, indispensable, imperfect though its indication may be. It is certainly an aid to our judgment of the condition of a drinking water, being to Frank- land's carbon process something the same as the albuminoid ammonia method is to his nitrogen one. Frankland has fully acknowledged this relation in his latest work, and has proposed a series of factors by which to multiply the oxygen absorbed, so as to express the result in terms of organic carbon. These factors are based on the observed relations betAveen the two processes in a very large number of experiments, and are formed by dividing the average carbon by the average oxygen. The factors differ for different kinds of water in the following proportions :— River water, ^ = 2*38 Deep-Avell water, ,, = 5*80 Shallow-well water, ,, = 2-28 Upland surface Avater, ,, = 1'80 so that 1 centigramme of oxygen absorbed indicates a probable amount of only 1*8 of organic carbon in an upland surface Avater, but as much as 5*8 in a deep-Avell Avater. A mean of many comparative analyses indicates that 3*35 parts of oxygen absorbed per 100,000 is the equivalent of 1 part per 100,000 of organic carbon by Frankland's process. Xo process gives us thoroughly trustAvorthy information, but for the army or navy medical officer, or any one not provided Avith a Avell-appointed EXAMINATION OF SEDIMENTARY MATTER. 89 laboratory, the permanganate process, combined Avith the albuminoid ammonia process, gives as much information as is likely to be obtained at present, and sufficient for hygienic purposes. It must be remembered that the permanganate does not act upon fatty substances, starch, urea, hippuric acid, creatin, sugar, or gelatin. 6. Hardness.—The fixed hardness should not exceed 3° of the metrical scale. The total hardness may vary more, but if possible should not exceed 7° to 8°"5 (metrical). 7. Phosphates.—The presence of these in any marked quantity will generally corroborate inferences as regards seAvage contamination drawn from the other indications. Sulphates.—An excess of sulphates Avill in many cases also indicate oontamination, though they may, like chlorine, come from innocuous sources. 8. Metals.—Pure water should contain no heavy metal, although a trace of iron may be found sometimes. In some cases iron seems beneficial, as it helps to oxidise the organic matter. The presence of any other heavy metal ought to condemn the Avater. 9. The presence of hydrogen sulphide or alkaline sulphides ought to condemn the water. It is always advisable to get information if possible as to the usual com- position of a water to be examined, as even slight variations may suggest a •clue to the nature or cause of an impurity. The microscopic examination of the sediment ought ahvays to be performed where possible, as it often affords important information Avhen the chemical investigation fails. Thus, the presence of such objects as muscular fibre, wheaten starch cells, spiral vegetable fibres, mucous epithelium, disintegrating masses of paper, &c, are sufficient alone to condemn water (especially if it be from a shalloAV Avell), -even when the chemical constituents are within limits, as they are undoubted evidences of animal contamination, almost certainly seAvage. In such cases the nitric acid is nearly ahvays large in amount. Subjoined, on pp. 114-117, are analyses of typical Avaters divided into four -classes,—1. Pure and wholesome; 2. Usable ; 3. Suspicious ; and 4. Impure These are merely suggested as general guides, some latitude being necessary according to circumstances. Microscopic Examination of Suspended and Sedimentary Matter.— The suspended matters may be either mineral (sand, clay, chalk, fine films of mica, iron peroxide), or dead animal or vegetable matters, or living •creatures (plants and animals). To determine the nature of the suspended matters pour some of the water into a long glass as already described, and observe its appearance. Suspended sand or clay give a yellow or yelloAv-Avhite turbidity; vegetable humus and peat give a darkish, sewage gives a light broAvn colour; but the colour or turbidity alone is a very insufficient test. Then boil the Avater, and pour it back into the long glass. Sand, chalk, and heavy particles of the kind will be deposited; finely suspended sewage and vegetable matter is little affected, unless it be a chalk-water, Avhen the deposit of calcium carbonate may carry down the suspended matter. If the matter is entirely suspended, a drop of the water must be taken at once; but Avhen it can be obtained, a little of the sediment is more satis- factory. To get a sediment, the Avater should be placed in a conical glass •{the space of which ought to be rounded, not pointed, at the bottom), ■carefully covered and alloAved to stand for a feAV hours; the upper part ■of the Avater is then poured aAvay or siphoned off. The best kind of pipette 90 WATER. for taking up the sediment for transfer to the glass slide is a plain straight tube, without bulb and Avithout any narroAving to a point at either end ; the diameter may be from -^ to i of an inch (1*5 to 3 millimetres). An immense number of dead and hving things are often found in Avater, Avhich it would be impossible to enumerate, but Avhich may be conveniently con- sidered under the following heads :— (a) Mineral particles may be easily knoAvn; sand appears as large angular particles, often shoAving distinct conchoidal fracture; clay and marl as round smooth globules unaffected by acids ; carbonate of calcium (chalk) sometimes smooth, but often crystalline, soluble in acids with effervescence. Iron peroxide appears in reddish-broAvn masses of an amorphous character; it is easily dissolved in hydrochloric acid, and strikes a deep blue Avith the ferrocyanide of potassium (yelloAv prussiate). (b) Vegetable matters: portions of wood, leaves, bits of the veins,. parenchyma, or ducts are easily recognised. When vegetable tissue is more decomposed nothing is seen but a dark, opaque, structureless mass. Any dark formless mass of this kind in water is almost certainly decayed vegetable matter. Bits of textile fabrics, cotton, linen, are not uncommon, and are important as indicating that the water is contaminated Avith house refuse. So also the cells of the potato, or spiral threads of cabbage and other vegetables used by man, are of value as indications of the same kind. Spiral cells are very indestructible, and are often found in river-water to Avhich seAvage gains access. Carbonaceous masses also occur, either portions of soot from coal smoke, or bits of charred wood. Sometimes fragments of paper are met Avith, probably Avashed into the Avater from drains or cesspools. (c) Animal matters, consisting of bits of avooI, hair, and remains of animals of all kinds, such as Avings and legs of insects, spiders and their Avebs, portions of the skin of Avater animals, or of fish, &c, are not uncommon. SeAvage matters having a darkish-broAvn or reddish colour, and often in globular masses, and thus distinguishable from the flatter and more spread-out vegetable matter, are sometimes seen. Epithelium (from the skin of man) and hairs of animals are not unfrequent. The identifica- tion of these matters is of moment, as indicating the particular source of the contamination. Anything Avhich can be unequivocally traced to the habitations of man must ahvays cause the Avater to be regarded with suspicion, as, if one substance from a house can find its Avay in, others may do so too. (d) Bacteria or Schizomycetes.—These organisms or their spores are almost invariably present in water, sometimes in very great numbers. The consideration of their significance and the methods for their detection by cultivation will be discussed in the section upon the Bacteriological. Examination of Water. High powers (and preferably Avith immersion lenses) are required to see them properly. (e) Fungi.—Small and microscopic fungi are constantly present in Avater. They may be observed as spores, sporangia, or as mycelium. Both Aspergillus- niger and sarcina ventriculi present familiar instances of these forms. Fungi rapidly develop in any water containing nitrogenous, saccharine, and phosphatic matter; their spores being readily derived from the air. If fungi are present in any great number in a Avater sample, it is strong pre- sumptive evidence of impurity, and such Avater should not be used if it can be avoided, or certainly not until after filtration. The belief still prevails in some quarters that seAvage matter in Avater gives rise, Avhen sugar is added to the medium, to a special fungus, termed MICROSCOPIC EXAMINATION OF WATER. 91 Beggiotoa alba, formed of very small, spherical, transparent cells arranged in grape-like bundles and characterised by the presence of grains of sulphur in their substance. This organism is found in marsh Avater and in sulphur springs; it groAvs freely in Avater containing sewage, and also in the effluents from certain manufactories, especially sugar factories, tanyards, and in Avater rich in sulphates. It is, therefore, not characteristic of sewage, but merely indicates the presence of a considerable amount of decomposing organic matter in the Avater. (/) Algce, Diatoms, and Desmids are found in almost all running streams, and are also seen in many Avell Avaters. They cannot be held to indicate any great impurity; and to condemn Avater on account of their presence Avould be really to condemn all Avaters, even rain, in Avhich minute algoid A'esicles (protococci) are often found. The forms of the various conferva' in Avater are very numerous, some being coloured green, whilst at other times they are quite colourless, round, isolated, or clustered vesicles. The immature forms may not be easy of identification. The Diatoms are ahvays readily recognised and identified. It may be stated generally that organisms of a grass-green, such as the green algai, need not be objected to; but the bluish-green, such as the Oscilla- torians, Nostoc, &c, are less desirable; not that they are probably directly injurious, but as indicating an impure Avater, and as being apt to give rise ta an unpleasant ( " pig-pen " ) odour. Leptothrix ochrwa, which Avas at one time thought to be connected Avith a special disease poison, is really harmless, and is mostly found in Avaters containing a good deal of iron peroxide; such Avaters are usually singularly free from noxious organic matter. (g) Rhizopoda, especially amosbce and similar forms, may often be detected with high poAvers. They appear to indicate, like bacteria, the existence of putrefying substances, but this is not yet certain. They are not found in first-class waters. (h) Euglenai (of different species, such as E. viridis, E. piyrum, &c.) are found in many waters, especially of ponds and tanks. Ciliated, free, and rapidly moving infusoria, belonging to several kinds of common protozoa, such as kolpoda, paramecium, coleps, stentor, kerona, stylonychia, oxytricha,. &c, are also found. In many Avaters the living objects in the above five classes comprise all that are likely to be seen, but in the other cases there are animals of a larger kind. (i) Hydrozoa, especially the fresh-Avater polyps, are common in most still Avaters, and do not indicate anything hurtful. (k) Worms, or their eggs and embryos, belonging to the class Scolecida, may occur in water, and are of great importance. The eggs and joints of the tapeworm, the embryos of Bothriocephali, the eggs of the round and thread Avorms, and perhaps the worms themselves, the Guinea-Avorm, and other kinds of Filaria; the eggs of Dochmius duodenalis, and other distomata, and the embryos of Bilharzia, have all been recognised in Avater, though it has not yet been shown that in all cases they can be thus introduced into the human body. That Filaria sanguinis hominis may be taken in drinking Avater is more probable, seeing that its host, the mosquito, is developed in Avater, the larvae of the latter being found in great quantity in tanks and cisterns. Worms themselves cannot Avell be overlooked, but both eggs. and the free-moving embryos are sometimes difficult of identification. The greatest care should be used in examining Avater to detect ova. The presence of even common Anguillulce in water sIioavs generally 92 WATER. an amount of impurity, and such a Avater must be regarded Avith great suspicion. Small leeches also are not uncommon in both still and running Avaters. The wheel animalcules are common enough, and cannot be regarded as very important, though certainly Avhen they exist there must be a good deal of food for them, and consequently impurity of water. (?) Entomostraca such as the Avater flea, Daphnia pulex (fig. 5); Cyclops quadricornis (fig. 6) ; Sida, Moina, Polyphemus, and others are very common in the spring; they occur in so many good Avaters that they cannot be considered as indicating any dangerous impurity. It is said that they are only found near (Avithin one or two feet) the surface. Amphipoda (Gammarus pulex) may also be met Avith, as Avell as Isopoda (Asellus aquaticus) and Tardigrada (Avater bears), especially if Avater that has been stagnant gets Avashed into tanks, cisterns, or Avater-butts. (m) There are, of course, many other tolerably large animals often found in Avater; the larvae of the Avater beetle (Dytiscus), the Avater boatman or Fig. 6. skipjack (Notonecta glauca), and the pupa form of many insects, may be found, but they are chiefly in pond Avater. So many are the objects in water that the observer will be often very much at a loss, first, to identify them, and secondly, to knoAv Avhat their presence implies. The best Avay is first to see Avhat objects appear to be mineral, or non-living vegetable substances, and to fix the origin and estimate the quantity as far as it can be done. Then to turn to the living organisms and to look attentively for bacteria, amcebai, fungi, and ova, and small worms and leeches. If none of these exist, and if cultivations show the Avater to be fairly free from micro-organisms, the water cannot be considered dangerous. Ciliated infusoria of various kinds, and Diatoms, Desmids, and Algce, are chiefly important in connection with microscopic evidence of decaying vegetable matters, and Avith chemical tests shoAving much dissolved organic impurity in the Avater. BACTERIOLOGICAL EXAMIXATIOX OF WATER. It is only Avithin recent years that the presence of micro-organisms in water has been recognised, and attempts have been made to study their Fig. 5. BACTERIOLOGICAL EXAMINATION OF AA'ATER. 93 nature and significance. Miquel in Paris, Koch in Berlin, and Angus Smith in this country, Avere the earliest investigators in this line of research, but it is to Koch's method of plate cultivations in nutrient gelatin that Ave are chiefly indebted for the results that have been hitherto attained. By this method a small quantity of water is intimately mixed Avith fluid gelatin, Avhich is spread in a thin layer upon a glass plate and allowed to sohdify ; the germs or micro-organisms thus become fixed, and proceed to groAv or form " colonies," each germ groAving separately in the gelatin Avherever it may have lodged, and not interfering Avith the development of other germs. It is obvious that only such organisms as find this particular nutrient medium favourable to their groAvth Avill form colonies on the plates : there may be many other kinds Avhose presence is not revealed by this method of cultiva- tion : the gelatin process, hoAvever, is the one that has been usually employed, and it is at any rate of value in instituting a comparison between the organisms present in different waters, even if it does not shoAV the total amount of microbic life present in any of them. Moulds, yeasts and Schizomycetes or Bacteria are all found to be present in Avaters, but the significance, both pathological and hygienic, of the two former groups is of far less importance than that of the latter. The tAvo points that require attention are, first, to ascertain the number of micro-organisms present; and, secondly, to determine their nature, i.e., to differentiate between the several varieties that may be present, and especially to ascertain which are hurtful and which are harmless, when sAvalloAved in drinking Avater. As the whole success of any bacteriological observation depends primarily upon the absolute sterilisation of both apparatus and materials, and upon the proper preparation of culture media, it is necessary in the first instance to make some reference to both these points. Sterilisation of Apparatus, &c.—Small articles of glass and metallic articles can be sterilised by direct ignition in the flame of a Bunsen burner. A red heat is not necessary. If time is no object, both glass and metallic- objects may be sterilised by exposure to hot air in a hot-air sterilising oven. Glass vessels should be exposed to a temperature of 150° C. for tAvo or three hours; but it is important to remember that the temperature in these ovens: is by no means uniform, and care must be taken to see that the objects are so placed as to be really exposed to the desired temperature. Dry heat is inapplicable when articles of caoutchouc are to be sterilised : for them and other articles Avhich cannot be exposed without injury to hot air, sterilisation is readily effected by exposure to steam or moist heat by means of a " steam steriliser." By this apparatus, a uniform temperature of 100° C. is obtained, and for the sterilising of glass and other vessels an exposure of from one to tAvo hours is necessary. For culture media, such as potatoes and gelatin, which would suffer by prolonged exposure to sa high a temperature, the practice of intermittent sterilisation may be resorted to. This method involves the repeated submission of the substances to a high temperature for a short time only, at intervals of twenty-four hours. For such articles as will stand it, sterilisation may be also effected by simply boiling. In the case of a culture medium, like milk, it may be necessary to effect sterilisation beloAv 75° C, that is, beloAv the temperature of coagulation of albumin; in which case intermittent sterilisation at 60° C. is employed for one or two hours on five to eight days. Gases and some liquids are conveniently sterilised at times by means of filtration. This. principle is largely employed in the preservation of culture media in flasks, test-tubes, &c, from aerial micro-organisms by closing their mouths Avith "94 WATER. sterilised cotton-Avool stoppers. The sterilisation of liquids by filtration is best secured by passing them through either the Pasteur-Chamberland filter of unglazed porcelain, or the Berkefeld filter of infusorial earth. The application of chemical agents as a means of sterilisation, except under most unusual circumstances, is not suited to the ordinary routine of bacteriological investigations. Culture Media.—The more micro-organisms are studied, the more apparent does it become that the greatest diversity prevails in their taste for food, and that media, which are suitable for the growth of some forms, are quite unfitted for the cultivation of others. These facts have caused a ■considerable variety of materials to be proposed from time to time, as culture media for bacteria : the more important of them are the following :— Gelatin-peptone is, in many respects, the most important of all the •culture media : it may be best prepared in the folloAving manner :—A pound of beef, as free from fat as possible, is finely minced, and infused Avith one litre of cold water, and alloAved to stand for tAventy-four hours in a cold place or ice box : the Avhole mass is then strained through linen, and its original bulk made up with distilled water. To this clear filtrate is now added 100 grammes of gelatin, 10 grammes of dry peptone, and 5 grammes of common salt, after which the whole is placed in a steam steriliser for about an hour, until the complete solution of the gelatin and peptone has taken place. The resulting liquid will be found to have an acid reaction: this must now be carefully neutralised and rendered faintly alkaline Avith a solution of sodic carbonate. This alkaline liquid is now clarified by mixing Avith it the Avliite of three eggs, the whole being again placed in the steamer for half an hour. OAving to the coagulation of the albumin this rises to the surface, carrying with it any solid suspended particles. The whole is now strained again through linen until a clear and limpid liquid is obtained. Whilst still liquid, the filtrate is poured into test-tubes which have been previously sterilised and plugged with sterile cotton-wool. The most con- venient quantity to take for each tube is 10 c.c. On cooling, this gelatine peptone sets to a straAV-coloured transparent jelly. After the tubes are filled, and the cotton-wool stoppers replaced, they are at once steamed for ten to fifteen minutes, Avhich is repeated on the next tAvo days. Gelatin tubes thus prepared should be kept stored in the dark, Avith their avooI stoppers covered by an india-rubber cap to prevent evaporation and con- centration. Glycerin-gelatin-peptone.—By adding from 5 to 8 per cent, of glycerin to ordinary gelatin-peptone, before the jelly is finally sterilised, a most useful culture medium is obtained. Its chief advantage is that it keeps moist much longer than the ordinary gelatin-peptone, whilst most organisms thrive especially well upon it, this being particularly the case Avith the bacillus of tuberculosis. Agar-agar.—This is made in a similar way to the ordinary gelatin-peptone, the chief difference being that 20 grammes of agar-agar are used in the place of the 100 grammes of gelatin. When in a fluid condition agar looks transparent and of a rather dark yellow-brown colour, but when it solidifies it loses its complete transparency. Having a much higher melting point (90° C.) than gelatin (22° C), agar is very useful for cultivations which need to be kept at a high temperature; but owing to the separation of Avater on sohdification, it does not lend itself so satisfactorily to plate cultivations. After sterilising, it is often advantageous to allow the tubes to cool in an oblique position, as in this way a larger surface is obtained and PREPARATION OF CULTURE MEDIA. 95 the liquid Avhich separates out collects at the bottom of the tube. Glycerin- •agar is made by the addition of from 5 to 8 per cent, of glycerin after the filtration of the jelly. Potatoes.—The common potato is one of the most convenient culture media, not only because the majority of micro-organisms grow well upon it, "but also because its preparation is simple. After having been carefully washed and scrubbed with a nail brush the potato is peeled and cut into slices. These are transferred to sterilised shalloAV glass dishes, having overlapping glass covers : the dishes and their contained slices of potato are immediately placed in the steam steriliser, and alloAved to remain there for an hour or more; if necessary, they may be again sterilised on the following day. Potato-gelatin.—This was originally devised by Holz : it is prepared in the following manner:—After having been carefully washed and peeled, potatoes are then poAvdered by means of an ordinary grater. The gratings rare pressed through a clean cloth, the resulting juice being collected in a flask, which, on being plugged Avith cotton-wool, is alloAved to stand for twenty-four hours at 10° C. The liquid is next filtered, and the filtrate heated for half an hour in the steam steriliser, and again filtered. To 400 grammes of this now quite clear potato juice are added 40 grammes of igelatin, and the whole sterilised again for an hour, after Avhich it is filtered a,nd poured into test-tubes. When in the test-tubes, it is again sterilised for a quarter of an hour on three successive days. When finished, potato- gelatin is clear, transparent, and slightly broAvn in colour. In order to neutralise it, it is. necessary to add about 1*6 c.c. of deci-normal caustic potash to every 10 grammes. Beef Broth.—This is merely ordinary bouillon to Avhich an addition of 1 per cent, of peptone has been made. This peptone-broth is made in precisely the same manner as has been already explained for making .gelatin-peptone, the only difference being the omission of the gelatin. Milk often affords a good culture material, and may be prepared by simply placing some in sterile test-tubes, and steaming them in the steriliser at 100° C. for an hour on the first day, and for half an hour on the two folloAving days. This high temperature alters the chemical composition of milk; if this is undesirable, milk may be sterilised by heating it only to 60° C. for two hours on eight successive days. At this loAver temperature no •coagulation of the albumin takes place, and the milk, being rendered sterile, -can be preserved for some length of time. Although the foregoing do not constitute all the various culture media which have been proposed from time to time for micro-organisms, they practically meet the chief requirements of those making bacteriological examinations of water. Collection of Samples.—Few bacteriological examinations of water are of value unless promptly made upon samples which have been collected Avith precautions against contaminations. When possible, the inocula- tion of the culture medium is best done at the source : if this is not feasible, glass-stoppered bottles, holding about 200 c.c, which have been thoroughly sterilised with their stoppers, must be used for collection. These bottles should be rinsed on the outside Avith Avater, dipped below the surface, the stopper withdrawn, and again inserted when the bottle is full. If the samples are to be transported any distance, they should be packed in ice. So soon as received, the examination of the sample should be com- menced; while for delivering the measured volume of water a pipette sterilised in the hot air oven should be used. 96 AA'ATER. Culture Manipulations.—For the estimation and isolation of micro- organisms in Avater, Ave may employ conveniently either plate or roll cultures. Plate Cultures.—Having melted the gelatin in a tube by immersion in hot water, its cotton-avooI stopper is first singed in a Bunsen flame, and then carefully removed by gently twisting it out; the mouth of the tube is next quickly passed through the flame to destroy any organisms Avhich may be present upon it, and a measured quantity of Avater transferred from the sample to the test-tube by means of a sterilised graduated pipette. The water and gelatin are intimately mixed together by gently shaking or rolling the tube betAveen the fingers. The mixture is then quickly poured into a sterilised Petri dish to form a plate cultivation ; the gelatin becomes- solid in from 2 to 10 minutes, according to the temperature. The dish, Avith its cover, is then placed in an incubator at 18°-22° C, and the medium being spread out in a thin layer over the glass, its appearance can be readily noticed, and groAvths upon it examined. The actual quantity of the Avater to be added to each plate culture will necessardy vary Avith the quality of the sample; speaking generally, 0"5 c.c. is a suitable amount, but as little as 0*1 c.c. or even less may be required in some cases, Avhile in others 1 c.c. may not be too much. Roll Cultures.—Instead of pouring the nutrient medium, after seeding Avith the water sample, into a Petri dish, the cotton-wool plug may be replaced, and an india-rubber cap drawn over it. The tube is carefully rotated in a horizontal position in iced or cold water, so as to bring about the sohdification of the culture medium in an even layer over the inner surface of the tube. On keeping the tube at 18°-22° C. the colonies develop in the same manner as in the case of an ordinary plate. The method is open to the objection that when liquefying bacteria are present, as will generally be the case, the fluid will run doAvn and inoculate other portions of the layer. So soon as the colonies have sufficiently developed in either the plate or roll cultures, they must be carefully scrutinised under a low power of the microscope to ascertain Avhat characteristic appearances they present. Each colony, if it has had space to develop freely, is usually a pure culture; so that by removing a portion of any particular one by means of a sterile platinum needle to a test-tube containing some culture medium, the growth may be perpetuated in a state of purity. This " fishing out" of the colonies is comparatively easy when there are only a feAV on the plate, but somewhat difficult in crowded fields. Anaerobic Cultures.—Some micro-organisms, like the bacilli of malignant oedema and tetanus, are unable to groAv in the presence of free oxygen. To overcome this difficulty, special contrivances have to be employed for their cultivation and study. A very convenient method is the folloAving:— Take a large tube, charged Avith about 20 c.c. of gelatin-peptone or other medium, and seed with the infective medium in the usual way. The cotton- wool plug is removed, and immediately replaced by an india-rubber stopper, in which are two perforations fitted with glass tubes, one of these just opens into the test-tube while the other reaches nearly to the bottom. The stopper and tubes have been, of course, previously sterihsed. The longer glass tube is connected with a generator of hydrogen gas, and a fairly rapid current of hydrogen is then bubbled through the gelatin, which is kept fluid by immersing the containing tube in a beaker of hot water at 30° C. The hydrogen escapes through the shorter glass tube; when the gas has NUMERICAL DETERMINATION OF MICRO-ORGANISMS. 97 been passing for fifteen minutes or so, it is stopped, and the two glass tubes rapidly sealed Avith a bloAv-pipe. The rubber stopper is next thickly coated Avith melted paraffin, and the tube, if containing gelatin, is rotated horizon- tally in cold Avater until the culture medium congeals as a uniform film over the inside of the tube as in an ordinary roll culture. After incubation, the colonies of those organisms Avhich are capable of groAving in the absence of oxygen will appear. Numerical Determination of Micro-organisms in Water.—The counting of the number of organisms Avhich a given volume of water contains is most readily made by means of gelatin plate cultures. The frequency of liquefying micro-organisms in water renders roll cultures much less service- able. In all cases, at least, tAvo plate or Petri dish cultures must be set from each Avater sample. Supposing the Avater is fairly free from microbes, 1 c.c. may be taken for one plate, and 0*5 c.c. for the other; but, if the Avater is suspected of containing large numbers of bacteria, then it Avill be necessary to ddute, say, 1 c.c. of it 10, 20, 100, or even 500 times before seeding the plates. For dilution, sterilised natural water (not distilled water) is best employed. The plates are seeded and incubated in the usual manner, Fig. 7. while the counting of the resulting colonies is most conveniently made by an apparatus such as Wolffhiigel's (fig. 7). This consists of a special glass plate capable of being used upon a stand. The glass plate, ruled by horizontal and vertical lines into centimetre squares, some of which again are subdivided into ninths, is so arranged on a wooden frame that it can cover the nutrient plate without touching it. A lens may be used to assist in discovering minute colonies. If the colonies are very numerous, the number in some small divisions is counted, and then multiplying the average number on these squares or divisions by the total number of squares over which the plate extends, a fairly accurate estimate may be made of their numbers. The number of colonies found is then calculated on 1 c.c. of the original Avater, and, on the assumption that each colony springs, in the first instance, from a single microbe, the total result is expressed as so many micro-organisms in each c.c. of the water. The number of micro-organisms found in different water samples varies very much, not only according to their degrees of purity, but also according to season and length of time they have been kept before examination. The following Table, constructed from Frankland's and Miquel's results, shows the varying numbers of micro-organisms found in each c.c. of water from the Thames, Lea, and Seine; the collection of samples having been made at Hampton, Chingford, and Ivry respectively. G WATER. Thames. Lea. Seine. January,.....92,000 31,000 52,670 February, 40,000 26,000 43,120 March, . 66,000 63,000 34,710 April, 13,000 84,000 38,640 May, 1,900 1,124 12,930 June, 3,500 7,000 28,150 July, 1,070 2,190 14,130 August, . 3,000 2,000 6,780 September, 1,740 1,670 20,220 October, . 1,130 2,310 22,350 November, 11,700 57,500 37,720 December, 10,600 4,400 78,950 From this Table it will be seen that, as regards micro-organisms, these Avaters are purer in the summer months : this is probably due to the fact that during dry weather these rivers are mainly composed of spring-water, Avhile at other times they receive considerable washings from cultivated land. All rivers which flow through or near towns and inhabited areas invariably become bacterially impure, but frequently undergo marked purification through sedimentation and dilution as they flow along their course, provided they receive no further considerable intakes of surface and other drainage. It is exceedingly difficult to obtain precise facts concerning the number of micro-organisms present normally in different Avells. The principal source of error is due to the samples having been collected regardless of Avhether pumping had been going on or not. In a deep Avell at Xetley, Avhich had not been used for twenty-four hours, 109 micro-organisms were found per c.c.; after continuous pumping had been going on for two hours, the numbers had risen to 782, but subsequently, after six hours' continuous pumping, there Avere only 81 per c.c. It is probable that, in most wells, an enormous increase in the number of microbes in the water folloAvs any disturbance of the sediment or washing and splashing of the sides of the Avell; so that, if any accurate idea is required of the actual bacterial condition of the Avater entering or supplying a Avell, this will only be obtain- able after pumping has been going on continuously for some time. As a rule, deep wells possess a high degree of bacterial purity. Frankland's observations upon the deep-Avell Avater obtained from the chalk by the Kent Water Company for the supply of London clearly indicate this. He, however, offers the following instructive example of how rapidly the micro-organisms in deep-well water can multiply on standing. Number of Micro-organisms obtained from 1 c.c. of water. Date of Collection, April 15, 1886, April 17, 1886, April 14, 1886. after standing 1 day after standing 3 days at 20" C at 20° C Kent well sunk into chalk, . , 7 21 495 000 Spring-water which is properly protected from accidental fouling is commonly very^ free from micro-organisms. Lake-water is naturally °less so. But, even in lakes, the bacterial condition of the water may vary in different parts, being much more impure when taken from near the shore. As to sea-Avater, our knowledge is small, but the researches of Russell indicate that the distribution of bacteria in the sea is much greater in shallow waters and near the shore than out in the open ocean. MULTIPLICATION OF BACTERIA IN AVATER. 99 It is difficult to lay doAvn any standard of bacterial purity for drinkino Avater, in terms of permissible numbers, as the poAver of micro-organisms for good or evil depends not so much upon their actual quantity as upon their quality; that is, whether they are non-pathogenic or pathogenic. For general purposes, a good rule is, to regard no Avater as being a pure and wholesome one Avhich contains more than 100 micro-organisms in each c.c. when examined at once after collection. The existence of from 100 to 500 microbes per c.c. is suggestive of suspicion, while, as a rule, anything above this latter figure usually points to definite pollution. Care, hoAvever, must be taken that the application of these arbitrary standards is only made Avhen bacteriological examinations are made promptly, as any delay soon results in such an enormous increase in the number of micro- organisms in the sample that any opinion based upon their enumeration alone would be highly fallacious. In cases Avhere a delay between the •collection and examination of the sample is unavoidable, careful packing in ice is the only practicable remedy. Xo Avater sample Avhich has been -efficiently filtered should contain any micro-organisms; this point has, hoAvever, been dAvelt upon elsewhere. As to the multiplication of micro-organisms in water, on standing, some curious results have been obtained, chiefly by Frankland, Miquel, and Meade Bolton. Summarised, their observations indicate that bacterial multiplica- tion takes place more abundantly in pure, or in Avaters containing a small snumber of microbes originally, than in Avaters AAdiich are impure or contain a large initial number. Miquel observes, " that a rapid but transitory poAver of multiplication characterises the bacteria in pure spring-waters, whilst in impure waters, or in waters rich in microbes, the multiplication is sloio and persistent." He explains this phenomenon by the hypothesis that a parti- cular water acquires an immunity towards further attacks from its contained i bacteria. This immunity is due to the generation by the bacteria of soluble j and toxic products which inhibit their further groAvth and multiplication. ' These toxic products are destroyed on boiling, as a water which will not ; support further bacterial increase before boiling acquires it after boiling. ■ Pure spring-Avaters appear to be Avithout these bacterially generated products, hence the rapid and extensive increase of the few micro-organisms Avhich they originally contain. Vitality and Detection of Pathogenic Bacteria in Water.—Of far greater importance than counting the number of bacteria in a sample of drinking water is the determination of their nature and species. This is always a matter of some difficulty, and involves the expenditure of much time and labour in examining plate cultures, the making of innumerable cover-glass preparations, and the observation of the behaviour and growth >of individual species upon different culture media. The first step is to distinguish those organisms that exist naturally in the Avater, and are harmless, from those that are known to be pathogenic or dis- ease-producing, none of which (so far as our present knowledge goes) are known to be normal constituents of water. The indifferent or non-pathogenic organisms that have been found include •.some hundred species that have been described, besides very many other undetermined varieties, the characters of which are not sufficiently knoAvn . to Avarrant their description as distinct species. The pathogenic bacteria that have hitherto chiefly attracted attention as being found to occur in drinking water are: Bacillus typhi abdominalis, Koch's comma bacillus of cholera and bacillus anthracis. The typhoid bacillus has been found by several observers in connection Avith epidemics of enteric 100 WATER. fever: it has also, on the other hand, escaped the most careful search in some cases Avhere circumstances pointed to the Avater as the cause of the epidemic. Koch obtained cultivations of the cholera bacillus from tank Avater at Calcutta, and since then other observers have demonstrated its presence in other Avaters. These and other pathogenic bacteria have been introduced experimentally into samples of Avater of different kinds, and careful investigations carried out, as to whether or no such pathogenic organisms are capable of continuing. in an active state or propagating themselves under different circumstances.. Our most recent knowledge upon these points is available from Frankland and Marshall Ward's Third Report to the Royal Society Water Research Committee; their observations having been chiefly made upon the enteric fever bacillus and the B. coli communis. Their conclusions may be sum- marised as folloAvs :— 1. Typhoid bacilli, from ordinary cultures, on being introduced into steam' sterilised potable water, in such numbers as not to materially alter the composition of the latter, undergo no multiplication. This result is obtained, whether the Avater be a surface Avater like that of the Thames, an upland surface Avater like that from Loch Katrine, or a deep-well Avater. 2. Typhoid bacilli Avhich have undergone a prolonged and gradual training in more and more aqueous culture media appear to possess more vitality in potable waters than do bacilli Avhich are at once transferred into Avater from highly nutritive media. Further, any slight but distinct poAver of multiplica- tion which these trained bacilli appear to possess in potable Avater is probably effected at the expense of small quantities of food material introduced along Avith them at the time of infection, and not at the expense of the organic matter belonging to the Avater itself. 3. Although no instance of multiplication of the introduced enteric bacilli in sterilised Avaters was observed, on the other hand the bacilli were found to be possessed of very considerable longevity. This longevity Avas greatest in the Loch Katrine water (51 days), and least in the deep-well' Avater (20 to 32 days), and intermediate between the tAvo in Thames Avater. Of these three Avaters, the Loch Katrine contains the most, the deep-Avelli the least, and the Thames an intermediate amount of organic matter. A summer temperature of 19° C. (66°*2 F.) appears more prejudicial than a Avinter temperature of 8° C. (46° *4 F.). ^ 4. Enteric bacilli, from ordinary cidtures, on being introduced into similar but unsterilised potable waters as above, had the least longevity in Thames water (9 to 13 days), longest in deep-Avell water (33 to 39 days), and intermediate in the Loch Katrine water (19 to 33 days). This result is of very great practical importance as indicating the greater danger from enteric bacilli gaining access to deep wells than to surface waters. In actual daily life, this danger is increased by the fact that well-Avater is almost invariably consumed without storage, whilst surface waters are often stored for Aveeks, and in the case of upland surface waters, the storage not unfrequently extends over many months. The effect of temperature was the same in the case of unsterilised as sterilised waters. 5. The greater bactericidal poAver of unsterilised water is not apparently due to any remarkable multiplication of the Avater bacteria, or accentuated " struggle for existence " between the aquatic forms and the specific bacilli but rather to the elaboration of products by the aquatic bacteria Avhich are prejudicial to the enteric bacilli. This being the case, it may be that unsterile deep-Avell water does not contain those water bacteria Avhich are particularly fitted for successfully competing Avith the enteric bacilli, and that such Avater bacteria are only to be found in the unsterile surface waters. VITALITY OF PATHOGENIC MICRO-ORGANISMS IN WATER. 101 6. Unsterile Thames water appears to be peculiarly and thoroughly saturated with those bacterial products which- are prejudicial to the vitality of the enteric bacillus. 7. The addition of common salt to unsterile Thames Avater, in the pro- portion of from 0*1 to 3 per cent., causes an enormous multiplication of the water bacteria present, with a corresponding shortening of life of the enteric hacilli in this Avater. 8. When the B. coli communis, taken from ordinary cultures, is intro- duced into sterilised Avaters, it undergoes considerable multiplication; when under similar conditions the enteric fever bacillus does not multiply. The duration of hfe of the B. coli communis in steam sterilised Thames Avater extended over 75 days: in Loch Katrine Avater from 14 to 17 days: in very peaty water some 24 days. 9. In unsterile water, the B. coli communis persists in the living state for much longer periods than the enteric bacillus. In Thames Avater, its longevity was upAvards of 40 days, and in Loch Katrine Avater over 20 days. 10. In all waters, except Loch Katrine water, which had been sterilised by filtration through Pasteur-Chamberland or Berkefeld filters, a most remark- ably rapid disappearance of both enteric and common colon bacilli is observed. In connection with the question of the vitality of various pathogenic micro-organisms in Avater, the following table is not Avithout interest. In it are given the maximum periods at AAdiich any observer has been able to detect a particular bacterium after seeding Avater samples with it. The name of the observer is given in brackets ; while the average temperature at which the samples were kept may be taken to be 20° C. (68° F.). Unsterilised Sterilised t> Ordinary Drinking Ordinary Drinking Foul AVater. Distilled AVater. Mineral AA'ater. AVater. AVater. B. typhi abdominalis, . . 2 weeks 4 months 40 days 6 months 11 days (Uffelmann). (rfeiffer). (Bolton). (Braem). (Slater). Spirillum Choleras Asiatics, 30 days 7 months 11 months 20 days 9 hours (Koch). (Wolffhugel). (Frankland). (Nicati). (Slater). B. Anthracis (sporiferous), 7 months 7 months 2 months 60 days 5 months (Frankland) (Frankland). (Frankland). (Frankland). (Hochstetter). 95 days (Straus). 115 days (Straus). Staph, pyogenes aureus, . 20 days 10 months 50 days 11 days (Bolton). (Bolton). (Braem). (Slater). 15 days (Straus). 10 days (Straus). Strep, erysipelatis, .... 5 days 5 days 1 hour (Frankland). (Frankland). (Frankland). 19 days 6 days 19 days (Straus). (Bolton). (Straus). 20 days (Straus). 19 days (Straus). 2 days (Hochstetter). 1 day (Hochstetter). B. cholera? gallinarum, . 30 days (Straus). 8 days (Straus). B. of swine plague, . . . 17 days (Straus). 34 days (Straus). 50 days (Straus). 57 days (Straus). 7 days (Straus). 8 days (Straus). B. Finkler-Prior, .... 2 days 2 days 2 days 3 hours (Hochstetter). (Frankland). (Slater). (Slater). 73 days 18 days 73 days (Straus). (Frankland). (Straus). B. Tetani,....... 70 days 50 days 50 days 136 days (Schwarz). (Schwarz). (Schwarz). (Schwarz). Aspergillus flavescens, . . 56 days (Hochstetter). 56 days (Hochstetter). 102 WATER. Although a vast number of bacteria possessing pathogenic properties have been from time to time detected in natural Avaters, still, the propagation of the greater number of them is not commonly associated with water. Practically, the only human diseases of the zymotic class Avliich are believed to be commonly propagated by water are enteric fever and 1 Asiatic cholera, and the detection of their specific micro-organisms consti- I tutes the main aim of the bacteriological examinations of drinking Avaters. In consequence, hoAvever, of the enormous preponderance of the common water bacteria, the ordinary process of gelatin plate cultivations will only, in exceptional cases, result in the detection of the pathogenic species; hence, if these latter are to be detected with any ease or certainty, special methods must be adopted in which their growth and multiplication is favoured and stimulated, whilst the proliferation of the other bacteria is either delayed or checked altogether. It is this principle which underlies all the various methods devised for the detection and isolation of the bacteria of enteric fever and cholera. It is not here intended to describe in detail all the various procedures AAdiich have, in recent years, been proposed for this purpose, but merely to explain those particular methods Avhich in our hands have given the best results. Detection of the Enteric Fever Bacillus in Water.—The first difficulty which arises in any attempt to detect the Eberth-Gaffky bacillus in water is the fact that nearly ahvays associated Avith it are other organisms which so closely resemble it that their differentiation is a matter of extreme difficulty. Prominent among such microbes is the B. coli communis, which, Avhile being a normal inhabitant of the human bowel, is frequently found in great numbers in polluted streams, or Avells into which drainage has penetrated. Although, hitherto, no method has- been devised Avhich -will definitely eliminate the B. coli communis, and only permit of the growth of the enteric fever bacillus in cultures from water, if it be present therein, the tAvo micro-organisms present sufficiently distinctive characters, when groAvn upon certain media, as to enable us to differentiate between theni. For the practical detection of the enteric fever baciUus in Avater, the following method, devised by Parietti, is perhaps the best. This method is based upon the idea that few organisms can flourish in an acid culture medium so well as the Eberth-Gaffky bacillus; but, as the B. coli communis is equally capable of groAving in an acid medium, it practically only sifts out, as it Avere, these tAvo particular microbes from among a large number of others, leaving their ultimate differentiation to further culture characteristics. A series of test-tubes, each containing 10 c.c. of neutral bouillon, receive respectively 3, 5, 6, 7, 8 and' 9 drops of the folloAving solution :—carbolic acid, 5 c.c; pure hydrochloric acid, 4 c.c.; distilled water, 100 c.c. These tubes are incubated for twenty-four hours at 37° C. in order to destroy any organisms Avhich may have gained access during the addition of the solution. To the sterile tubes from 1 to 10 drops of the\vater under examination are added, Avell mixed, and incubated at 37° C. for twenty-four hours. They ' are then examined, and, if any of them appear turbid, plate cultures are set from them, and the resulting colonies carefully examined. If very feAV enteric bacilh are present, the incubation of the acidified broth must usually be prolonged for forty-eight or even seventy-two hours. It is sometimes necessary to make a second or even third series of phenolised broth cultures from the first series, oAving to the resistance shoAvn to the phenol by certain other organisms, notably, B. subtilis, B. mesentericus vulgatm, and others. The former species is often very difficult to eliminate. DETECTION OF PATHOGENIC BACTERIA IN AArATER. 103 In attempting to differentiate betAveen the B. coli communis and the Eberth-Gaffky bacillus, and apart from microscopic distinctions, attention may be directed to the three folloAving reactions :— (a) Whilst in sterile milk the enteric fever bacillus renders the liquid slightly acid and never coagulates it, the B. coli communis, at 37° C, coagulates the milk in from twenty-four to forty-eight hours, and at the same time renders it strongly acid. (b) When inoculated in melted gelatin-peptone, then alloAving the latter to solidify, and maintaining at 20° C., the B. coli communis, after twenty-four or forty-eight hours, invariably produces gas bubbles, Avhile the enteric fever baciUus does not do so. (c) A further distinction is the so-called indol-reaclion. To 10 c.c. of ordinary alkaline peptone-broth culture, which has been growing twenty-four hours in the incubator, add 1 c.c. of a solution of sodium or potassium nitrite (0'02 gramme in 100 c.c), and then a few drops of pure sulphuric acid. If indol is present, a rose to deep red colour is produced, due to the formation of nitroso-indol nitrate. B. coli communis yields this reaction, Avliile a growth of the enteric fever bacillus does not. In place of adding the nitrite and sulphuric acid to the culture, it is often sufficient to add only a drop or tAvo of nitric acid, Avhich is rarely free from nitrite. To assist the diagnosis of the enteric bacillus in the presence of the B. coli communis, "formalin " may be added to sterile neutral brothin the propor- tion of 1 to 7000. Whereas the colon bacillus will render this formalin- broth turbid in from 8-24 hours, the enteric bacillus refuses to grow and the liquid remains clear. Besides Parietti's method, there are those of Uffelmann, Vincent, Thoinot, Holz, Chantemesse, and Widal. While the first-named uses citric acid, the others employ varying proportions of phenol to hold in abeyance the ordinary bacteria: they, however, all fail to keep back the B. coli communis; hence, on subsequent plate cultiva- tion, the colonies obtained may be either those of the colon bacillus or of the enteric fever bacillus, with possibly those of a feAv other hardy forms, such as B. subtilis or B. mesentericus vulgatus. Any colonies at all resembling those of the Eberth-Gaffky bacillus must then be further examined, (1) microscopically ; (2) on potatoes ; (3) in milk; (4) in melted gelatin-peptone for gas bubble test; (5) in broth for indol reaction, before a definite opinion can be given. It must be borne in mind that Eberth's bacillus, when grown in phenolised broth, loses much of its motility; it also tends to occur as a diplo-bacillus, extremely short, almost like cocci; but when transferred to simple broth it regains its proper characters. Another convenient method for the detection of the enteric bacillus in Avater is to pass 250 c.c. or more of the sample through a sterile porcelain filter, and then transfer the deposit from the surface of the cylinder by means of a sterile brush into a small quantity of sterile water; the latter, Avhich then contains the bacteria from the original volume of water, should be treated by phenol-broth culture, or one of the other methods of de- . tection. A scheme showing the chief culture phenomena of the B. coli communis and other organisms which closely resemble the enteric bacillus is given on pp. 105-110. Detection of the Spirillum of Asiatic Cholera in Water.—The same difficulties as are met Avith in the case of the enteric fever bacillus are prominent in attempts to isolate and detect Koch's comma bacillus of cholera in water samples. It is Avell known that AAraters of Arery diverse 104 WATER. origins frequently contain comma-shaped bacteria, Avhich, unless very carefully examined, may be readily confounded Avith the cholera bacillus. For the identification of cholera commas in Avater, Koch has suggested the following method:— Add 1 gramme of peptone and 1 gramme of common salt to 100 c.c. of the water under investigation : Avell mix and incubate at 37° C. After intervals of 10, 15, and 20 hours, agar plates are set from this peptonised Avater, coupled Avith a careful microscopic examination of the mixture. Any colonies which appear on the plates, and Avhich resemble those of the cholera spirillum, are microscopically examined, and, if comma forms are found, are further inoculated into fresh tubes for accurate recognition of their species. Sanarelli has suggested the following alternative procedure:—To every 100 c.c. of the Avater under investigation, add 2 grammes of gelatin, 1 gramme of dry peptone, 1 gramme of common salt, and 0*1 gramme of potassium nitrate. The mixture is best made in large flasks, in Avhich, after being incubated for twelve hours at 37° C, a thin pellicle forms on the surface, in Avhich, if spirillar forms are present, they are readily recognised by the microscope. For their subsequent isolation, a small piece of the pellicle is removed, mixed with sterile Avater, and a gelatin plate cultivation set from the dilution. ! For the differentiation of the cholera bacilli from allied forms, Koch recommends the observation of the indol reaction, and of positive pathogenic effects on guinea-pigs. The indol reaction has already been explained in connection Avith the identification of the enteric fever bacillus. In the case of ordinary cultures of the cholera bacilli, the addition of sulphuric acid, free from nitrous acid, is alone necessary, as the nitrite is already present, having been formed by the reduction of nitrate in the peptone. Care has to be taken that the cultures are pure. Besides the comma bacillus of Koch, another spirillum gives the indol reaction : it is the Vibrio Metschnikovi. ( This_ has not yet Jbeen.found injvyater, and is further distinguishable from Koch's vibrio by its poAverfully pathogenic effects upon pigeons and guinea- pigs. The confirmation of cholera bacilli by animal experiment is best effected by taking a full needle-loop of the surface growth on an agar culture, distri- buting this in 1 c.c. of sterile broth, and injecting the latter into the peritoneal cavity of a guinea-pig of average size. The injection is quickly folknved by a fall in temperature, resulting in death. Though Koch claims that the cholera commas are the only spirilla Avhich Avill produce these symptoms in minute doses, Sanarelli and other observers have demonstrated that many varieties may exist in Avater, morphologically distinct from the cholera vibrio, but equally capable of producing a disease in man and animals identical Avith cholera. The evidence brought forAvard is so strong that Ave are compeUed to believe that possibly cholera symptoms are produced by more than one variety of vibrio, and that Koch's earlier and more,exclusive statement does not meet all requirements of.the case. Details as^to the preparation of stains and the manipulative procedures connected Avith the staining and preparation of specimens of bacteria are given in Appendix N. at the end of the volume. In the folloAving pages is given a scheme showing the culture phenomena of the more important and commoner forms of micro-organisms found in Avater. Those Avhich are pathogenic to either man or animals are printed in italics. Culture Phenomena of some of the more important Micro-organisms found in Water. Species. B. Anthracis. B. Subtilis. B. Ramosus. B. Mycoides. B. Vermicularis. B. Tetani. B. Fluorescens tenuis. B. Fluorescens longus. B. Fluorescens non - lique- faciens. Microscopic Appearance. 1 to 1-5 /i broad and 3 to 10 fi long-, with S(iuare cut ends. Often in long threads. Spores formed in presence of oxygen. Resemble anthrax, but narrower and with rounded ends. Have ilagella. Forms spores. A'ery motile. Resembles B. subtilis, 7 ju long and 17 ix broad. Has rounded "ends. Forms spores and threads. Slightly motile. Forms long threads Individual bacilli, •! ix long and about 1 f* broad. Forms lustrous oval spores Motile. Large bacilli, with rounded ends, similar to B. subtilis. Not motile. Straight bacilli, with rounded ends. Occurs singly or in long- threads. Forms spores. Slightly motile, but the spore-bearing forms are motionless. Short thick bacilli, 0-8 ^ broad and V5 fj. long. Have rotatory move- ment. Straight and bent rods or wavy threads. Short bacilli are very motile. Threads are motionless. Short fine bacilli, with rounded ends. Not motile. Gelatin Plates. Surface colonies appear as masses of convoluted threads. Liquefy. Surface colonics are lique- fied circles of greyish hue. Deep colonies ap- pear as white dots. Cloudy centres, with root- like extensions from margin. Liquefy. White cloudy patches, not unlike a mould. Liquefy. Irregular wrinkled colo- nies. Liquefy. Anaerobic. If grown in hydrogen not unlike colonies of B. subtilis. Shiny denticulated ex- pansions. Colours the gelatin green. Surface colonies have mother-of-pearl irides- cence. Do not liquefy. Surface colonies are mother - of - pearl like. Resemble fern leaves. Gelatin Tubes. Quickly liquefy with hair- like ramifications from needle path. Funnel - shaped liquefied channel. Flocculent matter collects at bottom. Surface has a pellicle; whole soon liquefies with grey woolly appearance. Similar to B. Ramosus. Shiny grey surface expan- sion. Slowly liquefy. Anaerobic. A cloudy growth, with radial extensions. Liquefy slowly. Non-liquefying. Coli mis gelatin green. Surface expansion is leaf-like. Blue - green fluorescent growth. Fluorescent shimmer along needle's path. Agar-agar. Form a dry grey expansion. White, opaque, wrinkled, and puckered expan- sion. Rapid growth, with character- istic branching. Mould-like ramifi- cations. Smooth, slow- growing, shiny, grey growth. Anaerobic. Grows well if 2 per cent, of grape sugar be added. Similar to growth Grey-yellow A b u n d a n t dry white growth. Moist white cream . like growth. Dry white uni- form expansion. Abundant grey- white shiny growth. Thick irregular flesh . coloured expansion. in gelatin. Greenish - yellow expansion. Green coloured surface expan- sion. irowtli, which later on becomes red-brown. Moist shining thin expansion. Diffused brownish growth. Culture Phenomena of some of the more important Micro-organisms found in Water—continued. Species. Microscopic Appearance. 15. Fluorescens liquefaciens. !>. Pnocvaneus. 15. Aquatilis fluorescens. D. Mitriscpticvs. B. Cuniculicida. B. Fuscus. B. Cajisidatm. B. Brunneus. Short bacillus, with constriction in middle. Occurs in pairs. Is very motile. Small slender bacilli. A'ery motile. Occur singly or in groups. Gelatin Plates. Small white dots. On liquefying, the whole gelatin assumes a green fluorescence. Irregular, liquefying, fluor- escent colonies. Short thin non-motile bacilli, with Surface colonies are like rounded ends. | fern leaves, and resemble mother-of-pearl. Aery small bacilli. Frequently in Do not grow on the sur- pairs. Non - motile and spore face. Deep colonics, re- forming, senible clouds. Liquefy. Non - liquefying. Small, round, finely granular colonies. Gelatin Tubes. Short broad bacilli, with rounded ends. Often arranged in figure of 8. Not motile. Not spore bearing. Thick rods, 1-4 ju. long and 0-8 /*. broad. Usually in pairs, some- times in chains. Motile and flagellated. Straight or bent rods, with rounded ends and irregular contour. Non- motile and non-spore bearing. Non-motile rod-like forms. Gener- ally in pairs, enclosed in a sort of capsule. Fine, slender, spore bearing non- inotile bacilli. Small white colonies, with greyish periphery. Margin often lobulated. Surface colonies are raised pin-heads, deep ones small yellow dots. Porcelain white pin-head colonies. Non-liquefy- ing. Thick, dirty white, drop- like colonies. Turn brown later on, White growth at first, followed by liquefaction and green fluorescence. Funnel shaped liquid de- pression. Green fluor- escence. Do not liquefy. Produce a green fluorescence. Grow very slowly. In deep parts produce a white diffused cloud. Delicate white serrated expansion. Rapid funnel-shapedlique- faction. Projecting button - like growth ; later on turns chrome-yellow. Does not liquefy. AVhole growth resembles a nail. Non - liquefying, shiny, white to grey-brown growth. Agar-agar. Moist greenish- white expansion; afterwardsgreen fluorescence. Similar to growth on gelatin. Restricted yellow- ish-white colo- nies. White shining growth. Similar to gelatin. Similar to gelatin, but stringy. As in gelatin. Potatoes. A brownish growth. Red-brown growth. If treated with ammonia turns green, with an acid red. Vigorous and ex- tensive g r e y growth. No growth. Grows only with difficulty. Dark chrome- yellow coarse growth. A'ellow, moist, stringy growth, with irregular edges. B. Cloacae. B. Ubiquitus. B. Prodigiosus. B. Rubidus. B. Aquatilis (a). B. Aquatilis (*>). B. Nubilus. B. Mesentericus. Fuscus. B. Mesentericus. Arulgatus. B. Typhi ab- dominalis. Short plump oval bacilli, with rounded ends. Often in pairs. A'ery motile. Short plump bacilli, not unlike micrococci. Non-motile. Non-motile cells. Often in pairs. 1-7 n long and 1 ju broad. A'ery motile medium sized bacilli, with rounded ends. Slender bacilli, with rounded ends. Hang together in pairs, or form wavy threads. Have a vibratory movement. Short straight bacilli, with pendu- lum-like movement. No spores. Slender bacilli, 3 /u. long and 0-3 p. broad. Possess violent rotatory movement. No spores A'ery motile short bacilli, with spores. Often in pairs or fours. Small fat bacilli, whose ends often stain better than the middle. Very motile and spore bearing. Very motile, short, plump bacilli, about three times as long as broad, with rounded ends. Flagellated, but without spores. No indol re- action in broth-peptone. Bluish expansion, with irregular notched edges. Quickly liquefy. Surface colonies resemble drops of milk. Turn brown later on. No liquefaction. Circular depressions, with red centre. Liquefy. Round granular colonies. with smooth rim and reddish centre. Liquefy. Liquefying colonies, with convoluted bands of threads from centre to the periphery. Raised white dots, like mother-of-pearl. Rapidly liquefying cloudy white patches. Rapidly liquefying round white centres. Circular yellow colonies which quickly liquefy. Large, spreading, greyish, iridescent colonies, with irregular edges. Have a peculiar woven struc- ture. Do not liquefy. Iridescentscumon surface, with a heavy llocculeut deposit on liquefaction. Nail-like growth, at first white, but turn to a brownish-grey. Liquefy as a conical sack, with a red llocculeut deposit. Liquefy with a brownish- red colour. Slow-growing faint yellow expansion. Non - liquefying. White pin-head growth. Series of horizontal, circu- lar, cloud-like plates along needle track. Liquid funnel-shaped de- pressions. Quickly liquefy, with a surface pellicle. Grows chiefly on the sur- face as a delicate, greyish- white, iridescent expan- sion, with irr.egular edge. Moist, shiny, por- celain-like sur- face growth. Metallic white to grey growth. Blood-red,smooth. and shining ex- pansion. Similar to gelatin. Small shining yellow growth. White moist ex- pansion. Thin, opalescent, blue or violet expansion. Dirty white growth. Grey-white moist growth. Raised! yellow- white growth. White and shiny growth. Metallic and bright red growth. Brownish-red growth. Grow only with difficulty. Smeary grey- white growth. Turns coffee- coloured later. Faintly visible yellow growth. Extensive brown to yellow wrinkled growth. Moist, tough, wrinkled, and stringy growth. Tough but almost invisible grey- white growth. Coagulates and acidifies. Coagulates and acidities. Acidifies, but does not co- agulate. Culture Phenomena of some of the more important Micro-organisms found in Water—continued. Specie;- B. Coli. commu- nis. B. AquatilisSiil- catus (a). B. Aquatilis Sul- catus (b). B. Lactis Aero- (jcncs. B. Tliolocidcum. B. Tuberculoai Proteus vulgaris, Proteus Zenkeri. Microscopic Appearance. Short bacillus, 0-4 ju. broad and 2 or 3 /u. long. Very variable, occasion- ally oval forms not unlike cocci are seen. Slightly motile. Only a few flagella. Does not form spores. Exhibits indol reaction in broth- peptone. Small rods, not unlike B. typhi abdom. A'ery motile. No spores. Motile small rods, with rounded ends. No spores. Non-motile, sporeless, short, plump rods. Often in pairs or in heaps. Short rods, with round ends. like the preceding. Very Slender bacilli, from l-5 to 3-5 ju. long. Non-motile. Spore forma- tion doubtful. Slightly bent bacilli, often woven into snake-like threads. No spores, but very motile. Bacilli, 0-4 /x broad and 1-6ju. long. Motile. Gelatin Dates. Non - liquefying, oval, smooth-rimmed, granu- lar colonies. Have a wavy lineal structure parallel to the peri- phery. Serrated colonies,with thin bluish edges aud white dense centres. Turn yellow later on. Similar to preceding, only edges are not so ser- rated. Non-liquefying moist por- celain white colonies. Surface colonies are like nail heads of an opaque white colour. Deep ones often resemble date stones in shape, and are olive green in colour. No growth. A'ellow - brown colonics, with a bristly edge, and innumerable tendril- like coils. Liquefy rapidly. Thick grey-white colonies which slowly liquefy. Gelatin Tubes. Grows more in depth than the enteric bacillus, whilst on surface re- sembles plate colonies. Non - liquefying. Flat white growth. Do. do. Nail-headed expansion on surface. Free growth along needle path. Moist, convex, surface growth, with a white thick band along needle path. No growth. Rapid liquefaction, with a thick deposit. Thin surface growth. Agar-agar. Dirty white faintly shiny expansions. Thick white growth, with odour of whey. Grey-white growth Moist thick expan- sion. Dirty white com- pact and wrin- kled surface growth. Moist thin grey- white expansion. Shiny grey growth, but occasionally very like the enteric bacillus. Thin cream- coloured growth. Grows best at 10° C. Y e 11 o w -b r o w n growth, with smell of urine. Cream-like white colonies, im- pregnated with gas. Lobular and well- defined expan- sion. Smooth whit( colonies. Dirty smeary growth. Acidifies and co- agulates. Proteus Mira- bilis. Vibrio Aquatilis. Spirillum Chol- eras Asiatica1. B. Choleroides. Spirillum Rub- rum. Vibrio Eerolin- ensis. Mierocooous Candicans. M. Aquatilis. M. C o n c e n • tricus. M. Agilis. Motile sporeless bacilli. Often nearly round. Bent bacilli. Very motile, with one cilium at one pole. Bent bacilli, like commas, often hanging together to form the letter S. A'ery motile ; each rod has one cilium attached to one end. Very like preceding, but move- ments less rapid. Short spirilla, very like but twice as thick as those of cholera. Having shining spots, regarded as spores. Almost identical with oholera vibrio. Miorocooci of irregular size. Not motile. Very small cocci. Usually in groups. Non-motile cocci. Often in irregular groups. Diplococci, also short streptococci. Circular white colonies, In deeper colonies zoo- gloea masses seen. Circular smooth rimmed brown colonies. Liquefy. Circular rough colonies, with granular contents. Have fine hairy exten- sions at periphery. Similar to above, only grows more superficially. Non-liquefying and slow growing colonies, with pale reel centres. Small transparent skin- like surface colonies. Circular smooth white colonies. edged Circular smooth - edged porcelain white colonies. Deep colonies have rough denticulated edge. Deep colonies are small bluish-grey dots. Sur- face colonies are brown- ish discs, with an irregu- lar edge; outside this is a lighter brown and granular ring. Flesh colour to pink lique- fying colonies. Grows best at 20° C. Thick moist surface pel- licle ; quickly liquefies. Only grow on the surface, followed by a basin-like depression. Slowly liquefies. Funnel- shaped or air bubble like depression. Lower part of needle path remains as a thin white thread. Only grows upon and liquefies the surface. Grows along needle track as wine - red colonies. No surface growth. Very like cholera vibrio, only it is slower in growing. Turbid glutinous liquefy- ing mass. Grows on surface and along the needle track. Non-liquefying. Non - liquefying. Blue - grey surface expansion, showing concentric circles. Liquefy slowly ; forming a pinkish-red pigment. Grey-white shin- ing growth. Grey-white shin- ing growth. Grows luxuriously, giving rise to an odour of methyl- mercaptan. Aloist shining grey expansion. Same as cholera vibrio. Dazzling white g r o w t h, like Chinese white. Similar to gelatin. Greyish expansion, with a serrated edge. Pinkish-red growth. No growth. Grows as a trans- parent greyish expansion on alkaline pota- toes. Deep red colonies, size hemp seed. Slow-growing. Same as cholera vibrio. White shiny ex- pansion. No growth. Thin yellowish- grey smeary growth. Pinkish-red pansion. [Culture Phenomena of some of the more important Micro-organisms found in Wider—continued. Species. Staph 11 loco c- cus Pjioijenes aureus. M. Fuscus. Streptococcus Mirabilis. Diplococcus luteus. B. Dilfusus. B. Guttatus. B. Iridescens. Cladothrix Dichotoma. M. Rosettaceus. Microscopic Appearance. Non-motile cocci, in heaps, or chains, or as diplococci. Non-motile elliptical cocci at times, very like short bacilli. Non-motile cocci. Often in long chains. Motile cocci, about 1*2 /u. in diameter. Thin slender bacillus, T7 /u. long and 0-5 broad. Often in pairs or threads. Motile. A'ery motile short bacilli, often in pairs or in groups. Form round spores. Oscillating rods, from 3 to 5 ju long. AYith spores. Long motionless filaments, branched and often united to form flaky zoogloea masses. Irregularly round or elliptical cocci, often arranged in bunches like grapes. Non-motile. Gelatin Plates. Gelatin Tubes. Orange-yellow raised colo- nies. Light brown circular aud liquefying colonies. Non-liquefying and slow- growing dots. Circular bright yellow tough colonies. Bluish-green colonies, with a serrated and lobular margin. Small white dots. Surface colonies are smooth rimmed, with brown centres. Irregular blue-green iri- descent colonies. Sur- face very much con- voluted and folded. Small yellow dots, with brown halo. On surface form brown buttons. Slowly liquefy. Non-liquefying small grey dots. On the surface they form shiningyellow drop-like expansions. At first grey streak. This slowly liquefies with formation of an orange colour. Sepia-brown surface pel- licle. Smells very foully. Faint film. and transparent Vigorous lemon - coloured growth on the surface. Very slowly liquefies. Only grows on the surface as a greenish - yellow expansion. Slowly liquefies. Bluish-white surface ex- pansion, with round ball- like colonies in eleeper parts. Liquefy very slowly. Thread - like growth in depth, which slowly liquefies, forming yellow Thin grey expansion. When liquefaction sets in it turns brown. Grow chiefly on the sur- face as rosette-like ex- pansions. Agar-agar. Potatoes. Similar to gelatin. Similar to gelatin. Tough shiny yellow growth. Deeper part of agar turns brownish. Yellow to cream- coloured expan- sion. Thin grey - white expansion. Thick shining yellow and iri- descent growth. Very adherent thick and shin- ing growth. Agar t u r n s brown. Smooth growth, with toothed border. Thin whitish growth, which becomes moist and yellow. Shiny brown ex- pansion. No growth. Dirty yellow ex- pansion. Has a mouldy smell. Thin greenish- yellow growth. Dull shiny yellow- ish-green growth. Dark yellow dry and rough growth. Grows best at 10° to 15° C. \'ellowish-grey ex- pansion. Coagulates. Coagulates. HYGIENIC VALUE OF A WATEK ANALYSIS. Ill Hygienic Value of a Water Analysis.—Some authorities have shown a desire to accept the numher of micro-organisms present in a water as the measure of its pollution, hut any attempt to set up a standard of purity hased upon the number of micro-organisms in a given quantity is as illogical as any chemical standard. Both depend upon quantity, Avhilst the real point at issue is the quality. Bacteriology, like chemistry, may tell us something of risk and impurity, hut neither can he depended upon to determine with certainty whether a water is actually injurious to health. To condemn one Avater because it yields a little more albuminoid ammonia than another, or because it contains a feAv more organisms than another, Avhen we know nothing of the nature of the substance yielding the ammonia, and nothing of the character of the organisms, is obviously so illogical as to be absurd. Chemical, microscopical, and bacteriological examinations must ahvays be associated with a thorough investigation of the source of the Avater to ascer- tain the possibility of contamination, continuous or intermittent. Then, and then only, if everything be satisfactory, Ave may be justified in speaking of safety and of freedom from risk; but Avhere either the chemical, microscopical, or bacteriological examination is unsatisfactory, the inquiry into the history of the water needs to be most careful and complete, and a guardedly-expressed opinion given only after a full consideration of the bearing of the one upon the other. The possibility of accidental pollution must never be overlooked; yet it often is overlooked, though it is to such accidental pollution that out- breaks of epidemic disease are to be most frequently attributed, and of this the analysis of the Avater sample, prior to the occurrence of the contamination, may teU us little or nothing. The danger of such pollution does not, unfor- tunately, vary with the amount of any constituent found in the water; and a source yielding a water of great chemical and bacterial purity may be as much if not more liable to occasional fouling than a source yielding water containing excessive quantities of chlorides and nitrates, or even of unoxidised organic matter, or large numbers of living organisms. Although a mere analysis cannot guarantee us purity and safety, yet it very frequently can reveal to us impurity and risk. When the source of a Avater, upon most careful examination, is found to be free from all danger of pollution, and the chemical examination proves that the inorganic con- stituents are unobjectionable both in quantity and quality, and that organic matter is absent or present in barely appreciable amount, then safety, so far as human foresight can be trusted, may be guaranteed. If organic matter be present in appreciable quantity—that is, if the water yields such a quantity of organic nitrogen and carbon, or albuminoid ammonia, or requires such an amount of permanganate for oxidation as to render it of suspicious or of doubtful purity—a study of the history of the Avater and of its geological source may, and generally does, enable an opinion to be formed as to the nature of the organic matter, and as to whether it is of an innocuous or dangerous character. Chemical analysis, therefore, has its use; it is only when it is made the sole arbiter between safety and risk that it is abused, and is liable to lead to errors fraught with most disastrous consequences. Let the analysis be as careful and complete as possible, hut let the results always be interpreted in the light afforded by a searching examination of the source of the sample. Let all so-called standards be abandoned as absurd, and let the opinion as to whether water is dangerous or safe be based upon a full consideration of all the factors. Fate of Micro-Organisms in Aerated Waters.—The extensive use in the present day of not only natural waters rich in carbonic acid, but also of many artificial waters prepared by forcing carbon dioxide into spring or distilled 112 WATER. Avater, demands some special notice as to the fate and multiplication of micro-organisms in them. A considerable literature has arisen of late years upon this subject, the chief Avorkers having been Hochstetter, Leone, Pfuhl, and Slater. Their observations have embraced not only the examination of aerated waters directly after their manufacture and on standing for varying periods, but also the fate and poAver of increase which different micro- organisms display, Avhen introduced into Avaters, either naturally or artificially charged Avith gases, more especially carbonic anhydride. The general result of our knoAvledge upon this subject appears to be that, so far as carbon dioxide is concerned, this gas exercises a retarding influence on the vitality of the bacteria present in Avater; but that, if the carbonic acid be allowed to escape, and the water be subsequently kept under sterile conditions, a rapid multi- plication of bacteria takes place. Some experiments made by ourselves indicate that the poAvers of increase by non-pathogenic bacteria, Avhen intro- duced into a carbonated Avater, varied Avith the nature of the particular organism employed. Thus the B. prodigiosus rapidly diminished in numbers, none being apparent after eleven days. The M. violaceus multiplied largely up to the tenth day: on the thirteenth day a distinct diminution was observed, Avhile after eighteen days, it could no longer be detected. Attempts Avere made also to ascertain Avhat effect varying degrees of pressure, under which the gas was forced in, had upon the bacteria: the results obtained seemed to indicate that this does not play any very important part. Hochstetter has observed that the bacilli of anthrax and cholera were killed by C09 in a few hours, but that those of enteric fever may remain alive for five days or more. Anthrax spores and some moulds, however, may retain their vitality for long periods. Though, undoubtedly, the general influence of forcing CO., into various kinds of water is to retard the multiplication of most forms of micro-organisms, if not in some cases to actually inhibit them, it must not be overlooked that the bacterial purity of the original water is very frequently nullified by contaminations which occur in the process of manufacture. Bacteriological Examination of Ice.—Numerous investigations have shown the frequent impurity of ice, both natural and artificial. The chemical examination is effected by wrapping a block of ice in a cloth, breaking it up Avith a hammer, placing a few fragments in a beaker and melting them in a Avater bath. As soon as the ice is melted, the water obtained is examined just as in the case of ordinary Avater. About 2 per cent, of the sohd constituents of the original Avater are said to pass into the I ice. For the bacteriological examination, a few fragments of ice are taken, passed through a Bunsen flame, and placed in a sterilised flask with a plug of cotton-wool. After thirty minutes, sufficient water will have been obtained to form plates, as in the examination of water. A very consider- able number of pathogenic bacteria resist even prolonged freezing, notably, the pyogenic staphylococci and streptococci. On the other hand, the bacilli of anthrax and of septicaemia in rabbits are rather readily destroyed. The ice contains about 10 per cent, of the number of bacteria in the water from which it was obtained: the number of its contained microbes does not generally decrease on being kept any length of time. As regards its hygienic qualities, ice must be judged exactly from the same point of vieAV as Avater. Examination of a Water-filter.—Theoretically, an ordinary domestic filter aims at keeping back the suspended substances completely: in. EXAMINATION OF FILTERS. 113 practice very feAv really do so, while metals are only partially arrested and organic matter even more variably affected. Yery few filters arrest the micro-organisms of Avater for any length of time, the majority greatly diminish the number of microbes for a Avhile, until the organisms multiply so much in the filter itself, that they grow through into the filtrate, making this latter often richer in bacteria than the original Avater before filtration. The manner in which the action of a filter may he tested as regards dissolved or suspended chemical substances, naturally folloAvs the lines of an ordinary chemical Avater analysis. For a bacteriological examination, the filter must be set in action in the proper manner, Avhen plate cultures for the enumeration of the contained micro-organisms are made up simul- taneously from the unfiltered water and filtrate at intervals of a few hours, then day by day, and the numbers compared. A thoroughly efficient filter should completely sterilise a Avater passing through it. Careful notice should be taken how the volume of water passing through the filter varies as time goes on: usually the quantity diminishes; similarly, note should be made as to the influence of pressure upon both the quantity and quality of the filtrate. Not the least important part about the examination of a filter is the ease with which it can be cleaned and re-fitted up. To bacteriologically test a filter, it is better to work with infusions or suspensions of micro-organisms which are easily demonstrable: Bacillus prodigiosus and other colour-producing varieties are particularly suitable. In the case of small domestic filters, one may Avork with pathogenic forms, such as those of enteric fever, cholera, anthrax or their spores. Recent researches have clearly shoAvn that feAv domestic filters yield a filtrate perfectly free from micro-organisms, particularly if in use for any length of time. Even the sand filters of public Avater-works seldom do so. They appear to only act best Avhen the first precipitated matters, and especially a fine bacterial film, have been deposited upon the surface, and the grains of sand have become coated with a shmy mass of bacteria and more or less gelatinised products of their decomposition. Though, strictly speaking, no filter should aUow any micro-organisms to pass through it at all, the presence of more than 100 microbes per cubic centimetre in any recently filtered water should be sufficient to pronounce its action distinctly unsatis- factory. The following tables give an approximate view of the composition of drinking waters of the four classes mentioned on page 15, but it must be clearly borne in mind that they are not submitted as standards, but must be regarded merely as types of analytical results. [Tables. H 114 WATER. 1. Pure and Wholesome Wat) 1-3 20° )) 1-5 25° J ) 1*8 30° n 2*1 35° j j 2-5 40° j) 3-0 45° ? •> 3-6 50° >j 4 2 55° >•> 4*9 60° 5-8 At 65° F . 6*8 grains 70° > j 7*9 ,, 75° )> 9*2 „ 80° 10*7 ,, 85° )> 12-4 „ 90° »j 14-3 ,, 95° >i 16-6 ,, 100° ») 19-1 „ 110° > j 25*5 ,, 120° > j 34-0 ,, 130° i > 42*5 ,, 126 AIR. Or in another way, it can be said that a quantity of completely moist air at 32° F. holds in suspension an amount of Arapour equal to T£o-th part of its own Aveight, at 59° F. ^th, at 86° F. ^th, at 113° F. ^Vth> and at 140° F. yjj-th. Expressed mathematically, it can be said that while the temperature advances in arithmetical progression, the poAver of the air to retain vapour increases Avith the rapidity of a geometrical series having a ratio of tAvo. When Avatery vapour mixes with dry air, the volume of the latter is increased : if the weight of the original volume of dry air be knoAvn, it will be found that, for the same volume, the addition of the water vapour has lessened the weight, and that the diminution in weight is proportionate to the amount of vapour added. The weight of a cubic foot of dry air at 50° F., and under a pressure of 29*92 inches of mercury, is 546*8 grains, and that of a cubic foot of vapour at the same temperature and same pressure is 4*10 grains: the tAvo together should weigh 550*9 grains; but owing to the increase in volume of the air, which the addition of Avater vapour causes, namely, an increase from unity to 1*0121, we find that a cubic foot of saturated air at 50° F. weighs only 544*3 grains. In other Avords, dry air is heavier than moist air, and the diminution in weight, which follows the addition of Avatery vapour, is proportionate to the temperature, because the higher the temperature of the air, the greater is the amount of vapour that it can take up. Watery vapour, as it exists in the atmosphere, exerts an elastic or expan- sive force in all directions. This is sometimes called the tension of aqueous vapour, and is dependent upon temperature, it is also capable of doing work, as expressed by the height in inches of a column of mercury which it can support. The elastic force or tendency to escape from containing vessels, Avhich vapour has, increases Avith a rise in temperature, until the boiling point of water is reached, Avhen it exactly equals the normal pressure of the atmosphere. The amount of moisture in the air can be determined by causing a current of air to Aoav slowly through tubes containing hygroscopic substances, such as caustic potash or hydrochloric acid, and then, by Aveigliing, to note the exact increase in weight which has taken place, and knowing the exact volume of air which has been passed through, to calculate the moisture present as a percentage. It is more usual, however, to determine the atmospheric moisture by means of instruments called " hygrometers," par- ticulars of which are given in a subsequent chapter. The amount of aqueous vapour occurring in the air, at different places, naturally varies very much, less being found inland with a low temperature than out at sea with a high temperature. For the same locality, daily fluctuations of atmospheric humidity take place, depending in most cases upon changes of temperature; thus on the sea coast the absolute humidity of the air increases from sun- rise until about 2 p.m., when a corresponding diminution sets in and continues until sunrise again. Inland, the same sequence of events occurs during the Avinter months, but in the summer there is usually a slight fall followed by a rise between the hours of 4 and 6 p.m. After 6 o'clock the decrease of vapour is gradual until sunrise the next morning. Important as are the facts relating to the chemical composition of the air, still, when considered in special reference to the mechanics and problems of ventilation, the physical properties of air are more important. The reason of this is, that the movements of air currents, with which ventilation is intimately concerned, depend upon differences in weight between adjacent equal volumes of air. WEIGHT OF AIR. 127 Weight of Air.—That air has Aveight is shown by the fact that if a glass globe of known capacity be taken, exhausted of all air by means of an air- pump and then weighed, its weight then will be less than it Avould be if air were alloAved to enter it. If the capacity of the globe be known, the difference between the tAvo weights is the Aveight of that volume of air. The weight, however, of a given volume of air differs under varying circum- stances. We have already seen Iioav, if the temperature and pressure be the same, a cubic foot of air weighs heavier Avhen dry than when moist. Similarly, if the moisture and pressure be the same, it Aveighs more at a lower temperature than at a higher one, and its Aveight increases Avith the pressure, if the temperature and moisture be the same. Hence to determine the weight of a given volume of air, by comparing it Avith a standard fixed by experiment, we must knoAV not only the proportion of contained watery vapour, but also the temperature and pressure. Effects of Temperature.—'When air, under constant pressure, is heated, it expands or increases in volume according to a definite laAv (Charles), Avhich is, that for each degree of temperature added to its heat, it expands a certain constant fraction of its own volume, this fraction being known as the co-efficient of expansion. For each degree Centigrade from 0° to 100°, this co-efficient is for air 0*003667 ; for each degree on the Fahrenheit scale, betAveen 32° and 212°, it is 0*002036; thus, 1 litre of air at 0° C. will become 1*003667 htre at 1° C, and 1-03667 htre at 10° C.; or at any given temperature t, it Avill become 1 + (0*003667/°) litre. In the same Avay, 1 cubic foot of air at 32° F. will be 1*002036 cubic foot at 33° F., and at any given temperature t above 32° F. its volume will be found by the formula, V = 1 + (0*002036 x(t- 32)). To find, therefore, Avhat the observed volume of air or gas v', at the observed temperature, t° C, Avould be when reduced to 0° C, we have, v : v' = l : 1 +(0*003667/°) 0_____v\l____ •'• v ~ 1 + (0*003667/°)' Effects of Pressure.—Under varying conditions of pressure, but a constant temperature, the volume of a gas is inversely proportionate to the pressure (Boyle's law). If a litre of gas at one atmosphere be subjected to the pressure of two atmospheres, its volume will be but half a litre; if the pressure be increased to four atmospheres, the volume will be reduced to one quarter of a htre, and so on. This can be expressed in another way, thus, if under a pressure of p millimetres or inches of mercury, the volume of air be v, its reduced volume vn, under normal conditions of 760 mm. or 29"92 inches of mercury, may be found by the following equation:— v : vn= 760 : p v. p • vn =----. 760 As the temperature and pressure always exist together, both these factors must be taken into account in reducing volumes of air or gas to standard conditions of temperature and pressure; that is, to 0° C. or 32° F., and to 760 mm. or 29*92 inches of mercury respectively. In actual practice it is more convenient to make these two corrections together, and write a single formula, thus :— ^=T60(l + (0^of6670),inwIlich 128 AIR. v — volume of air required under normal conditions of temperature and pressure, o = observed volume of air, p = observed pressure under Avhich the air exists. An example may make this more evident. Example.—A volume of air at 20° C. and 720 mm. pressure measures 1000 litres; what will be its volume under standard conditions ? Applying the formula, -we get, v- _____1000x72°_____= 882-6 litres. 760(1+ (0-003667x20)) Although Boyle's laAv tells us that, the temperature remaining the same, the volume of a given quantity of gas is inversely proportional to the pressure to Avhich it is subjected, still, as the quantity of the gas remains the same, its density must obviously increase as its volume diminishes ; therefore, it folloAvs that for the same temperature, the density of a gas, and therefore its weight, is proportional to its pressure. By Charles' laAv, on the other hand, though the volume increases directly Avith temperature, the density or weight varies inversely. If we remember, therefore, that a litre of dry air at 0° C. and 760 mm. weighs 1'293 grammes, and that density varies inversely as absolute temperature, and directly as pressure, it is obvious that for any volume v, at any pressure p, and at any temperature t°, the Aveight W will be :— w = 1*293 xvx p_ ~ 760(1 + (0*003667lT/))" Example.—Thus, 1000 litres of dry air which, at 0° C. and 760 mm., Aveigh 1293 grammes, would only weigh 1141 grammes at 20° C. and 720 mm., because, ,„ 1-293x1000x720 AA =760(l + (0-003667x20)) = 1141 Srammes- In the case of a volume of moist air, the calculation of the weight is not quite so simple. As this determination involves a knowledge of the hygro- metric condition of the atmosphere, and references to tables of the tension of aqueous vapour, it Avill be more conveniently considered in a subsequent chapter. Diffusion of Air.—The diffusibility of gases is well known, being, accord- ing to the law of Graham, " inversely as the square roots of the densities." Thus, if we take two vessels of equal size, the one containing oxygen and the other hydrogen, and separate them by means of a porous plug, Ave shall find diffusion take place in the proportion of 4 parts of the hydrogen into the oxygen to every 1 part of the oxygen into the hydrogen. This exact ratio of diffusion is explained by the fact that the density of the hydrogen is 1 as compared with the 16 of the oxygen, consequently the diffusion force is inversely as the square roots of these numbers, that is, it is inversely as 1 is to 4, or just four times as great in the one which has one-sixteenth the density of the other. It is this faculty of diffusion, possessed by the air and all gases, which conduces so largely to the composition of air being kept constant, and which enables the carbon dioxide so freely formed in our large towns and cities, by combustion and respiration, to be rapidly removed from where it is formed to other parts, where the processes of vegetation and sunlight can break it up into carbon for the food of plant life and oxygen for the use of men. Apart from this, the variations in density of different masses of air play an important part in the maintenance of ventilation. DIFFUSION OF AIR. 129 The velocity Avith which a mass of air, of knoAvn density, diffuses into a Aracuum is expressed by the formula, v — ,j2gh ; in which h represents the pressure under which the air flows, expressed in terms of the height of a column of air, which Avould exert the same pressure as does the effluent air. Thus, if air, under standard pressure, were to flow into a vacuum, this pressure or h is equal to that exerted by a column of air capable of counter- poising the Aveight of a column of mercury 760 mm. high. As mercury is about 10,500 times denser than air, the equivalent column of air would be 10,500 x 760 = 7980 metres. In the formula, # represents the accelerative force of gravity per second, being in these latitudes 32 feet or 9*8 metres. The velocity, then, with which air, under ordinary pressure, would flow into a vacuum would be, v = J2x 9*8 x 7980 = 395*5 metres per second. This, hoAvever, would only be in the first second of time, and owing to a gradual accumulation in the vacuum, a gradual diminution in the difference of pressure between the inside and outside of the vacuum would ensue for each succeeding second. Hence, if during the act of diffusion the pressure in both spaces be noted at certain intervals and be expressed by h, h', the velocity of diffusion at each of these periods would be more correctly calculated from the formula :— v= J2xgx(h- h'). In actual practice, the chief cause of the alterations in the relative densities of the two masses of air, and consequently of their motion, is the elevation in the temperature of one body of air over that of the other; hence, to determine the velocity with which one diffuses into or rushes to occupy the space of the other, we must further modify the formula, thus:— v = J2 x g x (h - li) x (t - /') x a, in which / is the temperature of the warmer volume and /' that of the colder volume of air; while a is the co-efficient for expansion of gases. As we shall see, later on, this formula is purely theoretical, and needs to be only employed after certain corrections for friction, curves, and changes in size or shape of openings have been applied. Besides the diffusion and movement of adjacent volumes of air, caused by different densities, there is a constant tendency towards diffusion between similar bodies of air, even though apparently separated one from the other. In this case, the current occurs, not through free openings, like doors, windows, or shafts, but through the capillary pores of the separating medium; and may be from the cooler and denser toAvard the warmer and rarer body, or vice versa. IMPURITIES IN AIR. A vast number of substances, vapours, gases or solid particles continually pass into the atmosphere. Many of these substances can be detected neither by smell nor taste, and are inhaled without any knowledge on the part of those who breathe them. Others are smelt or tasted at first; but in a short time, if the substance remains in the atmosphere, the nerves lose their delicacy; so that, in many cases, no warning, and in other instances slight warning only, is given by the senses of these atmospheric impurities. As if to compensate for this, a constant series of processes occur in the atmosphere or on the earth, which keep the air in a state of purity. I 130 AIR. Gases diffuse, and are carried away by Avinds, and thus become so diluted as to be innocuous; or are decomposed if compound, or are Avashed down by rain; sohd substances lifted into the air by winds, or by ascensional force of evaporation, fall by their oAvn Aveight; or if organic, are oxidised into simple compounds, such as Avater, carbon dioxide, nitric acid, and ammonia ; or dry and break up into impalpable particles, which are washed down by rain. Diffusion, dilution by winds, oxidation, and the fall of rain, are the great purifiers ; and, in addition, there is the Avonderful laboratory of the vegetable world, which keeps the carbon dioxide of the atmosphere Avithin certain limits. If it Avere not for these counterbalancing agencies, the atmosphere would soon become too impure for the human race. As it is, it is wonderful how soon the immense impurity, which daily passes into the air, is removed, except when the perverse ingenuity of man opposes some obstacle, or makes too great a demand even upon the purifying powers of Nature. The air passing into the lungs in the necessary and automatic process of respiration is draAvn successively through the mouth and nose, the fauces, and the air-tubes. It may consist, according to circumstances, of matters perfectly gaseous (as in pure air), or of a mixture of gases and sohd particles, mineral or organic, which have passed into the atmosphere. The truly gaseous substances will doubtless enter the passages of the lungs, and will meet there with the delicate tufts of blood-vessels, through which the blood flows Avith great velocity, and from which they are sepa- rated only by a most delicate epithelium; there the gases will be absorbed, and if, as has been calculated, the surface of the air-cells is as much as from 10 to 20 square feet, we can well understand the ease and rapidity with Avhich gaseous substances will enter the blood. The solid particles or molecules entering with the air may lodge in the mouth or nose, or may pass into the lungs, and there decompose, if of destructible nature; or may dissolve or break down if of mineral formation; or may remain as sources of irritation until dislodged; or perhaps become covered over Avith epithelium like the particles of carbon in the miner's lung, or may pass into the epithelium, and enter the body through the lymphatics. If such particles lodge in the mouth or nose they may be swallowed, and pass into the alimentary canal, and it is even more probable that this should be the case with all except the lightest and most finely divided substances, than that they should pass into the lungs. Although incapable of present proof, there is some reason to think that some of the specific poisons, which float about in an impure atmosphere, such as those which arise from enteric or cholera evacuations, may produce their first effects, not on the lungs or blood, but on the alimentary mucous membrane, with which they are brought into contact Avhen swallowed. Though no very precise classification can be made of the various im- purities which vitiate the air, for practical purposes it is convenient to divide them into (1) Suspended matters ; (2) Gaseous and other offensive substances yielded by factories, workshops, mines, sewers, marshes, and cemeteries; (3) Products from combustion or artificial lighting; (4) Products from respiration and perspiration. Suspended Matters.—An immense number of substances, organic or inorganic, may be suspended in the atmosphere. From the soil the winds lift silica, finely powdered silicate of aluminum, carbonate and phosphate of calcium, and peroxide of iron. Volcanoes throw up fine par- ticles of carbon, sand, and dried mud, which, passing into the higher regions may be carried over hundreds or even thousands of miles. SUSPENDED MATTER. 131 The animal kingdom is represented by the debris of the perished creatures which have hved in the atmosphere, and also it Avould appear that the ascensional force of evaporation will lift even animals of some magnitude from the surface of marsh Avater. From the vegetable Avorld pass up seeds and debris of vegetation, pollen, spores of moulds and bacteria, as Avell as innumerable volatile substances or odours. From the sea the wind lifts spray, and the chloride of sodium becoming dried is so diffused through the atmosphere that it is difficult, on spectrum analysis, to find a spectrum Avithout the yelloAv line of sodium. The Avorks and habitations of man, however, furnish matters probably of much greater importance from a hygienic point of view. In the external air, the suspended matters are partly mineral, partly organic. The mineral matters consist largely of silica, iron, chalk, clay, soot, salt, &c. As rain not only prevents such particles being lifted by the Avind, but also washes suspended matters out of the air, it naturally folloAvs that there are more present in the atmosphere during dry weather. The organic suspended matters are principally pollen, algae, fragments of Avood, hair, straw, stable manure, debris of insects, &c. In Avarm climates diatoms may be found; while in the large manufacturing toAvns of thisand other countries the air is often laden with soot and dust of organic origin, which floats in considerable quantities near the ground surface. Even in ■country districts the suspended matters are not inconsiderable in the outer air, such substances as epidermis of hay, fragments of Avood, linen and cotton fibres, feathers, carbon, mineral grains and epithelium having been collected. The number of bacteria in the external air depends largely upon local conditions, particularly whether there is moisture, nutritive material, and a suitable degree of warmth (at least 60° F.). They seem to be chiefly derived from the soil surface by the agencies of wind and traffic move- ments : this explains why they are so numerous in towns, but comparatively scarce in high mountains, over desert plains, or on the sea. It is not known definitely how far bacteria can be carried by wind, but as dust can be conveyed to an almost indefinite distance, it is not unnatural to presume that bacteria may also be carried over considerable distances, particularly if adhering to dust particles. Fischer states that he could find no bacteria in the air at a greater distance than 120 miles from land. Dry winds and drought appear to favour an increase of bacteria in air, Avhile moisture lessens them. These results are possibly due partly to an increased dispersion of micro-organisms from the soil in dry weather, and partly to a condensation and sinking of dust by aqueous vapour which washes the air and brings back the greater number of bacteria to the earth. All observations show that in the outer air the pathogenic bacteria are comparatively few as compared with the saprophytic. As a mean of six years' observations, Miquel found at Montsouris 450 micro-organisms per cubic metre of air; in Paris streets the average number was 900. In the Dundee experiments of Carnelley, Haldane, and Anderson the _ average number_ of organisms was less than one per litre of air; the proportion to moulds being as 1 to 3. The present state of our knowledge goes to show that in the open air the dilution of bacteria is so great, and the number of pathogenic forms so small, that no danger is to be feared from them unless they originate from local sources of impurity. Rooms inhabited by Healthy Persons.—In all inhabited rooms which are not perfectly ventilated, the presence of scaly epithelium, single and 132 AIR. tesselated; round cells like nuclei, portions of fibres (cotton, linen, avooI), portions of food, bits of human hair, Avood, and coal, can be found in addi- tion to the bodies Avhich are present in the external air, though mineral matters and vegetable matters are not so plentiful, as the comparative still- ness of the air alloAvs them to fall. Carnelley, Haldane, and Anderson show that there is an enormous increase of bacteria in croAvded and ill-ventilated rooms, whilst the moulds do not increase to the same extent. When the moulds and bacteria in the external air Avere as 2 to 6, in houses of four rooms and upwards they Avere as 4 to 85, in two-roomed houses as 22 to 430, and in one-roomed houses as 12 to 580. These are the actual numbers found per 10 litres of air. In some cases articles of furniture may furnish certain substances; the flock wall-papers, coloured green by arsenical preparations, give off little particles of arsenical dust into the room; and it has been shown by Fleck that the arsenious acid in the ScliAveinfiirth green, when in contact with moist organic substances, and especially paste or size, forms arseniuretted hydrogen, which diffuses in the room, and is no doubt the cause of some of the cases of arsenical poisoning from green papers. Sick Rooms.—In addition to being vitiated by respiration, the air of sick rooms is contaminated by the abundant exhalations from the bodies of the inmates, and by the effluvia from discharged excretions. The amount of organic matter is known to be large, but it is difficult at present to give a quantitative statement. The peculiar smell of a hospital is indeed very remarkable, and its similarity in hospitals of different kinds seems to show that the odorous substance has a similar composition in many cases. The reaction of ozone is never given in such an atmosphere. The scaly and small round epithelia found in most rooms are in large quantity in hospital wards; and probably, in cases Avhere there is much expectoration or exposure of pus or puriform fluids to the air, the quantity Avould be still larger. In the well-ventilated Avards of the Dundee Royal Infirmary, Carnelley, Haldane, and Anderson found a very small number of micro-organisms. Considering that the pleuro-pneumonia of cattle is probably propagated through the pus and epithelium cells of the sputa passing into the air cells of other cattle; that even in man there is evidence of a pneumonic or phthisical disease being contagious, the presence in the air of these cells, which possibly may contain the tubercle Bacillus or its spores, is worthy of all attention. The strong evidence adduced by Ransome and others sIioavs that tubercu- losis attaches itself to particular small localities; Avhile Cornet has demon- strated the bacilli to be present not only in the air and dust but also on the walls of rooms occupied by phthisical persons. The organism causing erysipelatous inflammation has also been found in the air and in the dust from beneath the floor of a room occupied by persons suffering from ery- sipelas. In small-pox wards Bakewell also found unequivocal evidence of small-pox matter in the air. Workshops, Factories, and Mines.—Grinding of steel and iron, and stones; making metallic and pearl buttons; melting zinc; melting solder; carding and spinning textile fabrics of all kinds; grinding paint; making cement, and in fact almost innumerable trades cause more or less dust, derived from the fabrics and materials, to pass into the air. Sigerson found a black dust composed of carbon, iron and ash, in metal shops. In the air of a printing office there Avas enough antimony to be chemically detected. In the air of stables Avere equine hairs, epithelium,. moth-cells, ovules, and various fungi. IMPURITIES FROM TRADES AND MIXES. 133 In addition to these suspended matters, Avhich vary Avith the kind of work, the air of Avorkshops is largely contaminated by respiration and by the combustion of gas. In mines the suspended matters are made up of the particles of the par- ticular substance Avhich is being Avorked, or of rock excavated to obtain metals, of sooty matters from lamps and candles, and of substances derived from blasting. It is noticeable that in all these cases it is the solid inorganic suspended matters of the air, consisting of dust of various kinds, A\rhich are so injurious to health: as a rule, these are only so by virtue of their mechanical irritat- ing influences upon the mucous membranes, particularly the lungs. It is their physical conditions as to roughness, angularity or smoothness, rather than their mere nature, which influences their power for evil; though possibly in some cases they may also serve as vehicles for conveying specific infective disease factors, more especially that of tubercle. Offensive Gases from Trades.—In the neighbourhood of certain factories or industries more or less dangerous and offensive gases are frequently to be found polluting the air. In some instances these impurities have only the effect of diluting the oxygen in the air, being themselves physiologically harmless. Examples of this exist in the excess of hydrogen and choke- damp in mines, Avhich appear to do more harm by lessening the atmospheric oxygen for respiration than by any special poAver of their own. In other cases, where many chemical agents are used, extremely noxious gases are frequently emitted into the air. The gaseous Avaste products of the chief industries are as follows :— Hydrochloric acid gas, from alkali works. Sulphur dioxide and sulphuric acid, from copper works—bleaching. Hydrogen sulphide, from several chemical works, especially of ammonia. Carbon dioxide, carbon monoxide, and hydrogen sulphide, from brick-fields and cement-works. Cai-bon monoxide, from iron furnaces, may amount to from 22 to 25 per cent., from copper furnaces, 15 to 19 per cent. Organic vapours, from glue refiners, bone-burners, slaughter-houses, knackeries. Zinc fumes, from brassfounders. Arsenical fumes, from copper smelting. Phosphoric fumes, from manufacture of matches. Carbon disulphide, from some india-rubber works. The majority of the gaseous products from industries are both irrespirable and offensive, the more markedly hurtful being the vapours of chlorine, iodine, bromine, arsenic and phosphorus, with carbon monoxide, sulphuretted hydro- gen and the compounds of carbon and sulphuric acid. It is true that, unless favoured by particular conditions of wind and weather, in most instances the presence of these gases is not noticed by any one outside the factories in Avhich they are produced; still the majority are so irritating as to constitute, if present in any appreciable quantity, very serious atmospheric impurities. Air in Mines.—In the metalliferous mines the air, according to Angus Smith, is poor in oxygen (205 per 1000 sometimes) and very rich in carbon dioxide (7'85 per 1000 volumes on a mean of many experiments). It also contains organic matter, giving, Avhen burnt, the smell of burnt feathers, in uncertain amount. These impurities arise from respiration, combustion from lights, and from gunpoAvder blasting. This latter process adds to the air, in addition to carbon dioxide, carbon monoxide, hydrogen and hydrogen sulphide, various solid particles, consisting of suspended salts, Avhich may amount to as much as 6 or 7 milligrammes in each cubic metre of air. These suspended substances are principally potassium sulphate, carbonate, hyposul- 134 AIR. phite, sulpiride, sulphocyanide, and nitrate, carbon, sulphur, and ammonium sesquicarbonate. Much of this may be avoided by the process of getting coal by means of compressed quicklime, which is slaked in holes drilled in the coal. Nasmyth's investigations upon the air of coal mines sIioav that the average amount of carbon dioxide present in moderately deep mines is 1*81 per 1000, and in deep mines of over 100 fathoms, 219 per 1000; the oxygen in deep mines was 204 vols, per 1000; and the amount of oxygen required to oxidise oxidisable matter, both in the deep and moderately deep mines, was 30 vols, per million. In shalloAV pits the air at the bottom of the doAvncast shaft appears to be very good indeed, but in the deeper pits the air samples Avere never as good as obtained from shallow ones. The oxidisable matter seems to vary, but the methods available for this determination explain the differences in the different results. Although micrococci and bacteria, as Avell as yeasts and moulds, were readily demonstrated as being present in large numbers in the air of all mines, still the micro-organisms do not seem to follow any fixed rule, as in one very bad sample of air, as regards carbon dioxide, there were none, Avhile the same air soon after yielded tAventy colonies per litre. In mines, stagnation of air and high temperature are the most favourable circumstances for their growth, but the presence of men and horses is more so. The relative humidity of the air in mines varies from 85 to 95 per cent.: practically, it is nearly ahvays saturated. This excessive humidity is cer- tainly not desirable from a sanitary point of view, but there is no evidence that it conduces to bad health among the miners. The temperature of mine air is Avonderfully uniform, there being neither the great vicissitudes of temperature as above ground nor the frosts. Haldane's inquiries into the cause of death in mines after explosions shoAV that death chiefly results from suffocation due to the deficiency of oxygen, Avhich becomes displaced by the products of the explosion, i.e., after-damp. Suffocation by deficiency of oxygen occurs when the respired air contains less than 8 per cent, of oxygen, being ushered in by an extremely sudden attack of muscular paralysis, so that there is little Avarning of the danger Avhen air is inspired deficient in oxygen, and little chance of escape owing to the muscular failure. Suffocation through excess of carbon dioxide is quite different, as it is preceded by gradual respiratory distress in which the neuro-muscular system is aroused to greater activity. In mines, after ex- plosions, in addition to the deficiency of oxygen, danger exists from the after-damp containing often at least two noxious gases in fatal quantities, these being carbon monoxide and hydrogen sulphide. Black-damp, sometimes also called choke-damp, is one of the gases often found in coal mines. It is distinguished from fire-damp by the fact that it is not explosive when mixed Avith air, but extinguishes fire, and from after- damp by the fact that it is not the product of an explosion, but collects in the workings under ordinary conditions. Like fire-damp and after-damp, it pro- duces fatal effects Avhen inhaled in sufficient concentration. Haldane's obser- vations show that undiluted black-damp consists of nitrogen containing a seventh of its volume of carbonic acid. A mixture of about 16 per cent, of black-damp and 84 per cent, of air extinguishes lights, Avhereas a mixture of about 60 per cent, of the black-damp and 40 per cent, of air are required to produce immediate danger to life. Black-damp is the residual gas left on slow oxidation of the carbon and hydrogen of coal by air. Its dangerous physiological action is due to deficiency of oxygen, not to excess of carbonic acid. The effect first appreciable Avhen increasing proportions of black-damp are breathed is due, hoAvever, to carbonic acid alone. AIR OF SEWERS. 135 Air of Sewers.—The air of cesspools, and especially of the cemented pits, which are still common in many continental toAvns, and which receive little beyond the solid and liquid excreta and some of the house Avater, is generally highly impure. Levy refers to an extreme case, in Avhich the oxygen Avas lessened to 20 per 1000, the nitrogen being 940 and the carbon dioxide 40. In this case apparently no other gases Avere present; but in most instances there is a variable amount of hydrogen sulphide, ammonium sulphide, nitrogen, carbon dioxide, and carburetted hydrogen, in addition to foetid organic matters. These organic matters are in large amount; 62 feet of the air of a cesspool destroyed, in Angus Smith's experiments, as much potassium permanganate as 176,000 cubic feet of pure air, though perhaps some hydrogen sulpiride may have been also present. In seAvers the products of decomposition are variable, as not only solid and liquid excreta and house Avater, but the washings and debris of the streets, the refuse of trades, &c, pass into the sewers. As a rule, the products of decomposition of seAvage appear to be much the same as noted above—ATiz., foetid organic matters, carbo-ammoniacal substances condensing Avith the water of the air on the cold walls, carbon dioxide, nitrogen, and hydrogen sulphide. The proportions of these gases are vari- able ; the most common are carbon dioxide and nitrogen; marsh gas is found Avhen oxidation is impeded, and hydrogen sulphide and ammonium sulphide, Avhich form in the sewage in most cases, are liberated from time to time. The gases, however, are, as a rule, of far less importance than the foetid organic matters, the exact nature of which it Avould be most desirable to examine more thoroughly. The organic vapour is carbo-ammoniacal; the putrid substance in the seAvage appears, from Odling's observations, to consist largely of amines. The composition of sewer air will, of course, vary infinitely with the amount of gases disengaged and the degree of ventilation in the sewer. The quantity of oxygen is sometimes in normal amount; it may, however, be diminished in very badly constructed sewers. Parent-Duchatelet gave an analysis of the air of a choked sewer in Paris, which contained only 137*9 per 1000 of oxygen, and no less than 29*9 per 1000 of hydrogen sulphide. Excluding this analysis, the greatest impurity in the old Parisian sewers was 34 per 1000 of carbon dioxide and 12*5 per 1000 of hydrogen sulphide. The lowest amount of oxygen Avas 174 per 1000. Hydrogen sulphide was present in 18 out of 19 cases, the mean of the whole 19 cases being 8*1 per 1000. The mean amount of carbon dioxide in 19 cases was 23 per 1000. In the present London seAvers of good construction the air is much less impure. Letheby found only 5*32 per 1000 of C02, a good deal of ammonia, and. only traces of hydrogen sulphide and marsh gas. Miller's experiments in 1867 gave a mean of only 1*06 per 1000 of C02 in 18 analyses, and 3*07 per 1000 in 6 other instances, the oxygen 207*1 per 1000. No hydrogen sulphide was present. Russell examined the air in the sewers of Paddington ; the most impure air contained 207 oxygen, 787*98 nitrogen, and 5*1 volumes of carbon dioxide per 1000; there was very little ammonia, and no hydrogen sulphide. In 1877 Beetz, in Munich, found 3*14 vols. C02, and 0*22 vol. NH3 per 1000, as an average of 5 analyses. It is evident that, if we take the carbon dioxide and hydrogen sulphide as indices, sewer air has no constant composition. It is sometimes almost as pure as the outside air, while at other times it may be highly impure. But these gases are probably the least important ingredients of sewer air ; that organic matters are present is evident from the peculiar foetid smell, and in some cases they are in large amount; 8000 cubic feet of the air of 136 AIR. a house into which seAver air had penetrated destroyed more than 20 times as much potassium permanganate as the same quantity of pure air (Angus Smith). Fungi and bacteria groAV rapidly in such air, and meat and milk soon taint when exposed to it. We must also suppose, for facts leave us no other explanation, that those agencies which produce enteric fever may also be present. Whether small- pox, scarlet fever, &c, can OAvn a similar channel of distribution is uncertain, although they are no doubt aggravated by it; that dysentery and diarrhoea may also be caused by exhalations proceeding from a foul seAver we cannot doubt, but the precise agency is here also unknoAvn. Diphtheria and acute f ollicular tonsillitis are also associated with seAver air; and, if the disease does not originate de novo, Avhen once it breaks out, its tendency is to spread where the air and soil are polluted by seAvage. The experiments of Frankland show that solid or liquid matter is not likely to be scattered into the air from the seAvage itself by any agitation it is likely to undergo, until gas begins to be generated in it. He found that no ordinary agitation (even greater than seAvage is likely to meet with) Avould scatter particles of lithia solution into the air, but that the burst- ing of bubbles of carbon dioxide was sufficient to effect it. Hence he argues (with apparent truth) that sewage becomes dangerous in this Avay only after the setting in of decomposition, so that if Ave take proper steps to carry away sewage at once the danger becomes reduced to a minimum. J. D. Robertson, of Penrith, has made bacteriological investigations into the air of seAvers, and has found various forms of cocci, bacteria, and bacilli to be present, besides moulds. The most common forms Avere bacilli, which showed a great preponderance over micrococci; Avhereas in the open air, cocci forms Avere more numerous than bacilli. The average number of micro-organisms per litre was 4*2 in sewer air (15 experiments) and 5*7 in open air (10 experiments). The experiments of Carnelley and Haldane on the air in the seAvers of the Houses of Parliament, and in Dundee, led them to the following con- clusions :—(1) That the air of the seAvers was much better than might have been expected; (2) that the carbonic acid was about twice, and the organic matter rather more than three times as great as in the outside air at the same time, whereas the number of micro-organisms was less; (3) that, in reference to the quantity of these three constituents, the seAver air Avas in a very much better condition than that of naturally ventilated schools, and that, Avith the notable exception of organic matter, it had likewise the advantage of mechanically ventilated schools; (4) that the sewer air contained a much smaller number of organisms than any class of house. In the Westminster sewer the C02 ranged from 0*49 to 0*89 per 1000 vols., the oxygen required for oxidisable matter from 1 to 12*9 vols, per 1,000,000, and the micro-organisms from 0*5 to 38 per litre; in the Dundee sewers these numbers Avere respectively 0*55 to 1*09, 3*1 to 18*2, and 2*5 to 25. The average results of the whole series Avere— co2. Oxygen. Micro-organisms. In sewers, .... In outside air, 0-75 0-37 7*2 2-2 8*9 15-9 AIR OF MARSHES AND CEMETERIES. 137 They consider that the carbon dioxide is chiefly due to the oxidation of organic matter in the seAvage and seAver air, and that the micro-organisms present in seAver air are derived from the outside air and not from the sewage itself. These observations have been recently confirmed by Parry Laws ; Avhile Arthur has shoAvn that bacteria can undoubtedly grow up the sides or walls of the damp nutrient seAvers, and if these latter become at all dry, air currents readily detach and disperse them. Possibly in this way some micro-organisms may get set free in seAver air from the actual sewage, and that the micro-organisms present in seAver air are not so much derived from the outside air as has hitherto been thought. The truth probably lies between the tAvo. Air of Marshes.—The air of typical marshes contains usually an excess of carbon dioxide, which amounts, perhaps, to 0'6 or 0'8 or more per 1000 volumes. Watery vapour is usually in large quantity. Hydrogen sulphide is present, if the water of the marsh contains sulphates, which in presence of organic matter are converted into sulphides, from Avhich SH2 is derived by the action of vegetable acids. Marsh gas is also often present, and occasion- ally free hydrogen and ammonia, and, it is said, hydrogen phosphide. Organic matter also exists in considerable quantity, and seems to have much the same character always. It blackens sulphuric acid Avhen the air is drawn through it; gives a reddish colour to nitrate of silver; has a flocculent appearance, and sometimes a peculiar marshy smell, and, heated with soda-lime, affords evidence of ammonia. Besides the organic matter, various vegetable matters and animals, floating in the air, are arrested Avhen the air of marshes is draAvn through Avater or sulphuric acid, and debris of plants, infusoria, insects, and even, it is said, small Crustacea, are found; the ascensional force given by the evaporation of Avater seems, indeed, to be sufficient to lift comparatively large insects into the air. Although the researches of Klebs, Tommasi-Crudeli and Laveran have clearly demonstrated malaria to be dependent upon the presence of a micro-organism in the blood, still it has not been so far demonstrated outside the body ; and nothing has ever been found in either the air of marshes or other malaria disposed localities which in any Avay appear to be associated Avith or throAV any light upon the life history of this micro-organism. Marsh air has been said to be deficient in ozone, but the observations of Burdel do not confirm this. Impurities from Cemeteries.—The decomposition of bodies gives rise to a very large amount of carbon dioxide. It has been calculated that, when intramural burial Avas carried on in London, 2\ millions of cubic feet of carbon dioxide were disengaged annually from the 52,000 bodies then buried. Ammonia and an offensive putrid vapour are also given off. The air of most cemeteries is richer in C02 than ordinary air (0*7 to 0*9 per 1000), and the organic matter is perceptibly larger when tested by potassium permanganate. In vaults, the air contains much carbon dioxide, carbonate or sulphide of ammonium, nitrogen, hydrogen sulphide and organic matter. Impurities from Fires and Artificial Lights.—As coal is the chief material used for combustion in our fires, it constitutes the main source of impurities to the atmosphere from various means of heating. For the complete combustion of 1 ft) of coal at least 160 cubic feet of air are required by theory, but in actual practice from half to twice as much air must be supplied, making the average amount required per pound of coal to be from 240 to 300 cubic feet. During combustion about 1 per cent, of the coal is given off into the air as soot and tarry products, Avith large quantities of 138 AIR. carbon dioxide and carbon monoxide. The actual amounts of these gases given off will depend upon the degree of perfection of the combustion ; but it has been calculated that for every ton of coal burnt in London something hke three tons of carbon dioxide are produced. In addition to these impurities, the atmosphere receives from the burning of coal, carbon disulphide, ammonium sulphide, water, and occasionally sulphu- retted hydrogen, as Avell as sulphur, sulphur dioxide, and sulphuric acid. Ordinary coal contains from half to seven per cent, of sulphur, and it is not unusual to find in the outer air, in manufacturing districts, from half to one grain of sulphuric acid per 1000 cubic feet of air. Wood produces, on combustion, carbon dioxide and monoxide, Avith more water but less sulphur compounds than coal does. The impurities from coke and peat are somewhat similar to those from coal. In cases where the combustion is incomplete or the supply of oxygen is insufficient, much of the carbon becomes incandescent in an atmosphere highly charged with and practically consisting of carbon dioxide, combining Avith it to form carbon monoxide, thus, C0 -f- 2C02 = 4CO. The blue flames so often seen at the top of a well-draAving clear fire consist of burning carbon monoxide, which has been produced by the carbon dioxide, formed at the loAver part of the fire, having to pass over the red-hot coal on its upward way to the chimney. This carbon monoxide is largely given off from charcoal fires and " slow combustion " stoves, and is, moreover, very much more poisonous than the dioxide. The products of the combustion of coal and Avood pass into the atmos- phere, and usually are at once largely diluted. Diffusion and the ever- moving air rapidly purify the atmosphere from carbon dioxide. It is not so, hoAvever, Avith the suspended carbon and tarry matters, which are too heavy to drift far or to ascend high. As a rule, the particles of carbon are not found higher than 600 feet; and the way they accumulate in the lower strata of the atmosphere can be seen by looking at any lofty building in London. The air of London is so loaded Avith carbon, that even Avhen there is no fog, particles can be collected on an aeroscope when only a very small quantity of air is drawn through. Sulphurous and sulphuric acids also appear to be less rapidly removed, as Angus Smith found a perceptible quantity in the air of Manchester; and the rain-water is often made acid from this cause. With regard to the impurities added to the air, consequent on artificial lighting, we find that the chief sources of light are candles, oil, and coal gas, and that the chief products from the more or less complete combustion of these illuminants are carbon dioxide and water, with the addition, in the case of gas, of several products from the combustion of sulphur. Now, the unit adopted in this country for the measurement and comparison of all lights is a sperm candle of a size knoAvn as " sixes," burning 120 grains per hour, and which gives a light known as "one candle poAver." Such a candle, on analysis, contains:— Carbon,........80*0 per cent. Hydrogen,........13-0 ;) (> Oxygen,........6-0,,,, and, on complete combustion, yields equal volumes of carbonic acid and Avater to the air, namely, 0'41 cubic foot. The French unit of light is the light given out by one Carcel burner, and equals 9*3 English standard candles. What is knoAvn as Harcourt's standard flame gives a light equal to that IMPURITIES FROM ARTIFICIAL LIGHTS. 139 of one English standard candle. It consists of an air-gas flame, 2\ inches in height, rising from an opening \ inch in diameter. The flame is that of a mixture of air and pentane : 576 volumes of air being mixed with one of liquid pentane at 15°*6 C. (60° F.); or if both are in the form of gas, 20 of air to 7 of pentane. Although various kinds of oil have been employed for illuminating purposes, paraffin, OAving to its cheapness and high illuminating value, is the only one hoav in extensive use. Ordinary paraffin, on analysis, gives the following composition :— Carbon, ........ 86'0 per cent. Hydrogen, ........ 14*0 ,, ,, When burnt in the better kinds of lamps, the average consumption per candle poAver of this oil is just 62 grains per hour, giving off on combustion in that time 0*28 cubic foot of carbonic acid and 0'22 of a cubic foot of Avater vapour. In the inferior class of lamps, the consumption of oil is often double the above amount, accompanied by the production of 0-5 of a cubic foot of carbon dioxide and the consumption of the oxygen of about 3-2 cubic feet of air. The chief popular illuminant is gas. Ordinary coal gas is a mixture of gases, consisting mainly of hydrogen and hydrocarbons, produced by the dry or destructive distillation of coal. The coal is heated, without contact of air, in iron retorts, and the products of its destructive distillation are made to pass, firstly, through condensers in which, as a result of the cooling they are subjected to, the heavy coal tar and the lighter ammoniacal tar- liquor are condensed, and are then collected in tanks; and secondly, the gas is led through purifying chambers, containing either moist slaked lime or ferric oxyhydrate spread on shelves, either of which removes the gaseous impurities containing sulphur, the former removing carbon dioxide as well; finally the gas is passed into a gasometer for storing purposes. The following statement of the analysis of two London gases may be accepted as fairly representing the composition of coal gas generally :— South Metropolitan The Gaslight and Gas Company. Coke Company. 50-16 53*36 36-25 32-69 3-50 3-58 5*68 7-05 o-oo 0-61 4-10 2-50 0-31 0-21 100*00 100-00 In some analyses the carbon monoxide has been as high as 11 per cent., and the light carburetted hydrogen 56 ; in such cases the amount of hydro- gen is small. As much as 60 grains of sulphur have been found in 100 cubic feet of gas. According to the standard of the Metropolitan Gas Referees, all gas must be Avholly free from H2S, the maximum of sulphur (in compounds other than H2S) allowable is 17 grains per 100 cubic feet, and the maximum of ammonia is 4 grains per 100 cubic feet. In badly purified gas there may be a great number of substances in small amount, especially hydrocarbons and alcohols, such as propylene, butylene, amy- lene, benzole, xylol, some of the nitrogenous oily bases, such as pyrrol, picoline, &c. Hydrogen, Saturated hydrocarbons, Unsaturated hydrocarbons, Carbon monoxide, Carbon dioxide, Nitrogen, Oxygen, 140 AIR. The constituents of coal gas may be divided into three groups, diluents, illuminants, and impurities. The diluents are gases Avliich, Avithout confer- ring much luminosity on coal gas when burnt, yet serve the important purpose of diluting down the heavy hydrocarbons, which by themselves Avould yield a smoky flame; the diluents are hydrogen, methane, or marsh gas, and carbonic oxide: they constitute about 90 per cent, by volume of the coal gas. The illuminants are hydrocarbon gases or vapours rich in carbon, and to their presence the luminosity of coal gas AAdien burnt is due; they are ethene or defiant gas, acetylene, and benzene vapour: they constitute about 6 per cent, by volume of the coal gas. The impurities constitute the remain- ing four volumes, and consist of nitrogen derived from a little air getting into the retorts Avhen opened for recharging, and of some carbon dioxide, with traces of sulphur compounds Avhich may have escaped removal in the purifiers. When the gas is partly burnt, the hydrogen and light and heavy, car- buretted hydrogens are almost destroyed; nitrogen (67 per cent.), Avater (16 per cent.), carbon dioxide (7 per cent.), and carbon monoxide (5 to 6 per cent.), with sulphur dioxide and ammonia, being the principal resultants. And these products escape usually into the air of rooms. With perfect combustion there Avill be little carbon monoxide. Every cubic foot of ordinary coal gas yields, on combustion, roughly half its oAvn volume, or 0*52 cubic foot of carbon dioxide, and 1*34 cubic foot of Avater vapour: therefore, knowing Iioav much gas per hour each burner consumes, the average being from 3 to 6 cubic feet, there is no difficulty in calculating the vitiation of air from these sources. Combustion, however, in ordinary burners is never absolutely complete : and even with a 16-candle gas very slight traces of carbon monoxide will generally escape combustion, Avhilst Avith a rich gas distinct traces of acetylene are also given off. In other words, the actual products of combustion given off by gas will vary much Avith the quahty of the gas used, and the completeness of the process; the usual products being carbon dioxide, carbon monoxide, compounds of ammonia, Avatery vapour, and various compounds of sulphur. These latter, if present, are particularly injurious to health, but there is reason to believe that their existence in gas-lit rooms has been much exaggerated. For every 100 cubic feet of gas consumed, containing 20 grains of sulphur, there would be 0*032 cubic foot of sulphur dioxide formed, while with an impurer gas, containing 30 grains of sulphur per 100 cubic feet, the sulphur dioxide resulting would amount to 0*048 cubic foot. Except under very unusual circumstances, ventilation would reduce these quantities in nearly the same ratio as the carbon dioxide, the total volume of sulphur dioxide due to the combustion of the gas being reduced to very minute traces, or something like 0*0625 grain of sulphur as sulphurous acid per 100 cubic feet of air. Speaking generally, it may be said that each cubic foot of gas, burnt per hour from the ordinary burners, vitiates as much air as Avould be rendered impure by the respirations of an individual; it, at the same time, will raise the temperature of 31,290 cubic feet of air 1° F., and yields 217 calories (a kilogramme of water heated 1° C), or 860 British heat units (a pound of water heated 1° F.). The following table shoAvs the relative amounts of oxygen removed from the air, and carbon dioxide, Avatery vapour, and heat calories produced, per hour, by various forms of artificial light: with these facts are also incorporated the candle poAver, and the number of adults who would exhale the same amount of carbon dioxide in the same time. IMPURITIES FROM ARTIFICIAL LIGHTS. 141 Quantity Candle Oxygen C02 Jloisture Heat Vitiation consumed. power. removed. 10-7 C. ft. produced. produced. Calories produced. equal to Adults. Tallow candles, . 2200 grains. 16 7*3 c ft. 8-2 c ft. 1400 12*0 Sperm candles, 1740 „ 16 9-6 ,, 6*5 ,, 65 „ 1137 n-o Paraffin oil lamp, 992 „ 16 6*2 ,, 4-5 „ 3*5 ,, 1030 7*5 Kerosene oil lamp, 909 ,, 16 5-9 ,, 4-1 ,, 3-3 ,, 1030 7-0 Coal gas, Xo. 5 batsAving burner, 5-5 c. ft. 16 6*5 „ 2*8 „ 7 3 „ 1194 5-0 Coal gas, Argand burner, 4-8 ,, 16 5*8 ,, 2*6 „ 6-4 ,, 1240 4-3 Coal gas, regener- ative burner, 3-2 ,, 32 3*6 „ 1*7 „ 4*2 „ 760 2-8 Coal gas, "Welsbach incandescent, 3*5 ,, 50 4-1 „ 1*8 „ 4'7 „ 763 3-0 Electric incandes- cent light, 0-3 lb coal. 16 0*0 ,, 0*0 ,, 0*0 „ 37 o-o It is sufficiently obvious from the above facts that the most hygienic source of light is the electric incandescent lamp, inasmuch as all other sources of artificial illumination, being dependent on the absorption of oxygen from the air, result in the vitiation of the atmosphere by products which are more or less injurious to health. The electric arc light, which is not contained in a closed globe, is said to vitiate the air by the formation of nitric acid, but even if so, its effects in this direction are much less hurtful than gas, oil, or candles. Of the various forms of light derived from coal gas, that yielded by the Welsbach or incandescent gas-burner stands out pre-eminently as the best. In view of the fact that the use of these burners has recently increased in a remarkable manner, some observations upon their general construction and hygienic value may not be inappropriate. The Welsbach incandescent gas-burner (fig. 8), when complete, may be said to consist of two essential parts. The first is an ordinary but carefully adjusted burner of the Bunsen type, in which air is mixed with the gas before it burns in the proportion of 30 of gas to 70 of air, producing a colourless or faintly blue flame. The second part is a fine gauze-like mantle composed of nitrates of the rare earths, cerium, lanthanum, thorium, and zirconium, which is suspended in the flame by means of a forked support of raagnesian silicate, itself luminous when hot. The flame and mantle are inclosed in a chimney of glass or other transparent material, which, besides serving as a protection for the fragile mantle from accident, keeps the flame perfectly steady. The principle of the Welsbach burner is similar to that of other systems of lighting in use, which depend upon the light emitted by an incandescing body. Incandescence is " the brilliant glow given out by certain refractory bodies when they are heated up to a definite point." The light from an ordinary flame is due to the incandescing particles of carbon Avhich are set free from the decomposition of the hydrocarbons during the stages of combustion. Lewes explains the various changes taking place in a luminous gas flame in the following way:—" In the inner zone of the flame, the con- stituents of the gas undergo various decomposition and interactions, Avhich culminate in the conversion of the heavier hydrocarbons into acetylene, carbon monoxide being also produced ; and these, with the products of combustion and residual hydrogen, pass into the next phase of action. Here the acetylene, formed in the inner zone, becomes decomposed by heat, with 142 AIR. liberation of carbon, which at the moment of production is heated to incan- descence by the combustion of the carbon monoxide and hydrogen and gives luminosity to the flame." In the Welsbach burner, the incandescence is due to the heating of a net-work of oxides of certain rare earths, which emit, at the temperature of the Bunsen flame, a bright, steady, and powerful white light. It affords, in fact, an admirable illustration of the conversion of heat into light rays. The Bunsen flame, though very hot, is Avithout luminosity, because " the nitrogen of the air acts in the normal flame by so diluting and protecting the hydrocarbons that a far higher temperature is needed for their decom- position : this action gives time for the oxygen of the air to consume them, without liberation of carbon, and hence without luminosity" (Lewes). In the incandescent burner, however, by allowing the flame to play upon a refractory body, in the form of a mantle, the heat undergoes a change into the closely allied phenomenon of light. From the hygienic standpoint, the Welsbach burner is simply an ordinary Bunsen burner, over the flame of Avhich is hung a network of incombustible material that is intensely luminous when raised to the temperature of the Bunsen flame. In the Clamond system of incandescent gas- lighting, a similar result is obtained by a hood of magnesia and zirconia, which is heated to incan- descence by an atmospheric burner; in the LeAvis system, again, there is a small hood of platinum; so, in the Sellon light, a cone of metal gauze is used; while in the Swedish system of Farneh- jelm there is an extensive use of small pencils of magnesia and zirconia, fixed to a frame in the form of a comb over the flame of a water-gas burner. The complete combustion of a given volume of coal gas must, of course, on theoretical grounds, give rise to the production of exactly the same pro- ducts of combustion in whatever burner the gas is burned. "It follows, therefore, that if the consumption of gas be Ioav, the evolution of products Avill be proportionately reduced, so that, apart from mere questions of economy, a burner that consumes a relatively small amount of gas, to say nothing of the superior light it gives, must be preferable on that account from the hygienic point of view." The marked hygienic advantages offered by the Welsbach burner, in this direction, are well shoAvn in the foregoing tabular statement, based upon the vitiating effects and varying rates of consumption of different forms of artificial light. It should be observed in addition, however, that the vitiation of air with carbonic acid gas by one Welsbach burner, giving a 50 candle power light and consuming 3*5 cubic feet of gas, is less than one-half that produced by an oil lamp of 16 candle power, and consuming a little over two ounces of oil. As clearly demonstrated in a very lucid report, upon the incandescent gas light, pubhshed by the Lancet on Jan. 5th, 1895, and to which we are indebted for the following figures, the Welsbach burner affects the atmos- phere far less for evil, judging from the carbonic acid and heat produced IMPURITIES FROM ARTIFICIAL LIGHTS. 143 than any other existing type of burner. Thus, "Avhile the increase of carbonic acid per candle power is only 0*365 in the case of the Welsbach light, it is 1*9 in the case of Argand burners, 2*86 in the batswing, and T56 in oil lamps "; and the increase of temperature in a room with a Welsbach burner per candle power is " only 0*116 compared Avith the Argand, 0*59°, the batswing, 0*807°, and oil lamps, 0*468°." Of all the systems of artificial lighting in common use at the present time, we are bound to place, for reasons already detailed, the incandescent electric light in the first rank from the point of vieAv of health. " From the same point of view we are bound to place next, the incandescent gas-light in its present improved form. It is less productive of carbonic acid gas than the average oil lamp, and consumes not quite one-half less gas than the ordinary burners, giving rise, therefore, to the evolution of half the heat, and half the amount of carbon dioxide, while its illuminating power expressed in candles is more than three times as great as the best ordinary gas-burners or in- candescent electric light, each of Avhich rarely exceed 16 candle power." The only gas-light which at all approaches it, in its hygienic advantages, is Siemen's regenerative burner, but that has one-third less illuminating power and is less well adapted for general domestic use. The relative merits of the other forms of artificial light are sufficiently manifest from the figures given above to require no special criticism. Carnelley and Mackie have shoAvn that the combustion of coal exercises a marked effect on the organic matter in the air of toAvns; but that the com- bustion of coal gas in a room has not much effect in increasing the organic matter, whereas a burning oil lamp has a marked effect. In tobacco smoke are contained particles of nicotine or its salts (Heubel), and probably of picoline bases. There is also much carbon dioxide, rammonia, and butyric acid. Bipley Xichols has investigated the air in smoking cars on American railways, and found the C02 to range from 0*98 to 3*35 per 1000, with a mean of 2*278 : in ordinary non-smoking cars the C02 varied from 1*74 to 3*67, with a mean of 2*32, so that there Avas not much difference as far as carbon dioxide went. As regards ammonia, hoAvever, the difference Avas great, for (taking the external air ratio as 100) he found in the smoking car from 310 to 575, whilst in the ordinary cars it Avas only 135 to 175. None of the peculiar products of the combustion of tobacco were found. Summing up, we may say that the chief' changes produced in the air by the use of artificial lights are elevation in temperature, the addition of moisture, carbonic oxide, carbon dioxide, nitric and nitrous acid, compounds of ammonia, and of sulphur, marsh gas, carbon particles and acids of the fatty group. Apart from these added impurities, the air suffers by the withdrawal of a certain amount of oxygen. Impurities from Respiration.—It will materially aid our conception of the nature and amount of the impurities added to the air by respiration if we contrast the chemical composition of 100 parts of ordinary atmosphere •Avith 100 parts of expired air, in respect of their chief constituents. Ordinary air. Expired air. Oxygen,.......20*96 16*40 Nitrogen,.......79*00 79'19 Carbon dioxide,......0'04 4'41 From this it will be seen that the expired air contains more than a hundred times more C02, nearly five per cent, less 02, and a small amount of N2 more than the atmospheric air. Hence, during respiration more 144 AIR. oxygen is taken into the body from the air than carbon dioxide is given off; so that the volume of the expired air is from TV to -V smaller than the volume of the air inspired, both being calculated as dry, at the same temperature and pressure. This diminution of the volume of expired air is, however, far more than compensated by the Avarming which the inspired air undergoes in the respiratory passages, so that eventually the volume of the expired air is really one-ninth greater than the air inspired. The relation of the 02 absorbed to the C02 given off is as 4'57 : 4*38. This is expressed by the " respiratory quotient " : — CO, = 4^8 905. 02 4*57 This ratio, betAveen the amount of oxygen absorbed and the amount of carbon dioxide exhaled, varies in different animals; being for man 0*87 to 0*9, for horses 0*97, for oxen and sheep 0*98, and for dogs and cats about 0*75. The changes produced, therefore, in air by respiration are, eleva- tion in temperature, increase of moisture, increase in volume and changes in chemical composition. An average adult gives out at each respiration 22 cubic inches of air, and, assuming that he breathes eighteen times a minute, the total quantity of air which passes out of the lungs in the tAventy-four hours is 570,240 cubic inches, or 330 cubic feet. If Ave further assume that the expired air contains 4*4 per cent, of carbon dioxide, the average adult at rest evolves 14*52 cubic feet of this gas in the tAventy-four hours, or 0*6 cubic foot per hour; this amount is, however, largely increased by exertion, and may, in the case of a man doing hard work, reach 37 cubic feet in the twenty-four hours, or, say, 1*6 cubic foot of carbon dioxide exhaled per hour. In the case of big men, say 12 stones in Aveight and at rest, the C02 given off hourly from the lungs is not less than 0-72 cubic foot. Women give off less, about 0"6; while children and old people give off a smaller amount. The quantity given off by women, say 0*6, may be adopted for a mixed community. The amount of carbon dioxide in pure air being assumed to be on an average 0*4 per 1000, the quantity in the air of the rooms vitiated by respiration varies within wide limits, and many analyses will be found in books. The following table is a part of the numerous experiments on barrack-rooms by de Chaumont on this point, in which the amount of carbon dioxide in the external air Avas simultaneously determined. The analyses were made at night, when the men Avere in the rooms. The cubic space per head was 600 feet in the barracks and from 1200 to 1600 in the hospitals:— C02 in C02in Room. External Largest Mea Respiratory Air. Amount found. Amount. Impurity. Barracks. Gosport New Barracks, .... 0'430 1-846 0-645 0*215 Anglesey Barracks, .... 0 393 1-971 1-404 1-011 Aldershot,...... 0*440 1-408 0-976 0-536 Chelsea, ....... 0-470 1-175 0-718 0-248 Tower of London,..... 0'420 1-731 1338 0-898 Fort Elson (Casemate)..... 0*425 1-874 1-209 0-784 Fort Brockhurst (Casemate), . 0-422 1-027 0-838 0-416 AIR VITIATED BY RESPIRATION. 145 i C02 in Room. Mean Respiratory Impurity. External Air. Largest Amount found. Mean Amount. Military and Civil Hospitals. Portsmouth Garrison Hospital, Portsmouth Civil Infirmary, . Herbert Hospital,..... Hilsea Hospital, ..... St Mary's, Paddington, .... Military and Civil Prisons. Aldershot Military Prison— Cells, . Gosport Military Prison—Cells, Chatham' Convict Prison—Cells, Pentonville Prison—Cells—Jebb's system, 0-306 0'322 0-424 0'405 0-560 0-409 0-555 0-452 0-420 2-057 1-309 0-730 0-741 1-534 3-484 2-344 3-097 1-926 0-976 0-928 0 472 0-578 0-847 1-651 1-335 1-691 0-989 0-670 0-606 0-048 0-173 0-287 1-242 0-780 1-239 0-569 The last column of the table shows the condition of the ventilation as measured by the carbon dioxide; it is very satisfactory in the newer barracks (Gosport and Chelsea), but is much less so in the older barracks and case- mates. The Herbert and Hilsea military hospitals show excellent ventilation, Avhile the old-fashioned Portsmouth garrison hospital is in this respect in- different. The prison cells shoAV, in all cases, a very high degree of respira- tory impurity, and this must be one of the depressing influences of long cell confinement. Wilson gives some important information on this point. In cells (in Portsmouth Convict Prison) of 614 cubic feet, ahvays occupied, he found the C02 = 0*720 per 1000; the prisoners Avere healthy and had a good colour. In cells of 210 cubic feet, occupied only at night by prisoners employed outside during the day, he found 1*044 per 1000 of C02: the occupants Avere all pale and anaemic. The carbon dioxide of respiration is equally diffused through the air of a room; it is very rapidly got rid of by opening AvindoAvs, and in this respect differs from the organic matter, and probably from the watery vapour ; neither appears to diffuse rapidly or equably through a room. The amount of carbon dioxide is often much greater than in the above in- stances. In a boys' school, with 69 cubic feet per head, Roscoe found 3*1 parts of C02 per 1000. In one-roomed houses in Dundee 3*21 per 1000 was found as a maximum by Carnelley, Haldane, and Anderson; this was 2*63 above the external air. In a schoolroom, naturally ventilated, with an average of 168 cubic feet per head, the mean C02 was L86 and the maxi- mum 3*78 ; in another, with the same space, but mechanically ventilated, the average was L23 and the maximum 1*96. In the Dundee Eoyal Infirmary (space per head from 1034 to 3182) the C02 ranged from 0*41 to 0*78, or a range of respiratory impurity between 0*06 and 0*37. In a horse stable at the Fjcole Militaire the amount was 7 per 1000. At Hilsea, with a cubic space of 655 cubic feet per horse, the amount was 1*053 ; and in another stable, with 1000 cubic feet per horse, only 0*593 per 1000 (de Chaumont). Marcher found 8-5 in a stable in Gottingen, and no less than 17'07 in a byre. F. Smith has shown that the carbon dioxide determinations in stables are greatly influenced by the amount of ammonia in the air interfering with the reaction, thus indicating a factitious purity of atmosphere. The amount of water given off to the air by respiration of course varies K 146 AIR. with the temperature and condition of humidity of the inspired air, as Avell as with the size of, and Avork being done by, each individual; but as an average for tAventy-four hours, the amount may be taken as being 10 ounces, or 284 grammes. To this must be added some 20 ounces more of moisture given off by the skin. This is equivalent to about 550 grains per hour. If Ave assume the average temperature of occupied rooms to be 15°*6 C. ( = 60° F.), this means that enough moisture is given off by the human body, in repose, every hour sufficient to saturate 90 cubic feet of air. It is this tendency to become saturated with moisture from the lungs and skin that makes the air of crowded rooms so uncomfortable. Carnelley's experiments sIioav that for every part of carbon dioxide found in the air, 2*7 volumes, or 1*1 part by weight, of moisture have been given off by each person inhabiting the room. The organic matters contained in expired air are small in quantity and of unknoAvn nature. If a large quantity of such air be draAvn through distilled Avater, or if its moisture be condensed by cold, the liquid thus produced contains nitrogenous matter, has a peculiar, unpleasant odour, and usually soon putrefies. This organic matter is apparently partly suspended, and is made up of small particles of epithelium and fatty matters detached from the skin and mouth, and partly of an organic vapour from the lungs and mouth. The organic matter from the lungs, Avhen draAvn through sulphuric acid, darkens it; through permanganate of potash, decolourises it; and through pure water, renders it offensive. Collected from the air by con- densing the watery vapour on the sides of a globe containing ice, it is found to be precipitated by nitrate of silver, to decolourise potassium permanganate, to blacken on platinum, and to yield ammonia. It is therefore nitrogenous and oxidisable. It has a very foetid smell, and this is retained in a room for so long a time, sometimes for four hours, even Avhen there is free ventilation, as to show that it is oxidised sloAvly. It is probably in com- bination with water, for most hygroscopic substances absorb it largely. It is absorbed most by wool, feathers, damp walls, and moist paper, and least by straAV and horse-hair. The colour of the substance influences its absorption in the following order:—black most, then blue, yelloAv, and white. It is probably not a gas, but is molecular, and floats in clouds through the air, as the odour is evidently not always equally diffused through a room. In a room, the air of Avhich is at first perfectly pure, but is vitiated by respiration, the smell of organic matter is generally perceptible when the carbon dioxide reaches 0*8 per 1000 volumes, and is very strong when the carbon dioxide amounts to 1 per 1000. Carnelley, Haldane, and Anderson found that there Avas a general rela- tionship, so that a high carbon dioxide is, as a rule, accompanied by a high organic matter, and vice versd, although this is by no means always the case. When the air of inhabited rooms is drawn through pure Avater, and the free ammonia got rid of, distillation with alkaline permanganate, by the method of Wanklyn, gives a perceptible quantity of " albuminoid ammonia." In a bed-room at 9 p.m., A. Smith found 0*1901 milligramme in 1 cubic metre of air; at 7 a.m. there were 0*3346 milligramme in each cubic metre. The average of eight observations in the external air (at Portsmouth) gave 0*0935 of free ammonia and 0*0886 of albuminoid ammonia in milli- grammes per cubic metre. In the Portsmouth General Hospital the free ammonia Avas as high as 0*855, and the albuminoid 1*307. The Dundee experiments, already cited, state the organic matter in vols. of oxygen required to oxidise it per 1,000,000. This is equal to c.c. per cubic metre, each c.c. of oxygen weighing 1*13 of a milligramme. The NATURE OF THE ORGANIC MATTER IX EXPIRED AIR. 147 results are much higher than those of previous observers, the mean oxygen for organic matter in the external air in the toAvn being 8-9, and in the suburbs 2*8 vols, per 1,000,000; they Avould equal 12*7 and 4 milli- grammes respectively. In dAvellings it Avas found to increase, though not to the marked extent that Avas observed in bacteria, but the increase Avas suffi- ciently proportionate to the carbon dioxide to support the vieAv that they are generally coincident, although varying much in individual cases. On the other hand, there seems little relation betAveen the carbon dioxide and the number of micro-organisms. In 1888, BroAvn-Sequard and d'Arsonval reported, as the result of repeated experiments, that the condensed liquid from expired air contains a volatile poison resembling a ptomaine; and if a f eAV cubic centimetres of this liquid be injected into rabbits they rapidly die. Earlier observers had obtained similar results by enclosing animals in glass cases, absorb- ing the carbon dioxide produced, and supplying oxygen: yet death ensued. The experimental results of Hermann, Dastre, Loye, and others are suggestive of the condensed fluid being Avithout any toxic qualities. Leh- mann and Jessen state that neither the condensed vapour of expired air nor its distillate, Avhen injected either subcutaneously or into the peritoneal cavity of rabbits, has any effect upon their health. They also have shown that individuals can inspire with impunity air that has passed through the condensed vapour of expiration. According to them, no analytical methods at i;heir disposal could detect the presence of poisonous alkaloids in the Avater condensed from expired air : it contains, hoAvever, traces of ammonia, smell portions of organic matter, some hydrochloric acid, and yields a peculiar odour on being heated. On the other hand, Merkel has published an account of experiments Avhich appear to be inconsistent Avith the belief that no volatile poison, other than carbon dioxide, is present in expired air. The more recent investiga- tions upon this point in this country, notably by Haldane and Smith at Oxford, indicate that the results by both the injection and ventilation methods of BroAvn-Sequard, d'Arsonval, and Merkel must be capable of some other interpretation than that expired air contains organic matter Avhich is of the nature of a volatile poison. Their chief conclusions are to the effect that (1) the immediate dangers from breathing air highly vitiated by respiration arise from the excess of carbonic acid and deficiency ■of oxygen, and not from any special poison; (2) that any hyperpnoea which ensues is due to excess of carbon dioxide, and not to the corresponding •deficiency of oxygen; the hyperpnoea usually appears Avhen the carbon dioxide is present to the extent of from 3 to 4 per cent.; (3) that the frontal headache so commonly produced by vitiated air is due to the excess of carbon dioxide; (4) that hyperpnoea from defect of oxygen begins to be appreciable when the oxygen in the air breathed has fallen to a point Avhich appears to differ in different individuals. Very similar conclusions have been formulated by Bergey, Weir Mitchell, and Billings as the result of their inquiry into "the composition of expired air and its effects upon animal life." They believe that the discomfort produced by croAvded, ill-ventilated rooms in persons not accustomed to them is not due to the excess of carbon dioxide, nor to bacteria, nor, in most cases, to dusts of any kind. The two great causes of such discomfort, though not the only ones, are excessive temperature and unpleasant odours. These odours, which are perceptible to most persons on passing from the outer air into a crowded unventilated room, may be due in part to volatile 148 AIR. products of decomposition contained in the expired air of persons having decayed teeth, foul mouths, or certain disorders of the digestive apparatus, and in part to volatile fatty acids produced from the excretions of the skin, and from clothing soiled Avith such excretions. The direct and indirect effects of odours of various kinds upon the comfort, and perhaps also upon the health, of men are probably more considerable than are indicated by any tests noAV knoAvn for determining the nature and quantity of the matters- wliich give rise to them. Though the matter is one which still requires more elucidation, still the weight of evidence is greatly against the older view that the so-called organic matter of expired air possesses any toxic properties, but much in favour of the belief that it is the excessive presence of carbon dioxide and diminished amount of oxygen Avhich renders air vitiated by respiration so hurtful. DISEASES PRODUCED BY IMPURITIES IX AIR. As possible and actual causes of diseased conditions, the impurities present in the air may be considered as to whether they exist (1) in the form of dust or particulate matter from fields, rooms, mines, or workshops; (2) in the form of gases or volatile effluvia arising from factories, drains, sewers,. graveyards, or brickfields; (3) in the form of products of normal respiration and perspiration. Effects of Dust and Particulate Matter.—The effect which is produced on the respiratory organs by substances inhaled into the lungs has long been known. Ramazzini and several other writers in the last century, and Thackrah more than fifty years ago in this country, directed special atten- tion to this point, and since that time a great amount of evidence has accumulated, which shows that the effect of dust of different kinds in the- air is a far more potent cause of respiratory diseases than is usually ad- mitted. Affections of the digestive organs are also caused, but in a much slighter degree. The respiratory affections are frequently recurring catarrhs (either dry or with expectoration)' and bronchitis, with subsequent emphy- sema, although this sequence appears from the figures given by Hirt to be not quite so frequent as was supposed, perhaps from the cough not being violent. Acute pneumonia, and especially chronic non-tubercular phthisis, are also produced. The suspended matters in the air which may produce these affections may be mineral, vegetable, or animal; but it would seem that the severity of the effects is chiefly dependent on the amount of dust, and on the_ physical conditions as to angularity, roughness, or smoothness of the particles, and not on the nature of the substance, except in some special cases. A large number of the unhealthy trades are chiefly so from this cause. That summer catarrh or hay fever is produced in many persons by the pollen from grasses, especially Anthoxanthum odoratum, trees or floAvers, is uoav generally admitted. It is also knoAvn that the spores of certain fungi may cause skin diseases in men, and that some forms of Tinea and also Favus are thus sometimes spread seems certain. The probable diffusion of malaria by a particulate organism is very generally recognised, while that the infective matters of such diseases as scarlet fever, small-pox,. measles, typhus, enteric fever, plague, pertussis, influenza, and others may in some cases reach the person through the medium of air, as well as by Avater or food, cannot be doubted. Whether some of these contagia can find nourishment, and thus grow in the air, is yet doubtful, but it seems clear, however, that they can retain the poAvers of growth for some time, a& EFFECTS OF DUST AND PARTICULATE MATTER. 149 shoAvn by the fact that the small-pox and scarlet fever poisons are able to infect the air of rooms for Aveeks and months. The specific poisons manifestly differ in the ease with Avhich they are oxidised and destroyed. The poison of typhus is very readily got rid of by free ventilation, by means of Avhich it must be at once diluted and oxidised, so that a few feet give, under such circumstances, sufficient protection. This is the case also Avith the poison of oriental plague, Avhile, on the other hand, the poisons of small-pox and scarlet fever Avill spread in spite of very free ventilation, and retain their poAver of causing the same disease for a long time. In the case of malaria the poison can certainly be carried for long distances, but Iioav far this is dependent upon the action of Avinds alone, apart from the aid of insects (mosquitoes), is at present uncertain. Some have supposed also that the poison of cholera can be diffused by the Avind 0Arer considerable areas, but the most recent observations on its mode of spread lead to the conclusion that the portability of the poison in this Avay has been greatly overrated, if it is not absolutely non-existent. But the specific poisons are not the only suspended substances which thus float through the atmosphere. There can be no doubt that while purulent and granular ophthalmia most frequently spread by direct transference of the pus or epithelium cells, by means of toAvels, &c, and that erysipelas and hospital gangrene, in surgical Avards, are often carried in a similar way, by dirty sponges and dressings, another mode of transference is by the passage into the atmosphere of disin- tegrating pus cells and putrefying organic particles, and hence the great effect of free ventilation in ophthalmia and in erysipelas and hospital gangrene. In these diseases great evaporation from the walls or floor seems in some way to aid the diffusion, either by giving a great degree of humidity or in some other Avay. The practice of frequently Avashing the floors of hospitals is Avell known to increase the chance of erysipelas, and this might be explained by the moisture and subsequent drying helping the development and subsequent dissemination of minute organisms. The effects upon health of air AAdiich is rendered impure by mineral dust and dust from fabrics is clearly sliOAvn by the experiences of miners, flock-dressers, paper-makers, feather-dressers, shoddy-grinders, Aveavers, Avire- grinders, masons, file-cutters, button-makers, and various other classes of artisans. The case of miners is particularly instructive. Writing, in 1862, upon the conditions under Avliich miners worked, Sir J. Simon states that the air of coal-mines, " besides being chemically insufficient for respiration, also carries Avith it into the miner's lungs more or less irritant material—material which, though the air Avere ever so Avell oxygenated, would itself tend to produce bronchitis—namely, soot, grit, and the acid fumes of combustion." He further goes on to show that at that time, Avith one exception, the miners in England as a class break down prematurely from bronchitis and pneumonia caused by the atmosphere in which they live and Avork. The one exception Avhich he gives is the case of the Durham and Northumberland colliers, AAdio, OAving to the mines in those counties being exceptionally well ventilated, do not appear to suffer from an excess of pulmonary disease, or do so only slightly. Other Avriters sIioav equally that, thirty years ago at any rate, the air of mines was bad not only from respiratory vitiation, but from suspended matter, and its effect on the health of the miners Avas correspondingly bad. In the present day, owing to sanitary legislation, the air of mines generally may be said to be fairly good. Ventilation is more or less efficiently carried 150 AIR. out, particularly in the mines of the Xorth of England, Avhich are less dusty, and at the same time more readily ventilated than those of the Midland counties and of South Wales. Statistics show that phthisis, contrary to general opinion, is not an excessively common disease among miners. The special decrease in diseases of the lungs among the South Stafford- shire colliers, following improved ventilation of the mines, has been pointed out by Underbill; Avhile Kasmyth, in a report upon the air of some Scotch coal-mines, considers that miners now have as good health, if not better, than above-ground labourers, at least so far as regards respiratory diseases. Arlidge, hoAvever, dissents from this opinion. Although, thanks to the introduction of efficient ventilation, of shortened hours of labour, and to the increased attention given to the hygiene of mines, the general health of miners is better than it Avas a generation ago, still much dust is present in the air of even the best managed mines, and the underground Avorkers not only necessarily breathe large amounts of it, but suffer from its effects. The extreme fineness of coal dust diffused in pit Avorkings is shoAvn by its liability to take fire and cause explosions. This dust when inspired enters Avithin the lung tissue, colours it both superficially and deeply in proportion to the amount and duration of its inhalation, and provokes subinflammatory lesions ending in fibrosis, arid marked by symptoms of chronic bronchitis and by dyspnoea. Usually a considerable time elapses before the lungs take much notice of the foreign matter. When cough is established, expectoration folloAvs. The curious delay in the appearance of expectoration, especially that of a purulent character, is a feature that helps to separate cases of dust-diseased lung from the tuber- culous. In like manner does the usual absence of haemoptysis. Again, lung lesions from dust are not provocative of fever, as is tuberculosis; diarrhoea is no feature of them, nor is aphonia. The pathology of the morbid changes in these cases is that of a sloAvly generated fibrosis of the lung; it is not peculiar to coal mining, but folioavs the continuous inhalation of other dusts besides that of coal. In the pottery trade all classes of workmen are exposed to dust, especially, however, the flat-pressers. So common is emphysema that it is called " the potters' asthma." So also among the china scourers ; the light siliceous dust disengaged in great quantities is the cause of much disease. The grinders of steel, especially of the finer tools, suffer perhaps the most of all from the effects of dust, though of late years the evil has been some- Avhat lessened by the introduction of wet-grinding in some cases, by the use of ventilated Avheel-boxes, and by covering the work Avith linen covers Avhen practicable. The Avearing of masks and coverings for the mouth appears to be inconvenient, otherwise there is no doubt that a great amount of the dust might be stopped by very simple contrivances. Button-makers, especially the makers of pearl buttons, also suffer from chronic bronchitis, and from the so-called fibroid phthisis. So also pin- pointers, some electro-plate Avorkmen, and many other trades of the like kind, are more or less similarly affected. In some of the textile manufactures much harm is done in the same Avay. In the carding rooms of cotton, and avooI, and silk spinners there is a great amount of dust and flue, and the daily grinding of the engines disengages also fine particles of steel. Since the cotton famine, a size com- posed in part of china clay (35-35 grains of clay in 100 of sizing on an average) has been much used in cotton mills, and the dust arising has produced injurious effects on the lungs of the weaver. EFFECTS OF DUST AND PARTICULATE MATTER. 151 In order to communicate the necessary amount of humidity, without which the warp thus sized Avith china clay could not be Avoven, of late years steam has been injected into the Aveaving sheds, so that the weavers, instead of breathing in dust, fill their lungs Avith moisture, and work all day in damp clothes, becoming very liable to bronchitis, &c, on leaving the over-heated factory. In flax factories a very irritating dust is produced in the process of hackling, carding, line preparing, and toAV-spinning. In shoddy factories, also, the same thing occurs. These evils appear to be entirely and easily preventible. In some kinds of glass-making, also, the workmen suffer from floating particles of sand and felspar, and sometimes potash or soda- salts. The makers of grinding-stones suffer in the same way; and children Avorking in the making of sand-paper are seriously affected, sometimes in a very short time, by the inhalation of fine particles of silica into the lungs. In making Portland cement, the burnt masses of cement are ground down, and then the powder is shovelled into sacks; the workmen doing this cough a great deal, and often expectorate little masses of cement. Some of them have stated that if they had to do the same Avork every day it would be impossible to continue it on account of the lung affection. Sir Charles Cameron has called attention to the fatal effects of vapours of silicon fluoride in making superphosphate; it forms a gelatinous deposit on the mucous membrane of the air-passages, and causes death by suffoca- tion. The makers of matches, who were exposed to the fumes of phosphorus, suffered formerly from necrosis of the jaAv, if there were any exposed part on which the fumes could act. This, hoAvever, is noAV obviated by the use of amorphous or red phosphorus, which is harmless. In making bichromate of potash, the heat and vapour employed carry up fine particles, Avhich lodge in the nose and cause great irritation, and finally ulceration, and destruction of both mucous membrane and bone. Those avIio take snuff escape this. The mouth is not affected, as the fluids dissolve and get rid of the salt. The skin is also irritated if the salt is rubbed on it, and fistulous sores are apt to be produced, No effect is noticed to be pro- duced on the lungs. Washing the skin with subacetate of lead is the best treatment. In the process of sulphuring vines the eyes often suffer, and sometimes (especially Avhen lime is used with the sulphur) decided bronchitis is produced. In some trades, or under special circumstances, the fumes of metals, or particles of metallic compounds, pass into the air. Brassfounders suffer from bronchitis and asthma as in other trades in which dust is inhaled; but in addition they also suffer from the disease described as " brassfounder's ague." It has been thought to have been produced by the inhalation of fumes of zinc oxide; the symptoms are tightness and oppression of the chest, with indefinite nervous sensations, followed by shivering, an indistinct hot stage, and profuse sweating. These attacks are not periodical. They are probably due to an admixture of zinc and copper poisoning. Coppersmiths are affected somewhat in the same way, by the fumes arising from the partly volatilised metal, or from the spelter (solder). Tinplate workers also suffer occasionally from the fumes of the soldering. Plumbers, also, are noAV and then affected by the fumes of solder, of 152 AIR. Avliich lead is a principal ingredient, as Avell as by handling the metal itself. Nausea and tightness of the chest are the first symptoms, and then colic and palsy. Manufacturers of AA-hite lead inhale the dust chiefly during the handling of the jars containing the converted metal—the carbonate—and during the process of crushing. Its subsequent grinding is done wet. House painters also inhale the dust of white lead to a certain extent, though in these, as in former cases, much lead is swalloAved from want of cleanliness of the hands in taking food. Workers in tobacco factories suffer in some cases, and there are persons who can never get accustomed to the Avork; yet with proper care and ventilation it appears that no bad effects ordinarily result. Workers in mercury, silverers of mirrors, and Avater gilders (men Avho coat metal with an amalgam of mercury and gold) are subject to mercurial- ismus. Electricity has rendered gilding Avith the aid of mercury to some extent obsolete; Avhile modern invention has replaced the older method of silvering mirrors by one largely devoid of its evils, namely, by precipitating metallic silver upon the surface of the glass from a tartrate of the metal. Workmen avIio use arsenical compounds, either in the making of wall papers or of artificial flowers, &c, suffer from slight symptoms of arsenical poisoning, and many persons Avho have inhaled the dust of rooms papered Avith arsenical papers have suffered from both local and constitutional effects. Arsenic has been detected in the urine of such persons. From an account of the diseases among Avorkmen in France employed in making patent fuel, a mixture of coal-dust and pitch, it appears that they suffer from melanodermy, cutaneous eruptions, and epithelial cancers, affec- tions of the eyes, ears, and nose; bronchitis with pulmonary pseudomelanosis; and gastro-entero-hepatic disorders. Hirt also mentions some of the diseases produced among Avorkmen by the various tar-products. Effects of Gases and Volatile Effluvia.—The evidence regarding the influence of gases and other emanations upon health is both indefinite and discursive. It -will, hoAvever, be most conveniently considered in the folloAv- ing manner:— Ammoniacal Vapours.—An irritating effect on the conjunctiva seems to be the most marked effect of the presence of these vapours. There is no evidence shoAving any other effect on the health. Hydrochloric Acid Vapours in large quantities are very irritating to the lungs; when poured out into the air, as was formerly the case in the alkali manufactures, they are so diluted as apparently to produce no effect on men, but they completely destroy vegetation. In some processes for making steel, hydrochloric, sulphurous and nitrous acids, and chlorine are all given out, and cause bronchitis, pneumonia, and destruction of lung tissue, as well as eye diseases. Carbon Bisulphide.—In certain processes in the manufacture of vulcanised india-rubber a noxious gas is given off, supposed to be the vapour of carbon disulphide. It produces headache, giddiness, pains in the limbs, formication, sleeplessness, nervous depression, and complete loss of appetite. Sometimes there is deafness, dyspnoea, cough, febrile attacks, and even amaurosis and paraplegia. The effects seem due to a direct anaesthetic effect on the nervous tissue. Carburetted Hydrogen.—A large quantity of carburetted hydrogen can be breathed for a short time,—as much, perhaps, as 200 to 300 volumes per 1000. Above this amount it produces symptoms of poisoning, headache, vomiting, convulsions, stertor, dilated pupil, &c. EFFECTS OF GASES AND VOLATILE EFFLUVIA. 153 Breathed in small quantities, as it constantly is by some miners, it has not been shown to produce any bad effects; but there, as in so many other cases, it is to be Avished that a more careful examination of the point Avere made. Without producing any marked disease, it may yet act injuriously on the health. Hirt says that cases of chronic poisoning are not un- common. Corfield has also noticed this. Carbon Monoxide.—Of the immense effect of carbon monoxide there is no doubt. Less than 3 vols, per 1000 have produced poisonous symptoms, and more than 10 per 1000 is rapidly fatal to animals. It appears that the gas, volume for volume, completely replaces the oxygen in the blood, and cannot be again displaced by oxygen, so that the person dies asphyxiated ; but Pokrowsky has shown that it may gradually be converted into carbon dioxide, and be got rid of. It seems, in fact, as Hoppe-Seyler conjectured, to completely paralyse, so to speak, the red corpuscles, so that they cannot any longer be the carriers of oxygen. Observations sIioav that, in addition to loss of consciousness and destruction of reflex action, it causes complete atony of the vessels, diminution of the vascular pressure, and slowness of circulation, and finally paralysis of the heart. A very rapid parenchymatous degeneration takes place in the heart and muscles generally, and in the liver, spleen, and kidneys. Hirt says that at high temperatures (25° to 32° C. = 77° to 90° F.) it produces convulsions, but not at low temperatures (8° to 12° C. = 46°to54° F.). Two cases of poisoning by this gas occurred at Leeds in 1889 : the men Avere found dead in a cabin, Avhere there had been an escape of " water gas," Avhich contains from 30 to 40 per cent, of carbon monoxide. The gas being inodorous and unirritating, produces its poisonous effects insidiously, one of the early symptoms being loss of the power of movement, or even of the desire to make any exertion. It is stated that one part per 1000 of CO, corresponding approximately to 2*5 per 1000 of water gas, is injurious. Water gas being inodorous, requires to be " odorised " to be used with safety : mercaptan and pyridine are employed for this purpose. Many cases of water-gas poisoning, due to carbon monoxide, have lately been reported in America. Hydrogen Sulphide.—The evidence Avith regard to this gas is contra- dictory. While dogs and horses are affected by comparatively small quanti- ties, and suffer from purging and rapid prostration, men can breathe a larger amount. When inhaled in small quantities, and continuously, it has appeared in some cases harmless, in others hurtful. Thackrah, in his inquiries, could trace no bad effects. It is said that in the Bonnington chemical works, Avhere the ammoniacal liquor from the Edinburgh gasAvorks is con- verted into sulphate and chloride of ammonium, the workmen are exposed to the fumes of ammonium and hydrogen sulphides to such an extent that coins are blackened; yet no special malady is known to result. The same observations have been made at the Britannia-metal works, where a super- ficial deposit of sulphide is decomposed Avith acids. Hirt has no doubt of the occurrence of chronic poisoning among men Avho work among large quantities of the gas. The symptoms are chiefly weakness, depression, perfect anorexia, slow pulse, furred tongue, mucous membrane of the mouth pale, as is also the face. Sometimes there is a furunculoid eruption on different parts of the body. In some cases there are vertigo, headache, nausea, diarrhoea, emaciation, and head symptoms. He notices differences of susceptibility, Avhich is also sometimes increased with custom. 154 AIR. So large a quantity of hydrogen sulphide is given out from some of the salt marshes at Singapore that slips of paper moistened in acetate of lead are blackened in the open air; yet no bad effect is found to ensue. On the other hand, some of the Avorst marshes in Italy are those in Avhich hydrogen sulphide exists in large quantity in the air; and it has been sup- posed that the highly poisonous action of the marsh gas is partly OAving to the sulphuretted hydrogen. Again, in the making of the Thames Tunnel, the men were exposed to hydrogen sulphide, which Avas formed from the decomposition of iron pyrites: after a time they became feeble, lost their appetites, and finally passed into a state of great prostration and anaemia: several died. Nor, so far as is knoAvn, Avas there anything to account for this except the presence of this gas. Roburite, a mixture of di-nitro-benzene, chloro-nitro-benzene, and ammonium nitrate, has lately been used as an explosive in coal-mines, as it has the advantage of not producing any flame such as might ignite coal dust, or any inflammable gas in the mine. Miners making use of this compound have been found to suffer from pains in the head and stomach, difficulty of breathing on exertion, and loss of muscular poAver; with, in severe cases, blueness of lips, high-coloured urine and loss of consciousness. These symptoms may be acute or chronic : they are characteristic of nitro-benzene poisoning. Other persons, not handling the roburite cartridges, but exposed to its fumes, suffered from headache, tightness across the forehead, loss of muscular power, drowsiness, and occasionally vertigo, folloAved by vomiting. Carbon monoxide is produced by its explosion, and every care should be taken to remove the fumes by thorough ventilation. SomeAvhat similar symptoms, but especially marked cyanosis, have been noted in connection Avith the manufacture of the " Sicherheit explosive." Nitro-benzol, formed by the action of nitric acid upon benzol and used in some manufactures, is closely allied to the foregoing. long exposure to its vapour produces stupor; if the vapour is inhaled in a concentrated form, the droAvsiness passes in a short time into complete coma. The mind remains clear until the stupor suddenly comes on, when the insensibility is usually complete. Death frequently ensues in a feAv hours. Letheby, avIio had considerable experience of these fumes, attributed the symptoms which they produced to the conversion Avithin the body of nitro-benzol into aniline, but this vieAv has not been confirmed by experimental facts. Myrbane is a form of nitro-benzol, having only slightly poisonous properties, unless taken or inhaled in large amount. OAving to its bitter- almond odour and taste, it is used as a scent for soaps and pomades, also to- give flavour to SAveetmeats. Sulphur Dioxide.—The bleachers in cotton and Avorsted manufactories, and storers of Avoollen articles, are exposed to this gas, the amount of which in the atmosphere is, however, unknoAvn. The men suffer from bronchitis, and are frequently salloAv and anaemic. When sulphur dioxide is evolved in the open air, and therefore at once largely diluted, as in copper smelting, it does not appear to produce any bad effects in men, and indeed persons living in volcanic countries have some- times a notion that the fumes of this gas are good for the health; de Chaumont Avas told so by the people in the neighbourhood of Vesuvius. When, hoAvever, it is Avashed doAvn Avith rain, it affects herbage, and, through the herbage, cattle; it is then said to cause affections of the bones, falling off of the hair, and emaciation. EFFECTS OF INDUSTRIAL GASES. 155 A table (from Lehmann) is given beloAv, which shoAvs the concentrations at Avhich some important industrial gases occasion injury to health. Concentrations Concentrations Concentrations which occasion which rapidly bearable for 30 to only trifling symp- Authorities. cause dangerous 60 minutes without toms after an injury. grave effects. action of some hours. Hydrochloric acid, 1*5 to 2 per 0-05 to 0-1 0-01 per 1000 Matt, Disserta- 1000 per 1000 tion Wurzburg, 1889. Sulphur dioxide, 0*5 per 1000 0'05 or less per 1000 Ogata, Arehiv. f. Hyg., iii. Carbon dioxide, . About 30 per cent. 6 to 8 per cent. 1 to 2 per cent. Emmerich and Herter, Zeit.f. phys. Chcmie, Ammonia, . 2*5 to 4*5 per 1000 0-3 per 1000 0-1 per 1000 Matt, loc. cit. Chlorine and Bronrine, . 0-04 per 1000 0-004 per 1000 0-001 per 1000 Matt, loc. cit. Iodine, 0-003 per 1000 0-005 per 1000 Matt, loc. cit. Hydrogen sul- phide, 0-5 per 1000 0-2 per 1000 0-1 per 1000 Lehmann, Zeit. Carbon di-sul- f. Hyg., xiv. phide, . 0-01 per 1000 0-002 per 1000 0-001 per 1000 Lehmann, Be-richt der Bay. Akad.,M.a,xc\x^, 1888; alsoArch. f. Hyg., xv. Carbon monoxide, 2-3 per 1000 0-5 to 1 per 1000 0-2 per 1000 Max Gruber, Arch. f. Hyg., ii. Effects of Effluvia from Brickfields and Cement Works.—The fumes from burning bricks differ in composition according as to whether they are burnt in kilns or clamps. In kiln burning, the bricks are burnt by the aid of coal, no combustible material being mixed Avith the bricks. In clamp burning, the green bricks are mixed Avith a small proportion of ashes or other debris, and then arranged in layers alternating Avith breeze, so as to form a quadrangular pile. The breeze is set alight by means of small Avood and coal fires. Clamp burning is distinctly offensive, as, in addition to the ordinary gases of combustion, certain pyroligneous matters are emitted Avhich have an intensely disagreeable odour; these objectionable effects mainly result from, the use of household refuse in the construction of the clamps. The effluvia from brick clamps and kilns are usually acid, irritat- ing and injurious to vegetation. Clamp burning should not be permitted in populous neighbourhoods. Kiln burning, if carried out in Avell constructed kilns provided Avith a long chimney shaft, can be conducted Avith but little offence. The manufacture of the so-called Roman cement, made from the septaria nodules found in the London clay, creates little nuisance, as the stones are calcined in open kilns like lime kilns. The manufacture of Portland cement is less satisfactory. This cement is made from a mixture or Avet mud com- posed of chalk and clay, and the chief nuisance arises during the burning of this mixture, Avhereby large quantities of carbon dioxide, carbon monoxide, hydrogen sulphide and volatile cyanides are emitted. The evolution of cyanides is particularly intense AAdien the clay used contains much nitrogenous 156 AIR. matter. Experience sIioavs that the emanations from open kilns in the manufacture of Portland cement are clearly injurious to health. The fumes should always be discharged from a tall chimney, not less than 150 feet high. Effects of Effluvia from Offensive Trades.—The chief industries in AAdiich offensive effluvia are generated are:—Pig, horse, and coav keeping, tanning and leather dressing, glue or size making, fell-mongering, the manu- facture of oxalic acid, paper and Avood pulp, also the making of sal- ammoniac and coal gas, the distillation of tar and of palm oil, also the manufacture of carbolic acid, alkali, salt, sulphuric acid, picric acid, and the various aniline dyes. In the majority of these trades large quantities of very disagreeable vapours are constantly produced, Avhich often spread for long distances, and are at the same time most offensive. In the case of businesses involv- ing the keeping of animals, impregnation of the atmosphere with ammonia is the chief offence. In tanning and leather dressing, glue or size making, and fell-mongering, ammonia and other products of the decomposition of animal matters generally are objectionably obvious. From india-rubber factories the chief smell is a peculiar india-rubber odour, together with an odour of tar oil and sulphuretted hydrogen. The making of oxalic acid from sawdust entails the evolution of very acid and irritating fumes; similarly, in the making of paper and Avood pulp, a peculiar and offensive odour of an indefinite nature is a constant feature. The presence of alkaline sulphide vapours is the chief objection to the making of sal-ammoniac, coal gas, carbolic acid, and the distillation of tar. The extremely irritating acrolein vapours are the product of linoleum factories, and distilleries of palm oil, "foots," and other kinds of grease. From alkali Avorks, the acid fumes produced are sulphuric acid, sulphurous acid, nitric acid, various other noxious oxides of nitrogen, sulphuretted hydrogen and chlorine. In the case of the making of sulphuric acid, the chief effluvia are caused by the escape of sulphurous acid and the higher oxides of nitrogen; Avhile fumes of hydrochloric and sulphurous acids largely result from the manu- facture of salt, and the heavy odour of essence of myrbane Avith nitrous acid is the chief effluvium from the making of picric acid and the aniline colours. Although these industrial gases frequently constitute a nuisance, it is difficult in the greater number of instances to bring forward any positive evidence of insalubrity. The odours, hoAvever, in most cases are, so bad that rules have to be enforced to secure the conveyance in covered carts or receptacles, of all offensive matters in or about the business premises. Similarly, in order to prevent nuisance from the vapours given off in boiling processes, all such operations need to be conducted in closed vessels, each having a pipe to lead the steam into a furnace flue. In other cases, the arrest of offensive gases is secured by condensation in a special apparatus, or their absorption is effected by lime and other chemical means. Effects of Effluvia from Sewers and House Drains.—Cases of asphyxia from hydrogen sulphide, ammonium sulphide, carbon dioxide, and nitrogen (or possibly rapid poisoning from organic vapours), occasionally occur both in sewers and from the opening of old cesspools. In a case at Clapham, the clearing out of a privy produced in twenty-three children violent vomiting and purging, headache and great prostration, and convulsive twitching of the muscles. Tavo died in tAventy-four hours. These are instances of mephitic poisoning in an intense degree; but AAdien men have breathed the air of a neAvly-opened drain in much smaller EFFECTS OF EFFLUVIA FROM SEWERS AND HOUSE DRAINS. 157 amounts, marked effects are sometimes produced; languor and loss of appetite are followed by vomiting, diarrhoea, colic, and prostration. The effluvia which have produced these symptoms are usually those arising from a drain which has been blocked for some time. When the air of sewers penetrates into houses, and especially into bed-rooms, it certainly causes a greatly impaired state of health, especially in children. They lose appetite, become pale and languid, and suffer from diarrhoea; older persons suffer from headaches, malaise, and feverishness; there is often some degree of anaemia, and it is clear that the process of aeration of the blood is not perfectly carried on. In some cases decided febrile attacks lasting three or four days, and attended Avith great headache and anorexia, have been knoAvn. Houses into which there has been a continued escape of sewer air have been so notoriously unhealthy that no persons would live in them, and this has not been only from the prevalence of fever, but from other diseases. The effect on the men who work in sewers Avliich are not blocked, or temporarily impure from exceptional disengagement of hydrogen sulphide from any cause, has been subject to much debate. The air in many sewers in London is not very impure; the analyses of Letheby and Miller, and those of Carnelley, have shown that generally the amount of carbon dioxide is very little in excess of that in the external air, and that there is hardly a trace of hydrogen sulphide or of foetid organic effluvia. The air in the house drains is often, in fact, more impure than that of the main seAvers. This is the case also in other places, and is to be accounted for by the numerous openings in the sewers, by the porosity of the Avails, by the continual ventilation produced by the air being drawn into houses, and by the amount of water in the seAvers being often so great, and its Aoav so rapid, as to materially lessen deposits and other sources of generation of gas. The evidence is, on the Avhole, opposed to the view that seAver-men suffer in health in consequence of their occupation. A more recent inquiry conducted into the health of the seAver-men in London did not detect any excess of disease among them, and in Liverpool also the sewer-men are said to have good health. The workmen employed at the various sewage outfalls, who, though not in the sewers, breathe the effluvia arising from the settling tanks, do not find it an unhealthy occupation. It does not appear, therefore, that at present the workmen connected Avith fairly ventilated seAvers shoAV any excess of disease; at the same time, it must be allowed that the inquiry has not been very rigorously prosecuted, and that the length of time the men work in sewers, their average yearly mortality, discharge from sickness, loss of time from sickness, and the effect produced on their expectation of life, have not been perfectly determined. The air of sewers passing into houses aggravates most decidedly the severity of the exanthemata, more especially such diseases as erysipelas, hospital gangrene, and puerperal fever; it has probably an injurious effect on all diseases. That pneumonia may be connected with effluvia from seAvers and house drains was shoAvn in the epidemic at Middlesborough, Avhere Ballard found good reason for attributing considerable influence to defective drainage as an agency in the incidence of the disease. Three diseases in particular have been supposed to arise from the air of sewers and faecal emanations, viz., diarrima, enteric fever, and diphtheria. With regard to the production of diarrhoea from faecal emanations, it Avould seem that the autumnal diarrhoea of this country is intimately con- nected Avith the temperature of the soil, and usually commences when this 158 AIR. reaches 56° F. at a depth of 4 feet from the surface. It is worst in the badly seAvered districts, and is least in Avell-drained districts, and in wet years. It has been checked in London by a heavy fall of rain. All those points seem to connect it with faecal emanations reaching a certain rapidity of evolution in consequence of high temperature, deficient rain, and perhaps relative dryness of the atmosphere. At the same time, there is a connection betAveen this disease and impure Avater. It may own a double origin, and in a dry season both causes may be in operation. That enteric fever may arise from the effluvia from seAvers is a doctrine still generally held in this country, but is supported by imperfect evidence. There are several cases on record in Avhich this fever has constantly prevailed in houses exposed to sewage emanations, either from bad sewers or from want of them, and in which proper sewerage has completely removed the fever. Many of these occurred before the water-carriage of enteric fever was recognised, arid it is open to argument whether the amelioration in health, which followed the introduction of well constructed seAvers and drains in these cases, was not due to the removal of sources of pollution to local water supplies rather than to the removal of facilities for the entrance of sewer air and gas into the houses. In other cases Avhere stress has been laid upon the influence of sewer air and sewer gases escaping into dwellings as the probable cause of subsequent cases of enteric fever occurring therein, it has been frequently overlooked that concurrent circumstances often were an intermittent water-supply, and infection of the drinking Avater by specifically tainted matter sucked up into cisterns or pipes from the trapping bends of faultily planned and constructed drains. The well-known outbreak of enteric fever at Caius College, Cambridge, investigated by the late Sir G. Buchanan, was traced by him to a broadly similar cause. The outbreak in question was mainly limited to a particular section of the College, known as Tree Court: and owing to the extraordinary arrangement of the water-supply and Avater-closets in this part of the College, the system of pipes for the water-supply became, at times, not only the means of ventilating the sewers and drains into the building, but were also the means by which, if a certain trap happened to be full of excrement, that excrement was sucked up into the water-main of Tree Court, and subsequently distributed with the water throughout the Court. In this case, the entrance of excretal matter into the water-supply was surely an etiological factor of greater importance than the escape of seAver gas or air into the building 1 The view that there is a connection between sewer air and enteric fever has been much combated by German writers, notably by Soyka and Nageli. Their contention is that enteric fever is not due to the influence of sewer air, because it is rare that such air gets into houses; and experiments are cited to prove this. It is, hoAvever, admitted and demonstrated by Soyka, in the table which he gives, that a similar improvement in the health of towns has followed the introduction of proper drainage in the cities of Germany as has been observed in this country. This he attributes to the cleansing of the soil and local sources of water-supply by the removal of seAvage matter. Nageli positively denies the possibility of specific disease being conveyed through emanations from drains or cesspools. Although it seems difficult not to admit that the effluvia from sewers and drains may predispose towards the incidence of enteric fever, there are yet some remarkable facts Avhich can be cited on the other side. Thus it has been repeatedly denied that enteric fever is more common among sewer-men than others, and later inquiries among the seAver-men of RELATION OF SEWER AIR TO SPECIFIC DISEASES. 159 London seem to bear out the assertion. But, as already stated, the air of London seAvers is really very pure; and some of the men may be protected by previous attacks, for enteric fever is a most common disease among the poorer children in London. The evidence is very strong that the men employed at the sewage tanks and on the seAvage farms, and their families, do not sIioav an unusual amount of enteric fever; nor do the persons living in adjacent houses. Noav, if sewage emanations can cause enteric fever, it might be expected that we should by this time have had plenty of evidence of this special effect in connection with seAvage farms generally. The possibility that the adult persons submitted to seAvage emanations may have had enteric fever in early life, and are therefore insusceptible, may explain some cases of escape, even Avhen faecal emanations are con- stantly breathed. But it Avould be impossible to extend this argument to the cases of immunity in children, unless Ave suppose that enteric fever in children is constantly overlooked, and is as common as measles, which seems unlikely. There are, hoAveArer, still some other difficulties. The investigations of AndreAves and Parry LaAvs show that seAvage, even in the absence of the norurd micro-organisms which it contains, is clearly an unfavourable medium for the groAvth of the enteric fever germ, and that sewer air is by no means rich in micro-organisms, and is particularly poor in those forms which are most commonly met Avith in sewage itself. From the inquiries of these observers and of others, it would appear that, so far as bacterio logical analysis goes, there is no ground for believing that sewer air plays any part in the conveyance of enteric fever; but are the conditions under which the bacteriological examinations of seAvage and of sewer air are made .such a to give us absolute assurance on these points? In spite of its apparent bacteriological innocuousness, no one entertains the least doubt that r-eAver air is a constant source of ill-health, and if this is not to be referred to micro-organisms, to what may it be ascribed? There is undoubtedly a poisonous agency at work when sewer gas is inhaled, which, though it may not directly act, yet so prepares the soil that the system is unable to resist the invading organism when it comes. The spread of diphtheria has been ascribed to the pollution of air by emanations from sewers, and certainly in many outbreaks there has been a connection between the sanitary condition of a district and the incidence of the disease; houses or groups of houses to which sewer gas has gained access through faulty traps having especially suffered. Direct proof of such a causal connection has not yet been afforded, and it must be admitted that diphtheria has up to recent years been a disease of country districts rather than of regularly seAvered towns ; at the same time, if th • seAverage arrangements are defective, allowing the escape of seAver air into dwellings, especially sleeping-rooms, it is a priori probable that the sewer gases, by giving rise to a relaxed and unhealthy condition of the mucous lining of the throat, may increase the liabihty to attack by diphtheria in the event of exposure to specific infection. In connection with the possible relation of sewer air to specific diseases, some very original investigations by Alessi are of value. He has noted the effect of inhaling sewer air and the gases from putrefying materials upon animals; rats, rabbits, and guinea-pigs being selected. After exposure to seAver air, Avliich Avas accomplished by placing them in a box with a perforated bottom communicating directly with a drain, they were inocu- lated with a small quantity of only a slightly virulent cultivation of the 160 AIR. enteric fever bacillus, Avhilst other animals Avere similarly treated, except that they Avere not compelled to inhale seAver air, but Avere kept in their ordinary surroundings. Rats, after breathing this more or less foul air, began to lose their vivacity, and after a time greAV thin, although they ate voraciously, and out of forty-nine Avhich Avere inoculated with the enteric fever bacillus, thirty-seven died, exhibiting the typical symptoms of enteric fever infection. Of those forty-one rats, hoAvever, which, although infected with enteric fever, had not breathed seAver air, only three succumbed. Thus, the inspiration of drain air had so far predisposed these animals to infection from enteric fever, that a small dose of an almost harmless growth of this organism proved very fatal to them. Guinea-pigs and rabbits, exposed in like manner to gases from materials in a condition of active decomposition, also acquired a predisposition to typhoid infection, for out of seventy-two guinea-pigs inoculated, fifty-seven died, Avhilst not one of those treated with the infective agent of enteric fever in ordinary surroundings succumbed. Similarly, every one of eleven rabbits, treated and exposed to seAver air, died, but not one of the inoculated animals when kept in fresh air. Alessi also found that the inhalation of gases from putrid substances enabled a small dose of a Aveakened culture of the B. coli communis, normally present in the intestine, to produce fatal results when purposely introduced into the animals thus exposed. He also ascertained that it Avas during the first two Aveeks of exposure to noxious gases that the animals were most easily predisposed to enteric fever infection, for no less than 90 per cent, of all the animals inoculated during the first fortnight died, whilst 76 per cent, succumbed of those inoculated in the third week. This fact, Alessi says, may partly explain how it is that some people avIio habitually breathe contaminated air do not appear to suffer any evil results, having gradually in course of time become accustomed to it, whilst a stranger exposed to the same conditions, without previous experi- ence, may suffer very severely. The personal factor, or degree of pre- disposition, hoAvever, whilst varying in different animals, would also vary in different people. These investigations and results, without being considered conclusive, must be regarded as a noteAvorthy and an important contribution to our knowledge of the distribution of disease, and in some respects afford- ing a remarkable experimental confirmation of the wisdom of a policy of sanitation which is dictated equally by instinct and intuition. Effects of Emanations from Faecal Matter thrown on the Ground.— Owing, doubtless, to the rapid movement of the air, there is no doubt that the excreta of men and animals throAvn on the ground and exposed to the open air are less hurtful than sewer air, and probably in proportion to the dilution. When there are accumulations in close courts, small back-yards, &c, the same effects are produced as by seAver air. When faecal matters are used for manure, and are therefore speedily mixed with earth, they seldom produce bad effects. OAving, doubtless, to the great deodorising and absorb- ing poAvers of earth, effluvia soon cease to be given off. An instance is, however, on record, in which two cases of enteric fever were supposed to arise from the manuring of an adjacent field. Clouston has also shown by evidence, which seems very strong, that dysentery Avas produced in an asylum by the exhalations from sewage, which Avas spread over the ground (a stiff brick clay subsoil) about 300 yards from the asylum. The case seems a very convincing one, as the possibility of the action of other causes (impure water, bad food, &c.) was excluded; but it appears to have been due to the improper treatment of the sewage, Avhich was alloAved to become EFFECTS OF EFFLUVIA FROM SEWAGE. 161 putrid and form a filthy morass. It is stated in some works that disease is frequently produced by the manuring of the ground, but there seems to be no satisfactory evidence of this. Carpenter has shown, from the history of the Beddington sewage farm, that no harm to the neighbourhood had accrued from the irrigation with the Croydon sewage during tAventy years, and subsequent experience has only confirmed his statements. It has been said that if the sewage matter can be applied Avhile perfectly fresh to the ground, no harm results; but if decomposition has fully set in, it is not so completely deodorised by the ground. In China, Avhere faecal matter is so constantly applied in agriculture, the air is often filled Avith very pungent effluvia, yet no bad effect is produced. Effects of Emanations from Streams polluted by Faecal Matter.—The evidence on this point is contradictory. Parent-Duchatelet investigated the effect produced on the health of the inhabitants of the Faubourg St Marceau, in Paris, by the almost insupportable effluvia arising from the Bievre, Avliich received a large portion of the sewage of the quarter. He asserts that the health was not at all damaged, though he admits that there is truth in the old tradition at the Hotel Dieu, that the cases from St Marceau were more severe than from any other place. The opinion of the late W. Stokes, as to the slight influence of the effluvia from the river Liffey on the health of the residents along the quays in Dublin, is to the same effect. M'Wilham found that the emanations from the Thames had no deleterious effect on the health of the Custom-House men employed on the river. The amount of diarrhoea was even below the average. Sir R. Rawlinson states that a careful house-to-house visitation had been made in some of the Avorst districts of Lancashire (in Manchester, on the banks of the Medlock, for instance) without finding any great excess of disease. On the other hand, in the reports of Sir Lyon Playfair is some strong evidence that the general health of the people suffered from the emanations of the putrid streams of the Frome and the tributaries of the Irk and Med- lock ; that they Avere pale, in many cases dyspeptic; that fevers (enteric) prevailed on the banks is asserted by some observers, but rather doubted by others; but none seem to have any doubt that the fevers when they occurred were much worse. Cholera in Manchester Avas severe along the banks of some of these streams, but that was probably due to the water being drunk. It is very likely that the discrepancy of evidence may arise from the amount of water which dilutes the faecal matter being much greater in some cases than in others. In the case of the Thames, the dilution was after all very great, and this was the case, in part at any rate, in the Bievre, as the stream was in some places 6 and 7 feet deep. The evaporation from such a body of water, hoAvever offensive it may be, must be a very different thing from the effluvia coming off from the masses of organic matter laid bare by the almost complete drying up of streams into which quantities of faecal matter are discharged. When sewage matter is poured into the sea, and washed back by the tide, it becomes a source of danger. It was remarkable in the evidence given before the Royal Commission on Metropolitan Sewage Discharge, 1882-84, how little direct proof of specific disease, due to the pollution of the Thames, Avas obtained, although there was no doubt about the production of nausea and diarrhoea, and other minor evils. Indeed, the Commissioners themselves had good proof of this, for, after a trip of inspection from Woohvich to Greenhithe in July 1884, L 162 AIR. three of them and their clerk Avere seized Avith griping pains and smart diarrhoea the same night, caused apparently by the offensive state of the river. Effect of Manure Manufactories.—The manure manufactories at present existing in this country do not appear to produce any bad effects. They are generally at some little distance from towns, and the effluvia are soon diluted. But if situated in toAvns they are nuisances, and may be hurtful. In 1847 evidence was given to show that a manure manufactory situated in Spitalfields, and about 100 feet from the Avorkhouse, caused bad diarrhoea Avhenever the wind bleAv in that direction. The cases of disease in the Avorkhouse infirmary also acquired, it is said, a malignant and intractable character. In France the Avorkmen engaged in the making of " poudrette " do not in any Avay suffer, except from slight ophthalmia. When the poudrette is decomposing, and large quantities are brought into small spaces, as on board ship, serious consequences may certainly result, the chief symp- toms produced being intense pain in the head and limbs, with vomiting, great prostration and diarrhoea. In bone manure factories it has been shown that arsenic is given off in the fumes in considerable quantity, arising from the use of impure sulphuric acid. Effects of the Air of Graveyards.—There is some evidence that the dis- turbance of even ancient places of sepulture may give rise to disease. Vicq d'Azyr refers to an epidemic in Auvergne caused by the opening of an old cemetery ; the removal of the old burial-place of a convent in Paris produced illness in the inhabitants of the adjoining houses. In India, the canton- ment at Sukkur Avas placed on an ancient Mussulman burial-ground, and the station was most unhealthy, especially from fevers. The effect of effluvia from comparatively recent putrefying human bodies has been observed by many Avriters. Rammazzini states that sextons enter- ing places where there are putrefying corpses are subject to malignant fevers, asphyxia, and suffocating catarrhs; and Tardieu has collected a very con- siderable number of cases, not only of asphyxia, but of several febrile affec- tions produced by exhumations and disturbance of bodies. The late Sir E. ChadAvick, and the General Board of Health, also summed up evidence, which showed that in churchyards thickly crowded with dead, vapours were given off which, if not productive of any specific disease, yet increased the amount both of sickness and mortality. In some instances, this might have been from contamination of the drinking water; but in other cases, as in the houses bordering the old city graveyards, where the water was supplied by public companies, the air also must have been in fault. In the houses which closely bordered the old city yards, which were croAvded with bodies, cholera was very fatal in 1849, and, according to some practitioners, no cases recovered. All other diseases in these localities Avere said to have assumed a very violent and unfavourable type. Hirt says, on the other hand, that when grave-diggers are protected from the acute effects of carbon dioxide, their calling is not unhealthy; their death-rate he gives at 17 per 1000, and their mean duration of life at 58 to 60 years. This, however, is in Germany, where, as he admits, there is less crowding of graveyards than in England or France. Nageli, arguing probably from similar data, thinks that graveyards may exist in the midst of towns Avithout danger to health provided precautions be taken with reference to the drainage and ventilation of the soil, and the safe-guarding of the water-supply. Effects of Air vitiated by Respiration.—If we disregard the presence, in expired air, of the so-called and more or less hypothetical organic matter the chief causes of discomfort, folioAving the use of air vitiated by respiration EFFECTS OF AIR VITIATED BY RESPIRATION. 163 are the deficiency of oxygen, excess of carbon dioxide, and increased heat and moisture. The influence of a deprivation of oxygen, in producing a condition of hyperpnoea, appears to be largely subordinate to that of an excessive presence of carbon dioxide. The normal quantity of this latter gas, in air, being from 0*3 to 0*4 volume per 1000, it produces fatal results Avhen the amount reaches from 50 to 100 per 1000 volumes; while at an amount much below this, say 15 to 20 per 1000, it produces, in some persons at any rate, severe headache. Some persons can inhale, for a brief period, considerable quantities of carbon dioxide Avithout injury; and animals can be kept for a long time in an atmosphere highly charged Avith it, provided the amount of oxygen be also increased. In the air of respira- tion, headache and vertigo are produced when the amount of carbon dioxide is not more than 1*5 to 3 volumes per 1000; but then organic matters, and possibly other gases, are present in the air, and the amount of oxygen is also lessened. Well-sinkers, when not actually disabled from continuing their work by carbon dioxide, are often affected by headache, sickness, and loss of appetite; but the amount of carbonic acid has never been actually determined in these cases. The effect of constantly breathing an atmosphere containing an excess of carbon dioxide (up to 1 or L5 per 1000 volumes) is not yet perfectly knoAvn. Angus Smith attempted to determine its effect per se, the influence of the so-caUed organic matter of respiration being eliminated. He found that 30 volumes per 1000 caused great feebleness of the circulation, Avith, usually, slowness of the heart's action: the respirations were, on the contrary, quickened. These effects lessened Avhen the amount was smaller, but Avere perceptible Avhen the amount was as low as 1 volume per 1000—an amount often exceeded in dAvelling rooms. At the same time, this is not the case always, for in the air of a soda-water manufactory, when the carbon dioxide was 2 per 1000, Smith found no discomfort to be produced. The effects noticed by Smith have not been observed in experiments upon animals by Demarquay, Midler, and Eulenberg, nor in other cases in men, as in the bath at Oeynhausen, where no effect is produced by the air of the room in which the bathers remain for 30 to 60 minutes, although it contains a large percentage. Hirt finds no symptoms of chronic poisoning by C02, even in trades where acute poisoning occasionally occurs. The presence of a very large amount of carbon dioxide in the air may lessen its elimination from the lungs, and thus retain the gas in the blood, and in time possibly may produce serious alterations in nutrition. The importance of the role played by the heat and capacity for moisture of ah vitiated by respiration is often overlooked. We have already seen that expired air is practically of the same temperature as the body, 37° C. ( = 98°'6F.), and saturated Avith water vapour, consequently any volume of air much vitiated by respiration soon becomes heated air and more or less saturated with moisture. Now air which is loaded with moisture transmits, in each unit of time, much more heat than air which is dry. Hence, when air, at a high temperature, is saturated with watery vapour, it communicates heat to the body, producing an oppressive sensation; but when the tem- perature of the saturated air is lower than the temperature of the body, the transfer of heat is the other way, producing a sensation of cold. A low temperature with a dry atmosphere is therefore more comfortable than a higher temperature when the air is loaded with moisture, for no other reason than that it favours the prompt and regular removal of body heat by combined conduction and evaporation. It is precisely in this quality that air, vitiated by respiration, is so Avanting, with the result that it causes a 164 AIR. sense of unpleasant oppression so characteristic of ill-ventilated and over- croAvded rooms. The effect of air much fouled by respiration is very marked upon many people, producing heaviness, headache, inertness, and in some cases nausea. When' the air has been rendered very impure, it is commonly rapidly fatal, as in the cases of the Black Hole at Calcutta; of the prison in Avhich 300 Austrian prisoners Avere put after the battle of Austerlitz (Avhen 260 died very rapidly); and of the steamer " Londonderry." This vessel left Sligo for Liverpool on the 2nd December 1848, and stormy Aveather coming on, the captain forced 200 steerage passengers into their cabin, Avhich measured 18 feet by 11 feet, and 7 feet in height. The hatches Avere battened doAvn and covered with tarpaidin. When the cabin Avas opened 72 persons Avere found dead, and several expiring. The poisonous agencies Avhich probably bring this sequence of events about appear to be a deficiency of oxygen coupled Avith an excess of carbon dioxide, though the symptoms are not those of pure asphyxia. If the persons survive, a febrile condition is usually left behind, A\diich lasts three or four days, folloAved often by boils and other evidences of affected nutrition. When air more moderately vitiated by respiration is breathed for a longer period, and more continuously, its effects become complicated with those of other conditions. Usually a person avIio is compelled to breathe such an atmosphere is at the same time sedentary, and, perhaps, remains in a constrained position for several hours, or possibly is also under-fed or intemperate. But allowing the fullest effect to all other agencies, there is no doubt that the breathing the vitiated atmosphere of respiration has a most injurious effect on the health. Persons soon become pale, and partially lose their appetite, and after a time decline in muscular strength and spirits. The aeration and nutrition of the blood seem to be interfered Avith, and the general tone of the system falls below par. Of special diseases it appears pretty clear that pulmonary affections are more common. Such persons do certainly appear to furnish a most undue percentage of phthisical cases, that is, of destructive lung-tissue disease of some kind. The production of phthisis from impure air (aided most potently, as it often is, by coincident conditions of want of exercise, want of good food, and excessive work) is no new doctrine. Baudelocque long ago asserted that impure air is the great cause of scrofula (phthisis), and that hereditary predisposition, syphilis, uncleanliness, want of clothing, bad food, cold, and humid air, are by themselves non-effective. Carmichael, in his work on scrofula, gave some most striking instances, where impure air, bad diet, and deficient exercise concurred together to produce a most formidable mortality from phthisis. In one instance, in the Dublin House of'Industry, where scrofula was formerly so common as to be thought contagious, there were in one ward, 60 feet long and 18 feet broad (height not given), 38 beds, each containing four children; the atmosphere was so bad that in the morning the air of the ward Avas unendurable. In some of the schools examined by Carmichael the diet was excellent, and the only causes for the excessive phthisis Avere the foul air and the want of exercise. Carnelley, Haldane, and Anderson show that in Dundee the ratio of phthisis and other disorders of a similar character increases with the croAvding and foulness of the air; being at the rate of 3*26 per 1000 in houses of 4 rooms and upwards ; 5-52 in houses of 3 rooms; in tAvo-roomed houses, 6*41; and in one-roomed houses, 7*14. EFFECTS OF AIR VITIATED BY RESPIRATION. 165 In prisons, the great mortality AAdiich formerly occurred, as for example at Millbank (Baly), seemed to be owing to bad air, conjoined Avith inferior diet and moral depression. / The now Avell-knoAvn fact of the great prevalence of phthisis in most of 1 the European armies (French, Prussian, Russian, Belgian, and English) can ! scarcely be accounted for in any other Avay than by supposing the vitiated j atmosphere of the barrack-room to have been chiefly in fault. This is the I conclusion to which the Sanitary Commissioners for the army came in their • Avell-known report. And if Ave must also attribute some influence to the pressure of ill-made accoutrements, and to the great prevalence of syphilis, still it can hardly be doubted that the chief cause of phthisis among soldiers has to be sought somewhere else, Avhen Ave see that, Avith very different duties, a variable amount of syphilis, and altered diet, a great amount of phthisis has prevailed in the most varied stations of the army, and in the most beautiful climates: in Gibraltar, Malta, Ionia, Jamaica, Trinidad, Bermuda, &c, in all Avhich places the only common condition was the vitiated atmosphere which our barrack system everyAvhere produced. And; as if to clench the argument, there has been of late years a most decided decline of phthisical cases in these stations, Avhile the only circumstance Avliich has notably changed in the time has been the condition of the air. So also the extraordinary amount of consumption which has prevailed among the men of the Royal and Merchant Navies, and which, in some men-of-war, has amounted to a veritable epidemic, is attributable to the faulty ventila- tion and to contagion following on this. Formerly the deaths from phthisis in the Royal Navy averaged 2*6 per 1000 of strength, and the invaliding 3*9 per 1000. The amount of con- sumption and of all lung diseases was remarkably different in the different ships. Bryson traced this clearly to overcrowding and vitiation of the air, noticing also that in several cases the disease appeared to be propagated from person to person. The production of phthisis in animals confirms this vieAv. The case of the monkeys in the zoological gardens, narrated by Arnott, is a striking instance. Cows in close stables frequently die from phthisis, or at any rate from a destructive lung disease (not apparently pleuro-pneumonia); while horses, who in the worst stables have more free air, and get a greater amount of exercise, are little subject to phthisis. But not only phthisis may reason- ably be considered to have one of its modes of origin in the breathing an atmosphere contaminated by respiration, especially by the respiration of those affected Avith pulmonary tuberculosis, but other lung diseases, bronchitis and pneumonia, appear also to be more common in such circumstances. Both among seamen and civilians Avorking in confined close rooms, who are other- Avise so differently circumstanced, Ave find an excess of the acute lung affec- tions. The only circumstance which is common to the tAvo classes is the impure atmosphere. In addition to a general impaired state of health, arising, probably, from faulty aeration of the blood, and to phthisis and other lung affections, Avhich may reasonably be believed to have their origin in the constant breathing of air vitiated by the organic vapours and particles arising from the dried sputa of infected persons, it has long been considered, and apparently quite correctly, that such an atmosphere may cause a more rapid spread of several specific diseases, especially diphtheria in schools, also typhus, plague, small- pox, scarlet fever, and measles. This may arise in several Avays: the specific poisons may simply accumulate in the air so imperfectly changed, or they may grow in it (for though there may be an analogical argument 166 AIR. against such a process, it has never been disproved, and it is evidently not impossible); or the vitiated atmosphere may simply render the body less resisting or more predisposed. The air of a sick ward, containing as it does an immense quantity of organic matter, is Avell knoAvn to be most injurious. The severity of many diseases is increased, and convalescence is greatly prolonged. This appears to hold true of all diseases, but especially of the febrile. The occurrence of erysipelas and hospital gangrene is, in fact, a condemnation of the sanitary condition of the Avard. It has been asserted that hospital gangrene is a precursor of exanthematic typhus, but probably the introduction at a par- ticular time of the specific poison of typhus Avas a mere coincidence. But, doubtless, the same foul state of the air which aids the spread of the one disease would aid also that of the other. Of the products of combustion Avhich pass into the general atmosphere, the carbon dioxide and monoxide are so largely and speedily diluted that it is not likely they can have any influence on health. The particles of carbon and tarry matter, and the sulphur dioxide, must be the active agents if any injury results. It has been supposed that the molecular carbon and the sulphur dioxide, instead of being injurious, may even be useful as disinfect- ants, and Ave might a priori conclude that to a certain extent they must so act; but certainly there is no evidence that the smoky air of our cities, or of our colliery districts, is freer from the poisons of the chief specific diseases than the air of other places. The solid particles of carbon, and the sulphur dioxide, may, on the other hand, have injurious effects. It is not right to ignore the mechanical effect of the fine powder of coal so constantly draAvn into the lungs, and even the possibility of irritation of the lungs from sulphur dioxide. Certain it is, that persons Avith bronchitis and emphysema often feel at once the entrance into the London atmosphere ; and individual experience will probably lead to the opinion that such an atmosphere has some effect in originating attacks of bronchitis and in delaying recovery. But statistical evidence of the effect of smoky toAvn atmospheres in pro- ducing lung affections on a large scale cannot be given, so many are the other conditions Avliich complicate the problem. There is, however, no doubt of the evil effect of the London atmosphere during dense fogs : Avitness the effect upon the animals at the cattle shoAV at Islington in December 1873, and the increased mortality from lung diseases during foggy weather. The effect of breathing the products of combustion, of gas especially, is more easily determined. In proportion to the amount of contamination of the air, many persons at once suffer from headache, heaviness, and oppression. Bronchitic affections are frequently produced, which are often attributed to the change from the hot room to the cold air, but are really probably owing to the influence of the impure air of the room on the lungs. The effects of constantly inhaling the products of gas combustion may be seen in the case of workmen Avhose shops are dark, and avIio are compelled to burn gas dvu-ing a large part of the day; the pallor, or even anaemia and general Avant of tone, which such men sIioav is OAving to the constant inhala- tion of an atmosphere so impure. EXAMINATION OF AIR. 167 EXAMINATION OF AIR. For hygienic purposes, in the practical examination of air, the chief points to which attention needs to be directed are, the collection of the sample, the examination of the air by the senses, estimation of oxygen, estimation of carbon dioxide, determination of the oxidisable and organic matter, estima- tion of carbonic oxide, the presence of ozone, the determination of aqueous vapour and an examination of the suspended matter and micro-organisms. Collection of the Sample.—All air samples should be collected at the time when the atmosphere Avill afford its greatest evidence of pollution, as, for instance, in the case of a bedroom, the air should be taken when its usual occupants have been in it some hours. For the actual collection of the sample, large, wide-mouthed, glass-stoppered jars, holding from three to four litres, are the most convenient. These need to be most thoroughly cleansed with distilled water before use, inverted to run dry, and stoppered, a label being finally attached for stating the current temperature and pressure. To fill the jar with the air sample, either of the two following methods may be employed. 1. The air may be bloAvn in by belloAvs which are provided with a long nozzle capable of reaching to Avithin an inch of the bottom of the jar: this insures that the air which originally filled the jar will be entirely displaced from below upAvards. 2. The jar may be accurately filled with distilled water, then inverted, emptied and alloAved to drain dry in the room, the air of which it is desired to collect; as the water flows out, some of the air rushes in to fill its place. Special care needs to be observed that no breath is introduced into the jar. The vessel is at once closed with an air-tight stopper or india-rubber cap, and the label inscribed with the current temperature, barometric pressure, and cubical capacity of the jar. Examination by the Senses.—From a practical point of view, this is of the first importance, as although carbon dioxide, carbonic oxide, marsh gas, and several other vapours cannot be detected by the smell, still minute quanti- ties of organic effluvia, traces of sulphuretted hydrogen, of coal gas, of carbon disulphide, and of various other substances are readily noticed by the sense of smell, particularly if at all trained or cultivated to acuteness. The special value of the sense of smell in recognising the peculiar foetid odour so characteristic of occupied rooms, was first clearly shoAvn by de Chaumont, aat1io further indicated the importance of observing it on first entering a room from the open air. He also pointed out the marked influence which atmospheric humidity has in rendering the smell of organic matter percep- tible, an increase of 1 per cent, in the humidity being as powerful, in this respect, as a rise of 2°'32 C. (4°*18 F.). As the sense of smell soon becomes blunted, it is important, when attempting any examination of the air by the senses, to record the impression received immediately after entering the suspected or vitiated air from the open, and not to delay it until one has been in the apartment some length of time. As a preliminary procedure, the reaction of an air sample may be noted. Although the air over open country and the sea is really neutral, cases do occur in which ammonia may be present in such amount as to produce a faint alkaline reaction, or, as in the case of some toAvns, so much sulphurous acid may be present as to make the air ^distinctly acid. The observations can be most readily made by exposing, for an hour or two, pieces of moistened litmus and turmeric papers, and then noting the colour changes that take place. 168 AIR. Estimation of Oxygen.—For this determination there are three well- known methods, namely, the pyrogallic acid process, the combustion process with excess of hydrogen, and the nitric oxide method. As neither of the first two are strictly available in presence of carbon dioxide, the third procedure is the one most readily applicable for hygienic estimations. The most convenient apparatus is Hempel's gas burette and absorption pipette. It consists of two upright glass tubes, one of Avhich is graduated into cubic centimetres, and the other plain. The graduated tube is narroAved almost to capillarity at the top, and draAvn out so as to take an india-rubber connecting-tube. Both tubes are fitted into stands at the bottom, and connected Avith each other by a Avide rubber tube. The graduated upright burette is designed for the reception and measurement of the air or gas. The plain upright burette is the pressure-tube, its function being to regulate the pressure in the other tube (see fig. 9). Fig. 9. In order to use the burette, Avater must first be introduced, so as to rather more than half fill it. By raising the pressure-tube, the water will be caused to fill the graduated tube. By lowering the pressure-tube, a sample of air may thus be draAvn into the graduated tube, which is left open at its upper end. So soon as air has been draAvn into the graduated tube, a pinch- cock is made to close the upper connecting rubber tube, thereby confinino the air sample in the graduated burette. The next operation is to read off the volume of air. For this purpose it must be placed under the current barometric pressure by raising or loAverino- the pressure-tube until the level of the Avater is the same in both tubes. If the graduated tube be noAV read off, the volume of air in it can be expressed in ESTIMATION OF OXYGEN. 169 c.c. Having been measured, the air sample is submitted to certain reactions in Avhat is called an absorption pipette. By a reference to the figure, this Avill be seen to consist of tAvo glass bulbs, the lower one having a larger diameter than the upper, and capable of holding at least 150 c.c. of the reagent to be employed, Avhile the upper one should have a capacity of at least 100 c.c. By means of india-rubber connecting-tubes and bent capillary glass tubes, the gas burette is placed in communication Avith the absorption pipette. The india-rubber connections should be bound with thin copper Avire, and the respective tubes provided Avith pinch-cocks; these latter need to be carefully closed before any manipulation of the connections takes place. The particular method for estimating oxygen is based upon the well- knoAvn reaction between oxygen and nitric oxide, thus, 2NO + 02 = 2N0.2. The NO., is absorbed by Avater; there is, therefore, a contraction of three volumes for every one volume of oxygen. The mode of operation is to add excess of nitric oxide to the sample of air, and then to read the contraction. One-third of the contraction is the volume of the oxygen in the sample. Some nitric oxide is prepared by the action of dilute nitric acid on copper turnings, the gas being preserved in a bell jar over Avater. The absorption pipette is next charged Avith Avater, and a sample of air having been drawn into and measured in the gas burette is then, after connecting the burette Avith the pipette, passed over into the absorption pipette and there allowed to remain Avhile nitric oxide is introduced into the gas burette and its volume measured. This being done, the nitric oxide is passed over to the ah in the absorption pipette. Immediately the Avell-knoAvn reaction takes place, and ruddy fumes of N02 make their appearance in the bulb of the absorption pipette. The absorption of these fumes by the water is very quick. The gas is passed backwards and fonvards once or tAvice, the fumes disappear, and the final reading at once made. Example.—Say 50 c.c. of air are drawn into the gas burette and duly passed over, after connection, into the absorption pipette containing water. Say, further, that 25 c.c. of N02 are drawn in, measured, and also passed over into the air in the absorption pipette. After the reaction has taken place and is completed, presume the resulting volume of air is found to be 44'2 c.c. ; that is, 50 + 25 or 75 c.c. has become 44*2 c.c, being a contraction of 30-8 c.c. : one-third of this contraction, or 10-27 c.c, is the volume of oxygen present in the air sample of 50 c.c.; or in other words, 20*54 per cent. In this, and all other processes of gas analysis, since the conditions of temperature should remain constant throughout the estimation, it is of importance that the gas burette, after it has been charged, should not be handled except by its iron stand. Estimation of Carbon Dioxide.—The determination of this gas in air is of the greatest general importance, mainly because, as a product of both respiration and combustion, it affords an important index as to the extent to Avhich other impurities co-exist. The procedure for its estimation in most common use is Pettenkofer's alkalimetric method. The rationale of the process is as follows :—Clear lime-Avater or baryta-water, both being strongly alkaline media, Avill readily absorb carbon dioxide: the absorption of this Aveak acid Avill diminish the alkalinity or causticity of the original lime or baryta-Avater. If, therefore, the degree of alkalinity of either of these media be known both before and after exposure to the carbon dioxide, the difference will represent the amount of C02 which has combined Avith the lima or baryta. To carry out the process it is necessary to have a clean glass vessel capable of holding aboilt.a gallon or 4*5 litres. The capacity of this jar is determined by filling it with water at 15° C. ( = 59° F.), and measuring the contents 170 AIR. by means of a litre or pint measure, one fluid ounce equalling 28*4 c.c. As already explained, the most convenient Avay of collecting the air sample is to fill the jar with Avater and empty it in the place, the air of which is to be examined, and then alloAving it to drain for a while. When this has been done, 60 c.c. of clear lime or baryta-water are put in, and the mouth of the jar closed Avith an india-rubber cap. The vessel is agitated, so that the lime or baryta-Avater may run over the sides and thus become intimately exposed to the action of the air contained in the vessel. The same is then alloAved to stand for hah an hour or longer. The causticity of the lime or baryta-Avater is next determined by titration with a solution of crystallised oxalic acid, made by dissolving 2*25 grammes of the acid in a litre of distilled water. One c.c. of this solution exactly neutrahses one milligramme of lime, CaO, or 2*73 milligrammes of baryta, BaO. For the actual determination of causticity, 30 c.c. of the lime or baryta-water are taken and exactly neutralised with the oxalic acid solution, good turmeric paper, or rosolic acid or phenol-phthalein being used as indicators. If rosolic acid be used,, a feAv drops of a solution made by dissolving 0*5 gramme of rosolic acid in 100 c.c. of 80 per cent, alcohol may be added to the lime or baryta-water. If phenol-phthalein be employed, a suitable solution is made by dissohdng 5 grammes of the phenol-phthalein, with the aid of 25 c.c. spirits of Avine, in 500 c.c. of distilled water. The amount of I lime in the 30 c.c. taken, will be then equal to the number of c.c. of the oxalic acid used; it is usually somewhere between 34 and 41 milligrammes. In the case of baryta the amount in the 30 c.c. will be 2*73 times the number of c.c. of the oxalic acid used. In the same manner, after the lime or baryta placed in the jar has absorbed the C02 of the air in the vessel, 30 c.c. of it are taken out and tested for causticity with the oxalic acid, the difference between this and the previous determination shoAving the milligrammes of lime or baryta precipitated or combined with the carbon dioxide. Before proceeding further with the calculation, it is necessary to estimate, subject to corrections for tenrperajjure and barometric pressure, the volume of air contained in the jar, "reducing the same to normal conditions of 0° C. and 760 mm. This reduction to normal conditions of temperature and pressure is necessary, because the calculation of the volume of C02 from weight of C02, as based upon the analysis or titration of the lime or baryta- Avater, is expressed in these terms, and. the conditions in both cases must be alike in order to compare them. Besides these necessary corrections for temperature and pressure, the volume of the 60 c.c. of lime or baryta-water put in the jar must be deducted before the nett volume of air in the vessel can be accurately stated. The milligrammes of lime or baryta, calculated from the difference of the causticities, are next converted into terms of C02 by calculation of the ratio betAveen their molecular weights, and then the C02 converted from milli- grammes or measures of weight into cubic centimetres or measures of volume, in the ratio of as 1*9707 is to 1 : because, carbon dioxide being 22 times heavier than hydrogen, and 1 litre of hydrogen at 0° C. and 760 mm. weigh- ing 0*08958 gramme, therefore 1 litre of C02 at 0° C. and 760 mm. weighs 22x0*08958=1-9707 gramme, and 1*9707 milligramme of C02 under standard conditions of temperature and pressure measure 1 c.c. Having determined the exact volume of C02 present in the known volume of air, the proportion present is readily expressed as either a percentage or as so many parts in a thousand. The precise working of this determination Avill be more readily apparent after the consideration of an example. ESTIMATION OF CARBON DIOXIDE. 171 Example.—Say, in a room with the temperature at 20° C. and barometric pressure at 720 mm., a sample of air is collected in a jar, having a capacity of 4*460 litres, and that 60 c.c of lime-water are placed in the vessel for estimation of the contained CO.,. Whilst the jar is set aside, 30 c.c. of the lime-water are titrated with the oxalic acid solution, neutrality being obtained with 40 c.c of this acid solution, indicating 40 mgms. of lime as being present in the lime-Avater. The gross capacity of the jar is recorded to be 4460 c.c, but, deducting 60 c.c. for the space occupied by the added lime-water, this gives 4400 c.c. nett as the space available for the air sample at the recorded current temperature and pressure of 20° C. and 720 mm. This, reduced to the standards of 0° C. and 760 mm., gives 3885 c.c. as the corrected volume of air operated upon, or really present, in the jar under standard conditions of temperature and pressure : thus,— 4400x720 _ 760(1 + (0-00366 x 20))_d00J C*C' Presume, after being exposed to the action of the air in the jar, 30 c.c. of the lime-water, removed from the vessel, show a causticity equal to 34 c.c. of the oxalic acid solution, indicating the presence in that lime-water of 34 mgms. of lime. The difference between this amount of lime and that shown to be piesent in 30 c.c of lime- water before exposure to the air gives 40 - 34 or 6 mgms. of lime as having com- bined with the C02 of the air sample from 30 c.c; but as 60 c.c. of lime-water were put in, this means 12 mgms. of lime as the total loss due to the C02. Since lime, CaO, is to carbon dioxide, C02, as 56 is to 44, therefore 12 mgms. of lime equal 9'4 mgms. of C02. But milligrammes of C02 are to cubic centimetres of C02 as 1 *9707 is to 1, therefore 9*4 mgms. C02 equal 4'76 c.c. of C02. Now the true capacity of the jar, under standard conditions, we have found to be 3885 c.c, and in this we have found 4*76 c.c. of C02, Avhich is, in amount, equal to 1-22 c.c. or volumes of C02 in 1000 c.c. or volumes of air. A popular method for estimating carbon dioxide in air has been suggested, by Cohen and Appleyard. The method depends upon the fact that if dilute lime-Avater, coloured with phenol-phthalein, containing insufficient lime to combine Avith the carbon dioxide present, be shaken with the air sample, the rate of absorption of the gas will vary with its volume. The time required to decolourise the indicator -will therefore give the quantity of C02 present. The folloAving apparatus and chemicals are required :—(1) A clear glass stoppered bottle of 22 fluid ounce capacity; (2) some phenol-phthalein solution prepared as stated above ; (3) a standard lime solution prepared by diluting 10 c.c. of saturated lime-Avater to 1 litre. The process is conducted as follows:—Rinse the bottle out Avith water, fill, and empty in the place where the air is to be examined, allowing it to drain for a minute. Add 0*25 c.c. of indicator solution and 10 c.c. of the dilute lime-water, finally stoppering and Avell shaking the bottle with both hands until the pink colour vanishes. The time required Avill indicate the condition of the atmosphere. The folloAving determinations have been made, in which the amount of C02 has been ascertained by Pettenkofer's method:— Time in mins. required Percentage of CO., to decolourise the solution. by Pettenkofer's method li....... 0-160 14 • 0*138 H 0*128 3| . 0-077 34 . 0-070 4 0-053 4i • 0-051 5 0-046 51- . 0-044 61 . 0-042 7h 0-035 172 AIR. On this basis the folloAA'ing table may be taken to indicate roughly the condition of the air:— Time. Condition of Air. Under 3 minutes, ....... Bad. Above 3 and under 5 minutes, .... Fair. Above 5 minutes,...... . Good. An ingenious apparatus has been designed by 0. Schulz, in Avhich a measured quantity of a standard carbonate of soda solution is placed in a long test-tube, and air drawn through it by means of an aspirator ; the soda solution is coloured with phenol-phthalein, and, when the colour is dis- charged, it indicates that neutralisation has been effected by the C02 in the quantity of air drawn through. The amount of C02 can then be calculated according to the strength of the soda solution. It must be understood that none of the methods hitherto used for the determination of carbon dioxide in the air give quite accurate results, but Pettenkofer's is the most convenient for ordinary use, and is sufficiently accurate for practical purposes. The results differ considerably if the quantities of air treated vary, therefore uniformity in this point is desirable. Determination of the Organic and Oxidisable Matter.—The nitrogenous matter existing in the air may be in the form of dead or living matter of very various kinds. Its chemical determination practically resolves itself into washing the air, by agitation in distilled water, and then estimating the nitrogen, the free and albuminoid ammonia, as well as the nitrous and nitric acid as described in methods of Avater analysis. The mere presence of free ammonia may be determined by exposing strips of filtering paper, dipped in Nessler's solution or in ethereal solution of the alcoholic extract of logwood ; the former becomes yellow, the latter purple. Chapman, finding that water did not sufficiently absorb the nitrogenous substances in ah, proposed to heat finely-powdered pumice-stone to redness, to moisten it Avith pure Avater, and then to place it over some coarse pieces of pumice-stone supported on wire in a funnel; a definite quantity of air (say 100 litres) is then draAvn through the funnel. The pumice-stone is transferred to a retort containing water freed from ammonia, and distilled as in the determination of the albuminoid ammonia of water. Angus Smith took a bottle of about 2000 c.c. capacity, placed in it 30 to 50 c.c. of the purest water, drew into it the air to be examined, and then agitated the water in the bottle, and proceeded as in Wanklyn's and Chapman's Avater test. The most convenient Avay is to draw the air, by means of a measured aspirator, through a succession of wash bottles, each containing 100 c.c. of Avater perfectly free from ammonia, and then to determine the free and albuminoid ammonia by Wanklyn's method. Another plan is to lead a definite quantity of air through a clean curved tube, surrounded by a freezing mixture; the AVater of the air condenses, and with it much of the organic matter; the tube is then Avashed out with pure water, the Avashings are put into a retort with ammonia-free water, and distilled as usual. After passing through the tube the air should be led through pure Avater to arrest the portion of organic matter that always escapes condensation. The quantity of air draAvn through must, of course, be accurately determined by a properly arranged aspirator, and the results then calculated in milligrammes per cubic metre. For the estimation of the oxidisable matters in the air in terms of oxygen, a definite quantity of air is drawn through a solution of permanganate of DETERMINATION OF THE OXIDISABLE MATTER. 173 potassium of known strength, and the amount of undecomposed permanganate is determined by oxalic acid or sodium thiosulphate. Or part of the Avater through which the air has been draAvn for the ammonia determinations may be examined in the same way as in the case of drinking water. Carnelley and Mackie shake the air up in a bottle Avith a measured quantity of per- manganate, and afterAvards determine the amount of bleaching by comparison Avith a sample of distilled Avater to Avhich permanganate solution is care- fully added from a burette. The solution of permanganate used is of 1000 strength, of Avhich 1 c.c. = 0*008 milligramme of oxygen, = 0*0000056 litre N of oxygen at 0° C. and 760 mm. It is usually kept at -j- strength and diluted as required, about 50 c.c. of dilute sulphuric acid (1 in 3) being added to each litre of the Aveak solution. The samples of ah are collected in Avell-stoppered jars of from 4 to 5 litres capacity; 50 c.c. of the milli-normal permanganate solution are then run into the jar, Avliich is at once tightly stoppered and well shaken for at least five minutes. 25 c.c. of the permanganate are then withdrawn by a pipette and then placed in a glass cylinder holding about 250 c.c. Then another 25 c.c. of the permanganate solution are placed in a similar cylinder, both diluted up to 150 c.c. Avith distilled Avater and allowed to stand for ten minutes, after which the tints of the cylinders are compared. Into the decolourised cylinder more permanganate is run in from a graduated burette, until the tints of both cylinders are of the same intensity. The amount of solution added from the burette is a measure of the bleaching effected by the knoAvn volume of ah on half the permanganate. This multiplied by 2 gives the amount. The results may either be expressed in terms of the number of c.c. of the milli-normal solution bleached by 1 litre of air, or by the number of volumes of oxygen required to oxidise the organic matter in, say, a million volumes of air. Example.—25 c.c. of solution from a 4*5 litre jar, in which 50 c.c. had been placed, required 3 c.c. of the permanganate to bring it up to the standard tint, or the whole 50 c.c. would have required 6 c.c. This represents the number of c.c. of permanganate solution bleached by 4500-50 = 4450 c.c. of air, consequently—--= 1'348 c.c. is the bleaching effected by 1 litre of air. But 1 c.c. of KMn04 solution = 0 0000056 litre of oxygen, .-. l-348 c.c. KMnO4 = 0'00000755 litre of oxygen is required to oxidise the organic matter in 1 litre of air, or 7'55 volumes of oxygen to oxidise the organic matter in a million volumes of air. The method is highly ingenious and can be rapidly performed. Some difficulty may be experienced at first in matching the tints, and in some samples of very foul air no amount of permanganate solution will bring the decolourised sample up to its colour. The permanganate acts upon various matters in the air besides the putrescible organic matters, more particularly upon nitrous acid and hydrogen sulphide; this fact renders it an unsatisfactory test for organic matter, but as a test for organic matter and other impurities co-existing, it affords a useful reaction. The presence or absence of sulphuretted hydrogen in air may be detected by either exposing strips of paper moistened with lead acetate to the air, or by drawing the air through a solution of the same salt. If there is merely a dark colour, but no precipitate, the amount may be estimated on colorimetric principles, that is, the colour may be imitated by acting upon a similar bulk of lead acetate solution by water containing knoAvn quantities of hydrogen sulphide. 174 AIR. Estimation of Carbonic Oxide.—There is no easy and quantitative chemical test for this dangerous gas ; the best qualitative test is that of Vogel, which is based upon the spectroscopic examination of haemoglobin, and is so delicate that it can detect 0-03 per cent. To the sample of air collected in a jar a little pure Avater is added, and into this a drop or two of blood from a pricked finger is made to fall. This diluted blood is next well shaken up Avith the air in the jar, and then a small quantity is placed in a spectroscope, for an examination of its absorption bands. As so examined, the appear- ance in the spectrum will be that of oxy-hsernoglobin. Oxidised haemoglobin shows two well-marked bands in the yellow and in the green parts of the spectrum, both lying between D and E ; a little ammonium sulphide is noAV added and the bottle well shaken; if carbonic oxide is present the spectrum Avill undergo no change, but if absent, the ammonium sulphide will reduce the haemoglobin, as indicated by a single absorption band in the spectrum occupying an intermediate position Avith regard to the two original bands. When carbonic oxide is suspected of existing in the air in large quantities, an estimation of this gas can be made by noting the volume of air absorbed by a solution of subchloride of copper in a Hempel apparatus. The sub- chloride of copper is prepared by digesting oxide of copper and copper turnings in strong hydrochloric acid. Since the presence of oxygen in the air somewhat impairs the poAvers of the copper solution, it is necessary, in order to successfully carry out this estimation, to first remove the oxygen, as already described, and then pour 50 c.c. of acid subchloride of copper solution into an absorption pipette, into which the air sample (now deprived of oxygen) must be repeatedly passed until a constant reading is obtained. The loss, in volume, is due to carbonic oxide. Determination of Ozone and Watery Vapour.—The most common test for ozone is that of exposing to the atmosphere faintly reddened litmus paper, Avhich has been moistened with potassium dioxide and then dried. If ozone be present, this becomes blue, owing to the breaking up of the potash salt and liberation of alkali. A more detailed account of ozonometry and criticism of its exact value is given in the chapter dealing with meteorology and meteorological observations. The hygrometric condition of the air is ascertained in various ways, especially by the use of the dry and wet bulb thermometer and different kinds of hygrometer. The special facts relating to their construction and methods of use are given in the chapter upon meteorology. Determination of Sulphurous Acid.—For this estimation are required (1) a deci-normal solution of sodium thiosulphate, made by dissolving 24*8 grammes of Na2S2035H20 in a litre of distilled water. One c.c. of this solution will exactly decolourise 12*65 milligrammes of iodine, forming colour- less sodium tetrathionate and sodium iodide; (2) a deci-normal solution of iodine made by dissolving 12*65 grammes of iodine in a litre of water. As iodine is rarely very pure and somewhat volatile on weighing, it is usually better to prepare the solution by first dissolving 13 grammes of iodine, and then rubbing it up in a little water with 20 to 25 grammes of potassium iodide, diluting to 1 litre, and diluting still further until 10 c.c. of the preceding deci-normal sodium thiosulphate solution exactly suffice to decolourise 10 c.c. of the iodine solution, Avhich had been coloured blue by the addition of a few drops of starch solution. The reaction being according to the formula: 2Xa2So03 +12 = Na2S406 + 2NaI. The experiment is carried out by exposing a given volume of air to say EXAMINATION OF SUSPENDED MATTER AND MICRO-ORGANISMS. 175 20 c.c. of the iodine solution in an absorption pipette, when the follow- ing reaction ensues if sulphurous acid be present: S02 +12 + 2H20 = S04H2 + 2HI. In other Avords, 64 milligrammes of sulphurous acid exactly convert 253 milligrammes of iodine into hydrogen iodide, or 3-2 milligrammes exactly decolourise 1 c.c. of a deci-normal solution of iodine. If, after exposure to a given volume of air for ten minutes in an absorp- tion pipette, as already described under the head of oxygen determination, the iodine solution be titrated with the deci-normal solution of sodium thiosulphate, each decrease of a c.c. of the thiosulphate solution required indicates 3-2 milligrammes of sulphurous acid as present in the given volume of air. Example.—Say, by means of a Hempel's apparatus, 180 c.c of air have been exposed In an absorption pipette for ten minutes to 20 c.c. of deci-normal iodine solution, which previously had been found to accurately correspond with 20 c.c. of a deci-normal thio- sulphate solution. After exposure to the air, on re-titration the 20 c.c. of iodine solution only required 18'6 c.c. of thiosulphate to exactly decolourise. Therefore, 20-18*6 or 1-4 c.c. of thiosulphate solution less, now required by the iodine solution, represents the iodine converted into hydrogen iodide by the sulphurous acid present in the 180 c.c. of air. Or, 1-4x3-2 = 4-48 milligrammes of S02 present in 180 c.c. of air or 0-024 part in 1000 of air. Determination of Hydrogen Sulphide.—The quantitative estimation of this gas can be made in air in a similar manner. One c.c. of deci-normal iodine solution decomposes 1*7 milligramme of sulphuretted hydrogen; therefore, each c.c. of the sodium thiosulphate solution less used after absorption than for the titration of the same volume of the original solution of iodine, indicates the equivalent absorption of 1*7 milligramme hydrogen sulphide. The amount present, then, in 1000 volumes of the air is readily calculated. Examination of Suspended Matter and Micro-organisms. —From time to time various methods have been suggested for the examination of the sus- pended matters in air. One of the earliest methods Avas to aspirate large volumes of air slowly through distilled Avater, placed in a series of small wash bottles, each holding about 100 c.c. The suspended or solid matter was allowed to settle, the supernatant fluid siphoned off and the specimens from the residue examined microscopically. A later development was Pouchet's aeroscope and. Marie-Davy's modifica- tion of it. These instruments practically consist of a closed glass vessel, perforated by two glass tubes: each tube is bent at a right angle, one being much shorter than the other. The longer tube, inside the cylinder or vessel, is drawn to a fine point and made to impinge upon a circular glass plate, which has been previously smeared with glycerin. The apparatus is con- nected by means of the short tube with an aspirator, which, on being worked, causes air to be sucked in by the longer tube: the air, so draAvn, falls as a spray upon the glass slide, the sticky surface of which retains the suspended matters. The simplest methods for examining the micro-organisms in air consist in exposing plates of glass or microscopic slides coated Avith glycerin, or a mixture of glycerin and glucose, or even coated with nutrient gelatin. Sterilised potatoes have been similarly exposed. Upon these various micro- organisms settle and subsequently develop: all these procedures are, how- ever, crude and open to many sources of error. When specimens are only desired, and not an idea of the number for a given volume of air, Koch's method is useful. He employs a glass jar about six inches high, the neck of which is plugged with cotton-wool. In the interior is a shallow glass 17G AIR. capsule, Avhich can be removed by means of a brass lifter. The Avhole is sterihsed by exposure to 150° C. for an hour. The nutrient gelatin of an ordinary stock tube is liquefied by heat and the contents emptied into the glass capsule. The jar is now exposed to the air to be examined, for a definite time, the cotton-wool plug replaced, and the Avhole jar set aside for the colonies to develop. For more accurate results Hesse's apparatus may be employed (fig. 10). This consists of a glass cylinder about 18 inches long and 2 inches in diameter. At one end a piece of india-rubber sheeting is stretched and firmly bound round the end of the glass cylinder to prevent air being sucked past it. The other end of the cylinder is closed with a tight-fitting plug of india-rubber, through Avhich a glass tube passes. From this tube passes a piece of india-rubber tubing to a litre bottle filled with water, and from this bottle to a second litre bottle another tube passes: Avhen not in action, this tube is shut off. Along the bottom of the glass cylin- der are placed 50 c.c. of nutrient jelly, sohd when cooled. The cylinder rig- 10- rests on a tripod stand similar to those used by photographers. The nutrient jelly, india-rubber caps, tubing, cyhnder, &c, are sterilised in the usual manner by steaming in a steriliser repeatedly, and the tubes with their layers of jelly are kept sufficiently long, before using, to see that there is nothing growing upon them. When it is wished to operate, the india-rubber sheeting is perforated by a heated needle or pin, making a very small hole, and the pinch-cock opened: water passes slowly from the upper to the loAver bottle, and when it is empty a htre of air has been supposed to pass into the cyhnder, and to deposit its contained microbes. As many litres of water as desired can be run out simply by reversing the position of the bottles. When the ah is very foul, one htre will be sufficient, as the colonies otherwise would be too close and run into each other. When the operation is over, sterihsed india-rubber caps or pieces of cotton-wool, also sterilised, are bound over the ends of the Hesse tube, and it is then placed in either an incubation chamber or other suitable place. After twenty-four hours or longer, the colonies may be counted. At one time the glass cylinders were used with a coating of gela- tin all round the interior, but this is difficult to obtain, and in practice it is found that the microbes gravitate and settle on to the layer at the bottom of the tubes. The method of Hesse is very elegant, and has many advantages : from the length of the surface of the jelly exposed, separate colonies form, often giving pure cultivations, and their growth can be studied as on a glass plate, and inoculations can be readily made in the usual manner. There are undoubtedly objections, some of which apply to all bacterial methods, and others Avhich apply specially to this one in particular. The chief objection appears to be, that, although you run off a htre of water and although the capacity of the glass cylinder is also about a litre, it does not follow that a htre of air has been drawn from the outside. The first EXAMINATION OF MICRO-ORGANISMS PRESENT IN AIR. 177 half of the air contained in the glass cylinder may be removed, but after that, or even before it, the air from the outside and the air inside diffuse and commingle, so that a mixture of these will be aspirated out, and in consequence a litre of air will not have passed in. This defect makes the method doubtful as a quantitative test. Another objection is, that one cannot be sure that all microbes are deposited : true, we find in practice that the colonies are found in greatest abundance at the end furthest from the aspirator and gradually diminish inAvards, but still one cannot be certain that some micro-organisms have not escaped. NotAvithstanding these objec- tions, the method is one of considerable practical value. In order to obviate some of the difficulties and objections experienced with Hesse's apparatus, Percy Frankland aspirates the air through small glass tubes, 5 inches long and ^ inch internal diameter, in which are placed two plugs of sterilised glass avooI; these plugs retain the germs, and are then introduced into flasks containing nutrient gelatin, and well shaken up. The gelatin solidifies on the sides of the flask, and the colonies can be examined readily through the glass. The glass avooI mixes so intimately with the gelatin that it does not interfere with the easy perception of colonies Avhen they develop. Powdered sugar may be used instead of glass wool. The gelatin may also be poured into Petri's dishes in the ordinary Avay, instead of being allowed to solidify within the flasks. A very similar plan is that of Petri, Avho employs calcined sand as a filter, in grains of 0*25 to 0*5 mm. in size. Two such sand filters, each 3 centimetres in length, are kept in position within small glass tubes by means of small wire caps. The whole, after sterilisation, are connected with an aspirator and air drawn through, the sand being subsequently transferred to liquefied gelatin as in Frankland's method. It is impossible to say definitely, at present, which of these methods is the better; but a large number of observations indicate that the use of glass wool or of sand filters, with a subsequent preparation of plate cultures from them, is preferable to the growth of colonies in a long tube, such as Hesse's. The actual varieties of micro-organisms which have been found, by one or other of these methods, in the ah, are considerable, and in the majority of cases moulds are much less frequently found than bacteria. The purer ah is, the more generally do the numbers of bacteria and moulds approxi- mate. In inhabited rooms, when the air becomes -vitiated, the bacteria increase, while the moulds are affected hardly at all. The effect of stirring up dust is to increase the ratio of bacteria to moulds. On the other hand, if the air be allowed to remain quiet for any length of time, the bacteria, or rather the particles to which they are attached, settle out much more rapidly than moulds. The ratio of bacteria to moulds in the air, on still and windy days and in dry and damp weather, is shown in the following table. Other things being equal, there are fewer bacteria in the air on damp or still days than on dry or windy days. The moulds seem to be much less affected by either wind or dryness. Still, damp days. Windy, damp days. Still, dry days. Windy, dry days. Bacteria, 36 — or as 1 : 1 37 63 — or as 1*26 : 1 50 70 — or as 2*6 : 1 27 106 ---or as 14*1 : 1 7*5 Moulds, M 178 AIR. BIBLIOGRAPHY AND REFERENCES. Adams, On the presence of Arsenic in the Vapours of Bone Manure, Lond., 1876. Albrecht, Handbuch der Praktischen Gcwerbehygiene, Berlin, 1894. Alessi, Central, fur Bakterien und Parasitenkuiulc, Bd. xv. No. 7. Arlidge, Milroy Lectures upon Occupations and Trades in Belation to Public Health, Lond., 1889. Arthur, " Bacteriology of Sewer Air," Sanitary Becord, Nov. 10, 1894. Balfour, "Vital Statistics of Cavalry Horses," in the Journ. Statis. Soc, Lond., June 1880. Ballard, "Report upon the Middlesborough Epidemic," Supp. to 18th Annual Beport to the Local Gov. Board, 1889. Bergey, Weir Mitchell, and Billings, Report upon " The Composition of Expired Air and its Effects upon Animal Life," Proc. National Acad, of Sciences, New York, 1895 ; also summarised in Science, vol. i. No. 18, p. 481, May 3rd, 1895. Billings, Ventilation and Heat- ing, New York, 1893. Blackley, Experimental Besearches on the Causes and Nature of Catarrhus AUstivus, Lond., 1873. Buchanan, Beport on certain Sizing Processes in the Cotton Manufactures of Todmorden, 1872 ; also 9th Bep. of Med. Off. to the Brivy Council; also "Report upon an Outbreak of Enteric Fever in Caius College, Cambridge," Sujm. to 2nd Annual Beport of Med. Off. to the Local Gov. Board, 1874. Carnelley, Bhil. Trans. Boy. Soc. Lond., vol. clxxviii., 1887 ; also Proc. Roy. Soc. Lond., vol. xii. p. 238; also vol. xlii., June 1887. Carpenter, A., Traits. Intemat. Med. Cong., Lond., 1881; also Brit. Med. Journ., June 22, 1889. Chadwick, Sir E., Report upon Interments in Towns, Lond., 1868. Cornet, Zeitschr. fur Hygiene, Bd. v., 1889. Cunningham, "Microscopical Examination of Air in India," Bep. San. Commiss. India, Appendix, Calcutta, 1872. De Chaumont, Lectures on State Medicine, Lond., 1875. Ferguson, "On some of the Constituents of the Atmosphere," San. Journ. for Scot- land, Glasgow, 1876, p. 181. Fodor, Hygienische Untersuchungen u. Luft, Boden und Wasser, Braunschweig, 1881. Frankland, Broc. Roy. Soc. Lond., 1877. Frankland, P., Bhil. Trans. Boy. Soc. Lond., 1887, p. 113. Greenhow, Bapers relating to the Sanitary State of the People of England, Lond., 1858. Haldane, "The Physiological Effects of Air vitiated by Respiration," Journ. Path. and Bacteriology, vol. i., 1892, pp. 168 and 318. Hermans, Archiv. f. Hygiene, Bd. i., 1883. Hesse, Mittheil. Kaiserl. Gesundheitsampte, 1882. Hirt, Die Krank- heiten der Arbeiter, Erste Theil : " Staub inhalations Krankheiten," Berlin, 1871. Lehmann, Methods of Pract. Hyg., trans, by Crookes, Lond., 1893. Lehmann and Jessen, Archiv. f. Hyg., x. p. 367. Letheby, Article upon " Sanitary Science" in Encyclopaedia Britannica. Levy, Annuaire de VObscrv. de Montsouris, 1882 ; also Traite d'Hygiene, 1886. Lewes, " Gas Lighting and Ventilation," Journal of Gas Lighting, Lond., July 1893. Lissauer, Deutsche Vierteljahrschrift filr offentliche Gesundheitspflege, 1881. Loye, Memoires de la Soc. de Biologie, Paris, 1888-1891. Marcet, " The History of the Respiration of Man," being the Croonian Lectures, 1895, Lancet, June 22, 29, and July 6, 1895. Merkel, Archiv. f. Hygiene, 1892, xv. p. 1. Miescher, Archiv. f. Anat. u. Phys., 1885. Milroy, Report on Health of the Royal Navy, Lond., 1862. Miquel, Orcjanismes vivants de VAtmosphere ; also in Annuaire de VObserv. de Montsouris, 1884, p. 533. Nageli, Die Niederen Pilze, 1877. Nasmyth, " Report on the Air of Mines," Brit. Med. Journ., 1888, vol. ii. p. 222. Ogle, Supp. to i5th Report of the Registrar-General, 1885. Parent-Duohatelet, Hygiene Publique, Paris, 1836. Parkes, E. A., Various Reports upon Hygiene in A. M. D. Reports, more particularly in 1862-3 ; also Beport on the Cholera in Southampton in 1866, to the Med. Off. of the Privy Council. Parry- Laws, "On the Ventilation and Condition of London Sewers," Report to London County Council, 1894. Pettenkofer, "Uber den Kohlensauregehalt der Luft in der libyschen Wiiste, uber und uuter der Bodenoberflache," Zeitsch. f. Biol., Miinchen, 1875, xi. 381-391 ; also in the Handbuch der Hygiene u. Gewerbe-Krankheiten BIBLIOGRAPHY AND REFERENCES. 179 Berlin, 1887. Playfair, Second Beport of Health of Towns Commission, Lond., 1887. Preece, "Sanitary Aspects of Electric Lighting," Proc. San. Institute, Lond., 1890, vol. xi. p. 267. Ramazzini, Les Maladies de VArtizan, Paris, 1842. Rauch, Intra-mural Interments in Cities, their Influence upon Health and Epidemics, Chicago, 1866. Raavlinson, Beport of Committee on Sewage, Lond., 1864, p. 174. Robertson, "A Study of the Micro-organisms in Air, especially in Sewer Air," Brit. Med. Journ., Dec. 15, 1888. Sigerson, " Further Researches on the Atmosphere," Brit. Med. Journ., June 1870, p. 638. Simon, Sir J., Public Health Biports, Lond., 1887. Simon, R. M., Birming- ham Med. Rev., May 1887. Smith, Angus, Air and Rain, 1862 ; also Report upon Mines, Blue Book, 1864 ; also " On the Air of Towns," Quart. Journ. Chem. Soc, Lond., 1859, xi. 196 ; also " On Organic Matter in the Air," Chem. News, Lond., 1870, xxi. 64. Smith, Fred., Veterinary Hygiene, Lond., 1890. Smith and /Sutherland, Report upon Extra-mural Interments, 1850. Soyka, "Uber die Bestimmung der organischen Substanzen in der Luft," Amtl. Ber. deutsch. Naturf. u. Aertze, Miinchen, 1877, i. 349. Spear, Local Government Board Beport, 1890. Tardieu, Diction. d'Hygiene, Paris, 1866. Thackrah, Effects of Arts, Trades, and Professions upon Health, 1832. Tidy, " On Air Analysis," Med. Times and Gaz., Lond., 1873, i. 137. Tyndall, Phil. Trans. Boy. Soc. Lond., 1876, Part 1 ; also Floating Matter in the Air, in Belation to Butrefaction and Infection, Lond., 1881. Wanklyn, "On the Differences between Wholesome and Unwholesome Air," Lancet, 1865, i. 60. Weaver," On the Quality of Atmospheric Air in Public and Private Buildings in Leicester," Lancet, July and Aug. 1872, pp. 7, 150 and 223. Wilson, Handbook of Hygiene, Lond., 1892. CHAPTER III. VENTILATION AND HEATING. Ix the last chapter sufficient evidence was given to indicate the intimate connection betAveen impaired health, Avhether in man or animals, and defective ah supplies as to render any repetition of either facts or figures unnecessary here. It is essentially to correct any evils arising from faulty conditions of the air in houses, factories, or other enclosed spaces that the theory and practice of ventilation aims. The term ventilation, however, is not ahvays used in the same sense, being frequently confused with aeration. In simple aeration of a room the air is changed but once or at intervals, whereas in true ventilation the air is constantly changed by the passing out of a portion of the enclosed air, and the entrance of other ah to take its place. Regarded, therefore, as the continuous, and more or less systematic, reneAval of air in a room or other closed space, the term ventilation may be strictly defined as the removal or dilution, by a supply of pure ah, of the pulmonary and cutaneous exhalations of men or animals, and of the products of combustion from lights in ordinary dAvelling-houses, to which must be added, in factories, dust from industrial processes, and in hospitals, the effluvia which proceed from the persons and discharges of the sick. Involving, as it does, the introduction of pure external air in continuous currents, its diffusion, and the constant removal of a corresponding volume of air more or less fouled by gases, vapours, moisture and particulate matter,. or which is heated above the degree which is consistent with comfort and health, the subject of ventilation is one of some complexity, and is closely connected Avith the facts which concern the production and distribution of heat. In studying, therefore, the allied subjects of ventilation and heating, we have to remember the chemical and physical properties of air, to bear in mind the various sources of its contamination, as well as the forces which are available for moving it in the direction best suited for our purpose, coupled with a consideration of the arrangements of flues, shafts, &c, best adapted to secure the entrance, diffusion, and exit of the amount of air required. Notwithstanding the existence of a vast amount of hterature upon these subjects, both from the purely hygienic and the purely engineering or architectural points of view, still the conditions of ventilation and heating in the greater number of dwelhngs and public buildings must be said to be unsatisfactory. In this country, the great majority of habitations have no systematic scheme of, or special provisions for, ventilation, and even in the greater number of churches, schools, theatres, courts of justice, and public assembly rooms, in which some openings do exist for the entrance and exit of ah, it is rare to find satisfactory ventilation. The causes of this appear to be partly apathy and ignorance on the part of the people, partly an inability on the part of architects and engineers to accept a definite standard as to quantity of air reqiured, and partly the question of cost. In respect FRESH AIR REQUIREMENTS OF THE HEALTHY. 181 of this last factor, it is important to remember that in most cold climates it is difficult to combine good ventilation and sufficient heating with cheapness of construction in building; possibly the question of expense might be considerably modified, were the matter of ventilation and heating duly considered in the beginning, and not taken up as after-thoughts when every detail as to construction has been decided upon. When this fact is more fully appreciated by architects and builders, doubtless considerable improve- ments, as to both ventilation and heating, will soon be apparent. This subject may be conveniently considered under the folloAving heads:— 1. The quantity of fresh air required for the purposes defined above. 2. The methods by which this quantity may be supplied. 3. The methods of heating and cooling. 4. The method of examining whether ventilation and heating are sufficient or not : or in other words, ascertaining that the air of inhabited rooms is pure, according to a certain standard. QUANTITY OF AIR REQUIRED FOR VENTILATION. The quantity of air required for ventilation will naturally depend upon the nature and amount of the air impurities requiring dilution and removal. These have been already considered, in the preceding chapter, and, disregard- ing details, practically consist of impurities from respiration and from artificial lights. Of these various impurities, no matter whether from respiration or illumination, the carbon dioxide is accepted as the chief measure of ah vitiation. This is so, not because the carbon dioxide exists in such amount as to much influence health, but because it appears to exist in a constant ratio with the other offensive and possibly more dangerous impurities. And as it is very readily determined with sufficient accuracy for practical purposes, it is taken as a convenient index to the amount of the other impurities in general. Fresh Air requirements of the Healthy.—Taking the carbon dioxide as the measure of the impurity of the air vitiated by respiration and transpira- tion, in short, from the person in any way, Ave have to ask, What is to be considered the standard of purity of air in dAvelling-rooms ? We cannot demand that the ah of an inhabited room shall be absolutely as pure as the outside ah; for nothing short of breathing in the open air can insure perfect purity at every respiration. In every dAvelling-room there will be some impurity of air. The practical limit of purity will depend on the cost which men are willing to pay for it. If cost is disregarded, an immense volume of air can be supplied by mechanical contrivances, but there are comparatively feAv cases in which this could be allowed. Without, however, attempting too much, it may be fairly assumed that the quantity of air supplied to every inhabited room should be sufficient to remove all sensible impurity, so that a person coming directly from the external air should perceive no trace of odour, or difference between the room and the outside air in point of freshness. This is now pretty generally admitted as the most convenient practical standard, precautions being taken that the air space be entered directly from the external air, or as nearly so as possible, for the sense of smell is rapidly dulled. In 1875, de Chaumont showed from a large number of observations that the sense of smell, carefully employed, gives a very fair idea of the amount 182 VENTILATION AND HEATING. of impurity in an air space. In these experiments, the amount of carbon dioxide in the external air was determined at the same time, so that the respiratory impurity was accurately knoAvn. Dividing the observations into groups, the folloAving results Avere obtained:— 1. Fresh, or not differing sen-sibly from the outer air. 2. Rather close. Organic matter becoming perceptible. 3. Close. Organic matter disagreeable. 4. Very close. Organic matter offensive and op-pressive ; limit of differentiation by the senses. Mean C02 per 1000 vols. reduced to 0° C. ( = 32° F.), due to respiratory impurity, ( 0-1943 0-4132 0-6708 0-9054 It -will thus be seen that the smell of organic matter is, on an average, imperceptible to the sense of smell when the coincident C02, due to respiratory (or personal) impurity, does not exceed 0*1943 per 1000; and that Avhen it reaches 0*9054, smell is no longer able to detect shades of difference. We may therefore take 0*2 per 1000 in round numbers as the maximum amount of respiratory impurity admissible in a properly ventilated air space. This relation between the smell and air vitiation of an inhabited room varies greatly under certain circumstances. Thus the smell of organic con- tamination from respiration may not be perceptible when the C02 is as high as 0*5 per 1000, and yet be very decided when the C02 does not exceed 0*3 per 1000. These differences depend largely upon the amount of moisture present and the temperature. In adopting any standard of air purity, as expressed by the proportion of carbon dioxide present, Ave must not forget that, although hitherto it has been assumed that the carbon dioxide found, in excess of that which exists in the outer air, is all due to respiration, such is not always the case. Some may be due to gas or candles. Similarly, in instances where some of the air impurity may not be readily appreciable by a chemical test, the vitiation as indicated by a greater or less amount of carbon dioxide may be wide of the mark. Subject to these considerations, we may practically accept the carbon dioxide present in any given air sample as the best and most reliable index of air pollution. Having fixed upon a standard of respiratory impurity permissible in a properly ventilated air space, it is easy to calculate the amount of air needed to dilute the air expired by a person for a given time, so that the carbon dioxide contained in the resulting mixture shall not exceed this standard. The amount of carbon dioxide, over and above that in the inspired air, which is expired by an individual during an hour, varies with his Aveight and body activity. Pettenkofer, whose experiments are still the most trustAvorthy, ascertained that a man of tAventy-eight years of age, Aveighing 132 ft> avoir., evolved per hour at night during repose 0*56 of a cubic foot of carbon dioxide, and 0*78 in the day time, using very moderate exertion; during hard Avork the same man evolved 1*52 per hour. These amounts give the folloAving:— In repose, . . 0*00424 cub. ft. of C02 per lb of body-Aveight. In gentle exertion, 0*00591 ,, ,, ,, In hard work, . 0*01152 ,, „ AMOUNT OF FRESH AIR REQUIRED. 183 These figures are nearly in the ratio of 2, 3, and 6, and this may serve as a guide to the proportions of fresh air required. If we uoav take the average Aveight of adult males at 150 ft) to 160 ft), adult females at 100 lb to 120 ft), and children at 60 ft) to 80 ft), Ave should have the following amounts of carbon dioxide evolved per hour in repose :— Adult males, . . 0 636 to 0*678 cubic foot. ,, females, . . 0*424 to 0509 ,, Children, . . . 0*254 to 0*339 The estimate for children is probably too little, as tissue change is more active in their case. For a mixed community a general average of 0*6 of a cubic foot per hour may be adopted; but for adult males, such as soldiers, it is advisable to adopt 0*7 to 0*72. By dividing the amount of carbon dioxide exhaled in an hour by the permissible limit of respiratory impurity, de Chaumont suggested the number of cubic feet of air per hour required per person: this is now the standard most generally accepted by all sanitarians. It is conveniently expressed by the following formula:— — = d, P Avhere e = the amount of C02 exhaled by one individual in an hour, p = the limit of admissible impurity (stated per cubic foot), and d = the required dehvery of fresh ah in cubic feet per hour. If we take e at the general average of 0*6 of a cubic foot, then ——— = 3000 : or, putting e at a ° ' 0*0002 r b 0*7 higher figure, say 0*7, then ^r} = 3500 *. or, putting e still higher, say 0*92 0*92, then ^^ = 4600. For mixed communities, under ordinary conditions, 3000 cubic feet per hour is the accepted standard allowance per person. This formula may also be used conversely, in order to find from the con- dition of the air the average amount of fresh air which has been hitherto supplied and utihsed. For this purpose we simply substitute for p (the admissible hmit) pv the observed ratio : thus,— = d. Example.—Let us suppose that the total C02 in a room, after occupation, is found to be l'l per 1000, or 0-0011 per cubic foot, that in the outer air being 0*0004 : therefore plt or the observed ratio of respiratory impurity, is 0*0011 - 0*0004 or 0*0007 ; then— = d, Pi or——-— = 857 cubic feet of air, have been supplied during the period of occupation. By a transposition of the last formula, Ave can calculate the probable condition of the atmosphere in a room into which a given quantity of air has been or is being delivered: thus, -5 = pv Example.—If five persons occupy a room of 6000 cubic feet space for six hours, what percentage of C02 would be present at the end of the time, supposing 8000 cubic feet of fresh air have been supplied per hour ? Presuming that each person gives off 0-6 cubic foot.of C02 per hour, therefore five persons in six hours exhale 0*6x5x6 = 18 cubic feet of C02, and this Avill represent e or 184 VENTILATION AND HEATING. the observed ratio of respiratory impurity : d, or the total amount of fresh air available, will be 54,000 cubic feet, because 6000 were originally present in the room and 48,000 are added during the six hours : then, 2 = pi becomes rlono = Pii or 0*00033 per cubic foot or 0-033 per cent. That is, the added respiratory impurity is 0*033 per cent.; but the air of the room originally may be presumed to have contained 0*04 per cent, of CO.,, therefore the total percentage of C02 in the air asked for=0*033 + 0 04 or 0-073 per cent. It must be observed that in applying these formulae, the primary value of e must be changed with different conditions. For children, it averages 0'4; for adults under ordinary circumstances 0-6; for adult males, such as soldiers, 0*72 has been suggested; while for adults employed in arduous work, possibly as much as 2 cubic feet may be taken as the average hourly exhalation of carbon dioxide. For a long time after this subject first attracted attention the amount of fresh air supposed to be necessary was put at too low a figure. Even the figures of Morin, which Avere a great advance at the time, are insufficient. He proposed 2118 cubic feet (60 cubic metres) for barracks at night, and Ranke adopts the same figures. Roth and Lex adopt the maximum of total impurity at 0*6 per 1000, which includes 0*4 of initial C02; and as they estimate the expired C02 as 20 litres, or 0*706 cubic foot per hour, they give the hourly quantity of air as 100 cubic metres, or 3533 cubic feet. It is highly desirable that some general agreement should be come to as to the amount of, air necessary, even if it be admitted that the deshed amount cannot always be obtained. If we adopt the following amounts of C02 as being evolved during repose, Ave shall not be far from the probable truth:— Adult males (say 160 lb weight), . . . 0*72 of a cubic foot. ,, females ( ,, 120 lb ,, ), . . 0*6 ,, Children ( ,, 80 lb „ ), . . 0*4 ,, Average of a mixed community, . .0*6 ,, Under those conditions the amount of fresh air to be supplied in health during repose ought to be— For adult males, . . 3600 cubic feet per head per hour = 102 c. m. „ ,, females, . . 3000 ,, ,, ,, = 85 ,, „ children, . . 2000 ,, „ ,, = 57 „ ,, a mixed community, . 3000 ,, ,, ,, = 85 , The amount for adult males as above given is just over 100 cubic metres, or, if we state it at 3600 cubic feet, it is just one cubic foot per second. These numbers are easy to remember. When we have to deal with places, the inmates of which are actively employed, such as workshops and the like, the amount of air supplied must be proportionately increased. We have seen that in light work the carbon dioxide evolved per hour is nearly 0*006 of a cubic foot per ft) of body- weight, and in hard work more than double that amount,—so that for a man of 160 ft) weight we should have— In light work, . . 0*95 of a cubic foot of C02 evolved per hour. In hard work, . . 1-84 ,, ,, This Avould argue a delivery of fresh air as follows :— In light work, .... 4750 cubic feet. In hard work, .... 9216 FRESH AIR REQUIREMENTS OF THE SICK. 185 Carnelley, Haldane, and Anderson, basing their opinion not only upon the average presence of carbon dioxide in the air, but also upon the organic matter and number of micro-organisms, proposed that instead of taking 0*6 cubic foot of C02 per 1000 as the limit, that the standard should be 1*0 for dwelhngs and 1*3 for schools. In the case of organic matter, that not more than two volumes of oxygen should be required for oxidation per million volumes of air, and that the micro-organisms should not exceed 560 per cubic foot of air. The above figures for carbon dioxide are inclusive of that ordinarily present in the air, and certainly give a very liberal margin, Avhich ought not to be transgressed. If accepted, the respiratory impurity permissible in dwellings Avould be as high as 0*6 for dAvellings and 0*9 for schools, in place of de Chaumont's general permissible respiratory impurity of 0-2. On this basis, the hourly need of fresh air in dAvellings would not exceed 1000 cubic feet per head, and in schools be but 550 cubic feet. Experience, so far, has not justified the general acceptance of those low standard allowances of fresh air per hour. In mines, experiments show that, if it is wished to keep up the greatest energies of the men, no less than 6000 cubic feet per hour must be given ; if the quantity be reduced to a third or half, there is at once a serious diminution in the amount of work done by the men. This amount of fresh air includes, of course, all that Avanted in the mine for horses, lights, &c. Fresh Air requirements of the Sick.—In making differential experiments among the healthy and the sick, it has been found that among the former the smell of organic matter was still imperceptible when the air contained 0-208 per 1000 of respiratory impurity as carbon dioxide; but in hospitals containing ordinary cases it was quite distinct when the C02 reached 0*166. From this we may conclude that the minimum amount of fresh air for hospitals ought to exceed that required in health by at least one-fourth. If 3000 cubic feet per hour be admitted as a general average in health, we may demand in round numbers 4000 in sickness; and if we have to deal Avith adult males only, such as soldiers, 4500 per head per hour. When we have to deal with serious cases, a still greater amount must be given, reaching 5000, 6000, or even more if possible—in fact, the supply should be unlimited. These vieAvs are in accordance Avith the results of experimental inquiry. In some diseases, so much organic substance is throAvn off that scarcely any ventilation is sufficient to remove the odour. In some of the London hospitals de Chaumont found that there was still a close smell when 5000 cubic feet and even more were supplied, but the distribution was not perfect. Even when 3600 feet were supplied and utilised (as calculated from the C02), the ward Avas not free from smell. The great value of fresh air and of cubic space is now fully recognised in the treatment of surgical cases; and it is well known that in typhus fever, and also in small-pox and plague, the free exposure of patients to fresh air is as important a part of the treatment as the administration of suitable diet and medicines. Even temperature must be sacrificed to a considerable extent in order to obtain fresh ah, if a choice requires to be made between the two. Fresh Air required for Artificial Lights.—The same principles which govern the calculation of fresh air, needed to dilute and remove respiratory impurities, apply equally to the case of air vitiation from gas-lights, lamps, and candles. If the products of their combustion are allowed to pass into rooms, fresh air must be supplied to dilute and remove them. Although the contaminations, especially in the case of gas, are very great, it is estimated that for their proper dilution the amount of fresh air supply, in 186 VENTILATION AND HEATING. relation to the carbon dioxide evolved, need not be so great in their case as for breath impurities. It has been calculated that for every cubic foot of coal gas burnt, 500 cubic feet of fresh air must be introduced hourly to properly dilute the products of combustion; and this is not too much if Ave remember that a cubic foot of good coal gas produces 0*5 cubic foot of carbon dioxide, and that sulphur dioxide and other substances may be also formed. An ordinary flat flame burner Avill burn at least 5 cubic feet of gas per hour, and in the course of an evening of four hours, will generate at least 10 cubic feet of carbon dioxide, and, assuming that a supply of 1000 cubic feet of fresh air are needed for every cubic foot of carbon dioxide pro- duced per hour, we shall require for this gas-burner alone some 10,000 cubic feet of air to be supplied during the evening, or about 2250 cubic feet per hour; unless, of course, the products of combustion are removed by a special channel. We have already seen that, the power of illumination being equal, gas produces less carbon dioxide than candles; but usually so much more gas is burnt that the air is much more contaminated; there is also greater heat and more watery vapour. These products should never be allowed to escape into the air of a room, for the bad effects of breathing the products of gas combustion are only too Avell knoAvn. One ft) of paraffin oil demands for complete combustion 138 cubic feet of air; and to keep the air perfectly pure, nearly as much air must be introduced for 1 ft) of oil as for 15 cubic feet of gas. In mines, 60 cubic feet of ah per hour are allowed for each light; the lights, however, are usually dim and the combustion imperfect, facts Avhich indicate the fresh air allowance to be inadequate. Speaking generally, and under equal conditions of illuminating power, an ordinary five foot, flat flame gas-burner needs two- thirds the supply of fresh air per hour as required by an adult: the incandescent gas-lights on Auer's principle appear to need slightly less or about half the amount proposed for grown-up individuals, while ordinary paraffin lamps need quite as much fresh air as do adults. If gas is burnt in a room only in small quantities, or if only a feAv candles or a small oil lamp are used, it is seldom necessary to take them into account in estimating the amount of fresh air required; but where many gas-burners are used, or many candles and lamps are alight, the degree of air vitiation resulting from them needs to be considered in estimating the amount of fresh air to be supplied to inhabited rooms, in order to keep the contained atmosphere in a sufficient state of purity consistent with comfort and health. Hitherto, tins point has been much neglected. The general use of incandescent electric lamps entails no extra provision of fresh air, as they do not contribute any impurity to the atmosphere. Fresh Air required for Animals.—This is a matter which has not received much attention, though very important. Marcker gives the folloAving:— For large cattle (viz., oxen, &c.) 30 to 40 cubic metres per hour for every 1000 ft) Aveight, or 1 to 1| cubic foot for every pound of weight. For small cattle (viz., sheep, &c.) 40 to 50 cubic metres per hour for every 1000 ft) weight, or 1| to If cubic foot for every pound of Aveight; the higher quantity being given on account of the more rapid tissue change in the smaller animals. These quantities seem absurdly small, and the chief reason for so limiting them seems to have been the fear of loAvering the temperature- too far. This is an erroneous view : animals properly fed will thrive better in a well-ventilated place at a Ioav temperature than in a warmer place ill- ventilated. There seems no reason Avhy the same rule should not apply to animals as to man, in which case something like 20 to 25 cubic feet per hour per pound of body-Aveight ought to be supplied. A horse or a coav ought, FRESH AIR REQUIRED FOR REMOVAL OF MOISTURE. 187 therefore, to have from 10,000 to 20,000 cubic feet per hour,—in short, it ought to be practically in the open air. From F. Smith's experiments, and using de Chaumont's formula, - = d> Avhere e (in a horse) equals LI3, it is shown that the amount supplied ought to be 5650 cubic feet per hour, if the limit of respiratory impurity be assumed at 0-2 per 1000. From the experiments given in Smith's work the amount of air supplied ranged from 38,000 cubic feet per hour to 2900; in the latter case the smell is described as abominable. It is clear, therefore, that the amount of air ought to be as large as possible, and fortunately in the case of animals this can be accomplished without any great difficulty; as F. Smith considers that Avith proper feeding and attention the air about a horse may be changed every three minutes, or twenty times an hour, without danger, although the coat may not turn out so glossy as in a Avarmer stable. Carl Dammann estimates that a horse or a cow Aveighing 1000 ft) should have 50 cubic metres of air or about 1800 cubic feet per hour for ventilation. Jc He uses the formula, «=----, in Avhich y is the amount of air in cubic p — q metres per hour; k is the amount of C02 exhaled by the animal per hour; p is the limit of impurity of C02 in the stable air; and q is the quantity of C02 in the outer or incoming air. For small animals he estimates that the supply should be 60 cubic metres or 2100 cubic feet of air per hour for each 1000 lb of animal weight. The smaller animals appear to require more air in proportion to their weight than do the larger ones, while the so-called Avild animals need more than the domesticated. Monkeys, in particular, require a comparatively liberal allowance of fresh air to keep them in good health. Fresh Air required for Removal of Moisture.—In all the foregoing considerations the chief need of fresh air has been emphasised in special reference to the removal or dilution of organic and inorganic impurities in the air. It plays, hoAvever, a very important part in the removal of excessive moisture. Watery vapour, it must be remembered, is given off into the air, not only in respiration, but also largely by artificial lights, and not a little of the discomfort attending vitiated atmospheres is due to the large amount of their contained moisture. Both de Chaumont and Billings have laid special stress upon the importance of humidity in connection with ventilation. The former says that an increase of one per cent, of humidity has as much influence on the condition of an air space, Avhen judged of by the sense of smell, as a rise of 4*18 degrees of temperature in Fahrenheit's scale, equal to 2°*32 C, OI- L'S 6 R. Our every-day experience confirms this. From the state of the air as regards humidity, information may sometimes be obtained which is just as valuable as the determination of so much carbon dioxide. Thus, a room at the temperature of 70° F., and with a humidity of 90 per cent., con- tains 7*2 grains of aqueous vapour per cubic foot: suppose the outer air to be at 50° F. with the same percentage of humidity; this would give 3*69 grains of aqueous vapour in each cubic foot of outer air. Now from 73 to 75 per cent, of humidity being the generally accepted standard of moisture usually present in the atmosphere of this country, consistent with comfort, in order to reduce the humidity of the room from 90 per cent, or discomfort to, say, 75 per cent, or comfort, or in other words, to a condition in which only 6 grains of moisture were present per cubic foot, we must add the following amount 7*2 x 6 of fresh external air: -------= 1'95, or nearly tAvice the volume of air 1 88 VENTILATION AND HEATING. in the room. If the occupants of the room have each 1500 cubic feet, it follows that either their supply of fresh air is short by nearly 3000 cubic feet per head per hour, or else that there are sources of excessive humidity within the room AAdiich demand immediate removal. Regarded in this manner, a sufficient supply of fresh air is just as important for loAvering the atmospheric humidity in an enclosed space as it is for diluting or Removing either carbon dioxide or organic effluvia. While 75 per cent., at a temperature of from 60° F. (15°*6 C.) to 70° F. (21°*1 C), may be taken provisionally as a standard of humidity for climates like our own, in drier climates, like America, the standard or mean percentage of moisture may be as low as 30 or 40. In Germany, 50 per cent, is looked upon as an average humidity, Avhilst in England this Avould indicate an uncomfortably dry atmosphere. METHODS BY WHICH THE NECESSARY QUANTITY OF FRESH AIR CAN BE SUPPLIED. This subject is largely an engineering problem, and involves the considera- tion of certain preliminary matters, especially facts relating to cubic space and the various forces concerned in ventilation. Cubic Space.—This is an important factor in ventilation in some cases, while in others it is of but secondary value. Sufficient has been said in the preceding pages to show that the hurtful matters in the air of an occupied room are constantly and equably produced, uniformly diffused, and fairly represented by the carbon dioxide present. It has further been explained that 0*2 of C02 per 1000 of air, in round numbers, may be taken as the maximum amount of impurity admissible in a properly ventilated air space. Adopting, then, this standard as the measure of the permissible maximum of impurity, the next point to be determined is the quantity of pure external air which should pass through the air of a room, vitiated by respiration, per head per hour, in order to keep the carbon dioxide at this ratio, assuming a general average of 0"6 of a cubic foot per head per hour to be given out. This question we have seen to be answered in terms of a standard of 3000 cubic feet. On this basis the following table has been constructed, showing the degree of fouling of the air in terms of carbon dioxide by respiration, and the amount of fresh air necessary, under different conditions of cubic space, to dilute to the given standard of 0*2 C02 per 1000 volumes of air, exclusive of the amount originally present in the air:__ 'Amount of cubic space (=breathing space) for one person in cubic feet. Ratio per 1000 of C02 from respiration at the end of one hour, if there has been no change of air. Amount of air necessary to dilute to standard of 0-2 during the first hour. Amount necessary to dilute to the given standard every hour ■ after the first. 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 100 200 300 400 500 600 700 800 900 1000 6-00 3-00 2-00 1-50 1-20 1-00 0-86 0-75 0-67 0-60 2900 2800 2700 2600 2500 2400 2300 2200 2100 2000 CUBIC SPACE. 189 The above table refers to rooms occupied for several hours consecutively, such as sitting-rooms, bed-rooms, hospital wards, &c, and in each case, no matter what the breatlhng space per head may be, we find 3000 cubic feet of fresh air to be necessary each hour after the first to dilute to the given standard. When we come to inquire whether there is no minimum size of space through which the fresh air has to pass, Ave find that this will entirely depend on the rate at which air can be taken through the space without the movement being perceptible or injurious, and the size of the space is of con- sequence chiefly in so far as it affects this condition. The larger the air space, the less is the necessity for the frequent renewal of air, and the less the chances of draught. Thus a space of 100 cubic feet must have its air changed thirty times in an hour, if 3000 cubic feet of air are to be given, Avhile the space of 1000 cubic feet need only have it changed three times in an hour for an equal ventilation. When the most perfect mechanical means are employed, the air of even a small air space can be changed sufficiently often without draught. Thus, in Pettenkofer's experimental room at Munich, the air space is 424 cubic feet, and 2640 cubic feet can be drawn through by a steam-engine in an hour Avithout perceptible movement; in other words, the change is six times per hour nearly. With the best mechanical contrivances, and with disregard of cost, we are therefore certain that a cubic space of 600 feet Avould be sufficient, and there is every probability that engineers could ventilate even a smaller space Avithout perceptible movement. But if the mechanical contrivances are of an inferior kind, and par- ticularly if natural ventilation is used, the difficulties of ventilating a small space are considerable, and are caused not so much by the rate of move- ment of the greater part of the air in the room as by the rate at the open- ings where the fresh ah comes in very quickly, and causes currents in the room. Suppose, for example, a space of 500 cubic feet occupied by one person, who has to be supphed with 3000 cubic feet in an hour; if the inlet opening be 12 square inches, the rate of movement through it Avould be 10 feet per second, or nearly 7 miles per hour; if 24 square inches, it Avould be 5 feet, or about 3*4 miles per hour. In either case, in such a small room, the air could not be properly distributed before reaching the person, and a draught would be felt. If instead of 500 cubic feet of space 1000 be given, the problem is easier, for the small current of fresh air mix- ing with the larger volume of air in the room is more easily broken up, and the inmate being further from the opening, the movement is less felt. The question, in fact, turns in great measure on the power of introducing the air Avithout draught. If the reneAval of air is carried on by what is termed natural ventilation, under the ordinary conditions of this climate, a change at the rate of six times per hour, as in Pettenkofer's room, could not be attempted. Even five times per hour would be too much; for, in barracks with 600 cubic feet per head, the rooms are cold and draughty when anything approaching to 3000 cubic feet per head per hour are passing through; that is, a change of five times per hour for each 600 cubic feet of air space. A change equal to three times per hour is generally all that can be borne under the condi- tions of warming in this country, or that is practically attainable Avith natural ventilation, and if this be correct, from 1000 to 1200 cubic feet should be the minimum allowance for the initial air space. With good warming and an equable movement, which, however, are not always easy to get, there might be larger inlets, and therefore more easy distribution and a smaller air space to begin with. If the inlets are 48 1 190 VENTILATION AND HEATING. square inches, the rate through them to supply a space of 500 cubic feet Avith 3000 cubic feet per hour Avould be only 2\ feet per second; and if, as should be the case in artificial ventilation, the inlet is 72 or 80 square inches in size, the rate would only be a little over \\ feet per second, Avhich would be imperceptible even at the orifice. But there is an argument against a small cubic space, even with good mechanical ventilation, viz., that if any- thing arrests the mechanism for a time, the ratio of impurity from respira- tion increases much faster in a small than in a large space. The warmth of the moAdng air influences the sensation of the persons exposed to it. At a temperature of 55° or 60° F., a rate of \\ feet per second ( = 1 mile per hour nearly) is not perceived; a rate of 2 to 2\ per second (1*4 and 1*7 mile per hour) is imperceptible to some persons; 3 feet per second (2 miles per hour nearly) is perceptible to most; a rate of Z\ feet is perceived by all persons; any greater speed than this will give the sensa- tion of draught, especially if the entering air be of a different temperature, or moist. If the air be about 70° F., a rather greater velocity is not perceived, Avhile if it be stiU higher (80° to 90° F.), the movement be- comes again more perceptible, and this is also the case if the temperature be beloAv 40° F. If the air could be warmed to a certain point in a cold climate, or if the climate be warm, there may be a much more rapid current, and consequently a smaller cubic space might be given. The subject of ventilation is in cold climates connected inseparably Avith that of warming, for it is impossible to have efficient ventilation in cold Aveather without warming the air. The amount of cubic space thus assigned for healthy persons is far more than most people are able to have; in the crowded rooms of the artisan class, the average entire space would probably be more often 200 to 250 cubic feet per head than 1000. The expense of the larger rooms Avould, it may be feared, be fatal to the chance of such an ideal standard being generally carried out; but, after all, the question is, not Avhat is likely to be done, but what ought to be done; and it is an encouraging fact that in most things in tins world, when a right course is recognised, it is somehow or other eventually followed. So, in the case of soldiers, the amount of authorised regulation space (600 cubic feet) is below the standard now given, but still the space is as much as can be demanded at present, as it has been found very difficult, Avithout incurring greater expense than the country would bear, to give every man even the 600 cubic feet. In the metropolitan lodging-houses 30 superficial and 240 cubic feet are allowed; in the section-houses of the metropolitan police 50 superficial and 450 cubic feet are given. The Local Government Board allows 300 cubic feet for every healthy person in the dormitories of poor-houses, and from 850 cubic feet and upAvards, according to circumstances, as far as 1200 cubic feet for each sick person. In the Poor-law schools 360 cubic feet are given per head. In Dublin, an allowance of 300 cubic feet is required in the registered lodging-houses. While the theoretical requirements for a child in an elementary school is 400 cubic feet, and for a lad in a large public school 500 cubic feet, as minima, we find that the London School Board do not allow more than 130 cubic feet. The Education Department of the Privy ■Council endeavour to secure at least 80 cubic feet and 8 square feet for each unit of average attendance in the infant schools, and 10 feet of floor area Avith a cubic space of about 125 feet to each child in other schools. Accord- ing to the model bye-laws of the Local Government Board, 300 cubic feet are allowed in common lodging-houses for each person above 10 years, and CUBIC SPACE IN REGARD TO VENTILATION. 191 150 cubic feet for each person younger. Other customary amounts of cubic space per head are 1000 feet in middle-class houses, 500 in good secondary schools, and 212 in ordinary one-roomed houses. For sick persons the cubic space should be more than for healthy persons. We are to remember that there are other impurities besides those arising from respiration and transpiration, and that immediate dilution and as speedy removal as can be managed are essential. "Very much the same considerations apply to sick as to healthy men, except that the alloAvance of air in all cases of acute diseases must be greater; and, therefore, especially if natural ventilation be employed, the cubic space has to be enlarged also, to insure good distribution without draught, for surface chilling must be carefully avoided. Admitting that, in hospitals, a minimum of 4000 cubic feet of fresh air per patient per hour should be supplied, if the change of air is to be three times per hour, as the best available rate of movement, the cubic space must be about 1300 cubic feet. A consideration of another kind may aid in determining the question as regards sick men. In hospitals a certain amount of floor space is indispensably necessary ; first, for the lateral separa- tion of patients; secondly, for convenience of attendance. For the first object, the greater floor space the better; and in respect of the second, Sir H. Acland has clearly shown that the minimum floor space for convenient nursing should be 72 square feet per bed. In a ward of 12 feet in height, this Avould give only 864 cubic feet, which is much too small. Considering, hoAvever, the immense benefit to patients of pure air, and the practical experience of hospital physicians, it is very desirable not to fix the floor and cubic space of hospital Avards at the minimum of Avhat may suffice. The deshe of most hospital physicians and surgeons is to obtain for their patients, if they can, a floor space of 100 to 120 square feet, and a cubic space of 1500 to 2000 cubic feet, and in this they are right. It must be distinctly understood that a minimum of floor space must be insisted upon in aU cases, not less than -^ of the cubic space. An idea prevails among many people that cubic space may take the place of change of ah, so that, if a larger cubic space be given, a certain amount of change of air may be dispensed Avith, or less fresh air be required. This is quite erroneous : even the largest space can only provide sufficient air for a limited time, after Avhich the same amount of fresh air must be supplied hourly, whether the space be large or small. Even in a space of 10,000 cubic feet per head, the limit of admissible impurity would be reached in a few hours, after which the same hourly supply of 3000 feet would be as necessary as in a space of 100 feet. This is shown by the table given on page 188, and may be also mathematically demonstrated by the following formula given by Donkin:— P P _a { x = p-\— - — 2*718 - ~c" in Avhich r a a & is the condition of the air as to C02 per foot at the end of the time t; p is the C02 per cubic foot in the outer or fresh air introduced; P the C02 expired per hour per man ; a the incoming air in cubic feet per hour; 2*718 is the exponential function; and c is the cubical capacity of the air space. It will be at once seen by the above formula that when it is wished to maintain the space c at the purity of the outer air, and that x and p gradually approximate to each other, the numerical value of the last term in the equation diminishes rapidly as t increases until it becomes insensible; with 192 VENTILATION AND HEATING. it then disappears the quantity c or the value of the cubical capacity of the air space. It folloAvs then that it is immaterial what the size of the air space is, for the same amount of fresh air will be needed to keep it sweet, be it large or small. Example.—Suppose, in a room containing 1000 cubic feet of space, a man giving off 0-6 cubic foot of CO., remains for t hours, and 3000 cubic feet of fresh air are introduced 0-6 0-6 _ 3Q0Q< hourly. Applying Donkin's formula, Ave get, a3=0'00°'i + 3ooo~30002' 100°- This being worked out, according to the varying values of t, we find that the units of carbon dioxide per cubic foot of air are, 0*0004 at first, 0*00059 after one hour, 0-0005995 after two hours, and 0-00059997 after three hours ; so that even after two hours the air of the room will have sensibly reached the final or permissible condition of 0-0006 C02 per cubic foot. If the room contained 10,000 cubic feet, the approximation to the final state would be less rapid, but equally certain as time elapsed. The question really resolves itself into, Avhat is the ratio of a to c, or in other words, Avhat is the least amount of c through Avhich a can be passed Avithout causing inconvenience from draughts ? Under ordinary circum- stances, and without artificial methods of warming the incoming air, the answer has been given as an original air space of close upon 1000 cubic feet. These considerations as to the imperfect value of cubic space alone have suggested the rule that, in computing cubic space for purposes of ventilation, the heights of rooms above 12 feet should be largely disregarded. The cubic space required for animals has not been very carefully examined. Certain animals, notably pigs, sheep, horses, and cattle generally, emit large quantities of marsh gas from the intestines. Our chief knowledge as to the oxygen consumed, the carbon dioxide and marsh gas given off by animals, is derived from Reiset's observations. The following is an abstract of his Avork:— Weight of Animal in Kilos. Oxygen con-sumed in Grammes per hour. Oxygen con-sumed per Kilo, of body-weight. Carbon Dioxide exhaled in Grammes. Nitrogen exhaled in Grammes. Marsh Gas exhaled in Litres. Sheep, . 67-7 33-51 0-495 42 63 0-246 1-4 Calves, . 97-3 45-87 0-480 54-54 0280 1-3 Pigs, 105 6 49-30 0-477 60-50 0-025 o-i Oxen, 230-0 11050 0-480 128*80 0-293 3-07 Horses, . 250-0 117-42 0-470 131-62 0-295 3-66 An average-sized sheep spoils 112 litres or 3'9 cubic feet of air per hour; calves spoil 154 litres or 5'4 cubic feet; moderate-sized pigs spoil 166 litres or, say, 6 cubic feet of fresh air hourly ; rabbits about 10 litres or 0*35 cubic foot; fowls 1 htre or 0*035 cubic foot; a dog of medium size, 23*5 htres or 0*83 cubic foot; a cat weighing 10 t> spoils 17*8 litres or 0*6 cubic foot of fresh air per hour. On the basis of respiratory impurity alone, we may reckon that calves and pigs vitiate the air rather more than a man does ; about 10 sheep foul the ah in the same degree as 8 men; Avhile 14 rabbits or 140 chickens are equal to a man in this respect. As a matter of fact, these animals con- taminate the ah more than the above, because they are always associated with their own excreta. If Ave folloAved the rule for men, and gave one- third the quantity of ah supplied per hour, this would give for horses and cattle from 3000 to 7000 cubic feet. This, however, is probably not necessary, because change of air can be carried on more freely than in SOURCE AND DISTRIBUTION OF AIR SUPPLIED. 193 Cubic feet Cubic feet r head per hour. of space. 22 4 222 44 360 72 474 95 3120 604 3510 702 7920 1584 7920 1584 human habitations, and animals cannot close ventilators as men will often do. A floor space of 100 to 120 square feet would probably be sufficient, giving a space of 1200 to 1800 cubic feet, according to the height of the budding. If this could be secured, there is every probability that the results Avould be excellent. We might put the estimate roughly at 2 cubic feet of space for every pound avoirdupois the animal weighs, the floor space being not less than TXT of the cubic capacity. Another rule might be to give 600 times the amount of air spoilt, which is practically the rule employed in the case of adult men : an adult man renders, we know, 5 cubic feet of ah absolutely irrespirable every hour, and 600 times this or 3000 cubic feet per hour of fresh air is the generally recognised amount required to keep the ah of a room in the highest degree of practicable purity. On the same principle, if we multiply the cubic feet of air Avhich the different animals render irrespirable by 600, we get the following theoretical quantities of air Avliich should be supplied per hour to animals :— Fowls. Rabbits, Cats, . Dogs, . Calves, Pigs, . Oxen, . Horses, Formerly, in the cavalry stables of the British army each horse had 1605 cubic feet and 100 square feet of floor space. At present the superficial area of army stables has been fixed as folloAvs :—for the stall alone, 52 feet; for the stall and share of passage, 91 feet. F. Smith considers that the stall alone should be 70 feet, and the stall and share of passage, 100. In the Army Horse Infirmaries the superficial area is to be 137 square feet, or 200 Avith share of passage; loose boxes 204, and the cubic space 1900 feet per horse. In the stables of cattle there is often excessive overcrowding, and it is Avell known that there is a vast amount of disease among them, Avhich, however, is seldom allowed to go far, as they are sent to the butcher. Ballard, who paid great attention to the cattle plague in Islington, recom- mended that at least 1000 cubic feet should be allowed per animal. Source and Distribution of Air Supplied.—In order that the object of ventilation shall not be defeated, it is necessary that the air entering a room shall be pure. The air must be the pure external air, and not be derived from places where it has stagnated and taken up impurities; if it is drawn along passages or tubes, and through louvres or basements, these should be capable of inspection and cleansing. All delivering air-shafts should, if possible, be short and easily cleaned. This is an important rule, and should lead to the rejection of all plans in which the air-shafts are long and inacces- sible. Several instances have occurred of air being distributed by costly appliances, but drawn from an impure source, or allowed to be contaminated on its passage. Instead of perforated bricks, there should be sliding panels, or hinged flaps, so that the tube may be easily reached. In towns it may be necessary to filter the air, which is often loaded with the products of combustion and other impurities. The air may requhe to be warmed to 60° or 65° F., or cooled accord- ing to the season or locality. The warming in cold and temperate climates is a matter of necessity, as, if discomfort is caused by cold draughts, N 194 VENTILATION AND HEATING. ventilation openings are certain to be closed. When the external tempera- ture is low, the air supplied will often require to be moistened as well as warmed. This can be done by either injecting clean steam or Avater spray, or simply by exposing a water surface to the air. For these islands, a humidity of 75 per cent, is the most general requirement. The distribution in the rooms should be perfect, that is, there should be uniform diffusion of the fresh air through the rooms. The best way of ascertaining this is to compare the amount of ah utilised, as calculated from the observed carbon dioxide, with the actual movement of air, as measured with the air-meter. If the distribution is good, the tAvo quantities ought not to differ materially. Much difficulty is found in properly managing uniform diffusion, and it requires careful arrangement of the various openings. The distributing plans should, if possible, prevent the chance of breathed air being rebreathed, especially in hospitals. As the ascent of respired ah is rapid, on account not only of its temperature, but from the force with which it is propeUed upwards, the point of discharge for patients in bed should be above. By some it has been argued that it is better that the foul air should pass off below the level of the person, so that the products of respiration may be immediately drawn down below the mouth, and be replaced by descending pure air. But the resistance to be overcome in drawing doAvn the hot air of respiration is so great that there is a considerable waste of power, and the obstacle to the discharge is sometimes sufficient, if the extracting force be at all lessened, to reverse the movement, and the fresh air forces its way in through the pipes intended for discharge. This plan, in fact, must be considered a mistake. In the case of vapours or gases the proper place of discharge is above; but heavy powders, arising in certain arts or trades, which from their weight rapidly fall, are best drawn out from below. Finally, in determining the plan of ventilation of a room, the whole budding must be treated as one system, and the plan of air circulation drawn out for the whole. It is useless having a system which is only workable in a room so long as all the doors are shut, if one of the conditions of the room being used is that the doors be frequently open. This is particularly necessary in ordinary dAvelhng-houses, and it practically amounts to saying that every outlet for air should be supplied with an adequate air inlet, so that there shall be no head between different rooms. Forces concerned in Ventilation.—All ventilation methods are based either upon forces continually acting in nature, which produce what has been called natural ventilation; or upon forces set in action by man, which produce the so-called artificial ventilation. This division is convenient, but not strictly logical, as the forces which act in natural do so also in artificial ventilation to a certain extent. These forces are practically three, namely, diffusion, winds, and the difference in weight of masses of air of unequal temperature. Diffusion.—As every gas diffuses at a certain rate, viz., inversely as the square root of its density, there is a constant escape of any foreign gas into the atmosphere at large. From every room that is not air-tight Pettenkofer and Roscoe have shown that diffusion occurs through brick and stone, and it is probable that one of the evils of a neAvly built and damp house is that diffusion cannot occur through its walls. But ordinary plastered and papered Avails reduce diffusion to a most insignificant amount. Through chinks and openings produced by imperfect carpentry the air diffuses fast and Roscoe found that when he evolved carbon dioxide in a room the amount had decreased one-half from that cause in 90 minutes. WIND AS A VENTILATING AGENT. 195 The amount of purification produced by diffusion under ordinary circum- stances is shown by observation to be insufficient; and, in addition, organic substances, Avhich are not gaseous, but molecular, are not affected by it. As a general ventilating power, it is therefore inadequate. Winds.—The action of wind is a powerful ventilating agent in various ways. If it can pass freely through a room, with open doors and AvindoAvs, the effect it produces is immense. For example, air moving only at the rate of 2 miles an hour (which is almost imperceptible), and allowed to pass freely through a room 20 feet broad, will change the air of the room 528 times in one hour. No such powerful action as this can be obtained in any other Avay. The wind will pass through Avails of Avood (single-cased), and even of porous bricks or stone; and perhaps this Avill account for the fact that such houses, though cold, are healthy habitations. By covering a brick Avith wax, or enclosing a portion of a brick wall in an air-tight box, Pettenkofer has shown that the force of the breath will drive air through the brick, and Avill blow out a candle on the other side if the current of air be collected in a small channel. The force required to drive the air through is, however, really considerable, as the air in the brick must be brought into a state of tension. Marcker has given the following as the amount of air passing in one hour through a square metre of wall space, when the difference of temperature is 1° C.:—Sandstone, 1*69 ; limestone, 2*32 ; brick, 2-83 ; tufaceous lime- stone, 3'64 ; and loamy brick, 5*12 cubic metres of air. The little porosity of sandstone depends on the amount of moisture it holds. The moisture, in fact, greatly influences the transit. Plaster, however, appears to arrest wind, if it be true, as stated, that in the interior of some thick walls, after many years, lime has been found still caustic ; and Marcker also notices the obstructive effects of mortar. There are two objections to winds as ventilating agents by perflation. (1) The air may be stagnant. In this country, and, indeed, in most countries, even comparative quiescence of the air for more than a few hours is scarcely known. Air is called " still" when it is really moving 1 or H mile an hour. The average annual movement of the air in this country is from 6 to 12 miles per hour; but it varies, of course, greatly from day to day, and in different places. (2) A much more serious evil is the uncertainty of the movement, and the difficulty of regulation. When the velocity reaches 5 or 6 feet per second, unless the air be warm, no one Avill bear it. The wind is therefore excluded, or, if allowed to enter directly through small openings, is badly distributed. Passing in with a great velocity, it forces its way like a foreign body through the air in the room, causing draughts, and escaping, it may be, by some opening without proper mixing. A current entering in this way may be measured for many feet. But the Avind acts in another way. A moving body of air sets in motion all air in its vicinity. It drives air before it, and, at the same time, causes a partial vacuum on either side of its own path, towards which all the air in the vicinity flows at angles more or less approaching right angles. In this way a small current moving at a high velocity Avill set in motion a large body of air. The wind, therefore, blowing over the tops of chimneys, causes a current at right angles to itself up the chimney, and the unequal draught in furnaces is OAving, in part, to the variation in the velocity of the Avind. Advantage, therefore, can be taken of this aspirating power of the wind to cause a movement of air up a tube. The wind, however, may impede ventilation I 196 VENTILATION AND HEATING. by obstructing the exit of air from any particular opening, or by bloAving down a chimney or tube. This is, in fact, one reason of the failure of so many systems of ventilation; they may Avork Avell in a still atmosphere, but the immense resistance of the Avind has not been taken into account. At 3 miles an hour, the pressure of the wind is f of an ounce on each square foot; it is 1 ounce at 3J miles; 2 ounces at 5 miles; 4 ounces at 7 miles; \ pound at 10 miles; and 1 pound at 14 miles. In some systems of ventilation the perflating power of the wind has been used as the chief motive agent. In Egypt the Avind is alloAved to bloAv in at the top of the house through large funnels. This plan has been in use from time immemorial. This was the case in Sylvester's plan, which was used at Derby and Leicester fifty or sixty years ago. A large coavI, turning toAvards the Avind, was placed in a convenient spot near the building to be ventilated—a little above the ground if in the country, or at some height if in a town. The Avind blowing doAvn the cowl, passed through an underground channel to the basement of the house, and entered a chamber in which Avas a so-called cockle-stove or calorifere of metal plates or water or steam pipes, by which the air was warmed. It then ascended through tubes into the rooms above, and passed out by a tube or tubes in the roof, which.were covered by cowls turning from the wind. So that the aspira- tory poAver of the air Avas also used. This plan is extremely economical, but the movement of the air is unequal, and it is difficult to regulate it. It has been proposed to place a fan in the tunnel to move the air in periods of calm, and the plan then becomes identical in principle, and almost in detail, Avith the method of Van Hecke. In the ventilation of ships the Avind is constantly used : and by Avind sails, or by tubes Avith coavIs turning towards the wind, air is driven between the decks and into the hold. In using the wind in this Avay, the difficulty is to distribute the air so that it shall not cause draught. This is best done- EFFECTS OF UNEQUAL AVEIGHTS OF AIR. 197 hy bending the tubes at right angles two or three times, so as to lessen velocity, or by enlarging the channel toAvards the opening in the interior of the vessel, and by placing valves to partially close the tubes, if necessary, and by screens of Avire gauze. If perforated plates or Avire gauze are used, care must be taken to see that they are constantly kept clean, as they very soon get clogged with dirt. It should also be understood that the delay by friction through fine Avire gauze is exceedingly great. In all cases in Avhich the air of a room, as in a basement storj7-, or in the hold of a ship, perhaps, is likely to be colder than the external air, and when artificial means of ventilation cannot be employed, the Avind should be taken advantage of as a motive agent. The aspiratory power of the wind and the production of a head for venti- lation, by the motion of air over the mouth of a tube, can be secured by covering air-shafts Avith cowls, which both aid up-currents and prevent down-draughts. This is practically the idea with Avhich all the varieties of up-cast ventilators are constructed, hoAvever varied may be their external appearance. Cowls are uncertain in their action Avhen fixed to buildings, owing to the variability of the Avind-currents, due to the effects of the surfaces of the buildings themselves. Although many forms of cowl have been designed to render them serviceable, no matter from Avhich direction the wind bloAvs, there are practically only tAvo types: namely, those Avith rotating coavIs and those with fixed Aranes. Of the former type, Banner's cowl (fig. 11) may be regarded as a specimen: it sets itself by means of a wind vane so that the opening ahvays faces aAvay from the Avind. The latter type is represented by Boyle's ventilator: in it the vanes are fixed, as shown in fig. 12, so that from AAdiatever direction the Avind blows, the motion of the air is ahvays tangential to the shaft opening. In all forms of cowl the air-current is both variable and small, and very liable to be overAveighted by the head from some other opening, so that what was primarily intended to be an up-cast often becomes a down-draught shaft. Effects of Unequal Weights of Air.—Though constituting one of the causes of Avind itself, it is necessary, in discussing ventilation, to look upon it as if it were an independent force. If the air in a room be heated by fire, or by the presence of men and animals, or be made moister, it endeavours to expand: and if there be any means for it to escape, a portion of it will do so, and that which remains will be lighter than an equal bulk of the colder air outside. The outer air will then rush into the room by every orifice, until the equality of weight outside and inside is re-established. But as the fresh air Avhich comes in is in its turn heated, the movement is kept up in a constant stream, cold air entering by one set of openings, and hot air escaping by another. We have noAV to inquire how the rate of this constant stream of air may be calculated. The mode most generally used is based on two Avell-knoAvn laws: first, that the velocity in feet per second of falling bodies is equal to nearly eight times the square root of the height through which they have fallen; and second, that fluids pass through an orifice in a partition Avith ■a velocity equal to that Avhich a body Avould attain in falling through a height equal to the difference in depth of the fluid on the tAvo sides of the partition. This is frequently called the rule of Montgolfier. The formula is v = J2gii: in Avhich g is the acceleration of velocity in each second of time, viz., 32-18 feet, and H is the height of the descent. When simplified out, this formula becomes z* = 8N/H. The pressure of the air upon any surface may be represented by the weight of a column of air of uniform density of a certain height. Thus the pressure of the atmosphere at the 198 VENTILATION AND HEATING. surface of the earth is nearly 15 ft) on the square inch, and this would be the weight of a column of air of about 5 miles in height. Air, there- fore, rushes into a vacuum with a velocity equal to that which a heavy body would acquire in falling from a height of 5 miles, viz., 1300 feet per second. But if, instead of rushing into a vacuum, it rush into a chamber in Avhich the air has less pressure than outside, its velocity will be that due to a height Avhich represents the difference of pressure outside and inside. In ordinary cases this difference of pressure cannot be obtained by direct observation, but must be inferred from the difference of tempera- ture of the outer and inner air. We have already learnt that air is dilated one part in 491 of its volume (0*00203) for every degree Fahrenheit, or one part in 273 (0*00366) for every degree Centigrade that its temperature is raised; consequently, the difference of pressure outside and inside will be as follows:— The height from the aperture at Avhich air enters to that from which it escapes, multiplied by the difference of temperature between outside and inside and by the co-efficient of expansion. Example.—Say the height of a column of air in a chimney, between its throat and aperture of exit, be 20 feet, and that, owing to a fire in the grate below, its temperature be 15° F. above that of the outside air. Then the height to produce velocity of an in- floAvingand colder current will be 20x15x0-00203 = 0-609 foot, and the velocity will be 8^0*609 = 8 x 0-781 = 6-248 feet. This, however, is the theoretical velocity. In practice, an allowance must be made for friction of \, \, or even \, according to circum- stances. The deduction of \ would leave 4 "686 linear feet per second as the actual velocity. If this be multiplied by the area of the opening, in feet or decimals of a foot, the amount of air is expressed in cubic feet per second, and multiplying further by 60 gives the amount per minute. If in this particular case the area of the chimney throat be a square foot, the amount of air escaping by the chimney under the above circum- stances, and of course replaced by a similar volume of fresh and colder air, will be 281 cubic feet per minute. A table is given on page 242, in Avliich this calculation has been made for all probable temperatures and heights ; but it must be remembered that the movement is greatly influenced by Avind. This cause of movement is, of course, constantly acting Avhen the tempera- ture of the air changes. It will alone suffice to ventilate all rooms in Avhich the air is hotter than the external air, but will not ansAver Avhen the air to be changed is equal in temperature to, or colder than, the external air. As its action is equable, imperceptible, and continuous, it is the most useful agency in natural ventilation in cold climates, in inhabited and warm rooms; and in all habitations arrangements should be made to alloAV it to act. As the action increases Avith the difference of temperature, it is most powerful in winter, when rooms are artificially Avarmed, and is least so, or is quite arrested in summer, or in hot climates, Avhen the internal and external temperatures are identical. Influence of Friction upon Air-currents.—The amount of loss produced by friction from various causes is often overlooked, and its neglect is apt to lead to failure and disappointment. The chief causes of loss are the folloAv- ing :— 1. Length of Tube or Shaft.—Here with equal sectional areas the loss is dhectly as the length, so that if Ave take a shaft of 30 feet as a standard, a shaft of 40 feet long would have an increased friction of one-third. 2. Size of Opening.—For similar sections the friction is inversely as the diameter. Thus for tAvo openings, respectively 1 and 2 feet in diameter the friction at the smaller opening will be tAvice that of the larger. In this Avay dh-iding up an opening into a number of smaller openings, the aggre- INFLUENCE OF FRICTION ON AIR CURRENTS. 199 gate of which is equal to the original opening, produces a loss by friction in the direct ratio of the diameters. An opening of 1 square foot divided into four openings of i of a square foot loses in the ratio of 1 : |, being respectively the diameters of the openings. When the shapes of the openings are not similar, the ratio may be stated as that of the square roots of the areas. Thus 1 square foot divided into nine openings, each equal to |- of a square foot, will lose in the ratio of 1 : ^, the square roots of the respective areas. 3. Shape of Opening.—A circular opening may be taken as the standard, that being the figure Avhich includes the greatest area Avithin the smallest periphery. The loss sustained from any other shape being used Avill be proportionate to its difference from a circle enclosing a similar area. Thus, if we have two openings, each of 1 square foot area, the one being a circle and the other a square, the length of periphery of the latter will be 4 square feet, of the former 3|; therefore the velocity of the current through the 31 7 square opening will be -2 or — of that through the circular opening. 4 8 4. Angles in the Tube or Shaft.—This is a most serious cause of loss. The exact formula has not been distinctly determined, but it may be accepted, as in accordance with experiment, that every right angle diminishes the current by one-half, so that two right angles in a tube would reduce it to \, and so on. Yet it is no uncommon thing to find tubes and shafts bent recklessly at numerous angles to fit a cornice or architrave, to save expense and appearance. In smooth channels the co-efficient of friction is represented by ^---r-gTj, 0 being the angle at any bend of the shaft or tube. For more general application,------- is probably better : in either case, an angle of 90° shows a loss from friction of one-half. At 60° the friction is A, at 45° it is -|, and at 30° it is 4. 5. The presence of dust, soot, or dirt of any kind seriously interferes with the current, but this may of course be obviated Avith a moderate amount of care and attention. It is obvious that attention to the above points is necessary to obtain success in any scheme of ventilation. Example.—Let us suppose a straight shaft 30 feet long, sectional area circular, of 1 square foot,—the current through this giving a sufficient amount of air for the purpose required. Let it be necessary to produce a similar amount of ventilation in another place, but to use smaller shafts, square in section, area of each | of a square foot,—each shaft being 40 feet long, and having one right angle in its course ; what would be the relative amounts of air available, other things being equal ? Taking the circular shaft, we have length of shaft 30, length of periphery 3^, total 33\ = friction. In the four smaller shafts we have length 40, length of periphery of each 2, which multiplied by 4 = 8, total 48 : the right angle doubles the friction, so that 48 x 2 = 96 as compared to 33^. Thus the result would be nearly as 3 to 1 in favour of the single shaft. It Avould be obviously necessary to treble either the number of the smaller shafts or the size of each of them. It is advisable generally to Aviden slightly the openings of shafts, especially if they are of small diameter, as the current tends to be contracted and obstructed at that point. At every change of direction the same thing takes place. Hence the desirability of rounding off angles as much as possible, where they cannot be altogether avoided. It is generally best to have the sections of shafts circular or elliptical instead of rectangular, for not only is there less loss by friction originally, 200 VENTILATION AND HEATING. but there is less chance of lodgment of dust, &c, and they can be more easily and thoroughly cleaned. It must not be overlooked that the specific gravity of vitiated air, as com- pared Avith pure air, is often as important as friction in hindering ventilation action. Usually the specific gravity of foul air is greater than that of fresh air; for instance, taking pure air as unity, the gravity of air containing 0*8 part of carbon dioxide per 1000 Avould be 1*0016, Avhile that of air fouled by organic vapours Avould be greater still. This explains Avhy contaminated air tends to cling or hang about particular parts of rooms, or, if there are no air currents, smells are so often apt to flow down towards basements of houses from the upper stories. It is obvious that in such cases calculations based upon the movements of absolutely pure air may be considerably in error. Natural Ventilation.—Of all the methods of natural ventilation, the simplest and most obvious is that of more or less open doors and windoAvs ; but this arrangement, except in the warmest summer weather, causes draughts, and is unpleasant. To secure adequate perflation, all windoAvs should, if possible, be placed on opposite sides of a room, while, too, each of such windows should be made to open at the top. Owing to air flowing against the body, at or even slightly above the temperature of a room, causing a sensation of cold or draught, it is necessary for comfort that air should be introduced into and removed from inhabited, rooms at those parts where it will not give rise to sensible draughts. In the large majority of houses, even in these days, ventilation arrangements are either of the most crude and haphazard kind, or else absolutely wanting. The greater number of hving-rooms depend for their supply of fresh air upon just so much as can find its Avay in through doors, windows, or through cracks and crevices around and under doors and windows, or even through the floor; and for the escape of foul air, upon what goes up the chimney, if a fire be alight, or Avhat can get out through doors and windows; the general result being that either the chamber is so cold and draughty that no one can live comfortably in it, or so hot, close, and stuffy that health is affected. All ventilation methods aim at avoiding these results, by providing, in the first place, inlets or means of entrance for the fresh ah, and outlets or means of escape for the impure air. Total size of all the special openings, whether intended for Inlets or Outlets.—As the movement of air increases with temperature, the precise size of the ventilating apertures can only be fixed for a certain given temperature; and as the efflux of hot air increases Avith the height of the column, supposing the temperature is equal throughout, a different size has also to be fixed for different heights. This causes a difficulty in fixing the proper size for ventilating openings in the case of natural ventilation, because the conditions are so variable. The theoretical size for any required change of air, supposing the conditions are constant, can be obtained by the use of the folloAving formula, suggested by de Chaumont:— — — D--------= I or O. 200f(Jh(t -fi)x 0-002) Where D = delivery per hour in cubic feet; 200 is a constant; / is the co- efficient of friction; h is the height of the heated column of air; t its temperature; tl that of the outer air; 0*002 the ratio of expansion of ah for each degree F.; I indicates inlet, O indicates outlet, both in square inches; Avhile I and O combined are often Avritten as <£. A converse formula to the SIZE OF INLETS AND OUTLETS. 201 foregoing is useful to find the delivery per hour, under conditions 7), t, and tl, and Avhen the area of the inlet or outlet is knoAvn : it reads thus, 200f(Jh(t -11) x 0*002)0 = D. The different expressions for time and space require a factor 200 or 100, which is thus obtained: Seconds in an hour 3600^^ ^^ Square inches in a square toot 144 multiplied into J2g or 8, Avhere <4x0*059or 1#lg ft ^ win be 5o° +459*4 = 509*4, H is 50, and T will oU x bU be 228°+ 459 *4 = 687*4: that is, 1*18 x 509*4 S = 50-x(687*4-509*4)xl500 = 101-29 S(*Uare feet Very frequently, instead of a fire or hot-water coils, lighted gas is used to cause a current, and if the gas can be applied to other uses, the plan is an economical one. In theatres, the chandehers have long been made use of for this purpose. It is calculated that each cubic foot of gas burnt is capable of extracting 3000 cubic feet of air; thus twenty burners, each consuming 5 feet of gas hourly, will withdraw 300,000 cubic feet of air, corresponding to the complete renewal six times in the hour of the air of a hall 100 feet x 25 feet x 20 feet. Though the extracting power of gas under suitable tubes is undoubtedly large, its practical value as a ventilat- ing agent may be overrated, as generally its special flue is in a position most 0 210 VENTILATION AND HEATING. unfavourable for general ventilation. This is particularly the case Avhen the gas is intended to be both an illuminant and a means of ventilation, as in public halls, Avhere the air must be very impure before a central chandeher is effective in removing impurity. Extraction by the Steam-Jet.—The moving agent here is the force of the steam-jet, Avhich is allowed to pass into a chimney. The cone of steam sets in motion a body of air equal to 217 times its oavii bulk. Tubes passing from different rooms enter the chimney beloAv the steam-jet, and the air is extracted from them by the strong upAvard current. This plan is best adapted for factories with spare steam. It Avas employed for some time in the ventilation of the House of Lords, but Avas finally abandoned. In some collieries the steam-jet has been tried with great success, as at Lower Moor near Oldham, Avhere the " apparatus consists of 72 vertical pipes 5 feet long and 7 inches in diameter, fitted to a frame on the top of the upcast shaft; into each is inserted a steam pipe having a nozzle -fy inch in diameter, supplied Avith steam at a pressure of 38 ft). Rough as it is, this apparatus exhausts 16,000 cubic feet per minute." The principle of action of a steam-jet is similar to the production of a head by the passage of Avind over an aperture, that is, by a loAvering of pressure in the vicinity of the aperture. Steam-jets appear unsuited for exhausting large quantities of air at low pressures. Extraction by Pumps.—This method is employed at some collieries, and was also used at the St Gothard Tunnel Avorks. One of the best known in England of this class of mechanical ventilators is that of Struve of SAvansea. It con- sists of a gasometer-like piston, Avorking in a large brick chamber filled with Avater. The air is admitted and expelled by flap valves. Those at Cwm Avon are 18 feet in diameter, and have a stroke of 7 feet working eight strokes a minute. With a water-gauge of 3 inches, this machine exhausts 50,000 cubic feet a minute. The air-pumps in the St Gothard works were cylinders hung at each end of a rocking beam, which alter- nately dipped into water-tanks. The tops of the cylinders were fitted Avith outlet valves, while the space to be ventilated was connected by pipes and inlet valves with the cylinders. Each time the cylinder rose, it filled with air from the tunnel, which was expelled through the valves in the top when it fell. They worked efficiently with a water- gauge of 6 inches. Lemielle's Extractor is a huge drum Avith movable vanes, placed excentric- ally in a casing so that they he close against the drum on one side, but expand as they pass on the other, and thus sweep out, as it were, a certam amount of air at each revolution. Except in a few collieries these ventilators are not much used : their effective power appears to be under 40 per cent, of the gross boiler power. EXTRACTION AND PROPULSION OF AIR BY FANS. 211 Extraction and Propulsion by Fans.—These are very largely used in tunnels and collieries. A fan ventilator is nothing but a wheel formed by a number of vanes attached to an axle. When the Avheel is rapidly rotated, air is carried along by the vanes, finally leaAdng the tips of the vanes tangentially with a velocity practically equal to that of the vane tips. As the wheel rotates, the air tends to move from the axis to the circumference, causing thereby a lessening of pressure at the axis. One of the best of these fans is Guibal's (fig. 19), which is enclosed in a circular cover, Avith openings at the axle and an opening at the periphery which leads into a tube along Avhich the air is discharged. By placing the axis of the wheel excentrically with regard to the circle of the enclosing case, an appreciable space is formed, between the periphery of the revolving vanes and the cover, gradually increasing up to the discharging tube. This arrangement materially saves the kinetic energy of the wheel by saving loss of poAver in the production of eddies. When working, air is drawn through the apertures near the axle, and driven into and along the tube. In the best forms of these fans the size of the delivery aperture can be altered by means of a shding door, the aperture itself is trumpet-shaped, and the vanes are so shaped that, though tangential to the aperture at the axle, they are at right angles to the periphery at the tip; this enables the ah to shde on to the vanes Avithout loss of energy in eddies. One of these fans is working at Thirslhigton colliery, being 36 feet in diameter and 12 feet wide, and revolving at eighty, discharges 80,000 cubic feet of air per minute under a water-gauge of 6*2 inches. For ventilating tunnels, the best agents are undoubtedly fans. This is well seen in the case of the Lime Street Tunnel, Liverpool, and the success attending the working of the pneumatic tube between Euston and the General Post Office, London. This tube is tunnel-shaped, 4 feet wide and 4*5 feet high: it is worked by a fan in Holborn, 22 feet in diameter, and revolving 160 times a minute. It discharges 20,000 cubic feet of air per minute, and enables the carriage to travel at a speed of 15 miles an hour; the water-gauge shoAvs 10 inches of pressure. The best fans appear to utilise only 15 per cent, less than the indicated poAver of the engine which drives them. The Blackman Air-Propeller is a kind of fan (fig. 20) much used in ventdation. It is claimed for this agent that the larger sizes will give 12,000 cubic feet and the smaller ones 6000 cubic feet of air per minute for each horse power expended in driv- ing them. This estimate is based upon there being no resistance against the air except that from the machine itself. In actual practice, considerable resistance results from the ducts of the ventilation system as well as from the machine. In the ventilation of mines, the resistance to the movement of the air due to friction from the gallery surfaces, abrupt turns, expansions and con- tractions of ducts, and from eddies is often very great, so much so that a large part of the power employed to produce air-currents is needed to 212 VENTILATION AND HEATING. overcome this resistance. The friction increases in direct proportion to the area of the surface, and as the square of the velocity of the current. According to Atkinson, for every 1000 feet per minute velocity, the average co-efficient of friction in mines is 0*0217 ft* per square foot of surface. In artificial and other ventilation problems, especially in mines and tunnels, the weight in pounds of air per square foot required to give a velocity to a column of air is usually called the " head," just as in the case of furnaces it is calculated as the difference in height of two columns of air of equal weight, but of different temperatures. The total resistance to the flow of air due to friction, &c, in any given system of air-circulation may be represented as the resistance which would be given by an orifice of a certain size in a thin plate, for a certain head of air, which may be called the resistance of the mine or tunnel. If the head be stated as so many foot-pounds of force required to drive a pound of air through a given orifice,. and the flow of air be expressed in cubic feet per second, then the ratio of the head to the square of the flow is a constant, which is inversely propor- tional to the square of the area of the orifice. This constant is practically the resistance of the orifice, and the head equals R.V2., when R is the resistance and V is the flow. Now the pressure of 1 foot of air at 60° F. is 0*0765 lb per square foot, and the pressure of 1 inch of Avater is 5*2 ft> per square foot; and as it is often convenient to state this force in terms of either pounds of air per square foot or of inches of water, in order to reduce the result in pound-feet n*n*7fi f^ of air to its equivalent in inches of water, we must multiply it by-------or divide by 68. Further, knowing the head required, in terms either of feet of air or inches of water, to maintain a definite circulation of air, it is easy to cal- culate the horse power, H.P., necessary to generate that head, by multiplying the head, H, by the weight, W, in pounds of the cubical dehvery per second, and dividing by the value of a horse power in foot-pounds per second. Hx W Taking this latter to be 550 foot-pounds, we get H.P. = m For most practical purposes of mine or tunnel ventilation, the folloAving KV2PL formula, by Morrison, is suitable : H = -—-—, where H is the head in feet A of air, K is the co-efficient of friction or 0*03, V is the velocity in thousands of feet per minute, P is the perimeter of the cross section in feet, L is the length of the passage in feet, and A is the area of the same in square feet. For chcular passages, taking D for the diameter, the formula becomes H = KV2 x jj ; if the passage is very short in proportion to the diameter, the formula for chcular passages becomes H = KV2 x ——~r----^, and that for irregular shapes, H = KV2 x-----t---- • Example I.—What is the head required to ensure a current of air at the rate of 5 miles an hour through a tunnel 5 miles long, and whose sectional area is 200 square feet, with a perimeter of 40 feet ? Also, what horse power is needed to maintain this ,_ J0 T «• tt 0*03 x0-4402x 40x26400 „„ head? In this case, H=---------^---------=30*66 feet of air or 0'45 inch of ,, „„ 30*66x1460x0-0765 water ; and the H.r. =-------^^-------= 6'22 horse power. Example II.—Calculate the horse power required to deliver 300,000 cubic feet of air CALCULATION OF HEAD FOR AIR CURRENTS. 213 an hour, assuming the head for the circulation is equivalent to one-tenth inch of water pressure. In this case, H = 0*1 inch of water and AV = 5*2x83*3; therefore H.P. = °'lx5'2x83'3 = 0*0787 horse power. 550 Example III.—What is the head required to impart a current ot 5 miles an hour through a short circular passage 25 yards long and 5 feet in diameter ? In this case, H=0-03 x 0*4402x4(75t25°^ = l,51 foot of air, or 0*022 inch of water. 5 Example IV.—What is the head required to impart a current at the rate of 5 miles an hour through a short tunnel of irregular shape, 1000 yards long, and whose sectional area is 200 square feet, with a perimeter of 40 feet ? Here H = 0-03 x 0*4402 x-----^------ = 4*64 feet of airor0-068 inch of water. The use of blowing machines for ventilation has been knoAvn since 1734, Avhen Desaguliers invented a fan or Avheel enclosed in a box. The fan, if small, is Avorked by hand as in the machine largely used in India, under the name of the Thermantidote. Larger fans are worked either by horses or by steam engines. The amount of ah delivered can be told by timing the speed of revolution of the extremities of the fan per second, or per minute; the effective velocity is equal to f ths of this, and this is the rate of movement of the ah. If the section area of the conduit be knoAvn, the number of cubic feet discharged per second, minute, or hour can be at once calculated. The power of this plan is very considerable. With a fan of 10 feet diameter, revolving sixty times per minute, the effective velocity is 1414 feet per minute. The rate of movement in the main channel should not be more than 4 feet per second; the conduits must gradually enlarge in calibre ; and the movement, Avhen the air is delivered into the rooms, should not be more than 1J foot per second. This plan is very AA-ell adapted for those cases in Avhich a large amount of air has to be suddenly supplied, as in croAvded music halls and assembly rooms. St George's Hall at Liverpool is ventilated in this way, which, after thirty years' experience, is still considered satisfactory. The air is taken from the basement; is washed by being draAvn through a thin film of Avater throAvn up by a fountain ; is passed into calorifores (in the whiter), Avhere it can be moistened by a steam-jet, if the difference of the dry and wet bulb be more than four to six degrees, and is then propelled along the channels which distribute it to the hall. In summer, it is cooled in the conduits by the evaporation of Avater. In the present day, Root's bloAver (fig. 21) or a machine worked by rotating pistons is largely used. In principle it is a revolving pump, in which two pistons, each shaped like a figure of 8, are worked on parallel axles inside a box with two openings. As the pistons rotate, the air is draAvn in at one opening and driven out at the other. In all machines of this type it is evident that a definite volume of air is transmitted at each stroke, and knowing this volume from measurements of the machine, the actual delivery per second is readily worked out from the speed of revolu- tion, and whatever head is needed to drive that volume will be supplied from the source of poAver Avhich drives the fan. It will be readily understood that any given scheme of ventilation need not, necessarily, be limited to either extraction or propulsion, but may be carried out by a combination of both methods, as in the present Houses of Parliament. Air is admitted into the chamber of the House of Commons through 214 VENTILATION AND HEATING. openings in the floor, having been previously warmed, moistened, or cooled according to the requirements of the season. The vitiated air is extracted through the perforated ceiling, and is conducted through a shaft to the base of the Clock Tower, where a large fire is maintained at the bottom of an upcast shaft. At the Hopital Necker in Paris, and in many other places, the plan of Van Hecke is in use. A fan, Avorked by an engine, drives the air into small chambers in the basement, where it is warmed by cockle stoves, and then ascends into the rooms above and passes out by outlet shafts con- structed in the Avails. The system is effective and economical, though it is Fig. 21. only just to say that, the use of the fan excepted, it is precisely similar in principle to Sylvester's. Comparative Value of Ventilation Methods.—In endeavouring to com- pare extraction methods with those of propulsion in attempts to ventilate mechanically, we find that there are some objections to both. When extraction of air is produced by fire and hot-air shafts, there is often inequality of draught due to the impossibility of keeping the fire at a constant height. Another difficulty arises from the inequality of the movement from different rooms. From rooms nearest the shaft, and Avith the straightest connecting tubes, there may be a strong current, whhe from distant rooms the friction in the conduits is so great that little air may pass. The greatest care is therefore necessary in calculating the resistance, and in apportioning the area of the tubes to the resistance. This plan is, indeed best adapted for compact buildings. Occasionally, if the friction be great', from too small size or the angular arrangement of the conduits leading to COMPARATIVE VALUE OF VENTILATION METHODS. 215 the hot-shaft, there may be no movement at all in the conduits, but a down-current to feed the fire is established in the shaft itself—a state of things Avhich Avas discovered by Sanderson to exist formerly in the ventila- tion of St Mary's Hospital in London. The possibility of reflux of smoke, and perhaps of air, from the shaft to the rooms, is another objection of some Aveight, to which must be added the impossibility of properly controlhng the places where fresh air enters. It Avill flow in from all sides, and possibly from places Avhere it is impure, as from closets, &c.; air is so mobile that with every care it is difficult to bring it under complete control—it -will always press hi and out at the point of least resistance. The advantages of ventilation by propulsion are its certainty, and the ease with Avhich the amount throAvn in can be altered. The stream of air can be taken from any point, and can, if necessary, be Avashed by passing through a thin film of water, or through a thin screen of moistened cotton, and can be Avarmed or cooled at pleasure to any degree. In fact, the engineer can introduce into this operation the precision of modern science. The disadvantages are the great cost, the chances of the engine breaking down, and some difficulties in distribution. If the air enter through small openings at a high velocity, it Avill make its way to the outlets without mixing. The method requires, therefore, great attention in detail. As to the relative value of natural and artificial ventilation, Ave find circumstances differ so widely that it is impossible to select one system in preference to all others. In temperate climates, in most cases, especially for dwelling-houses, barracks, and hospitals, natural ventilation, Avith such powers of extraction as can be got by utilising the sources of Avarming and lighting, is the best. Incessant movement of the air is a law of nature. We have only to aUow the air in our cities and dwellings to take share in this constant change, and ventdation Avill go on uninterruptedly without our care. In some circumstances, hoavever, as in the tropics, Avith a stagnant and Avarm air; and in temperate climates, in certain buildings where there are a great number of smaU rooms, or Avhere sudden assemblages of people take place, mechanical ventilation must be used. So much may be said both for the system of extraction and propulsion under certain circumstances, that it is impossible to give an abstract preference to one over the other. In fact, it is evident that the special conditions of the case must determine the choice, and Ave must look more to the amount of air, and the method of distribution, than to the actual source of the moving poAver. But in either case the greatest engineering skill is necessary in the arrangement of tubes, the supply of fresh air, &c. The danger of contamination of air as it passes through long tubes, and the immense friction it meets Avith, must not be overlooked. The cost of the various plans -will depend entirely on circumstances, the nature of the building, the price of materials, coal, &c. On the Avhole, the plans of ventilating and Avarming by hot-Avater pipes, and Van Hecke's plan, are cheaper than the method by propulsion by means of a large fan; but the latter gives us a method which is more under engineer- ing control, and is better adapted for hot climates Avhen it is desired to cool the air. By means of damp canvas air-screens or filters placed at both inlets and outlets, cleansed, tempered, and humidified air may be propelled through narroAv Avedge-shaped openings in the ceilings, and then, by means of a simple form of spreader, be evenly distributed through buildings. This arrangement has already been successfully applied to several hospitals 216 VENTILATION AND HEATING. by Messrs Key and Henman, and certainly seems the proper plan, as it not only ensures the delivery of clean air, but also purifies that emitted from the building. Comparing two sets of schools in Dundee, Carnelley, Haldane, and Anderson have shoAvn that mechanical ventilation has the advantage. In naturally ventilated schools, the average amount of CO., Avas 1*86 per 1000 vols., the organic matter 16*2 (vols, oxygen required per million vols, of air), and the micro-organisms 152 per litre; Avhile in mechanically ventilated schools, the C02 was 1*23, the organic matter 10*1, and the micro-organisms 16*6 : and not-withstanding this greater purity of the air, the temperature was considerably higher in the latter. The incoming air is warmed by being driven by means of fans over hot pipes, and then delivered into the rooms, about 5 feet from the floor, through shalloAV broad openings; the outgoing air is drawn up from apertures about 2 feet from the floor into a chamber in the roof, and thence out through valved louvres. The mean delivery of air (calculated from the C02) in the mechanically ventilated rooms was 670 cubic feet per head per hour,—in those naturally ventilated, only 400 ; the range in the former being from 375 to 1680, and in the latter from 175 to 1370. In neither case, hoAvever, Avas the ventilation A-ery good. METHODS OF HEATING AXD COOLIXG. Just as, in discussing the problems of ventilation, Ave Avere largely con- cerned in considering the various natural and mechanical processes involved in air movement, so noAAr, in dealing with the problems relating to the heating of buddings, Ave have to discuss the laAvs governing the production and distribution of heat. In actual practice, the problems of ventilation are very closely associated Avith the problems of heating, because heat is one of the most important agents in ventilation, and the distribution of heat is commonly dependent upon the distribution of heated air or Avater. Production and Measurement of Heat.—The production of heat for the purposes of heating and ventilating buildings is commonly effected by the combustion of fuel. The chief constituents of fuels are carbon and hydrogen, with various chemical combinations of these tAvo elements; Avhile the principal products of their combustion are carbon dioxide and water. For measuring and comparing quantities of heat, a unit of measure is required, and that which is most commonly used in this country is the amount of heat required to raise a pound of Avater 1° F., say from 32° F. to 33° F. This is sometimes spoken of as the British thermal unit. In the metrical system, the unit of heat is the calorie, or the amount of heat required to raise a kilogramme of Avater from 0° C. to 1° C. It is some- times convenient, in ventilation and heating problems, to express the amount of heat in terms of force. When so expressed, the British thermal unit is equivalent to 772 foot-pounds of force, and the calorie is equal to 423*985 kilogramme-metres, each kilogramme-metre being equal to 7*2 foot- pounds, or one calorie is equal to 3*968 ft) Fahrenheit units. The quantity of heat produced by the combustion of a fuel is approxi- mately the sum of the quantities of heat Avhich the hydrogen and carbon contained in it would produce separately by their combustion. When hydrogen and oxygen exist in a compound in the proper proportion to form Avater, these constituents have no effect on the total heat of combus- tion, and it is only the surplus of hydrogen above that Avhich is required SPECIFIC HEAT. 217 by the oxygen that is to be taken into account. The heat of combustion of one pound of pure carbon is 14,500 British thermal units, and that of one pound of pure hydrogen is 62,032 : from these principles and data is deduced the folloAving general formula for the total heat of combustion of any compound, of which the principal constituents, carbon, hydrogen and oxygen, are knoAvn :— h= 14,500 | C + 4*28(H- -V- in which h is the total heat of one pound of the compound in British thermal units, C, H, and O are the fractions of one pound of the compound consisting respectively of carbon, hydrogen and oxygen, Avhile 4*28 is a constant deduced from the ratio of 14,500 to 62,032. On the basis of this formula, the folloAving table of the total heat from combustion of one pound of each of the fuels has been prepared. Fuel. Carbon. Hydrogen. Oxvgen. Yields British thermal heat units. One pound. It). It. it). Charcoal, ... . ! 0*930 13,585 Coke, . 0-940 13,630 Coal—Anthracite, i 0-915 0*035 0-026 15,225 ,, Bituminous, 0-900 0-040 0-020 15,370 ,, Cannel, 0-880 0-052 0-054 15,837 i> 0-810 0-052 0-040 14,645 ,, Lignite, . 0 700 0*050 0-020 11,745 Peat, . 0-580 0-060 0-310 9,660 Wood—dry, 1 0-500 7,245 Petroleum, . S 0-840 0-160 21,930 Specific Heat.—As Ave have chiefly to do Avith questions involving the amount of heat in different quantities of ah, water and watery vapour, the exact amounts of heat Avhich can be stored in equal weights of these different substances, by raising their temperatures through the same range, becomes of material importance. The heat capable of being stored or retained in this Avay is called the specific heat, and is uusally described as being so many units required to raise the temperature of 1 ft) of the substance through 1° F. From the folloAving table of specific heats, it -will be easy to compare the efficiency of different substances for the storage of heat. Water requires Ice ,, Steam ,, Copper ,, Iron ,, Brass ,, Firebrick 1 Wood / Air (expanding) „ 0'2380 ,, (volume constant) 0-1690 1-0000 British thermal unit to raise the temperature of 1 lb through 1° F. 0-5040 0-4800 0-0951 0-1140 0-0939 requires 0-2000 From this table it is evident that, weight for weight, water will absorb more heat for the same rise of temperature than any other substance, hence the comparative economy secured by using water as a carrier of heat, instead of air. In the case of the former it is unity, Avhile for the latter it varies from 0*169 to 0*238, according as to whether the volume of the air mass is constant or expanding. 218 VENTILATION AND HEATING. Assuming that the volume of air is constant, the folloAving table from Billings sIioavs the number of thermal units required to heat a given volume of dry air a certain number of degrees Fahrenheit, commencing at 32° F. Cubic Feet. Heated. 1°. 2°. 3°. 4°. »°. <>". '"■ N\ 9°. 100 1*92 3-84 5*76 7-68 9-60 11-52 13-44 15-36 17-28 200 3-84 7-68 11-52 15-36 19-20 23*04 26*88 30*72 34-56 300 5-76 11*52 17 28 23-04 28-80 34*56 40-32 46-08 51-84 400 7 68 15 36 23-04 30-72 38-40 46*08 53-76 61-44 69-12 500 9-60 19-20 28*80 38-40 48-00 57-60 67-20 76-80 86-40 600 11-52 23-00 34*56 46*08 57 60 69-12 80-64 9-216 103-68 700 13-44 26-88 40*32 53-76 67-20 80-64 94*08 107*52 12096 800 15-36 30-72 46*08 61-44 76-80 9216 107*52 122-88 138-24 900 17*28 34*56 51*84 69-12 86-40 103-68 120-96 138*24 155-52 From tins table it is easy to calculate the amount of heat required to raise the temperature of any given volume of air through any number of degrees of temperature. Example.—It is required to know how many thermal units are necessary to heat 14,000 cubic feet of air from 32° F. to 60° F. or 28° F. Then 7000 cubic feet heated 28° = 3763 thermal units. 7000 „ „ „ =3763 7526 Distribution of Heat.—In order to thoroughly understand the principles of applying heat, it is necessary to remember that the heat evolved from fuel is disseminated to surrounding bodies by conduction or immediate contact, by radiation, and by convection. Conducted heat passes from one particle of matter to another when they touch, that is, are separated by insensible distances. Heat is conducted through all solids, but to a very limited degree only by liquids and gases. Bodies which are good conductors rapidly give off their heat to the surrounding air or to anything in contact Avith them : in like manner, if colder, they withdraw heat from other bodies. A table of conductivities or conducting powers is given beloAv; Avhile the amount of heat, H, flowing per hour through an area, A, in square feet of I inches thickness of a substance Avhose conducting power is K, Avhen the difference of temperature is f F., may be calculated by the formula, H = K^-f. Substance. C "n^c"n« P™"!in lt« lah. units (K). Substance. Conducting power in 11) Fah. units (K). Copper, . 3225-0 Water, . 5*82 Iron, 477-4 Air, . 016 Lead, 113-0? Wool, . . 0*32 Slate, 16-0? Fossil meal, i Brick, 4-3 Glass, . . 660 Fire-brick, 5*1 Eider-down, . 0-31 Asphalte, 3-79 Slag-wool, . . 0-314 Oak (across fibres), . 1-70 Asbestos, ? Radiation is not only the most common, but probably the most Avasteful of the Avays by Avhich heat is distributed. Eadiated heat is propagated in OPEN FIREPLACES. 219 straight lines in all directions with equal intensity, the effect lessening according to the square of the distance : thus, if the heat at one foot distance from a fire be 1, then at ten feet it Avill be one hundred times less. If radiant heat fall on a solid body, it is reflected in the same Avay as light, but some of the heat is absorbed, the amount reflected and absorbed being in inverse proportion to one another, and largely dependent upon the surface, colour and nature of the body, as well as upon the difference of temperature betAveen the receiving and radiating bodies. Speaking generally, we may say that good radiators are good absorbers: good reflectors are bad radiators: transparent bodies are bad radiators. Different transparent substances often exhibit remarkable variability as to radiation. Dry air is very transparent, but, if moist, is often more or less opaque, and becomes heated itself AAdien heat is radiated through it. Similarly, a glass plate, 0*37 inch thick, will absorb half the energy of radiation which falls upon it, but transmitting the other half; hence thick glass is often effective in screening off heat from the sun or fire, whhe at the same time transmitting the light. The convection of heat is that mode in which heat is propagated in liquids and gases, and is dependent upon that characteristic of those bodies Avhich alloAvs the portions of them Avhich have been heated to expand and rise, their place being taken at once by colder parts. A sort of circulation of the water or air is set up, and the whole mass soon Avarmed. Every person in a room causes convection currents by the heat conducted to the air in contact Avith Ids skin or clothes; while the air of a room, with a fire in it on a cold day, is in a highly complex state of movement, from a similar cause. The convection currents produced by fires and by the human body in an atmosphere colder than itself not only carry off some heat but incidentally provide the body Avith a supply of fresh air. When the temperature of the surrounding air is nearly that of the body, this natural replacement of air does not take place, necessitating an artificial movement of the air either by means of fans or by punkahs as in the East. Disregarding any particular variations in the source of heat, that is, whether from coal, coke, Avood, gas or oil, we can say that the principal methods of Avarming and heating houses or rooms may be classed as either open fires, closed fires or stoves, and pipes containing either heated air, hot water, or steam. Open Fireplaces.—Long-established custom and prejudice have caused open fires to be the means of heating nine-tenths of the houses in England, notAvithstanding the fact that they are really the most costly and imperfect means of heating, as evidenced by the fact that they only render available 13 per cent, of the total heat capable of being yielded by coal or coke, and only 6 per cent, of that by Avood, the rest being lost in the air, or escaping as unconsumed carbon up the chimney. The actual heating effect of open grates is most unequal in different parts of a room, but on account of the cheerful light which they emit, and the ventilation Avhich they ensure, open fires Avill ahvays be preferred as the pleasantest and healthiest mode of heating. FolloAving Teale, the chief practical points to be aimed at in making open fireplaces may be summarised as folloAvs :—(1) Use as little iron, but as much fire-brick, as possible. (2) The back and sides should be made of fire-brick. (3) The back of the fireplace should lean or hang over the fire, while the throat of the chimney should be contracted. (4) The bottom of the fire should be deep, from before back. (5) All shts in the bottom of the fire should be as narrow as possible. (6) The bars in front should be narroAv. (7) The space beneath the fire should be closed in front 220 VENTILATION AND HEATING. by a close-fitting iron shield or " economiser." The object of this latter point is to secure as complete combustion as possible of the fuel at the bottom of the fire by the exclusion of cold air. In the use of an ordinary open fireplace, about one-eighth of the heat given off by the fuel consumed is utihsed on the air of the room. All open grates should be made so as to have the fuel slowly and completely consumed, while the draught up the chimney should not be in excess of ventilation requirements. To calculate the quantity of air required for the combustion of any given fuel we may use the formula, 12C + 36( H- -^-J, which is based on the fact that 72 parts by Aveight of air represent 16 of oxygen: the Aveight of air theoretically necessary is therefore 12 times 'that of the carbon + 36 times that of the hydrogen, less f that of any oxygen that may be present in the fuel itself. If the unit employed be 1 ft), Ave may obtain the volume of air at 32° F. by multiplying the weight of air, obtained by the formula, by 12*844, this figure being the volume Avhich 1 lb of air occupies in cubic feet at that temperature. In actual practice, from half as much again to twice tins theoretical quantity of air is found necessary. Thus, 1 ft) of coal requires 300 cubic feet of air, and 1 lb of dry Avood needs 160. Most English grates consume 8 ft) of coal in an hour: this means 2400 cubic feet hourly, but in actual practice something like 20,000, or even 40,000, cubic feet of air pass up the chimney ; in which case, supposing the room contains 4000 cubic feet of space, the air in it gets changed from 5 to 10 times in the hour according to the strength of the fire. If the incoming air were warm, this hberal ventilation Avould be excellent, but, unfortunately, it rarely is so, but is in the main quite cold, finding entrance through the floor, or by chinks round the windoAvs or beneath the door. If the whole of the heat generated in the combustion of coal Avere utilised, 1 ft) would suffice to raise a room, 20 feet square by 12 feet high, 10° F. above the temperature of the outer air, that is, making no allowance for loss by ventilation and conduction. To save some of the large margin of 87 per cent, of practically Avasted fuel has been the object of many "improved fireplaces." One of the first improvements in fireplaces was the securing of increased radiation from the burning fuel. This is best attained by either regulating the shape of the stove so that its coverings are inclined at an angle of 135* to the back of the grate, or by making the fireplace as much as possible of material Avhich, Avhile having a high radiation poAver, is but a poor conductor of heat. Beference to page 219 Avill indicate that fireplaces on this account should be made as far as possible of fire-brick, and the amount of metal about them reduced to a minimum. Several grates improved in this direction are now in the market, more particularly some made by Doulton, Avhich are constructed almost entirely of fire-clay or pottery. Fireplaces have further been improved by surrounding the stove by an air-space Avith tAvo openings Avhich communicate, one with the external air, and the other Avith the room. The air entering this chamber behind the grate becomes warmed by passing over the heated back portion of the fire- place, and then ascends by a separate shaft or by an iron pipe placed in the chimney to enter the room near the ceiling. The ventilating fireplace of Sir D. Galton (fig. 22), largely used in military barracks, is a very good form of this class of fire-grate. Boyd's Hygiastic grate is another con- structed on the same principle, but delivers the heated air through an opening just above the fire under the mantel-shelf. Both these grates reduce the Avasted heat by about one-fourth. It is, hoAvever, important FIREPLACES, 221 that the air which enters by these ventilating fireplaces should not pass over any iron surface which is heated to a red heat, as, owing to the direct ^action of the oxygen of the air upon the carbon of the cast iron, and the frequent decomposition of the atmospheric carbon dioxide by the red-hot -metal, free carbon , monoxide may be generated. To these reasons may be Fig. 22. added the fact that, if any carbonic oxide is formed in the fire, some of it Avill pass out through the red-hot metal to the external air. " Slow-combus- tion grates," having solid floors, are now much used. The fuel, which is piled up against the back, burns away mostly at the upper part, where the current •of air strikes the top of the fuel on its way to the chimney. The fuel is ■brought well forward, so that the heat may be radiated freely, and the / 222 VENTILATION AND HEATING. flanks of the fireplace are splayed for the same reason. The fire is lighted at the top, and gradually burns downwards. In some other grates, economy of loss of heat is gained by limiting the amount of air carried up the chimney Avithout having taken part in the combustion. This loss of heat can usually be restricted by narrowing the chimney and its orifices, but care needs to be taken that the proper pro- portions of the chimney and its openings are maintained, so that the efficiency of the fireplace, as a ventilating and warming apparatus com- bined, is not interfered Avith. To secure this, Morin recommends that the temperature of the air in the chimney should be at least 45° F. or 25° C. above that of the outer air, and that the smoke should not issue from a chimney at a greater velocity than 10 feet per second, and that the top orifice of the chimney should be one-half of that of the chimney itself. The following table, by Morin, gives the dimensions of the chimney flues needed for rooms of different sizes, Avhen an ordinary open fireplace is used. Capacity of room in cubic feet. Volume of air to be Sectional area of the removed by the chimney | rectangular chimney in each hour in cubic feet. square feet. Diameter of cylindrical chimney in feet. 3,500 17,500 4,200 21,000 5,300 26,500 6,350 31,750 7,750 38,750 9,200 46,000 10,600 53,000 0-99 1*19 1-48 1-78 217 2-57 2-97 0-88 0-98 1*08 1*21 1-31 1-44 1-54 For ventilating grates, Morin recommends the following proportions :— Capacity of room in Volume of air to be Sectional area of Sectional area of flue supplied per hour in chimney flue in for fresh air in cubic feet. square feet. square feet. 3,500 17,500 0-54 1-5 4,200 21,000 0-66 1-8 5,300 26,500 0-81 2-3 6,350 31,750 0-97 27 7,750 38,750 1-20 3-3 9,200 46,000 1-40 3-9 10,600 53,000 1-60 4-6 In Sylvester's grates, Avhich have been adopted -with advantage in both pubhc offices and private houses, the fuel is placed upon a grate, the bars of Avhich are on a level with the floor, and air is supplied to the ash-pit below by a series of passages which pass under a hearth composed either of separate bars of iron, arranged in front of the grate, or of ornamental tiles. The heat from the fire is made to warm the hearth and the air passing beneath it, Avhile the low position of the fire, and the angle of inclination given to the sides and back of the grate, tend to disperse the heat more effectually than in the ordinary open fireplaces. The sides and top of these stoves are made of double casings of iron, and in the sides a series of vertical plates is enclosed, which collect a great portion of the heat generated by the fire. The extent of these plates is so proportioned to the fuel CLOSED FIRES OR STOVES. 223 consumed that the air can never rise above 212° F. or 100° C. under any circumstances. This arrangement converts the sides and top of the stove into an air-chamber, into Avhich, by an opening at the bottom, fresh air is allowed to enter. The air traverses in its ascent the various compartments formed by the parallel plates, is Avarmed, and escapes at the top by an opening into the room. In order to prevent the heated air being too dry, a vessel containing Avater is introduced into the top of these grates, where it evaporates, and yields moisture to the air. Figs. 23 and 24 represent these stoves, one being intended to fit into an ordinary chimney recess, while the other stands forward into the room. At the back of the grate is a series of louvres, by opening or closing Avhich, a greater or less draught can be created, according to the amount of combustion required. Closed Fires or Stoves.—The simplest definition of a stove is that of a chamber constructed to disseminate heat by the direct contact of air with the heated surface, Avhich is obtained by burning fuel on a grate, closely surrounded on all sides, except below the bars, by a good conducting or absorbing material. If the fire is not required to materially assist in Fig. 23. Fig. 24. ventilation as Avell as in heating, the enclosing of the fire in a chamber affords a considerable economy in the consumption of fuel, as the air supplied is entirely hmited to that taking part in the combustion, and only the products of that combustion escaping by the chimney or smoke flue. The materials used for the construction of stoves are cast iron, sheet iron, bricks or tiles; and much of the success of stoves depends upon the facility with which the materials of which they are constructed communicate the heat they receive. When the fuel is rapidly burnt in a stove, so as to evolve at once the entire amount of heat it is capable of affording, the temperature produced is often greater than is required. Iron, therefore, which conducts and radiates heat almost as rapidly as it is received, is not an appropriate material for communicating a uniform temperature, say of about 68° F. Clay, in the form of bricks or tiles, is decidedly preferable, as no matter Avith what degree of rapidity its temperature is raised, it evolves its heat slowly and gradually. From the given quantity of air ( = A) which the stove must heat hourly (to t°) to make up for the loss by coohng and 224 VENTILATION AND HEATING. ventilation, the corresponding amount of clay surface may easily be calculated. The mean Aveight of a cubic foot of fire-clay is 62 ft): a cubic foot of air at 68° F. Aveighs 0*037 ft), therefore, 1680 times less than an equal bulk of clay; the same amount of heat produces the same rise of temperature in equal masses of both, the specific heat of each being about one fourth that of Avater. The heat, therefore, required to raise 1680 cubic feet of air to the desired temperature or t° above the outer air, will be sufficient to produce the same effect in 1 cubic foot of clay. The latter, however, becomes hotter from the fire and warms the air in contact Avith it, by cooling gradually from a maximum temperature, or T°, to a temperature t'°, Avhich is sensibly higher than t". The heat evolved during cooling will warm a greater body of air to t° in the ratio of as f is to (T° -1'°), At" Avhence we obtain the formula, x = —-7^- as giving the volume of lo80(l —t ) fire-clay corresponding with the body of air to be heated. Iron stoves are often objectionable, because they occasion an unpleasant .smell, and produce headaches. The smell is commonly caused when, by Avant of attention, some part of the stove is allowed to become red-hot, and the dust particles in the air, coming in contact Avith it, are charred; often a slight smeU comes from the iron itself. Another objection exists in the fact that iron, when red-hot, permits the passage of carbon monoxide and other gases through it. If Avater is not placed on a stove, the air becomes heated without acquiring an amount of moisture commensurate with its increased temperature, and is proportionately unpleasant. In stoves of the simplest construction, the fire is surrounded directly by the surface to be heated, which, being placed unprotected in the room, radiates heat and warms the air by direct contact, the smoke passing away into the chimney. The relative heating surface needed for any given space may be approximately calculated from the facts established by Peclet, that a square foot of sheet iron, freely exposed to the air, will yield about 200 heat units per hour; a square foot of cast iron 500 ; and bricks or tiles, fths of an inch in thickness, 180 units, supposing the fuel to be consumed in such a manner as to yield in each case 0*8 of its heating power. The Meidingen stove is a slow-combustion stove much used in Germany : it consists of an inner cyhnder with fluted rings enclosed in a double casing, through which the outer air can be passed and warmed before entering the room. A door fixed in the grate regulates the draught and the rapidity of combustion. Saxon SneU's stove has a small boiler placed behind the grate, which communicates with a series of iron pipes: these are filled with Avater, and air admitted to the room between them. The products of combustion are carried off by a flue. What are called American stoves, are stoves specially constructed for burning anthracite coal, which does not burn freely in any open grate, in consequence of the cooling action exerted by the large quantity of air necessarily admitted to the fuel. So liable is anthracite coal to be extinguished by sudden coohng, that it is found more advisable to feed the fire from above than from the side by a fire door, as in ordinary stoves; hence these American stoves are of peculiar construction. In Nott's stoves, the grate bars are curved, so as to form together three parts of a cylinder, and firmly attached to side plates, so that the whole grate can be moved by a handle outside the stove, round an axis to which the side plates are fixed. One-third of the convex side of the grate cyhnder is required as a support for the fuel; by means of the handle, the other tAvo-thirds can be alter- GAS STOVES. 225 nately brought to occupy its position, and by this rotating motion the ashes are caused to fall through the bars. In Spoor's stove, also much used in America, the hot gases are made to traverse the sides of the stove in an upward and doAvmvard direction before escaping into the chimney. Olney's stove is very similar to Nott's, except that the escape for the gases is confined to one aperture, Avhilst in Nott's there are tAvo, at different elevations. In some stoves, the heating surface is surrounded by an outer casing open at the top and bottom, through which the air of the chamber or air from the outside is caused to circulate and become warmed in its ascent. These arrangements are often called cockle stoves : large stoves on this plan used on the Continent are known as caloriferes. The stove introduced by the late Mr Napier (fig. 25) is designed to economise sohd fuel, and has arrangements by Avhich the hot gases are made to descend before entering the chimney. This principle of conducting the gases downwards before they are allowed to escape is scien- tifically correct, because the heavier or cooler gases escape first, the hotter gases being kept longer in contact Avith the radiating surfaces of the stove : better diffusion of the hot gases is also obtained in this way. Experiments made with this stove show that one having 24 square feet of heating surface, in a room of 5000 cubic feet, by burning 1 lb of coke hourly for ten hours a day, kept the room as fresh as, and hotter than 30 ft) of the same coke burned in either an American stove, or 40 ft) of good coal burning hourly in an ordinary open fireplace. Gas Stoves. — The use of apphances for using illuminat- ing gas as fuel in heating and cooking has largely increased of late years, several exhibitions of such appliances having greatly stimulated the introduction of improved forms. Gas stoves without cliimneys, that is, those from which the products of combustion are allowed to escape into the air of the room which is being heated, are obviously funda- mentally wrong, and are only used where health is sacrificed to economy of gas. Under certain circumstances, gas is a more economical fuel than coal: Avhere heat is required quickly and only for a short time, the waste which necessarily accompanies the fighting of a coal fire is far more than equivalent to the higher cost of the gas. In reference to this aspect of the question, the following experiments are of interest, particularly as they indicate that a gallon of water may be more economically brought to the boding point by a gas stove than by a recently lighted coal fire. P r 226 VENTILATION AND HEATING. Coal used. Wood used. Time employed. Total cost. With fire, . With gas, . 4£ lb. Id. Avorth. 4-5 cubic feet of gas at 3s. 2d. per 1000. 56 minutes. 21 minutes. TJ&Ofld. yVffOfld. There is, therefore, according to this estimate, an economy in cost of just 33 per cent., and a saving in time of nearly two-thirds, besides great cleanli- ness and comfort, in the use of gas. Speaking generally, there may be said to be four common forms of gas stove in general use : these are (1) coke and asbestos or hollow ball refractory fuel stoves, (2) reflector stoves, (3) condensing stoves, (4) calorigen stoves. Stoves fitted with coke, asbestos fibre, common peroxide of manganese, pumice stone, and fire-brick, and lighted by Bunsen burners, are relatively popular, OAving to the fact that the fuel is rendered incandescent, with a close resemblance to the glow of an ordinary coal fire. These stoves yield radiant heat only as a rule, though a few are made with attached hot chambers to give off heated currents of air. They are, in the main, good stoves, but somewhat extravagant as gas consumers, and always needing a flue to carry off the products of combustion, and which as Avell takes much of the heat which they produce as so much Avaste. Gas fires of this kind for an ordinary room consume on an average 15 cubic feet of gas per hour; that amounts to about |d. per hour, taking gas at 3s. per 1000 cubic feet. Fletcher of Warrington says that gas fires cost from Id. to 4d. per hour, but quotes no experiments to show this : much will obviously depend upon the local cost of gas. Reflector stoves have usually a naked gas flame, backed by a glass or metal reflector. They are bright and cheerful looking, but give out little heat, and unless provided -with a flue—which more often than not is not provided—very considerably add to the vitiation of the air. Condensing stoves are those so constructed that the water vapour, which is one of the products of gas combustion, is condensed by passing through upright tubes, and then caught in a tray beneath. This condensed vapour naturally carries down with it some if not all the sulphur products, but fails to remove any of the carbon dioxide which, notwithstanding all statements to the contrary, really escapes into the room. For this reason, these stoves always require a flue; unfortunately, their heating powers are small. The essential defects of all the three preceding forms of gas stoves are a disproportionately low amount of heat gained as compared with the high expenditure of gas, due mainly to a failure to rob the products of combus- tion of their heat before they escape out of the stove in as large a degree as is consistent with ensuring their escape from it. It is at once obvious that this can be most effectively secured by bringing the heated combustion products into contact with a large metalhc area, so arranged that the heat which it absorbs shall be given off either by direct radiation, or by the conducting influence of air-currents flowing over it. Of stoves which provide luminous flames, or a source of radiant heat as Avell as a supply of fresh heated air, those of Adams and Fletcher may be taken as examples : while of the numerous stoves which merely supply heated air, those of George and Bond will serve as specimens. In Adams' stove (fig. 26) a mixture of gas and air is burned in a series of fire-clay burners. These are arranged upon a tray, which is drawn forAvard for hghting: in a short time the burners become red hot, GAS STOVES. 227 and a small supply of gas then suffices. The heated products of combus- tion are passed, over a large surface formed by sheet-iron partitions, the other side of Avhich is traversed by the air Avhich is being heated : a, certain amount of radiation also takes place from the red-hot brick burners. The Avaste hot gases escape by a chimney at about 240° F, while a supply of fresh air is drawn in and rapidly heated to 180° F. at a rate of about 200 cubic feet per cubic foot of gas burned per hour. In Fletcher's gas stove use is made of simple illuminating flames from ordinary burners for the supply of radiant heat; the hot combustion pro- ducts ascend in con- tact Avith vertical tubes, AAdiich are thus heated, and induce a current of air through them, the air being dehvered heated at the top (fig. 27). In George's Calorigen stove the body is made of rolled iron, and contains a coil of wrought iron tubing open at the top. This at its lower end is carried through the outer Avail either above or beloAv the floor to a point from which an appropriate supply of fresh air can be obtained. The cylindrical metal body of the stove has connected with it two pipes, one an upper one for carrying aAvay the products of combustion into the outer air, while the loAver one brings in fresh air to support combustion. The action of the stove is simple: the heated combustion products not only heat the outer metal case, and through it the air in contact with it, but also heat the current of air constantly passing up through the coiled tube into the room. Bond's Euthermic stove (fig. 28) consists of a corrugated metal cylinder which, as in George's Calorigen, constitutes the stove body: above this, it ■discharges into a flue for the escape of the combustion products, while below it is open for the location of a gas jet and a supply of air. Inside tins metal cyhnder is a metal drum, having an inlet tube, E, beloAv, for bringing fresh air, and open at its upper end, to allow of air which is heated in its passage through the stove to escape into the room. The corrugation of the cylinder secures not only an increased superficial surface for the heated products of combustion to yield their heat into the room direct from the outer surface of the corrugation, but also from the inner surface of the ■contained drum to the air within it. Of these stoves, the Euthermic is perhaps the best, mainly on account 228 VENTILATION AND HEAT1NC. of its open bottom rendering it a true ventilating agent, inasmuch as the air needed for the gas combustion has to be draAvn from the room itself, and by that means favours a continuous change of air through it. This is not well secured in the others, all movement of air through the tubes being largely dependent upon the conditions which exist in the room for allowing air into and out of them, and is but slightly influenced by the pure and simple action of the stoves themselves. For supplying the gas which is now usually supplied to gas stoves, use is made of so-called atmospheric burners constructed on the same principle as Bimsen burners. From the supply pipe the gas passes by a nozzle into a small chamber provided Avith perforations, behind the nozzle, through which air passes. The air and gas mix, and, escaping by the jets, on ignition burn with a non-luminous, faintly blue, smokeless, but extremely hot flame. If the supply of gas be too small, it burns at the nozzle, producing an easily Fig- 27. Fig. 28. recognised odour of half-burnt gas. This "burning down " always occurs if the gas is turned too low, or when the gas is exposed to a sudden draught It constitutes a serious drawback to the use of gas fires. If by chance burning back occurs, the gas should be turned off completely and re-lighted at the proper opening. Many atmospheric burners are now made with devices for preventing the lighting back, one of the best being to cover the openings at which the gas burns with fine wire gauze.« Oil Stoves.—Under some circumstances the use of oil'stoves such as those made by Bippingille, affords a convenient means of heating apart- ments. This is a matter of great practical importance often in country places, and where no chimneys are available to carry off the products of combustion. The problem how to make a stove that shall not require a flue is one that has occupied the minds of many inventors, and although it is easy to say that so long as carbon dioxide is one of the products of com- bustion the thing is impossible, there is a good deal of experience to show HEATING BY HOT AIR. 229 that a considerable degree of heat may be safely obtained from the com- bustion of hydrocarbons, Avithout any other flue or outlet than is required for the removal of the products of respiration of those avIio dwell in the room. We do not think that the experience has yet been accumulated AAdiich Avould enable us to speak positively of the innocuousness of a con- siderable admixture of carbonic acid Avith the air Ave breathe, but the knowledge that in hundreds of cases oil stoves are used for heating living- rooms and even bed-rooms Avithout apparent injury to the occupants, makes one feel fairly confident that the products of the complete combustion of hydrocarbons are not injurious Avhen mixed Avith such an amount of air as is sufficient to dilute to a proper degree the respiratory products. It has elseAvhere been explained that anything over 0*6 of CO., per 1000 of air may be taken as indicating concomitant and hurtful organic impurity of the atmosphere of dwelling-rooms, but that is so mainly on the assump- tion that the carbon dioxide is the product of animal respiration. It is probable that this permissible limit of carbon dioxide does not apply Avith the same force to cases in Avhich it is formed by lamps and stoves. At present Ave have no very complete data as to the exact proportion of carbon dioxide which it is safe to breathe for long periods, but the probabilities are that danger does not arise until a far larger ratio is reached than would be produced by an oil stove warming a room in Avhich there is sufficient ventilation to keep it sAveet, even if no stove Avere present. Experiments show that, provided the combustion of the oil is complete, and that the ventilation is sufficient for the ordinary effects of respiration, the use of oil stoves for heating purposes may be advantageously employed in both ordinary day and sleeping rooms. The efficiency of oil stoves is increased by placing over them a diffuser or radiator, so as to prevent the heated products ascending direct to the ceiling: care needs also to be taken that only the better kinds of mineral oil are used; if inferior qualities of oil are burnt, perfect combustion is more difficult to obtain. Heating by Means of Hot Air.—When Avant of space or other considera- tions render it desirable to remove stoves or fires away from the rooms to be heated, the necessary quantity of air can be Avarmed in another part of the building, and conducted by air flues into the different rooms or passages. This arrangement is eminently suitable for large public buildings. When the supply of heated ah is abundant, and is transmitted to the apartments Avith some force by means of fans, no extra outlet for the vitiated air is necessary, sufficient ventilation being afforded, in small rooms and not overcroAvded with inmates, by the unavoidable cracks and crevices around doors and windows. If, however, the rooms are at all crowded, special means of ventilation must be provided. With a vieAV to economise the heat of the air, which has already circulated once through the apartments, two methods have been proposed : one consists in reconducting the air to the heating surface of the stove, and again transmitting it to the spaces to be Avarmed; the other conducts the used air to the ash-pit of the stove to supply oxygen for combustion, when the higher temperature, as compared Avith the external atmosphere, Avhich it still retains, will more than com- pensate for the lesser proportion of oxygen which it affords. Supposing that proper ventilation can be kept up in the rooms by means of doors and Avindows, the first method is obviously advantageous, as the Avarm air streaming in will force out that already in the room, and thus produce a condition of affairs in Avhich the natural tendency of the outer air to force its way through crevices Avill cease Avith all its attendant disadvan- tages. The methods of heating by hot air are not desirable for buildings in 230 VENTILATION AND HEATING. £|ffllffl|fk Avhich the number of rooms heated varies, because the proper relation between the dimensions of the heat generating stoves and the supply of hot air cannot be easily apportioned to meet a fluctuating demand. On the other hand, this manner of heating is economical, as only one stove is required and its fuel more completely consumed than if the same quantity were distributed in separate stoves, while there is the further advantage of a uniform and equable heat proceeding from the floor level. The actual generating hot-air stoves are constructed according to either of tAvo systems. In one, the smoke and hot gases from a fire are caused to circulate in an extensive series of stoneAArare or metallic flues, and the air to be warmed, supplied from the outside of the building, is conducted around these flues, Avhere it absorbs heat. In the other, the air to be heated is conducted through metallic or stoneA\rare pipes, round which the flame and smoke of a fire are alloAved to play. In both systems, about 10 square feet of heating surface per pound of coal consumed is found practically to Avork well. The forms of apparatus constructed by different inventors for heating air are numerous, but they all conform in principle to one or other of the foregoing systems. Perhaps one of the most successful is the " Convoluted Stove " of Messrs Constantine & Son of Manchester, and applied to the heating of the Manchester Royal Exchange, Pantechnicon, Concert Hall, Theatre Eoyal, and to the Arlington Street Turkish Baths in Glasgow. In fig. 29 is shown a horizontal section of the stove with its brick-work casing Avhich forms the air-circulating space. The stove is on the model of a " gill" stoAre, but Avith the gills made holloAv. In order to diffuse the hot gases and flame into the grooves of the gills and to preArent the too rapid escape of heat by the chimney, fire-brick slabs are placed across the fire space and form a roof to the combustion chamber, or baffle plate to the flames. Security against overheating is obtained by having the proportion of heating to grate surface as large as 100 to 1. In the Manchester Royal Exchange, where the space is 1,500,000 cubic feet, a uniform temperature of 50° to 56° F. is maintained by two of these stoves Avith an expenditure of only 2\ cwts. of coke in the twenty-four hours. The arrangement is very simple : fresh air is draAvn from the top of the building doAA-n a shaft, 6 feet square, through a cold chamber at the bottom, in Avhich it is filtered, and is then passed through the Avarming chamber to tAvo flues Avhich run the full length of the hall, Avith branch flues into the plinths of the columns, from Avhich the Avarm air is delivered. In the Arlington Baths, GlasgoAv, and the Llandudno Hydropathic Establishment the use of these stoves for supplying hot air has been equally satisfactory : in the former place " the cubic capacity of the hot and hottest rooms is 17,700 feet, giving a proportion of 1 square foot of cast-iron heatine surface in the stoves to about 23*8 cubic feet of contained space. The heating and ventilation of these rooms is obtained by a consumption of from 48 to 60 cAvts. of gas coke per Aveek of fifty-fh-e hours." Heating by Water and Steam.—Both -water and steam are often used HORIZONTAL SECTION. Fig. 29. HEATING BY HOT WATER AND STEAM. 231 as means of carrying heat, in consequence of the high specific heat of the former, and the large quantity of latent heat in the latter. The quantities of heat contained in equal weights of Avater and air at the same temperature are m the ratio of 421 to 100 : or the heat which is set free when water cools down one hundred degrees is sufficient to raise the temperature of 4*21 times as much air to the same amount. Therefore, the heat destined for a given quantity of air can be retained in a much less quantity of water, Further, a greater effect is produced when water, in the form of steam, is made the carrier of heat, because 1 lb of water vapour at 100° C. (212° F.) will, in condensing to form boiling water, give off sufficient heat to raise the temperature of 5*36 lb of water, or 4*21 x 5'36 = 22'5 lb of air raised to 100° C. or212° F. Heating by hot-water pipes is either conducted on the so-called low- pressure system, or on Perkins' high-pressure principle. In a low-pressure water system, the pipes are about 4 inches in diameter, and arranged in a double row to alloAv of the water circulating. The boiler in connection with it is commonly placed in the basement of the building, and from its upper part runs a main pipe, ending in branches, which extend to the furthest end of the building : these then return underneath the others, unite into another single pipe, and then re-enter the boiler at its bottom. The circula- tion of the water is dependent upon the water, after being heated, being fighter than Avhen cold, and as such tending to rise to a higher level: this, having ^ given up its heat to the various rooms, returns cooled by the loAver pipe. The heat of the pipes is controlled by a valve which can be opened and closed at will. A feed pipe from'a supply cistern enters the return pipe near the boiler, -while an escape of air is provided at the highest point of the system. The circulation being open to the air at one point, the highest temperature possible at or near the top, where this opening is, does not exceed 100° C. or 212° F.: at the deeper portions it may be higher, but the average tempera- ture in a loAv-pressure circulation rarely exceeds 212° F. The calculation of the flow of water in the circulation is A'ery similar to that of air; the head being due to difference of densities betAveen hot and cold Avater. To find the head for any circulation, this latter may be conveniently divided into foot sections by horizontal parallel planes, one foot apart. By measur- ing the temperature of the Aoav and return pipes in each section, the head of the whole circulation will be the sum of the differences of temperature of corresponding sections, multiphed by the co-efficient of expansion of water. The average temperature in the flow, and return pipes will be between 92° F. and 212° F., and for this range the mean co-efficient of expansion of water is 0*000318, hence the head for each foot section =0*000318 (t - t'). If the total sum of the differences of temperature is negative, it is evident* that the circulation is in the opposite direction. However small the head may be, there will be a Aoav of some sort, provided there is a continuous channel filled with water from the boiler and back again. The precise velocity of flow of water in the circulation depends not only on the head but upon the resistance of the whole channel. Its computation is subject to the same laws as those governing resistance in air-channels, but as the calculation for a hot-water system would be very intricate, most hot-water engineers work empirically from known successful arrangements to any new one required. In Perkins' high-pressure system the Avater is completely enclosed in Avrought-iron pipes, whose internal diameter is f inch, external 1TV inch, and sufficiently strong to withstand the pressure corresponding to very high temperatures. Thus, the pressure of steam, or the pressure required to 232 VENTILATION AND HEATING. prevent steam forming at 212° F., is 14| ft) per square inch, at 300° F. it is 67 ft), and at 400° F. it is 250 ft) per square inch. The narroAv iron pipes are so arranged as to form a complete circuit, part of it being coiled Avithin and exposed to the heat of a fire. At the top of the circuit there is a series of larger pipes called expansion tubes : these contain half air and half water, and therefore allowing for the expansion of the latter. When the pipes have been filled with Avater, they are closed with screAv plugs, making the whole circuit practically a closed vessel full of water except at the top, Avhere there is a httle air. The temperature is regulated by fixing the pro- portion of pipe within the fire to that outside as 1 is to 10. Once started, the circulation of water within these high-pressure pipes is very rapid, while the temperature usually reaches 300° F. This system has faults due to the irregularity of temperature at different parts of the same coil, and the rapidity with which the heat diminishes on lowering the fire. High- pressure water pipes are also very hable to overheat the air, a fact which renders them objectionable for heating houses : on the other hand, they are very useful for heating disinfecting chambers and drying closets, where a small space is required to be quickly raised to a high temperature. Wher- ever there is a high-pressure water circulation, it must not be forgotten that, although the Avhole is closed up, the Avater in it wastes to a small extent, necessitating the periodical opening of the plugs and the addition of a little fresh water. It has already been explained that steam heats much more effectively than water, and that 1 ft) of steam at 100° C. will, in condensing to form boiling Avater, yield sufficient heat to raise 22*5 ft) of air to 100° C. (212° F.). Methods of heating by steam are based upon this fact that, if steam be conducted to suitable condensing pipes or tubes, they then will impart the generated heat to the surrounding air. The pipes destined to carry the steam to the place of condensation are chosen of narrow bore (about 1*5 inch) and, to avoid all condensation in transit, are surrounded Avith a thick covering of felt: the condensing pipes are of copper or cast iron, and at least four times as Avide, and must be so arranged that the air can escape Avhen the steam is first admitted. Whatever form is given to the appa- ratus, ample means must be afforded for the removal of the condensed water, and a special set of pipes, conducting it back to the boiler, is generally employed for this purpose. One of the best modes of employing steam is shown in fig. 30. There is only one pipe through which the steam ascends from the boiler and also one extensive coil of pipe by Avhich the condensed water returns. A cock should be shown in the draAving at the top of the pipe, to alloAV air to escape. When placed in the place to be heated, this apparatus HEATING BY HOT AVATER AND STEAM. 233 •practically becomes a steam stove. If at a distance and surrounded with a case, through the bottom of which air enters, the Avarmed air may be trans- mitted to a higher position. If the diameter of the pipes is small, the length must be increased in proportion to afford a sufficient heating surface. A question of very practical importance is how much hot-water piping of given external diameter is necessary for the heating of a given room or series of rooms. The answer to this question depends upon a large number of conditions, more especially the loss of heat by conduction through the walls and Avindows, as wed as that carried aAvay by the air in the process of ventilation. Much of our information on this matter is due to Hood, who -says, " The quantity of air to be warmed per minute in habitable rooms and in pubhc buildings must be from 3*5 to 5 cubic feet for each person the room contains, and 1*25 cubic foot for each square foot of glass." According to the same authority, an iron pipe, 4 inches in external diameter, loses 0*851 of a degree of heat (Fahr.) per minute (or 1° F. in seventy seconds) when the excess of its temperature is 125° F. above that of the surrounding air. Hood estimates also that 1 foot of a 4-inch pipe will heat 222 cubic feet of ah 1° F. per minute when the difference of temperature of pipe and temperature of air is 125° F. Putting it in another way, we can say that one British thermal unit will heat 50 cubic feet of ah 1° F., and that the amount of heat given off from iron pipes containing steam or hot Avater is 1*75 thermal unit per hour per square foot of radiating surface for each Fahrenheit degree of difference between the temperature of the pipe and that of the surrounding air. Hence, to find the number of square feet of radiating surface required to heat a given supply of air to a given temperature, multiply the number of •cubic feet of air per hour by the difference between the temperature of the ■cold air supply and that to which it is to be heated, and divide it by 50: ;this will give the number of thermal units required; then, dividing these by the difference between the temperature of the radiating surface and that of the surrounding air multiplied by 1*75, the number of square feet of surface required will be found. Example.—A room receiving 6000 cubic feet of air per hour is required to have its ■temperature raised from 32" F. to 70° F. by a radiating surface whose temperature is 210° F. How many square feet of radiating surface are needed to do this work ? Then, 60Q0 x38 = 4560 thermal units, and -*"*92— = 18*6 square feet. 50 140x1-75 ^ This calculation does not allow for the loss from windows and walls. To obtain the amount of radiating surface required for a given room, and to compensate for heat lost by radiation from windows, doors and walls, Baldwin and J. H. Mills give the following rules :—Take the difference in temperature in degrees Fahrenheit between the lowest outside temperature to be provided for and the temperature at which the room is to be kept, and ■divide it by the difference in degrees Fahrenheit between the temperature of the pipes and the temperature at which the room is to be kept. Multiply the quotient thus obtained by the number of square feet of glass plus the number of square yards of external wall surface in the room, and the product will be the number of square feet of radiating surface required. Ecample.—Suppose we have a room, containing 2000 cubic feet, with 36 square feet of ■window glass and. 20 square feet of external wall surface, which has to be kept at 70° F. when the outside air is 10° below zero, the temperature of the radiating surface being 80 210D F. Then, ^77 x 56 = 32 square feet of radiating surface required. This calculation does not provide for any leakage of air through crevices, 234 VENTILATION AND HEATING. or for any change of ah by ventilation. To make allowance for this, we must make the additional calculation of multiplying the number of cubic feet of air per hour by the number of degrees Fahrenheit which they are to be heated and divide the product by 12,500. The quotient is the number of square feet of radiating surface required. Example.—Let us suppose the same room as above, only that the air is to be changed three times an hour to provide for its constant occupancy by two persons, or 60001 cubic feet of air must be delivered hourly. Then, ~Ta'KQrr"= 38*4, Avhich, added to- 32, gives in round numbers 70 square feet of radiating surface required. The following table, from Hood, shoAvs the length of 4-inch pipe at 200° F. necessary to warm 1000 cubic feet of air at varying internal and external temperatures. If the diameter of the pipe is increased in any ratio, the length required will be reduced in the same ratio: thus, 100 feet of 4-inch pipe can be replaced by | of 100 feet = 133 feet of 3-inch pipe, and so on. Temperature , in degrees Fahrenheit, at which the room is required to he kept. Temperature of External Air. 4-V. 50°. 55°. 60°. 65°. 70°. 75°. 80°. 85°. 90°. 10° Fahr. 126 150 174 200 229 259 292 328 367 409 12° „ 119 142 166 192 220 251 283 318 357 399 14° „ 112 135 159 184 212 242 274 309 347 388 16° „ 105 127 151 176 204 233 265 300 337 378 18° ,, 98 120 143 168 195 225 256 290 328 368 20° ,, 91 112 135 160 187 216 247 281 318 358 22° „ 83 105 128 152 179 207 238 271 308 347 24° „ 76 97 120 144 170 199 229 262 298 337 26° „ 69 90 112 136 162 190 220 253 288 327 28° „ 61 82 104 128 154 181 211 243 279 317 30° ,, 54 75 97 120 145 173 202 234 269 307 32° „ 47 67 89 112 137 164 193 225 259 296 34= „ 40 60 81 104 129 155 184 215 249 286 36° ,, 32 52 73 96 120 147 175 206 239 276 38° „ 25 45 66 88 112 138 166 196 230 266 40° „ 18 37 58 80 104 129 157 187 220 255 42° „ 10 30 50 72 95 121 148 178 210 245 44° „ g 22 42 64 87 112 139 168 200 235 46° „ 15 34 56 79 103 130 159 190 225 48° „ 7 27 48 70 95 121 150 181 214 50° ,, 19 40 62 86 112 140 171 204 52° ,, 11 32 54 77 103 131 1 161 194 To use the table, find in the first column the temperature of the outer ah, and at the top of one of the other columns find the temperature at which the room is to be maintained : then in this latter column, and on the hue which corresponds with the external temperature, the required number of feet of 4-inch pipe at 200° F. will be found which will heat 1000 cubic feet of air per minute. If the high-pressure system is employed, the necessary area of pipe surface is very much reduced in consequence of the higher temperature which is reached. The length of pipe required can be usually found from the 2'252d(t' — i) formula, —ta/t - t'Y =^' ^n ^hich ^ *s *he cuhic feet of air to be waimed per minute, f is the temperature to be obtained in the iccm, t is the tempera- ARTIFICIAL COOLING OF AIK. 235 ture of the outer air, D is the external diameter of the pipe, and T the temperature of the pipes : L being the length of pipe required. Artificial Cooling of Air.—Any consideration of the subject of ventila- tion would necessarily be incomplete, if reference were not made to methods for cooling the air, for although, in this country, the general problem of maintaining the air of an inhabited room at a temperature most suitable for its occupants involves the consideration of how to heat the air rather than to cool it, still there are countries and circumstances in Avhich the question of reducing the air temperature is one of paramount importance. The simplest method to adopt for preventing direct radiation of the sun from entering rooms is to shut doors and Avindows, and covering them with either blinds or louvre shutters. In countries, like India, where the outside air is often excessively dry, it can be cooled by being made to pass over wet surfaces of linen or tatties made of khus-khus grass. Some years ago, it was suggested by Jeffreys to supply cooled air to the hospital and barracks at Cawnpore by passing the air, before delivery into the rooms, through underground channels. This, though ingenious, is not a desirable method, as the air is hkely to be fouled in its passage beneath the earth, unless very special precautions are taken to keep the channels dry and clean. Owing to the development of a demand for artificial ice, and the supply of cold air in ships employed for the carriage of meat, a considerable impetus has been given of late years to the invention of machines and methods for artificial cooling. Practically, cold can be produced in one of three ways : namely (1) by the expansion of air; (2) by the expenditure of mechanical Avork in the evaporation of a liquid; (3) by the evaporation of a A*olatile liquid in one vessel, the vapour so formed being absorbed by water or some other liquid in another vessel connected with the first. 1. The remarkable changes of temperature produced by the rarefaction and condensation of air was pointed out in 1845 by Joule. The following table shows the effect of the dynamical coohng of air by reduction of pressure to 30 inches, from the pressure as stated in the first column, Avithout allowing any heat to be communicated to it during expansion} the original temperature at 30 inches of pressure being 60° F. (iShaAv). Initial pressure of the Temperature after Initial pressure of the Temperature after air in inches of mercury. expansion. air in inches of mercury. expansion. 31 55 -1 Fahr. 60 - 33°-9 Fahr. 32 50° -4 ,, 70 - 52°"4 „ 33 45°*9 ,, 80 - 67°-7 ,, 34 41°-6 ,, 90 - 80°-8 ,, 35 37°*5 ,, 100 - 92° -1 „ 40 18°*7 ,, 200 -15S°-5 ,, 50 -n°*o ,, 300 -191°-6 ,, Thus it Avill be seen that if a jet of air at 60° F. were bloAvn into a room by a pressure behind it of 10 inches of mercury above the ordinary barometric pressure, so that the air would find itself in the room suddenly under the ordinary pressure of 30 inches, the temperature of that air Avould be 13°*3 F. below freezing, presuming that there is no gain of heat from friction at the nozzle. On this principle it is possible, by means of suitable arrangements of expansion cylinders, to furnish a supply of air cooled by expansion to a temperature considerably below that of the surrounding 236 VENTILATION AND HEATING. bodies. If the air Avere compressed instead of being rarefied, a correspond- ing rise of temperature would be produced. This principle of dynamical eooling has now been applied to the refrigeration chambers of ships convey- ing meat from the colonies, where, by first compressing the air in a suitable ■engine, it is then passed cooled to an expansion engine, Avhich finally delivers the air cooled to an extent depending on the difference of its pressure in the compressed and uncompressed states. It is not improbable that in the near future, with a supply of compressed air at ordinary temperatures and by an expansion engine, every householder may not only get ice-cold air, but so produce ice if wanted. Its applicability to Indian -life is obvious, Avhere the use of refrigerating engines, as now employed on board ships for the meat refrigerating chambers, will pro- bably gradually replace the crude and cumbrous thermantidote of the present day. 2. ^Ye know that Avater evaporates at all temperatures, and that the amount of evaporation really depends upon the pressure to which the surface is exposed. If, therefore, tAvo vessels, each containing a volatile liquid, be in communication through an air-pump, and the pump be worked, any air or vapour in the one vessel Avill be gradually pumped out and delivered to the other. In other Avords, continuous evaporation will take place in one vessel, and continuous condensation in the other. As a result of evaporation, there is an absorption of heat from the one vessel, and, as a result of condensation, a development of heat in the other. If an arrange- ment be made for transferring the condensed hquid back to the evaporating vessel, the process may go on continuously. If heat is wanted, the cold vessel should be surrounded with an ample supply of water to keep up its temperature : if cooling be desired, the heat produced by the condensation may be allowed to pass into the outside air or a tank of Avater. The pro- duction of cold on this principle by the evaporation of methylic ether is now one of the methods of cooling ships employed in the carriage of meat. By the coohng apparatus, the meat is kept in a current of dry air very near the freezing point, and thus kept fresh during long voyages. 3. In Carre's ammonia machine for the production of ice, a solution of ammonia gas in water is placed in a vessel connected with a condenser. If the vessel is heated and the condenser be immersed in a cold-water tank, the ammonia is driven off from its solution, and, condensing to a hquid in the condenser, gives out heat in so doing to the surrounding water in the tank. If the A-essel be noAV immersed in cold water, and the condenser be surrounded by the water it is required to freeze, the cooled water in the vessel reabsorbs the ammonia vapour and reduces the pressure in the condenser, accompanied by a large reduction of temperature in the hquid in it and in the water surrounding it. By a continuous repetition of the process, successive quantities of heat are removed from the Avater surround- ing the condensed ammonia, until it actually freezes. By this method, ice can be made at a cost of only twopence per hundredweight. As to the advantages and disadvantages of the various systems of heating and ventilating, no better summary can be given than that by the late Prof. CarneUey in his Report on the Cost and Efficiency of the Heating and Ventilation of Schools, made to the School Board of Dundee in 1889. The Report is a complete arrangement of the results of an investigation of 323 schools, and extracts from it are best quoted in their original form. COMPARISON OF VENTILATION AND HEATING METHODS. 237 Open Fires. Advantages— 1. More cheerful. 2. First cost much less than hot-pipe systems. 3. Keeps air fresher than hot pipes, owing to draught up chimney. 4. So far as the Dundee schools are concerned, the temperature in the open-fire- schools was higher than in those heated by hot pipes. 5. The rooms of these schools will probably need painting less frequently than those heated by other systems. Disadvantages— 1. Greater labour in service. 2. Slightly greater annual cost than stoves, or steam-pipes, or large hot-watey pipes. 3. Unequal distribution of heat. 4. Air more highly charged Avith micro-organisms. Stoves. Advantages— 1. Smallest first cost. 2. Least annual cost. 3. Probably more effective heaters than open fires. D isad vantages— 1. Greater labour in service. 2. Require more attention than open fires. 3. More liable to smoke than open fires. 4. More liable to get out of repair than open fires. 5. Not so cheerful as open fires. Hot Pipes. Advantages— 1. Less labour in service than either open fires or stoves. 2. The class is not disturbed as in the case of the mending open fires and stoves. 3. More equal distribution of heat. 4. Air less charged with micro-organisms than when open fires are used. 5. On the whole the annual cost is probably slightly less than with open fires, but more than with stoves. Disadvantages— 1. Not so cheerful as open fires. 2. First cost much more than in the case of open fires or stoves. 3. Air not so fresh as with open fires. Of Hot-pipe Schools— 1. Small high-pressure pipes are cheaper in first cost than large low-pressure pipes. 2. In those schools examined, the air was better in rooms heated by small high- pressure pipes than in those heated by large low-pressure pipes. 3. It takes longer to get up heat with large than with small pipes. 4. Small pipes are less obtrusive in the rooms. Mechanical Ventilation. Advantages— 1. Much greater purity of air as regards all the constituents. 2. Efficiency of ventilation much more independent of the weather ; whereas with other systems the ventilation is worst when most needed. 3. The schools are warmer. 4. More equal distribution of heat and of fresh air. 5. Very effective in diminishing the number of micro-organisms, not only at the time the mechanical ventilation is in operation, but also for a long time after it has been stopped. 6. Reduces draughts to a minimum. In fact, the mechanical system heats and ventilates far better in every respect than any other system, and is, therefore, far more conducive to health and comfort and to success in teaching and learning. ■ 238 VENTILATION AND HEATING. Disadva ntages— 1. Greater first cost. 2. Greater annual cost (except in the case of very large schools). 3. Though in towns where several schools were heated and ventilated mechani- cally, there would not need to be more than an ordinary caretaker in each of such schools, yet one of these should be a man who had some knowledge of gas-engines, &c, so that he could attend to any repairs which might be necessary. Such a man Avould require a somewhat higher wage than an ordinary caretaker. This, however, would amount to very little if distributed over a number of schools. In the same Report, as regards efficiency, the following summary is given :— (a) Radiation v. Conduction.— With those systems in which the rooms are heated by radiation rather than by conduction, the air is much more highly charged with micro- organisms than Avith those systems in which the rooms are heated more by conduction than by radiation. (6) Manchester Grates v. Ordinary Grates.— As regards open fires, " Manchester grates " are much more effective in keeping the air of the rooms pure than ordinary grates. (c) Mechanical v. the Ordinary Systems.—Mechanical ventilation and heating is undoubtedly far more effective in maintaining the purity and temperature of the air in schools than any of the ordinary methods usually adopted, and is hence more conducive to health and comfort. {d) Gas-engines v. Water-engines.—Gas-engines are much cheaper and more effective than water-engines for driving the fans. (e) Power of Gas-engine required.—A 2 H.P. gas-engine is amply sufficient for driving 4-ft. Blackman fan ; while a 1 H.P. is sufficient for six of Cunningham's fans. (/) Blowing in v. Exhausting the Air.—The former is preferable. \g) Inlet Shafts. —One large fresh-air inlet shaft is much better than several small ones, and the entrance to the shaft should be as free as possible. (h) Air Filters.—These are best employed, made of coarse jute cloth, to remove soot and dirt. (i) Blackmail's v. Cunningham's Fans.—When properly arranged, a 4-ft. Blackman fan appears to be more effective, and costs less, both in first and annual cost, than the five or six Cunningham's fans usually employed to do the same work. Cunningham's fans are, however, more independent of the weather than are Blackman's or Aland's fans. {■>) Blackman's v. Aland's Fans.—The former are the better and more suitable. \k) Otto v. Stockport Gas-engines.—The former are the preferable. (1) Time required to change the Air of a School by Mechanical Ventilation.—By mechanical ventilation the whole of the air in a school may be easily changed in less than fifteen minutes, and when the system is well arranged in less than ten minutes. EXAMINATION OF THE SUFFICIENCY OF VENTILATION. The sufficiency of ventilation should be examined— 1st, By determining the amount of cubic space and floor space assigned to each person, and their relation to each other, and by determining the amount of movement of the air, or, in other words, the number of cubic feet of fresh air which each person receives per hour. 2nd., By examining the air by the senses, and by chemical, biological, and mechanical methods, so as to determine the presence, and, if possible, the amounts and characters of suspended matters, including micro-organisms, organic vapour, carbon dioxide, hydrogen sulphide, watery vapour, am- monia, &c, as already explained in the previous chapter. Measurement of Cubic Space.—The three dimensions of length, breadth, and height are simply multiplied into each other. If a room is square or oblong, Avith a flat ceiling, there is, of course, no difficulty in doing this, but frequently rooms are of irregular form, with angles, projections, half- circles, or segments of circles. In such cases the rules for the measurement of the areas of circles, segments, triangles, &c, must be used. By means MEASUREMENT OF CUBIC SPACE. 239 of these, and by dividing the room into several parts, as it Avere, so as to measure first one and then another, no difficulty Avill be felt. After the room has been measured, recesses containing air should be measured, and added to the amount of cubic space; and, on the other hand, sohd pro- jections, and solid masses of furniture, cupboards, &c, must be measured, and their cubic contents (which take the place of air) deducted from the cubic space already determined. The bedding also occupies a certain amount of space; a soldier's hospital mattress, pillow, three blankets, one coverlet, and two sheets will occupy almost 10 cubic feet—about 7 if tightly rolled up. It is seldom necessary to make any deduction for tables, chairs, and iron bedsteads, or small boxes, or to reduce the temperature 'of the air to standard temperature, as is sometimes done. A deduction may be made, hoAvever, for the bodies of persons living in the room; a man of ordinary size may take the place of about 2\ to 4 cubic feet of air (say 3 for the average). The weight of a man in stones, divided by 4, gives the cubic feet he occupies. Thus a man weighing 12 stones occupies 3 cubic feet. In hnear measurement, it is always convenient to measure in feet and decimals of a foot, and not in feet and inches. If square inches are measured, they may be turned into square feet by multiplying by 0*007 Area of circle, . >> »> • Circumference of circle, Diameter of circle, Area of ellipse, . . Circumference of ellipse, Area of a square, Area of a rectangle, . Area of a triangle, Area of a parallelogram, . Rules—Area or Superficies. = D2 x -7854 (or irr2, where r is the radius). = C2x -0796 (org). = D x 3-1416 (ir2r). = 0 4- 3-1416 ( = —) or C= x -3183. (" Multiply the product of the two diameters by -\ -nu(f±). • (Multiply half sum of the two diameters by I «■•■«• {-'-?}• = j Square one of the sides, or multiply any two sides \ into each other. = f Multiply two sides perpendicular to each \ other. _ / Base x \ height, or \ Height x \ base. Fig. 31. Divide into two triangles by a diagonal, and take sum of the areas of the two triangles. ^\ Fig. 32. ^Any figure bounded by right lines, Fig. 33. Divide into triangles, and take the sum of their areas. 240 VENTILATION AND HEATING. To § of product of chord and height add tho cube of the height divided by twice the chord (CAxHx§) + =3-. Fig. 34. Cubic Capacity of a Cube or a Solid Rectangle.—Multiply together the three dimensions, length, breadth, and height. Cubic Capacity of a Solid Triangle.—Area of section (triangle) multiplied by depth. Cubic Capacity of a Cone or Pyramid.—Area of base x J height. Cubic Capacity of a Dome.—Two-thirds of the product of the area of the base multi- plied by the height (area of base x height x §). Cubic Capacity of a Cylinder.—Area of base x height. / 47rr3\ Cubic Capacity of a Sphere.—J)'' x *5236 ( or -g— I. The cubic capacity of a bell-tent may be taken as that of a cone resting on a short cylinder. The cubic capacity of an hospital marquee must be got by dividing the marquee into several parts—1st, body; and, 2nd, roof :— 1. Body, as a solid rectangle, with a half cylinder at each end. 2. Roof, solid triangle, and two half cones. The total number of cubic feet, with additions and deductions all mader must then be divided by the number of persons hving in the room; the result is the cubic space per head; whilst the total area of floor space divided by the number of persons gives the floor space per head, which should be as near as possible TV of the cubic space. Determination of Air Movement in a Room.—The direction must first be determined, and then the rate of movement. Fhst enumerate the various openings in the room—doors, windows, chimney, special openings, and tubes—and consider which is likely to be the direction of movement, and whether there is a possibility of thorough movement of the air. Then, if it is not necessary to consider further any movement through open doors or windoAvs, close all these, and examine the movements through the other openings. This is best done by smoke disengaged from smouldering cotton-velvet, and less perfectly by small balloons, light pieces of paper, feathers, &c. The flame of a candle, which is often used, is only moved by strong currents. It may be generally taken for granted that one half of the openings in a room will admit fresh air, and half wiU be outlets. But this is not invariable, as a strong outlet, like a chimney, may draw air through an inlet of far greater area than itself, or may draw it through a much smaller area with an increased! rapidity, The direction being known, it is only necessary to measure the discharge through the outlets, as a corresponding quantity of fresh air must enter. By the Anemometer.—This is best done by an anemometer, or air-meter,. of which there are several in the market. The one commonly used is in principle that invented by Combes in 1838: four little sails, driven by the moving air, turn an axis with an endless screw, which itself turns some small toothed wheels, which indicate the number of revolutions of the axis, and consequently the space traversed by the sails in a given time, say one minute. By a careful graduation of each instrument, the rate per second is determined, and indicated by a small dial and index. A very beautiful instrument of this kind has been made by Casella of Holborn (fig. 35). It is thus used:—Being set at the zero point, or the reading of the instrument at the time being recorded, it is placed in the current Area of segment of circle, CALCULATION OF VELOCITIES OF AIR CURRENTS. 241 of the air: if it is placed in a tube or shaft, it should be put well in, but not quite in the centre, as the central velocity is always greater than that of the side; a point about two-fifths from the sides of the tube will give the mean velocity. The time when the sails begin to move is accurately noted, and then, after a given time, the instrument is removed, and the movement in the time noted is given by the dial. If this linear discharge is multiphed by the section area of the tube or opening (expressed in feet or decimals of a foot), the cubic discharge is ob- tained. If the current varies in intensity, the movement should be taken several times, and the mean calculated; but if the tube is so small that the sails approach closely to the circumference, the results cannot be depended on. If placed at the mouth of a tube, it often indicates a much feebler current than reaUy exists in the tube. The cubic discharge per minute being knoAvn, the amount per hour is obtained by multiplying by 60, and this divided by the number of persons in the room, gives the discharge per head for that particular aperture. By the Manometer.—Sanderson has made an ingenious alteration of a manometer described by Peclet, which can also be employed to measure the pressure, and, by calculation, the velocity, of the air. The current of ah is aUowed to impinge on a surface of water, and the height to which the water is driven up a tube of known inclination and size gives at once a measure of force. But, as necessitating a little calculation, this instrument is less useful than the anemometer, though it is adapted for cases where the anemometer cannot be used, as it may be connected by a long tube with a distant room, and probably would be well fitted to measure constantly the velocity in an extraction shaft. The velocity of the air-current is conveni- ently calculated by the following formula: v = 3*784 J- in which w is expressed in millimetres of water as read off on the manometer, while s is the specific gravity of 1 litre of air at the existing temperature and height of the barometer. By Calculation.—Supposing the external air is tranquil, and that the only cause of movement is the unequal weights of the external colder and the internal warmer air, the amount of discharge may be approximately obtained by the law of Montgolfier, already given. There is a fallacy, however, as the amount of friction can never be precisely known. Still, as an approximation, and in the absence of an anemometer, the rule is useful; and the following table has therefore been calculated. On testing this table, however, by the air-meter, it has been found to give too much when the tubes are long, on account of the great friction, and it is therefore advisable to make a further deduction of £th when the Q 242 VENTILATION AND HEATING. shaft or tube is long, and is at the same time of small diameter. If the tube have any angles, or is curved, this table is too imperfect to be used, unless attention be paid to the correction for friction already noted. If the movement of the external air influences the movement in the room, as when the Avind bloAVs through openings, calculation is useless, and the anemometer only can be depended on. Table to show the Velocity of Air in linear feet per minute. Calculated from Montgolfier's formula ; the expansion of air being taken as 0*002 for each degree Fahrenheit, and one-fourth being deducted for friction. {Round numbers have been taken.) MS "3 c Difference between Internal and External Temperature. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 30 10 88 102 114 125 135 144 153 161i169 176 183 190 197 | 204 210 216 222 228 233 239 244 249 254 279 11 92 107 119 131 141 151 160 169 177 185 192 200 207 i 213 220 226 233 239 245 250 256 261 267 292 12 96 111 125 136 147 158 167 176,185 193 201 209 216j223 230 237 243 249 255 261 267 273 279 305 13 100 116 130 140 153 164 174 183:192 201 209 217 225 ! 232 239 246 253 259 266 272 278 284 290 318 14 104 120 135 147 159 170 181 190 200 209 217 225 233 241 248 255 262 269 276 282 289 295 301 330 15 108 125 139 153 165 176 1S7 197 207 216 225 233 241 249 257 264 272 279 266 292 299 305 312 341 16 111 129 144 158 170 182 193 204 213 223 232 241 249 257 265 273 281 288 295 302 309 315 322 353 17 115 133 148 162 176 188 199 210 220 230 239 248 257 265 274 282 289 297 304 311 318 325 332 363 18 118 136 153 167 181 193 205 216 226 237 246 255 264 274 282 290 298 305 313 320 327 335 342 374 19 121 140 157 172 186 198 210 222 233 243 253 262 272'281 289 298 306 314 321 329 336 344 351 384 20 125 144 161 176 190 204 216 228 239 249 259 269 279; 288 297 305 314 322 330 338 345 353 360 394 21 12S 147 165 181 195 209 221 233 245 255 266 276 286 295 304 313 321 330 338 346 354 361 369 404 22 131 151 169 185 200 214 226 239 250 261 272 282 292 302 311 320 329 338 346 354 362 370 378 414 23 134 154 173 189 204 218 232 244 256 267 278 289 299 309 318 327 336 345 354 362 370 378 386 423 24 136 158 176 193 209 223 237 249 261 273 284 295 305 | 315 325 335 344 353 361 370 378 386 394 432 25 139 161 180 197 213 227 241 254 267 279 290 301 312 ! 322 332 342 351 360 369 378 386 394 402 441 26 142 164 183 201 217 232 246 259 272 284 296 307 318 328 338 348 358 367 376 385 394 402 410 450 27 145 167 1871205 221 237 251 264 277 290 302 313 324 335 345 355 365 374 383 392 401 410 418 458 28 147 170 190 209 225 241 255 269 282 295 307 319 330! 341 351 361 371 381 390 399 408 417 426 467 29 150 173 194 212 229 245 260 274 287 300 312 324 335 ! 347 357 368 378 388 397 407 416 425 433 475 30 153 176 197 216 233 249 264 279 292 305 318 330 3411 353 363 374 384 394 404 414 423 432 441 483 31 155 179 200 219 237 253 269 283 297 310 323 335 347 358 369 380 391 401 411 420 430 439 448 491 32 158 182 204 223 241 257 273 288 302 315 328 341 353 364 375 386 397 407 417 427 437 446 455 499 33 160 185 207 226 245 261 277 292 307 320 333 346 358 370 381 392 403 414 424 434 443 453 462 506 34 162 188 210 230 248 265 282 297 311 325 338 351 363 375 387 398 409 420 430 440 450 460 469 514 35 165 190 213 233 252 269 286 301 316 330 343 356 369 381 393 404 415 426 436 447 457 467 476 522 36 167 193 216 236 255 273 290 305 320 334 348 361 374 386 398 410 421 432 442 453 463 473 483 529 37 170 196 219 240 259 277 294 310 325 339 353 366 379 392 404 415 427 438 448 459 470 480 490 536 38 172 198 222 243 262 281 298 314 329 344 358 371 384 397 409 421 432 444 454 465 476 486 496 543 39 174 201 225 246 266 284 302 318 333 348 362 376 389 402 414 426 438 450 461 471 482 492 503 651 40 176 204 228 249 269 288 305 322 338 353 367 381 394 407 420 432 444 455 467 477 488 499 509 558 45 187 216 241 264 286 305 324 341 358 374 389 404 418 432 445 458 471 483 495 506 518 529 540 591 50 197 228 254 279 301 322 341 360 377 394 401 426 441 455 469 483 496 509 522 534 546 558 569 623 3 4 5 6 7 ' 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 30 Example.—To use the table, determine the height of the warm column of air from the point of entrance to the point of discharge. Ascertain the difference between its tem- perature and that of the external air. Take out number from table, and multiply by the section-area of the discharge-tube or opening, in feet or decimals of a foot. The result is the discharge in cubic feet per minute, multiply by 60—result, discharge per hour. Height of column, 32 feet; difference of temperature between internal and external air. 17 deg. Looking in the table, we find opposite to 32 and under 17, 375 feet. That would be for an area of 1 square foot. But supposing our air opening to be only § of a foot, we must multiply 375 by |— thus, 375 x-75 = 281-25. Therefore we get 281-25 feet (per minute), multiplied by 60 = 16,875 feet per hour. l J It is obvious that, in the preceding methods, all windows and doors opening into the room must be closed, and only those openings intended for the passage of air be allowed to remain open. Example.—-Presume a room is measured and found to contain 1500 cubic feet of air. The observations made have shown that the total outlets measure a square foot and that the average velocity of the outgoing air-current is 80 feet per minute. This shows that 4800 cubic feet of air are passing through the outlets per hour, and the capacity of the room being 1500 cubic feet, this volume of air is being completely renewed a trifle more than three times an hour. EXAMINATION OF THE EFFICIENCY OF VENTILATION. 243 A very ingenious method for determining the entire exchange of air going •on, including not only the amount passing in and out through ventilators, but also that escaping through cracks and fissures, has been suggested by Pettenkofer. It is based upon the fact that if in a closed room we have any easily recognised gas such as C02, the amount of fresh air entering the room in a given time may be determined by the dilution which this gas undergoes in the time. This plan is very suitable for testing systems of so-called natural ventdation. Pettenkofer closes all openings into the room, and then artificially generates an excessive amount of C02 in the air of the room by burning stearine candles. These candles burn about 9*5 grammes per hour, each gramme yielding 1*404 litre of C02. When the experiment is begun the air of the room should contain 5 or 6 parts of this gas per 1000, the exact amount being determined and recorded. The doors and windows are kept closed, and samples of the air taken from about the centre ■of the room at intervals of half an hour for one hour after the ventilators are ■opened. To avoid grave errors, due to opening doors and the exhalation of C02 by the breath, it is better to arrange, by means of an aspirator and a tube passed through the keyhole, or other small opening, for samples to be taken without opening the door. "When the necessary number of samples ihave been collected and examined, as explained in the last chapter, the calculation of the rate at which ventdation has been going on is made from ■the following formula by Seidel:— x = 2*303 x m x log £---, ° r-a In which x is the amount of air which has passed into the room, 2*303 is a ■constant, m is the cubic contents of the room in feet, p is the amount of C02 present in the air of the room at the beginning of the experiments, of avhich there are practically two, namely, one for the first half hour and one for the second, P is the amount of C02 present at the end of each experi- ment, and a is the amount of C02 present in the outer air. Example. —Presume that, the cubical contents of the room being 2000 feet, by the analytical method already explained, the amount of C02 has been found to be as follows:— At the beginning, 3 "6 per 1000; after 30 minutes, 3*2 per 1000 ; after 60 minutes, 2*8 per 1000, and in the open air, 0-4 per 1000. For the first half hour we get, x=2*303 x 2000 x log ~ or x=2*303 x 2000 x 0*0579742 = 267 cubic feet of air passed in during first half hour. And for the second 3 "2 — 0*4 halfhour,a;=2-303x2000xlog^g3^7, or x =2-303 x 2000 x 0-0669220 = 308 cubic feet of air passed in during second half hour. Therefore, for the entire hour, we have 267 + 308 = 575 cubic feet of air passing into a room of 2000 cubic feet capacity. At this rate, the entire volume of air in the room would require 3*4 hours for its complete removal, a rate of ventilation which we have learnt to be quite inadequate. When this method is used for determining the amount of ventilation of rooms provided with inlets, provision must be made for closing them from Avithout, in order to obviate inaccuracies likely to result if doors be opened. To make any ventilation inquhy complete, supplementary observations would need to be made, not only as to the C02, but also as regards oxidis- able and organic matter, as well as to humidity, temperature, suspended matter, micro-organisms, and the various other details mentioned when con- sidering the practical examination of air. When these final analyses have been made, the amount of air per head per hour, supplied and utilised, can he readily calculated as before explained, and compared with the amount of 244 VENTILATION AND HEATING. movement determined by the anemometer. If the quantities accord fairly, the distribution may be considered good: on the other hand, if they differ, an excess by the air-meter shows bad distribution, whilst a deficiency indicates some other source of incoming air not yet observed. BIBLIOGRAPHY AND REFERENCES. Anderson, "On Emission of Heat by Hot-water Pipes," Proc. Inst. C.E., xlviii. p. 257. Arnott, On the Smokeless Fireplace, Lond., 1855. Atkinson, Pract. Treat, on the Gases of Coal Mines, and the General Principles of Ventilation, Lond., 1889. Baldwin, "Hot-water Heating and Fitting," New York Engineering Record, 1889. Billings, Ventilation and Heating, New York, 1893. Box, A Practical Treatise on Heat, 7th edit., New York, 1891. Briggs, " On the Ventilation of Halls of Audience," Trans. Amer. Soc. C.E., vol. x., 1881, p. 53. Carelle and Herscher, Trait6 de physique industrielle, production et utilisation de la chaleur, Paris, 1892. Carnelley, Beport on the Ventilation and Heating of Schools to the School Board of Dundee, 1889 ; also Broc. Boy. Soc. Lond., 1887. Coleman, " On Air-refrigerating Machinery," Broc. Instit. C.E., vol. lxviii. p. 146. Damman, Die Gesundheitspflege landwirtschaftlicher Haussdngetiere, Berlin, 1892. Daniel, "On Mechanical Ventilation," Proc. Instit. Mech. Engin., 1875, p. 317- De Chaumont, " On Ventilation and Cubic Space," Lancet, Sept. 1866 ; also Edin. Med. Journ., May 1867 ; also "On the Theory of Ventilation," Proc. Roy. Soc. Lond., No. 168, p. 187, 1875, and No. 171, 1876 ; also Lectures on State Medicinet Lond., 1875 ; also Three Reports on the Sanitary Condition of St Mary's Hosp., Lond., 1875-6 ; also various Reports in Army Med. Dep. Reports, vols. vi. to x. Degen,. Prac Handbuch f. Einrichtungen der Ventilation u. Heizung in Offentlichen u. Privatgebauden nach dem System der Aspiration, Munchen, 1878. Deville and Troost, "On the Escape of Carbon Monoxide from Stoves," Comptes Rendus de I'Acad. Franc, Jan. 1868. Donkin, Report of Committee appointed to consider the Cubic Space of Metropolitan Workhouses, Blue Book, 1867. Eassie, Sanitary Arrangements for Dwellings, Lond., 1874. Galton, Sir D., Healthy Dwellings, Clarendon Press, 1880. Haller, Die Luftung und Erwarmung der Kinderstube u. des Krankenzimmers, Berlin, 1860. Hawksley, Proc. Instit. C.E., vol. vi. p. 192. Hood, Treatise on Warm- ing and Ventilation, Lond., 1869. Kennedy, " On the Employment of Compressed Air for the Production of Cold," Proc. Brit. Assoc, 1889, p. 448 ; also in Engineering, Sept. 13, 1889. Leeds, A Treatise on Ventilation, New York, 1871. Marcker, Untersuch. u. nat. u. Kiinstliche Ventilation, Gottingen, 1871. Mills, J. H. On the Production and Application of Heat to the Warming and Ventilation of Build- ings, Boston, U.S.A., 1890. Mills and Rowan, Fuel and its Application, Lon- don, 1889. Morin, Bapport sur la Chauffage et la Ventilation des Batiments du Palais de Justice, Paris, 1860; also Etudes sur la Ventilation, Paris, 1863 ; also Man- uel Pratique du Chauffage et de la Ventilation, Paris, 1874. Morrison, " On th» Ventilation of Tunnels," Proc. Instit. C.E., 1876. Murgue, Theories and Practice of Centrifugal Machines, translated by Steavenson, London, E. & F. Spon Charing Cross, 1883. ' & Peclet, Traiti de la Chaleur, 3me edit., Paris, 1861. Pettenkofer, Uber den Luft- wechsel in Wohnegebduden, Munchen, 1858. Planat, Cours de Construction civile Premiere partie: "Chauffage et Ventilation des lieux habites," Paris, 188o! Putnam, The Open Fireplace in all Ages, Boston, U.S.A., 1881. Putzeys, Hygiene des agglomerations militaires, et la construction des Casernes, Liege, 1892. Ramsay, Treatise on Ventilating and Working Collieries, Lond., 1882. Rankine The Steam-Engine, London, 1873. Reid, Illustrations of the Theory and Practice of Ven- BIBLIOGRAPHY AND REFERENCES. 245 tilation, Lond., 1844. Reiset, " Upon the Physiology of Respiration in Animals," in Hoppe Seyler's Bhysiolog. Chemie, Bd. ii. s. 536, Berlin, 1879. Reports—Of •Committee appointed to inquire into the Cubic Space of Metrop. Workhouses, 1867 ; also Report of Barrack and Hospital Improvement Committee upon Ventilation of Cavalry Stables, 1866 ; also Reports upon the Ventilation of the Houses of Parlia- ment, 1832, 1835, 1837,1841, 1843, 1846, 1847, 1848, 1852, 1854,1866,1884, 1886 ; Reports of Metropol. Board of Works on the Ventilation of Sewers, 1866-1868-1873 ; Report of Parliamentary Committee on the Ventilation of Mines, 1850; Report of Parliamentary Commiss. on the Warming and Ventilation of Dwellings, 1857 ; also Report of Commission appointed to inquire into the Condition of all Mines in Great Britain, Lond., 1864 ; Report of Commissioners of Patents on the Specifications relating to Ventilation, a.d. 1632 to 1866, Lond., 1872. Richard, "Sur la toxicite de Pair expire," Rev. d'Hyg., 1889, xi. p. 338. Ritchie, Treatise on Ven- tilation, London, 1862. "Shaw, Proc. Roy. Soc Lond., March 1890 ; also article on " Ventilation and Heating " in Stevenson and Murphy's Treatise on Hygiene, Lond., 1892. Smith, F., Veter- inary Hygiene, Lond., 1887 ; also in Journ. Physiol., vol. xi., 1890. Thompson, Sir W., " On Heat" in Ency. Brit., 9th edit. Wilson, Treatise on Bractical and Theoretical Mine Ventilation, New York, 1891. Wolpert, Tlieorie und Praxis der Ventilation und Heizung, Braunschweig, 1880. CHAPTER IV. FOOD. In the widest acceptation of the term, Food includes everything ingested, which goes directly or indirectly to the growth or repair of the body or to the production of energy in any form. In this way it would include not only those organic and mineral solids and the usual beverages recognised as dietetic, but also water and air. For it is quite obvious that without water no function of the living body would be possible, whilst the production of energy is mainly, if not entirely, caused by the union of the atmospheric oxygen with the organic matter of the food or the tissues of the body itself. Although these facts are distinctly recognised, it has generally been the practice to restrict the term " food " to those substances which are capable of oxidation and those which act as directors or regulators of nutrition, to the exclusion of air and water,—these two last being usually considered under separate heads. No one group even of this rough classification is capable of sustaining healthy life alone, and a combination of all, or nearly all, the different constituents of diet is required to accomplish the best results. It is also necessary to limit the application, " food," so as to ex- clude generally medicines and poisons, which, on the one hand, either act or are intended to act upon processes of unhealthy nutrition, or, on the other hand, prevent the processes of healthy nutrition, and so induce un- healthy nutrition and ultimately dissolution. Even here the line cannot be too strictly drawn, for in many cases it is a question more of quantity than kind that determines the direction of the action. The enumeration and classification of the foods or aliments necessary to maintain human hfe in its most perfect state have been usually based on the deduction of Prout that milk contains all the necessary aliments and in the best form. The substances in milk are—1st, the nitrogenous matters, viz., the casein principally, and, in smaller quantities, albumin, lacto-protein, and perhaps other proteid bodies; 2nd, the fat and od; 3rd, sugar in the form of lactose; 4th, water and salts, the latter being especially combinations of magnesium, calcium, potassium, sodium, and iron, with chlorine, phosphoric acid, and, in smaller quantities, sulphuric acid. In addition to their occurrence in milk, which is admitted to be a perfect food for the young, this enumeration of aliments appears to be justified by two considerations. First, that the different members of each class, inter se, have a remarkably similar composition, Avhile there are broad lines of physical and chemical demarcation between the classes; and secondly, that the different classes appear to serve different purposes in nutrition, and are all necessary for perfect health. The various substances which constitute food are conveniently spoken of as proximate principles, because, consisting as they do of carbon, hydrogen, oxygen and nitrogen, combined more or less into highly complex bodies, PROXIMATE PRINCIPLES—PROTEIDS. 247 they really are elementary constituents or proximate principles of the human organism. These elementary or proximate principles may be conveniently classified as folloAvs :— ! Nitrogenous, as proteids or albuminoids. I Fats or hydrocarbons. Non-nitrogenous, < Starches and sugars or carbo-hydrates. ( Vegetable acids. Inorganic,.... Mineral salts. Food accessories, . . Such as tea, coffee, &c. It must be noted that the simplest diAdsion of the organic constituents of food is into the nitrogenous and the non-nitrogenous, or those which contain nitrogen and those which do not. Now, the proteids alone contain nitrogen. Just as the greater part of the air is made up of nitrogen, so is the greater part of our body (bone excepted) made up of proteid, or nitrogen contain- ing substances. A large amount of nitrogen in the form of urea, uric acid, and other substances, is daily being lost from our bodies by the urine; and to repair this loss, a daily intake of nitrogenous food is required. The only form of nitrogen food Avhich the body can make use of is that of proteid or albuminoids. A plant equally needs nitrogen, but this it obtains from the ammonia and nitrates of the sod, which are much simpler bodies than proteids. Proteids may be regarded as the most important food-stuffs, as they are the only organic food-substances of which it can be said with certainty that they are indispensable, and that they cannot be replaced by any other nutrient material. They are to be found in every animal and vegetable tissue, forming the chief part of every cell, and are never absent from any vegetable or animal food. All proteids resemble each other in being composed, in similar weight proportions, of carbon, hydrogen, oxygen, nitrogen, and sulphur, with occasionally a httle phosphorus. Their general percentage composition may be taken as being: nitrogen, 16 parts; carbon, 54 parts; oxygen, 22 parts; hydrogen, 7 parts; and sulphur, 1 part. The chemical constitution of proteids is not knoAvn, but the nitrogen seems to exist in two distinct conditions, partly loosely combined, so as to yield ammonia when they are decomposed, and partly in a more fixed condition. The proteid molecule is not only very large, but also very complex : a small part of it is composed of substances from the group of aromatic bodies, Avhich become so con- spicuous during putrefaction, while a larger part belongs to the fatty bodies, as during the oxidation of albumin, fatty acids are especially developed. Carbo-hydrates may also appear as decomposition products. In the alimen- tary canal, proteids are changed into peptones, whhe the chief products derived from their oxidation within the body are C02, H20, and urea, which latter contains nearly all the nitrogen of the proteids. The chief character of proteids is that they are colloids, and, therefore, do not diffuse easily through animal membranes: they are also amorphous and do not crystallise, hence are isolated with difficulty. Some are soluble, others are insoluble in Avater : they are insoluble in alcohol and ether, rotate polarised light to the left, and when burned give off an odour of burned horn. They are precipitated from their solution by various metallic salts and alcohol; they are coagulated by heat, mineral acids, and the pro- longed action of alcohol. Caustic alkalies dissolve them, and from this solution they are precipitated by acids. 248 FOOD. Chemically, the proteids can be recognised by the folloAving reactions :— 1. When heated with strong nitric acid, they give a yellow colour, which, on the subsequent addition of ammonia, turns a deep orange. This is the so-called xantho-proteic reaction. 2. With nitrate of mercury, they give a precipitate, and when heated with this reagent above 60° C. they give a red one, probably owing to the formation of tyrosin. 3. The addition of a few drops of a dilute solution of cupric sulphate, and the subsequent addition of caustic potash, gives a violet colour which deepens on boiling. The same colour is obtained by adding a feAv drops of Fehling's solution, the so-called biuret-reaction. 4. When rendered strongly acid Avith acetic acid and boiled with an equal volume of a concentrated solution of sodic sulphate they are precipi- tated. This method is used for removing proteids from other liquids, as it does not interfere with the presence of other substances. Saturation with sodio-magnesic sulphate precipitates the proteids but not peptones, and the same is the case if saturated with neutral ammonium sulphate. The proteids, Avhen regarded as foods, are divisible into tAvo great groups, according to their nutritive value. The more nutritious one is the group of true proteids, consisting of albumin, myosin, glutin, legumin, casein, globulin, syntonin, fibrin, and peptones : in them the proportion of nitrogen to carbon is nearly as 2 is to 7. The other, or less nutritious class is sometimes called the albuminoid group : its members include substances obtained only from animals, such as gelatin, chondrin, ossein, and keratin : in these latter, the proportion of nitrogen to carbon is as 2 is to 5^. The first group of proteid foods is the most important: it may be divided into:—Native albumins, such as serum albumin and egg albumin. They are soluble in water, and are not precipitated by alkaline carbonates, common salt, or by very dilute acids. Their solutions are coagulated by heating at 65° to 73° C. Globulins.—The myosin of muscle, the globulin of the serum and of the blood, and the vitellin of egg-yolk are examples from the animal kingdom, while from the vegetable world are the globulins contained in the cereals and leguminosae. These native proteids are insoluble in distilled water, but soluble in dhute neutral saline solutions, such as NaCl, KC1, NH4C1, and MgS04. These solutions are coagulated by heat and precipitated by the addition of a large quantity of water. Derived Albumins.—Syntonin or acid albumin and alkali albumin formed by the action of dilute acids and alkalies on ordinary proteids. Closely allied to alkali albumin is casein, or the chief proteid in milk and the legumin and conglutin of peas, beans, &c. None of these proteids are coagulated by heat, but can be precipitated from solution by sodic chloride, acetate or phosphate or by neutralisation by alkalies and acids respectively. Insoluble Proteid*.—That is, those insoluble in Avater and in sahne solutions at ordinary temperatures, such for instance as the fibrin of blood and the glutin of wheat. Albumoses and Peptones.—The former are found largely in the cereals, and are probably very Avidely distributed in the vegetable kingdom. In the animal kingdom they are merely bodies formed by the action of pepsin upon ordinary proteids, the albumoses being precursors of the peptones. The latter are remarkable for their extreme ditfusibdity and ready absorp- tion by the alimentary canal. Owing to the easiness of their digestion, these forms of proteid are uoav largely given in the various kinds of partly HYDROCARBONS—CARBO-HYDRATES. 249 artificially digested foods for the sick, though it must be remembered that they do not possess the same nutritive value as the real proteids of food. The second group of the proteid foods is sometimes called the albuminoids. The substances contained in this group closely resemble true proteids in their origin and composition, and are amorphous non-crystalline colloids. 'Though some of them do not contain sulphur, their reactions and decom- position products closely resemble those of the proteids. The chief members of this group are gelatin, mucin, chondrin, ossein, keratin, and Jiuclein. These bodies are easily dissolved in hot Avater, and yield more or less the same products after digestion as the true proteids, but appear, on the whole, to have a less nutritive value than them. Gelatin is the only important member of this group; it contains a larger percentage of nitrogen than the ordinary proteids, namely, from 17 to 18 per cent., and differs also in some chemical reactions, as Avell as not yielding tyrosin on decomposi- tion. Fats or Hydrocarbons.—These are combinations of a trivalent alcohol, glycerin, with three molecules of monobasic acids, principally stearic acid, palmitic acid, and oleic acid. They aU contain hydrogen and oxygen, but no nitrogen, and may be represented by the general formula C10H18O. The proportion of oxygen in them, however, is insufficient to combine with ^11 the hydrogen present so as to form water. When taken as food, the fats are chiefly in the form of neutral fat, but may also exist in the form of iatty acids and of their compounds, the alkaline soaps. The neutral fat taken as food ahvays contains free fatty acids in greater or less proportion, and in some foods, such as cheese, the fatty acids may exist in large pro- portions indeed. Carbo-hydrates occur in plants and animals, and are so-called because, in addition to at least six atoms of carbon, they contain hydrogen and oxygen in the proportion in Avhich these occur in water. They are all .solid, chemically indifferent, and without odour. They have either a sweet taste (sugars) or can be readily changed into sugars by the action of dilute acids; they rotate the ray of polarised light either to the right or left, and, as far as their chemical constitution is concerned, may be regarded as hexatomic alcohols in which two atoms of hydrogen are Avanting. Until recent times the true chemical nature of these bodies was not understood, but the researches of E. Fischer have shown that the simplest carbo-hydrates {the old grape-sugars or glucoses) are aldehydes or ketones of a hexatomic alcohol, having the formula C6H8(OH)6. Just as during the oxidation of ordinary alcohol, C2H60, the aldehyde C2H40 is formed, so from mannitic alcohol the molecule C6H120(3, representing the simplest carbo-hydrate, is produced. Such carbo-hydrates are spoken of as Monosaccharids, and the best known are glucose, lsevulose, and galactose. These monosaccharid molecules may link together (polymerise) with the loss of water. When two such molecules thus unite, Disaccharids are produced, and these really split to yield their constituent monosaccharids. The most important of these are maltose, formed from two molecules of ■dextrose, and cane-sugar, formed from a molecule of dextrose connected to a molecule of laevulose, and milk-sugar or lactose, in Avhich dextrose and galactose are linked together. Further combination (polymerisation) and dehydration produces a set of bodies having molecules of increased size. The simpler members of this series, or those most nearly resembling the sugars, are the dextrins, while among the more complex are starch and glycogen. The whole series may be conveniently called Poly sacchar ids. In some of the higher 250 FOOD. members of the group, such as the starches, more than a hundred monosaccharid molecules may be connected together. These polysaccharide tend to break down into their constituent disaccharid and monosaccharid molecules. A comprehension of these facts is essential for a study of the changes which these food-substances undergo in the animal body. In the first group, or the monosaccharids, we have the following:— Grape-sugar, Cf)H1906 (glucose, dextrose or diabetic sugar), when occur- ring in animal tissues, is mainly formed by the action of diastatic ferments upon other carbo-hydrates during digestion. In the vegetable kingdom, it is extensively distributed in the sweet juices of many fruits and flowers. It is formed from cane-sugar, maltose, dextrin, glycogen, and starch by boiling them with dilute acids. By fermentation with yeast, it splits up into alcohol and C02 ; with decomposing proteids it splits into two molecules of lactic acid, while this latter, under the same conditions in alkahne solutions, splits up into butyric acid, C02 and H2. Galactose is obtained by boding lactose or milk-sugar with dilute mineral acids: it crystalhses, is fermentable, and gives all the reactions of glucose* Its specific rotatory power is + 88°*08 for Aj or median yellow ray of light. Lxvulose, sometimes called invert sugar, occurs as a colourless syrup in honey and juices of some fruits. It is non-crystallisable, and rotates - 106° for Aj. In the second group, or disaccharids, Ave have carbo-hydrates which may be regarded as anhydrides of the monosaccharids, with the formula of C12H22On. Thus, Lactose or milk-sugar occurs only in milk. It rotates polarised light + 61°*5 for Aj, and is much less soluble in water and alcohol than grape-sugar. When boiled with dilute mineral acids, it passes into galactose, and can be directly transformed into lactic acid only by fermenta- tion : the galactose, however, is capable of undergoing alcoholic fermentation with yeast (koumiss). Maltose has one molecule of water less than grape-sugar, and is the final product of the action of diastase on starch. It has a rotatory power of +155°, and is soluble in alcohol. Cane-sugar or saccharose occurs in sugar-cane and some plants; it does not reduce a solution of copper, is insoluble in alcohol, is right rotatory, 73°*8 for Aj, and not capable of fermentation. When boiled with dilute acids, it becomes changed into a mixture of glucose and laevulose (invert sugar). In the third group we have carbo-hydrates with the formula, wC6H10O5, which may be regarded as anhydrides of the second group. The chief among them are :— Starches, which constitute the chief portion of the seeds of the various cereals and potatoes. Starch combines with iodine to form a blue colour, constituting thereby a simple test for its presence. In cold water or alcohol, starch is insoluble, but at 72° C. (161°*6 F.) it swells up in water and forms a mucilage. Starch-grains always contain more or less cellulose and a sub- stance, erythrogranulose, which is coloured red with iodine. Heat and dilute acids, also the digestive ferments in the saliva, pancreatic and intestinal juices, convert starch into a gum-like substance, called dextrin, and if carried further into grape-sugar. Glycogen, or the so-called animal starch, has a dextro-rotatory power of 211°, and does not reduce cupric oxide. It occurs in the liver, muscles, and various other tissues of man and animals. It occurs also in the oyster and some other molluscs. Dextrin occurs in beer, and in the juices of most plants. In water, it forms a sticky solution, from Avhich it is precipitated by alcohol or acetic VEGETABLE ACIDS—MINERAL SALTS. 251 acid; it also slightly reddens with iodine. Dextrin is largely present irt the crust of bread, and if examined with polarised light in dilute solutions, rotates + 222° for Aj. It is further formed from cellulose by the action of dilute sulphuric acid. Among carbo-hydrates of this group must be included cellulose and pectose. Cellulose constitutes the chief framework of plants, it is quite- insoluble, and apparently without any dietetic value. When boiled with dilute sulphuric acid, it yields dextrin and glucose. In a similar way, pectose or vegetable jelly is found in various ripe fruits, being really a later stage of the insoluble body present in most unripe fruits, and known as pectin. Its precise composition is unknown. Vegetable Acids.—These, though not strictly speaking foods, play so- important a part in preserving the health of man that they demand some considerable notice. The chief among them are tartaric, citric, mahc, oxalic,. and acetic acids. Tartaric acid, C4H606, exists largely in grape juice chiefly as the acid tartrate of potassium ; Citric acid, C6H807, is found in oranges, lemons, and gooseberries; Malic acid, C4H605, is met with in fruits belong- ing to the rose order, such as apples and pears; Oxalic acid, C2H204, is present largely in rhubarb and sorrel; Acetic acid, C2H402, constitutes the active element in vinegar. Except it be the latter, all these vegetable acids contain more than sufficient oxygen to convert all their hydrogen into water.. These acids exist mainly in fresh fruits and vegetables, either as free acids or in combination Avith alkalies as alkaline salts, and, when taken into the body, form carbonates, Avhich exercise a controlhng influence in preserving; the alkalinity not only of the blood but other fluids; they also furnish a small amount of energy and heat by oxidation. Their absence for any length of time from any dietary leads to a peculiar lowering or weakening- of the blood, resulting in the disease called scurvy. It is possible that some of these acids are not only derived from fruits and vegetables, but also in a small degree from the splitting up of carbo-hydrates, so that even the latter, in an indirect way, help in maintaining the alkalinity of the blood and other animal fluids. Mineral Salts.—Among the mineral salts which constitute a part of the proximate principles of food must be included chloride of sodium or common salt, the phosphates of hme, potash, soda, and magnesium, along with small quantities of sulphates and possibly iron. These, in their various and respective ways, are essential for the repair and growth of all parts of the body. The uses of the chlorides, as typified by common salt, are very important. The complete withholding of ordinary salt from food leads to rapid disease and even death. The chlorides generally keep in solution the globulins of the blood and other fluids, while at the same time they are the source of the hydrochloric acid of the gastric juice, and materially aid in the solution of albumin. The phosphates of lime, potash, and magnesia contri- bute, especially in the young, to the formation of bone; while iron forms an important part of the haemoglobin of the red blood-corpuscles. THE NUTEITIVE FUNCTIONS OF THE FOOD-STUFFS. The physiological evidence that these classes of aliments serve different purposes in nutrition is not so complete as that of their chemical differences. A broad distinction must, of course, be drawn between the nitrogenous and non-nitrogenous substances. Modern researches, which have much modified our opinion of the direction in which the potential energy of the 252 FOOD. ■dietetic principles may be manifested (as heat, or electricity, or mechanical movement), and of the mode in Avhich the nitrogenous substances in par- ticular aid or restrain this transformation, do not impeach the proposition that the presence of nitrogen in an organised structure, and its participation in the action going on there, is a necessary condition for the manifestation ■of any energy or any chemical change. Whether, when energy is mani- fested, the nitrogenous framework of any nitrogenous structure is a mere stage on which other actors play, or whether it is used up and destroyed, or is, on the other hand, built up or renovated during action, is, so far as ■classification of food is concerned, a matter of no consequence. In the digestive tract, both animal and vegetable proteids are trans- formed by the gastric juice into syntonin, albumoses, and peptones; by the pancreatic juice into peptones and an intermediate body, while part of the peptone is further spht up into leucin and tyrosin. Gelatin is also trans- formed into albumoses by the stomach and small intestine, but keratin is not digested by the stomach, only by the pancreatic juice. Briicke thinks that some of the native proteids, taken as food, may be absorbed as such, but the more general opinion is that proteids are absorbed mainly if not only in the form of albumoses and peptones. Albumoses and peptones thus form an important element in artificial foods for invalids, but it is more than doubtful Avhether they possess the same nutritive value as the ordinary proteids of food. The great danger in regard to them is, that when a large quantity is given, much of the peptone is spht up by the pancreatic juice into leucin and tyrosin, and may thus be lost as food to the organism. The following considerations seem to prove the necessary participation of the nitrogenous structures in manifestations of energy. Every structure in the body in which any form of energy is manifested (heat, mechanical motion, chemical or electrical action, &c.) is nitrogenous. The nerves, the muscles, and gland cells, the floating cells in the various liquids, the semen and the ovarian cells, are all nitrogenous. Even the non-cellular liquids passing out into the alimentary canal at various points, which have so great an action in preparing the food in different ways, are not only nitrogenous, but the constancy of this imphes the necessity of the nitrogen, in order that these actions shall be performed; and the same constancy of the presence of nitrogen when function is performed, is apparently traceable through the whole world. Surely such constancy proves necessity. Then, if the nitrogen be cut off from the body, the various functions languish. This does not occur at once, for every body contains a store of nitrogen, but it is at length ine-vitable. Again, if it is wished to increase the manifestation of the energies of the various organs, more nitrogen must be supphed. The experiments of Pettenkofer and Voit sIioav that the nitrogenous substances composing the textures of the body determine the absorption of oxygen. The condensation of the oxygen from the atmosphere, its conversion into its active condition (ozone), and its apphcation to oxidation are, according to their experiments, entirely under the control of the nitrogenous tissues ■(fixed and floating), and are apparently proportional to their size and vigour, and to changes occurring in them. The absorption of oxygen does not determine the changes in the tissues, but the changes in the tissues determine the absorption of oxygen. In other words, Avithout the parti- cipation of the nitrogenous bodies, no oxidation and no manifestation of energy is possible. The experiments show that the absorption of oxygen by the lungs is dependent on its disposal in the body, and that this disposal is an direct NUTRITIVE FUNCTIONS OF THE FOOD-STUFFS. 253 relation Avith the absolute and relative amount and action of the nitrogenous structures. Mechanical motion, electricity, or heat may be owing to the oxidation of fat or of starch, or of nitrogenous substance; but whatever be the final source, the direction is given by the nitrogenous structures. The proteids are further a source of fats and possibly of carbo-hydrates,. so that they really play two parts, first, that of regulators of oxidation and of the transformation of energy; and second, they may form a non- nitrogenous substance Avhich is oxidised and transformed. That fats are formed from proteids is shoAvn by the following: 1. Carnivora giving suck, Avhen fed on plenty of flesh and little fat, yield milk rich in fat. 2. A cow Avhich produces one pound of butter daily does not take nearly this amount of fatty matter in her food, so that the fat would appear to be formed in this case from vegetable proteids. That the proteids are a source of carbo-hydrate also, is shown by the fact that, in an animal deprived of glycogen by strychnine poisoning, this carbo-hydrate appears again in the liver and muscles under the influence of chloral, even though the animal is starved. As to how this is brought about, considerable diversity of opinion prevails. The question practically is, does the proteid molecule contain carbo-hydrate molecules which are set free when it breaks down; or do the elements of the proteid molecule^ after breaking doAvn and then becoming part of the protoplasm, change' into the carbo-hydrate molecule? According to Pfhiger, the latter is the probable explanation, whde Pavy attempts to furnish evidence that the proteid molecule does contain a carbo-hydrate moiety, which is the source of carbo-hydrates formed from proteids. No matter which view is correct,, the fact that proteids are a partial source of both fats and carbo-hydrates must not allow us to consider a proteid as an aliment which may replace fat or starch or sugar in the case of man. The digestive system of man is framed so differently from that of the carnivora, that fat must be taken in its own form, for it either cannot be formed in sufficient quantity from proteids, or the body is poisoned by the excess of nitrogen which is necessarily absorbed to supply it. The use of fats in the organism is that they are sources of energy and of heat to the body. In the majority of national dietaries, fat finds a place, and in some cases, as that of the Esquimaux, it is greatly increased in the dietary. When hard work is to be done, an excess of fat is involuntarily taken. Whatever the mixture of fats taken in as food, the fat of the body always has the same composition; this fact agrees with the conclusion that the deposition and metabolism of fat in the body is due to cell activity, and that the fat comes in part from the proteid, and part from the carbo- hydrate foods. The consumption of carbo-hydrates spares not only proteid food, but also fat. They lessen the need of fat by being a source of energy in the body, and thus when present in a diet poor in fat, they diminish the oxidation' of fat in the body. The experiments of E. Smith, Haughton, and others,. on muscular action, prove that we must look for the main source of energy which is apparent during muscular action in the oxidation of the non- nitrogenous substances, but no experiments have yet shown whether these are fats or carbo-hydrates. It seems to be inferred that it is fat which is thus chiefly acted upon, but this opinion is rather derived from a reference to the universal presence of fat when energy is manifested, to the known necessity of it in diet (for though the dog and the rat (Savory) can live on fat-free meat alone, man cannot do so), and from the large amount of energy its oxidation can produce, than from actual observation. If it were 254 food. true, a broad distinction would be at once drawn between fatty and starchy food, but it is not experimentally proved. If, on the other hand, it were ■certain that the starchy ahments formed fat in the human body as a rule, this would be a reason for draAving no distinction between the groups. Independent of the argument drawn from bees fed on sugar alone and forming Avax, from the fattening of ducks and geese, and the older experi- ments on pigs, the later experiments of Lawes and Gilbert seem to show ■clearly that the fat stored up in fattened pigs cannot be derived from the fat given in the food, but must have been produced partly from nitrogenous substances, but chiefly from the carbo-hydrates. So also it seems now probable that the fat in milk is not derived at once from blood, but from •changes of albumin in the lacteal gland cells. There seems no reason why Ave should not extend the inference to man. If so, a man could hve in perfect health on a diet composed only of fat-free meat and starch, Avith salts and water, just as he can certainly live (though perhaps not in the highest health) on meat, fat, salts, and water. The carbo-hydrates Avould then be proved to be able to replace fats. The experiment has not yet been performed, or at least recorded, but it seems important it should be. Many authorities state that fat is formed directly from carbo-hydrates, and the weight of evidence appears to favour this view; but whether it is so formed directly, or indirectly, by retarding the metabolism of the fatty and proteid constituents of the food, there is no doubt that the consumption of carbo-hydrates results in the formation of fat within the body. Grouven's experiments also suggest that in cattle the carbo-hydrates may spht up in the alimentary canal into glycerin, lactic and butyric acids, and carbon dioxide and marsh gas. If this be true, in the herbivora the starches would be merely another form of fat. In man it has been pointed out that, as fermentative changes occur in the small intestines with the production of lactic acid, so the butyric acid fermentation may possibly take place in the sugar of the intestinal contents. By this change the sugar would be removed from the carbo-hydrate group into the fatty acid group, and, as Foster says, " put on its way to become fat." The possibihty of the conversion of fats to carbo-hydrates in the animal body has so far not been fully investigated. Seegen has suggested that fats do yield sugar in the body, but his experiments are unsatisfactory. The glucoside constitution of proteid matter, and the partial origin of carbo-hydrates from proteids, as advanced by Pavy, has already been mentioned: he further maintains that the carbo-hydrates, stored as glycogen, or as they pass through the intestinal wall, go to form proteid. Possibly he is right: but to argue, as he does, from plants to animals is somewhat dangerous. Though asparagin and carbo-hydrates may be built into the protoplasm molecules of plants, the direct experimental evidence against the utilisation of the former substance in animals is very strong. His further views that carbo-hydrates are changed to fats is in conformity with the results of many experimenters, though how this actually takes place is not quite so clear. As to the changes which the carbo-hydrates of food undergo in the ahmentary canal, the most recent research has demonstrated the important action of the intestinal secretions in bringing about the complete conversion of polysaccharids and disaccharids to monosaccharids. Starches and maltose are entirely converted to dextrose, while cane-sugar is spht into dextrose and lsevulose. It is probable that the conversion of starch is not ahvays completed before absorption, and that some of the lower dextrins NUTRITIVE FUNCTIONS OF CARBO-HYDRATES, SALTS, AND AVATER. 255 may pass through the intestinal wall along with dextrose. Cane-sugar, too, when in excess, may escape conversion and pass into the blood as such. On the other hand, milk-sugar does not appear to be acted upon unless by the intestinal bacteria, which split it up in part to lactic acid, &c. An argument against the fats and carbo-hydrates being mutually re- placeable under ordinary conditions in the diet of men is drawn from a consideration of the diets used by all nations. In no case in which it can TDe obtained is an admixture of starch, in some form, with fat omitted. Moreover, in all cases (except in those nations, like the Esquimaux, who are under particular conditions of food) Ave find that the amount of fat taken is comparatively small as compared with that of starches. The fats when taken into the body enter like the proteids into the structure of the tissues, ■of which fat forms in probably all cases an essential part. The carbo- hydrates, on the other hand, in the human body do not appear to be parts of the tissues, though they are contained in the fluids Avhich bathe them, or are contained in them. The special direction which the chemical changes in the carbo-hydrates take in the body seems also to point to special duties. Thus, the formation of lactic and other acids of the same class must arise from carbo-hydrates chiefly or solely. But the formation of these acids is certainly most important in nutrition, for the various reactions of the fluids, which offer so striking a contrast (the alkalinity of the blood, the acidity of most mucous secretions, of the sweat, urine, &c), must be chiefly owing to the action of lactic acid on the phosphates, or the chlorides, and to the ease with which it is oxidised and removed. If the direction of the changes which the carbo-hydrates undergo within the body is different from that of the fats, the products of these changes must be inferred to play dissimilar parts. Without pushing these arguments too far, and with the admission that the subject is stdl obscure, we are fairly entitled to assert that the two groups of fats and carbo-hydrates are not so immediately and completely convertible as to permit us to place them together in a classification of diets. The salts and water are as essential as the nitrogenous substances. Lime, -chiefly in the form of phosphate, is absent from no tissue; and there is reason to think no cell growth can go on without it; certainly, in enlarging morbid growths, and in rapidly growing cells, it is in large amount. When phosphate of calcium was excluded from the diet, the bones of an adult goat were not found by H. Weiske to be poorer in lime, because pro- Tjably hme was drawn from other parts; but the goat became weak and dud, so that nutrition was interfered with. Experiment has shown that the -growth of wheat is more quickly and effectually checked by the absence of phosphoric acid than of any other constituent from the soil. The lowest forms of hfe will not grow without earthy phosphates. Magnesia is probably also an essential constituent of growth in some tissues. Potash and soda, in the forms of phosphates and chlorides, are equally im- portant, and would seem to be especially concerned in the molecular currents; forming parts of almost all tissues, they are less fixed, so to speak, than the magnesian and lime salts. It is also now certain, that the two alkahes do not replace each other, and have a different distribution; and it is so far observable, that the potash seems to be the alkali for the formed tissues, such as the blood cells or muscular fibre; while the soda salts are more largely contained in the intercellular fluids which bathe or encircle the tissues. The chlorine and phosphoric acid have also very peculiar properties,—the 256 food. former apparently being easily set free, and then giving a very strong acid, which has a special action on proteids, its presence being also necessary for maintaining the globulin in solution: the latter has remarkable combining- properties with alkalies. Both are furnished in almost all food; the sodium chloride also separately. Carbonic acid is both introduced and made in the system, and probably serves many uses. Iron is, of course, also essential for certain tissues or parts, especially for the red blood-corpuscles, and for the colouring matter in muscle, and in small quantity is found almost in every tissue and in every food. The sulphur and phosphorus of the tissues appear to enter especially as such with the proteids. Some salts, especially those Avhich form carbonates in the system, such as the lactates, tartrates, citrates, and acetates, give the alkalinity to the system which seems so necessary to the integrity of the molecular currents. The state of malnutrition, which in its highest degree we call scurvy, appears to follow inevitably on their absence; and, as they exist chiefly in fresh vege- tables, it is a well-known rule in dietetics to supply these with great care, though their nutritive poAver otherwise is small. So important are those substances, that they might well be placed in a separate class, although Pavy remarks that " these principles are hardly of sufficient importance, in an alimentary point of view, to call for their consideration under a distinct head." Surely this is an under-estimate of their importance, considering the inevitable malnutrition that follows on their absence. In addition to the substances composing these four classes, there are others which enter into many diets, and which have been termed " accessory foods " or by some writers " force regulators " (like the salts). The various condi- ments which give taste to food, or excite salivary or alimentary secretions and tea, coffee, cocoa, alcohol, &c, furnish the chief substances of this class. Much discussion has taken place as to the exact action in nutrition of these substances, but little is definitely known. With regard to the necessity of all four classes of aliments, it can be affirmed with certainty that (putting scurvy out of the question) men can live for some time and can be healthy with a diet of proteids, fat, salts, and water. But special conditions of life, such as great exercise, or exposure to very low temperature, appear to be necessary, and under usual conditions of hfe health is not very perfectly maintained on such a diet. It has not yet been shown that men can hve in good health on proteids, carbo-hydrates, salts, and water, &c, without fat. The exact effect produced by the deprivation of any one of these classes is not yet known. An excess of the proteids causes a more rapid oxidation of fat (and in dogs an ehmination of water), while an excess of fat lessens the absorption of oxygen, and hinders the metamorphosis of both fat and albu- minous tissues. The carbo-hydrates have the same effect when in excess, and appear to lessen the oxidation of the two other classes. It is generally admitted that the success of Banting's treatment of obesity is owing to two actions: the increased oxidising effect on fat consequent on the increase of meat (especially if exercise be combined), and the lessened interference with the oxidation of fat consequent on the deprivation of the starches. Health cannot be maintained on proteids, salts, and water alone; but on the other hand, it cannot be maintained without them. A classification, on a' simplified plan, may be made as follows :— CLASSIFICATION OF FOOD STUFFS. 257 1. Proteids. All substances containing nitrogen, of a composition iden- tical with, or nearly that of albumin; proportion of nitro- gen to carbon being nearly as 2 to 7, or 4 to 14. 1 {a). Substances containing a larger proportion of nitrogen and apparently less nutritious. Proportion of nitrogen to car- bon about 2 to 5|, or 4 to 11. 1 (b). Extractive matters, such as are contained in the juice of the flesh. ( 2. Fats (or Hydrocarbons). Substances containing no nitrogen, but made up of carbon, hydrogen, and oxygen ; the pro- portion of oxygen being less than sufficient to convert all the hy- drogen into water. Proportion of unoxidised hy- drogen to carbon about 1 to 7. 3. Carbo-hydrates. "i Substances containing no | nitrogen, but made up of carbon, hydrogen, and oxygen ; the oxy- | gen being exactly sufficient to )■ convert all the hydrogen into water. Proportion of water to carbon j being about 3 to 2. J Examples. Functions. f Albumin, Formation and repair Fibrin, of tissues and fluids of | Syntonin, the body. Myosin, Regulation of the ab- Globulin, sorption and utilisation Casein, of oxygen. Albumoses, May also form fat and ..Peptones, carbo-hydrate, also yield energy under special conditions. qj In most foods, the 2 ( Glutin, above, both animal and ■g < Legumin, vegetable, are largely %p (Albumoses, converted into albu- t> moses and peptones dur- ing digestion. Native albumoses are present in many cereals. Gelatin, These perform the Ossein, above functions less per- Chondrin, fectly, or only under Keratin, particular circumstances. These substances ap- pear essential as regu- lators of digestion and assimilation, especially with reference to the gelatin group. Olein, Stearin, Margarin, Starch, Dextrin, Cane-sugar, Grape-sugar, Lactose (or milk-sugar), Supply of fatty tissues, nutrition of nervous sys- tem. Supply of energy and animal heat by oxida- tion. Production of energy and animal heat by oxidation. Form fats and possibly some pro- teid. 3 (a). Vegetable acids {andpectous~\ substances ?) Substances containing no nitrogen, but made up of carbon, hydrogen, and oxygen ; the oxy- }- Malic gen being generally in greater amount than is sufficient to con- vert all the hydrogen into L water. Oxalic acid, Tartaric,, Citric ,, Acetic Lactic r In these the"| I oxygen is more J than sufficient | to convert all the hydrogen [ Jnto water. In these there is no excess of | oxygen. J Preserving the alkalinity of the blood by conver- sion into carbon- ates ; furnish a small amount of energy or animal heat by oxida- tion. 4. Salts (mineral), f Sodium chloride, | Potassium ,, -J Calcium phosphate, j Magnesium „ I Iron, &c, Various : support of bony skeleton, supply of -HC1 for digestion, &c. Regulators of energy and nutrition. R 258 FOOD. THE NUTRITIVE VALUE OF THE FOOD-STUFFS. In the preceding section Ave have learnt the part the various food-stuffs play Avhen taken into the body : it is noAV necessary to learn their nutritive value. To begin with, if we lift a Aveight by our hands, muscular force is employed in the act, and the energy evolved in this or any other muscular action must have its origin or source in something. As a matter of fact, the energy so evolved has its source in the material Avhich has been supplied to the body in the form of food. Every process of our bodies, no matter whether it be the moving of a hand or a foot, the beating of our heart, or the secretion of saliva, is attended with some manifestation of energy, and this energy is shoAvn in one or other of two forms, namely, either mechanical labour or heat. These facts Avill be more clearly understood if it is borne in mind that Avhat is called energy in an agent is merely an expression that that agent is capable of doing work, and that the quantity of energy it possesses is measured by the amount of work it can do. An agent or force is said to do work when it produces any change in the condition of bodies: therefore energy is the capacity for producing physical change. This capacity for producing change or energy is of two kinds, namely, kinetic energy or the energy of movement, and potential energy or that of position. This latter term means various forms of energy which are suspended in their action, and which, although they may cause motion, are not in themselves motion. Thus, a coiled Avatch-spring possesses energy of position or potential energy, and only wants a touch to transform the energy of position into energy of movement, or potential into mechanical energy. Moreover this transformation of potential into kinetic energy, or vice versd, can take place without any part of the energy being lost, and it is further possible to convert the whole of the energy possessed by any body into heat. Thus if a piece of lead be thrown from a high tower to the ground, and if it strike some hard, unyielding substance, the movement of the lead mass is not only arrested but its kinetic energy is transformed into violent vibratory movements of the lead atoms. As a result of this violent vibration of atoms, heat is produced, and the amount of this is pro- portional to the kinetic energy of the lead, which again was proportional to its potential energy when in position on the tower. In the human body the ordinary movements of the whole system and of individual organs are constantly being transformed into heat. If we regard, therefore, the food we consume as the direct source of all this heat and the mechanical energy displayed by the body, it is obvious we can obtain by their measurement a fair idea of the nutritive values of various food-stuffs. The problem is, however, not of a uniformly simple nature. In the case of the water and mineral salts of the food, their nutritive value is not difficult to ascertain, because they are simple bodies, and do not undergo any very great chemical change in the body. The nutritive value of the proteids, fats, and carbo- hydrates, however, is not so easy to determine, because not only are they complex bodies in themselves, but, moreover, undergo complicated and ill- understood changes within the body; their nutritive value, therefore, cannot be very accurately expressed. The simplest measure of the potential energy is the amount of heat which can be obtained by complete combustion of the chemical compounds representing the potential energy. The various statements as to the amount of potential energy possessed by various food-stuffs and expressed either in terms of heat or work, are based upon the researches and dis- coveries of Mayer and Joule, that the amount of power or energy which HEAT EQUIVALENTS OF THE FOOD STUFFS. 259 can be obtained from a given Aveight of matter is connected with and proportional to the heat given out during its combustion. As a standard of measure of heat, we have the "heat-unit," or calorie. This heat-unit, or calorie, is the amount of energy required to raise the temperature of 1 gramme of water 1° C. The heat-unit corresponds to 425-5 units of work, which are gram-metres : that is, the same energy required to heat 1 gramme of water 1° C. Avould raise a weight of 425-5 grammes to the height of 1 metre; or a weight of 425*5 grammes, if allowed to fall from a height of 1 metre, Avould by its concussion produce as much heat as would raise the tempera- ture of 1 gramme of water 1° C. According to the English system, the heat-unit is the amount of energy required to raise the temperature of a pound of water 1° F., and will, if manifested as a mechanical force, raise 772 lb. a foot high, or, what amounts to the same thing, 1 ft. 772 feet high. Thus the dynamic or mechanical equivalent of one degree of heat on the Fahrenheit scale is said to be 772 foot-pounds. Adopting the Centigrade scale, then the mechanical equivalent of 1° C, or 1°'8 F, will be 1389 pounds: that is, the energy AAdiich Avill raise the temperature of 1 lb. of water 1° C, or 1°*8 F, wdl be capable, as a motive power, of raising 1 lb. in weight 1389 feet high. In England, the amount of work done is commonly expressed as foot-tons or tons lifted 1 foot, whde in France it is often expressed as kilogram-metres or kdogrammes lifted 1 metre. Units of work, expressed according to the continental system as gram- metres, can be converted into foot-pounds by multiplying them by 0*007233, and into foot-tons by dividing by 311,000. Similarly, kilogram-metres are converted into foot-pounds by multiplying by 7*233, and into foot-tons by dividing by 311. Applying this principle, that as heat production is related to the amount of chemical action ensuing so hkewise is mechanical power production, we find that as a measure of the utility of food, the value of the various food principles as mechanical power producers will correspond with their value as heat producers. Those food principles, which by oxidation give rise to the greatest amount of heat, will, of course, theoretically have the greatest capacity for the production of working power; that is, will possess the greatest potential energy. This theoretical potential energy is not only different in the case of each class of food-stuffs, such as proteid, fat, and carbo-hydrate, but differs also in different foods of each of these classes. In the case of many food-stuffs, their actual value in respect of capacity for heat production has been determined experimentally, and expressed in relation to the performance of work. The heat-equivalent of the organic substances cannot be exactly computed from the known heat-equivalents of carbon and hydrogen, because of the amount of heat which is set free by the union of the oxygen with the carbon and hydrogen; further, a part is used up in the separation of the hydrogen atoms from the carbon atoms, and of the carbon atoms from each other. This amount of heat may vary greatly in different compounds, because the atoms are more or less firmly combined with each other, and varying amounts of heat are set free by their union. Metameric compounds are known to produce different heat-equivalents. To overcome these difficulties, the heat-equivalents of foods have been determined by direct calorimetric methods, first by Frankland, then by an improved method by Stohmann and Rechenberg, lastly by Danilewski and by Rubner. Taking the above mentioned estimate of the mechanical equivalent of heat as a basis of calculation, the following table has been con- structed, showing both the units of heat and energy developed by one ounce 260 FOOD. and one gramme of various substances when fully oxidised : the units of heat and energy being expressed according to both the English and metric systems. One ounce (dried) yields One gramme [dried) yields Substance. English Energy as Metric Energy as Kilo- Heat-units. Foot-tons. Heat-units. gram-metres. Acetic acid, 394 135 3,505 1,489 Albumin (egg), . 628 216 5,577 2,370 Ale (Bass's), 754 260 6,682 2,841 Alcohol (fluid ounces), 786 271 6,980 2,966 Arrowroot, . 438 151 3,912 1,664 Bacon. 997 344 8,847 3,760 Barley meal, 417 144 3,703 1,574 Barley (pearl), 414 143 3,678 1,563 Beef, fat, 1,017 351 9,069 3,860 Beef, lean, . 572 197 5,103 2,170 Biscuit, 417 144 3,703 1,574 Bread (wheaten). 490 169 4,351 1,849 Butter, 815 281 7,264 3,077 Cabbage, 417 144 3,703 1,574 Carbon, 910 314 8,080 3,434 Carrots, 310 107 2,752 1,169 Casein, 658 227 5,855 2,488 Cellulose, . 466 160 4,146 1,762 Cheese, 687 237 6,095 2,590 Chondrin, . 552 190 4,909 2,086 Dextrose, . 443 153 3,939 1,674 Eggs, 745 257 6,610 2,809 Fibrin (blood). . 620 213 5,508 2,340 Fish (white), 553 191 4,912 2,087 Gelatin, 618 213 5,493 2,334 Glutin, 690 238 6,141 2,610 Glycerin, 484 166 4.305 1,829 Horseflesh, . 542 187 4,809 2,043 Hydrogen, . 3,880 1,337 34,462 14,664 Lactose, 412 142 3,667 1,558 Liebig's Extract, 495 171 4,400 1,870 Macaroni, . 411 142 3,652 1,552 Maltose, 467 161 4,163 1,769 Milk (cows), 644 222 5,733 2,436 Milk (human), . 545 188 4,837 2,055 Oatmeal, 443 153 3,935 1,672 Peas, . 551 190 4,889 2,077 Pemmican, 849 293 7,531 3,202 Peptone, 553 190 4,914 2,088 Potatoes, 475 164 4,234 1,799 Poultry, 556 192 4,934 2,098 Rice, . 540 186 4,806 2,042 Starch (wheat), . 504 174 4,479 1,903 Sugar (cane), 374 129 3,348 1,423 Sugar (grape), . 368 127 3,277 1,394 Tartaric acid, 158 54 1,408 598 Urea, . 238 82 2,121 903 Vinegar, 74 25 660 280 A table of this kind is useful in showing what can be obtained from our food, but it must not be supposed that the value of food is in exact relation to the possible energy which it can furnish. In order that the energy shall be obtained, the food must not only be digested and taken into the body properly prepared, but its energy must be developed at the place and in the manner proper for nutrition. The mere expression of potential energy POTENTIAL ENERGY OF THE FOOD STUFFS. 261 cannot fix dietetic value, which may be dependent on conditions in the body unknown to us. In the case of non-nitrogenous foods, it is probable that the same heat- equivalent is produced in our bodies as in a calorimeter, because the ultimate products of their combustion are the same; but it is different in the case of food containing nitrogen. In a calorimeter, nitrogen is liberated in a free state from nitrogenous food-stuffs, but after the decomposition and oxidation in the body of a nitrogen containing food, the nitrogen issues, as an organic compound, in union with carbon and hydrogen, and, in the case of man, principally as urea. Ordinary albumin, which may be taken as a fair type of the proteids, yields about one-third of its weight as urea. In order, therefore, to ascertain the heat-equivalent of the proteid in our organism, we must deduct one-third of the heat-equivalent of urea from that of the albumin. But this figure would come out rather too high, because the nitrogen leaves our body not only as urea, but partly as a compound con- taining more carbon and hydrogen. We shall be nearer the mark if we subtract at least 800 metric heat-units, per gramme, from the heat-equivalent of any proteid in the above table; thus, taking albumin and potatoes as examples, we obtain a figure from the proteid which is only a httle higher than that from the carbo-hydrate. As a store of energy in our bodies, there- fore, the carbo-hydrates are, in a quantitative respect, about equivalent to the proteids. The heat-equivalent of fats, on the other hand, is twice as great. From what has been said, it is evident that it is difficult to compare rightly the potential energy available by the burning of a food-stuff outside the body with that which is obtained as the result of combustion within the body, and in attempting to estimate the nutritive values therefrom, allow- ance must be made for the different degrees of digestibility, the effects of cooking, and even the actual bulk taken. In the case of fats, their nutritive value seems to depend largely on their digestibihty, whde of the carbo-hydrates there is httle reason to think that starch, grape-sugar, or cane-sugar differ much in their nutritive value, though Lawes' and Gilbert's experiments in- dicate that cane-sugar is more fattening than starch. Among the proteids, we know that gelatin and chondrin have a lower nutritive value than the ordinary proteids, and that vegetable proteids are as nourishing as the animal. As illustrative of the loss on the consumption of different foods, the following table is suggestive:— There ai'e wasted per cent, of the Ingested. On the consumption of Dry substance. Nitrogen. Salts (ash). Beans (boiled), . 18 3 30*2 28-3 Bread, 4-4 22*2 21-3 Broccoli, 15-0 18*0 19-0 Cabbage, 16*2 17*5 18-4 Carrots, 21-0 39 0 34 0 Eggs, . 5 2 2*6 18*2 Macaroni, , 5-0 14*0 23-0 Maize, , 7-0 15-0 30-0 Meat, . 5-1 2*6 18-1 Milk (by adults), 9*5 10-5 42*5 Milk (by children), 6*2 4-4 42*2 Pease pudding, . 9-0 175 32-5 Potatoes (boiled), 9*2 32-2 15-8 Rice pudding (boiled), 4 1 20-5 15-0 Rusks, .... 5 0 20'0 21*0 These results having been obtained by Rubner, Prausnitz and others. 262 FOOD. To foods which, when burnt, yield the same number of heat-units, the term isodynamic has been applied, as expressing in terms of energy their equival- ence to each other; that is to say, that so much proteid is isodynamic with so much fat or carbo-hydrate. Rubner has calculated that 100 parts of fat during combustion, whether within or without the body, yield as much heat as 213 parts of albumin, as 232 parts of starch, as 234 parts of cane- sugar, and as 256 parts of dextrin. These, however, are scarcely practically useful values, since, as we have already learnt, the several nutritive sub- stances are not perfect substitutes for each other. Some German authorities,. notably Kb'nig and Emmerling, have endeavoured to obtain a nutritive value of the food-stuffs as based on their market price ratios. Using the term "nutrient unit" as representing a mere national economic standard, they say that— 1 part of carbo-hydrate has the value of 1 nutrient unit. 1 part of fat has the value of 3 nutrient units. 1 part of proteid has the value of 5 nutrient units. We ascertain how many nutrient units are contained in 100 parts of a substance, as calculated out from its analytical constituents: the more such units it contains, the greater is its economic value. Further, we may calcu- late how many nutrient units we can obtain in any case for so much money, say, for instance, one shilling (Lehmann). Thus for instance, say 100 parts of bread contain 8 of proteid, 1*5 of fat and 50 of carbo-hydrate. Then (8 x 5) + (1*5 x 3) + (50) = 94*5, or the- sum of nutrient units per 100 pounds of bread, and if we take bread to be roughly a penny a pound, we get rather more than 11 nutrient units for one- shilling. In the same way, further values can be worked out for other articles of diet, and comparisons made between them. For the purpose of economic comparative statements of dietaries, this method is extremely in- genious, but actual figures of value will obviously vary in different places and at different periods according to the prices prevaihng. With regard to mechanical labour and the amount of energy expended by the body, it is considered that 300 foot-tons or 93,300 kilogram-metres of external work over and above what is done by the functional activity of the body itself is a good day's work. With regard to heat produced in and by the body, no accurate knowledge is available; but the ratio between the amount of mechanical labour done and heat produced by an adult during an ordinary day's work is about one-sixth mechanical labour to five-sixths heat. It is primarily to meet these losses, or to furnish sufficient energy for labour and heat production in the body, that we require and actually take; food. In round numbers, it may be said that the internal work and heat of the body amount to the following:— Work of circulation, . . 242 foot-tons or 75,200 kilogram-metres. Work of respiration, , . 39 „ 12,100 '„ Calorific work, .... 2519 „ 783,400 }, Of the total energy developed by oxidation of the food in ihe body, it has been estimated by Helmholtz that the animal economy is capable of turning only one-seventh to the account of external work, after allowing for the internal work of the body. The late Professor de Chaumont reckoned the internal work to be equal to about 2800 foot-tons daily, and, according to him, to get an ordinary day's work done (say 300 foot-tons), Ave require five times that- amount of energy (1500) in addition to the quantity needed for the body's internaT QUANTITY OF FOOD NECESSAKY. 263 work ; or 1500 plus 2800 = 4300 foot-tons to be provided from the material taken in as food. The proportionate increase he formulated thus :— 300x(5 + y + |- + y+ ....) = 300x14 = 4200. This means that if Ave Avant a harder day's work done, say 450 foot-tons, not (450 x 5) = 2250 foot-tons of energy must be supplied, but (300 x 5) + (300x 7>j = 2550, and so on in proportion; 2800 foot-tons being supplied hi addition for the internal work, or 2550 plus 2800 = 5350 foot-tons. The actual productive Avork is : 300 x(l + -^- + ^---r--£-.... ) = 300 x 2 = 600. That is, the greatest amount of mechanical work that can be per- formed by the body under ordinary circumstances is 600 foot-tons. The potential energy to be supplied to obtain this Avork is 4200 foot-tons, with 2800 foot-tons added for internal work, making a total of 7000 foot-tons, or the maximum amount of energy that the body is able to deal with in the food. The folloAving estimates have been made as to man's Avork :— Light work, from 150 to 200 foot-tons, or from 46,600 to 62,200 kilogram-metres each day. Average „ 300 „ 350 „ „ 93,300 „ 108,800 Hard ,, 450 „ 500 ,, „ 139,900 ,, 155,500 ,, „ Laborious ,, 500 „ 600 „ „ 155,500 „ 186,600 ,, „ QUANTITY OF THE FOOD-STUFFS REQUISITE TO PRESERVE HEALTH. So far, Ave have discussed the nature, uses, and nutritive values of the food-stuffs individually ; it is necessary noAV to consider them collectively in reference to their poAvers of maintaining life—whether any one of them alone is capable of supporting vitality—or what combinations and what quantity of them experience and experiment teach us are useful in the food of man. There is abundant evidence to prove that no one group of the ahmentary substances is alone sufficient to sustain life for any length of time, but that a mixed diet is necessary. Such evidence is derived from instinctive proclivities, from considerations of the comparative anatomy of our digestive organs, from experience and experiment. That man cannot live upon any one group of the food-stuffs is shown by an examination of the needs of the body, as demonstrated by the daily loss by the kidneys, bowels, skin, and lungs. Various experiments by Parkes, Smith, Playfair, Haughton, Fick, and Ranke have shoAvn that an average man gives off 307 grains of nitrogen and 4700 grains of carbon daily. If he wishes to keep in health, this daily loss of nitrogen and carbon must be made up by a corresponding intake of those elements with his food. If such a man subsisted only on a carbo-hydrate food-stuff—say, for instance, bread, which contains 116 grains of carbon and 5*5 grains of nitrogen in each ounce—he Avould, in order to obtain the 307 grains of nitrogen needed by him, have to consume 3*1 ft) of bread, while at the same time the necessary quantity of carbon is contained in 2*5 lb. Or, to take the supposititious case of a man wishing to live on beef (representing the proteids), and having a composition of 60 grains of carbon and 10*3 grains of nitrogen in each ounce, he would, in order to obtain his 4700 grains of carbon, have to eat daily no less than 4-7 lb of that substance, while the required 307 grains of nitrogen are contained in 1*3 lb. Therefore, to obtain 264 FOOD. the proper quantity of carbon, he Avould be consuming a quantity of meat Avhich contains nearly four times the amount of nitrogen actually required. The general principles of diet may be summed up thus :—(1) No single nutritive principle, whether nitrogenous or non-nitrogenous, can support life except for a very short time. (2) Life may be supported upon one nitrogenous and one non-nitrogenous principle for a very long time, but for a permanency salts would require to be added. Thus, proteids and fats, or proteids and starches, would support life. (3) For the best forms of diet, both fats and carbo-hydrates are needed in addition to nitrogenous matter, and in all probability both starch and sugar among them. It would also appear that a due admixture of more than one form of nitrogenous principle is advisable. Standard Diets.—Experience teaches us that our requirements as to food vary much with our exposure to different conditions, and that according to the expenditure of our bodies so should the materials be supplied which are best calculated to yield Avhat is wanted. The human body has been com- pared to a machine, but it differs therefrom in this, that wear is constantly going on independently of any useful work done, which is not the case in a mechanical engine. Determinations as to the quantity of food daily required by the body have been obtained by means of extended observations of the diets of classes and communities, and also by estimating the sum of excreted matters, which, of course, must be compensated by a suitable supply of food. As the daily average output of a man weighing 70 kilogrammes or 11 stones is 230 grammes of carbon and 15 of nitrogen, it is clear that if his health and bodily weight are to be maintained, his daily diet must contain these elements in the proportion mentioned. But for the maintenance of nitrogenous equilibrium it is not required that the loss of nitrogen from the system should be just balanced. If nitrogen is not sufficiently supplied in the food it will still continue to be eliminated, its source being the meta- bolism of the tissues which contain it. The nitrogen import has to be considerable, in order that the equilibrium may be maintained—viz., three times the amount of nitrogen excreted when no food is taken. The channels by which this element leaves our body are the kidneys, intestine, lungs, and skin; nearly the whole of it comes away by the kidneys in the form of urea, so that the quantity of urea eliminated is taken as the measure of the nitrogenous disassimilation of the system. Thirty grammes or 500 grains of urea are regarded as the normal daily amount, and in 30 grammes of urea there are 14 of nitrogen. Add to this the quantity that leaves by the intestine—viz., 10 per cent, of the total nitrogen eliminated —and we have an accurate statement as to the daily nitrogen export, for the amount discharged by the lung in the form of ammonia in the expired air is infinitesimal, and the same remark applies to escape by the skin. A systematic examination of the diet tables of the industrial classes shoAvs that, with few exceptions, individuals are not taking in their food that excess of proteid or animal food necessary to maintain their nitrogenous equilibrium. It is probable that poor people when long underfed become accommodated to a low minimum, and that health may for a time be thus well maintained, but this takes place at a sacrifice, for experience indicates that where the nitrogen import is kept at the minimum for any lengthened period, the individuals subsequently become the subjects of tuberculous disease. From the researches of Playfair, Smith, and others, the usual range, in STANDARD DIETS. 265 the diet of an adult man, of nitrogen is daily from 250 to 350 grains, or from 16 to 23 grammes. The extremes being 180 grains (11*6 grammes) in a minimum or sustenance diet to 500 grains (32*4 grammes) taken during very great exertion. Of carbon, the daily need seems to be from 3500 to 6500 grains, or from 230 to 420 grammes. Smith's observations shoAV from 135 grains (8-7 grammes) of nitrogen and 3270 grains (212 grammes) of carbon in the diet of London needlewomen, to 350 grains (23 grammes) of nitrogen and 6200 grains (400 grammes) of carbon in that of radway navvies. The diets in English convict prisons show the nitrogen and carbon to vary from 226 and 4356 grains (14*5 and 282 grammes) in the light labour diets, to 263 and 5013 grains (17 and 323 grammes) in the hard labour. The carbon seems to vary from 3600 to 5800 grains (233 to 374 grammes) in diets generally. Weston, while walking 50 miles a day on the flat, and doing something like 790 foot-tons of external work, consumed daily on an average 545 grains (35 grammes) of nitrogen and 7880 grains (510 grammes) of carbon, or just about twice the amount of each which will support ordinary work. The more recent inquiries of Oliver into the nature and amounts of the daily dietaries of the working classes are in accordance Avith the above figures. The experiments of Parkes and Pettenkofer upon men to a great extent confirm the conclusions as to the daily needs of man as drawn from a study of class diets. The amounts of carbon and nitrogen taken daily in food are of the highest importance, since these are the chief elements which undergo metabolism in the body. In 100 grammes of proteid there are 54 of carbon, 16*1 of nitrogen, and 7*1 of hydrogen; in the same quantity of fat there are 76*5 of carbon and 10*9 of hydrogen; whilst in carbo-hydrate there are 44 of carbon. According •'to Ranke, fat contains 79 per cent, of carbon, and carbo-hydrate, i.e., starch, 37 of carbon. The folloAving table shows the quantity of carbon, nitrogen, &c, in each ounce of the various dried food-stuffs :—• One ounce (dried). Nitrogen. Carbon. Hydrogen. Sulphur. Proteids, .... Fat..... 70 grains. 212 grains. 336 „ 8 grains. 48 ,, 6 grains. Carbo-hydrates:— 1. Starch, 194 „ 2. Cane-sugar, 3. Grape-sugar, 4. Milk-sugar, 184 „ 175 „ 175 „ The total carbon in an ounce of proteid is 233 grains, but of this 30 grains are only metabolised as far as urea, and oxidised as carbon monoxide; making allowance for this, we have a nett total equal to 212 grains of carbon fully oxidised from each ounce of dry proteid. Assuming these compositions in terms of nitrogen and carbon of the various food-stuffs, and accepting that the daily need of an average adult, weighing 150 lb or 68 kilogrammes, to keep in health is equal to 307 grains (20 grammes) of nitrogen and 4700 grains (305 grammes) of carbon, certain standard diets have been compiled. The folloAving proposed by Moleschott may be accepted as the most representative, though, perhaps, the fat is stated rather too low. 266 < food. For 300 foot-tons, or 93,000 kilogram-metres. For 323 foot-tons, or 100,000 kilogram-metres. For 480 foot-tons, or 150,000 kilogram-meties. Oz. av. Gram. X. grs. C. grs. Oz. av. 4-94 3-17 1531 1-13 Gram. N. grs. C grs. Oz. av. Gram. N. grs. 420 C grs. 1272 1411 3230 Proteids, . Fats, Carbo-hydrates, Salts, Total water-free food, 4-59 2-96 14-26 1-06 130 84 404 30 321 973 994 2710 140 90 434 32 346 1047 1065 2909 6*00 4-00 17*00 1*50 170 113 481 42 22-87 648 321 4677 24'55 696 346 5021 28*50 806 420 5946 As standard diets for bare subsistence and for rest, the following may be taken:— Subsistence. Rest. Ounces avoir. Grammes. N. grains. C grains. Ounces avoir. Grammes. N. grains. C grains. Proteids, . Fats, Carbo-hydrates, Salts, Total water-free food, 2-0 0-5 12-0 0-5 57 14 340 14 140 424 168 2280 2-5 1-0 12 0 0*5 71 28 340 14 175 530 336 2280 15-0 425 140 2872 16-0 453 175 3146 The subsistence diet is calculated as sufficient for the internal mechanical work of the body, but it is doubtful if an average man could exist on it without losing Aveight, as it supposes absolute repose. The diet for rest supposes very gentle exertion, and is probably the minimum f0r a male adult of average size and weight, say 150 3b or 68 kilo- grammes. Each constituent named above is, theoretically, absolutely water-free, but practically the amount of water present in the so-called solid food Avould be from 100 to 150 per cent, more, so that the weights respectively would be, about 32 to 40 ounces gross (907 to 1134 grammes). For mere subsistence, without doing visible work, a man therefore requires about -^ of an ounce of water-free food for each lb weight of his body, or about y^ of his total weight every twenty-four hours. Assuming the water-free food to be 23 ounces, and a man's weight to be 150 lb, each lb weight of the body receives in twenty-four hours 0*15 ounce, or the whole body receives nearly y^- part of its own weight. Expressed in another way, for every kilogramme of body weight there should be 2 grammes of proteid, 1*5 gramme of fat, 6 grammes of carbo- hydrate, and 0*5 gramme of salts—in all about 10 grammes or 1 per cent. of sohd food. This is the dry food, but a certain amount of water (between 50 and 60 per cent, usually) is contained in ordinary food, and adding this to the water-free solids, the total dady amount of so-called dry food (exclusive of liquids) is about 48 to 60 ounces. In addition to this, from 50 to 80 ounces of water are taken in some liquid form, making a total supply of Avater of STAXDAED DIETS. 2G7 70 to 90 ounces, or an average of 0*5 ounce for each pound weight of body. The proportion of the nitrogenous substances to the fats, carbo-hydrates, and salts in the standard diets is practically as follows :—Proteids 100, fats 65, carbo-hydrates 315, and salts 23. In all diets, a certain proportion between the carbon and nitrogen ought to be maintained; in the best diets this is, nitrogen 1 to carbon 15. This average amount of food and water varies considerably from the following causes:— 1. Individual conditions of size, vigour, activity of circulation, and of the eliminating organs, &c. No men eat exactly the same, and no single standard will meet all cases. The usual average range in different male adults is from 40 to 60 ounces of so-called solid food, and from 50 to 80 ounces of Avater. The foUowing table, after Kbnig, shows the minimum daily need of food- stuffs at different ages :— Age or Condition. Proteids. Fats. Carbo-hydrates. Ounces. Grammes. Ounces. Grammes. Ounces. Grammes. Child up to H year, . Child from 6 to 15 years, Adult man, Adult woman, . Old man, . Old woman, 0-7-1-26 2-45-2-8 4-1 3-2 3 5 2*8 20-36 70-80 118 92 100 80 1-1-6 1-3-1-75 1-96 1-54 2-38 1-75 30-45 37-50 56 44 68 50 2*1-3-1 8-75-14 17-5 14-0 ■ 12-25 9-1 60-90 250-400 500 400 350 260 2. Differences of exertion. If men are undergoing great exertion they take more food, and, if they can obtain it, the increase is especially in the classes of proteids and fat. This would represent of so-caUed solid food from 66 to 77 ounces (1870- to 2180 grammes). The amount of water is also increased, but is very various according to- circumstances, and is apparently not so much augmented as the solid food. 3. Differences of climate. It is a matter of general belief that more food is taken in cold seasons and in cold countries than in hot. It is supposed that more energy in some form (finally in that of heat) is necessary, and more food is required; but there may be other causes, such as varying exertion. Having, therefore, an established series of dietetic standards and a knowledge of the chief points to which attention must be directed in regard to food, it is important to be able to examine any given diet in the light of these facts, and be able as well to construct a dietary. To do this, however, it is necessary to have some knoAvledge of the mean composition of the various articles of diet. The following table, constructed from various sources, shows the percentage composition of the more ordinary articles of food :— 268 FOOD. Articles of Food. Beef, lean, ,, medium, ,, very fat, Veal, lean, „ fat, . Mutton, medium, ,, very fat, Pork, lean, „ fat, Bacon, dried, . Ham, smoked, . Meat powder, dried, Horseflesh, Herring, . Pike, Carp, Salt cod, . Canned meat (American) Corned beef (Chicago), Pemmican, Poultry, . Ham sausage, Beef sausage, Eggs, hen's, Milk, cow's, „ goat's, ,, condensed, English, ,, ,, Swiss, sweetened, ,, ,, ,, unsweetened, Cream, Butter, fresh, . ,, salt, Margarin, Cheese, Dutch, . „ single Gloster, ,, poor quality, Eels, Goose, Bread, average wheaten, Biscuits, . Flour, wheat of average quality, Barley meal, Oat meal, . Maize, Macaroni,. Arrowroot, Potatoes, . Peas, Rice, Turnips, . Parsnips, . Carrots, . Cabbage, . Soja beans, Cocoa powder (Dutch), Chocolate (French), . In 100 parts. Proteids. Fats. Carbo-hydrates. Salts. Xitrogen. 3-2 20*0 3-5 1-6 20*5 8-4 1-6 3-28 16*75 19-0 3-5 2-68 18*88 4-41 0*5 3-02 19*20 7*20 1*33 3-07 17-11 5*77 1-33 2 73 16-62 25 61 1-10 2*65 20-25 6-81 1-10 3 24 14-54 37-34 0-80 2*32 8-80 73-30 2-90 1-40 24-00 36-50 10-10 3*84 69*50 5*84 6*42 13 25 11-12 21*71 2-60 1-10 347 14 55 9*00 1-78 2-32 18-42 0*53 1-00 2-94 21-86 1-00 1*33 3 49 27-00 0-36 22-00 4-32 29-00 11-50 3*60 4-64 23-30 14 00 4*00 3-72 35-40 55*20 1*8 5-60 21-00 3-80 1-2 3-36 12-87 2443 10-52 3*3 2-05 27-31 19*88 15*10 5*5 4-36 13-50 11-60 10 216 4-20 3*70 4*50 0-7 0-67 4-29 4-70 4*60 076 0-68 12-00 8-40 50-80 2-00 1-92 12*30 11-00 48*70 2-40 1-96 11-35 11-25 13*35 2-00 1-81 2-70 26*70 2-80 1*80 0 43 2-00 85*00 80*00 1-00 3-00 0 32 075 82*00 5-22 012 28*00 23-00 i bo 7-00 4-48 31-00 28-50 4-50 4-96 32-00 9-00 f-bo 4-00 5-12 12-50 28 50 1-50 2-00 16 00 45-50 0-50 2-56 8*00 1-50 49 20 1-30 1-28 10-60 1-30 73*40 1*70 1-70 n-oo 2-00 71*20 0-80 1-76 12-70 2-00 71*00 3-00 2*03 1260 5-60 63*00 3-00 2-01 10-00 6*70 64*50 1-40 1-60 9-00 0-30 76*80 0-80 1-44 0-80 83-50 0-30 0-12 2-00 6'l6 21-00 1-00 0-32 22-00 2*00 53 00 2-40 3-52 5-00 0-80 83*20 0-50 0-80 1-00 0-20 6-80 1*00 0-16 1-30 0-70 14-50 1-00 0-20 1-00 0-20 10-00 1-00 0 16 5*00 0-50 7-80 1-20 0-80 33-40 17*70 29-10 4*10 5-34 19*66 13*61 12*60 360 313 6*18 20*00 54-00 2*20 0-98 CALCULATION OF DIETS. 269 Calculation of Diets.—Of course the above figures are largely approxi- mate, but are sufficiently accurate for the calculation of any dietary, the mode of doing which is very simple. The quantity of uncooked meat or bread being known, and it being assumed or proved that there is no loss in cooking, a rule of three brings out at once the proportions. Thus, the ration allowance of meat for soldiers being 12 ounces, 2*4 ounces, or 20 per cent., is deducted for bone, as the soldier does not get the best parts. The quantity of proteid 20*5 x 9*6 in the remaining 9*6 ounces will be---^^— = 1*96, the fats will be 0*8064, and the salts 0*1536 ounce. So again, in the case of eggs, if two eggs be used, each weighing 2 ounces, 10 per cent, must be deducted for shell from the weight of egg. This gives 3*6 ounces as the nett weight of egg available, and taking the composition of eggs to be as given in the table, we get, proteids 0*48 ounce, fats 0*41 ounce, and 0*036 ounce of salts from the two eggs. Whenever practicable, the nutritive value should be calculated on the raw substance, as the analyses of cooked food are more variable. Allowance must then be made for any loss which occurs in cooking: this should not be great, but very often in ordinary domestic cooking this may amount ta as much as 30 or 40 per cent. In a converse way, supposing a diet is required to yield 5 ounces of proteid,. 3 ounces of fat, 15 ounces of carbo-hydrate, and 1 ounce of salt, we can calculate how much bread, salt butter, and Dutch cheese would be needed to supply it:— The percentage composition of these may be taken to be :— Proteids. Fats. Carbo-hydrates. Salts. Bread, . 8 1 50 1-5 Salt butter, . . 80 3 0 Dutch cheese, 28 23 1 7*0 Calling the bread a, the butter b, and the cheese c, we get the following equations :— 8a + 28c (1) 100 =5 (proteid). la+ 805 +23c (2)----jqq----= 3 (fats). 50a + lc (3) 10f) =15 (carbo-hydrates). Simplifying these equations, we get the following :— (l)8a + 28c =500. (2) la + 80S + 23c = 300. (3)50a + lc =1500. These can be further resolved thus :— (3) 50a+ lc = 1500 x 28 = 1400a + 28c = 42,000 ,^ o oo c«a 8a + 28c= 500 (1) 8a + 28c= 500 -^------^-^ a = 29'8 ounces. If a=29'8, then equation 3 becomes— lc = 1500-1490. c=10 ounces. If a = 29*8, and c = 10, then equation 2 becomes— 805 = 300-20*8-230. 805 = 40-2. 5 = 0*5 ounce. The answer being a, that is the bread, =29*8, or say 30 ounces. 5, ,, ,, butter, = 0-5, or half an ounce. c, ,, ,, cheese, = 10*0 ounces. 270 FOOD. To find the salts, we say— 29 "o XI a no- Since the bread contains 15 per cent. .'. —Jqq—=0 ^' ounce. 0-5x3 rvrnK .. butter „ 3 „ •*• ,nrr =° 015 » ^ 0-700 100 10x7 ,, cheese ,, 7 ,, •'• 100 The total salts are . • • 1*162 ,, That is from 30 ounces of bread, 10 ounces of Dutch cheese, and \ ounce of salt butter we can obtain 5 ounces of proteid, 3 ounces of fat, 15 ounces of carbo-hydrates, and 1 ounce of salts. Although such a diet fulfils theoretical requirements, practical experience would soon show that it was insufficiently varied. It is the great diversity which exists as regards the food consumed by the human race in all parts of the world that is the most remarkable feature in the study of dietaries Some people live upon a wholly vegetable, others on a wholly animal and others on a mixed diet. It has already been explained how unsuited any sinode vegetable food, such as bread, or any single animal food, such as melt, is to supply the daily requirements of the body, and how a judicious mingling of the various food-stuffs affords the greatest nourishment in the least bulk The mixed diet may be regarded as that which in Nature s plan is designed for man's sustenance. On this he appears to attain the highest intellectual and physical vigour, and it is this diet which he con- sumes by general inclination when circumstances allow the inclination to , and will range from this to 1200 ft). The French rules fix the minimum at 250 kilogrammes (= 550 ft>). The mean weight in France is 350 kilogrammes (= 770 ft)). A cow may weigh a few pounds less; a good fat cow will weigh from 700 to 740 lb. A heifer should weigh 350 to 400 lb. The French rules fix the minimum of the cow's weight at 160 kilogrammes ( = 352 ft>). The mean weight of cows in France is 230 kilogrammes ( = 506 ft)). There are several methods of determining the weight; the one most commonly used in this country is to measure the length of the trunk from just in front of the scapulae to the root of the tail, and the girth or circum- ference just behind the scapulae; then, by multiplying the square of the girth by 0*08 and the product by the length, the dimensions in cubic feet are obtained; each cubic foot is supposed to weigh 42 ft) avoirdupois. The formula is (C2 x 0*08) x L x 42 ; or |(C2 x 5L) ; the result in either case gives the weight in pounds avoirdupois. The animal is divided into carcass and offal; the former includes the whole of the skeleton (except the head and feet), with the muscles, membranes, vessels, and fat, and the kidneys and fat surrounding them. The offal includes the head, feet, skin, and all internal organs except the kidneys. An ox or cow gives about 60 per cent, of meat, exclusive of the head, feet, liver, lungs, and spleen, &c. The skin is Jg of the weight; the tallow Tx¥. In very fat cattle the weight may be 5 per cent, more, and in very lean cattle 5 per cent, less than the actual weights found by this rule. A full-grown sheep will weigh from 60 to 90 ft), but the difference in different breeds is very great. It also yields about 60 per cent, of avadable food. The average weight of a sheep in India is from 30 to 40 ft). A full-grown pig weighs from 100 to 180 ft) or more, and yields about 75 to 80 per cent, of available food. Age.—The age of the ox should be from three to eight years, and a heifer or cow not under two or more than four years old; the age is told chiefly by the teeth, and less perfectly by the horns. The temporary teeth are in part through at birth, and all the incisors are through in twenty days ; the first, second, and third pairs of temporary molars are through in thirty days; the teeth are grown large enough to touch each other by the sixth month ; they gradually wear and fall in eighteen months; the fourth permanent molars are through at the fourth month; the fifth at the fifteenth; the sixth at two years. The temporary teeth begin to fall at twenty-one months, and are entirely replaced by the thirty-ninth to the forty-fifth month; the order being—central pair of incisors gone at twenty-one months; second pair of incisors at twenty-seven months; first and second temporary molars at thirty months; third temporary molars at thirty months to three years; thh-d and fourth temporary incisors at thirty-three months to three years. The development is quite complete at from five to six years. At that time the border of the incisors has been worn away a little DISEASES OF ANIMALS USED FOR FOOD. 283 below the level of the grinders. At six years the first grinders are begin- ning to wear, and are on a level with the incisors. At eight years the wear of the first grinders is very apparent. At ten or eleven years the used surfaces of the teeth begin to bear a square mark surrounded, with a white line ; and this is pronounced on all the teeth by the twelfth year; between the twelfth and fourteenth year this mark takes a round form. The rings on the horns are less useful as guides. At ten or twelve months the first ring appears; at twenty months to two years, the second; at thirty to thirty-six months, the third ring; at forty to forty-six months, the fourth ring; at fifty-four to sixty months, the fifth ring, and so on. But at the fifth year the first three rings are indistinguishable, and at the eighth year all the rings. Besides, the dealers file the horns. In the sheep, the temporary teeth begin to appear in the first week, and fill the mouth at three months; they are gradually worn and fall at about fifteen or eighteen months. The fourth permanent grinders appear at three months, and the fifth pair at twenty to twenty-seven months. A common rule is "two broad teeth every year." The wear of the teeth begins to be marked at about six years. Sheep fit for slaughter should always have a clean even set of teeth. In the army, those with broken teeth are rejected. The age of the pig is known up to three years by the teeth; after that there is no certainty. The temporary teeth are complete in three or four months; about the sixth month the premolars, between the tusks and the first pair of molars, appear; in six or ten months the tusks and posterior incisors are replaced; in twelve months to two years the other incisors; the four permanent molars appear at six months; the fifth pair at ten months; and the sixth and last molars at eighteen months. Condition and Health.—The condition of live cattle is generally told by the handling points, of which as many as twelve are given, but only five need be mentioned, as an animal which is good in these five points is sure to be good in the rest. They are the natches, or the bones by the side of the tail, the twist, the flank, the cod or udder, and the rib. The flesh on all these handling points should feel compact and firm, the twist or parts between the two buttocks should stand prominently out, the flank should be the full of the hand and should appear to meet your hand and drop into it as you handle the animal, the rib should be well covered with compact flesh, and the cod or udder should be a large lump of firm fat. In half-fed animals the flesh will not be so firm to the touch as in fully fed ones; the meat of such half-fed cattle wastes very considerably in the cooking, owing to the cells of the adipose tissue being filled with imperfectly formed fat. To be able to tell the condition of a beast by handling requires some practice. As showing health, we should look to the general ease of movements, the quick bright eye; the nasal mucous membrane red, moist, and healthy- looking ; the tongue not hanging; the respiration regular, easy; the ex- pired air without odour; the circulation tranquil; the excreta natural in appearance. When sick, the coat is rough or standing; the nostrils dry or covered with foam; the eyes heavy; the tongue protruded; the respiration diffi- cult ; movements slow and difficult; there may be diarrhoea; or scanty or bloody urine, &c. In the cow the teats are hot. Diseases of Animals used for Food.—The diseases of cattle which the inspecting officer should watch for are— 1. Pleuro-pneumonia.—The commencement of the attack is very in- sidious : it is not easily recognised at first. The temperature 284 FOOD. soon rises to 104° or 105° F. and the animal refuses food; a short dry cough develops and the breathing becomes laboured and painful. 2. Foot-and-Mouth Disease (murrain, aphtha, or eczema epizootica).— At once recognised by the examination of the mouth, feet, and teats. 3. Cattle Plague (typhus contagiosus, Steppe disease, Rinderpest).— Recognised by the early prostration (hanging of head, drooping of ears), shivering, running from eyes, nose, and mouth, peculiar con- dition of tongue and lips, cessation of rumination, and then by abdominal pain, scouring, &c. 4. Anthrax,.—This either appears as a general, or as a localised affec- tion : in the former case it is called apoplectic anthrax, splenic fever, or anthrax fever: in the latter, anthracoid erysipelas or carbuncular fever. If boils and carbuncles form, they are at once recognised : if there is erysipelas, it is called black quarter, quarter ill, or blackleg (erysipelas carbunculosum), and is easily seen. The peculiar organism, Bacillus anthracis, may be detected in the blood. 5. Tuberculosis (perlsucht, "grapes").—Sometimes acute, more often chronic: at first dulness and indifference, increased sensibility, especially of back-muscles and chest-walls, but no emaciation and no diminution of production of milk; later, emaciation comes on, loss of appetite, shortness of breath, and cough; these symptoms become intensified, with hectic. 6. Actinomycosis.—Caused by " ray-fungus"; attacks by preference the lower jaw and tongue, also the lungs and bones; leads to general malnutrition, and is sometimes fatal. 7. Dropsical affections from kidney or heart disease. 8. Indigestion, often combined with apoplectic symptoms. A great number of other diseases attack cattle, which it is not necessary to enumerate. All the above are tolerably easily recognised. The presence of Tamia mediocanellata cannot, it would seem, be detected before death. The diseases of sheep are similar to those of cattle; they suffer also in certain cases from splenic apoplexy or "braxy," which is considered by Professor Gamgee to be a kind of anthrax, and is said to kill 50 per cent. of all young sheep that die in Scotland; the animals have a "peculiar look, staggering gait, bloodshot eyes, rapid breathing, full and frequent pulse, scanty secretions, and great heat of the body." The disease is induced by errors in feeding. The small-pox in sheep (Variola ovina, clavelee of the French) is easily known by the high fever, especially during the pustular stage, by the flea- bitten appearance of the skin in the early stage, and by the rapid, appearance of nodules or papulae and vesicles. The sheep is also subject to black quarter (Erysipelas carbunculosum); one limb is affected, and the limp of the animal, the fever, and the rapid swelling of the limb are sufficient diagnostic marks. The sheep, of course, may suffer from acute lung affection, scouring, red water (haematuria), and many other diseases. Of the chronic lung affections, one of the most important is the so-called " phthisis," which is produced by the ova of Strongylus filaria. This entozoon has not yet been found in the muscles, and the meat is said to be good. The rot in sheep (fluke disease) is caused by the presence of Distomum hepaticum in large numbers INSPECTION OF MEAT. 285 in the liver, and sometimes by other parasites. The principal symptoms are dulness, sluggishness, followed by rapid wasting and pallor of the mucous membrane, diarrhoea, yellowness of the eyes, falhng of the hair and dropsical swellings. The animal is supposed to take in Cercaria (the embryotic stage of distoma) from the herbage. The so-called "gid," " sturdy," or " turnsick," is caused by the development of Ccenurus cere- bralis in the brain. The pig is also attacked by anthrax in different forms, by muco-enteritis, and by hog cholera. The swelling in the first case, and the severe fever* accompanied with foetid diarrhoea and prostration in the second, are suffi- cient diagnostic marks. It has no relation whatever to enteric fever in man (Walley). The condition of the flesh is similar to that produced by septic disease, and it is totally unfit for human food. Cobbold pointed out that the pig is affected, both in America and Australia, with a large parasite (Stephanurus dentatus). This worm is found chiefly though not solely in the fat, and is at first free and then encysted; the cyst is large, and may be If inch in length and i inch in diameter. The full grown worm may be as much as 1J inch in length. Three to six eggs are found in the cyst, and the young worms migrate. During their migration, it has been surmised that they cause the "hog cholera." The so-called measle of the pig is caused by the presence in the muscular connective tissue of Cysticercus cellulosce. During life there are few indica- tions of the existence of this worm in the animal: the only positive sign to be obtained is in the mouth, where it may be detected on the inferior and lateral aspect of either side of the tongue, or between this and the lower jaw. The body of the animal has a bloated appearance, and a soft flabby feel; and on firm pressure a crackling sensation may be imparted to the fingers. Trichina spiralis has its habitat also in swine: it is not confined to the muscle alone, but has been demonstrated in the fat of the body of the pig in large numbers. Animals fed on such fat did not, as a rule, become trichinised. Its presence is indetectable before death, unless found in the muscles under the tongue. Inspection of Meat.—Meat should be inspected, in temperate climates, twenty-four hours after being kdled; in the tropics, earlier. The following points must be attended to :— (a) Quantity of Bone.—In lean animals the bone is relatively in too great proportion; taking the whole meat, 17 to 20 per cent, may be allowed. (b) Quantity and Character of the Fat.—The amount of fat varies with the feeding of the animals. In a fat ox it constitutes about one-third of the flesh, in a fattened pig one-half. In beef surplus fat is the excessive fat at the kidneys, pelvic cavity, cod fat, and udder. In mutton that on the back and in the region of the kidneys. In thin or badly fed animals the fat may be as low as 1 per cent, of the meat. The fat usually solidifies after death, and in beef consists chiefly of palmitates, in bacon oleates, in mutton stearates, these respective kinds of fats being soft and fusible in the order named. The colour varies from white to straw colour and yellow, being whiter in young bulls than in bullocks and cows. The kind of feeding has an effect on the colour of the fat; some oil-cakes give a marked yellow colour. The fat of the horse is always of a yellow colour, and softer; it has a rather unpleasant sickly taste. Gamgee stated that pigs fed on flesh have a peculiarly soft diffluent fat, and emit a strong odour from their bodies. According to the same authority, 286 FOOD. the butchers rub melted fat over the carcass of thin and diseased animals to give the glossy look of health. (c) Condition of the Flesh.—The muscles should be firm, and yet elastic; not tough; the pale moist muscle marks the young animal, the dark- coloured the old one; the muscular fasciculi are larger and coarser in bulls than oxen. A deep purple tint is said to indicate that the animal has not been slaughtered, but has died with the blood in it (Letheby). When good meat is placed on a white plate, a little reddish juice frequently flows out after some hours. It should be tolerably dry after being exposed for a short time to the atmosphere : it should possess a pleasant sweet flavour, and when heated should give a savoury odour. Good meat has a marbled appearance from the ramifications of little veins of fat among the muscles •(Letheby). There should be no lividity on cutting across some of the muscles; the interior of the muscle should be of the same character, or a little paler; there should be no softening, mucilaginous-like fluid, or pus, in the intermuscular cellular tissue. This is an important point, which should be closely looked to. The intermuscular tissue becomes soft, and tears easily when stretched in commencing putrefaction. The degree of freshness of meat in commencing putrefaction is judged of by the colour, which becomes paler; by the odour, which becomes at an •early stage different from the not unpleasant odour of fresh meat, and by the consistence. Afterwards the signs are marked, the odour is disagree- able, and the colour begins to turn greenish. In diseased meat there is a disagreeable odour, sometimes a smell of physic; very evident when the meat is chopped up and drenched with warm water. It is a good plan to push a clean knife into the flesh up to its hilt. In good meat the resistance is uniform; in putrefying meat some parts are softer than others. The smell of the knife is also a good test. Cysticerci and Trichince should be looked for. (d) Condition of tlie Marrow.—In temperate climates the marrow of the hind legs is solid twenty-four hours after killing; it is of a light rosy red. If it is soft, brownish, or with black points, the animal has been sick, or putrefaction is commencing. The marrow of the fore legs is more diffluent; something hke honey—of a light rosy red colour. Age.—In the young animal the bones are small, soft, porous, and of a pinkish colour, but as the animal grows older the bones become large, harder, less porous and whiter in colour. The inside part of the ribs is very pink in young animals, but as age increases the pinkness fades away and the ribs at about six or seven years old become quite white. The tops of the spinous processes forming the chine are in the young animal com- posed of gristle, but ossify about the age of six years. The pubes or aitch- bone is only joined by gristle in the young animal, but this ossifies also about the age of six years. Before this gristle has ossified, the butcher divides it with his knife in dressing the animal and the blue cartilage is plainly seen in the side or quarter afterwards, but after it has ossified the saw has to be resorted to. In an old cow which has had several calves, the aitch-bone is very thin and very hard and the pelvic cavity is large. If the head is left attached to the carcass the age can be told with great certainty by the teeth. Bovines. 2 years old,.....2 permanent teeth. 3 ,,,,..... 4 ,, ,, 4 ,, ,,.....6 ,, ,, 5 ,,,,..... o ,, ,, DISTINCTIONS OF SEX. 287 After six, the teeth get worn down gradually, the centre incisors first, then the ones next to them, and so on. Sheep. . 2 permanent teeth. • 4 • 6 • • 8 „ And after this the teeth become worn down, as in the case of bovines. Distinctions of Sex.—In the hind quarter of ox beef is situated at the root of the pizzle, the erector muscle, which is about 3 inches in length by l1 inch in breadth. In the bull this muscle is much more fully developed than in the ox ; and in the bull this muscle is much wider, darker in colour, and coarser in grain. The pizzle in the ox is small and undeveloped, not thicker than the finger, but in the bull it is largely developed; it is often split and partly removed in order to make it appear of the same size as that of the ox, or entirely removed, and the retractor muscle left in. There is more cod fat in ox than in bud beef, and in the bull the cavity is generally seen from which the testicle has been removed. In bull meat generaUy, owing to the superior muscular development of that animal, the proportion of muscular tissue or lean meat is much greater than it is in the ox. In the bull the fat is not " marbled " through the lean as is the case with well-fed oxen. This gives the whole quarter of hull a darker and redder appearance than that of the ox. The lean of the young ox is juicy, smooth, and silky to the touch, florid in colour and marbled with fat; but in the bull it is coarse and stringy in texture, harsh to the touch and the marbling absent. The bony structure, and especially the aitch-bone, is very much more massive in the bull than in the ox. The chief distinguishing features of a fore quarter of an ox from that of a bull is the collar or crest, which in the bull is very large and muscular, requiring at least the whole hand to grasp it, but in the ox is very much smaller, and can be grasped between the forefinger and thumb. In the ox there is a plentiful coating of fat on the exterior coming right to the point of the shoulder, but in the bull the exterior coating of fat is almost entirely absent, the lean being directly covered by the outer skin. In the hull the brisket is coarser, harder, and darker than in the ox. The quarters of bull stags present very much the same characteristics as those of bulls, but in a somewhat less degree. A bull stag is an animal which has been castrated too late in life, or has had one testicle or a part of one left in. A cow which has had no calf is called a heifer, but the term heifer by itself is often apphed to a young cow that has not had more than one calf. The.principal means of distinguishing cow from heifer beef is the udder. In the heifer the udder is but slightly developed; it is in fact enveloped in fatty tissue, and forms a uniform thick wall on either side of the flank. When a cow has had one calf, the surface of the udder will be slightly soft, hut the main portion will still consist of solid fat, and the small ducts through which the milk has come will be just visible. After the second calf the udder will be composed partly of a tough, hrown, spongy substance and partly of fine fat, and the ducts through which the milk has come will be very much larger. As the number of calves the cow has had increases, the udder becomes looser, browner, and more spongy in appearance. To make the hind quarter of a cow resemble 1 year old, 3 ., „ 4 „ ., 288 FOOD. that of a heifer, the udder is cut out while the carcass is warm and the skin cleverly fixed over the excised part. It is very difficult to tell the fore quarter of a heifer from that of an ox. In the fore quarter of a cow the chief indications that the animal is old are the bleached ribs, want of fat on the ribs, a very prominent scapula or shoulder-bone, with a hollowness or falling away on either side of it. The flesh of the heifer is generally silky and juicy to the touch. In the old cow it is generally coarse, dry, and stringy. There is a want of marbling of fat and the fat streaks are poor or absent altogether. The differences of sex in sheep can be told in much the same way as in cattle. The ram in relation to the wether presents very much the same appearances as the bull does in relation to the ox. The ram has a thick neck, a generally muscular and massive appearance, and a pizzle twice as thick as an ordinary lead pencil. The wether has a thin neck and a pizzle about the size of a lead pencil. In old ewes the surface of the kidney fat and also the back will be much veined; the knuckle cartilages, instead of showing the pinkish blue colour of young animals, will be quite bleached, and the udder large and spongy, the holes through which the milk has come being visible. Horse Flesh.—This can be detected by the horse having eighteen pairs of ribs, while the ox has only thirteen pairs; the tongue of the horse is smooth at tip and base of blade, and the ox's tongue is rough; the colour of the flesh of the horse is much darker and coarser in fibre than that of the ox; and the bones are heavier than the ox; the whole of the fat of the horse is oily, yellow, has a disagreeable flavour, and is separated from the lean. The odour of the meat is different from that of beef. Goat Flesh.—The flesh of an old goat is dark, harsh, and strong, with a peculiar goaty smell; the shanks of the fore and hind legs are very thin, ribs white, outer coating of carcass deep red, neck very thin in nanny-goat and very thick in the he-goat. Sausages.—Decomposing sausages are difficult of detection until the smell alters. Artmann recommends mixing the sausage with a good deal of water, boiling and adding freshly-prepared lime water. Good sausages give only a faint, not unpleasant, ammoniacal smell; bad sausages give a very offensive, peculiar ammoniacal odour. Refrigerated Meat.—This is largely imported from North America. The meat is wrapped in thin canvas, and hung up in specially constructed chambers in ships, through which a current of cold air is continually passing The air is pumped into the chamber at such a temperature as to keep the* carcasses a few degrees above freezing point, but never to allow them actually to freeze. It is, generally speaking, excellent meat, the produce of very good, well-fed cattle. Refrigerated meat can be distinguished by— 1. The bruised condition of the shanks, owing to the chain which is passed round the hind legs during the process of slaughtering. 2. The fat of the meat is pink, owing to its being stained by the juice of the lean meat which escapes. 3. The outside of the meat wdl present a dead colour, when compared with the lustre seen on the outside of good fresh meat. 4. The dressing is not always so clean and neat as in English dressed meat, and the pizzle and root are always entirely removed. On removing the canvas cloth a slightly unpleasant smell is sometimes perceptible, but care should be taken not to reject the meat without further examination, as the smell may only be a surface smell caused by the cloth. Plate I. V/ctANewmanchr lit i^iy. 7, Hmd quxxrter of Cow or Heifer. ' „ 2, Hvndrqiuzrter o f BvdL „ 3, HurtcLq vuirter of Ox MICROSCOPIC EXAMINATION OF MEAT. 289 When this is removed the fore and hind quarters should invariably be cut through in the ordinary manner, when, if any taint exists, it will be easily detected. Frozen Meat.—This is imported largely from Australia and South America. It can easily be distinguished, before it is thawed, by its cold, hard touch. The fat is not stained, as in the case of refrigerated meat. When frozen meat has been thawed, the outside will have a wet, parboiled appearance, and there will be oozing and dripping of liquid from the meat. The fat is of a deadly white colour. The flesh has a uniform pink appear- ance owing to diffusion of the colouring matter of the blood, and on a fresh section being made, the watery condition will be very apparent: this loss of juice must be, more or less, deteriorating to its quality. Frozen mutton comes generally from Australia and New Zealand ; being naturally drier than beef, it suffers but little deterioration in the freezing process. Salt Meat.—It is not at all easy to judge salt meat, and the test of cook- ing must often be employed. The following points should be attended to :— \a) The salting has been well done, but the parts inferior.—-This is at once detected by taking out a good number of pieces; those at the bottom of the cask should be looked at, as well as those at the top. (b) The salting well done, and the parts good, but the meat old—Here the extreme hardness and toughness, and shrivelling of the meat, must guide us. It would be desirable to have the year of salting placed on the cask of salt beef or pork. (c) The salting icell done, but the meat bad.—li the meat has partially putrefied, no salting wdl entirely remove its softness; and even there may be putrefactive odour, or greenish colour. A slight amount of decom- position is arrested by the salt, and is probably indetectable. Cysticerci are not killed by salting, and can be detected. Measly pigs are said to salt badly, but according to Gamgee this is not the case. (d) The salting badly done, either from haste or bad brine.—In. both cases signs of putrefaction can be detected ; the meat is paler than it should be ; often slightly greenish in colour, and with a peculiar odour. It should be remembered that brine is sometimes poisonous ; this occurs in cases where the brine has been used several times ; a large quantity of animal substance passes into it, and appears to decompose. The special poisonous agent has not been isolated, but is probably a ptomaine. Microscopic Examination of Meat.—In the flesh of cattle, or of the pig, Cysticerci may be found. Cysticercus cellulosai of the pig gives the meat a pale flabby appearance, making it soft and apparently dropsical. The cysts are generally located in very large numbers in the liver, giving that organ on section a mottled appearance. They are generally visible to the naked eye as smaU round bodies; when placed under a microscope with low power, their real nature is seen; they are sometimes so numerous as to cause the flesh to crackle on section. The smallest Cysticercus noticed by Leuckart in the pig was about -jfoths of an inch long and T|h)ths hroad ; but they are generally much larger, and will often measure to T2ffths or T3^ths or |ths of an inch. In some countries they are extremely common in cattle (Cysticercus bovis), and have been a source of considerable trouble in North-West India. The muscles of the haunch are those most frequently affected. Cyshcerctis of the ox produces in man Taenia mediocanellata. In sheep Cobbold described a small Cysticercus with a double crown of hooks, 26 in number. He thought that possibly a special Tcenia might arise from this. Oldham de- scribes Cysticercus tenuicollis (from Tcenia marginata of dogs) as common in 290 FOOD. the sheep of the Punjaub; it has four suckers and a double coronet of 32 hooks. In diagnosing Cysticerci of pork the hooklets should always be seen. Trichince may be present in the flesh of the pig ; if encapsuled they will be seen with the naked eye as small round specks; but very often a microscope is necessary. A power of 25 to 50 diameters is sufficient. The best plan is to take a thin slice of flesh; put it into liquor potassze (1 part to 8 of water), and let it stand for a few minutes till the muscle becomes clear ; it must not be left too long, otherwise the Trichince will be destroyed. The white specks come out clearly, and the worm will be seen coiled up. If the capsule is too dense to allow the worm to be seen, a drop or two of weak acetic acid should be added. If the meat is very fat, a little ether or benzine may be put on it in the first place. The parts most likely to be infected are said to be the muscular part of the diaphragm, the intercostal muscles, and the muscles of the eye and jaw. In diagnosing Trichince, the coded worm should be distinctly seen. Stephanurus dentatus in the pig has already been referred to. The so-called Psorospermia, or Rainey's capsules, must not be mistaken for Trichina;, nor indeed with care is error possible. These are small, almost transparent, bodies, found in the flesh of oxen, sheep, and pigs. They are in shape oval, spindle-shaped, or sometimes one end is pointed and the other rounded, or they are kidney-shaped. The investing membrane exhibits delicate markings, caused by a linear arrangement of minute, hair-like fibres, which are stated to increase in size as the animal gets older. They sometimes are pointed, and the appearance under a high power (1000 diameters) is as if the investment consisted of very delicate, transparent, conical hairs, terminating in a pointed process. The contents of the cysts con- sist of granular matter, the granules or particles of which, when mature, are oval, and adhere together, so as to form indistinct divisions of the entire mass. The length varies from ^th to |th of an inch. They are usually narrow; they lie within the sarcolemma, and appear often not to irritate the muscle. Up to the present time no injurious effect has been known to be produced on men by these bodies, notwithstanding their enormous quantities in the flesh of domestic animals, nor have they been discovered in the muscles of men. But in pigs these bodies sometimes produce decided illness ; besides general signs of illness, there are two invariable symptoms, viz., paralysis of the hind legs, and a spotty or nodular eruption. In sheep, they have been known to affect the muscle of the gullet, and produce abscesses, or what may be called so, viz., swellings sometimes as large as a nut, and containing a milky, purulentdooking fluid, with myriads of these capsules in it. Sheep affected in this way often die suddenly. It is by no means improbable that some effect on man may be hereafter discovered to be produced. Some bodies, which have been also termed Psorospermia, found in the liver and other parts of the rabbit, and in the liver of man, and which have been described by many observers in different terms, may possibly be found in other animals, as they have been seen in the dog by Virchow. They are quite different from Rainey's corpuscles; they are oval or rounded bodies at first with granular contents, and then with aggregations of granules into three or four rounded bodies, in which something hke a nucleolus is seen. They have often been mistaken for pus cells. Some other bodies occur in the flesh of pigs, the nature of which is not yet known. Wiederhold described a case in which little white specks, with all the appearance at first of encapsuled Trichince, were present • their real nature, however, could not be determined. EFFECTS ARISING FROM MEAT OF ALTERED QUALITY. 291 Virchow has described little concretions in the flesh of the pig, which •seemed to be composed of guanin; these were also at first taken for encap- suled Trichince. Roloff has noted little hard round nodules in the flesh of the pig; some seem very small, others as large as the head of a pin, with little prolongations running to the surrounding muscular fibres to which they are attached. On the outside of these bodies are bundles of fine hairs or needles, sometimes arranged in quite a feather-like form. The bodies have a great resemblance to the guanin bodies of Yirchow, but the needles are not crystalline. Roloff asked if these bodies were of post-mortem origin. It is hardly necessary to state that in cutting across meat small bits of tendons or fascia, sometimes very hke a little cyst, will be found; but common care will prevent a mistake. Diseases arising from altered Quality of Meat.—A very considerable quantity of meat from diseased animals is probably brought into the market, but the amount is uncertain. 1. The flesh of apparently healthy animals may produce Poisonous Symptoms.—Among the Mammalia the flesh of the pig sometimes causes diarrhoea—a fact noticed by Parkes in India, and often mentioned by others. The flesh is probably affected by the unwholesome garbage on which the pig feeds. Sometimes pork, not obviously diseased, has produced choleraic symptoms. In none of these cases has the poison been isolated. 2. The flesh of healthy animals, when decomposing, is eaten sometimes without danger; but it occasionally gives rise to gastro-intestinal disorder— vomiting, diarrhoea, and great depression; in some cases severe febrile symptoms occur, which are like typhus, on account of the great cerebral complication. Cooking does not appear entirely to check the decomposition. It appears to be, in some cases, the acid fluids of cooked meat which promote this alteration. Sausages, and pork-pies, and even beefsteak-pies, sometimes become poisonous from the formation of a ptomaine. The symptoms are severe intestinal irritation, followed rapidly by nervous depression and collapse. Neither salts nor spices hinder the production of this poison. If the meat is kept in dark, damp, and unventilated places, to which sewer gases can gain access, the probability of the development of poisonous properties in the meat is largely increased. In many cases of meat poison- ing this fact has been clearly brought out. The remedy for this is obvious. Ballard has reported two remarkable cases of poisoning by ham and hot baked pork. The first occurred at Welbeck in 1880, and the second at Nottingham in 1881. In both instances a number of persons who partook of the meat were taken ill, and some died. Klein examined the meat, and found it loaded with Bacilli, which were also found in the organs of the fatal cases. Guinea-pigs and mice, inoculated with the fluids of the body, died with pneumonia and peritonitic symptoms: Bacilli were found in the organs. Another case of sausage poisoning, which occurred at Chester, has been recorded by Ballard, presenting different characters. The symptoms were those of gastro-intestinal irritation, which passed off, but was followed by pneumonia, that proved fatal. No post-mortem examination could be made. In the Welbeck and Nottingham cases there was an incubation period; in this case the dlness came on at once: in the former the poison was probably that of an acute specific disease; in the latter an organic chemical poison. Many similar cases have since been recorded, all of which were associated 292 FOOD. with the development of ptomaines in the meat; the only common factor being, as stated above, the insanitary conditions under which the meat was kept. 3. The fresh and not decomposing flesh of diseased animals causes in many cases injurious effects. A good deal of difference of opinion, however, exists on this point, and it would seem that a more careful inquiry is necessary. The probability is that, when attention is directed to the subject, the effect of diseased meat will be found to be more considerable than at present believed. At the same time, we must not go beyond the facts as they are at present known to us, and at present certainly bad effects have been traced in only a few instances; perhaps the heat of cook- ing is the safeguard. The flesh of animals killed on account of accidents is usually dark and discoloured by reason of not having been bled; the thoracic and abdominal walls are stained from contact with viscera; the odour is offensive, and there is discolouration from incipient decomposition. Most meat of this class must always be condemned. If the injuries are localised, and the animal at once slaughtered, the carcass being properly dressed, the undamaged parts are normal in condition, and may be eaten without injury. If an animal is killed by lightning, the flesh putrefies so rapidly that it cannot escape detection; the same applies to apoplexy. In each case the peritoneum and pleura are discoloured, the flesh has a pungent odour and a dark colour gorged with blood, and the whole exterior is dark red. The flesh of over-driven animals is harsh in character and wanting in that juicy characteristic noticed in good, well-fed animals which have been rested! before slaughter. Carcasses of animals slaughtered before, during, or immediately after parturition are not necessarily unfit for food. If there is evidence of ex- travasation or inflammation of the pelvic cavity, and the flesh elsewhere pale and livid and ill-set, it should be condemned. But if it be a case of abnormal presentation, and the animal be slaughtered and properly bled and dressed, the flesh may be perfectly fit for consumption. The meat is not apparently altered in the early stage of acute inflammatory disease, and it is said that some of the primest meat in the London market is taken from beasts in this condition ; it is not known to be injurious, but it has been recommended that the blood should be allowed entirely to flow out of the body, and should not be used in any way. It is now generally accepted that tuberculosis in cattle cannot exist without the tubercular bacillus having been the exciting cause. Certain predispos- ing conditions may be present in the case of all animals, such as malnu- trition, bad ventilation, damp soil, hereditary predisposition, &c. The bacillus gains access to the body either by inhalation of contaminated ah, by inoculation, or by the ingestion of food containing the specific organism or its spores: these when swallowed adhere to the mucous mem- brane of the different organs, and may there undergo further development: from the mucous surfaces they pass into the surrounding tissues and to the lymphatic glands, which become largely affected: after them the serous membranes of the abdomen and thorax are the most frequent seat of the disease. Cattle, pigs, poultry and rarely sheep are all liable to be affected with tubercle, but it is in cattle, and more especially milch-cows, that tubercu- losis is met with. The organs most frequently affected are the lungs, liver kidneys, and brain, and, in the cow, the udder. In cattle localised tubercu- losis is the exception. The muscles appear to be rarely affected, although bacilli have been found in the expressed juice, which had infective EFFECTS OF TUBERCULOUS MEAT. 293 properties : they have also been found in the blood and in the secretions of the diseased organs. From the appearance presented by tubercular deposits in the serous linings of the thorax and abdomen, animals suffering from well-marked symptoms are said to have the "grapes"—the little nodules in the sub- stance of organs resemble fruit stones, and are called "kernels." There may be no visible symptom of the disease in the animal, unless in the case of an acute attack, in which case there is always fever and rapid wasting of the body. When the disease attacks the external organs, such as the udder, there is generally no constitutional disturbance; this is much more likely to be present when the internal viscera are affected, so that an animal may be extensively diseased and yet exhibit no symptom to call for special attention. The question of the use of the flesh, as of the milk, of tuber- culous animals has been extensively debated. From the nature of the case there is great difficulty in obtaining direct evidence of the transmission of the disease from animals to man. According to Johne, the flesh of tuberculous animals may be eaten if the tuberculosis is not general, but the internal organs affected and the lymphatic glands should be destroyed. In general tuberculosis the flesh should not be eaten. The Commission appointed in Victoria, Australia, to report on the extent of tuberculosis, considered that the meat of animals strongly affected with the disease should be forbidden, but in less severe cases it could be consumed. According to the experiments of Kastner infection is not to be feared except in those rare cases in which tubercles are found in the muscles. In nine out of eleven cases he has, however, obtained positive results by the injection of the juice expressed from the confiscated flesh of seven tuber- culous animals. In the light of his previous experiments he states that complete calcification of the tuberculous processes in the animal would appear to render the chances of infection slight, but if caseous masses are found, the dangers of infection must be admitted. In some other experi- ments by Steinheil, it appeared that tuberculosis could be transmitted to guinea-pigs, by administering the expressed juice from flesh in which no tubercles could be seen. At the Congress on Tuberculosis, held at Paris in 1888, Nocard intro- duced the subject of transmission by meat of infected animals, and con- sidered that their flesh could be eaten with safety, when the tubercles were limited to the viscera and lymphatics; and was only exceptionally danger- ous when the disease was generalised: the general opinion, however, was that all tuberculous meat should be condemned, and finally the Congress passed a resolution to this effect. An official decree was promulgated by the French Government in July 1888, forbidding the sale of tuberculous meat, (1) if the lesions are gener- alised ; (2) if the lesions, though localised, have invaded the greater part of an organ, or are manifested by an eruption on the walls of the chest or of the abdominal cavity: such flesh not to be used for feeding animals but destroyed. In Austria when the tuberculosis is localised the meat is passed as healthy. According to a recent Prussian rescript, the flesh of tuber- culous cattle is looked upon as dangerous to health, either when the flesh contains tuberculous nodules or when the tuberculous animal is wasted, even if no such nodules are present in the flesh. The great infrequency of tuberculous nodules in the muscles is also referred to. A judicial inquiry of great importance was held at Glasgow before Sheriff Berry in June 1889. The question was whether sanitary authorities could condemn a whole carcass, however sound it might appear, if tubercle 294 FOOD. was undoubtedly present, however localised it might seem to be. Much expert evidence was given on both sides. The Sheriff decided that the evidence clearly showed that the disease, though to the naked eye only local, was in point of fact generalised; that the bacilli, which are the cause ' of tuberculosis, were found in a portion of the body, which, in the ordinary course, would not have been " stripped," or removed; that cooking was not certain to destroy such bacilli; that tuberculosis was proved to be trans- missible from animal to man by ingestion of meat; that therefore there is danger to the public health in the consumption of such meat. The Report of the recent Royal Commission appointed to inquire into the effect of food derived from tuberculous animals clearly indicates that the danger is a real one, especially with regard to the meat of tuberculous bovines. Martin's evidence, in particular, shows that a great difficulty exists with regard to meat, inasmuch as a number of butchers are very careless in the cutting up of carcasses partially affected with tuberculosis. Matter finds its way to the knives used, and this is transferred to joints which would otherwise remain untainted. Roasting before a fire was the least, and boihng the most, effective method of cooking the flesh. Epidemic pleuro-pneumonia is a disease peculiar to the ox, and is a contagious inflammation of the lungs and pleura; but it has never been transmitted to other than bovine animals, its effects are localised in the lungs alone, and even in these organs the disease is a limited one. In the advanced stages, and when a large area of lung tissue is destroyed, with extensive pleurisy, the flesh becomes altered in colour and consistence. ^ The rule is to pass the carcasses of animals affected with pleuro-pneumonia as marketable and innocuous, if they present no departure from natural conditions. Anthrax occurs in cattle, sheep, horses, and sometimes pigs; the disease is rapidly fatal, the animal often dying within a few hours. It is readily transmissible to other animals by inoculation. The specific micro-organism associated with this disease—Bacillus anthracis—is found chiefly in the blood and spleen of infected animals, and is rod-shaped, multiplying by division, and can be artificially cultivated when spores make their appearance, which, when injected into other animals, germinate into characteristic bacdli. This disease is known in man as " wool-sorters'" disease, and the usual mode of infection in such cases is by inhaling the spores adhering to the wool of animals dead of anthrax or by inoculation into abrasions upon those handling it. In animals the hver, kidneys, and spleen are congested, the spleen being much enlarged, congested, and dark in colour, and sometimes found to be ruptured—a condition which gives rise to the name of " splenic fever" or " splenic apoplexy." " Black-quarter " or " quarter ill" is an anthracoid disease characterised by haemorrhagic effusion into the subcutaneous or intermuscular tissues of one or both of the anterior or posterior extremities. This disease is very infectious and fatal. Characteristic bacilli are found in the extravasations and in the abdominal viscera. Fleming considers that the facility with which anthrax can be com- municated by actual contact with matter impregnated with the virus, and the great rapidity with which putrefaction sets in after death, prove the inadvisability of using the flesh for food. Walley goes so far as to say that, however firm and good the meat may appear to be, it should be unhesitat- ingly condemned and destroyed if indubitable evidence of the existence of anthrax is forthcoming. EFFECTS OF DISEASED MEAT. 295 The flesh of an infected animal should not be consumed even if slaughtered in the earhest stage of its illness. The flesh should be at once destroyed : decomposition is very rapid. Braxy.—According to Walley, the term " braxy " is used in a very vague and indefinite manner with regard to sheep; in some instances referring to a cachexy from bad feeding, in which case the flesh is not deleterious, though unmarketable; in other instances being applied to conditions result- ing from anthrax and septicaemia, when the flesh should certainly be condemned. Acute rheumatism in cattle is sometimes known as "joint-ill" or "joint-felon." The serous fluid effused into the joints may become purulent, and abscesses may sometimes be found in the neighbourhood of the affected joints. The meat becomes dropsical and the carcasses of animals so affected are totally unfit for human food. Small-pox of Sheep.—The flesh has a peculiar nauseous smell, and is pale and moist. It produces sickness and diarrhoea, and sometimes febrile symptoms. Foot-and-Mouth Disease.—Levy states that at different times (1834, 1835, 1839) the aphthous disease has prevailed among cattle both at Paris and Lyons without the sale of the meat being interrupted or giving rise to bad results. Occasionally in chronic cases, or when the infected animals have been exposed to wet or neglect, the flesh may become deteriorated to an extent which renders it unfit for food. In ordinary cases the condition of the carcass differs in no respect from that of one which has been slaughtered in perfect health. Of course the affected parts should not be used for food. Cattle Plague (Rinderpest).—A priori, such flesh would be considered highly dangerous, and the Belgian Academy of Medicine so consider it; but there is some strong evidence on the other side. In Strasbourg and in Paris, in 1814, many of the beasts eaten in those cities for several months had rinderpest, and yet no ill consequences were traced. But it may be questioned whether they were looked for in that careful way they would be at the present day. Some other evidence is stronger : Renault, the director of the Veterinary School at Alfort, made, for several years after 1828, many experiments, and asserts that there is no danger from the cooked flesh of cattle, pigs, or sheep dead of any contagious disease (" quelle que soit la repugnance bien natureUe que puissent inspirer ces produits"). So, also, during the occurrence of the rinderpest in England (1865), large quantities of the meat of animals killed in all stages of the disease were eaten without ill effects. In Bohemia also, in 1863, the peasants dug up the animals dead with rinderpest, and ate them without bad results. The constitution is, however, gravely affected, and at the present time the majority of experts condemn the flesh as unfit for human food. Rabies in the dog and cow produce no bad effects. Walley, however, is of opinion that the flesh of an animal that has suffered from rabies should not knowingly be passed as fit for food. ^ Swine fever, called also " hog cholera," " soldier," &c, is a very fatal disease amongst swine. It is very difficult to detect in the early stages of its development, and in the varying modes of its onset and progress shows an analogy with typhoid fever in man. The post-mortem appearances are also somewhat similar—ulceration and inflammation of alimentary canal, most commonly the large intestine, being present. This disease is one which renders the flesh of the animal unfit for consumption. Parasitic Diseases. — Cysticercus cellulosce of the pig gives rise to a 296 FOOD. disease known as "measles" and produces Tcenia solium in man, and that of the ox and cow Tcenia mediocanellata. These entozoa often arise from eating the raw meat, but neither cooking nor salting are preservative, though they may lessen the danger. Smoking appears to kill Cysticerci, and so, according to Delpech, does a temperature of 212° F. Lewis found that a much lower temperature sufficed. When Cysticerci had been exposed for five minutes to a heat of 130° F. he could detect no move- ments, and he considered that a temperature of from 135° to 140° F. for five minutes would certainly kdl them. Lewis considered there was no danger if the cooking were well done, as the temperature of Avell-done meat is never below 150° F. Trichina spiralis in the pig gives rise to the curious Trichina disease caused by the wanderings of the young Trichina'. The affection is highly febrile, resembling enteric fever, or even typhus, or acute tuberculosis, but attended with excessive pains in the limbs and cedema. Boils are also sometimes caused. The eating of raw trichiniferous pork is the chief cause, and the entozoon is not easily killed by cooking or salting. A tem- perature of 144° to 155° F. kills free Trichina', but encapsuled Trichina; may demand a greater heat (Fiedler). During cooking a temperature which will coagulate albumin (150° to 155° F.) renders Trichince incapable of propagation, or destroys them. As a practical rule, it may be said that if the interior of a piece of boiled or roasted pork retains much of the blood- red colour of uncooked meat, the temperature has not been higher than 131° F., and there is still danger. Intense cold and complete decomposition of the meat do not destroy Trichince. Hot smoking, when thoroughly done, does destroy them (Leuckart); but the common kinds of smoking, when the heat is often low, do not touch Trichina; (Kiichenmeister). Distomum Hepaticum in Sheep.—It is said that many persons will eat freely of, and even prefer, the liver of the sheep full of flukes. No direct evidence has been given of the production of disease from this cause, at least in this country. The affected liver should in all cases be destroyed and the carcass should be condemned if it be deteriorated. In Iceland Echinococcus disease, which affects a large number of persons, is derived from sheep and cattle, who, in their turn, get the disease from Tcenia of the dog (Leared and Krabbe). Wet seasons are conducive to the spread of the disease, as the eggs and embryo of the parasite are developed in water. Glanders and farcy in horses do not appear to produce any injurious effects when such horseflesh is eaten as food. Parent-Duchatelet quotes two instances, in one of which 300 glandered horses were eaten without injury. In 1870, during the siege of Paris, large quantities of flesh from horses with farcy and glanders were eaten without producing ill effects. Medicines, especially antimony, given to the animals in large quantities, have sometimes produced vomiting and diarrhoea. Arsenic, also, is occasion- ally given, and the flesh may contain enough arsenic to be dangerous. Enteric Fever.—In Germany five outbreaks have been recorded of an illness resembling enteric fever, and resulting from eating the flesh of calves. The Andelfingen epidemic in 1839 followed a banquet, at which from 500 to 600 people were present: of these, 450 were attacked: the symptoms were very much those of enteric fever, but only nine cases were fatal: the usual enteric ulcerations were said to be found. At Kloten in 1878, 717 persons were affected: rose-coloured lenticular spots were usually abundant; the mortality was small, but typhoid lesions were present. The other outbreaks occurred at Birmenstorf, Wiirenlos, and Spreitenbach, in 1879, 1880, and 1881, the numbers affected being much smaller. In two FISH. 297 of the calves lesions resembling those of enteric fever were observed post- inortem. Unfortunately the observations were not conducted in a manner calculated to prevent criticism, and the question therefore cannot be considered as settled; but the possibility of the transmission of enteric fever from man to animals, and vice versd, must not be overlooked. FISH. Of the great nutritive value of fish as an article of diet, there can be no doubt. The varieties which are used as food are almost infinite, and whole populations appear to exist on it. It is less satisfying and not so stimulating as the flesh of animals, but is easily digested. Its use is greatest in those places where it is readily caught, and recommends itself on account of its abundance and cheapness. Lately it has been said that fish diet predisposes to diseases of the skin, especially leprosy; but the evidence on this point is not by any means conclusive: indirectly this connection, or alleged predis- position, may be associated with the poverty prevalent in those countries where the poorer classes are obliged to subsist altogether on this class of food, and where meat is never partaken of, and indicates that fish should not alone be the source from which nitrogenous food is taken. Fish contains a large proportion of phosphorus, which makes it a suitable diet for those who have to perform much brain work; and for this class, who are mostly of sedentary habits, it has the further advantage of being easily digestible as well. The flavour and digestibdity of fish depend on the amount of fat it con- tains, which varies in different species, the white fish, as sole and whiting, containing a small proportion, whereas the salmon and eel have a large amount. As a rule, white fish have least oil. The following table gives the composition per cent, of some of the most important kinds:— Water. Proteids. Fat. Salmon (Pavy), . 77*00 16-10 5-50 Herring..... 80-71 10-11 7-11 Sole,..... 8614 11-94 0-25 Mackerel, .... 6870 23-50 6-76 Eel (Letheby), . 75-00 9-90 13-80 White fish (Pavy), 78-00 18-10 2-90 Inspection of* Fish.—As in the case of animals, fish when eaten should be fairly fresh. A fresh fish is firm and stiff: the drooping or not of its tail is a fair criterion of freshness in a fish. Flat fish keep better than herrings or mackerel. Cod, haddock, and whiting keep the best, particularly if rinsed with salt water and stored in a cool place. All fish intended for food should be unbruised, unbroken, and clean. If the scales are dull and damaged it is very suggestive of either ill usage or staleness; softening in places indicates the same. The inspection of " food fishes " may be divided into two heads, namely, ground and surface fish. It is an established fact that decomposition in the surface fishes, such as herrings, mackerel, sprats, mullet, pilchards, &c, is extremely rapid. Ground fish, like halibut, skate, cod, sole, plaice, turbot, &c, decompose much less 298 FOOD. rapidly, and if properly packed remain fresh and fit for human food from seven to ten days after being taken from the sea. Fish which have been ungutted are the most difficult to inspect, more especially those with large oily livers. Externally they appear good, the eyes being bright, gills red, but internally they are full of decomposition and decay. With strong pressure of the thumb and fingers upon the under side, the deeper flesh readily crushes, leaving the skin only between the fingers. This is an infallible test of unsoundness. Immediately after death the blood of fish becomes congealed. When decomposition sets in, on cutting the fish this blood will run out as a liquid of a dull red colour, and giving off an offensive smell. On removing the bones, moreover, each one leaves a dull red mark, showing where the decomposition processes are extending to the more solid portions of the fish. To avoid rapid decomposition, all fish should be at once bled and gutted on being caught; neglect of this pro- cedure is the cause of a very large amount of fish quickly decomposing, and being in consequence condemned for use as food. Shell-fish form not only an important article of food, but are extensively used alive as bait. Mussels and oysters are unfit for food very soon after death. Crabs and lobsters, if boiled a few hours after death, are nearly flavourless, decomposition being much more rapid than if killed just before cooking. No crab may be held in possession or exposed for sale less. than 4^ inches across the back, and no lobster less than 8 inches from beak to tail when extended flat, the penalties being in these cases £2 for the first offence, and £10 for the second and every subsequent offence. Under the Crab and Lobster Act, no crab may be consigned for sale with spawn out- side attached to the tail, but the lobster may. Parasites of Fish.—The majority of fishes are infested with different kinds of parasitic worms. As examples of this excessive parasiticism, von Linstow assigns to the cod nine species of nematoda, fifteen cestodes and five trematodes; the herring is credited with six nematodes, three cestodes, three trematodes; the salmon with five nematodes, nine cestodes, six trematodes. Fortunately, the greater number of these are killed in cooking, while none of them, so far, are known to be parasitic or hurtful to man. The oyster, which is the one fish eaten raw in this country, is at times afflicted with a trematode worm, but we have no evidence to show that it has ever adapted itself to live in man. The only parasitic worm known, with any certainty, to be conveyed to man through fish is the Bothriocephalus latus. The encysted stage of this worm is passed in either the pike or the turbot. These fish, moderately smoked or salted, are, or were till recently, almost the staple food round Dorpat in the Baltic Provinces; when eaten, the encysted worms, which of course are not killed by the processes of preparation, become in their new and appropriate environment the sexual tapeworm; but so far as is known, if eaten by other than the specific hosts, for example, by other fish, they die without assuming the sexual form. Fish, particularly decomposed and some preserved fish, undoubtedly contain various kinds of bacteria. Edington, in reporting to the Scotch Fishery Board, has demon- strated the presence of bacilli as the cause of the red coloration in some salt fish. Experiments made, by various observers, have shown fish to be incapable of tubercular infection even when kept in water largely impreg- nated with tubercle bacilli. Poisoning by Fish.—The flesh of apparently healthy fish may produce poisonous symptoms. This is the case with certain kinds of fish, especially in the tropical seas. There is no evidence that the animal is diseased, and EGGS. 299 the flesh is not decomposed: it produces, however, violent symptoms of two kinds—gastro-intestinal irritation and severe ataxic nervous symptoms, with great depression and algidity. The httle herring (Clupea harengo minor), the silver fish (Zeus gallus)r the pilchard, the white flat-fish, and others, have been known to have these effects. Mackerel has been known to produce poisonous symptoms, probably owing to the fish undergoing rapid decomposition. When the fish is cooked immediately after being caught, it does not appear to produce any bad effects. If possible, some means should be adopted to retain fish alive until they are required for the table: and they should be eaten the earliest moment after capture. Oysters and shell-fish (even when in season) have been known to pro- duce poisonous symptoms. The production of nettle-rash in some persons from eating shell-fish need scarcely be mentioned. When decomposing, they produce more marked symptoms of the same kind. Mussels and oysters, especially those taken from water to which sewage gains access, have been found to possess at times very poisonous properties, and are probably also a not infrequent source of enteric fever. Various bacteria have been isolated from fish. Recently Arustamoff has bred from sturgeons two mobile short bacilh, microscopically similar to each other, one of which liquefies gelatin while the other does not. Both were infectious to rabbits, yielding from their cultures poisonous toxines. The symptoms produced were the same as those following meat and sausage poisoning. The processes of drying, pickling, salting, and smoking are employed for the preservation of fish. Each process considerably lessens its digestibUity, and therefore unsuits it for either the dyspeptic or the invalid. Moreover, unless the fish, originally, be thoroughly sound, there is reason to believe that preservation processes may aggravate the capabilities of fish to produce irritant symptoms; upon this point, however, our present knowledge is very inexact. EGGS. Though both duck's eggs and those of sea fowl are used, those of the hen are the usual form in which eggs are eaten as food. The average weight of a hen's egg is about 58 grammes, or about 2 ounces avoir.: 10 parts are shell, 60 white, and 30 yolk. The white contains chiefly egg- albumin, with a trace of fat and a small proportion of salts; the yolk con- tains a globulin (vitelhn), a large quantity of fat and more salts than the white. Duck's eggs contain more fat than do those of the hen. Traces of grape-sugar have been found in some egg yolks, while of the mineral con- stituents iron in organic combination is the most important. In the yolk, potassium salts and phosphates predominate; in the white, sodium salts and chlorides are in excess. Gautier claims to have isolated albumoses and ptomaines from eggs : both these bodies are probably the result of decom- position processes. The following table represents the average composition of ordinary hen's eggs :— AVater. 73-50 85-50 51-03 Proteids. Fats. Salts. Whole egg (with shell), White of egg, Yolk of egg, 13-50 12-87 16-12 11-60 0-25 31-39 1-20 0-63 1-01 soo FOOD. For preservation, eggs are packed in saAv-dust or salt, or are covered with gum, butter, or oil, or placed in lime-water to which a little cream of tartar has been added. Boiling for half a minute also keeps them for some time : in fact anything which excludes air will preserve them. The lime-water is said to give them a peculiar taste and makes the albumin more fluid. Eggs do not appear to suit all people, and if at all decomposed should not be eaten. According to Rubner, about 20 per cent, of the proteids from eggs appear unabsorbed in the faeces, while rather more of the fat also escapes unutilised. MILK. Milk not only constitutes the chief diet for children up to some eighteen months of age, but also enters very largely into the food of adults. All milk may be regarded as nothing more than an emulsion of fat containing proteids, salts, and carbo-hydrates in solution in water. The average com- position of milk per 100 parts from the chief sources as used by man is shoAvn in the following table :— Proportion of Kind of Milk. Specific Gravity. Total Solids. Proteids. Fats. Carbo-hydrate. Salts. AVater. nitrogenous to non-nitrogenous constituents. Human, . . . 1027 12-60 2-29 3-81 6-20 0-30 87-40 as 1 is to 4"4 Cow's, . . . 1032 12-83 3-55 3-69 4-88 071 87-17 ,, 1 „ 2-5 Mare's, . . . 1035 9-21 2-00 1-20 5-65 0-36 90-79 » 1 „ 3-4 Ass's, .... 1026 10-40 2-25 1-65 6-00 0-50 89-60 „ 1 ,, 3-4 Goat's, . . . 1032 14-30 4-30 4-78 4-46 0-75 85-71 „ 1 ,, 2-0 Buffalo's, . . 1032 18-60 6-11 7-45 4*17 0-87 81-40 ,. 1 ., 1'9 Although all the above are used at times by man for food, the most important kinds are undoubtedly human milk and cow's milk; and these differ from each other in some essential particulars. As seen by the pre- ceding table, while there is more carbo-hydrate in human milk than in cow's, the reverse is the case with the proteids and salts; the fat being much the same in them both. Ass's milk, except in regard to its fat, is most like human milk; but mare's milk contains even less fat and proteid than the ass's; Avhile, on the other hand, milk from both the goat and buffalo are very rich in fat. The proteids of milk consist largely of casein; but there is also some albumin, with traces of globulin. The casein probably exists in milk in combination with phosphate of lime, which helps to keep it in solution. The salts of mdk are both numerous and various, being composed really of all the mineral constituents necessary to the growing body. Citric acid is a normal constituent of the milk of various animals. In human milk, the quantity is about 0*5 gramme to the litre, in cow's milk about 1*5 grammes. It does not appear to be dependent upon citric acid present in the food. Minute amounts of nitrogenous bases and a starch converting ferment also occur. The fat of milk is nothing more than minute oil globules suspended in the milk, and which, upon standing, rise slowly to the surface, forming cream. One part of cream is said to correspond roughly to 0*2 of fat; the proportion of cream yielded by a pure milk varies, but may be said to MILK AS AX AKTICLE OF DIET. 301 average 8 per cent., being as high as 14 in some cases, and as low as 6 in others. The amount found in a given time is no measure of the richness of the milk ; water added to milk causes a more rapid separation of the cream. When milk is subjected to centrifugal action, as in the separator so largely used now in commercial dairies, a much larger proportion of cream is obtained than by the mere skimming process. As a result of this, skim milk contains 1 per cent, of fat, while separated milk has practically none. The carbo-hydrate of milk is a peculiar sugar, somewhat like cane-sugar, and called lactose or sugar of milk, C12H.2,On + H20. It is a hard variety of sugar, grating under the teeth, and tastes but slightly sweet: it rotates polarised hght +61°*5. This body, like other sugars, undergoes fermenta- tion under the influence of micro-organisms, and one especially, caUed the Bacterium lactis, abounds in dairies and other places where milk is kept. This micro-organism converts the milk-sugar into lactic acid, while at the same time the proteids are partly decomposed and partly coagulated, the mflk itself becoming sour with enclosure of the fat in the coagulated casein. After the lactic acid fermentation of mdk has set in, the casein gradually decomposes, and, during the early decomposition of the proteids, very fre- quently highly poisonous compounds are formed, such often being' the cause of the violent poisonous effects which at times are produced by ice-creams and other articles of food into the making of which milk enters. Many other micro-organisms produce coagulation of milk, notably the Bacillus butyricus of butyric acid fermentation. Some others have the power of changing the colour of milk, particularly if lactic acid fermenta- tion has occurred. Thus the Bacillus cyanogenus causes blue milk ; the Bacillus synxanthum causes yellow mdk; the Micrococcus prodigiosus- produces red milk; whhe other bacteria at times cause milk to become ropy and stringy.^ In nearly all these cases, the milk is apt to cause diarrhoea, and is unsuited for food. Alcoholic fermentation of the milk-sugar can also be set up by certain micro-organisms. " Koumiss " is the result of the alcoholic fermentation of mare's milk, and " Kefir " is that of cow's, goat's, and sheep's. The following analysis of Russian koumiss will give an idea of its. composition:— Acid, as lactic Casein, . Sugar, . Fat, Alcohol, Ash, Water, . Total,.....100*00 Boding of mdk produces coagulation of the albumin, some obscure changes in the sugar, and greater coalescence of the fat globules. Micro- organisms and ferments are at the same time destroyed, a fact which explains the better keeping quahties of boded milk. Hot weather tends to hasten fermentation and decomposition in milk. # As an article of diet, milk holds the highest place. When digested, either by the gastric or pancreatic juices, milk clots, the casein being preci- pitated as large curds. The curds are subsequently changed to albumoses and peptones by the digestive ferments, a bitter substance being formed, which makes all peptonised milk unpleasant in taste. For infants, human, mare's, and ass's milk constitutes a typical food, the 1*96 2-11 0'40 1-10 212 0*34 91-97 302 FOOD. nitrogenous and non-nitrogenous constituents being in the right proportion, or as 1 is to 4*4 : whereas, in cow's milk the ratio is as 1 is to 2*5, a fact Avhich renders the milk of the cow, by itself, not a perfect food. This fact is of great practical importance, as if cow's milk is to become a complete and true food for either young children or adults, its non-nitrogenous organic food-stuffs must be increased by adding sugar or arrowroot to it. The artificial approximation of the composition of cow's milk to that of the human being is best carried out in the following manner :—" The cream is separated from a pint of milk, and the casein of one-half of the skimmed milk coagulated with a small quantity of rennet and strained off. To this Avhey, the cream which has been removed and the rest of the skimmed milk is added. The composition of this artificial human milk varies: it contains on the average a little over 2 per cent, of proteid, 4*5 per cent, of fat, 5 per cent, of lactose, and 0*6 per cent, of salts." To render ordinary cow's milk suitable for infants or others whose ■digestive powers are feeble, it must be diluted with either water, lime- water, or barley-water: dilution lessening the size of the casein clots and indirectly favouring their digestion. After dilution, sugar should be added to cow's milk to bring it nearer to the human standard: the proportion to be added should be about 30 grammes of lactose to each litre of diluted milk, or about three-fifths of an ounce to each pint. The exact dilution to which the milk should be submitted of course varies with the child's age; thus, for the first month of life, two parts of water must be added to one of mdk; after the second and third months, more milk may be added, until about the sixth month the child attains to undiluted milk. These must be taken only as general statements, as frequently milk needs to be more •diluted even than this. The percentage composition of dduted cow's milk Avith added lactose may be thus given as quoted by Martin:— AVater. Proteids. Fats. Lactose. Salts. Proportion of nitrogenous to non-nitrogenous food-stuffs—as Cow's milk with equal parts of water, Cow's milk with two parts of water, 90-59 9273 1-77 1-18 1-85 1-23 5-44 4-63 0-35 0-23 1 :4 1 : 4*8 Accepting this statement, and assuming that a child at five months requires about 2 litres of mother's milk daily, representing nearly 45 grammes of proteid, 80 grammes of fat, 125 grammes of sugar, and 6 grammes of salts : it would require, therefore, 3 litres of milk diluted with 2 parts of water to obtain similar amounts of the food-stuffs. In the case of an adult requiring daily 4*59 ounces of proteid, 2*96 ounces of fat, and 14*2 ounces of carbo-hydrate, and assuming that 1 litre (35 ounces) of average cow's milk contains 1*24 ounce of proteid, 1*29 ounce of fat, 1*7 ounce of lactose, and 0*27 ounce of salts, it would require at least 4 litres or about 7 pints of milk to furnish him with the necessary amount of proteid, while at the same time the fats and water would be in excess and the carbo-hydrates deficient. Variations in the composition of normal cow's milk are of frequent occur- rence, and may result not only from the kind of feeding, but also from peculiarities of race, the time since calving, and methods of milking the cow. As evidence of this we find that, in what are really normal milks, the specific gravity may range from 1*027 to 1*034, the water may vary from VARIATIONS IN THE COMPOSITION OF MILK. 303 85 to 88 per cent., the proteids from 2*5 to 5 per cent., the fat from 2*75 to 6 per cent., the lactose from 3*5 to 6 per cent., and total solids from 11*5 to 15 per cent. The effect of diet is largely shown by the increase of sugar found in the milk of cows fed upon fodder rich in carbo-hydrates, such as carrots and beet- xoots. The addition of proteid in the diet raises the casein but not the fat. Cows which are fed much upon refuse from breweries and distilleries commonly yield an abundance of milk, but it is simultaneously poor in fats and other solids. Diseased potatoes and turnips in the food of cattle without actually affecting the goodness of milk, often cause it to smell and taste unpleasantly. The quantity of milk yielded by a cow, and its proportion of total solids and fats, often vary in opposite directions. Some cows, like the Dutch, which produce an abundance of milk, usually yield low percentages of fat! Alderneys, on the other hand, commonly yield a milk rich in fat; others like the long-horned cows, yield large quantities of casein. As a rule, the proportion of total sohds in a milk is stable. They practically never fall helow 11*5, and commonly average between 12 and 13 per cent. Though the fats yielded by the milks of different cows are apt to vary much, the " sohds not fat " fluctuate relatively less. These rarely fall below 8*5' per cent., a figure which is now generally accepted as the minimum standard of a pure and normal milk. This question of the variations in the composition of milk is one of some complexity : in every district observations on the average composition of milk need to be collected for the several months of the year, as it is only by mean values for extensive districts or entire counties that we can arrive at any correct opinion, or formulate standards. In skimmed milk, the proportion of fat varies greatly: extreme figures cannot be given, but the specific gra-vity usually amounts to from 1*032 to 1*035, unless it has been simultaneously watered. Separated milk, or that which has had its cream removed by a separator, contains from 0*2 to 0*6 per cent, of fat, and has a specific gravity of from 1*033 to 1*036. A mixture of skimmed evening mdk and new morning mdk, or of milk which lias been partially freed from cream, is sometimes sold as "half mdk." Its average composition and condition is not easily defined. The milk secreted in the early stage of lactation, known as colostrum, is very rich in proteids, due probably to an incomplete transformation of the epithelial lining of the ducts. The colostrum corpuscle is characteristic of milk of this period, while the large proportion of serum-albumin and casein present is often sufficient to coagulate the milk on boiling. Konig gives the following as a percentage composition of cow's colostrum milk:—water 74*67, casein 4*04, albumin 13*6, fat 3*59, lactose 2*67, and salts 1*67. After the colostrum stage, the milk of the cow gradually alters in quality. TJp to the second month after delivery, the casein and fat are increased! From the tenth to the twenty-fourth month the casein diminishes, while the fat becomes less from the fifth to the twelfth. The lactose lessens during the first month, but increases during the eighth, ninth, and tenth months. The salts appear to increase up to the fifth month, after which they steadily -diminish. How far the age of the cow, or the number of calvings, influence the milk is but little understood. As a rule, cows are not allowed to calve before the third or fourth year, pregnancy lasting 284 days: colostrum is secreted for a short time before and after delivery, and then milk for 300 )9 There has been much discussion whether the milk from foot-and-mouth disease in cows can cause affections of the mouth, or give rise in human beings to any disease similar to that of cattle. Pigs can certainly get the disease from the mdk of the cow; sheep and hares, which also have the disease, perhaps get it from the saliva on herbage. In men the evidence is discordant, and in a great measure negative; still there are some striking cases, which seem sufficient to prove that disease of the mouth (aphthous ulceration, general redness, diphtheritic-like coating, swollen tongue), and sometimes, though rarely, an affection of the feet may occur. Some positive evidence has been adduced by M'Bride, Gooding, Hislop, Latham, and Briscoe. A remarkable outbreak, which took place in Aberdeen in April 1881, has been recorded by Beveridge. The symptoms were febrile, and seem to have resembled those of foot-and-mouth disease. A marked feature in the illness was subsequent enlargement of the lymphatic glands of the neck. The cases were limited to the area of a particular milk supply, 88 per cent. of the fanhlies using the milk being attacked. In 1884, at Dover, there suddenly broke out an epidemic of sore throat, with vesicular eruption of the throat or lips, enlarged tonsils, and in most cases also enlargement of the glands of the neck. The symptoms resembled the aphthous fever of cattle, or foot-and-mouth disease. There were 205 cases in one week, all supplied with milk from one dairy, but living in different parts of the toAvn, and with no other common condition but that U 306 FOOD. of milk supply. Foot-and-mouth disease existed at one of the farms from which this dairy derived its milk. Tuberculosis in coavs (Perlsucht) affects the milk, and may lead to the same disease in man; during the early stages, the quantity is sometimes increased; it contains usually an excess of water and alkaline salts, Avhile deficient in fat, sugar, and proteids. It is now knoAvn that tuberculosis can be transmitted from the coav to other animals through milk, that it is a disease very prevalent amongst cows, and that it is the same disease as in the human species. There is also some evidence to show that tuberculosis may be transmitted from the coav to man. A distinction, however, must be made betAveen the milk from coavs with tubercular udders and that from animals affected with general tuberculosis, as the tubercle bacilli are rare, in milk unless the udders are tuberculous. Animals can be given tuberculosis by feeding them Avith milk from tubercular cows. Boiling the milk is a preventive measure of the first importance, as the tubercle bacilli are destroyed by heat. Zymotic Diseases.—Milk may also be a means of conveying the poisons of enteric fever, of scarlet fever, of diphtheria, and of cholera. In the first, it has probably usually arisen from the watering of the milk with impure Avater containing the agent, or from the use of foul water in washing out the milk vessels; but it may possibly have in some cases arisen from the enteric effluvia being absorbed by the milk. The scarlet fever and diph- theria poisons have probably got into the milk from the cuticle or throat discharges of persons affected with those diseases, who were employed in the dairy while ill or convalescent. But the investigations by Power and Klein, in connection with the Hendon outbreak, seem to sIioav that cows are liable to a disease Avhich, although comparatively mild as regards the animal itself, is capable of communicating scarlatina to man. Klein, by means of careful cultivations, has shoAvn that the micrococci found in such milk are probably identical with those found in scarlatina, and that they may be capable of exciting the disease in animals. There seem also grounds for believing that milk may be the means of transmitting diphtheria from diseased cows, apart from direct contamination from human beings. That mdk is not only a probable but an actual agent in the dissemination of enteric fever has long been recognised. This may occur either by adulteration of the milk with impure water containing the specific microbe; or by the use of similarly befouled water in washing out the milk vessels; or even from the milking of the cows by a person whose hands have been soiled by the enteric dejecta. An interesting case, illustrating this last method, is related by Welply as having occurred at Bandon in 1893, in which the central focus of the disease was a large creamery, and the medium was the separated milk distributed therefrom. Allen, of Pieter- maritzburg, and Power have reported cases which would seem to indicate that enteric fever may be transmitted to man by mdk of cows suffering from a simdar malady. Though their facts are very suggestive of this sequence of events, they cannot be quite accepted as altogether conclusive. Just as enteric fever, scarlet fever, and diphtheria may be disseminated by the specific infection of milk, so may cholera be similarly conveyed. Simpson of Calcutta gives the particulars of an outbreak of cholera on board the ship " Ardenclutha" lying off that port, in which the poison seemed undoubtedly to have been conveyed by milk. Of the crew of this ship, all those who drank milk brought by a particular native milkman suffered. The milk seller was traced, and found to live near a tank into which dejecta from a cholera patient found access; and he confessed to PRESERVED MILKS. 307 habitually diluting his milk, one-fourth, Avith Avater from this tank. All other hkely causes were inquired into, and negatived before this apparently clear causative connection Avas discovered. Vaughan of Michigan has demonstrated, in old and stale milk, the presence of a ptomaine-like body which is toxic to animals. It appears to be found in marked quantity in cheeses and ice-creams, and is probably the cause of many of the cases of poisoning by those articles Avhich are on record. Other cases are known in AAdiich milk, stored in dirty pans and in unAvholesome or filthy surroundings, has given rise to most alarming symptoms. What are the precise changes induced in milk by these condi- tions is not well understood, but the probable decomposition is a transforma- tion of the proteids into highly poisonous benzene derivatives, the most important of Avhich is diazobenzene, commonly knoAvn as tyrotoxicon. Preserved Milks.—The simplest method, for the preservation of milk, is to boil it and then tightly cork the vessel; but, as a rule, this preservation is only temporary. The same end is attained by adding antiseptics, such as salicyhc acid, boric acid, and formalin, to the milk, either before or after it has been boiled. The common forms, hoAvever, of preserved milk are the concentrated ones, such as the dried milk, and the so-called condensed milks Avith or Avithout sugar. Those without sugar keep less well than those with sugar, once the tin in Avhich they are sold is opened. The majority of condensed milks are made by evaporating down the original milk to a third or a quarter, and then adding sugar to it; this added sugar tends to make condensed milks rather fattening; but on the Avhole their nutritive value is below that of the fresh article, simply because the great majority of the so-called condensed milks in the market are nothing more than condensed separated milks (that is, milks from which nearly the whole of the cream has been mechanically separated) mixed with sugar, and really containing very Ioav percentages of fat—so Ioav as to be negligible quantities so far as value to the consumer is concerned. Of course, there are notable exceptions to this rule; such condensed milks being actuaUy condensed whole milks as distinguished from the compara- tively worthless condensed separated milks. A clear understanding upon this subject is very necessary in the interests of the feeding of infants. "Milk" at no time should be construed so as to mean "thinned milk," nor does it mean " separated milk." These, which are, as every one knows, articles of commerce, should be described at all times by their distinctive titles. Condensed milk means condensed whole milk, and if a preparation which has been obtained by condensing separated milk is called condensed milk, its sale as such amounts to a distinct fraud upon the public. A large proportion of these so-called condensed or preserved milks are found on analysis to be prepared entirely from skimmed milk, and show an average of only 0*72 per cent, of fat. Some brands, prepared from partly skimmed milk, or from skimmed milk to which a small proportion of un- skimmed mdk has been added, show an average of 3*14 per cent, of fat. Samples of condensed genuine full-cream milk, such as the well-known "Milkmaid" brand prepared by the Anglo-SAviss Condensed Milk Com- pany, have yielded from 10 to 12 per cent, of fat. Unfortunately, in the present state of the laAv, as interpreted by some eminent judicial authorities, condensed skimmed milk, that is to say, milk deprived of one of its chief constituents, namely, fat, in the absence of Avhich it ceases to be milk in the true sense of the word, may lawfully be labelled "condensed milk," although when sold uncondensed. it must be distinctly stated at the time of sale that it is skimmed milk; that is, a small 308 FOOD. milk vendor is fined for selling Avhat a condensed milk manufacturer is at liberty to sell provided he condenses it first, and in an obscure manner states upon the tin that the tin "contains skimmed milk," although upon the face of the same label it is described as " condensed milk." This defect in the state of the law regarding milk constitutes an anomaly, which, in the interests of the public health, it is to be hoped future legislation will soon remedy. Strictly speaking, both "Koumiss" and "Kefir," which are fermented milks of the mare, are forms of preserved milk, both containing lactic and carbonic acids, with some alcohol. In kefir, the casein is partiaUy changed into albumose and peptone. Both these forms of fermented and partially digested milk are used as food for the sick, or those in whom digestion is feeble. The percentage composition of some preserved milks is given in the folloAving table :— o fl I p 3 1 ►J 5 M> si < < 3 13 h'5 la 5 Scherff's con- densed milk, . 72-87 8-20 6-62 10-63 1-68 Nestle's con- densed milk, . 25-35 30-77 8-14 14-20 19-60 1-94 American con- densed milk, . 50-35 18-89 13-36 14-82 2-58 Irish Co. 's con- densed milk, . 25*83 35 67 3-40 15-00 18-00 2-10 Loefiund's con- densed milk, . 57*79 15-24 7-22 17-55 2-20 Loefiund's (Alpine Co.) condensed milk, 59-23 11-90 11-71 14-82 2-34 ... Cow brand con- densed milk, . 32-00 16-18 0-32 17-00 24-70 1-80 Milkmaid brand condensed milk, 25-25 14-35 12-25 11-91 34*18 2-06 Swiss compressed extract of milk, 0-72 34-48 1-87 55-58 ... 7 35 Koumiss from mare's milk, . 90-63 2-24 1-46 1-77 0-22 1-91 0-91 0*86 i f f> 91-97 211 1-10 0-40 0-34 2*12 1-96 Koumiss from cow's milk, 88-28 2*66 1-83 4-09 0-43 1-14 0-55 0*86 0-16 Kefir, 90-22 3*49 1-44 2-40 0-68 0-75 1-02 Cross brand con- densed milk, . 31-00 15-32 0-96 16-00 34-82 1-90 Goat brand con- densed milk, . 32-60 16-11 0-56 16-44 32-29 2-00 EXAMINATION OF MILK. Although the milk from individual coavs varies largely in composition, yet the mixing of the milk given by a herd averages the general composi- tion within certain limits. The examination of a milk sample is intended primarily to determine whether it is what it is said to be; that it is pure and Avholesome; and that it has not been adulterated or sophisticated so as- EXAMINATION OF MILK. 309 to be, in any Avay, detrimental to health. The chief adulterations of milk are:— 1. The addition of water (not necessarily pure water). 2. Removal of part of the cream and adding Avater to bring the specific gravity up to the normal; or removal of the cream from the evening milk and adding the morning milk. 3. The addition of starch, flour, gum, dextrin, or glycerin. 4. The addition of bicarbonate of soda, borax, boric, and salicylic acid and formalin as preservatives. In the examination of a milk sample, attention should be directed to the following prehminary observations :— The Physical Characters.—Placed in a narrow glass, the milk should be quite opaque, of full white colour, Avithout deposit, and Avithout peculiar smell or taste. When boiled it should not change in appearance. Reaction.—Reaction should be slightly acid or neutral, or very feebly alkaline; if strongly alkaline, either the cow is diseased (?) or there is much colostrum, or sodium carbonate has been added. Milk, AAdien just draAvn from the cow, is sometimes both acid and alkaline; that is, it turns blue litmus red, and turmeric broAvn, giving Avhat is known as the " amphioteric " reaction. This is probably due to the presence of acid phosphates of the alkalies. Strong acidity means the presence of lactic or butyric acid, and is indicative of retrograde changes in the milk. Strong alkalinity may mean cither a diseased milk, or added sodium bicarbonate. The Cream.—When milk is alloAved to stand, some of the fat rises gradually, and forms a rich layer, constituting cream. Its proportion de- pends on several conditions, and can be readily determined in the f olloAving way. Put some of the milk in a long glass, which is graduated to 100 parts; a 100-centimetre or litre measure will do, or a glass may be specially pre- pared by simply marking Avith compasses 100 equal lines on a piece of paper, and gumming it on the glass. Allow it to stand for twenty-four hours in a cupboard secured from currents of air. By this means the per- centage of cream can be seen, and the presence of deposit, if any, observed. There should be no deposit till the milk decomposes; if there be, it is pro- bably chalk or starch. The cream should be from y^^-ths to y^ths; it is generally about y^ths; in the milk of Alderney cows it will reach y^ths or y^ths. The time of year (as influencing pasture), and the breed, should be considered. Unfortunately the amount of cream formed in a given time cannot be taken as a measure of the richness of the milk. Water added to milk causes a more rapid separation of the cream, and milk subjected to centrifugal action yields a much larger percentage of cream, practically all the fat being removed. The following analytical averages shoAV this very clearly:— Wliole Milk. Skimmed Milk. Cream. Specific gravity, 1032 1034 1015 Total solids, 14-10 9*60 26-98 Casein, 356 3 75 1-13 Fat, 5-05 0-02 21*95 Lactose, . 4-70 5-05 3*32 Salts, 0-79 0-78 0-58 For the detection of the more common adulterations of milk, namely, the removal of cream and addition of water or other matters, recourse must be made to the following determinations. Specific Gravity.—In all milks the specific gravity is understood to be taken at 15° C. or 60° F.; if at other temperatures, the result must be 310 FOOD. corrected for 15° C. by a reference to the table given on page 311. The instrument usually employed is a lactometer. The specific gravity of normal milk varies between 1*027 and 1*034, being less in proportion as the fat is greater. A milk, the specific gravity of which has been raised by removal of fat (skimming), can be restored to its original specific gravity by adding water, so that this determination by itself cannot be taken as a reliable index of the character of a sample. But taken in conjunction Avith the figures for total solids or for fat, it is of the greatest value, and con- stitutes a reliable check upon other determinations. Expressed in general terms, it may be said that the specific gravity of milk falls one degree for each rise of 10° F. above 60° F., and that, at that temperature, there is a loss of three degrees of gravity for every 10 per cent. of water added. OAving to the fact that milk, especially when first draAvn, often contains bubbles of air, care must be taken in mixing the samples before taking the density, and to alloAV sufficient time for the escape of any bubbles that may be present. Total Solids.—Evaporate a knoAvn quantity, say 2 c.c, of the milk to dryness in a flat and shallow dish, and weigh. Calculate out as a per- centage. The heat employed should not exceed 100° C. (212° F.) and should be continued for at least three hours, taking care that there is no- charring. The specific gravity of the mdk being knoAvn, the amount taken can be readily calculated. Thus, 2 c.c. of milk, whose specific gravity is 1*032, would Aveigh 2*064 grammes, and if after evaporation this amount of milk gave a solid residue of 0*284 gramme, the percentage of total solids yielded by the sample Avould be --- — = 13*76. The total solids found ought not to be beloAv 11*5, but more usually average betAveen 12 and 13 per cent. Ash.—The residue or dried solids, in the last determination, may be incinerated, re-weighed, and calculated out in a similar manner as so much ash. In normal milks this averages about 0*73 per cent., and in no case should fall below 0*7 ; if the milk be watered, it will be less. Any marked degree of alkalinity or effervescence of the ash Avith hydrochloric acid will suggest the addition of a carbonate. The ash of milk may be said to have the folloAving average composition :— Ca, 18*78 NaCl, 10*73 KC1, 26*33 KHO, 21*44 PA, 19*00 H„S04, 2-64 f.;pa, 0-21 Silica, traces Fat.—The estimation of the fats constitutes a very important determina- tion. This is best done by means of the apparatus of Gerber or of Soxhlets, in which ether is made to pass repeatedly through the sohds of milk, dried after being mixed Avith plaster of Paris, or soaked up by bibulous paper (Adams' method). The solids dried alone are inconvenient, as they become horny in consistence, and are thus acted upon with difficulty by the ether. The ether carries doAvn with it the fat. The ether is then evaporated and the fat weighed. Should the milk have become sour, Adams recommends the addition of ammonia, which restores the fluidity without otherAvise affecting the constituents. Table for correcting the Specific Gravity of Milk according to Temperature (after Vieth). II Degrees of the thermometer (Fahrenheit). 16 17 48 49 | 50 51 52 53 54 55 56 57 58 59 60 61 02 o: 61 65 66 67 63 69 70 71 72 73 74 75 1020 19 0 1 191 19-1 19 2 , 19-2 19-3 194 19-4 19-5 19-6 19-7 19-8 19-9 19 9 20-0 20 1 202 20 2 20 3 20-4 20 5 20 6 20-7 20 9 21 0 21-1 21-2 213 21-5 21-6 1021 20 0 20-0 ! 20 1 20 2 20-2 203 20 3 20-4 20-5 20-6 20-7 20-8 20-9 20 9 21-0 21 1 21-2 21 3 21 4 21-5 21-6 217 21-8 22-0 22 1 22-2 223 22-4 22-5 22-6 1022 21 0 21-0 21-1 21 2 21-2 21-3 21-3 21-4 21-5 21-6 21-7 21-8 219 21-9 22-0 22 1 22-2 22 3 22 4 22-5 22'6 22-7 22-8 23-0 23 1 23-2 23 3 23-4 23-5 23-7 1023 22 0 220 22 1 22 2 22 2 22-3 22-3 22-4 22-5 22-6 22-7 22-8 22-8 22-9 230 23 1 23-2 23 3 23 4 23-5 236 237 23-8 24-0 24 1 242 24-3 24-4 24 6 24-7 1024 22 9 23 0 23-1 23 2 23 2 23-3 23 3 234 23-5 23 6 23 6 237 23 8 23 9 24'0 24 1 24-2 24 3 24 4 245 24-6 24-7 24-9 25-0 25 1 25-2 25 3 25-5 25-6 25 7 1025 23 9 24-0 24-0 24 1 241 24-2 24-3 24-4 24-5 24-6 24-6 24-7 24-8 24 9 25-0 25 1 25'2 25 3 25 4 25-5 25 6 25-7 25-9 200 26 1 262 26-4 26-5 26-6 26-8 1026 24 9 24 9 25-0 25 1 25-1 25'2 25 2 25-3 25-4 25-5 25-6 25 7 25 8 25-9 26 0 26 1 26-2 26 3 26 5 26-6 26-7 26-8 27-0 27 1 27 2 27-3 27-4 27-5 27-7 27-8 1027 25 9 25 9 26 0 26 1 26 1 26-2 26-2 26 3 26-4 265 26 6 26-7 26-8 26-9 27 0 27 1 27-3 27 4 27 5 27-6 27-7 27'8 28-0 281 28 2 28 3 28-4 286 28-7 28-9 1028 2G S 26'8 26 9 27 0 27-0 27 1 27'2 27-3 27 4 27-5 27 6 27-7 27-8 27-9 28 0 28 1 28-3 28 4 28 5 28-6 2S-7 28-8 290 29-1 29 2 29-4 29-5 29'7 29-8 29-9 1029 27 8 27-8 27 9 28 0 28-0 281 28-2 28-3 28-4 28-5 28-6 28-7 28-8 28-9 29-0 29 1 29-.1 29 4 29 5 29-6 29-8 29 9 30-1 30 2 30 3 30 4 30 5 307 30-8 310 1030 28 7 28-7 28-8 28 9 290 291 29-1 29-2 29-3 29-4 296 29-7 298 299 30-0 30 1 30-3 30 4 30 5 30-7 30-8 30-9 31-1 31-2 31 3 31-5 31-C 31-8 319 32-1 1031 29 6 29-6 29-7 29 8 29-9 30 0 30-1 302 30 3 30-4 30-5 30-6 30-8 30-9 310 31 2 31-3 31 4 31 5 31-7 31-8 32-0 32-2 32 2 32 4 325 32-6 32-8 33-0 33-1 1032 30 5 30 5 30-6 30 7 30-9 310 31-1 31-2 313 314 31-5 31-6 31-7 319 32 0 32 2 32 3 32 5 32 6 32-7 32-9 330 33 2 33-3 33 4 33-6 33-7 33-9 34 0 34-2 1033 31 4 31-4 315 31 6 31-8 319 32 0 321 32 3 32'4 32-5 32-6 32-7 32 9 33-0 33 2 333 33 5 33 6 33-8 33 9 34-0 34-2 34-3 34 5 346 34-7 34-9 34 5 35'2 1034 32 S 32 3 32-4 32 5 32-7 32 9 33 0 33 1 33-2 33-3 335 33-6 33-7 339 34-0 34 2 34 3 34 •5 34 6 34-8 34-9 35-0 35-2 35 3 35 5 35-6 35-8 36-0 36-1 36 3 1035 33 1 33 2 33-4 33 5 336 33-8 339 34-0 34-2 34 3 34-5 34-6 347 34-9 35-0 35 2 35'3 35 ■5 35 6 35-8 359 36-1 36-2 36-4 36 5 36-7 36-8 37-0 37 2 37-3 312 FOOD. What is knoAvn as the Werner-Schmid method is a fairly satisfactory means for the determination of fat, and is especially suitable for sour milk. Measure 10 c.c. of the milk into a long test-tube of 50 c.c. capacity, graduated to tenths of a c.c, and add 10 c.c. of strong hydrochloric acid. After mixing, the liquid is boiled for one minute. The tube and contents are cooled in Avater, 30 c.c. of well washed ether added, shaken, and allowed to stand until the line of acid and ether is distinct. The cork is taken out, and a double tube arrangement, like that of the ordinary wash bottle, inserted. The lower end of the exit tube is adjusted so as to rest immedi- ately above the junction of the ether and acid. The ethereal solution of fat is then blown out, and received into a weighed flask. Two more portions of ether, each of 10 c.c, are shaken Avith the acid liquid, blown out and added to the first. The total ether is then distilled off, the fat dried, Aveighed, and calculated as a percentage. A simple but approximate estimate of the fat in milk can be made by means of the degree of transparency of the liquid, as determined by Vogel's lactoscope. Vogel's instrument consists of a little cup, formed by two parallel pieces of glass, distant 0*5 centimetre from each other, and closed everywhere except at the top, so as to form a little vessel. Varying quantities of milk (say 2 to 5 c.c.) are weU mixed up with 100 c.c. of distilled water in any ordinary measuring glass. The parallel glass cup is then filled Avith this diluted milk, and a candle, placed about 1 metre from the eye ( = 39*37 inches), is looked at in a rather darkened room; if the flame of the candle is seen, the milk is poured back into the large measure; more milk is added to it, and it is poured again into the parallel glass, and the light is again looked at; the experiment ends when the contour of the light is completely obscured. The candle should be a good one, but the difference in the amount of light is not material. The percentage amount of fat in the milk is then calculated by the following formula (which has been determined by a comparison of the results of the instrument, and of chemical analysis): x being the quantity of fat sought, and m the number of c.c. of milk which, added to the 100 c.c. of water, suffice to obscure the light. m Example.—Say 3 c.c. of milk, added to 100 of water, were sufficient to obscure the light, the percentage of fat is— 23 '2 x = —r- +0-23 = 7-96 per cent. Several investigators have, from time to time, proposed formulae by Avhich, when any two of the data, specific gravity, fat, and total solids, are known, the third can be calculated. At times these formulas are very serviceable. That of Hehner and Richmond is the best, and is now very extensively used, being based on an extensive range of observation and perfect processes of fat extraction. The formula is as follows :— F = 0*859 T-0*2186 G, in which F is the fat, T the total solids, and G is the specific gravity. This formula does well for ordinary milks, but in the case of poor skim milks, it has been found necessary to modify it as follows :— F = 0*859 T - 0*2186 G - 0*05 (^ - 2*5~). This correction is only to be applied when G, divided by T, exceeds 2*5. ESTIMATION OF LACTOSE. 313 In these formula?, G represents the last tAvo units of the specific gravity and any decimal. Thus, if the observed gravity be 1029*7, G Avill be 29*7. Example.—Applying the formula, in the case of a milk whose specific gravity is 1029 -5, and whose total solids are 12-5, we find the fats to be 4'28 per cent. So, in the case of a poor milk Avhose specific gravity is 1032, and total solids 9'77, the fats per cent, are found to be but 1*36. A ready means of applying this formula is afforded by the use of Richmond's slide rule. This has three scales, two of which, for total solids and fat respectively, are marked on the body of the rule, while that for the specific gravity is placed on the sliding portion. The divisions of the scales are arranged as folloAvs :—On the total solids scale, 1 inch is divided into tenths; on the fat scale, P164 inch is divided into tenths; Avhile on the specific gravity scale, 0'254 inch is divided into halves. To use the rule, adjust the figure of the observed specific gravity to that of the total solids found, Avhen the arrow point will indicate the percentage of fat; or, if the fat be knoAvn, then by adjusting the arrow point to the graduation corresponding to the fat found, the figure for the specific gravity will coincide Avith that for the total solids. This slide rule does not allow for the correction for poor skim milks, but the error from this cause does not exceed 0*08 per cent., and may be practically disregarded. For cases in which the fat and specific gravity are knoAvn, Richmond has recently proposed the folloAving new formula for calculating the total solids :—T = —-—. This simple formula is correct within 0*2 per cent, up to 6 per cent, of fat. It is still more accurate if 0*05 per cent, be added for each 1 per cent, above 3 per cent., and subtracted for each 1 per cent. below 3 per cent. A milk scale to express the same relation may be con- structed on which 1 per cent, total solids =1 inch, 1 per cent, fat =1*2 inch, or 5 per cent. = 6 inches, and 1 degree of gravity = ^ inch ; if the zero on the fat scale be placed on a hne with 5 per cent, on the total solids scale, the arroAv Avill be in its correct position, or 0*14 inch below 20 degrees on the specific gravity scale. Casein.—Take a Aveighed or measured quantity of milk; add two or three drops of acetic acid, and bod. Add a good deal of Avater; allow to stand for tAventy-four hours; pour off the supernatant fluid; wash the precipitate Avell with ether at 80° F.; dry and Aveigh. Calculate the per- centage as casein; it is difficult to free it entirely from fat. Wanklyn recommends the albuminoid ammonia process, as in the case of nitrogenous matter in water, one part of casein yielding 0*065 of ammonia. This determination is not often required. The serum-albumin may be estimated in the whey after clotting a measured quantity of mdk by rennet. A measured amount of the filtered whey is precipitated by excess of alcohol, the precipitate collected, washed Avith ether and alcohol, dried and weighed. Lactose may be determined either by means of a saccharometer, or by a standard solution of copper. Of the various kinds of saccharometer, the so-called half-shadow instru- ments are the most satisfactory. They are so arranged, by the use of a semi-circle of thin quartz, that the field is divided into semi-circles which are equally illuminated when the instrument registers zero. On the introduc- tion of a tube carrying the sugar solution, the illumination becomes unequal, and the angular rotation of the analyser which is required to restore the original condition, measures the rotation Avhich has been caused by the sugar. 314 FOOD. In the various transition tint saccharometers, as Avell as in Schmidt and Haensch's latest form of half-shadow instrument, the graduated scale does not directly give measurements in angular degrees, but expresses a percent- age of sugar directly in terms of cane-sugar. The optical acthdty of a sugar is variously expressed according to the source of light used. In the literature upon this subject, Ave find the activity expressed as [a]D, [a]j, &c When a sodium flame, or a Bunsen burner in the middle of which is a pellet of sodium held on a platinum wire, is the source of light employed, it is indicated by [a]D, while the symbol [a]j represents light from a candle or strong gas flame; this is sometimes called the yellow ray. When it is necessary to determine optical activities for rays of other refrangibility, say for the lithium or thallium flame, it is only necessary to colour the Bunsen flame Avith these metals in the same way as in the case of sodium above. The readings are then [a]Li and [a]Th. In the Soleil-Duboscq saccharometer the scale is so constructed that the 100 point is recorded by a solution of cane-sugar in a 200 mm. tube con- taining 16*35 grammes of pure cane-sugar per 100 c.c; consequently, each degree of the scale represents 0*1635 gramme of cane-sugar per 100 c.c. According to O'SuUivan, 100 divisions of this instrument correspond to 24° angular rotation for the mean yelloAV ray; hence one division of this scale equals 0*24 angular degree ray j or [a]j# In the Soleil-Ventzke-Scheibler saccharometer, and in Schmidt and Haensch's modification of it, the scale is so constructed that the 100 point is recorded by a solution in a 200 mm. tube containing 26*048 grammes of pure cane-sugar per 100 c.c; consequently, each division of the scales on these instruments represent 0*26048 gramme of cane-sugar per 100 c.c. Taking the value of [a]j for cane-sugar as 73°*8, 100 divisions of the Ventzke scale are equal to 38°-4 [al; that is to say, that a solution con- taining 26*048 grammes of cane-sugar per 100 c.c, and which produces a rotation of 100 divisions on the Ventzke scale, would record on instruments having angular graduation a rotation for the same ray through an angle of 38°*4; hence one division of the A'entzke scale equals 0°*384 angular measurement. When the degrees of angular rotation produced by a solution of a knoAvn sugar are known or determined, the percentage composition of that solution 100a equals----,> where a equals the observed angular deviation, and r is the specific rotation of the sugar, while I is the length of the tube in decimetres. Conversely, the specific rotatory power or r equals ----j, where the other symbols being as before, c is the strength of solution employed. Therefore, in order to calculate the specific rotatory power from observations made with either the Soleil-Duboscq or Soleil-Ventzke-Scheibler and Haensch instruments, the equations stand [a]j = -7^7, and [a]j = • respectively. From the foregoing data, and by experimental observation, the following table has been constructed :— USE OF THE SACCHAROMETEIi. 315 Scale divisions on a S.-V.-S. or S. and H. Rotatory Power [a], at 15° ■5 C of various Sugars. Saccharometer corre- + equals right. - equals left sponding to a one per cent, solution of the sugar. Dextrin, ..... + 222°-0 + 11-53 Cane-sugar, .... + 73°-8 + 3-84 Lactose, ..... + 61°-5 + 3-20 Maltose,..... + 155°*0 + 8-05 Dextrose, ..... + 59°-0 + 3-07 Lsevulose, ..... -106°-5 - 5*54 Invert-sugar, .... - 23°-75 - 1-24 In order to facilitate calculations of percentages of various sugars by those using either a Soleil-Ventzke-Scheibler, or Schmidt and Haensch's saccharometer, the following factors may be used, and by which scale divisions on those instruments may be multiplied, to obtain percentage statements of the particular sugars being examined. These factors are obvious deductions from the preceding statement. Kir d of Sugar. Saccharometer Factor. Dextrin, . 0-08C6 Cane-sugar, 0-2604 Maltose, . 0-1240 Dextrose, 0-3258 Lactose, . 0-3126 Lsevulose, 0-1805 Invert-sugar 0-8094 Before the estimation of lactose can be made in milk by means of the polarimeter or saccharometer, certain proteids which are always present in milk, and which possess a leftdianded rotation, must be removed as Avell as the fat. The most reliable method for ensuring this appears to be that recommended by Wiley, which is as follows :— The sp. gr. of the milk is first determined; if this should be 1026 (water =1000) or thereabouts, 60'5 c.c. of the milk are transferred to a 100 c.c. flask and 1 c.c. of mercuric nitrate solution, or 30 c.c of mercuric iodide solution (preferably the latter), added. The liquid in the flask is then made up to 102*4 c.c. with distilled water, Avell shaken up, filtered bright, and polarised in the 200 mm. tube of the saccharometer. The volume is made up to 102*4 c.c. because the precipitated albumin occupies a volume of about 2*4 c.c, so that the solution is really diluted to 100 c.c. Should the sp. gr. of the milk be 1030, 60 c.c. are taken instead of 60'5 c.c, and if the sp. gr. be 1034, 59-5 c.c. are taken. The room and milk should be at one constant temperature, and the polarisation taken at the same, about 15° C. being the best suited for the purpose, although a few degrees above or below will not appreciably affect the results. In the absence of mercuric nitrate or iodide solution, the proteids may be precipitated from the milk by means of acetic acid and heat as subsequently explained in the copper process for the estimation of lactose. Acetic acid 316 FOOD. is less preferable, as it often fails to remove all the albumins. The mercuric solutions are prepared as folloAvs :—Mercuric nitrate by dissolving mercury in double its weight of nitric acid (sp. gr. 1*42), then adding to the solution an equal volume of Avater. One c.c. of this reagent is sufficient to precipitate the proteids in 50 to 60 c.c. of milk. The mercuric iodide solution is made by taking potassium iodide 33*2 grammes, mercuric chloride 13*5 grammes, acetic acid (sp. gr. 1*04) 20 c.c, and Avater 640 c.c. Of this solution 30 c.c. are required for 50 to 60 c.c. of milk. The presence of mercury in the filtrate (Avhey) when these reagents are used is objectionable, as the filtrate can only be used for the single purpose of polarimetrical observations. To determine the lactose by the copper solution, Ave require a standard solution to be made by taking 34*64 grammes of pure copper sulphate and dissolving in 200 c.c. of distdled Avater. Take also 173 grammes of tartrate of sodium and potassium and dissolve in 480 c.c. of solution of caustic soda or potash. Mix the tAvo solutions slowly, and dilute AAdth distilled Avater to one litre. One c.c. of this solution is reduced by 5 milligrammes of either glucose or invert-sugar, and by 6*67 milligrammes of lactose. To estimate the milk-sugar by means of this solution, take 10 c.c. of milk, add a few drops of acetic acid, and Avarm—this coagulates the casein with the fat; then make up to 100 c.c. with distilled water, filter, and put the filtered whey (which ought to be as clear as possible) into a burette. Take 10 c.c. of standard copper solution, put it in a porcelain dish, and add 50 c.c. of distilled water; boil; as soon as it is in brisk ebullition drop in the whey from the burette ; take care that the liquid is boiling all the time; continue the process until the copper is all reduced to red suboxide and no blue colour remains in the supernatant liquid; but stop before any yehW colour appears. Read off the amount of whey used, and divide by 10; the result is the amount of milk which exactly decomposes 10 c.c. of the copper solution. The 10 c.c. of the copper solution are equal to 0*0667 gramme of lactose. The amount of lactose in the 10 c.c. of milk is then known by a simple rule of three; and the amount in 100 c.c. of milk is at once obtained by shifting the decimal point one figure to the right. Example.—-15 c.c. of diluted whey were required to reduce the 10 c.c. of copper solution; — = 1*5, the amount of original milk; 0 0667 + 1*5 = 0*0445 gramme of lactose in 1 c.c. ; therefore 0-0445 x 100 = 4'45 per cent. Microscopic and Bacteriological Examination of Milk.—It is always advisable to examine a milk sample microscopically. The only strictly normal constituents of milk are the round oil globules of various sizes in an envelope and a little epithelium. The abnormal constituents are epithelium in large amount, pus, conglomerate masses, and casts of the lacteal tubules. The added ingredients may be starch grains, portions of seeds, and chalk (round and often highly refracting bodies, Avith often a marked double out- line, and at once disappearing in acid). Colostrum, occurring for three to eight days after the birth of the calf, is composed of agglomerations of fat vesicles united by a granular matter. Milk from a healthy coav is secreted free from microbes; but micro-organ- isms ahvays find their Avay into the milk from the surface of the udder, from the hands of the mdker, from particles of dung, from the milk cans, or from the air of the cow sheds. The average number of micro-organisms found in samples of milk by us is not less than 400,000 per cubic centimetre. Other observers have given the number found in other milk supplies at an BACTERIOLOGICAL EXAMINATION OF MILK. 317 even higher figure, but it must be remembered that in any numerical examination the sources of error are very numerous. OAving to its peculiar composition, milk ahvays constitutes a favourable medium for various forms of microbes, Avhich multiply rapidly in it if the milk is not at once exposed to very Ioav temperatures. Repeated examinations have shown that the residues of milk in the excretory ducts of the udder are frequently rich in bacterial life, and that it is the earher portions of milk drawn off at a mdking which are the most common source of infection; for this reason, they should as a rule be rejected. The method of examination of milk is that customary for other liquids. Cover-glass preparations are readily prepared by placing the smeared and dried cover-glasses in a small capsule containing 5 c.c. of chloroform and 1 c.c of a saturated alcohohc solution of methylene blue. After five minutes, the chloroform is evaporated, the glasses rinsed in water and examined in the usual manner. Examination of the milk by cultivation is more important; on account of the great number of micro-organisms usually present, free dilution is necessary; of culture media, agar is perhaps the best for milk. The species commonly found in milk are: B. acidi lactici, B. butyricus, M. fluorescens liquefaciens, B. mesentericus vulgatus, B. subtilis, B. coli communis, and various indeterminate cocci. Blue milk contains B. cyanogenus ; red mdk the B. prodigiosus or Sarcina rosea; yellow milk the B. synxanthus of Fliigge ; Avhile the ropy and slimy milks contain special forms, the identity of which is as yet uncertain. In some bitter tasting milks, the Proteus vulgaris has been noted, associated with a coccus and a short thick bacillus Avhose species is unknown. The presence of the Oidium lactis, the Monilia Candida or Oidium albicans, and various other forms of fungi, may be also readdy detected in many samples of milk by plate cultures set from them in the usual manner. All these micro-organisms find their way into milk only during or after mdking. Under certain circumstances, pathogenic microbes may be present and even increase in milk. Mdk draAvn from diseased cows may contain various pathogenic forms, especially the bacilli of tuberculosis, or cocci which produce suppuration. The detection of the tubercle bacillus in mdk by direct culture therefrom is difficult; it is much more reliable to inject from 10 to 15 c.c of the suspected mdk, as fresh as possible, into the peritoneal cavity of a guinea- pig. After four weeks, the animal should be kdled, when, if the bacilli had been present, there is found the characteristic appearance of peritoneal tuberculosis. These facts regarding the general bacterial impurity of milk samples suggest the urgent need of reforms in connection with both the milking of cows and of the sale of mdk generally. The following suggestions have been formulated by a special commissioner of the British Medical Association, AA'hen reporting on the milk supply of London. They are sufficiently to the point as to merit adoption, not only in the metropolis but elsewhere. 1. "That all mdking be carried on in the open air, the animals and operators standing on a material which is capable of being thoroughly washed, such as a floor of concrete or cement. . Such a floor could be easily laid down in any convenient place which can be found. The site chosen should be removed from inhabited parts as far as possible, and should be provided Avith a plentiful water supply." 2. "That greater care be expended on the personal cleanliness of the cows. The only too familiar picture of the animal's hind quarters, flanks, and sides being thickly plastered with mud and faeces is one that should be common no longer. It would not be difficult to carry out this change; indeed, in the 318 FOOD. better managed of our large dairy companies' farms such a condition no longer prevails, but in the smaller farms it is but too frequently met with." 3. "That the hands of the milker be thoroughly washed before the opera- tion of milking is commenced, and that after once being washed they be not again employed in handling the cow otherAvise than in the necessary operation of milking. Any such handling should be succeeded by another Avashing in fresh Avater before again commencing to milk." 4. " That all milk vendors' shops should be kept far cleaner than is often the case at present. That all milk retailing shops should be compelled to provide proper storage accommodation, and that the counters, &c, should be tiled." Formation of an Opinion as to Adulteration of Milk.—It has already been indicated that the favourite sophistications of milk consist, on the one hand, of the more or less complete removal of the cream, and on the other, of the addition of water. If milk is deprived of a large part of its lightest constituents, the fat, it becomes specifically heavier, and a simple determina- tion of its specific gravity reveals the fraud. But if to a milk which, in spite of its fat, is still heavier than Avater on account of its dissolved sohds, water be added, its specific gravity will fall below the normal limits and thus betray the adulteration. It is, hoAvever, evident that simultaneous skim- ming and Avatering, if carried out under the guidance of the lactometer, may produce a spurious milk of the same specific gravity as the new or original milk. " Experienced milk sophisticators, hoAvever, have other methods more difficult to detect than this crude one of mere dilution. The introduction of cream separators has given them the opportunity of removing very cheaply and quickly almost the whole of the fat from milk, dividing the milk, in fact, into a cream much better than what is produced by ordinary skimming, and a skim milk, beside which ordinary ' skim' is rich indeed." " The sophisticator has thus the power of either separating his milk in a moderate degree, just taking from it what, from his point of view, is the ' excess' of cream; in other Avords, reducing its cream to the lowest saleable standard without exposing himself to any such risks of detection as Avould attend the process of 'Avatering,' a process by which the total non- fatty solids might be so reduced as to lead to detection of the fraud; or he may take off aU the cream, using the ' skim' to dilute or standardise other fresh milk; or he may sell the 'skim,' and leaving it to the retailer to produce, by judicious mixture of his two churns, any quality of milk Avhich the character of his district or the carelessness and indifference of his customers may appear to require ; or, finally, he may use the skim milk for making cheese, substituting a sufficiency of some other form of fat for the cream he has abstracted." If carried out judiciously, and kept within the limits imposed by the standard Avhich the magistrates will accept, it is next to impossible to prove this form of sophistication, except one discover the source of the milk, and have an opportunity of milking the coavs from which the suspected milk is stated to have been draAvn. Given these circumstances, it is possible to be morally certain that a fraud has been committed. Speaking of this difficulty of detecting watered and skimmed milk, the Report of the Local Government Board for 1892-93 says: "No doubt the chief obstacle in the way of further progress in this matter is to be found in the fact that, in the present state of science, analysis fails to distinguish between OPINION AS TO ADULTERATION OF MILK. 319 the Avater Avhich is a natural constituent of all milk and that which has been added by the dairyman, and therefore an analyst hesitates to condemn a sample of exceedingly poor milk because it may possibly be the genuine product of an old and ill-fed coav, although it has much more probably received an addition of water. He appreciates the fact that the Acts are intended to prevent the sale not of articles of poor quality, but of those Avhich have been fraudulently tampered with; and it Avould not be in accordance Avith their design that a poor man should be subjected to penal proceedings because his coav does not produce as good milk as the better- bred and better-fed herd of his richer neighbours. It is the border cases Avhich create the main difficulty." The case for the owners of poor pastures and the breeders of weedy cows could not be better put. On the other hand, Avriting on the same subject, Hehner observes as follows: " OAving to the natural variation in the composition of milk, the public analyst is bound to pass as genuine all milks Avhich are at least equal in composition to the poorest genuine milk yet found, although in the great majority of cases thus passed, he has to do with milk artificially and not naturally weak," shoAving Iioav this interpretation of the statute tends to degrade the average supply to the level of the loAvest knoAvn milk. Watering involves the risk that organisms pathogenic to man may pass into the milk with the water and even multiply there. In comparison with watering and skimming all other methods of sophistication are rare in the present day, though, formerly, the addition of chalk, milk of lime, gum, starch, and sugar Avere not infrequent. As regards the removal of cream, an important distinction must be made between removal by a centrifugal separator and removal by skimming. The former method, beyond reducing the nutritive value of the milk, adds no further dis- advantage, as the creaming is effected rapidly, and the milk remains fresh. The other method, or skimming, is slow, and not only deprives the milk of its cream, but also involves the changing of the hquid from the category of ■a fresh to that of a more or less sour milk. Watering alone is detected by a loAver specific gravity and a diminished quantity of cream. Creaming alone is detected by a heightened specific gravity and a diminished quantity of cream. When both are resorted to, the cream Avill be small in amount, but the specific gravity may be normal. When a quantitative analysis can be made, watering alone is indicated by a general lowering of the constituents, Avhich, however, preserve their normal proportions to each other. Creaming alone is indicated by a lessened amount of fat, but a normal amount of everything else, except total solids. Creaming and Avatering may be known by a general loAvering of all con- stituents, but the deficiency in fat will be most marked. The decision as to the addition of water and the removal of cream from milk is notoriously difficult, chiefly owing to the want of knowledge as to what was the original composition of the milk from Avhich the sample was taken. To meet this difficulty, and to prevent adulteration, many efforts have been made to establish a minimum for the composition of normal milk. Standards, proposed some years back, requiring a high proportion of non- fatty solids, were based upon analyses by methods which failed to com- pletely extract all the fat. Since improved methods of analysis have been adopted, it is now generally accepted that the minimum standards for milk should be:—Fat 2*75 per cent., sohds not fat 8*5 per cent., and ash 0*7 per cent. Assuming that the ash of a normal milk is never less than 0*7 per cent., the amount of added water can be calculated as follows:— 320 FOOD. Example.—Let a be the observed percentage of ash in a given sample of milk, and A be the normal amount; then 100---— =per cent, of water added. If a = 0*5, and A = 0*7 then 100-----^— =28-6 per cent, of water added to the sample. In a similar Avay the amount of " solids not fat" may be used as a. standard, taking them to be not less than 8*5 per cent. Example.—Thus, say the total solids found in a milk sample are 12*1 per cent., and the fat is found to be 4*1 per cent. ; obviously the solids not fat are 8 per cent. Then ——— =94*1 per cent, of the sample is pure milk, or there has been nearly 6 per cent. of water added. Lescoeur has suggested a means of detecting a watered milk and one from which cream has been abstracted by an examination of the milk serum. Coagulation of the milk is readily brought about by adding a trace of rennet, and the serum then separated by filtration. The density of milk serum thus obtained varies from 1-029 to 1*031 at 15° C. In some samples it has been found as low as 1*027, and this may be taken as the minimum limit. The extract of this milk serum should be determined also. The amount varies from 6*7 to 7*2 per cent., the mean being 7 per cent, and the mini- mum 6*7 per cent. Every milk sample, therefore, Avhich yields a serum having a density lower than 1*027, and the extract of which does not amount to 6*7 per cent., may be looked upon Avith suspicion, and regarded as having been watered. The following figures shoAV the effect of added Avater on the serum of a pure milk:— Density Dry extract at 15° C per cent. 1*0300 7-0 1-0275 6-4 1-0251 5-9 1-0230 5-5 Pure milk,...... ,, ,, +10 per cent, of water, „ „ +20 „ „ . . „ „ +30 „ ,, . In mdk which has curdled naturally, the serum, in spite of its different composition, gives almost the same results as does the neutral serum prepared by rennet. Hence no modification of this method is necessary for curdled milk. Starch, dextrin, or gum is at times added to milk to conceal the thinness and bluish colour produced by added water. Add iodine at once for starch; bod with a drop of acetic acid, and add iodine for dextrin, or add lead acetate and then ammonia, when a white precipitate falls. Cane-sugar.—This carbo-hydrate is not a common addition to milk, being only usually met with in samples of preserved and concentrated milks. The diagnosis of a mdk adulterated with cane-sugar depends upon : (1) .Any considerable want of agreement between the results from the copper process and the polarimeter. (2) Any considerable rise in the amount of copper reduced, or any increase of rotating power after inversion of the sugar in the whey, by means of citric acid and heat, or by invertase, which reagents only affect the cane-sugar and not the lactose. (3) The separation and preparation of the osazone from Lie whey by means of sodic acetate and phenyl-hydrazin hydrochlorate. Lactosazone is alone obtained by treat- ment Avith phenyl-hydrazin; cane-sugar giving no osazone until inverted, it DETECTION OF MILK SOPHISTICATIONS. 321 then gives an osazone not to be distinguished from glucosazone. Lactosa- zone is freely soluble in hot alcohol, and none separates on cooling, unless the solution be highly concentrated. On the other hand, glucosazone requires repeated boiling in considerable quantities of absolute alcohol before it dissolves. Lactosazone is warty or starch-like in appearance, whereas glucosazone is always in the form of needle crystals. Glycerin has been sometimes met Avith. The milk will be sweeter than usual, and there wdl be a difficulty if not impossibility in drying the solids by evaporation. . Chalk, to neutralise acid, and to give thickness and colour. Let it stand for deposit; collect and wash deposit, then add acetic acid and water; after effervescence, filter, and test with oxalate of ammonium. Sodium Carbonate.—Very difficult of detection unless the milk be alka- line. Determine the ash, and see if it effervesces; if so, either some carbonate has been added, or, if the sodium have united with lactic acid, this will be converted into carbonate; enough lactic acid to give an effer- vescing ash does not exist normally in good milk. Salt has been found added to milk in a case at Glasgow, to the extent of 0*14 to 0*21 per cent., equal to 98 and 147 grains per gallon. This will be detected by the excess of ash which may be dissolved and the chlorine determined in the usual way. Milk is often boiled to preserve it: it may then take up from the vessel lead, copper, or zinc, if these metals are used. Cream is adulterated or made up with magnesium carbonate, tragacanth, and arrowroot. The microscope detects the latter, and particles of magne- sium carbonate (round) can also be seen, and found to disappear with a drop of acid. It is also said that yolk of egg is added both to cream and milk. Boracic acid may be detected as follows :—The milk should be first well shaken up, as calcium borate is liable to settle; 5 or 6 c.c. are then taken and evaporated in a flat dish to about one-third. A few drops (5 or 6) of strong HC1 are added and the evaporation is continued, whilst the flame of a Bunsen burner is directed across the dish. If any appreciable quantity of boron is present, the flame will be tinged green. Salicylic acid is shown by the deep purple colour produced on the addition of solution of ferric chloride. The constant addition to milk in the present day of formalin, which is a 40 per cent, solution of formaldehyde, as a preservative agent demands a short reference. The formalin used in the trade for preserving milk is a solution of 5 ounces of pure formalin to one gallon of water, corresponding to 2 ounces of formaldehyde in 160 ounces, or 1 in 80. This is used in the proportion of half a pint to the churn of 17 gallons, and does not impart any taste or smell to the milk even after boihng. With the addition of formalin in this strength, the mdk keeps fresh for at least three days, and corresponds to one part of formaldehyde in 21,760 parts of milk, or 1 cubic centimetre of formalin in 8,704 cubic centimetres of milk. One gallon of the diluted formalin as used by the milk vendors does the same work as 10 pounds of the preservative powder, also used by them, containing 75 per cent, of boric acid and 25 per cent, of borax. Though there is no evidence to show that formalin is in any way injurious to health, it is important to bear in mind that the addition of formalin to milk frequently causes an increase in the amount of total solids as subsequently determined on analysis. This effect appears to be due partly to polymerisation of the aldehyde, and conversion into a non-volatile body, and partly to a conversion of the lactose into galactose. X 322 FOOD. The detection of formalin in milk is conveniently made in the following manner. A solution of diphenylamine in water is made, just sufficient sulphuric acid being added as will effect solution. The liquid to be tested (or, if preferred, a distdlate of the mdk) is added to this solution and boiled. In the presence of formaldehyde a white flocculent precipitate is deposited, which is often coloured green, if the acid used contain nitrates. It is usually more convenient to distd the mdk sample over into the diphenyl- amine solution, and then to boil. Tyrotoxicon.—For the detection of this poisonous body, the folloAving procedure is suggested. Add to the milk sodium carbonate to decided alka- linity ; shake up with an equal bulk of ether; separate the ethereal layer and allow it to evaporate; dissolve in water; filter, and evaporate the filtrate. A mixture of equal bulks of pure phenol and sulphuric acid strikes an orange-red or purple colour with very small traces of tyrotoxicon. BUTTER. As an article of diet, butter supplies to most people the largest amount of fat which they take. Many persons take from 1\ to 2 ounces daily, if the butter used in cooking be included, and the average amount for persons in easy circumstances is 1 ounce daily. Butter appears to be easily digested by most persons, except when it is becoming rancid. It then causes dyspepsia and diarrhoea, but as a rule it may be said that decomposing fats of all kinds disagree. Composition.—Butter is really the fat of milk clotted together, and consists chiefly of neutral fats mixed with water and small amounts of casein and salts. Average butter may be said to have the following composition per cent. : Fat, 78 to 94; curd, 1 to 3; water, 8 to 12 ; salt, 0 to 7. The flavour of a good butter is due to butyric and caproic acids, which constitute about 8 per cent, of the fat, the rest being composed of glycerides of oleic, stearic, and palmitic acids. Water.—The average amount of water varies from 8 to 12 per cent., but may be higher, even in genuine butter, although this is not usual. Hassall has found as much as 15| per cent, in fresh, and 28^ per cent, in salt butter. Bell records as much as 20*75 per cent, of water in a genuine sample; there was, however, 3*82 of salt present. The retail dealer, by beating up the butter in water, endeavours to increase the amount. This can be detected by evaporation in a water bath; if the quantity of water be very large, melting the butter will show a little water below the oil. An unusuaUy small amount of water is suspicious, as suggestive of the presence of foreign fat. A good butter should not contain more than 12 per cent, of water. Curd or Casein.—All butter contains some casein, as some mdk is taken up with the cream. The best butter contains least. The amount can be told roughly by melting the butter in a test-tube. The casein collecting in the bottom does not exceed one-third of the height of the contents of the tube in the best butter, or between one-third and one-half in fair butter. In bad butter it may reach to more than this. A better plan is dissolving the fat by ether, washing and then weighing the remainder; the casein then weighs from 0*5 to 3 grains in every 100 of very good butter. In bad butter it is much more than this. The rancidity of butter is owing chiefly to changes in the fat, produced ADULTERATIONS OF BUTTER. 323 apparently by alterations in the casein, and therefore the greater amount of casein the more the chance of rancidity. Fat.—The fat amounts to from 84 to 90 per cent, of the butter. Butter oil consists of volatile fatty acids (butyric, caproic, caprylic, and capric) and of non-volatde acids (stearic, palmitic, and oleic), all combined with •glycerin. In examining it, the butter should be melted in a beaker-glass placed in hot Avater, and the fat then poured from off the casein, and allowed to cool. It then forms a solid and usually yellow mass, with the •characteristic smell of butter. If transferred, when in a melted state, to a previously weighed beaker and then re-Aveighed, its percentage amount is readily calculated. Salt is added to all butter. It preserves it by checking the decom- position of the casein. In fresh butter it should not be more than 0*5 to 2 per cent. (2 to 8 grains per ounce); in salt butter, not more than 8 per cent. <(35 grains per ounce). To determine the salt, wash a weighed portion of butter thoroughly Avith cold distilled water, and determine the chloride of ■sodium Avith standard nitrate of silver. An excess of salt is accompanied generally by an excess of water, and frequently by an excess of curd. Adulterations.—Butter is frequently adulterated with lard, and with beef, mutton, and horse fat, or Avith vegetable oils. In a process devised by Mege- Mouries, fresh beef suet is converted into a kind of butter (oleo-margarine). But the original process was so complicated that it would not pay a dis- honest tradesman to do it, and it could only be practised on a large scale. A similar substance from ISlew York was brought into the market under the name of Butterine. Oleo-margarine used to be generally defined as a preparation of animal fats, whereas animal fat beaten up with milk was ■called Butterine. Large quantities are manufactured in Holland and other •countries and sent over to this country. It appears to be a wholesome fat, and as long as it is sold honestly as a substitute for butter, but not as genuine butter, its introduction constitutes a boon to many on account of its ■cheapness. The Act of 1887 has now decided that the name Butterine .shall be no longer used, and that all artificial butter shall be known as Margarine. In the United States it is termed oleo-margarine. Butter is sometimes adulterated by beating up with water: this is frequent in the tropics. It is also sometimes mixed with milk. Potato or other starches are sometimes added. This is a rare adulteration, and is detected by iodine, either at once or after melting. Gypsum and sulphate of barium have been added, it is said; this must be very rare, and can be detected by melting and pouring everything off the insoluble powder, or by incinerat- ing. Annatto is frequently used to colour butter; it is, however, harmless. Examination of Butter.—As practically the only adulteration of butter is the substitution of foreign fats such as tallow, lard, palm oil, rape-seed oil, or cocoa-nut oil, for milk fat, the examination of butter turns mainly upon the properties and composition of the fat. For the detection of an admixture of foreign fats, several methods have been proposed, the principal being: (1) taking the specific gravity of the fat; (2) determining the melting point of the fat, after separation from the other constituents; (3) •determination of the fixed fatty acids; (4) determination of the volatile fatty acids. The specific gravity of the butter fat can be determined by melting it at 100° F., and then weighing in a specific gravity bottle. That of water being -unity, a pure butter fat has usually a specific gravity of 0*911 to 0*913; an adulterated butter one of 0*902 to 0*904, and an artificial butter one as low as 0*859 to 0*861. 324 FOOD. Determination of the melting point of butter fat after separation from the casein.—Some of the fat should be put into a Avide tube, and placed in an evaporating dish with water; a thermometer should be in the water and another in the fat. Raise the temperature of the water very gradually ; remove the lamp from time to time, so that the temperature of the fat may rise slowly. Note the temperature when it begins to melt; when it is completely melted; and when (after removal from the warm Avater) it begins to recongeal, and becomes quite solid. The melting points are, however, not constant, owing to the variable amounts of stearin and olein and the volatile fatty acids, but still they run within tolerably narrow limits. Butter fat is the most easily melted, and requires the greatest amount of cooling before solidifying; usually there is a difference, often 12° to 15°, between the points of commencing and completed melting. The determination of the melting point is, however, certainly more useful in proving that the butter has only slight admixture, than in proving com- plete purity, i.e., the presence of a small quantity of lard or beef dripping: would not raise the melting point sufficiently for detection. In the case of beef dripping, also, the melting point is rather close to that of butter. Temperature of Melting and Solidifying (Degrees Fahr.). Melting. Solidification. Commencing. Completed. Commencing. Completed. Butter fat, . Lard, .... Beef dripping, Mutton dripping, . Palm oil, Degrees. 65-68 76-80 68-85 86-100 81-92 Degrees. 80-90 100-115 100-120 140-150 110 Degrees. 70-80 90-100 90-100 120-130 88 Degrees. 60-82 71-75 72-76 86-92 69 Determination of the fixed fatty acids.—This, though rather a difficult process to do, is most generally relied upon for giving an opinion as to the genuineness of butter. It is based on the fact that, when saponified Avith a caustic alkali such as soda or potash, and then decomposed with hydrochloric acid, the individual fatty acids which go to make up butter are obtained. A certain number of these are soluble in water Avhile others are not, and it is owing to the insoluble fatty acids obtainable from butter differing in amount from those obtainable from other animal fats that pure butter can be detected from artificial. The figures being, that if the insoluble fatty acids are over 89 per cent, there is an admixture of foreign fat. In a good butter the volatile fatty acids should not fall below 5 per cent. The process may be thus carried out. Melt some of the butter in a test-tube or small beaker over a water bath, and allow the water and solid particles to subside as much as possible ; then pour the melted fat upon a dry filter, care being- taken to keep the aqueous solution in the tube or beaker, so as not to con- taminate the fat. A double funnel, one with a warm water jacket, is very convenient in order to keep the fat in a state of fusion. After filtering the fat through into a beaker, allow to cool and Aveigh. Next take out, with a glass rod, 3 or 4 grammes of the fat and put it into a large deep and perfectly dry porcelain evaporating dish. Noav re-weigh the beaker and the fat left in it; the loss in weight will represent the amount of butter fat about to be operated upon. The fat which Avas placed in the evaporating DETERMINATION OF FIXED FATTY ACIDS IN BUTTER. 325 dish is iioav melted on a Avater bath, and about 50 to 70 c.c. of pure methy- lated spirit or absolute alcohol added. A clear yellow solution is formed. Now add from 1 to 2 grammes of caustic soda or potash, or 5 c.c. of a saturated solution of these alkalies in alcohol; agitate by means of the glass rod, heating all the Avhile, but taking care not to heat to boiling point, as loss by spurting would be inevitable. Saponification proceeds rapidly, and is, in the case of butter fat, evinced by the strong smell of butyric ether, resembhng the odour of pine-apples. After 2 or 3 minutes, add a feAv drops of distilled Avater : if turbidity, caused by undecomposed fat, ensues, continue the heating a little longer, the turbidity usually dissolving in the excess of alcohol. Keep on adding small quantities of Avater from time to time, until a considerable addition of it to the solution of soap no longer causes any precipitate of fat. Saponifica- tion is complete when any amount of dilution does not affect the trans- parency of the liquid. Should it happen that the water has been added too quickly, fat separates in the form of oily droplets, Avhich uoav no longer dissolve in the too dilute alcohol. In this case, an additional quantity of alcohol may effect the solution, but it is preferable to begin the experiment afresh with a new quantity of butter fat. The alcoholic solution of soap is continuously heated over the water bath until all smell of alcohol has passed off; if all the alcohol is not removed some of the fatty acids still remain in solution. When this has been done, the dish is nearly filled with water, in which the gelatinous soap, which has separated out on evaporating the hquid, readily dissolves. Dilute hydrochloric acid is now added, until strong acid reaction results, to liberate the fatty acids. These rise quickly to the surface as a Avhite or creamy scum, with the evolution of a strong and disagreeable smell of butyric acid. The separated fatty acids are heated for half an hour on the water bath, until they are perfectly fused into a clear oil, and the acid liquid below is also clear. Care should be taken that the water does not evaporate much. Meanwhile, dry and weigh a filter of about five inches in diameter. Moisten the filter and fill the jacket with boiling AA'ater ; then transfer every trace of oil from the dish and glass rod to the filter. Carefully wash out all the fatty acids from the dish to the filter by means of boiling water, and continue Avashing the filter well, until the filtrate gives no reaction with litmus paper. Usually about a litre of Avater is required. After all the water has run through the filter, the funnel in which it has been is emptied of its contained hot water, and the whole plunged into a beaker filled Avith ■cold water, so that the levels of the fat inside and the water outside the funnel are the same. "When the fatty acids are quite solidified, the filter is -carefully taken out of the funnel, placed in a small weighed beaker and dried for two hours. It is now re-Aveighed, and the amount of insoluble fatty acids calculated as a percentage of the butter fat. Example.— The following may be taken as an illustration of this determination :— Beaker and butter fat, Beaker, Butter fat taken, Filter, Beaker, Beaker and filter, Beaker, filter, and fatty acids, Insoluble fatty acids, . 40-4337 grammes. 37-1506 3-2831 0-5830 20-9967 21-5797 24-4505 2-8708 or 87*42 per cent. of the butter fat. 326 FOOD. The percentage of insoluble fatty acids in butter fat, made from the milk of cows of the most varied breed, varies usually between 86*6 and 87*5, though in some rare instances it falls as low as 86*3, and rises as high as 88*5 per cent. A fair average is represented by the figure 87*3 per cent. All other animal fats furnish, on an average, 95*3 per cent, of insoluble fatty acids, or, in other words, there is a standard difference of 8 between the percentage of insoluble fatty acids in normal butter fat and that in other animal fats. From the percentage of the insoluble fatty acids found, it is, therefore, easy to draw conclusions as to the genuineness or otherwise of any given sample of butter. If the quantity of insoluble fatty acid be lower than 88 per cent., the butter must be declared genuine; if, however, the fatty acids are higher than 88*5 per cent., we may conclude that adulteration with foreign fat has taken place. This statement will be perhaps clearer if apphed to an actual example. Example.—Say a sample of butter has been examined, and found to have the following percentage composition :—"Water 12, Curd 1*5, Salts 2, Fat 84*5. The fixed or insoluble fatty acids have been estimated, by the foregoing method, and found to constitute 92*3 per cent, of the butter fat. Assuming that there is a standard difference of 8 per cent. between the fixed fatty acids yielded by a pure butter fat, and that in foreign or other animal fats ; and taking the observed difference between the fatty acids found in the sample and that yielded by pure butter fat to be 5, or 92*3 - 87*3 = 5, we get the following equation to represent the percentage of foreign fat, or adulteration, in the sample. As the constant difference, between the fixed fatty acids in normal butter and that in foreign fat is to the observed difference, between the fatty acids found in the sample and those yielded by pure butter fat, so is the percentage of fat in the sample to the percentage of foreign fat in the sample ; or, 8 : 5 : : 84*5 : x, which equals 52*81 parts of foreign fat in 100 parts of the sample, that is, there is but 31*69 per cent, of true butter fat in the- sample. Determination of the Volatile Fatty Acids.—As an alternative to the foregoing determination, the following process, originally proposed by Reichert, and modified by Meissl and Wollny, affords a fairly reliable method of butter analysis. It is carried out as follows :— Five grammes of the clear filtered butter fat are saponified on a water bath in a flask, capable of holding 300 to 350 c.c, with 10 c.c. of a solution of pure caustic potash in 70 per cent, alcohol (20 grammes KHO in 100 c.c. alcohol). When the fat has completely dissolved, the alcohol is driven off slowly by gentle evaporation. The soap is then dissolved in 100 c.c. of Avater, decomposed with 40 c.c. of dilute sulphuric acid (1 in 10), and HO1 c.c. distilled off, a few small pieces of pumice stone having been added. 100 c.c. of this distillate are filtered and titrated with deci-normal alkali, rosolic acid or phenolphthalein being used as an indicator. The number of c.c. used is increased by -^ corresponding to the total quantity of the distdlate. The tAvo chief sources of error in this method are a loss of butyric ether, and a gain by absorption of carbonic acid, hence it is advis- able to carry out the saponification under a reflux condenser, and both distil off the alcohol and dissolve the soap in water in a closed flask. Five grammes of genuine butter yield a distillate requiring from 28 to 31 c.c. of deci-normal alkali. Simdar amounts of artificial butters, such as margarine, yield distillates requiring less than 1 c.c. of the alkali, and various butter mixtures demand intermediate quantities. CHEESE. 327 CHEESE. This is made from milk by the action of rennet, and consists of coagulated casein, with varying proportions of fat and salts. The different qualities of cheese depend mainly upon whether they are made from pure milk, from skimmed milk, or from a mixture of skim and whole milk. Thus, Cheddar, double Gloucester, Cheshire, and some American cheeses are made from whole milk, Avhile Stilton is made from Avhole milk to which cream is added. Dutch, Parmesan, Suffolk, and Somersetshire cheeses are made from skimmed milk. Cream cheese consists of the fresh curd which has been moderately pressed ; it is eaten without being alloAved to ripen. When a cheese is kept, it undergoes a change knoAvn as "ripening," which is essentially a decom- position, whereby the casein undergoes a fatty change, including the formation of lime salts of the fatty acids and the production of a soluble compound of phosphoric acid with casein, from the phosphate of lime usually present in milk. As an article of diet, cheese is very valuable, being particularly rich in both proteid and fat: about -J- K> contains as much proteid as 1 lb of meat, and ^ lb as much fat. It does not, hoAvever, keep well in warm climates, and is occasionally very indigestible. The percentage composition of some of the more common varieties is as follows :— Water. Proteids. Fat. Free Acid as Lactic Acid. Salts. Cheddar, Cheshire, Single Gloucester, Dutch, . American Red, Gorgonzola, Gruyere, Roquefort, Camembert, . 35-60 37-11 35-75 41-30 28-63 32-50 32-00 26-50 51-90 28-16 26-93 31-10 28-25 29-64 32-80 35*10 32-90 18*90 31*57 30-68 28*35 22-78 38-24 31-20 28*00 32-30 21-00 0-45 0-86 0-31 0-57 4-22 4-42 4-49 7-10 3-49 3-50 4-80 4-40 4-70 The quality is known by the taste. The only adulteration is from sub- stances added to give weight. Starch is chiefly employed, and can be detected by iodine. There is usually about 5 or 6 per cent, of salt. Sulphate of copper and arsenious acid are sometimes used to destroy insects; the rind is then the most poisonous part. Copper is detected by ammonia or potassium ferrocyanide. Arsenic by any test (Reinsch's or Marsh's). Sometimes cheese becomes sour, particularly if made from sheep's milk, and may cause diarrhoea. The occasional production of the ptomaine tyrotoxicon should be remembered when poisonous symptoms arise. Acarus domesticus, Aspergillus glaucus (blue and green mould), and Sporendonema casei (red mould) occur during decay. During decay, also, the fat augments at the expense of the casein; leucin is produced, with valerianic and butyric acids. Lactic acid is also often produced, from the lactose of the milk contained in the cheese. The aroma of cheese partly arises from this decomposition, and the production of volatile acids. The maggots or larva? of a fly (Piophila casei) are well knoAvn, and are frequently present in cheese undergoing decomposition. 328 FOOD. WHEAT. As an article of diet, wheat is poor in Avater but rich in solids, therefore very nutritious in small bulk : the whole grain is somewhat indigestible, but when its outer coats are removed, is readily digested. The proteids in Avheat are large and varied, consisting chiefly of a globulin and an albumose Avhich, under the action of water, give rise to what is knoAvn as glutin. Whether all the globulin and albumose is transformed into glutin is un- certain, but the weight of evidence is in favour of the view that some escapes in a soluble form. The starchy substances are large, 60 to 70 per cent., are very digestible, and consist mainly of starch, sugar and dextrin. A nitrogenous ferment, called cerealin, is also contained in Avheat, being closely associated with the internal coat of the grain. This body, like diastase, acts energetically in transforming starch into dextrin, sugar and even lactic acid. There is also present a small amount of fat, while the salts are chiefly phosphates of potash and magnesia. The chief defect in wheat, as an article of diet, is its poverty in fats and in vegetable salts Avhich may form carbonates in the system. The average percentage composition of a wheat grain is as folloAvs :— Water, Proteids, . Fat, . Carbo-hydrate, Cellulose, . Ash, . . 13*37 . 1204 ' fio.gt f Phosphates of Potash, Magnesia, and Lime. ' . | Iron. * f.^ I Soda. * x /8j Chlorine. Silica. I Carbonic acid. As usually prepared, the grain is separated into flour and bran; the mean being 80 parts of flour, 16 of bran, and 4 of loss. The flour is itself divided into best or superfine, seconds or middlings, pollards or thirds or bran flour. In different districts different names are used. The wheats of commerce are named from colour or consistence (hard or soft, white or red); the hard wheat contains less water, less starch, and more glutin than the soft wheat. The medical officer will seldom be called on to examine wheat grains, but if so, the following points should be attended to. The grains should be well filled out, of not too dark a colour; the furrow should not be too deep; there should be no smell, no discoloration, and no evidence of insects or fungi. The heavier the Aveight the better. In examining wheat, or any other cereal grains, it is necessary to prepare them beforehand by soaking for some time in water. It will then be found easy to demonstrate the different structures. By means of a needle and a pair of fine forceps the different coats can be removed seriatim, sometimes quite separately, but generally more or less in combination. After examin- ing the separate coats, sections may be made of the whole grain, so as to see the structures in situ. The hairs are generally found in a bunch at the end of the grain. The starch grains are best demonstrated by picking out a little from the centre of the grain; water mixed with a little glycerin forms the best medium for demonstration. To each Avheat grain there are four envelopes, surrounding a fine and very loose areolar tissue of cellulose filled with starch grains. The outer coat is made up of two or three layers of long cells, with slightly beaded walls, run- ning in the direction of the axis of the grain. The hairs are attached to this coat, and are prolongations, in fact, of the cells. In the finest flour, the hairs and bits of this and the other coats may be found. EXAMINATION OF WHEAT. 329 The second coat, counting from without, is composed of a layer of shorter cells, more regular in size, Avith slightly rounded ends and beaded walls, and lying at right angles to the first coat, or across the axis of the grain. It is impossible to mistake it. The third coat is a delicate diaphanous, almost hyaline membrane, so fine that its existence Avas formerly doubted. Maddox, however, has distinctly shown it to have faint lines crossing each other diagonally, which may be cells. With a little care, it is very easily demon- strated. In the transverse section of the envelope it appears as a thin white line. Internal, again, to this coat Avhat appears to be another coat can sometimes be made out; it is a very fine membrane, marked with widely separated curved lines, which look like the outlines of large round or oval cells. The internal or fourth coat, as it is usually called, is composed of one or two layers (in places) of rounded or squarish cells filled with a dark substance which can be emptied from the cells. When the cells are empty, they have a remote resemblance to the areolar tissue of the leguminosae, and there is little doubt that from this cause adulteration with pea or bean has been sometimes improperly asserted. The starch grains of wheat (fig. 36) are very variable in size, the smallest Fig. 36. Fig. 37. being almost mere points, the largest TTro~o~th of an inch in diameter or larger. In shape the smallest are round, the largest round, oval, or len- ticular. It has been well noticed by Hassall that there is often a singular want of intermediate-sized grains. The hilum, when it can be seen, is central, the concentric lines are perceived with difficulty, and only in a smaU number; the edge of the grain is sometimes turned over so as to cause the appearance of a slight furrow or line along the grain. Very weak liquor potassae causes little swellings; strong liquor potassae bulges them out, and eventually destroys them. The wheat grains should be carefully examined for any diseased forms. Frequently small, short, thick and blackish grains are found. If these characteristically modified grains be steeped in water for some hours, the microscope will reveal inside them briskly mobile worms from 0*6 to 1 mm. in length. These are known as the Anguillulce tritici, and the disease they give rise to is called gout or cockle disease, from the slight resemblance of the grains to the seeds of Agrostemma. A number of fungi of the family of the Ustilagineae frequently destroy 330 FOOD. corn grains. The chief of these are Ustilago carbo, Tilletia caries, and Tilletia Icevis. Ustilago carbo or smut forms a black dusty powder, occupy- ing the glume in place of the grain, which is entirely destroyed. The spores are almost regularly globular, light brown and smooth (fig. 37 [3]).. Tilletia caries and T. Icevis, sometimes called the canker or stinking disease of wheat, are fungi which, microscopically, are very similar to each other, and fill the grains with a moist, smeary, black powder. Microscopically, the spores of Tilletia are larger than those of Ustilago. In T. caries, they are globular or roundish with net-hke ridges; in T. Icevis, they are more irregular and smooth (fig. 37 [2]). If flour be adulterated with rye, it may contain the mycelium of a fungus called the Claviceps purpurea or ergot of rye (page 343). At present, however, it is rare to find ergot in flour, as it is carefully sought out on account of its value as a drug. Wheaten flour is of two kinds, the one ordinarily used being white, the other, whole meal, being of a dark colour, owing to the admixture of bran. In the market there are several varieties, according to the completeness of the milling. The most highly milled flours are the whitest, and contain least bran and cellulose; they lose in the process some proteid and some salts, but this loss is largely compensated by the fineness of the bread prepared from it. The chief flours in the market are in the order of their excellence, Vienna whites, best whites, best households, second households, and others much inferior in quality. There are also brown meal and whole meal. The percentage composition of three typical wheat flours may be thus stated:— AVater. Proteid. Fat. Carbo-hydrate. Cellu-lose. Salts. Proportion of nitrogenous to non-nitrogenous food-stuff. Fine flour, Coarse flour, . Whole meal, . 13-37 12-81 13-00 10-21 12-06 11-70 0-94 1-36 1-70 74-71 71*83 69-90 0-29 0-98 1-90 0-48 0-96 1-80 1 is to 7-4 1 „ 5-3 1 „ 6-3 Of the carbo-hydrates in flour, 66*28 per cent, is starch, 4*09 is dextrin, and 1*86 per cent, is sugar. It is an open question whether the separation of the bran from the finest flour is altogether desirable, as the bran contains often as much as 15 per cent, of nitrogenous matter, with 3*5 per cent, of fat, and 5'7 per cent, of salts. On the other hand, if the bran is used, it seems probable that much is left undigested, and all the nutriment which is contained in it is not extracted. A plan was suggested by Mege-Mouries, Avhich seems to save all the most valuable parts of the bran; the two or three outer and more or less siliceous envelopes of the wheat are detached, and the fourth or internal envelope is left. Several plans of decorticating wheat have been proposed, but none of them at present have superseded the old system of grinding. If the whole wheat is used, it should be ground very fine, as the harder envelopes are irritating, and it is well to remember that for sick persons Avith any boAvel complaints bread must be used entirely without bran. Dysenteries have been found most intractable, merely from attention not being directed to this simple point. It is all the more necessary to insist upon this, as Avhole-meal bread has been much recommended and used of late. At the same time there is no doubt that whole-meal bread, Avell made, is more nutritious than the fine white bread now so generally used. The WHEATEN FLOUR. 331 principal constituents lost with the bran are fat and salts, the analysis of whole meal showing a marked excess of these over best sifted flour. There is also a certain loss of nitrogenous matter, some of which is beheved to aid digestion. But for the irritating qualities of the outer envelopes (which have, however, been much diminished by modern processes), whole-meal bread would be a more valuable nutrient. Several fungi are found in wheat flour. The most common are the Ustilagineaa already mentioned and an Uredinaceous species called the Puccinia graminis (fig. 38). It is easily recognised by its round dark sporangia, which are either contoured Avith a double line, or are covered with little projections. The accompanying drawing shoAvs a section through Fig. 38. part of a grain of wheat attacked by puccinia; the sprouting teleutospores are clearly seen growing on the surface of the grain. The symptoms which this fungus may give rise to have not been well described, there being some doubt as to whether it really is injurious to man at all. The Acarus farinas (fig. 39) is by no means uncommon in inferior flour,, especially if it is damp. It does not necessarily indicate that leguminous seeds are present, as stated. It is no doubt introduced from the grain in Fig. 40. the mill, as it has been found adhering to the grain itself. It is at once recognised. Portions of the skin are also sometimes found. The presence of acari always show that the flour is beginning to change. A single acarus may occasionally be found in good flour, but even one should be looked on with suspicion, and the flour should be afterwards frequently examined to see if they are increasing in numbers. In flour which has gone to extreme decomposition, and is moist and becoming discoloured, vibrios and other forms of bacterial life are frequently seen. They cannot be mistaken. Another organism occasionally met with in flour is the Calandra granaria or weevil (fig. 40), while somewhat rarer are the larvse of various kinds of Fig. 39. 332 FOOD. moth, more particularly Ephestia elutella and Ephestia kuehniella belonging to the micro-lepidoptera. Adulterations of Flour.—At present there is very little adulteration of wheat flour in this country, but with rising prices the case might be different. Abroad, adulteration is probably more common, and the medical officer must be prepared to investigate the point. The chief adulterations are by the flour of other grains, viz.:— Barley, Oat, Potato, Rye, Beans and peas, Rice. Maize, | The greater number of these are easily recognised by the microscope, and will be considered in more detail under their respective headings. Other adulterations are by mineral substances, viz.:— Alum, Gypsum, Clay, Powdered flint, Calcium and magnesium carbonates. These are best detected by chemical examination. Among the rarer adulterations of flour are Linseed, BuckAvheat, Millet, Melampyrum, Lolium temulentum, and some other grains : they can be con- veniently discussed in this place. Linseed is not a common adulterant. Its envelopes are peculiar: the external is made up of hexagonal cells containing oil: the second of round cells: the third of fibres : and the fourth of angular cells containing a dark reddish colouring matter. Buckwheat, hke rye, is sometimes found in wheat coming from the Baltic. Its starch grains are small and round and adhere together in masses. Under a high power there are indications of concentric rings. Bread made from flour prepared from this grain has a darkish, somewhat violet colour. Millet is a frequent adulterant of flour in India, China, Egypt, and Western Africa. The starch grains are very small, round, and tolerably uniform in size. Melampyrum arvense, or purple cow-wheat, has been occasionally mixed with flour: it is not injurious, but gives the bread made from the flour which contains it a peculiar smoky-violet or bluish-violet tint. This appears to be due to a colouring matter in the seed, which, when warmed with an acid, gives the violet tint. Lolium temulentum, or Darnel seeds, occasionally have been found in flour. They do not affect the colour of the bread, but produce vertigo, halluci- nations, dehrium, and narcotic symptoms. The detection of lolium is best effected by means of alcohol, which gives a greenish solution with a dis- agreeable repulsive taste, and on evaporation a resinous, yellow-green and unpleasant extract is left. Pure flour gives with alcohol only a clear straw-coloured solution, Avith a more or less agreeable taste. Of the preparations of flour, bread is the most important: while of less importance are biscuits, macaroni, and vermicelli. Examination of Flour.—Every sample of flour should be examined microscopically, physically, chemically, and practically by making bread. While adulterations are best determined by the microscope on the lines aheady indicated, the quahty is best demonstrated by attention to the foUoAving points. Sight.—The flour should be quite white, or with the very slightest tinge EXAMINATION OF FLOUR. 333 of yellow ; any decided yellow indicates commencing changes ; the amount of bran should not be great. Touch.—There should be no lumps, or, if there are, they should at once break down on slight pressure ; there must be no grittiness, which shows that the starch grains are changing, and adhering too strongly to each other, and will give an acid bread. There should, however, be a certain amount of cohesion when a handful of flour is compressed, and if thrown against a Avail or board some of the flour should adhere. When made into a paste with water, the dough must be coherent, and draAV out easily into strings. Taste.—The taste must not be acid, though the best flour is slightly acid to test-paper. An acid taste, showing lactic or acetic acid, is sure to give an acid bread. Smell.—There must be no smell of fermentation or mouldiness. Age of flour is shown by colour, grittiness, and acidity. Amount of Water.—Weigh 1 gramme, spread it out on a dish, and dry either by a water bath or in a hot-air bath or oven, the temperature not being allowed to go above 212°. The flour must not be at all burnt or much darkened in colour. Weigh directly the flour is cold; the loss multiplied by a hundred is the percentage of water. The range of water is from 10 per cent, in the best dried flours to 18 per cent, in the Avorst. The more water the greater liability of change in the flour, and, of course, the less is the amount of nutriment purchased in a given av eight. If, then, the water be over 18 per cent., the flour should be rejected ; if over 16, it should be unfavourably spoken of. Amount of Glutin.—Weigh 10 grammes and mix by means of a glass rod ■with a little water, so as to make a well-mixed dough, adding the water slowly from a burette : usuaUy for 10 grammes of flour not more than 4*2 c.c. of water are needed. When made, let the dough stand for a quarter of an hour in an evaporating dish ; then pour a little water on it; work it about with the rod, and carefully wash off the starch; pour off, from time to time, the starch water into another vessel. After a time, the glutin becomes so coherent that it may be taken in the fingers and worked about in water, the water being from time to time poured off till it comes off quite clear. If there is not time to dry the glutin, then weigh; the dry glutin is rather more than one-third the weight of the moist; 1 to 2*9 is the usual proportion; therefore divide the weight of the moist glutin by 2*9. If there be time, dry the glutin thoroughly, and weigh it. This is best done by spreading it out on a crucible lid and drying it in the bath. The dry glutin ranges from 8 to 12 per cent.; flour should be rejected in which it falls below 8. If there is much bran, it often apparently increases the amount of glutin by adhering to it, and should be separated if possible ; in fact, the glutin, as thus obtained, is never pure, but always contains some bran, starch, and fat. The glutin should be able to be drawn out into long threads ; the more extensible it is the better. It is always well to make two determinations of glutin, especially if there is any disputed question of quality. Amount of Ash.—Take 2 grammes; put into a porcelain or platinum crucible, and incinerate to a white ash. Weigh. The ash should not be more than 2 per cent., or probably some mineral substances have been added; it should not be less than 0*5, or the flour is too poor in salts : it generally ranges between 0*7 and 0*9 per cent. If the ash be more than 2 per cent., add hydrochloric acid, and see if there be effervescence (magnesium or calcium carbonate). Dissolve, and test for lime with oxalate of ammonium, and then for magnesia, in the same way as in 334 FOOD. Avater. As flour contains both lime and magnesia, to prove adulteration the precise amount of lime and magnesia must be determined by weighing the incinerated calcium oxalate, or the magnesium pyrophosphate. If there is no effervescence add water, and test for sulphuric acid and lime, to see if calcium sulphate (plaster of Paris) has been added. In normal flour the amount of sulphuric acid is very small. Notice, also, if the ash be red (from iron). If clay has been added, it will be left undissolved by acids and water. If magnesium carbonate has been added, the ash is light and porous and bulky. An easy mode of detecting large quantities of added mineral substances is given by Redtenbacher; the flour is strongly shaken with chloroform; the flour floats, whde all foreign mineral substances fall. This is a very useful test. If the water be small, the glutin large, and the salts in good quantity, the flour is good, supposing nothing is detected on microscopical examina- tion. But in all cases it is well, if time can be spared, to have a loaf made. Practical Test by Baking.—Make a loaf, and see if it is acid when fresh, and how soon it becomes so; if the colour is good ; and the rising satis- factory. Old and changing flour does not rise well, gives a yellowish colour to the bread, and speedily becomes acid. Excess of acidity can be detected by holding a piece of bread in the mouth for some time, as well as by test-paper. Test for Ergot.—There is no very good test for ergot when it is ground up with the flour. Laneau's plan is to make a paste with a weak alkaline solution; to add dilute nitric acid to slight excess, and then alkali to neutralisation; a violet-red colour is said to be given if ergot is present, which becomes rosy-red when more nitric acid is added, and violet when alkali is added. Wittstein considers this method imperfect, and prefers trusting to the peculiar odour of propylamine (herring-like smell) developed by liquor potassae in ergoted flour. BREAD. If carbon dioxide gas is, in any way, formed within or forced into the interior of dough, so as to divide the dough into a number of little ca-vities, bread is made. There are practically two kinds of bread, namely, that made by means of yeast, and that aerated by chemical means or the non- fermented bread. The ordinary process of bread-making consists really of three stages ; namely, the preparation of the leaven or ferment, the prepara- tion of the " sponge," and the making of the dough. One sack of flour, weighing 280 lb, is usually reckoned to yield from 376 to 384 ft> of bread, or from 94 to 96 quartern loaves, and in making bread from this amount of flour the following procedure is usually adopted. First, the ferment or leaven is made with 8 to 12 lb of boiled potatoes mashed into a thin paste. After cooling to about 80° F., or 27° C, a quart of brewer's yeast and 2 Bb of flour are added. In this mixture of potato starch, flour, and yeast, the yeast decomposes the proteids of the flour and the starch, forming maltose, dextrin, and peptone-like bodies. At the same time the yeast becomes very active. The process is allowed to go on for five hours. To the ferment when ready, one-third of the sack of flour, 48 ounces of salt, and 30 quarts of water are added. If the flour is very good, the salt is not necessary : and even with the inferior flours, if at all in excess, wdl BREAD AND BREAD-MAKING. 335 check the fermentation. The resulting mixture constitutes the " sponge," in which very active fermentation goes on : after about five hours, the sponge breaks, owing to the development of large quantities of carbonic acid and alcohol from the maltose and dextrin. When the sponge has broken twice, the dough is formed by adding to the sponge the remainder of the sack of flour and some 30 quarts of water. This rises in an hour or so, and is then transferred to an oven for an hour and a half. Though the tem- perature of the oven varies from 400° to 450° F., or from 204° to 232° C, the actual temperature of the dough does not rise much over 212° F., or 100° C. In this stage the chemical processes are not very active, but the bread gradually becomes well aerated, and its constituents, undergoing a kind of automatic digestion, improve both in flavour and aroma. In the non-fermented breads, the carbon dioxide is disengaged by mixing sodium or ammonium carbonate with the dough, and adding hydrochloric, tartaric, phosphoric, or citric acids. Baking powders are compounds of these substances. In what is called Dauglish's patent aerated bread, the carbonic acid is forced through the dough by pressure. About 20 cubic feet of C02, derived from chalk and sulphuric acid, are used for 280 lb of flour, and about 11 cubic feet are actually incorporated with the flour. It is claimed for unfermented breads that they do not contain alcohol, acetic acid, and other products of excessive fermentation, but the advantage is a doubtful one, as the action of yeast partially digests the starch, changing it into maltose and dextrin; while the proteids of flour are also largely converted into albumoses or other peptone-like bodies. Chemical Composition of Bread.—From what has been said about the making of bread, it is obvious that bread differs in composition from flour. The percentage composition of some ordinary breads is given in the follow- ing table:— Water. Proteids. Fats. Starch. Sugar. Cellu-lose. Salt. Ratio of nitro-genous to non-nitrogenous food-stuffs. White bread, average quality, . . White bread, fine quality, . White bread, coarse quality, . Whole-meal bread, 40*10 35*59 40-45 43*40 8*00 7-06 6-15 11-10 1-50 0*46 0-44 0*40 49*20 52*56 49-04 41-90 4*02 2*08 0*32 0*62 1-70 1-30 1-09 1-22 1-50 1 is to 6*3 1 „ 7*5 1 „ 8*1 1 „ 4*0 As an article of diet, bread has very similar advantages and disadvantages as flour. It is rich in proteid and starch, but poor in fat and salts. Roughly speaking, its nitrogen is to the carbon as 1 is to 21. To make it a perfect food, it therefore requires more nitrogen. Its poverty in fat is curiously exempli- fied by the constant practice of using fat with it, butter for the rich and -dripping or fat bacon for the poor. As to the relative advantages of the various methods of making bread, it must not be overlooked that yeast bread is nothing more nor less than a partially digested flour, and as such holds a ■superior dietetic position to the non-fermented forms of bread. Special Points about making of Bread.—It may be of bad colour from old flour: from grown flour (in which case the changes in the starch have •generally gone on to a considerable extent, and the bread contains more sugar than usual, and does not rise well), and perhaps from bad yeast. The 336 FOOD. colour given by admixture of bran must not be confounded with yelloAvness of this kind. Bread is also dark coloured from admixture of other grains, as already noticed under flour (rye, buckwheat, melampyrum, sainfoin, &c). Bread may be acid, from bad flour giving rise to an excess of lactic and perhaps acetic acids, or, it is said, from bad yeast. In finding the cause of acidity in bread, look first to the flour, which may be old and a little discoloured, and too acid; if nothing can be made out, examine the yeast, and change the source of supply ; then look to the vessels in which the dough is kneaded, and to the water. Enforce great cleanliness on the part of the men Avho make up the dough. Bread is frequently heavy and sodden from bad yeast fermenting too- rapidly, or when the fermentation has not taken place (cold weather, bad water, or some other cause will sometimes hinder it), or when the wheat is grown; AAdien too little or too much heat has been employed. It is said also that if the flour has been dried at too great a heat (above 200° F.) the glutin is altered and the bread does not rise well. It is bitter from bitter yeast. Bread becomes mouldy rapidly when it contains an excess of water. Rice is used as an addition because it is cheaper; it retains water, and therefore the bread is heaAder. Rice bread (if 25 per cent, of rice be added) is heavier, of closer texture, and less filled with cavities. Potatoes are some- times added, but are generally used only in small quantity with the yeast. Alum is added to stop an excess of fermentation, when the altering glutin or cerealin acts too much on the starch, and it also whitens the bread; it does not increase the amount of water; it enables bread to be made from flour which otherwise could not be used. Sulphates of copper and of zinc, in very small amount, are sometimes employed for the same purpose. For acid flour, lime-water is used instead of pure water; lime-water has this advantage, that, while it does not check the fermentation of yeast, it hinders the action of diastase on starch. It must be caustic lime-water, and not chalk and Avater, as sometimes is the case. Loaves are generally weighed when hot, and that is considered to be their Aveight. After being taken from the oven bread begins to lose weight. The loss of weight depends upon size, amount of crust, temperature, and movement of air. In a sheltered place, at ordinary temperature, a 2-lb loaf, baked Avith crust all over, loses about f per cent, in cooling, and from 1 to 1^ in five hours. A similar loaf, with only top and bottom crust, loses 3 per cent, in cooling, and about 4 per cent, in five or six hours. A loaf with four sides crust loses 2 per cent, in cooling, and retains its weight without much further loss for five hours. For each of six sides that is not crust there is a loss of weight of about 1 per cent, in the first five hours. At the end of twenty-four hours the proportion is about one-half more, and the total loss is doubled at the end of seventy-two hours (three days). If the bread is baked in larger loaves (4 5>, for instance) the loss will be propor- tionately less, the ratio of the evaporating surface to the bulk of the loaf being diminished. When loaves become stale they can be dipped in water and rebaked, they will then taste quite fresh for tAventy-four hours ; after that they rapidly change. Diseases connected -with the Quality of Flour and Bread.—Frequently the flour is originally bad: it may be ergoted, or grown and fermenting, or affected with fungi. Fermenting flour produces dyspepsia and diarrhoea : EFFECTS OF BAD BREAD. 337 the heat and moisture of the stomach doubtless excite at once very rapid fermentation : the proteids, already metamorphosing, act energetically on the starch, and carbon dioxide is rapidly developed; hence uncomfortable feelings, flatulence, imperfect digestion, and diarrhoea. It is to remedy this condition of flour that alum is added, and some of the effects ascribed to alum may be really owing to the flour. The most important disease connected with flour is, however, ergotism; this is less common in wheat than in rye flour, but yet is occasionally seen. Sometimes ergoted meal produces at once violent stomach and intestinal symptoms, at other times primary digestion is well performed, and the early symptoms are great general depression and feverishness, ushering in the local symptoms of acrodynia. The flour may have been originally good, but altered either from age or im- perfect drying. The bread made from such flour is often acid, and sometimes highly so, sufficient to produce diarrhoea, though such bread has sometimes been used for a long time without this effect; usually persons will not eat much of it, and thus the supply of nutriment is lessened. If the bread be too moist, fungi form, and Oidium aurantiacum, in particular, has been known to give rise to little endemics of diarrhoea. Mucor mucedo either does not produce this, or does so but rarely. It is not known that Acarus, so common in flour, has any bad effects when eaten. Of the various substances added from time to time to flour, alum is the chief : there has been much difference of opinion as to its effects. It has been asserted to produce dyspepsia; to lessen the nutritive value of bread by rendering the phosphoric acid insoluble, and to be also a falsification, inasmuch as it permits an inferior flour to be sold for a good one. The last allegation is no doubt correct; the second probably so, as there is little doubt of the formation, and none of the insolubility, of aluminum phosphate. The first point is more doubtful, though several physicians of great authority have considered its action very deleterious, and that it causes dyspepsia and constipation. Pereira considered that whatever may have been the effect in the case of healthy persons, sick persons did really suffer in that way. A question like this is obviously difficult of that strict proof we now demand in medicine. Seeing, indeed, that the usual effect of bad flour is flatulence and diarrhoea, if constipation were decidedly produced by bread, it would be more likely to proceed from alum than from any other ingredient of the bread. Looking again to the fact that sometimes bread has contained large quantities of alum,—sometimes as much as 40 grains in a 4-lb loaf, and probably more,—we get an amount in an ordinary meal Avhich (if the aluminum phosphate is an astringent) might very well cause constipation. Looking, then, to the positive evidence, and the reasonableness of that evidence, it seems extremely likely that strongly alumed bread does produce the injurious effects ascribed to it. Sulphuric acid is said to be added, before grinding, to flour instead of alum, it having the same power of restraining decay. For the same reason sulphate of copper is added. The amount is so small that it seldom produces any symptoms: still it is possible that some anomalous cases of stomach irritation may be owing to this. Lead poisoning is extremely rare as a consequence of the eating of bread. Alford records a case in which it occurred, owing to holes in some mill- stones having been repaired with the molten metal, and where old wood which had been painted was used for heating the baking oven. The symptoms produced by bread containing Lolium temulentum have already been described: while as to the effect of flour from grains other Y 338 FOOD. than wheat, it is not knoAvn whether the addition of potatoes, rice, barlejr, peas, &c, in any way injures health, except as it may affect nutrition or digestion. Occasionally, in times of famine, other substances are mixed— chestnuts, acorns, &c In 1835, during famine, fatal dysentery appeared in Konigsberg owing to the people mixing their flour with the pollen of the male catkin of the hazel bush. In India the use of a vetch, Lathyrus sativus (kisarl-dal), -with barley or Avheat, gives rise to a special paralysis of the legs when it exceeds one-twelfth part of the flour; L. cicera has the same effect. During the siege of Paris, straw, to the extent of one-eighth, was introduced into the bread ; this had a very irritating effect. EXAMINATION OF BREAD. There should be a due proportion—not less than 30 per cent.—of crust, which should be yelloAvish-brown, firm, and not aerated; the external sur- face should not be burnt. The amount of crust can be readily estimated by carefully paring it off Avith a sharp knife, weighing, and then calculating it as a percentage of the weight of the whole loaf. The crumb should be permeated with small regular cavities; no parts should be heavy, nor with- out these little cells; the partitions between the cavities should not be tough; the colour should be white or brownish from admixture of bran; the taste not acid, even when held in the mouth. If the bread is acid the flour is bad, or leaven has been used; if the colour changes soon, and fungi form, the bread is too moist; if sodden and heavy, the flour is bad, or the baking is in fault; the heat may have been too great, or the sponge badly set. The purely chemical examination of bread should be directed chiefly to the determination of the water and acidity, and of the presence of alum or sulphate of copper. Amount of Water.—This should be calculated on the whole loaf, and determined separately in both the crust and crumb. Usually it amounts to about 16 per cent, in the crust, and from 35 to 45 per cent, in the crumb. On the whole loaf it should not be more than 45 per cent.; if more, the bread is pro tanto less nutritious, and liable to become mouldy sooner. The determination is readily made by taking a weighed quantity of the powdered bread, drying in a hot-air bath or oven, re-weighing, and calculating out as a percentage. If a loaf be found to have 24 per cent, of crust and 76 per cent, of crumb, with 16 per cent, of Avater in the crust and 40 in the crumb, the statement for the moisture in the whole loaf Avill, therefore, stand as follows:— ^x24 = 3-84 40x76 = 30:40 100 34*24 percentage of water in the whole loaf. Degree of Acidity.—This is a someAvhat important determination, and can be readdy made by means of a standard alkaline solution, prepared by taking hquor sodas or liquor potassae of pharmacopceial strength, and dilut- ing with 8 or 9 parts of distilled water, so that 10 c.c. exactly neutralises 10 c.c. of a deci-normal solution of oxalic acid. If so prepared, 1 c.c. of the alkahne solution equals 6 milligrammes of glacial acetic acid, in terms of which the acidity of bread is usually expressed. The acidity of bread is con- veniently determined by soaking, for an hour, 10 grammes in 100 c.c. of distilled water, macerating, and then titrating with the standard alkaline DETECTION OF ALUM IN BREAD. 339 solution; either litmus and turmeric papers or phenolphthalein may be used as indicators. As in the case of the moisture, so the acidity should be separately estimated for the crust and crumb, and then calculated on the whole loaf. The actual acidity found will vary; even the best bread is shghtly acid. It generally averages from 4*5 to 6 grains per pound, or from 0*064 to 0-086 per cent. Eight grains per pound, or 0'114 per cent., of .glacial acetic acid ought certainly to be the limit. Amount of Alum.—The determination of the presence of alum is not difficult, but a quantitative analysis is necessary, as even unalumed bread may contain an appreciable amount. As a qualitative test, a decoction of logwood may be used; a piece of pure bread and a piece of suspected oread are put into a glass containing freshly prepared decoction, and left for twenty-four hours ; the pure bread is simply stained, the alumed bread is dark purplish, as the alum acts like a mordant. For a quantitative estimation, the following process suggested by Dupre, and modified by Wanklyn, is the best. Take the ash of a quarter of a pound of bread, place in a porcelain dish and moisten Avith 3 c.c. of pure hydrochloric acid to separate silica; add 30 to 50 c.c. of distilled water, boil, filter, Avash the filter well with boiling water; add to the filtrate, which contains the phosphates of calcium, magnesium, aluminum, andiron, 5 c.c. of liquor ammonias (sp. gr. 0*880), which causes a precipitate of these phosphates; then add gradually 20 c.c. of strong acetic acid, which partially clears the fluid by dissolving the phosphates of calcium and magnesium; bod and filter. The undissolved part is a mixture of phosphate of aluminum and phosphate of iron; wash precipitate well with boiling water, dry, ignite, and weigh. The iron must noAV be determined in this precipitate. This may be done hy the permanganate, but Wanklyn's colorimetric test is probably better; it is as foUows:—Dissolve 1 gramme of pure iron Avire in nitro-hydrochloric acid, precipitate the ferric oxide with ammonia; wash the precipitate, ■dissolve it in a httle hydrochloric acid, and dilute to 1 litre: 1 c.c. there- fore equals 1 milhgramme of metallic iron; when used it is diluted 1 in 100 so as to make a solution of which each c.c. contains xg-Q-th milligramme ( = 0*01 of a milhgramme) of metallic iron. To use this, dissolve the phosphates of aluminum and iron (obtained by the above described process) in 3 c.c. of pure hydrochloric acid, and dilute to 100 c.c. Avith distilled water. Test the solution to see if it give a deep colour with a ten per cent. solution of ferrocyanide of potassium; if the colour is not too deep take 50 c.c. of the solution, and dilute up to 100 c.c. with distilled water: but if it be deep take a smaller quantity, stdl diluting up to 100 c.c. with dis- tilled water. Put it into a cylindrical glass and add 1*5 c.c. of the solution of ferrocyanide of potassium, and 1 c.c. of strong hydrochloric acid: a blue colour is given. Into another glass as much of the standard iron solution is •dropped in as will produce a similar colour. The bulk being made up to 100 c.c. with distilled water and 1*5 c.c. of ferrocyanide solution and 1 c.c. of strong hydrochloric acid being added. This procedure of " Wanklynising" is analogous to that of " JSTesslerising " for ammonia. The amount of iron is then read off and calculated as phosphate (1 of iron = 2*696 FeP04). Deduct the weight from the total weight of phosphate of aluminum and iron; the remainder is phosphate of aluminum ( = A1P04), of which 1 part equals 0*42 alumina, or 2*1 dry or 3*9 crystallised potassium alum; or 1*9 dry or 3*7 of crystallised ammonium alum, which last is almost the only kind now in the market. Calculate as crystallised ammonium alum, A1NH4 ^S04)2 12H20, and express as grains per pound. 340 FOOD. Example.—Weight of capsule + phosphatic ash = 19*155 grammes. „ ,, alone =19*060 ,, 0*095 Weight of ash of filter paper =0*005 ,, Nett weight of phosphatic ash = 0*090 ,, (FeP04 + A1POJ. After solution and dilution of the ash to 100 c.c, 5 c.c. of it required 12 c.c. of the 100 x 12 standard iron solution : then, ---^---= 240 c.c. for the Avhole 100 c.c. 240x0-01 = 2-4 mgm. of Fe in I lb of bread. 2-4 x 2-696 = 6-46 mgm. FeP04, or 0-00646 gramme in \ lb of bread. Then, 0-090 or total phosphates of iron and alum less 0'00646 or phosphate of iron gives 0*08354 gramme of phosphate of alum in \ lb of bread : and 0*08354 x 3*7 = 0*3091 gramme A1NH4 (S04)2 12H20 in \ tb of bread. 0*3091x4x15*5 = 19-16 grains „ ,, per lb of bread. Alum is not much used, except with inferior bread: the object of its addition is to arrest the change in the glutin. The amount of alum in bread is said to be, on an average, 3 ounces to a sack or 280 3b of flour; if the sack gives 105 4-lb loaves, there wdl be 3 grains in a pound of bread; but if crystallised alum is meant by this, there will only be about 1\ grain of dry alum. This amount must, therefore, be deducted from the alum found in the bread examined, the result then giving the amount of the salt added : or in other words, any excess over 12 grains in a 4-R> loaf must be regarded as an adulteration. A.very good witness, in the inquiry into the grievances of the journeymen bakers, gave the quantity in alumed bread to be 41*6 grains per 4-ft) loaf, or 10*4 grains per pound. When mixed with flour and baked the alum is decomposed : part of the alumina combines most strongly with phosphoric acid; and either this or the alum itself is presumed to be in combination with the glutin; potassium disulphate is probably formed. Cupric Sulphate.—Cut a smooth slice of bread, and draw over it a glass rod dipped in potassium ferrocyanide. If copper be present, a brick-red colour is given by the formation of ferrocyanide of copper. The test is very delicate. This is believed to be a very rare adulteration in England. It has been said that cobalt is used instead of copper, but it is also probably very rare; it can be detected by the blueness of the ash. Potatoes.—If potatoes in any quantity have been added, the ash of the bread, instead of being neutral, is alkaline; tins can only occur from sodium carbonate having been added, or from the presence of some salts of organic acids,—citrates, lactates, tartrates, which form carbonates on incineration. But if it be from sodium carbonate, the solution of bread will be alkaline, so that it can be known if the alkalinity is produced during incineration. If so, it is almost certain to be from potato. The ash of bread ought never to be over 3 per cent. BISCUITS. The simplest biscuits are merely flour and water, but the majority have slight additions of butter, sugar, and flavouring substances, with milk, eggs, &c. What are known as diet or digestive biscuits contain some bran. Aber- nethy biscuits contain caraway seeds. Cracknels are glazed with white of egg, while macaroons and ratafias are flavoured with sweet and bitter almonds. Ginger, lemon, orange-peel, and many other flavours and spices are used as ingredients in fancy biscuits and cakes. Biscuits should be well baked, but not burnt: of a light yellow colour, BISCUITS—BARLEY. 341 should float and partially dissolve in water. When struck, they should give a ringing sound, and when put into the mouth should thoroughly soften down. All biscuits should be free from weevils. All the plainer varieties of biscuit may be considered as more nutritious than bread, in the propor- tion of 5 to 3. They are more digestible when not very dense, and Avhen they have been browned by baking, so as to turn much of their starch into dextrin. Like flour, biscuit is deficient in fat, and after a time seems difficult of digestion. Perhaps the Avant of variety is objectionable, but it is quite certain that men do not thrive well upon it for long periods. The essential differences betAveen biscuits and bread are that they are not vesiculated, and they are baked until they contain scarcely any Avater, sometimes not even 5 per cent. There are, of course, some exceptions to this rule, especially in the case of the fancy biscuits. Strictly speaking, a biscuit is that which has been twice cooked or baked, but this definition will not apply to the generality of biscuits now made. A few kinds are really put twice into the oven; such are rusks, which are made from flour, milk, butter, and sugar, first lightly baked as a kind of bread, then cut into shces and again put into a sharp oven so as to scorch both sides. They are afterwards thoroughly dried by a lovrer degree of heat continued for some hours. The percentage composition of two varieties of plain biscuit may be taken to be as follows :— Water. Proteids. Fat. Starch. Sugar. °w" Salt. lose. Ratio of nitro-genous to non-nitrogenous food-stuffs. Navy biscuit, . Milk biscuit, . 10-20 9-45 10-90 7-18 1-60 9*28 75*00 1 ... 57*18 15-92 1-20 0*16 1*10 0*83 1 is to 7 1 „ 1*4 From the foregoing, it Avdl be readily seen that biscuits contain a much smaller quantity of water and a larger proportion of proteid and carbo- hydrate than bread. Weight for weight, they are therefore more nutritious than bread, and being easdy transported are useful as a substitute for bread, when this cannot be obtained. Besides biscuits and bread, other preparations from flour are macaroni and vermicelli. Macaroni is made from the " hard " wheats of Italy and France. These wheats yield large quantities of glutin, which readily per- mit of the manufacture of the macaroni of commerce. Macaroni is a valuable food, little appreciated in these islands, and of a fairly constant composition. It contains, on an average, 13 per cent, of water, 9 of proteids, 0*4 of fat, 76*7 of carbo-hydrates, and 0*9 per cent, of salts. Vermicelli closely resembles macaroni in both its composition and nutritive properties. BARLEY. As an article of diet, barley has the same advantages and disadvantages as wheat. It is said to be rather laxative. The barley grain contains about as much proteid as wheat, but these do not, on the action of water, form glutin, but remain in a soluble form as globulin, albumin, and albu- mose. It is difficult to say how far this affects its nutritive value, but it undoubtedly affects the capability of barley being made into bread, and as such being largely used as an article of diet. 342 FOOD. The envelopes of barley are the same in number as those of Avheat, but they are more delicate. The outer coat is described usually as having three layers of cells; the Avails of the external layer are beautifully waved, but not beaded; the individual cells are smaller than those of the outer coat of wheat. The second coat, disposed at right angles to the first, as in wheat, is hke the second coat of Avheat, except in being more delicate and not beaded. The third is hyaline and transparent, Avith faint cross-lines, as in wheat. The fourth has' the cells similar in shape to the corresponding wheat coat, but they are very much smaller, and often arranged in two or three layers. The starch grains of barley are very like the wheat, with a central hilum and obscure marking, but are on the whole smaller; some have thickened edges, instead of the thin edges of the wheat starch grains, but it is very difficult and sometimes impossible to distinguish them. It is therefore specially to the envelopes that we must attend. When the whole barley grain is ground, it forms barley-meal; when de- prived of its husk, and roughly ground, it constitutes Scotch, milled, or pot barley. Pearl barley is the grain deprived of the husk, rounded and polished by rubbing. So-called patent barley is merely pearl barley crushed to the state of flour. Barley-Avater is prepared from pearl barley, "and forms a slightly nutritive hquid for infants and the sick. Malt is the product yielded when barley has been allowed to germinate, and the germination stopped at a certain point by exposure to heat on a kiln. As a result of this process, the starch of the grain is largely converted into sugar by the development Avithin the barley grain of a peculiar active nitrogenous ferment called diastase. There being little or no glutin in barley, it cannot be made into ordinary bread; when barley bread is made, it is usually from a mixture of barley-meal with wheaten flour. Barley cakes are eaten in some places on the score of economy; but, as compared with those made from wheat, are less palatable and less digestible. The diseases Avhich may arise from altered quality of barley are the same as those from wheat, namely, indigestion, flatulence, and diarrhoea. There appears to be nothing peculiar in the action of diseased barley as distin- guished from diseased wheat. RYE. Although little used in this country except for malting, rye in the northern countries of Europe is largely used for making bread. In its per- centage composition, rye closely resembles wheat, its proteids forming, on the addition of water, a kind of glutin. Rye bread is dark in colour, some- Avhat heavy and very acid; but falling little short of wheaten bread in nutritive value. Rye bread is indigestible and apt to cause diarrhoea. If mixed with two parts of Avheat flour, rye flour makes an excellent bread. Percentage Composition of Rye Bread. AVater. Proteid. Fat. 1 Starch. Sugar. i Cellulose. Salts. German rye bread, . . 42*26 \ 6'11 1 0*43 j 46-94 black bread, . ! 43-42 I 7'59 1*51 I 41-87 i j ■ j 2-31 3-25 0'49 0-94 1*46 1-42 ERGOT OF RYE. 343 Fig. 41. The envelopes of rye are very like those of wheat, and can perhaps hardly be distinguished from them. The recent starch grains (fig. 41) are also like those of Avheat, but they are much more distinctly spherical. They have also sometimes a peculiar rayed hilum, which used to be thought peculiar to the older and drier grains. It is, however, to be seen even in the starch of fresh soft grains. In the starch of wheat, this rayed hdum is only met with occasionally, when the grain is very old or dry. If rye is mixed in any quantity Avith ordinary wheat flour it is readily discoverable by baking, as it makes a dark, acid bread. Rye is subject to a very peculiar fungus disease due to the permanent mycelium of the Secale cornutum, which grows at the expense and in place of a grain of the corn, producing what is called an ergot of rye. If we take a spike of ergotised rye, we see one or more of the rye grains replaced by blackish horn- like growths, tAvice or three times as long and stout as the normal rye grains (fig. 42). This is the ergot, and when fresh has a faint sickly odour, Avith a bitter and nauseous taste; from it ergotine is pro- duced. This black grain or ergot is not a perfect fungus, but is really a sclerotium or permanent my- celium of the Secale cornutum. If this sclerotium or ergot be placed in a clean, moist, shady place it will germinate (fig. 43), producing on its surface several club-shaped growths. Each little white stemmed off- shoot from the ergot has a small spherical head of a beautiful purphsh colour. This growth is noAV the perfect condition of the ergot, and is termed Claviceps purpurea. The claviceps derives its nourishment from the ergot, and after it has appeared the ergot collapses and perishes. If one of the heads or clubbed ends of the claviceps be cut through longitudinally, it will be found to have the structure as shown in fig. 44. Its outer surface is seen to be packed all round with small flasks, conceptacles or perithecia, with their mouths all opening to the outside. Each single perithecium is closely packed with fine long trans- parent bladders, each of which again contains some eight or ten fine, long, attenuated bodies which are sporidia or spores. When ripe, these needle-like spores are ejected into the air, AA'hence they ultimately find attachment to the base of the pistil of a flower of rye. Here it germinates to form, in course of time, a sclerotium or ergot, with a subsequent development of the claviceps stage. When the ergot gets mixed with rye grains, it becomes ground down with them, and the resulting bread gives rise to a disease in men called ergotism, the symptoms of which are vomiting, diarrhoea, fol- lowed in severe cases by either loss of sensibility, Fig. 42. 344 FOOD. gangrene or paralysis. The disease is practically unknoAvn in this country, and much less prevalent now than formerly abroad. On account of their Fig. 43. Fig. 44. size, the ergots can be readily sifted from the unaffected grains: as already stated, the ergot is carefully sought out, OAving to its value as a drug, and for this reason is rarely found in flour. OATS. Fig. 45. As met with in commerce, oats consist of the seeds of the Avena sativa enclosed in their husks. When deprived of this integument, the grain goes by the name of groats or grits, used in making porridge: and these groats, when ground down fine, constitute oat-meal, from which gruel is made. Of all the cereals, oats rank next to wheat as articles of food, being noticeable for containing large amounts of proteid and fat — particularly the latter. Oats resemble barley rather than wheat, in that their proteids do not form glutin on the ad- dition of water: on this account oat-meal cannot be vesiculated and made into bread like wheaten flour. It is, hoAvever, made into thin cakes by mixing into a paste with Avater, and then baking on an iron plate. Owing to the large amount of cellulose which they contain, this is apt to irritate the intestines, and more or less interfere with digestion. In oats, there are two or three envelopes: the outer coat contains longi- tudinal cells; the second contains obliquely transverse cells, which are not very clearly seen; the cells are wanting in parts, or pass into the cells of the third coat; the third a layer, usually single, of cells like the fourth coat of Avheat. The husk must be detached before the envelopes are looked for, for lining it is a layer of wavy cells, like the external envelope of barley, which might mislead. The starch-cells are small, many-sided, and cohere into com- posite round bodies, which (fig. 45) are very characteristic, and which can be broken down into the separate grains by pressure. A high power is necessary for the examination of these grains. The oat starch does not polarise li^ht and there is usually no difficulty in their detection by means of the microscope. OATS-—RICE. 345 In the form of oat-meal, oats can be taken for long periods without distaste, and in this form constitute a material part of the dietary of the Scotch peasantry. The chief adulterations of oat-meal are barley meal and the husks of barley, of wheat and of the oat itself. A single look through the microscope usually detects the round and smooth barley starch, while the envelopes are recognised with very httle more trouble. Occasionally rice and maize are added. In a good oat-meal there should be a fair proportion of envelope, but the meal should be devoid of any branny character, which usually arises from barley husks. The starch should not be discoloured, and the whole sample free from acari. RICE. The whole grain (paddy) deprived of the husk is sold as rice. There are many varieties, of different colours and composition. The amount of nitro- genous matter varies greatly, from 3 to 7*5 per cent. As an article of diet it has the advantage of an extremely digestible starch grain, and, like the other Cerealia, there is a great admixture of substances; it is, however, poorer in nitrogenous substances than wheat, and is much poorer in fat. Consequently, among rice-feeding nations, leguminous seeds are taken to supply the first, and animal or vegetable fats to remedy the latter defect. Rice is also poor in salts. It is essentiaUy a carbo-hydrate food, and, if properly and suffi- ciently cooked, is very digestible. It is best cooked by thoroughly steaming; if boiled in water, it loses some of its already small quantity of proteid and saline matter. It cannot be made into bread, but is much used in France for mixing with wheaten flour to make the very white bread which is in request in that country. The husk of rice is very peculiar; on the outer coat are numerous siliceous granules, arranged in longi- tudinal and transverse ridges; there are also numerous hairs, some of which are seated over stomata. BeloAv this, there is a membrane of transverse and longitudinal rough edged fibres, whde below these again is a fine membrane of transverse angular cells, covering a further delicate membrane of large cells. The starch grains (fig. 46) are very small, angular under low power, but faceted and compressed under high powers. They cannot be mistaken for the round cells of wheat, but may be confounded with oat starch, from which, however, they are distinguished by the absence of the compound cells or glomeruli. Their shape is also a little like maize, but they are very much smaller. 346 FOOD. MAIZE. Though not much used in England, maize or Indian corn is an important food in America and in Italy, where it is called polenta. In its nutritive value, maize resembles oats, containing a large quantity of fat. When made either into cakes or porridge, it affords a valuable food. Maize, being deficient in glutin, does not make good bread; it is, moreover, harsh in flavour. This defect is largely removed by treating it Avith caustic potash, a procedure which is the foundation of the process for making it into the common commercial articles extensively sold under the names of oswe^o corn-flour and hominy. If imperfectly cooked, or at all decomposed, maize may give rise to very disturbing symptoms. The grain, too, is liable to a peculiar disease due to a fungus called Sporisorium maidis, which gives rise to a disease in man known as " pellagra," and closely resembling scurvy. Tins affection is not uncommon in Lombardy,. where much maize is eaten as food. The coats of maize are two, the outer being made up of many strata of cells; there is no transverse second coat as in wheat; the internal coat consists of a single stratum of cells like the fourth of wheat, but less regular in shape and size. The cellulose, through the seed holding the starch in its meshes, forms a very characteristic structure, which on section looks like a pavement made of triangular, square, or polygonal pieces; the cells are filled with the starch grains, which are very small, and compressed, so as to have facets (fig. 47). They are very different from the smooth, uncompressed round cells of wheat. The starch grains of oats, rice, and maize somewhat resemble each other, in being all faceted. The maize starch grains are much larger than the other two, with a distinct hilum ; oat and rice starch grains are smaller than those of maize, and are usually without a hilum, whhe both the oat and rice grains have a tendency to collect together into clumps. Fig. 47. MILLET AND BUCKWHEAT. Various grains belonging to the Cerealia or to other natural orders, and havmg similar properties, are used as food in different countries. Of these the chief are the different millets, used largely in Africa, Italy, Spain, Portugal, and some parts of India and China. English Xnmc"> Common millet, Small millet, Spiked millet, Golden-coloured millet, Botanical Names. Indian Xames. ( Sanwa Chenawari Ranicum miliaceum, 1 (Hindustani). / Varagii (Tamul). (Sorghum or Panicum vul- j J?*™* (,irabic)- 1 gare, \ Cholam (Tamul). f Joar or Joaii (Hind.). Pencillaria spicata, I gSJ™ ?r BfiJri (Hind.). * [ Kambu (Tamul). Sorghum saccharatum. PEAS AND BEANS. 347 English Names. Italian millet, German millet, Indian Names. I Kalfi kangni (Hind.). j Tenay (Tamul). (Ragi or Raggy (Hind., I Canarese, and Tamul). 1 Murha and Maud in the N". V. Prov. of Hindustan. The millets are very similar in composition, their ash being particularly rich in silica and phosphates. Botanical Names. Setaria Italica, Setaria Germanica. Eleusine corocana, Ratio of nitro- Carbo- Cellu- genous to non- AA ater. Proteids. Fats. hydrates. lose. Salts. nitrogenous food-stuffs. Common millet, . 11-79 10-51 4-26 68-16 2-48 2-80 1 is to 6-89 Small millet, 11*46 8-96 3-79 70-25 3-59 1-95 1 „ 8-26 Spiked millet, 11-72 8-61 3-54 71-31 3-40 1*42 1 ,, 8-69 Golden-coloured millet, 15-17 9-26 3-36 67*99 2-51 1*71 1 „ 7-70 Italian millet, 12-04 7-40 3-87 74-21 1-37 1*11 1 ,, 10-55 German millet, 11-92 8-41 3-62 71-50 3-25 1*30 1 ,, 8-93 Raggy or Ragi, . 13"2 7-30 1-50 73-20 2-50 2-30 1 ,, 10-23 Buckwheat, . 12-68 10-18 1-90 71-73 1-65 1-86 1 „ 7-22 Millet bread is very good, and some Avas issued to the troops in the last China Expedition. This should ahvays be done in a millet country, if wheat or barley cannot be got. In Northern China millet is almost exclusively used. Raggy or Ragi (Eleusine corocana) is largely used in Southern India and in some parts of Northern Hindustan, and is considered even more nutritive than wheat. It is capable of being preserved for many years in dry grain pits. Buckwheat (Fagopyrum esculentum) is not so likely to be used. It is poor in nitrogenous substances and fat, and contains a good deal of indiges- tible cellulose, but it makes fairly palatable cakes. PEAS AND BEANS. These belong to the Leguminosae, and in respect of dietetic properties are broadly distinguished from other vegetable foods by their large amount of nitrogenous substance, called legumin or vegetable casein, which is probably largely derived, during extraction, from certain globulins and albumoses present in these seeds. The character of the proteids in the leguminous plants has not been very well investigated; our fullest knowledge relates to the kidney bean, Phaseolus vulgaris, which contains two globulins and legumin. The two globulins, known respectively as phaseolin and phaselin, are both very soluble in dilute saline solutions, from which they are precipi- tated by acids, the precipitates being soluble in common salt solution. By prolonged dialysis of their solutions, they separate out and thereby become partially insoluble in brine. The following analysis of those globulins by Osborne is interesting as typical of the proteids of this group of seeds. Phaseolin. Phaselin Carbon, 52-58 51*60 Hydrogen, . 6-84 7*02 Nitrogen, 16-47 14-65 Oxygen, 23*55 26-24 Sulphur, 0*56 0*49 100*00 100*00 348 FOOD. The advantages of peas and beans as articles of diet are the great amount of legumin and salts, especiaUy those of potash and lime. Their disadvan- tages he in their great indigestibility and poorness in fat and sodium chloride. Rubner has shown that from about 21 to 30 per cent, of the nitrogen of peas passes out undigested in the faeces as compared with 13 to 14 per cent. of the nitrogen of white bread, and about 17 per cent, of black bread. The existence of sulphur frequently causes flatus from the production of hydrogen sulphide. Still they are a most valuable article of food, and always ought to be used when much exercise is taken, as they constitute an exceUent addition to meat and the other cereals. Both men and beasts can be nourished on them alone for some time ; in fact, added to rice, they form the staple food of large populations in India. Closely allied to peas and beans are Lentils (Ervum lens), Gram (Phaseohts Mungo), Soja beans (Soja hispida), Lablab beans (Dolichos lablab), and Dal (Lathyrus sativus). Lentils contain a large amount of proteid, are rich in iron and phosphate of hme, and have the advantage over peas of containing no sulphur. " Revalenta" is prepared from lentils. Gram, although chiefly used for horses and cattle, is sometimes employed as food for men in India, making palatable and nutritious cakes. Soja or Soy beans, from the large amount of fat they contain, approximate in composition to the oily seeds such as linseed, pea-nuts, walnuts, hazel-nuts, and almonds. Lablab beans are obtained from a pulse groAvn in India not only for its ripe seeds, but also for its green pods, which are used as a vegetable. The Dal is a vetch used occasionally in Europe and constantly in India, when mixed with Avheat or barley flour, for bread. When used in too great quantities, it produces constipation, colic, and some form of indigestion, and, if eaten in excess, paraplegia. It is also injurious to horses, but less so to oxen. To this group belong also the seeds of the Peruvian food, the Chenopodium Quinoa. The starch grains of the Quinoa are said to be the smallest known. It may be worth remarking that this seed is very rich in salts (2'4 per cent.), and particularly so in iron (0"75 per cent.); indeed, it is the richest in iron of any vegetable. It is possible that it might be a useful food in some cases of illness. It is fairly nutritious and digestible. The following table shows the percentage composition of some of the more common leguminous seeds:— AVater. Proteid. Fat. Carbo-hydrate. Cellu-lose. Salts. Ratio of nitro-genous to non-nitrogenous food-stuffs. Pea flour, Green peas, Dried peas, Bean flour, Dried beans, Fresh French 1 Haricot beans, Lentil flour, Gram, Soja beans, Lablab beans, Lathyrus sativ Yellow lupin s leans us, 3eds, 11-41 78-44 13-92 10-29 13-49 88-75 11-24 10-73 10-80 15-70 12-10 12-74 13-98 25-20 6-35 23-15 23-19 25-31 2-72 23-66 25-46 22-20 33*40 24-40 24-08 38-25 2-01 0-53 1-89 2-13 1-68 0-14 1*96 1*83 2*70 17*70 1*50 2*38 4*38 57*17 12-00 52-68 59-37 48-33 6-60 55-60 57-35 54-10 26-00 57*80 51-38 25-46 1-32 1-87 5-68 1-67 8*06 1*18 3*88 2-01 5-80 310 1-20 6-60 14-12 2-89 0-81 2-68 3'35 3-13 0-61 3-66 2-67 4-40 4-10 3-00 2-82 3-81 1 is to 2-3 1 „ 18 1 „ 2-2 1 ., 2-6 1 „ 1-9 1 „ 2-4 1 „ 2-4 1 ,, 2-3 1 ,, 2-7 1 ,, 1*2 1 „ 2-5 1 „ 2-2 1 „ 08 It Avill be noticed how great is the difference between the composition of POTATOES. 349 fresh and dried peas; roughly, 1 part of the dried pea equals, by weight, 4 parts of the green in proteids and carbo-hydrates. The starch grains of peas and beans (fig. 48) are characteristic, being oval or kidney shaped : they have no clear hilum, but usually a deep central Fig. 48. longitudinal cleft, or at times an irregularly shaped depression. The addition of hot water to pea or bean flour causes the emission of the typical beany smell. Pea flour is sometimes met with as an adulterant of wheat flour, but rarely to a greater extent than 4 per cent., as it makes the bread heavy and dark. POTATOES. These may be considered as occupying a place next in importance to the seeds of the cereals as articles of vegetable food. The potato, used as food, constitutes the tuber or exuberant growth of a portion of the underground stem of the Solanum tuberosum. The tuber develops into a thick fleshy mass, retaining its buds under the name of " eyes," each of which eyes or buds is capable of independent growth when in a detached or isolated state. In its chemical composition the potato shows a large proportion of starch with a very small quantity of proteid. The juice of the potato is acid, due to the presence of a certain amount of free citric acid with citrates of potassium, sodium, and calcium. In its dietetic value, the potato is both a carbo-hydrate and an anti-scorbutic. As the amount of salts is small, and that of water large, at least 8 to 12 ounces of potatoes should be taken daily, if no other vegetables are eaten. The starch grains of the potato (fig. 49) are characterised by being large oyster-shaped granules with well-marked concentric rings, and a clear though small hdum at the narrow end. Weak liquor potassae (1 in 10) swells them 350 FOOD. out greatly after a time, Avhile wheat starch is little affected by this strength. Potato starch is largely used for adulterating the more expensive farinaceous dietetic preparations: though cheaper, there is nothing to shoAV that potato starch is less nutritious than other starches. Potatoes require to be cooked before being eaten: this may be done by either steaming, boiling, baking, or frying. The heat coagulates the albuminous juices, and the absorbed Avater swells up and distends the starch grains. When these changes are complete, the potato is said to be mealy or floury : when these changes are only partially completed, and the starch cells imperfectly broken up and separated, the potato remains more or less firm, and is spoken of as being close, waxy, or watery. The potato plant is sometimes affected with a fungus—the Phytophera infestans—which causes the disease knoAvn as potato murrain. This can be readily detected by the micro- scope. The disease commences in the leaves of the plant, and thence extends to the stem and on to the tubers. On the surface of the latter, brown spots make their appearance, penetrate the potato, and eventually cause it to rot and decay. The quality of the potato is usually judged by its size, firmness, and absence of fungus disease. A still better judgment may be formed by taking the specific gravity, and using the foUowing tables :—Multiply the specific gravity by the factor opposite it, and divide by 1000 : the result is the percentage of solids :— Fig. 49. Specific gravity, between 1061-1068 1069-1074 1075-1082 1083-1104 Factor. 16 18 20 22 Specific gravity, _, between 1105-1109 24 1110-1114 26 1115-1119 27 1120-1129 28 If the starch alone is to be determined, deduct 7 from the factor, and proceed as before ; the result is the percentage of starch. If the specific gravity of the potato is— Below Between Between Above Above 1068 1068-1082 1082-1105 1105 1110 The quality is very bad. ,, inferior. ,, rather poor. „ good. ,, best. As, however, the medical officer wdl seldom have an hydrometer which Avill give so high a specific gravity, and must work, therefore, with a common urinometer, the folloAving plan must be adopted :—Take a sufficient quantity of water, and dissolve in it \ an ounce or an ounce of salt, and take the specific gravity ; then add another \ ounce or ounce, and take again the specific gravity; do this two or three times, so as to get the increase of specific gravity for each addition of a known quantity of salt; then add salt enough to bring up the specific gravity to the desired amount. This is, ARROWROOTS—TAPIOCA—SAGO. 351 of course, not quite accurate, but in the absence of proper instruments it is the only plan that seems feasible. For the preservation of potatoes, sugar, in the form of molasses, is the hest plan on a large scale; a cask is filled with alternate strata of molasses and peeled and sliced potatoes. On a small scale, boiling the potatoes for a few minutes wdl keep them for some time. Free exposure to air, turning the potatoes over and at once removing those that are bad, are useful plans. The preserved potatoes are sliced, dried, and granulated, and Avhen weU prepared, are extremely useful. The Sweet Potato and the Yam are somewhat similar to the ordinary potato, and form good substitutes when potatoes cannot be obtained. They are very rich in salts, and are therefore excellent anti-scorbutics. As judged by their composition, Beetroot and Jerusalem artichoke are closely alhed to the potato, but as foods they are of very subsidiary impor- tance. The relative percentage composition of these vegetable foods is shown below. Proteid. Fat. Carbo-hydrate. Salts. Cellu-lose. A\Tater. Ratio of nitro-genous to non-nitrogenous food-stuifs. Potatoes, Beetroot, Jerusalem artichoke, 2-00 1-15 1-76 0-16 o-io 0-14 21-00 14-35 16-29 1-00 0*73 1-08 0-70 0-91 1-49 75-14 82-76 79-24 1 is to 10-6 1 „ 12-5 1 „ 9-3 Young unripe potatoes, and also those which have been kept too long and are sprouting, contain solanine, especially in the skin and in the shoots. Ripe potatoes which have reached their full size are either very poor in solanine, or totally free from this alkaloid. There is reason to believe that the poisonous character of solanine in potatoes is largely exaggerated, and that the diseases of cattle ascribed to the consumption of solaniferous potato waste from distilleries have been partly infectious diseases and partly poison- ings from ptomaines. Potatoes are further said to lose the chief part of their solanine by boiling. On keeping, there ensues in the potato a slow ■decrease of the starch, which passes temporarily into dextrin, and in small quantities into sugar. Kramer has recently described a bacillus, nearly allied to the B. butyricus, as the cause of the wet-rot in potatoes. If the spoiled parts are cut away, the remainder may be eaten without injury : the decayed part tastes and smells badly. Frozen potatoes are often destroyed by putrefaction after thawing, but before they putrefy they are not hurtful to health. Tubers bared of sod become dark coloured next the stem; their pungent taste is said to be due to solanine. ARROWROOTS, TAPIOCA, AND SAGO. The arrowroots are obtained from various sources. Originally, the term arrowroot was apphed to the starch from the tuber or rhizome of the Maranta arundinacea, because that root was supposed to have the power of counteracting the effects of poisoned arrows. The term is now applied to a great variety of starches, but, strictly speaking, should be limited to those 352 FOOD. known in commerce as Canna, Curcuma, Maranta, and Tacca arrowroots. The roots of the plants are dug up when about a year old, Avashed, and reduced to a pulp. Tins is repeatedly Avashed, passed through coarse sieves to separate the fibres, and the starch alloAved to settle, which again is Avashed and dried. When finished ready for exportation, arroAvroot is a white, tasteless, odourless substance, firm to the feel, and producing, on pressure, a shght crackling noise. Arrowroot, being a pure starch, has no dietetic value beyond that peculiar to this substance. It is chiefly used as a bland article of food for invalids, or, in an ordinary way, as blancmange, puddings, and biscuits. Maranta arrowroot, sometimes spoken of as Bermuda arrowroot (fig. 50), is derived from the Maranta arundinacea, a plant growing in Jamaica and Bermuda. It is judged by its whiteness, by its grains being aggregated into little lumps, and by the jelly being readily made, and being firm, colourless, transparent, and good tasted. The jelly remains firm for three or four days without turning thin or sour, Avhereas potato flour jelly in twelve hours may become thin and acescent. Under the microscope the starch grains are easily identified. They are shghtly ovoid, like potato starch, but have a mark or line at the larger end (the hilum of the potato starch is at the smaller end); the concentric lines are well marked. The most common adulterations are sago, tapioca, and potato starch. AU these starch grains are readily detected by the microscope. The starch grains of St Vincent arrowroot have the same character as those of Bermuda arrowroot, and it is almost impossible to distinguish them. Curcuma arrowroot is furnished from the Curcuma angustifolia, a species of turmeric plant. Its starch grains under the microscope are large and Fig. 51. Fig. 52. oblong (fig. 51), marked with very distinct concentric lines, which, however, in the majority of cases, are not complete circles. The hilum is often indistinct and always at the smaller end. Tacca arrowroot is obtained from the Tacca oceanica, growing in Tahiti. Its Granules are truncated, or wedge-shaped at one end. Their striation is indistinct with a more or less circular hdum. These starch grains are SAGO. 353 practically indistinguishable from those of Rio arrowroot (fig. 52) obtained from Jatropha manihot or Cassava growing in the Brazds. It is from the finest part of the pith of this plant that commercial tapioca is made. Tapioca is often adulterated with potato starch and sago, both of which are easily detected by the microscope. Canna arrowroot or " Tous les Mois " (fig. 53) is furnished by the Canna edulis, a native of the West Indies. Its starch grains are very like those of potato, but they are much larger, flatter, and have more definite striae. The hilum is at the smaller end of the grain. Sago is derived from the sago palm, Sagus farinifera, but some inferior kinds are obtained from the Cycas circinalis. The starch grains are very similar to those of tapioca, but larger (fig. 54). Granulated sago is either "common" or "pearl"; the latter is chiefly used in hospitals. The starch is soluble in cold as well as in hot water. The starch grains are elongated, rounded at the larger end, and compressed at the other; and hence their shape is quite different from the potato starch. The hilum is a point, or more often a cross, slit, or star, and is seated at the smaller end, Avhereas in Maranta arrowroot the hilum is at the larger end. Rings are more or less clearly seen. Fig. 54. In the market is a factitious sago made of potato flour. This is sometimes coloured red or brownish, either from cochineal or sugar. In thirty specimens Hassall found five to be factitious. The microscope easily detects potato starch. Under the name of British ArroAvroot or " Farina," potato starch is sold in the market, so white and crackling, and making so good a jelly, that it is not ahvays easy to distinguish it from Manihot. The microscope at once detects it. The pear-shaped grains, marked hilum towards the smaller end, and the swelling with weak liquor potassae, render a mistake impossible. In making the jelly a much larger quantity is required than of Maranta arroAvroot. Maranta arundinacea, mixed with twice its weight of hydro- chloric acid, produces a white opaque paste, whereas potato starch treated similarly produces a transparent acid jelly-like paste. As it is sometimes difficult to remember the characters of the different forms of starch, their microscopical differentiation may, to a certain extent, be facilitated by a tabulated arrangement such as the following:— Z 354 FOOD. I. Starches Avith isolated smooth or unfacetted grains, being originally free in the cell cavity. General Characters. Particular Characters. Form. Hilum. f Grainslarge. Hilum at the small end. L—Contour ovoid. Hilum eccentric. ( Form. Hilum. Outline even. Hilum distinct. Continuous rings, oblique, including more than half the grain. Outline even. ( IIHum distinct. Continuous j rings, nearly J transverse, in- j cludinglessthan I Hilum indistinct. B.—Contour oval. Grains me- dium sized. Hilum at the larger end. Hilum longitudinal, linear lateral. half the grain. Outline uneven, often with beak- like projections. Outline more even, beak less frequently seen. Grains often broad and reniform. Grains narrower and more uni- form. I C.—Contour/ round. \ Hilum central. ( Form lenticular. ..Form spherical. Hilum slit-like, triradial or crucial. Hilum similar, but less apparent. Hilum cleft-like, puckered, irreg- ular. Hilum less puck- ered and more regular. f Surface convex at the hilum. Grainslarge and I minute only. \ Surface depressed at the hilum. Grains large, medium - sized, and minute. Hilum often deep- ly fissured, star- like. Potato; Brit- ish arrow- root. Tous-les-Mois (C anna) arrowroot. Curcuma ar- rowroot. Bermuda {Maranta) arrowroot. St Vincent arrowroot. Bean starch. Pea starch. Wheat starch. Barley starch. Rye starch. II. Starches with the grains faceted by original juxtaposition in the cell caAdty. Hilum central. t*H A.—Often presenting the rounded free surface of, grains originally super ficial in the cluster. f Hilum of- ten caver- nous. Hilum stel- late. f Hilum stel- late. B.—Altogether faceted. -j | Hilum in- conspicu- L ous. f Grains very large, with a central sinus or | cavernous antrum. (Rings, sinuous, ir- regular. ) Grains small. (Sago in miniature.) ( Grains small. -! (Like Tapioca with- in out preparation.) f Grains small. -J (Discoidal with fa- \ ceted margin.) In rounded glomeruli or compound grains, and free in the cells. | Closely packed in the cells I and fixed. Grains minute. Sago. Tapioca. Rio arrow- root. Maize. Oats. Rice. SUGAR—HONEY—SACCHARIN. 355 SUGAR. There are two chief varieties of sugar iioav found in the market, namely, sugar from the sugar-cane, Saccharum officinarum, and beet-sugar from the Beta vulgaris. Cane-sugar is either white or brown. The Avhite cane-sugar contains, per cent., 93*33 of saccharose, 1*78 of dextrose, 0*35 of proteid, 0*30 of gum, 0*91 of so-called extractives, 0*76 of salts, and 2*16 of water. Brown sugar contains more water than the white, the amount varying from 4 per cent, in the better kinds to 10 per cent, in the coarser varieties. Its colour is due to invert sugar, of Avhich there is 4 or 5 per cent, present. Beet-sugar contains, in 100 parts, 94*5 of saccharose, 0*18 of invert sugar, 1*93 of water, and 3*37 of extractives, gums, and vegetable acids. Honey differs from ordinary sugar in containing more dextrose and laevulose than saccharose. Its precise composition varies very much, but, as an average, it may be said to have, in 100 parts, 72*88 of invert sugar (laevulose 38*65, dextrose 34*23), 0*22 of dextrine, 1*76 of saccharose, 0*71 of wax, 0'76 of proteid, 2"82 of non-saccharine substances, 0*25 of ash, 0*028 of phosphoric acid, and 20*6 parts of water. Honey is often adulterated with cane-sugar, or Avith sugar made from starch and with inert matter (Martin). The total invert sugar may be as high as 80 per cent., or as low as 64, but the laevulose is ahvays in greater proportion than the dextrose. Examination of Sugar.—Sugar should be more or less white, crystalline, not evidently moist to the touch, and should dissolve entirely in Avater, or leave merely small fragments, which, on examination with the microscope, will often be found to be bits of cane. The whiter the sample, the less usually is the percentage of water. The unpurified sugars contain nitrogenous matters Avhich decompose, and a sort of fermentation occurs. The sugar-mite is often found in such sugar, while fungi are very frequently present. The actual amount of sugar present in a sample may be con- veniently estimated by dissolving 5 grammes in distilled water and making up to 100 c.c. Of this solution, 10 c.c. are diluted to 100 c.c. with water and from 1 to 2 c.c. of hydrochloric acid added. Boil away one-third of the volume, cool, neutrahse with sodium carbonate, and then make up to original bulk of 100 c.c. Titrate some of the copper solution, as used for lactose (page 316), Avith this solution of inverted sugar and calculate out as a percentage of cane-sugar: each c.c. of the copper solution equalling 5 milligrammes of inverted sugar. Saccharin.—In this place it is convenient to mention saccharin (orthobenzoic sulphinide) Avhich has appeared in the trade as a white inodorous poAvder, three hundred times as sweet as cane-sugar. Pure saccharin is sparingly soluble (1 in 260) with a faint acid reaction, but lately an alkaline salt has been introduced. Avhich is more readily dissolved. Its taste is slightly aromatic, and its after-taste irritating only when the powder itself, or a concentrated solution, is tasted: dilute solutions have a purely sweet flavour. Saccharin is recommended as a substitute for cane- sugar. As 2 grains of saccharin suffice to give 1000 grains of starch sugar the same sweetening power as that of 1000 grains of cane-sugar, it is likely that substitutions of a cheaper for a more expensive material will be attempted in this direction. The detection of saccharin may be effected by extracting the dried substance with anhydrous ether: if the evaporated residue have a sweet 356 FOOD. taste, saccharin is present, all sugars and also glycerin being insoluble in ether. According to the experiments of all observers, saccharin is non-poisonous, even in continuously large doses; but since it has no nutritive value, its substitution for a carbo-hydrate reduces nutritive value. A substitution of pure starch-sugar, sweetened up with saccharin for an equal Aveight of cane- sugar, cannot be regarded, physiologically speaking, as an injury. If the use of saccharin is thus hygienically unobjectionable, a declaration of its presence should be unconditionally demanded. The antiseptic and anti- zymotic properties of saccharin have no practical value. SUCCULENT VEGETABLES AND FRUITS. This class of vegetable foods contains articles of diet winch supply water, vegetable acids, and salts to the body. Their chief value depends upon their anti-scorbutic properties, as their absence for any lengthened period from a diet leads to the production of scurvy. To all succulent vegetables, common salt is added in cooking ; and to some, butter is a valuable addition. The fruits are rich in water, vegetable acids, and salts of the organic acids: they are eminently anti-scorbutic, especially the lemon. Some, like the cocoa- nut, are rich in oil, Avhile others, like the banana, contain large quantities of sugar. Except for their anti-scorbutic properties, and their-pleasant taste, the fruits are quite subsidiary as articles of diet. The percentage com- position of some ordinary vegetables and fruits is given in the following table:— AVater. Pro-teids. Fat. Starch. Glucose. Cellu-lose. Salts. Malic Acid. Oxalic Acid. Pectose and Gum. Citric | Acid. ; Cabbage, Carrots, Cauliflower, . Celery, . Lettuce, Spinach, Turnips, Rhubarb, Apples, . Dates, . Gooseberries, . Figs, . . 85-50 87-80 90-89 93-30 96-00 88-47 90-78 95-10 83-00 20-80 86*00 17*50 5-00 1-00 2-48 1-20 070 3-49 1-18 0-90 0-40 6-60 0-40 6-10 0-50 0-20 0-34 0-20 058 0*22 0V20 0 90 7*80 9-60 3-34 1-60 1-00 4-34 5'89 3-00 6-40 1-21 2-20 o'-io 2*10 6-80 54-00 7-00 57-50 0-91 0-90 0-50 0-93 1-13 1-10 3-20 5-50 2-70 7-30 1-20 1-00 0-83 0-80 1-00 2-09 0-80 0-50 0-40 1-60 0-50 2-30 1-00 0-30 5*20 12-30 1-90 5-40 ... ... 1*50 Vegetables scarcely require any very critical hygienic examination : if they have become too old and Avoody, they are inferior in nutritive value, and are imperfectly digested : stale vegetables are equally inferior in value and far from appetising. If vegetables are watered with sewage or drainage containing the ova of the Taeniae, the latter may find their Avay into man, and grow up to cysticerci: pathogenic bacteria may possibly be introduced in the same way; in fact, there is reason to believe that in this manner watercress, growing in seAvage-polluted streams, has been on several occasions the source of enteric fever outbreaks. According to Lominsky, various bacteria penetrate into the roots of young SUCCULENT FRUITS—MUSHROOMS. 357 plants but do not increase there. Some pathogenic species, if inoculated into living leaves, are said not merely to maintain themselves, but even to multiply. These observations, hoAvever, require verification. De Loos has recorded a remarkable instance of lead poisoning from vegetables being groAvn upon soil over some disused Avhite-lead Avorks. He states that 650 grammes of turnips had absorbed 10 milligrammes of lead, six carrots 17 milligrammes ; and four lettuces had taken up as much as 130 milligrammes of lead. Frequently cases of poisoning arise from mistakes as to the identity of vegetable species. Thus fool's parsley (uEthusa cynapium) is mistaken for true parsley, Avater hemlock (Cicuta virosa) for celery, and (Enanthe crocata for carrot. Dried vegetables are uoav produced of excellent quality, and Avhen properly prepared taste as if fresh. They appear to present no special points for hygienic criticism. Unripe fruit, rich in cellulose, acids, and in tannin, but poor in sugar, often occasions intestinal catarrh. The popular characteristics of ripeness should suffice for an experienced observer. For stone fruits and berries, the colour, consistence, and taste should be noted: in the case of seed fruits, such as apples and pears, it is advisable to examine whether the pips have taken a brown colour. Mouldy fruit should invariably be rejected. Dried fruits often require examining for dirt, sand, mould, and mites. In some specimens of American tinned fruit a small proportion of zinc has been detected. Among the fruit juices, currant and cherry juice are of less interest than raspberry. The juices are attempted to be obtained from the pressed and SAveetened fruits partly by boiling, and partly by fermentation. Frequently the colour suffers by unsuitable preparation or preservation, and is artificially heightened by vegetable colours, such as that from infusions of the field poppy or more commonly by means of aniline dyes. There is no objection to the use of these latter if employed in small quantities and provided they are free from arsenic and other impurities. Mushrooms and the fungi generally, in spite of the high percentage of nitrogen in their solids, do not rank higher in nutritive value than the majority of vegetables. Like the latter, they yield an edible food only in presence of much Avater; their nitrogen is largely referable to Avorthless amido-compounds, Avhile the utilisation of their albumin is imperfect. There are no general characters for the recognition of edible fungi. It must be borne in mind that the virulence of many poisonous kinds varies according to the year and locality. It is obvious that of the kinds knoAvn as wholesome, only such specimens must be gathered as are fresh, not decayed or damaged by rain. All mushrooms must be carefuUy cleaned before use. It is not advisable to preserve portions of dishes of mushrooms which have not been consumed. The use of dried mushrooms is as far as possible to be avoided : they are seldom correctly determined, often imper- fectly cleaned, dusty and perforated by insects. PREPARED CONCENTRATED AND PRESERVED FOODS. This is a very important subject, but one upon which considerable mis- conception exists, OAving to a confusion of ideas betAveen concentration and preservation. It is obvious Iioav important it must be in time of Avar to have a food Avhich may be at once nutritious, portable, easily cooked, and 358 FOOD. not hable to deterioration. In this connection, however, it must be remembered that a man must get his 260 to 300 or even 350 grains of nitrogen, and 8 to 12 ounces of carbon, in each twenty-four hours, besides some hydrogen and salts. The work of the body Avhen in activity cannot be carried on Avith less; and at present these elements cannot be presented to us in a digestible form in a smaller bulk than 22 or 23 Avater-free ounces. Concentration at present cannot be carried beyond this, and practically has not really been carried to this point. Life, hoAvever, and vigour may for some days be preserved with a much less amount; and the total amount of food has been reduced to 11 Avater-free ounces daily, Avith full retention of strength for seven days, though the body Avas constantly losing weight. For expeditions of three or four days, if transport Avere a matter of great difficulty, soldiers might be kept on from 10 to 12 ounces of Avater-free food daily, provided they had been fully fed beforehand, and subsequently had time and food to make up the tissues of their OAvn bodies, which Avould be expended in the time, and Avould not have been replaced by the insufficient food. When Ave inquire into the concentrated foods now in the market, some of Avhich profess to supply all the substances necessary for nutrition, Ave find many of them not very satisfactory. They are often not so concen- trated as they might be, or are deficient in important principles, or are disagreeable to the taste. The truth is, Ave cannot so concentrate food- stuffs down to a portable or convenient size, and at the same time obtain from them the full nutritive value of the original or fresh articles. Recog- nising this fact, it is better to divide all the so-called concentrated and preserved foods into (1) those which are really prepared as emergency rations, aiming at supplying more or less of the daily needs of the body in a minimum bulk, and (2) those which are essentially preserved food-stuffs. Prepared Emergency Foods or Rations.—These naturally afford the greatest interest to the soldier, sailor, hunter, and explorer, or other persons engaged upon expeditions where ordinary articles of food are difficult to obtain, and when circumstances of transport render the use of easily cooked, compact and portable substances absolutely necessary. Foods of this kind constitute the so-called "iron" or "eiserne" ration of the Germans and other armies; by which allowance is understood those ahments given to each soldier in the field for emergencies. Many different preparations have been recommended for this purpose, and among them we may include the various ErbsAvursts and pea-sausages, the meat powders, meat biscuits, con- centrated soups, meat extracts, and different compound rations made up of two or more preserved food-stuffs. The original ErbsAvurst of the Germans Avas a sausage of pease with bacon fat. Numerous preparations of this kind are now in the market; they consist in the main of poAvdered pease Avith bacon or beef fat and condiments, the Avhole being enclosed in a waterproof cover, and then issued as a sausage or packet. Some few also contain poAvdered beef. The nutritive value of the several kinds is given in the table Avhich folloAvs. Erbswurst soon becomes distasteful, causing digestive derangements from its excess of fat; it at the same time lacks the sustaining qualities of fresh meat. The pea-soup tablets of Neumann are made of meat juice with pea flour. Their relatively high amount of salts is said to be due to sodium chloride. It would be necessary to take 21 ounces of this preparation to get the proper quantity of proteid, yet Avith that one would obtain only 0*6 ounce of fat, which is absolutely insufficient. A similar defect is present in the pease and haricot cakes of Schorke, and the meat cakes of Konig of Mayence. PREPARED EMERGENCY FOODS. 359 Rumford's ration contains pieces of meat with flour, pearl barley, and salt. Like Schorke's preparations, it does not constitute a complete aliment. Edward's desiccated soup was well spoken of in our own army durinc several campaigns. It consists of a mixture of beef and vegetables, and is easily prepared by boiling an ounce in a pint of water. Allusion may here be made to "panole," which is a preparation made of ground parched Indian corn 3 parts, and sugar 1 part. It has been largely used in the expeditions on the south-west frontier of the United States, and has a high reputation in the American army. An English and at the same time a very good preparation is Morel's field ration, sold as a sausage, Aveighing 18 ounces. Equally good articles are Moir's sausage and Corbin's pea and lentil pastes. In all this class of pre- pared or emergency rations, Ave find a marked excess of fats and carbo- hydrates. The salts are variable, though in all cases much in excess of the meat quantities. Although these preparations yield the alimentary elements of a complete food, yet they are in such proportion as only to serve as food for a limited time. Further, in most of them the albumin is vegetable, being derived from peas and beans. It is true the chemical values of animal and vegetable albumin are the same, yet experience shows the former to be very much more easily and completely assimilable than the latter. Another class of preparations are the various meat cakes and meat biscuits; in them the proteids are mainly derived from animal sources and not from the legumes. The meat is dried and finely poAvdered, and represents in nutritive value about four times its Aveight of ordinary meat with bone. In England, the chief meat powder is Johnson's, which makes an excellent soup. In Germany, Hoffmann's meat powder is Avell spoken of, especially when made up into different kinds of cake or biscuit, with either beans, rice, barley meal, Avheat flour, or potatoes. In 100 parts this meat poAvder con- tains 73 of albumin, 7 of salts, 10 of water, and 1 of hydrochloric acid. Hoffmann's meat cakes are agreeable, portable, and very easily cooked. If consumed for many days together, the digestion becomes disturbed and the appetite fails. Taken Avith biscuits, they have been largely used and tried in the United States army, but not received with sufficient favour to Avarrant their regular issue. Erdmann's meat powder is similar to other preparations of this kind. The majority of meat biscuits noAV in the market are as a rule nothing more than meat powders mixed with flour and Avater. Owing to the extreme heat to which they are exposed in baking, the meat in them is usually rendered valueless. A large number of them, from time to time, have come under notice at Netley, but the greater number have failed to present any very distinctive points of merit. The French speak highly of a meat cake pre- pared by Scherer-Kestner who, by the admixture of pepsin, really obtains the formation of a digestible biscuit. Analogous to this of Kestner's, there exists in Germany a biscuit made by Schill, in which the water is replaced by defibrinated blood. According to Heidlesheim and Voit, this contains 26 per cent, of proteid and only 2*5 per cent, of fats; but beyond being highly assimilable, it is not of much use as a prepared food. Another food is "Courousa" made by Jacqiiier of Nantes, and which has been tried in the Russian army. Each ration of it weighs 12*75 ounces, and is supposed to contain elements for a day's nourishment. Experience shows its qualities to be indifferent. The Russian Government prepares and issues to its troops a variety of prepared foods or rations similar to the meat cakes of Hoffmann, already noticed. They consist mainly of finely poAvdered meat mixed Avith barley or peas, or oat-meal, or cabbage, or potatoes and mushrooms. Their 360 FOOD. use in the Russian army is highly extolled, being issued in daily rations of 25 ounces. They are, however, admitted to be difficult of digestion and probably very unsuited for Western nations. A special preparation, made by Grouvel of Paris, was largely tried by the French War Office a few years ago; 11 ounces being said to afford a day's aliment. Its composition was roughly 20 parts of beef, 48 parts of pea-flour, 20 parts of fat, and 12 parts of condiment. Although it appeared to be considerably superior to the Erbswursts and German pea-sausage, its general utility was not manifest. The concentrated soups and meat extracts date from the introduction of Liebig's well-known preparation. Numerous articles of this kind are noAV in the market, notably those of Brand, Kemmerich, and others, which exist chiefly in the form of fluid meats, essences, extracts, &c. These, from their composition, are not capable of replacing a true alimentary substance, nor even are they the representation of the least quantity of meat, either roast or boiled. They are merely the juices of meat, not the meat itself. An extraordinary large number of these meat extracts are now in the market, but it is only too probable that many of them are not true meat extracts, but artificial substitutes. A good meat extract should have less than 20 per cent, of water: it should contain almost 25 per cent, of its weight of mineral meat salts, one quarter of which should be phosphoric acid in combination Avith potash, not Avith lime : it should, when dissolved in warm water, yield but an insignificant precipitate on the addition of double the amount of alcohol: it should be solid or nearly so, free from all excremen- titious odour and from a burnt flavour. Experiments indicate that diets composed exclusively of meat extracts kill animals more quickly than total deprivation of food : these preparations are not, however, quite without alimentary value. They act as stimulants, food regulators, and digestive agents, rather than as providers of nitrogenous matter. It would be a fatal mistake to use these extracts, deluded by their portability, and with the idea that they in small compass contained considerable reparative materials : they are essentially alimentary aids and not true foods. If used solely in that sense, they can be turned to very good account as stimulants during and after very great exertion. A number of condensed soups are now made mixed Avith vegetables; these, if used with biscuits or bread, constitute articles of considerable value for use in times of emergency, and when the more ordinary aliments are not available. Of all the prepared foods, the army rations made by Moir, Maconochie, and other makers appear best to conform to the ideal type of an emergent ration. They exist in several varieties, consisting of mixtures of either beef or mutton with potatoes, carrots, onions, beans, gravy, and pickles. Some also contain bacon fat and brawn, the whole being cooked and contained in hermetically sealed tins of small size, and may be eaten either cold or warmed up. In a sample recently examined by us, were found 7*2 ounces beef and fat, exclusive of bone, 6*7 ounces of mixed vegetables, and 6*1 ounces of gravy, or 20 ounces of fresh and Avholesome food. In another tin, were found 9*2 ounces of mutton, without bone, 6*8 ounces of vegetables, and 3 ounces of gravy, or 19 ounces of fresh and palatable food-substances, pre- senting all the qualities of fresh meat and fresh vegetables. In some other examples of these prepared foods, cocoa constitutes one of the elements, being placed in a separate section of the tin. The accompanying table gives the percentage composition of some of the prepared foods just considered; but it must be borne in mind, Avhen judging the merits or demerits of this class of aliment, that not only must their nutritive value be taken into account, but also their portability, durabihty, PRESERVED FOODS. 361 palatableness, and readiness for cooking. On the Avhole, it must be con- fessed that this question of preparing emergent foods has not been yet satis- factorily solved; much remains still to be accomplished. Percentage Composition of some Preserved and Prepared Foods. ■ .rt HP .^9 tip 5^ o -p. « o3 c £ -3 Erbswurst (German), 7*03 21*00 4 12 8-14 4-37 4-37 22-20 45-76 4*00 ,, (Knorr's), 10*86 17*50 2-62 9-64 2-62 2-62 23-96 35-74 11-94 „ (Moir's),. 8-51 15*75 3-50 9-62 2-19 0*44 23-38 47-91 4-44 Pease sausage (Moir's), 11-40 21*00 4-75 9-26 5-68 1*31 32-30 27-40 7*90 Hoffmann's meat cake, 6 45 24-24 24-76 39-73 4*82 Neumann's pease cake, 9-51 20-53 3-66 53-10 13*20 Schorke's bean cake, 7-98 16 72 17-20 42-10 16*00 Rumford's soup cake, 13-40 16 20 1-80 56-30 12*30 Konig's meat biscuit, 5-10 8-30 6-10 76-70 3*80 SchilPs ,, . . 14-50 24-70 2-50 56-70 1*60 Dunmore's ,, . . 11-89 10*81 8-06 67"94 1-30 Armebis ,, . . 8-51 15-75 15-80 58-04 1-90 Cheese biscuits (Dunmore's), . 11-35 11-37 15-84 59-63 1-80 Emergency ration (Woolwich), 6-94 8-00 18-11 65-58 1-37 GrouvePs army ration, 14-71 30-57 18-77 31-45 4-50 Moir's soldier's ration, 53-91 23-44 2-62 10*16 2*43 8*23 14-72 612 1-80 Morel's field ration,. 27-45 32-94 23-60 10-54 5-47 Pemmican (Australian), . 2-39 51-70 3:64 41-86 5-46 0-74 42-08 3-65 Maconochie's service ration, 76-59 9-72 5-48 5'-88 2-33 Courousa, .... 21-03 24-10 21-22 27*35 6-30 Panole, ..... 7-83 7-50 4-50 72*67 7-50 Meat extract (Queensland), 16-31 57-61 6*44 2-59 48*58 2-25 22-21 Concentrated beef-tea (Mason's), 47-74 47-78 0-22 20*15 10-00 17*41 5-38 Essence of mutton ,, 90-23 9-33 o-n 2*08 1-31 5-83 1-15 Meat extract (Armour Co.), 19-44 47-00 7 00 3-06 36-94 1-62 29-00 Johnston's fluid beef, 38-93 45-90 10*01 7-00 4-37 24-51 1-64 13-53 Beef extract (Armour Co.), 15-22 55-77 2-67 6*95 3-50 42-65 2-17 26-80 Pea-soup (Lazenby), 14-16 22-75 4-37 10*50 3-50 4-37 1-60 53-58 7-90 Meat peptone (Koch), 40-60 49-69 1-45 17-50 12-78 17-96 2-87 6-84 ,, ,, (Kemmerich), 38-29 5026 1-05 14-26 17*85 17-10 2*54 8-90 Bovril lozenges, 18-30 61-2Q 3-02 27-38 13*76 17-04 6*78 10*93 8-78 Bovinine (Bush's), . 81-44 16-16 9*48 1-29 5-39 0*18 1*45 0-77 Corned beef (M'Neill's), . 59-16 24-92 12*59 3-32 Compressed beef (Queensland), 61-28 31-05 5*83 1-83 Kreochyle Co. 's liquid meat, . 81-22 15-37 4-45 3-76 0*81 6-35 1-22 2-19 Liebig's extract, 19-33 46*48 0-84 7-64 2*95 35-05 1-92 32-26 Preserved Foods.—Speaking generally, the methods employed to pre- serve food-stuffs are based upon one or more of the following plans:—1. Freezing or refrigerating. 2. Salting, and the use of various chemical agents. 3. Drying. 4. The exclusion of air, and hermetically sealing in tin cases. The employment of freezing and refrigerating is noAV extensively applied to the preservation of meat during long voyages from the Colonies and South America, the carcasses reaching this country in excellent condition; but the method is hardly applicable for the preservation of meat in the sense in which meat is understood to be preserved in this section. Salting of meat is a well-known form of preserving. Owing to the great loss of the nutritive qualities, which meat suffers in the process, the use of salted meat to any extent is not to be recommended. Besides salt, all 362 FOOD. kinds of chemical agents have been tried as food preservers, more particularly boracic and sahcylie acids, together with coatings of fat, glucose, and gelatin. Meat is also preserved in tin cases, either simply by the complete exclusion of air (Appert's process) or by partly excluding air and destroying the oxygen of the remaining part by sodium sulphite (M'Call's process). It is not necessary to raise the heat so high in this case, but the meat is less sapid. Meat prepared in either way has, it is said, given rise to diarrhoea, but this is simply from bad preparation: Avhen Avell manufactured it has not this effect. Meat is also preserved by draAving off the air from the case, and substitut- ing nitrogen and a little sulphur dioxide (Jones and Trevithick's patent), or the air can be heated to 400° or 500°, so as to kill all germs (Pasteur), and then allowed to flow into an exhausted flask. Various other plans have been proposed, such as the use of antiseptics, borax, boric acid, salicylic acid, glycerin, &c, and various preparations such as glacialin, boro-glyceride, and the like, consisting of mixtures of two or more. Of these preparations, boric acid and glycerin appear to be the least hurtful; but food to which these substances have been added is liable to cause gastric derangement, and they are not to be recommended. To dried food, its unattractive appearance and insipidity afford many objections. In this category we may consider such forms of dried meat as the tassajos and charqui of South America, the biltong of the Kaffirs, the kelea of the Arabs, and the dauer fleisch of the Germans. Dried Cerealia.—Many flours, if Avell dried, will keep for a long time. There are noAv in the market different kinds of malt biscuit and granulated malt food. Liebig's food for infants is composed of equal parts of wheaten flour and malt flour mixed with a little potassium carbonate and cooked with 10 parts of milk. The wheat and malt flour are usually cooked and sold in powder ready to be boiled with the milk. Dried Bread.—In addition to biscuit already described, bread has been partially dried by being pressed in an hydraulic press (Laignel's method). Much water flows out, but when taken out the bread stdl feels moist. In a day or two, however, it becomes as hard as a stone, and in a year's time will be found good and agreeable. Placed in water, it sloAvly sAvells. The " pain biscuite " of the French army is bread dried by heat. Dried Potatoes are sold in two forms—sliced and granulated. In either case the potato is easily cooked, and is very palatable. It should be soaked in cold water first for some time, then slowly boiled, or, what is much better, steamed. The directions for cooking EdAvard's preserved potato. (which is granulated) are: "To three-quarters of a pound add about one quart of boihng water, stirring it at the same time; cover it closely; the basin or vessel used should be kept hot; let it stand for ten minutes ; then well mash, adding butter, salt, &c, at discretion." It is stated to be equal to six times its bulk of the fresh vegetable, but this is hardly borne out by analysis : four times is as high as it would be safe to allow. The analysis shows that a pound of preserved potato contains the sohd matter of only 3i pounds of ordinary fresh potatoes. Driecl Vegetables (other than Potatoes).—Dried and compressed vegetables of all kinds (peas, cauliflowers, carrots, &c.) are now prepared, especially by Messrs Masson and Challot, so perfectly that, if properly cooked, they furnish a dish almost equal to fresh vegetables. Analysis shows that' dried compressed cabbage contains the solids of seven times its Aveight of fresh cabbage, whilst the mixed vegetables contain fire and a half times the solids of the fresh vegetables. They must be cooked very sloAvly. If there is PRESERVED FOODS. 363 any disagreeable taste from commencing putrefaction, which is very rare, a little chloride of hme removes it at once. Potassium permanganate can be also used for this purpose. As anti-scorbutics, dried are said to be inferior to fresh vegetables, but are still much better than nothing. Dried Apples in slices are now imported largely from America : they are palatable Avhen cooked, and would be a useful article in the field. Dried Milk is also met with in the form of a poAvder, but is less prefer- able to preserved milk sold in the hquid form, as during the process of manufacture very considerable loss of casein takes place. Dried Eggs.—The yolk is not easily kept after drying, but the white can be so; it is cut into thin scales, and forty-four eggs make about one pound. The yolk and white are also mixed with flour, ground rice, &c, and are then dried. The tinned foods stand out pre-eminently as the best of all kinds of preserved food. Not only meats, but nearly every variety of aliment has been and can be preserved by means of hermetically sealing. The potted and preserved meats, such as the Chicago and Australian kinds, speak for themselves. From analysis, their nutritive qualities appear to be nearly identical with fresh meat, wlhle the absence of bone renders them, weight for Aveight, of increased value, to say nothing of their compactness, durability, and portability. Their saltish taste renders their prolonged use distasteful, but a greater employment of pickles and condiments will in great measure meet this defect. Among this class of preparations, Pemmican deserves to take a high place. It has been extensively used in Arctic voyages, and is made of the best beef and fat rolled and dried together : sugar, with raisins and currants, are some- times added to it, and Avith these latter it is of undoubted high anti-scorbutic value. Its analysis shoAvs that, in itself, it offers all the elements of a true food. In regard to other organic products, the processes of preservation by tinning have reached considerable perfection, notably in the case of milk, fruit, and vegetables. Concentrated Milk.—Milk is evaporated at Ioav steam heat to the con- sistence of a thick syrup, and white sugar is added. After opening the tins the samples remain good for over a month. The amount of sugar, hoAvever, is very large; in one sample it was found to be as much as 167 lactose and 60*7 cane-sugar. Other samples, such as the Swiss and Bavarian (Loef- iund's), are preserved without extra sugar, and are reduced in bulk to a half or a quarter of the original: these, hoAvever, must be used as soon as possible after the tin is opened, for they do not keep like the sweetened preparations. The general composition and nutritive value of some of these preserved milks has been aheady mentioned. Preserved Fruits and Vegetables, that is, those preserved in tins in their natural condition, are much to be preferred, both as being more palatable, and as being more nutritious, and better anti-scorbutics than the dried varieties. They occupy, however, much greater bulk, and are liable to be contaminated by metallic poisons (copper, lead, tin, zinc) from a solution of these metals by acids formed during fermentation or preservation. Green vegetables, especially beans and peas, when preserved in tins, are frequently coloured by sulphate of copper. The amount found varies from none to as much as 3 grains per tin. This addition is quite unnecessary, as the public would soon become accustomed to yellowish or pale green vegetables, provided they were assured that such colours Avere the natural result of preservation processes. 364 FOOD. Hoav far various preservative and colouring chemical agents should bo allowed to be added to foods, and to what extent, Avhen so added, they influence health, has been a matter of some discussion. Practically, boracic acid, sulphurous acid, and salicylic acid are the only chemical preservative, and salts of copper the only colouring agents in general use : and although Ave are unable to fix any precise quantity, or any exact limit of time at which these several substances act harmfully, we are justified in demanding at least:—1. That the kind and quantity of the preservative or colouring agent added be always stated on the label. 2. That milk and other articles specially used by children should not contain any preservative addition Avhatever. 3. That the minimum quantity of the agent required for the preservation or colouring of the fresh article should not be exceeded. Even admitting that preservative and colouring agents are relatively harmless, their general use should be discouraged, as they facilitate an uncleanly and slovenly treatment of food, rendering it possible to preserve articles of diet, often in incipient decomposition, for some time with an appearance of freshness which is altogether false, besides favouring trade frauds and possible dangers to health. BIBLIOGRAPHY AND REFERENCES. Adametz, "Die Bakterien normaler und abnormaler Milch," Centralblatt f. Bakter., viii. p. 109. Arustamoff, "On the Presence of Pathogenic Bacteria in Sturgeons," Centralblattf. Bakter., x. p. 114. Baginsky, " Zur biologie der normaler Milchkothbacterien," Zcit. f. phys. Chemie, Bd. xii. p. 443. Beaumont, Experiments and Observations on the Gastric Juice and the Phys. of Digestion, Edin., 1838. Bell, Sir J., Analyses and Adulterations of Foods, Lond., 1883. Blyth, Foods, Composition and Analyses, Lond., 1882 ; also The Chemistry of Foods, 2 vols., Lond., 1889. Bunge, Physiol, and Patholog. Chemistry, trans, by Wooldridge, Lond., 1890. Church, Food, its Sources, Constituents, and Uses, Lond., 1882; also Food Grains of India, Lond., 1886. Creighton, Bovine Tuberculosis in Man, Lond., 1881. Daxileavski, Pfliiger's Archiv, xxxvi., 1885, p. 237. De Chaumont, "The Soldier's Ration," Sanitary Record, Feb. 5th, 1876. De Loos, "On the Production of Plumbism by Vegetables," Jahrcsberichte fur Pharmakologie, 1877, p. 536. Drechsel, "Eiweisskorper," in Ladenburg's Handwbrterbuch der Chemie; also Journ. f. praktische Chemie, N.F. xix., 1879. Duclaux, Le Lait, Paris, 1887. Dufour and Constantin, Nouvelle fiore des Champignons, Paris, 1891. Fischer, Handbuch der Kohlenhydrate, Berlin, 1891 ; also various papers in Berichte der Chem. Gesellsch., xxvi. p. 2400. Fleischmann, Article " Milch," in Dammer's Lexikon der Verfalschungen. Forster, Article "Ernahrung," in Ziemssen's Handbuch der Hygiene, 1882. Frankland, Phil. Mag., Sept. 1866, vol. xxxii. p. Gamgee, Physiological Chemistry, Lond., 1893. Graham, Chemistry of Brcadmaking, Lond., 1880. Gray, " Report on Two Cases of Fatal Poisoning of Children appar- ently due to the Milk Supply," Practitioner, Jan. 1894. Hammarsten, Zeitsch. f. Phys. Chemie, Bd. xix. p. 19. Harvey, Report to Local Govern. Board on Fever at Svjanage in 1886, apparently due to watered Mdk. Hassall, Food, its Adulterations, and the Methods for their Detection, Lond., 1876. Hehner and Angell, Butter, its Analysis and Adulterations, Lond., 1877. ' Jago, The Science and Art of Br cadmaking, Lond., 1895. Jessen and Lehmann, "Uber Saccharin," Archiv. f. Hyg.,x. p. 61. Johne, Der Trichinenschauer, Berlin, 1889. Kastner, "On Tuberculous Meat," Munch. Medicin IVochenschr., May 17, 1893. Kayser, "Etudes sur la fermentation lactique," Ann. de I'lnstitut Pasteur, No. BIBLIOGRAPHY AND REFERENCES. 365 vi., 1894. Knieriem, ''Uber die Verwerthung der Cellulose im thierischen Organismus,"^etY./. Biol.,xxi. p. 87. Koch, A., " Vergleichendebakteriologische Untersuchungen iiber die Haltbarkeit der Norweger und Nordsee-Schellfische," Mittheil. der Sektion f. Kiisten u. Hochseefscherei, No. 8, August 1894. Konig, Procent Zusammensetzung der menschl. Nahrungs-Mittel., Berlin, 1888 ; also Chemie der menschlichen Nahrungs und Genussmittel, Berlin, 1882 ; also Article " Mehle," in Dammer's Lexikon der Verfalschungen. Kossel, Untersuch. iiber die Nucleine, Strassburg, 1881 ; also papers in Zeitschrift f. physiolog. Chemie, vol. vi. p. 422, and vol. vii. p. 7, 1882. Landois and Stirling, Human Physiology, 3rd Edit., Lond., 1888. Laaves and Gilbert, "On the Sources of the Fat in the Animal Body," Phil. Mag., 1866. Leffmann and Beam, Analysis of Milk and Milk Products, Philadelphia, 1893. Lehmann, Methods of Practical Hygiene, trans, by Crookes, Lond., 1893. Leich- mann, '' Uber die freiwillige Siiuerung der Milch," Milch Zeitung, 1894, No. 33, pp. 523-525. Lescojiur, "The Detection of Watered Milk by the Examination of the Milk Serum," Analyst, Sept. 1895, p. 200. Levy, TraiU d'Hygiene, Paris, 1879. Lominsky, "On the Presence of Bacteria in Plants," Centr. f. Bakt., viii. p. 325. Macfarlane, "On the Fluctuating Composition of Cow's Milk," Deutsch. Molkerei Zeitung, 1891, p. 5. Martin, Article on "Food," in Stevenson and Murphy's Treatise on Hygiene, Lond., 1892. Meinert, Armee u. Volks Ernahrung, Berlin, 1880 ; also Massen-Ernahrung, Berlin, 1885. Mott, Effects of Alum on the Human System when used in Baking Powders, New York, 1880. Munk and Uffelmann, Die Ernahrung des Gesunden und Kranken Menschen, Vienna and Leipzig, 2nd Ed., 1891. Noorden, Pathologie des Stoffwechscls, Berlin, 1892. Oliver, "The Diet of Toil," Lancet, 1895, i. p. 1629. Paton, "Physiology of the Carbohydrates," Edin. Med. Journ., Dec. 1894. Pavy, Treatise on Food and Dietetics, Lond., 1875 ; also Physiology of the Carbohydrates, Lond., 1894. Pfeiffer, Die Analyse der Milch, Wiesbaden, 1887. Playfair, On the Food of Man in Relation to his Useful Work, Lond., 1865. Polit and Labit, Etude sur les Empoisonnements Alimentaires, Paris, 1890. Prausnitz, "On the Absorbability of Milk," Zeitschrift f. Biol., vol. xxv., 1889, p. 533. Ralfe, An Enquiry into the general Bathology of Scurvy, London, 1877. Ranke, Physiologie des Menschen, Berlin, 1868. Rechenberg, Journ. f. prakt. Chem., N.F. xxii., 1880, pp. 1 and 223. " Report on the Milk Supply of London," Brit. Med. Journ., 1895, vol. ii. pp. 41, 150, 230, and 321. Report of Committee on Scurvy in the Arctic Expedition of 1875-76, Lond., 1877. Richet, Du Sue Gastrique chez I'homme et les animaux, Paris, 1878. Roth, "Uber das Vorkommen von Tuberkelbacillen in der Butter," Korrespondenzblatt f. Schweiz Aerzte, 1894, No. 17, p. 521. Rubner, Various papers on the "Digestibility of Proteids," in Zeitsch. f. Biologie, more particularly in xv. p. 115, xvi. p. 119, xix. p. 45, and xxi. pp. 250 and 337 ; also Lehrbuch der Hygiene, Leipzig, 1889. Senckpiehl, Uber Massener Krankung nach Fleischgenuss, namentlich durch Wurst und Fischgift, Dissertation, Berlin, 1887. Simpson, "On the Spread of Cholera by Milk," Practitioner, 1887. Smith, Annual Report to Privy Council, 1863-4. Spooner, " Dietary Scales in connection with the Health of Seamen," Transac. 7th Internat. Congr. of Hygiene, Lond., 1891, Section viii. p. 41. Stiles and Hassall, A Revision of the Adult Cestodes of Cattle, Sheep, and allied Animals, U. S. Department of Agriculture, Bureau of Animal Industry, No. 4, Washington, 1893. Stohmann, Journ. f. prakt. Chemie, N.F. xix. p. 236, 1879 ; also in Landwirthschaftl. Jahrb., 1884, pp. 531-581. Stone, "On the Carbo- hydrates," Chemical News, Aug. 31, Sept. 7 and 21, 1894. Strumpell, "Digestibility of Proteids," Deutsch. Archiv. f. Klin. Med., 1876, vol. xvii. p. 108. Stutzer, " On Meat Extracts," Analyst, 1885. Tiemann, Comptes Bendus, cxvii., Sept. 25th, 1893. Tollens, Handbuch der Kohlen- hydrate, Breslau, 1888; also various papers in Berichte der Chem. Gesellsch., especially xxvi. p. 1799. Uffelmann, "Uber den Eiweissgehalt und die Verdaulichkeit der Essbaren Pilze," Archiv. d. Hygiene, vi. ; also Das Brot und desscn didtetischer Werth, Berlin, 1884. 366 FOOD. Vallin, ' Rapport sur 1 Emploi de l'Acide Salicylique," Bulletin de VAcademic, 1887. Vogel, Article "Milch," in the Vereinbarungcn der Bayer Chemiker, Berlin, 1885. VoiT, von, Bhysiologie des allgemeinen Stoffwechsels und der Ernahrung, vol. vi. of Hermann's Handbuch der Physiologie, Leipzig, 1881; also "Die Verkostigung der Gefangenen in dem Arbeitshause Rebdorf," Munch. Med Woclienschrift, 1886, Nos. 1 to 4. Walley, Practical Guide to Meat Inspection, Lond., 1890. Weiske, "On the Digestibility of Cellulose," Zeitsch. f. Biol., vol. vi., 1870, p. 456.' Weli>ly, "Creameries and Infectious Diseases," Lancet, April 21, 1894. Wilckens' "Uber die Vertheilung der Bakterien in Milch durch die Wirkung des Centrifugierens," Oesterr. Molkereizeitung, 1894, No. 14. Wiley, Foods and Food Adulterants, Washington Government Printing Office, 1892. Williams, Chemistry of Cooking, Lond., 1892. Wollny, " On the Reichert-Meissl Method of Butter Analysis," Analyst, Nov. 1887. Wylde, The Inspection of Meat, London CHAPTER V. BEVERAGES AND CONDIMENTS. Almost as important to civilised man as the food-stuffs, which are absolutely necessary for existence, are substances which enable food to be taken with pleasure or relish: such substances have been appropriately called food acces- sories. The Germans call them " means of enjoyment," as distinguished from the true foods or " means of nourishment." They include substances varying from the simplest aromatic principles, such as one smells when meat is ■cooking, or condiments and spices, to the more complex alcoholic and non- alcoholic drinks which so largely enter into the daily dietaries of both civilised and uncivilised peoples. The general action of the food accessories seems to be to stimulate digestion, either directly by affecting the digestive ■organs, or indirectly through the central nervous system. The condiments are mainly added to food as flavouring agents; they include such articles as mustard, pepper, onions, cloves, nutmeg, cinnamon, salt, and vinegar. Excepting the two last, all these owe their value as food accessories to aromatic oils which they contain. These essential oils are all stimulants directly of the muscular movements of the digestive organs and of the secretion of their juices; but if taken in excess, easily induce gastric catarrh and exhaustion of the mucous hning of the stomach. The influence of common salt has already been discussed. The food accessories taken in as beverages may be divided into three groups:—(1) The liquids containing alcohol, such as beer, wine, &c; (2) the hquids containing the active principles caffeine or theobromine, such as tea, coffee, Paraguay tea, cocoa, &c; (3) the liquids containing large quantities ■of the organic acids and their salts, such as lime or lemon juice and vinegar. The alcoholic beverages owe their action as food accessories chiefly to the ethylic alcohol they contain; and the effect of the different alcohohc drinks is, broadly speaking, proportional to the amount of alcohol present in them, but not entirely so, since many of them owe part of their effect to the action of certain aromatic substances and other principles. For these reasons, therefore, the presence of these other principles must be considered as well as the alcohol in deciding the utihty or otherwise of any given alcoholic drink. For the sake of convenience, and also according to the amount of alcohol they contain, the alcoholic beverages may be divided into beers, light wines, sweet wines, and spirits. BEER. The usual definition of beer was, that it is a fermented infusion of malt flavoured with hops. This, however, is not quite correct, at the present day, as sugar largely takes the place of malt, and other vegetable bitters 368 BEVERAGES AND CONDIMENTS. that of hops; so that probably a more accurate definition would be, to call it a fermented saccharine infusion to Avhich has been added any Avholesome bitter. Formerly the substitution of quassia, gentian, calumba, or any other bitter in place of hops Avas illegal, but now it is not the case, with the result that all kinds of bitters may be used, provided they are wholesome. As a matter of fact, hoAvever, in the best beers even now, the only bitter used is hops. Modern beers may be divided into two great groups, namely, the non- malt beers and the malt beers. What are called non-malt beers are those made by a yeast fermentation of an infusion of sugar, mainly derived from starch chemically or artificially converted, as by the action of sulphuric acid. Malt beers are the result of a similar yeast fermentation of an infusion of sugar, only in this case the sugar is derived from the natural conversion of grain starch by means of germination or malting. In both instances, the resulting liquor is an alcoholic one in which a portion of the alcohol becomes transformed into aldehyde and subsequently by a further oxidation changed into acetic acid. The actual preparation of malt and the subsequent brewing of beer is practically as follows. The maltster first soaks his barley in a cistern for some fifty hours: he then transfers it to the "couch" and twenty-four hours later spreads it out on floors in a malting. Here he leaves it for ten or four- teen days, during which time germination takes place and the grain sprouts. After this sprouting has taken place sufficiently, all germination action is arrested by drying the grain over a kiln. It is now malt, and if tasted is distinctly sweet, owing to the conversion of the grain starch into sugar by the action of the diastase ferment. After the dried malt has been sifted or screened so as to break off all the sproutings, it passes into the hands of the brewer, who, after crushing it, places it in his mash tub with water warmed to about 160° F. This water completes the transformation of the starch into grape-sugar and dissolves it, causing the resulting liquor, or ivort as it is called, to have a decidedly sweet taste. In the case of a brewer using chemically converted starch (saccharum) or a mixture of it Avith malt, a similar treatment with warm water would be followed by the production of a sweet liquor or wort. When the conver- sion of the starch into sugar is sufficiently complete, all chance of further conversion is stopped by boiling the wort, which also acts in coagulating the albumin which the water has dissolved out of the grain; advantage is also taken of the boiling to add hops which aid further in clearing the wort by coagulating the remaining albuminous matters, besides imparting to it their characteristic bitterness. Both the length of the boiling and the quantity of hops added vary, according to the richness of the wort in sugar, and with the quality of beer it is intended to make. The next step in breAving is to run off the boiled liquid into shallow vessels, in which they are cooled to the best temperature for fermentation. If "top" yeast is intended to be used, this temperature is 60° F., but if what is called " bottom " or sedimentary yeast, as used in Bavaria, a much lower temperature is preferable. When at the required heat, the liquid is run into the fermenting tun and a sufficient quantity of yeast is added. It is usual to use a yeast obtained from a kind of beer different from that which it is proposed to make; the whole is allowed to ferment slowly for six or eight days. During this time, the sugar splits up into alcohol which remains in the beer, and into carbonic acid gas which, for the most part, escapes into the air. The most essential points in brewing are the facts that the quantity of yeast to be added and the temperature at which VARIETIES OF BEER. 369 fermentation is alloAved to take place, vary with different kinds of beer; also that yeast works better Avhen transferred from one kind of beer to another; and that the fermentation must be so regulated that the whole of the sugar contained in the wort is not transformed into alcohol, as if it is all so transformed the beer has no keeping power; that is, it would turn sour in the casks. This turning sour is due mainly to the passage of the alcohol into aldehyde and the subsequent oxidation of this into acetic acid. There are many varieties of ales and beers, the chief being: Pale and Mild Ales, made from the finest dried malt and the best hops; the mild ale is usually sweeter, stronger, and less bitter than the pale. Porter is nothing more than a weak mild ale, coloured and flavoured with roasted malt. Stout is a richer and stronger kind of porter. The German Beers are fermented by means of sedimentary yeast as distinguished from the surface yeast used in England. Their fermentation is carried on at a lower tem- perature than in the case of British beers. They contain also less alcohol than the Enghsh, but are richer in carbonic acid gas, and keep better. Lager and Bock beer is made from a stronger wort, and is proportionately richer in alcohol and malt extract. The Belgian beers are made with unmalted wheat and barley; they take long periods to ferment, doing so spontaneously, no yeast being added; as a rule, they are hard from the presence of much acid. Bottled beers are all bottled while fermentation is going on, and owe their sparkling and frothing to the excess of carbonic acid in them. German Wlvite beer is an acidulous beverage chiefly obtained from barley and Avheat malt by rapid top fermentation, the properties of which differ much at different places. It is mostly sold in bottles. When required in bottles in a briskly effervescing state and clear, an addition of an enhvening material is necessary in the form of cane-sugar. Only by this means can a productive secondary fermentation be kept up in the bottles, as the main fermentation almost entirely consumes the fermentable material. The Vienna beers, like the German lighter beers, are remarkable for producing neither intoxication nor drowsiness, due principally to the small quantity of alcohol they contain. The German or Bavarian process of brewing differs in several important points from that practised in England, and Ave may refer to these points for an explanation of the qualities—especially in regard to flavour, alcoholic strength, and the quantity of malt and hop extractives which sharply distin- guish German from English beers. Thus the peculiar qualities, especially the flavour, of German or Austrian beers are doubtless to be ascribed, in a large measure, first to the fermentation being very slow, and carefully restricted to a low temperature; secondly, the employment of sedimentary yeast tends to render the products of a simpler, and doubtless more whole- some, nature than those which are evolved when a more rapid fermentation is allowed to proceed, such as occurs when a comparatively high tempera- ture and top-growing yeast are adopted. Again, the quantity of hops used in the brewing of German beers is much less than is employed in this country, whhe in Bohemia and Bavaria the hops are gathered earlier, so as to exclude much of the narcotic principles which longer growth fosters. Since, as is well known, the constituents of the hop are distinctly narcotic, this, in addition to the decreased percentage of spirit, would account for the com- parative absence of drowsy symptoms when Bavarian, German or Austrian beer is drunk, but Avhich so frequently follow the consumption of English beers. It has already been mentioned that a yeast that is formed by a violent or racy fermentation and at a higher temperature, as employed in English 2A 370 BEVERAGES AND CONDIMENTS. breAving, has more active qualities than yeast formed at a loAver temperature and by sIoav fermentation. The first spreads itself rapidly over the surface of the fluid and is termed "superficial" yeast, Avhile the second sinks to the bottom of the vessel and there continues its action; it is, therefore, terme< 1 "sedimentary" or bottom yeast, and is what is employed in German breweries. The important advantage of the use of a yeast growing at a Ioav temperature in brewing is that Avhile the normal functions of the yeast are free to act, yet the same cold discourages the groAvth of disease ferments, and a healthier beer is ensured. Composition of Beer.—The specific gravity varies from 1006 to 1030, or even more. The average in English ales and porters is from 1010 to 1014. The percentage of extract is from 4 to 15 per cent, in ale, and from 4 to 9 per cent, in porter. It is least in the bitter, and highest in the sAveet ales. The alcohol varies from 1 to 10 per cent, in volume. The free acidity Avhich arises from lactic, acetic, gallic, and malic acids ranges (if reckoned as glacial acetic acid) from 18 to 45 grains per pint. The fermentation produces, besides alcohol and carbonic acid, a little glycerin and succinic acid. There is a small quantity of albuminous matter in most beers, but not averaging more than 0*5 per cent. The salts average 0*1 to 0*2 per cent., and consist of alkahne chlorides and phosphates, and some earthy phos- phates. There is a small amount of ammoniacal salt. The dark beers, or porters, contain caramel and assamar. Free carbon dioxide is always more or less present; the average is 0*1 to 0*2 part by weight per cent., or about If cubic inch per ounce. Volatile and essential oils are also present. A more exact statement of the percentage composition of various beers is presented in the following table :— Specific Gravity. Malt Extract. Alcohol. Free or Total Acidity as Acetic Acid. co2. Ash. AVater. Burton ale, 1032 14-50 5-90 79-60 Scotch ale, 1030 1090 8-50 0*15 80-45 Bass's XX, 1014 5*10 4-43 0*180 Cheap draught ale, . 1006 2-75 3-00 0203 J > it 97 • ' 1009 3-50 3-00 0*203 London porter, 1021 6-80 690 0*212 86-30 >> >» • • 1022 7*16 4-21 0-168 Cheap draught porter. 1011 4*00 3-00 0-156 >» >> 5) • 1014 5-00 3-50 0-162 Berlin ale, 1019 6-30 7-60 0*17 0-188 85-93 Belgian faro ale, 1008 2-90 4-90 0*20 0*142 92-00 Bock beer, 1027 9-20 4-20 0*17 0*263 86-49 Lager beer, 1016 5-79 3-90 0*19 0-228 90-08 Bavarian beer, 1022 5-40 3-50 0*22 0-290 91*10 Vienna beer, . 1021 610 3-50 0-19 0-210 Of the constituents of beer it is necessary to specially notice the Avater, the malt extract, the bitters, and the ash. The water used in brewing should, of course, be free from all injurious impurities, and especiaUy from any organic matters undergoing change. It is weU known that variations in the mineral constituents of the water used in brewing exert an important influence on the character of the finished beer. Hard and somewhat saline water, for instance, is preferred in the brewing of pale and bitter ales in tins country, since it extracts less colouring matter and, what is more important, less albuminous matter from the malt. COMPOSITION AND NUTRITIVE VALUE OF BEER. 371 It is the latter substances Avhich, Avhen present in excess, are fatal to the prime condition of English breAved ales. Thus in England hard waters are in general use for breAving. On the other hand, the German brewer uses a softer and practically non-saline water, which extracts a greater amount of albuminous principles. How much common salt is present, is mainly interesting because in prosecutions for the addition of salt to beer, the defence frequently is, that the latter is a natural component of the beer from the water used in the breAving. As brewers, commonly, use hard Avaters, it is obvious that the waters in particular localities may contain varying quantities of salt. Generally speaking, the water used in different breAveries gives quantities from 10 to 15 grains per gallon. The malt extract is really the sum of the non-volatile constituents, and represents the residue of the extractive substances of the Avort which have not been volatilised as carbonic acid during fermentation. In reality it consists of dextrin, sugar, cellulose, albuminous substances, and some fat from the malt or "saccharum" used, with lupulite and hop resin. Formerly, beer bitters were, by law, compelled to be derived solely from hops; but since the repeal of the hop duty in 1862, any bitter may be used, provided it is harmless. From time to time various objectionable bitters, such as picric acid, picrotoxin or colchicine, have been identified in beers, but only very rarely; in fact so rarely, that they may be practically said to be now never used for the purpose. In the same way, quassiin, gentianin, absynthin, aloin, and some other more or less doubtful bitters have been found in beers, but extremely rarely. The chief bitter employed in beer to give it the characteristic flavour is that derived from hops. Hops are the cones or strobdes of the Humulus Lupulus. They contain about 4 per cent. of the astringent substance tannin, 1*5 per cent, of a fragrant essential oil, and much resin. These substances are chiefly found in the yellow glandular secretion of the hop cones, called lupidin or lupidite. The ash of beer contains the mineral constituents that previously existed partly in the water, partly in the hops, and partly in the malt used. The ferric oxide, some phosphoric acid, a little lime and magnesia, with much of the sdica remains undissolved and does not pass into the beer, the remainder is dissolved. The folloAving table, from Wynter-Blyth, gives the average com- position of the beer ash of commerce :— Beer Ash. Potash,........37-22 Soda,.........8-04 Lime,.........1*93 Magnesia, ........ 5 "51 Iron oxide,....... . traces Sulphuric acid, ....... 1*44 Phosphoric acid,.......32*09 Chlorine,........2*91 Silica,.........10-82 Nutritive Value of Beer.—The action of beer upon tissue change, so far as is known, is supposed to be one of lessened excretion, the urea and pulmonary carbon dioxide being both decreased. If this be the case, it is not owing to the alcohol, at least in moderate dietetic doses, but of some of the other ingredients; but the experiments require repetition. On the nervous system the action is probably the same as that of alcohol. The peculiar exhausting or depressing action of beer taken in large amount has been ascribed by Ranke to the large amount of potash salts, but probably the other constituents (especially the hop) are also concerned. When beer is taken in daily excess, it produces gradually a state of 372 BEVERAGES AND CONDIMENTS. fulness and plethora of the system, which probably arises from a continual, though slight, interference Avith elimination both of fat and nitrogenous tissues. When this reaches a certain point appetite lessens, and the forma- tive power of the body is impaired. The imperfect oxidation leads to excess of partially oxidised products, such as oxahc and uric acids. Hence many of the anomalous affections, classed as gouty and bihous disorders, which are evidently connected Avith defects in the regressive metamorphosis. Sir Wm. Roberts states that malt liquors hamper sahvary digestion in exact proportion to their acidity, and retard peptic digestion altogether out of proportion to their percentage of alcohol; but digestion is assisted by a moderate quantity of light beer, especially when it contains free carbon dioxide. The question, What is excess? is not easy to ansAver, and will depend both on the composition of the beer and on the habits of life of those who take it; but, judging from the amount of alcohol which is allowable, from one pint to two pints, according to the strength of the beer, is a sufficient amount for a healthy man. In consequence of the abundant proportion of sugar and dextrin, and the appreciable amount of albumin, beer has decidedly a nutritive value Avhich is not insignificant. Even the alcohol, setting aside its toxic properties, must be viewed in a limited sense as a nutritive substance. Hitherto, no attempt has been made in this country to lay down any standards of composition for beer, with a view to control the nutritive value of this im- portant means of popular enjoyment and nutrition. Beers or porters con- taining less than 3 per cent, of alcohol and 4 per cent, of extract, must be pronounced weak, of inferior value, and not calculated to keep. While for ordinary ales, professing to be of fair or ordinary quality, the extract and alcohol may not unreasonably be expected to be each 4 per cent.: porters of the same class should yield at least 5 per cent, of extract and from 4 to 5 per cent, of alcohol. This is equivalent to expecting that the beer be brewed from an original wort having a specific gravity of from 1042 to 1054. Beers which, instead of being made from malt alone, receive additions of starch, maltose, potato sugar, &c, are relatively poorer in nitrogenous sub- stances, ash and especially phosphoric acid. These non-malt beers retain their carbonic acid very imperfectly, hence readily get flat. Many of the Ger- man and Austrian beers, which contain small quantities of alcohol and large extracts, are to be more regarded as food and drink than are the average British ales. In the former there is a lessened change by fermentation of the extract into alcohol and carbonic acid, whereby a greater nutritive residue in the form of malt extract is present, whereas in the British beers the reverse is generally the case. What is known as " small beer " is a thin beer often drawn for workmen and servants, containing only 1 to 2 per cent, of extract, about 1 per cent. of alcohol, and from 0*06 to 0*08 of ash. This beer is obtained by a repeated! extraction of the malt which has been once used for ordinary beer, and then treating the resulting thin wort as for beer. The keeping properties of this liquid are very low, it readily becomes yeasty and sour, and has, practically, no nutritive value at all. Adulterations of Beer.—The chief and simplest adulteration of beer is by the addition of water. Another very common adulteration is salt, the object of tits addition being not so much to develop the flavour and to preserve the liqupr, as to produce a craving for more drink. The use of gypsum, of which we have before spoken, can hardly be regarded as an adulteration. Sulphuric acid is occasionally added to clarify beer, and to- EXAMINATION OF BEER. 373 give it the hard flavour of age; alum has been knoAvn to be used for the same purpose. To lessen excessive acidity sodium bicarbonate may be added: while sometimes publicans seek to give flat beer the semblance of freshness by means of effervescing poAvders containing tartaric acid along with sodium bicarbonate, Avhich develop carbonic acid in the beer. Liquorice and sugar are both knoAvn to be added, occasionally, to give body to thin and watery beers and to improve their colour. A mixture of alum, salt, and sulphate of iron is also sometimes added to beer to give it a " head " Avhen flat. Inasmuch as Ave are not able noAV to limit our conception of ideal beer to its being a beverage consisting purely of barley malt, water and hops, we are unable to consider the various substitutes for barley malt, such as wheat, rice, maize, potato starch, maltose, glucose, &c, as in any way adulterants. Our position is somewhat similar in regard to the various substitutes for hops; these are not adulterants unless hurtful bitters. Mention has been already made of the fact that, at times, wormAvood, marsh-rosemary, bitter- clover, box tree, holy thistle, centaury, gentian, quassia, and various other bitters of a more or less harmless nature may be added to beer, while occasionaUy others of a more objectionable character, such as colchicum, picrotoxin and aloin, have been used; still the employment of these is so exceptional, and the use of genuine hops so general, that the serious con- sideration of beer adulteration or sophistication by these means is unnecessary. EXAMINATION OF BEER. The most important points to be observed in the examination of beer are: —1. Its physical characters. 2. Specific gravity at 15° C. or 60° F. 3. Determination of the proportion of alcohol. 4. Determination of the extract. 5. Determination of the degree of acidity. 6. Determination of possible adulterations. 1. Physical Characters.—The beer should be transparent, not turbid. Turbidity arises from imperfect brewing ^©r^clarifying, or from commencing changes. If the latter, the acidity will probably be found to be increased. The amount of carbon dioxide disengaged should neither be excessive nor deficient. The taste should be pleasant. If bitter, the bitterness should not be persistent. It should not taste too acid. Smell gives no indication till the changes have gone on to some extent. If there is any turbidity, microscopic examination will usually detect the cause. 2. Determination of the Specific Gravity.—The beer, after it has been brought to the required temperature of 15° C. or 60° F., is well shaken in a flask, half filled, to expel carbonic acid, and filtered through wadding to remove froth; the specific gravity is then determined by means of an accurate hydrometer. The specific gravity should be taken both before and after driving off the alcohol. From the reading, after de-alcoholisation, an approximate conclusion can be formed of the amount of solids or extract present, by dividing by 4 the excess of the gravity reading over 1000, or by 0*004 the excess of the gravity over unity. Of course the more extract, the greater is the body of the beer. Before de-alcoholisation, in the better class of beers the specific gravity will vary from 1010 to 1025, and in the inferior kinds from 1006 to 1014. 3. Determination of the Alcohol.—There are various ways of determin- 374 BEVERAGES AND CONDIMENTS. ing the amount of alcohol in beer, Avine and spirits : for the medical officer, one of the two following will be sufficient. Measure a certain quantity of the alcohohc fluid, and take the specific gravity at 60° F. 1st. Place in a retort and distil at least tAvo-thirds. Take the distillate, dilute to original volume with distilled water, determine the specific gravity at 60° F. by a proper instrument, and then refer to the annexed table of specific gravities—opposite the found specific gravity the percentage of alcohol is given in volume and in weight. 2nd. Then, to check this, a plan recommended by Mulder may be used. Take the residue of the liquid in the retort, dilute Avith water to the original volume, and take the specific gravity at 60° F. Then deduct the specific gravity before the evaporation from the specific gravity after it, take the difference, and deduct this from unity (the specific gravity of water), and look in the table of specific gravities for the number thus obtained; opposite will be found the percentage of alcohol. The results of these two methods should be identical. Table of Percentages of Absolute Alcohol at 60° Fahrenheit. Vols. Weight S] :>ecific Vols. Weight Specific Vols. AVeight Specific Vols. AA'eight Specific per per g ■avity per per gravitv per per gravity per per gravity cent. cent, at 60° F. cent. cent. at 60° F. cent. cent. at 60° F. cent. cent. at 60° F. 0 0 1 0000 26 21-30 •9689 51 43-47 •9315 76 69-05 •8739 1 0*80 9976 27 22-14 ■9679 52 44-42 ■9295 77 70-18 •8712 2 1*60 9961 28 22-99 •9668 53 45-36 ■9275 78 71-31 •8685 3 2-40 9947 29 23-84 ■9657 54 46-32 •9254 79 72-45 •8658 4 3-20 9933 30 24-69 •9646 55 47-29 ■9234 80 73 59 •8631 5 4-00 9919 31 25-55 •9634 56 48-26 •9213 81 74-74 •8603 6 4-81 9906 32 26-41 •9622 57 49-23 •9192 82 75-91 •8575 7 5-62 9893 33 27-27 •9609 58 50-21 •9170 83 77-09 •8547 8 6 43 9881 34 28-13 ■9596 59 51-20 •9148 84 78-29 •8518 9 7-24 9869 35 28-99 •9583 60 52-20 •9126 85 79*50 •8488 10 8-05 9857 36 29-86 •9570 61 53 20 •9104 86 60*71 •8458 11 8-87 9845 37 30-74 •9556 62 54-21 •9082 87 81*94 •8428 12 9-69 9834 38 31-62 •9541 63 55-21 •9059 88 63*19 •8397 13 10-51 9823 39 32-50 •9526 64 56-22 •9036 89 84 46 •8365 14 11-33 9812 40 33-39 •9510 65 57*24 •9013 90 85*75 •8332 15 12-15 9802 41 34-28 •9494 66 58-27 •8989 91 87*09 •8299 16 12-98 9791 42 35-18 •9478 67 59-32 •8965 92 88*37 •8265 17 13-80 9781 43 36-08 •9461 68 60-38 •8941 93 89*71 •8230 18 14-63 9771 44 36-99 •9444 69 61-42 •8917 94 91*07 •8194 19 15-46 9761 45 37-90 •9427 70 62-50 •8892 95 92*46 •8157 20 16-28 9751 46 38-82 •9409 71 63*58 •8867 96 93-89 •8118 21 17-11 9741 47 3975 •9391 72 64-66 •8842 97 95-34 •8077 22 17-95 9731 48 40-66 •9373 73 65-74 •8817 98 96-84 •8034 23 1878 9720 49 41-59 •9354 74 66-83 •8791 99 98-39 •7988 24 19-62 9710 50 42-5-2 •9335 75 67-93 •8765 100 100-00 •7939 25 20-46 9700 | If there is no retort available, this second plan may be used with an ordinary evaporating dish, the alcohol being suffered to escape. The plan is very useful for medical officers, and if conducted with reasonable care and slowness of evaporation so as not to char the residue and render it insoluble, gives very satisfactory results. Example.—Say 200 c.c. of beer are taken, and its sp. gr. at 60° F. is found to be 1*012 ; after boiling down to one-third, it is allowed to cool, and made up with distilled Avater to 200 c.c. Its sp. gr. is noAV taken again at 60° F., and found, say, to be 1-020. The difference between the first sp. gr. and the second is 0*008, and EXAMINATION OF BEER. 375 this deducted from 1-000 gives 0-9920; on referring to the table, we find that the nearest specific gravity given to this figure is 0-9919, corresponding to 5 volumes ol alcohol per cent., and that consequently 0-9920 lies between 0-9919 and the one next above, namely, 0'9933, and that the percentage of alcohol corresponding to 0-9920 is something betAveen 4 and 5 volumes. To find exactly how much it is, we calculate the proportional part. The difference between the gravities for 4 and 5 volumes per cent. of alcohol is 00014, and as the calculated gravity of 0'9920 is 0-0013 different from 0*9933, the one above it, and 0*0001 different from the one below it, the percentage of alcohol corresponding to it may be said to be 4, corresponding to 0*9933, plus If of 1, or 0*928, which gives the exact volume percentage of alcohol, corresponding to a sp. gr. of0*9920 as being 4-928. v B Alcohol is sometimes stated as weight in volume and not as volume in volume. If the percentage of alcohol in volume be multiplied by 0*8, the weight of the alcohol is given per cent. If the percentage of alcohol in weight is multiplied by 1*25, the volume is given. If the percentage volume of alcohol be multiplied by 1*76, and the weight in volume by 2*21, the amount of proof spirit is given. 4. Determination of the Extract.—This can be estimated by taking a given quantity of the beer, evaporating down to dryness in a weighed capsule, re-weighing and calculating out the resulting residue as a percent- age ;_ or, it can be determined indirectly, as already explained, from the specific gravity of the de-alcoholised beer. In the example given above, the extract would be calculated, by this method, as being 0*020 divided by 0*004 or 5 per cent. Complementary to this estimation, it may, sometimes, be necessary to determine Avhat Avas the original extract of the wort before fermentation set in. As on fermentation about two parts by weight of sugar yield one part of alcohol, by doubling the alcohol found in the beer, and adding it to the extract found by direct estimation, we may calculate, approximately, Iioav much extract the wort really contained before fermentation was established, or in other words, what has been the concentration of the wort. Thus, say in the preceding example Ave find 5 per cent, of extract and 4*92 per cent. of alcohol: then (4*92 x 2) + 5 = 14*84 as the probable percentage of extract in the orginal wort, with a probable specific gravity of 1059. These figures are accurate enough for a general or rapid statement, but by means of ,, , . 100(E + 2-0665A) . ,., ^ tne formula iqo+P0665A >in which E = extract, and A = alcohol, we may calculate the original extract still more accurately: 10Pn^ + 2'0665 x 4'92) = J 100+1*0665x4-92 14*41, and presuming that the specific gravity of that Avort would rise 4 degrees above 1000, or 0*004 degree above unity for each 1 per cent, of extract in it, Ave can conclude that the specific gravity of that original wort Avas 1057 or 1*0576, according to Avhich way we choose to state it. 5. Determination of the Acidity.—This is a very important matter, as the increase of acidity is an early effect when beer is undergoing changes. It may be stated either as a percentage, or in grains per pint. The acidity of the beer consists of two kinds. Volatile acids, viz., acetic and carbonic. Non-volatile acids, viz., lactic, gallic or tannic, malic, and sulphuric, if it has been added as an adulteration. To determine the acidity of beer we must use an alkaline solution of known strength, 1 c.c. of which is equal to 6 milligrammes of glacial acetic acid (C2H402) or to 9 mdligrammes of lactic acid (C3HG03). This is the same alkaline solution as was needed for estimating the acidity of bread (page 338). & 376 BEVERAGES AND CONDIMENTS. Total or Free Acidity.—Take 10 c.c. of the beer to be examined, and drop into it the alkaline solution from a burette, till exact neutrality (as tested by turmeric and litnius papers) is reached. Then read off the number of c.c. of alkaline solution used ; multiply by 6, and the result will be the amount of total acidity in the quantity of beer operated on, expressed as milligrammes of glacial acetic acid (the symbols being always used in the report). By shifting the decimal point two places to the left, the amount per cent, is given. To bring percentage into grains per pint multiply by 700 to bring to grains per gallon, and then divide by 8 to bring to grains per pint; or, what is the same thing, multiply at once the number of c.c. of alkahne solution used by 5-25 (short factor). The total acidity can be divided into fixed and volatile by evaporation. Wlide the total acidity is being determined, evaporate another measured quantity of beer to one-third, make up to the original bulk with distilled Avater, and determine the acidity. The acetic and carbonic acids being volatile are driven off, and lactic and other acids remain. Deduct the amount of alkaline solution used in this second process from the total amount used, and this Avill give the amount required for the volatile and fixed acidities respectively; express one in terms of acetic, the other of lactic acid. Short factor for lactic acid = 7*875. The fixed acidity is greater than the volatde in almost all beers, and sometimes five or six times as much. Example.—10 c.c. of beer took 5 c.c. of alkaline solution : 5 x 5*25 = 26'25 grains of glacial acetic acid per pint = total acidity. After boiling and making up to original bulk with distilled Avater, 10 c.c. took 4 c.c. of alkaline solution : 4 x 7*875 = 31*5 grains of lactic acid per pint=fixed acidity. The difference between the amounts of alkaline solution used, 5-4 = 1 multiplied by 5 "25, gives the volatile acidity. Generally speaking, the amount of total acidity of beer given in books is too great. It is seldom found to be more than 30 grains per pint, or 0*342 per cent., and even rarely reaches that; sometimes it is not more than 12 or 14 grains, or about 0*150 per cent. In thirty-one kinds of porter and stout the acidity per pint varied from 25*22 grains (the highest) to 14*14 grains (the loAvest amount). In twenty-three kinds of ale the highest and the lowest amounts per pint .were 34*39 and 7*97 grains. 6. Determination of Adulterations.—The most important are the following :— Water.—Probably the most frequent adulteration ; detected by taste; determining amount of alcohol and specific gravity of the beer free from alcohol. Alcohol.—Seldom added; the quantity of alcohol is large in proportion to the amount of extract, as determined by the specific gravity after separa- tion of the alcohol. Sodium or Calcium Carbonate in order to lessen Acidity.—Neither adulteration can be detected Avithout a chemical examination. Evaporate beer to a thick extract, then put it in a retort, acidulate Avith sulphuric acid, and distd; if calcium or sodium acetate be present, acetic acid in large quantity Avill pass over. The extract ahvays contains some acetate, but only in small quantity. Lime.—Evaporate to dryness another portion of beer, incinerate, dissolve in weak acetic acid, and precipitate by ammonium oxalate. In un- adulterated beer the precipitate is moderate only. Sodium Chloride.—This is hardly an adulteration, unless a very large quantity is added. Take a measured quantity of the beer; evaporate to WINE. 377 dryness; incinerate at as low a heat as possible; dissolve in water, and determine the sodium chloride by the standard solution of nitrate of silver. Ferrous Sulphate.— If the beer be hght-coloured a mixture of potassium ferricyanide and ferrocyanide may be added at once, and will give a precipitate of Prussian blue; if the beer be very dark-coloured, it must be decolourised by adding solution of lead subacetate and filtering. Or evaporate a portion of beer to dryness and incinerate; if any iron be present the ash is red ; dissolve in Aveak nitric acid, and test with potassium ferrocyanide. Tavo grains of ferrous sulphate to nine gallons of water give a red ash. The ash of genuine porter is always white, or greyish-white. Sulphuric acid is added to clarify beer, and to give it the hard flavour of age. If the beer be pale, add a feAv drops of hydrochloric acid, and test Avith barium chloride. A very dense precipitate may show that sulphuric acid has been added, but it must be remembered that the water used in brewing may contain large quantities of sulphates. (The Burton spring- water is rich in calcium sulphate.) If there be a large precipitate, then determine the acidity of the beer before and after evaporation; if the amount of fixed acid be found to be very large, there will be no doubt that sulphuric acid has been added; or precipitate Avith baryta, and weigh. Mulder recommends that the extract of the beer be heated, and the sulphur dioxide Avhich is disengaged led into chlorine water ; sulphuric acid Avill be found in the chlorine water, and may be tested for as usual. Alum.—Evaporate to dryness; incinerate, and proceed exactly as in the analysis of alum in Bread. The substance added to give " head " to beer is a mixture of alum, salt, and ferrous sulphate. Liquorice.—Evaporate 1 litre of the beer to half its volume, and on coohng, precipitate with a slight excess of concentrated plumbic acetate. After twelve or twenty-four hours, the precipitate is filtered, well washed, and rinsed into a flask, so that the Avhole makes up to 300 to 400 c.c. The liquid is then heated for an hour, and sulphuretted hydrogen passed into it, whde still warm, until the lead compounds are decomposed. After well shaking, the cold liquid is filtered through a folded filter and the sul- phuretted hydrogen washed out. The lead sulphide on the filter retains the glycyrrhizinic acid of the liquorice. It is washed with 200 c.c. of 50 per cent, alcohol into a flask, heated to boiling and filtered. The filtrate is evaporated to a feAv c.c, and a few drops of ammonia added, which turns the pale yellow liquid brown-yellow; the latter is then evaporated to dryness, the residue dissolved in 3 c.c. of water and filtered. The filtrate possesses the characteristic taste of liquorice, if this latter be present, and separates out a flocculent resinous mass (glycyrretin) on heating with a few drops of hydrochloric acid on the water bath. The residue from a beer free from liquorice possesses no taste, or only a slightly bitter one, and gives at the most only a whitish turbidity. Other substances have been supposed to be used as adulterants, and formerly this was the case, but not of late years. WINE. The term wine is held to mean " the fermented juice of the grape with such additions only as are essential to the stability or keeping quality of the wine." This definition admits as wines those beverages Avhich, made from grape juice, require to preserve them the addition of spirit, as in the 378 BEVERAGES AND CONDIMENTS. case with some Avines from Spain and Portugal; but it excludes the so-called British Avines, which are not made from the juice of the grape at all, and those wines from other countries Avhich are fortified Avith spirit when they require no such addition. When the sugary juice of a fruit, such as the grape, is left to itself at a moderate temperature, fermentation takes place from the influence and action of germs which adhere to the skin of the grapes and are introduced into the " must " on pressing; this process differing very much from that in the making of beer, when the starchy or sugary infusion or wort is boiled, and then yeast added to make it ferment. During the fermentation of the fruit juice, a part or whole of the sugar is converted into alcohol. Various ethers, Avhich give the characteristic flavour or bouquet to wine, are formed, as well as acetic, malic, succinic, and other acids. The essential acid of wine is tartaric acid; much of this crystallises in the casks as cream of tartar or tartrate of potash. The newer Avines contain aldehyde, which is very intoxicating, later on this gets oxidised into acetic acid, and, if exposed to the ah long enough, all the alcohol in a wine will be converted into this: acid so as to practically become ordinary wine vinegar. Much of the colour, taste, and character of wines depends upon how far they are made from the grape juice only, or hoAv much this is mixed with the seeds and skins of the fruit. The seeds are rich in tannin and a bitter principle, while the skins yield a colouring matter, some flavouring principle, and tannin. If it is desired to produce white Avine, the " must" is quickly pressed away from the skins and stalks : while for red wine the skins of purple grapes are allowed to ferment along with the must, yielding thus a wine rich in tannin and colouring matter. Red wine (French), . (Rhine), . (Austrian), , (Hungarian), . (Spanish), (Australian), . . (Cape), . . White wine (French), „ „ (Rhine), „ ,, (Austrian), . ,, ,, (Hungarian), Moselle, .... Champagnes (Cliquot), . ,, (Rbderer), . ,, (Monopole), Tokay, Port, . Sherry, Madeira, Marsala, Malaga, 0-9982 0 9966 0-9958 0-9952 0-9975 0-9982 0 9976 0-9963 1-0005 09949 0-9955 0-9964 10565 1-0572 10280 0-9943 10081 0-9932 10003 10022 1-0694 7-80 2-56 0-57 10-08 3 04 0-52 8-49 2-54 0-62 902 254 0-67 12-31 3-63 0-49 14-10 2-96 0-58 11-36 2-86 0-62 10-31 3-03 0-66 800 2-60 0-81 7-93 2-13 0-67 8-00 2-33 0-69 7-99 2-24 079 10 20 19-75 0 60 9-50 20-24 0-70 8-21 10-15 0-57 1205 3-26 0 68 16-69 8-05 0-40 17-45 3-98 0-45 15-40 5-52 0-43 15-85 5-27 0-49 11-93 21-73 0-55 0-730 0-810 0-790 1-090 0-970 0-850 0-680 0-770 0-720 1-130 0-970 0-230 0-430 0-520 0-740 0-510 0-248 0-249 0-241 0-215 0-610 0-461 0-550 0-250 0-248 0-189 0-204 0-175 0 120 0-120 0135 0 240 0"233 0-380 0-350 0-380 0-410 17-520 18 500 8-450 1040 5-843 2-120 3-230 3-530 17-110 0-180 0-158 0-110 0-150 0-220 0-233 0-226 0-630 0-430 0-043 0-026 0-034 0-021 0-048 0-022 0027 0 031 0 041 0 027 0-020 0-041 0-106 o-ioi 0-091 0-242 0-195 0-231 0-098 0-085 0-081 0-075 0 068 0 059 0-108 0-102 0-206 0-149 0142 0-187 0-030 0-037 0-038 0-027 0-019 0-230 0032 0-046 0 034 0-016 0012 0 016 0-035 0031 0-031 0 060 0-029 0-049 0-033 0-033 0-024 0-221 0-220 0-225 0-038 U-020 0 034 I 0-039 0 036 i 0-026 0 025 0 022 0-017 0-025 0'030 0 023 0-128 0 075 0-114 0 043 Composition of Wines.—According to the absence or presence of sugar in them, wines are conveniently divided into two great classes, namely the light red and white wines, from which sugar is either entirely absent or present in only very small amounts, and the sweet wines, such as Port, Sherry, and the Champagnes, in which sugar largely is present. The light wines and the sparkling Avines differ slightly in the amount of their COMPOSITION OF WINES. 379 contained alcohol, but chiefly differ in the quantity of their ethers and aromatic substances. The champagnes differ largely from the ports and sherries in their effects, but as they contain frequently large amounts of sugar, they are best classed Avith them under the same heading of sweet Avines. The composition of wines, it will be readily understood, is some- Avhat complex, and moreover very variable. So far as it is possible to summarise this information, the chief constituents and their percentage proportions are given in the preceding table, compiled mainly from large numbers of analyses made by Nessler and Borgmann. Alcohol.—With regard to the amount of alcohol Avhich a wine contains there is no constancy. All Avines can be divided according to their alcoholic strength into two classes; the natural wines, containing from 6 to 13 per cent, by weight of alcohol, and the fortified wines containing from 12 to 22 per cent, by weight of alcohol. The limit of alcoholic distinction between these two great classes of wine Avill be more readily understood if it be borne in mind that during the fermentation of any sugary liquid or mass, that process usually ceases when the alcohol formed reaches 14 per cent., so that any excess of alcohol over that amount must, of necessity, have been added artificially. The ports and sherries are all largely fortified Avith added alcohol; while many of the inferior clarets and champagnes are subject to very sirmlar additions. The strongly alcoholic and fortified Avines are slow to undergo change, hence keep well; but the lighter and natural Avines deteriorate rapidly when exposed to air. Ethers.—The chief of these present in wine are oenanthic, citric, malic, tartaric, acetic, racemic, butyric, caproic, caprylic, and some other ethers of indefinite composition. The " bouquet" of wine is partly owing to the volatile ethers and partly to extractive matter. The characteristic odour of wine is mainly due to oenanthic ether. Albuminous Matters—Extractive Colouring Matter.—The quantity of albumin is not great; the extractives and colouring matter vary in amount. The colouring matter is derived from the grape skins; it is naturally greenish or blue, and is made violet and then red by the free acids of wine. The bluish tint of some Burgundy wines is owing, according to Mulder, to the very small amount of acetic acid Avhich these wines contain. It is, according to Batilliat, composed of tAvo matters—rosite and purpurite. With age, changes occur in the extractive matters; some of it falls (apothema), especially in combination with tannic acid, and the Avine becomes pale and less astringent. Sugar exists in varying amounts, and in the form, for the most part, of fruit sugar. Sherry generally contains sugar, but not ahvays; it averages 8 grains per ounce, and appears to be highest in the brown sherries, and least in Amontillado and Manzanilla. In Madeira it varies from 6 to 66 grains per ounce; in Marsala a httle less; in Port, from 12 to 28 grains per ounce, being apparently nearer the latter in the finest wines. In Cham- pagne it amounts to from 6 to 28 grains, the average being about 24 grains; but a good deal of Champagne is noAV drunk as " vin brut," without any sugar. In the Clarets, Burgundy, Bhine, and Moselle Avines it is absent, or present in small amount. Fat.—A small amount exists in some wine. Free Acids.—Wine is acid from free acids and from acid salts, as the potassium bitartrate. The amount varies from 2 to 3 grains per ounce. The principal acids are racemic, tartaric, acetic, malic, tannic (in small quantities), glucic, succinic, lactic (?), carbonic, and fatty acids, such as formic, butyric, or propionic. Some acids are volatile besides the acetic, 380 BEVERAGES AND CONDIMENTS. but it does not seem quite certain what they are. The tannic acid is derived from the skins : it is in greatest amount in neAv port Avines : it is trifling in Madeira and the Rhine wines; it is present in all white and most red-fruit wines, except champagne. The tannic acid on keeping pre- cipitates with some extractive and colouring matter (apothema of tannic acid). Salts.—The salts consist of bitartrate of potassium, tartrate of calcium and sodium, sulphate of potassium, a little phosphate of calcium and mag- nesium, chloride of sodium, and iron. The magnesia is in larger amount than the hme, and exists sometimes as malate and acetate. A little man- ganese and copper have been sometimes found. In Bhine wine a little ammonia is found (Mulder). The total amount of salts is 0-l to 0*3 per cent., i.e., about 9 to 26 grains per pint, or \ to 1\ grain per ounce. The salts can only be detected by evaporation and ignition. The total solids in wine vary from 3 to 14 per cent., or in some of the rich liqueur-like wines to more. The specific gravity depends upon the amount of alcohol and of solids, and varies from 0*973 to 1*002 or more. Artificial Improvement of Wine.—There are several processes Avhich are frequently employed for either artificially improving wine, or increasing its volume. Thus, the addition of alcohol to the wine renders it stronger and more permanent; so, too, the addition of glycerin makes it sweeter and fuller in the mouth, and various essences render it more fragrant and highly flavoured. Various colouring matters and preservative agents are also frequently added to wine, to improve its appearance and keeping qualities. Of the processes which aim exclusively at an increase of volume, the chief is the addition of alcohol and water, sometimes with glycerin. What is called " gallising " is the dilution of the " must," when it is too acid, by means of water until its acidity becomes normal (say 0*5 per cent.), and then adding cane or grape-sugar until it contains from 20 to 30 per cent. Yeast wines are obtained by causing sugar water to ferment Avith wine- yeast, with an addition of tartaric acid. Latterly much wine has been obtained by fermenting water and raisins, with the occasional addition of suitable ingredients. A manufacture of artificial wine from water, sugar, tartaric acid, and alcohol is by no means unknoAvn. Apart from adulterations in the direction of added spirit and artificial colouring, the most common sophistication of wine is " plastering " to secure clearness and dryness. The term " dryness," as applied to wines, is meant to express a flavour Avhich is not that of sweetness. It has already been stated that the fermentation of grape juice, in the formation of wine, is the result of a vegetable growth, which the " must" or juice of the grape obtains spontaneously. Two distinct effects follow the growth of this fungus or process of fermentation; one is, the sugar of the "must" is converted into alcohol; the other is that the greater part of the albuminous or nitrogenous part of the " must" is consumed as food by the fungus. If left alone, the fer- mentation goes on untd either all the sugar is used up, or until the supply of sufficient albuminous matter is exhausted. Now, it will be readily under- stood that the relative proportions of these present determine which of the two gets exhausted first; and if the sugar is used up before the albuminous food of the fungus, a dry or not sweet wine is produced, Avhile if the nitrogenous food is exhausted first, the remaining unfermented sugar pro- duces a sweet AA'ine. Since the juice of the ripe grape contains from 10 to 30 per cent, of sugar, there is a very Avide range. A large number of people dislike sweet wines, hence the demand for what is called a dry Avine. Erom Avhat has been stated as to the difference NUTRITIVE VALUE OF WINE. 381 in origin of a naturally SAveet wine and a naturally dry Avine, it will be apparent that the poorer the grape the drier the wine made from it; but the yield from a poor grape is less than that from a rich one, hence naturally dry wine costs more to produce than naturally SAveet wine. It will also be apparent that the conversion of naturally sweet wines into dry ones will not be difficult, and since there is a demand for dry wines the artificial conversion is frequently performed. It is carried out either by making the wine from unripe or poor grapes, in which case the yield of alcohol and flavour are both low; or it is done by adding some nitrogenous material such as gelatin, isinglass, or white of egg to the " must," so as to feed the yeast fungus until all or nearly all the sugar in the grape has been con- verted into alcohol. This procedure is sometimes called fining in the wine trade, and is the least objectionable of all methods of artificial drying, being, as it is, almost identical with the natural cause of wine dryness! Unfortunately, there are other methods adopted which are less commendable but more common. These consist often in making an imitation of the natural dryness of wine by adding factitious salts and fortifying with alcohol. The sugar stUl exists as largely as before, only its taste is disguised. Perhaps the most general method of increasing the dryness of a given wine is that of adding mineral acids and mineral salts, more particularly gypsum, or Spanish earth. This is technically known as "plastering," because gypsum is plaster of Paris. This being largely sulphate of lime modifies the chemical characters of the wine by decomposing the cream of tartar or potassium tartrate into calcium tartrate, potassium sulphate and free tartaric acid, at the same time altering the colouring matter and chang- ing the neutral organic compounds which exist in grape juice. The use of gypsum materially clears a wine, making it look brdliant; this is explained by the fact that the resulting sulphate of potash is much more soluble than the antecedent tartrate of potash. To a certain extent, after the addition of gypsum, much of the tartaric acid of wine is replaced by sulphuric acid, a body which renders wine, so altered, distinctly unsuitable for dady use. The sherries suffer the most from plastering—so much so, that some chemists advise that the plastering of wines should be called adulteration. The chemistry of plastering may be thus written :— Gypsum Potassium Acid potassium Calcium bitartrate. sulphate. tartrate. CaS04 + C4H5K06 = S04HK + C4H4Ca06. A further transposition may ensue, such as the following, though, according to Boos and Thomas, it is questionable. Acid potassium Acid potassium Neutral potassium ,„ . . sulphate. phosphate. sulphate. 1 hosphonc acid. S04HK + P04H2K = S04K2 + P04H3. The nutritive value of the wines is small, and in the main subsidiary to the stimulating properties of their contained alcohol. The clarets and fighter wines are more or less anti-scorbutic, owing to the presence of the organic acids. Port and sherry appear to predispose to gout. The presence of some albuminous principle in wine may give it a slight nourishing value, but in favour of such a view the evidence is small. Like the malt liquors, the wines act as stimulants to the secretion of gastric juice, but they all have a well-marked retarding effect on the chemical process of gastric digestion. According to Eoberts, this retarding effect of both malt liquors and wines is not proportional to the amount of alcohol contained in them : there is some- 382 BEVERAGES AND "CONDIMENTS. tiring else which is more retarding than alcohol. Of the Avhies, port and sherry delay gastric digestion the most. Hock and claret have a less retarding effect, and champagne even still less. The retarding effects on digestion of Avines and malt liquors is probably due to the neutral inorganic salts present, but the question cannot be yet regarded as settled. EXAMINATION OF WINE. This Avdl be directed to ascertain Quality and Adulteration. The Quahty of Avine can be best determined by noting the colour, trans- parency, and taste, and then determining the following points :— Specific Gravity.—In the best clarets, before the loss of alcohol, the specific gravity is very nearly that of Avater. In some claret examined by Hoffmann, the specific gravity was 0*99952 and in others as low as 0*995. A low specific gravity shows that alcohol has been added, or that the solids are in small amount. Amount of Alcohol.—A very small amount may show the addition of Avater, a large amount the addition of spirits. Its determination should be made as for beer. Amount of Extract.—This may be estimated directly by evaporation of 50 c.c. on the water bath in a weighed capsule and calculating the residue as a percentage. Indirectly, the extract of wine may be ascertained from the specific gravity of the de-alcoholised liquid as explained in the examina- tion of beer, but the result is only approximate. Amount of Free Acidity.—This is an important point, as it seems clear that some persons do not readily digest a large amount of acid and acid salts. The amount is determined by the alkaline solution, as used for ascertaining the acidities of bread and beer. The total or free acidity is generally reckoned as crystallised tartaric acid (C4H606), 1 c.c. of the standard alkahne solution being equal to 7*5 milligrammes. There is both fixed and volatile acidity; the relative amount of the two is difficult to determine satisfactorily, as some acid may be formed on distillation. The distillation should be conducted at a low temperature, so as not to decompose the fixed compound ethers. The volatde acidity is reckoned as glacial acetic, the fixed as tartaric acid. All the acidities of wine are usually reckoned as grains per ounce, but occasionally are stated as percentages. Example.—Say 10 c.c. of wine are exactly neutralised by 9*5 c.c. of standard alkaline solution : 9*5 x 7*5 = 71 25 milligrammes of tartaric acid in 10 c.c. of wine : this 71 -25 x 7 = 498-75 grains of tartaric acid in a gallon of wine, and 498*75-f-160 = 3-ll grains of tartaric acid per ounce, or 0*712 per cent., of total or free acidity. After de-alcoholisation, say 10 c.c. require 5 c.c. of alkaline solution: then —,-„— 160 = 1*65 grain per ounce, or 0'377 per cent., of fixed acidity as tartaric acid. The difference between the amounts of alkaline solution used, 9-5-5 = 4*5 multiplied by 6 x 7---160 = 1 15 grain per ounce, or 0*27 per cent., of volatile acidity as acetic acid. The amount of free acidity varies greatly even in the same kind of Avines; the least acid wines are Sherry, Port, Champagne, the best Claret and Madeira; the more acid wines are Burgundy, Rhine Avine, Moselle. The amount of free acid in good Clarets is equal to 2 to 4 grains of tartaric acid per ounce; in common Clarets and in Beaujolais it may be 4 to 6 grains, and in some extremely acid wines it may be even more than this. In the best Champagnes it is 2 to 3 grains usually; but it has been known to reach in excellent Champagne 1*12 per cent., or 4*9 grains per ounce. In ADULTERATIONS OF AVINE. 383 Port it averages 2 to 2\ grains, but may reach 4 grains; in Sherry, 1\ to 2\ grains; in the Rhine wines, 3J to 4 or 6 grains. Thudichum and Dupre state that in good sound wine the amount of free acidity ranges from 0*3 to 0*7 per cent., or from 1*3 to 3 grains per ounce. Excessive acidity of wine can be corrected by adding neutral potassium tartrate. Milk is also often used. The addition of the carbonated alkalies, or of chalk, alters the bouquet of the wine. When wine becomes stringy, in which case acetic and lactic acids are formed, it may be improved by adding a little tea; about one ounce of tea boiled in 2 quarts of water should be added to about 40 gallons of wine. Bitter Avine is treated with hard water or sulphur; bad smelling wine with charcoal; too astringent wine with gelatin; wine AAdiich tastes of the cask with olive oil. Amount of Sugar.—This can be estimated by means of the copper solu- tion used in the determination of lactose (page 316). It is, however, neces- sary to render the Avine alkaline by an addition of sodium carbonate and to decolourise before using the Eehling solution. Strongly coloured wines, If their proportion of sugar is low, may be decolourised with purified animal charcoal; but if the sugar exceeds 0*5 per cent, with basic lead acetate, and then to receive more sodium carbonate. As animal charcoal retains sugar from strong sugary solutions, its use is inadmissible for wines containing much sugar. If there is reason to suspect cane-sugar, the sugar must be in- verted by boiling with hydrochloric acid, the sugar re-determined with copper and the cane-sugar calculated frorfi the difference. As an alternative to the use of Fehhng's solution, the saccharometer may be employed, after decolour- isation of the wine. In using the copper solution for determining the sugar, if any substance exists which is still turned green by the alkali of the Eehling solution, the wine must be neutralised, evaporated to dryness, and the sugar dissolved. As a rule, the estimation of Avine sugar by means of the copper solution gives 0*5 per cent, too much sugar, and a correction to this amount should be made. Adulterations of wine wdl be best detected by attention to the follow- ing :— Water, if added, will be knoAvn by taste, by the amount of alcohol, and the specific gravity after the elimination of the alcohol. Distilled Spirits.—Known by determining the amount of alcohol, the normal percentage of the particular kind of wine being known. By frac- tional distdlations the peculiar-smelling fusel oils may be obtained; or merely rubbing some of the wine on the hand, and letting it evaporate, may enable the smell of these ethers to be perceived. Artificial Colouring Matters.—For distinguishing between the genuine colouring matter of wine and artificial admixtures, Dupre suggests the use of cubes of gelatin made by dissolving 5 grammes of gelatin in 100 c.c. of distilled water; when cold, cut into cubes about f inch square; immerse in the wine, and examine after twenty-four to forty-eight hours. If the wine is pure, the colour is confined almost to the margin, or does not extend in- wards more than £ inch. Most other colouring matters permeate the jelly; an exception is furnished by Rhatany root, the colouring matter of which acts like that of wine. Lime Salts.—If wine has been plastered, the lime salts are large. The only precise way of detecting this adulteration is by evaporating to dryness, incinerating, and determining the amount of lime. But the following method is shorter, and will generally answer. The natural lime salts of wine are tartrate and sulphate; Avhen lime is added an acetate of calcium is formed. 384 BEVERAGES AND CONDIMENTS. Evaporate the wine to -j^th; add tAvice its bulk of strong alcohol; the calcium acetate is dissolved, but not the sulphate or tartrate; filter and test Avith oxalate of ammonium; if a large precipitate occur, lime has probably been added. Tannin may be detected either by chloride of iron or by adding gelatin. But as tannin exists naturally in most of the red wines (Port, Beaune, Roussillon, Hermitage, &c), the question becomes often one of quantity. The amount of tannin can be estimated by drying the tanno-gelatin, weigh- ing it, and calculating on the basis that each 100 parts contain 40 of tannin. Alum.—-This is detected precisely in the same manner as in bread. Evaporate a pint of the wine to dryness; incinerate, and then proceed as directed in the Examination op Bread. Lead.—Evaporate to dryness, and incinerate; dissolve in dUute nitric acid, and test as directed in the Examination of Water. Copper.—Decolourise with animal charcoal, and test at once with ferro- cyanide of potassium. Port wine, as sold in the market, is stated to be a mixture of true Port, Marsala, Bordeaux, and Cape wines with brandy, although at present it is probably purer than it used to be, purer perhaps than most other wines. Inferior kinds are still adulterated with logAvood, elderberries, catechu, prune juice, and a little sandalwood and alum. N SPIRITS. Of all the alcoholic beverages, spirits contain the largest amount of alcohol. They are all made by the distillation of alcohol from the fermenta- tion of various saccharine or starchy materials. The more common spirits in this country are brandy, whisky, rum, and gin. The basis of all of them is ethylic alcohol, mixed with water; but they all contain other alcohols, usually classed together under the name of fusel oil, various compound ethers and fragrant bodies produced during distillation. It is the varying pro- portions of these latter which give the respective spirits their characteristic taste and aroma. After being kept for some years, spirits become mellowed or softened down; this was formerly supposed to be due to the diminution of the so-called fusel od, but it is now more generally regarded as due to a lessening both in quantity and quality of the empyreumatic or flavouring substances. The foUoAving table gives the chief points of importance :— Name. Sp. gr. at 60° F. Alcohol per cent. Solids per cent. Ash per cent. Acidity per ounce, reckoned as tartaric acid. Sugar per cent. Brandy, . Gin, Whisky,. Rum, 0 929-0 934 0-930-0-944 0-915-0-920 0-874-0-926 45-55 40-50 50-55 50-60 1-2 1-2 06 1-0 0-05-0 2 01 trace o-i 1 grain 0-2 0-2 0 5 0 or traces 1 0 0 Brandy is made by the distillation of fermented grape juice. When first distdled it is colourless, but gradually darkens with age, though too often artificially coloured by means of burnt sugar. Pure brandy consists of WHISKY—GIN—RUM. 385 water, alcohol, acetic acid, acetic and oenanthic ethers, a volatile oil, colour- ing matter, and tannin. It usually contains from 45 to 55 per cent, of alcohol. The best kinds come from France, the more inferior from Spain, Portugal, and Italy. The chief adulterations are water, cayenne pepper, burnt sugar, and acetic ether. Some of the cheaper brandies are not made from grape juice at all, but are mere imitations, made from corn spirit, flavoured and coloured. According to Wynter-Blyth, a very usual process of making brandy artificially in England is to add to every 100 parts of proof spirit from J to 1 2b of argol, some bruised French plums, and a quart of good Cognac; the mixture is then distilled, and a little acetic ether, tannin, and burnt sugar added afterAvards. Whisky is really one of the corn spirits, being made from malted grain. The more inferior kinds are prepared from oats, barley, or rye, or from potatoes mashed up with malted barley and then roughly distilled and burnt in order to give it the peculiar smoky flavour characteristic of some varieties. Whisky usually contains from 40 to 50 per cent, of alcohol. Its adulterations are much the same as those of brandy. G-in, in this country, is usually made from a mixture of malt and barley, flavoured not only with juniper berries, but with oil of turpentine, orange peel, and several other aromatic substances. In Holland, it is made from unmalted rye, and barley malt with juniper berries. In consequence of the juniper and turpentine contained in gin, it is a direct stimulant to the kidneys. It usually contains from 40 to 50 per cent, of alcohol. Its chief adulteration is water, which makes it turbid; to remove this, alum and acetate of lead are employed, followed by the addition of sugar and cayenne pepper to sweeten it and give it pungency. Speaking generally, gin is the spirit of Avhich most is annually consumed by the public, and the spirit which is most often adulterated. Rum is a spirit obtained by distiUation from the fermented skimmings of sugar boders or the drainings of sugar barrels (molasses). Like brandy, it is colourless when first distilled, but it is, later on, artificially coloured with burnt sugar. The peculiar flavour of rum is due to butyric ether and a volatile od; the amount of alcohol present in rum is from 50 to 60 per cent. An imitation flavouring identical with that of the Jamaica rum, so often flavoured with slices of pine-apple, is made by distilling butter with sulphuric acid and alcohol, and then, by means of the resulting butyric compound, a factitious rum can be made from malt or molasses spirit. When quite pure and free from water, alcohol is termed absolute alcohol, having a specific gravity, at 60° F., of 0*79381 : when mixed with 16 per cent, of water, it is called rectified spirit, and when mixed with 56*8 per cent., volume in volume of water, it constitutes proof spirit. Proof spirit is a term constantly in use for excise purposes, signifying a ddute spirit of definite strength. If expressed as volume in volume, proof spirit contains 56-8 per cent, of absolute alcohol: if as weight in weight, 49*25 per cent. : if as weight in volume, 45*4 per cent. : the remainder in each case being distilled water. The ratio of alcohol to proof spirit in each of these cases being for volume in volume, as 1 is to 1*76 : for weight in weight, as 1 is to 2*03 : and for weight in volume, as one is to 2-21. We can, therefore, if in any case the percentage of contained alcohol be known, calculate the amount of proof spirit present by multiplying the given per- centage of alcohol by any of the foregoing ratios. Spirits which are weaker than proof are described as being under proof; when stronger than proof, as being over proof. Thus, say a sample of whisky is found to contain 70 per cent., volume in volume, of alcohol; 2B 386 BEVERAGES AND CONDIMENTS. then 70x1*76 = 123*2, and the excess of this product over 100, or 23*2, gives the number of degrees over proof which the sample is. If, on the other hand, it contained but 24 per cent, of alcohol, volume in volume, then 24 x 1*76 = 42*24, and by just so much as this figure is greater or less than 100, so is the sample degrees over or under proof, that being, in this case, just 57°*76 under proof. Conversely, if the degree of strength of any spirit over or under proof be knoAvn, the percentage of alcohol present can be calculated either as volume in volume, Aveight in weight, or weight in volume. Thus, say a sample of brandy be x degrees over proof; then ———-- gives the percentage, volume in volume, of alcohol Avhich it contains. , , 100-SB . If it be x degrees under proof, then , „„ gives the percentage, volume in volume, again of alcohol. The Sale of Food and Drugs Amendment Act, 1879, allows brandy, Avhisky, or rum to be 25 degrees under proof; equal to 42*6 per cent, of absolute alcohol, volume in volume, or 34*1 per cent, of weight in volume. This gives a specific gravity of 0*947. Gin is allowed to be 35 degrees under proof, equal to 36*9 per cent, volume in volume, or 29*5 per cent. Aveight in volume of absolute alcohol. This gives a specific gravity of 0*956. Proof spirit contains 56*8 volume in volume, or 45*4 weight in volume of absolute alcohol, sp. gr. 0*920, or 49*24 weight in Aveight per cent. Although the alcohol in spirits can be determined by means of the specific gravities before and after de-alcoholisation, as explained for beer and wines, still the strength of spirits is freqently ascertained by the use of Sikes' hydrometer, and a book of tables for its employment. A sample of the spirits to be tested is poured into a trial glass, and the temperature ascertained by means of a thermometer in the usual way. The hydrometer is taken, and one of the weights is attached to the stem beloAv the ball: it is then pressed down to the 0 on the stem. If the right weight has been selected it will float up to one of the divisions on the stem. The number on the stem is then read off and added to the number on the loeight; the sum is called the indication. The book of tables is then opened at the temperature first found, and the indication looked for in one of the columns : opposite it will be found the strength of the spirits over or under proof. If at the temperature 60° F. the indication is 58*8, then opposite this will be found zero, that is, the spirit is the exact strength of proof. If the indica- tion is 50, then opposite that is 12*8, or the spirit is 12-8 over proof: if the indication is 70, then opposite is 18*9, or the spirit is 18-9 under proof. The meaning of these expressions is—(1) If the spirit be 12-8 over proof, then, in order to reduce it to proof, 12'8 gallons of water must be added to 100 gallons of the spirit: the resulting mixture will be proof ; (2) if the spirit be 18*9 under proof, this means that 100 gallons contain only as much alcohol as 81*1 (i.e., 100-18-9) of proof spirit: to raise it to proof it would have to be mixed with an equal quantity of spirit as much above * -+• -u i -4. a . 100-18*9 + 118*9 n_ proof as it is below it, so that-----------------= 100. The presence of sugar or extractives renders the use of the hydrometer faUacious unless the spirit is distilled off and the instrument then used on the distiUate. NUTRITIVE VALUE OF ALCOHOL. 387 THE DIETETIC USE OF ALCOHOL AND ALCOHOLIC BEVERAGES. In endeavouring to determine the dietetic value of alcoholic beverages, it is desirable to see, in the first place, what are the effects of their most important constituent, viz., alcohol. Three sets of arguments have been used in discussing this question, •drawn, namely, from—-1, the physiological action of alcohol; 2, experience of its use or abuse; and 3, moral considerations. The last point Avill not be further alluded to, for without underrating the great Aveight of the argument draAvn from the misery which the use of alcohol produces,—a misery so great that it may truly be said, that if alcohol Avere unknown, half the sin and a large part of the poverty and unhappiness in the world would disappear,—yet this part of the subject is so obvious that it seems unnecessary to occupy space with it. The argu- ments, however, Avhich are strongest for total abstinence, are drawn from this class. Xor does any one entertain a moment's doubt that the effect of intemperance in any alcoholic beverage is to cause premature old age, to pro- duce or predispose to numerous diseases, and to lessen the chance of living very greatly. All statistics from life assurance offices and other provident institutions put this in a very strong light. The physiological argument for the use or disuse of alcohol requires to be used Avith caution, as our knowledge of the action of pure alcohol (much more of the alcoholic beverages) is imperfect. When taken into the stomach, alcohol is absorbed without alteration, or is perhaps in some small degree converted into acetic acid, possibly by the action of the mucus or secretion of the stomach. The rate of absorption is not known, and it has been supposed that when given in very large quantities it may not be absorbed at all. It has not, however, been re- covered from the faeces in any great amount. After absorption it passes into the blood, and, according to Schmiedeberg, forms a compound with haemoglobin, which more readily gives off oxygen than haemoglobin itself. The result of this is that alcohol lessens oxidation in the blood and tissues. Most of the alcohol taken is oxidised in the body, the products being excreted in the urine. In dietetic doses, some of the alcohol may be detected in the expired air, but it can be detected in the urine only when the dose is excessive. The presence of alcohol in the urine is, therefore, to some extent, a chemical test of an excess of alcohol having been taken. The place where the partial oxidation of alcohol occurs is yet doubtful; but it is not impossible that the transformation should take place in the various gland-cells in which almost all, or all, the changes in the body occur. As the change out of the body which most easily occurs is the formation of acetic acid, it seems at present most likely that some of the alcohol is thus transformed. The acetic acid Avould then unite Avith the soda of the blood, and a carbonate would eventually be formed which would be eliminated with the urine, as in the case when acetates are taken. This would account for the pulmonary carbonic acid not being increased. If this view be correct, the use of alcohol in nutrition would be limited to the effects it produces, first as alcohol, and subsequently as acetic acid, when it neutralises soda, and is then changed into carbonate. The first point only (its effects as alcohol) need be considered. In very small quantities it appears to aid digestion; in larger amount it ■checks it, reddens the mucous membrane, and produces the " chronic 388 BEVERAGES AND CONDIMENTS. catarrhal condition " of Wilson Fox, viz., increase of the connective tissue between the glands ; fatty and cystic degeneration of the contents of the glands, and, finally, more or less atrophy and disappearance of these parts. Taken habitually in large quantities it lessens appetite. The action of small quantities on the amount of bile, or glycogenic sub- stances, or on the other chemical conditions of the liver, is not known. Applied directly to the liver by injection into the portal vein, it increases the amount of sugar (Harley). Taken daily in large quantities, it causes either enlargement of the organ by producing albuminoid and fatty deposit, or it causes at once, or following enlargement, increase of connective tissue,. and, finally, contraction of Glisson's capsule, and atrophy of the portal canals and cells, by the pressure of a shrinking exudation. The exact amount necessary to produce these changes in the liver and stomach has not yet "been fixed with precision. It is said to lessen the amount of carbon dioxide (and of watery vapour ■?)* in the air of expiration, though there are some discrepancies in experiments Avith different kinds of spirits. E. Smith, for example, found the expired carbon dioxide lessened by brandy and gin, but increased by rum. It is very important that these experiments should be repeated, but they show,. at any rate, that the usual effect is not to increase the carbon dioxide. In large quantities habitually taken it also alters the molecular constitution of the lungs, as chronic bronchitis and lobar emphysema are certainly more common in those avIio take much alcohol. Alcohol, in healthy persons, increases the force and quickness of the heart's action. It further tends to increase the blood pressure, and to increase the flow of blood from the arteries into the veins. The effect on the blood pressure is, however, largely counterbalanced by a coincident dilatation of the cutaneous blood-vessels, which thus become flushed, and tend to produce more or less sensible perspiration. In most persons, alcohol appears to act at once as an anaesthetic, lessening: also the rapidity of impressions, the power of thought, and general acute- ness and the perfection of the senses. In other cases it seems to cause increased rapidity of thought, and excites imagination, but even here the power of control over a train of thought is lessened. In no case does it seem to increase accuracy of sight; nor is there any good evidence that it quickens hearing, taste, smell, or touch; indeed, Edward Smith's experi- ments show that it diminishes all the senses. In almost all cases moderate quantities cause a feehng of comfort and exhilaration, which ensues so quickly as to make it probable that the local action on the nerves of the stomach has at first something to do with this. Afterwards the increased action of the heart may have an effect. Different spirits act differently on the nervous system, owing probably to the presence of the ethers and oils. Absinthe appears especially hurtful, apparently from the presence of the essential oils of anise, wormwood, and angelica, as well as from the large amount of alcohol. In spite of much large experience, it is uncertain whether alcohol really- increases mental power. The brain circulation is no doubt augmented in rapidity; the nervous tissues must receive more nutriment, and for a time must work more strongly. Ideas and images may be more plentifully produced, but it is a question whether the power of clear, consecutive, and continuous reasoning is not always lessened. In cases of great exhaustion of the nervous system, as when food has been withheld for many hours and the mind begins to work feebly, alcohol revives mental power greatly, probably from the augmented circulation. But, on the whole, it seems- DIETETIC VALUE OF ALCOHOL. 389 questionable whether the brain finds in alcohol a food which by itself can aid in mental Avork. After taking alcohol, voluntary muscular poAver seems to be lessened, and this is most marked when a large amount of alcohol is taken at once; ■the finer combined movements are less perfectly made. Whether this is by direct action on the muscular fibres, or by the influence on the nerves, is not certain. In very large doses it paralyses either the respiratory muscles or the nerves supplying them, and death sometimes occurs from the inter- ference Avith respiration. A small quantity of alcohol does not seem to produce much effect, but more than 2. fluid ounces manifestly lessens the power of sustained and strong muscular Avork. In the case of a man on whom Parkes experi- mented, 4 fluid ounces of brandy ( = L8 fluid ounce of absolute alcohol) did not apparently affect labour, though it could not be affirmed it did not do so; but 4 ounces more given after four hours, when there must have been some elimination, lessened muscular force; and a third 4 ounces, given four hours afterwards, entirely destroyed the poAver of work. The reason Avas evidently twofold. There Avas, in the first place, narcosis and blunting of the nervous system—the will did not properly send its commands to the muscles, or the muscles did not respond to the AArill; and, secondly, the action of the heart was too much increased, and induced palpitation and breathlessness, which put a stop to labour. The inferences were, that even any amount of alcohol, although it did not produce symptoms of narcosis, Avould act injuriously, by increasing unnecessarily the action of the heart, which the labour alone had sufficiently augmented. These experiments are in accord with common experience, which shows that men engaged in very hard labour, as iron-puddlers, glass-blowers, navvies on piece-work, and prize-fighters during training, do their work more easily without alcohol. In the exhaustion following great fatigue, alcohol may be useful or hurtful according to circumstances. If exertion must be resumed, then the action of the heart can be increased by alcohol and more blood sent to the muscles; of course, this must be done at the expense of the heart's nutri- tion, but circumstances may demand this. In the case of an army, for example, called on to engage the enemy after a fatiguing march, alcohol might be invigorating. But the amount must be small, i.e., much short of producing narcosis (not more than -| fluid ounce of absolute alcohol), and, if possible, it should be mixed Avith Liebig's meat extract, which, perhaps on account of its potash salts, has a great power of removing the sense of fatigue. About two ounces of red claret wine with two teaspoonfuls of Liebig's extract and half pint of Avater is a very reviving draught, and if it could be issued to troops exhausted by fatigue, would prove a most useful ally. But when reneAved exertion is not necessary it would appear most proper after great fatigue to let the heart and muscles recruit themselves by rest; to give digestible food, but to avoid unnecessary and probably hurtful quickening of the heart by alcohol. Hoav far alcohol sensibly loAvers the temperature of the body in health is still a matter of dispute, but there is no doubt that in some cases of fever, especially in children, alcohol does lower the temperature. Lauder Brunton has suggested that, in health, it tends to lower the body tempera- ture in two ways: first, in medium doses, "by dilating the cutaneous vessels, Avhereby more blood comes to the surface of the body, and thus more heat is lost by radiation and by means of the increased perspiration; second, when given in large doses, by lessening the processes of oxidation 390 BEVERAGES AND CONDIMENTS. in the body." Although there are doubts Avhether alcohol really lowers the temperature of the healthy body, there is no doubt Avhatever that it loAvers the natural resistance of the body against cold. "When a person is exposed to extreme cold for long periods, as in the Arctic regions, he may derive some temporary comfort and sensation of warmth from taking alcohol; but his poAver of resistance to the intense cold is lessened, and instances have been recorded Avhere death has occurred under such conditions during sleep." Under circumstances of great heat, the evidence is almost equally con- clusive against the use of spirits or beverages containing much alcohol. It seems quite certain, also, that not only is heat less well borne, but that heat-stroke is predisposed to. When there is want of food, it is generally considered that alcohol has a sustaining force, and possibly it acts partly by keeping up the action of the heart, and partly by deadening the susceptibility of the nerves. It was formerly supposed that it lessened tissue-change, and thus curtailed the Avaste of the body; but this is not true of the nitrogenous tissues, and it is not yet quite certain in respect of the carbonaceous. It seems unlikely that alcohol would be applied differently during starvation and during usual feeding. Cases are recorded in Avhich persons have lived for long periods on almost nothing but Avine and spirits. In most cases, hoAvever, some food has been taken, and sometimes more than Avas supposed, and in all instances there has been great quietude of mind and body. It seems very doubtful Avhether in any case nothing but alcohol has been taken; and, in fact, Ave may fairly demand more exact data before Aveight can be given to this statement. There are instances for and against the view that spirits are useful against malaria. On both sides the evidence is defective; but there are so many cases in which persons have been attacked Avith malarious disease who took spirits, that it is Impossible to consider the preventive poAvers great, even if they exist at all. On the other hand, when teetotallers have escaped malaria there have been other circumstances, such as more abundant food and better lodging, which will explain their exemption. The probability is, that the reception and action of malaria are not influenced by the presence or absence of alcohol in the blood unless the amount of alcohol is so great as to lessen the amount of food taken. Alcohol is contra-indicated where zymotic diseases generally are likely to be prevalent, as it retards due elimination of effete azotised products, and thus renders the system more prone to disease. On the other hand, there is no direct evidence that teetotallers are more exempt from cholera, yellow fever, and other zymotics than those who use alcohol Avith *moderation. The question arises, is alcohol desirable as an article of diet in health ? To it a satisfactory ansAver can hardly be given, Avith our present knoAvledge. The data for passing a judgment are partly physiological, but still more largely empirical. The obvious useful physiological actions of alcohol are an improvement in appetite, produced by small quantities, and an increased activity of the circulation, which, within certain limits, may be beneficial. It is difficult to perceive proof at present of any other useful action, since it is uncertain whether, during its partial destruction in the system, it gives rise to energy. In cases of disease, in addition to its effect on digestion and chculation, its narcotising influence on the nervous system may be sometimes useful. Beale suggests that it may restrain the rapidity of abnormal growth or develop- ment of multiplying cells, and that by such arrest it may possibly diminish bodily temperature; but proof of this has not been given. DIETETIC VALUE OF ALCOHOL. 391 The dangerous physiological actions in health, when its quantity is larger, are evidently its influence on the nervous system generally, and on the regulating nerve-centres of the heart and vaso-motor nerves in particular; the impairment of appetite produced by large doses; the lessening of muscular strength; and remotely the production of degenerations. Except when it lessens appetite, it does not alter the transformation of the nitrogenous tissues and the elimination of nitrogen; nor can it be held to be absolutely proved to lessen the excretion of carbon. If it did so, this effect in health would be simply injurious. It is a matter of the highest importance to determine when the limit of the useful effect of alcohol is reached. The experiments are feAv in number, but are tolerably accurate. From experiments made by Anstie, an amount of one fluid ounce and a half (42*6 c.c.) caused the appearance of alcohol in the urine, which Anstie regards as a sign that as much has been taken as can be disposed of by the body. Parkes and Wollowicz obtained almost precisely the same result. When only one fluid ounce of absolute alcohol was given none could be detected in the urine. They found that in a strong healthy man, accustomed to alcohol in moderation, the quantity given in twenty-four hours that begins to produce effects which can be considered injurious is something between one fluid ounce (= 28*4 c.c.) and tAvo fluid ounces (56*7 c.c). The effects Avhich can then be detected are slight but evident narcosis, lessening of appetite, increased rapidity of rise in the action of the heart, greater dilatation of the small vessels as estimated by the sphygmograph, and the appearance of alcohol in the urine. These effects manifestly mark the entrance of that stage in the greater degrees of which the poisonous effects of alcohol become manifest to all. It may be considered, then, that the limit of the useful effect is produced by some quantity betAveen 1 and 1| fluid ounce in twenty-four hours. There may be persons Avhose bodies can dispose of larger quantities; but as the experiments were made on two poAverful healthy men, accustomed to take alcohol, the average amount Avas more likely to be over than under stated. In Avomen, the amount required to produce decided bad effects must, in all probabihty, be less. For chddren, there is an almost universal consent that alcohol is injurious, and the very small quantity which produces symptoms of intoxication in them indicates that they absorb it rapidly and. tolerate it badly. Assuming the correctness of these experimental data, which, though not extensive, are yet apparently exact, it is evident that moderation must be something beloAv the quantities mentioned; and considering the dangers of taking excess of alcohol, it seems Avisest to assume 1 to 1| fluid ounce of absolute alcohol in twenty-four hours as the maximum amount which a healthy man should take. It must be admitted that this is provisional, and that more experiments are necessary ; but it is based on the only safe data we possess. One ounce is equivalent to 2 fluid ounces of brandy (con- taining 50 per cent, of alcohol); or to 5 ounces of the strong wines (sherries, &c, 20 per cent, of alcohol); or to 10 ounces of the weaker wines (clarets and hocks, 10 per cent, of alcohol); or to 20 ounces of beer (5 per cent, of alcohol). If these quantities are increased one-half, 1^ ounce of absolute alcohol Avill be taken, and the limit of moderation for strong men is reached. This standard appears to be fairly correct; since, from inquiries of many healthy men avIio take alcohol in moderation, Parkes found that they seldom exceeded the above amounts. Women, no doubt, ought to take less; and alcohol in any shape only does harm to healthy children. Another question noAV arises, to which it is more difficult to reply. Is 392 BEVERAGES AND CONDIMENTS. alcohol, even in this moderate amount, necessary or desirable? are men really better and more vigorous, and longer lived -with it than they would be without any alcohol 1 If distinctly hurtful in large quantities, is it not so in these smaller amounts 1 There is no difficulty in proving, statistically, the vast loss of health and life caused by intemperance; and the remarkable facts of the Provident Institution show the great advantage total abstainers have over those Avho, though not intemperate, use alcohol more freely. But it is almost impossible, at present, to compare the health of teetotallers Avith those who use alcohol in the moderate scale given above. In both classes are found men in the highest health, and Avith the greatest vigour of mind and body; in both are to be found men of the most advanced age. If the question is looked at simply as a scientific one, it is hardly possible at present to give an answer. Failing in accurate information on this point, the usual arguments for and against the use of alcohol cannot be held to settle the point. These are— (a) That the universality of the habit of using some intoxicating drink proves utility. This seems incorrect, since Avhole nations (Mohammedan and Hindoo) use no alcohol or substitute; and since the same argument might prove the necessity of tobacco, which, for this generation at any rate, is clearly only a luxury. The Avide-spread. habit of taking intoxicating liquids merely proves that they are pleasant. (b) That if not necessary in healthy modes of life, alcohol is so in our artificial state of existence, amid the pressure and conflict of modern society. This argument is very questionable, for some of our hardest Avorkers and thinkers take no alcohol. There are also thousands of persons engaged in the most anxious and incessant occupations who are total abstainers, and, according to their own account, AA'ith decided benefit. (c) That though it may not be necessary for perfectly healthy persons, alcohol is so for the large class of people Avho live on the confines of health, Avhose digestion is feeble, circulation languid, and nervous system too excit- able. It must be allowed there are some persons of this class who are benefited by alcohol in small quantities, and chiefly in the form of beer or light wine. Unless these persons wilfully deceive themselves, they feel better, and are better, with a little alcohol. (d) That common experience on the largest scale shows that alcohol in not excessive quantities cannot be an agent of harm; that it is and has been used by millions of persons Avho appear to suffer no injury, but to be in many cases benefited, and therefore that it must be in some way a valuable adjunct to food. A grand fact of this kind must, it is contended, override all objections based on physiological data, which are confessedly incomplete, and which may have left undiscovered some special useful action. It must be admitted that this is a very strong argument, and that it seems incredible that a large part of the human race should have fallen into an error so gigantic as that of attributing great dietetic value to an agent which is of little use in small quantities, and is hurtful in large. At first sight the common sense of mankind revolts at such a supposition, but the argument, though strong, is not conclusive ; and unfortunately we know that in human affairs no extension of belief, hoAvever wide, is per se evidence of truth. (e) That though a man can do Avithout alcohol under ordinary circum- stances, there are certain conditions when it is useful. These considerations make it difficult to avoid the conclusion that the dietetic value of alcohol has been much overrated. It does not appear DIETETIC VALUE OF ALCOHOL. 393 possible at present to condemn alcohol altogether as an article of diet in health, or to prove that it is invariably hurtful, as some have attempted to do. It produces effects which are often useful in disease and sometimes desirable in health, but in health it is certainly not a necessity, and many persons are much better without it. As noAV used by mankind (at least in our own, and in many other countries), it is infinitely more powerful for evil than for good; and though it can hardly be imagined that its dietetic use wdl cease in our time, yet a clearer vieAV of its effects must surely lead to a lessening of the excessive use Avhich now prevails. As a matter of public health, it is most important that the medical profession should throw its great influence into the scale of moderation ; should explain the limit of the useful poAver, and sIioav Iioav easily the line is passed which carries us from the region of safety into danger, when alcohol is taken as a common article of food. In the previous remarks, the effect of alcohol only has been discussed, but beer and Avine contain other substances besides alcohol. In beer there appear to be four ingredients of importance, viz., the extractive matters and sugar, the bitter matters, the free acids, and the alcohol. The first, no doubt, are carbo-hydrates, and play the same part in the system as starch and sugar, appropriating the oxygen, and saving fat and proteids from destruction. Hence one cause of the tendency of persons avIio drink much beer to get fat. The bitter matters are supposed to be stomachic and tonic; though it may be questioned whether Ave have not gone too far in this direction, as many of the highest priced beers contain now little else than alcohol and bitter extract. The action of the free acids is not known; but their amount is not inconsiderable; and they are mostly of the kind which form carbonates in the system, and which seem to play so useful a part. The salts, especially potassium and magnesium phosphates, are in large amount. It is evident that in beer we have a beverage Avhich can answer several purposes, viz., can give a supply of carbo-hydrates, of acid, of important salts, and of a bitter tonic (if such be needed), independent of its alcohol, but whether it is not a very expensive Avay of giving these substances is a question. In moderation, it is no doubt well adapted to aid digestion, and to lessen to some extent the elimination of fat. It may be inferred that beer -will cause an increase of Aveight of the body, by increasing the amount of food taken in, and by slightly lessening metamorphosis; and general experience confirms those inferences. When taken in excess, it seems to give rise to gouty affections more readdy even than wine. In wine there are some proteid substances, much sugar (in some wines), and other carbo-hydrates, and abundant salts. Whether it is that the amount of alcohol is small, or whether the alcohol be itself, in some way, different from that prepared by distillation, or Avhether the co-existence of carbo-hydrates and of salts modifies its action, certain it is that the moderate use of Avine, which is not too rich in alcohol, does not seem to lead to those profound alterations of the molecular constitution of organs Avhich follow the use of spirits, even Avhen not taken largely. Considering the large amounts of vegetable salts Avhich most wines contain, it may reasonably be supposed that they play no unimportant part in giving dietetic value to Avine. Indeed, it is quite certain that, in one point of vieAV, they are most valuable; they are highly anti-scorbutic, and the arguments of Lind and Gillespie, for the introduction of red Avine into the Royal Navy instead of spirits, have been completely justified in our own time by both French and English 394 BEVERAGES AND CONDIMENTS. experience. It is noAV certain that Avith the same diet, but giving in one case red wine, in another rum, the persons on the latter system will become scorbutic long before those avIio take the wine. This is a most important fact, and in a campaign the issue of red wines should never be omitted. The ethers may also be important if, as indicated by Bernard, and recently pointed out by Sir B. W. Forster, they excite the flow of the pancreatic secretion, and thereby promote the absorption of fat. In spirits, alcohol is the main ingredient, chiefly in the form of ethyl- alcohol, though there are small amounts of propyl-, butyl-, and in some cases amyl-alcohols. In addition, there are sometimes small quantities of ether; and, in some cases, essential ods (as apparently in absinthe, and in one kind of Cape brandy), Avhich have a poAverful action on the nerves. But spirits are, for the most part, merely flavoured alcohol, and do not contain the ingredients which give dietetic value to wine and beer. They are also more dangerous, because it is so easy to take them undiluted, and thus to increase the chance of damaging the structure and nutrition of the albuminous structures with which they come first in contact. There is every reason, therefore, to discourage the use of spirits, and to let beer and wines, with moderate alcoholic poAver, take their place. Some of the undoubtedly deleterious effects of crude spirits must be ascribed to the presence of furfurol, and other bodies which both diminish in quantity and change in quality, as the spirit "mellows" with age. These substances, as present in new spirit, tend to derange digestion and also appear to have a profound effect upon the nervous system. TEA. Tea consists of the dried leaves of a shrub called the Camellia, thea, Avhich grows in China, India, Ceylon, and Japan. As met with in everyday life, tea-leaves are curled, but they uncurl on being placed in hot Avater, and when so treated are found to have a characteristic shape and structure. The border is serrated nearly, but not quite to the stalk; the primary veins run out from the midrib nearly to the border, and then turn in, so that a distinct space is left between them and the border. The leaf may vary in point of size and shape, being sometimes broader, and sometimes long and narrow. The border and the primary venation distinguish it from all leaves (fig. 55). The leaves which it is said have been mixed Avith or substituted for tea in this country are the wdloAv, sloe, oak, Valonia oak, plane, beech, elm, poplar, hawthorn, and chestnut; and in China Chlor- anthus inconspicuus and Camellia Sasanqua are said to be used. Of these the willow and the sloe are the only leaves which at all resemble tea-leaves. The Avillow is more irregularly, and the sloe i.s much less perfectly and uniformly serrated. To examine the leaves, make an infusion, and then spread out a number of leaves; if a leaf be placed on a glass shde, and covered with a thin glass, and then held up to the light, the border and venation can usually be Avell seen. Fig. 55. TEA. 395 The leaves of the Yalonia, if used, are at once detected by acicular crystals being found under the microscope. Sometimes exhausted tea-leaves are mixed Avith catechu or Avith a coarse powder of a reddish-brown colour, consisting chiefly of powdered catechu. Gum and starch are added, the leaves being steeped in a strong solution of gum, which, in drying, contracts them. The want of aroma, and the- collection at the bottom of the infusion of powdered catechu, or the detec- tion of particles of catechu, Avill at once indicate this falsification, which is, however, very uncommon. Sand and magnetic oxide of iron are added by the Chinese. At first the latter Avas mistaken for iron filings; and when it was proved to be really magnetic oxide, it Avas suggested that it came accidentally from the soil where the tea was cultivated, but there exist good reasons for considering its presence to be due to wilful addition. Practically all tea in the market is grown from the same species of shrub, the various names given as indicating different kinds are only trade names, and do not indicate really different varieties of tea-leaf so much as different qualities dependent upon mixing or blending, and on the age of the leaves, or on the sod on Avhich the plant has been grown. In all cases, the leaf most highly valued is the small top leaf of the twig and the bud. Possibly these small leaves are neither finer in quality nor richer and better in flavour than the leaves next in succession, but being more tender and softer in structure give better and more flavoured infusions. The various teas knoAvn under the trade names of Orange Pekoe, Pekoe, Suchong, Congou are all the same in respect of origin; they are picked at the same time from the same shrub. The bud and top leaf constitute Orange Pekoe, the two or three larger leaves growing on the same twig a httle lower doAvn are Suchong, and below that the leaves become Congou. The most simple division of teas is into the green and the black; both are from the same plant, the only difference is their colour. Green tea is now httle used, in consequence of the disrepute into which it fell as the result of the artificial colouring it received; but real green tea owes its coloration to being dried over wood fires when fresh. Black teas owe their colour to the leaves having been allowed to lie in heaps for twelve hours, during which they undergo a process of fermentation and are afterwards dried slowly over charcoal fires. " Brick tea " is made from the refuse, broken leaves and twigs, moulded into shapes. " Lie tea " consists of the dust of tea and other leaves made up by means of gum or starch into little masses, Avhich are coloured or painted so as to resemble black or green tea; it is called " lie " tea because it is a false article and not tea at all. In selecting a fine tea, one should not be guided by any trade name, but determine, by pouring a little boiling Avater over the leaves and examining them, whether the leaf was a Avhole leaf and not a large leaf cut into small pieces. The larger the leaf, the Aveaker Avill be the infusion and the less the value. What are called " digestive " teas are varieties in which the tannin of the tea has been so altered by electrical treatment that it does not precipitate gelatin, and interferes but httle Avith the digestion of starch. The average percentage composition of tea may be expressed as folloAvs :— Water, Thein, Tannin, Oil, . Extractives, Insoluble organic matter, Ash, .... 8-0 2-6 14-0 0-4 15*0 54*0 fi#0/ Potash, iron, silica, \ alumina, magnesia. 396 BEVERAGES AND CONDIMENTS. There is rather more tannic acid, and more thein and aetherial oil, in green than black tea, but less cellulose: otherwise the composition is much the same. The most essential points in making good tea of the finest quality, and Avith the least waste, are to have actually boiling Avater, and tea-leaves so crushed and subdivided that the largest possible surface is rapidly exposed to the boiling water in infusing it. This explains why the best tea infusion in the world is that made by the Japanese from their carefully prepared "tea powder," which is made by crushing to a fine powder certain well-selected leaves. The tea bricks of China probably owe their superiority to being Avell-crushed leaves of good quality. About -f-ths of the soluble matters in the tea-leaves are taken up by the first infusion with hot water. If Avater contain much hme or iron it Avill not make good tea; in each case the water should be well boiled with a little carbonate of soda for fifteen or twenty minutes, and then poured on the leaves. In the infusion are found dextrin, glucose, tannin, and thein. About 47 per cent, of the nitrogenous substances pass into the infusion, and 53 per cent, remain undissolved. If soda is added, a still greater amount is given to Avater. The amount of tannin taken up by the infusion varies according to the character of the tea as Avell as the time the infusion is allowed to stand: the folloAving numbers are given by Hale White :— rer cent, by weight after 3 minutes. After 15 minutes. Finest Assam,......11-30 17*73 Finest China,......7 *77 7 -97 Common Congou,.....9'37 11'15 As an article of diet, tea seems to have a decidedly stimulant and restora- tive action on the nervous system, folloAved by no after-depression. This effect is mainly due to the alkaloid thein which it contains, aided, perhaps, by the warmth of the infusion. Thein or caffein is chemically trimethyl xanthin or methyl theobromine, CsH10N4Oo. Though considered to be chemically identical with caffein, thein differs somewhat from it in physio- logical action. After taking tea, the pulse is a little quickened, the action of the skin increased, and that of the bowels lessened. The kidney excretion is httle affected, at most the urea is slightly diminished, but the evidence with respect to this is somewhat contradictory. Roberts has shown that tea retards both salivary and peptic digestion, and it is probable that most of the symptoms resulting from excessive consumption of tea are those of delay of digestion, that is, of food remaining undigested in the stomach. A pre- valent idea is that the tannin, in tea, chiefly produces the disturbances of digestion so commonly associated with abuse of tea; according to Roberts, however, it is not clear what constituent of tea is the really active agent in producing dyspepsia. Examination of Tea.—Judge of the aroma of the dry tea and its infusion; spread out the leaves and see their characters; collect anything like mineral powder and examine under microscope. The microscope will also shoAV if the tea has deteriorated by keeping; sometimes acari, fungi, and bacteria may be found. The tea should not be too much broken up, or mixed up Avith dirt. Spread out, the leaves should not be all large, thick, dark, and old, but some should be small and young. There will always be in the best tea a good deal of stalk and some remains of the flower. In old tea much of the aetherial oil evaporates, and the aroma is less marked. The infusion should be fragrant to smell, not harsh and bitter to taste, EXAMINATION OF TEA. 397 and not too dark. The buyers of tea seem especially to depend on the smell and taste of the infusion. Formerly, the chief adulteration of tea was by mixing Avith it other leaves, such as those of the sloe and willoAv, which have a superficial resemblance to tea-leaves. At the present time the chief adulteration of tea is the admix- ture of old and exhausted tea-leaves, while in the inferior kinds there is often clay, lime, or ferruginous sand. The total soluble matters obtainable from tea are a ready and convenient index of its quality : they are estimated by infusing a Aveighed quantity with an excess of distilled water, and evaporating this down to dryness; the amount of extract so obtained should be at least 30 per cent. If the sample contain many exhausted leaves, the amount of extract obtained will be, of course, less than this. To make the infusion, take 10 grammes of tea, and infuse in 500 c.c. of boiling distilled or rain Avater. Let it stand five or six minutes before smell- ing and tasting it. Exhaust the leaves by boiling with successive portions of water, until no colour is given up to the water. Measure the total amount of the infusion and decoction mixed together; take 100 c.c. and dry it in a water bath, and weigh. Calculate out the percentage. The sp. gr. of the infusion will be found, if made from a good tea, to vary from 1011 to 1015. Example.—The total quantity of the infusion from 10 grammes of tea was 1890 c.c. ; 100 c.c. taken and dried yielded 0-21 of extract; then -^— x 0*21 = 3 969 of extract in 10 grammes ; this multiplied by 10 = 39'69 per cent. The exhausted leaves may also be dried and weighed, the loss represent- ing the amount of extract, which ought to correspond with the amount obtained directly. The ash should also be determined; 5 or 10 grammes are to be incinerated; the ash is generally grey, sometimes slightly greenish. Any excess above 6 per cent, is suspicious; if above 8 per cent, on the perfectly dry tea, adultera- tion is certain. About one-half of the ash is soluble in water; the solution is often (but not always) pink, from the presence of manganese. The amount and character of the ash form good means of detecting the use of exhausted leaves. The acidity of the infusion, and the amount of tannin and thein, may also be determined; as also the chlorine, alkalinity, and iron of the ash. The best tests of the quality of the tea are the aroma and the physical characters. Extraction of Thein.—Occasionally it may be desired to determine the quantity of thein. Take 10 grammes of tea, exhaust with boiling water, and add solution of subacetate of lead; filter; pass hydrosulphuric acid through to get rid of excess of lead; filter; evaporate to small bulk, and add a httle ammonia; add more water, decolourise with animal charcoal, and evaporate slowly to small bulk. White feathery crystals of thein form, which should be collected on filtering paper, dried at a very Ioav heat, and weighed. Determination of Tannin.—Make an infusion and add solution of gelatin; collect precipitate, dry and weigh—100 = 40 of tannin. COFFEE. Coffee is the seed or berry of the Caffea Arabica, a plant growing in most parts of the tropics, but chiefly in Arabia, Abyssinia, Ceylon, and the West Indies. After the seeds have been roasted to a chocolate brown, they are 398 BEVERAGES AND CONDIMENTS. ground to a poAvder in a mill, and then used in the form of a decoction or infusion. The percentage composition of unroasted coffee may be expressed as follows:— Water, . 11-23 Nitrogenous matter, 12-07 Caffein, 1*21 Fat, 12-27 Sugar or dextrin, . 8-55 Tannin, 32-79 Cellulose, 18-17 Salts, . . . . 3-71 The chief properties of coffee depend upon an aromatic oil and the alkaloidal body, caffein. Caffein itself is a nitrogenous crystalline alkaloid, identical with thein; in the roasting of coffee, this body is not destroyed, but dissociated, as it were, from its previously existing combination with tannin. During the same process, the sugar and dextrin are changed into caramel, and the gas and Avater of the berry driven off. Fig. 56. As an article of diet, coffee stimulates the nervous system, and in large doses produces tremors. Caffein given to animals augments reflex action, and may produce tetanus, or peculiar stiffness of muscles. It increases the frequency of the pulse in men (but taken in large quantity diminishes it), and removes the sensation of commencing fatigue during exercise. It has been said (J. Lehmann and others) to lessen the amount of urea and phosphoric acid, but this is doubtful. It appears, hoAvever, to increase the urinary water. The pulmonary carbon dioxide is said to be increased (E. Smith), as Avell as the action of the skin. Sir W. Roberts' experiments showed that coffee does not retard the sahvary digestion as compared with tea, and he considers that this can be accounted for by the fact that in coffee tannin is replaced by caffeo-tannic acid. Coffee, however, was found to exercise a greater retarding influence on stomach digestion than tea, on account of its being taken in much stronger infusion. It slightly increases the action of the kidneys, and with some stimulates the intestines so as to act as an aperient. COFFEE—CHICORY. 399 To make good coffee, the berry must be freshly roasted. Good drinkable coffee requhes as much as an ounce of recently roasted and ground coffee to each large cup, the result of Avhich means that the cost of a cup of good coffee, including milk and sugar, is about tAvopence. The prevalent custom of making coffee in this country is to use barely an ounce to two pints of water, the resulting infusion being more or less maAvkish, tasteless, and wanting in stimulating properties. Detection of Adulterations.—The adulterations of coffee are chiefly •chicory, but at times dates, beans, maize, and acorns have been added. ■Chicory is a legal addition to coffee, provided such admixture is stated, no limit being fixed as to their relative proportions : as a rule, it amounts to about 30 per cent. The addition of chicory to coffee is considered by most people to add to its flavour. It is probable that much of the present decadence of coffee drinking is due to want of care in its preparation, and the excessive addition of chicory, whereby the resulting infusion is wanting in the desired alkaloid caffein. Chicory is the dried and powdered root of the wild endive (dehorium intybus). In composition it differs much from coffee, containing no caffein, less fat, but more sugar. It may be readily distinguished from coffee by the fact that when thrown into water it rapidly sinks and colours the liquid hrown, while coffee floats and does not yield any colour. The surest test, however, is microscopical examination, as both the cells and dotted ducts of ■chicory (fig. 56) are quite characteristic: at least nothing like them exists in coffee. The long cells of the testa of coffee berries are equally marked (fig. 57). The interior of the berry also presents characters which are quite ^evident: an irregular areolar tissue containing light or dark yellow angular masses and oil globules, such as are very different from any adulterations. The little corkscrew-like unrolled spiral fibres are chiefly found in the bottom of the raphe. 400 BEVERAGES AND CONDIMENTS. The percentage of ash has been suggested as a means of detection. Coffee yields about 4 per cent., of which four-fifths are soluble in Avater : chicory yields only about 5 per cent., of Avhich only one-third is soluble. Chicory contains a notable amount of sugar, 10 to 18 per cent., Avhereas roasted coffee has never more than 1 per cent. Wanklyn has proposed to make this a basis of detection, using the standard copper solution. Other methods for the estimation of chicory in mixtures of coffee and chicory are based respectively upon the specific gravity of the infusion, and upon the amount of solid extract obtainable from it. Take 10 grammes of the sample, infuse in 100 c.c. of water, boil for half a minute, filter, and after filtrate cools to 60° F., take the specific gravity. The sp. gr. of a 10 per cent, infusion of pure coffee is 1010, that of a similar infusion of pure chicory, 1022 : that is, a standard difference of 12 between the two specific gravities. Example.—Say the sp. gr. of the infusion made from sample = 1014, then difference between sp. gr. of sample and coffee or 1014-1010 = ^ of 100 = 33*3 per cent, of chicory ; then difference between sp. gr. of sample and chicory or 1014-1022 = /^ of 100 = 66*7 per cent of coffee. Next place the filter with the coffee dregs on it into a large flask with 150 c.c. of water. Stir gently, boil for five minutes, allow sediment to subside, filter off the supernatant hquid and add filtrate to the original filtrate obtained above. Allow to cool, measure, and make up with distilled water to 250 c.c.: mix the whole thoroughly, then pipette 50 c.c. (= 2 grammes of the sample) of this infusion into a weighed capsule. Evaporate to dryness over a water bath, re-Aveigh, and calculate solid extract as a percentage. Treated as above, chicory gives a mean percentage extract of 70; while coffee gives a remarkably constant percentage extract of 24; or a standard difference of 46. Consequently, we have percentage of coffee = 100 (70 - percentage of extract found) 46 ' Example.—Say 50 c.c. of infusion ( = 2 grammes of the sample) have yielded 1*03 gramme of extract: this equals 51-5 percentage of extract, and■ ' ~51'5? = 4Q per 46 *■ cent, of coffee in the sample. Roasted corn or beans are at once known by the starch grains, which commonly preserve their characteristic form. Iodine turns them at once blue, while the infusion will also give a blue with iodine. Potato starch is also at once detected, there being nothing hke it in coffee. Sago starch which is sometimes used, is also easily detected. The presence°of sugar can be readdy estimated by the standard copper solution: if caramel has been added, the extract will be found to be brittle, dark coloured and bitter to the taste. Occasionally, chicory itself is adulterated with mangel-wurzel, parsnip carrot, acorn, or sawdust. The cells of mangel-wurzel are like chicory but much larger; those of carrot and parsnip are something like chicory! hut contain starch cells; the starch grains of the acorn are round or oval with a deep culvert depression, or hilum. The infusion of chicory is not' turned blue by iodine; when incinerated the ash of chicory should not be less than 5 per cent. DESCRIPTION OF PLATE II. Fig. 1.—Cofpee. A loose mesh of irregularly hexagonal cells, thick Availed, and enclosing oil drops Avith amorphous material. Fig. 2.—CoPFEB ADULTERATED AVITH CHICORY. Chicory alone appears in this field. It is a mass of confused cellular tissue traversed by tAvo broad bands Avith transverse markings. These bands are the juice ducts. Fig. 3.—Mustard. Fine granular masses, Avith drops of oil. Fig. 4.—Pepper. Adulterated Avith Avheat (the large round grains), maize (the next smaller angular grains), and buckAvheat (the smallest angular grains). Fig. 5.—Cayenne. This is from a genuine specimen. Fig. 6.—Compound Ginger. Consisting chiefly of Avheat, maize, and saAv-dust. The mass in the upper right-hand corner shoAvs the characteristic structure of soft Avood. (To Binder—To face Plate II) PLATE II. Fig. 1.—Coffee. Fig. 2.—Coffee and Chicory. Fig. 3.—Mustard. Fig. 4.—Pepper and Wheat. Fig. 5.—Cayenne. Fig. 6.—Compound Ginger. KOLA, COCA, AND COCOA. 401 PARAGUAY TEA, KOLA, AND COCA. Paraguay tea, sometimes known as mate, is obtained by roasting the leaves of Ilex paraguayensis and exposing them to the action of the sun. It is much used in various parts of South America. The mean of several analyses of dried mate show it to contain 3*87 per cent, of proteids, about 3 per cent, of fats and resinous oil, 2*38 per cent, of sugar, 3*92 per cent, of salts, about 1 per cent, of thein and 4 per cent, of tannin. About 24 per cent, of the sohds are soluble in water. Its infusion has an action similar to other thein-containing beverages, but is more apt, it is said, to cause digestive disturbance. Closely allied to Paraguay tea is G-uarana, obtained by roasting the seeds of Paullinia sorbilis. It contains nearly 5 per cent, of thein or caffein, and has some medicinal value in migraine. Kola is prepared from the seeds of the Sterculia acuminata, a tree resembhng the chestnut and growing wild on the west coast of Africa. Its percentage composition is as follows: water 11*9, proteids 6*7, fat 0*68, starch and sugar 36*5, caffein 2*42, tannin 1*6, cellulose 33*7, ash 6*5. It is, therefore, closely allied to tea and coffee, but differing from them in the relatively large amount of alkaloid which it contains. Kola nuts are hard and irregularly shaped, of a reddish-brown colour, and presenting a faintly aromatic odour. When powdered, their taste is bitter, leaving a harsh and earthy flavour on the palate. Kola has some shght fatigue-dispelling poAver, if masticated, or taken when freshly ground in the form of an infusion like coffee. It increases the urinary water, and reduces the total solids of the urine, especially the ex- tractives ; it acts as a stimulant to the nervous system, and increases arterial tension; its stimulating and sustaining quahties are, however, largely over- rated. True kola nuts are someAvhat difficult to obtain; many of these nuts now in the market are not those of Sterculia acuminata at all, but those of Garcinia kola and Sterculia cordifolia, species which do not contain caffein, and which, consequently, are more or less without any physiological action. Coca, from the leaves of Erythroxylon coca, when chewed, is said to have a similar action to that claimed for kola, namely, to take away the feeling of fatigue after and during excessive exertion. It is much used as a stimulant in Peru, and contains the alkaloid cocaine, the use of which as a local anaesthetic is well known. Some observations upon the sustaining and stimulating properties of coca-leaves have been made on soldiers, both during and after long marches, but with only indifferent success. The ill- success which has attended various attempts to use both kola nuts and coca- leaves, by Europeans, as stimulants during unusual bodily exertion, is probably due to the fact that the normal diet of Europeans is rich in stimulant extractives of the xanthin group. Consequently, the consumption of substances, however rich in caffein, by them, would have less effect than on the indigenous races of Africa or South America, whose ordinary dietary is of a less stimulating character. COCOA AND CHOCOLATE. Cocoa is the roasted seed of the Theobroma cacao, growing chiefly in the West Indies. Cocoa nibs are the seeds or beans roughly broken; flake cocoa is the same completely ground and crushed ; soluble cocoa is the same 2C 402 BEVERAGES AND CONDIMENTS. freed from cellulose; Avhile prepared cocoa is the same after half or more of its contained oil or fat has been removed, and in most cases starch and sugar added. The percentage composition of cocoa beans may be said to bo as follows:— Water,.........6*0 Theobromine,........1*5 Fat..........50*0 Starch,.........10*0 Salts..........3*6 Gum..........8 0 Cellulose,........20-9 The active principle of cocoa, theobromine, is closely related to caffein, being dimethylxanthine, C7H8N402. Its physiological action is chiefly exerted on the muscular system, and is a greater restorer of muscular activity than either thein or caffein. Its effect on the nervous system is not weU defined. The adulteration of cocoa is chiefly in the direction of the addition of sugar and starch, which the microscope will detect; while, by some, the removal of the fat, so as to reduce it below 20 per cent., is regarded as an adulteration. Apart from cocoa, by nature, containing nitrogenous and fatty matter, in its commercial forms it contains so much starch and sugar that it is rightly regarded to some extent not only as a proteid and fatty food, but also a carbo-hydrate one. Cocoa differs much from both tea and coffee in having but little stimulant action, but it does possess some nutritive value, and, as such, may in a limited sense be regarded as a food. The starch grains of cocoa are small and embedded usually in the cells. The presence of starch grains of cereals, arrowroot, sago, or other kinds of starch, is at once detected by the microscope. Sugar can be detected by the taste, and by Fehling's solution. Mineral substances are best detected by incineration, digesting it in an acid and testing for iron, lead, &c. Chocolate is a preparation of cocoa, from which the greater part of the fat has been removed, and which, after being mixed with sugar and various flavouring substances, is made into a paste with water, and then pressed in moulds. LEMON AND LIME JUICE. These juices contain free acids in large quantities, chiefly citric, and a little mahc acid, sugar, vegetable albumin, and mucus. Lemon juice is the expressed juice of the Citrus limonum, and lime juice that of the Citrus limetta. The British Pharmacopoeia directs that lemon juice should have a specific gravity of 1039, and should contain 32*5 grains of citric acid per ounce. The Board of Trade standard for lemon juice is a specific gravity of 1030, when de-alcoholised, and an acidity equivalent to 30 grains per ounce of citric acid. It occasionally may be met with, with a density as high as 1050. Lime juice has usually a less specific gra-rity than lemon juice, of about 1037 or 1035, and also contains less acid, or about 32*22 grains per ounce. As found in commerce, for merchant snipping, or used in the Royal NaAry, the lime or lemon juice is chiefly prepared in Sicdy or the West Indies; it is mixed Avith spirit (usually brandy or whisky, which gives it a slightly greenish-yellow hue), and olive oil is poured on the top. Sugar is added to it when issued, to make it more agreeable to taste, in the proportion of half its weight. Lemon juice is usually issued in bottles LEMON AND LIME JUICE. 403 containing from three to four pints, not quite filled, and covered with a layer of olive oil. About 1 ounce of brandy is added to each 10 ounces of juice. Sometimes the juice is boiled, and no brandy is added; the former kind keeps better. Both are equal in anti-scorbutic power. Good lemon juice will keep for some years, at least three years; bad juice soon becomes turbid, and then stringy and mucilaginous, and the citric and mahc acids decompose, glucose and carbon dioxide being formed. Some turbidity and precipitate do not, however, destroy its anti-scorbutic powers. As found in the market, it is frequently mixed with water, and some- times with other acids, such as tartaric and sulphuric acids. The lime juice used in the Arctic Expedition 1875-6, gave on analysis 27 grains of citric acid per ounce as issued, that is, after being fortified with about 15 per cent, of proof spirit. Before fortifying it contained 32 grains. Some samples analysed at Netley shoAved a density of 1023 as issued, and of 1035*7 after de-alcoholisation: the extract was about 8*5 per cent. The unfortified juice froze at 25° F., the fortified remained liquid down to 15° F. Prolonged freezing at a temperature of nearly 0° F. produced no change in the character or amount of the constituents. In the examination, the points Avhich seem of consequence, in addition to the determination of the free acidity, are the fragrancy of the extract and the alkalinity of the ash, pro-ving the existence of some alkahne citrate. The latter can, however, be imitated, but the fragrancy cannot be so. Examination of Lemon or Lime Juice.—This will have reference to both quahty and adulterations. 1. Pour into a glass, and mark physical characters; turbidity, precipitate, stringiness, &c. The taste should be pleasant, acid, but not bitter. Add hme water, and bod; if free citric acid is present, a large precipitate of calcium citrate is formed, which redissolves as the solution cools. Evaporate carefuUy in order to prepare an extract, and to test the fragrancy, &c. 2. Take the specific gravity, remembering that spirit is present; then, if necessary, evaporate to one-half to drive off alcohol, dilute to former amount, and take specific gravity at 60° F. 3. Determine acidity by the standard alkaline solution. Express the acidity as citric acid (C6H807); 1 c.c. of the alkahne solution = 6*4 milli- grammes of citric acid. As the acidity is considerable, the best way is to take 10 c.c. of the juice, add 90 c.c. of water, and take 10 c.c. of the dilute fluid, which wdl give the acidity of 1 c.c. of the undiluted juice. If the number of c.c. used for the diluted juice is multiplied by 2*8, it gives the acidity in grains per ounce. 4. Test for adulteration, -viz:—(a) Tartaric Acid.—Ddute and filter, if the lime juice be turbid; add a little solution of acetate of potash; stir well, without touching the sides of the glass, and leave for twenty-four hours; if tartaric acid be present, the potassium tartrate will fall. (b) Sulphuric Acid.—Add barium chloride after filtration, if necessary; if any precipitate falls, add a little water and a few drops of dilute hydro- chloric acid to dissolve the barium citrate, which sometimes causes a turbidity. (c) Hydrochloric Acid.—Test with silver nitrate and a few drops of dilute nitric acid. (d) Nitric Acid.—This is an uncommon adulteration; the iron or brucine test can be used as in the case of water. Factitious Lemon Juice.—It is not easy to distinguish well-made factitious lemon juice; about 552 grains of crystallised citric acid are dis- solved in a wine pint of water, which is flavoured with essence of lemon 404 BEVERAGES AND CONDIMENTS. dissolved in spirits. This corresponds to about 19 or 20 grains of dry citric acid per ounce. The flavour is not, however, like that of the real juice, and the taste is sharper. Evaporation detects the falsification. Use of Lemon Juice.—In mihtary transports, the daily issue of one ounce of lemon juice per head is commenced when the troops have been ten days at sea, and by the Merchant Shipping Act (1867) the same rule is ordered, except when the ship is in harbour, and fresh vegetables can be procured. It is mixed with sugar. If preserved vegetables can be procured, half the amount of juice Avill perhaps do. In campaigns, when vegetables are deficient, the same rules should be enforced. On many foreign stations, where dysentery takes a scorbutic type (as formerly in Jamaica, and even of late years in China), lemon juice should be regularly issued, if vegetables or fruit cannot be procured. Substitutes for Lemon Juice.—Citric acid is the best, or citrate of sodium; then perhaps vinegar, though this is inferior; and lowest of all is citrate of potassium. The tartrates, lactates, and acetates of the alkahes may all be used, but there are no good experiments on their relative anti- scorbutic powers on record. If milk is procurable, it may be allowed to become acid, and the acid then neutralised with an alkali. The fresh juices of many plants, especially species of cacti, can be used, the plant being crushed and steeped in Avater; and in case neither vegetables, lemon juice, nor any of the substitutes can be procured, we ought not to omit the trial of such plants of this kind as may be obtainable. VINEGAR. Ordinary commercial vinegar is really a more or less impure acetic acid, containing besides acetic acid, alcohol, acetic ether, sugar, extractive matters, alkaline acetates, and a variable amount of salts. It usually also contains some sulphuric acid, Avhich by law must not exceed one-thousandth part of its weight of pure acid. There are four kinds of vinegar commonly in use in Europe. These are Malt Vinegar, Wine Vinegar, Vinegar from starch, sugar, &c, and Wood Vinegar. The acid in all these products is identical, but there are distinct differences of flavour and odour between them. Owing, however to the addition of colouring matter and flavouring essences, it is often very'difficult to detect the sources of some of the inferior vinegars. All varieties of vinegar, except that obtained by means of the destructive distdlation of wood, are formed by the oxidation of alcohol. Malt vinegar, which constitutes the greater part of the vinegar used in this country, is derived from the acetous fermentation of a wort made from malt and barley. It is of a distinct brown colour, having a specific gravity of from 1016 to 1019. It commonly contains traces of alcohol, 0*4 per cent, of extract, 4 per cent, of acetic acid, and about 0*1 per cent, of sulphuric acid. Wine vinegar is chiefly used on the Continent, where it is prepared from grape juice and inferior new wines, that made from white wine being the most esteemed. These vinegars vary in colour from straw to red, have usually an alcohohc odour, and a specific gravity of from 1015 to' 1022. They usually contain 1 per cent, of alcohol, 1 per cent, of extract, from 5 to 6 per cent, of acetic acid, with small quantities of tartaric acid and tartrate of potash. EXAMINATION OF VINEGAR. 405 The chief adulterations of vinegar are water, mineral acids, especially sulphuric, metals, such as copper, arsenic, lead and tin, pyroligneous acid and various organic substances, such as colouring agents and capsicum. Examination of Vinegar.—This will have reference to both quality and adulterations. There are several kinds of vinegar noAV in the market, known by the numbers 16, 18, 20, 22, and 24. Numbers 22 and 24 are the best, and contain about 5 per cent, of pure glacial acetic acid. The inferior kinds contain 3 per cent, or even less. The Society of Public Analysts have adopted 3 per cent, as the minimum of acetic acid permissible. Quality.—1. Take specific gravity : white wine vinegar varies from 1015 to 1022, malt vinegar from 1016 to 1019. If below this water has been added. 2. Determine acidity of 10 c.c. with the alkaline solution. It is generally best to dilute the vinegar ten times with distilled Avater, and to take 10 c.c. of the diluted vinegar. Multiply the c.c. of alkaline solution used by 0*6; the result is acetic acid per cent. Example.—10 c.c. of diluted vinegar took 8 c.c. of alkaline solution: 8x0*6 = 4*8. per cent, of acetic acid. An alternative method of estimating the strength of vinegar has been suggested by Wynter-Blyth. Distil 110 c.c. until 100 c.c. have come over, that is, ten-elevenths. The 100 c.c. will contain 80 per cent, of the whole acetic acid present in the 110 c.c. and may be titrated, or the specific graAdty of the distiUate taken, and the percentage of acetic acid found from the folloAving table :— Specific gravity. Per cent, of acetic acid. Specific gravity. Per cent, of acetic acid. 1001 1 1016 11 1002 •2 1017 12 1004 3 1018 13 1005 4 1020 14 1007 5 1022 15 1008 6 1023 16 1010 7 1024 17 1012 8 1025 18 1013 9 1026 19 1015 10 1027 20 The acidity of English vinegar is chiefly caused by acetic and sulphuric acids, but it is usually calculated at once as glacial acetic acid. If it falls below 3 per cent., water has probably been added. If the specific gravity be Ioav, and the acidity high, excess of sulphuric acid may have been added. Sodium carbonate or ammonia gives a purplish precipitate in wine vinegar, but not in malt vinegar. If excess of sulphuric acid be suspected, it must be determined by baryta; this requires care, as sulphates may be introduced in the water. Hydrochloric acid and barium chloride are added; the sulphate of barium collected, dried, weighed, and then multiplied by 0*412, gives the weight of sulphuric acid. Adidterations.—Water; sulphuric acid in excess; hydrochloric acid 406 BEVERAGES AND CONDIMENTS. (uncommon) ; or common salt (detected by nitrate of silver and dilute nitric acid); pyroligneous acid (distil and re-distil the distillate, the residue Avdl have the smell of pyroligneous acid); lead; copper from vessels (evaporate to dryness, incinerate, dissolve in weak nitric acid, divide into two parts, pass hydrogen sulphide through one, and test for copper in the other by ammonia, or by a piece of iron Avire) ; corrosive sublimate (pass hydrogen sulphide through, collect precipitate); capsicum, pellitory, or other pungent substances (evaporate nearly to dryness, and dissolve in boiling alcohol, evaporate to syrup, taste ; burnt sugar gives a bitter taste and a dark colour to the syrup). The presence of copper in the vinegar used for pickles may be easily detected by simply inserting the bright blade of a steel knife. Many vinegars, especially the weaker and inferior kinds, often contain in extra- ordinary abundance Anguillula oxyphila or vinegar eels, these being minute worms from 1 to 2*5 mm. in length. Lindner and others have endeavoured to show that these worms have an injurious action upon those drinking the vinegar. Beyond rendering the condiment somewhat disgusting to the eye, it is doubtful whether they have any prejudicial effect. As an article of diet, vinegar holds the same rank as the vegetable acids generally. It tends to maintain the alkalinity of the blood and the liquids which bathe the tissues. The acetic acid is largely converted into carbon- ates in the body, and in doses of from half to one ounce daily, vinegar is a valuable anti-scorbutic. But this valuable dietetic quality is partly counter- balanced in English vinegar by the unfortunate circumstance that sulphuric acid (T^Vo~th in weight) is allowed to be added to it, and thus a strong acid is taken into the body, which is not only not useful in nutrition, but is hurtful from the tendency to form insoluble salts of lime. This defect is not present in the Avine vinegar from the Continent. If taken Avell diluted with water, vinegar makes a useful and far from disagreeable drink. MUSTARD. Mustard is the seed of the Sinapis alba and Sinapis nigra. Commonly sold as a powder, it is liable to considerable adulteration by being mixed with different kinds of the starches or with turmeric. Good mustard is known by the sharp acid smell and taste. Its chief adulterations can be usually detected with the microscope. Further, the microscopic characters of mustard seed are equally well marked. The outer coat of the white mustard consists of a stratum of hexagonal cells, perforated in the centre, and other cells which occupy the centre portion of the hexagonal cells, and which escape through the opening Avhen swollen from imbibition of water (fig. 58). These cells are beheved to contain the mucilage which is obtained Avhen mustard is placed in water. There are two internal coats made up of small angular cells : the structure of the seed consists of numerous cells containing oil, but no starch. The black mustard has the same characters, Avithout the infundibulum cells. Pure mustard contains 13*95 per cent, of carbo-hydrates, 0*66 per cent. of volatde oh, and 35*42 per cent, of fixed oil. In an adulterated mustard, the carbo-hydrates may be as high as 67 per cent, sometimes, and the fixed oils as low as or even beloAv 7 per cent. PEPPER. 407 PEPPER. There are two kinds of pepper, the black and the white. Black pepper is obtained from Piper nigrum, while white pepper is the same decorticated. Dried black pepper contains about 7*87 per cent, piperin and fixed oil, with not less than 50 per cent, of carbo-hydrate which is transformable into sugar. Tins quantity of carbo-hydrate has been suggested as a test for the purity of pepper. In white pepper, the piperin and fixed oil is about 8*24 per cent., and the carbo-hydrates 64*95 per cent., of which 47 per cent, is starch. The microscopic characters of pepper are rather complicated; there is a husk composed of four or five layers of cells and a central portion. The cortex has externally elongated cells, placed vertically, and provided Avith a central cavity, from which fines radiate towards the circumference; then come some strata of angular cells, which towards the interior are larger, and filled with oil. The third layer is composed of woody fibre and spiral cells. The fourth layer is made up of large cells, which towards the interior become smaller and of a deep red colour; they contain most of the essential oil of the pepper. The central part of the berry is composed of large angular cells, about twice as long as broad (fig. 59). Steeped in water, some of these cells become yelloAV, others remain colourless. It has been supposed that the yelloAV cells contain piperin, as they give the same reactions as piperin does: the tint, namely, is deepened by alcohol and nitric acid, and sulphuric acid applied to a dry section causes a reddish hue. White pepper is the central part of the seed, but some small particles of cortex are usually mixed with it. It is composed of cells containing very 408 BEVERAGES AND CONDIMENTS. small starch grains. Hassall says that the central Avhite cells arc so hard that they may be mistaken for particles of sand. A httle care would avoid this. The starch grains are easily detected, however small, by iodine. Pepper is adulterated with linseed, mustard husks, wheat and pea flour, rape cake, and ground rice. The microscope at once detects these adulterations. Pepper is also largely adulterated with husks and palm-nut powder (Poivrette), and with mineral substances : these latter may be separated by shaking up with chloroform. No pure pepper should give less than 50 per cent, of reducing sugar on the ash-free substance (piperin and piperidine reducing the Fehling's solution); palm-nut powder gives 23 per cent. (Leng). Fig. 59. Neuss recommends covering the powder with pure hydrochloric acid: true pepper becomes intensely yellow, and from among it other substances can be picked out. Pepper dust is merely the sweepings of the warehouses. Rape or linseed cake, cayenne and mustard husks, are mixed with pepper dust, and it is then sold as pepper. SALT. The purity of ground salt is known by its Avhiteness, fine crystalline character, dryness, complete and clear solution in water. The coarser kinds containing often chloride of magnesium, and perhaps hme salts, are darker BIBLIOGRAPHY AND REFERENCES. 409 coloured, more or less deliquescent, and either not thoroughly crystalhsed or in too large crystals. In large masses rock salt is often of a reddish colour, which disappears on grinding. Dietetic Use of the Condiments.—The various condiments owe their action as food accessories to the aromatic oils which they contain. These oils or active principles have practically three kinds of action. In the first place they are antiseptic, and by virtue of this property serve to prevent acid fermentation in the digestive tract. They are also stimulants of diges- tive juices, and of peristaltic action. Taken in quantity and by themselves, possibly some act as stimulants of the nervous system, but this action is quite independent of their role as food accessories. BIBLIOGRAPHY AND REFERENCES. Anstie, Stimulants and Narcotics, their Mutual Relations, Philadelphia, 1865 ; also On the Uses of Wines in Health and Disease, New York, 1870. Aubry, Articles "Beer," "Yeast," " Hops," and " Malt," in Dammer's Lexikon der Verfalschungen. Bell, Sir J., Report on British and Foreign Spirits to a Committee of the House of Commons, 1891. Blyth, Foods, their Composition and Analysis, Lond., 1882. Borgmann, Anleitung zur chemischen Analyse des Weines, Wiesbaden, 1884. Brunton, Pharmacology, London, 1890. Church, Food, its Sources, Constituents, and Uses, London, 1882. Dujurdin-Beaumetz, "On the Poisonous Effects of Alcoholic Impurities," Comptes Bendus, lxxxi. p. 192. Gardner, The Brewer, Distiller and Wine Manufacturer, Lond., 1883. Griffin, Chemical testing of Wine and Spirits, Lond., 1872. Hasterlick, Kritische Studien u. die bisherigen Methoden zum Nachzueis fremder Farb- stoffe im Wein, Dissertat. Erlangen, 1889. Hassall, Food and its Adulterations, London, 1876. Hooper, Manual of Scientific and Technical Brewing, Lond., 1885. Kramer, " On the Action of Bacteria on the Breaking or Inversion of Wine," Land- wirthschaftliche Versuchstationen, xxxvii. p. 325. Lehmann, Methods of Practical Hygiene, translated by Crookes, Lond., 1893. List, "Die Schaumweine," Proc. 8th Congress of Bavarian Chemists, Wurzburg, 1889. Maitz and Morris, Text-book of the Science of Brewing, with Plates, London, 1891. Marquard, Article '' Essig," in Dammer's Lexikon der Verfalschungen. Matthews and Lott, The Microscope in the Brewery and Madhouse, including recent researches in connection with Lager Beer, Yeast, > 2 ,, 276 »» 3 ,, 3*23 ,, and carrying 34 tt> 3*50 Walking and carrying 63 lb, 118 1b, ,, 4 miles per hour, 6 Riding and trotting, Swimming, Treadmill, 3-84 4-75 5-00 7-00 4-05 4-33 5*50 The great increase of air inspired is more clearly seen when it is put in this way: under ordinary circumstances, a man draws in 480 cubic inches per minute; if he walks four miles an hour he draws in (480 x5 = ) 2400 420 EXERCISE. cubic inches; if six miles an hour (480 x 7 = ) 3360 cubic inches. Simul- taneously, the amount of carbon dioxide in the expired air is increased. The most rehable observations in this direction are those made by E. Smith, Hirn, Speck, and Pettenkofer and Voit. As there is no doubt that the peculiar means of investigation render the experiments of the last-named authors as accurate as possible in the present state of science, they are given briefly in the f oUowing table :— Absorption and Elimination in Rest and Exercise. AVeldit of man experimented upon, \ Absorption 60 kilos = 132 lb avds. | of Oxygen in Grammes. Elimination in Grammes of— Carbon Dioxide. AA'ater. I'rea. Rest-day,.....I 708 9 Work-day,.....9545 911-5 1284-2 828-0 20421 372 37-0 Excess on Avork-day (with exception \ oak.r of urea),.....\ ^45"o 372 7 1214-1 -02 In other Avords, during the work-day 3790 grains, or 8*66 ounces, of oxygen Avere absorbed in excess of the rest-day, and 5751 grains, or 13*15. ounces, of carbon dioxide in excess were evolved. Expressing this 'as carbon, an excess of 1046 grains, or 2*39 ounces, were eliminated on the work-day!! There was an excess of oxidation of carbon equal to 41 per cent., and it must be remembered that the so-called " work-day" included a period of rest; the work was done only during the working hours, and was not excessive. It Avill be observed from these experiments that a large amount of water was eliminated during exercise, whde the urea was not really changed. It seems certain that the great formation of carbon dioxide takes place in the muscles; it is rapidly carried off from them, and if it were not so it would seem highly probable that their strong action becomes impossible At any rate, if the pulmonary circulation and the elimination of carbon dioxide are m any way impeded, the power of continuing the exertion rapidly lessens. The watery vapour exhaled from the lungs is also largely increased during exertion. Muscular exercise is then clearly necessary for a sufficient elimination of carbon from the body, and it is plain that, in a state of prolonged rest either the carboniferous food must be lessened or carbon will accumulate Excessive and badly arranged exertion may lead to congestion of the lungs, and even hsemoptysis. Deficient exercise, on the other hand is one of the conditions which favour those nutritional alterations in the lung which we class as tuberculous. Certain rules flow from these facts. During exercise the action of the lungs must be perfectly free; not the least impediment must be offered to the freest play of the chest and the action of the respiratory muscles The dress and accoutrements of the soldier should be planned in reference to this fact, as there is no man who is called on to make, at certain times, greater exertion. And yet, tdl a very recent date, the modern armies of Europe were dressed and accoutred in a fashion which took from the soldier in a great degree, that power of exertion for which, and for which alone, he is selected and trained. EFFECTS ON THE CIRCULATION AND SKIN. 421 The action of the lungs should be Avatched Avhen men are being trained for exertion; as soon as the respirations become laborious, and especially if there be sighing, the lungs are becoming too congested, and rest is necessary. A second point is that the great increase of carbon excreted demands an increase of carbon to be given in the food. There seems a general accord- ance among physiologists that this is best given (as far as digestion permits) in the form of fat, and not of starch, and this is confirmed by the instinctive appetite of a man taking exertion, and not restrained in the choice of food. _ A third rule is that, as spirits lessen the excretion of pulmonary carbon dioxide, they are hurtful during exercise; and it is perhaps for this reason, as Avell as from their deadening action on the nerves of volition, that those Avho take spirits are incapable of great exertion. This is now well under- stood by trainers, who allow no spirits, and but little wine or beer. It is a curious fact, stated by Artmann, that if men undergoing exertion take spirits, they take less fat. Oxidation of fat is interfered with, and therefore less fat is required. Water alone is the best liquid to train on. A fourth rule is that, as the excretion of carbon dioxide (and perhaps of pulmonary organic matter) is so much increased, a much larger amount of pure air is necessary; and. in every covered building (as gymnasia, riding- schools, &c), where exercise is taken, the ventilation must be carried to the greatest possible extent, so soon does the air become vitiated. On the Circulation.—The action of the heart rapidly increases in force and frequency, and the flow of blood through all parts of the body, including the heart itself, is augmented. The amount of increase is usually from ten to thirty beats, but occasionally more. After exercise, the heart's action falls below its normal amount; and if the exercise has been exceed- ingly prolonged and severe, may fall as low as fifty or forty per minute, and become intermittent. During exertion, when the heart is not oppressed, its beats, though rapid and forcible, are regular and equable; but when it becomes embarrassed, the pulse becomes very quick, small, and then unequal, and even at last irregular. When men have gone through a good deal of exertion, and then are called upon to make a sudden effort, the pulse may become very small and quick (160-170), but still retain its equability. There seems no harm in this, but such exertion cannot be long continued. The ascension of heights greatly tries a fatigued heart. The accommoda- tion of the heart to great exertion is probably connected with the easy flow of blood through its OAvn structure. Certain forms of chronic disease of the heart have been treated by the "mountain cure," introduced by Oertel; but very great caution is required in carrying out this treatment, and high elevations are contra-indicated in these affections. Excessive exercise leads to affection of the heart,—rupture (in some few cases), palpitation, hypertrophy in a good many cases, and. more rarely valvular disease. These may be avoided by careful training, and a due proportion of rest. Injuries to vessels may also result from too sudden or prolonged exertion. The sphygmographic observations of Fraser on the pulses of men after rowing show how much the pressure is increased. Deficient exercise leads to weakening of the heart's action, and probably to dilatation and fatty degeneration. In commencing an unaccustomed exercise, the heart must be closely Avatched; excessive rapidity (120-140), inequality, and then irregularity, Avill point out that rest, and then more gradual exercise, are necessary, in order that the heart may be accustomed to the work. On the Skin.—The skin becomes red from turgescence of the vessels, and 422 EXERCISE. perspiration is increased; Avater, chloride of sodium, and acids (probably in part fatty) pass off in great abundance. Some nitrogen passes off in a soluble form as urea, but the amount is extremely small; it is increased on exertion with the increased perspiration. No gaseous nitrogen is given off in healthy men from the skin. The amount of fluid passing off is not certain, but is very great. Speck's experiments show that it is at least doubled under ordinary conditions. Pettenkofer and Yoit's experiments sIioav even a larger increase. The usual ratio of the urine to the lung and skin excreta is reversed. Instead of being as 1 to 0*5 or 0*8, it becomes as 1 to 1*7 or 2, or even 2*5. This evaporation reduces and regulates the heat of the body, which would other- wise soon become excessive; so that the body temperature rises little above the ordinary temperature. No amount of external cold seems to be able to check the passage of fluid, though it may partly check the rapidity of evaporation. If anything check evaporation, the body-heat increases, and soon languor comes on and exertion becomes difficult. During exertion there is little danger of chill under almost any circum- stances ; but Avhen exertion is over, there is then great danger, because the heat of the body rapidly declines, and falls below the natural amount, and yet evaporation from the skin, Avliich still more reduces the heat, continues. The rules to be drawn from these facts are—that the skin should be kept extremely clean; during the period of exertion it may be thinly clothed, but immediately afterwards, or in the intervals of exertion, it should be covered sufficiently Avell to prevent the least feeling of coolness of the surface. Flannel is best for this purpose. On the Voluntary Muscles.—The muscles grow, become harder, and respond more readily to volition. Their groAvth, however, has a limit; and a single muscle, or group of muscles, if exercised to too great an extent, will, after growing to a great size, commence to waste. But this seems not to be the case when ah the muscles of the body are exercised, probably because no single muscle or group of muscles can then be over-exercised. It seems to be a fact, hoAvever, that prolonged exertion, without sufficient rest, damages to a certain extent the nutrition of the muscles, and they become soft. The rules to be drawn from these facts are, that all muscles, and not single groups, should be brought into play, and that periods of exercise must be alternated, especially in early training, Avith long intervals of rest. On the Nervous System.—The effect of exercise on the mind is not clear. It has been supposed that the intellect is less active in men who take ex- cessive exercise, owing to the greater expenditure of nervous energy in that direction. But there is no doubt that great bodily exercise is quite consistent with extreme mental activity : and, indeed, considering that perfect nutrition is not possible except Avith bodily activity, Ave should infer that sufficient exercise would be necessary for the perfect performance of mental work. Doubtless, exercise may be pushed to such an extreme as to leave no time for mental cultivation; and this is perhaps the explanation of the proverbial stupidity of the athlete. Deficient exercise causes a heightened sensitive- ness of_ the nervous system, a sort of morbid excitability, and a greater susceptibility to the action of external agencies. On the Digestive System. -The appetite largely increases with exercise, especially for meat and fat, but in a less degree, it would appear, for the carbo-hydrates. Digestion is more perfect, and absorption is more rapid. The circulation through the liver increases, and the abdominal circulation is carried on Avith more vigour. Food must be increased, especially nitrogenous substances, fats, and salts and of these especially the phosphates and the THE ELIMINATION OF NITROGEN. 423 chlorides. The effects of exercise on digestion are greatly increased if it be taken in the free air, and it is then a most valuable remedy for some forms of dyspepsia. Conversely, deficient exercise lessens both appetite and digestive poAver. On the Generative Organs.—It has been supposed that puberty is delayed by physical exertion, but perhaps the other circumstances have not been allowed full weight. Yet, it would appear that very strong exercise lessens sexual desire, possibly because nervous energy is turned in a special direction. On the Kidneys.—The water of the urine and the chloride of sodium often lessens in consequence of the increased passage from the skin. The urea is not much changed, but the uric acid and also apparently the pigment increase after great exertion. The phosphoric acid is not augmented unless the exertion is excessive ; while the sulphuric acid and free carbonic acid are commonly increased (North). The exact amount of the bases has not been determined, but a greater excess of soda and potash is eliminated than of lime or magnesia: nothing certain is knoAvn as to hippuric acid, sugar, or other substances. In the careful observations made by Pavy on Weston, the pedestrian, it was found that all the constituents of the urine Avere increased, except the chlorine and the soda, which were notably diminished, especially the chlorine; the magnesia was also lessened, but in a much smaller degree. In these experiments, however, the diet was not uniform, and the exercise was excessive. On the Bowels.—The general effect of exercise is to lessen the amount of excreta passed, partly probably from a reduced amount of water entering the intestines. The experiments of Parkes and North indicate that the amount of nitrogen voided by the boAvels is not much altered. On the Elimination of Nitrogen.—A great number of experiments have been made on the amount of nitrogen passing off by the kidneys during exercise, notably by Parkes, A^oit, Pettenkofer, Banke, Smith, Haughton, and others. The amount of urea has been usually determined, and the nitrogen calculated from this. The observations have been commonly made by determining the nitrogenous excretion in twenty-four hours with and Avithout exercise; but in some the period during Avhich work was actually performed was compared with previous and subsequent equal rest periods. Some experiments were performed on men who took no nitrogen as food ; others were on men on a constant diet, so that the variation produced by the altering ingress of nitrogen was avoided as far as possible. In this place it is impossible to give an account of these long researches, and therefore only a short summary can be given. (1) When a period of exercise is compared after an interval with one of rest (the diet being with- out nitrogen or with uniform nitrogen), the elimination of nitrogen by the kidneys is decidedly not increased in the exercise period. The experiments on this point are now so numerous.that it may be stated without doubt. It is possible that the elimination may even be less during the exercise than during the rest period. (2) When a day of rest is compared with a day of Avork (i.e., a day with some hours of work and some hours of rest), the amount of nitrogen is almost or quite the same on the two days; if anything there is a slight increase in the nitrogen on the rest-day. In a day of part exercise and part rest, it is quite possible that there may be compensatory action, one part balancing the other, so as to leave the total excretion little changed. (3) When a period of great exercise is immediately followed by an equal period of rest, the nitrogenous elimination is increased in the latter. 424 EXERCISE. Meissner's observations shoAV that this is in part OAving to increased discharge of kreatin and kreatinin ; Parkes' observations also show an increase of non- ureal nitrogen. But the urea is also slightly increased in this period. (4) When tAvo days of complete rest are immediately folloAved by days of common exercise, the nitrogenous ehmination diminishes during the first day of exercise (Parkes). North's experiments in the main confirm the observations of Parkes, but he shoAvs that the effects of heavy labour are more immediate and severe than Avas shown by those observations. North found that deprivation, or an excessive output of nitrogen, Avas followed by retention and absorption. There is also a tendency to the storage of nitrogen in the system under ordi- nary conditions, which sIioavs a tendency to economy in the body. From this we might deduce the value of a good diet as providing a reserve against a period of deprivation or excessive Avork. A similar tendency to the storage of nitrogen was shoAvn in the case of Weston, Avhose ingesta or egesta were examined by Wynter Blyth. On the whole, if the facts have been stated correctly, the effect of exercise is certainly to increase the elimination of nitrogen by the kidneys, but Avithin narrow limits, and the time of increase is in the period of rest succeeding the exercise; Avhereas during the exercise period the evidence, though not certain, points rather to a lessening of the ehmination of nitrogen. It would appear from these facts that well-fed persons taking exercise Avould require a little more nitrogen in the food, and it is certain, as a matter of experience, that persons undergoing laborious work do take more nitrogenous food. This is the case also Avith animals. The possible reason of this Avill appear presently. On the Temperature of the Body.—As already stated, the temperature of the body, as long as the skin acts, rises little. Clifford-Allbutt, from observations made on himself when climbing the Alps, found his temperature fairly uniform; the most usual effect was a slight rise, compensated by an earher setting in of the evening fall. On two occasions he noticed tAvo curious depressions, amounting to no less than 4°*5 F.; he believes these Avere due to Avant of food, and not to exercise per se. In experiments on soldiers Avhen marching, Parkes found no difference in temperature; or if there was a very slight rise, it was subsequently compensated for by an equal fall, so that the mean daily temperature remained the same. A decided rise in temperature during marching would therefore show lessening of skin evaporation, and may possibly be an important indication of impend- ing heatstroke. Changes in the Muscles.—The discussion on this head involves so many obscure physiological points, that it Avould be out of place to pursue it here to any length. The chief changes during action appear to be these:—There is a considerable increase in temperature, which, up to a certain point, is proportioned to the amount of work. It is also proportioned to the kind, being less when the muscle is alloAved to shorten than if prevented from shortening; the neutral or alkaline reaction of the tranqud muscle becomes acid from para-lactic acid and acid potassium phosphate ; the venous blood passing from the muscles becomes much darker in colour, is much less rich in oxygen, and contains much more carbonic acid; the extractive matters soluble in Avater lessen, those soluble in alcohol increase ; the amount of water increases, and the blood is consequently poorer in Avater ; the amount of albumin in tetanus is less according to Banke, but Kuhne has pointed out that the numbers do not justify this inference. Liebig stated that the kreatin is increased (but this Avas an inference from old observations on the EFFECTS UPON THE MUSCLES. 425 extractum carnis of hunted animals, and requires confirmation). Sarokin has stated the same fact in respect of the frog. The electro-motor currents show a decided diminution during contraction. That great molecular changes go on in the contracting muscles is certain, but their exact nature is not clear; according to Hermann, there is a jelly- like separation and coagulation of the myosin, and then a resumption of its prior form, so that there is a continual splitting of the muscular structure into a myosin coagulum, carbon dioxide, and a free acid, and this constitutes the main molecular movement. But no direct evidence has been given of this. The increased heat, the great amount of carbon dioxide, and the disappear- ance of oxygen, combined Avith the respiratory phenomena already noted, all seem to show that an active oxidation goes on, and it is very probable that this is the source of the muscular action. The oxidation may be con- ceived to take place in two ways : either during rest oxygen is absorbed and stored up in the muscles and gradually acts there, producing a substance Avhich, A\'hen the muscle contracts, sphts up into lactic acid, carbon dioxide, &c.; or, on the other hand, during the contraction an increased absorption of oxygen goes on in the blood and acts upon the muscles, or on the sub- stances in the blood circulating through the muscles. The first view is strengthened by some of Pettenkofer and Yoit's experiments, which show that during rest a certain amount of storage of oxygen goes on, which no doubt in part occurs in the muscles themselves. Indeed, it has been inferred that it is this stored-up oxygen, and not that breathed in at the time, which is used in muscular action. The increased oxidation gives us a reason why the nitrogenous food must be increased during periods of great exertion. An increase in the supply of oxygen is a necessity for increased muscular action : but Pettenkofer and Yoit's observations have shoAvn that the absorption of oxygen is dependent on the amount and action of the nitrogenous structures of the body, so that, as a matter of course, if more oxygen is required for increased muscular work, more nitrogenous food is necessary. But apart from this, although experiments on the amount of nitrogenous elimination show no very great change on the whole, there is no doubt that, with constant regular exercise, a muscle enlarges, becomes thicker, heavier, con- tains more solid matter, and in fact has gained in nitrogen. This process may be slow, but it is certain; and the nitrogen must either be supplied by increased food, or be taken from other parts. Although Ave do not know the exact changes going on in the muscles, it seems certain that regular exercise does produce in them an addition of nitrogenous tissue. Whether this addition occurs, as usually believed, in the period of rest succeeding action, when in some unexplained Avay the destruction, which it is presumed has taken place, is not only repaired, but is exceeded (a process difficult to understand), or whether the addition of nitrogen is actually made during the action of the muscle, must be left undecided for the present. The substances which are thus oxidised in the muscle, or in the blood circulating through it, and from Avhich the energy manifested, as heat or muscular movement, is believed to be derived, may probably be of different kinds. Under ordinary circumstances, the non-nitrogenous substances, and perhaps especially the fats, furnish the chief bodies acted upon. But it is probable that the nitrogenous substances also furnish a contingent of energy. The exact mode in which the energy thus liberated by oxidation is made to assume the form of mechanical motion is quite obscure. The Exhaustion of Muscles.—There seems little doubt but that this 426 EXERCISE. is chiefly owing to tAvo causes—first, and principally, to the accumulation in them of the products of their OAvn action; and, secondly, from the exhaus- tion of the supply of oxygen. Hence rest is necessary, in order that the blood may neutralise and carry aAvay the products of action, so that the muscle may recover its neutrahty and its normal electrical currents, and may again acquire oxygen in sufficient quantity for the next contraction. In the case of all muscles these intervals of action and of exhaustion take place, in part even in the period which is called exercise, but the rest is not suffi- cient entirely to restore it. In the case of the heart, the rest betAveen the contractions (about tAvo-thirds of the time) is sufficient to alloAV the muscle to recover itself perfectly. The body after exertion absorbs and retains water eagerly; the water, though taken in large quantities, does not pass off as rapidly as usual by the kidneys or the skin, and instead of causing an augmented metamorphosis, as it does in a state of rest, it produces no effect whatever. So completely is it retained, that although the skin has ceased to perspire, the urine does not increase in quantity for several hours. The quantity of Avater taken is sometimes so great as not only to cover the loss of weight caused by the exercise, but even to increase the Aveight of the body. We can be certain, then, of the absolute necessity of Avater during and after exercise, and the old rule of the trainer, who lessened the quantity of water to the loAvest point which could be borne, must be wrong. In fact, it is now being abandoned by the best trainers, who allow a liberal alloAv- ance of hquid. The error probably arose in this way: if, during great exertion, water is denied, at the end of the time an enormous quantity is often drunk, more in fact than is necessary, in order to still the overpower- ing thirst. The sAveating which the trainer had so sedulously encouraged is thus at once compensated, and, in his view, all has to be done over again. All this seems to be a misapprehension of the facts. The body must have water, and the proper plan is to let it pass in in small quantities and frequently ; not to deny it for hours, and then to allow it to pass in in a deluge. The plan of giving it in small quantities frequently does aAvay with two dangers, viz., the rapid passage of a large quantity of cold water into the stomach and blood, and the taking of more than is necessary. General Effect of Exercise on the Body.—As judged by the preceding facts, the main effect of exercise is to increase oxidation of carbon and perhaps also of hydrogen; it also eliminates water from the body, and this action continues for some considerable time; after exercise the body is therefore poorer in Avater, especially the blood; it increases the rapidity of chculation everywhere, as well as the pressure on the vessels, and therefore it causes in all organs a more rapid outfloAv of plasma and absorption,—in other words, a quicker reneAval. In this way also it removes the products of their action, Avhich accumulate in organs, and restores the power of action to the various parts of the body. It increases the outflow of warmth from the body by increasing perspiration. It therefore strengthens all parts. It must be combined with increased supply both of nitrogen and carbon (the latter possibly in the form of fat), otherAvise the absorption of oxygen, the molecular changes in the nitrogenous tissues, and the elimination of carbon, will be checked. There must be also an increased supply of salts, certainly of chloride of sodium; probably of potassium phosphate and chloride. There must be proper intervals of rest, or the store of oxygen, and of the material in the muscles Avhich is to be metamorphosed during contraction, cannot take place. The integrity and perfect freedom of action both of the lungs and heart are essential, otherAvise neither absorption of oxygen nor AMOUNT OF EXERCISE TO BE TAKEN. 427 elimination of carbon can go on, nor can the necessary increased supply of blood be given to the acting muscles Avithout injury. In all these points, the inferences deducible from the physiological inquiries seem to be quite in harmony with the teachings of experience. AMOUNT OF EXEECISE WHICH SHOULD BE TAKEN. It would be extremely important to determine, if possible, the exact amount of exercise Avhich a healthy adult, man or Avoman, should take. Every one knows that great errors are committed,; chiefly on the side of defective exercise. It is not, however, easy to fix the amount even for an average man, much less to give any rule which shall apply to all the divers conditions of health and strength. But it is certain that muscular work is not only a necessity for health of body, but for mind also; at least it appears that diminution in the size of the body from deficient muscular work seems to lead in two or three generations to degenerate mental formation. The external work which can be done by a man daily has been estimated at ith of the work of the horse; but if the work of a horse is considered to be equal to the 1-horse poAver of a steam engine (viz., 33,000 pounds raised 1 foot high per minute, or 8839 tons raised 1 foot high in ten hours), this must be an over-estimate, as yth of this would be 1263 tons raised 1 foot in a day's work of ten hours. As already stated elseAvhere, a usual day's work for an adult ranges from 300 to 450 foot-tons. The following table, by Haughton, may be useful as expressing the amount of Avork done, under certain forms of labour. Labouring Force of Man. Kind of AVork. Amount of Work. Authority. Indian dhooli bearer, .... 600 tons lifted 1 foot. de Chaumont. Indian hill coolie ..... 500 , ? Pile driving,...... 312 „ Coulomb. Pile driving,...... 352 Lamande. Turning a winch, ..... 374 Coulomb. Porters carrying goods and returning ) 325 „ unladen, . . . . . . ) " Pedlars always loaded, .... 303 Porters carrying wood up a stair and \ returning unloaded, . . . . j 381 j j Paviours at work, ..... 352 Haughton. Military prisoners at shot drill (3 hours), ] 310 „ and oakum picking, and drill, . . / " Shot drill alone (3 hours), 160-7 ,, " The hardest day's work of twelve hours noted by Parkes was in the case of a workman in a copper rolling-mdl. He stated that he occasionally raised a weight of 90 pounds to a height of 18 inches 12,000 times a day. Supposing this to be correct, he would raise 723 tons 1 foot high. But this much exceeds the usual amount. The same man's ordinary day's work, Avhich he considered extremely hard, was raising a weight of 124 lb 16 inches 5000 or 6000 times in a day. Adopting the larger number, this would make his work equivalent to 443 tons lifted a foot; and this was a hard day's Avork for a poAverful man. Some of the puddlers in the iron country, 428 EXERCISE. and the glass-bloAvers, probably Avork harder than this; but there are no calculations recorded. From the statement of a pedlar, his ordinary day's Avork was to carry 28 lb 20 miles daily. The Aveight is balanced over the shoulder,—14 ft) behind and 14 lb in front. Assuming the man to Aveigh 160 ft), the work is equal to 443 tons lifted 1 foot. It would, therefore, seem certain that an amount of work equal to 500 tons lifted a foot is an extremely hard day's work, which perhaps feAv men could continue to do. 400 tons lifted a foot is a hard day's work, and 300 tons lifted a foot is an average day's work for a healthy, strong adult. The work usually calculated for a horse in the army is 3000 foot-tons, and -fth of this is just 430, nearly the Avork of the pedlar above mentioned. The external work is thus 300 to 500 tons on an average; the internal Avork of the heart, muscles of respiration, digestion, &c, has been variously estimated; the estimates for the heart alone vary from 122 to 277 tons lifted a foot. The former is that given by Haughton, who estimates the respiratory movements as about 21 tons lifted a foot in twenty-four hours. Adopting a mean number of 260 tons for all the internal mechanical work, and the external work of a mechanic being 300 to 500 tons, this will amount to from |th to -J-th of all the force obtainable from the food. The exertion which the infantry soldier is called upon to undergo is chiefly drill, and carrying weights on a level or over an uneven surface. By his philosophical studies and Avritings on this subject, Haughton has shown that walking on a level surface at the rate of about 3 miles an hour is about equivalent to raising ^th part of the weight of the body through the distance Avalked; an easy calculation changes this into the weight raised 1 foot. When ascending a height, a man of course raises his whole weight through the height ascended. TV, * i • (W + W)xD „ „ lfie formula is ---^q----* C = foot-tons : where W = weight of the person, and W the weight carried, both in pounds; D the distance, in feet; and C the coefficient of traction; 2240 is the number of pounds in a ton: the distance walked in miles must be multiplied by 5280 to bring it to feet. The result is the number of tons raised one foot. Using this formula, and assuming a man to weigh 160 ft) with his clothes, Ave get the following table :— Kind of Exei cise. AVork done in Tons lifted one foot. Walking 1 mile, 18*86 2 >> . 37*72 „ 10 >j 188*60 >. 20 !J 1-1 jj and carrying 60 Rj, 25*93 2 >) >> 51*86 ,. 10 >j !> 259*30 „ 20 >> >> 518-60 It is thus seen that a march of 10 miles, with a Aveight of 60 lb (Avhich is nearly the weight a soldier carries when in marching order, but Avithout blanket and rations), is a moderate day's work. A 20 miles march, with 60 ft) weight, is a very hard day's work. As a continued labouring effort, Haughton believes that walking 20 miles a day, without a load (Sunday being rest), is good work (323 tons lifted a foot); so that the load of 60 ft) additional would make the work too hard for a continuance. It must, however, be remembered that it is understood that the walking is on level ground, and is done in the easiest manner to the person, and that the Aveights Avhich are carried are properly disposed. The labour is CALCULATION OF WORK DONE. 429 greatly increased if the Avalk is irksome, and the Aveights are not well adjusted. And this is the case with the soldier. In marching, his attitude is stiff; he observes a certain time and distance in each step; he has none of those shorter and longer steps, and slower and more rapid motion, which assist the ordinary pedestrian. It may be questioned, indeed, whether the formula does not under-estimate the amount of work actually done by a soldier. The Avork becomes heavier, too, i.e., more exhausting, if it is done in a shorter time; or, in other words, velocity is gained at the expense of carrying poAver. The velocity, in fact, i.e., the rate at which work is done, is an important element in the question, in consequence of the strain throAvn on the heart and lungs. From certam calculations made by Weber, Haughton determined the coefficients of resistance for three velocities, as follows :— Miles per hour. Coefficient of Resistance. 1*818 4*353 10-577 T5"TTF Interpolating betAveen these numbers we can obtain the coefficients at other velocities. The following table shoAvs the coefficients, the distance in miles that would equal 300 foot-tons for a man of 160 tt>, and the time in hours and minutes that would be required -without rest:— A'elocity in Miles Coefficient of per hour. Resistance. 10 ITS-ITS 1 rFTI TTTfl ITT? 1 7-HIT Distance for Men of Time required in 160 lb, to equal Hours and Minutes. 300 foot-tons. H. M. 30-2 30 12 21*2 10 36 16*3 5 24 13-3 3 18 11-2 2 36 9-6 1 36 8-5 1 12 7-6 0 57 6-9 0 46 6-3 0 38 or this may be stated thus : the residual resistance equivalent to the erect posture is equal to gg^, or 0*01505; for every mile of velocity per hour add gg^p or 0*01117; thus for three miles an hour we have 0*01505 + (0*01117 x3) = 0*04856, or ^-g, as above. The coefficient ^ corresponds very nearly to 3*1 miles an hour, and this appears to be the rate at which the greatest amount of work can be done at the least expenditure of energy. As regards velocity, Haughton states the " Law of Fatigue " as follows :__ " When the same muscle (or group of muscles) is kept in constant action till fatigue sets in, the total work done, multiphed by the rate of work, is constant." The "Law of Befreshment" depends on the rate at which arterial blood is supplied to the muscles, and the "Coefficient of Befresh- ment " is the work restored to the muscles in foot-pounds per ounce of muscle per second; for voluntary muscle it is on an average 0*1309, and for the heart 0*2376, or exactly equal to the work of the heart, which never tires. In the University boat races, when the speed is about a mile in five minutes, or 18*56 foot-tons in five minutes, the work is not apparently very hard, but it is very severe for the time, and has considerable effect on the circulatory system. 430 EXERCISE. Some experiments made by Xorth, upon himself, are remarkable as having been done under circumstances of great precision. His weight Avas 132 ft), and he carried 28 ft), the total Aveight being 160 ft). In his first experiment he walked 30 mdes at 4*28 per hour; work done, 712 foot-tons. Second experiment—32 miles at 4*57 per hour; work done, 728 foot-tons. Third experiment—33 miles at 4*71 per hour; work done, 843 foot-tons. Fourth experiment—47 miles at 4*7 per hour; Avork done, 1200 foot-tons. Looking at all these results, and considering that the most healthy life is that of a man engaged in manual labour in the free air, and that the daily work will probably average from 250 to 350 tons lifted 1 foot, Ave can, perhaps, say, as an approximation, that every healthy man ought, if possible, to take a daily amount of exercise in some way, Avhich shall not be less than 150 tons lifted 1 foot. This amount is equivalent to a walk of about 9 miles; but then, as there is much exertion taken in the ordinary business of life, this amount may be in many cases reduced. It is not possible to lay down rules to meet all cases ; but probably every man with the above facts before him could fix the amount necessary for himself with tolerable accuracy. In the case of a soldier, if he were allowed to march easily, and if the weights were not oppressively arranged, he ought to do easily 12 miles daily for a long time, proAnded. he was allowed a periodical rest. But he could not for many days, without great fatigue, march 20 mdes a day with a 60 ft) load, unless he were in good condition and well fed. If a greater amount still is demanded from him, he must have long subsequent rest. But all the long marches by our own or other armies have been made with- out weights, except arms and a portion of ammunition. Then great distances have been traversed by men in good training and condition. V. Harley's observations indicate that the periods of digestion, as well as the kinds of food taken, have a marked influence on voluntary muscular ■energy, and that, irrespective of the influence of food, there is a periodical diurnal rise and fall of power for the performance of muscular work. He shows that more work can be done after than before mid-day ; the minimum being about 9 a.m., and the maximum about 3 p.m. Sugar taken early in the evening is capable of obhterating the diurnal fall in muscular power that ■occurs at this time, and increases the resistance to fatigue. Harley states that the effect of sugar is so great that the amount of work performed on a diet of sugar alone is almost equal to that obtained on a full diet; fatigue, however, setting in sooner. Moderate smoking, although it may have a slight influence in diminishing the power of doing voluntary muscular work, neither stops the morning rise, nor, when done early in the evening, hinders the evening fall. These conclusions are very interesting, but having been made exclusively upon a small group of muscles of the forearm under very artificial conditions, it is doubtful whether they can be accepted entirely for the whole body. What is known as " training " is a systematic effort to increase breathing power: to make the muscular action more -vigorous and enduring, and to lessen the amount of fat. This is obtained by a very careful diet, containing httle or no alcohol; by regular and systematic exercise; and by increasing the action of the eliminating organs, especially of the skin. What the trainer thus accomplishes is in essence the following: a concordant action is established between the heart and blood-vessels, so that the strong action of the heart, during exercise, is met by a more perfect ddatation of the vessels, and there is no blockage of the flow of blood; in the lungs, the blood not only passes more freely, but the amount of oxygen is increased ; BIBLIOGRAPHY AND REFERENCES. 431 this gradual improvement in breathing poAver is Avell seen Avhen horses are Avatched during training. The reciprocal action of heart and blood- vessels is the most important point in training ; the nutrition of nerves and muscular fibres improves from the constant action and the abundant supply of food; the tissue changes are more active, and elimination, especially of carbon, increases. A higher condition of health ensues, and, if not carried to excess, "training " is simply another word for healthy and vigorous living. BIBLIOGBAPHY AKD BEFEEEXCES. Allbutt, Alpine Journal, May 1871. Blyth, Proc. Roy. Soc. Lond., 1884, xxxvii. p. 46. De Chaumont, Appendix 24 to Report of Committee on Outbreak of Scurvy, Blue Book, 1875 ; also Lectures on State Medicine, Lond., 1875, p. 46. Fraser, Journ. of Physiology, Nov. 1868. Harley, Journ. of Physiology, xvi. Nos. 1 and 2, 1894, p. 97. Haughton, A New Theory of Muscular Action, Lond., 1870 ; also Principles of Animal Mechanics, Lond., 1873. Hermann, Untersuehungenuber den Stoffwechsel der Maskeln, Berlin, 1865; also Weitere Untersuch. zur phys. der Muskeln, 1867. Hirn, Ludwig's Physiol., 2nd ed., Bd. i. p. 743. Lagrange, Physiology of Exercise, Lond., 1889. Lee, Exercise and Training, Lond., 1880. Maclaren, On Training, Lond., 1882. Marcet, "The History of the Respiration of Man," being the Croonian Lectures for 1895. Lancet, June 22nd and 29th ; also July 6th and 13th, 1895. Morgan, University Oars, Lond., 1877. North, "On the Elimination of Nitrogen during Exercise," Proc. Roy. Soc. Lond., xxxvi. p. 11, and xxxix. p. 46. Parkes, Proc. Roy. Soc. Lond., Nos. 89 and 94, 1867 ; also Nos. 127 and 136 ; also On the Composition of the Urine, Lond., 1860. Pavy, Lancet, Dec. 1876. Power, " On the Excretion of Nitrogen by the Skin," Proc. Roy. Soc. Lond., 1882, xxxiii. p. 354. Speck, Archiv. des Vereins.f. wiss. Heilkunde, Bd. vi. p. 285. Smith, "Onthe "Work of the Horse," Veterinary Hygiene, Lond., 1887. Voit, von, Zeitsch. f. Biol., ii. and iii. ; also in Ranke's Physiol, des Menschen, p. 551. CHAPTER VIII. SOIL. Though the term soil may, in a general sense, be taken to express all the portion of the earth's crust Avhich by any property or condition can affect health, it is usual and convenient to divide all soils into an upper or surface sod and a deeper or subsoil layer. While the former or surface soil consists in the main of the products of the decay of large quantities of both animal and vegetable matter, constituting mould or "humus," the latter, strictly speaking, results entirely from the breaking up of the underlying primitive rocks, under the influence of water, gases and other agencies, and constitutes thereby an intermediate stage between the subjacent rock formation and the upper layers of true soil or mould. The relative thicknesses of these two layers constantly varies, for while the surface sod may be measured often only in inches or a few feet, the subsod may extend some hundreds of feet in depth. The expression rock is here used in its geological sense, as meaning any hard or soft material which goes to form the solid earth, and includes clays, loose sands, and gravels. Since the chief origin of the surface layers of the ground is from the gradual disintegration of rocks, the nature and composition of a soil in any given place wdl greatly vary, according to the geological history of the locality. Hence, from the nature of the soil, we can infer what is the quahty of the rock that hes beneath it, or knowing what is the underlying rock, we may fairly correctly form an opinion as to the character of the overlying sod. Thus, sandstones, when disintegrated or denuded, will produce sandy soil, and a clay, a clayey sod, or if the two kinds of rock be together, they wdl produce a loam or sandy clay: the resulting sods being also more or less mixed with the remains of vegetable and animal matter. Owing, however, to the action of rain and other forces constantly moving matters to a greater or less distance from their source, the soils of various localities do not necessarily and strictly correspond to the rocks beneath them, but may result in such instances of a clay soil overlying a sandstone, or a highly fertile soil being found to rest upon a substratum of rock which, from its known composition, must,- on disintegration, obviously produce a poor one. Similarly, the continual advance of sand over a country, under the action of the prevalent wind, has utterly ruined many fertile tracts, as, for example, the sandy region known as the " Landes " along the shores of the Bay of Biscay, and the " Dunes" of Norfolk and North Wales. THE GEOLOGICAL ORIGIN OF SOILS. Recognising the origin of all sods from the disintegration of rocks, it is of primary importance, for a complete comprehension of the nature of soils, to have some idea as to the composition of these earlier formations. All MINERAL CONSTITUENTS OF SOIL. 433 rocks are made up of one or more minerals. Those which contain more than one mineral are merely mechanical mixtures of them and not chemical compounds. Minerals, on the other hand, have, as a rule, a more or less definite chemical composition, which can be expressed by a formula: they, however, differ very greatly in composition. Some consist of only one element, others of two: in the latter case, one element is often a metal, as in pyrites, a compound of iron and sulphur : or fluor, which is a compound of calcium and fluorine. The elements constituting a mineral may, how- ever, be both non-metals, as in the case of silica, which consists of silicon and oxygen. The greater number of minerals consist of at least three elements, and form salts of a very complicated nature. This is particularly the case Avith those salts in which a non-metallic oxide like silica has combined Avith tAvo or more metalhc bases. Certain elements greatly pre- ponderate in soils : those most frequently met with are, oxygen, silicon, aluminium, calcium, magnesium, sodium, and potassium. The minerals may be classified in the folloAving manner:— Elements.—Native gold, silver, and copper: carbon as graphite and diamonds : sulphur. Sulphides of zinc (blende), lead (galena), copper (copper glance), mercury (cinnabar), hon (pyrites), arsenic (realgar and orpiment), antimony (stibuite), and mispickel, which is a combination of iron with arsenic. Cldorides of sodium (rock salt) and of ammonium (sal-ammoniac). Fluorides.—Fluor-spar or the fluoride of calcium. Oxides.—Cuprite or the oxide of copper: spinel or a compound of magnesia, aluminium, and oxygen : magnetite or the magnetic oxide of iron, Fe304 : haematite, another oxide of iron, frequently met with in an earthy condition and known as red ochre : corundum, a sesquioxide of aluminium, which as a red crystal is the ruby, when blue, the sapphire, and in other tints is the emerald, topaz, and amethyst: pyrolusite, an ore of manganese; cassiterite or the common tin ore of Cornwall: quartz, or crystallised silicon, and famihar under the various forms of flint, Brazilian pebbles, cairngorm, agate, opal, chalcedony, and jasper. Carbonates of iron (chalybite), calcium (calcite and aragonite), magnesium (magnesite), barium (witherite), zinc (calamine), strontium (strontianite), copper (malachite), and a double carbonate of calcium and magnesium known as bitter spar or dolomite. Sulphates of calcium, existing as selenite, gypsum, alabaster or anhydrite, and of barium in the form of heavy spar. Silicates.—These are of a complex and variable constitution: the chief being hornblende, felspar, and mica. Hornblende is a dark green silicate of calcium, magnesium, and iron together often with aluminium. It enters largely into the formation of rocks, and a fibrous form is in daily use as asbestos. Closely allied to hornblende are augite, jade, meerschaum, and serpentine. The felspars are silicates of aluminium, united with one or more metalhc oxides. Next to quartz, they constitute the most important rock-forming minerals. The micas form another group of silicates of very varied composition, consisting chiefly of aluminium, potassium, magnesium, and hon, with a little fluorine and water. Closely allied to them are other silicates, such as beryl, leucite, tourmaline, chlorite, and glauconite. Other salts are represented by borax or borate of sodium, nitre as nitrate of potassium and apatite, a phosphate of calcium with fluorine and chlorine. Organic mineral matters are common in the form of amber and coal. Of the foregoing minerals, practically only four enter largely into the formation of rocks: they are quartz, felspar, hornblende, and mica. The 2e 434 SOIL. resulting rock formations have been divided by geologists into three principal kinds according to their mode of origin, namely the igneous, the aqueous or sedimentary, and the metamorphic. Igneous Rocks.—These are all believed to have been derived from the original molten matter of the once fluid earth : some having solidified at a considerable depth, while others have been forced upwards and then cooled and sohdified at or near the surface. These rocks contain a great number and variety of minerals: these latter being for the most part double sihcates of great complexity. The minerals may be in a coarse crystalline condition as in granite, or indistinguishably mixed as in the basalts, or fused into a glass as in obsidian, or loose and open as in pumice, or stratified as in volcanic ash. These varieties of texture are mainly to be explained by the different conditions under which the rock has cooled. All the various minerals of igneous rocks are built up of silica, alumina, lime, oxide of iron, soda, potash, magnesia, and water. They exist chiefly as quartz, felspar, and mica. The first is pure silica ; felspar is a silicate of aluminium and of potassium, sodium, or calcium. Unlike quartz, which is most durable, felspar is prone to break down under the influence of exposure to air and rain into clay, which is nothing more than an aluminous silicate. Mica, like quartz, is not very liable to chemical change, but, by continued friction, breaks into a fine scaly sand or dust. The other minerals of the igneous rocks are mostly sihcates of calcium, magnesium, aluminium, and iron. Silica, either free or combined, being the most prominent constituent of the igneous rocks, its varying percentage is often made use of to classify them : those having above 60 per cent, being called acidic, and those having less, basic. The more general classification of the igneous rocks is into the Plutonic or those coarse crystalline rocks which have cooled slowly far beneath the surface, and the Volcanic or the scoriaceous, glassy and compact rocks which have been cooled at or near the surface. These can further be subdivided, if necessary, into acidic and basic. Of the plutonic rocks, the chief type is granite, which forms a considerable portion of the earth's surface. The crystals of granite lie closely packed in a matrix of transparent quartz. The silica of the quartz and that existing in the felspar, mica, and other minerals of granite constitutes from 62 to 80 per cent, of the whole Aveight, so that it belongs to the acidic class. If hornblende is present in addition to the ordinary constituents of a granite, it is termed syenitic granite. The basic plutonic rocks are chiefly mixtures of felspars with hornblende, augite, or mica; many of them are green in colour, and are knoAvn technically as diabase, gabbro, aphanite, and diorite. A crystalhne mixture of hornblende and felspar is called syenite. Of the volcanic rocks, the chief are basalt, dolerite, trachyte, obsidian, pumice, and phonolite. The broken material emitted from volcanoes is called "ash," and when more or less solidified is called tufa. The half molten rocky material from volcanoes is the lava. This lava, when dense and columnar, as in Staffa, is basalt; if coarser, it is called dolorite. The term trap is given to certain dark basaltic lavas, which are found spread out in great sheets over large areas in the Deccan and SAveden. Aqueous Rocks.—These are composed of small particles which are derived from the wearing away of other rocks and of matter which has been deposited from solution or suspension in water, or from organic materials. They are often called sedimentary rocks from their mode of formation, and are of four chief kinds, namely, the argillaceous, the arenaceous,' the calcareous, and the organic. AQUEOUS AND METAMORPHIC ROCKS. 435 Argillaceous rocks are the result of the sedimentary deposit of mud and clay, and consist largely of impure silicate of aluminium. The various claystone formations, such as the Lias, Oxford, Kimmeridge, Wealden, and London clays, are the products of these rocks: so are the shales, wlhch are merely hardened and laminated clays. Arenaceous rocks are those formed of sand or minute rounded grains of quartz. These grains, indifferently held together by clay, silica, iron oxides, or carbonate of hme, constitute the argillaceous, siliceous, ferruginous, and calcareous sandstones and grits. Conglomerates are rocks of this class, formed by pebbles or shingle cemented together, while a breccia rock is one Composed of rough and angular fragments similarly cemented. Both the argillaceous and arenaceous rocks are essentially, in their mode of origin, sedimentary. Calcareous rocks are those which are formed of the material which has been dissolved in water and deposited therefrom by chemical action. Of this class are the various limestones, Avhich have been deposited from solu- tion by loss of carbonic acid on exposure to the air. The deposition of ] carbonate of lime from aqueous solutions at the present time is familiar in s the so-called petrifying springs, and in the growth of stalactites. Some limestones are formed of little spherical grains, like the roe of a fish; these are called oolite. When consisting of an admixture of carbonate of hme and carbonate of magnesia, limestones are termed dolomites. Another rock of this class is gypsum. Flints and chert are other instances of chemical action, by which the silica scattered through the chalk has been dissolved by percolating water, and then deposited as we now find it. By a some- what similar process, large nodules of carbonate of lime, called Kunkur, are formed in beds of clay in parts of India. They contain some clay, and when ground up make a kind of cement. Organic rocks are those aqueous rocks which consist mainly of limestones derived from the shells or other hard parts of marine organisms, and of carbonaceous beds formed of plants. Among the limestones of organic origin are the coralline and crinoidal limestones, consisting largely of the remains of corals, molluscs, and crinoids. In the same way originated the shell marls and shell sands, while chalk itself, being of marine origin, is composed mostly of the remains of Foraminifera. Of the organic rocks derived from plants, coal, peat, lignite, jet, plumbago, anthracite, and bitu- men are conspicuous examples. Metamorphic Rocks.—Any mass of rock which has been altered when in situ, as distinguished from that which has been worn away, broken up and deposited elsewhere, as a sedimentary rock, is said to be metamorphic. Of these metamorphic rocks, there may be said to be two groups : one, contain- ing those rocks which have not been so altered as to prevent the recognition of their original condition, and the other, including those whose primitive state is quite obhterated by chemical and other changes. The first group embraces the slates, mica and marl slates, marble and quartzites; in which the original clay, limestone, and sandstone formation are respectively still discernible. The second group comprises the true metamorphosed rocks. They are characteristic of Wales and the Highlands of Scotland, and are suggestive of the influence of subterranean heat, combined with great pressure and the presence of water, whereby they have become foliated or schistose. The most abundant rock of this class is gneiss, which is really a granite altered by pressure. The other schistose rocks are the various schists, such as mica-sclust, hornblende-schist, talc-schist and others produced from sandy 436 SOIL. and clay deposits, the relative amount of either substance determining the character of the schist. Formation of Soils.—From the foregoing geological survey it is clear that the igneous and metamorphic rocks are almost entirely silicates, while the softer aqueous or sedimentary rocks consist mainly of silicates, carbonates, and oxides. Changes of temperature, largely aided by frost, have cracked and broken up these various rocks mechanically. By the influence of rain and air, carbonic acid and oxygen have entered the interstices of the rocks and acted chemically upon their constituents. The carbonic acid, dissolved in water, has assisted in the disintegration of granites and basalts, by con- verting their contained felspar into a soluble carbonate, Avhich, being readily carried off, has left a residue of clay behind : so that what was originally a hard granite rock has become a disintegrated mass of clayey gravel, represent- ing the natural soil of a granite district. Basalt suffers in the same Avay, breaking up into a gritty clay containing nodular masses of greyish coloured stone, as noticeable on the moors of north Yorkshire. Upon the limestones, the carbonated Avaters have acted in a similar manner, sloAvly dissolving away the carbonate of lime and leaving undissolved the clay and flints. This clay with flints constitutes the natural soil of the chalk districts, while the clay without the flints is familiar in the limestone regions. Both by means of water and air, oxygen acts upon the various substances in the rocks, convert- ing the carbonates and silicates of iron into oxides, and contributing not a little to the varying colours of different soils. In these and other ways the external surfaces of rocks become "weathered." Generally speaking, the acid igneous rocks decompose into clay, silica, and alkahne carbonates, thus Aveatheringinto clayey sods which contain particles of quartz, felspar, and mica, as evidenced by the loams so commonly found over granites and schistose rocks. The basic rocks resolve largely into clay and carbonates of calcium, magnesium, and iron, yielding marls or coloured clays. The formation of surface sods, from the weathering and decomposition of rocks, is by no means a purely chemical process caused by the direct action of rain and air, but is also in large part aided by the presence and action of both animal and vegetable life. From both animals and plants there is furnished, to the soil, matter, Avhich not only adds to its bulk, but enriches it and renders it still more suitable for plant life. This is continually being removed by rain, which either runs off or through it, and, as continually, is replenished by the breaking up of the rocks below and the decaying vege- table matter above. The upper layers, in which organic matter predominates, are carried down by rain, and the loAver and more mineral portions are brought to the surface by burrowing insects, worms, moles, and rabbits. In this manner the organic and inorganic matters of the earth are constantly being intermingled and renewed, and the soil both increased and improved. To these agencies must be added the constant action of wind and rain in moving soil from one part to another and the substitution of new surface soil by the upraising of a certain amount of material from deeper strata. Being composed partly of inorganic matter derived from the subsod by the process of weathering, and partly of the products of decomposition of animal and vegetable matter, most soils contain in abundance the compounds which plants require, such as nitrogen, lime, potash, soda, magnesia, silica, and phosphoric acid; but these substances are in an insoluble condition and only rendered assimilable by plants, after a sIoav conversion into soluble compounds by the agency of various forms of bacteria. This process, com- bined with the decomposition of vegetable remains, results in the formation of the so-called "humus." Yery little is known with regard to the exact CONFORMATION AND ELEVATION. 437 composition of humus. Some attempts have been made to separate it into constituent parts, and certain acids have been found, some of Avliich, such as Crenic acid, C12H1208, are soluble in both water and alkalies : others, such as Humic acid, C21H24012.3H20, being insoluble in water but soluble in alkalies : whilst others again, such as Ulmic acid, C40H28O12.H2O, are insoluble in both Avater and alkalies. The colour of humus is said to depend upon the nature of the acid present, ulmic acid giving a brown, and humic acid a black mould. SOIL FEATURES WHICH INFLUENCE CLIMATE AND HEALTH. There are certain general features of soil Avhich materially influence both climate and health: they are, its Conformation and Elevation, the amount of Vegetation present upon it, its contained Air and Water, its Temperature and power for absorbing or retaining Heat, and lastly, the nature and number of its contained Micro-organisms. Conformation and Elevation.—The relative amounts of hill and plain; the elevation of the hills; their direction; the angle of slope; the kind, size, and depth of valleys; the chief watersheds, and the direction and dis- charge of the water-courses; the amount of fall of plains, are the chief points to be considered. Among the hills the unhealthy spots are enclosed valleys, punch-bowls and any spot where the air must stagnate, such as ravines or places at the head or entrance of ravines. In the tropics especially raAdnes and nullahs are to be avoided, as they are often filled with decaying vegetation, and currents of air frequently traverse them. During the heat of the day the current of air is up the ravine, at night down it. As the hdls cool more rapidly than the surround- ing plains, the latter current is especially dangerous, as the air is at once impure and cold. The Avorst ravine is a long narrow valley, contracted at its outlet, so as to dam up the water behind it. A saddleback is usually healthy, if not too much exposed; so are positions near the top of a slope. One of the most difficult points to determine in hilly regions is the probable direction of winds; they are often deflected from their course, or the rapid cooling of the hdls at night produces alteration. On plains the most dangerous points are generally at the foot of hills, especially in the tropics, where the water, stored up in the hills and floAving to the plain, causes an exuberant vegetation at the border of the hills. A plain at the foot of hills may be healthy, if a deep ravine cuts off com- pletely the drainage of the hill behind it. The next most dangerous spots are depressions below the level of the plain, and into which therefore there is drainage. Even gravelly soils may be damp from this cause, the water rising rapidly through the loose soil from the pressure of higher levels. Elevation acts chiefly by its effect in lessening the pressure of the air, and in increasing the rapidity of evaporation. It has a powerful effect on marshes, high elevations lessening the amount of malaria, partly from the rapid evaporation, partly from the greater production of cold at night. Yet malarious marshes may occur at great elevations, even 6000 feet. Vegetation.—The effect of vegetation on ground is very important. In cold climates the sun's fays are obstructed, and evaporation from the ground is slow; the ground is therefore cold and moist, and the removal of Avood 438 SOIL. renders the chmate milder and drier. The extent to AA-hich trees impede the passage of Avater through the soil is considerable. In hot countries vegetation shades the ground and makes it cooler. The evaporation from the surface is lessened; but the evaporation from the vegetation is so great as to produce a perceptible lowering effect on the temperature of a place. Pettenkofer calculated that from an oak tree the evaporation equalled 212 inches, whde the rainfall was only 25*6 inches; tins shoAvs how much water Avas abstracted from the soil, and how the air must have been moistened and cooled. Observations in Algeria have shown that Eucalyptus globulus absorbs and evaporates eleven times the rainfall; extremely malarious places being rendered healthy in this way in four or five years. The hottest and driest places in the tropics are those divested-of trees. Vegetation produces also a great effect on the movement of air. Its velocity is checked; and sometimes in thick clusters of trees or underwood the air is almost stagnant. If moist and decaying vegetation be a coincident condition of such stagnation, the most fatal forms of malarious disease are produced. It may thus do harm by obstructing the movement of air; on the other hand, it may guard from the currents of impure air. The pro- tective influence of a belt of trees against malaria is most striking. In a hygienic point of vieAV, vegetation must be divided into herbage, brushwood, and trees; and these should be severally commented on in reports. Herbage is always healthy. In the tropics it cools the ground, both by obstructing the sun's rays and by aiding evaporation; and nothing is more desirable than to cover, if it be possible, the hot sandy plains of the tropics with close-cut grass. Brushwood is frequently bad, and should often be removed. There is, however, evidence that the removal of brushwood from a marsh has increased the evolution of malaria, and that, like trees, brushwood may sometimes offer obstruction to the passage of malaria. It must also be remembered that its removal will sometimes, on account of the disturbance of the ground, increase malarious disease for the time; and therefore, in the case of a temporary camp in a hot malarious country, it is often desirable to avoid disturbing it. When removed, the work should be carried on in the heat of the day, i.e., not in the early morning or in the evening. W. North instances the case of Cisterna, where the removal of macchia (i.e., brushwood, &c), though long objected to on account of supposed protection from malarial currents, Avas the means of improving the healthiness of the district. Trees should be removed with judgment. In cold countries they shelter from cold winds; in hot they cool the ground; in both they may protect from malarious currents. A decided and pernicious interference Avith the movement of air should be almost the only reason for removing them. In some of the hottest countries of the world, as in Southern Burmah, the in- habitants place their houses under the trees with the best effects; and it was a rule with the Romans to encamp their men under trees in all hot countries. The kind of vegetation, except as being indicative of a damp or dry soil, does not appear to be of importance. Ground Air.—The hardest rocks alone are perfectly free from air; the greater number even of dense rocks, and all the softer rocks, and the loose soils covering them, contain air. The amount is in loose sands often 40 or 50 per cent.; in soft sandstones, 20 to 40 per cent. The loose soil turned up in agricultural operations may contain as much as 2 to 10 times its OAvn volume of air. GROUND AIR. 439 The nature of the air in soils has been examined by a good many observers; it is mostly very rich in carbon dioxide, is very moist, and probably contains effluvia and organic substances, derived from the animal or vegetable constituents, Avhich have not yet been properly examined. Occasionally it contains carburetted hydrogen, and in moist soils, when the water contains sulphates, a httle hydrogen sulphide may be found. It has been examined by Nichols in America, Fleck in Dresden, Fodor in Buda- Pesth, LeAvis and Cunningham in Calcutta, and many others. Pettenkofer was one of the first to point out the excess of carbon dioxide in ground air, as compared Avith that in atmospheric air. According to him, the amount increased Avith the depth from which the air was drawn, and was moreover much influenced by the season of the year, the greatest quantity, at a given depth, being obtained in July, and the least in January. This was at Munich. Fodor, at Buda-Pesth, and Fleck, at Dresden, obtained very simdar results, their figures being:— At a depth of 1 metre, 0*9 to 1*0 vol. of C02 per cent. >i j> 2 ,, 2*9 ,, 3'0 ,, ,, ,, „ „ 4 „ 3-0 „ 5-4 „ „ 6 „ 7-9 ,,100 „ Both Pettenkofer and Fleck were of opinion that this carbon dioxide was due to the decomposition of organic substances, and that it might afford an approximate index of the degree of soil pollution. Fodor has, however, shown that a very foul soil, if at the same time permeable, contains less carbon dioxide than a cleaner but less permeable soil: and suggests that although the carbon dioxide is probably produced by the decomposition of organic matters, it does not afford so much a means of estimating the degree of pollution, as of the permeability of the soil. LeAvis and Cunningham, in their observations at Calcutta, found results somewhat similar to those of Fodor, the carbon dioxide being greatest in the lower strata examined. They considered that the fluctuation in the amount of carbon dioxide must be due to one or other of two causes: (1) variation in amount produced; (2) variation in amount accumulated, Avhich would depend on the amount of sod-ventilation; and that this latter cause was the most operative in Calcutta. The carbon dioxide increased Avith the rainfall, the effect of the rain being to close the pores in the upper layers of the soil and so retain the carbon dioxide. Soil temperature they did not consider to have any effect. The composition of soil air differs at different times and seasons, the absolute and relative amounts of the constituents varying under varying conditions. Just as the carbon dioxide increases so does the amount of oxygen decrease with the depth from Avhich the soil air is withdrawn. Some figures given by Fodor gave from 18 to 21 per cent, of oxygen at a depth of 1 metre, and 18 per cent, at 4 metres. In some freshly manured moist soil, Boussingault found the percentage of carbon dioxide to be as much as 9*5, and that of oxygen only 10. From this it would seem that, on air passing into soil, its oxygen enters into chemical combination with carbon derived from animal and vegetable matter, and thus becomes replaced by an equal volume of carbon dioxide. However, this is not always the case, as occasionally the percentage amounts of 02 and C02 together in soil air are such as to suggest the possible union of some of the oxygen with hydrogen to form water, and with nitrogen to form nitrates: while the carbon dioxide which is formed may dissolve in the water in the soil, or unite with ammonia and the earthy salts to form bicarbonates. On this 440 SOIL. point, some experiments have been made by us, which shoAV that if air be driven through a cylinder, packed with ordinary moist earth, less carbon dioxide will be recovered from it, after passing through the soil, than was originally present in it. When dry sand was used, the air passed through it unaltered. Other observations made by Roller show that many of the differences between the atmosphere and ground air may be due to different soils having varying absorptive poAvers for different gases. Thus a rich loam absorbed much more nitrogen than oxygen, and no soil appeared to absorb either of these gases in exactly the same relative proportions in Avhich they were mixed in the atmosphere. Some observers have noted that, occasionally, the carbon dioxide in the ground air is greater in amount than corresponds to the oxygen absorbed from the atmosphere. Schlosing has explained this as being due to the vital action of putrefactive organisms : for if air, containing different amounts of oxygen, be drawn through earth containing putrefactive organisms, not only Avas the carbon dioxide largely increased, but oxygen Avas diminished along Avith a reduction of the nitrates, present in the soil, into nitrites and even ammonia. In this case the organisms had evidently used not only the atmospheric oxygen, but also abstracted some from the organic matters and nitrogen salts in the soil. This sequence of events further explains why , increased amounts of carbon dioxide are found in the deeper earth layers, particularly after or during periods of Avarmth and moderate moisture, that is, at a time Avhen organisms concerned in decomposition processes would be in a state of greatest activity. The marked effect of rainfall and heat upon the amount of carbon dioxide in the soil has been emphasised by LeAvis and Cunningham and ourselves, the increase of rainfall and warmth being quickly attended by an increase of carbon dioxide, while in dry cold weather the quantity of carbon dioxide is reduced. Such an increase after rain and heat is probably due to a blocking up of the pores of the superficial soil layers, synchronous with an increased production whereby an accumulation of carbon dioxide takes place in the'deeper portions. The presence of much moisture in a soil is invariably coincident Avith a fall in the amount of carbon dioxide in the soil air owing to absorption by the water. Some daily variations of carbon dioxide in the ground ah have been noticed, but appear to depend less upon processes of soil activity than on rain, Avind, and changes of atmospheric pressure. These two latter do not appear to exert any very great influence, and are evidently secondary to rainfall as factors in the greater or less existence of carbon dioxide in soil air. The nitrogen present in the ground air is almost constant, being the same as that in the atmosphere, namely, about 79 per cent. Besides oxygen, nitrogen, and carbon dioxide, the ground air contains about 85 per cent, of humidity, together with various products of fermentation and decomposition, such as ammonia, ammonium sulphide, hydrogen sulphide, and marsh gas: these latter, however, rarely existing in large amounts. OAving to the constant reduction, in the sod, of the various oxidised states of nitrogenous organic substances into ammonia, under the influence of bacteria, this gas, although present in the ground air, cannot be taken as an index of either pollution or putrefactive changes. Provided the air be taken from soils Avhich have practically the same degree of permeability, the relative amounts of C02 found in it Avill furnish the best evidence as to their relative impurity : but if the permeabihty of soils vary, the amount of carbon dioxide in the soil air is not a reliable index of either purity or impurity. The subterranean atmosphere thus existing in many loose soils and rocks AMOUNT OF AIR IN SOILS. 441 is in continual movement, especially when the soils are dry; the chief causes of movement are the diurnal changes of heat in the soil, and the fall of rain, which must rapidly displace the air from the superficial layers, and, at a later date, by raising the level of the ground water, will slowly throw out large quantities of air from the soil. Fodor considers the temperature of the air, the ground temperature, the action of the winds, rainfall, barometric pressure, and level of ground water to be all influential in causing movement of the ground air, and consequent relative change in its constituents. Local conditions must also influence the movement; a house artificially warmed must be continually fed Avith air from the ground beloAv, and doubt- less this air may be drawn from great depths. Coal gas escaping from pipes, and prevented from exuding by frozen earth on the surface, has been known to pass sideways for some distance into houses. The air of cesspools and of porous or broken drains will thus pass into houses, and the examination of drains alone often fails to detect the cause of effluvia in the house. The unhealthiness of houses built on "made soils," for some time after the sods are laid doAvn, is no doubt to be attributed to the constant ascent of impure air from the impure sod into the warm houses above. To hinder the ascent of air from below into a house is therefore a sanitary' point of importance, and should be accomplished by paving and concreting, or asphalting the basement, or, in some cases, by raising the house on arches off the ground. The improvement of the health of towns, after they are well paved, may be partly owing to lessening of effluvia, though partly also to the greater ease of removing surface impurities. In some malarious districts great benefit has been obtained by covering the ground with grass, and thus hindering the ascent of the miasm. As a rule, it is considered that loose porous soils are healthy, because they are dry, and, with the qualification that the soil shall not furnish noxious effluvia from animal or vegetable impregnation, the rule appears to be correct. It is, however, undoubted that dry and apparently tolerably pure soils are sometimes malarious, and this arises either from the soils being really impure, or from their porosity allowing the transference of air from considerable distances. Even on the purest soils it is desirable to | observe the rule of cutting off the subsoil air from ascent into houses. The amount of air in soils can be roughly estimated, in the case of rather loose rocks, by seeing how much water a given bulk will absorb, Avhich can be done by the following plan:—Weigh a piece of dry rock, and call its Aveight W : then weigh it in water and call this Aveight Wx: then take it out of the water saturated with moisture, and Aveigh it again; call this Aveight W2. We then have— —^L_ -yr—=percentage of air. Example.—A piece of dry rock weighs 100 grammes (W): when Aveighed in water it weighs 60 (Wx); weighed out of water, but saturated, it weighs 110 (W2): then "inn-fifl ==4n^'^* an(^ ^1"'s multiplied by 100 gives 25 per cent, of porosity. When the soil is loose, Pettenkofer adopts the following plan :—Dry the loose sod at 212° F. (100° C), and powder it, but without crushing it very much; put it into a burette, and tap it so as to expel the air from the interstices as far as possible ; connect another burette by means of an elastic tube with the bottom of the first burette and clamp it on close to the end 442 SOIL. of the latter; pour water into No. 2 burette, and then, by pressing the clamp, allow the Avater to rise through the soil untd a thin layer of water is seen above it; then read off the amount of water used out of the second burette. The calculation— Amount of Avater used x 100 _ . . Cubic centimetres of dry soil ^ Example.—BO c.c. of soil were put in the burette ; it took 10 c.c. of water to reach to the top: then —==— = 33 3 per cent, of porosity. Renk's plan is very simple. Take a measured quantity of soil, say 50 c.c, shaken well together, so as to represent its natural condition as much as possible, and put it into a 200 c.c. graduated glass measure : then pour in 100 c.c. of water, and shake well so as to expel all air. Allow it to stand a little, and read off the point at Avhich the water stands. Suppose it stands at 125 c.c, then the 50 c.c. of soil and the 100 c.c. of water, when shaken together, only occupy a space of 125 c.c, the difference, 25 c.c, representing 25 the bulk of ah displaced from the 50 c.c. of soil: therefore ~ x 100 = 50 per cent, of air or porosity in the sample of soil. The examination of soil air can be best carried out by inserting into the soil leaden or iron tubes provided at their ends with perforated bulbs. To facilitate the introduction of these tubes, a hole must be dug, in the bottom of which broken bricks or large stones should be placed, and the bulbed ends of the tubes fixed at varying depths among them, the pit being after- wards filled and rammed in with the displaced soil. It'is advisable that the disturbed earth be allowed to remain a month or more, before observa- tions are made, so as to allow the soil to regain its ordinary condition. The tubes so placed in the earth should be next connected with an aspirator, capable of holding 2 htres of air : while intervening between the tubes and the aspirator must be arranged the usual appliances for the estimation of carbon dioxide, of oxygen, organic matter or micro-organisms in air. It is not necessary here to describe any of these procedures, as they are explained in another chapter : it is sufficient to point out that the essence of these arrangements is to be able to extract air from varying soil depths and then cause it to pass over or into certain reagents, contained in suitable apparatus, so as to complete the determination required. Ground Water.—The water present in soils is divided into moisture and ground water. When air as well as water is present in the interstices the soil is merely moist. The ground water may be defined, after Pettenkofer, as that condition in which all the interstices are filled with water, so that, except in so far as its particles are separated by solid portions of soil, there is a continuity of water. Other definitions of ground water have been given, but it is in this sense it is spoken of here. Moisture of Soil.—The amount of moisture depends on the power of the soil to absorb and retain water, and on the supply of Avater to the soil either from rain or ground water. With respect to the first point, almost all soils will take up Avater. Pfaff has shown that dried quartz sand in a filter can take up as much as 20 per cent, of water, and, though in the natural condition in the soil the absorption would not be so great, there is no doubt that even the hardest sands retain much moisture. After several months of long-continued drought, Church found a fight calcareous clay loam subsoil to contain from 19 to 28 per cent, of Avater. GROUND WATER. 443 A loose sand may hold 2 gallons of water in a cubic foot, and ordinary sandstone may hold 1 gallon. Chalk takes 13 to 17 per cent.; clay, if not very dense, 20; humus, as much as 40 to 60, and retains it strongly. The so-called " cotton-soil" of Central India, wlhch is derived from trap rock, absorbs and retains water with great tenacity; the driest granite and marbles will contain from 0*4 to 4 per cent, of Avater, or from 5 to 50 pints in each cubic yard. The moisture in the soil is derived partly from rain, to Avhich no soil is absolutely impermeable, as even granite, clay slate, and hard limestone may absorb a httle. Practically, however, soils may be divided into the im- permeable (unweathered granite, trap and metamorphic rocks, clay slate, dense clays, hard oolite, hard hmestone and dolomite, &c.) and the permeable (chalk, sand, sandstone, vegetable soils, &c). The amount of rain passing into the sod is influenced, however, by other circumstances—by the declivity and inchnation of the soil; by the amount of evaporation, which is increased in summer; by hot winds; and by the rapidity of the fall of rain, which may be greater than the soil can absorb. On an average, in this country, about 25 per cent, of the rain penetrates into the sand rock, 42 per cent, into the chalk, and from 90 to 96 per cent, into the loose sands. The rest evaporates or runs off the surface by the lines of natural drainage. The rapidity with which the rain-water sinks through soil evidently varies Avith circumstances; in the rather dense chalks it has been supposed to move 3 feet doAvnwards every year, but in the sand its movement must be much quicker. The moisture of the soil is not, hoAvever, derived solely from the rain; the ground water by its OAvn movement of rising and falling, by evaporation from the surface of the subterranean water, and by capillary attraction, makes the upper layers of the soil wet. By these several agencies the ground near the surface is in most parts of the world kept more or less damp. Daubree estimated the height to which Avater is raised by capillarity as follows:— 30 centimetres in sands. 60 „ ,, calcareo-argillaceous soils. 150 „ „ clays and compact marls. In the superficial sod layers, the capillary action appears to be greatest for clays and least for chalks: humus and sand occupying an intermediate position. As regards the affinity of soils for water and their capabilities for moisture, a distinction must be made between the permeability and absorp- tive power of a soil. A permeable soil, by allowing water or moisture to pass through it, contributes to the supply of the ground water, Avhile an absorptive soil really retains the moisture. Miers and Crosskey have explained the action of the soil in regard to water as being of a threefold nature. They say, it may act merely as a strainer allows fluid to pass through itself : it may take up water just as blotting paper takes up ink : or it may be saturated by water and retain it, as a sponge, immersed in water, is saturated by liquid which flows from it when the sponge is lifted out. This involves a distinction between permeability, imbibition and saturation .* because, the amount of water which percolates through the soil is due to its permeability, that which is retained as moisture in the soil is due to its power of imbibition, while that lying in the subsoil, in the form of ground water, depends upon the saturation. Practically, the relation to 444 SOIL. Avater of a given soil depends upon all these three qualities, and according as the one or other is most prominent, so -will the soil be drier or damper. Thus, sandstones are very permeable but not absorptive, the same is the case with the hmestones, chalk and schistose rocks. Generally speaking, soils which possess a great capacity for imbibition are not very permeable, and conversely the most permeable soils have the least storage capacity. The best test of permeability of a soil will be the rapidity with which percolation takes place through it. A number of experiments made indicate that water passes through clay the most slowly, and gradually increases in rapidity through marls, granitic soils, loams, limestone, coarse sand, basaltic soil, and fine sand. Warrington found that at Rothamsted only 7 inches of rain, out of an annual fall of 28 inches, percolated, during the year, through 3 feet of clayey gravel: while Prestwich relates that "on the chalk hills it takes four to six months for rain to pass from the surface to the line of Avater level at the depth of 200 to 300 feet, so that the heavy rainfall of winter is not felt in the deep springs for some months." Absorption, being mainly dependent upon capillary action, is always greater for rocks or soils Avhich consist of fine particles: the following table summarises a large number of observations :— Granites will absorb from 0*1 to 0*4 per cent, of Avater. Shales „ 0*3 ,, 1*5 Basalts ,, 0-3 „ 3-0 Sandstones ,, 0-5 ,, 10-0 Dolomites ,, , 0*5 ,, 5-0 Limestones ,, 1-0 ,, 16-0 >» > If expressed as the proportion of the volume of water taken up to the volume of the soil, Ave get the following results :— Humus,........70 per cent. Clay.........60 Fine limestone,...... . 44 ,, Sand,........40 ,, Regarding the value of a rock or soil as a water-bearing stratum being mainly dependent upon its capacity for saturation, the following figures from Delesse are interesting:— Sandstone will retain 29 per cent, of water. Chalk „ ,, 24 „ Clay „ „ 20 „ Clay Avith chalk ,, 19 ,, Basalt will retain 0*3 ,, Granite ,, ,, 0*1 ,, The determination of moisture in soil can be made by drying 10 grammes at a temperature of 110° C, then Aveighing, when the difference of the tAvo observations will represent the amount sought. The quantity of moisture Avhich a given soil sample is capable of taking up, may be determined by placing the previously dried soil under a bell-jar over water and noticing the resulting increase of weight. The amount of actual moisture found in soils appears to vary with the depth and the amount of contained organic matter, being diminished as deeper layers are penetrated and as the quantity of organic material decreases. The moisture varies not only from year to year, but from month to month, reaching in Europe generally a maximum in May and then falling during the summer until late autumn. In the deeper soil layers, the maximum of moisture is not attained till midsummer. The minimum found MOVEMENT OF GROUND WATER. 445 by Fodor in Buda-Pesth at 1 metre was 5*9 per cent., while at 4 metres it was 3*2 per cent. Decomposition, in soil, ceases when the moisture falls below 1*5 per cent., but is most active when the amount is about 4 per cent. A sample of surface soil, taken at 6 inches, consisting of loose sandy loam, examined by one of us in India, contained but 2 per cent, of moisture. The Ground or Subsoil Water.—The subterranean continuous water, known as ground or subsoil water, is at very different depths below the surface in different soils; sometimes it is only 2 or 3 feet from the surface, in other cases as many hundreds. This depends on the compactness or permeability of the soil, the ease or difficulty of outfiW, and the existence or not of an impermeable stratum near or far from the surface. It is an error to look upon the ground water as a subterranean lake or sea, with an even surface hke ah ordinary sheet of water, for it is not necessarily horizontal, and in some places it may be brought nearer to the surface than others by peculiarities of ground. The water is in constant movement, in most cases flowing towards the nearest water-courses or the sea; the rate of movement has not yet been perfectly determined. In Munich, Pettenkofer reckons its rate as 15 feet daily; the high water in the Elbe moves the ground water in the vicinity at the rate of about 7 or 8 feet daily. Fodor gives the mean rate at Buda-Pesth as 53 metres (174 feet), with a maximum of 66 metres (216 feet) in twenty-four hours, reckoning by the rise of the wells following the rise of the Danube. The rate of movement is not influenced solely by compactness or porosity of soil, or inclination. The roots of trees exert a great influence in lessening the flow; and, on the other hand, water runs off more rapidly than before in a district cleared of trees. The level of the ground water is constantly changing. It rises or falls more or less rapidly and at different rates in different places; in some cases its movement is only a few inches either way, but in most cases the limits between its highest and lowest levels in the year are several feet (in Munich about 10). In India the changes are greater. At Saugor, in Central India, the extremes of the soil water are from a few inches from surface (in the rains) to 17 feet in May. At Jubbulpore it is from 2 feet from the surface to 12 or 15. At Calcutta, Lewis and Cunningham found the water level to vary between 5 and 15 feet below the surface. The causes of change in the level of the ground water are the rainfall, pressure of water from rivers or the sea, and alterations in outfall, either increased obstruction or the reverse. The effect of the rainfall is sometimes only traceable weeks or even months after the fall, and occasionally, as in plains at the foot of hills, the level of the ground water may be raised by rainfalls occurring at great distances. The pressure of the Avater in the Rhine has been shown to affect the water in a well 1670 feet away. The pressure of the Danube at Buda-Pesth is found to influence a well at a distance of 2700 feet (Fodor). In a place near the Hamble River (Hampshire) the tide was found to affect the water of a well at a distance of 2240 feet, the well itself being 83 feet deep and 140 feet above mean water-level. A uniformly low ground water, say 15 to 20 feet, is most healthy, but a uniformly high ground water, say 3 to 5 feet, is preferable to one that is fluctuating, especially if the hmits be wide. It must, however, be borne in mind that it is not the ground water itself that is the cause of disease, but the impurities in the soil which the varying level of the ground water helps to set in action. Measurement of the Ground Water.—The height at which water stands in wells is considered to give the best indication of the height of the ground water. Pettenkofer uses a rod on which are fixed a number of 446 SOIL. little cups, and, when let down into the Avell and drawn up again, the uppermost cup Avhich contains water marks, of course, the height of the Avater; the length of the cord or rod used for letting down the cups being known, the changing level of the well can be estimated to within half an inch. Some precautions are necessary in making these observations: if a rope is used it may stretch with use, or in a hot dry wind, or contract in Avet weather, and thereby make the observation incorrect; local conditions of wells, proximity to rivers, &c, must be learnt, else what may be termed local alterations in a' well may be Avrongly supposed to mean changes in the general level of the ground water. It is necessary, therefore, to make the observations simultaneously in many wells and over a considerable district. The observations should be made not less often than once a fort- night, and oftener if possible, and be carried on for a considerable time before any conclusions are drawn. Pettenkofer also uses a large float which is suspended by a chain travel- ling over a pulley: this supports an indicator at its other end, which marks the height on a fixed scale. Method of rendering Soil Drier.—There are two plans of doing this,— deep drainage and opening the outflow. The laying down of sewers often carries off Avater by leaving spaces along the course of the sewers, but this is a bad plan; it is much better to have special drains for ground water laid by the side of or under the sewers. Deep soil drainage (the drains being from 8 to 12 feet deep and It) to 20 feet apart) is useful in all sods except the most impermeable, and in the tropics should be carried out even on Avhat are apparently dry sandy plains. In some cases soil may be rendered drier by opening the outflow. This is an engineering problem which medical officers can only suggest. The clearing of water-courses, removal of obstructions, and formation of fresh channels are measures which may have an effect over very large areas which could not be reached by ordinary drainage. Soil Heat.—Under this heading is involved the questions of the capacity of sods for both absorbing, retaining and giving off heat, as well as the facts regarding mere soil temperatures. It is a matter of common know- ledge that certain soils are warmer than others, that is, they are more easdy heated by the sun's rays, or in other words have a lesser or greater specific heat. The specific heat of any body is defined as being that amount | of heat necessary to raise its unit mass through 1° C.: the unit of heat I adopted being the quantity of heat needed to raise 1 kdogramme of water through 1° C. The specific heat of water is usually taken as unity, and on this basis, from the following table, it wiU be seen that the chief soils and their constituents have a distinctly lower specific heat than water, and that consequently all of them are more easily warmed than water. Clay has a specific heat of 0*160 Quartz , > 91 0*188 Felspar , ) >) I J 0*190 Granite , ' ii 0*192 Calcite , > 9 1 II 0*204 Mica , > 9 J II 0*205 Slate , 9 9) n 0*207 Limonite , ) j 0*221 Limestone , 9 ii 0*245 Loam , > )l >i 0*259 Basalt , ii 0*270 Sand , 1 > > n 0-275 Marl , 11 0*284 Humus , 1 ) 1 ii 0-600 SOIL TEMPERATURES. 447 Complementary to the foregoing, may be taken the two folloAving tables, quoted by Lloyd from experiments made by Liebenberg of Halle. Gain of Heat by Soils. After \ hour. After 1 hour. After 2 hours. Original Tempera- ture. 2 cm. 5 cm. 2 cm. 5 cm. 2 cm. 5 cm. Lime sand, . 21° C. 29° C. 27°*5 C. 32° C. 31°*5 C. 36°*5 C. 37°*0 C. Tertiary clay, 21° 30° 27°*5 33° 30°*0 36°*3 35° *0 Tertiary sand, 21° 30° 28° *0 33° 32°-5 37°*5 36°*5 Marl, . 21° 31° 28°*5 34° 32°*5 39°*0 37°*5 Meadow loam, 21° 32° 27° "5 37° 36°*0 40°-5 38°*5 Rich loam, . 21° 32° 29° *0 36° 34°*0 41°*5 39°-5 Basalt, 21° 33° 28°*5 35° 33°*0 42° *0 38°-0 Water, 21° 26° 26° *0 29° 5 29°*5 31°*0 31°*0 Loss of Heat by Soils. Original Temp. After J hour. After 1 hour. After 2 hours. Coarse sand, . Fine sand, Marls, . Loams, . Clay, . 41°*25 C. 41°-75 40°*00 40°-00 39°*50 29°*75 C. 28°*25 27°*50 27°*00 26°*00 24°-25 C. 23°'25 23°-00 22°-00 21°-50 19°-75 C. 18°*75 18°-50 18°*00 18°-00 With regard to the heat retaining power of some soils, the folloAving are the results of Schubler's observations :— Power of retaining Heat, 100 being assumed as the standard. Sand with some lime, . 100-0 Clayey earth Pure sand, 95-6 Pure clay, Light clay, 76-9 Fine chalk, Gypsum, 722 Humus, . Heavy clay, . 71-11 68*4 66*7 61-8 49*0 These tables all shoAV that not only does sand warm much more rapidly than clay, but also that the presence of organic matter in any sod causes it to possess a relatively greater power of absorbing heat. These facts are probably due to the peculiar behaviour of water to heat. Water is both a had absorber and bad radiator of heat, hence soils which contain much water, such as a damp clay, have a higher specific heat than dry porous soils, like sand, and consequently warm slowly and are often spoken of as " cold sods." This is in accordance with everyday experience. The rapidity with which soils radiate heat is not necessarily equal to their power of absorbing it, but will depend somewhat on their colour and the kind and thickness of the vegetation growing upon them. It is notorious that dark materials always absorb more radiant heat than light ones: "it has been found, for instance, that with the same exposure to the sun, a white sand attained a temperature of 43° C, while a black sand rose to 50° C." 448 SOIL. Generally the radiating power is more rapid than the absorbing: soils cool more rapidly than they heat. Some of the marshes in Mexico cool so rapidly at night that the evolution of malaria is said to be stopped, and the marsh is not dangerous during the night. Jourdanet states that while a thermometer marked zero on the ground, it recorded 14° C. at a distance of 16 feet above the ground. Vegetation and herbage greatly lessen the absorption of heat by a soil, at the same time making radiation more rapid. On the Orinoco, a naked rock has been known to have a temperature of 48° C, Avhde an adjacent rock covered with grass had a temperature of but 30° C. Not only does the amount of radiation differ in different soils, but a change is produced in the heat by the kind of soil. The remarkable researches of Tyndall have shown that the heat radiated from granite passes through aqueous vapour much more readily than the heat radiated by water (though the passage is much more obstructed than in dry air). In other Avords, the luminous heat rays of the sun pass freely through aqueous vapours and fall on water and granite; but the absorption produces a change in the heat, so that it issues again from water and granite changed in quality. Besides the excess of heat absorption over heat radiation, it is probable that sods obtain a considerable amount of heat by virtue of the chemical actions which are constantly taking place within them; "it having been proved by numerous observers that the growth of plants is always accom- panied by a rise in temperature, which again is related to the rapidity of their vital processes." The heat liberated by the condensation of gases may, too, be a not inconsiderable source of warmth. It will be readily understood, from the above considerations, that the temperature of the soil is but rarely that of the atmosphere, but more often higher: and, too, that the earth's temperature is different in different places. Fodor was one of the first, from his observations made at Buda- Pesth, to point out that the surface soil is warmer by day and colder by night than the air, but that the subsoil reaches its maximum and minimum heat later than the surface soil, so that it is colder in summer but warmer in winter than the superficial layers. His observations give the following results:— Average maximum temperature, at \ to 1 metre in depth, was found in August. ,, ,, ,, 2 metres ,, „ September. ,, >> >) 4 ,, ,, ,, October. ,, minimum ,, | to 1 metre ,, ,, January or Feb. ,> ,. .i 2 metres ,, „ April. Fodor's results and those of others indicate the greatest range of tempera- ture in the superficial sod: at 18 inches below the surface there occurs in Europe a variation of from 15° to 20° C. below the monthly mean, while at 10 feet deep the variation is as little as from 3° to 5° C. There is a marked difference in the manner in which the surface soil temperatures foUow variations in the. atmospheric heat, as compared with the temperatures of the deeper layers. While the temperature of the surface soil will quickly respond to small changes in heat of the air, that of the soil below the surface folioavs even great variations of air temperature but slowly. Thus, after a series of cold or warm days, it will be three or more days before the sod temperature, at a depth of half a metre, will accommodate itself to that of the air. At greater depths the stability of the soil temperature is even greater. SOIL TEMPERATURE. 449 t The sun's rays would appear to cause two currents of heat in soil: one Avave is diurnal, the heat passing doAvn in temperate climates to about 4 feet in depth during the day, and receding during the night, the depth, however, varying with the nature of the soil and with the season : the other wave is annual, the amplitude of which diminishes with the depth till it ceases to be perceptible. Forbes has shown, from observations made in Edin- burgh, that the annual variation is not appreciable loAver than 40 feet below the surface, and that under 24 feet the changes of temperature are small through the year. The depth at Avhich the annual variation ceases, or where the temperature is constant, depends on the conductivity and specific heat of the sod: but particularly on the difference between the summer and winter temperatures. The rate at which the annual wave of heat is propagated doAvn- Avards is so slow, that at Edinburgh, at a depth of 24 feet, the highest annual temperature does not occur till January, and the lowest not till the middle of July : thus reversing the seasons at this depth. At Greenwich, at 25^ feet, these phases of the annual temperature occur on November 30th and June 1st. Some observations, made in the Punjab, showed that at 20 feet the annual maximum was reached in September and the minimum in March. Accord- ing to Everett, the heat of the earth's surface is not influenced by the flow of heat from below upwards, but is determined entirely by atmospheric conditions. The temperature gradient averages an increase of heat down- wards of 1° F. for each 50 feet roughly : which makes the soil heat gradient five times steeper than that of air. The soil temperature gradient is steepest beneath gorges and least so beneath ridges : hence the underground isothermals (annual) are flatter than the uneven surfaces above them. The increase or extension of heat through any cubic area of soil is about equal to the product of the temperature gradient by the conductivity, so that it includes convection by the percolation of water as well as conduction proper : as a result of this, in comparing different strata of soil, the heat gradient varies in the inverse ratio of the soil conductivity. In Calcutta, Lewis and Cunningham found that the temperature of the soil varied with the season. In hot weather the thermometer stood highest in the air, next highest in the upper stratum of the soil, and lowest in the lower stratum. In cold weather the conditions were exactly reversed, the ah being coolest and the lowest stratum of soil the hottest. During rain, however, these relations were not constant. Since the effect of cold, generated by nocturnal radiation, mostly accumulates on the earth's surface, while the effects of solar radiation are spread to some height by ascending currents from the heated ground, it might be expected that the mean annual temperature of the soil surface would be loAver than that of the air resting on it: this is precisely what is found to be the case. On the other hand, the deeper layers of the earth are often Avarmer than the atmosphere, and do not display the same extremes of heat as does the,air. This is seen in the case of deep springs which get their source from depths greater than that to which the annual variation of soil heat penetrates, and have in consequence a constant temperature throughout the year, and further, if they come from a depth much greater, they give a close approximation to the mean annual temperature of the place. Reflection of Light.—This is a matter of colour; the white glaring soils reflect light, and such soils are generally also hot, as the rays of heat are also reflected. The effect of glare on the eyes is obvious, and in the tropics this becomes a very important point. If a spot bare of vegetation, and with a white surface, must be used for habitations, some good result might be obtained by colouring the houses pale blue or green. 2 F 450 SOIL. The effect of soil temperature upon disease is undoubtedly important, more particularly with regard to malaria, cholera, and epidemic diarrhoea. These relations will be considered later on, Avhen discussing the influence of soil generally to special diseases. Estimation of Soil Temperatures.—~No difficulty should be experienced in making these observations. One or more shafts or tubes should be bored into the soil to the required depth : the sectional diameter of these tubes may vary from 2 to 8 inches. Into the tubes, boards or blocks of wood should be made to fit, carrying the thermometers at suitable depths; the open- ing or mouth of the tube being closed with an accurately fitting cap or plug. The observations should be taken at the same hour every day, the thermo- meters immediately returned into the soil, care, of course, being taken, before so doing, to raise the registering index of the minimum, and to depress that of the maximum instrument well above and below the temperature of the soil. Micro-organisms in Soil.—It has for some years been known that ordinary garden soil and agricultural humus contained large numbers of micro-organisms belonging to the Schizomycetes and other allied groups of the lower Fungi. Schlb'sing and Muntz in 1877-78, and Warington about the same time, showed that the process of nitrification that takes place in soils is a fermentative process, excited and carried on through the agency of a minute organism, just as ordinary fermentation is carried on by torula. Miquel in 1879 attempted to estimate the number of germs present in sods of different kinds. Since then, Koch, Frankel, Fliigge, the Franklands, and other observers have pursued the subject, which opens out a large field for investigation of great importance : these researches have yielded results from which some conclusions may be drawn, though at the present stage of the inquiry this should only be done with caution. The existence of micro-organisms in soil is not surprising, when one considers that in many kinds of ordinary soil all the conditions necessary for their growth and multiplication are present, namely, a supply of nutritive substance derived from the decomposition of organic matter, with moisture, access of air, and a suitable temperature. All of these conditions are commonly found in the superficial much more than in the deeper layers of the soil, and it is accordingly in the former rather than in the latter that microbes are found to exist in the greater numbers : below 12 to 15 feet in depth they are comparatively few. The greater the organic pollution of the soil, the greater the number of microbes present; the most suitable conditions of moisture and temperature no doubt vary in regard to different species, neither dryness nor complete saturation, nor the extremes of heat and cold, being favourable to the development of many forms at present investigated. The actual numbers of germs found, or calculated, by different observers vary very considerably, and are perhaps of not much importance, but there is a pretty general agreement in regard to these two points : (1) the larger the amount of organic matter in the soil, the greater the number of micro- organisms ; (2) whatever the nature of the soil, the number of micro- organisms diminishes as the depth increases. AU forms of bacterial life have been found to be present in soil: in the moist and superficial layers, micrococci are the more numerous, Avhile in the drier and deeper portions, bacilli are present in the largest numbers. As Fliigge has shown, some species are markedly prominent, and are found in the most varied places, while others occur in only limited areas. It is probable that large numbers and kinds of bacilli are also present in the soil in the form of spores. Practically, all the micro-organisms found in soil may be divided into the saprophytic and the pathogenic. MICRO-ORGANISMS IN SOIL. 451 The former probably includes a large number of species, Avhich up to the present have not been differentiated; according to Arnould, no more precise distinction can be drawn than between those which oxidise, and those that de-oxidise or reduce. Of these the oxidisers are the most numerous and important, including those through whose agency the process of nitri- fication takes place; this, though originally supposed to be the work of one specific " nitrifying ferment," is in all probability effected by several differ- ent forms, not as yet distinguished from each other by specific characters. The butyric ferment of Pasteur (Clostrydium butyricum), which is a reducing bacterium, is likewise noAV considered to be not one but several species; other observers have described other reducing forms. Possibly the same species may be at one time an oxidiser, at another a reducing ferment. The pathogenic bacteria occur with such frequency in the earth that no material produces infection so easily as soil. Well-known pathogenic inhabitants of the soil are the bacilli of malignant oedema, of infective tetanus, the bacillus septicus agrigenus, and the anthrax bacillus. With soil, too, ,are probably often associated Eberth's bacillus of enteric fever, the malarial plasmodium, the vibrios of cholera, some forms of pneumococci ■(Sherrington), and an as yet not isolated microbe connected with the occurrence of epidemic summer diarrhoea. The local and seasonal variations in the distribution of .some infective diseases led Pettenkofer and others to beheve that the soil had a specific influence on the development and spread of infective germs, and that there was a constant connection between soil and epidemics.' The negative results of direct experiments and a fuller knoAvledge of the fate and behaviour of various bacteria in soil have rendered the general acceptation of this view to be impossible. Our present know- ledge indicates that the pathogenic micro-organisms are not, as a rule, propagated in sod, because the saprophytes naturally existing therein find the conditions more favourable for their development, and overcome the pathogenic species in the struggle for existence. Koch and others have tried to cultivate Bacillus anthracis in various kinds of soil, but without success; in sod previously sterdised, however, this species has been made to undergo development, the conditions obviously being very different from those that exist under any natural circumstances. Speaking generally, bacteria meet with unfavourable nutritive conditions in the sod, and their multiplication occurs only very exceptionally even in impure soil. Fliigge considers that on the surface of the soil pathogenic bacilli may find such conditions of moisture and temperature as are favourable to their germination and the production of new bacilli; but that they will speedily cease to exist, the vegetative form being easily overcome by saprophytes. The deeper layers of the soil, on the other hand, are favourable for the preservation of the spores of pathogenic organisms, though not for their multiplication; it is because they do not develop, but remain in the spore form, the temperature and other surrounding circumstances being unsuitable to germination, that they are preserved, vitality being maintained, though dormant. Soyka's experiments with anthrax bacilli indicate that, in their case at least, the sod exercises no marked or specific influence on the formation of spores. Observations made with other pathogenic forms similarly show the sod to be deficient in any special power of furthering spore formation. The preservation of non-spore-bearing bacteria in soil has been explained by Soyka as likely to often occur, because in that medium they are rarely likely to become completely dried, even in the driest of soils, owing to the 452 SOIL. layer of aqueous vapour Avhich so tenaciously surrounds the elements of the soil. The length of life of micro-organisms in the soil depends almost entirely on the amount of moisture present. Peat appears to be very hostile to many forms of bacteria; Avhy so, is not precisely known, but is very generally attributed to the presence of complex acids. Even granting the frequent preservation of pathogenic bacteria in soil, it must be remembered that this preservation is not an exclusive attribute of soil, and that, in the case of the infective diseases, this action or Avant of action of the soil can but rarely influence the spread of epidemics. Much interest attaches to the question, how do the preserved bacteria spread from the soil to man 1 The action of winds and the blowing about of bacteria-laden dust is only conceivable from the superficial layers of very dry soils. In some countries, notably in the East, and especially where excreta are superficially dug into or carelessly spread upon the ground, wind action probably is a more potent factor in the spread of disease than is generally recognised. In this country and Europe generally the possibility of a detachment and carrying away of soil bacteria by currents of air is only present in the latter end of summer, or in autumn, and quite absent when rain renders the outer surface of the earth moist. In estimating the value of the ground water and the water derived from it for drinking and other purposes, as means of distributing soil bacteria, we must take into consideration the enormous capacity of soil for retaining, as it were in a mesh, even such minute bodies as bacteria. The soil is, in fact, an excellent microbic filter and " where there is a thick layer of soil above the ground water, this mode of transport cannot come into play " ;. but where the ground water is only separated by thin layers of loose soil from the surface, or when fissures or cracks permit a ready communication between cesspools and wells, then the bacteria will pass from the soil to man. Although the sod acts as a good filter, holding back most of the | organisms, Dempster has demonstrated that it is possible for cholera / commas to be carried through two feet and a half of porous soil by a current of water. Occasionally micro-organisms may be conveyed from the soil to the domestic economy by articles of food which grow in the soil or by animals, but such modes of transference must obviously be the exception rather than the rule. The most important result of the presence of micro-organisms in soil appears to be the carrying on of a process of oxidation of the dead organic matter that finds its way into the ground, the process of nitrification that has already been alluded to; the nitrogen of organic bodies is first turned into ammonia, and this is successively changed into nitrites and nitrates. That tins action was due to some property residing in the soil itself was shown by the experiment of Schlosing; if a weak solution of ammonia is applied to a mixture of calcined sand and chalk and freely exposed to the air, no oxidation will take place, even after several weeks; if then a morsel of garden soil be added, in a few days nitrites and nitrates will be detected. This action is entirely arrested by the introduction into the soil of vapour of chloroform, Avhich paralyses all fermentative organisms. Hoppe-Seyler, Fleck, and other observers consider the process to be a purely chemical one, not needing the presence of any living agent; but the fermentative theory, promulgated by Schlosing and Muntz and Warington, has the sanction of WoUny, Fodor, Soyka, and others. The nitrifying power of different soils varies very considerably, depending partly on the nature of the soil itself, partly on the amount of ferment present (this in turn depending both on the number and nature of the micro-organisms), and being affected also by COMPARISON OF SOILS. 453 conditions of temperature and moisture. It appears to be of the first neces- sity that the soil should be alkaline, the carbonates of potash and lime being the most usual constituents, and after these, lime and magnesia; a quartz sand without lime is unfavourable to nitrification. The most favourable temperature is 37° C. The soil must be moist, and must also be penetrated by air; the successful purification of sewage by the method of intermittent downward filtration, as compared Avith filtration from below upwards, depends upon this; by.the latter method the access of air is prevented and nitrification retarded. Along Avith the oxidation of nitrogenous organic m atter into nitric acid proceeds the oxidation of organic carbon into carbonic acid, the one action being in fact the complement of the other. THE COMPARISON OF DIFFERENT SOILS. In examining the influence upon health of the soil round any dAvelling, it is probable that the immediate local conditions are of more importance than extended geological inquiries: it is, so to speak, the house and not the regional geology which is of use. Still the general geological conditions, as influencing conformation and the movement of water and air through and over the country, are of great importance. The healthiness of a soil depends chiefly on the folio whig factors :—(1) considerable slope and permeability, so that water runs off readily and regularly, rendering both the soil and the air above it dry; (2) vegetation not excessive; (3) absence of organic emanations; (4) purity of Avater-supply. In reference to these points, the different sods can be thus critically examined. The Granitic, Metamorphic, and Trap Rocks.—Sites on these formations are usually healthy; the slope is great, Avater runs off readily; the air is comparatively dry; vegetation is not excessive; marshes and malaria are comparatively infrequent, and few impurities pass into the drinking water. When these rocks have been Aveathered and disintegrated, they are supposed to be unhealthy. Such soil is absorbent of Avater; but evidence as to the effect of disintegrated granite or trap is really wanting. In Brazil the syenite becomes coated Avith a dark substance, and looks like plumbago, and the Indians believe this gives rise to "calentura," or fever. The dark granitoid or metamorphic trap or hornblendic rocks in Mysore are also said to cause periodic fevers. The Clay Slate.—These rocks precisely resemble the granite and granitoid formations in their effect on health. They have usually much slope; are very impermeable; vegetation is scanty; and nothing is added to air or to drinking water. They are consequently healthy. Water, however, is often scarce; and, as in the granite districts, there are swollen brooks during rain, and dry water-courses at other times, swelling rapidly after rains. The Sandstones.—The permeable sandstones are very healthy; both soil and air are dry; the drinking water is, however, sometimes impure, and may contain large quantities of chlorides, especially in the New Red Sand- stone when rock salt abounds. If the sand be mixed with much clay, or if clay underlies a shallow sand-rock, the site is sometimes damp. Carboniferous Formations.—The hard millstone grit formations are very healthy, and their conditions resemble those of granite. The drinking water is generally pure and fairly soft. The Limestone and Magnesian Limestone Rocks.—These so far resemble the former that there is a good deal of slope and rapid passing off of water. 454 SOIL. Marshes, however, are more common, and may exist at great heights. In that case the marsh is probably fed with water from some of the large cavities, which, in the course of ages, become hollowed out in the hmestone rocks by the carbonic acid of the rain, and form reservoirs of water. The drinking water is hard, sparkling, and clear. Of the various kinds of hmestone, the hard oolite is the best, and magnesian is the worst; and it is desirable not to put stations on magnesian hmestone if it can be avoided. TJie Chalk.—The chalk, when unmixed with clay and permeable, forms a. very healthy soil. The air is pure, and the water, though charged with calcium carbonate, is clear, sparkling, and pleasant. Goitre is not nearly so- common, nor apparently calculus, as in the limestone districts. If the chalk be marly, it becomes impermeable, and is then often damp and cold. The lower parts of the chalk, Avhich are underlaid by gault clay, and which also receive the drainage of the parts above, are often very malarious; and in America some of the most marshy districts are on the chalk. Gravels of any depth are always healthy, except when they are much below the general surface, and water rises through them. Gravel hdlocks are the healthiest of all sites, and the water, which often flows out in springs near the base, being held up by underlying clay, is very pure. Sands.—There are both healthy and unhealthy sands. The healthy are the pure sands, which contain no organic matter and are of considerable depth. The air is pure, and so is often the drinking water. Sometimes the drinking water contains enough iron to become hard, and even chaly- beate. The unhealthy sands are those which, like the subsoil of the Landes, in south-west France, are composed of siliceous particles (and some iron) held together by a vegetable sediment. In other cases sand is unhealthy, from underlying clay or laterite near the surface, or from being so placed that water rises through its permeable soil from higher levels. Water may then be found within 3 or 4 feet of the surface; and in this case the sand is unhealthy and often malarious. Impurities are retained in it, and effluvia traverse it. In a third class of cases the sands are unhealthy because they contain soluble mineral matter. Many sands (as, for example, in the Punjab) con- tain much magnesium carbonate and lime salts, as well as salts of the alkahes. The drinking water may thus contain large quantities of sodium chloride, sodium carbonate, and even lime and magnesian salts and iron. Without examination of the water it is impossible to detect these points. Clay, Dense Marls, and Alluvial Soils generally.—These are always to be regarded with suspicion. Water neither runs off nor rims through; the air is moist; marshes are common; the composition of the water varies, but it is often impure wiver ay. S > CS Death-Rate. ■*2«" -° S^ 81)2 a «S Sands. Clays. AVith Gravel. Without Gravel. Sands. Clays. 5 CO Hastings, 95 5 Cianbrook, i 6 .S4 9 84 16 (East Grinstead, 12 82 6 82 18 "jTunbridge, 1 •24 7 04 4 76 24 (Hambledon, . (Battle, . 49 20 31 59 41 80 20 SO 20 (Rye, 4 79 17 79 21 < Maidstone, 43 1 45 ii 66 24 (Cuckfield, 21 1 2-3 48 5 69 31 Uckfield, 1 82 17 82 18 (Hailsham, (Ticehurst, 34 61 4 61 38 67 33 67 33 Tenterden, 29 42 29 42 08 Horsham, 56 44 44 56 Petworth, 30 70 SO 70 474 SOIL. Buchanan's conclusions have been subjected to much criticism, notably by Kelly, the Medical Officer of Health for East Sussex, who has ex- pressed doubts of there being any intimate relation between dampness of the soil and phthisis. He finds that in the years 1861-70, the order in which the several districts have to be placed in regard to their death-rates from phthisis is different from that given by Buchanan for 1851-60. He points out that most of the impervious beds are to the north of the South Downs, and that consumption seems most common in places which are bleak and exposed as well as damp. He insists on the fact that in West Sussex (as indeed throughout England and Wales) there has been of late years a great decrease in the mortahty from consumption, although there has been no change in the drainage of Sussex. Kelly is inclined to attribute it mainly to the progress Avhich has taken place in the social state of the rural population. These more recent inquiries, when contrasted with Buchanan's earlier ones for the same localities, do not so much indicate the earlier conclusions to be wrong, as that all varieties of soil being now equally healthy, the cause of the phthisis which still occurs has to be sought for in other directions than soil dampness. It is probable that dampness is merely one of the many factors which are concerned in causing a predisposition to phthisis. On low-lying, damp soils colds and catarrhs are notoriously more common than on high and dry situations, and the tubercle bacillus, which is the exciting cause of phthisis, finds a favourable nidus in these cases. We have no reason to think that sod in any particular condition affords a more favourable medium for the preservation of the bacillus than do other materials. Even admitting that' sod dampness may favour the prevalence of phthisis by tending to lessen the resistance of the individual to the specific bacillus, it is obvious that many other conditions, such as overcrowding, poverty, ill-feeding, and general neglect of children, may all equally exercise a poAverful influence on phthisis mortahty. Rheumatism.—In respect of soil influences it is necessary to make a distinction between chronic rheumatism and acute rheumatism or rheumatic fever. It is well known that the chronic rheumatic diseases prevail most in deep and damp valleys, along sea-coasts, the shores of rivers, and in places which are much exposed to wind. Whatever connection chronic rheumatism and allied affections may have to soil states, is probably only in so far as altitude, configuration, and physical characters of the soil affect the climate of particular places. Of all soil conditions, dampness is that which will be most likely to predispose to chronic rheumatism, because it makes a locality cold; and this is particularly likely to occur on clays in low-lying districts. Beyond this general statement we cannot go. As relates to acute rheumatism or rheumatic fever, the facts are not so simple. The tendency of modern thought is to regard rheumatic fever as a specific febrile disease dependent upon a specific micro-organism. A study of its epidemic prevalence shoAvs that, at intervals of a few years, rheumatic fever tends to prevail epidemically. These epidemics occur in or just folio-wing years of sparse rainfall. This produces its effect by its influence in causing a warm and dry subsoil, usually with an exceptionally low ground AA-ater. Prom this point of view, rheumatic fever is essentially a soil disease, having close relationships Avith erysipelas and other septicaemic diseases. The explanation of the epidemic prevalence of rheumatic fever, as well as erysipelas and puerperal fever, lies in the favouring influence of a dry and warm subsoil on the specific contagia of the three diseases. Whether these contagia are alternately parasitic and saprophytic, or each SOIL IX RELATION TO TETANUS AND YELLOW FEVER. 475 case implies a fresh infection from the soil, is still doubtful. It is noticeable that the conditions of soil producing rheumatic fever and chronic rheumatism appear to be almost exactly opposed to each other. The seasonal distribu- tion of the two diseases is also dissimilar. Rickets.—Although most authorities are agreed that this disease is primarily a disorder of, nutrition, the outcome of either hereditary taint or defective and improper food in early hfe, still the remarkably definite relation which rickets appears to bear to climate has induced some writers to think it is in some manner dependent on the nature of soil. Hirsch has very clearly shown how countries, with a cold and wet climate subject to frequent changes in weather, are, if not the exclusive home of rickets, at least its headquarters. Oppenheim, arguing from its frequency on marshy plains or in valleys, has suggested that it is in some way related to malaria: especially as it is rarely met with Avhere the soil is dry or at great altitudes. It is doubtful whether these facts are anything more than coincidences : even if not so, much more evidence must be produced before the soil can be rightly regarded as in any Avay directly influencing the etiology of rickets. Tetanus.—Formerly, a distinction was made between a traumatic and an idiopathic form of this disease; but at the present time, the belief prevails that tetanus only results from traumatic infection. The agent which produces this affection is, hke that of malignant oedema, an anaerobic bacillus, frequently present in garden and other soil. JSIcolaier was the first to demonstrate that when soil from gardens, roads, or fields was subcutane- ously inoculated into guinea-pigs and mice, symptoms identical with tetanus were induced. The researches and experiments of Bassano have demon- strated the wide distribution of the tetanus germ in soil, besides indicating that neither climate nor meteorological conditions have much influence on the life of these micro-organisms. The extensive presence of the tetanus bacilli in soil explains why tetanus is more common after wounds on the hands and feet than on any other part of the body; and why it is more frequent amongst children who play about bare-footed than amongst adults. Gardeners and grooms are especially liable to it. The peculiar frequency with which grooms and others, in contact Avith horses, are attacked with tetanus has induced Verneud to think that the disease is of equine origin : and that horse dung is the most potent source of tetanus dissemination. Verneuil's views are largely supported in Prance, although negative evidence comes from the Xew Hebrides to the effect that though horses are unknown, yet tetanus is very common there. In regard to this controversy as to the equine origin of tetanus, Xocard has aptly remarked " to pretend that the tetanic action of soil is due to the dung of horses, more than to that of oxen or sheep, is to say that tetanus is more frequent in the country than in the towns, where horses are much more numerous, a statement absolutely contrary to the facts." Although we cannot accept the equine theory of the origin of tetanus, we must take care not to err too much the other way and attribute its causation exclusively to soil. We must admit, the evidence points to the soil as being the chief medium of conveying infection, still the tetanus bacillus can exist in or on other articles and places, such as the coat of a horse or other animal, in hay, on a rusty nail, or on surgical and veterinary instruments. Yellow Fever.—The whole history of yelloAV fever goes to show that though at one time and another its diffusion has been wide, still its native habitat is much less extensive. The extent of its diffusion indicates an independence of geological origin of soil. On the other hand, the prevalence of the disease along the banks of tropical rivers, Avhich are dry at certain 476 SOIL. periods, and in the Ioav parts of tropical sea-ports, particularly those abut- ting on or overhanging harbours, stagnant Avaters, or foul foreshores, clearly defines the existence of a porous, loose, and periodically saturated soil as being a constant concomitant of yellow fever. No evidence appears to be available regarding the microscopic life present in soils of these kinds, neither are there any data which sIioav that soil temperature, taken alone, has any bearing upon the occurrence of this peculiar disease in its endemic home. Although we do not knoAV exactly AArhat is the infective agent of yellow fever, yet, judging from its analogy to other infective diseases, such agent is in all likelihood a micro- organism : and that this microbe is a soil resident is suggested by a curious incident which occurred near Lima in 1880. A number of troops were engaged in throAving up an earthwork, Avhich involved the digging up of an old cemetery, in which victims of an antecedent epidemic had been buried. Within a Aveek over 50 per cent, of those engaged upon the work Avere attacked by yellow fever. The phdosophical and remarkable theory regarding the pecuhar origin of tins disease, as elaborated by Creighton from the forgotten writings of Audouard, has a direct interest and bearing upon the connection between the affection and soil processes. The Audouard-Creighton theory of the evolution of yellow fever is that its advent into the world coincided with the rise of the slave trade, and that its habitat has been and is the ports of debarkation of these slaves. It is perfectly well known, from the writings of both Lind and Bancroft, that the slaves on the slave ships did not suffer from yellow fever, but much from dysentery. According to Audouard, yellow fever originated at all its endemic centres from the filth of the slave ships, which filth was the putrid dysenteric discharges of the sick negro. Regarded in this light, yellow fever has been given us in the dejecta of another race, which, brought in considerable quantities in the bilges of ships to ports, has there been discharged into harbour mud and soil. The scourings of these ships, fermenting and multiplying in the harbour and shore mud, has generated a specifically poisonous virus wlhch has been only too readily carried from harbour to harbour. In connection with this view, it is curious to note the fact that yellow fever is most persistent at places where there has been least cleansing of harbours, beach, or foreshore by the natural action of the tides, or where much stagnation of the harbour Avater exists, as in places hke Havana, Port Royal, BridgetoAvn, and Port- au-Prince. Though up to the present the isolation and identity of the yellow fever poison has not been made, still there is much to make us regard it as being essentially a mud or soil-contained poison, and the mud or soil, Avhere it has accumulated for a time, continues to be an endemic focus of the disease. Until we know more as to what is the nature of the yellow fever virus, Ave must leave it an open question as to how far the soil acts as only a nidus for it, or how far it exercises any specific influence on its growth and spread. As in the case of the other infective diseases, it is probable that the soil only furnishes a suitable medium in Avhich the yellow fever poison may remain and multiply, and that, of itself, the soil is quite devoid of any special vitahsing influence upon the cause of the disease. EXAMINATION OF SOIL. 477 THE BACTERIOLOGICAL EXAMINATION OF SOIL. It has already been indicated that most soil samples are exceedingly rich in bacteria: the majority of these, as agents of putrefaction and nitrification, play a distinctly beneficial part in nature : a few others, Avliich are patho- genic to both animals and man, appear to be possessed of less obvious advantages. Though the presence of even large numbers of micro-organ- isms in an earth sample is not necessarily an indication of its being either unsuitable for a building site, or as a source of Avater-supply, still the recognition and differentiation of various species, in some cases, is im- portant. Such a procedure is obviously one of considerable difficulty, involving great care and patience : and before anything of a pathogenic nature could be definitely stated to be present or not, necessitates the isolation of various colonies, the application of various methods of culture, staining and even experimental inoculations on animals. To obtain a cultivation of the microbes in soil, a sample of the latter must be first dried and then triturated. It may then be shaken up Avith distilled water, and from this a drop transferred to sterihsed bouillon or gelatin. Again, a small quantity, after drying and trituration, may be sprinkled over the surface of nutrient gelatin prepared for a plate culti- vation. In another method, the gelatin is liquefied in a test-tube, the powdered earth added, evenly distributed throughout the medium, and from it a plate culture made. In such a plate culture, by means of a suitably ruled glass plate and divided into centimetre squares, it is easy to count the number of colonies which develop in a given area, and from them calculate the number of bacteria that were originally present in the given sample of earth. For the differentiation of particular species, the individual colonies should be examined by cover glass preparations, and by fractional cultivation upon gelatin, potatoes, and other media. A more difficult procedure is to aspirate the ground air from different soil depths and then cause it to pass slowly over the surface of Gelatin whereby such micro-organisms as may be present attach themselves and eventually develop upon the nutrient medium, where they can be subse- quently examined. THE PHYSICAL AND CHEMICAL EXAMINATION OF SOIL. Though more often required for agricultural than for hygienic purposes, a complete examination of a soil should include the folloAving points :__ Mechanical Condition.—The degree of density, friability, and penetration by water should be determined both in the surface and subsoil. Deep holes, 6 to 12 feet, should be dug, and water poured on portions of the soil. Holes should be dug after rain, and the depth to which the rain has pene- trated observed. In this way the amount of dryness, the water-level, and the permeabihty can be easdy ascertained. The surface or subsod can also be mechanically analysed by taking a weighed quantity (100 grammes), drying it, and then picking out all the large stones and weighing them, passing through a sieve the fine particles, and finally separating the finest particles from the coarser by mixing with water, allowing the denser particles to subside, and pouring off the finer suspended particles. The weight of the large stones, plus the weight of the stones in the sieve and of the dried coarser particles, deducted from the 478 SOIL. total weight, gives the amount of the finely divided substance, Avhich is probably silicate of aluminum. Temperature.—The temperature at a depth of 2 or 3 feet, at two to four o'clock in the afternoon, Avould be an important point to determine in the tropics, and also the temperature in early morning. Hygroscopic Moisture.—Place 5 grammes of air-dry oil in a flat-bottomed and tared platinum dish: heat in an air bath to 45° C. for eight hours : cool and weigh: repeat the heating, cooling, and weighing at intervals of an hour till constant weight is found, and estimate the moisture by the loss of weight. Weigh rapidly to avoid absorption of moisture from the air. Water Holding Power.—In the throat of a clean 3-inch glass funnel place a very small filter, just large enough to prevent the soil from running through the stem : wet the filter and add 100 grammes of the air-dried soil: from a burette pour water on the soil, till it is thoroughly wet and a few ■drops pass through : let it stand undisturbed till no more water flows from the soil, the funnel being covered with a glass plate to prevent evaporation. Return the water which has filtered through to the burette. The number of ■c.c. taken up by the soil wdl show the percentage capacity of the soil to hold water. In using this process, in order to secure uniform results, the soil should be simply poured into the funnel and not pressed or packed in any way. The soil should not be handled or shaken. Capillary Power.—This is determined by filling a long glass tube with soil, placing the lower end in water, and marking the height to which the Avater ascends, as shown by the changed colour of the soil in the tube. Volatile Matter.—The platinum crucible and 5 grammes of soil, used to ■determine the moisture, are heated to low redness. The heating should be prolonged till all organic material is burned away, but below the temperature at which alkahne chlorides volatilise. Moisten the cold mass with a few drops of a saturated solution of ammonium carbonate, dry, and heat to 65° C, to expel excess of ammonia. The loss in weight of the dry soil represents organic matter, water of combination, salts of ammonia, &c. Water-soluble Materials.—To prepare a water extract of the soil, a percolator of glass or tin may be employed. It should be large enough to hold 1 kilogramme of soil. Pour sufficient ammonia-free distilled water on the soil to moisten it all, and let the whole stand undisturbed for half an hour, then add more water till a litre of filtrate is secured. If the soil extract is cloudy, filter through a plain filter. Soluble Solids.—Evaporate 100 c.c. of the filtrate to dryness in a tared dish: each gramme of residue will represent 1 per cent, of water soluble matter. Test this dry residue for nitrates by pouring over it 10 c.c. of pure H2S04, holding in solution 4 mgms. of brucine sulphate. Chlorides.—Titrate 100 c.c. of the filtrate or soil extract with standard deci-normal silver nitrate, adding a feAv drops of a solution of K2Cr04 as an indicator. Sulphates.—Precipitate these from 100 c.c. of the soil extract with BaCl2, in the presence of a few drops of HC1. Reserve the rest of the soil extract for a subsequent quantitative estimation of nitrates. Acid-soluble Materials.—Place 10 grammes of air-dried soil in a 200 c.c. glass flask, add 100 c.c. of pure HC1, insert the stopper, wire it securely, place in a steam bath, and digest for thirty-six hours at the temperature of boiling water. Pour the contents of the flask into a small beaker, wash out the flask with distilled water, add the washings to the contents of the beaker and filter through a washed filter. The residue is the amount insoluble in hydrochloric acid. Add a few drops of HN03 to the filtrate, and evaporate EXAMINATION OF SOIL. 479 to dryness on the water bath: take up with hot Avater and a feAv drops of HC1, and again evaporate to complete dryness. Take up as before, and filter into a litre flask, washing with hot Avater. Cool and make up to 1 litre. This solution may be marked "A." The residue is soluble silica. Ferric and Aluminium Oxides.—To 100 c.c. or 200 c.c, according to the probable amount of iron present, of the solution "A," add NH4OH to alka- hne reaction (avoiding excess) in order to precipitate ferric and aluminic oxides and phosphates. Expel the excess of ammonia by boiling, allow to settle, decant the clear solution through a filter, add 50 c.c. of hot distilled water, boil, settle, and decant again. After pouring off all the clear solution possible, dissolve the residue with a few drops of HC1 with heat and add just enough NH4OH to precipitate the oxides. Wash by decantation with 50 c.c. of distilled water, and then transfer all the precipitate to the filter and wash with hot distilled water till the filtrate becomes free from chlorides. Save the filtrate and washings, which may be marked solution "B." Dry the precipitate and filter at 45° C, transfer the precipitate to a tared crucible, burn the filter and add the ash to the precipitate, heat the whole red hot, cool, and re-weigh. The increase of Aveight, minus the ash of the filter and the phosphoric acid (to be determined subsequently), represents the weight of the ferric and aluminium oxides. Ferric Oxide.—Precipitate 100 c.c. of solution " A " with NH4OH, wash the precipitate with hot water, dissolve while wet in dilute H2S04: reduce hy the addition of granulated zinc, free from iron, and estimate ferric oxide by a standard solution of KMn04. To prepare the potassium permanganate solution, dissolve 3-156 grammes of pure crystallised permanganate in a litre of distdled water, and preserve in a ground glass stoppered bottle shielded from the hght. Standardise from time to time this permanganate solution with pure ferrous sulphate. This method of estimating iron depends upon the fact that KMn04, in the presence of a ferrous salt, oxidises to the ferric state. The solution made as above after addition of the zinc is one of a ferrous salt: as the KMn04 falls into this solution, a pink blush is formed, but disappears on stirring as long as a ferrous salt remains unoxidised to ferric. As soon as all is oxidised to the ferric state, the pink remains per- manent. Knowing, after standardisation, the oxidising value of each c.c. of KMn04 in terms of Fe203, this, multiphed by the number of c.c. used, gives the amount of ferric oxide in 100 c.c. of solution "A" or 1 gramme of air- dried soil. The weight of ferric oxide, so found, deducted from the total weight of ferric and aluminium oxides, with corrections for filter ash and phosphoric acid, will give the weight of alumina in 1 or 2 grammes of soil, according as 100 or 200 c.c. of solution were originally taken. Phosphoric Acid.—Take another 100 c.c. of solution "A" and neutralise with ammonia, and add about 15 grammes of dry ammonium nitrate. Next precipitate, by adding 50 c.c. of molybdic solution, made by dissolving 100 grammes of molybdic acid in 400 c.c. of ammonia, the solution then being poured into 1250 c.c. of nitric acid. Filter, and wash with a solution of ammonium nitrate, made by dissolAdng 200 grammes of the salt in water and then made up by further additions to 2 litres. The precipitate on the filter is then dissolved in ammonia and hot water, washed into a beaker, making a bulk of not more than 100 c.c. This solution is nearly neutralised with HC1, cooled, and then magnesia mixture run in slowly, accompanied by vigorous stirring. After fifteen minutes, add 30 c.c. of ammonia, filter the precipitate which forms, wash with dilute ammonia, ignite, and weigh. The magnesia mixture is made by mixing 110 grammes of crystallised magnesium 480 SOIL. chloride, 280 grammes of ammonium chloride, and 700 c.c. of ammonia, and then making up to 2 htres. Manganese.—Concentrate solution " B " to 200 c.c. or less : add NH4OH to alkalinity : add bromine water and boil: as the bromine escapes, alloAV to cool somewhat, add more ammonia and bromine and heat again. This process is continued until the manganese is completely precipitated, which it will be in about an hour; the solution is filtered while warm, the pre- cipitate well washed, dried, ignited, and weighed. Estimate as Mn304. Lime.—If no manganese is precipitated, add to solution " B," or to the filtrate and washings from the last procedure, 20 c.c. of a strong solution of NH4C1 and 40 c.c. of a saturated solution of (NH4)2C204, to completely pre- cipitate all the lime as oxalate, and convert the magnesia into soluble magnesium oxalate. Heat to boiling, and let stand for six hours till the calcium oxalate settles clear, decant on to a filter, pour 50 c.c. of hot distilled water on the precipitate, and again decant on to a filter, transfer the pre- cipitate to the filter, and finally wash it free from all traces of oxalates and chlorides. Dry and ignite the precipitate, weigh and estimate as CaO : care- fully moisten with H2S04, heat gently and weigh as CaS04. Magnesia.—Concentrate the filtrate and washings from the last procedure to 200 c.c, place in a half-litre flask, add 30 c.c of a saturated solution of Na2HP04 and 20 c.c. of concentrated ammonia, cork the flask and shake violently, till crystals form, then set the flask to cool. Filter off the clear liquid through a tared Gooch filter, transfer the precipitate to the filter, and Avash with dilute ammonium hydrate (1 to 3) till the filtrate is free from phosphates ; dry and ignite the crucible, to form magnesium pyrophosphate. The increase of Aveight x 0*36024 = MgO. Sulphuric Acid.—Evaporate 200 c.c. of solution " A " nearly to dryness to expel the excess of acid: then add 100 c.c. of distilled water, boil, and add 10 c.c. of a solution of BaCl2 and continue the boiling for five minutes. When the precipitate has settled, pour the clear liquid on to a tared Gooch filter, treat the precipitate with 50 c.c. of boiling water, and transfer the precipitate to the filter, and Avash with boiling water tdl the filtrate is free from chlorides. Dry the filter and ignite. The increase in weight is barium sulphate, which x 0*412 = S04 in 2 grammes of air-dry soil. Potash and Soda.—To another 200 c.c. of solution "A" add BaCl9 in slight excess, and make alkaline with ammonia to precipitate sulphuric and phosphoric acids, ferric oxide, &c Then precipitate the calcium and barium by (NH4)2C204. Evaporate the filtrate and washings to dryness, heat to decompose oxalates and expel ammonia salts, dissolve in 25 c.c. of distilled water, filter and wash the precipitate : add to the filtrate and wash- ings 10 c.c. of baryta water and digest for an hour. Filter and wash the precipitate, add ammonium carbonate to the filtrate to complete precipitation of the baryta, filter and wash this precipitate. Evaporate the filtrate and washings in a tared dish, gently ignite residue to expel ammonia salts, cool and weigh. The increase of weight represents chlorides of sodium and potassium in 2 grammes of soil. If the potassium chloride be separated and estimated by platinic chloride, and its weight subtracted from the weight of the chlorides of potassium and sodium, the difference wdl represent sodium chloride. Nitrogen of the Soil—The nitrogen compounds in the soil maybe placed in three classes :—(1) The nitrates and nitrites, existing as soluble salts ; (2) ammonia, or organic nitrogen easily converted into ammonia; (3) the humus nitrogen, or the inert nitrogen of the soil. Active Soil Nitrogen.—For reducing the nitrates to ammonia, and at the CHEMICAL EXAMINATION OF SOIL. 481 same time to bring ammonia salts and organic nitrogen into a condition for separation by distiUation, the best material is sodium amalgam. This may be readdy prepared by placing 100 c.c. of mercury in a half litre flask, covering the warmed mercury with melted paraffin, and dropping into the flask at short intervals pieces of metallic sodium the size of large peas (taking care that the violence of the reaction does not project the contents from the flask), till 6*75 grammes of sodium have combined Avith the mercury. The amalgam contains 0*5 per cent, of sodium, and may be preserved in- definitely under the covering of the paraffin. To estimate the active soil nitrogen, weigh 50 grammes of air-dried soil and place it in a clean mortar. Take 200 c.c. of ammonia-free distilled water, rub up the sod with a part of the water to a smooth paste, transfer this to a flask of 1 htre capacity, washing the last traces of soil into the flask with the rest of the Avater. Add 25 c.c. of the hquid sodium amalgam, and shake so as to well distribute the amalgam through the soil. Insert a stopper with a valve, and set aside in a cool place for twenty-four hours. Pour into the flask 50 c.c. of milk of lime, and distil on a sand bath 100 c.c. into a flask containing 20 c.c. of deci-normal sulphuric acid, and titrate with deci-normal soda solution, using dimethyl orange as an indicator. Estimate the nitrogen of the ammonia found as active soil nitrogen. If the ammonia produced is too small in amount to be readily estimated volumetricaUy, determine the ammonia by Nesslerising the distillate. Estimation of Nitrates in the Soil.—When it is desired to estimate separately the nitrates in the sod, the following method may be used. Evaporate 100 c.c of a sod extract to dryness: dissolve the soluble portion of the residue in 100 c.c. of ammonia-free water, filtering out any insoluble residue, place the solution in a flask, and add 10 c.c. of liquid sodium amalgam, insert stopper with valve, set aside in a cool place to digest for twenty-four hours, add 50 c.c. of milk of hme, distil and titrate as above, finally estimating the nitrogen as N205. If the amount of nitrates is small, Nesslerising may be substituted for titration. An approximate estimation of the nitrates may be made by evaporating a measured quantity of a soil extract, say 5 c.c, on a porcelain crucible cover, having first dissolved a minute fragment of pure brucine sulphate in the sod extract. When dry, pour over the residue concentrated H2S04, free from nitrates, and observe the colour reactions produced. A simple pink in- dicates about the two-thousandth part of a mdligramme, reckoned as KN03; a pink Avith faint reddish lines about the three-thousandth of a milligramme; a reddish colour about a four-thousandth part, and a distinct red a five- thousandth part of a milligramme. Blank experiments to test the acid and the brucine will be required before confidence can be placed in such estimations. Total Nitrogen of Soil.—The total nitrogen of soils may be determined by the usual combustion with soda-lime, but this process is often unsatis- factory because of the large amount of material required when the organic matter or humus is small in amount. A modification of the Kjeldahl method is more easy to carry out and gives equally satisfactory results. Place 20 grammes of soil in a Kjeldahl flask, and add 20 c.c. of H2S04 (free from ammonia) holding in solution 1 gramme of salicylic acid. If the sod contain much lime or magnesia in the form of carbonate, more acid may be needed, enough being added to secure a strongly acid condition of the flask contents. Add gradually 2 grammes of zinc dust, and mix by shaking. Heat to boihng in a sand bath and boil for ten minutes. Add 1 gramme of mercury and continue boihng for one hour, adding 10 c.c. of H2S04 if the flask contents are likely to become 2h 482 SOIL. solid. Cool, and Avash out the soluble matter Avith 200 c.c. of pure water, leaving the heavy earthy materials. Rinse the residue with another 100 c.c. of Avater and add this to the first washing. Place this soluble acid extract in a litre digestion flask, add 35 c.c. of a solution of potassium sulphide, and shake to secure intimate mixture. Introduce a feAv fragments of granulated zinc, pour in 75 c.c. of a saturated solution of caustic soda, connect the flask with a condenser, and distil 150 c.c. into a flask containing 20 c.c. of deci-normal sulphuric acid and titrate Avith deci-normal soda solu- tion. Enter the nitrogen obtained from the ammonia produced in this operation as total soil nitrogen. The difference between the total soil nitrogen and the active soil nitrogen will express the inert nitrogen of the soil. Carbon Dioxide.—Introduce 5 grammes of soil into a small wide-mouthed flask and moisten with a little Avater. A short test-tube is filled two-thirds Avith HC1 and introduced so that its top rests against the shoulder of the flask, and that no acid escapes. A perforated cork with two tubes is now attached. One tube reaches to the bottom of the flask and extends well above the cork and is itself closed by a small cork. The other tube, which does not extend much below the cork of the flask, is bent thrice at right angles, and finally fitted into a wider tube 8 inches long and drawn to a point at its further end. This tube has a plug of cotton wool at either extremity, the intermediate space being filled with small fragments of neutral calcium chloride, previously well dried. The whole apparatus is now weighed. After Aveighing, the flask is slightly inclined, so that a little acid Aoavs out of the tube: it is then mixed with the soil by gentle agita- tion : this is repeated until the soil ceases to effervesce. The flask is then warmed : when nearly cold, the small cork in one of the tubes is removed, and air slowly drawn through the apparatus by suction apphed to the piece of india-rubber tubing attached to the open end of the calcium chloride tube : this is continued until all the carbon dioxide has been removed : the httle cork is now replaced, and the apparatus, Avhen quite cold, weighed: the loss in weight is carbon dioxide. Some practice is needed to get fairly exact results with this apparatus. The following table gives the analyses of several kinds of soil, as made SL fent observers: they are of interest, as showing how one soil may differ from another in composition. 1 Lincolnshire Fen Soil. (Wilson.) Bedfordshire Loam Soil. (Voelcker.) Gloucester-shire Stiff Clay Soil. (Voelcker.) Essex Marl. (Voelcker.) Maltese Chalk Marl. (Playfair.) Punjab Alluvium. Moisture, Organic matter anc combined Avater, Ferric oxide, . Alumina, Lime, Magnesia, , Potash, . Phosphoric acid, Sulphuric acid, Carbon dioxide, Chlorine, Silica and insoluble matter, 1 17-73 23-40 4-89 4-18 1-95 0-21 0*11 1-20 0-15 0-72 0-03 45-43 19-61 8-85 6-35 3-43 0-48 0-46 0-33 0-22 0-14 0-05 60-08 15-53 3-62 1-76 1-70 0-74 0-60 0-27 0-38 75-40 3-51 10-50 5-36 2-19 17-62 0-25 0-62 0-77 0-04 0-92 0-07 58-15 7-62 9-33 1-11 3-26 23 77 0-53 0-55 0 90 0-12 0-03 52-78 3-06 4-56 3-32 7-43 1-60 0-44 0-52 0-91 78-16 100-00 100-00 10000 | 100-00 i 100-00 100-00 BIBLIOGKAPHY AND REFERENCES. 483 BIBLIOGRAPHY AND REFERENCES. Adams, " On the Relationship between Diphtheria and Movements of the Ground Water," Proc. 8th Internal. Congress of Hyg. ccnd Demog., Buda-Pesth, 1894. Airy, Proc. Internat. Med. Congress, 1881. A. M. D. Reports, various papers, notably in years 1871, 1872, 1873, 1882, 1885. Arnould, "Les Micro-organismes dans le sol," Annates d'Hygiene, 1885. Ballard, Local Government Board, Report of Med. Officer, 1888. Barnes, Brit. Med. Journ., vol. ii., 1888. Baumoarten, Studicn iiber die Absorptionsfahigkeit der Bodenarten, Munchen, 1889. Beare, Proc. Instit. of Civil Engineers, 1892, pp. 341-369. Bird, Manual of Geology, Lond., 1894. Brewer, " On the Origin and Constitution of Soils," Connecticut State Bd. of Agricul., 1877-8. Buchanan, 9th and 10th Bep. Med. Off. Privy Council, 1866-7. Buhl, Zeitsch. f. Biologic, Bd. i. p. 1. Burdon-Sanderson, Report on Health of Liverpool. Cameron, Trans. Roy. Acad, of Med. in Ireland, vol. vi., 1888. Copeman, Article on "Soil," in Stevenson and Murphy's Treatise on Hygiene, vol. i., 1892. Cunning- ham, lZth Ann. Rep. of San. Comm. with Govt, of India, 1878 ; also in Sci. Mem. of Med. Offs. of Army of India, Calcutta, Parts iii. andiv., 1888-9. Daubree, Les Eaux Souterraines, Paris, 1887. De Chaumont, Lectures on State Medicine, 1875. Delesse, "Duree des paves et des gres," in Ann. des Bonis et Chaussees, vol. v., 1854. Dempster, " Influence of Different Kinds of Soil on the Cholera and Typhoid Fever Organism," Brit. Med. Journ., i., 1894, pp. 1126 and 1140. Ebermayer, Die physical Eimccrkungen des Waldcs auf Luft u. Boden, Berlin, 1875. Everett, Beport of British Association, 1879. Podor, Hygienische Untersuchungen iiber Luft, Boden, und Wasser, Braunschweig, 1882. Forbes, Edin. Meteor. Beports, 1S83-4-7. Frankland, Zeitsch. f. Hygiene, Leipzig, 1889, vi. p. 373. Hirsch, Geograph. and Historical Bathology, New Sydenham Soc, 1886. Hunt, Chemiccd and Geological Essays, Lond., 1879. Kelly, Broc. Brit. Med. Assoc, 1886. Latham, Transac. Sanit. Instit., 1886. Lewis, Physiol, and Patholog. Besearches, Lond., 1888. Lloyd, Science of Agriculture, Lond., 1884. Miers and Crosskey, The Soil in Relation to Health, Lond., 1893. Nichols, Sixth Rep. of Massachusetts Board of Health, 1875. North, " Lectures on Malarial Fevers," Brit. Med. Journ., vol. i., 1887. Pettenkofer, Zeitsch. f. Biol., 1871, vii. p. 395 ; also Die Boden und sein Zusammen- hang mit der Gesundheit des Menschen, Berlin, 1882. Pfaff, Zeitsch. f. Biol., Bd. iv. p. 249. Poore, "The Living Earth," Lancet, vol. ii., 1890. Prestwich, Geological Conditions affecting the Water Supply to Houses and Towns, Oxford, 1876. Ransome, "Soils and Sites," Health Lectures, Lond., 1884-5. Reuk, "Uber die Permeabilitat des Bodens fur Luft," Zeitsch. f. Biol., Munchen, 1879, xv. p. 205. Smolensky, "Uber den Kohlensauregehalt der Grundluft," Zeitsch. f. Biol., 1877, xiii. 383. Soyka, " Der Boden," Handb. d. Hyg., Leipzig, 1887 ; also Zeitsch. f. Hyg., 1887, ii. p. 96. Tomkins, Brit. Med. Jour., 1889, ii. p. 180. Warington, Journal of Chem. Soc. Lond., 1884, vol. xlv. Wolffhugel, " Uber den Kohlensauregehalt im Gerbllboden von Munschen," Zeitsch. f. Biol., xv. p. 98. Wollny, Der Einfluss der Panzendecke auf der Physic Eigenschaften des Bodens, Berlin, 1877. CHAPTER IX. HABITATIONS. " Whoever considers carefully the record of the mediaeval epidemics, and seeks to interpret them by our present knoAvledge of the causes of disease, will surely become convinced that one great reason why those epidemics were so frequent and so fatal was the compression of the population in faulty habitations. Ill-contrived and closely packed houses, with narrow streets, often made Avinding for the purposes of defence; a very poor supply of water, and therefore a universal uncleanhness; a want of all appliances for the removal of excreta; a population of rude, careless, and gross habits, living often on innutritious food, and frequently exposed to famine from their imperfect system of tillage,—such Avere the conditions which almost throughout the whole of Europe enabled diseases to attain a range, and to display a virulence, of which we have now scarcely a conception. The more these matters are examined, the more shall Ave be convinced that we must look, not to grand cosmical conditions; not to earthquakes, comets, or mysterious waves of an unseen and poisonous air; not to recondite epidemic constitutions, but to simple, familiar, and household conditions, to explain the spread and fatality of the mediaeval plagues." GENERAL CONDITIONS OF HEALTH. The diseases arising from faulty habitations are in great measure, perhaps entirely, the diseases of impure air. The site may be at fault; and from a moist and malarious sod excess of water and organic emanations may pass into the house. Or ventilation may be imperfect, and the exhalations of a crowded population may accumulate and putrefy; or the excretions may be allowed to remain in or near the house; or a general uncleanhness, from want of water, may cause a persistent contamination of the air. On the other hand, these five following conditions insure healthy habitations :— 1. A site dry and not malarious, and an aspect which gives light and cheerfulness. 2. A pure supply and proper removal of water; by means of Avhich perfect cleanliness of all parts of the house can be insured. 3. Asystem of immediate and perfect sewage removal, which renders it impossible that the air or Avater shall be contaminated from excreta. 4. A system of ventilation which carries off all respiratory impurities. 5. A condition of house construction Avhich insures perfect dryness of the foundation, walls, and roof. In other Avords, perfect purity and cleanliness of the air are the objects to be attained. This is the fundamental and paramount condition of healthy EFFECTS. OF OVERCROWDING. 485 habitations; and it must over-ride all other conditions. After it has been attained, the architect must engraft on it the other conditions of comfort, convenience, and beauty. The inquiries Avhich have been made for many years in England have fihoAvn Iioav badly the poorer classes are lodged, both in town and country, and how urgent is the necessity for improvement. Various Acts have been passed for the purpose of improving the condition of the dwellings of the Avorking classes, but either from lack of energy in carrying out their provisions, or from the difficulty of proving that a dAvelling is injurious to health unless it is in extremely bad condition, these Acts have had hitherto only partial effect. In towns, density of population has a direct influence on the mortality~of" its inhabitants. Ogle, in the Supplement to the 45th Annual Report of the Registrar-General, illustrates the connection between the aggregation of the population and the death-rate, and clearly shows that after the density has reached a certain degree of intensity, it begins to exert an appreciable effect. Russell also points out the evils connected Avith overcrowding, and shows that Aberdeen, with a population of 13*6 per cent, living in one room, has the lowest death-rate of eight of the large Scotch cities, and that tins rises pari passu with the diminution in the size of the average house, until we reach GlasgoAv with 24*7 per cent, of its population living in one room, and the highest death-rate. Back-to-back houses illustrate very clearly the effect of density of population, involving as they do deficient light and ventilation and imperfect sanitary arrangements. Tatham has shown that at Salford the mortality from all causes, from pulmonary diseases, from phthisis, and from the seven chief zymotic diseases taken together, as well as from diarrhoea alone, increases pari passu with the pro- portion of back-to-back houses. "The more croAvded a community, the greater, speaking generally, is the amount of abject Avant, of filth, of crime, of drunkenness, and of other excesses, the more keen is the competition and the more feverish and exhausting the conditions of life; moreover, and perhaps more than all, it is in these crowded communities that almost all the most dangerous and unhealthy industries are carried on. It is not so much the aggregation itself, as these other factors which are associated Avith aggregation, that produce the high mortality of our great towns or other thickly populated areas." Parr states that it is proved beyond doubt that if the population be the same in other respects, an increase of density implies an increase of mor- tality ; and he gives five groups of cases, shoAving the varying mortality Avith density of population. Where the population was 86 persons to 1 square mile, the mortality was 14, 15, or 16 per 1000. Where the population was 172 persons to 1 square mile, the mortahty was 17, 18, or 19 per 1000. Where the population was 255 to 1 square mile, the mortality Avas 20, 21, and 22 per 1000. Where the population was 1128 persons to 1 square mile, 23, 24, or 25 per 1000. Where the population was 3399 persons to a square mile, the mortality Avas 26 per 1000 and upwards. The later returns of the Registrar-General for England and Wales prove that where crowding exists it is a source of ill-health. There is also another factor which commonly accompanies overcrowding, and wlhch reacts upon the community in the form of increased morbidity and mortality rates, and that is an abnormally high birth-rate. In the slums of large cities, and crowded dwellings, there are invariably high birth and death rates. The following tables illustrate this fact:— 486 HABITATIONS. Table of Six Densely Populated Towns, 1892. Town. Population. Persons per acre. Birth-rate per acre. Death-rate per 1000. London, .... 4,263,294 57-1 30*9 20-6 Liverpool, .... 513,790 98-6 347 24*7 Plymouth, .... 85,610 58*3 29-1 18*8 Bolton, .... 116,261 48*4 327 22*8 Manchester, 510,998 40-0 33-7 23*8 Salford, .... 210,058 38-9 35-9 24*6 Averages of the six towns, 56-88 32-83 22*55 Table of Six Toions not so Densely Populated, 1892. Town. Population. Persons per acre. Birth-rate per 1000. Death-rate per 1000. Croydon, .... Huddersfield, Nonvich, .... Halifax, .... Bradford, .... Oldham, .... 106,152 96,599 102,736 84,097 219,262 134,221 11-8 8-2 13-7 22-3 20-3 28-4 26-5 23*0 30*5 25-9 27-2 29-1 15*8 18-1 20-0 19*5 18*0 22-0 Averages of the six towns, 17-45 27-03 18*90 In the Report to the Local Government Board by Ballard, upon the causation of the annual mortality from diarrhoea, he shows that, among the more important conditions influencing diarrhoeal mortality, aggregation of the population favours, and dispersion over an area disfavours, diarrhoea, and that density of buildings, of Avhatever kind, upon an area promotes diarrhoeal mortality. Sites.—In towns and villages, the sites of additional or substituted dwellings are generally fixed irrespective of the advice of anyone. In the case of isolated dwellings, however, Avhere selection can be made, adverse conditions in the site may render the best designed and best built structure unhealthy. It is therefore desirable to knoAv what to select, or at least understand what to avoid in making a selection. The question involves the following considerations:— 1. The aspect or exposure to wind, light, and air. 2. The ground or soil on which it is proposed to budd. 3. The surroundings of the site. Aspect and shelter have each their bearing on the salubrity and equality of temperature. While the situation should afford a free circulation of air about the dwelling, it is advisable to avoid exposure to a prevailing cold Avind, and it may be necessary even to secure shelter from this by means of a belt of trees or some rising ground. But neither aspect nor shelter has an influence so great as the condition of the ground or soil beneath and surrounding the dAvelling. Dryness of site is essential to both these advantages. A damp subsoil SITES. 487 for the foundation of a house is known to favour the prevalence of disease, and is, perhaps, one of the most fruitful sources of impurity of air in dwellings. Wherever possible, the soil or ground itself ought to be porous, such as gravel or sand, which allows the water to run freely away, or chalk, Avhieh retains but comparatively little moisture, and does not cause damp- ness to collect about the house. The next best soils on which to build are rocks, such as granites, clay slates, limestones, or sandstones; nearly all these have a good slope, and are easily drained. The loams and stiff clays are not, as a rule, good soils for building purposes, as, unless well drained, they are apt to hold Avater; if, however, adequately drained, these are not necessarily unhealthy. In these sods numerous drains are requisite to overcome the retentive properties which such soils possess. The greater the number, the better Avill that purpose be fulfilled. In free soils, i.e., sand, gravels, and chalk, as a rule, no advantage is gained by multiplying drains beyond the minimum number that will lower the subsoil water, and they should be as far removed from buddings as possible. Pure chalk forms a healthy site, being perme- able ; but if the chalk be mixed with clay (marl), or be underlaid with clay, it becomes impermeable and damp. If of any thickness and not situated in a hollow, gravel beds make good building sites. The worst soils are the shallow beds of gravel or sand lying on clay; these are frequently water-logged and proportionately bad; the same remark applies to reclaimed lands near the mouths of rivers and the so-called alluvial lands, which consist of soils that are really the deposit or sludge from rivers. Alluvial tracts are almost invariably unhealthy, owing not only to their dampness, but also to the large quantity of organic matter which they contain. These soils and sites are peculiarly liable to produce chronic rheumatism, ague, and various forms of malarial fever, as Avell as catarrhs and neuralgia. If the site is artificially made, care must be taken to see that the subsoil is free from organic pollution of any kind. In the low-lying parts of towns and cities, or where the subsoil has been excavated for sand. or gravel, the place is used frequently as a tip for rubbish of all kinds until the level is raised to a sufficient height to allow of its being utihsed for building purposes. From a report made by Parkes and Burdon-Sanderson on the sanitary condition of Liverpool, experiments, having for their object to ascertain Avhat the effect of time had been on the organic matters which, together Avith cinder refuse, had been used to fill up inequalities of ground, tended to show that the process of decay of all the most easily destructible matters, including vegetable refuse, is completed in three years; but it is very doubt- ful if modern methods of investigation would not prove that this limit of time is far too short to allow such a site to be built upon, unless the whole ground surface or site of such building be asphalted or covered with a layer of concrete cement or some other impermeable material. This concrete should be 6 inches thick : its component parts should be ballast, consisting of broken stone, gravel or burnt clay of a clean descrip- tion and Portland cement of the best quality, in the proportion of five of ballast to one of cement, with enough sand to fill up interstitial spaces. It is desirable to cover the ground forming the base of the dwelling with concrete extending from one outside wall to the other. This will not only prevent dampness and "ground air" rising from the underlying soil into the house, but it will also prevent any liquid refuse sinking into the ground to pollute the soil beneath. As a rule, cellars under houses add to their 488 HABITATIONS. healthiness, especially if properly built on an impervious flooring and adequately ventilated. In all sites it is important to notice the distance of the ground water from the surface. If this AA^ater is too near the ground level, the site will be damp : it ought never to be nearer the surface than 8 feet, and, if possible, should be at least 15 or 20 feet beloAv the ground line. When- ever ground is Avater-logged, owing to Avant of an outlet, Avhether the soil be an open gravel or dense clay, it Avill afford a bad site, unless the subsoil water is loAvered by drainage to such a sufficient depth as not only to reduce evaporation, but to prevent the rising of moisture up to the cellar floors and the foundations of the dwelling. There is reason to beheve that frequent and sudden changes of Avater- level are specially unhealthy, and where these occur the place will not be a good site. Statistics for many years go to sIioav that AA-here the ground water level has been loAvered and the soil made drier, there the public health has improved. Buchanan, in his report upon the influence of sewage Avorks on the public health, states that the general death-rate of Newport in South Wales Avas reduced 23 per cent., while phthisis was reduced 32 per cent. At Cardiff the general death-rate was reduced 24 per cent, and the death-rate from phthisis 17 per cent. At Salisbury the general death-rate was reduced 9 per cent., and that due to phthisis 49 per cent. The most essential points to be sought for in regard to a choice of site for building purposes are as folloAvs :— 1. A moderately elevated spot, so that a fall from the building may be secured in one direction at least, sheltered from the north and east, but not so shut in as to impede the free circulation of air round and over it. 2. The site should, if possible, be upon a porous soil, such as gravel and sand, care being taken to see that the subsoil is sufficiently permeable to secure thorough drainage, either naturally or artificially. When a house must be built on a retentive soil great precaution must be taken effectually to drain the subsoil and to obviate the dampness of the site as much as possible by the use of concrete. 3. The ground water should not be nearer the surface than 8 feet, and not subject to either great or sudden fluctuations. 4. The surface soil and subsoil, no matter what their nature, should be clean and not fouled by either seAvage or refuse. 5. The site must also be chosen that sufficient facilities shall be secured for drainage and Avater-supply. Construction of Dwellings.—The foundations ought to be sufficiently solid and deep enough in the ground to give firmness to the building. When the ground is soft, or a solid foundation cannot be reached, the walls should be built upon a solid platform of concrete or stone, Avhich should be at least four times as broad as the Avails. The bases of the walls themselves should be expanded into Avhat are called footings, the lowest course of which should be at least tAvice the breadth of the Avail. The height of the footings ought not to be less than tAvo-thirds of the Avail thickness. To prevent moisture from rising up the Avails of dAvellings, it is now usual to build them on a layer of concrete. In addition to this base of concrete, it is necessary to have a layer of impervious material, i.e., a damp-proof course within the wall itself. The proper height at which to insert a damp-proof course in external walls is a feAv inches above the natural ground line, and in internal walls on a level Avith the bottom of the concrete. Damp-proof CONSTRUCTION OF DAVELLINGS. 489 courses are made of different materials. Sometimes a double course of slates bedded in cement is used: sometimes a layer of sheet lead is placed throughout the Avhole length of the Avails; perforated stoneAvare tiles embedded in cement have also been applied to the same purpose; these have the double advantage of not only preventing the uprising of moisture, but they also act as a means of ventilating the spaces between the ground beneath and the joists of the floor. All dwellings possessing basement floors under the level of the natural sur- face of the ground should have outside areas or dry passages between the ground and their walls. This can usually be secured by digging away the earth on the outside to below the level of the floor so as to form a dry area. As an alternative plan to this, a device recommended by the Local Government Board in their Model Bye-kws may be employed; this consists in making the wall hollow up to a point above the ground level, and then inserting tAvo damp-proof courses, one at the bottom of the hollow, and beloAv the floor level, the other at the top of the IioIIoaa-, and, therefore, above the Fig. 65. outside ground level. By this means the inner Avail is quite shut off from the soil. Both these arrangements are shoAvn in fig. 65. The materials generally used for the construction of Avails of dwelling- houses are bricks, stones, and wood. Bricks are made from three kinds of earth, namely, pure clays, marls, and loams. Pure clay consists chiefly of alumina and silica; marls are clays having a considerable amount of lime in them; while the loams are light and sandy clays. Few bricks are made solely from any one of these earths, but rather from an admixture of all three. Bricks are burnt in kilns or clamps. Kiln-burnt bricks are more uniform in quality than clamp-burnt: the latter have part of the fuel mixed with the clay, and traces of it can be detected in the bricks after they are burnt. A good brick should be regular in shape, well burnt, of a uniform colour, and when struck give a clear metallic ring. A good ordinary brick should not weigh less than about 5 lb, and usually measures 9 inches long, 4^ inches broad and 2\ inches thick = 101-]- cubic inches. The dimensions vary slightly in Scotland and Ireland. Ordinary bricks absorb about one-sixth 490 HABITATIONS. of their weight of Avater; very hard bricks, such as the blue Staffordshire, about one-fifteenth or one-tAventieth. So porous are ordinary bricks that both rain and air can be easily driven through them ; in fact, so much is this the case that it is desirable in all dwellings that the outer walls should, if of brickwork, be at least a brick and a half thick (14 inches), so that in addition to the bricks there may be in the structure of the wall itself a layer of mortar. Mortar is a compound of one part of lime with three parts of clean sharp sand made up with fresh water. Sand is added to check shrinkage, either in drying or by absorption of carbonic acid from the air. Bricks are superior to any other material for house wads. Two kinds of stone are generally used for house building; they are sand- stone and limestone. Sandstone has been described as sand made into a cake with clay, lime, and oxide of hon. It is the varying amount of this latter which gives the various colours to it, such as red, yellow, and grey sandstone. Limestone is rock composed mainly of carbonate of hme. Like bricks, stone is both porous and absorbent of water, but in a less degree. No woodwork should be placed in a wall except where it is necessary for carrying the floors or roof, or for fixing the fitments of a building, and then it should be so arranged that the shrinking or decay of the wood will' not affect the strength of the wall. When the ends of flooring or other timbers are placed in the wall for support, they should rest on stone- templates, and space for ventilation should be left all round them: the wall above must not rest upon them. Wood enters largely into the construction of the inner fittings of all dAvellings. In its natural state it is very absorbent, and the unavoidable cracks and crevices admit both air and water. The chief kinds used are ash, beech, oak, elm, pine, and larch. The first four differ from the latter in being free from turpentine. Good timber should be close and straight grained, free from cracks and dead knots, and well seasoned. The walls of all dAvelling-houses should be most carefully built from the foundations upwards, whether of brick or stone, with a layer of mortar not only between each course, but under the first course and well fitted into the vertical joints. Bricks are laid in beds or courses, and are usually spoken of as being bonded together. English bond is the strongest and simplest for all ordinary work. The heading and stretching courses generally alternate, but not necessarily. No bricks in the same course should break joint with each other. Plemish bond shoAvs headers and stretchers alternately in each course. It is not so strong as Enghsh bond, but gives a better appearance, as a smoother face can be shown on both sides. The thickness of the external Avails of dwelling-houses is determined by the size of the building, more particularly by its height. According to the Model Bye-laws of the Local Government Board, the minimum thickness should be as follows:—When a wall is not over 25 feet in height, if it does not exceed 35 feet in length and do not comprise more than two stories, it shall be 9 inches for its whole height, but if it do comprise more than two stories or exceed 35 feet in length, it shall be 131 inches below the topmost story and 9 inches for the rest. When walls are over 25 feet high and not exceeding 35 feet in length, they should be 13^- inches thick below the topmost story and 9 inches for the rest; but if they be longer than 35 feet, then they must be 18 inches thick for the height of one story, then 13 J inches thick for the rest of the height beloAv the topmost story, and 9 inches thick for the rest of its height. Walls over 35 feet high must be 18 AVALLS AND ROOFS. 491 inches thick for the first two stories and 13J inches for the rest. If over 50 feet in height, Avails should be 22 inches thick for the height of one story, then 18 inches for the next two stories, and finally 13J for the rest of the height. Walls built of cut stone need be no thicker than those of brick, but if of rough stone or flint and boulders, they should be at least one-third thicker. Walls made of both brick and stone are not uncommon; the chief point about them is the need of careful bonding together of the two elements. Occasionally walls are made of concrete either rammed doAvn in layers, or else built of concrete blocks Avell cemented together. Wood is at times used in making the upper part of the outer walls of houses; when so employed, it needs to be backed with at least 4| inches of brickwork and Avell bonded together. Owing to the absorbent and porous nature of all these materials, special care must be taken that outer walls constructed of them do not admit damp, especially when in positions much exposed to rain and wind. Different means are adopted for resisting the effects of driving rain; in some parts, vertical slating of the external walls is used, while in other places plain tiles are substituted, and present a much more agreeable appearance. HoUow external walls are almost sure preventives against damp, and by their adoption in exposed localities the dAvelling is not only rendered drier, but is made warmer in winter and cooler in summer. They consist of two thicknesses of brickwork separated by an air space of 2 or 3 inches, with a carefully devised admission of outer air, Avhich should circulate through the hollow spaces. The two thicknesses should be tied together by bonding ties of iron; bricks are not recommended for this purpose, for any existing outside moisture can be absorbed by the end of the brick, and through it conveyed inwards, thus neutrahsing the benefit that would otherwise be derived. A damp-proof course is needed at the top of exposed walls, such as parapets and chimneys; this is usually provided by finishing the top of the wall either AAith a stone or letting it project an inch or two over the side, or else having an impervious damp-course laid in the wall or chimney at its junction with the roof. During the building of house walls, care should be taken that the chimney flues are properly constructed. They should be made as straight as possible and separate one from another. The circular form is the best. as it is easy to clean, and the draught is more regular through it. They should contain no woodwork, and may with advantage be lined with a casing of sheet iron, an arrangement which not only disconnects the flue from the house structure, but favours cleansing and the maintenance of an up-draught. All chimneys should be higher than surrounding buildings, so that they may be in no way sheltered when the wind is in a certain direc- tion, nor a down-draught set up. Defects in roofs of buddings are a frequent cause of dampness. The more common materials used in making roofs are slates and tiles, and less often, thatch, wood, zinc and corrugated iron. Slates should be hard yet not brittle, free from streaks or flaws and give a metallic ring when struck. They should not absorb more than 5 per cent, of water in twenty-four hours. If stood half their depth in water for several hours, the moisture should not rise to the top. They should be uniform in size, thickness, and colour, roughish and not greasy on the surface, free from white iron pyrites, and from large crystals of yellow pyrites; if of poor quality they are apt to scale and readily break away. Tiles, like bricks, are made of clay, but need more careful drying and burning. They should be hard and as little 492 HABITATIONS. absorbent of Avater as possible. Thatch forms a warm and dry roof, but is very liable to be infested by birds and vermin; the danger from its liability to fire is great, and on this account it is seldom used. AYood is also used, but is open to the same objection. Zinc and corrugated iron are not suited for dwelling-houses; they are extremely hot in summer and cold in Avinter. In all buildings it is important to see that there is a frameAvork sufficiently strong to bear the weight of the material and in addition a certain amount of snoAV; in England this is not likely to accumulate to a greater depth than 6 inches and may be taken at 5 ft) per superficial foot of horizontal surface. The effect of Avind has also to be provided for, and this may be taken at 50 lb per square foot on the surface perpendicular to its direction. Rankine states that the maximum observed in Great Britain is 55 ft). The framework is usually made of Avood. The angles of roofs for different coverings are as follows :—Zinc, 4°; large slates, 22°; ordinary slates, 26°*3; pantiles, 24°; thatch of straAv, 45°; plain tiles, 45°. House roofs should always be covered with boarding laid at right angles to the rafters, and, if possible, some non-conducting material between this and the slates, such as " Slag-felt," which not only makes the house cooler in summer, but Avarmer in winter. Laths are nearly always substituted for boards in roofs; this should not be, as they are much less satisfactory. When slates are used they should be fastened to the boards with zinc nails; composition nails are sometimes used but the heads break off. If iron nails are used they should be galvanised, or boiled in linseed oil. The part of each slate exposed to view is called the gauge. The lap is the distance which the loAver edge of any course overlaps the slates of the second course beloAv, measuring from the nail hole; it should not be less than 2 inches, but 3 inches is better. The flatter the pitch the greater the lap required. Tiles are often fastened with Avooden pegs or hung on tAvo special projections. Zinc and iron roofs are laid nearly flat in widths, with their edges overlapping to alloAV for expansion and contraction. The gutters round chimneys and party Avails where they join the roof are frequent places for leaks; they all should be made of lead, the edges of which should pass Avell into the brickwork ; cement, if used for this purpose, is hable to crack. The eaves of roofs are finished in different ways. If eaves-boarding is used, they should come out some distance beyond the Avails, and be provided with a gutter so as to throw off the rain well away from the house. These gutters should be made of cast iron : for an ordinary roof they may be 5 inches deep with a slope of 1 in 10 inches; but they are usually fixed horizontally for appearance sake, and must then be larger than is necessary to- carry off the water. The gutters should discharge into rain pipes made also of cast iron, 4 inches in internal diameter and placed at intervals of 50 feet. These rain-water pipes should discharge into properly ventilated rain-water tanks, or over a drain covered by a grating. They should never be directly connected Avith drains or seAvers, neither should they be placed with their heads just beloAv bed-room windoAvs, more particularly Avhen they empty into a tank. Por the inner walls of a house, the use of plaster of a coarse quality covered by a thin layer of a finer kind is almost universally adopted to cover the internal Avail surfaces; this surface is generally papered. This practice has many disadvantages; the plaster, being porous, absorbs the moisture of the internal air, and with it any organic matters present in the air of inhabited rooms; Avhile paper, unless varnished, cannot be Avashed, and much dirt sticks to it. The flock papers and their cheap imitations are particular offenders in these respects. Limewashing is preferable to unglazed FLOORS. 493 and flock papers ; in all cases Avhere it is necessary to repeat lime Avashing, the Avail should be first scraped and the old coat thoroughly removed. Ploors are best made of impervious materials which can be washed. Wood, stone, or tile constitute the chief. Stones or tiles are suitable for sculleries and passages, but are cold for kitchens and living-rooms. Wood makes the best flooring, particularly if of hard Avood, such as oak or teak laid as parquet flooring. These, hoAvever, are very expensive. The ordinary Avood floor is generally made of deal. If made of deal, a floor can be well laid doAvn, provided that care be taken to tongue and groove the planks which constitute it. Cracks and crevices in floors should be avoided, as the enclosed space beloAv, between them and the ceiling of the next room, is apt to become a huge receptacle for dirt of all kinds. In the commonest description of floors, the edges of the boards are merely placed true and the boards are laid side by side as close as possible and then fixed by one or two nails driven into each joist. Their edges are then said to be plain or butt-jointed. This mode of laying boards is only tolerable in inferior buildings, as open joints invariably occur, owing to the unavoidable shrink- age of the boards. The grooved and tongued joint consists of forming a groove or channel along the edge of one board, and a projection or tongue Avhich resembles a continuous tenon to fit it on the edge of the other board, each board having a groove on one edge and a tongue on the other. When face-naded, each board should have tAvo nails where it crosses the joist. Skirtings are employed to hide the joint between the Avails and floor boards. They should, where possible, be of tiles, iron or cement, but if of Avood, they ought to be let into a groove in the floor, a device which will serve to prevent draughts coming through, and also the accumulation of dust in the holes and cracks Avhich are invariably formed by the shrinking of the joints and skirtings. When rooms in consecutive stories are only separated by a single floor, measures must be taken to prevent the passage of sound and smell. " Slag- felt," a patent preparation of slag-wood, has remarkable properties of deadening sound ; it further has the advantage of being fire-proof and does not harbour vermin. "Pugging," which generally consists of plasterers' rubbish, saw-dust, tan, chopped straAv, dried_ moss, &c, is objectionable, and should not be used for obvious reasons. It remains noAV to consider a few of the chief points as to the design and arrangement of dAvelling-houses. The chief object should be to make every use of the whole space in order to get as much accommodation and comfort as possible. If possible, rows of houses should run north and south, and ah square buildings should have angles in these directions, so as to get some sunlight in every room. In many modern houses the most frequent error is perhaps the cramped space allowed for halls and staircases. Plenty of space should be given for them, as, Avith ventilating windows at the top, they constitute the central ventilation of the house. All the rooms should be so placed as to get light and air directly from the outside ; and if there be any passages or lobbies they should be similarly lighted and aired. No room or closet which is not in direct communication with the outer air ought to be used as a sleeping-room. The size of rooms will depend upon questions of cost, convenience, and the purpose for which they are intended. The height of rooms should not be less than 9 feet and rarely need exceed 12 feet. Every room should have at least one window in it which opens to the outer air direct; if possible, it should open half its size, extending nearly to the top of the room and equal in area to at least one-tenth of the floor space. In addition, 494 HABITATIONS. every habitable room must have a fire-place and ought also to have some ventilating aperture, the sectional area depending on the size of the room and the number of occupants. In the construction of dwellings, one of the most important points is to select a proper position for water-closets. They should be placed in a separate or outstanding part of the house; and where there are several Avater- closets, these ought to be built one over the other, and quite confined to one part of the building. The closets themselves should be of the best construc- tion and efficiently disconnected from the drains. Each closet ought to have at least one Avindow of a minimum superficial area of 2 square feet opening direct into the outer air, and also have some means of special ventdation, so as to secure a circulation of air independently of that of the house. The floor and walls to a height of 5 or 6 feet should be of glazed tiles, and the remainder of the wall and ceiling ought to be varnished or painted. The more detaded account of the ultimate disposal of the contents of water-closets, &c, as well as their form and construction, is given in Chapter X. Artisans' Dwellings.—dn selecting a site, it is of great importance to secure sufficient area, a well-drained subsoil and a suitable aspect. The buildings should occupy about one-third of the entire site, leaving two-thirds for air, light, approaches, &c. The height of the buildings should not exceed five stories above the ground, on account of fatigue in ascent and obstruction of light and air. The yards are best spread with a 9-inch layer of cement concrete laid to falls for drainage; it may be finished with a coating of tar-paving. Staircases in blocks of artisans' dwellings should be built against an outside wall, so that Avindows may light them: the staircase should be made of stone or concrete, so as to resist the action of fire. The minimum width should be 6 feet 9 inches. Internal corridors are specially to be avoided, as they are difficult to light and consequently are usually dirty. The internal arrangement of a tenement should, as far as possible, assimilate to that of a well-planned country cottage, the size and number of the rooms depending upon local circumstances. A convenient size for the living-room or kitchen is 11 feet wide by 13 feet from front to back, the fireplace being so placed as to afford ample room in case of emergency for a bedstead. The windoAvs should not be less than 3 feet 6 inches in width, and should extend to within 6 inches of the ceiling, in order to obtain the utmost light and ventdation. The room should be fitted with a cooking range 3 feet in width and provided with an oven. A food store, ventilated from the external air, should also be available. In the Peabody Buildings the sinks as well as the water-closets are on the staircase landings, and used jointly by the occupants of tAvo or more tenements; they should be open to the constant inspection of the superintendents. The bed-rooms vary in size; usually they are about 13 feet by 9 feet. Fanlights over the doors are useful as ventilators. Every bed-room should have a fireplace, which wdl act as a ventilator. The Model Bye-laws of the Local Government Board suggest 300 cubic feet of air space for each adult and 150 for each child as a minimum in a sleeping- room ; it is necessary, therefore, to provide floor space equivalent to at least 6 feet 6 inches by 5 feet for each adult, and 5 feet by 5 feet 3 inches for each child. In the country more space is available, and a labourer's cottage comprises SCHOOLS. 495 generally a living-room with a small scullery attached, and sufficient bed-room accommodation. The most economical arrangement is found in a two- storied building, the height of the loAver story of Avhich should be 9 feet, and that of the upper not less than 8 feet. The living-room should have a minimum floor area of 150 square feet and be fitted with a cupboard for storing food, also lighted and ventilated by a separate window. The scullery adjoining the living-room should be 10 feet by 1\ feet; and there should be, if possible, a Avell-lighted, cool and dry pantry Avith an entrance from the scullery. The bed-rooms for adults should have at least 80 feet of floor area, and those for children 50 feet: all the rooms should have fire- places in them. The privy accommodation and places for deposit of refuse are in these houses best placed out of doors. They should be conveniently placed and afford as much privacy as is possible. Schools.—The Education Department of the Privy Council requires all schoolrooms to have a width from 18 feet to 22 feet, and states, that if the width does not exceed 20 feet, groups of three long desks must be used, but if the AAidth is 22 feet, then dual desks, five toavs deep, must be used. Each child or scholar must be allotted 18 inches on the long desks Avith gangAvays 18 inches wide between the groups. When the dual desks are used, and which are 40 inches long, then the gangways between them need be only 16 inches. The height of the rooms must be from 12 to 14 feet; these dimensions give an average floor space of 10 square feet and a cubic space of about 125 feet to each child. In infant schools, the floor space demanded is only 8 square feet per child, which, with rooms of the fore- going measurements, gives scarcely 100 cubic feet per head. These standards are decidedly low, and are only permissible if the warming and ventilation arrangements are so complete that the air of the room will be constantly changed without draught or unduly affecting the room tem- perature. The theoretical requirements for a child in an elementary schoolroom are 400 cubic feet, and for a boy in a large public school, 800 cubic feet as minima; such amounts will, however, seldom if ever be obtained. The best means for heating large schoolrooms is by steam or hot-water pipes connected with some central apparatus in the basement. The hghting of schoolrooms is of great importance. The window area should not be less than one-tenth of the floor area, and may with advantage be made quite one-sixth. Every window should be carried up to the ceding and be made to open from the top. They should be so placed as to permit of light being received direct from the sky into the room. Roof lighting Avhere practicable is the very best, but failing this, opposite Avindows facing east and west are to be recommended, since in rooms so arranged there is during school hours no direct sunlight for the greater part of the year. Should circumstances permit, windows may be made in the north wall also, as, excluding sunshine, there can never be too much light. If this is not possible, the Avindows should be so arranged as to admit the light on the left side of the pupils. For artificial lighting, electric lights or the incandescent gas light is preferable to oil or gas, not only on account of the greater purity and intensity of the light, but even more from the absence of heat and of the products of combustion Avhich add so much to the deteriora- tion of the air. The size and position of school desks and seats are closely connected with lighting and its influence on the eyesight. The height of the desk above the bench should be such that, when the child is sitting down, he can place both his forearms comfortably on the desk, Avithout raising or depressing his 496 HABITATIONS. shoulders; the height of the desk above the floor or surface on Avhich the foot rests should correspond Avith the length of the child's leg from knee to heel. When the child is sitting doAvn, his legs should not dangle in the air, nor should his knees be elevated above the bench. The desk should slope gently; the slope should not exceed an angle of 20°, or a difference betAveen the upper and loAver edge of the desk of about 3 inches vertically. The seat should be from 10 to 12 inches AAide and hollowed out towards the back to the depth of an inch. Every seat should have a back to support the sitter, hollowed in such a Avay that the upper part of it may fit the concavity of the back. The folloAving table gives the measurements of the " Hygienic" desk devised by Priestley Smith and which completely fulfils all the above conditions. Height of Scholars. Xo. l. 3 ft. 6 in.-l ft. No. 2. 4 ft.-4 ft. 6 in. No. 3. 4 ft. 6 in.-5 ft. No. 4. 5 ft.-5 ft. 6 in. Height of seat from floor, . 13 ins. 14i ins. 16 ins. 18 ins. Breadth of seat, 10 „ H ,, 12 ,, 13 „ Height of seat to edge of desk, . 8 ,, 8S „ H „ 10J „ Height of seat to top of back, 20 ,, 22 ,, 24 „ 26h „ " Overhang " of desk, 1 „ 1 ,, n „ n „ Play of desk, .... 4i „ 4* ,. G ,, 6 ,, Breadth of desk (front to back),. 15 ,, 15 „ 17 „ 17 „ As regards school dormitories, the usual width of the room in the Poor- Law schools is 18 feet, each bed having a minimum of 3 feet 9 inches of wall space, 36 feet of floor area, and 360 cubic feet of space. If the room is only 15 feet wide, the wall space is increased to 4 feet. There is reason to beheve that very few private schools, even those of the better class, afford more than 300 cubic feet of space per head in their dormitories, an alloAvance which is quite inadequate. Dukes advocates for this climate 800 cubic feet of space with some 70 square feet of floor area for each child in all school dormitories, and certainly the amount of ventilation necessary to keep a smaller space wholesome would be found almost intolerable in cold weather. The system of closed cubicles adopted in some of the large public schools is to be condemned on sanitary grounds; neither should dormitories be used as places to study in during the day. The ventilation of dormitories should be carefully seen to; where gas is used for lighting, means should be adopted to carry off the products of combustion, so as not to deteriorate the ah: on no account should it be used for heating purposes. In school lavatories, supervision needs to be exercised to see that all children wash daily, and that no two of them use the same water. Each child should have a separate towel, and the use of roller towels forbidden. The regulations of the Local Government Board lay down that bathing arrangements in the Poor-Law schools must admit of every child being bathed at least once a Aveek in winter and twice a week in summer, and certainly in other schools the bathing facilities ought not to be less. The amount of closet accommodation for schools is of importance; it should be at least 15 per cent, for girls, and 10 per cent, for boys with in addition 5 per cent, of urinals. The closets should be placed out of doors at a convenient distance and well lighted. The kind best adapted for EXAMINATION OF DWELLINGS. 497 schools is the trough or flush closet. Several schools have tried the dry earth system, but with only partial success : it is quite unsuitable for closets for girls for obvious reasons. In all schools a proper cloak-room should be provided. The result of heaping together a mass of foul garments may be easily imagined; zymotic disease or vermin may be disseminated, and clothes acquire a disagreeable odour. Examination of Dwellings, &c.—In examining a house to discover the sources of unhealthiness, it is best to begin at the foundation, and to con- sider first the site and basements, then the living and sleeping rooms (as to size, cubic contents, and number of persons, and condition of walls and floors), ventdation, water-supply, and plans of waste-water and sewage removal, in regular order. The following memorandum, written by Eassie, shows the general principles on which engineers usually examine a house. '' Sanitary engineers consider that an unusual smell is generally the first evidence of something wrong, and that, traced to its source, the evil is half cured. They inspect first the drainage arrangements. If the basement generally smells offensive, they search for a leaking drain-pipe, i.e., a pipe badly jointed or broken by settlement, and these will often show themselves by a dampness of the paving around. If, upon inquiry, it turns out that rats are often seen, they come to the conclusion that the house drain is in direct communication with the sewer, or some old brick barrel-drain, and therefore examine the traps and lead bends which join the drain-pipes to see if they are gnawed or faulty. If the smell arises from any particular sink or trap, it is plain that there is no ventilation of the drain, and more especially no disconnection between the house and the sewer, or, at least, no trap at the house-drain delivery into the sewer. If a country house be under examination, a smell at the sink Avill, in nearly every case, be traced to an unventilated cesspool; and, in opening up the drain under the sink, in such a state of things, they will take care that a candle is not brought near, so as to cause an explosion. If the trap is full of foul black water, impregnated with sewer air, they partly account for the smell by the neglect of flushing. If the sink, and kitchen, and scullery wastes are in good order, and the smell is still observable, they search the other cellar rooms, and frequently find an old floor-trap without water, broken and open to the drain. If the smell be ammoniacal in character, they trace the stable-drains and see if they lead into the same pit, and if so, argue a weak pipe on the route, especially if, as in some London mansions, the stable-drains run from the mews at the back, through the house, to the front street sewer." *' Should a bad persistent smell be complained of mostly in the bedroom floor, they seek for an untrapped or defective closet, a burst soil-pipe, a bad junction between the lead and the cast-iron portion of the soil-pipe behind the casings, &c, or an improper connection with the drain below. They will examine how the soil-pipe is jointed there, and, if the joint be inside the house, will carefully attend to it. They will also remove the closet framing, and ascertain if any filth has overflowed and saturated the flooring, or if the safe underneath the apparatus be full of any liquid. If the smell be only occasional, they conclude that it has arisen when the closet handle has been lifted in ordinary use or to empty slops, and satisfy themselves that the soil-pipe is unventilated. They, moreover, examine the bath and lavatory waste-pipes, if they are untrapped, and, if trapped by a sigmoidal bend, whether the trapping water is not always with- drawn owing to the siphon action in the full-running pipe. They will trace all these Avater-pipes down to the sewer, ascertain if they wrongly enter the soil-pipe, the closet- trap, or a rain-water pipe in connection with the sewer." '' If the smell be perceived for the most part in the attics, and, as they consider, scarcely attributable to any of the foregoing evils, they will see whether or not the rain-water pipes, which terminate in the gutters, are solely acting as drain ventilators, and blowing into the dormer windows. They will also examine the cisterns of rain- water, if there be any in the other portions of the attics, as very often they are full of putridity." " A slight escape of impure air from the drains may be difficult to detect, and the smell may be attributed to want of ventilation, or a complication of matters may arise from a slight escape of gas. Neither are all dangerous smells of a foul nature, as there is a close sweet smell which is even worse. Should the drains and doubtful places have been previously treated by the inmates to strongly smelling disinfectants, or the vermin 21 498 HABITATIONS. killed by poison, the inspectors of nuisances will find it difficult to separate the smells. In such a case, however, they will examine the state of the ground under the basement flooring, and feel certain that there are no disused cesspools, or any sewage saturation of any sort. They will also ascertain if there be any stoppage in the drain-pipes, by taking up a yard trap in the line of the drain course, and noting the reappearance of the lime-water which they had thrown down the sinks. And invariably, after effecting a cure for any evil which has been discovered, they will leave the traps cleaned out and the drains well flushed." " A thoroughly drained house has always'a disconnection chamber placed between the house drain and the sewer or other outfall. This chamber is formed of a raking siphon, and about two feet of open channel pipe, built around by brickwork and covered by an iron man-hole. Fresh air is taken into this chamber by an open grating in the man- hole, or by an underground pipe, and the air thus constantly taken into the chamber courses along inside the drain, and is as continuously discharged at the ventilated continuations of the soil-pipes, which are left untrapped at the foot, or at special ven- tilating pipes at each end of the drain. This air-current in the drain prevents all stagnation and smell." '' When a house is undergoing examination, it is wise to test for lighting-gas leakages, and there is only one scientific method of doing so, which is as follows :—Every burner is plugged up save one, and to that is attached a tube in connection with an air force- pump and gauge—the meter having been previously disconnected. Air is then pumped into the whole system of pipes, and the stop-cock turned, and if, after working the pump for some time, and stopping it, the gauge shows no signs of sinking, the pipes may be taken as in safe condition ; but if the mercury in the gauge falls, owing to the escape of air from the gas-tubes, there is a leak in them, which is discoverable by pour- ing a little ether into the pipe close by the gauge, and recommencing pumping. Very minute holes can be detected by lathering the pipes with soap and water, and making use of the pump to create soap bubbles." " Besides the drainage, they will, especially if they detect a bad and dank smell, see if it arises from the want of a damp-proof course or of a dry area, see if there be a wet soil under the basement floor, a faulty pipe inside the wall, an unsound leaden gutter on the top of the wall, or an overflowing box-gutter in the roof, a leaky slatage, a porous wall, a wall too thin, and so on." " They will also keep an eye upon the condition of the ventilating arrangements, and whether the evils complained of are not mainly due to defects there. The immediate surroundings of the house will also be noted, and any nuisances estimated." "Sanitary inspectors, whilst examining into the condition of the drains, always examine the water cisterns at the same time, and discover whether the cistern which yields the drinking water supplies as well the flushing water of the closets. They will also ascertain if the overflow pipe of the cistern, or of a separate drinking-water cistern, passes directly into the drain." " If the overflow pipe be siphon-trapped andrthe water rarely changed in the trap, or only when the ball-cock is out of order, they will point out the fallacy of such trapping, and, speaking of traps generally, they will look suspiciously on every one of them, endeavour to render them supererogatory by a thorough ventilation and disconnection of the drains." Hospitals.—The term " hospital" includes a great variety of institutions ha-ving for their object the treatment and care of the sick. These institu- tions may be divided into two main sections : (1) general hospitals, and (2) special hospitals. General hospitals will include all the hospitals which receive all kinds of medical and surgical diseases except infectious fevers and chronic incurable and mental diseases. They include county infirmaries and the large and increasing class of buildings called cottage hospitals and the infirmaries built and administered under the Poor-Law system. Special hospitals include fever and small-pox, lying-in, consumption, children, incurable and chronic, convalescent, sea-bathing, eye, ear, throat, skin and cancer hospitals. This group of hospitals can be further and conveniently divided into (a) those not for infectious diseases, and (b) those for infectious diseases. All that has been said in respect of site, surroundings, and construction of houses and schools apphes with still greater force to hospitals. As chari- GENERAL HOSPITALS. 499 table institutions, existing for the purpose of affording medical and surgical aid to the sick poor, hospitals, on economical grounds, have largely to be so constructed that the patients may be grouped together in general wards. It is this aggregation of large numbers of sick or diseased persons under one building that constitutes the most important factor in hospital hygiene. It has long been known that overcrowding in the wards of hospitals is produc- tive of the worst results, particularly in surgical wards, where the neglect of proper sanitary measures produces the class of diseases knoAvn as " septic," of which Avell-known forms are erysipelas and blood-poisoning. Bearing this fact in mind, Ave are able to understand that the chief conditions to be avoided in all hospitals are : (1) insufficiency of cubic space; (2) inefficient ventdation; (3) improper arrangements for the removal of excreta, refuse, soded linen, dressings, poultices, &c.; (4) faulty arrangements of the buildings. General hospitals should always be placed within a reasonable dis- tance of the population whose needs they serve. This essential feature naturaUy raises a difficulty as to site, especially in the large toAvns. The importance of a free air space round about a hospital cannot be over- estimated, and, as dlustrating the value attached abroad to this condition, the foUowing table by Gordon Smith is both suggestive and interesting:— Name of Hospital. Approximate area of site per bed in square feet. Friedrichshain (Berlin),......1713 Tempelhof ,, 1308 Moabit ,, 1144 University (Halle), 1575 University (Heidelberg), 1070 Bourges (France), . 1600 St Eloi (Montpelier), 1615 St Denis (France), 1685 Antwerp (Belgium), 1126 John Hopkins (Baltimore), 1679 St Thomas's (London), 660 St George's ,, 166 Middlesex ,, 273 Great Northern Central (Lone Ion), 293 The remarkable disparity of the approximate area of the site per bed between some of the Continental and English hospitals is at once obvious, but in several of the institutions in the foregoing list the very large pro- portion of site area to bed is due to the fact that the ward pavdions are all limited to one story. Owing to the great value of land, this mode of con- struction can rarely be adopted in this country, more especially in London or the larger provincial towns. In every hospital of whatever size there must always be :—(a) Adminis- tration offices; (b) wards and their offices; (c) operation room, with subsidiary rooms; (d) out-patient department; (e) mortuary and post- mortem room; to these will be added in the case of very large hospitals, (f) laundry; (g) nurses' home; (h) medical school. The precise disposition of these several parts of the hospital, in relation to each other, of necessity greatly depends on the size of the hospital, and on the shape and area of the site. In Heidelberg, Berne, Baltimore and several other continental hospitals each of these departments has been placed in an absolutely separate building, and in some cases (Baltimore) uncon- nected by even covered ways. The drawbacks to this mode of arrange- ment are : (1) the great extent of land necessarfly occupied ; (2) the greater proportional cost of both land and buildings as well as of administration. The value of a sufficiency of open space about a hospital is undoubtedly 500 HABITATIONS. very great, but in cases Avhere the cost of land is so great as it is in Lon- don and some provincial towns the absolute necessity for so large an area of site per bed may reasonably be questioned. The chief defect usually met with in the older and in some of the newer hospitals is the absence of effec- tive separation of the wards from the other parts, with due regard to economy of construction. Consequently, it may be stated that the really essential principles which should guide us in constructing a hospital are,. briefly : (1) an avoidance of all intimate connection between the wards and the administration buildings; (2) separation of medical from surgical wards; (3) complete atmospheric disconnection between the wards on the one hand, and the mortuary, laundry, and out-patient department on the other. To secure these results, the most common plan now is to build hospitals upon what is called the pavdion system. This system is merely the arrang- ing, on a plot of ground, of a series of one, two or more story buildings, called pavilions, and connecting them together by corridors or covered ways. The individual pavhions or blocks of buildings may be of any shape or size, as, for instance, in the new Great Northern Central Hospital, London, where, although there are both circular and oblong wards, they are all practically isolated from each other and from the rest of the hospital. Care should be taken to see that the various buildings are not so close to each other as to seriously interfere with the free circulation of air, or shut out light. A good rule to adopt is, if of two buildings one is higher than the other, the distance between them must be equal to the height of the higher; if two buddings are of the same height, then the distance must be one and a half times their height. While no particular hospital can be quoted as an ideal or perfect type of what a hospital should be both in planning and construction, still, as illustrating how the essential principles of the separation of parts can be complied with upon a comparatively small area of site per patient, few exist- ing hospitals afford this object lesson so well as the Great Northern Central of London. The general arrangement of the administration block will necessardy vary with the size of the hospital. For a large budding the offices Avill be numerous and the residential part extensive ; but the modern custom of housing the nursing staff in a separate budding very much reduces the amount of accommodation to be provided in the main administration block. In some modern hospitals, the kitchen offices, with the dormitories for servants, are placed in a separate block, thus still further reducing the main block. Practically, the administration block of most hospitals com- prises the secretary's office, board-room, residences for medical staff, matron and secretary, steward's office, storerooms, kitchen offices, and servants' dormitories. To these may be added a consultation room for the professional staff and an office for the matron. The kitchen offices may be advantage- ously placed on the top floor, and the stores in the basement, with com- munication between the two by means of a lift and speaking-tube. Separate dining-rooms should be provided for male and female servants. Wards.—The ward of a hospital may be regarded as the central unit of hospital construction. The buildings in which they are placed should be detached, on the pavilion system, and so disposed as to obtain the greatest amount of air and light. With detached buildings the size of a hospital is- dependent merely on the facility of administration. There can be no doubt that the necessity for an unlimited supply of air is the cardinal consideration in the erection of hospitals, and, in fact, must govern the construction of the buildings. For many diseases, especially the acute, the merest hovels with plenty of air are better than the most GENERAL HOSPITALS. 501 costly hospitals Avithout it. It is ill-judged humanity to overcroAvd febrile patients into a building, merely because it is called a hospital, when the very fact of the overcroAvding lessens or even destroys its usefulness. In order to keep the air in a hospital pure, it is necessary to fix some standard for the minimum cubic space required by each sick person, and to provide for a change of atmosphere sufficient to maintain health, but not so frequent as to cause draughts. It may be laid down as a good rule that the number of patients under one roof or in any one pavilion should not exceed 100 to 120 ; for surgical cases, 80 to 100 Avould be better. As a general rule, it may be said that large wards are more readily ventilated, warmed and managed than small ones. The most general form of hospital wards is rectangular; but in a few hospitals they are circular; and in the John Hopkins Hospital, Baltimore, there are octagonal wards. The dimensions of wards are dependent upon the number of patients to be accommodated and the amount of cubic space to be allotted to each. Rec- tangular wards vary from 24 to 30 feet in width, 13 to 14 feet in height, and from 30 to over 100 feet in length. Each patient should have from 100 to 120 square feet of floor area, and from 1500 to 2000 cubic feet of air space. For fever, severe surgical or lying-in cases, the requirements are greater, being about 3000 cubic feet of air space and 140 square feet of floor area. Experience sIioavs that nursing is best carried out Avhen the number of beds in a Avard do not exceed thirty or thirty-two. These beds are best arranged with their heads to the wall and facing into the ward. Each bed should be placed between two windows, or, at most, two beds in between two Avindows. Where possible, the ventilation should be natural, i.e., dependent on the movement of the outer air, and on inequalities of weight of the external and internal air. The reason of this is, that a much more efficient ventila- tion can be obtained at a cheaper cost than by any artificial means. Also, by means of open doors and windows, we can obtain at any moment any amount of ventdation in a special ward, whereas local alterations of this kind are not possible in any artificial system. The amount of air, also, which any artificial system can give cheaply is comparatively limited. The amount of air should be restricted only by the necessity of not alloAving its movement to be too perceptible. Ventdation by windows and fireplaces, assisted by additional inlets and outlets, is the usual system employed in this country. Inlets are made independent of the windows; usually a Sherringham valve is placed near the ceding, or a Tobin's tube with openings at about 6 feet from the floor level. If the incoming air is too cold this may be warmed by passing it over a steam coil or hot-water pipes. It may further be filtered and washed by passing it through moist canvas screens as carried out at the NeAV General Hospital in Birmingham. Windows are best placed opposite one another, and should extend from 3 feet above the floor to within 6 inches of the ceiling; the upper part may be so made as to fall inwards and form a hopper ventilator. They should all be capable of being opened at their upper parts. One square foot of window area may be provided for every 80 cubic feet of space in the ward. With an open fireplace in a ward, the chimney acts as an extracting shaft if a fire is kept burning, and for this reason it should be placed in the centre of a Avard; it also distributes thence its heat more equably. As additional outlets, vertical shafts should be carried from the room to above the roof; these are best made of galvanised iron, and may be fitted at the 502 HABITATIONS. top Avith a Boyle's ventilating cowl or some similar contrivance : they should be perfectly straight and vertical, any bends only cause friction. They should be of such a size as Avill ensure a moderate current of air through them. The movement of air in the shaft will depend on the move- ment of the external air, but will rarely be less than 3 or 4 feet per second. These shafts should never exceed 12 square inches in area. With proper inlets for air, these shafts will afford continuous and adequate ventilation, and may be supplemented as occasion requires by opening the AvindoAvs. With a proper system of ventilation in Avhich large masses of cold air are continually replacing a large volume of heated air, a proper system of warming the wards is essential. The open fire is not sufficient for this purpose^ and this has to be supplemented by some other _ method. High-pressure hot-Avater pipes or loAV-pressure steam pipes carried round the outer Avails of the Avard is the most convenient arrangement. Some- times pipes of different dimensions are used, so that each pipe may be turned on separately, or used in combination with another: this plan allows of the temperature of the wards being regulated to any degree of heat; it may be so arranged that the incoming air may be Avarmed by passing over some branch of these steam pipes, and this would prevent the feeling of draught from the cold air entering through the open inlets. In some hospitals, as the Eppendorf Hospital at Hamburg, steam pipes are placed beneath the floor : in such an arrangement, which is generally applied to a building of one story, the floor is laid with "terazzo" (pieces of marble laid in cement); this plan is inadmissible Avith wooden floors; under the flooring are a series of channels 2 feet 6 inches wide, in each of which runs a steam pipe, supported on iron rails. The steam is supplied by a boiler, each pavilion being provided Avith its own boiler. In addition in each ward are two steam radiators Avhich are connected by tubes Avith the outer air. This system of heating the floors of wards is generally adopted on the Continent noAV; it is claimed for it that it has the following advantages : (1) it renders possible the use of an impervious material for floor surfaces; (2) that the greatest Avarmth is at the part needed, that is, nearest the feet; and (3) the air being constantly circulating, the system materially assists ventilation. In one-story buildings, in place of outlet shafts as described above, ridge ventilation is usually resorted to: the best form is a " roof lantern " running about two-thirds the length of the ward. The position of water-closets and sinks is a matter for careful considera- tion. The most complete severance of all atmospheric connection betAveen the ward and the closets should be aimed at, and this is best attained when the closets are entered from an intervening lobby or from the open air. In some of the most recently built hospitals the form of the intervening lobby is a sort of covered bridge, the object being to give as free play as possible to the air, so as to prevent stagnation in the vicinity of the Avard. The removal of excreta must be by water, except in the tropics, Avhere this plan is not ahvays available. In hospitals, nothing else can be depended upon, as regards certainty and rapidity. The best arrangement for closets is not the handle and plug, wlhch very feeble patients Avill not hft; but a bell-pull Avire or chain connected with a Avater-Avaste preventer that has a siphon action; a very short pull of the chain is sufficient to set the siphon acting and ensure proper flushing by the most careless persons. This plan is better than the self-acting spring seat, Avhich is not ahvays easily depressed by a thin patient. The number of Avater-closets required may usually be reckoned as one for every twelve beds. In close proximity to GENERAL HOSPITALS. 503 the closets should be a separate space, enclosed for a slop sink, and also for keeping bed pans, &c. It should be provided with water for washing these vessels. The place should have ample light and preferably be provided with a glass panel in the door, so as always to be under inspection. It should be ventilated direct into the outer air. The floors of hospital wards should,- if possible, be fire-proof. Such a floor may be constructed of iron beams embedded in cement, on which is laid a solid and impervious floor surface. Sohd oak or teak parquet laid on the surface of the cement is the best arrangement, but is expensive. Tongued floors of the same AA^ood, with the intervening spaces filled in with Avhite lead or marine glue, forms an excellent floor and is cheaper. Such floors, if properly laid and of well-seasoned wood, when paraffined, form a Fig. 66. practically impervious solid surface. The paraffin treatment of floor surfaces is as folloAvs :—The paraffin is melted and then poured on the floor, and ironed into it with a box-iron, heated from the interior by burning charcoal; it penetrates about a quarter of an inch into the wood. The excess of paraffin is scraped off, and the floor brushed Avith a hard brush; a httle paraffin in turpentine is then put on and the flooring is good for years. The material best adapted for the wall surfaces of a Avard is perhaps one of the most difficult problems in hospital construction. Various means have been taken to secure a truly impervious surface, and Parian cement Avas supposed to fulfil the necessary requirements. In practice, however, it Avas found to be anything but impervious, and experiments made show it to be almost as absorbent as ordinary plaster. The best material is, perhaps, fine plaster, AAdiich can be Avashed as often as desired, and colour-Avashed 504 HABITATIONS. with caustic lime. To facilitate cleaning, and to prevent stagnation of air, it is advisable to round the angles formed at the junction of the wall with the ceiling and wall with floor and the vertical angles of the walls. The various forms of wards which have been adopted in hospitals are connected with the period in which the hospital Avas built. Since the pavilion system has become that now almost universally adopted, cross ventdated single wards is the form generally used. In it the windows face each other at equal distances on each side of the Avard, while the beds are arranged in two rows. The Lariboisiere Hospital at Paris (fig. 66), the Herbert Hospital at Woolwich (fig. 67), and the Cambridge Hospital at Aldershot are examples of this class on a large scale. Circular wards for hospitals were first advocated in this country by the late Professor Marshall, F.E.S., the advantages claimed for them being: (1) freedom of frontage to all points of the compass, and consequently greater accessibility to both hght and air; (2) greater area within a given length of Fig. 67. wall; (3) greater facilities for administration and cleanliness. Circular wards now exist both in this country and on the Continent, notably at Antwerp, Gravesend, Burnley, Liverpool, and Greenwich. The differences between one circular ward and another lie mainly in the mode of attachment to the central or main building and in the treatment of the central part. In some the rooms on either side of the corridor of approach abut on the circle, whhe in others the attachment is by a corridor only. At Burnley a staircase to the roof occupies the central part, Avhile at Liverpool and Green- wich the central portion is occupied by stoves Avith smoke and ventilating shafts. At the John Hopkins Hospital at Baltimore two octagonal wards are conveniently arranged so as to allow free access of air and light to the adjoining pavihons; it was also found that if the ordinary rectangular ward was selected for the site, it would have come too close to the nurses' home. Bath-rooms and lavatories are generally placed for the purposes of con- GENERAL HOSPITALS. 505 venience and economy Avith the water-closets in the projecting wings. The same necessity does not, hoAvever, exist for cutting them off from the ward by an intervening lobby. The floor of the bath-room should be of impervious material, preferably that called "mischiati." This is formed of cubes of marble laid close together, but without any attempt at regularity of pattern; a lattice Avooden standing-board should be placed over it. The bath-room and lavatory should be heated by hot-water pipes. Lavatory basins should be provided in the proportion of about one to every six patients. Ward sculleries are usually attached to each Avard, where the plates, &c, used by the patients are Avashed, and where simple articles of food are cooked. It should be provided with a small cooking range. A sink with hot and cold water laid on is also necessary. The nurses' room is generally placed at the end of the ward, but not communicating directly into it; it has, however, usually a small Avindow looking into the Avard. It was formerly used as a combined sitting-room and bed-room. Under the modern system of nursing, where the duties are assigned for regular hours and where nurses are relieved in turn, there is no necessity for their sleeping near the wards, nor is it advisable that they should do so. This room can hardly be considered absolutely necessary in a modern well ordered hospital. Operating Room.—In all hospitals where surgical cases are received, a special room must be set apart where operations are performed. It must be within easy access of the Avards, yet completely severed from aerial con- tact with them: neither must there be any connection Avith the kitchen, laundry, or mortuary. Its best position is in a separate wing connected to the main corridor by an intercepting lobby and so situated with relation to adjoining buildings that it is not overshadowed or overlooked by them. It should be so placed as to have free access of light, preferably from the north. In its construction everything of an absorbent nature should as far as possible be eliminated. The floor is best made of " mischiati " mosaic laid on concrete, and may be finished with a slight fall to the external Avail Avhere an iron pipe will carry away the water used for washing purposes : the walls up to a height of seven feet are best lined with marble, above this they may be finished Avith fine plaster and cement, which, with the ceiling, should, be painted and varnished. The tops of sinks, and basins, and the shelves should be made of glass, which is not only imper-vious but enables dust or dirt to be easdy seen. The windows should be made flush with the wall and made to open for the purposes of ventilation : they should be glazed with plate glass and be very large. The room should be heated with hot-water coils. Both hot and cold water should be supplied for the basins and cold water for the sink. Fresh-air inlets should be provided, and in some cases it may be advisable to filter the incoming air through cotton wool. Outlet shafts Avith an opening into them near the floor of the room should also be provided. In large hospitals it is desirable to provide also a room for the administration of anaesthetics. The Oid-patient department should be on one floor only, and entirely detached from the main buildings of a hospital. It should consist of a spacious and well-ventilated waiting hall; a sufficient number of consult- ing rooms readily accessible from the waiting room; a dispensary with small waiting room attached, so placed that patients do not have to re- enter the main waiting hall after they leave the consulting room; water- closets and lavatories for both males and females. 506 HABITATIONS. The Mortuary should be a detached building and single story where possible. In the case of a crowded site, it may be conveniently placed at the top of a building, communication thereto being made by an outside staircase and lift. The mortuary should include, besides the room Avhere several dead bodies may be placed at one time, a small room where one body can be separately vieAved by friends. Attached to the dead-house, but having no communication Avith the inspection room, should be a post-mortem room. This must be top-lighted, Avith a floor of some impervious material, made to fall to a channel under the table. The walls should be lined with glazed bricks or tiles, the table should be of marble on an iron frame, and the shelves should be of the same material. A large and deep sink must be provided, and the Avaste pipe therefrom treated in the same way as a soil-pipe. An efficient trap must be placed immediately under the sink, and the pipe taken out through the wall into a vertical pipe, which must be carried up in full diameter as a ventilator. Non-infectious Special Hospitals.—Although in all matters of structural hygiene these hospitals require the same care as the ordinary hospitals, still, in addition, they present some special needs. Thus, ophthalmic hospitals need the removal of sharp angles in wards against which bhnd or partially blind persons may accidentally injure themselves, and the provision of handrails on both sides of staircases. Open fireplaces are a mistake in these hospitals, as often the flickering flame of a fire is both trying and injurious to diseased eyes. Consumption hospitals require special Avarming and ventilation arrangements for their inmates, as well as liberal provision for those able to get up and move about. The most prominent need in all children's hospitals is an isolation ward, as young children are extremely susceptible to infectious diseases. Convalescent hospitals are more properly homes for those recovering from acute illness, rather than mere hospitals for the sick. In the same Avay, cancer and incurable hospitals need to conform more to the freedom and independence of home hfe than to the more rigid arrangements of the institutions for treating acute cases. Lying- in hospitals, from the peculiar nature of the cases they receive, should be constructed with small rooms and not Avith large wards. Every such hospital should be provided Avith an isolation ward, absolutely distinct from the rest of the building. Infectious Disease Hospitals. —These are quite a class by themselves; they may be either permanent or temporary buildings. It is, as a rule, undesirable to select any site for an isolation or infectious hospital which is less than some two acres in extent, and even then regard should be had to the need for extension of hospital buddings, whether for temporary purposes, or owing to increase of population. Moreover, in determining the locality Avhere such a hospital should be placed, the Avholesomeness of the site, the character of the approaches, together with the facihties for water-supply and for slop and refuse removal, are matters of primary importance. Sites for hospitals designed to receive small-pox require a very much larger space about them than sites for other infectious diseases hospitals. Small-pox hospitals are apt to disseminate small-pox, and their sites should therefore be placed outside towns, and should indeed be sought at places as far distant from any populated neighbourhood as considerations of accessi- bility permit. The Local Government Board have suggested that, with a view of lessening the risk of infection, a local authority should not con- template the erection of a small-pox hospital— PLATE III. E LE VATION. .V JS ilnrnhh- luillix ijjii) tutlh ComrnuJcx tviil Itr rrt/nrrrt/. Ihr Ihr itarttx: H7irn inusrx hr<1n*in.s urr- nrl ftrctnhil in the mrv-Uikcrx mtCuifr, liny mny lir fu:r .-i/vrfY ol' Ihr tntrtt- (a.) Thii dutmux ahmM. it W K*t Wiltc kcundary Scale 16 It ta una uich.. INFECTIOUS DISEASE HOSPITALS. 507 1st. On any site where it would have Avithin a quarter of a mile of it as a centre either a hospital, whether for infectious diseases or not, or a workhouse, or any similar establishment, or a population of 150-200 persons. 2ndly. On any site where it would have Avithin half a mile of it as a centre a population of 500-600 persons whether in one or more institutions or in dwelling-houses. It must also be understood that, even where the above conditions are strictly fulfilled, there may be circumstances under which the erection of a small-pox hospital should not be contemplated. Cases in Avhich there is any considerable collection of inhabitants just beyond the half-mile zone should always call for especial consideration. It has been suggested that small-pox hospitals may be so constructed as not to be dangerous to neighbouring habitations; and that this can be done by a system of passing through a furnace all outgoing air from infected Avards and places. But, thus far, the efforts made in this direction cannot be regarded as having successfully attained the end in vieAv. More promis- ing, however, is the system suggested by Key and Henman, whereby the outgoing air is made to pass through canvas screens, and in so passing is exposed to the action of a disinfectant. Reference has already been made to the need, in isolation hospitals, of greater cubic space and ventilation. Owing to the remarkable tendency to aerial spread of infection in the diseases taken to infectious hospitals, the communication -with the outside Avorld has in them to be kept under the strictest control and each disease isolated separately, and kept, if possible, in separate blocks or buildings, the communication between which should be absolutely forbidden. Each block, besides wards, closets, bath-rooms, and sinks, should have linen, store, and fuel rooms, as well as a nurse's room. The disinfecting chamber, mortuary, and stables for ambulances and horses should also be clearly disconnected from all other parts of the building. Considerable controversy has taken place as to whether infectious hospitals should be permanent buildings or merely temporary ones. The truth pro- bably lies in the view that all administrative arrangements, and a certain limited accommodation for the infectious sick, should be in permanent buddings, which, existing thus ready to hand in non-epidemic times, can be quickly supplemented by additional wards in either huts or tents within a few days, in case of widespread epidemics. Some means of isolation are needed in every community at all times, and it is a sounder policy to be able to delay and prevent epidemic outbreaks by isolating the first feAv sporadic cases as they occur, in a small but permanent infectious hospital, than have to grapple with epidemics already in full existence by means of hastily constructed, and often expensive, temporary structures. Many materials have been suggested for the construction of these temporary buildings, more particularly wood, galvanised iron, canvas, and water-proof paper. Although they are comparatively cheap and rapidly erected, temporary hospitals should never be regarded as able to supersede per- manent buildings of brick or stone; their true use is to supplement not to supersede. Moreover, they are extremely difficult to ventilate, and to warm in winter or to cool in summer. Their durability is small, and their proper disinfection is almost impossible. Of course they can be burnt when done with; but if epidemics of infectious disease rapidly succeed each other, the renewals of temporary hospital buddings will soon exceed the cost of structures of a more permanent nature. As infectious hospitals, unlike the great bulk of general and special hospitals, are in no sense charitable institu- 508 HABITATIONS. tions, but really pubhc buddings provided and supported by rates, the true bearing and merits of the question whether these hospitals should be temporary or permanent buildings is one which intimately concerns.the interests of every citizen. The extent of hospital accommodation which it is necessary or desirable to provide must depend upon the population and other conditions peculiar to the district it has to serve. Whatever may be the amount of accom- modation to be provided, the general principles of arrangement.will remain the same. In a memorandum on the provision of Isolation Hospital Accommodation by local authorities, the Local Government Board have pointed out that large villages and groups of adjacent villages Avill commonly require the same sort of provision as towns. "Where good roads and proper arrangements for the conveyance of the sick have been provided, the best arrangement for village populations is by a small building accessible from several villages; otherwise the requisite accommodation for (say) four cases of infectious disease in a village may at times be got in a fairly isolated and otherwise suitable four-room or six-room cottage which has been acquired by the Authority; or by arrangement made beforehand with some trustworthy cottage-holders, not having children, that they should receive and nurse, on occasion, patients requiring such accommodation." " In towns, hospital accommodation for infectious diseases is wanted more constantly, as well as in larger amount than in villages; and in towns there is greater probabihty that room wdl be wanted at the same time for two or more infectious diseases which have to be treated separately. The per- manent provision to be made in a town should consist of not less than four rooms in two separate pairs; each pair to receive the sufferers from one infectious disease, men and women of course separately. The number of cases for which permanent provision should be made must depend upon various considerations, among which the size and the growth of the town, the housing and habits of its population, and the traffic of the town Avith other places, are the most important. There is no fixed standard, therefore, by which the standing hospital requirements proper for a town can be measured. Furthermore, it is to be remembered that occasions will arise (as where infection is brought into several parts of a town at one time) Avhen isolation provision, in excess of that commonly sufficient for the town, will become needful." " For a town the hospital provision ought to consist of wards in one or more permanent buildings, with space enough for the erection of other wards, temporary or permanent. Considerations of ultimate economy make it wise to have permanent buildings sufficient for somewhat more than the average necessities of the place, so that recourse to temporary extensions may less often be necessary. In any case it is well to make the administrative offices somewhat in excess of the wants of the permanent wards; because thus, at little additional first cost, they will be ready to serve, when occasion comes, for the wants of temporary extensions." An isolation or infectious disease hospital, of whatever size, should consist of (1) a detached administrative block; (2) wards, Avith their offices in separate pa"vilions, or blocks, or cottages, at safe distances, providing for the separation of the sexes, and for patients suffering from different diseases; (3) outhouses, such as laundry, stores, disinfecting apparatus, mortuary, &c. The administrative block should minister to the whole hospital, except perhaps when small-pox is isolated. In these cases, nurses attending small- pox should be accommodated in rooms apart from the general administrative building. If obliged to sleep in the administrative building, they should PLATE IV. infectious Diseases Hospital. Local Gov»n»»t Soako HmiUMLL S W. . . . ttmliiiil INFECTIOUS DISEASE HOSPITALS. 509 change their clothes and take a bath on going off duty. No food clothino- earthenware, furniture, &c, should get mixed in the Avork of administration The block or ward used for one disease should be at least 40 feet from the Avard occupied by patients suffering from any other disease. When a patient is admitted, he should be sent into the receiving room of the block set apart for his disease. If there is doubt as to the nature of the disease, he should be sent to an isolation ward untd a diagnosis can be definitely made. If there is no doubt about the case, it should be sent to the ward intended for it The patient, if able to bear it, should be undressed in the bath-room, bathed' provided with a clean night-dress, and put to bed. His own clothes should be put immediately into the disinfecting chamber. If necessary, they should be destroyed. All bed-clothes, linen, toAvels, &c, in an infectious hospital should be marked separately for each disease, stored in its special depart- ment, and on no account used in any other part of the building. Care should be taken to prevent clothes becoming infected in the laundry. The clothes from each department should be thoroughly disinfected before beino- taken to the laundry. When dry, the clothes should at once be brought back and stored in their special department. All spoons, knives, forks, feeding-cups, glass and earthenware should be of different patterns for each disease, or differently marked for each depart- ment, and washed and stored there. The main articles of food should be conveyed to each block in utensils belonging to the administrative block by a person not engaged in any of the wards, and then transferred into utensils belonging to that block. Nurses should keep to one disease exclusively Avhen on duty. The simplest type of isolation or infectious disease hospital is that shown in Plate III., suggested by the Local Government Board. It must comprise three separate buddings: (1) the administrative block, comprising accom- modation for a caretaker, kitchen offices, and two or three rooms for nurses • or it may be simply a cottage containing a living-room and two or three bed- rooms for the caretaker, with the kitchen offices; (2) a block for patients ; and (3) the wash-house, mortuary, and disinfection chamber block. The ward block shown on the same plan provides accommodation for two patients of each sex, with two nurses' ante-rooms on the ground floor and their bed-rooms above. The third block contains a mortuary, wash-house and small disinfecting chamber. It will be obvious that such a hospital provides the smallest possible amount of accommodation, and contemplates the reception of patients suffering from one disease only. In Plate IV., a rather larger hospital building is shown, the plans and sections providing for six and ten patients. These may be regarded as typical isolation blocks in which patients of each sex, and suffering from two- distinct diseases, can be treated. This block is the most important one and Avhatever else is omitted this must always be provided. A convenient dis- position of buildings upon the site is also indicated on the same sheet. In Plate V. is shown the plan and section of a small pavilion adapted to receive six male and six female patients suffering from one kind of infectious disease. " It will be found that in all the plans proper standards of space are observed, namely, not less than 2000 cubic feet of ah space, than 144 square feet of floor space, and 12 linear feet of wall space to each bed; and that means are provided for the adequate ventilation and warming of wards and for securing them from closet emanations and the like. In plan A, earth- closets, in other plans water-closets, are indicated as the means of excrement. disposal. The latter are to be regarded as preferable where efficient seAvers, 510 HABITATIONS. are available. Places for Avashing and disinfection, and for a mortuary are indicated. It will be observed that an interval of 40 feet is everyAvhere interposed between every building used for the reception of infected persons or things and the boundary of the hospital site. This boundary should have a close fence of not less than 6 feet 6 inches in height, and the 40 feet of interval should not afterwards be encroached on by any temporary build- ing or extension of the hospital. In the construction and arrangement of such temporary buddings as may at times be wanted in extension of the permanent hospital, the same principles should be held in vieAv." In all hospitals for infectious diseases provision must be made to prevent, if possible, the conveyance of infection to the outside world, either by patients on their discharge or by nurses or servants going outside the gates. For patients on their discharge a suite of three rooms communicating with each other should be arranged. The first room should be just sufficiently large for one person to undress in; in this room the patient leaves his or her infected clothing. The second or intermediate room is a bath-room. After bathing, the patient enters the third room, where he puts on a complete suit of clean, or preferably new clothing. Having dressed, he should leave the building by a door leading directly into the open air, and should not again enter any part of the hospital buildings. For the staff, ample bathing accommodation should be provided; and, as far as possible, it should be made a rule that no one employed in the hospital wards should leave the grounds without having previously bathed. It is obvious that such a rule as this cannot be rigidly enforced, but, all the same, the means of complying Avith it should be provided, and its observance should be encouraged as far as possible. BIBLIOGRAPHY AND REFERENCES. Bailey-Denton, A Handbook of House Sanitation, Lond., 1882. Billings, Hospital Construction and Management, New York, 1876 ; also Description of the John Hopkins Hospital, New York, 1890. Burdett, Hospitals and Asylums of the World, Lond., 1891. Degen, Die Kasernen und Krankenhaixser der Zukunft, Berlin, 1883. Galton, Healthy Dwellings; Oxford, 1880; also "Notes on Hospital Construction," Brit. Med. Journ., 1883, ii. p. 422 ; also Healthy Hospitals, Oxford, 1893. Hagemeyer, von, Das allgemeine Krankenhaus der stadt Berlin im Friedrichshain, Berlin, 1879. Hooper, "On Artisans' Dwellings," Trans. San. Instit., vol. xi. p. 201. ; Le Fort, Note sur quelques points de Vhygiene hospitaliere en France et en Angleterre, Paris, 1862. Marshall, "Note on the New Hospital at Antwerp, with Remarks on the Advantages of the Circular Ward System," Brit. Med. Journ., 1882, ii. p. 349; also On the Circular System of Hospital Wards, Lond., 1878. M'Neil, The Prevention of Epidemics and the Construction and Management of Isolation Hospitals, Lond., 1894. Memorandum on the Provision of Isolation Hospital Accommodation by Local Authorities, issued by the Local Government Board, 1892. Mouatt, "On Hospital Construction and Management," Lancet, 1883, ii. p. 615. Nightingale, Miss, Notes on Hospitals, Lond., 1863. Power, On the Use and Influence of Hospitals for Infectious Diseases, Supplement to 10th Report of Med. Off. to Local Government Board, 1882. Beport of the Small-pox and Fever Hospitals Commission, Lond., 1882; also Beport on Infectious Diseases Hospitals, issued by Local Government Board, C. 3290, issued 1882, re-issued in 1884. Smith (Gordon), " On the Planning and Construction of Hospitals," Trans. Epid. Soc, 1882, ii. p. 142 ; also " Notes on Modern Hospital Construction," Practitioner, June 1888. G DEHIND EACH BED ST" SECTION ON LINE A.A. H «^yin«[pJ Jhrarf partition 6 6 high aiul 6 vIV Hie floor \CASEMENT WINDOW SwR GRATING AT FLOOR LEVEL PLAN OF A WARD PAVILION FOP 12 BEDS. CHAPTER X. DISPOSAL OF SEWAGE AND REFUSE. The term " Sewage " is here used in its Avidest sense, and is meant to in- clude the sohd and hquid excreta of men and animals; the refuse from houses (dust, ashes, &c.) and the waste waters from sinks and lavatories; the hquid and solid refuse from stables, coAvsheds, and slaughter-houses; the waste waters used for trade purposes, and the sweepings of streets and alleys. "When men live in thinly-populated countries, following, as they will then do, an agricultural or nomad life, they wiU not experience the consequences of insufficient removal of excreta. The sewage matter returns at once to that great deodoriser, the sod, and, fertilising it, becomes a benefit to man, and not a danger. It is only when men collect in communities that the disposal of sewage becomes a matter literally of hfe and death, and before it can be settled the utmost skill and energy of a people may be taxed. The question of the proper mode of disposal of sewage has been some- what perplexed by not keeping apart two separate considerations. The object of the physician is to remove as quickly as possible all excreta from dwellings, so that neither air, water, nor soil shall be made impure. The agriculturist wishes to obtain from the sewage its fertilising powers. It is not easy to satisfy both parties, but it wdl probably be conceded that safety is the first thing to be sought, and that profit must come afterwards. Composition of Sewage.—Sewer water varies very much in its composi- tion, being sometimes very turbid and highly impure ; in other cases hardly more impure than water from surface wells. The Rivers Pollution Com- missioners gave (1868) the followingas the average composition of sewage from towns sewered on the water-closet system and from towns using middens:— Average Composition of Sewage, in Parts per 100,000. •^ o "o "-H to jS r0 S .2 c 5I 3 s s < P to ° 8 S 3 .5 o 3' Suspended Matters. "3 'S to O *3 o Midden towns, . Water-closet towns, . 82-4 72-2 4*181 4 696 1-975 2-205 5-435 6-703 6-451 7-728 11-54 10-66 17-81 24-18 21-30 20-51 3911 44-69 Amount of Solid and Liquid Excreta.—The amount of the bowel and kidney excreta varies in different persons and with different modes of life. On an average, in Europe, the daily solid excreta are about 4 ounces by 512 DISPOSAL OF SEWAGE AND REFUSE. weight, and the daily liquid excreta 50 ounces by measure for each male adult. "Women and children pass rather less. Yegetarians pass more solid excreta than those living on a mixed diet, but this is chiefly OAving to the large proportion of water in their food. Taking all ages and both sexes into con- sideration, we may estimate the daily amount per head of population in Europe at 2\ ounces of faecal and 40 ounces of urinary discharge. The following table gives the average amounts in ounces of fasces and urine passed daily by an adult male (15 to 50 years of age) (Lawes). Fresh Excrements. Dry Substances. Mineral Matter. Carbon. Nitrogen. Phosphates. Fasces, . Urine, . 4-17 46-01 1*041 1-735 0-116 0*527 0*443 0-539 0-053 0-478 0-531 0 068 0-189 Total, . 50-18 2-776 0*643 0-982 0-257 Eresh healthy faecal matter from persons on mixed diet, unmixed with urine, has an acid reaction, and this it retains for a considerable time; it then becomes alkahne from ammonia. If free from urine it usually decom- poses slowly, and in hot weather often dries on the surface and subsequently changes but little for some time. The urine, when unmixed with faecal matter, also retains its natural acidity for a variable number of days,— sometimes three or four, sometimes eight or ten, or even longer, and then becomes alkaline from ureal decomposition. When the faeces and urine are mixed, the formation of ammonium carbonate from ureal decomposi- tion is much more rapid; the solid excreta seem to have the same sort of action as the bladder mucus, and the mixed excreta become alkahne in twenty-four hours, while the separate excreta are still acid. And in its turn the presence of the urine seems to aid the decomposition of the solid matter, or this may be perhaps from the effect of the hquid, as pure water seems to act almost as rapidly as urine in this.respect. Pappenheim states that the absorption of oxygen by the faeces is greatly increased when urine is added. When the solid excreta and urine are left for two or three weeks, the mixture becomes usually extremely viscid, and this occurs, though to a less extent, when an equal quantity of pure water takes the place of urine. The viscidity is prevented by carbolic acid. When the solid excreta (unmixed with urine) begin to decompose, they give out very foetid substances, which are no doubt organic; hydrogen sulphide is seldom detected, at any rate by the common plan of suspending paper soaked in lead solution above the decomposing mass. When heated, a large quantity of gas is disengaged, which is inflammable, and consists m great measure of carburetted hydrogen. When (instead of being dry) urine is present, ammonia and foetid organic matters are disengaged in large quantity. When water is also present, and if the temperature of the air is not too low, not only organic matters but gases are given out, consist- ing of light carburetted hydrogen, nitrogen, and carbon dioxide. Hydrogen sulphide can be also disengaged by heat, and is almost always found in the hquid, usually in combination Avith ammonia, from which it is sometimes liberated and then passes into the air. The Waste Waters from Houses.—This is a very complex liquid The REMOVAL OF EXCRETA BY DRY METHODS. 513 kitchen sink waters contain vegetable, animal, and other refuse, and that from baths and wash-houses soap and dirt from the surface of the body and from clothes. These waste waters, when mixed with the drainage from stables and cowsheds and from slaughter-houses, with the urine from public urinals, form the sewage of non-water-closet towns where privies and cess- pools are used. The sewage from these waste Avaters is so impure that there is no object in providing a separate system to deal with human excreta; there is a remarkable similarity between the sewage of midden towns and those in which water-closets are used. Trade and Manufacturing Refuse.—In manufacturing towns a large proportion of waste is passed into the seAvers. These waste waters are of very variable composition, many of them being mixed Avith the special matters made use of in the different manufacturing processes, as in dye- Avorks, chemical works, papermaking, woollen works, &c. METHODS OF REMOYAL OF EXCRETA. While all wdl agree in the necessity of the immediate removal of excreta from dwellings, the best modes of doing so can hardly be said to be yet settled. The fact is, that several methods of removing sewage are apphcable in different circumstances and their relative amounts of utihty depend entirely on the condition of the particular place. The different plans may be conveniently divided into :— 1. The dry method. 2. The water method. Removal of Excreta by Dry Methods. The use of sewers and methods of removing excreta by water are in many cases impracticable. Either a fall cannot be obtained; or there is insufficient water; or the severity of the climate freezes the water for months in the year, that removal by its means cannot be attempted. Then either the excreta will accumulate about houses, or must be removed in substance daily or periodically. Even when water is abundant, and sewers can be made, many agriculturists are in favour of the dry system, as giving a more valuable fertilising product; and various plans are in use. Middens.—In places where no facihties exist for the use of water-closets, recourse has to be had to some dry method of removing excreta from the house. This, in many cases, necessitates such arrangements as middens or privies and pail closets, in which are used ashes, earth, &c. Until recent times, open middens or pits were the almost universal receptacle for the excretal and other waste matters of the habitation, over which was erected some primitive form of privy. The institution of middens or the setting aside of some spot for depositing filth and refuse was no doubt a great advance on depositing everything anywhere. Unfortunately, middens, objectionable as they are, still exist, in some form or other, in rural districts and in certain towns. In these places it is attempted to minimise the pestilential odours which arise from them by an admixture of ashes, which to a certain extent keeps them dry and delays putrefaction. The original midden pit was a hole dug in the ground full of rotting and offensive matter and giving rise to offensive gases and liquids, which only too readily polluted both the soil around houses and the wells near them. 2 K 514 DISPOSAL OF SEWAGE AND REFUSE. Yarious improvements have from time to time been attempted upon the old midden pit, and where these remain, their existence is subject to certain definite rules and conditions. The general rule now is that for the old midden pit, dug in the ground, should be substituted a small receptacle intervening between the seat of the closet and the floor. The model Bye- laws of the Local Government Board for the construction of privies and middens in new buildings are to the following effect. The midden or privy must be at least 6 feet away from any dwelling and 50 feet away from any well; ready means of access must be provided for the scavenger, so that the contents need not be carried through a dwelling; the privy must be roofed to keep out the rain and provided with ventilating apertures as near the top as possible; that part of the floor which is not under the seat must not be less than 6 inches above the level of the adjoining ground and more- over be flagged or paved with hard tiles having an inclination toAvards the door of the privy of one half inch to the foot, so that liquids spilt upon it may run down outside and not find their way to the receptacle under the seat; the size and capacity of this receptacle may not exceed 8 cubic feet, by which limitation a weekly removal of its contents is necessitated; the sides and floor of this receptacle must be of some impermeable material, the floor being at least 3 inches above the adjoining ground level; the seat of the privy should be hinged, so as to allow of the ashes being throAvn in and the receptacle unconnected with any drain or sewer. Middens constructed and maintained under these conditions, lessens the danger of percolation of filth into the soil or of fouling the wells; while the pollution of ah is safe- guarded to a great extent by keeping the contents in a dry and inodorous condition. No matter how well conducted and supervised, middens are objectionable. Their success depends on proper scavenging arrangements and efficient sanitary supervision. Tub and Pail Closets.—These are really nothing but middens having a limited capacity, in which the ash-pit is represented by a movable receptacle, such as a tub or pail, placed under the seat for the removal of the excreta. In this system the filth removal is easier and the air pollution less than when midden contents are removed. The pails, whether of wood or of galvanised iron, should have close fitting hds and be both air and water tight. Tarred oak is the best material for making pails, as they last longer and are easily repaired. The structure of the closet in which the pails are used should be similar to that proposed for middens. The pail or tub should be removed at least once a week and a clean one substituted for it. In order to delay decomposition and to avoid smells, the contents of the pail (faeces and urine) must be kept as dry as possible, and this is effected by the addition of some absorbent substance, such as dry earth, ashes, or charcoal, or the pail may be lined with some absorbent material, such as peat. If the urine and faeces remain without admixture with any such substances, they rapidly undergo decomposition, but in this state they have a higher com- mercial value as manure than if mixed with ashes, charcoal, or earth. Yarious modifications of this system are adopted in various towns. In Nottingham not only ashes but all the other household refuse is added to the pad, while in Leicester and Birmingham the pails only receive excreta. In Manchester the ashes are sifted and only the finer portion is allowed to faU into the pads. In Halifax the Goux system is in use; the pail or tub is hned with some absorbent material, such as peat, or a mixture of tan, saw-dust, and soot, the object being to render the contents drier and less offensive. The material used is pressed firmly to the sides of the pail, by means of a mould, which is afterwards withdrawn, leaving a cavity in the CHARCOAL AND EARTH CLOSETS. 515 centre for the reception of the excreta. Nothing but faeces and urine should find a place in these pails, as the absorbent capacity of the material is limited: the contents should be removed every two or three days and a fresh pail provided. A separate receptacle is used for ashes, house refuse, &c. The use of sifted coal ashes form very efficient desiccators, but the deodorising effect is very slight. The mixture of coal ashes and excreta usually finds a sale, but the profit is much greater if no ashes are mixed with it. Wood ashes are far more powerful as deodorisers, but it is not easy in this country to have a proper supply. Charcoal Closets.—There is no better deodoriser than charcoal. Animal charcoal is too expensive, but peat charcoal is cheaper; according to Danchell, 3 ounces of peat charcoal are equal to lh lb of earth; and this author states that the cost of charcoal for a family of six persons Avould only be Is. 6d. per month. A plan has been proposed by Stanford which may obviate the difficulty of price. Stanford proposes to obtain charcoal from sea-weed; the charcoal is cheap, and remarkably useful as a de- odoriser. The charcoal itself contains 63 per cent, of carbon, 34 per cent. of ash, and only 2*6 per cent, of water. It has no oxidising effect, and merely acts as a- dryer (Corfield). After it has become thoroughly impregnated Avith faeces and urine, the mixture is recarbonised in a retort, and. the carbon can be again used; the distilled products (ammoniacal hquor, containing acetate of hme, tar, gas) are sufficient to pay the cost, and it is said even to give a profit. The closet used with this carbon is, in principle, similar to Moule's earth closet, with various improvements for more thoroughly mixing the charcoal and sewage. The advantages claimed by Stanford's process are a complete deodoris- ing effect; the small amount of charcoal required as compared with dry earth (three-fourths less required) ; the value of the dry manure, or of the distdled products, if the mixture is reburnt; and, in the last case (burning), the complete destruction of all noxious agencies. In using it the mixed charcoal and sewage may be stored for some months Avithout odour in some convenient receptacle outside, but not under the house. The reburning of the mixture can be done in a gas retort, or a special retort is built for the purpose ; the charcoal left in the retort is returned to the house. Earth Closets.—Neither ashes or charcoal have the same beneficent and disintegrating action on the excreta as dry earth. Since the late Rev. Henry Moule pointed out the powerful deodorising properties of dried earth, many different closets have been proposed. Moule's earth closet consists of a wooden box, with a receptacle beloAv, and a hopper above, from which dried earth falls on the sewage when the plug is pulled up. The earth is previously dried, half a pound of the dried earth per head dady being the usual allowance. For a single house the earth can be dried over the kitchen fire; but if a village is to be supplied a small shed, fitted with tdes, below which smoke pipes from a small furnace pass, is required. The earth used in the closet is sufficient to deodorise the sohd excreta and the portion of the urine passed with them, but the rest of the urine and house water has to be carried off in pipes, and disposed of in some other way. The receptacle is emptied from time to time, and the mixture is stored until it can be applied to land. Its value, however, is not great, as. most of the nitrogen disappears in a gaseous form. Indeed, so complete is the disintegration of organic matter that even paper dis- appears, and the earth after redrying has been used again and again. The best kinds of earth for the purpose are loamy surface soil, vegetable 516 DISPOSAL OF SEAVAGE AND REFUSE. mould, dry clay or brick earth. Chalk, gravel, or sand are not suitable. Care must be taken that the earth is sifted and dry. If dried in a stove or over a hot floor, the temperature must not be raised sufficiently high to sterilise it. Earth dried in the sun acts most efficiently. Care has to be taken that each particular stool is covered at once with the earth and no slop water added to the pail contents. The advantages of this plan are obvious; its disadvantages are the necessity of collecting, and drying, and storing the earth, Avhich, for cottagers who have little space, and possibly no means of getting earth, is a serious matter. The supply of dried earth to large towns is almost a matter of impossibdity, so large is the amount required. Again, the attention necessary, to prevent the house water being thrown in, and to remove the soil at sufficiently short periods, sometimes mditates against its success. If a pail closet has to be used, from a sanitary point of view the earth closet is the very best form,, as, if properly managed, the closet is free from smell, and the process of removing the contents not offensive. The system of adding weak disinfectants in order to control the smell is based entirely on a misconception of the process. These inhibit, if they do not destroy, the action of the nitrifying ferment in the earth and render it sterile: there is, therefore, no disintegration and oxidation of organic matter, and the whole process by which the organic substances are destroyed is arrested. It is because of the absence of the nitrifying organisms in such soils as chalk and sand that these soils, being relatively sterde, are not suitable for the purpose. The use of all disinfecting and deodorising powders in earth closets should therefore be prohibited. The contents of earth closets require no further treatment, and may be applied at once to the land. In agricultural districts, after admixture with fine ashes, the manure from middens and pails may be used on land, but there is always a difficulty of disposing of it to farmers; it is best suited for heavy clay soils. In some towns where the midden and pail system is still in use, the crude contents are converted into a dry manure, which can be transported in bags or casks : it is, however, very offensive. In Manchester Fryer's patent method is in operation, and it is also being applied, in whole or in part, at Birmingham and at Leeds. It consists of a destructor, which reduces to slag all the more bulky town refuse, such as cinders and ashes, broken earthenware and glass, which cannot be dealt with except by being accumulated in a rubbish heap. This slag is ground, mixed Avith hme, and sold as mortar. The apparatus is so arranged that none of the heat is lost, while the heated products of combustion pass over fresh portions of material and prepare it for combustion. The mass is reduced in bulk to one-third. Other refuse, such as condemned food, vegetable garbage, street sweepings, and the like, are reduced to charcoal in another apparatus caUed the carboniser. The carbon thus produced is used for disinfecting purposes, for decolourising the waste water from factories, &c. The excreta proper are collected in pads and reduced to small bulk by drying in a closed apparatus, called the concretor, the ammonia being fixed by the sulphuric acid fumes produced by the other processes. By this means the contents of the pails are reduced to one-twelfth, and a valuable manure obtained, which may be either in the form of poudrette or mixed with a little charcoal. Similar plans of disposing of town refuse are in operation in GlasgoAv, Leeds, Bradford, Stafford, Birmingham, Blackburn, and elsewhere. This system has been favourably reported on as the best REMOVAL OF EXCRETA BY WATER. 517 avadable means for disposing of toAvn refuse. " Not only are poisonous and disgusting elements dealt with and satisfactorily disposed of, without nuisance of any kind, but products having a marketable value can be and are produced without any infraction of true hygienic principles, whilst at the same time they may have the effect of materially reducing the expenses " (Saunders). Movable tubs or pails are also in use in many continental towns. They are usually placed in the basement of houses and are capable of holding from fifty to sixty gallons of hquid ; they are connected with the closets by means of an iron or stoneware pipe. As a rule there are no traps, and the sewer gases readily enter and diffuse themselves through the dwelling. In Paris the contents of these cesspools are collected in tanks outside the city, Avhere the liquid part is allowed to evaporate or run to waste into the nearest water channel; the solid part is dried by being spread out on the surface of the ground, where it is allowed to accumulate for many months. It is then sold under the name of poudrette. There have been great discussions as to the salubrity of the French poudrette manufactories, and the evidence is that they are not injurious to the workmen or to the neighbourhood, although often disagreeable. Ap- parently the poudrette may undergo a kind of fermentation which renders it dangerous, as Parent-Duchatelet has recorded two cases of outbreaks of a fatal fever (enteric 1) on board ships loaded with it. Removal of Excreta by Water. This is the cleanest, the readiest, the quickest, and in many cases the least expensive method. The Avater supplied for domestic purposes, which has possibly been raised to some height by steam or horse power, gives at once a motive force at the cheapest rate; while, as channels must neces- sardy be made for the conveyance away of the Avaste and dirty water which has been used for domestic purposes, they can be used with a httle alteration for excreta also. It would be a waste of economy to allow this water to pass off without applying the force which has been accumulated in it for another purpose. Slop-Closets.—In some towns, particularly in the north of England, where a sufficient water-supply is not available or where it is not utdised for flush- ing and washing out water-closets, advantage is taken of the household waste water to do the necessary cleansing. There are two kinds of slop-closets, viz., those in which the waste Avater is allowed to run directly into the basin, and those in which, Avith a view to give a better flush, the waste hquid is collected in a suitable contrivance, called a tipper, and then discharged from time to time in a sudden forcible stream : these latter are called " automatic slop-closets." The advantages claimed for this class of closets are that (1) on sanitary grounds they appear to be satisfactory apphances; that (2) the trouble arising from frozen pipes and cisterns in the case of ordinary water-closets placed in outbmldings practically need not be considered in the case of slop- closets; that (3) by utihsing the slop water of a household for flushing closets considerable economy is effected in the consumption of water, and the volume of sewage to be dealt Avith at the outfall is lessened. The best type of closet of the non-automatic form is perhaps that known as Fowler's closet, largely in use in Newcastle, Salford, and Hanley. The general arrangement of these closets Avdl be readdy seen from fig. 68. The objections to these closets are (1) that the stream of water is not 518 DISPOSAL OF SEWAGE AND REFUSE. sufficient to keep them clean, and (2) that the back and sides get fouled by the excrement falling against them. These closets to AA7ork properly should have a fall of 5 feet to the seAver for the soil pipe. Another form of slop-closet is that of Hill, in use at Birmingham, and in Fig. 68. Avhich either a siphon-cistern or tipper is used to collect the slop water and then discharge it in a sudden flush. The tipper is preferable to the siphon tank as the latter fails sometimes to act owing to clogging Avith greasy water. A number of these closets can be placed on one drain, a single trap Fig. 69. serving for the Avhole; a ventilation shaft is proA-ided at the upper end. Fig. 69 shoAvs this arrangement. An improvement of these closets are the various kinds of automatic slop- closet, in Avhich the slow and uncertain trickle of the slop water from the sinks is replaced by a sudden gush of the slop Avater after storage in either SLOP-CLOSETS. 519 siphon-cistern or tipper. The tipper is merely an iron or earthenware vessel, so shaped and balanced on pivots that when full the weight of the contained hquid overbalances it and causes its contents to be suddenly poured down the pipe. There are several kinds of these automatic slop- closets ; in some the tipper is placed close to the sink discharge pipe (top Fig. 70. flushing), in others the tipper is placed well aAvay from the slop stone and more or less in a piece with the lowest section of the closet-shaft (bottom flushing). The best form of these closets appears to be Duckett's of Burnley (fig. 70). The tippers to be effectual must contain at least three gallons of water for single closets and five gaUons if flushing two or more closets in a row. Some kinds, such as Whalley's, do not have a self-acting tipper, but are dis- charged by pulling up a handle. Others have the tipper situated at the side or back of the closet basin (fig. 71). The various automatic slop- closets appear to be advan- tageous in that their original cost is small, they consume less water and produce less sewage, and, too, are less apt to freeze or get out of order than the ordinary water-closets ; -p?. *+ against them are the facts that yx„ -} they are unsightly, less cleanly than water-closets owing to the fouhng and lodgment of excreta on the sides; the sewage is exceeding foul, much fouler than is the case where the closets in use are ordinary Avater-closets with a clean water flush. This is accounted for by the fact that it is composed solely of the slop water of cottages and the excreta and urine of the inhabitants. The concentrated 520 DISPOSAL OF SEAVAGE AND REFUSE. quality of the seAvage, and its tendency to rapid putrefaction, increase the difficulties connected with its ultimate disposal. The use of slop-closets can only be recommended out of doors, and where the sewers have a good fall, and Avhere a public service of water is laid on to each house. It is also important that each house should have a separate closet. Subject to these conditions these slop-closets may be of use and value in places where it is desirable to economise the Avater. Trough closets are those in which a long metal or earthenAvare trough partially filled Avith water passes beneath the seats of the closets, placed side by side, and receives the excreta from them. These troughs are regularly flushed by the discharge of a volume of water, either by an attend- ant or automatically by a siphon-cistern or tilting receiver and the contents carried away to the sewer through a trap at the end of the trough. These closets are adapted for schools, factories, and groups of artisans' houses, being little liable to damage by rough usage, or get out of order; the only desideratum being a good large drain Avell jointed with cement and plenty of Avater. Their draAvbacks are, original cost, the large quantity of water used and the alarming noise and splashing which results if the flushing happens to take place when the seat is in use. Trough closets, Avhether automatic or otherwise, can only be used where good drains exist and a supply of water is laid on. Water-Closets.—The essential features of a good water-closet are, a basin or other suitable receptacle of some non-absorbent material and of such shape and capacity as to allow the excreta to fall free of the sides and directly into the water in the basin. There may be said to be five distinct types of Avater-closets now in general use; they are, the pan or container closet, the long hopper, the valve or plug closet, the wash-out and the wasli- down closet. The pan or container closet is noAV being abandoned, although still to be found in many dwellings and public buildings. It consists of a conical pan surrounded by a container, and having at the bottom a small movable pan, usually of tinned copper, to receive the excreta; this holds a certain amount of water, and is intended to act as a water seal or trap. Frequently, from failure of water, defective apparatus, or from the copper being eaten through by oxidation (not uncommon when there are nitrates in the water-supply), the pan is empty, so that free passage is given to noxious gases. Add to this that the container is always more or less filthy, and that the soil pipe from it usually terminates in a D trap, and we have one of the worst com- binations from a sanitary point of view. All such closets ought to be definitely abolished. The Model Bye-laws of the Local Govern- ment Board prohibit the fixing in any neAv water-closet of what is known as a "con- tainer" or D trap. A diagram of a closet _ constructed with these arrangements is ^dj%Vyj - s^js/a'lec shown in fig. 72. The long hopper closet P"'Pe ^-y^^/ll/ is a deep conical basin ending in a bent tube or siphon trap and Avhich, from its shape and construction, is extremely liable to be- come filthy by the fouling of its sides; the flow of Avater is sluggish and in its spiral course round the basin fails to cleanse it. WATER-CLOSETS. 521 The valve or plug closet (fig. 73) is an improvement on the tAvo pre- ceding forms; but in recent years has been superseded by other and better kinds. Its chief faults were that it was comphcated, its plug or valve often leaked and failed to keep a supply of Avater always in the basin, while at the same time it was difficult to keep clean; another defect dfrffifafiffl^ was that, if by chance the ymflMMWh siphon trap became unsealed, xw/fwMyMM foul air could escape up into llllllllll^ the house from the soil pipe vffltMfMwk ____________^i through the overflow pipe. xmMmWa S$Z^1----------M Of the modern forms of :%§llllill lf?if~* M water-closet the best kinds yWumMkA (H)%p^;J^^H^/ are the Avash-out and the ^llllllllll |1I ^^r'-H-z^r short hopper or wash-down l^illllllllj ^11 J^~-1&a closet. Both of them are made out of a single piece of earthen- Avare. In the Avash-out closet {fig. 74) a certain amount of Avater is kept in the basin by means of a dam or ridge over AAdiich the excreta are carried by a flush of water. The objections to this closet are, that the water in the basin is not sufficient to cover the excreta, and that part beyond the ridge and near the outlet is liable to get foul from insufficient flushing; in some varieties of this closet the ridge is made too high, with the result that, unless the flush be good, the contents are not at once carried away. Of the short hopper or wash- down class (fig. 75) one of the best is the "Deluge," which is provided Avith a flushing rim from Avhich the water flows in such a manner and direction that the basin is kept constantly clean. In these forms of water-closets the back of the cone should be made as vertical as possible, so that the excrement drops into the water of the trap and not upon the sides of the basin. A recently introduced and good type of water-closet is that known as the " Century closet" (fig. 76). By reference to the illustration it Avill be seen that the service pipe from the cistern has two connections to the closet—one leading into the basin in the usual manner, the other leading into the top of the long leg of a siphon pipe. The flush from the cistern is thereby divided into tAvo streams—one flushes the basin, the other rushes down the siphon leg, expels the air through the puff pipe, starts the siphonic action and empties the basin, which is refilled with clean Avater by a simple after-flush arrange- ment in the cistern. The quantity of Avater required for flushing closets is three gallons, and Fig. 73. ��94787642 99999999999999 522 DISPOSAL OF SEWAGE AND REFUSE. to avoid waste should not exceed three and a half gallons. The closet should be flushed from a waste-preventing cistern placed not less than 4 feet above the seat, the service or supply pipe being 1| to 1| inch in diameter. The flushing water should on no account be supplied from i a cistern or service pipe which supplies water for household purposes; but each closet should have its own separate cistern. They are usually made of iron and those with a siphon action are best. A very short pull of the chain will put the siphon in action, when the whole contents of the cistern are discharged. The overflow pipe from the cistern should dis- charge direct through the wall into the outer air, a feAv inches from the brickwork; it should under no circumstances be allowed to discharge into any pipe connected with closets. Water-closets should always be placed against an outside Avail of a build- ing, in which is a window which should open quite to the ceiling. If possible, it should be in an outbuilding or a projection Avith thorough ventdation between it and the house; the air from the closet should find easy exit to the external air and not pass into the house. The points to be looked to in examining closets are—l*t, that the amount Fig-' 75. Fig. 76. and force of water is sufficient to sweep everything out of the siphon ; 2nd, that the soil pipe is ventdated beyond the siphon by being carried up full-bore to the top of the house ; 3rd, that the junctions of siphon and soil pipe and of the lengths of the soil pipe are perfect. Many methods have been proposed to secure a perfect joint between the outlet and ventdation connections of a stoneware closet with the house drain; lead traps have usually been adopted, the joint to the stoneware being on the house side of the trap and the connections rendered tight by red lead, putty, or other bedding. While this overcomes the difficulty of the joint, it necessitates the use of a material (lead) which readily becomes coated and is liable to corrode. By the use of such a connection as Doulton's metallo-keramic joint an absolutely perfect connection may be made by the mcorporation of the stoneware and metal at the point of junction. It is generally desirable to have slop-sinks separate from water- closets ; their connections with the drain demand the same care and attention as those of water-closets. The waste pipe from the sink should be made of stout lead, not less than 10 lb to the square foot, in order to resist the- action of hot and cold water; they are usually 3 inches in diameter, with SOIL PIPES. 523 a 3-inch siphon Avater seal and are carried separate from the soil pipe, to terminate in the open air 18 inches above a gully trap. Waste pipes discharging water from kitchen sinks, scullerys, &c, and bath waste pipes carrying away Avater from baths, should not connect dhectly Avith any drain, but must discharge into the open air, about 18 inches above a grating covering a good water trap ; they should not be made to open under the grating, as sewer gas may be sucked up through the pipes by the higher temperature in the house. Waste pipes should also have a siphon trap (fig. 78) with a 3-inch Avater seal. They should not be connected with any soil pipe. Soil pipes for carrying away sewage must be placed outside the building and protected as far as possible from the direct rays of the sun, so as to aAroid its becoming bent from expansion or the joints opening. They should be 4 inches in diameter and carried up full-bore to above the eaves of the house and terminate away from all chimneys and windows; an upcast cowl is sometimes placed over the top, but this is not necessary; thin wires may be strung across to exclude birds, &c. Drawn lead is the best material; seamed lead pipes should never be used. Soil pipes, whether inside or outside buddings, should be made of such material that its weight shall be in the following proportions to length and internal diameter :— Lead. Iron. Diameter. AVeight per 10 feet length not less than AVeight per 6 feet length not less than 3 inches 4 „ 5 6 63 1b. 73 „ 83 ,, 104 ,, 125 ,, i 37 lb. ^ in- metal 42 „ 62 ,, 103 ,, 138 „ Cast-iron pipes are cheaper, but they must be strong and the inner surface as smooth as possible; when cast-iron pipes are used it is advisable to coat them with Angus Smith's composition, which renders the inner surface perfectly smooth; all joints should be caulked with molten lead. As it is difficult to make a perfect joint with iron pipes, they should never be placed inside the house. The connection between the soil pipe and drain should always be outside the house, and an air and siphon disconnecting trap should be placed at this point where this is possible. With an air disconnecting trap at the bottom of the soil pipe, and where the pipe is taken, without bends, to a level above the roof, there should be a constant current of 'pure air through the soil pipe. "When the closet is used the flush of water through the pipe wdl draw air in from the open top and thus keep the soil pipe clean and sweet. If the trap of the closet should fail from any cause, by this arrangement air and not sewer gas would escape into the house. With the air disconnecting trap at the bottom of the soil pipe, it is advisable to place an ordinary siphon trap before it joins the drain, so that the inlet for air may be as free from sewer gas as possible ; this is particularly necessary in those cases in Avhich it is not possible to have an air disconnecting trap at the bottom of the soil pipe. Traps.—These are used as barriers to keep the sewer air in the drains from entering the house or' from polluting the surrounding air. The 524 DISPOSAL OF SEWAGE AND REFUSE. method by which the sewer air is kept back is by the interposition of water between the inlet and the outlet of the trap. This "water seal" should have at least a depth of three-quarters of an inch, so as to provide a sufficient and constant barrier against the passage of sewer air. There must be no angles or projections in the trap itself, which Avill prevent the passage of sohd matter or favour its deposit, as this would undergo putrefaction; the trap should be self-cleansing as far as possible, and every portion should be washed at every flush. Surface traps should never be placed on the ground floor in houses or cellars, but outside the budding, and so situated that if from any cause sewer air escaped through them, it would do so into the open ah and not into the house. There is almost an infinite variety of traps ; those most usually met AA-ith in practice may be conveniently divided into the siphon, the midfeather, the flap-trap and the ball-trap). The simplest form of siphon trap is an ordinary pipe with a bend in it, so that there is always a water seal between the inlet and outlet. It is a useful trap, and efficient if the curve is deep enough, so that there is a certain depth of water (not less than f inch) standing above the highest level of the water in the curve ; the water, however, is liable to be sucked out of it, if the pipe be too small, owing to the Avater being carried away, when it Fig. 77. runs full, by the siphon action of the pipe beyond. If two siphons succeed each other in the same pipe, Avithout an air opening between, the one AA-ill suck the other empty. _ The siphon trap shown in fig. 77a is a good form of intercepting trap for disconnecting the house drain from sewer or cesspool. It has a flat external bottom which ensures its being laid level; there are two openings in addition to the inlet and outlet, one of which may be made to act as an air inlet by being carried up by means of pipes to the surface of the ground where it should be covered by an open grating, and the other beyond the seal, which may be used for cleaning the drain. Another form of siphon trap is shown in fig. 77b. This is a bad form of trap. The bottom of the trap being rounded is difficult to keep in its proper position; there is no provision for ven- tilating the drain in the shape of an inlet opening on the house-side of the water seal, and no means of cleansing the drain beyond the seal; floating matters, such as paper, &c, often accumulate in the central shaft and the dip is not sufficient to wash out the trap. The siphon bends in the waste pipes from baths and sinks should be furnished with a screw at the lowest point, to allow of unstopping (fig. 78). The midfeather is in principle a siphon; it is merely a round or square box, with the entry at one side at the top, and the discharge pipe at a corresponding height on the opposite side, and between them a partition reaching below the lower margin of both pipes. Water, of course, stands in the box or receptacle Fig. 78. TRAPS. 525 to the height of the discharge, and therefore the partition is always to some extent under water (fig. 79). The extent should not be less than f of an inch. Heavy substances may subside and collect in the box, from which they can be removed from time to time; but as ordinarily made it is not a good kind of trap, as it favours the collection of deposit, a'nd is not self-cleaning. Another bad form of trap is the D trap (fig. 80). It is usually found in connection with soil pipes; there is a large surface which becomes coated Avith filth, and foul air is generated. This trap is generally rectangular in section and has too many sharp angles and projections which prevent its being self-cleansing: it should therefore never be used. Bell-traps, though constantly used for sinks and sometimes for gullies, are very defective traps. They should be condemned wherever they are met with. This trap (fig. 81) is unsealed whenever the perforated bell cover is removed, and the small quantity of water which forms the water seal soon evaporates. In order to hasten the flow of water through the discharge pipe the cover is frequently taken off, leaving the waste pipe untrapped; the bell is easily broken off from the perforated plate, in Avhich case it no longer constitutes a trap, and sewer gas escapes. The flap is used only for some drains, and is merely a hinged valve which allows water to pass in one direction, but which is so hung as to close after- Fig. 79. Fig. 80. Fig. 81. Avards by its own weight. It is intended to prevent the reflux of water into the secondary drains, and is supposed to prevent the passage of sewer gas; it is, however, a very imperfect safeguard. The ball-trap is used in some special cases only; a ball is lifted up as the Avater rises, untd it impinges on and closes an orifice. It is not a very desirable kind. However various may be the form and details of the water trap, they can be referred to one or other of these patterns. A grease-intercepting chamber is sometimes necessary to prevent the deposit of grease or sand in the drain. This chamber is generally made of hollow stoneware, with a tight iron cover, and ventilated. The hot water from the sink is cooled on entering the chamber, the grease solidifies and rises to the top, the sand sinking to the bottom; the grease and sand must be removed periodically. The outlet of the trap is at the bottom, and as the grease floats on the top of the water and becomes solid on cooling, it can be readily removed from time to time. The size of the chamber should be proportional to the amount of sink water to be passed through it, so as to prevent the displacement of the body of water in the trap too rapidly, in order that the grease, being chilled, may be deposited in it. The trap should be. easdy accessible for periodical cleaning. Buchan's disconnecting and ventilating drain trap is much used (fig. 82): the soil pipe and drain are both 4 inches in diameter; there is a fresh air 526 DISPOSAL OF SEWAGE AND REFUSE. inlet and an opening beyond the water seal for cleaning, Arc.; the seAvage enters the trap with a considerable fall and the trap is flushed clean. The ordinary form of gully trap (fig. 83) is a very simple and efficient form of trap, so far as the drainage of the yard and rain-water pipes is con- cerned; but it is essential that it should be periodically cleaned out and deposits removed. The openings should never be beloAV the grating, but all pipes be made to discharge above it. A good form of disconnecting trap for sink and slop waters is Deans' Fig. 82. Fig. 83. Fig. 84. (fig. 84), which is fitted with a bucket; this can be lifted out by means of a handle, so that any grease or deposit can be easily removed. The Bye-laws of the Local Government Board require that " the waste pipe from any bath, sink (not being a slop-sink constructed or adapted to be used for receiving any sohd or liquid filth), or lavatory, the overflow pipe from any cistern and from every safe under any bath or water-closet, and ,__..^ _,___... . j-, >__u j,__ every pipe in such building ,"'H- ,"__1,___j'J , ifCT ';!f%i—.— for carrying off waste Avater, to be taken through an ex- ternal wall of such budding, and to discharge in the open air over a channel leading to a trapped gully at least 18 inches distant." The trap as shown in fig. 85 is in compliance Avith this bye-law; the gully is fitted with a bucket which can be lifted out by the handle, so that its contents can be easdy removed. The bucket is provided with a flange round the top, and fits the sides of the trap accurately, so that dirt is unable to pass into it when it is being removed. Efficiency of Traps. — Water should stand in a trap at least f of an inch above openings, and it should pass through sufficiently often and with sufficient force to Fig. 85. �25238349514 EFFICIENCY OF TRAPS. 527 clear it. An essential condition of the efficiency of all traps is that ' they should be self-cleansing. Many traps are so constructed that no amount or velocity of water can clear them. Such traps are the common mason's or dip-trap (fig. 79), and the old D trap, both of which are simply cesspools, and could never be cleaned without being opened up. Such traps ought to be unhesitatingly condemned. Traps are often ineffec- tive :—1. From bad laying, which is a very common fault. 2. From the Avater getting thoroughly impregnated with sewer effluvia, so that there is escape of effluvia from the water on the house side. 3. From the Avater passing too seldom along the pipe, so that the trap is either dry or clogged. 4. From the pipe being too small (2 or 3 inches only), and " running full," which will sometimes suck the water out of the trap; it usually occurs in tins way, as frequently seen in sink traps; the pipe beyond the trap has perhaps a very great and sudden fall, and when it is full of water it acts like a siphon, and sucks all the water out of the trap; to avoid this, the pipe should be large enough to prevent its running full, or the trap should be of larger calibre than the rest of the pipe. This, however, will not always prevent it, as even 6-inch pipes have sometimes sucked a siphon dry. The question has been very carefully investigated, in America, by Philbrick and Bowditch, whose report has shown the danger Disconnecting Man-hole. Perforated Iron Door. Fig. 86. of unsiphoning to which small pipes are exposed. The remedy appears to be to introduce an air-vent at the crown of the trap and not to have too small a pipe, especially when several pipes unite in one general waste. Their experiments also showed how unsiphoning might take place from the pressure of descending Avater from upper floors, so that air might be forcibly driven into the house when upper closets or sinks were used; but with proper ventilation these dangers may be completely obviated. 5. Traps may perhaps be inefficient from the pressure of the sewer air, combined Avith the aspirating force of the house displacing the water, and aUowing the air uninterrupted communication between the sewer and the house. ■ The extent of the last danger cannot be precisely stated. From a long series of observations on the pressure of the air in the London sewers, Burdon-Sanderson ascertained that in the main sewers, at any rate, the pressure of the sewer ah, though greater than that of the atmosphere, could never displace the water in a good trap. In a long house drain which got clogged, and in which much development of gaseous effluvia occurred, there might possibly be for a time a much greater pressure, but whether it would be enough to force the water back, with or without the house suction, has not yet been experimentally determined; water siphon traps act efficiently so long as they are not emptied by any siphon action beyond. But the 528 DISPOSAL OF SEWAGE AND REFUSE. reasons already given show that Ave ought not to place dependence solely on traps, they should be treated merely as auxiliaries to a good drainage system. In arranging the house pipes the sink and Avater-Avaste pipes must not be carried into the closet soil pipes, but must empty in the open air over a grating. (See fig. 85.) In the case of soil or water-closet pipes, there must be also a complete ah disconnection betAveen the pipe and drain by means of one of the contrivances noAV used by engineers. At the point where this disconnection is made there ought to be some easy means of getting at it for inspection. Man-holes.—In the event of a drain terminating in a man-hole or discon- necting chamber, a special form of disconnecting trap is used. The Kenon air chamber and trap is one now generally recommended. It serves to cut off aerial communication with the sewer and at the same time to facilitate inspection and cleansing. A long straight pipe unites the longer arm of the siphon to the chamber, and by its means the drain beyond the siphon can be cleansed; the orifice of this pipe is covered by a movable lid. Man-holes should be introduced where tributary sewers join; they should mark off sections where the sewer has to alter its straight course. A man- hole chamber (figs. 86, 87, 88) is built of brickwork, set in cement, and the drain or sewer is continued along the floor of the chamber by means of open half-channel pipes set in a bed of cement. The surface of the concrete Fig. 87. Fig. 88. should be raised some inches above the edges of the half-channel pipes to prevent the sewage from overflowing on to the floor of the chamber, and it should be lined with cement all over so as to present a smooth and impervious surface. All street man-holes should be fitted with a perforated hon grid; a tray placed beneath the grating will catch any dirt that may enter, and still allow of the free circulation of air in the sewers. In the case of private drains the man-hole lids are made air-tight, with the exception of the terminal one, which should be open so as to provide for a current of ah along the sewer. Drains and Sewers.—Drain means any drain of, and used for the drainage of, one building only, or premises within the same curtilage, and made merely for communicating therefrom with a cesspool or hke receptacle for drainage, or with a sewer into which the drainage of two or more buildings or premises occupied by different persons is conveyed. Sewers include sewers and drains of every description, except drains to which the word "drain," as above defined, applies. In other words, a sewer is a drain receiving the drainage of two or more buildings, and may be an open channel, such as a polluted water-course, as well as an under- ground culvert. Under the Metropolitan Local Management Act, 1862, this distinction between drain and sewer is not accepted, but a combined drain is deemed to remain a drain. So, again, in urban districts which DRAINS AND SEWERS. 529 have adopted the Public Health (Amend.) Act, 1890, the interpretation of "drain" is different. Whereas, under Public Health Act, 1875, if one or more houses drain into a common pipe, such common pipe or combined drain is a seAver; but under section 19 of the Amended Act this common pipe is deemed to be a sewer only if all the houses belong to one owner; if they belong to more than one owner, then the combined drain is a drain repairable at the owners' expense, and not a sewer repairable at the expense of the sanitary authority. The function of a drain is to carry aAvay as rapidly as possible to the sewer or cesspit the waste products that are capable of being removed by the agency of Avater. In order to do this, it must be made of such a form as will cause the least resistance to the free passage of its contents, and be constructed of materials that Avill permit of no leakage of surface waters into the drain, or of sewage into the ground; the joints between the different sections must be also made impervious, so that the whole drain is both air and water-tight throughout its entire length, except at those exits which are provided for the purposes of ventilation. The usual form of drain is a circular pipe, made in lengths of about two feet, in glazed stoneware, semi-vitrified ware, or of cast-iron or other suitable material. They must be of adequate size : for small houses 4 or 5 inches in diameter; for larger houses 6-inch pipes may be necessary, and for hospitals or other large institutions 9-inch pipes. They should be well glazed inter- nally. If the drain is made of cast-iron, the weight and thickness of the pipes in proportion to the diameter should be as follows:— Internal diameter. Per 6 ft. length. Inches. Not less than 3^......42 lb ^ in. metal. 4......62 „ | „ „ 5 ...... 103 ,, x^ ,, ,, 6 ...... 138 ,, -g ,, ,, Laying of Drains.—They should be laid very carefully on concrete on all sides. If the ground on which the pipe has to be laid is not solid, or if there is any likelihood of subsidence taking place, the pipes must be laid in a bed of concrete of sufficient thickness. Sometimes in very loose soils even piling for the depth of a foot must be used besides the concrete; the foundation of concrete should support the pipes in their length and not at the sockets only; it should never be less than 3 inches under the centre of the pipe. Each length of stoneware pipe is provided at one end with a socket into which the spigot of the next pipe fits. The space between the spigot and the socket is generally filled in with cement to make the joint water-tight, but care must be taken that this does not penetrate to the inside of the pipe and afterwards obstruct the flow of seAvage. Another joint is made by casting on to the spigot and socket a specially prepared patent material, the two rings being fixed with a composition of Bussian tallow and resin, finally adding a ring of cement outside the joint. Stanford's joint is composed of boiled tar (1 part), clean sharp sand (1 part), and sulphur (1| part). Clay luting should never be permitted, as it is washed out of the joints in a short time. In wet sods it may be necessary to drain the subsoil, and this may require per-vious drains or drain-sewers. If pipe-sewers only are used, the subsoil water remains unaffected, except so far as a small portion may find its way along the channels formed by the pipe. Sometimes pervious drains of earthenware are laid down to carry off the subsoil water. Brooks of Huddersfield has combined in one system a drain and sewer, in which there is an arrangement for subsoil drainage under the sewer pipe (fig. 89). In 530 DISPOSAL OF SEWAGE AND REFUSE. this arrangement the subsoil drain and pipe-rest is first laid and clay-jointed ; the cement-jointed pipe-seAver is laid after Avards on this, with the result of getting a better laid seAver, and at the same time effectually carrying off the subsoil water. © |py0 Q Fig. 89. Fig. 90. The "junction" of pipes is accomplished by special pipes, known by the names of single and double squares, curved or oblique junctions, according to the angle at which one pipe runs into the other (fig. 90). The square T"^ junctions are undesirable, as blockage wdl always occur, and the oblique junctions should be insisted upon. When a smaller pipe opens into a larger, LAYING AND CLEANSING OF DRAINS. 531 a taper pipe should always be used, the calibre being contracted before it enters the receiving pipe. All jointing must be in good cement, unless special patent joints (such as Stanford's) are used. Clay jointing is Avholly inadmissible. Drains should never, if possible, be carried under the house: but when this is unavoidable, there should be a distance equal to the diameter of the drain between its highest point and the surface of the ground under the building; the pipe should be taken in a straight line from one point to the other, Avith a man-hole or access pipe at each end, and it should be com- pletely embedded in cement Avith solid concrete 6 inches thick all round; or the pipe may be taken above the basement floor and exposed throughout its course. In such case it should be made of cast-iron with lead jointings. In the United States, where this alternative system is adopted, this is made compulsory. The drains should end outside the house, and as far as possible every house pipe should pass outside and not inside or between walls to meet the drain. The object of this is that any imperfection in the pipe should not allow the pipe air to pass into the house. At the junction of the house pipe and drain there should not only be a good water trap, but also complete \ ventdation and connection Avith the outside air at the point of junction. The rule', in fact, should be, that the union of any house pipe whatever with the outside drain should be broken both by water and by ventilation. It is hardly possible to insist too much on the importance of this rule of discon- nection between house pipes and outside drains. A general scheme for the arrangement of house drains, and showing the chief points here mentioned, is given in fig. 91. The "Durham" system of house drainage has recently been introduced into this country from America. The pipes are of wrought-iron lined with asphalte, and are joined together by wrought-iron collars and cast-iron bends and junctions. It is said that by this ^^—x system faulty joining is an impossibdity; but ^—^^jfTr----\Tr-7- the effect of changes of temperature on their y~j[) Jj 1) ' stability is not stated. Events have shown Avhat a risk the richer classes in this country Fig. 92. often run, Avho not only bring the drains into their houses, but multiply water-closets, and often put them close to bed-rooms. The simple plan of disconnection with ventilation, if properly done, would guard against the ■otherwise certain danger of sewer gas entering the house. Houses Avhich have for years been a nuisance from persistent smells have been purified and become healthy by this means. Every house drain should be trapped as near as practicable to its junction with the public sewer. Cleansing of Pipes and Drains.—Pipes are cleaned by flexible bamboo or jointed rods with screws and rollers to loosen sediment. The safest plan of cleaning drains is from man-holes, the drains being laid in straight lines from man-hole to man-hole. By this means obstructions are easily detected and removed. Most engineers noAV lay down a half round pipe where required, raise up the sides in cement, and cover the space over Avith an air-tight iron cover. The use of movable caps runs the risk of leakage, it being difficult to make the Fig. 93. 532 DISPOSAL OF SEAVAGE AND REFUSE. drain water-tight again after removing the cap, but -with care such caps (see fig. 92) are useful Avith small pipes, Avhere man-holes cannot be employed. I Drain pipes should also be cleared out by regular flushing Avhen necessary. This may be done by means of an automatic apparatus such as Field's flush tank (fig. 93). By regulating the Aoav of Avater it may be made to empty itself as often as necessary. Tanks of this description Avhich are connected with large seAvers are usually built in brickwork, but those for drains and smaller seAvers are made of galvanised wrought-iron. In the case of ordinary drains, these tanks usually hold from 80 to 100 gallons of Avater, the diameter of the discharge pipe being 4 inches. Fall of Drains.—The fall or inclination given to a drain must depend on the circumstances of the case, but it may be taken as a general rule that a house drain should have a fall of about 1 in 50. Maguire gives the follow- ing rule for determining the fall necessary:—Multiply the diameter of the drain in inches by 10 : thus a 4-inch drain should have a fall of 1 in 40 ; a 6-inch drain 1 in 60. The fall should be such that the scouring of the drains can be effectually accomplished without the use of special flushing; on the other hand, the inclination must not be too great, or the liquid portion flows away too rapidly, leaving the sohd matters behind. To prevent as far as possible the occurrence of deposits, pipes of greater diameter than 6 inches should not be used. When the current of water is feeble, automatic flushing tanks may be placed at the upper end of the drain. The inclination at which house drains are laid depends on the velocity of the current that is desired to be attained. For house drains it is recom- mended that this should be 4^ feet per second in circular pipes running two-thirds full, and 3 feet per second running a quarter full. All house pipes (except the soil pipe), including rain-water pipes, should end below in the open air, not less than 18 inches distant from the gully trap, so as to completely disconnect them from the drain. Rain-water pipes should not be made to act as ventilators to any drain, as, independent \ of their smaU size, which often leads to blockage," they are often full of rain, and cannot act at the time when ventilation is most required. They are also apt to deliver sewer gas into garret windows. The plan is objec- tionable, and ought to be abandoned. To Test Drains and Pipes.—Pipes and traps are generally so covered in that they cannot be inspected; but this is a bad arrangement. If possible, all cover and skirting boards concealing them should be removed, and the pipe and trap underground laid bare, and every joint and bend looked to. But supposing this cannot be done, and that we must examine as well as we can in the dark, so to speak, the following is the best course:—Let water run down the pipe, and see if there is any smell; if so, the pipe is full of foul air and wants ventilation, or the trap is bad. If a lighted candle, or a bit of smouldering brown paper, is held over the entrance of the pipe or the grating over a trap, a reflux of air may be found with or without water being poured down. It should be noticed, also, whether the water runs away at once, or if there is any check. This is all that can be done inside the house; but though the pipe cannot be disturbed inside, it may be possible to open the earth outside, and to get down to and open a drain; in that case, pour water mixed with lime down the house pipe; if the whitened water is long in appearing, and then runs in a dribble merely, the drains Avant flushing; if it is much coloured and mixed with dirt, it shows the pipes and trap are foul, or there is a sinking or depression in SEWERS. :>?,3 some part of the drain Avhere the Avater is lodging. The pipe should then be flushed by pouring doAvn a pailful of lime and Avater till the lime-Avater Aoavs off nearly clear. If any doubt exists as to the integrity of the pipes or drains, the water test may be used. This is done by carefully plugging the outlet into the seAver or cesspool, and filling the drain full of Avater until it reaches the level of one of the traps. The main drain should be so constructed as to be capable of resisting a pressure of at least 2-feet head of water. If after one or tAvo hours there is no change in the level of the water, it may be con- sidered sound; on the other hand, should it subside, leakage must be taking place either from broken pipes or imperfect joints. Soil pipes may be tested in the same Avay by plugging the drain at the junction, as Avell as the various closet connections. This test is a very severe one. Or, the drain may be filled Avith smoke by a forcing apparatus, Avhen the situation of a leak wiU be detected by the presence of the smoke—smoke rockets have been recently introduced for this purpose ; also glass grenades charged with pungent chemicals (Banner's patent). The simplest method, perhaps, is to pour down the pipe, at the highest part, an ounce of oil of peppermint Avith a few gallons of hot water; as this is a very volatile oil, there is no difficulty in tracing whence the odour is emitted, and so detecting any leak. Yard traps are often very foul, and if the trap-Avater be stirred, gas bubbles out, which is a sign of great foulness or that the traps are seldom used. Sewers are conduits employed to remove waste Avater and waste products suspended in water from houses, or to carry aAvay rain. Among the waste products may be the solid and liquid excreta of men and animals, or the refuse of trade and factory operations. Or seAvers may be used merely for the conveyance of dirty house water, without the admixture of excreta or trade refuse. It is quite impossible that any town or even any large number of houses can be properly freed of its Avaste water without sewers, and in more or less perfect condition they are to be found not only in all modern but in most ancient cities. Originally, no doubt, they were mere surface channels, as they are still in many towns ; but for the sake of appearance and inoffensive- ness, the custom must have soon arisen of placing them underground, nor in modern towns could they now be arranged otherAvise. In some large towns there are many miles of sewers constructed often with great skill and science; these serve in some instances as the channels not only for rain, but for natural streams Avhich have been enclosed. The sewers form thus in the subsoil of toAvns a vast network of tubes, connecting every house, and converging to a common outlet where their contents may be discharged. In some toAvns the seAvers carry away none of the solid excreta, though probably urine enters in all cases. In most towns, however, solid excreta in greater or less quantity enter, OAving especially to the prevalent use of Avater-closets, or to the drainage of middens and manure heaps. Whether the solid excreta pass in or not, the liquid in the sewers must ahvays contain either suspended or dissolved animal or vegetable matters derived from the refuse of houses. It is generally warmer than the water of streams, and is of no constant composition : sometimes it is very turbid and highly impure; in other cases it is hardly more impure than the water of surface wells. The suspended matters are, hoAvever, generally in larger proportion than the dissolved. In some cases the seAver Avater is in greater amount than the water 534 DISPOSAL OF SEWAGE AND REFUSE. supplied to the town and the rainfall together. This arises from the subsoil Avater finding its Avay into the seAvers. One ton of London or Rugby seAvage contains only from 2 lb to 3 lb of sohd matter (Lawes). One ton of Southampton seAvage contahis about 2 lb dissolved and 1| lb to 1J lb suspended matter. The average composition of seAver water in toAvns Avith Avater-closets is : organic matter, 39*6; nitrogen, 8-87; phosphoric acid, 224; potash, 2-9 parts per 100,000. The Rivers Pollution Commissioners give 7*728 parts per 100,000 of total combined nitrogen, 6*703 of ammonia, and 10*66 of chlorine. Under the microscope, seAvage contains various dead decaying matters, and, in addition, large numbers of Bacteria and amcebif orm bodies, as Avell as ciliated infusoria. Fungi, especially Paramecia (spores and mycelium), are seen, but there are few Diatoms or Desmids, and seldom any of the forms of higher animal life. The sewers of a town are for the most part used also to carry off the rainfall, and, indeed, before the introduction of water-closets they were used only for this purpose and for taking away the slop and sink water of houses. In countries with heavy rainfall, and in this country in certain cases, the rainfall channels are distinct from the sewers, and often having their outfalls in an entirely different direction. This arrangement is some- times called the "separate system." The separate system consists in providing two separate channels; one to carry off the rain and storm Avaters, the washing of streets and open spaces ; the other to carry off the sewage. The former discharge their contents into the nearest river or water-course; the latter will convey the sewage to be treated in some one of the methods described subsequently. The advantages claimed for this are that smaller seAvers are required, and that the amount of seAver-water is less, richer in quality and more regular in flow; no storm- Avaters enter the sewers to flood the loAver districts of a toAvn, and no road detritus is washed into the sewers. The disadvantages are that separate channels have to be provided, and rain-water washes away much that would pollute a stream; the scouring effect of rain on sewers is also lost, but this is a doubtful objection. Adoption of either plan must depend on local circumstances. This method will be considered further subsequently. - Whether the solid excreta are allowed to pass in or not, it is clear that the dirty Avater of the seAvers must in some Avay be disposed of. It is in every case more or less impure, containing animal and vegetable substances in a state of commencing decay, Avhich pass readily into putrefaction. The readiest mode of getting rid of it is to pass it into streams, Avhere it is at once subjected to the influence of a large body of water, and where the solid matters become either slowly oxidised, or form food for fishes or water plants, or subside. Although from an early period streams were thus contaminated and their Avater, originally pure, Avas thus rendered unfit for / use, it is only lately that a strong opposition has arisen to the discharge ( into streams. This is owing partly to the greater pollution and nuisance caused by the more common use of Avater-closets and the largely increasing trade of the country, which causes more refuse to be sent in, and partly to the evidence which has been brought forAvard of the diseases which are caused by drinking water made impure in this way. To prevent the nuisance and danger caused by the pollution of streams, many actions at laAv have been brought, and in some cases special Acts of Parliament have forbidden the discharge of sewer-water into certain rivers until after efficient purification. The Rivers Pollution Act of 1876 noAV deals with the question, SEAVERS. 535 its provisions having come into operation on the 15th August 1877. This Act has been further amended (1893) so as in future to prevent the pollution of any river. If seAvage is now conveyed into any stream, after passing through a sewer vested in a sanitary authority, no matter Avhen the seAver was constructed, it is an offence for the sanitary authority to continue to alloAV its passage into the stream. There is now probably a general agreement as to the, principle on which . this difficult question should be dealt Avith. Animal substances in a state \ of decay can be best prevented from contaminating the air, the soil, or the 1 Avater of streams by imitating the operations of nature. In the endless cycle of physical change, decaying animal matters are the natural food of plants, and plants again form the food of animals. It so happens that, with the exception of some mineral trades, the waste products of Avhich are hurtful to agriculture, many of the substances con- tained in the seAvage of our toAvns are adapted for the food of plants, and we seem to be on sure ground Avhen we decide that it must be correct to submit these matters to the action of plant life, and thus to convert them from dangerous impurities into Avholesome food. The difficulty is, hoAvever, with the application of the principle, and at the present moment there is the utmost diversity of opinion on this point. It seems, however, that we may divide the opinions into two classes. According to one opinion, the proper mode is to bring the Avaste Avater of towns, when it contains fertilising matters, at once to the ground, and, after the arrest of substances which may block the pipes, to pour it over the land in such a way as may be best adapted to free it from its impurities and to bring it most rapidly and efficiently under the influence of growing plants. The other opinion objects to this course on two grounds,—first, that the substances are not brought to the ground in the most convenient form for agriculture, and also that the plan entails evils of its own, arising from the immense quantity of water brought upon the land, and from the difficulty of efficient management. The advocates of this second view would, there- fore, use some plan of separating the impurities of the water, and would then apply them in a solid form to the land, or use them for some other purpose, as in General Scott's plan of adding the materials for cement and then making this substance. The purified water would then be filtered through land, or passed into streams, Avithout further treatment. In the case of the sewage containing materials not adapted for agriculture, both parties Avould deal with it in the same Avay, viz., purify it by chemical agencies or filtration, and then alloAV the Avater to flow off into streams, Avhile the solid products would be disposed of in the most convenient way. These general vieAvs apply to any sewer water, whether it contains solid excreta or not, although if these excreta can be perfectly excluded the seAver Avater is less offensive, though not much so, when the volume of Avater is large. It has hitherto been often poured into streams Avithout previous purification, but now this practice is prohibited by laAv, with certain reservations. In any system for the removal of excreta by water, it is obvious that certain conditions of success must be present, without which this plan, so good in principle, may utterly fail. These conditions are, that there shall be a good supply of Avater, good seAvers, ventilation, a proper outfall, and means of disposing of the sewage. If these conditions cannot be united, Ave ought not to disguise the fact that sewers, improperly arranged, may give rise to no inconsiderable dangers. They are underground tubes, con necting houses, and alloAving possibly, not merely accumulation of excreta 536 DISPOSAL OF SEAVAGE AND REFUSE. but a ready transference of gases and organic molecules from house to house, and occasionally also causing, by bursting, contamination of the ground, and pollution of the water-supply. And all these dangers are the greater from being concealed. It is probably correct, as has been pointed out, that in deep-laid sewers the pressure inwards of the water of the surrounding soil is so great as frequently to cause an overflow into the sewer, and so prevent the exit of the contents; but, in other cases, the damage to the sewer may be too great to be neutralised in this way, and, in the instance of superficially laid and choked-up pipes, the pressure outwards of the contents must be considerable. These defects of sewers are now obvi- ated, by using good material, having better construction, good ventilation, sufficient water-supply, and adequate means of sewage disposal. Engineers are by no means agreed as to the quantity of water required for preventing deposits in sewers intended for the removal of excreta. Twenty-five gallons per head per diem, on the authority of Brunei, is the amount required to keep common sewers clear, and even Avith this amount there should be some additional quantity for flushing. But in some cases a good fall and well-laid sewers may require less, and in other cases bad gradients or curves or workmanship may require more. It is a question whether rain-water should be allowed to pass into sewers; it washes the seAvers thoroughly sometimes, but it also carries debris and gravel from the roads, which may clog; Avhile in other cases storm Avaters may burst the sewers, or force back the sewage. To obviate this, storm overflows have to be provided; of these there are about fifty within the metropolitan area, to relieve the low-level sewers on both sides of the Thames. Main Sewers.—House drains end in a channel or sewer which is common to several drains and is of larger size. These sewers, up to 18 inches in diameter, are generally made of Avell glazed earthenware pipes; for larger sewers well-burnt impervious brick is used, moulded in proper shape, and set in Portland cement or concrete. The surface should be rendered in pure Portland cement to a perfectly smooth face, and in case of brick culverts the rendering should be carried up to at least one-half their depth. Engineers take the greatest care with these brick sewers; they are most sohdly put together in all parts, and are bedded on a firm unyielding bed. Much discussion has taken place as to their size, but the question is so complicated by the admission of rain-water, that it is difficult to lay down any fixed rule, at least as regards the main channels. All other sewers, however, should be small, and Avith such a fall as to be self-cleansing. The shape now almost universally given, except in the largest outfall part, is that of an egg with the small end downwards, so that the invert is the narrowest part (fig. 94). The object of this is to secure the maximum scour- ing effect with a small quantity of water. Fig. 94. When the quantity of sewage is small the lesser diameter of the invert of the egg-shaped sewer affords a better scouring power than the larger diameter of an equivalent circular sewer, Avhde the increased size of the former conduit affords the requisite space for an increasing outflow. The best form of egg-shaped seAver is where the horizontal diameter is two-thirds of the vertical height, the radius describing the invert being one-fourth the horizontal diameter. CALCULATION OF DISCHARGE FROM SEAVERS. 537 The semi-circle drawn upon the horizontal diameter becomes the upper part of the seAver, Avhile the segment drawn on the radius forms the invert. Pipes for conveying sewage should have their joints set in cement to prevent leakage. With an ordinary socket joint tarred gasket should be used to prevent the cement entering the joint; each joint should be care- fully examined on the inside, and any cement that may have been pushed into the interior removed before the next length of pipe is laid, so as not to obstruct the proper Aoav of seAvage. The joints of pipes set in cement cannot be opened for examination in case of stoppage without breaking one of the pipes; to obviate this, Doulton has introduced a self-adjusting joint in which no cement is required, and which is not supposed to be injured by settlement. Another joint is Archer's patent air and water-tight joint; a luting of clay is first introduced and the spigot of one pipe is pressed into the socket of the other; liquid cement is then poured in at an opening in the top of the socket after the pipes have been adjusted. The clay merely prevents the cement from entering the interior of the pipes. Sewers.should be laid in as straight lines as possible, AArith a regular fall; tributary sewers should not enter at right angles, but obliquely; and if the sewer curves, the radius of the curve should not be less than ten times the cross-sectional diameter of the sewer. Sewers of Unequal sectional diameter should not join with level inverts, but the lesser, or tributary sewer, should have a fall into the main seAver at least equal to the difference in the sectional diameter. If a man-hole is used for a junction, the bottom can always be constructed so as to give the required curve in the direction of the flow of the current. Calculation of the Velocity of Flow in Sewers and of their Discharge. ■—In order to prevent deposit in sewers from 6 to 9 inches in diameter a velocity of not less than 3 feet per second should exist; for sewers of 12 to 24 inches the velocity should not be less than 2\ feet per second, and for larger sewers 2 feet per second. These velocities would require a fall of from 1 in 140 to 1 in 200 for pipes from 6 to 9 inches in diameter, and of 1 in 400 to 1 in 800 for pipes from 12 to 24 in diameter, and for larger sewers 1 in 244 to 1 in 784 according to size. The fall should be equable without sudden changes in level. In some cases a fall is almost impossible to obtain, as, for instance, at Southport, in Lancashire, Avhere the ground is nearly a dead level. The fall there is about 1 in 5000, and never exceeds 1 in 3000. In such a case the drain would have to be cleaned either by locks or valves (flushing-gates) to retain a portion of the contents for a time, and then set them free suddenly in order to flush the next section, or by special arrangements, such as Field's flush-tank, or Shone's ejector. To calculate the discharge from seAvers, several formulae have been given, of Avhich the folloAving is the most simple:— V = 55x(VDx2F). V = velocity in feet per minute. D = hydraulic mean depth in feet. F = fall in feet per mile. Then, if A = section area of current of fluid, VA = discharge in cubic feet per minute. To use this formula, the hydraulic mean depth Avhen the seAvage is flow- ing, and the amount of fall in feet per mile, must bo first ascertained. The " hydraulic mean depth " is the section area of current of fluid divided 538 DISPOSAL OF SEWAGE AND REFUSE. by the Avetted perimeter. In circular pipes it is always ^th the diameter, Avhether running full, half full, or otherwise. This may be shoAvn thus: Let r = the radius of section: then the peri- tt)'" r meter = 7r2r, and the section of fluid (or area of circle) = -nr2, then g =~k, i.e., \ the radius or \ the diameter. Example.—Let the sewer be 12 inches in diameter and circular in shape ; then the h/draulic mean depth is 3 inches or 0*25 of a foot; let the fall in feet per mile be 73 ; then we have 55 x \/*25 x 146 = 333 feet per minute A-elocity ; then the sectional area of the pipe running full = 0-7854 of a square foot, and 07854 x 333 = 261 cubic feet discharged per minute. In egg-shaped seAvers, the hydraulic mean depth varies with the volume of water AoAving through them, but in sewers constructed on the usual plan, where the transverse diameter is § of the vertical, the hydraulic mean depth is as follows :— Running full, transverse diameter x 0'2897 gfull, „ „ x 0-3157 4 full, „ ,, x 0-2066 The " wetted perimeter" is that part of the circumference of the pipe Avetted by the Auid. In an egg-shaped sewer under these three conditions it equals the transverse diameter multiplied by 3*9649, 2*3941, and 1*3747 respectively. The fall in feet per mile is easily obtained, as the fall in 50 or 100 or 200 feet can be measured, and the fall per mile calculated (5280 feet = 1 mile). This may be done by dividing 5280 by the denominator of the fraction; thus a fall of 1 foot per mile is 1 in 5280, a fall of 1 in 100 = 52*80 feet per KOOf) mde; 1 in 30 = „» =176 feet per mile, and so on. The following table taken from Wicksteed shows the velocity in feet per mile and the gradient required for pipes of various diameters:— Sewers. Velocity in feet Gradient per minute. required. 4 inches 240 1 in 36 6 „ 220 1 65 8 „ 220 1 „ 87 9 ,, 220 1 „ 98 10 ,, 210 1 „ 119 15 ., 180 1 „ 244 18 ,, 180 1 ,, 294 21 „ 180 1 » 343 24 ., 180 1 ., 392 30 „ 180 1 ,, 490 36 ,, 180 1 ,, 58 S 48 „ 180 1 „ 784 To shoAV the inclination required to produce different velocities in pipes, BaldAvin Latham gives the f olloAving table :— Diameter in inches. Rate of Inclination for Velocity per second. 2 feet. 3 feet. 4 feet. 5 feet. 6 feet. 4 1 in 194 1 in 92 1 in 53 1 in 34 1 in 24 6 292 137 80 51 36 8 389 183 106 69 48 9 437 206 119 77 54 10 486 229 133 86 60 12 583 275 159 103 72 VENTILATION OF SEWERS. 539 In this table the velocity in feet multiplied by the inclination equals the length of the sewer to which the calculation applies. E.ixonplc.—If the velocity is 6 feet per second in a pipe whose diameter is 4 inches, then 6 x 24 = 144 feet is the length of the seAver. Bailey-Denton has calculated the discharge from different sized pipes running full at different velocities and the fall required to produce these velocities; these are given in the folioAving table :— Diameter of Pipe. 180 ft. per minute, 3 ft. per second. 270 ft. per minute, 4i ft. per second. 360 ft. per minute, 6 ft. per second. 540 ft. per minute, 9 ft. per second. Inches. Fall. Gallons per minute. Fall. Gallons per minute. Fall. Gallons per minute. Fall. Gallons per minute. 3 4 6 9 1 in 60 lin 92 1 in 138 1 in 207 54 96 216 495 1 in 30 4 1 in 40 8 1 in 61-2 lin 92 81 144 324 742-5 1 in 17-2 1 in 23*0 1 in 34-5 1 in 51-7 108 192 432 990 1 in 7-6 1 in 10-2 1 in 15 3 1 in 23-0 162 288 648 1485 Beardmore states that the folloAving bottom velocities have the effect stated on the different materials particularised :— 30 feet per minute will not disturb clay with sand and stones. 40 ,, ,, move along coarse sand. 60 ,, ,, ,, fine gravel, size of peas. 120 ,, ,, ,, rounded pebbles 1 inch diameter. 180 ,, ,, ,, angular stones If inch diameter. Movement of Air in Sewers, and Ventilation.—It seems certain that no brick sewer can be made air-tight; for on account of the numerous openings into houses, or from leakage through brickwork, or exit through gratings, man-holes, and ventilating shafts, the air of the tubes is in constant connection with the external air. There is generaUy, it is believed, a current of air Avith the stream of water, if it be rapid. The tension of air in main sewers is seldom very different from that of the atmosphere, or if there be much difference equilibrium is quickly restored. In twenty-three observations on the ah of a Liverpool sewer, it Avas found by Parkes and Burdon-Sanderson that in fifteen cases the tension was less in the sewer than in the atmosphere outside (i.e., the outside air had a tendency to pass in), and in eight cases the reverse; but on the average of the whole there was a slight indraught into the seAver. In the London sewers, on the other hand, Sanderson noticed an excess of pressure in the sewers. Reeves believes that temperature is an important factor in influencing the movement of air in sewers; when the temperature of the seAver, and that of the outside air, is the same or nearly so, stagnation follows. If at any time there is a very rapid flow of water into a sewer, as in heavy rains, the air in the sewer must be displaced with great force, and possibly may force weak traps; but the pressure of air in the seAvers is not appreciably affected by the rise of the tide in the case of seaboard towns. The tide rises slowly, and the air is displaced so equably and gradually through the numerous apertures, that no movement can be detected. It is not possible, therefore, that it can force water traps in good order, Avhen there are sufficient ventilating apertures. On the contrary, the bloAving off of steam, or the discharge of air from an air-pump (as in some trade operations), greatly heightens the pressure, 540 DISPOSAL OF SEWAGE AND REFUSE. and might drive air into houses. So also the Avind bloAving on the mouth of an open sewer must force the air back with great force. It is, therefore, important to protect the outfall mouth of the seAver against wind by means of a flap, and to prohibit as far as possible steam or air being forced into seAvers. To how great an extent the openings into houses thus reduce the tension of the air in main seAvers it is difficult to say, but there can be little doubt that a large effect is produced by houses which thus act as ventilating shafts. When a sewer ends in a cul-de-sac at a high level, seAver gas will rise and press with some force; at least in one or tAvo cases the opening of such a cul-de-sac has been folloAved by so strong a rush of air as to show that there had been considerable tension. It is also highly probable from the way in Avhich houses, standing at the more elevated parts of seAvers and communi- cating with them, are annoyed by the constant entrance of sewer air, while houses lower doAvn escape, that some of the gases may rise to the higher levels. That no sewer is air-tight is certain, but the openings through which the air escapes are often those we should least desire. It is, therefore, absolutely necessary to provide means of exit of foul and entrance of fresh air, and not to rely on accidental openings. The air of the sewer should be placed in the most constant connection with the external air, by making openings at every point AAdiere they can be put Avith safety. In London there are numerous gratings which open directly into the streets, and this plan, simple and apparently rude as it is, can be adopted with advantage wherever the streets are broad; the openings should be in the middle of the roadway, and not near the pavement. But in narrow streets, or when too near the pavement, the seAver gratings often become so offensive that the inhabitants stop them up. In such cases there must be ventilating shafts of as large a diameter as can be afforded, running up sufficiently high to safely discharge the sewer air. In some of these cases it may be possible to connect the seAvers with factory chimneys. The sewer should never be connected with the chimneys of dwelling-houses. It has been suggested that pipes should be carried up through the street gas lamps, for the purpose of ventilating the sewers, so that the sewer air would be subjected to the gas Aame, and rendered innocuous, and a constant current kept up. fin making openings in sewers it seems useless to follow any regular plan. The movement of the sewer air is too irregular to alloAV us to suppose it can ever be got to move in a single direction, though probably the most usual course of the air current is with the stream of Avater, if this be rapid. The openings should be placed wherever it can conveniently be done Avithout creating a nuisance. Some of these openings will be inlets, others outlets, but in any case dilution of the sewage effluvia is sure to be obtained. Bawlinson considers that every main sewer should have one ventilator I every 100 yards, or 18 to a mile, and this should be a large effective opening. But there may be cases Avhen special appliances must be used. For example, in what are called " seAvers of deposit," as when the outAoAV of the sewer water is checked for several hours daily by the tide or other causes, it may be necessary to provide special shafts, and the indication for this Avill be the evidence of constant escape of seAver air at particular points. The use of charcoal trays has not answered the expectations that Avere formed of them. Their use is now discontinued. It is of importance that, to all sewers capable of being entered by a man, there should be an easy mode of access. Man-holes opening above, or, INSPECTION AND FLUSHING OF SEAVERS. 541 Avhat is better, at the side, should be provided at sueh frequent intervals that the sewers can be entered easily and inspected at all points. The man-holes are sometimes provided Avith an iron shutter to prevent the seAver ah passing into the street, or by the side of the man-hole there may be a ventilating chamber. Objections to Sewers.—The main objections are as follows:— 1. That, as underground channels connecting houses, they allow transference of effluvia from place to place.—The objection is based on good evidence, but it must be said in' reply that, if proper traps are put down, and if air disconnection, in addition, is made between the outside drains and the house pipe, such transference is impossible. The objection is really against an error of construction, and not against the plan as properly carried, out. Besides, the objection is equally good against any kind of seAver, and yet such underground conduits are indispensable. 2. That the pipes break and contaminate the ground.—This is a great evd, and it requires care to avoid it. But such strong pipes are noAV made that, if builders Avould be more careful to make a good bed and to connect the joints firmly, there would be little danger of leakage, as far as the pipe drains are concerned, and not much damage of the main brick sewers. All pipes, however, ought to be actually and carefully tested after being laid and before being covered in, otherwise it is impossible to insure their being Avater-tight, even when everything is sound to all appearance. 3. That the water-supply is constantly in danger of contamination.—This also is true, and as long as overflow pipes from cisterns are carried into sewers, and budders will not take care to make a complete separation between water pipes and refuse pipes, there is a source of danger. But this is again, clearly an error in constructive detad, and is no argument against a proper arrangement. Inspection of Sewers.—The inspection of sewers is in many towns a matter of great difficulty, on account of the means of access being insuffi- cient, and also because the length of the sewers is so great. Still inspection is a necessity, especially in the old flat sewers, and should be systematically carried out, and a record kept of\ the depth of water, the amount of deposit, and of sewer-slime on the side or roof. Choking of and deposits in sewers are due to original bad construction, too little fall, sharp curves, sinking of floor, want of water, check of flow by tides ; all these conditions favour the subsidence of suspended matters. Well-made sewers with a good supply of water are generally self-cleansing, and quite free from deposit, but this is, unfortunately, not always the case. Even in so-called self-cleansing sewers, it has been noticed by Rawlinson that the changing level of the water in the sewers leaves a deposit on the sides, which, being alternately wet and dry, soon putrefies. In foul sewers a quantity of shmy matter collects on the crown of the sewers; it is sometimes from 2 to 4 inches in thickness, and is highly offensive. When obtained from a Liverpool sewer by Parkes and Burdon-Sanderson, it was found alkaline from ammonia and containing nitrates. On microscopic examination, this Liverpool sewer-slime contained a large amount of fungoid growth and Bacteria. There were also Acari and remains of other animals and ova. When deposits occur, they are either removed by the sewer-men or they are carried away by flushing of water. Flushing of Sewers.-r-This is sometimes done by simply carrying a hose from the nearest hydrant into the sewer, or by reservoirs, provided at certain points, which are suddenly emptied. The seAvage itself is also used 542 DISPOSAL OF SEWAGE AND REFUSE. for flushing, being dammed up at one point by a flushing gate, and when a sufficient quantity has collected the gate is opened. An automatic system is, however, preferable, such as is carried out by Field's annular siphon, before mentioned, or by Shone's ejector. Almost all engineers attach great importance to regular flushing, and practically the only advantage of allowing the rain to enter the sewers is the scouring effect of a heavy rainfall Avhich is thus obtained. This, hoAvever, is so irregular that it is but a doubtful benefit. Where there is no deposit, foul cases are not generated. This is shown in the case of Bristol, where the main sewer is neither ventilated nor flushed, and is stated to require neither the one nor the other, there being no deposit nor accumulation of foul gas. DISPOSAL OF SEWAGE. The difficulty of the plan of removing excreta by water really commences at the outfall. This difficulty is felt in the case of the foul water flowing from houses and factories without an admixture of excreta almost as much as in sewer Avater with excreta. The exclusion of excreta from seAvers, as far as it can be done, would not solve the problem—Avould, indeed, hardly lessen its difficulty. In seaboard towns the water may Aow into the sea, but in inland toAvns it cannot be discharged into rivers, being now prohibited by law. Independent of the contamination of the drinking water, sewage often knls fish, creates a nuisance which is actionable, and in some cases silts up the bed of the stream. It requires in some way to be purified before dis- < charge. At the present moment the disposal of seAvage is the sanitary problem of the day, and it is impossible to be certain which of the many plans may be finally adopted. It Avill be convenient to brieAy describe these plans. Storage in Tanks—Cesspits.—The sewage runs into a cemented tank with an overAoAv pipe, Avhich sometimes leads into a second tank similarly arranged. The solids subside, and are removed from time to time; the liquid is allowed to run away. Instead of letting the liquid run into a ditch or stream, it has been suggested to take it in drain pipes, \ to 1 foot under ground, and so let it escape in this way into the subsoil, where it will be readily absorbed by the roots of grasses. The fat, grease, and coarser solids should be intercepted in a proper trap, and removed as found necessary. The liquid portions may be discharged periodically by means of an automatic Aush-tank. In a light soil this could no doubt be readily done; and if the drain pipes are well laid, a considerable extent of grass land could be supplied by this subterranean irrigation. The tank plan is, however, only adapted for a small scale, such as a single house or small village, and there should be ventilation between the tank and the house in all cases. This plan is applicable to the disposal of slop Avaters in villages, even when the excreta are dealt with by dry methods. This is really a modification of the old cesspit plan, which is stdl in use in most rural districts; but unless the cesspit is at a considerable distance from any habitation, and far removed from all sources of water-supply, it should be replaced by a cemented tank. In any case, ventilation and complete disconnection are absolutely necessary. Discharge into the Sea.—This method consists of the direct discharge of the sewage at ebb tide, so as to carry out the sewage to a distance from the shore, and diffuse it into the sea before the tide begins to Aow. Where PRECIPITATION PROCESSES. 543 tidal currents exist, the point of discharge should be situated below the place in the direction of the falling tide and not above it. The greatest difficulty with such outfalls is at low water. As the flow of sewage in seAvers towards the outfall is continuous, the best method is to conduct the sewage into a tank or reservoir, where it can be stored, and discharged into the sea at suitable states of the tide. This plan has recently been adopted at Margate. Sewage should not be discharged into tidal estuaries, as it is never carried any great distance away from the shore, OAving to currents and the rise of the tide; the sewage is very frequently taken back and deposited near the outfall or on the foreshore. This system is only available for a limited number of places situated near the sea coast, and cannot be employed for the disposal of sewage of inland towns. Precipitation.—Tins process consists in collecting the sewage in tanks, thus allowing a large volume to remain comparatively quiescent, so that the sohd particles subside. In order to produce greater purification, the sewage in the subsiding tanks is mixed with some chemical agent or precipitant. The solids formed, in settling, take down with them the suspended matters in the sewage together with some of the dissolved organic impurities; the proportion, of course, varies with the amount of solid matters precipitated. The effluent from the tanks then flows at once into a river or stream, or may be passed over land, or be filtered through it. A large number of methods have been suggested in order to secure adequate precipitation. The Lime Process.—The purest lime only should be used. Before being added to the sewage, it must be reduced to the " milky" condition and thoroughly incorporated with the sewage. The quantity of lime required is 1 ton to each million gallons of sewage (15*68 grains per gallon), but the tendency is to reduce the quantity of lime to the smallest effective amount, since an alkaline effluent is liable to undergo putrefaction. Lime and chloride of lime are said to be good precipitants; one-third of a grain of chloride of lime per gallon prevents the growth of seAvage fungus; it is especially useful in hot weather. Lime and Sulphate of Alamina.—The quantity of lime added first to the sewage should be just sufficient to make it slightly alkaline—probably from 5 to 7 grains per gallon wdl be required; it should be added in the form of mdk of hme, and thoroughly mixed with the sewage. A solution of crude sulphate of alumina is then added and the sewage again stirred. In the alka- line sewage the alumina wdl be precipitated, and, combining with the organic matter, wiU form a bulky insoluble precipitate which deposits in the tanks. Lime and Proto-Sulphate of Iron.—This process is used by the London County Council in connection with the metropolitan sewage. The quantities recommended are 3*7 grains of hme in solution, and 1 grain of proto-sulphate of iron per gallon of sewage. This method of precipitation is said to be a good one, and produces a fairly clean effluent, but the smell often is so disagreeable that it cannot be discharged into the river during warm weather at all states of the tide. Dibden proposes to use manganate of soda and sulphuric acid in order to destroy any offensive odour after chemical precipitation. Lime and Black-ash Waste.—This is the residue from the manufactures carried on at alkali works, and is used in conjunction with lime. At Wimbledon, where this process was tried, it was found that, while the sludge was greatly increased in quantity, the effluent was not appreciably affected. Hie ABC process (Sellar's patent) consists in the addition of a mixture of alum, charcoal or refuse from prussiate Avorks, and clay. Blood 544 DISPOSAL OF SEWAGE AND REFUSE. Avas at one time employed, but is not found to be necessary and is some- times omitted. The alumina precipitated by the lime forms a very bulky precipitate, well suited to the entanglement of suspended matters. The clearance of the sewage is more perfect than Avith lime alone, but other- wise the process and the objections are the same, while the cost is greater. The whole of the phosphoric acid is precipitated as aluminum phosphate. To a gallon of sewage Avater there should be added 73| grains of aluminum sulphate, 31 grains of sulphate of zinc, 73J grains of charcoal, and 16f grains of quicklime. The manure from this process is perceptibly superior to that resulting from the lime process. The sludge is pressed in filter presses, and subsequently dried in steam cylinders and sold as a granular manure containing about 20 per cent, of moisture. The process is in opera- tion at Aylesbury and Kingston-on-Thames, being carried on by the Native Guano Company. Ferrozone and Polarite Process.—In this process, the introduction of the precipitating material "Ferrozone" is folloAved by the filtration of the effluent through polarite: this latter material consists of about 50 per cent. of magnetic oxide and carbide of iron combined Avith silica, lime, and alumina in an insoluble form. Ferrozone consists largely of proto-sulphate of iron. The process is noAV in use at Acton and Hendon. Spencer's magnetic carbide of iron has also been used as a filtering medium for sewage effluents and yields very similar results. The Amines Process.—This process consists in the employment of from 30 to 50 grains of lime per gallon of sewage and about 3 grains of herring brine; the volatde matters produced, composed of amines and ammonia, are passed into the crude sewage, which, it is said, is completely sterilised by this means. It is in use at Wimbledon Sewage Works and Farm. Sulphate of iron Avas advocated by Conder as a precipitant; it is applied in direct proportion to the quantity of putrescible matter to be dealt with. It is said to destroy all smell and. to render the effluent and precipitant inoffensive. Character of the Effluent Water.—The effluent water from all these processes is merely clarified sewage; it contains ammonia, together with some soluble organic matter, as well as phosphoric acid, and it would thus appear that nearly the whole of the substances which give fertilising power to sewage remain in the effluent water. When sewage is clarified by any of these plans and freed from suspended matters, it is not likely to cause a nuisance if discharged into a fairly rapid river, if the ordinary volume of water is considerably greater than the effluent. It is now universally recognised that it is unsafe to use any river or stream as a source of water-supply which has at any time received sewage or sewage effluents higher up in its course. It is even doubtful whether sewage can be sufficiently purified by filtration through land or other filter- ing media to render the water into which it is discharged a safe source for drinking water. Many analyses are given in the First and Second Reports of the Rivers Pollution Commissioners, from which it appears that on an average the chemical processes remove 89*8 per cent, of the suspended matters, but only 36*6 per cent, of the organic nitrogen dissolved in the hquid. Crookes' analyses show that the ABC process, when well carried out, removes all the phosphoric acid. Voelcker's analysis of the effluent water treated by the acid phosphate of aluminum shows that it contains more ammonia than the original seAver water, less organic nitrogen by one-half, and less phos- phoric acid. The clear fluid is well adapted for market gardens; the plants DISPOSAL OF SLUDGE. 545 groAvn as vegetables for the table are sometimes injured by irrigation with unpurified effluent Avater. Disposal of Sludge.—This is ahvays a great difficulty. Efforts have been made, in connection with the chemical processes, to utilise the sludge as manure. The best method of utilising the sludge is by separating the liquid from the sohd matter, so as to reduce the bulk as much as possible, and this should be done speedily, so as to alloAV of no putre- faction. «■ The deposit obtained from these processes is sometimes collected and dried on a hot floor, a stream of hot air being allowed also to pass over it. There is some little difficulty in drying it, and it is said to be expensive both in labour and fuel and there is a liability of nuisance through offensive odours. In Birmingham the sludge, after precipitation with lime, is con- veyed by the main conduit to the land and disposed of by ordinary irrigation. One acre a week is used, upon which 500 tons of sludge a day are put. It is then cropped for three years before being again used. At Ley ton, West Ham and elseAvhere the sludge, which contains 90 per cent. of water, is pressed in patent presses and dried until it contains only 21 per cent, of moisture. It is then in the form of solid dry-looking cakes, which may be taken for laying on land, making cement, &c. At Southampton, ferrozone is used as a precipitating agent, the effluent is expelled into the river by a Shone's ejector, and the sludge by a similar process is projected to the corporation works, where it is mixed with road sweepings and ashes. This mixture finds a sale at 2s. 6d. a ton among the farmers in the neighbourhood. In general, the deposit appears to possess small agricultural value, although it is occasionally saleable. The price obtained rarely exceeds one-third of the theoretical or chemical value. Thus the product by Ander- son's process at Coventry is estimated theoretically at 16s. 9|d. per ton; the practical value is only 5s. 6d. to 8s. 4d. The profit is not large, and in some instances there has been even a loss. Another method of disposal is to burn the sludge in a " destructor." At Ealing, Avhere this practice is adopted, no difficulty has been found in dispos- ing of the refuse and sludge by means of the destructor, the mass being reduced to clinker one-fourth the bulk of the original. A special furnace is found necessary to destroy the gases generated on their passage from the furnaces to the chimney shaft. Instead of using the dried deposit as manure, Scott proposed to make cement, and for this purpose added hme and clay to the sewer water. The deposit contains so much combustible matter that it requires less coal to burn it than would otherwise be the case. Scott also proposed to use the burnt material as manure to lime the land in some cases. The plan recommended for the treatment of the Thames sewage, as given by the Royal Commissioners on Metropolitan Sewage Discharge, was to adopt some method of precipitation at the outfalls at Barking and Crossness, to compress the sludge into cakes, and as a temporary measure let the effluent pass into the Thames. The plan now adopted is as follows: the chemical precipitants are added to the sewage in covered reservoirs; it is then transferred from the precipitating tanks to special settling tanks, from thence the sludge is pumped into a specially designed steamship and dis- charged under water far from land. The clarified effluent Aoavs into the Thames. As an alternative method the sludge, left in the bottom of the tank after precipitation, may be got rid of by allowing it to Aow in a semi- solid condition in raised carriers on to land, and there distributed, being ultimately dug into and incorporated with the soil; or it may be subjected 2 M 546 DISPOSAL OF SEAVAGE AND REFUSE. to hydraulic pressure, getting rid of a large part of the moisture, and made into solid cakes, Avhich are sold as manure. Intermittent downward filtration is defined by the Metropolitan SeAv- age Commission as "the concentration of seAvage at short intervals on an area of specially chosen porous ground, as small as Avill absorb and cleanse it, not excluding vegetation, but making the produce of secondary import- ance." The intermittency of application is a sine qud non, even in suitably constituted soils, whenever complete success is aimed at. The purification of seAvage by the soil is duevfo (1) the soil acting as a mechanical filter, removing the suspended matters in the seAvage, and (2) to the oxidising power of the soil by which the organic matters are converted into nitrites, nitrates, and carbonates. This oxidising power is partly due to the air contained in the interstices of the sod, but chiefly to the presence of a nitrifying ferment in the soil, and more especially in rich surface soils, such as mould and loam. Nitrification is confined to the same range of temperature, which limits the vital activity of these micro-organisms; it almost ceases near the freezing point and increases in activity Avith a rise of temperature until 37° C. is reached; the action then diminishes and ceases altogether at 55° C. These organisms are confined to the upper layers of the soil and are most abundant in the first six inches. Other conditions necessary for the due performance of their function are a supply of air, and the presence of a salifiable base, such as lime, soda or potash, with Avhich the nitric acid as formed may be combined. Dyke, in explaining the system as carried out at Merthyr-Tydvil, lays down the following conditions as essential to ensure success:—There should be—1st, a porous soil; 2nd, an effluent drain, not less than 6 feet from the surface; 3rd, proper fall of land to allow the sewage to spread over the whole land; and, 4th, division of filtering area into four parts, each part to receive sewage for six hours, and to have an / interval of eighteen hours. He considers that an acre of land would take ' 100,000 gallons per day, equal to the sewage of 3300 people. At Merthyr- Tydvil 20 acres of land were divided into five plots, which sloped towards the effluent drain by a fall of 1 in 150. The Avhole of the 20 acres thus divided was underdrained at a sufficient depth to secure aeration 6 feet below the surface. The surface was ploughed in ridges, on which vegetables were sown; the seAvage (strained) passed from a carrier along the raised margin of each bed into the furrows. The effluent water was stated to be pure enough to be used for drinking purposes. Since 1872 broad irrigation has been carried on as well. Another case of marked success with intermittent filtration is that of Kendal. The best soil for filtration appears to be a loose marl, containing hydrated iron oxide and alumina, but sand and even chalk produce excellent results. But in order that filtration shaU be successful it is necessary that the amount of filtering material shall be large; it must not be less than 1 cubic yard for 8 gallons of sewage in twenty-four hours, and in the case of some soils must be more. If the drains are 6 feet below the surface, then an acre will contain 9680 cubic yards of filtering material, and at 8 gallons per yard an acre would suffice for 77,440 gallons, or the sewage of 2580 people at 30 gallons a head. These views are, however, subject to . some modification, since it has been more recently shoAvn that all the oxida- tion is carried out in the first two, or at the outside three feet of depth. It would, therefore, seem as if we could not greatly increase the amount of sew- age in proportion to the soil. Beds 3 feet in depth would probably be found sufficient, but in this case the superficial extent must be increased in proportion as the depth of the underdrainage is diminished, in order to secure the neces- sary quantity of filtering material for purification. Crops may be grown on IRRIGATION. 547 the land, and indeed it is desirable that they should be. The Rivers Pollu- tion Commissioners state that one acre is required to purify the sewage of 2000 persons. According to Tidy, 1 acre is sufficient for the seAvage of from 5000 to 7000, if it has been previously efficiently precipitated. Condition of the Effluent Water.—When 5*6 gallons of sewage were filtered in tAventy-four hours through a cubic yard of earth, it was found by the Rivers Pollution Commissioners that the organic carbon was reduced from 4*386 parts to 0*734, and the organic nitrogen from 2*484 parts to 0*108 part in 100,000. The Avhole of the sediment was removed. Nitrates and nitrites, which Avere not present before filtration, are found afterAvards, showing oxidation of organic matters. The chlorine, however, remains unchanged, remaining in very much the same proportion in the effluent as in the sewage. The effluent Avater is clear and bright; it generally attains a high standard of cleanliness, and may be allowed to pass into streams otherAvise clean and unpolluted. Irrigation.—By irrigation is meant " the distribution of seAvage over a large surface of ordinary agricultural ground, having in vieAv a maximum growth of vegetation (consistently Avith due purification) for the amount of sewage supplied." It is essential that the sewage should not merely run over, but through, the land, before passing out as an effluent. For this purpose it is desirable that the sewage should be brought to the land in as fresh a state as possible. The seAvage is usually warmer than the air at all times, and will often cause growth, even in winter. The effect on growing plants, but especially on Italian rye-grass, is very great; immense crops are obtained, although occasionally the grass is rank and rather Avatery. For cereals and roots it is also well adapted at certain periods of growth, as well as for market vegetables when the viscid parts are separated. When the sewage permeates through the soil there occur— 1st, a mechanical arrest of suspended matters; 2nd, an oxidation producing nitrification, both of which results depend on the porosity and physical attraction of the soil, and on the influence of micro-organisms; and, 3rd, chemical interchanges. The last action is important in agriculture, and has been examined by Bischof, Liebig, Way, Henneberg, Warrington, and others. Hydrated ferric oxide and alumina absorb phosphoric acid from its salts, and a highly basic compound of the acid and metallic oxide is formed. They act more powerfully than the silicates in this way. The hydrated double sihcates absorb bases. Silicates of aluminum and calcium absorb ammonia and potassium from all the salts of those bases, and a new hydrated double sihcate is formed, in which calcium is more or less perfectly replaced by potassium or ammonium. Humus also forms insoluble compounds with these bases. Absorption of potash or ammonia is usually attended with separation of hme, which then takes up carbonic acid. The best kind of soil is a friable loam; but other soils, such as sands, gravels, &c, when properly managed, are capable of purifying sewage. The soil must be properly prepared for sewage irrigation; either a gentle slope, or a ridge with a gentle slope on each side, of about 30 to 60 feet wide,'with a conduit at the summit, or Aat basins surrounded by ridges, are the usual plans. The sewage is allowed to trickle down the slope at the rate of about 8 feet per hour, or is let at once into the Aat basin. The Avater passes through the soil, and should be carried off by porous earthen- ware underdrains 2 inches in diameter, from 4 to 6 feet deep, and from 20 to 100 feet apart, according to the porosity of the sod, and thence into the nearest Avater-eourse. The sewage should reach the ground in as fresh a state as possible; it is 548 DISPOSAL OF SEAVAGE AND REFUSE. usuaUy run through coarse strainers (and this is ahvays advisable) to arrest any large substances Avhich And their Avay into the sewers, and to keep back the grosser parts which form a scum over the land; it is then received into tanks, whence it is carried to the land by gravitation, or is pumped up; but this latter procedure is costly. The "carriers" of the sewer Avater are either simple trenches in the ground, or brick culverts, or concreted channels, and by means of simple dams and gates the Avater is directed into one or other channel as may be required. Everything is now made as simple and inex- pensive as possible—underground channels and jets, hydrants, hose and jets, are too expensive, and overweight the plan with unnecessary outlay. The amount of land required is, on an average, 1 acre to 100 persons; \ this is equal to a square of 70 yards to the side, and will take 2000 gallons in twenty-four hours. Later experience seems to show that with proper management less land is required. At Croydon, the sewage is applied in the proportion of about 200 persons for each acre; the soil, however, is rather retentive, Avhich causes the sewage to Aow over the surface of the land rather than percolate through it, the greater part of the purification being accomplished by exposure to the air and the action of vegetation. The effluent is clean and free from suspended matter before it passes into the stream. The sewage is applied intermittently Avhen the plants are growing; but in winter it is sometimes used constantly, so as to store up nourishment in the soil for the plant-growth in the spring. In Paris, part of the sewage is treated by irrigation without precipitation. At Gennevilliers, 20 milhons of cubic metres of sewage are pumped on to specially prepared land, on which vegetables, fruit trees, rye-grass, &c, are grown. The sewage never touches the vegetation growing in the irrigated ground. It is distributed throughout the entire plain by furrows, and the practice of flooding the land is not resorted to. The land is thoroughly underdrained, and the effluent issues in a clear and bright stream in which fish are preserved. It is intended to treat the Avhole of the sewage by this method as soon as the necessary works can be erected and sufficient land made available. The same system is adopted at Berlin. One acre of land suffices for the sewage of 142 people, but the very favourable subsoil of the Berlin farms must be taken into account, as light land can undoubtedly receive more sewage than heavy land. In irrigating the plots the sludge goes on to the land with the seAvage, except that where grass plots are sewaged the sludge is intercepted in shallow catch pits, as the sludge is found to interfere Avith the growth of grass. When dry, it is dug out, and finds a ready sale among the farmers. Condition of the Effluent Water after Irrigation.—When the sewer water passes over and not through the soil, it is often very impure, and even suspended matters of comparatively large size (such as epithelium) have been found in the water of the stream into which it flows. It requires, therefore, that care shall be taken in every sewage farm that the water shall not escape too soon. Letheby rated the cleansing power of sod much lower than the Rivers Pollution Commissioners or the Committee of the British Association, and his analyses make it at any rate quite certain that the proper purification of the sewage demands very careful preparation of the ground in the first instance, and constant care afterwards. But the chemical evidence of the good effect of irrigation is too strong to admit a doubt to exist. The foUowing table shows the standard of purity which v'Z- proposed by the Rivers Pollution Commission:— GENERAL INFLUENCE OF SEWAGE FARMS. 549 Standard of River* Pollution Commissioners. Maximum of Impurity permissible in 100,000 parts by iceight of the liquid. Dry mineral matter in suspension. Dry organic matter in suspension. In Solution. Colour. 0rgamc | carbon. Organic nitrogen. Any metal ex-cept Calcium, Magnesium, Potassium, or Sodium. Arsenic. Chlo-rine. Sulphur as SH2, or sulphate. 3 1 Shown in 1 a stratum 1 of 1 inch 2 . in a white plate. 0-3 2 0-05 1 1 A certain degree of acidity or alkalinity is also ordered not to be sur- passed. The objection to the plan is not merely the doubt about the sub- stances represented by organic carbon or nitrogen, but also because the standard does not take into consideration the volume of water into Avhich the foul water flows. The Thames Conservancy Commissioners adopt a standard for effluent seAvage as follows :— Must not exceed in 70,000 parts. In 100,000. Suspended matters, ..... 3 parts. 4'3 Total solids,......70 ,, 100-0 Organic carbon, ...... 2 ,, 3-0 ,, nitrogen, ..... 0*75 ,, 1*1 The folloAving table gives the results of analyses of the Berlin effluents :— Average Percentage of Dissolved Organic Pollution removed. Berlin Effluents. As expressed in parts of Permanganate of Potash reduced. Organic Ammonia. Broad irrigation : grass plots. Average of 71 samples, ..... Filtration beds. Average of 76 samples, ,, tanks. ,, 36 ,, 93 89 92-56 82 60 98*15 97*72 94-83 These figures show the great purity of the Berlin effluents, and prove the satisfactory results that can be obtained from a large and well-managed seAvage farm. Sanitary condition of the Population living on Sewage Farms.—That seAvage farms, if too near to houses and if not carefully conducted, may give off disagreeable effluvia is certain; but it is also clear that in some farms this is very trifling, and that when the sewage gets on the land it soon ceases. All those who have visited the farms bear testimony to the absence of any smell in the fields, and only in one or two places near a sluice-outlet could any unpleasant smell be perceived when the sluices were opened. As regards health, it has-been alleged these farms may—1st, give off effluvia which may produce enteric fever, or dysentery, or some allied affection; or, 2nd, aid in the spread of entozoic diseases; or, 3rd, make ground swampy and marshy, and may also poison Avells, and thus affect health. The evidence of Edinburgh, Croydon, Aldershot, Rugby, Worthing, Birmingham, Paris, Berlin, Romford and the Sussex Lunatic Asylum, is very 550 DISPOSAL OF SEAVAGE AND REFUSE. strong against any influence in the production of enteric fever by seAvage farms' effluvia. Clouston records an outbreak of dysentery in the Cumber- land Asylum; but the disease in this case appears to have been caused by the inefficient manner in AA-hich the irrigation Avas carried out, rather than to the process itself. SeAvage is still applied to the grounds of this asylum, and from 1874 to 1887 no disease or nuisance of any kind was caused by the sewage farm. Letheby also records an outbreak of enteric fever at Copley, when a meadow was irrigated -with the brook water containing the seAvage of Halifax. The statistics of the population residing on the Berlin seAvage farms is almost conclusive evidence that they do not exert any influence in the production of disease. The average annual population during the five years 1885-89 AA-as 1580 : of these 968 or 61 per cent, were men, 285 or 18 per cent. Avere Avomen, and 327 or 21 per cent, were children under fifteen years of age. The death-rates per 1000 from all causes were 11*24 in 1885, 9*22 in 1886, 14*83 in 1887, 6*79 in 1888, and only 4*81 in 1889. Of the total deaths 16 per cent, occurred among men, 9 per cent, among women, and 75 per cent, among chddren. The death-rate from the seven principal zymotic diseases was 4*32 in 1885, 3*69 in 1888, 4*15 in 1887, 1*13 in 1888, and nil in 1889, the mean rate during the period from these causes being 2*53. Only one death Avas due to enteric fever during the period under review. Evidence of this kind is so strong as to justify the view that the effluvia from a well-managed sewage farm do not produce enteric fever or dysentery, or any affection of the kind. At Eton, where some cases of enteric fever were attributed to the effluvia, Buchanan discovered that the sewer water had been drunk; this was probably the cause of the attack. With regard to the second point, the spread of entozoic diseases by the carriage of the sewage to the land was at one time thought probable, though as solid excreta from towns have been for some years largely employed as manure, it is doubtful whether the liquid plans would be more dangerous. The special entozoic diseases which it is feared might thus arise are Tape- worms, Round icorms, Trichina, Bilharzia, and Distomum hepaticum in sheep. Cobbold's latest observations showed that the embryos of Bilharzia die so rapidly that, even if it were introduced into England, there would be little danger. The Trichina disease is only knoAvn at present to be produced in men by the worms in the flesh of pigs which is eaten, and it is at least doubtful whether pigs receive them from the land. There remain, then, only Tapeicorms and Round ivorms for men and Distomum hepaticum for sheep to be dreaded. But, with regard to these, until positive evidence is produced, this argument against seAvage irrigation may be considered to be unsupported. It is not improbable that alkaline sewage may destroy organisms, like the ova of tapeworms, whose natural habitat is the acid secretion of the human intestine. An epidemic of "Enterocolitis," due apparently to the presence of Trichocephalus, occurred at Pierrefeu (Var) amongst the patients of an asylum. Between Jan. 1888 and March 1889 there Avere 137 cases amongst the inmates (more than half), together with 17 employes. There was no epidemic outside the asylum. It was attributed to the watering of the gardens with sewage Avater; the use of the vegetables was stopped, and the illness ceased. The third criticism appears to be true. Unless the system is properly carried out the land may become sAvampy, and the adjacent wells polluted, and possibly disease be thus produced. But this is owing to mismanage- ment, and when a sewage farm is properly arranged it is not damp and the Avells do not suffer. THE SEPARATE AND LIERNUR SYSTEMS. 551 Modifications of the Wet Method of Removing Excreta. The Separate System.—By this term is meant the arrangement which carries the rain-water in separate channels into the most convenient water- course. Ward's celebrated phrase, " the rain to the river, the seAvage to the soil," is the principle of this plan. Its advantages are that the sewers can be smaller; that the amount of sewer water to be dealt Avith atthe outfloAv is much less in quantity, more regular in flow, more uniform in composition, and richer in fertflising ingredients, and is, therefore, more easily and cheaply disposed of. The grit and debris of the roads also are not carried into the seAvers; and the storm waters never flood the houses in the Ioav parts of the town. The disadvantages are, that separate channels and pipes have to be provided for the rain; that the rain from all large cities carries from roofs and from streets much organic debris which pollutes streams, and that the scouring effect of the rain on seAvers is lost, though this last is a very questionable objection. The adoption of one or other system -will probably depend on local condi- tions. If a town in Europe lies low, and it is expensive to lift sewage; if land cannot be obtained; or if the natural contour of the ground is very favourable for the Aoav of rain in one direction, while it is convenient to carry the sewage in another, the separate system would be the better. So also in the tropics, Avith a heavy rainfall and a long dry season, the providing of sewers large enough to carry off the rain Avould be too expensive for all except the richest cities, and the disposal of the storm water would be difficult. In all cases in which rain enters the seAvers, some plan ought to be adopted for storm waters. If irrigation is the plan carried out, the sewage becomes so dilute and so large in quantity in storms, that the application to land is usually suspended, and the seAvage is alloAved to pass at once into streams. In this way the evil which irrigation is intended to prevent is produced, though, doubtless, the sewage is highly dilute. In London the storm waters mingled with sewage are alloAved to Aoav into the Thames, special openings being provided. The Liernur System.—A Dutch engineer, Captain Liernur, proposed some years since an entirely novel plan. ]Sro water or deodorising powders are used; the excreta fall into a straight earthenAvare pipe, leading to a smaller iron siphon pipe, from which they are extracted periodically by exhaustion of the air. The extracting force which can be used (by an air pump Avorked by a steam engine) is said to be equal to a pressure of 1500 lb per square foot, which is sufficient to draw the excreta through the tubes Avith great rapidity. The plan has been tried on a small scale at Prague, Rotterdam, Amsterdam, Leyden, and Hanau, also at Briinn, Olmutz, and St Petersburg, and the opinions concerning it are very various. It does not render sewers unnecessary ; indeed, the system contemplates that every house is provided Avith two sets of drains—one for household Avaste waters and rain-Avater, and the other for the fsecal matters from closets without Avater-supply, and for bed-room slops containing urine. The first set of pipes are connected Avith the drains in the street Avhich receive rain-water and the waste waters from factories, and which finally discharge their contents into the nearest river or water channel. The second set of pipes, as described above, are connected with an iron reservoir placed beloAV the surface of the level of the street, from Avhich the seAvage is sucked into 552 DISPOSAL OF SEAVAGE AND REFUSE. reservoirs outside the town, Avhere it is further concentrated by heat, and dried in revolving cylinders, Avhence it passes out as a poAvder, and is sold for manure. The system is not a good one, as the pipes get clogged sooner or later with faecal matter. There is also evidence of offensive odours being generated, either from the street reservoirs or from the closets; to prevent this Avater is used, which interferes AAdth the proper Avorking of the system. The Berlier system, a modification of the preceding, is in use in one of the districts of Paris. The principle is extraction by exhaustion of air. The sohd matters are separated by an intercepting wire basket, called a receiver, and the liquid sewage Aoavs into an air-tight evacuator, to which an exhaust is attached, which Avorks automatically, and is therefore an improve- ment on the Liernur system. Shone's Ejector System.—This is an opposite plan to Liernur's, the agent being compressed air instead of exhaustion. The leading feature of the system is the method of raising the seAvage by means of compressed air at such pohits as are convenient on its course to the outfall. The sewage is received into " ejectors," and after a certain quantity has entered, it is acted upon by compressed air, and, by an arrangement of valves acting automati- cally, is forced either to an outfall direct, or into a closed iron main. It has been applied at Wrexham, at Eastbourne, at Southampton, the Houses of Parliament, and elsewhere. It seems especially useful where the ground is flat and where it is difficult to get a fall. It works automatically, and gives very little trouble. Webster's Process—Electrolysis.—This process consists in allowing ordinary sewage to flow through channels in Avhich are placed iron plates or electrodes, set longitudinally, with the usual battery connections with the positive and negative terminals of a dynamo. The sewage in its passage through these channels is said to become entirely split up by the action of the electric current upon the chlorides always present in the sewage. At the positive pole the chlorine and oxygen given off combine with the iron to form a salt Avhich is probably hypochlorite, and at the same time carbon- ate of iron is assumed to exist in solution, which not only deodorises the faecal matter by removing sulphuretted hydrogen, but also acts as a carrier of oxygen from the air by being alternately reduced to ferrous and oxidised back to ferric oxide. The process, therefore, although an electrical one, depends upon the production of certain chemical salts. The continuous formation of the iron oxides, in their nascent state, and the thorough mixing of them with the sewage, are the special features of the process. This method of treating sewage adds but httle to the sewage itself, and therefore limits the quantity of sludge to the lowest amount consistent with the removal of the suspended solids from the sewage. This system has been under trial at Crossness and Bradford; the sewage of the latter town contains a large proportion of manufacturing refuse, and is. considerably altered by the admixture of dyes, acids, alkalies, organic matters, and grease from the woollen manufactories. The average composition of the Bradford sewage before the electrical treatment, and of the effluent after it, are as follows:— Total solids, After ignition, . Loss on ignition, Chlorine, . Free ammonia, . Albuminoid ammonia, Sewage before the Effluent after the Electrical Treatment. Electrical Treatment. 127 grains per gallon. 66 grains per gallon. ™ .. » 47 „ „ 38 9, „ 19 !0 „ „ 9 „ „ 32 parts per million. 21 parts per million. 15 ,, ,, 5 HERMITE AND SCOTT-MONCRIEFF PROCESSES. 553 This analysis shows that something like 70 per cent, of the putrescible and noxious portion of the sewage is removed by electrolysis. The micro- scopic examination of the sewage before treatment revealed an abundance of infusoria, bacteria and low forms of organic life, while in the effluent no living organisms could be detected. From investigations conducted in Paris, the micro-organisms were reduced in number from 5,000,000 per cubic centimetre of raw sewage to 600 in the effluent. There is, therefore, every reason for believing that in electricity as used in Webster's patent Ave have an agent capable of purifying even the worst seAvage to such a degree as to render it fit to enter an ordinary stream. The cost involved is, however, large, on account of the immense quantity of iron employed and the large amount of tank room necessary. , The Hermite Process. —This method consists in the electrolysis of sea- water and the subsequent flushing of the contents of water-closets with a definite quantity of the resultant fluid. The Hermite fluid is a chemically active fluid prepared by electrical means. The sewage is never in contact with the current, as is the case in the Webster process, nor does the process pretend to secure the precipitation of organic matters. It claims rather to effect the complete deodorisation and sterilisation of sewer contents. The system is based upon the electrolysis of sea-water. The electric current decomposes the chloride of magnesium, while the chloride of sodium acts as a conductor. The result is a liquid disinfectant of some power. It is almost odourless, leaves no residuum Avhen used for purposes of flushing, and is perfectly inoffensive. The solids in the sewage are nearly all dis- solved, and the organic matter rendered for the most part innocuous. The resultant liquid is odourless, docs not readily decompose, and contains little else besides the disinfectant and a httle phosphates. Experiments at Worthing go to show that this fluid deodorises but does not destroy or remove organic matters, although there is little doubt that certain of them are partially changed and most probably those which are more readily putrescible. While these things are true and are so far satisfactory, there must also be certain draAvbacks in the system which were indicated in these experiments. Electrolysed sea-water is rapidly reduced in strength by common newspaper, and as this is always present in a sewer, it must seriously affect the activity of the liquid, even if it does not withdraw the active constituent entirely. Soap or domestic waste has the same effect, so that the entire contents of the seAver rapidly appropriate the chlorine strength of the liquid. Again, if the chlorinated body be in excess, when its action is complete, it is not admissible to pour an effluent containing free chlorine or its equivalent into rivers. For many purposes the use of electro- lysed sea-water will be of advantage; it could be used, for example, to flush the heading of drains and sewers, or it could be discharged into sewage outfalls. The method would, hoAvever, appear to be an expensive one. Bacteriological examination of the effluent showed that although it was not absolutely free from micro-organisms, their numbers were reduced to such an extent that it was practically sterile; colonies of the Bacillus coli communis were absent, and it is therefore probable that the Bacillus typhosus or the bacillus of cholera Avould be unable to resist the action of the Hermite fluid. A strength of from 0*5 to 0*6 gramme of chlorine per litre is all that is considered necessary to destroy these micro-organisms by this method of sewage treatment. This system possesses many advantages and is well worthy of a more extended trial. Scott-Moncrieff Process.—Instead of endeavouring to sterilise the sewage, Scott-Moncrieff proposes to facilitate the processes of putrefaction 554 DISPOSAL OF SEWAGE AND REFUSE. by placing the seAvage under specially favourable conditions to bring about that end, so that complex organic matters may be broken down as rapidly as possible into a series of lower compounds. This method consists essentially in passing the seAvage upwards through a filtering medium 14 inches in depth and composed of successiA-e layers of flint, coke, and gravel. The process is not a neAv one, and upAvard filtration has long since been abandoned in favour of doAvmvard filtration through the soil. The vigorous action of the putrefactive organisms are relied on, and the conditions produced by them to destroy or render inert any pathogenic micro-organisms which may happen to be present. So far, the results obtained by this method are not such as to lead us to expect that it will be adopted generally. The Influence of Sanitary Works upon Public Health.—Reference has elsewhere been made to the possibility of seAvers being the channels by Avhich enteric fever and cholera have been propagated from house to house, and from Avhich emanations, causing .diarrhoea and other complaints, may arise. Admitting the occasional occurrence of such eases, it remains to be seen Avhether the sanitary advantages of sewers may not greatly counterbalance their defects. The difficulty of proving this point statistically consists in the number of other conditions affecting the health of a toAvn in addition to those of seAverage. Buchanan has, hoAvever, given some valuable evidence on this point, Avhich has been well commented on by Sir J. Simon. He inquired into the total death-rate from all causes, and the death-rate from some particular diseases, in tAventy-five toAvns before and after sanitary improvements, Avhich consisted principally of better Avater-supply, seAverage, and town conservancy. The general result is to sIioav that these sanitary improvements have resulted in a lowering of the death-rate in nineteen out of twenty-five towns, the average reduction in these nineteen cases being 10*5 per cent. The reduction of enteric fever was extremely marked, and occurred in tAventy-one towns out of tAventy-four, the average reduction being 45*4 per cent, in the deaths from enteric fever. In nine toAvns the reduction exceeded 50 per cent., being highest in Salisbury, where the former rate of 0*75 per 1000 Avas reduced to 0*175 per 1000—a reduction of over 75 per cent. In ten towns the reduction varied between 33 and 50 per cent.; in tAvo there was only a slight reduction. In three cases there was an augmentation of enteric fever. The reason of the increase in these towns (Chelmsford, Penzance, and Worthing) is explained by the fact of insufficient ventilation of the sewers, combined Avith backing up of sewage in them, so that sewer gases found their Avay into the houses ; these cases afford excellent instances of the unfavourable part badly-arranged sewers may play in this direction. In 1869 (the first year in Avhich enteric fever is shoAvn in the Registrar-General's returns as separate from "fever") the death-rate from enteric fever in England and Wales was 0*39 per 1000 of the population, and has steadily declined to the present time, the death-rate in 1890 being only 0*179 per 1000; in 1891, 0*169 per 1000; in 1892, 0*137 per 1000, and in 1893, 0*229 per 1000, a reduction of nearly 50 per cent. in twenty-five years. Soyka has given some interesting statistics of German toAvns with regard to this point. In Hamburg the enteric deaths per 1000 total deaths have fallen from 48*5 to 10*5 ; in Dantzig from 26*6 to 2*3. In Munich the enteric deaths per 1000 living have fallen from 1*15 (1866-1880) to 0*16 (1881-1888), the city drainage having been completed in 1888. During this period, the population of Munich had increased from 152,000 in 1866 to 278,000 in 1888, or nearly doubled. The sudden loAvering of the enteric fever mortality took place immediately after the COMPARISON OF DIFFERENT METHODS. 555 drainage was completed in 1881: the neAv Avater-supply Avas not provided until some years after. Diarrhoea has also been reduced, but not to such an extent; and in some towns it has increased Avhile enteric fever has simultaneously diminished. But the term diarrhoea is so loosely used in the returns as to make any deduction uncertain. Cholera epidemics Buchanan considers to have been rendered "practically harmless." The immense significance of this state- ment will be at once appreciated. Whether the result is OAA-ing solely to the sewerage or to the improved water-supply, Avhich is generally obtained at the same time, is not certain. Phthisis, which Buchanan and Bowditch find to be so much influencd by dampness of soil, does not appear to have been affected by the removal of excreta per se,—at least toAvns such as AlnAvick and Brynmawr, Avhich are thoroughly drained, show no lowering in the phthisical mortality. In fifteen towns out of the tAventy-five examined, the phthisis death-rate exhibited a very considerable reduction. This reduc- tion can only be attributed to the drying of the subsoil which followed on the laying of the main seAvers in these towns. Where the drying of the subsod was greatest and Avhere it Avas most needed, as in Salisbury, Banbury, Rugby, and Ely, there the mortality from phthisis showed the greatest reduction. Buchanan states that croup and diphtheria had increased in all the twenty-five towns during or after their sanitary improvements. In many cases it was coincident with the introduction of the new system and increased after their completion. That diphtheria figures largely in the mortality returns of towns can no longer be denied ; the explanation of its increase is still wanting, but it is evident that the sanitary improvements which have had such a marked effect on enteric fever have had hitherto little influence in controlling this disease. As far as can be seen, the effect of good sewerage has therefore been to reduce the general death-rate, especially by the reduction of deaths from enteric fever and from cholera (and in some towns from diarrhoea), but partly, in all probability, by general improvement of the health. Their action has been, in fact, very much in the direction we might have anticipated. It may be observed that this inquiry by Buchanan does not deal with the question as between sewers and efficient dry methods of removing excreta (on which point we possess at present no evidence), but between sewerage and the old system of cesspools. Comparison of the different Methods.—Much controversy has arisen on this point, though it does not appear that the question of the best mode of removing excreta is really a very difficult one. It is simply one which cannot be always answered in the same way. It will probably be agreed by all that no large town can exist without seAvers to carry off the foul house water, some urine and trade products, and that this sewage must be purified before discharge into streams. The only question is, whether feecal excreta should also pass into the sewers. It will also be, no doubt, admitted that no argument ought to be drawn against sewers from imperfection in their construction. The advocate of Avater removal of solid excreta can fairly claim that his argument pre- supposes that the seAvers are laid with all the precision and precaution of modern science; that the houses are thoroughly secured from reflux of sewer air ; that the water-closets or water-troughs are properly used; and that the other conditions of sufficient water-supply and poAver of disposal of the sewage are also present. If these conditions are fulfilled, what reason is there for keeping out of the seAver water (which must, under any circum- 556 DISPOSAL OF SEAVAGE AND REFUSE. stance of urban life, be foul) the solid excreta, AAdiich, after all, cannot add very greatly to its impurity, and do add something to its agricultural value ? That it is not the solid excreta alone which cause the difficulty of the dis- posal of sewer water is seen from the case of Birmingham. That town is sewered; when it contained nearly 400,000 inhabitants, it was in the greatest difficulty Iioav to dispose of its sewer water; yet the solid excreta of only 6 per cent, of the inhabitants passed into the seAvers, while the solid excreta of the remainder were received into middens. The problem of disposal was as serious for Birmingham as if all the excreta passed in. This difficulty has now been overcome, by the use of the lime precipitating process and the passing of the seAvage on to land. An innocuous effluent is obtained, and the sewage of over 606,000 people is dealt with, the excreta of the whole population passing into the sewers. The great difficulty, in fact, consists not so much in the entrance of the solid excreta into sewers as in the immense quantity of water Avhich has to be disposed of in the case of very large inland toAvns with water-closets. If water-closets are not used, the amount of water supplied to towns, and the amount of sewage, are both considerably lessened. Looking to all the conditions of the problem, it appears impossible for all towns to have the same plan, and the circumstances of each town or village must be considered in determining the best method for the removal of excreta. London is particularly well adapted for water sewerage, on account of the conformation of the ground north of the Thames, of the number of streams (which have all been converted into sewers), and of the comparative facility of getting rid of its sewage. The same may be said of Liverpool and many other towns. In many towns where land is available, the immediate application to land, either by filtration or irrigationv may be evidently indicated by the conditions of the case, while in others precipitation may have to be resorted to before application to land. It does not appear that precipitation should in all cases precede irrigation or filtration, though mechanical arrest of the large suspended matters is necessary. There may be some towns, again, in which the impossibility of getting water or land may necessitate the employment of dry removal; and this is especially the case with small towns and villages, where the expense of good sewers and of a good supply of water is so great as to render it impossible to adopt removal by water. It may, indeed, be said that, in small toAvns in agricultural districts, the dry removal, if properly carried out, will be the best both for the inhabitants and for the land. The view here taken that no single system can meet all cases, and that the circumstances of every locality must guide the decision, is not a com- promise between opposing plans, but is simply the conclusion which seems forced on us by the facts of the case. It does not invahdate the conclusion already come to, that, Avhere circumstances are favourable for its efficient execution, the water-sewerage plan (with or without interception of rainfall) is the best for large communities. BIBLIOGRAPHY AND REFERENCES. 557 BIBLIOGRAPHY AND REFERENCES. Angell, "The Treatment and Disposal of Sewage and SeAvage Sludge," Trans. San. Instit., vol. xiii. p. 209. Bailey-Denton, Handbook of House Sanitation, Lond., 1882 ; also Sanitary Engineer- ing, Lond., 1877. Berringtox, "Report on the Wolverhampton Sewage Works," Proc. Inst. Civil Engineers, Paper No. 2576, vol. ex., 1891-92; also Part iv., 1892. Boavditch, The Siphonage and Ventilation of Traps, being a Report to the National Board of Health, New York, 1882. Broavn, Report on Experiments in Trap Siphonage at the Museum of Hygiene, Nan/ Department, U.S.A., Washington, 1886. Chadavick, Sir E., "Sanitary Sewage and Water Supply," Trails. San. Instit., vol. ix. p. 343. Corfield and Parkes, Treatment and Utilisation of Sewage, Lond., 1887 ; also Article in Stevenson and Murphy's Treatise on Hygiene, vol. i. p. 805. Crimp, Sewage Disposal Works, Lond., 1894; also Sewage Treatment, Lond., 1893. Dyke, "On the Downward Intermittent Filtration of Sewage at Merthyr-Tydvil," Brit. Med. Journal, Aug. 25, 1888. Fischer, "Die Menschliche AbfallstofFe," published as a Supplement to Deutsche Viertelj.f. Offentl. Gesundht., 1882. Hanson, " The Use of Black Ash Waste in the Treatment of Sewage and Foul Water," Trans. San. Instit., vol. xi. p. 201. Latham, Sanitary Engineering, Lond., 1873. Letheby, The Seivage Question, Lond., 1872. Maguire, Domestic Sanitary Engineering and Plumbing, Dublin, 1890. Middleton, " House Drainage," Trans. San. Instit., vol. ix. p. 273. Palmberg, Public Health and its Application, edited by NeAvsholme, Lond., 1895. Ratcliffe, Beport on the Dry Methods of Bemoval of Sewage, Twelfth Report of the Med. Off. to the Privy Council, Lond., 1870, pp. 80 and 111. Reid, Bractical Sanitation, Lond., 1895. Beport of Commission on the Sevjage of Towns, Lond., 1861. Beport of East London Water Committee, Lond., 1867. Beports of Rivers Pollution Commissioners, since 1870, vols. i. to vi. Beport of the Birmingham Sewage Inquiry Committee, 1871. Beport on Town Sewage, issued by Loc. Govern. Board, 1876. Beport on Metropolitan Sewage, Lond., 1884. Beport on the Puri- fication of Sewage, by the State Board of Health, Massachusetts, Boston, 1890. Beport on Quantity of Water necessary for Water-Closets, hy the Committee of the Sanitary Institute, Lond., 1893. Beport of Royal Commission on the London Water Supply, 1894. Robinson, "Sewage Disposal," Trans. San. Instit., vol. x. p. 194. Roechling, " The Sewage Farms of Berlin," Broc. Inst, of Civil EngiiJ., vol. cix., 1891-2 ; also Part iii., 1892. ^ Simon, Sir J., Bublic Health Beports, republished by Sanitary Institute, 1887. Smith (Angus), Beport on the Bivers Pollution Prevention Act, Lond., 1882. Soyka, " On the Health of German Towns," Deutsch. Viertelj. fur Offentlich. G-esundheit,. Bd. xiv. Heft 1, 1882, p. 33. CHAPTER XL PARASITES. In its Avidest sense, the name of parasites has been given to all those creatures which are nourished Avholly or partially at the expense of other living organisms. As thus understood, parasitic life is, therefore, an exceedingly widespread phenomenon, and includes not only vegetable and animal parasites, but also parasites on vegetables and on animals. The length of parasitic existence, and the degree and nature of the benefit Avhich the parasite thus obtains, varies greatly vrith different species; and the effect produced by the parasite upon its host ranges from an almost im- perceptible one to complete destruction. At one extreme are certain forms Avhich, while drawing the nourishment necessary for life from their hosts, yet do so in such fashion that both organisms continue to hve in intimate association, and apparently with mutual advantage. Erom these we can pass, by a series of gradations, to parasites of such destructive influence as to cause widespread death to certain animal and vegetable forms of life. This physiological and pathological group is closely related to another, the saprophytes, which obtain their nourishment from the dead remains of organisms. From the foregoing necessarily abbreviated statement we observe not only the enormously wide prevalence of parasitism—" the number of parasitic individuals, if not indeed that of species, probably exceeding that of non- parasitic forms"—but its very considerable variety in degree and detad. The majority of parasites, indeed, derive their main support from their host, but of these some are free, wandering about from animal to animal, some are attached permanently to the exterior of their victim, while others again are concealed within its body. In some cases, the parasitism is only temporary, in others it is a life-long habit. The majority are free in their youth, Avhile some pass their early life as parasites, becoming free in their mature state, and others again spend their whole life on their host. Some classification of these various parasitic forms is necessary. Van Beneden introduced the term commensals or messmates, including fixed and free partners, as distinguished from true parasites. In this classification there is no attempt to define the degree of dependence or the closeness of association, except in the general distinction between parasites and mess- mates. Leuckart distinguishes parasites as ecto- and endo-parasitic, and divides the former into temporary and permanent. Endo-parasites he divides according to the nature and duration of their strictly parasitic life. (1) Some having free-living and self-supporting embryos, Avhich become sexually mature either in their freedom, or only after assuming the parasitic habit. (2) Others Avith embryos which, without having a strictly free life, yet pass through a period of active or passive Avandering, living for a Avhile in an intermediate host. They may either (a) escape to pass CLASSIFICATION OF PARASITES. 559 their adult life in freedom, or (b) they may become sexual, or (c) they may bore their way to another part of the body, or (d) most frequently they pass to their final host either directly Avhen their intermediate host is devoured as food, or indirectly seeking for themselves another intermediate host, or producing asexual forms Avhich do so. (3) Others again having no free-living or even migratory embryonic stage, but passing through their com- plete life-cycle in one host. This somewhat detailed classification has at least the advantage of clearness, and of sliOAving to some extent the various degrees of parasitism : but it is confined, like Beneden's, entirely to animals living as parasites upon other animals, and fails to include those vegetable forms which inhabit a living organism and obtain nourishment from its body. A more physiological classification has been proposed by Kossmann, deahng Avith the organisation and habit of the parasite. Briefly explained, it consists of two great classes : (1) vegetative forms, or those without in- dependent digestive organs; and (2) those Avith independent digestive systems Avhich include, hoAvever, such a variety of details, as to make it almost impossible to establish any logically accurate divisions. Any strict classification of such a variety of organisms as the parasites, having only in common the physiological correspondence of their mode of life, is almost impossible, and the most that can be done is to point out the existence of a series of adaptations varying Avith the intimacy and constancy of the associa- tion, and the degree of dependence. The history of the medical aspects of parasitism is not extensive. Although from the time of the ancient Arabian physicians some diseases, such as itch, have been referred to parasites, it was not till within the last forty years that, with the rise of experimental helminthology, a scientific conception of the parasitic theory of disease elaborated that systematic war- fare against all forms of parasitism Avhich now occupies so important a place in preventive medicine. The parasites of man cover a Avide range in the animal and vegetable world, and embrace species from such diverse organisms as the Schizomy- cetes, the Blastomycetes, the Hyphomycetes, the Protozoa, the Insecta, the Arachnida, the Suctoria, the Nematoda, the Cestoda, and the Trematoda. Of these the parasitic bacteria or Schizomycetes will not be included in this article, as their importance in morbid processes, and particularly in the infective diseases, is such as to require separate and very special treatment. Some further reference to them Avill be found in the chapter which discusses the infective diseases. BLASTOMYCETES, OR YEASTS. A familiar example of this group is torula, Avhich is capable of producing alcohol when growing in substances containing glucose. By torula is under- stood an oval micro-organism, varying in size from 3 to 6 //., and consisting of a membrane and protoplasmic contents, including often one or two vacuoles. A characteristic feature of these organisms is that they multiply by budding and not by fission. A very large number of different species of torulas have been described, especially in connection with alcoholic fer- mentation. These organisms are of interest to the hygienist in two ways: (1) by their constantly being present in the air, soil, and water; and (2) by a species of torula being connected with a well-defined disease known as thrush in infants. 560 PARASITES. Oidium albicans, or the active cause of thrush, is a torula morphologically identical with the species connected with alcoholic fermentation. Upon saccharine cultures, poor in water and cut off from the air, this torula grows like yeast and excites fermentation. Upon nutrient media, rich in nitrogen and Avater, it forms articulated filaments, longer or shorter, which in many places support rounded or oval conidia. Upon gelatin plates, it develops as coarsely granulated groAvths, reminding one of yeast colonies; it does not liquefy the gelatin. It is pathogenic for poultry and pigeons on inoculation in the crop, Avhere it develops a characteristic aphthous membrane. HYPHOMYCETES, OR MOULDS. This group comprises organisms " which consist of cells multiplying by fission, and which, by continued linear and lateral multiplication and by elongation, form branched mycelial threads; each of these is composed of cylindrical cells." The actual mature cells consist of a faintly granular protoplasm contained in a cellular sheath. The ripe cells are separated from one another by transverse septa; this is, hoAvever, not present in the young cells.. In some species of this group, the terminal threads, by a simple process of fission, produce free cells which are conidia or spores. These species are known as oidium, the chief being oidium lactis, the oidium of favus, the oidium of ringworm and of pityriasis versicolor. The spores, by germina- tion, elongate, groAv, divide, septate, and ultimately give rise to a branched mycelium of cylindrical cells. Other species, like Aspergillus, Mucor, and Penicillium, under favourable conditions with free exposure to the air, present a more complicated mode of spore formation; but when unfavourably situated behave like an oidium, forming spores by simple fission of the terminal cells of the filamentous threads. Oidium lactis is an often abundant inhabitant of sour milk, bread, paste, potato, and gelatin. It is said to have no pathogenic properties. It appears as a Avhitish filamentous growth, Avith spherical or oval spores, measuring 7 to 10 /x. Achorion Schbnleini is the oidium of favus, and like that of ringworm (Trichophyton tonsurans), and of pityriasis versicolor (Microsporon furfur), closely resembles, both in its cultural and morphological characters, the oidium lactis. Upon serum, it forms elliptical conidia without special supporters. Upon gelatin, it groAvs slowly Avith gradual liquefaction, first as a whitish, flocky layer, and then thick, dry, and white. It grows also on agar and potato. The Trichophyton tonsurans is very like the above, but the filaments are more rectilinear. It only grows at an incubation tempera- ture and on an alkaline medium. It liquefies gelatin, grows on agar and serum but not on potato. Aspergillus.—The various forms of Aspergillus are only observed saprophytically in man, especially in the lungs, external auditory meatus, and middle ear. The spores, introduced into the vascular system of animals, establish metastatic foci in the various viscera. To this group also belong Saprolegnia, Botrytis Bassiana, and possibly Actinomyces or the ray fungus. Saprolegnia are colourless threads, forming dense radiating tufts which occur on li-ving and dead animal and vegetable matter in fresh water. The filaments penetrate into the substratum, and branch more or less in the sur- rounding Avater. This parasite attacks fish and tritons, producing a diseased PROTOZOA. 561 condition of the skin, Avhich may be ultimately fatal. In salmon it produces the common disease of salmon. Botrytis Bassiana.—This occurs as colourless hyphse and spores, the former being usually simple, but sometimes united in arborescent stems. This fungus is the cause of muscardine, a fatal disease of silk-worms, and occurs also in various other caterpillars and insects. An obscure mycelium, which, penetrating the skin and subcutaneous tissue, sets up suppuration and ulceration, has been described as the cause of a disease known in India as " madura foot." According to Kanthack, it somewhat resembles, if it is not actually, the following:— Actinomyces.—This is a fungus, commonly called the "ray fungus," which is common to both man and animals, producing a pathological con- dition known as actinomycosis. The parasite appears in the form of a rosette of pyriform or club-shaped elements. The little masses are colour- less, white, or of a yellowish-green tint and visible to the naked eye. Having gained access to the living organism, this fungus sets up inflamma- tion in its neighbourhood, resulting in the formation of a neoplasm, com- posed chiefly of round cells, resembling a tuberculous nodule. These nodules may break down and suppurate, or may go on increasing in size. In cattle, the jaws are usually affected. The organism may also occur in the ahmentary tract, the lungs, subcutaneous and intermuscular tissues. The various situations in Avhich this organism is found suggest that its usual habitat is in the outside world, and that it is introduced into the body from without. The most generally accepted view now is that the natural habitat of the ray fungus is on the cerealia, that it lives on these parasiti- cally (especiaUy upon barley), and through and from these enters the animal body through wounds, abrasions, &c. Microscopic examination of the actinomycotic masses shows the central part to be made up of fine granules, or of fine branched threads; next is a zone of coarser granules, due to optical sections of the fine fibres, while at the periphery of the mass are glistening, radially aggregated, flask or club- shaped bodies. OccasionaUy, the central zone is found calcified. Consider- able controversy has existed, as to the precise nature of this fungus. In the present day, it is very generally accepted that the club-shaped bodies are sprouting parts and conidia-bearing ends, the threads being analogous to the mycelium of an oidium-like fungus. Actinomycosis has been transmitted from cattle to cattle by inoculation, and a rabbit has been infected by means of a piece of human actinomytic tumour, introduced into the peritoneal cavity. The actinomyces, on blood serum and on agar at 37° C, forms whitish granules, reaching its maximum growth in six days. The granules show branched mycehal threads with club-shaped bodies. Similar development can be obtained in broth and on gelatin ; this latter, however, liquefies. PROTOZOA. Along Avith the vegetable parasites above described and the larger animal intruders, to be discussed subsequently, we have in the course of years become acquainted Avith a series of small pathogenic animals, not sufficiently known as yet from the zoological point of view, but probably belonging to the group of the lowest protozoa. Unfortunately, our methods of investiga- tion are still imperfect; the forms of the organisms in question being scarcely 2N 562 PARASITES. distinguishable from leucocytes, or cell nuclei. Though the literature of this subject is very considerable, hitherto the significance of these organisms has been shown chiefly for some of the lower animals rather than for man. Some instances of these organisms are :— Amoeba dysenterise.—Various observers, notably Losch, Kartulis, and Councdman, have described round or slightly oblong bodies, consisting of an outer pale homogeneous substance enclosing a somewhat greenish highly refractive mass, containing vacuoles and a nucleus, as being present in certain forms of dysentery. A characteristic feature of these amoeba-like bodies is movement, consisting first of a progressive movement, and secondly of a protrusion and withdrawal of pseudopodia, both of which vary in activity. Entering probably with the food, these protozoa pass on untd the large intestine is reached, where the alkalinity necessary to their growth is obtained. Here they penetrate and undermine the mucous membrane, pro- ducing their effects by liquefying the tissues, and thus causing ulceration and necrosis. In the mucous membrane they are found chiefly in the lymph spaces, blood-vessels, and in the gelatinous contents of the ulcers. They may penetrate to the liver. Kartulis succeeded in obtaining pure cultures in alkaline infusion of straw by inoculation from a case of dysentery, and injections of these cultures into the rectum of cats produced local symptoms of the disease; no results followed when the amoebae were administered by the mouth. Miescher's Tubes.—Sometimes in the muscles of mice and other animals, Avhite streaks are visible to the naked eye, as fine Avhite streaks between the muscle fibres. Examination with a low power shoAvs them to be composed of tubular granular masses, several millimetres long and about twice as thick as the muscle fibres. They all taper towards the extremities. Under a higher power, a capsule can be made out, while the contents are pale, crescentic, reniform corpuscles, rounded and shghtly attenuated at the ends, and often containing a vacuole. In the larger capsules, there are formed tubes of the second and third degree, or spherical masses, each surrounded by a thin capsule, one within the other. On teasing out a part of the fresh muscular tissue, many of the tubes become broken, and innumerable isolated crescentic spores are obtained. ~No movement is possessed by the tubes or individual spores. Erom the crescent-shaped bodies, which are con- sidered as the typical contents of the tubes, there proceed nucleated forms resembling gregarines, which on the addition of an acid emit two filaments from one end. The transfer of these structures to other warm-blooded animals by inoculation, or in food, has hitherto failed. The prevalent belief is that they enter the animals by an intermediate stage of development, probably passed in a snail. In man only isolated cases of this infection have been observed Nuverricht has described a fatal case which had the aspect of a poly- myositis, as in an infection of trichinae. How such parasites enter the human system is obscure, though Rabe states that he has observed a case after eating pork containing psorospermia; there is some reason to think, however, that in Rabe's case more complicated causes existed. Fowls some- times contain the same tubes, but Leuckart does not feel satisfied that these parasites are real psorospermia. Coccidia.—By coccidia we understand a large group of parasites which live parasitically within the cells, and which have hitherto been observed chiefly in rabbits, where the full-grown parasite (Coccidium oviforme) is 35 p. long and 15 p. broad; simdar forms have been found in dogs, calves, sheep, and birds. Their entire development appears to take place in the PROTOZOA—LNSECTA. 563 epithelium cells of the liver and boAvel. Coccidia have also been described by Podwyssozki as occurring in the human liver. The life history of Coccidium oviforme has been largely explained by the two Pfeiffers. The earher known form is that of the young amoeboid parasite, which penetrates into an epithelial cell of the bowel or liver, and when fully grown becomes encapsuled as a thin bladder. Within this develop numerous daughter cysts or cells, at first of a rounded shape, each of which becomes a falciform body. The falciform cyst bursts, the enclosed bodies become free amoeboids, penetrate at once new cells, and begin afresh their destructive activity. If the disease involve the liver, larger sections of the liver tissue constantly become involved, degeneration by pressure of many liver lobules takes place, leading ultimately to death. Outside the body, coccidium undergoes similar changes, and when the encysted organism finds access, again, through water or food to the alimentary canal, the capsule becomes dissolved, the spores are set free, and these germinate into granular, spherical bodies to form the typical oval coccidium. The contagious epithe- lioma of poultry and pigeons is occasioned by a similar organism, whilst the Molluscum contagiosum of man is due to the same or similar parasites (Xeisser). Coccidia have also been described by Pfeiffer and others in the epithelium in cancer, variola, vaccinia, varicella, herpes zoster, and other vesicular eruptions; the weight of opinion, however, in this country inclines rather to regard these bodies as derivatives of the cell nucleus than as of the nature of extraneous parasites. Flagellate Protozoa.—More highly differentiated are the forms Tricho- monas and Circomonas and other flagellated monadinae known to inhabit the bodies of vertebrate and invertebrate animals. The genus Trichomonas has been found by Pfeiffer in the oral and pharyngeal mucus of pigeons affected with the chronic necrotic thickening of the mucous membrane called diphtheria. He regards Loffler's bacilli in this affection as a septic complication, and maintains that the disease is caused by the trichomonas, though the same organism is constantly to be found in healthy pigeons. The mature organisms are oval or semi-lunar, with four flagella at the head, a divided one at the tail and an undulating marginal membrane. By losing their tails, these organisms pass into an amoebic condition of great contrac- tility, ending in final encystment and spore formation. The genus Circomonas, a minute club-shaped cihated protozoon, smaller than Trichomonas, possessed of no envelope and having a pointed prolonga- tion at one end and a fine flagellum at the other, has been found in the intestine of man in cholera, diarrhoea, and dysentery. Other species of flagellate monadinae have been described by Lewis, Evans, Koch, and Crook- shank as occurring in the blood of horses, camels, dogs, rats, and badgers. Alhed to the forms described above are those detected by Laveran and now universally recognised as exciters of malaria. The more important characters of these haematozoa will be mentioned in the next chapter, under the head of Malaria. INSECTA. Instances of the so-called free parasitism, partial parasitism, and of true parasitism, due to insects, are by no means uncommon in man. Flies, bugs, fleas, and hce come under this category: these exercise their parasitism either by making man the host of their larvae, for which a temporary sojourn in the organs of a warm-blooded animal is a necessary factor for their development, or play the parts of free and true parasites by temporary 564 PARASITES. or permanent attachment to the person, for the purpose of deriving susten- ance. Thus it is by no means a rare occurrence—particularly in tropical countries—to find larvae developing in Avounds or sores, or in such accessible but sheltered parts as the nostrds, ears, and even conjunctival sacs. Some of these larvae become a source of very great danger, owing to the rapidity with which they rapidly destroy the tissues in which they are lodged. Other larvae proceed to development by penetrating under the skin of their temporary host, lodge there, and groAv at the expense of the tissues on which they feed, causing pain, irritation, and not infrequently sores Avhich in unhealthy climates are not Avithout danger. Of this kind of ecto-para- sitism, the foUowing are the chief forms :— Blaps mortisaga, or churchyard beetle, has on several occasions been found to be present in the human body. Cobbold records a case in Avhich several perfect insects and 1200 larvse were passed by the bowel. The Tenebrio molitor is a closely allied species whose larvae have been found passing from the human body. CEstrus hominis.—This insect, in the so-called " hot" condition, and also- several other varieties, have been found in man. The late Dr Livingstone is known to have been afflicted Avith the larvae of a species of this fly during the course of his African travels. Cuterebra noxialis.—The larva of this fly is the so-called Macaco worm of Central America. The perfect insect is about 17 mm. long, has a yellow head and face, a brown body striped with grey, and a blue abdomen. It frequents the outskirts of woods, depositing its eggs on man, cattle, and dogs. The larvae, when hatched, penetrate the skin, giving rise to much irritation: they attain a length of about a quarter of an inch, and possess two strong buccal hooklets and a series of spines on the front half of the body. Anthomyia canicularis.—The larvae of this fly are quite common in man : while several cases of parasitism from the maggots of the bluebottle, or Musca vomitoria, have been recorded by Sells and Cobbold. Lucilia hominivora.—The revolting parasitic habits of the maggots of this species are difficult to realise. It is an inhabitant of America, being found from the United States in the north to the Argentine Republic in the south. An allied species has been met with in India. The perfect insect is about 10 mm. in length, -with a blue thorax and brown Avings. The larvae measure 12 to 15 mm. The fly deposits her eggs in wounds, sores, the nose and ears of men and animals. On being hatched, the larvae, by means of two powerful buccal hooks, attack the tissues, which they devour rapidly, producing often extensive mutilations. They have been known to devour the soft parts at the back of the mouth and nostrils, including the pharynx, glottis, tympanum, deep structures at the base of the cranium, and even passing into the frontal sinuses. Ochromyia anthropophaga.—This is a native of Senegambia, where its larva is known as the cayor worm. The insect is believed to lay her eggs in the sand, whence the larvae emerge, and, an opportunity occurring, penetrate the skin of man or animals. Underneath the skin the lame groAv, giving rise to inflamed swellings: in seven days they leave their temporary host and pass into the pupa stage. Once the larvae have emerged, the sores so produced quickly heal. As examples of free parasitic insects we may quote the midge, the flea, many well-known gnats and bugs, and also the following:— Culex anxifer, or mosquito. Probably many species attack man as well as animals. The importance of these insects as intermediate bearers of human filarise wdl be alluded to elsewhere. INSECTA—ARACHNIDA. 565 Glossina morsitans, or tsetse fly, is a notorious insect found in South Africa, where it is terribly destructive to horses, oxen, sheep, and dogs. Its bites, however, though very annoying, do not prove fatal to man. Pulex penetrans.—Under the name of the jigger or chigoe, this is a Avell- knoAvn and excessively troublesome insect, found in the West Indies, tropical America, and some parts of Africa, particularly Algeria, the Soudan, and Zanzibar. The chigoe hves on the ground, and is most abundant in dry sandy soils, particularly near the sea shore. Dirty native cabins are a very favourite haunt for this insect. It attacks all warm-blooded animals, fix- ing itself indifferently on the first that comes in its way. In size, the chigoe is smaller than the common flea: it is reddish-brown in colour and has a large head Avith a broad, deep abdomen. Both the male and female are, for the most part, free parasites, the male being ahvays so, and the female up to the time of impregnation. They suck the blood by piercing the skin on every avadable chance, dropping off Avhen gorged. "While the male retains the ordinary habits and form of a flea, the female, when she has been im- pregnated, bores her way into the skin of the foot, leg, thigh, scrotum, or other parts of the body, and becomes by the Fi 9~K_Fulexpendm Female enormous development of the ovary, an(j maie. a simple motionless bladder embedded in the flesh, around Avhich, in course of time, when the eggs have to be extruded, a certain amount of inflammation arises. In due time, these are hatched, producing a larva which, after enclosing itself in a cocoon and passing through a nympha stage, emerges in eight or ten days time as the perfect insect. Of the true parasitic insects affecting man, the chief is the Pediculus or louse. Five distinct species are recognised as human parasites, namely, the head louse, the clothes louse, the distemper louse, the pubic louse, and the louse of the eyelids. The lice found on negroes and other native races Avere at one time thought to be distinct species: this, however, is not so. Occa- sionally one or more species of bird lice have been found on man, and may be regarded as human parasites. This has occurred particularly in the case of Ornithomyia avicularis, Avhich frequently infests cage birds. In like manner, one or more forms of lice infesting common foAvls may attach themselves to man. ARACHNIDA. Amongst the trachearian section of this great class of arthropodous invertebrates there are numerous parasitic species Avhich attack man and animals. They are more familiarly knoAvn as mites (acaridae), ticks (ixodidae), and pentastomes (pentastomidae). Of the mites, the chief human parasite is the common itch insect. 566 PARASITES. Acarus scabiei, or human itch insect, has been described under a number of synonyms: it is probable that most of the so-called species infesting our domestic animals, as weU as that called the Norway itch insect, are mere varieties of the common species (fig. 96). The burrowing of this insect causes much itching and some rash. It is the female only Avhich thus penetrates the skin and causes the characteristic symptoms of the disease knoAvn as scabies : for bur- rowing beneath the cuticle, she lays her eggs at the end of the burrow, Avhere they hatch, and the young insects then commence to burroAv afresh in other directions. In France, the face mite, or Demodex folliculorum, is a fruitful source of personal disfiguration. A variety infests the dog. The ticks are less frequently met Avith, as human parasites, in this country than in some parts of the tropics. Some of these arachnidans are terrible blood-suckers, more par- Fig. 96.—Acarus scabiei. ticularly Argas persicus and A. chinche, found respectively in Persia and Columbia. The camel tick and the various forms of ixodes are disgusting and highly venomous species occasionally found on man, producing severe pain; they are probably identical Avith one or other of the ticks known to infest domesticated animals. Man is occasionally the host of sexually incomplete forms (pentastomidae) of as yet incompletely known arachnidans. Pentastomum denticulatum.—This is the sexually incomplete state of the mature form known as P. tumioide*, which resides in the nasal chambers of the dog and other animals. In the larval form, as P. denticulatum, it infests the liver and lungs of man. Formerly, these two pentastomida? were thought to be distinct, until Leuckart succeeded in rearing the so-called P. denticulatum in the intestine of the rabbit from the eggs of P. tctnioides, and traced the development of the young P. denticulatum into the adult P. tamioides by placing the embryo in the nasal cavity of the dog. The life history of this parasite appears to be briefly this. The young form inhabits cysts in the liver and lung of herbivorous mammals: presently the young animal breaks through its cyst and makes its way into the body cavity, after causing con- siderable injury to the tissues during its transit, and occasionally even causing the death of its host. Some- times it wanders again into the viscera or into the lym- 97.—Pcntasto- phatics. If the body of its host be devoured by a dog (SlSS91 °r SOme carnivorous animal> tllG y°unfer Pentastomum, if not already encysted, finds its Avay directly through the nares into the olfactory cavity, Avhere it attains sexual maturity. The SUCTORIA—NEMATODA. 567 P. denticulatum has often been found in the liver and lungs of man in various parts of Europe: its organs of locomotion are hooks and spines which are developed towards the close of the resting stage, and finally laid aside after they have served their purpose. Pentastomum constrictum.—This parasite is not un- common in Egypt, the Soudan, and West Coast of Africa. It is the larval form of an arachnid, of which the adult stage is still unknown. It has a Avhite, annulated, cylindrical body, Avith a rounded anterior, but rather conical posterior end. The ventral surface is flattened, the entire parasite measuring about 15 mm. in length by less than 3 mm. in breadth. It has four foot-claws near the mouth. The elongated abdomen displays twenty-three rings, placed at tolerably regular intervals. It differs from P. denticulatum, which we have seen to be the Fig- 98-— larval form of P. tamioides, in not possessing integumentary Pentastomum spines, and m being a much larger parasite. It is found /after Aitken). coded upon itself in a cyst, situated, generally near the surface of the liver, in such a way as to be perceived through the fibrous capsule of the organ. SUCTORIA. A vast number of suctorial annehds attack man in such a way as to deserve the title of parasites. In this category come the ordinary leeches, besides numerous aberrant forms which have only been imperfectly described. Hsemopis sanguisuga.—This, the common horse leech, is found in all parts of Europe, in Egypt, and throughout North Africa. This species often attacks man in warm climates, attaching itself to the mucous surfaces of the nose and pharynx, and even entering the larynx and air passages. Men are much debilitated by them at times: and in the event of their entering the air passages, death by asphyxia may ensue. There is no doubt that these leeches enter the mouth by means of foul drinking water. Sanguisuga tagalla is a land leech found in Ceylon, where it lives in woods and in damp undergrowths. It is about an inch long, little thicker than an ordinary knitting needle, but extremely active. It lies among the leaves and grass, and attacks any man or beast which passes near it. Simdar land leeches are found in Java, the Philippines, in the Himalayas, Africa, Australia, and Chili. All varieties appear to possess great suctorial powers, and if disregarded, by producing repeated haemorrhages, may bring about a state of great debility. NEMATODA. The nematoid parasites are probably better knoAvn than any of the other parasites of man. This arises partly on account of the excessive prevalence of some members of the group, particularly the little thread-worm, partly from the circumstance that the large round worm bears a marked re- semblance to the common garden worm, and partly because the spiral flesh- Avorm plays an important role in the production of the epidemic disease known as trichinosis. In the case of those whose experience has been in the tropics, this group is further familiar as embracing the Guinea worm, various filarias, and other less common forms. 568 PARASITES. Oxynris vermicularis.—This is the common thread-worm, a Avell-knoAvn human parasite occurring in large numbers in the ca?cum and upper part of the colon. The female is about £ inch long, and the male ^ inch. The female gives off enormous numbers of colourless, oval, unsymmetrical eggs, each being 50 p. in length and about half as broad. These eggs have a rather thin shell with a double outline (fig. 1, Plate XI.), and may contain a Avell- developed embryo, Avhich, at first tadpole-like, rapidly assumes, under suitable conditions of heat and moisture, a vermiform character. For the purposes of infection it is alone necessary that the eggs of the Avorm be conveyed to the mouth and SAvalloAved. Their previous immersion in Avater for any length of time secures their destruction, by the bursting of the shell consequent upon endosmosis. The eggs are conveyed to the mouth in various Avays. Ordinarily children become infested by biting their nails, beneath the mar- gins of which the eggs lie concealed. Occasionally, the eggs are swallowed by accident during sleep, or the whole parasite may be conveyed to the mouth in a simdar manner. In Avhatever manner they may have been carried to the bearer, Avhen once the eggs have gained access to the stomach, their shells are dissolved by the gastric juice, and the larvae liberated. In the upper intestine, the larvae grow rapidly : here they undergo one or more changes of skin, acquiring sexual maturity Avithin a period of less than a month. Improperly cooked or raAV vegetables and Avater are the vehicles by Avhich they directly reach man from outside. Ascaris lumbricoides.—This is the common round Avorm, being in general appearance very like the ordinary earthworm. It is pinkish in colour, tapering at each 'end, and measuring some six inches long in the case of the males, and twelve inches in the case of the females. In man it usually infests the small intestine, Avhere it gives off large numbers of eggs. These, though colourless Avhen Avithin the Avorm, are usually broAvn Avhen seen Avithin faeces, OAving to the action of the bile upon the outer sheU, which is, moreover, characteristically nodulated (fig. 2, Plate XI.). In shape they are not unlike a barrel, and measure 65 ft long and about 45 y, broad. The inner layer of the shell is transparent, colourless, and rather thick, with a multiple outline. Hoav and Avhere the eggs develop is not known, but it is supposed to be in water or possibly in an intermediate aquatic host. Un- doubtedly it is chiefly by means of water that they reach man. Develop- ment extends over three or four months. Pigs being infested by the same Avorm, the water from streams or ponds in the neighbourhood of pig-sties becomes a dangerous source of infection, if employed for domestic purposes. The large lumbricoid Avorm of the horse is an entirely distinct species. Ascaris mystax.—This nematode is probably identical with the A. alata of Bellingham. Its stages of groAvth have been traced by Leuckart in the cat, in Avhose stomach specimens of the larvae were found, measuring only FV of an inch. From Hering's observations, it would seem probable that a period of three Aveeks is amply sufficient for the production of sexual maturity after the larvae have gained access to the body of the ultimate bearer. The bearer may be either man himself, or more commonly a cat, dog, or some carnivorous animal. Tricocephalus dispar, or the " Avhip-Avorm," is possibly the most common of all intestinal parasites affecting man in the tropics, and not infrequently met with in Europe. Its eggs are so characteristic (fig. 3, Plate VI.) that having once seen them it is not possible to mistake them for any other. Their usual size is 36 y, in length by 26 y. in breadth : in colour they vary from a yelloAvish-broAvn to red. The eggs are commonly voided by the Avorm into the boAvel, and Avhen discharged from the bowel the embryo is TRICHINA SPIRALIS. 569 not differentiated Avithin them. Its development remains in abeyance until the egg is carried into Avater or other damp medium. This happening, development proceeds, and on the egg being sAvalloAved by man in drinking Avater, the embryo is liberated in the alimentary canal, where it attaches itself to the mucous membrane of the caecum by means of the Avhiplash-like anterior part of its body (fig. 99). The development of this worm is sIoav, probably being rarely completed Avithin the year. The intermediate host is unknown, but the experiments of Davaine render it probable that infection takes place in a direct manner some time after the eggs have escaped the human bearer. The embryos will hve for many years in the free eggs, even if exposed to dryness. Trichina spiralis.—The larval forms are commonly spoken of as flesh- Avorms. The adult is a small worm, varying from y1^ to -J inch in length, Avhich not only attacks man, but also pigs and other animals, producing the disease knoAvn as trichinosis. In this disease, the muscles present a number Fig. 99.—Tricoccphalus dispar. Fig. 100.—Muscle containing Trichince spiralis. of ovoid cysts, about T\j- inch in length, just visible to the naked eye, within each of which is coiled an immature trichina, not much more than -j1^ inch long (fig. 100). If by chance the tissue or muscle containing the capsules be eaten, the capsule is dissolved, and the young worm is set free. This rapidly develops, and breeds so rapidly that Avithin a week the embryos of the trichina, by burrowing through the intestinal Avails, are able to find their way into all parts of the consumer's body, especially the muscles, in which they soon get encapsuled, to go through the same history again. When trichinosis occurs in man, it is generally due to the eating of the imperfectly cooked flesh of pigs suffering from the disease. It is somewhat common in Germany, Avhere sausages, hams, and pork are more often eaten than in this country. The symptoms of trichinosis are sickness, prostration, fever, and muscular pains. The mortality is often slight, but occasionally very high. Dracunculus medinensis, or Guinea-Avorm, and sometimes called Filaria 570 PARASITES. medinensis, is a parasite endemic in many parts of India, Persia, Arabia, Egypt, the West Coast of Africa, Demerara, the Brazils, and other tropical countries. The Guinea-worm disease is undoubtedly the same disease as the dracontiasis of Plutarch, and corresponds also with the Israelitish endemic affection described by Moses as due to fiery serpents. The curiously limited preva- lence of this parasite in certain districts was for many years inexphcable, until Fedschenko discovered the fact that a certain species of fresh-water cyclops, having apparently a very capricious distribution, is a necessary factor in the life history of the filaria. Consequently, the distribution of the Guinea-worm is bound up with and dependent on the distribution of the particular species of fresh-water crustacean which, in reality, acts as its intermediate host. Not only man, but oxen and some other animals, are affected Avith this filaria, or a parasite very closely alhed to it. As yet, the female dracunculus alone is known Avith certainty, though Charles has described structures in connection with two female dracunculi which are suggestive of the male dracunculus in coitu. Immature specimens of Guinea-worm vary in length from a few inches to as many feet. The mature worm is a long, milky- Avhite, slender, cylindrical organism, having a thickness of about y1^ inch, and not at all unlike a thick fiddle-string. Its actual length varies from 1 to 12 feet. The head of the worm is short and tapering, terminating in an oval irregular surface called the " cephalic shield." In the centre of this is a triangular buccal orifice, which leads to an alimentary canal, extend- ing along the whole length of the creature, and ending blindly. Close to the buccal orifice are two papillae, with six others at the circumference of the shield.; these are generally regarded as sensory organs. The posterior end of the parasite terminates in a blunt point which is often bent, like a hook, towards the ventral surface. Nearly the whole of the worm is occupied by a long, tubular, and embryo filled uterus. No trace of a vagina can be detected in the mature worm, though there is evidence to suggest that originally there was one. The emission of embryos appears to take place by the buccal orifice. Like many other animal parasites, its presence in the tissues of man is but a portion of its life history, and to complete its cycle of existence it requires to pass into the tissues of some other living organism. The worm, having gained access to man's body, probably in a larval form, lying in the body of the cyclops, bores its way into the tissues. When or where the sexes come together, and what are the subsequent steps in the development of the female, and Avhat becomes of the male worm, are unknown. After an interval of from nine months to a year, a stage of maturity appears to be reached, as indicated by the pre- sence of a Avorm many inches in length, embedded in the Yia. ioi.__Em- cellular tissue of the host, with an enormously developed bryo of Guinea uterus packed Avith mUlions of embryos. The embryo which Worm (after is emitted from man is aquatic in habit, and to further Bastian). develop needs to pass into water. In size the embryos measure ^ by 1 ^ 0 of an inch. They are distinctly flattened, tapering towards the head end, and terminating posteriorly in a long, slender, sharply-pointed tail (fig. 101). They are very active, SAvimming about hke ANCHYLOSTOMA DUODENALE. 571 a tadpole : they can be kept alive in moist earth or water for some twenty days. In water, if it meets its necessary intermediary host, the cyclops, the embryo filaria penetrates the little crustacean, and in its body, in about five weeks, undergoes considerable development towards a more mature condition. Lying in the body of the cyclops, it is supposed that the filaria Avaits an opportunity of being conveyed in drinking water to the stomach of its human host or of some other animal, whence it can continue its cycle of existence, as aheady described. The peculiar history connected with this parasite emphasises the value of a pure water-supply, as well as the importance of forbidding individuals washing in, or in the neighbourhood of, the drinking-water supply of a community. Anchylostoma duodenale.—Sometimes called dochmius duodenale, this is a short worm which attaches itself, often .h in large numbers, to the viUi of the small intestine. It is very Avidely distributed, being found in Europe, Egypt, Zanzibar, Gold Coast, West Indies, Brazil, Peru, Bolivia, Assam, Lower Bengal, Borneo, Java, and Austraha. It is the cause of the pathological condition known as anchylostomiasis, marked by a serious and often fatal form of anaemia, the result of the large amount of blood abstracted by the parasite. This entozoon is whitish in colour when empty, but reddish-broAvn when fiUed with blood. Its length is from 8 to 18 mm., with a breadth of about 1 mm. Both the males and females (fig. 102) are cyhndrical Avith conical pointed heads. The females have also a pointed posterior, but the males are readily dis- tinguished by having in this situation a pecuhar bell-shaped bursa copulatrix. The mouth is provided with four strong claw-like teeth. The adult animal lives generally in the jejunum or duodenum, the eggs (fig. 4, Plate VI.) being expelled with the faeces, and in which they can be readily detected by microscopical examination. The embryo is never found developed within the eggs in the faeces up to the time of their evacuation, but appears, on being discharged from the intestine, to undergo its primary development in wet soil, being much favoured by a high temperature and exposure to air. The young worm is very different from the adult, and shoAvs a typical rhabditic form, characterised by a spindle-shaped oesophagus ending in a chitinous bulb provided with three chitinous ridges, and an abruptly pointed tail. Under favourable conditions of warmth and moisture, the young larvae rapidly undergo development marked by an Fig. 102. — Anchylostoma duodenale (after Sonsino). a, Male ; b, Female!; c, Embryo. 572 PARASITES. incomplete kind of moulting, AAdiich gives them the appearance as if they Avere enclosed in a kind of case. The larva, having undergone some modifi- cations, especially in the digestive canal by the loss of its chitinous bulb, gradually becomes capable of assuming the parasitic state, requiring only an opportunity of being introduced into the alimentary canal of man to grow there into the adult anchylostoma. This simple course of development has been questioned by Giles, Avhose observations in Assam suggest that, though the embryo born of the parasitic Avorm reaches an adult free stage, it is only the progeny of this latter or the grandchildren of the parasitic Avorm, which are capable, after having reached a certain degree of develop- ment, of assuming the parasitic life on introduction to the human body. Though a similar heterogenesis is not unknoAvn in other nematodes, this account of the hfe history of anchylostoma is not as yet definitely accepted by helminthologists, as it is just possible that the free adult form observed by Giles may be only one of the many species of free nematodes known to live in mud, such for instance as Rhabditis terricola. Notwithstanding some uncertainty about the life history of anchylostoma, it is certain that damp soil is the medium in which the eggs, Avhen voided by man, undergo development. From the soil to the Avell is but a short step, and, either in water—especially muddy Avater—or in earth adhering to food, this Avorm is transferred to the human alimentary canal. That the soil plays an important part in the distribution of anchylostoma is further emphasised by the fact that certain classes are specially liable to contract anchylostomiasis, namely, those Avho handle earth, such as brickmakers, and those engaged in mining, tunnelling, and in general agricultural operations. These considerations indicate that prevention demands attention to rules applying both to the individual and to the community. The principal personal rules will be, careful washing of the hands and nails before eating, whenever mud has been handled; and the drinking of only filtered or boiled water. For the community, care needs to be taken that, in endemic areas, indiscriminate defecation over the country is not practised, coupled Avith suitable disinfection of the infected dejecta, and the promulgation of simple precepts of prevention suited to the understandings of native people in whom this parasite so extensively prevails. Ehabdonema intestinale.—This nematode was discovered by Normand in excrements passed by French soldiers suffering from the so-called Cochin China diarrhoea. It has since been found in the West Indies, Brazil, Egypt, Ceylon, Italy, and Germany, and commonly associated with anchylostoma. Of the adult parasitic form, only the female is knoAvn. She is a thin slender worm about 2 mm. long, the breadth being about -fa of the length (fig. 103). In the intestine the embryos are quickly hatched from eggs expelled by the worm, thus differing markedly from anchylostoma whose embryos are only hatched after the eggs are voided from the human intestine. The embryos, which are to be found in large numbers in the dejecta of affected persons, are about 0*3 mm. long, and 15 y. thick. They possess a sharp-pointed tail, and being rhabditiform, have a short oesophagus with two dilatations, resembling somewhat the embryos of anchylostoma. When discharged with the faeces, on these decomposing, the embryos rapidly die. But if they gain access to foul Avater, the embryos live and assume one of two different forms of development, according to the temperature. Under a low temperature (20° C.) they become filariform larva?, capable, if directly re-introduced into man, of growing into the adult parasitic form, without alter- nation into the adult free form. Under a higher temperature (30° C.) the embryo grows into the adult free form. This Avas formerly called Anguillula FILARLE SANGUINIS H0M1NIS. 573 stercoralis, and consists of males and females. It is shorter and thicker than the parasitic form. From these breed rhabditiform embryos, like those from the parasitic Avorrn, and these embryos then grow into filariform larvae, which only need introduction into the human intestine to develop into the adult parasitic form. The source of infection by this parasite is probably the same as in anchylostoma, namely, sod or foul water. Filariae sanguinis hominis.—There are three definite species of embryo Fig. 103.—Bhabdonema intestinale (after Sonsino). a, Adult female parasitic form ; b, Embryonic form ; c, Male adult free form ; d, Female adult free form ; e, Larval form. nematodes Avhich have been found in the blood of man, and to which the term Filaria sanguinis hominis may be appropriately applied. Adopting the nomenclature suggested by Manson, to whose writings and investigations Ave are mainly indebted for the following facts, the three species of haematozoa are Filaria nocturna, Filaria diurna, and Filaria perstans. These names have been given on the basis of certain individual peculiarities of habit characteristic of each of the three species. Thus, F. nocturna is present in the general circulation only during the night, F. diurna only so 574 FARASITES. during the day, AAdiile F. perstans is present both by night and day. It is essential, for a right comprehension of the somewhat complicated subject of blood filariae, to grasp the fact that all these organisms are only the embryos of certain other and mature parasites, which live and breed in remote parts of the body, and that, though the embryos may swarm within the blood, it is not necessary, in fact is exceptional, for the parent forms to be present in the circulation. As seen in freshly drawn blood the Filarial sanguinis are slender, long, transparent, and snake-like animals endowed with great activity. In the case of F. nocturna and F. diurna, this activity is exhibited chiefly as a constant lashing and wriggling without forward movement: whereas, with F. perstans, the wriggling is combined with a vermicular movement leading to distinct locomotion. The characteristic features of the three filariae are well described in the following table by Manson :— Filaria nocturna. Measures TV x -j^Vo'' Is provided with a sheath. Caudal end tapers gradu- ally for one-eighth or one- fifth of the length of the animal and ends in a sharp point. Cephalic end rounded off, and has obscure pouting movements produced by the movements of a six- lipped prepuce. From time to time a thick tongue-like organ, pro- vided with a delicate retractile spine, is pro- truded at cephalic end. Appears in the blood at night, disappearing from it during day. Has a wriggling but no locomotive movement. Well-marked granular ag- gregation about the junc- tion of the middle with the posterior third of the body in some specimens. [Has a V-shaped organ or luminous point behind the head. Possibly is a rudimentary vagina. Filaria diurna. or Measures Ty x a-1^" thereabouts. Is provided with a sheath. Caudal end tapers gradu- ally for one-eighth or one-fifth of the length of the animal and ends in a sharp point. Cephalic end rounded off, and has distinct pouting movements. Minute anatomy not known. Minute anatomy not known. Appears in the blood during the day, dis- appearing from it at night. Has a wriggling but no locomotive movement. Slightly marked granular aggregation about the junction of the middle with the posterior third of the body in some specimens. Has a V-shaped organ or luminous point behind the head. Possibly is a rudimentary vagina. Filaria perstans. Measures about y^g-" x ^tW Has no sheath. Caudal end tapers more gradually for two-thirds of the entire length of the animal, and is abruptly truncated where it be- comes reduced to one-third of the diameter of the thickest part of the body. Cephalic end is eitherconical or truncated, passing from one shape to the other by a peculiar jerking, extending and retracting movement. From time to time a minute tongue-like organ, pro- vided with a rectractile spine, is protruded and withdrawn at cephalic end. Present in the blood both by day and by night. Has a locomotive as well as a wriggling movement. Body homogeneous through- out, and no such aggrega- tion. Has no V-shaped organ. FILARLE SANGUINIS HOMINIS. 575 All these filariae exhibit a great tenacity for life, and can be seen alive for many days in ordinary slides, provided the blood be kept fluid by oiling the Fig. 104.—Filaria sanguinis hominis diurna. x 160. Fig. 105.—Filaria sanguinis hominis perstans. x 160, edge of the cover-glass. Mackenzie has shown that the curious phenomenon of filarial periodicity is in some way connected with the quotidian habits of sleeping and waking; and that if this habit of the host be inverted, so is 576 PARASITES. the periodicity of the filarial parasite inverted. The precise cause of this periodicity is not knoAvn, but there is reason to think that it is neither duo to any intermittent parturition on the part of the parent filaria, nor to any deficiency of oxygen in the blood, as has been suggested by Myers, but rather is an adaptation to the habits of their intermediate hosts. The life history and parental forms of these filariae have only been determined in regard to one of them, namely, the F. nocturna. The parent worm of this embryo is a peculiar nematode, usually associated with chyluria and elephantiasis, and known as the Filaria Bancrofti. As regards the mature forms of F. diurna and F. perstans practically nothing is known, though Manson has suggested that possibly the long but imperfectly known Filaria loa may be the parent form of F. diurna; and that certain hominivorous flies Avith diurnal habits may be its intermediary host. Manson has found a neAv and smaller variety of F. sanguinis hominis in a West Indian patient. Fig. 106.—Filaria sanguinis hominis nocturna. x 160. Filaria Bancrofti.—This is the mature or parent form of the F. nocturna, having its habitat in the majority of instances, if not in every case, in the lymphatic system. Usually the male and female are found together, but as yet, owing to only imperfect specimens having been examined, the precise anatomy of the male is not well known. The female is commonly about 3| inches long and yi^ inch thick, being smooth and cylindrical. The mouth is simple, circular, and destitute of papillae : close to and behind the head is the reproductive outlet. The tail is simple, blunt pointed, with anus imme- diately above the tip. While the alimentary tube is simple, the main part of the animal is occupied by the double uterine or ovarian tubes, usually stuffed with myriads of embryo filariae at all stages of development. The embryos on escaping from the parent within the lymphatic system pass periodically into the blood stream, where they are familiar as the F. sanguinis hominis nocturna. This periodical migration into the blood is apparently an adaptation to the habits of the mosquito, which is the PI ate VI. ^--^ ■><£>>? Mm*. 10 Ova of Parasites. "West.TTewma.TL iiiii. CESTODA. 577 intermediate host of this parasite. The mosquito, as every one knows, is most active at night, and when it bites the human host, these filariae either curl round or become entangled on its proboscis, and are then quickly transferred to its stomach. The greater number of the filariae so swallowed by the mosquito are digested or destroyed, but a certain few undergo development inside its body, and, when the mosquito retires to some water to lay eggs, or to eventually die, these filariae which have developed inside its body pass out by boring into the water, whence they get swallowed by man. Once inside the human stomach, the filariae bore their way into the lymphatics, finally reaching their permanent abode in some distant lymph- vessel, where, as the Filarial Bancrofti, they give rise to chyluria and elephantiasis, and breed, their progeny passing into the blood as before explained, till, released by the mosquito, they in their turn can complete their circle of development. Filaria loa.—Very little is known of this parasite, although it is by no means uncommon on the West Coast of Africa. It chiefly affects the subcutaneous tissues, being possessed of considerable powers of locomotion. It is often found in the loose cellular tissue beneath the conjunctivae, where it creates much irritation. Leuckart gives the length of this worm as from 30 to 40 mm., with the thickness of a fiddle string. One end is pointed, the other blunt, the latter probably being the head, as it is provided with a prominent papilla but no special armature. Nothing is known of its life history, but Manson, from the fact that it had been present at a previous date in a negro in whose blood he afterwards found F. diurna, has suggested that F. loa may turn out to be the female parental form of F. diurna. CESTODA. The Cestodes include the great group of tapeworms, which in reality are a multitude of organisms or zooids, arranged in single file. The head itself is merely the topmost zooid, modified in shape, and armed with sucking discs, so as to form a means of anchorage for the whole colony. An ordinary human tapeworm consists of about a thousand zooids or proglottides, each of which is sexually com- plete, and, when mature, capable of generating about 30,000 eggs. Assuming that the entire colony of a thousand zooids is renewed every three months, it fol- lows that a single tapeworm annually disperses about 120,000,000 eggs. Fortunately, compared with the quantity distributed, the number of eggs that survive and come to perfection as tapeworms is infinitesimally small. The chief cestodes, parasitic to man, are the following:— Taenia saginata, sometimes called T. mediocanellata, is the only cystic tapeworm with an unarmed head which occurs in man. It is, at the same time, the largest of the human taeniae, being about 8 metres long when extended, and composed of from 1000 to 1300 segments. These segments are remarkable for their size, breadth, and firm appearance. The largest measure 20 mm. in length, and from 5 to 7 mm. in breadth. The head of this parasite is hookless, has a j>t saginata. 2 o 578 PARASITES. / flattened crown, with a pit-like hollow in the middle, and has four large I and very powerful suckers, which, hoAvever, usually project only slightly, and are frequently surrounded by a black, broad, pigmented border (fig. 107). The complete development of the germ-producing organs takes place at about the 600th segment, while the embryos only attain maturity at about the 1000th segment. Each segment contains male and female organs, whhe the number of so-called " ripe " segments, present at any one time, averages about 200. The new formation or growth of the segments is so rapid that some ten proglottides are separated daily, even Avhen, as is the rule, only a single worm is present. The eggs of this Avorm (fig. 5, Plate VI.) have a thick shell, with a border of little rods. They are generally oval, and provided with the primordial yolk-skin; their average size is 0*03 mm. The normal abode of this parasite is the small intestine, to the walls of which it is fixed, usuaUy toAvards the upper end. The precise duration of its hfe is undetermined, but seems to be very long. The eggs are commonly expelled Avith the dejecta of the host, and the contained embryo does not undergo further development, unless it obtain access to the alimentary canal of the ox. From here the embryo passes into the voluntary muscles of the animal, where it remains as a bladder- Avorm, a simple scolex, known as the beef-measle or Cysticercus bovis. An ox, affected with this parasite, that is, acting as the intermediate host for the T. saginata, may contain many hundreds of the cysticerci, or bladder- worms, within its muscles. On the flesh of the animal (either raw or imperfectly cooked) so affected passing into the alimentary canal of man, the bladder-worms develop into the sexually complete adult form known as the T. saginata. The cattle in Abyssinia and the Punjab appear to be specially infected with the cysticerci of the T. saginata, this parasite being by far the most common of the tapeworms found in man in those countries. The only animal, besides the ox and goat, which has hitherto exhibited the bladder- worm of T. saginata, is the giraffe. How long the bladder-worm of T. saginata remains lhdng in its host can- not at present be decided, but we may reckon the length of its stay there at several years. It, however, survives only some fourteen days after the death of its host, and if the parts putrefy, will only survive a still shorter time. As regards the term of infection in man, usually some nine to twelve weeks must elapse after the ingestion of the cysticercus before the T. saginata gives off the first proglottides. Taenia solium.—This cestode, though usually regarded as the common tapeworm, is comparatively rare. It is chiefly found amongst the poor, who are large consumers of pork, which is often imperfectly cooked. In Iceland and Germany the pork tapeworm is rather more common than the beef tapeworm. In size, thickness, and number of segments, this species is considerably less than the last. Extended, it rarely exceeds 3*5 metres in length, while its segments average 850, and of these not more than 100 are ripe proglottides. The size of the greatest of these segments is about 12 mm. by 5 mm. The head (fig. 108) is about the size of that of a pin, has a spherical shape with prominent suckers. The apex is often coloured black, and bears a medium-sized rosteUum, with generally twenty-eight hooks. The sexual organs are usually fully developed at about the 400th segment. The eggs (fig. 6, Plate VI.) are almost round, being enclosed in a firm shell, whose outside is covered thickly with little rods. Sometimes the original clear egg-membrane persists within the sheU. The course of TAENIA SOLIUM. 579 development and hfe history of this parasite is analogous to that of T. saginata, with the exception that the corresponding bladder-worm (Cysticercus cellulosm) has a special preference for the muscles of the pig, but, according to Leuckart, is occasionally found in other animals. Its occurrence in the pig is usually very abundant, where it constitutes measly pork (fig. 109). The great majority of the cysticerci average between 3 and 4 mm. in size, but some are both larger and smaller. They are killed by exposure to a temperature of 50° C. It must not be overlooked that, although the pig is the most frequent intermediate host for this bladder-worm, man himself may become the intermediate bearer, as this cysticercus develops also within the human body. The above fact leads us to the question: By what way does man become infected by these embryos? An infection by some means must precede the appearance of cysticerci, and its channel can only be by the alimentary canal. The most direct and frequent source of infection is in Fig. 109.—Muscle containing Cysticerci cellulosce (after Leuckart). the eggs, which are dispersed about the abode of the tapeworm, and also widely distributed in the open ah with the excrement. These may reach man's digestive tract either by water, food, or by the hand. This latter vehicle of infection is by no means unknown in the case of children and the insane, whde the normal adult tapeworm patient may readily infect himself with the proglottides of T. solium during sleep, by lifting the hand to the mouth. These considerations suggest the special need of cleanliness when an inmate of the house suffers from this parasite. The hnen of the patient should be frequently changed, the buttocks, perineum, and hands frequently washed, the excreta carefully removed, and all voided proglottides burnt without touching the hands. Of all persons, the patient is himself in greatest danger of infection. The experimental evidence of this danger of self-infection has been supplied by Kiichenmeister, who reared both mature and immature taenia of this species in condemned criminals; Avlhle, under Fig. 108.—Head of T. solium (after Leuckart). 580 PARASITES. Leuckart's auspices several persons voluntarily alloAved themselves to become infected by sAvalloAving fresh and living pork measles. Taenia acanthotrias.—This is a somewhat uncommon parasite of man, and has hitherto only been observed in America. Only the bladder-Avorm is as yet known, being very hke Cysticercus celhdosce, and having its habitat in the muscles and brain of man. " It is distinguished by the arrangement and structure of the hook apparatus, AAdiich is composed of a triple circle of from fourteen to twenty-six slender hooks." Leuckart and Weinland both main- tain that this Cysticercus acanthotrias represents an independent species. The related Taenia is unknown, but it probably lives in the human intestine like T. solium; if so, the bladder-worm may possibly be found in some animal, such as the ox. Echinococcus hominis.—Man is occasionally affected with a dangerous parasite under the name of hydatid disease, which commonly affects the liver, but may occur elseAvhere. It is really the cysticercus stage of a tapeworm, which lives in the intestines of the dog, jackal, and wolf, and called the Tamia echinococcus. The adult tapeworm (fig. 110) is of comparatively small size, its total length being only some 5 millimetres; and has only three or four segments, of Avhich the last, when mature, exceeds all the rest' of the body in size. Its head is characterised not merely by its smaU size, but also by the possession of a prominent crown which surrounds the bulging rostellum, on which are from 28 to 50 thick solid hooks, arranged in two series. Behind the four suckers the head narrows to a neck, which then passes into the unsegmented anterior part of the body. The first segment is but faintly differentiated; the second is defined and contains elementary sexual organs. The third and last segment exhibits all the characters of sexual maturity, and contains some 500 spherical hard- shelled eggs, in which are the familiar six-hooked embryos.. Fig. 110.—Taenia Before the last or ripe segment is liberated, a new joint echinococcus appears; so that, for a while, four proglottides are dis- (after Leuckart). tinguishabie instead of three. On the escape of the eggs, the contained embryo does not undergo further development unless received into the body of the pig, ox, or possibly some other animals, and man, in Avhom, after burrowing to various parts of the body, more particularly the liver, it assumes the larval stage of a cysticercus or hydatid cyst. Unhke other cysticerci, this bladder-worm increases indefinitely in size, and also forms within itself secondary cysts, some of which, the so-called brood-capsules, contain one or more echinococci (scohces) and remain minute, while others, containing no scolex, enlarge and form other or daughter cysts, which again may produce new cysts by a process of budding. Separately, these scolices, formed within the parent cysticercus, represent as many tapeworms, and collectively they amount to many thousands. Thus, when a dog or a wolf swallows one of these hydatid cysts and its contained offspring, all the heads of the colony become con- verted into sexually mature T. echinococci in the intestine of the neAv host. This metamorphosis of the echinococcus heads into tapeworms takes place with great rapidity. Leuckart's feeding experiments resulted in mature worms being found in the seventh Aveek. How long the adult worm lives is not known, but analogy suggests that its period of existence within the intestine of the dog is not very short. Since the T. echinococcus especially TAENIA NANA. 581 inhabits the intestine of the dog, and the dog is one of the few animals in closest association Avith man, Ave are justified in regarding this animal as the only source of the human echinococcus disease. It is not difficult to under- stand how cattle become infected; for the proglottides and eggs of the echino- coccus tapeworm, voided so constantly, and in such large numbers, by the dog, readily find access on to straAv, grass, or even water, and with those articles of food and drink are consumed by the oxen. In the case of man, possibly the sequence of events is not much different. As with cattle, both pro- glottides and eggs of the tapeworm from the dog may in many ways be carried in food, especially uncooked vegetables, such as lettuces, or on the hands to the mouth, and thus reach the intestine. Probably a greater risk of infection lies in the habit which dogs have of licking the hands and faces of their masters, and that often after they have been smelling and snuffing about other dogs. These are considerations which should prevent our too familiar association with dogs, more particularly to avoid their licking us, and frequenting dwelhng-rooms or kitchens, to say nothing of keeping them clean, and that their excrement is not allowed to remain about. Moreover, full precautions should be taken to prevent infection of dogs by embryos of echinococcus, as may occur in slaughter-houses, where the so-called bladder- worms, or echinococcus cysts, from slaughtered and in- fected animals are often carelessly throAvn down. It is needless to say that dogs eating such echinococcus bladders would soon develop them into sexually mature echino- coccus tapeworms. Taenia nana.—Judging by the few cases Avhich have been observed, this is an uncommon parasite of man. It was originally discovered by Bilharz in Egypt, who describes it as being a small tapeworm, from 12 to 20 mm. long, and with a maximum breadth of half a millimetre. The front half of the body is threadlike, but posteriorly it enlarges somewhat quickly. The head is spherical and bears four suckers and a central rostellum, pro-vided with a single circle of from 22 to 28 extremely small hooks. The number of segments is not more than 170, of which the last contain thirty or more ripe eggs. Each segment is very short, being about four times as broad as long. The eggs (fig. 7, Plate VI.) are oval, with a thick but not radially striated shell. They measure from 30 y. to 50 y, in length, and 40 y, in breadth. Very little is knoAvn of the life history and origin of this worm, but, arguing from what is knoAvn of some allied species, it is supposed that the larval stage is passed in some insect or snad. Taenia flavo-punctata.—This is another very uncommon human parasite. Its length is about 1 foot. The front half of the animal consists of unripe segments, each of Avhich exhibits posteriorly a central yellow spot: this is the distended receptaculum seminis. In the posterior half of the body the segments are longer and broader, and without FiS- HL — Tcenia the yellow spot. In this situation the segments are of '" (after Leuck- a brownish-grey colour, owing to the abundant develop- ment of eggs. The eggs are very large (fig. 8, Plate VI.), having a diameter of some 70 millimetres. They have a smooth double envelope, which under 582 PARASITES. high power can be seen to be radially striated. Nothing is knoAvn of the hfe history of this Avorm: nor has its head been satisfactorily examined. Taenia Madagascariensis.—This intestinal cestode has only been met with in warm climates. It reaches a length of about 20 cm., with a breadth of 2*5 mm. It has usually 100 segments, in the interior of which are a number of small oval bodies, arranged in transverse rows, alternating with each other, but without touching at any point. These are balls of eggs, and amount in each proglottis to quite 150 : the number of eggs in each ball being about 400. The head of this worm has a rostellum with about ninety hooks. The worm itself has only been met with in chddren, and its hfe history is unknown. Taenia cucumerina.—This species of tapeworm is most frequent in cats and dogs; it has also been found in young children. Fig. 112 shows this worm in its natural size. The head is club-shaped, with a rostellum surrounded with four rows of hooks. Wlhle the first forty segments are insignificant in size, the re- mainder lengthen so much that they ultimately become four times as long as they are broad: the corners of these proglottides are rounded. The ripe segments are of a red colour, from the masses of broAvnish eggs shining through. The intermediate host of T. cucumerina is the dog and cat louse, in which it passes its larval condition as a cysti- cercoid. The probable life history is somewhat as follows. The eggs of the adult tapeworm make their way sooner or later from the excreta to the hairy skin of the cat or dog, and thence to Trichodectes or lice living upon it, in the interior of which insects the eggs change into cysti- cercoids. Cats and dogs are constantly licking themselves and devouring the hosts of these bladder-worms; from them the infection of man takes place either from the tongue of the dog which returns caresses by licking, or Fig. 112.—Tcenia through the hands, which stroke these animals. In children, imminerina (after wno treat both cats and dogs with famiharity, the facdities ;. £Qr jnfecyon are even greater than in adults. Bothriocephalus latus.—This is a short-jointed, broad and flat taenia of very considerable length, attaining usually some 27 feet. The number of segments may amount to as many as 3500. The body is thin and flat like a ribbon, especially towards the sides, while the median portion projects as a sort of pad or ridge. In the ripe proglottides, the uterus constitutes a characteristic feature of this tapeworm, being peculiarly stellate or rosette- shaped. The head is ovoid, fa inch long, and has two longitudinal grooves or suckers, but no hooklets. The eggs (fig. 9, Plate VI.) are oval, about T^D- inch in their shorter diameter, and provided with an operculum or lid at one end: the shell is brown in colour. The embryo is a cdiated organism with six hooks, and, in the free state, can hve and swim about in water for more than a week. Subsequently the cihated mantle is discarded. The intermediate host of this Avorm is beheved to be certain kinds of fresh-water fish, particularly the pike, into which the embryos enter directly from without by boring. Although all attempts to bring about an immigration of these embryos of bothriocephalus into fish have failed, the observation of larval forms of this tapeworm in the pike Fig. 113.—Head of Bothriocephalus latus. TREMATODA. 583 and turbot are sufficiently definite to warrant the belief that the intermediate host is one of these fishes. Possibly there may be tAvo intermediate hosts, the first being an aquatic invertebrate. As found in the pike, the larval worm of Bothriocephalus latus is not cystic, but round, long, narroAv and distended. Its length varies in this stage from 1 to 2*5 mm. Not only in man, but in cats and dogs, feeding experiments have given positive results. TEEMATODA. The members of this group are popularly called flukes, from the fact that the commoner species are flat, hke the flukes or blades of an anchor. The name trematodes was given them because they exhibit perforations or pores (trema, a pore) which Ave now recognise as suckers. The flukes are usually of small size, the largest being not more than 3 inches in length, and the smallest scarcely visible to the naked eye. Sexually, they are for the most part hermaphrodites, but in some the sexes are separate. Most of them have a simple diAdded intestine Avith tAvo caecal ends. Fasciola hepatica.—Tins is the common fluke, and measures from half to three-quarters of an inch in length. Its habitat is in the gall ducts and gall bladder of man, of sheep and other ruminants. The number of cases of human infection by this parasite are not large, but they are sufficiently numerous to indicate that it may be the cause of severe disorders, though not always fatal. The free life of the embryos is generally short, and in place of making their way into some inter- mediate host, such as one or more species of fresh-water snails, as do some allied forms, the embryos become encysted upon water plants and other objects, attached to which they are transferred to their final host, in whose body they attain maturity. The eggs of F. hepatica (fig. 10, Plate VI.) possess a thin brownish shell; they are operculated, and measure 140 //, by 90 p.. Distomum lanceolatum.—This is the smallest common Fig.114.— European fluke, being about one-third of an inch long, and in S^LeuckartT the few cases in which it has been found in man has been once associated with the last species. Its life history is not accurately known, but is similar to that of F. hepatica. The eggs of this parasite measure from 40 y. to 45 y. in length by about 20 //, in breadth; they have a thin brown operculated shell, and generally contain an already formed, partially ciliated embryo (fig. 11, Plate VI.). Distomum sinense and D. conjunctum.—The first of these is a small fluke, measuring seven-tenths of an inch in length, and found infesting the livers of Chinese and Japanese, in whom it often causes a severe hepatitis. Its cercaria, or larval stage, is not known, but probably infests a fresh-water mollusc. The eggs of the entozoon are oval with a double contour and an operculum. Their average size is about 30 y, or say g-g-Tjth of an inch. D. conjunctum is only three-eighths of an inch in length, and has been found in the livers of both dogs and man. No more is known of its life history than of D. sinense. Its eggs are similar in shape and appearance to those of the latter, the only distinction between them being that the eggs of D. conjunctum are slightly the larger of the two. Distomum crassum, sometimes called D. Buskii from the name of its 584 PARASITES. first discoverer, is the largest fluke found in man, measuring from 1 to 3 inches in length. Its favourite habitat is the duodenum. Neither its larval state nor intermediate host are known, though this latter is thought to be a species of Chinese oyster. The eggs of this fluke are large, 125 y by 75 y., thin-walled, oval, and filled Avith granular and somewhat high refracting matter. Distomum heterophyes is a very minute fluke, measuring no more than from 1 to 1*5 mm. It has only been twice found in man; on both occasions in Egypt. Its eggs are minute, oval, reddish-broAvn and with a thick shell. Size, about 25 y by 15 y,. Amphistomum hominis.—Very little is knoAvn of this parasite, which, untU now, has only been found in India. The eggs possess a shell with operculum, are oval-shaped, and measure 150 y. long by 72 y, broad. Its habitat is the intestine, but nothing is known of either its larval stage or life history. Distomum Eingeri.—Discovered first by Ringer in North Formosa, it has since been found also in Japan and Corea, usually inhabiting the lungs, but also the brain and sub-peritoneal tissues. It is a small, oval, thick, reddish-broAvn fluke, measuring about one-third inch in length by one-fourth inch in breadth. It has two suckers, the oval, which is terminal, being shghtly the larger; the ventral sucker is placed about one-third of the animal's length posterior to the oval one. This parasite gives rise, when situated in the lungs, to severe haemoptysis, and the diagnosis of this pulmonary helminthiasis depends mainly upon the recognition of the ova of this fluke in the sputum. These ova are dark broAvn bodies, measuring about -j^ inch by -gig- inch. They have a plain thick shell, the broader end being closed by a hd. Under suitable conditions of moisture, a ciliated embryo develops Avithin each egg. Manson, Avho has closely studied the eggs of this fluke, considers that, in water, the embryo distome seeks out an intermediary host in the shape of some mollusc or other fresh- Avater animal; and "that, after entering this, either by being swallowed or by penetrating its integument, it undergoes the complex metamor- phosis peculiar to the distomes. When this is completed it is either swalloAved by man, whUe still in its intermediary host; or, escaping from this, it attaches and encysts itself on some vegetable or other animal, and there aAvaits the chance of being transferred to a human stomach, from whence it afterwards Avorks its way to the lungs of its definitive host." Bilharzia haematobia.—This is a trematode worm, Avhich differs from those previously de- scribed by haAdng the male and female repro- ductive organs in separate individuals. The male is opal white, and measures about fa inch in length, by -^ inch or more in breadth. The female is grey or brownish in colour and both Fig. 115.—Male and Female longer and thinner than the male Avorm. Both Bilharzia (after Leuck- ma[e arid female possess tAvo suckers; the body ar '* of the male assumes a cylindrical shape, due to the lateral borders being bent inwards, constituting in this manner a sort of gynaecophoric canal for the female. The adult worms are generally BIBLIOGRAPHY AND REFERENCES. 585 found in the portal vein and its branches and tributaries; also in the small veins of the bladder, ureters, and inferior cava. They are frequent in Africa, especially Egypt, the Cape and Natal; also on the coast of Arabia. There is likewise evidence to sIioav that they occur in the He de Bourbon, Mauritius, and Brazil. Located within the visceral veins, the adult parasites, if present in any large numbers, -will soon make their presence felt. If many Avorms exist, a violent haematuria may occur, Avithout any warning. Experience has shown that, although haematuria invariably accompanies the disorder, the bleeding—in cases where but feAv Avorms exist—may be so slight as to escape, not only the eye of the victim, but even also that of the medical attendant. From this it folloAvs that the presence of the disease can only be certainly diagnosed by microscopic examinations of the urine and faeces to detect the eggs. These eggs (fig. 12, Plate VI.) are bright and translucent oval bodies, with a smooth surface and thin non-operculated shell, possessing a spine situated ordinardy at one end, but sometimes laterally. They have a length of 0*16 mm., and. a breadth of 0-06 mm. The embryo is ciliated, and if left in urine soon dies; in water, however, its vitality is both marked and sustained. According to Sonsino, the intermediary host of Bilharzia is a small fresh-water crustacean (amphypoda), on encountering Avhich, in water, the free embryo attacks at a vulnerable point, and, by means of the papiUa at its head, bores and forces its way into the animal's body after having rid itself of its covering of cilia. Having effected an entrance, it proceeds to encyst itself. The encysted larva, being transferred with the crustacean in drinking water to the human stomach, is then set at liberty; afterwards, penetrating the intestinal walls, it arrives in the portal vein, where, presumably, it completes its development. At one time it Avas suggested that the re-introduction of this parasite to man might be made through the skin, urethra, or anus Avhilst bathing, instead of by the digestive tract, but in the face of the precise observations of Sonsino, this hypothesis is as untenable as it is unnecessary. BIBLIOGRAPHY AND REFERENCES. Blanchard, "Note sur quelques vers parasites de I'homme," Comp. rend, de la Society de Biologic, Paris, Seance du 18 Juillet 1891. Bollinger, "Die Actinomy- kose," Centrl. f. d. Med. Wiss., 1877, No. 27. Braun, " Bericht. u. die Fort- schritte in der thierischen Parasitenkunde," Ccntr. f. Bakter. u. Parasiten, x. p. 389 ; also Die thierischen Parasiten des Menschen, Wurzburg, 1894. Cobbold, Entozoa, Lond., 1864, with a Supplement, 1869 ; also Human Parasites, Lond., 1882—this book gives an extensive literature up to that date. Crook- shank, " On Certain Forms of Hsematozoa," Journ. Boy. Microscop. Soc, Nov. 10, 1886. Davaine, TraiU des Entozoaires, Paris, 1877. Erni, " Report on Tricocephalus dispar and Beri-beri in Sumatra," as an Appendix to Kynsey's Beport on the Anaemia or Beri-beri of Ceylon, Colombo, 1887. Felkin, On the Geographical Distribution of some Tropical Diseases, Edin., 1889. Font, "De la Filariosis: exposicion del primer caso esporadico observado en Europa," Bev. de cienc. med. de Barcelona, 1894, pp. 73 and 94. Friedberger and Frohner, Lehrbuch der speziellen Bathologie tend Therapie der Hausthiere, Stutt- gart, 1889. Galloway, "On the Parasitism of Protozoa in Carcinoma," Morton Lecture, Brit. Med. Journ., Feb. 4, 1893. Giles, Report of an Investigation into the Causes of 586 PARASITES. the Disease known in Assam as Kdla-dzar and Beri-beri, Shillong, 1890. Guaavitz, "On the Oidium Favus," VirchoAv's Archiv., Bd. Ixx. p. 560. Israel, " Die Actinomykose," Virchow's Archiv., Bd. lxxiv., 187S. Johne, " Die Actinomykose," Centr. f. d. Medic. Wisscnsch., 1881, No. 15. Kanthack, " On the Fungus of Madura Foot," Proceed. Patholog. Soc. Loiul., Jan. 19, 1892; also Journ. Path, and Baeteriol., vol. i. p. 140. Kartulis, "On the Amceba of Dysentery," VirchoAv's Archiv., Bd. 118, 1889. Kuchenmeister, Barasiten, Leipzig, 1855. Laa'eran, Du Paludisme et de son Hazmatozoaire, Paris, 1891 ; also English translation published by New Syd. Soc, Lond., 1893. Leuckart, The Parasites of Man, English translation by Hoyle, Edin., 1886 ; also " Uber Taenia Madagascariensis,"' Separat Abdruck aus Verhandlungen d. Deutsch. Zool. Gesellsch., 1891. Leavis, Physiological and Pathological Besearches, Lond., 1888. Manson, The Filaria Sanguinis Hominis, and certain New Forms of Barasitic Disease in India, China, and Warm Countries, London, 1883 ; also Article on " Filaria Disease," in Davidson's Hygiene of Warm Climates, Edin., 1893, p. 738 ; also on "Distomum Ringeri," Ibid., p. 852; also on "Parasitic Skin Affections," Ibid., 928—these articles give copious references to the collateral literature. Neisser, "On Molluscum contagiosum," Vierteljhr. f. Dermat. u. Syph., 1888, No. iv. Neumann, Trait6 des Maladies parasitaires et microbiennes des Animaux domestiques, Paris, 1888; also English translation of same by Fleming, Lond., 1892. Pasquale, "Nota preventiva sulle febbri di Massanah," Estratto dal Giornale medico del B. esercito e delta B. marina, Roma, 1889. Peiper, Die Verbreitung der Echinokokken-krankheit in Vorpommern, Stuttgart, 1894. Pfeiffer, Die Protozoen als Krankheitserreger, Jena, 1890. Ponfick, "Die Actinomykose," Breslauer arztl. Zeitsch., i. p. 117 ; also Berlin. Klin. Wochensch., 1879 ; also Monograph., Berlin, 1881. Rabe, "On Psorospermia Infection," Adam's Wochenschrift, xx. p. 67. Roberts, "On the Present Position of Vegetable Hair Parasites," Brit. Med. Journ., 1894, No. 1761, p. 685. Ruffer and Walker, "On some Parasitic Protozoa found in Cancerous Tumours," Journ. Bath, and Bacterid., vol. i. p. 198—this paper gives a copious bibliography in connection with this subject. Sabouraud, " Etude des Tricophytes," Ann. de VInstitut Basteur, June 1893, p. 497 } also February 1894, p. 83. Sauvagean and Radais, " Sur les Genres Cladothrix, Streptothrix, Actinomyces," Annates de VInstitut Basteur, April 1892, p. 242. Soltmann, "Die Actinomykose," Breslauer arztl. Zeitschrift, 1885, No. 3. Sonsino, Article on "Intestinal, Hepatic, and Portal Entozoa," in Davidson's Hygiene of Warm Climates, Edin., 1893, p. 861—this contains many references to the collateral literature ; also " Contribution to the Life History of Bilharzia," Lancet, Sept. 9, 1893. Unverricht, " On Psorospermia Infection," Milnch. Med. Wochensch., 1887, No. 26. Van Beneden, Parasites, Lond., 1876. Woodhead and Hare, Pathological Mycology, Edin., 1885—this book contains a copious bibliography up to 1885. CHAPTER XII. THE INFECTIVE DISEASES. In the last chapter, a brief review was given of the most important facts and features in connection Avith the various fungi, monadinae, and other organisms, belonging to the animal kingdom, which, by virtue of a more or less marked parasitism, produce some well-defined disorders in man and animals. There remains, however, for consideration that large class of micro-organisms—the Schizomycetes or Bacteria—which, in the light of our present knowledge, are now regarded as the active causes of the infective diseases. That most of the infective diseases, hitherto analysed, oAve their origin to one or another species of these microphytes is sufficiently well recognised as to need no special demonstration in this place. Further, the general characters of bacteria, their general morphology, size, shape, motihty, powers, and mode of multiplication, are so well known, and con- stitute so large a portion of present pathological teaching, that detailed descriptions under these respective headings would be superfluous in a work of this kind upon Public Health. Recognising that the Prevention of the Infective Diseases can only rightly result by a proper comprehension of their etiology and natural history, it is intended, in this chapter, only to enumerate very briefly, and Avithout unnecessary discussion, the chief facts in regard to these aspects of some of the more important of the infective diseases. It is true, the term " infective" is open to some criticism, especially as applied to some individual diseases hereafter to be considered, but, as expressing the etio- logical sequence of events of the Avhole class, it presents advantages which are not to be ignored. Origin of the Infective Diseases.—It may be assumed that the occurrence of an attack of one of the infective diseases implies the action of microbial life, or the products of microbic life, upon the affected person; further, that the microbe did not arise into being independently, but was the progeny of a similarly endowed parental microbe. These assumptions, while removing aU misconception as to the idea of a possible spontaneous generation of disease germs, involve the acceptation of the belief that there is an unbroken continuity of disease descent from antecedent cases. This conception of the origin of the causes of disease, if interpreted literally, implies the belief that every single case of each infective disease is the offspring or result of an antecedent case of the same disease. A little re- flection and experience soon indicate that this doctrine is too inelastic for general acceptation, because certain of these diseases affect the lower animals as well as man, and consequently the antecedent case of a given instance of such disease need not be a human case: while, as regards others, which are known to affect man only, the pre-existing case must be sought in man alone. 588 THE INFECTIVE DISEASES. A fuller knowledge of the life history of some of the micro-organisms of disease has shoAvn that some are capable of existing outside the body for considerable periods of time, thriving and multiplying either upon human or animal tissues: others again are capable of thriving and increasing upon dead organic matter: Avhile some, though capable of existing outside the body for long periods, are apparently incapable of passing through their life cycle except in living human tissues—so that diseases due to them must arise by direct or indirect infection from a previous human case of the same disease. Hence, because one affirms the continuation of the hfe of the microbial causes of disease, from generation to generation, one does not necessarily aUege that human diseases only descend in a continuous series from one human case to another. Every-day experience teaches us that such is not the case. In fact, many attacks in man are due to micro- organisms which, although not developed de novo, are really derived from particular species that have not for generations found a habitat in man or other animals. Practically, in such an instance, so far as man is concerned, the disease has a new beginning. " The question, therefore, whether diseases do or do not descend in a continuous series from antecedent cases is one which must be worked out separately, as regards each disease, by a study both of the epidemiological behaviour of different diseases and the life history of the particular microphytes upon which such diseases depend." Another view of the matter presents itself, if Ave remember that neither a micro-organism nor any species need necessarily be pathogenic throughout each life cycle. It is a matter of common knowledge that variations of severity and type are observed between different epidemics, and between different periods of one and the same epidemic of a given disease. In the same way, individual cases in an epidemic vary both in type and severity. Allowing for possible differences in the persons attacked, and for possible differences of dose of the virus, there is always the possibihty of differences due to variations of pathogenic poAver on the part of the species of micro- organism. This latter may result from a variety of causes, such as warmth, light, moisture, and the suitability or otherAvise of the soil which they may happen to invade. In other words, it is often a question Avhether the in- fluence of the host, or medium in which the micro-organism grows, may not be capable of originating new varieties of disease. From these considerations, it is but a step to the question whether the pathogenic properties of some microbes are not acquired, by a process of adaptation to environment, in the transition from a purely saprophytic life to that of parasitism. These ideas of evolutionary changes on the part of the causes of disease are suggestive of an explanation of some apparent instances of de novo origin of disease, Avithout being inconsistent with the belief of the doctrine that there is "no hfe -without antecedent hfe" as apphed to the etiology of the infective diseases. In the present day, the question of the possible origin of these diseases is not one of spontaneous generation, but of evolution. Infection, Contagion, and Inoculation.—According to the manner in Avhich these diseases are transmissible from one person to another, so are they spoken of as being either infectious, contagious, or inoculable. As a certain laxity prevails in the use of these terms, their proper definition is of ; importance. By infection is meant the conveyance of the poison in some indirect way, through the medium of the air, water, soil, food, clothing, &c, j and its entrance within the recipient's body through the skin, or mucous membranes, but without any breach of continuity of surface. Contagion I means transference of the poison by actual contact, but without breach of surface in the recipient. Inoculation, on the other hand, implies the con- INCUBATION. 589 veyance of the poison, either directly by actual contact with the diseased body, or indirectly by means of some instrument or other article from the affected to the unaffected person, an essential feature of the procedure being some breach of surface in the skin or mucous membrane. "While some diseases are only capable of being transmitted by inoculation, others are both infectious and inoculable. Incubation.—Assuming that infective matter is living matter in the form of a primitive plant cell capable of growing and multiplying within the bodies of men and animals, the course of an infective disease is truly the life history, so to speak, of a lower plant, and as such has a period of development, a period of its greatest vigour, and a period of decline or death. ^ The time of development, or as it is usually called, the period of incubation, is a most important feature in all the infective diseases, and may be defined as that period which elapses between actual infection and the appearance of the first signs or symptoms of the disease. This period varies considerably as regards different infections, ranging from a few hours in the case of some of them to weeks in the case of others, and even years possibly in one or two others. The foUowing table, therefore, may be regarded only as an approximate statement:— Disease. Period of Incubation. Duration of Infectivity. Chicken-pox, 10 to 14 days. 3 weeks. Cholera, 1 to 5 ,, 3 ,, Diphtheria, . lto 8 ,, 6 Diarrhoea, . 1 to 4 ,, lto 2 ,, Enteric fever, 8 to 14 ,, 6 ,, Erysipelas, . 1 to 5 ,, 1 ,, Influenza, lto 4 „ 3 ,, Measles, 8 to 20 „ 4 ,, German measles, 6 to 14 „ 3 „ Mumps, 14 to 22 „ 3 „ Scarlet fever, 1 to 6 ,, 6 to 8 ,, Small-pox, . 12 6 ,, Tuberculosis, unknown During the whole disease. Typhus fever, 6 to 14 „ 4 „ Whooping-cough, 4 to 14 „ 8 „ For each different infection, however, the period is comparatively constant; though variation, within certain limits, occurs in different individual cases of the same disease, the period being more constant in some than in others. The incubation period is an important fact to know in connection with all infectious diseases, inasmuch as it enables us to say, when a person has been exposed to infection, that after the lapse of a certain number of days, if not already attacked, that person is safe and may mix with other people without risk to them. At present we know very httle about the changes which take place in the body during incubation, beyond that the poison is multiplying in some part of the system. The majority of these diseases have a short and limited course, ending either in death or recovery more or less complete. A few, like chicken-pox, mumps, and German measles, are remarkably mild in their symptoms; but, on the other hand, a few are liable to vary greatly in their intensity. This is particularly so with both scarlet fever and small-pox. A general rule seems to be that severity or mildness holds good for the majority of cases occurring in a given outbreak, but that the severer cases are more common in the 590 THE INFECTIVE DISEASES. earher part of an outbreak than in the latter. Age, sex, race, and season also have an important influence upon the severity of infectious disease attacks. Many curious facts relating to the peculiar action of the causes of these diseases upon the human body could be related; how in some cases only people of a certain age or sex suffer, while in others the attacks and deaths are largely confined to those of certain descent or parentage. These and many other points connected with infectious diseases are still but imperfectly understood. Manner and Periodicity of Prevalence of Infective Diseases.—It is not unusual to speak of the general manifestations of the infective diseases as being either epidemic or endemic. The term epidemic merely signifies a tendency on the part of the disease to spread over a large area of the earth's surface, or in a given community, regardless of local circumstances. The term endemic indicates that a disease tends to remain among the inhabitants of a particular locality, and is apparently largely influenced by local con- ditions. Going back to the first causes of these diseases, it would seem probable that epidemic diseases are due to micro-organisms which thrive best in liAdng animal tissues, whereas endemic diseases are mainly due to microbes whose habitat is outside human and animal bodies, and therefore largely influenced by local circumstances. The more recent inquiries of Ransome and Whitelegge indicate that the more common and fatal infective diseases " observe definite periodic times or cycles," which may be described as " a succession of waves, the periods covered by the waves differing for different diseases." These Avaves are of two essentially different kinds—the accidental and the fundamental. The former is a wave of mere prevalence, and, as Whitelegge puts it, " probably but a reflex of changes in the environment." The true or fundamental cycle or wave is characterised by an increase of both prevalence and severity, and often extends over a considerable number of years. Though possibly not altogether independent of changes in environment, the true wave of periodicity of the infective diseases is more probably associated with microphytic evolutionary processes ("Whitelegge). Immunity and Protection.—One of the most important facts in con- nection with the infective diseases is that one attack usually protects the sufferer from a second attack of the same affection. Of course this is not always the case; neither is the duration of the protective action at all constant. In some diseases, such as diphtheria, for instance, its duration is apparently only just sufficiently long to prevent the sick person reinfecting himself. In others it seems to last during the whole of life; in fact, in some cases may be transmitted from parent to child. Various explanations have been offered to account for the protection conferred by one attack against a second onset of these diseases; and also to account for the termination of actual attacks. It is difficult to explain the occurrence of most of these affections only once in the lifetime of one person, except on the supposition that in the course of each disease the blood or tissues undergo such a change that they no longer afford, and never will afford afterwards, the conditions necessary for the development of the particular microbe. "Whether this change is a removal of some chemical substance necessary for their growth, or the production and leaving behind of some direct or indirect product which prevents any further multiplication, or whether the ceUs and tissues are in some way modified during an attack as to be able to resist future attacks of the same microbe, is by no means clear. Probably other explanations may be given, but it is at least possible that in cases in which any one of the infectious diseases rages with marked -violence IMMUNITY AND PROTECTION. 591 Avhen introduced into a community that has been long free from it, this may be because the victims come of a stock Avhich has not for some genera- tions been exposed to the contagion. "What may be termed the original liability to attack by these diseases varies in different individuals, " some appearing by nature almost immune, Avhile others exhibit a marked degree of susceptibility." These differences are partly hereditary, and partly acquired. As an instance of the former, we have the marked tendency to phthisis observable in certain families; Avhde the familiar predisposing influences of overcrowding and other defec- tive conditions of life are examples of a possibly acquired liability to certain infections. This subject of immunity is of not only scientific interest, but also of great practical importance to the student of hygiene. The problem is further a complex one, and can only be solved by a careful consideration of all the facts concerning the diseases due to the invasion of the body by bacteria. " The first point to consider is the way in which bacteria act. It may be stated that all pathogenic bacteria produce their iU effects by means of the poisons they elaborate; these poisons are called toxins." Some bacteria, such as the diphtheria and tetanus bacdli, produce very active toxins; others, like the pneumococcus, produce very feeble toxins. Now certain bacteria, notably the bacilli of diphtheria and tetanus, when inoculated under the skin, do not invade the circulatory system nor the internal organs; they only multiply at the spot of inoculation, elaborating toxins which, after absorption, produce the characteristic symptoms of those diseases. Diphtheria and tetanus, therefore, may be regarded as types of toxic diseases. Tetanus is somewhat pecuhar, for tetanus spores, when freed from toxins by washing, produce no symptoms when injected under the skin; but do so at once if the tissue be injured, or other bacteria, themselves harmless, be simultaneously injected. "This association of bacteria is an important factor in many diseases, and must not be lost sight of in the consideration of their pathology." " In contradistinction to toxic diseases there are others which may be called septic." Examples of these are anthrax in rabbits, relapsing fever in man, and the disease caused by the pneumococcus in the rabbit. In these cases, the micro-organisms rapidly invade the whole body, and the blood and organs are found crowded with them after death. The toxins produced are apparently relatively feeble. Between the typically toxic and septic diseases there are all degrees of types. These considerations suggest that in the study of immunity we must bear in mind two points. " The one is the power of the body to destroy bacteria, or to inhibit their growth; the other is the power of the body to resist the effects of the toxins. In the case of septic diseases the former factor, and in the case of toxic diseases the latter factor, is the more important. Immunity may depend, therefore, upon either factor, or upon a combination of them both." Immunity may further be either natural or acquired. Before considering, however, the nature and causes of these two kinds of immunity, it is necessary to discuss briefly certain properties possessed by the cells and humours of the body in relation to bacteria. The most important of these, perhaps, is that of phagocytosis, or the power of ingest- ing bacteria and other foreign substances possessed by amoeboid cells; upon this phenomenon is based one of the most seductive theories of immunity, and for most of our knowledge upon this interesting subject we are indebted to Metchnikoff and his school. He has studied the process throughout the animal kingdom, and demonstrated how widely it is spread, Metchnikoff 592 THE INFECTIVE DISEASES. gives a large number of examples of phagocytosis among the invertebrata, and there is good evidence to believe that it is an important means of defence among these lower animals against the attacks of parasites. In the higher forms of the invertebrata the phagocytes become differentiated from the other cells of the body, but still retain their poAver of englobing foreign bodies. Thus, the introduction of a splinter of wood into the gelatinous bell of the medusa leads to an accumulation of phagocytes, and if the wood has been previously soaked in carmine, the particles of carmine are englobed by the phagocytes. Among the vertebrata, a very similar condition of affairs exists. The most important cells Avhich are phagocytic are certain kinds of leucocytes, but not aU. Yarious classifications of leucocytes are given. Metchnikoff divides them into four varieties :—(1) The lymphocyte, which is a small cell with a large round nucleus surrounded by a small amount of protoplasm. (2) The mononuclear leucocyte is a large cell Avith an oval or kidney-shaped nucleus, closely resembling certain endothelial cells. (3) The eosinophile cell, possessing a lobed nucleus, and containing in its protoplasm coarse granules which stain deeply with eosine. (4) The neutrophile leucocyte, containing a lobed nucleus, of which the individual portions are united by delicate nuclear filaments, giving the appearance of a multinucleated cell. The protoplasm contains granules which can only be obtained by a mixture of the acid and basic dyes. Hence the name neutrophile. " Of these leucocytes, the eosinophile cells and the lymphocytes do not possess phagocytic properties, while the mononuclear and the neutrophile cells are phagocytes, and even when removed from the body are capable of englobing foreign bodies." The other important class of phagocytes in the vertebrata are the endothelial cells of the vessel walls and of the lymphatics. That these varieties of phagocytes are capable of englobing not only foreign particles, but also dead and living bacdli, has been repeatedly demonstrated. " If anthrax bacilh are injected under the skin of a pigeon, a local inflammation occurs, and if the exudation is examined it will be found to contain a number of leucocytes, many filled with anthrax bacdli. If tubercle bacilh are injected into a rabbit's vein, the bacdli quickly disappear from the blood of the general chculation, and are then found in the endothelial cells of the vessels, especially in the liver" (Washbourn). This emigration of phagocytes through the vessel walls, and their accumulation around the spots of inoculation or irritation is due to what is called chemio- taxis, or the poAver possessed by various substances of attracting or repelling amoeboid cells. "When an attraction is exerted, we speak of positive chemio- taxis, and when repulsion, of negative chemiotaxis. It is a phenomenon which can be observed in the lowest forms of hfe. "In the vertebrata, chemiotaxis can be studied by inserting capillary tubes filled with various substances into the subcutaneous tissue, or into the peritoneal cavity. If the substances introduced exert a positive chemiotaxis, the tubes are fiUed with leucocytes, while if they exert a negative chemio- taxis, or are inert, no leucocytes are found in the tubes. The toxins produced by bacteria, especially those contained within their protoplasm, generaUy exert a positive chemiotaxis." Some are inert, and some are stated to possess a negative chemiotaxis. Chemiotaxis thus explains the accumula- tion of leucocytes around the spot of inoculation with certain bacteria, and the absence of any accumulation in other cases. Another factor of great importance in connection with immunity is the power possessed by the blood and other body fluids of destroying bacteria. IMMUNITY AND PROTECTION. 593 This was first discovered by Nuttal, and has been carefully studied by Behring, Buchner, and Nissen. It was shown by Buchner that in the case \ of blood the power resided in the blood-serum. "The best method of demonstrating this property is to inoculate the serum with a cultivation, and to estimate the number of bacteria present at different intervals by means of plate cultivations. At first the serum destroys many of the bacteria ; but this power of destruction is gradually lost, and then the bacteria are able to multiply without hindrance. It is supposed that the serum contains a substance called an alexin, which possesses bactericidal properties, while the bacilli secrete a substance called lysin, Avhich neutralises the alexin, and thus enables the bacteria to grow. Both these substances are hypothetical, and have not been isolated. Whether they exist or not, there can be no doubt that the bacteria, if present in large numbers, can resist the bactericidal properties of serum. The bactericidal properties of serum are very readily destroyed by physical agents, such as exposure to a temperature of 60° C." (Washbourn). On the other hand, there is good evidence to show that the bactericidal substances are secretions formed by certain of the leucocytes. Hankin lias suggested that the eosinophile cells "were cells which secreted alexins, and this view has been supported by the observations of Kanthack and Hardy. Some others, notably Buchner, have shown that inflammatory exudations containing many leucocytes possess more powerful bactericidal properties than the blood itself. The blood of animals which have been rendered immune by submitting the animal to a mild form of the disease by a process of vaccination, possesses properties which are quite distinct from the above mentioned bactericidal properties. These are the so-called anti-toxic properties of . blood. Behring and Kitasato first proved that the blood-serum of animals, j immunised to diphtheria and tetanus, possesses the power of annulhng the toxins of these diseases when injected into other animals. The recognition and practical application of this fact has been the means of introducing well- known and efficient therapeutic methods in connection with these diseases. Ehrlich has shown that the blood-serum of animals which have been habituated to large doses of the two vegetable poisons, ricine and abrine, possesses anti-toxic properties with regard to these poisons. The same prin- ciple has been applied to a number of bacterial diseases, it being generally shown that the blood-serum of immunised animals will protect other animals against the disease; the potency of the protective serum depending upon the state of immunity of the animal furnishing the serum. "A serum which is anti-toxic is also anti-biotic." Thus a serum which will protect an animal against the toxins of diphtheria will also protect it against inocula- tion Avith the living bacilli. The converse does not hold, for it has been shown in several instances that a serum which will protect perfectly against inoculation with living bacilli is quite inefficacious against their toxins. The bactericidal properties of a serum and its protective power are quite distinct properties, and must not be confused. Whde the former are very readily destroyed by heat, the latter are not so, and moreover, the protective substance can be precipitated in various ways without losing its efficacy. How and why the anti-toxic substance in the serum is formed is not very clear, but from the two facts that the potency of the serum is roughly pro- portional to the amount of toxin introduced into the body, and that the anti-toxic property is specific, that is to say, a diphtheria anti-toxin protects only against diphtheria, and a tetanus anti-toxin only against tetanus, we are led to the conclusion that the essential element in the anti-toxic serum is a derivative of the bacterial toxin. 2P 594 THE INFECTIVE DISEASES. Many animals are naturally immune to bacteria Avhich are highly patho- genic to other animals, but no one theory Avill account for all cases of natural immunity. In some cases the explanation is a simple one, and in others very complex. Frogs are immune to inoculation with the tubercle bacillus, chiefly because the temperature of the frog is not suitable for the growth of the bacillus. Fowls are insusceptible to inoculation with the tetanus bacillus, because their tissues are not affected by the tetanus poison, just in the same way as they are not affected by morphine. These explana- tions are not enough: we must explain how it is that the tubercle bacilli and tetanus bacilli are destroyed after introduction into the bodies of the , frog and fowl. This can only be by phagocytosis, or by means of the ' bactericidal properties of the fluids. Neither factor is sufficient to explain the destruction of the bacilli in every case of natural immunity. In some instances the bactericidal properties of the blood are quite sufficient explana- tion ; in cases where the fluids of the body possess no bactericidal properties, phagocytosis must be the most important factor in immunity. Metchnikoff looks upon it as the most important factor in all cases, but this is probably an over-estimation, as some of the arguments which have been brought for- ward in favour of this theory are, in the hght of our present knowledge, fallacious. The mere fact that the bacteria are taken up by the phagocytes is no proof of immunity, for in pigeons dying of swine erysipelas marked phagocytosis occurs. Again, when anthrax bacilli are injected into the circulation of susceptible rabbits, they are at once taken up by the phagocytes of the liver, and again set free to multiply freely in the blood. So again, the formation of an exudation rich in phagocytes at the point of inoculation is not sufficient evidence of the exclusive role of the phagocytes in the pro- duction of immunity, for such exudations contain many leucocytes which are not phagocytic, while the fluid portions of these exudations possess bactericidal properties. In most cases of natural immunity it is probable that the bacteria, when introduced, are destroyed partly by the bactericidal substances in the blood, and partly by the phagocytes. Possibly, in some cases the bacteria are destroyed by the bactericidal substances alone, the phagocytes only playing the secondary role of digesting the already dead bacteria. In others it is possible that the phagocytes alone destroy the bacteria. As regards acquired immunity, the problem is more complicated, because in addition to phagocytosis, and the action of the bactericidal properties of the blood, we must consider the protective power of the serum. It has already been indicated that the immunity acquired to toxic diseases by inoculations with attenuated cultivations, or by inoculations with very minute quantities of virulent cultures, is chiefly due to the anti-toxic properties of the blood which annuls the effect of the toxins upon the tissues. The bacteria are then destroyed by the phagocytes, for the blood-serum of animals immunised to toxic diseases like diphtheria and tetanus has no bactericidal properties. The phagocytic power of the cells was present in the animal before immunisation, but was apparently inhibited by the bacterial toxins. That this is the case is shoAvn in the case of tetanus, when the spores of the disease, freed from toxins by washing, are readdy destroyed by the phagocytes of susceptible animals. It is easier to render an animal immune to fatal doses of living bacteria than to fatal doses of their toxins. The serum of immunised animals is protective against inoculation with living bacteria, but not against their toxins, that is, it is anti-biotic but not anti-toxic. This fact renders the explanation of the immunity acquired to septic diseases somewhat difficult. ANTHRAX. 595 In some cases the immunity appears to be due to an increased bactericidal property of the blood; in other cases, the blood-serum of immunised animals has no marked bactericidal properties, and yet will protect perfectly. Such a preventive serum probably acts as a stimulant to the phagocytic cells, which then destroy the bacteria by intra-cellular digestion. The whole theory and explanation of immunity from infective diseases must be still regarded as being in a very incomplete state. It is too complex to be explained by any one theory. In each case we must consider several factors, and in the majority of cases several factors are concerned, sometimes one and sometimes another being the more essential. ANTHRAX. This is a fatal acute disease which fortunately affects cattle, horses, sheep, and goats more frequently than man. It is a widely spread form of disease, appearing with unusual frequency in certain districts, and rendering thereby these locahties especially dangerous to herds of cattle. The clinical aspects of the disease are different in different species of animals; in larger ones it is said to run a comparatively slow course, being accompanied Avith violent fever, and in most cases, but not always, ends in death. The smaller animals, such as mice and guinea-pigs, succumb to the disease almost without exception, but often without showing any striking symptoms up to the moment of death. On post-mortem examination, a con- spicuous symptom is the dark, congested, and enlarged spleen. In sheep and* cattle there occur haemorrhagic exudations under the skin of various regions : the exudation forming tumours of a dark to black gelatinous nature. Anthrax affects man in two forms, external and internal. External anthrax, or, as it is sometimes called, "malignant pustule," has its usual seat on the neck or face, being doubtless due to inoculation. The first local manifestation is the appearance of a papule or vesicle, which develops in the course of a few days into an inflamed indurated mass, with a central black slough. The surrounding tissues and the lymphatic glands are swollen and indurated. In rare instances the disease may remain local, and end in either resolution or suppuration. More commonly, however, constitutional symptoms appear, indicating general infection. Occasionally malignant pustule supervenes upon internal anthrax, which appears to be due to the inhalation or swallowing of the virus. Internal anthrax is only known as affecting wool-sorters, and as the result of the experimental infection of animals. After a very variable incubation period, ranging perhaps from two to twelve days, the early symptoms of internal anthrax are weariness, depression, chills, restlessness, and a tight feeling across the chest. This stage may last only a feAV hours, but more usually three to seven days, when graver symptoms set in suddenly. Prostration becomes extreme : pulse and respiration are hurried : temperature rises, but always marked by sudden remissions, accompanied by perspiration. Even in serious cases recovery may follow, but more commonly death ensues from syncope, pneumonia, or the exhaustion of diarrhoea. In cases of recovery the protection derived from the attack is very slight, if any. This form of anthrax is called Avool-sorters' disease, from its prevalence in the Bradford district among men employed in sorting certain foreign wools, particularly those of goats from Yan, in Armenia. More or less successful attempts have been made to render the sorting of wools, which experience has shown 596 THE INFECTIVE DISEASES. to be dangerous, safer, by prehminary disinfection or Avashing, cleanliness and ventdation of the sorting rooms, Avith the use of fan-blasts to carry aAvay the dust generated during the opening and sorting of the bales. To these precautions must be added Avashing of the hands before eating, and changing of clothes Avhen the work is done. A microscopic examination of the blood and spleen shoAvs the pathogenic microbe or Bacillus anthracis. When examined fresh, these bacilli are°non- motile rods, more or less truncated and homogeneous looking, varying a httle in size, according to the animal from Avhence they have been derived. They are usually from 5 to 20 y long and from 1 to 1*25 /x broad : Avithin the body they do not form spores. The longer bacilli or their chains show, Avithin a common sheath, cubical or rod-shaped cylindrical, square cut* stained masses of protoplasm : these are the real bacillary elements. These appearances are more pronounced and noticeable in specimens made from artificial cultures: in some anthrax-threads of cultures, all elements con- stituting a thread are separated one from another by a transverse septum. Anthrax bacilli readily admit of cultivation in feebly alkaline broth, or in gelatin, blood-serum, or on agar and potatoes. All the cultures have a more or less characteristic appearance : for instance, in a stab gelatin culture there is first a whitish line in the track of the needle, and from it fine filaments spread out in the gelatin. Occasionally a httle isolated spot develops, from Avhich rays extend in all directions, like the silky filaments of thistle-down. The gelatin slowly liquefies and the groAvth subsides as a flocculent mass. In stroke cultures on gelatin the streak of inoculation is marked after tAventy-four to forty-eight hours by a whitish-grey line, from Avhich a number of fine whitish threads shoot out horizontally. On agar a thick greyish film is noticeable after tAvo days. In broth at 37° C. a slight turbidity is seen after thirty-six hours, which gradually forms into a flaky and flocculent mass at the bottom. On potato at 37° C. a thick cohesive paste-like layer is formed; this is of a broAvnish colour. Anthrax bacilli, cultivated on the surface of a solid medium, or with free access to air, readily form spores which preserve their vitality for years. The bacilli themselves are readily destroyed by heat or other disinfecting agencies, but the spores are extremely resistant. Animals can be infected by inhaling or swallowing the spores, but not by the bacilli unless there is some abrasion, such as to allow practically of inoculation. The bacilli are destroyed by the gastric juice, spores are not. Klein has shown a further difference between bacilli and spores by results of inoculation. The former cause a slight and localised malady, the latter a severe constitutional illness which is usually fatal. The usual mode of infection, so far as man is concerned, is by inoculation, tanners, butchers, and others engaged in handling raAv hides being very liable to malignant pustule: it has been suggested that the poison may be carried by flies and other insects. Man may be also infected by inhaling or sAvalloAving spores in the form of dust, as in wool-sorters' disease. Although exact evidence is Avanting, it may be assumed that anthrax can be acquired by eating the flesh of diseased animals. Animals may contract anthrax by similar means as man : but probably their chief methods of infection are by inhalation and SAvalloAving. A field may become infected with anthrax, and healthy animals grazing on it, after the lapse of months or even years, may acquire the disease. The infection is probably imparted to the superficial layers of the sod by the blood or secretions of affected animals. Pasteur's suggestion, that the spores from buried carcasses are brought to the surface by earth-Avorms, has been shoAvn CEREBRO-SPINAL FEVER. 597 to be unlikely by Klein, for the simple reason that spores are not formed under such conditions, and that the rapid onset of putrefaction soon destroys all infectivity. With varying degrees of success, various attempts have been made to attenuate the growths of anthrax bacilli, and by successive inoculations of them to render animals resistant to the disease. The success of these methods depends, hoAvever, to a large extent on the primary degree of virulence of the bacilli at starting and the absolute purity of the resulting vaccines. While sheep, cattle, and rabbits that have once passed through a mild form of anthrax are, as a rule, refractory against further inoculation with virulent anthrax, this is not the case Avith some other animals, for instance, guinea-pigs. Klein has shoAvn that mouse's anthrax blood is attenuated anthrax, and can be used for the protective inoculation of sheep. Pigs are naturally difficult to infect, though they can be infected : adult rats, dogs, and cats are almost insusceptible: healthy fowls are quite so, though if their bodies be cooled down, they can be fatally infected. Prevention resolves itself into the need of obvious precautions for avoid- ing direct inoculation of a cut or abrasion from the carcass of an anthrax- ( affected animal. The flesh of such animals must be condemned as food. / As regards the trades affected, all dangerous wools should be disinfected by steam, or at least thoroughly wetted and sorted while damp, to avoid dust. Sorting rooms should be provided Avith an apparatus for extracting the dust, and be well \rentilated. In regard to cattle, it must be borne in mind that diseased animals do not transmit the affection to others in the ordinary way by association: the carcass of an animal dead from anthrax is more dangerous than the diseased animal was during life. In slaughtering diseased animals, effusion of blood should be avoided as much as possible. Burial of uncut carcasses Avith a sufficient covering of quicklime is the most simple and effective method of disposing of them. The organisms soon die ] Avhen access of air is prevented. If the carcasses are destroyed by burning or boihng, it is generally necessary to cut them in pieces first ; this is not only dangerous to the persons employed, but is calculated to spread the disease, unless the greatest care is observed to avoid spilling or effusing the body juices, and disinfectants freely used. As yet a satisfactory method or system of preventive inoculation has not been devised. CEREBRO-SPINAL FEYER. This is a disease Avhich appears to be more prevalent abroad than in this country : and in reference to its epidemic prevalence in various countries during the present century, a very considerable historical literature has accumulated. As regards this country, the most recent outbreaks have been in Dublin in 1885-6 and at Oakley in Suffolk in 1890. Some doubt has arisen as to whether the Oakley cases were those of true cerebro-spinal fever, chiefly on account of their low fatality, and the frequency with Avhich multiple cases occurred in the same families : on the other hand, the cases betrayed the existence, in the form of a small epidemic, of a disease which had for its main symptoms vertigo, headache, great drowsiness, marked retraction of the head, and in some instances opisthotonos and sub- sequent paralysis: in fact, constituting a malady chnically indistinguishable from cerebro-spinal fever. Mortality.—In well-marked epidemics, this has usually been very great, varying from 60 to 90 per cent. In non-epidemic periods, it is difficult to 598 THE INFECTIVE DISEASES. accurately determine what the mortality from this disease really is, as it is not unlikely that true cerebro-spinal fever is of more frequent occurrence than is generally supposed, OAving to errors of diagnosis betAveen tins and tubercular meningitis or indeterminate " fevers." The deaths recorded annually in England and "Wales as due to this disease, during the twenty years 1874-1893, have ranged from 13 in 1893 to 58 in 1878. Influence of Sex, Age, and Race.—It is difficult to find any difference in regard to the incidence of the disease upon the two sexes. As regards age, it usually attacks those approaching puberty, or in early adult life: it has been known, however, to occur in persons of all ages, though certainly rare among those beyond middle life. The evidence in respect of race indicates it to make no distinctions. Effects of Climate and Season.—Except for its occurrence in Fiji, in the unusually cool year 1885, we have no accounts of the prevalence of this disease in tropical climates. In all countries in Avhich it has been observed as an epidemic, this has usually occurred in either winter or spring, that is, in the coldest seasons of the year. Etiology.—Owing to the frequent manifestations of this disease in an epidemic form in public institutions, the earlier views regarding it indicated infection as a prominent factor in its diffusion. A close analysis of the more recent outbreaks indicates that cerebro-spinal fever varies considerably as regards infectiveness, and that, if directly communicable from person to person, it is communicable only in a very low degree (Simon). If not dhectly communicable, there are strong grounds for regarding it at least as being readily transported from place to place by infected persons and things. Fagge, quoting the views of Ferguson, veterinary surgeon to the Privy Councd in Ireland, suggests that " a contagious principle is given off by the sick, but that it has to undergo some transformation or intermediate stage of its development, possibly in another animal, before it can infect a human being," and that on each occasion " when the disease has prevailed in Ireland, it has co-existed with an epizootic of the same nature among pigs and dogs." Arguing from analogy with what we know to be the case in respect of other diseases, and bearing in mind that this affection has a tendency to prevail under conditions of overcrowding or defective ventilation, and to recur in districts which have suffered from previous epidemics, Ave are justified in believing that the cause of the disease is a micro-organism belonging to the class of facultative parasites, and as such capable of thriving and multiplying outside human or animal bodies. At present, this microbe has not been identified. Importance has been attributed by some observers to dampness of sod as an etiological factor in this disease, even so far as to allege that it is of malarial origin : as Hirsch has pointed out, the geographical distribution of the affection does not support this view. Prevention.—In our present condition of defective knowledge in regard to the exact origin of this disease it is difficult to formulate prophylactic measures. Isolation does not seem to be required, and Ave do not knoAV Avhat to disinfect. Free ventilation, good food, and avoidance of fatigue appear most essential. CHICKEN-POX. It was only towards the end of the last century that this disease Avas clearly distinguished from small-pox: but beyond a certain superficial resemblance there is nothing in common between the two diseases. Chicken- pox occurs as an epidemic, which very often coincides Avith epidemics of CHOLERA. 599 small-pox, and adds to the difficulty of diagnosis of mild cases of the latter. Persons of all ages are liable to attack, but children more so than adults. The mortahty is practically nil, though the Registrar-General annually records a few deaths from chicken-pox: how far these fatal cases may be set down to unrecorded deaths from small-pox is difficult to decide : possibly a large proportion may be so, Avithout error. The incubation period has been variously estimated from four to twenty- eight days: recent opinion sets it down at about fourteen days, for which reason the Association of Medical Officers of Schools insist upon a quarantine of eighteen days before re-admission to school, after exposure to infection. The characteristic vesicular eruption appears without any previous sickness, or at most with only some twenty-four hours of fever or malaise. It begins on any part of the body, and is added to irregularly by fresh crops for four or five days, during which time the constitutional symptoms are most irregular. The vesicles are not usually umbilicated, but this is not a reliable point for diagnosis, as among them are often some which are so. The vesicles consist of a single cavity, with a very thin covering, and with little or no hardness at the base. About the third day, the clear watery contents of the vesicles become turbid; within the Aveek a thin crust forms which eventuaUy falls off and leaves no cicatrix unless sores have been caused by irritation. The infection of chicken-pox is active from the very first, and is readdy imparted by contact or by means of fomites. As in small-pox, the length of infectivity will depend on the falling off of the crusts, which usually become detached in parts rather than entire. Attempts have been made to inoculate from the vesicles, but without success. Chicken-pox and smaU-pox are not mutually protective. CHOLERA. It is usual to speak of cholera ha-ving its endemic area in certain parts of India, more particularly the delta of the Ganges, but it is possible that other parts of Asia are also its endemic home. Although Portuguese writers refer to an extensive and fatal outbreak of this disease in India in 1503, it is not until the beginning of the present century that we have any scientific or systematic accounts of cholera. The first well-recorded pandemic diffusion of the disease dates from 1817, when there was a Avide- spread prevalence of cholera in Bengal, extending during the next two years throughout India and the greater part of Asia. Since then, at irregular intervals, it has spread in epidemic form over a greater or lesser part of the Avorld. It has followed, almost invariably, the lines of traffic by land or water, but no reason has been found for the apparently capricious way with which it has selected some routes and omitted others. The invasion of each new country along its line of march has been, in most cases, traced to infection through some communication with a country already attacked. In temperate climates the outbreak frequently subsides in Avinter, but often reappears with the warmer weather, and in some instances has recurred in the third year, apparently without fresh introduction. As an epidemic, cholera has appeared in England four times, namely, in 1831-2, 1848-9, 1853-4, and 1865-6; the disease having on these occasions slowly spread from India. On several other occasions the disease has invaded Europe, but failed to reach England. In July 1831 infection was carried to the Medway by ships from Riga; later in the same year it broke out at Sunderland and other northern ports, as a result of importation 600 THE INFECTIVE DISEASES. by ships from Hamburg. In the course of the next year it Avas extensively prevalent in Great Britain, extending later to Canada and the United States. In 1848 London Avas infected from Hamburg in September, and Hull and Sunderland in October from the same port: from these centres the disease at once spread. During the Avinter of 1848-9 cholera abated, but in the spring of 1849 it broke out again with increased vigour, finally disappearing in December, haAring caused 53,293 deaths, besides a heavy diarrhoeal mortality, part of which was probably due to cholera. In 1854 it Avas again severely epidemic in Great Britain, haAring been once more imported from Germany. During this year cholera caused over 20,000 deaths in England and Wales. The fourth epidemic invasion of Great Britain, in 1865, had a somewhat different history. Starting from the basin of the Ganges in 1863, cholera was carried by ships to South Arabia; it next broke out among the Mecca pilgrims, by whom it was carried to many places, among them Suez. From Egypt it spread along the Mediterranean littoral, extending through the whole of Southern and Central Europe. England Avas infected through Southampton from Alexandria during August, but only to a small extent. In the following spring the disease was again repeatedly imported from the Continent, and during that year something like 15,000 people died from cholera in the whole of England. Since then the disease has not prevailed as an epidemic in this country, though frequently imported and prevalent in various parts of Europe, more especially since 1884. During this year (1884) cases of cholera were three times brought in ships to England, but no spread of the disease occurred. The same thing occurred again in the tAvo next following years. In 1890 a recrudescence of cholera advanced from Persia and Central Asia, culminating in the infection of Hamburg on August 23rd, 1892. The mortality in Europe during the gradual extension of the disease westward in 1892 was very great. Two days after Hamburg was declared infected, three cases of cholera from that city arrived in London, and by the middle of October quite thirty cases had been brought to this country; but in no instance, so far as is knoAvn, did the disease extend to any person other than those arriving from abroad. Although at one time or another cholera has extended Avidely over the earth's surface, still it has, so far, never invaded Australia, the Pacific Islands, St Helena, Ascension, the east coast of Africa south of Delagoa Bay, Iceland, the Faroe Islands, the Hebrides, Orkney, and Lapland (Hirsch). Apart from the possible enjoyment of perhaps special sanitary advantages, more particularly pure and Avholesome water-supphes, local exemptions from cholera are mainly due to the relatively little communica- tion between the places in question and the continent of India, or other centres of endemic prevalence. Mortahty.—This is often enormous. Some figures, as regards cholera in this country, are shoAvn in the folloAving table:— 1831 1849 1854 1866 England and AA'ales. London. Total Cholera Deaths. Cholera Deaths per million living. Total Cholera Cholera Deaths per Deaths. ; million living. 30,924 53,293 20,097 14,378 2,225 3,034 1,094 685 11,240 6,784 14,137 6,182 10,738 4,288 5,596 1,842 CHOLERA. 601 English experience shows the prevalence and mortality of the disease to be greater in the second than the first year of the epidemic. The fatality of cholera is also very high, ranging commonly from 30 to 50 per cent, of those attacked: it is said to be greater at the beginning than during the later stages of an outbreak. Influence of Climate, Season, and Temperature.—Warmth is a predis- posing condition of great importance, but it is not, in itself, sufficient to cause an outbreak of cholera, nor does cold necessarily arrest it. That a certain degree of heat favours the activity of the poison is sufficiently evidenced by the fact that in Europe the disease has generally attained its greatest prevalence from June to August, subsiding during the winter, often only to reappear in the folloAving summer. There are, however, exceptions to this general rule: even in India the seasonal curve of cholera prevalence is not coincident ahvays with that of temperature. In Bengal there is a chief maximum of cholera deaths in April, with a smaller one in Novem- ber; in the Punjab the maximum prevalence is in August; in Bombay the maximum is in April; in the North-West Provinces and the Deccan m August; and in Madras there are two maxima, in February and September. In all these regions, except two, the highest mean temperature is reached in May or early June; in the Punjab and North-West Provinces it is in July. In Madras cholera mortality is at its minimum in June, when the mean temperature is at its highest. As regards rainfall, there can be no doubt that it has a marked influence upon the prevalence of cholera, and supplies a clue to many of the dis- crepancies in respect of the connection betAveen cholera and temperature. As a general rule, it may be asserted that not only is rain connected with the development and dissemination of cholera, but that in India no extensive epidemic can occur unless during or after rain. On the other hand, there can be no doubt that the reverse effect is not infrequent, particularly if the rainf aU be excessive, prevalence of the disease being prevented by destruction of the micro-organisms of the affection, partly as the direct result of the amount of water in the soil,-|and partly from their being carried further from the surface Avhere they are no longer among surroundings favourable to their existence. Influence of Race, Sex, and Age.—There is a general consensus of opinion among authorities that the incidence and severity of cholera are greater among negroes than Europeans, but as to the relative susceptibihty of other races little is known. The evidence as to influence of sex is imperfect: what there is, indicates that the general mortality is greater among males than females, but that the case fatality is in excess for females up to tAventy-five years of age, after Avhich it is greater for males. As regards age, apart from sex, the actual number of deaths is much greater during the extremes of life than during the middle periods. This is very much what might be expected. Etiology.—General sanitary defects, no doubt, are conducive to cholera prevalence and mortality, as determining the points of attack, especially by inducing a lowered standard of health with diminished powers of resistance, and by specifically fouling the air, soil, and water. The Avords of Sir John Simon, written in 1866, are as true of to-day as they were of thirty years ago. He says, " The diffusion of cholera among us depends entirely upon the numberless filthy facilities which are allowed to exist, and specially in our larger towns, for the fouling of earth, air, and water, and thus secondarily for the infection of man, with whatever contagium may be contained in the miscellaneous outflowings of the population. Excrement-sodden earth, excre- 602 THE INFECTIVE DISEASES. ment-reeking air, excrement-tainted water, these are for us the causes of cholera." Hence the disease attacks more especially the poorest quarters of towns. The poison doubtless gains access to the system by sAvallowing, more rarely by inhalation, the incubation period being from a few hours to three days : though it may apparently reach as much as ten days. The infection is given off in the discharges from the boAvels, and possibly in the vomit also. These may infect, as already explained, either Avater, milk, soil, or fomites. Etiologically, cholera exhibits some connection Avith, and likeness to diarrhoea. Marked prevalence of the latter disease is often noticed as a precursor of the former: while both appear to be associated with filth, and to be influenced by heat and certain physical conditions of the soil, more particularly porosity, a low level of the subsoil Avater, and a subsoil tempera- ture of 56° F. at 4 feet below the surface. Clinically, the two diseases are not unrelated, for such differences as there are betAveen the two maladies are mainly differences in degree of malignancy. The curious and remarkable etiological and clinical resemblance between cholera and diarrhoea (epidemic) has been ably discussed by Thompson and others, with the surmise that " cholera may after all be but an Asiatic variety of a disease known else- where as ' diarrhoea' and cholera nostras." Further, in regard to cholera in India, the deduction is permissible that in localities in which it is endemic, the soil is so charged with the necessary micro-organism that the disease, although doubtless diffused, even there, most frequently by water, is also probably occasionally disseminated by direct emanations from the soil. As we shaU see in a subsequent section, this proposition conforms closely with what are known to be the facts in connection with epidemic diarrhoea : and, put in other Avords, the diffusion of cholera in India and other endemic areas is practically identical with that of diarrhoea in England. Comple- mentary to this, the further deduction is permissible that when the cholera micro-organism is imported into countries where the conditions are less favourable to its vitality and multiplication in the soil, its opportunities for passing to man are limited mainly to occasions of conveyance by water and fomites. Without absolutely accepting these views, it must be acknoAV- ledged they are not antagonistic with the accepted facts concerning cholera diffusion and prevalence, and at the same time afford a "basis for reconcilia- tion between the Anglo-Indian and British schools with respect to the etiology of cholera." That cholera ultimately depends upon micro-organic life processes has been provisionaUy assumed in the preceding remarks. Since Koch dis- covered a comma bacillus in the evacuations and intestines of cholera patients, and adduced evidence in support of the view that this organism is the cause of the disease, the comma bacillus has become generally to be regarded as the real infective agent of cholera: though there have not been wanting competent critics who question the pathogenesis of this bacdlus. Cholera bacilh appear as rods curved in the direction of their long axis so as to resemble a comma in figure, hence the name "comma bacdlus." They have a twist in addition to this curve, so that they represent a kind of spiral bacteria: when connected in chains they give rise to corkscrew forms. A flageUum can be demonstrated at one end, but no spore formation. These commas feebly resist chemical reagents, being destroyed by the acid of the gastric juice, and refusing to grow upon feebly acid gelatin. They also perish at temperatures above 50° C., while drying causes speedy loss of the power of development. On gelatin plates, the individual colonies are round, and he in a funnel- Plate VII. i r ~\ o f**\ )i A' PZaie- culture, of Cholera, spvrillu. (x760) Stab cxxUbxre, of"Cholera^ spirilla. -vn, gehxt&z.. West Newma.ii c"hr. lltk SeetcoTVof'vrttestvn& from, cucase, of Cholerou. ( X WOO). CTnolera, CHOLERA. 603 shaped cavity, due to liquefaction of the medium : when vieAved with transmitted light and magnified, they look like ground glass, the edge of the colony being finely notched. In thrust cultures also the gelatin liquefies slowly, the liquefaction being chiefly seen on the surface, so that a bubble of air appears in the upper part of the funnel-shaped excavation. From this bubble a thin prolongation runs doAvn along the track of the needle. When liquefaction has gone still further the bacilli sink in the needle track, the bacilli falling to the bottom as a greyish-white sediment. These bacilli grow Avith a fair degree of luxuriance upon other media also, forming on beef bouillon a wrinkled membrane, while the broth itself remains toler- ably clear. They groAv also in sterihsed milk, producing coagulation, but in unsterilised milk undergo speedy destruction owing to the occurrence of acid fermentation. On agar the bacilli grow in the form of a whitish-grey shining expansion. On potato they thrive even when the surface shoAvs a slightly acid reaction, but only at from 30° C. to 40° C.: if the potato be saturated with a 2 per cent, solution of sodium carbonate, they will thrive both at 16° C. and at the higher temperature. Blood-serum is slowly liquefied by the growth of cholera bacilli (Plate YIL). In all old. cultures numerous involution forms are seen. Comma bacilli stain best with an aqueous solution of fuchsin, but are not coloured by Gram's method. Besides the cholera commas of Koch, various species of comma bacilli are known AAdiich present some points of resemblance to it, notably those of Finkler and Dencke, the spirillum of noma, and various spirilla found in mucous secretions. The Finkler-Prior bacillus, or Vibrio proteus, is some- what larger and thicker than Koch's bacillus, but the spirilla formed by it are never so long as the cholera forms. The culture on a gelatin plate liquefies so rapidly and extensively that the difference between it and a culture of cholera bacillus becomes at once apparent. Dencke's comma bacillus is more difficult to distinguish from that of cholera. It was groAvn by Dencke from old cheese, and scarcely differs from Koch's bacillus in its morphological relations. It is, however, dis- tinguished by its speedier hquefaction in gelatin, and the yellowish colour of the colonies. The Vibrio Metchnihovi, which was found by Gamaleia in the intestinal contents in a Russian disease of poultry, is a curved bacterium forming screw-shaped spirilla of considerable length, but which is much shorter and thicker than the cholera bacillus. Its accurate differentiation from Koch's comma is often extremely difficult. A peculiarly characteristic property of the cholera bacillus lies in the fact that cultures of the bacilli in media containing peptone give a reddish-violet colour in a short time when treated with pure hydrochloric or sulphuric acid. This coloration is sometimes spoken of as the indol reaction, since that substance gives a red colour with nitrous acid, the theory being that the cholera bacilli spht off indol from the peptone of the nutrient medium, and at the same time develop nitrites which are decomposed by the addi- tion of a strong acid. Of all the other morphologically and biologically simdar micro-organisms, Vibrio Metchnihovi alone gives this cholera-red reaction. It cannot be said that the final proof of the direct pathogenic relation of Koch's bacillus has yet been obtained by inoculation, although injections of cultivations into lower animals has been folloAved by death. On the other hand it has been urged by Klein and others that these experiments are inconclusive, death in the cases quoted being not so much induced by the 604 THE INFECTIVE DISEASES. comma bacilli as by the other means adopted, and that other bacilli may be substituted without altering the result. There can be no question that the Vibrio Metchnihovi is very nearly related to the cholera bacdlus of Koch : but that the various other forms of vibrio, Avliich have been described, are identical remains unproven. From all the evidence at our command, there- fore, it seems impossible to question the truth of Koch's original vieAvs regarding the existence of a specific bacillus in cases of Asiatic cholera, or to doubt that this specific bacillus is the particular spirillum known as the comma bacillus of cholera : particularly as this bacillus is invariably present, and intimately associated with definite changes in the intestine to be found in all cases of Asiatic cholera. Lastly, this bacillus is seldom, if ever, met Avith in the evacuations or in the intestines, either in health or disease, except Asiatic cholera. The precise parts taken by air, milk, soil, and water in the diffusion of cholera have already been considered elsewhere. Of these, brief mention need only again be made in respect of the two latter. The whole course of not only the last great epidemic of cholera in Europe in 1892, but of all others, especially in England, shoAvs that the disease is propagated mechanically, and that the influence of the soil as a mere influence of place and season is quite subsidiary. On the other hand, soil may, and doubtless does, serve as a medium in which the cholera virus can survive outside the human body. Confirmative of this view are the striking instances, from India, in which fresh sand, from the banks of rivers used as bathing places by the infected, placed in filters, has been the means apparently of giving rise to outbreaks of cholera to those partaking of the Avater filtered through it. As regards Avater, the earlier objections to the possibility of cholera commas conveying the disease, because of their alleged inability to survive any length of time in water, are no longer tenable. Many observers have shown that cholera commas not only live but multiply in drinking waters. Although results on this point have been conflicting and difficult fully to reconcile, still the inference is undeniable that cholera can be and is, more frequently than by anything else, conveyed and diffused by drinking water. Striking as are the historical facts in connection with the relation of cholera to water, we do not desire to suggest that water-carriage constitutes, even in Europe, the only means of the propagation of cholera. We wish specially to emphasise the fact that experience has proved that polluted Ayater-supplies have played at all times a conspicuous part in the dissemina- tion of the disease. At the same time, the behaviour of cholera, not only in India but in Europe, seems to require for its explanation a theory of the abdity of the cholera organism or virus to maintain life, or even pass through some phase of its life outside the animal body, most probably in the sod. It is not unlikely that it is capable, under certain circumstances, of escaping from the soil and infecting human beings, either directly or by fastening on to food. European experience has shown, over and over again, that cholera attains its widest diffusion during the second year of its epidemic appearance : and as the later diffusions were apparently connected Avith the earlier manifestations, it is not improbable that, during the interval, the cholera organism, " although reduced to a relatively latent condition, as regards pathogenic manifestation, must have continued its existence—presumably in the soil." In connection with this point, Sims Woodhead has pointed out that the generally accepted cholera organism, or comma bacillus, when grown anaerobically, gains increased virulence, but largely loses its poAver of CHOLERA. 605 resistance to germicidal agents. Conversely, when grown aerobically, it largely loses its virulence, but gains in resisting poAver. " Its cultivation in the bodies of human hosts, therefore, while augmenting its virulence, does not tend to preserve that section of a given crop which has taken to colonise in the human subject. On the other hand, its aerobic existence outside the human body, Avhile diminishing its ability for immediate harm to human beings, increases its ability of maintaining itself, and of migrating from the sod to man when favourable conditions shall come round." These facts further may explain why cholera displays so little tendency to spread immediately from person to person, but yet readily disseminates itself by fomites, such as infected body-hnen. Prevention.—Our course of action and duties in this respect cannot be more tersely stated than in the folloAving extract from a Memorandum, issued in 1892 to the Sanitary Authorities of England and Wales, by the Medical Officer of the Local Government Board. '' Cholera in England shows itself so little contagious, in the sense in which small-pox and scarlatina are commonly called contagious, that, if reasonable care be taken where it is present, there is almost no risk that the disease will spread to persons who nurse and otherwise closely attend upon the sick. But cholera has a certain peculiar infectiveness of its OAvn, which, where local conditions assist, can operate with terrible force, and at considerable distances from the sick. It is characteristic of cholera (and as much so of the slight cases where diarrhoea is the only symptom as of the disease in its more developed and alarming forms) that the matters which the patient discharges from his stomach and boioels are infective. Probably, under ordinary circumstances, the \ patient has no power of infecting other persons except by means of these discharges ; \ nor any power of infecting even by them except in so far as these matters are enabled to taint the food, water, or air which people consume. Thus, when a case of cholera is imported into any place, the disease is not likely to spread unless in proportion as it finds, locally open to it, certain facilities for spreading by indirect infection. '' In order rightly to appreciate Avhat these facilities must be, the following considera- tions have to be borne in mind:—First, that any choleraic discharge, cast without previous thorough disinfection into any cesspool or drain, or other depository or conduit of filth, is able to infect the excremental matters with which it there mingles, and probably, more or less, the effluvia which those matters evolve ; secondly, that the j infective power of choleraic discharges attaches to whatever bedding, clothing, towels, I and like things have been imbued with them, and renders these things, if not thoroughly disinfected, capable of spreading the disease in places to which they are sent for washing or other purposes ; thirdly, that if, by leakage or soakage from cess- pools or drains, or through reckless casting out of slops and Avaste water, any taint (however small) of the infective material gets access to wells or other sources of drinking water, it can impart to enormous volumes of water the power of propagating the disease. When due regard is had to these possibilities of indirect infection, there will be no difficulty in understanding that even a single case of cholera, perhaps of the slightest degree, and perhaps quite unsuspected in its neighbourhood, may, if local circumstances co-operate, exert a terribly infective power on considerable masses of population. '' The dangers which have to be guarded against as favouring the spread of cholera infection are particularly two. First, and above all, there is the danger of water- supplies, which are in any (even the slightest) degree tainted by house refuse or other like kind of filth ; as where there is outflow, leakage, or filtration from seAvers, house drains, privies, cesspools, foul ditches or the like into springs, streams, wells, or reservoirs, from which the supply of water is drawn, or into the soil in which the wells are situate—a danger which may exist on a small scale (but perhaps often repeated in the same district) at the pump or dip-well of a private house, or, on a large or even vast scale, in the case of public water-works. And secondly, there is the danger of breathing air which is foul with effluvia from the same sorts of impurity. " Information as to the high degree in which those two dangers affect the public health in ordinary times, and as to the special importance which attaches to them at times when any diarrhoeal infection is likely to be introduced, has now for so many years been before the public, that the improved systems of refuse removal and water-supply by which those dangers are permanently obviated for large populations, and also the minor structural improvements by which separate households are secured against them, ought long ago to have come into universal use. 606 THE INFECTIVE DISEASES. " So far, however, as this wiser course has not been adopted in any sanitary district, security must, as far as practicable, be sought in measures of a temporary and palliative kind. '' (a) Immediate and searching examination of sources and conduits of water-supply should be made in all cases where drinking water is in any degree open to the suspicion of impurity ; and the water both from private and public sources should be examined. Where pollution is discovered, everything practicable should be done to prevent the pollution from continuing, or, if this object cannot be obtained, to prevent the water from being drunk. Cisterns should be cleaned, and any connections of waste pipes with drains should be severed. "(6) Simultaneously, there should be immediate thorough removal of every sort of house refuse and other filth which has accumulated in neglected places ; future accumulations of the same sort should be prevented ; attention should be given to all defects of house drains and sinks through which offensive smells can reach houses ; thorough washing and lime_-washing of uncleanly premises, especially of such as are densely occupied, should be practised again and again. " It may fairly be believed that, in considerable parts of the country, conditions favourable to the spread of cholera are now less abundant than in former times ; and in this connection, the gratifying fact deserves to be recorded that during recent years enteric fever, the disease which in its methods of extension bears the nearest resemblance to cholera, has continuously and notably declined in England. But it is certain that in many places such conditions are present as would, if cholera were introduced, assist in the spread of that disease. It is to be hoped that in all these cases the local sanitary authorities will at once do everything that can be done to put their districts into a wholesome state. Measures of cleanliness, taken beforehand, are of far more importance for the protection of a district against cholera than removal or disinfection of filth after the disease has actually made its appearance." Preventive Inoculation.—Admitting the value and effectiveness of the principles above referred to, it is none the less certain that considerable communities are quite unable to command the conditions to be desired, and consequently the question has arisen as to the possibility of protecting the indi-vidual members of such communities from the danger of infection by the inoculation of minute doses of the poison which produces cholera. Although the idea of inoculation against cholera is not a new one, the first process established on a scientific basis was that of Haffkine. Recognising that the symptoms of cholera are due to the absorption of toxins generated by the specific bacillus in the intestinal tract, Haffkine's inoculation aims at acclimatising the system by the injection of an exalted virus much stronger than any which it is likely to encounter in the ordinary way of infection, so as to enable it to bear such quantities of cholera poison as may be absorbed from the intestine while an attack of the disease is running its course. The vaccine actually injected may contain the living bacilli, or be "phenolised" so as to kill them. Phenolised vaccines are less dangerous and less hable to contamination, and may be kept indefinitely in sealed tubes, but are not so powerful. The injection of cholera vaccine causes a rise of temperature accompanied by malaise and other slight general symptoms, which soon pass off: locally, however, severe inflammation follows, unless a prehminary injection has been made three to five days previously with a weak vaccine prepared from cultures attenuated by being grown in media kept continuaUy aerated, and at 35° C. The only local symptoms are then shght pain and oedema. After the symptoms have passed off, the animal is found to be scarcely affected by many times larger intra-peritoneal injections than suffice to kiU control animals not so protected. The symptoms foUowing injection into human beings, of whom some thousands have now been inoculated by Haffkine in India, are identical Avith those exhibited by animals; subsequent hypodermic injections with an exalted virus also producing the same results in both, so that, although, of course, human beings cannot be directly tested like animals, there seems DENGUE. 607 reason to believe that they are similarly protected. The method is now being subjected to extensive practical tests in many parts of India, but as yet the facts do not permit of definite opinions being given as to either its efficacy or otherwise. More recently, however, some doubt has been cast on the reality of the protection given by the process against the ordinary infection of cholera by Klein and Sobernheim, Avho find that precisely similar results can be obtained with Vibrio proteus, B. prodigiosus, B. coli communis, the enteric fever baciUus, B. subtilis, and Finkler's comma bacillus. Yaccination with an exalted virus prepared from any of these conferred immunity against the cholera bacillus or any of the others, when injected intra-peritoneally. They also found that guinea-pigs, protected by Haffkine's method, were kiUed by mtra-peritoneal injection of a gelatin culture of the cholera bacillus liquefied by its growth. These investigations on infection and immunisation, without justifying the absolute denial of the significance of experiments on animals in relation to the bacteria of cholera, certainly suggest that the idea must m any case be set aside that the symptoms observed after intra-peritoneal injection of comma bacdli in guinea-pigs are referable to an entirely specific process. DENGUE. As a specific febrile disease peculiar to warm climates, characterised by severe articular and muscular pains, and often by a cutaneous eruption, our earliest knowledge of dengue does not go farther back than 1780, when it prevaUed extensively in Egypt, Batavia, Spain, and Portuguese India. Its first recognition as a distinct disease was made during outbreaks in India in 1824, and subsequently in the West Indies and Southern States of America in 1827-8. Since then it has repeatedly been recognised and described in various tropical and sub-tropical countries, more particularly as endemic in Egypt, East Central Africa, Arabia, some parts of India, the Hawaiian Islands, Bermuda, and Honduras. In the intensity of its epidemic manifes- tations dengue closely resembles influenza: it spreads mainly by personal con- tact, adhering closely to lines of traffic, but sporadic cases are often observed to break out almost simultaneously in several parts over a Avide area. As the incubation period is very short, extending often only over a few hours, its " simultaneous " appearance needs to be interpreted with discrimination ' Influence of Season, Soil, and Locality.—The relation of the disease to heat is clearly defined. Even in tropical countries epidemics of dengue usually attain their maximum during the hot season, but do not always decline or die out in the coldest months. Rain appears to have only an indirect influence by its relation to temperature. _ The physical and geological characters of the soil appear to have no significance in respect to the sporadic or epidemic manifestations of the affection. As a rule, epidemics are limited to towns, especially to the low-lying, filthy, and overcrowded quarters, and the attack may be limited to such, or may involve the whole population. All ages and both sexes seem to be equally attacked: but its fatality is more marked in both the very young or very old. In some epidemics, a distinct tendency to abort has been noticeable among pregnant women attacked with dengue. Infectivity and Etiology.—There seems to be little room for doubt that dengue is highly infectious, although some authorities question this. From analogy the infection may be assumed to be microbial, parasitic, and to be given off usually by the breath, and possibly by the secretions and cutaneous 608 THE INFECTIVE DISEASES. emanations. Several observers have found what they believe to be parasitic bodies in the blood of patients suffering from the disease, but the specific agent has not been satisfactorily demonstrated. One attack usually confers a protection against a second infection, but in connection with this aspect of the disease, it is believed that if the eruption proper to the second stage of the affection fails to be clearly manifest, the patient is liable to relapses or recurrences. In some epidemics, epizootic disorders among horses and cattle are said to have synchronised with dengue in men. The precise value of this observation has not been made clear, nor has it been determined whether, in these instances, the animals suffered from dengue or not. The mortality from this affection is small, fatal cases occurring usually only in debilitated persons, or in the very young or old. DIARRHCEA. Although, in the ordinary sense of the term, diarrhoea is simply a physiological process and merely symptomatic of either the normal reaction of a healthy boAvel against irritating contents, or of some morbid internal condition, still considerable eAddence exists to show that the diarrhoea which contributes so large a share to the mortality of young children, especially at certain seasons of the year, is of a distinct kind and merely the most prominent manifestation of an epidemic disease belonging to the zymotic group. As affecting large numbers of persons at the same time and place, and displaying a decided affinity for certain populous places during certain seasons, the diarrhoea now to be discussed may be designated as Epidemic diarrhma: and, in the matter of its epidemiological features, its symptoms and pathology, constitutes a general disease, of which the diarrhoea is but one of its several symptoms. This view has for some years been recognised by the Registrar-General, who includes diarrhoea among his " Principal Zymotic Diseases "; Avhile the official nomenclature of the Royal College of Physicians also classifies epidemic diarrhoea with the " Specific Febrile Diseases." According to Ballard, " the leading phenomena of the disease are diarrhoea, vomiting, convulsive phenomena: a bodily temperature at certain periods above, at other periods below, what is normal; reduction in quantity or actual suppression of urine, embarrassed breathing, and, when looked for, commonly physical indications of pulmonary hypereemia or inflammation, pallor of surface of the body, loss of bulk and flesh, and exhaustion, Avith its various well-known clinical features. I must add, that occasionally there is jaundice. Now and then a (fugitive) rash has been observed on the body." After giving detaded remarks upon the various symptoms, he goes on to say that " I may here state my strong suspicion, almost my belief, that the malady usually characterised by diarrhoea may run its course from first to last, and even to death, without any remarkable diarrhoea at all. In other cases, although diarrhoea occurs, it is by no means the prominent symptom of the disorder : it may be comparatively of trifling amount or of short duration." Influence of Age, Sex, and Season.—This is by far the most fatal of the zymotics in infancy, causing a mortality of about 25 per 1000 births. From infancy the mortality diminishes until about the twentieth year, after which it again increases until the end of life. No age is exempt from attack, but the hability to attack seems to be slightly greater in the second year than DIARRHOEA. 609 the first, or at all events is far greater in the first tAvo years than in the third or later years. It is comparatively small in the first three months, and probably increases up to the end of the first or beginning of the second year. From a large experience in Leicester, Tomkins states that " infants and young children form only a small proportion of those attacked, although they furnish nearly the whole of the deaths." As regards sex, the liability to attack is greater among males at all ages. The mortality is greater for males in infancy and old age, but usually somewhat greater for females from the second or third to about the forty- fifth year. Fatal diarrhoea occurs at all seasons, but ahvays increases greatly in summer. Whitelegge has shown that, in London, the mortality curve, based upon the records of many years, indicates a slight rise throughout June, rapidly increasing in July, and reaching its maximum in the first week of August, after Avhich it again falls rapidly throughout September and October. During the rest of the year there is very little variation. The same facts apply closely for other large towns, where diarrhoea may be regarded as largely endemic. In both Leicester and Preston, which for some years past have enjoyed an unen-viable notoriety in this respect, epidemic diarrhoea causes a heavy annual mortahty. Infectivity and Etiology.—The incubation period is apparently very short, varying from a feAv hours to a couple of days. In many instances diarrhoea has appeared to be somewhat infectious by means of the excreta, but this is not an invariable rule; neither has the micro-organism upon Avhich it depends been identified with certainty. Tomkins has shown that the air is peculiarly rich in microbial hfe during diarrhoea epidemics : and among these prevalent micro-organisms are certain small bacilli, cultivations of which cause diarrhoea when swallowed. The same bacilli were isolated from samples of polluted soil by Tomkins, but he failed to establish its specific character as the real cause of the epidemic manifestation of this affection. The chief facts concerning the prevalence of this form of disease may be summarised in the terms of the results of Ballard's inquiry into its causation, as explained in his Report to the Local Government Board in 1887. Elevation of site influences diarrhoeal mortahty only in so far as it affects infant mortality from all causes. Soi^—Loose porous sod is most conducive to mortality from diarrhoea; particularly if coupled with organic fouling of the earth, no matter whether vegetable or excremental. Diarrhoea is prevalent upon sites such as "made soils " or on ground polluted by drain or cesspool leakage. Both excessive wetness and excessive dryness of soil seem to lessen diarrhoeal mortality, but a moderate dampness of soil favours it. Temperature.—The mortahty from diarrhoea is usually high when the air temperature is high, but this is only indirectly so, because the highest mortality coincides less with the highest readings of the air-thermometer than it does with the thermometers in the soil. The summer rise in the diarrhoea death-rate does not commence until the mean temperature of the 4-foot sod-thermometer has reached 56° F.; no matter what heat may have been recorded by the air and 1-foot soil-thermometers. The maximum mortahty and decline in the diarrhoea rate coincide with the mean weekly maximum and decline of the temperature recorded by the 4-foot earth- thermometer. 2Q 610 THE INFECTIVE DISEASES. Rainfall exerts little influence, except by its effects upon soil-temperature. The diarrhoea death-rate is greater in dry seasons and less in Avet ones. Wind lessens the mortality, but calm, stagnant days promote it. Social Position.—The diarrhoea prevalence and death-rate are notoriously greatest amongst the very poor. Want of cleanliness has a similar influence, and is, too, usually associated with poverty. Foul air from seivers and cesspools, and accumulations of filth, favour diarrhoea mortahty, while smoke and chemical effluvia are inoperative. Undefined foulness of drinking xcater is not responsible for ordinary epidemics of summer diarrhoea, though it may occasionally produce a few cases. Want of ventilation and light are particularly conducive to diarrhoeal mortality; especially associated as it is with overcrowding, back-to-back houses, dark courts, alleys, and streets. Density of buildings upon an area, irrespective of density of population, materially increases the tendency to diarrhoea. Food is closely concerned with the epidemic prevalence of diarrhoea, not by causing ordinary indigestion, but owing to its being contaminated with some substance, " which substance is by itself an efficient cause of the malady." The mortality is very high among the artificially or bottle-fed children ; the breast-fed infants being remarkably exempt. Maternal neglect conduces to much infant mortality; this is specially seen in the greater mortality among illegitimate children as compared with the legitimate. The occupation of females from home, by conducing to neglect and artificial feeding of infants, promotes diarrhoeal mortality. Upon these and other observations Ballard makes the inference "that the essential cause of epidemic diarrhoea resides ordinarily in the superficial layers of the earth, where it is intimately associated with the life processes of some micro-organism not yet isolated." "That the vital manifestations of such organism are dependent, among other things, perhaps principally upon conditions of season, and on the presence of dead organic matter, which is its pabulum." "That occasionally such organism is capable of getting abroad from its primary habitat, the earth, and having become air-borne, obtains opportunity for fastening on non-living organic material (especially food, whether inside or outside the body), which serves as a nidus and pabulum." " That from food and from organic matter in certain soils it can manu- facture a virulent chemical poison which is the material cause of epidemic diarrhoea." A distinction must be made between the epidemic diarrhoea indicated in the foregoing and certain epidemic outbreaks of diarrhoea which occa- sionally occur in public institutions. These latter can usually, upon investi- gation, _ be traced to articles of food or drink, especially water, when containing excess of mineral salts, sewage, or vegetable matter. Similarly, milk and butter, or cheese, may give rise to diarrhoea, owing either to fermentative changes in themselves or to fouling by some specific gas; especially when stored in cellars or ill-ventilated places. Tinned meats, pork pies, ham and game, or even fish, have on several occasions been traced as the ultimate cause of extensive diarrhoeal outbreaks. In these cases the poison partakes of the nature of a chemical body, the product of putrefactive changes in the food, and is altogether unassociated Avith the seasonal and teUuric conditions hitherto considered. Prevention resolves itself into the avoidance of organic pollution of the DIPHTHERIA. 611 soil, the absolute avoidance of " made soils " as sites for dAvellings, the exclusion of soil-air from the house, the careful storage of all food in suitably arranged and well-ventdated larders, and the disinfection of all excretal evacuations. DIPHTHERIA. Under the name of angina maligna, epidemics of this disease have been knoAvn since very early times : but as applied to epidemics of malignant sore throat destroying life by suffocation, attacking children rather than adults, and sometimes leaving paralytic sequelae, the name diphtheria dates only from about 1826. The history of this affection indicates a tendency to cyclical epidemicity, though the cycles "have extended over periods of various length, many of them only a feAv years, and others lasting several decades." This is particularly Avell shoAvn in the experience of England, Avhere locahsed outbreaks occurred from 1815 to 1825, after which the country was almost free from the disease until 1857, when, as part of a general prevalence over the whole of Europe, it appeared again. Since then the disease has practically never been absent from this country, and at the present time shows distinct indications of a tendency to increase in prevalence. Influence of Climate and Season.—Although no climate can be said to give immunity, the tropics suffer less than cold and temperate climates. The curves of both seasonal prevalence and mortality shoAV a marked relation to cold, both being greater during the autumn and winter than during the warmer months; the maximum mortality being reached in November and December, and the minimum in the summer. The same general relation of diphtheria prevalence to the seasons of the year appears to hold good as regards other countries. In Great Britain, atmospheric humidity is considered most favourable to the general prevalence of diphtheria, but American experience indicates that it can prevail with severity in very dry weather. How far the influence of season upon diphtheria prevalence is direct, by stimulating the activity of the microbial cause of the disease, and how far it is indirect, by increasing individual susceptibdity, is uncertain; but probably it acts in both ways. As Longstaff has insisted, there is little doubt but that anything which tends to damage the mucous hning of the throat, such as'ordinary catarrhs, predisposes to attack by diphtheria, and increases the general susceptibility of the body to infection, given the presence of the efficient cause of the disease. Influence of Age, Sex, and Race.—Of the whole number of deaths ascribed to diphtheria, 55 per cent, occur at ages under five years, and about 80 per cent, under ten years. As regards liability to attack, both Power and Thorne-Thorne have shown that the attack incidence of the disease, even apart from the influence of school attendance, is greatest upon children between the ages of three and twelve years. The mortality is greater among females than among males at all ages between three and forty-five years; after that period the male mortality seems to be slightly in excess of the female, just as it is during the first two years of hfe. The excess of female mortality at certain ages increases precisely as the age advances which fits the female more and more to take some share in the care of home3 and of relations during periods of sickness (Thorne-Thorne). As regards race, the balance of our present evidence seems to be in favour of the view that there is no racial immunity to this disease. Influence of Locality.—Until the last few years, diphtheria, according to 612 THE INFECTIVE DISEASES. all authorities, Avas especially a disease of sparsely populated localities; but noAV, one of its most striking characteristics is its tendency to prevail in towns, and in the more densely peopled areas. During the period 1861-70, while the diphtheria mortality rate per million living Avas, for England and Wales, 187, it was for London only 179. In 1871-80 the rates were 121 and 122 respectively, and in 1881-90 they were 163 for England and Wales and 259 for London. Thus, although there has been a decided increase in diphtheria mortality in the country generally, this increase has been relatively greater in the metropolis. But this urban invasion has been by no means limited to the metropolis, as Longstaff has clearly shoAvn that in each successive decennium the diphtheria mortahty of the towns generally has become relatively greater to that of the rural districts. This is well indicated in the following table of death-rates from diphtheria per million of population, according to density, as Avorked out by Longstaff:— Districts according to density of Population. 1855-60. 1861-70. 1871-80. Dense districts, or those with less than 1 acre per Medium districts, or those Avith from 1 to 2 acres Sparse districts, or those Avith over 2 acres per person, 123 182 248 163 164 223 114 125 132 It has elsewhere been pointed out that soil dampness appears to be closely associated Avith the prevalence of diphtheria; but admitting the material influence which this condition must have in impairing the general health of communities, and in establishing conditions of negative resistance in individuals against diphtheria, still, in the absence of any definite know- ledge that the special virus of diphtheria is a normal inhabitant of the soil, it is difficult to regard the influence of soil states as etiological factors in this disease other than as an indirect one. This view is submitted, however, without prejudice to the behef (in justification of which we have experi- mental facts) that the diphtheria micro-organisms may exist, for an indefinite period, dormant in soil, where, protected from light and excess of oxygen and supplied with a necessary amount of heat, they can regain their full energy as soon as the environment becomes more favourable. Mortahty.—That the annual death-rates from diphtheria have been rising slightly in England and Wales, more markedly in the large towns, and most markedly in London, is perhaps better indicated in the folloAving table, which shows the annual mortality from diphtheria, per million living, for the last twenty years. The rate for England and Wales in 1893 was 82 per cent, in excess of the average rate in the ten-year period 1883-92, which had been 175 per mdhon, and higher than in any pre-vious year on record with the exception of 1858 and 1859, in which years the rates had been 339 and 517 respectively. All the county rates from diphtheria, except the rates for Huntingdon, Dorset, Notts, Northumberland, and North Wales, exceeded in 1893 their decen- nial averages. In thirty-four counties the rates were loAver than the general rate in England and Wales, the excessive diphtheria mortality being limited to comparatively few counties, especially to London (758), Essex (557) Surrey (542), Sussex (473), Kent (433), Wilts (429), Suffolk (425), Oxford (422), Middlesex (413), and Bucks (367), all per million. These counties, DIPHTHERIA. 613 omitting Wilts, form a continuous area closely corresponding with Avhat is known as the South-Eastern diphtheritic region. The mortality from diphtheria in the ten counties above enumerated Avas 612 per million living, AAdiile in the remaining thirty-five counties of England and Wales the mean rate did not exceed 197 per million. The case mortality varies greatly in different epidemics, and there is little constancy even in the same epidemic. Hitherto, in Avell-marked cases it has been frequently 35 per cent, or more, but probably by " anti-toxin" treatment this rate may be considerably reduced. year. England and AVales. London. Thirty-three other Large Towns. 1874 150 120 1875 142 170 1876 130 110 1877 110 88 1878 140 150 1879 120 155 1880 110 144 18S1 120 170 18S2 152 220 160 1883 160 244 160 1884 186 240 170 1885 160 ■?.21 170 1886 150 210 160 1887 160 230 180 1888 170 300 210 1889 189 390 260 1890 180 331 240 1891 173 340 290 1892 222 440 270 1893 318 758 430 1894 610 380 InfectiA/ity and Etiology.—It is now Avell established that diphtheria is a highly contagious disease, transmissible from person to person, and having a contagium belonging to the group called fixed contagia. The incubation period is short, and has been between three and five days in most cases in Avhich exact determination was possible, but the range has been stated to be from a feAv hours to as much as eight or fourteen days. The early symptoms are often insidious, but in most cases the membrane is visible within a few days of the onset, if not at first. In non-fatal cases the disease usually runs its course in tAvo or three Aveeks. As regards the actual diffusion of the disease, direct infection from the case plays the chief part. In this process the virus is, probably, given off by the breath from the throat of the patient, but actual contact, as in kissing, and the attachment of the virus to drinking vessels and spoons is in many cases responsible for infection. Klebs Avas the first to draw attention to the presence of bacilli in diphtheria, an observation confirmed and elaborated by Lb'ffler. The bacilli are immotile, straight or slightly curved rods of about 6 y- by 1 p.. They grow well upon blood-serum, or upon glycerin-agar, and broth containing sugar. Generally speaking, they require a temperature for development of between 19° to 37° C. They retain their vitality even when completely dried, and Lb'ffler found them still capable of developing after 101 days. If diphtheritic membranes are protected from the action of light and kept 614 THE INFECTIVE DISEASES. dry, cultures retaining their virulence can be prepared from them even after three months. Upon gelatin, the bacilli form small, round, Avhite colonies, Avith a coarsely granular texture and irregular edges: they do not liquefy the medium. In stab cultures, little white dots may be observed. The growth upon ordinary agar is scanty, although luxuriant upon glycerin-agar. A greyish-white deposit is visible in forty-eight hours upon potatoes Avhich have been rendered feebly alkaline. On white of egg a rapid glistening yellowish-grey growth is obtainable at 37° C. in eighteen or tAventy hours. Often in diphtheritic membranes there occur tAvo species of bacdli, identical in morphological respects and in the mode of growth on various nutrient media; but one species is not constant, and is probably the pseudo-diphtheria bacillus of some Avriters, Avhile the other is constant in large numbers in all diphtheritic membranes : this second species is the one which is pathogenic, and is the diphtheria bacillus of Loffler, while the first is not pathogenic. They can be usually differentiated by the fact that the true diphtheria bacillus grows well in and on gelatin at 19° to 21° C.; the other does not grow on this medium beloAV 22° C. Numerous cocci are often found in the false membrane of diphtheria, and these were formerly looked upon as the cause of the disease: some, however, are streptococci, the rest are saprophytes (Plate YIIL). Yarious animals exhibit a high degree of sensibility to infection by inoculation subcutaneously Avith pure cultures of the diphtheria bacillus. These bacilli can be detected at the point of injection, but all the remaining organs and the blood are free. This fact, taken in conjunction with the observation of Roux and Yersin, that, after removal of the microbes by filtration, injection of a pure culture is still pathogenic, has suggested the belief that in diphtheria Ave have to deal with a chemical poisoning, the chemical poison being produced by the living bacilli in the diphtheritic membrane of the human disease, and in the case of experimental animals at the seat of inoculation, and, absorbed by the system, produces the whole general disease symptoms associated with, and characteristic of diphtheria. Martin has shown these same poisonous principles to be of the nature of a ferment, organic acid, and albumoses, and that, with some of these, diphtheritic paralysis can be produced. It is usually said that diphtheria confers no immunity against subsequent attack; this may be so, in respect of man, but undoubtedly some animals, such as the horse, are, if not actually immune against the toxic effects of the products of the diphtheria bacillus, certainly highly refractive. The practical recognition of this fact is, of course, the essence of the well-knoAvn procedure of treating the disease by injections of " anti-toxin " obtained from the serum of an immunised animal. The period of infectiveness has been variously stated by different observers as being from fourteen days to eight Aveeks: this, hoAvever, is probably an under-estimate, as Schafer has reported the persistence of Loffler's bacillus in the tonsillar mucus seven and a half months after recovery from an attack of diphtheria. Moreover, in this connection, Gresswell has observed that in certain individuals diphtheria may, so to speak, "become chronic, and subject from time to time, especially upon exposure to cold and damp, to recrudescence." It is needless to remark, perhaps, these considerations are of the utmost importance, and, if confirmed, will necessitate material modi- fications as to our estimate of the period of infectivity in cases of this disease. OAving to the statements of various authors, it Avas long a current belief Plate VIII. Plate culture oflJiphthjeruz.picxc^Lbu.s. Carer-glass specimen, fvorrc swfooce- of ( x 10). cuT)\fih£hervtxjo rrLerrvbrarve. (x 100) . SeciJjO'rv tkrovujh-an- {xr£&vorrv>fce6 ruidxiMe- vn. tortgvu*. of cur'-ox., (after Klexrv xSOO). Diphtheria and Actinomyces. We 61, Newman clew, li Ll DIPHTHERIA. 615 that a chronic infective process, observed in the mucous membrane of the mouth and pharynx of fowls and pigeons, was intimately connected with human diphtheria. This is now known not to be the case, as these necrotic processes are quite different diseases, both as to pathology and micro- organism. Cats, however, unquestionably suffer from a disease which bears a close affinity to human diphtheria. Klein has shoAvn that the cat is the only animal in which, either with diphtheritic membrane or with cultures of the bacillus, it is possible to produce a definite and striking result on the cornea and conjunctiva or on the fauces and palate. Further, cats suffer naturally from, and, by inoculation with human diphtheritic membrane, can be made to suffer from a form of broncho-pneumonia which, as evidenced by subsequent paresis and inflammation of the kidney, is evidently a disease equivalent to human diphtheria. Therefore, the cat must be considered as susceptible to human diphtheria, and capable of communicating the disease to other cats and also to human beings. Klein has further shoAvn that pure cultivations of the bacillus of diph- theria produce by inoculation a severe constitutional disease in cows. A sAvelling appears at the point of inoculation, increases for a week, and then subsides. Broncho-pneumonia sets in, crops of vesicles appear upon the teats and udders, and the kidneys undergo fatty degeneration. The fluid from the vesicles, and also the milk taken from healthy teats, with every precaution contain the same bacilli. Cats fed upon this milk develop in a few days a severe and often fatal illness apparently identical with that just described as occurring naturally in these animals and equivalent to human diphtheria. In the cat, as in the cow, the lung seems to be the chief seat. of the disease. As Klein says, it need hardly be added that these results lead in great measure to a right understanding of certain epidemics of milk diphtheria, and clearly show that, apart from human infection of the liquid, mdk may be a medium of infection from the cow, as in the cases at Camberley and YorktoAvn, Enfield, Barking and Croydon. Water has been suspected of conveying infection, but no complete demonstration has been made that diphtheria is ever transmitted by this agency. In a similar Avay, air has been credited with being the medium for disseminating this affection, but on very imperfect evidence. It is prob- able that cases of true wind-convection for any distance are of the utmost rarity. Thorne-Thorne has called attention to the special incidence of diphtheria attending schools, and concludes "that, apart from age and susceptibility, ' school influence' so-called tends to foster, diffuse, and enhance the potency of diphtheria, and this, in part at least, by the aggregation of children suffer- ing from that ' sore throat' which commonly is prevalent antecedent to, and concurrently Avith, true diphtheria." The period of life at which there is most susceptibility to acquire diphtheria is from three to twelve years of age, and school attendance increases the risks of personal infection by the aggregation and prolonged association of children together. So often have outbreaks of true and typical diphtheria, following minor throat illness, occurred in particularly isolated places, and under conditions which exclude the likelihood of their having resulted from any importation of the infection from elseAvhere, that an idea has grown that possibly ordinary sore throats may be able to acquire a progressive degree of the property of infectiveness. At present there is no precise knoAvledge as to the fact of this actually taking place; but it is suggestive of the need to correct any faulty sanitary conditions of schools and other buildings which may in any Avay tend to ill-health. 616 THE INFECTIVE DISEASES. For many years it Avas thought that accumulations of filth and drainage defects Avere the direct cause of the origin and spread of diphtheria. In the light of more recently acquired knoAAdedge, there is reason to think that this older behef must be modified, and that the true part which insanitary states play is by Avay of predisposing to infection by loAvering the standard of health rather than by being the actual origin of the disease. Prevention.—Of the first importance are isolation and disinfection. All insanitary conditions in and around the dwelling should be sought for and remedied. No children from infected households should be alloAved to attend school; and if diphtheria is at all prevalent in the district the schools should be closed. Failing this, the children attending should be medically examined daily, and all cases of sore throat segregated and forbidden to attend school until quite recovered. Milk-supplies should be inquired into, and any doubtful ones stopped at once. Milk should in all cases be boiled, especially that given to children. Isolation should be prolonged for about three Aveeks after disappearance of local symptoms; and bacterial cultivations from the throat secretions systematically made during convalescence, and so long as the bacilli are found isolation to be maintained. All expectoration and throat discharges should be either received into vessels containing a disinfectant, or preferably wiped off Avith rags which should be burnt. Disinfection of clothing, bedding, furniture, and rooms must be carried out in detail. There are some indications that injections of serum anti-toxin may be both preArentive as Avell as curative. Relation to other Diseases.—Diphtheria outbreaks are noticeable for being associated frequently AATith cases of so-called " croup," and with a series of antecedent cases of scarlet fever. Some doubt has long existed as to the precise meaning of these associated cases: the true explanation prob- ably is, that what is called croup is oftener than not unrecognised diphtheria, or, at least, a form of laryngitis. In the other association, it is probable that scarlet fever leads to more or less temporary damage to the mucous membrane of the throat, and in this manner predisposes to the reception of the diphtheria poison, causing a series of diphtheria cases to folloAv after a series of scarlet fever cases. Both diseases appear to be more prevalent during the autumn and Avinter than during the spring and summer. DYSENTERY. Formerly this disease was very prevalent in this country, but, in the present day, is practically confined to hot climates. Clinically, it may be described as an affection marked by frequent, bloody, mucous, serous or ichorous stools, accompanied with tormina and tenesmus, and often with some febrile disturbance. Pathologically, it may be regarded as a specific inflammation of the inner coats of the large intestine, having a tendency to terminate in ulceration, suppuration, or even gangrene of the affected tissues. The disease may be either acute or chronic, sporadic, endemic, or epidemic in its manifestations. Influence of Climate, Season, and Locality.—Dysentery being an ubiquitous disease, Ave find it prevailing at one time or another in all climates, but a close examination of its present-day distribution indicates its increased frequency, as an endemic disease, as we approach the equator. Accurate statistical facts in this connection are, however, difficult to obtain, as we have no data for satisfactorily determining the mortahty Avhich it DYSENTERY. 617 causes as distinguished from other " bowel complaints " among the native populations. Dysentery in all its forms is undoubtedly a seasonal disease. In Europe, as an endemic malady, dysentery has ahvays attained its maximum in summer and early autumn. In the United States, summer is also the season when it is most prevalent. Within the tropics, dysentery is usually most fatal in the third and fourth quarters, Avhen the temperature has begun to fall and the season to become dry. In India, as a Avhole, dysentery is a disease of the colder seasons : and among both Europeans and natives is most fatal in late autumn or early Avinter. While a high temperature is essential to the development of dysentery, as evidenced by its being a disease of Avarm seasons in Europe, its prevalence, in tropical countries, is only markedly manifest after the temperature has begun to fall, or even Avhen it has reached its minimum. Few facts in connection with the possible relation between dysentery and climate or season are more clear than those which indicate the influence of vicissitudes of temperature and exposure to cold in determin- ing attacks. The whole medical history of both our own and other armies, either in the pre-sanitary or present age, bristles with instances illustrative of the importance of these agencies in the predisposition to this affection. WliUe perhaps it cannot be maintained that the physical condition of the soil is altogether immaterial in respect to endemic dysentery, it is still certain that it is met with in both very dry and very marshy places. The disease is by no means rare on the bare rocks and burning sands of Aden, Avhile at the same time it is common in many of the jungly districts of Burmah and India. Speaking generaUy, the disease has a preference for damp and Avater- logged soils: and has often been associated with the drying up of marshes and ponds. There is, hoAvever, no evidence to sIioav that the geological con- stitution of the soil has any appreciable influence on the disease. On the other hand, soil contaminated with excremental matters is undoubtedly one of the most important causes of dysentery. Clouston described an outbreak of the affection in the Cumberland Asylum, traceable to the emanations of seAvage applied to land adjacent to the buildings. Millbank prison was another case in point, the repeated outbreaks of dysentery being due, as pointed out by Baly, to emanations from a moist subsoil loaded with the products of organic decomposition. More recently, Norman has given details of a similar out- break at the Richmond Asylum, near Dublin, Avhere, owing to the antiquity of the buildings, the primitive nature of the original arrangements for disposal of excreta, and the unscientific and frequent alterations which these had undergone, the soil under and around the Asylum had everywhere become saturated with sewage. The terrible outbreaks of dysentery in the armies of earlier times were doubtless largely attributable to the pollution of the localities on which large bodies of men and animals remained encamped for often many months, resulting in fouling of both soil and Avater. Influence of Diet.—Faulty dietary, especially coarseness of food, the prolonged and exclusive use of salt meat, indulgence in either alcohol or unripe or overripe fruits, are all indirect causes of dysentery by predisposing the system to infection. Of still greater importance is deficient nourishment, especially when manifested in the appearance of scurvy. The scorbutic con- dition modifies in a marked way the symptoms and course of dysentery, being, in fact, one of the most terrible phases of the malady. The instances in which outbreaks of dysentery have been traced to the use of foul water, particularly Avater polluted Avith faecal impurities, are very numerous. In fact, in the greater number of cases, the various contributing factors to the prevalence of dysentery are quite secondary to the influence 618 THE INFECTIVE DISEASES. of impure Avater. Of course, in some instances the Avater merely serves as a vehicle by means of which the specific cause of dysentery is introduced into the system: in others, it may act only as a predisposing cause of the infection, by virtue of an irritative action on the bowel. Influence of Malaria and Personal conditions.—All cachectic states of the constitution poAverfully predispose to dysentery; and malaria is no exception to the rule, as this cachexia gives rise to a particular form of dysentery Avhich is not always amenable to treatment. Formerly much stress Avas laid upon a fancied connection betAveen the two affections : it is now generally recognised that they both may run their course simultaneously without the one affecting the course of the other, or both may become aggravated by association. In the same manner, the geographical distribu- tion of dysentery does not correspond Avith that of malaria. Although it is quite common to find malaria and dysentery endemic in the same region, and even in the same place, this is by no means always the case; indeed, in some instances it would almost appear as if there were an antagonism, as regards locality, between the tAvo diseases. On the other hand, nothing is more common than an outbreak of dysentery in bodies of men who have been reduced by repeated attacks of malaria, subjected to fatigue, and exposed to the sun by day and chills by night. Personal conditions, such as age, sex, race, and length of residence in the tropics, appear to be without material influence in the causation of dysentery. It is true, coloured races suffer more than the white, but this is largely dependent on their coarse food, the impure Avater they often drink, and their more frequent exposure to wet, cold, and other unfavourable conditions. It is rare to find dysentery in towns; it is specially a disease of rural districts and small villages. Infectivity and Etiology.—At this period in the history of medicine it scarcely needs to be argued that dysentery is a specific disease and probably dependent upon a specific poison. Duncan, citing Roth, gives the following striking instance how dysentery is, in some instances, transportable, and spreads from the sick to the healthy. "A patient suffering from dysentery came to the Hotel Dieu from Madagascar. At the time of his admission there Avere no cases of dysentery in hospital. The man went out uncured. After eight days from his admission, cases broke out in the Hotel Dieu. The man from the hospital went to an inn; the waiter thereof was shortly seized with the disease. After leaving the inn, the man went to a village in Aube; in this village, again, cases broke out after his arrival. Finally, he went to a family at Brienne, and of that family several members were then seized with dysentery." Trousseau, Maclean, and Fayrer all insist strongly upon the infectious nature of the disease, and upon the risk attend- ing the retention of dysenteric stools in the wards of an hospital, and Ave ourselves have seen dysentery propagated to those treated in the same ward with dysenteric patients by the effluvia of their discharges. Besides the presence of undoubted infection in primary dysentery, there is also a probable acquired infection developed from primary diarrhoea, just as there is the probable occurrence of a progressive development of the property of infectiveness in simple "sore throat" up to a condition of diphtheria. The gradually developed infection of dysentery engrafted on diarrhoea is noAvhere better seen than in the experiences of military cam- paigns. Although true dysentery is a disease per se, still on service the causes predisposing to the ordinary forms of simple diarrhoea will, if persistent, also predispose to the true spreading epidemic of dysentery. Although as yet the relation of micro-organisms to true sporadic and DYSENTERY. 619 epidemic dysentery has not been fully Avorked out, yet in the aggravation of the lesion causing the primary diarrhoea, we may suppose the soil and environment to be gradually rendered fitting for the " contagium," and thus infected powers will be acquired. The infectivity of dysentery lies in the stools; and the doctrine that the dejecta of apparently simple diarrhoea cases can assume an infective character, especially when many patients are accumulated together in camps or barracks, should never be lost sight of. The etiology of dysentery, hoAvever, is by no means a simple question, as there can be no doubt that Avhat is clinically called dysentery is not in etiological respects one single disease, since, judging by the literature and diverse statements of observers, some dysenteries are caused by one form of organism, and others by another: also some are contagious, Avhile in others the discharges only become infective after they have undergone some changes outside the body. It is highly probable that the specific cause of dysentery is often introduced into the system Avithout giving rise to the disease. The healthy boAvel does not afford a favourable soil for its growth; it is only Avhen the intestinal mucous membrane is impaired, as by excessive or extreme vicissitudes of temperature, by exposure to cold, bad or deficient food, impure water, or by cachectic conditions such as scurvy or malaria, that it becomes vulnerable to the attacks of the lower organisms. The etiological importance of these diverse factors is limited entirely to their influence in disturbing the nutrition of the large intestine. As the specific cause of dysentery, Chantemesse and Widal have described short rods Avith rounded ends, but with scanty power of movement, in the contents and walls of the intestines, as Avell as in the spleen and abdominal glands in cases of dysentery. These bacilli stain badly and do not liquefy gelatin. On plate cultures they develop first as small white specks, which assume a yellow colour; but in some days the yellow colour vanishes, causing the colonies to become white and granular. Many cases of dysentery are, however, believed to be due to the action of a protozoon, named by Lbsch the Amozba coli, and by Councilman and Lafleur Amosba dysenterice. Kartulis has found these amoebae in cases of tropical dysentery, and also in twenty cases of abscess of the liver com- plicating dysentery. All these observers give good reasons for considering these amoebae the cause of dysentery, though others, like Massiatin, who has met with simdar bodies in intestinal diseases in Russia and elseAvhere, do not think so. For some further information regarding these amoebae, refer- ence may be made to page 562. Recently Ogata has found in the stools of patients suffering from an epidemic form of dysentery in Japan a short baciUus, about a quarter the length of the tubercle bacillus, Avliich in pure cultures appears to have given rise to dysenteric symptoms when introduced under the skin or absorbed by the buccal or intestinal mucous surfaces. Which of these various observations will be confirmed remains to be seen, but in any case Ave may accept it as settled that, in epidemic and endemic dysentery, we have to do with a parasitic disease. Prevention.—This will necessarily be based upon the etiology of the disease. Inasmuch as dysentery occasionally spreads in hospitals where large numbers suffering from the complaint are under treatment, the necessity of free ventilation, cubic space, the prompt and thorough disinfection of the stools, bed-pans, commodes and enema tubes are matters of the first import- ance. In camps, prophylaxis demands that the contents of latrines be dis- infected and buried deeply, Avell away from human habitations, or better still, that they be burnt. All drinking water should be protected from contamination, and Avhen open to the slightest suspicion, should be boiled. 620 THE INFECTIVE DISEASES. Finally, exposure to extremes of heat and cold, dampness, or to deficient and imperfect diet, are important predisposing causes to dysentery to be carefully guarded against, Avhether for individuals or bodies of men. ENTERIC FEYER. This disease is clearly traceable in the earlier records of medicine, but it Avas not until 1850 that Jenner Avas able to demonstrate its differentiation from typhus fever. Enteric fever is distinctly influenced by season, by far the greater number of cases in Europe and America occurring in the late summer and autumn; the least number of cases occur in April or May. This seasonal prevalence is equally well marked in the tropics. Hirsch has aptly called enteric fever the ubiquitous disease, for it is of practically Avorld- Avide distribution: for many years it was deemed to be less common in tropical than in temperate climates, but making allowance that certain forms of malarial fever have been frequently mistaken for enteric fever, it is probable that the idea was erroneous. It is beyond dispute that remittent fever in the tropics frequently simulates enteric fever in a remarkable degree, though the autopsy shows the characteristic lesion of the latter disease to be absent. Many cases of the so-called typho-malarial fever are doubtless of the same kind. Weather has no clear relation to enteric prevalence, except in so far that meteorological conditions may act by modifying the moisture and temperature of the soil, and that rain may either increase or diminish the chances of an outbreak according to the previous condition of the ground. Influence of Race, Sex, and Age.—Although negroes and other native races are apparently less liable to suffer in their native countries than non- acclimatised persons, there is no evidence to show that race of itself exercises any influence over liability to attack by this disease. Yery much the same conclusion may be drawn in regard to sex at all ages, though, if any- thing, males are apparently rather more susceptible than females. Accord- ing to some figures published by the Registrar-General in his Fifty-first Annual Report, and based upon the returns of the London Fever and Metro- politan Asylums Board's Hospitals, it Avould appear that, betAveen five and tAventy years of age, although more males are attacked, there is a greater fatality among females between those ages. It is possible there may be some fallacy underlying this statement, as the number of cases upon which the conclusions Avere based Avas not large. The influence of age is very marked in this disease: of 5911 cases recorded by Murchison, 26*86 per cent, were between the ages of fifteen and twenty, and 66*42 per cent. Avere betAveen the ages of ten and twenty-five. After thirty years of age the cases became fewer and fewer. Judging by the death-rate from enteric fever in this country, per miUion of living population, as furnished by the Registrar-General, the mortality is at its minimum in the first year of life for both sexes. It rises from the second to the fifth year, and then falls till the fifteenth, when it gradually rises until a maximum is attained in the age-period 20-25, after AA-hich it falls permanently. It is probable that true enteric fever is rare among infants and young children, and that many of the cases returned at those ages are due to faulty diagnosis. As in the case of some other diseases, the risk of a fatal termination steadily increases with age. Influence of Place.—European experience indicates that enteric fever is often more prevalent in toAvns than in the country, and often fixes persist- ENTERIC FEVER. 621 ently upon one district. As a rule, in such districts where the disease is endemic, it Avill be found that insanitary conditions abound, notably impure water-supply, defective methods and arrangements for disposal of excreta, combined with Avant of care for preventive measures. In these areas, neAv- comers are especially liable to attack. In connection Avith the endemic or epidemic prevalence of enteric fever, considerable importance has been attached to the role which pollution of the earth by excrementitious matter and movements of the ground water play. Pettenkofer and Buhl traced a connection, at Munich, betAveen the occurrence of enteric fever sickness and mortality and variations in level of thesubsoil water which has been confirmed by further observations in Berlin, various parts of Germany, and elseAvhere. According to these observations' the prevalence of and mortahty from enteric fever fall with the rise of the ground water, and rise with its fall: the level, hoAvever, reached by the disease being not in proportion to the then level of the subsoil Avater, but only to the range of fluctuation of it on each occasion. While doubtless true for Munich and the locahties in question, this relation does not appear to hold good universally. In many places Avhere enteric fever occurs the subsoU water is so deep, or its movements so trifling, that there is little probabihty of its producing any material effect. In the places Avhere the relation has been observed, the soil is porous, the ground Avater high, and leaking cesspools not only numerous, but in general proximity to wells and other sources of Avater-supply. Given these conditions, there is no difficulty in appreciating how the purity of water in weUs may be affected by changes in the level of the ground water, and, further, bearing in mind the readi- ness with which enteric fever is spread by means of specifically polluted Avater, the true value of the above mentioned observations as to a causal relation between the prevalence of the disease and the range of fluctuation of the subsoil Avater are manifest. Mortahty.—The foUowing table, from the Registrar-General's returns, Avill give some idea of the remarkable diminution in the number of deaths from enteric fever in England and Wales during the last twenty years. Year. Total Deaths. Death-rate per million living. Year. Total Deaths. Death-rate per million living. 1874 8861 374 1884 6380 236 1875 8913 371 1885 4765 178 1876 7550 309 1886 5061 184 1877 6879 279 1887 5155 185 1878 7652 306 1888 4848 172 1879 5860 231 1889 5011 176 1880 6710 261 1890 5146 179 1881 5529 212 1891 4875 168 1882 6036 229 1892 4037 137 1883 6078 228 1893 6801 229 Though the mortality in 1892, when the rate did not exceed 137 per million persons living, was the lowest on record, the returns for 1893 show a large increase, being higher than in any previous year since 1884. The increase in mortahty from this disease, during 1893, appears to have been general throughout almost the whole of England and Wales : Berkshire, Bucks, Wilts, Devon, and Worcestershire being the only counties in which the rate in 1893 did not exceed that in 1892. The counties which showed, in 1893, the largest excess, as compared with their respective averages in the preced- 622 THE INFECTIVE DISEASES. ing ten years, Avere Rutland, Sussex, Durham, East Riding of Yorkshire, Dorset, Lincoln, Hereford, Bedford, Cornwall, Wanvick, and Cheshire: the great increase in Sussex, which amounted to 282 per cent, of the mean rate, being mainly due to the epidemic at Worthing. The case mortality from this disease varies from 12 to 16 per cent. Incubation and Protection.—The latent period of enteric fever is liable to considerable variation. The most usual duration is about twelve to fourteen days, but it may range from a few days to thirty: it seems to be shorter when the poison is introduced by water, or by milk. The pecuharly insidious mode of onset renders any exact determination difficult. The actual illness commonly lasts three or four weeks, but is often protracted by relapses. How far the disease confers protection against a second attack is stiU doubtful, but the weight of opinion is undoubtedly in favour of the vieAV that it does confer immunity, possibly for life. Infectivity and Etiology.—Though some doubt exists as to whether the breath of those suffering from enteric fever is infective, there is none as to the infective nature of the excreta. Experience shows that enteric patients can be treated in large general wards side by side with other cases without danger to the latter. With scrupulous cleanliness, especially as regards the nurse's hands, and clothing or bedding soiled by the patient's discharges, there seems little tendency for the infection to spread. The stools and urine are probably infective throughout the whole period of the disease, and apparently gain in infectivity for some feAv days after discharge from the sick person. This fact renders the disposal of the excreta a matter of great importance. They need to be disinfected Avith mercuric chloride or other reliable disinfectant, and disposed of at once either by burning or burial deeply and Avell away from houses or sources of water-supply : in towns, necessity often compels them to be dealt with like other excreta, in which case, effective disinfection is of even greater importance. The remarkable ability of enteric fever to disseminate itself by means of water, milk, and other media, indicates the virus to be a living organism. Eberth first showed that in many cases of enteric fever there occur in the swollen mesenteric glands peculiar bacilh, rounded at their ends, motile, and occasionally including within a pale sheath one or more spore-like granules. Gaffky and numerous observers have confirmed these statements, and these bacilli are now, by many, if not most pathologists, considered as the microbial cause of enteric fever. These bacilli are three times as long as broad, their average length being from 2 to 4 y, and sometimes uniting to form what are apparently threads of considerable length. Spore formation in them is doubtful. They thrive whether oxygen is excluded or has free access, although in the latter case the growth is more vigorous : they readily stain with the aniline dyes, but yield up their colour on application of bleaching fluids, so that their demonstration in tissues is difficult. On the surface of gelatin plates, the colonies have a translucent filmy appearance with irregular outline, thin at the margin, thick and less translucent at the centre. Those growing in the depth appear as dots, whitish in reflected, brownish in transmitted light. There is no liquefaction of the gelatin. Stab cultures show on the surface a thin growth, which also takes place along the needle track. A grey slimy layer, covering the whole surface, develops on agar and blood-serum. On potatoes their growth is not absolutely characteristic. Broth is made uniformly turbid after forty-eight hours, a greyish, powdery or flocculent precipitate, but no distinct peUicle, being formed (Plate IX.). Rodet, Roux, and others have put forward the view that this baciUus, Plate DC. ;V«- J, o u 0 o' :'9- -,"■'• '*&* Plcdx, zulbare. of Enteric BouuZhz-s (xWO) . Sevtwrvofcvn.Ertfervc -ulcer (x450]. Section, of Spleen, frorn-a, case- of Enteric Fever- (x 7500/. StaJb culture, of Enteric. BcxxzIZvls vrtsgeLoutcn^. We st.lTe, wm a n clur. Titb.. Enteric Fever. ENTERIC FEVER. 623 knoAvn as the Eberth-Gaffky bacillus of enteric fever, iioav admitted to be almost constantly present in the alimentary canal, in the mesenteric glands, and in the spleen of cases of this disease, is no other than the Bacillus coli communis, Avhich is a constant and normal inhabitant of the bowels of man and animals under perfectly healthy conditions: and, further, they have contended that the B. coli passed with the normal dejecta is capable of acquiring in seAvage specific and virulent properties, so that when re- introduced by water, milk, or other articles of food into a normal individual, it has become endowed Avith the poAver of setting up in him the specific and communicable disease—enteric fever. In this vieAv enteric fever may—in so far as it is referred not to a microbe directly derived from antecedent enteric fever or other disease, but to a saprophyte that has become altered in its physiological effect by sojourn for a while in sewage—arise, so to speak, de novo. This contention is the outcome solely of bacteriological study, not of epidemiological observation and experience, and based mainly on the fact that it is often difficult to distinguish the B. coli from the bacillus of enteric fever. Recent and closer observations, however, have shown that these two micro-organisms are quite distinct, and as judged by their cultural beha-viour can be readily differenti- ated. In shape the Bacillus coli is an oval rod rounded at its ends, measur- ing about 0-5 y. broad and 2 y long : comparatively few attain the length of cylindrical rods. They are less motile than the Eberth bacillus, and grow rapidly on gelatin, in the shape of translucent filmy patches, irregular in outline, thin in the marginal, thick in the central part, but without liquefaction of the gelatin. The three principal cultural characters, however, by which the two organisms can be distinguished best and easiest are: shake cultures in melted gelatin, which is afterwards allowed to solidify, mdk cultures, and broth cultures. While the B. coli rapidly forms gas bubbles in gelatin shake cultures, the enteric bacillus does not do so; whde the B. coli curdles milk on incubation for two days at 37° C, the enteric bacillus does not do so; and Avhile the B. coli pro. duces indol in broth, after three days' incubation at 37° C, as shown by a pink to red reaction on addition of nitrous acid, the enteric bacillus does not do so. AU authors Avho maintain the change of the B. coli into the B. Eberth, assume that this change is accomphshed in sewage. As far as direct experi- ments can be made in this direction, they lend no support to this view, for it can be shown that the two microbes, while sojourning in sewage, maintain their biological characters unaltered. Moreover, direct observation proves that the tAvo organisms, when planted in sewage, behave in a strikingly different manner. While the Bacillus coli retains its vitality there, and undergoes multiplication, the bacillus of enteric fever, on the contrary, shows less vitality and soon diminishes in numbers till ultimately it altogether disappears, in some cases within a fortnight, and long before the nutritive material is exhausted. But as long as the enteric bacillus is present in such sewage it retains the same cultural characters as mentioned above, and the same applies to the Bacillus coli. An important fact that has resulted from experiments with sewage in connection with these micro-organisms is that the enteric bacillus, when planted in sewage to which 1 per cent, of potassium nitrate is added, retains its vitality for considerable periods and also undergoes rapid and marked multiplication. This seems capable of explaining the observations often made that the enteric bacillus in sewage percolating through the soil into water is capable of preserving for long periods its vitality. Sewage percolating through the soil takes up nitrates 624 THE INFECTIVE DISEASES. from the soil, hence in such a medium the enteric baciUus is capable of groAving and retaining its vitality. Although septic, toxic, and septicaemic results have been produced in rodents by the injection of enteric fever stools and enteric bacilli, it cannot be said that this disease has been communicated by any experimenter to the lower animals. This apparent failure to furnish the crucial argument in support of the view that Eberth's bacillus is the cause of this disease, is due probably rather to the fact that domestic animals are not susceptible to enteric fever, than to the fact that this bacillus is not the specific micro- organism. As far, then, as bacteriological evidence goes, there is no valid reason Avhy sanitarians should not continue to regard enteric fever as a specific disease derived from an antecedent case or cases of the same disease, and not, as has been suggested, on negative bacteriological and other evidence, as capable of originating de novo, that is to say, through the Bacillus coli or other intestinal microbes. While holding this view, our duty of preventing pollution with seAvage of drinking water, milk, &c, is not less incumbent. For, although without the enteric germ the Bacillus coli and other intestinal bacteria, we maintain, are not capable of causino- enteric fever, the presence of the B. coli, or any other well-knoAvn normal inhabitant of the intestines, in water nevertheless indicates a probable pollution Avith excremental matters, and amongst them possibly with specific—that is, enteric—excremental matter. In the actual dissemination of the disease, water has been repeatedly proved to play the most important part. Not only in this country, but abroad, various epidemics and groups of cases have been investigated, where a contamination of drinking water by sewage from drains or old cesspools, and, by inference, Avith enteric excreta, has been proved to be connected with the outbreak and spread of the disease. Complete and instructive evidences as to contamination of drinking water by enteric stools, and Avholesale infection by such water, are afforded by the Caterham epidemic in 1877, the Middlesbrough and Tees Valley outbreak of 1890-1, the Worthing epidemic of 1891-2, and many others to be found in the various supplements to the Reports of the Medical Officer to the Local Government Board. Further, Ballard has shown in his report on the Islington epidemic in 1870, that milk plays an important role in the dissemination of the enteric fever virus : such milk epidemics, where milk had directly, or by the vessels containing the milk, been brought into contact with sewage-polluted water, have been numerously recorded. Other outbreaks have been traced to infected milk-supplies, in which material evidence has been forthcoming to raise the question whether milk can obtain enteric fever infective qualities from an ailment of the cow, as in the case of diphtheria and scarlet fever. Such a sequence of events would explain many otherwise inexplicable epidemics, but the evidence in support of this view cannot yet be said to be convincing. Although it is true that, in the greater number of epidemics of enteric fever, the cases are due to specifically contaminated water or milk it is not safe to say that the disease is never conveyed by direct infection nor must we overlook other possible modes of the spread of this disease. In India and other countries where dry systems of conservancy are in force, a possible danger exists in the dislodgment of dried and imperfectly buried excreta from the soil, and their diffusion, as dust, by winds. If specifically infective, even in the absence of direct experimental evidence, few persons, who have knowledge of the circumstances of life of tropical countries, will be disposed to deny that such dried excretal matter possesses considerable ERYSIPELAS. 625 potentialities for evil. Some are of opinion that the B. Eberth is essentially a micro-organism of the soil, and capable of leading an independent life, and of reproducing itself in the earth. Our own observations indicate that in certain soils, rich in nitrates, this organism may retain its vitality for six or more months : if this be so, there is no difficulty in understanding why the disease often appears in the most diverse localities, where previous cases of the disease are difficult to trace. From time to time, a good deal of evidence has been forthcoming in favour of the view that the air and gases of sewers or drains which have become specifically contaminated may, if allowed to find its way into dwellings through defective house connections, cause enteric fever among the inhabitants of such dwellings. In the light of recent researches, which indicate that sewage is unable to give off micro-organisms to the air in contact with it, we find it difficult to accept this view as to the occasional origin of enteric fever cases; and are compelled to conclude that some more exact causation has been overlooked in those instances. The question whether enteric fever and malaria stand in any special relation to each other has been extensively discussed. There is some evidence to shoAV that, in some localities, there is a mutual antagonism between these two affections, and that where malaria is common, there enteric fever is rare, or absent. This, however, is by no means universal, nor does the converse always hold good. Our explanation of the pheno- mena as observed is that civilisation, by leading to cultivation and drainage of land, has tended to banish malaria, but at the same time possibly has disposed to the prevalence of enteric fever, by pollution of water, soil, and ah, as the result of an aggregation of people under circumstances of defective sanitation. The question has been further complicated by the suggestion, that some of the later supposed cases of enteric fever in malarial districts are but an altered type of malaria. In regard to this point, we think that, wlhle it is unAvise to accept the term typho-malarial fever as indicating a third form of disease, which is neither enteric fever nor malarial fever, it cannot be denied that the two latter diseases may co-exist. Prevention.—General measures will be to secure pure air, pure water, pure mdk, and to maintain all drains and sewers in good order. If any suspicion attach to either water or mdk it should be boiled. To guard ao-ainst the spread of the disease from the sick to the healthy, all stools and urine should be received into a vessel containing some strong disinfectant and at once covered up. After this, the excreta may be at once passed into a drain, or buried deeply in the earth, but this must not be done until the stool has been exposed to the action of a strong disinfect- ant for at least five minutes. If possible, all excreta should be burnt. All soUed linen should be at once placed in a vessel containing carbolic acid solution 1 in 20, untU they can be removed for proper disinfection by either boiling or exposure to moist heat in a disinfecting chamber. Isolation of the sick person is not necessary, but several patients ill with enteric fever should not be aggregated together in one ward. ERYSIPELAS. As a contagious and infectious disease, the chief evidence of which is a spreading inflammation of the skin, extending in some cases to the areolar tissue and accompanied by fever, erysipelas has been known since very early times It is met with all over the world, but less frequently in the tropics 2R 626 THE INFECTIVE DISEASES. than in more temperate climates ; it affects all races alike, and is especially fatal among the very young. It has been said that erysipelas is more common among women than men: this is probably true with respect to attack, but the deaths at all ages are greater among males. The total number of deaths returned from this disease in England and Wales in 1893 was 1921, of which 1025 were males and 896 were females; the mortality for all ages being at the rate of 64 per million persons hving, as compared with a rate of 49 per mdlion for the last five years. The deaths from erysipelas are usually above the average from the middle of September to March, and beloAv the average for the rest of the year. The absolute maximum for the year is commonly attained in the third week of November: Avhile the minimum period is from the middle of June to that of September. Longstaff has pointed, out that erysipelas has a mortality in inverse ratio to the rainfall, in this respect resembling scarlet fever: there is a further general resemblance in the seasonal curve of prevalence of erysipelas to puerperal fever, pyaemia, and rheumatic fever. Etiology.—Fehleisen was the first to clearly demonstrate that erysipelas is caused by a micro-organism which he named the Streptococcus erysipe- latosus : it is found at the edge of the inflamed skin, occupying the lymphatic channels and spreading along them as the disease advances. The cocci are from 0*3 to 0*4 y. in diameter: they are readily cultivated outside the body, and from the cultures true erysipelas can be induced in rabbits by inoculation. Associated with this streptococcus in erysipelas is usuaUy the Streptococcus pyogenes, and some observers go so far as to say that they really are the same organism, the former being merely an attenuated form of the latter. The facts that two species of streptococci can be originally obtained by culture from the erysipelatous skin, and their differences proved by inoculation into rabbits, seem definitely to contradict the above supposi- tion as to their identity. The cocci of erysipelas never enter the blood. Formerly it was usual to regard erysipelas as occurring either through a wound or without. To a large extent this distinction between traumatic and idiopathic forms of the disease has been replaced by the behef that every case is caused by the poison entering the system through a wound, though this in some instances may be so insignificant as to be overlooked. The disease is undoubtedly infectious, but possibly less uniformly so than many of the other infective diseases. The incubation period of erysipelas is evidently short, ranging from one to eight days, or more often from one to three or four days. In Fehleisen's inoculation cases on human beings for the removal of sarcomatous growths, the period was very short, varying from fifteen to sixty-one hours. The disease at times runs riot in hospitals, especially in surgical wards, the most important favouring circumstances being defective ventilation, overcrowding, want of cleanliness, and defective drainage arrangements. Some people seem to be more predisposed to erysipelas than others; among such are the intemperate, the badly fed, and those who have had it before. Our know- ledge at present is small as to what are the precise connections between erysipelas and the various forms of blood-poisoning, more particularly that peculiar kind of blood-poisoning associated with lying-in women or those recently confined. Evidence is strong that there is a relationship of some kind betAveen erysipelas and child-bed fever, as shoAvn by the familiar fact that Avomen in labour attended by doctors or midwives who are suffer- ing from erysipelas, or who even have been in contact with erysipelatous patients, commonly get blood-poisoning or puerperal fever. Similarly, nurses, midwives, and medical men Avho attend, or come into close contact GLANDERS. 627 with, women suffering from puerperal fever frequently themselves suffer from erysipelas; also that the new-born children of mothers, ill with child- bed fever, die in large numbers from erysipelas. To a less degree, erysipelas has some obscure relationship to diphtheria prevalence. Prevention is synonymous with attention to the sanitation of hospitals and institutions, especially the maintenance of ventilation, and cleanliness of wards. Hospital floors should be of hard wood, polished and readily cleaned by dry rubbing or sweeping. Cases of erysipelas should be isolated, and the Avard, if possible, evacuated, and the walls, floor, furniture, &c, carefully disinfected. GLANDERS. Fortunately, this is a comparatively rare disease in man, but not uncommon in horses, asses, mules, and other animals. It may be described as a sub- acute, infectious disease of the nasal mucous membrane, respiratory organs, and skin: when localised in the skin, the affection is termed farcy, but is identical Avith the more ordinary form. Whether affecting man or animals, glanders is remarkably fatal. In the human subject the disease is usuaUy acute, consisting of nodular deposits in the mucous membrane of the nose, particularly on the septum. The young nodules are of about the size of a hemp seed, deep seated, and surrounded by congested mucous membrane. Microscopically they resemble young tubercles : they soon enlarge, suppurate, and form ulcers. The nasal septum rapidly becomes riddled with abscesses : the cervical glands become swoUen and purulent, and the disease process extends to the pharynx, trachea, lungs, and larynx. In cases where the skin is involved, the process is very simdar. The chief source of infection is the horse. The virus does not appear to be capable of aerial transmission, except, perhaps, for very short ranges, and no evidence exists in support of infection by either water or milk. Inocula- tion is the chief mode of infection, so far as man is concerned, generally through a cutaneous wound; but it may occur without abrasion of skin or mucous membrane. The usual incubation period is from three to eight days, but in acute cases may be shorter. The cause is a bacdlus, usually present in the nodules, being more numerous before these latter have become purulent. The bacilli are slender rods with rounded ends, resembhng both in size and appearance the tubercle bacillus. They are easily cultivated at 35° to 38° C, on blood-serum, agar, potatoes, and other media. On boiled potato at 35° C. they form a characteristic brownish-yellow amber-coloured film. Inoculations of these artificial cultures into horses and asses produce typical glanders. The bacdli appear to be killed by drying, and by ten minutes exposure to 55° C.: in this respect they are less resistant than many other non-spore- bearing bacilli. Corrosive sublimate (1 : 5000) kiUs them in two minutes, and 5 per cent, carbolic acid in five minutes. The injection into horses, suffering from glanders, of chemical substances obtainable from cultures of the baciUus (mallein) produces a well marked rise of temperature; but no reaction follows in healthy horses. Mallein is prepared in the same way as tuberculin, and affords in doubtful cases a ready means of determining the diagnosis of glanders. Prevention will be best secured by early isolation of the infected man or animal. AU discharges from the nasal and respiratory mucous membranes should be disinfected and destroyed. Infected stalls and stables should be disinfected. Glandered horses should be destroyed, but this is not com- 628 THE INFECTIVE DISEASES. pulsory in the case of farcy. Though there is no evidence that the flesh of glandered animals used for food propagates the disease, still it is advisable that it should not be so consumed. HYDROPHOBIA. From very early times it has been knoAvn that dogs are liable to a fatal disease Avhich they transmit by their bite; and this disease when occurring in man was called " hydrophobia " from the dread of water, which is one of its chief symptoms. In the lower animals, however, this very symptom is absent, hence in them it is more commonly spoken of as rabies. Rabies may occur in many kinds of animals besides dogs. It is common in wolves, jackals, and foxes, and the bite of a rabid Avolf is notoriously the most dangerous of all. Cats are sometimes affected by it, but far less frequently than dogs. Among herbivora, horses, oxen, sheep, goats, pigs, rabbits, and guinea-pigs are capable of being infected experimentally by inoculation, or if they are bitten by rabid dogs. Rabies broke out as a destructive epidemic among the fallow deer at Richmond in 1889, and soon afterwards in the Marquis of Bristol's park. More than 450 died out of a herd of between 600 and 700 in the course of three months. There are tAvo varieties of the disease in dogs; one characterised by maniacal excitement, the other by paralysis of the jaw, so that it hangs down and allows a frothy saliva to run out of the mouth. In each form the bark is somewhat altered. Towards the last, the hind legs and the loins become paralysed so that the animal staggers about and falls. Rabies is always fatal in dogs, usually in a week after the symptoms have appeared, occasionally after nine or ten days. In rabbits the symptoms of rabies (transmitted from dogs) are like those of dumb madness, in the absence of excitement and the development of paraplegia, which, as in dogs, takes the form of acute ascending paralysis. The study of the disease when repro- duced by inoculation in animals shows a very similar series of symptoms to those which are characteristic in man. There is first a stage of excitement Avith visual delusions; then hyperaesthesia with reflex spasms ; next the stage of mania and (particularly in rabbits) paraplegia, corresponding to the dumb rabies of dogs; and lastly, death, often by sudden failure of the heart. At one time hydrophobia was supposed to occur chiefly in temperate chmates, but this is not the case, as it is by no means uncommon in India and Central Asia. The only part of the world in which it is as yet unknoAvn is Australia. Like other specific diseases it is often absent from a town or locality for several years together, until some accident introduces it and it becomes epidemic. In England the greatest number of cases of hydrophobia occur in London and the home counties, Lancashire, and the West Riding of Yorkshire. For London, the Registrar-General's returns show twelve deaths from hydrophobia in 1838, and four in 1839. Then only one, three, four, two, three, two, in the successive years to 1845, none in 1847, '49, and '52, and only one in 1846, '48, '50, '51, and '53. Seven were returned in 1854, and two in 1855 and '57. None in 1856, '58, '59, '60, '61, and '62. Two in 1863, and none again in 1864, but nine in 1865, and six in 1866. There were three in 1867 and '69, none in 1868 and '70; one in 1871, '72, and '73. Then there were nine in 1874, six in 1875 and '76, and sixteen in 1877 ; five in 1878, two in 1879, three in 1880, five in 1881, four in 1882, HYDROPHOBIA. 629 eight in 1883, nine in 1884, and in 1885 no less than twenty-seven. In 1886 the number suddenly fell to nine, after muzzling was enforced, and in 1887, '88 there were only tAvo and three deaths" respectively. Seven occurred in 1889, two in 1890, two in 1891, none in 1892, one in 1893, and one in 1894. According to the popular belief, the disease is more frequent in the hot season than during Avinter and spring. Of 132 cases throughout England and Wales, fifty-one occurred in July, August, and September. Hydro- phobia causes most deaths at ages between five and fifteen years, more males being affected than females. Bites about the face, and especially those inflicted by rabid wolves, are more deadly than others; the danger is less when the part bitten is protected by clothing. Of cases of bites by animals proved beyond doubt to be rabid (the proof being the occurrence of a genuine case of rabies in some person or animal bitten by them or inoculated from them), hydrophobia manifests itself in 15 per cent, of the persons bitten. By means to be described subsequently, this mortality may be reduced to at least 1*5 per cent., and by other preventive measures the disease can be and has been stamped out completely. Hydrophobia is doubtless caused in all cases by the transference to the patient of the specific virus of rabies, such transference being imparted to man and probably animals also by the bite of rabid dogs ; or more rarely of rabid wolves, jackals, foxes, and cats. The incubation period is most frequently about six Aveeks. When the infecting wound is on the face, the incubation is probably shorter. In chddren, also, it is usually shorter than in adults. In 132 cases of hydrophobia, selected by the Registrar-General (1886) on account of the circumstances being accurately known, the shortest incubation was eleven days in a child bitten by a rabid cat. In 23 cases it was under a month, in 64 between one and two months, in 21 between two and three months, in 124 it was under five months, in 127 under ten months, and in 130 under two years. In one case it was between three and four years, and in one other above four years. Experimental inocula- tion in dogs, rabbits, and other animals shows, on the AAdiole. shorter periods than when the disease dates from the infliction of a bite by a rabid dog; and when the virus is introduced, not subcutaneously but beneath the dura mater after trephining the skull, the period of incubation is measured by days, a week being a very frequent time. There is no doubt that the virus resides in the sahva and sahvary glands. Magendie long ago produced rabies in dogs by inoculating them with the saliva of hydrophobic patients. Pasteur demonstrated that the spinal cord is also the seat of the -virus, and that inoculations from it, especially if introduced under the dura mater of a dog after trephining the skull, will reproduce the disease in dogs and rabbits. Pasteur further showed that the virus, when propagated through a series of rabbits, increases rapidly in its -virulence; so that whereas subdural inoculation from the brain of a mad dog takes from fifteen to tAventy days to produce the disease, in successive inoculations in a series of rabbits the incubation period is gradually reduced to seven days. The spinal cord of these rabbits contains the virus in great intensity, but, when kept in perfectly dry air, the virus gradually diminishes in intensity. If, now, dogs are inoculated with cords preserved for from twelve to fifteen days, and then with cords preserved for a shorter period, i.e., with a progressively stronger virus, they gradually acquire immunity against the disease. A dog treated in this way will resist inoculation with material from a perfectly fresh cord from a rabid rabbit, which otherAvise would inevitably have proved fatal. Relying upon these experiments, 630 THE INFECTIVE DISEASES. Pasteur began inoculations in the human subject, using, on successive days, material from cords in which the virus was of varying degrees of intensity. The method of preventive injections noAV employed for human subjects may be thus represented :— Days of inoculation. Days' drying of the cords, 1st 14, 13 2nd 3rd 4th 5th 6th 7th 8th 9th 10th llth 12th 13th 14th l.-ith 12, 11 11, 10 10, 10 9, 9 9 8 8 8 7 7 7 6 6 5 " The material for injection is prepared by crushing portions of the dried spinal cord, and diffusing them in sterilised broth free from all risk of putrefaction, decomposition, or any change due to the presence of other micro-organisms; and the injection is made Avith syringes through fine tubular needles into the subcutaneous tissue. For transmission of rabies through rabbits, in order to obtain the spinal cords required for its preven- tion in other animals, injections of virus of highest intensity are made through minute holes in the skull into the space under the dura mater." It is surmised that the protection obtained is due to a chemical substance, and not to any real attenuation of the microbe, Avhich, so far, has not been isolated Avith any certainty; although both micrococci and bacilli have been found in the rabic cord. While the case mortahty of hydrophobia is practically 100 per cent, if untreated by inoculation, after treatment at the Pasteur Institute in Paris it has fallen to 0*5 per cent. In 1894 there Avere seven deaths out of 1387 cases. Deaths occurring during treatment, or Avithin fifteen days of last inoculation, are not included. While, in the opinion of unprejudiced critics, it is generally admitted that Pasteur has discovered an efficient and strictly prophylactic treatment of hydrophobia, the serious question remains whether the intended protective inoculation may not, if unwittingly employed on persons who have not really been infected before, produce a fatal form of the very disease against which it is supposed to protect. The difficulties in the way of a sound decision on this point are serious, and have not yet been satisfactorily overcome. Prevention.—Rabies can be stamped out by muzzhng all known dogs for a sufficient length of time, and destroying all others. This was done in Sweden many years ago, and the country remains free from hydrophobia. The same is the case in Berlin. In England, several local attempts have been made in the same direction, notably in 1885 in London, in 1886 in Nottingham, and in 1890 throughout Lancashire, Cheshire, the West Riding of Yorkshire, and London. These muzzling orders have always been followed by a cessation of rabies, but have been invariably relaxed too soon. The only effectual way to stamp out rabies is to enforce muzzling strictly throughout the island for at least a year. Under the Rabies Order of 1892, issued by the Board of Agriculture, County Councils have power to make regulations for muzzhng and other preventive measures. INFLUENZA. The recent series of epidemic visitations of this disease in this country have made its chief characteristics familiar to most people. Although the original home of this affection is not known, our knowledge is sufficient to convince us that it is a disease which has periodically prevailed in various INFLUENZA. 631 parts of the world as an epidemic since very early times. An analysis of the chief epidemics of influenza during the present century shows that its progress and prevalence are quite independent of race, climate, or season: that man is the chief vehicle of its diffusion: and that its epidemic prevalence attains its height amongst crowded communities. Although there is some indication of its preference for lines of traffic, the actual progress of an epidemic is very irregular. The interval between epidemics is variable: in England the chief out- breaks were in 1803, 1833, 1837-8, 1847-8, and some minor epidemics about every three years till 1860, when these practically ceased. Nothing was heard of the disease after 1860 until 1889, when a new series of epidemics began, each covering almost the whole country at intervals of about a year. Influenza epidemics differ in type from time to time, and there is also considerable variety in different centres during the progress of an epidemic as to the tendency to one or other group of local symptoms or comphcations. All epidemics, however, present the same general characters, such as "rapidity of dissemination, general independence of climatic, seasonal, age and sex influences, relative suddenness of onset as regards attack, and Ioav case mortahty " (Parsons). When the 1889 epidemic appeared in England some doubt was expressed by a few as to whether it was influenza at all, mainly owing to the improper and traditional apphcation of the term " influenza " during non-epidemic times to ordinary catarrh. Others were disposed to complicate the situation by the suggestion that the prevading epidemic was one of dengue. This latter is, however, " essentiaUy a disease of hot climates and seasons, seldom fatal, is unattended with pulmonary complications, almost always presents a rash, and is frequently followed by desquamation." Mortality.—It is estimated by the Registrar-General that in England and Wales, in the four years 1890-1-2-3, the aggregate loss from influenza was not fewer than 46,615 lives. Although in most parts of the country there has been a great decrease in influenza mortahty during the last year as compared with the preceding four years, nevertheless, in some parts of England and Wales, and notably in the metropolis, the disease may be con- sidered to be still fatally prevalent. " The deaths in England and Wales specially referred to influenza during 1893 numbered 9669, as against 4523, 16,686, and 15,737 respectively in the years 1890-1-2." The heaviest incidence of influenza in 1893 was in the metropolitan area, where the deaths attributed to that disease were equal to a rate of 351 per million, as compared with 325 for the rest of the country. Experience shows that a rise in the mortality from influenza has generally been attended by a rise in the mortality from lung and sometimes heart disease. During the years 1890-1-2-3, this has been specially conspicuous, so that the mortality attributable to influenza must therefore not be measured solely by the deaths registered as due to that cause, but the indirect effect of the malady as ex- pressed in the increased death-rate from certain other causes must also be taken into account. Accordingly, the Registrar-General estimates that, during the period 1890-1-2-3, the total number of deaths due directly or indirectly to influenza was not merely 46,615, but 125,000, or 1051 per million living. The case mortahty is variable, but generally low, averaging about 1 to 1*6 per 1000. The protection conferred by an attack is slight and evanescent, second and third attacks being common. Etiology.—The period of incubation appears to be short, from one to three days. The breath is in all probability infectious from the first, 632 THE INFECTIVE DISEASES. continuing to be so as long as the eighth or tenth day, and perhaps longer. Yarious hypotheses have been proposed to explain the cause of influenza, but in the light of Avhat we knoAV about other diseases, coupled with the general behaviour of influenza, the most probable one is that it depends upon a micro-organism. Though various species of bacteria have been described by different observers as present in this disease, those first described by Pfeiffer in 1892 as being constantly present in the bronchial sputum and pulmonary exudation in all cases of influenza are now generally regarded as the real microbial cause. The bacilli are very minute, about half the length but the same thickness as the bacilli of mouse septicaemia: in stained specimens they show a characteristic bipolar granule with inter- mediate clear part, hence closely resemble a diplococcus. They aggregate in clumps, occur in the leucocytes of the sputum, and also form chains; they disappear with the cessation of the disease. At 37° C. they grow in a characteristic manner in broth and agar. The broth remains clear, while a growth at the bottom of the fluid appears as whitish-grey granules and fluffy masses. On agar the growth forms minute translucent droplets, which have no tendency to coalesce; the bacdli do not grow on gelatin kept at 20° to 22° C. The presence of these bacilh in influenza and in no other disease has been confirmed by other observers. The curious tendency of influenza to recur at intervals in the same locality is suggestive that the contagion may be able to live and thrive for considerable periods outside the human body; but whether this is in the soil or in the bodies of domestic animals is unknown. That these latter creatures, particularly dogs and cats, suffer during influenza epidemics from symptoms extremely like it is generally accepted. Horses, also, are liable to a severe and often fatal disease, known as "pink-eye," which has been regarded as a form of influenza. Certainly on several occasions, both in England and elsewhere, epidemics of influenza have been preceded by out- breaks of " pink-eye "; but, as explained by Klein, there are grave reasons for doubting the transmissibility of influenza to lower animals. Prevention.—Isolation should be carried out from the earliest appearance of symptoms. During periods of epidemic prevalence, people should not con- gregate together, and public meetings should be avoided as much as possible. A regular life, plenty of open-air exercise short of fatigue, a proper number of hours in bed, and regular meals of good, simple food are among the best prophylactics. LEPROSY. This is a chronic infectious malady characterised by either the presence of tubercular nodules in the skin and mucous membranes or by degenerative changes in the nerves. At first these forms may be separate, but ulti- mately both are combined. Leprosy is one of the oldest of known diseases, and at present prevails widely, particularly in hot countries. In India it is estimated that there are some 300,000 lepers. In Europe, where it exten- sively prevailed in the Middle Ages, it has become almost unknown except in Norway. In America it exists in the Gulf States and in Mexico. In the Sandwich Islands leprosy has developed to an enormous extent; while in the West Indies the disease has been long endemic. Cause and Etiology.—A microscopic section made through a leprous tubercle shows the tubercle to be a granuloma, each and all of the cells of which are filled with minute bacilli. Hansen Avas the first to observe this LEPROSY—MALARIA. 633 fact, and regarded these baciUi as the virus of the disease. These observations have since been repeatedly confirmed by others. The lepra bacilli are on the average 4 to 8 y. long, and about 0*8 y, thick; in well- stained and well-washed specimens they resemble somewhat the tubercle bacilli, by shoAving segregation of the protoplasm (deeply stained granules) in a faintly stained sheath. Cultivations of these bacilli have not been satisf actorily carried out; while all inoculation experiments on animals have yielded only negative results. Leprosy attacks aU classes and persons of all ages. It is probably com- municated by contagion. Arning claims to have successfully inoculated in 1885 a Hawaiian con-vict, named Keanu, with leprosy; but subsequent criticism of this case suggests a possible mistake as to the inoculation having been successful, OAving to the fact that the man Keanu is one of a family of lepers, and that the disease as it appeared in Keanu was too rapid to have been the result of the inoculation by Arning. Leprosy is, apparently, only contagious in the same sense as syphilis, and just as accidental contamina- tion -with this virus is extremely rare so it is with leprosy. The closest possible contact may take place for years, as between parent and child, without transmission; but it is difficult to explain the rapid spread of the disease in the Sandwich Islands on any other vieAv than contagion, and yet it is strange that there is no evidence of a primary lesion or external sore comparable to that of syphilis. There is an increasing belief that in the majority of cases the disease is propagated by sexual congress, but the evidence is by no means definite. The disappearance of the disease in the Middle Ages was probably the result of the strict isolation of lepers enforced at that time. In more recent times, it is just possible that the affection may have been transmitted by vaccination, though there is no authentic case of such having happened. Hereditary transmission cannot be excluded, and there is no good reason why the disease should not be communicated, as is syphilis, from parent to child. Hutchinson believes that the disease is always associated with some special kind of food, particularly fish. He does not deny the specific nature of leprosy, or the possibility of contagion, but infers that it may be the fish diet which renders the patient susceptible, or even be the vehicle or medium with which the poison may be taken. So far, the general facts regarding the incidence of this disease do not lend much support to Hutchinson's views, but rather indicate the importance of keeping lepers as much isolated as possible, and otherwise treating it as being essentially a communicable disease. Prevention probably depends upon the removal of children of leper parents from the leprous surroundings, and their education in asylums under favourable hygienic conditions; the voluntary isolation of lepers in colonies or farms, and the abstention of lepers from the occupations of barbers and washermen or washerwomen, and from the sale of food. The Leprosy Commission have reported that compulsory segregation is quite unnecessary. MALARIA. The malarial diseases may be conveniently considered as a single group, although they include many varieties that have received names suggestive of specific distinctions between them. They all have a characteristic tendency to periodicity, and in their general etiological conditions appear to be closely related. How far the malarial poison is the same in all cases is etill undecided, but it is not unlikely that more accurate methods of research 634 THE INFECTIVE DISEASES. may ultimately establish specific distinctions betAveen the varieties of microscopic bodies A\-hich appear to stand in causal relation to the various forms of malarial fever. Geographical Distribution.—" Covering a broad zone on both sides of the equator, malarial diseases reach their maximum of frequency in tropical and subtropical regions. They continue to be endemic for some distance into the temperate zone, with diminishing severity and frequency toAvards the higher latitudes; in epidemic form they not infrequently appear in yet other regions, and in still wider diffusion with the character of a pandemic also beyond their indigenous latitudes" (Hirscli). The present distribution of malaria indicates it to be widely prevalent in a virulent form in tropical Africa, especially on the west coast. It also prevails in Algiers, and in the Nile Yalley of Egypt. In Asia, it is notoriously prevalent in India, China, Ceylon, Arabia, Afghanistan, Persia, and Syria. In the western hemi- sphere, it is met with in the West Indies, Peru, Brazil, Panama, and the southern and central parts of the United States. Of European countries, Italy suffers the most, and perhaps Great Britain the least, though even now the disease still hngers in the fen districts of Lincolnshire, and the counties of Norfolk, Huntingdon, and Cambridge. Although malaria is most prevalent and most malignant in tropical and subtropical countries, yet among such countries it appears to have a special affinity for certain parts. Thus, in India, the Presidency of Madras suffers much less than those of Bengal and Bombay. So also, on the West African coast, malaria " becomes less severe from Cape Lopez southwards, and this exemption becomes more and more marked the nearer we approach the Cape of Good Hope, Avhich itself enjoys, along with St Helena, an almost complete immunity from the endemic fever." New Zealand and Tasmania are said to be completely, and Australia almost completely, exempt. A point of some interest in connection Avith malaria is, that it, at times, has exhibited decided epidemic tendencies, extending to localities in which it is not commonly met with. This circumstance suggests the question whether there is any actual transport of the malarial organism beyond its ordinary endemic areas; or whether, in certain districts, organisms which are usually benign may not acquire pathogenicity as the result of some exceptional conditions of weather; or whether again these exceptional meteorological conditions may not operate indirectly by increasing the susceptibility of individuals, and thus render them " vulnerable to attack by organisms, indigenous to the neighbourhood, but not usually pathogenic." As to the possibility of the two latter hypotheses, we have no precise evidence, but the fact that some districts, which up to a certain time have enjoyed immunity from malarial disease, such as Reunion and Mauritius, have subsequently become endemic centres of that malady, is extremely suggestive of the possible transportation of the causative agent. Malaria may, without doubt, be conveyed by air currents, but for what distances is uncertain: in any case, its conveyance by air is, to a large extent, arrested by belts of trees and sheets of water, especially salt water. On the other hand, when favoured by ravines and heated currents of air, malaria can pass to a height which appears to differ in different climates, varying from 500 to 3000 feet. As regards sex and age influence, males appear to suffer more frequently than females, but possibly this is due to increased exposure to infection. No age can be said to be exempt, but attacks are certainly less frequent among the very young and the very old. Influence of Season and Locality.—Although in countries where malaria MALARIA. 635 is endemic the disease occurs in any season of the year, its general preva- lence, nevertheless, appears everywhere to be largely regulated by season, though the particular time of year in which it is most common varies in different countries. Even in the tropics, where malaria constantly prevails, there are minimum and maximum periods; the former corresponding to the summer and winter, the latter to the spring and autumn months. In temperate climates, there are only a feAv cases in the spring, but a large number of cases in September, October, and sometimes in November. In the most malarious districts in the tropics, the maximum prevalence is during and towards the close of the rainy season. In the temperate climates the relation between the rainfall and malaria is not so clear, the cases being often more numerous after a dry summer; but if either heat or moisture is excessive, the development of the virus is checked for a time. A tolerably high temperature appears to be one of the essential conditions for the development of the virus. The importance of the state of the soil in the etiology of malaria is universally recognised, and has already been discussed in a previous chapter. The disease is particularly common in low, marshy regions Avhich have an abundant vegetable growth. Estuaries, badly drained low-lying districts, the course of old river beds, tracts of land which are rich in vegetable matter, and particularly districts such as the Roman Campagna, which have been allowed to fall out of cultivation, are favourite localities for the develop- ment of the malarial poison. These conditions are most frequently found, of course, in tropical and subtropical regions, but it must not be overlooked that some of the most malarious districts of India are steep mountain slopes, and that many others both in India and elsewhere are equally free from moisture of the soil. Instances are common in which districts, previously healthy, have become temporarily or permanently malarious, without apparent change in their physical conditions. The proof of the close relation between malaria and the soil is completed by the fact that malarious soil conveyed in boxes to healthy districts has given rise to outbreaks of the disease. The Malarial Parasite.—Malaria being a specific disease, the presence of a specific organism is necessary, and the conditions of climate, season, and soil above described are to be regarded merely as more or less favour- able to its groAvth and dissemination. In 1880, Laveran, a French army surgeon, announced the discovery of a parasite in the blood of patients attacked by malarial fever. His observations have been since confirmed and extended by Marchiafava, Celh, Golgi, and many others. In fact, not a single observer who has had the necessary training and the material at his command has failed to demonstrate the existence of these parasites. The bodies which have been found invariably associated with all forms of malarial fevers belong to the protozoa; in some respects they resemble the monads and in others the sporozoa. In the blood of patients with malarial fevers the foUowing forms may be seen: (1) an unpigmented hyahne body within the red blood-corpuscles, which displays active movements; (2) a pigmented amoeboid body within the red blood-corpuscles, which, under certain circumstances, may increase in size and form; (3) a segmenting body, in which the protoplasm divides into a variable number of definite small spheres; (4) crescentic bodies, the so-called crescents, which develop within the blood-corpuscles and form characteristic and distinctive structures; (5) flagellate organisms, which may be seen to develop from the intra- cellular pigmented forms, or from ovoid bodies which are altered crescents; (6) free flagella. To the amoeboid forms within the red blood-corpuscles 636 THE INFECTIVE DISEASES. Marchiafava and Celli gave the name Plasmodium malarice, but this is probably an incorrect nomenclature, as the malarial parasite reaUy belongs to the class sporozoa amongst the protozoa. On Plate X. are represented various forms of this organism, as observed in the blood by Manson and others. The relation of the parasites to the symptoms of the disease has been Avorked out, in part, by Golgi, who has shoAvn that, corresponding to the paroxysm, there is a process of segmentation. But whether in these different forms we have really to deal with different species of the same group of parasites as Golgi and others incline to think, or rather with differences in the hfe history of the same species caused by unknoAvn condi- tions, is not decided. Though the relation of the different forms or phases of growth of the parasite to the varieties of malarial fever has not yet been thoroughly established, the following points may be here referred to. The typical intermittents are associated with large forms of the parasites, of which several varieties have been described. Golgi has described two distinct forms which he considers the causes of tertian and quartan fevers, and makes aU other types depend on combinations of these. This probably holds good for a large proportion of intermittents. With the remittents, Marchiafava and CeUi have described a distinct species, and look upon the crescents as representing a phase in its development. The pernicious malarial fevers are also associated with this variety, which the Italian observers caU the " small plasmodium." The crescents may occur also in acute cases, but are most constant in malarial cachexia. Both the crescents and the flageUate bodies may be regarded as atypical forms of the parasite. _ All attempts to cultivate these organisms outside the human body have given negative results, and their complete life history is not known. The general belief is, that the parasites do not exist as saprophytes, but live as parasites in either animal or vegetable organisms; possibly the mosquito is the intermediate host. Prevention.—The evidence with regard to the spread' of malaria by water is conflicting, but the following case recorded by Boudin is highly suggestive of such being by no means uncommon. "In this case 120 soldiers embarked in the transport ' Argo' at Bona in Algeria for Marseilles. During the voyage 111 of them, thirteen of whom died, suffered from different forms of malarial fever. Tavo other vessels, carrying between them 680 soldiers, also from Bona, and arriving at Marseilles the same day as the < Argo,' had no cases of illness at all, and the only ascertainable difference of circumstances between the troops in these ships and those in the ' Argo' was the difference of drinking water. The latter were excep- tionaUy supphed with water, which was said to have an unpleasant smell and taste, from a marsh near Bona; those on the other ships were supplied with good water. Finally, the nine soldiers on the ' Argo' who escaped were said to have purchased wholesome water from the crew of that vessel." If the ingestion is by water, a fresh source must be obtained. Well- water is generaUy safe, but not always. Rain-water may be unsafe, if the tanks are not clean. If a fresh source cannot be obtained, filtration and boiling, as well as infusion with tea or coffee, appear to be the best preventive measures. If the introduction be by air, and if the locality cannot be left, the most approved plan is elevation to at least 500 feet above the source of the poison in temperate climates; and 1000 to 1500 feet in the tropics, or higher still, if possible. ^ If this plan cannot be adopted, two points must be aimed at— viz., to obviate local, and to avoid drifting malaria. Thorough subsoil draining; fiUing up moist ground when practicable ; paving or covering the ground AAdth herbage kept closely cut, are the best plans for the first point. 3LATE X. J K L M N OP $ % /V*? ■9 MALARIA PARASITE. * 4 ^ Q *' - ^ <^ ^ V •" ft t ** * if ' N 0 P Q 4 MEASLES. 637 For the second, belts of trees, even walls can be interposed; or houses can be so built as not to present openings towards the side of the malarious currents. The houses themselves should be raised above the ground on arches; or, if wooden, on piles. Upper floors only should be occupied. The early morning air, for three hours after sunrise, should be avoided, and, next to this, night air. MEASLES. Although the original seat or native home of measles is unknown, there can be no doubt that it is a disease of very ancient origin, and in earlier times Avas often confounded with other maladies, more particularly small- pox and scarlatina. In the present day it is well established throughout Europe, Asia, America, and those parts of Africa of Avhich we have any exact information: in all these parts it occurs in frequent epidemics. Attempts have been made to show that measles assumes an epidemic or even pandemic character with a certain amount of regularity, almost amounting to a definite periodicity. Without going so far as to accept this vieAv entirely, it may be admitted that in large communities the disease does tend to occur epidemically at intervals of from two to four years, disappearing between these epidemic outbursts more completely than do some of the other exanthemata. In small communities, especially in rural districts, these intervals are not only less regular but longer. Influence of Climate and Season.—The practically universal distribution of measles throughout the world indicates that its occurrence is independent of chmatic influences: at the same time the influence of season is every- Avhere observed. In temperate climates, of 530 epidemics of measles in Europe and North America which Hirsch records, 339 occurred in the colder, against 191 in the warmer months. And the same thing has been observed in the tropics. In this country the effect of season upon urban measles has been studied by Buchan and Mitchell, and by the Registrar- General. The latter, from an analysis of the weekly deaths from measles in London for the fifty years 1841-90, points out that the weekly curve of deaths shows a double maximum and minimum, the larger maximum falhng in November, December, and January, with an extreme excess of 50 per cent, in the fourth week of December, and the smaller in May and June, with an extreme excess of 25 per cent, in the first week of June. The larger minimum falls in August, September, and October, extreme deficit being 45 per cent, below the average in the last week of September; and the smaller minimum in February and March, the extreme deficit being 30 per cent, below the average in the third week of February. Buchan and Mitchell's analysis of the London death-rates for the thirty years, 1845 to 1874, gives very similar results. These facts accord with the conclusions arrived at by both Ballard and Moore that a mean atmospheric temperature above 60° F. was not favourable to the spread of this disease, and. that a mean temperature below 42° F.. was equally inimical to its prevalence. Influence of Race, Sex, and Age.—Neither as to liabdity to attack nor to mortality does racial difference appear to have any effect. Similarly sex and age appear to be without direct influence upon liabdity to attack, but have some influence upon mortality. On the whole, the mortality is greater among males than females, especially among children under two years of a«e. About 98 per cent, of all deaths occur among chddren under ten years of age, 90 per cent, among those under five, 75 per cent, among those under three, and 60 per cent, among those under two (Squire),—the maximum 638 THE INFECTIVE DISEASES. mortality as Avell as the maximum rate of mortality being in the second year of life. Mortality.—Of late years the mortahty from this disease has undoubtedly shown a tendency to decrease. The following figures show the facts as given by the Registrar-General in his various reports for the last ten years :— England and AVales. Average Annual Death- Year. rate per million living for Total Deaths. Death-rate per million living. each Five-Year Period. 1884 11,324 419 1 1885 14,495 533 1 1886 12,013 436 1-467 1887 16,765 602 i 1888 9,784 347 J 1889 14,732 518 1 1890 12,386 439 1891 12,673 436 j-445 1892 13,553 460 1893 11,110 374 J The case mortality of measles is capable of varying within very Avide limits, ranging from as little as 2 per cent, in some outbreaks to 40 or 50 per cent, in others. In this connection possibly there are two causes at work, namely, extra intensity of infection and unfavourable surroundings, such as overcrowding, poverty, and fatigue. In an epidemic in Fiji in 1874 all these conditions were operative, together with a probable maximum susceptibility, with the result that the mortality was enormous. The marked influence of insanitary and other unfavourable surroundings upon measles mortality is well shown in mUitary experiences. " In Paris, during the siege (January 1871), out of 215 of the Garde Mobile who took measles, 86, or 40 per cent., died; and the mortality reached very nearly the same figure among the French troops who returned to Paris after the Italian War, 40 out of 125 cases dying in one hospital whose sanitary condition was bad." Even in this country the case mortality is higher always among the very poor, and in overcrowded districts. Etiology and Infectiveness.—Arguing from analogy we may assume that the virus of measles is a specific micro-organism, and such has been recently demonstrated in the blood by Czajkowski. The infection is held to be given off by the breath and mucus, possibly also by desquamating cuticle, though this is less certain. The poison undoubtedly is capable of being air-borne and tends to cling to fomites and to hang about ill-ventilated rooms. There is no evidence of its being conveyed by either water, milk, or food. Infection is probably always acquired by inhalation. The incubation period varies from eight to twenty days, the usual limit being about eleven days. The infective period, or that during which the patient is capable of infecting others, begins with the earliest symptoms. It is probably greatest during the pre-eruptive stage, and whde the catarrh and rash are present; there is reason, however, to think that it extends through- out the illness, and even to some extent during convalescence. As a general rule, it may be laid down that infectivity is usually over by the end of the fourth week, provided aU cough and desquamation have ceased. One attack of measles usually confers a lasting protection against future attacks; but second attacks sometimes do occur. MUMPS—PLAGUE. 639 Prevention.—This involves isolation of the sick, and arrest of contagious matter by inunction with carbolised vaseline or glycerin; antiseptic inhala- tions, and. use of rags for wiping the eyes and nose, these afterAvards to be burnt. Clothing, bedding, and rooms should be disinfected. MUMPS. This affection has, at times, all the characters of an epidemic disease, but it is probably endemic in certain localities, especially in large centres of population. At certain seasons, particularly in the spring and autumn months, the number of cases increase rapidly. It is most common in children from ten to fifteen years of age, but the greatest registered mortahty is among the very young. Males are, perhaps, more frequently attacked than females, though in institutions and schools the disease has been known to affect over 90 per cent, of all the children. Speaking generally, the mortahty from mumps is insignificant, some eighty deaths only being registered annually as due to this disease among the entire population of England and Wales. The infection of mumps is supposed to be given off by the breath, but as yet no specific organism has been isolated in respect of this infectivity. The period of incubation seems most usually to be from a fortnight to three weeks, and is probably seldom much less than twelve days. The period of infectivity seems to extend over at least three weeks. One attack of mumps usually confers immunity, but second attacks are not unknown. At times this disease occurs in close association with measles and diphtheria, and less often with scarlet fever; but whether this apparent relationship is anything more than an accidental one is doubtful. There is no evidence to suggest any connection between mumps and any particular conditions of soil. Prevention depends upon ordinary measures of isolation and hygiene. PLAGUE. The recrudescence in 1894 of the bubonic plague of history in Canton, Hong-Kong, and other parts of China demands a brief reference to this disease. The first historical notice of the plague refers to an epidemic in Libya about 98 a.d. ; but throughout the Middle Ages occur constant references to its epidemic prevalence not only in Persia, India, China, Syria, and Asia Minor, but also in Egypt, Arabia, North Africa, Italy, France, England, Germany, and Europe generally. Since 1841 the disease has been unknown in Europe. The whole history of the disease indicates its tendency to recur in places Avhere it has been once prevalent, and to be carried by trade routes from these centres. A consideration of the events in connection with its previous manifestations enables one to trace its carriage in every case to the affected districts from one or two places where it is, or has been endemic; these endemic foci being mainly the Euphrates Valley and Southern China. It appears to be confined to the northern hemisphere, and only to flourish between 20° and 40° north of the equator, and never to have existed in the New World at all. The disease is a specific disease, caused by a specific portable organism, Avhich has a variable length of life, according to the conditions in which it finds itself, and a varying virulence, also influenced by these conditions. The disease is intensely contagious, selecting usually the poorest classes as its victims, or those hving under chcumstances of overcrowding and in the 640 THE INFECTIVE DISEASES. absence of adequate ventilation, or a proper food supply. It is inoculable on certain mammals, producing in them a disease similar to that seen in human beings, and possibly may be communicable by animals to man : it becomes epidemic at times, and is readily communicated by person to person, under insanitary and squalid surroundings, stimulated apparently by unfavourable meteorological conditions, such as prolonged drought, &c. Kitasato and Yersin have demonstrated an organism in 25 out of 30 cases of the disease in the blood, spleen, and buboes of those affected. This organ- ism is an ovoid capsulated bacillus, the poles of Avhich are more readily stained than the middle. It is slightly motile, and grows best in blood-serum at 28° C. to 30° C. No spore formation has been observed. Mice, rats, and guinea-pigs inoculated Avith, or fed upon pure cultures of this bacillus present symptoms and pathological appearances identical with those of the human sufferer, the same bacdli being recoverable from the blood and viscera of the animals experimented upon. These bacilli have been detected in the dust and in earth from the floors of plague-stricken houses. Antecedent to epidemic outbreaks of plague, rats and mice appear to be affected with an epizootic disease, but the exact connection (if any) of which with plague is not known. The plague bacillus is remarkable for its polymorphism, and when culti- vated in the usual solid media it is seen to be accompanied by round figures hke cocci, and elongated bacilli. In liquid culture media it forms little chains of several members placed end to end. Often at the extremity or in the middle of the chaplet is seen a large very deeply stained sphere. On gelatin the microbic colonies are white, at first transparent, but presenting later a more opaque and yellowish centre. In broth or peptones it forms tiny pulverulent clots, Avhich settle to the bottom of the tube and along its sides. The broth remains clear. Prevention depends upon isolation of the sick, thorough disinfection of the clothing, and avoidance of overcrowding. PNEUMONIA. Under this heading we refer to an infectious and not infrequently epidemic form of pneumonia, indifferently spoken of as " epidemic pneumonia," " croupous or fibrinous pneumonia," "pneumonic fever," and " acute lobar pneumonia," occurring as a so-called idiopathic affection. Epidemics of this malady have been described in considerable numbers in England and various other parts of Europe during the last two centuries; the most recent epidemics of importance being those recorded for India (Punjab) in 1875 and 1882, and for this country those occurring at Middles- brough in 1888, and at Scotter in Lincolnshire in 1890. To these might be added many instances on record of outbreaks of pneumonia which, while remaining limited to a single household or small circle, presented facts strongly suggestive of specific infection. Influence of Climate and Season.—Assuming that pneumonia, even in its narrowest acceptation of fibrinous or so-called croupous pneumonia, is an anatomical term that includes several inflammatory processes differing from one another in their etiology, the curious prevalence of the malady in both cold and hot countries indicates that climate alone has not much influence upon its prevalence. This, however, is not the case in respect of season. Statistics everywhere show that more persons are attacked in the winter and spring than in the summer and autumn. Seitz's large statistics of 5905 cases in Munich give 32 per cent, in winter, 36*8 per cent, in spring, 15*3 per cent, in summer, and 15*7 per cent, in autumn. So also Hirsch, in an PNEUMONIA. 641 analysis of a large number of cases in various places, states that 29 per cent. Avere attacked in winter, 34*7 per cent, in spring, 18 per cent, in summer, and 18*3 per cent, in autumn. The seasonal curve of epidemic prevalence coincides very closely with that of sporadic pneumonia mortality, which has its maximum in December, and is high from November to April. From these facts, it is evident that the prevalence of pneumonia—epidemic or otherAvise—is associated with the colder months, and a closer analysis shows that in every climate the greatest prevalence of pneumonia occurs at the season of the most rapid and sudden changes of temperature, be it winter or spring, and in some measure varies with the intensity of changes of tem- perature. Nothing conclusive has been estabhshed as regards the influence of rainfall or soil conditions upon pneumonia, though it has been asserted that absence of rain and a Ioav level of the ground water are favourable conditions. Influence of Race, Sex, and Age.—No race can be said to be exempt, but many coloured races are especially susceptible to it. Longstaff, who has critically analysed the deaths from pneumonia, extending over some years, states that, as regards sex, the mortality is greater for males than females at all ages in the proportion of three to two. " The disparity is most marked at ages 35 to 65, when males suffer more than females, in the proportion of two to one." According to Wilson Fox and Huss's statistics, the fatality among the two sexes, given an equal number of attacks for each, is males ten, females fourteen, or in other words, that although the liabihty to attack is much greater in males, the habihty to death if attacked is greater in females. With respect to age, " the recorded mortality is highest at the extremes of life, being about three times as great in the first year of life as in old age." The minimum mortality is in the thirteenth year, after Avhich it steadily rises throughout the remainder of life. The case mortahty is actually greatest in advanced life. Of the general fatahty of pneumonia at all ages together it is difficult to quote exact figures, as this varies in different times and places. A general average puts it at about 10 per cent., but it has been as low as 5 per cent. A widespread and fatal epidemic of pneumonia occurred at Middlesbrough in 1888, and Avas investigated by Ballard. Out of 1633 cases in a population of 97,000, 369 ended fatally, the case mortality being 21 per cent. The poorer classes suffered more than the wealthy, and cases were exceptionally severe and numerous in the work- house, where grave sanitary defects existed. The workhouse children suffered six times, but adults only one and a half times as much as the corresponding classes outside. Exposure and fatigue seem to have acted as predisposing causes, and many apparent instances were recorded of direct infection from contact with a sick person. Etiology.—Of all factors, cold or chill has been thought to be one of the most important, and for years Avas regarded as the efficient cause of this disease. Undoubtedly pneumonia does follow promptly, sometimes, a sudden chilling or wetting, but in a large majority of cases no such history can be obtained. Exposure to extreme cold or sudden changes of tempera- ture may increase the activity of infection or the susceptibility of the individual, but nothing more. All depressing conditions, such as anxiety, fatigue, poverty and debility, predispose to pneumonia. Insanitary condi- tions, especially filth, overcrowding, and want of ventilation, act apparently as powerful, though not indispensable, predisposing causes. Effluvia from drains, sewers, and graveyards have also been held responsible for outbreaks. It is not unusual to find repeated outbreaks occurring in the same buildings, especially casemate barracks and prisons. 2S 642 THE INFECTIVE DISEASES. The pneumococcus of Frankel is the most constant organism in lobar pneumonia, and is now generally regarded as being the specific agent of the disease. It is identical with the micrococcus Avhich Pasteur and Stern- berg found in the saliva of certain individuals, and Avhich produces septi- caemia in the rabbit. It occurs occasionally in the nose, the larynx, and the Eustachian tube. According to Netter's observations, it is present in the buccal secretion in 20 per cent, of healthy persons. It persists for months or even years in the saliva of persons avIio have had pneumonia. The researches of Frankel, Weichselbaum, Gamaleia, and others show that it is by far the most constant organism in pneumonia, and that it occurs in the secondary processes of the disease, such as pleurisy, endocarditis, pericarditis, and meningitis. In the sputum it may be demonstrated by treating the ordinary cover-glass preparations with glacial acetic acid, and then, Avithout washing off the acid, dropping on aniline oil and gentian-violet, which is to be poured off and renewed two or three times. The organism is seen to be a somewhat elliptical lance-shaped coccus occurring in pairs, hence the term diplococcus by Avhich it is sometimes known. It is usually encapsulated. According to the modern view, pneumonia is an infective disease caused by this diplococcus, which has its seat of election in, and produces its chief effects on, the lung, and which can, under favouring circumstances, invade other parts of the body. It is a widespread organism, at times present, as before stated, in the buccal _secretions_of healthy persons. It is not improbable that the various predisposing causes, such as cold, exhaustion, and debility, loAver the vitality and render the individual susceptible, thus changing the character of the tissue-soil so that the virus can grow and produce its specific effects. Several varieties of the pneumococcus have been described, differing from one another in the symptoms they produce in animals. These varieties differ from one another only in virulence, and by suitable means can be converted. into one type. It is important, however, to bear in mind that the pneumococcus in the human subject varies enormously in virulence ; this fact partially explains the degrees of severity of the symptoms in different cases. Our knowledge of the toxins of the pneumococcus is still very defective. In artificial cultivations only feeble toxins are produced, and it is thus difficult to study their action carefully. There is, however, sufficient evidence to show that the toxins produce similar constitutional symptoms to those caused by infection with the pneumococcus. The fact that the pneumococcus is found in many diverse conditions has been urged by some as an argument against the view that it is the cause of pneumonia. We are unable to accept this argument, as it is a general laAv in pathology that the same micro-organism may produce a different train of symptoms according to the part attacked. The tubercle bacillus causes a different type of disease when it attacks the joints, lungs, brain, or peritoneum. We are just as much justified in speaking of a pneumococcal otitis or a pneumococcal pleurisy as we are of speaking of a tuberculous otitis or a tuberculous pleurisy. As Washbourn has pointed out, although the pneumococcus is the cause of croupous pneumonia, yet for the disease to develop there must be other factors than the mere presence of the micro-organism. " There must be some predisposing cause, for the pneumococcus is widely distributed, and is often present in the mouths of healthy persons without producing any ill effect. Under ordinary circumstances, the protective mechanism of the PUERPERAL FEVER. 643 body prevents invasion; but should the cocci be introduced in very large numbers, or should the natural resistance of the body be lowered, invasion occurs and the disease develops. In many cases both these factors operate. The introduction of a large number of germs perhaps determines the seasonal prevalence of the disease." "As to predisposing causes, influenza is the one best known. The other predisposing causes of pneumonia, such as cold and fatigue, are not capable of direc'3 proof. Experimental evidence tells us that exposure to cold and fatigue renders animals susceptible to bacterial infections which in the normal condition they were able to resist. It is interesting to note in this connection that the growth of the pneumococcus outside the body is greatly influenced by very slight changes in the composition of the medium. By analogy we might suppose that slight changes in the composition of the body fluids would be favourable or unfavourable to the growth of the coccus; but this analogy must not be strained, for it would be incorrect to compare too closely the conditions within the body Avith those occurring in test-tube experiments." In the Middlesbrough epidemic, above alluded to, and investigated by Ballard and Klein, the latter, Avhile failing to find Frankel's diplococcus in the morbid tissues, discovered large numbers of short bacilli, which he named Bacillus pneumonias. Inoculation of human lung-juice or of cultiva- tions of this bacillus into mice caused an acute disease, the chief and constant lesion of which Avas pneumonia; further inoculations from such mice imparted the same disease to other mice. Samples of bacon were purchased in the infected districts, and it was found that of mice fed upon this bacon a large proportion became ill, with the same symptoms as those detailed. The Bacillus pneumoniae was recoverable by cultivation from their tissues, and by inoculation the disease could be transferred to other mice. Whether the bacon had or had not become infected by human cases of pneumonia is not clear, but it may be suspected that the disease was capable of being spread by means of infected food. It may be added here that in two out of five cases of croupous pneumonia following after influenza Klein has found the same bacillus in large numbers, almost in pure culture, its cultural characters and its pathogenic action on mice being the same as in the Middlesbrough cases. It is probable that these Middlesbrough cases were exceptional forms of pneumonia, and possibly not unconnected with influenza, though how exactly so connected it is, at present, impossible to say. The incubation period of pneumonia appears to be short, frequently being about from five to seven days. Both the breath and sputa may be assumed to be infective. Prevention.—On the supposition that pneumonia is, or may be, infective, the sputa should be received into vessels containing some disinfectant. Soiled handkerchiefs should be well boiled before Avashing. Care should be taken to avoid chills and exposure to extremes of heat and cold. All dwelling-rooms should be scrupulously well ventilated, and care taken to see that sewer air does not gain access to the habitation. PUERPERAL FEVER. The deaths in England and Wales from this disease, as recorded by the Registrar-General, during the last ten years are given beloAV. From the following table it Avill be seen that the mortahty from puerperal fever, as registered, is showing a tendency to increase, the rate being calculated on 644 THE INFECTIVE DISEASES. the proportion of deaths from the disease to the annual number of births. Unless explicable by improved accuracy in certification, this increase in the puerperal fever mortality is remarkable, because the application of modern knoAvledge as indicated by the use of antiseptics and generally improved hygienic conditions in the management of lying-h hospitals has led to a very marked dechne in the puerperal fever mortality in such institutions. The increased and sustained mortality from this disease suggest that the conditions under which women are confined outside hospi als, especially in the homes of the poor, have not in an equal degree shared in the improved sanitary conditions of hospitals and maternity institutions. This improve- ment can only be brought about by a full appreciation of the fact that puerperal fever is essentially a septic process, the virus gaining access to the body through the mucous surfaces of the uterogenital tract, to which it may be readily conveyed from case to case by the hands, instruments, sponges, clothing, bedding, and other articles. Year. Puerperal Fever Deaths. Births. Puerperal Fever Deaths to a Thousand Births. 1884 2,468 906,750 2-7 1885 2,420 894,270 2-7 1886 2,078 903,866 2-3 1887 2,450 886,331 2-8 1888 2,386 879,868 2-7 1889 1,852 885,944 21 1890 1,956 869,737 2-2 1891 1,973 914,157 2-2 1892 2,356 897,957 2-6 1893 3,023 914,542 3-3 There is evidence to shoAV that the infection may come from various septic and decomposition sources other than those of the lying-in room; the chief sources of such infection being the handling of post-mortem materials, and the close attendance upon persons suffering from septic maladies. Allusion | has already been made to the fact that erysipelas may have some causal | connection with puerperal fever, while less definite evidence is forthcoming that possibly scarlet fever and other infectious diseases may operate in a I simdar manner. Besides these, various other causes play an indirect but none the less important part in the origin or at least the maintenance of puerperal fever. These are overcrowding, insufficient ventilation, drainage defects, accumulations of filth, and want of cleanliness generally. Nowhere have the influences of these conditions been more manifest than in the experiences of lying-in institutions and hospitals whose wards have been allowed to get overcrowded, imperfectly ventilated, and generaUy dirty. On the other hand, any marked improvement in these respects has always been followed by a marked diminution in puerperal mortality. Puerperal fever shows similar annual curves to those of rheumatic fever and erysipelas, not only in this country but also on the Continent. This does not necessarily or probably mean identity of virus, but it is suggestive that the view that want of antiseptic care alone accounted for puerperal fever is not tenable unless it be imagined that in England and in Germany there was in years of excessive mortahty from puerperal fever a conspiracy of careless- ness. The years of excessive puerperal fever prevalence are generally years of small rainfall, and marked by low levels of the ground Avater; and the explanation of its epidemic prevalence probably lies in the favouring influ- RELAPSING FEVER. 645 ence of a dry and warm subsoil on its specific contagium. From this point of view, puerperal fever is essentially a sod disease, having close relationships Avith erysipelas and other septicaemic diseases. Whether its contagium is alternately parasitic and saprophytic, or each case implies a fresh infection from the soil, is doubtful; but in any case, as based upon analogy with some other diseases, the belief is gaining ground that puerperal fever has wider etiological relations than has been hitherto generally recognised. RELAPSING FEVER. Under the names of " famine fever " or " bdious typhoid " this disease Avas first clearly recognised in 1739 in Ireland, where it still may be said to have its principal focus, at least so far as the United Kingdom is concerned. Epidemics of this affection have not been infrequent in Scotland, and have also occurred in England, Northern Europe, the Levant, India, and elsewhere. Relapsing fever appears to be entirely independent of soil and largely so of season or climate. It occurs remarkably often in connection with typhus fever, and is apparently closely related to it in etiology, as the two diseases frequently coincide, or one follows the other closely, or isolated cases of the one are observed during the prevalence of the other. This frequent associa- tion of the two diseases is mainly to be explained by the fact that their predisposing causes are simdar, the diseases themselves being specifically distinct. That the two diseases are distinct is believed mainly upon the following considerations: (1) that they present marked clinical differences; (2) that one disease does not protect against the other; (3) that the one disease does not give rise to the other; (4) that the peculiar spirdlum, characteristic of the blood of relapsing fever, is not observed in the blood of typhus patients. It is, however, only just to state that there have not been Avanting critics Avho have questioned the general accuracy of the second and third considerations. Even if both these considerations are found to be untrue, it may still be that the two diseases are mere evolutionary forms of a common stock, but " breeding true and consequently each producing only its own kind." The mortality from relapsing fever in England and Wales during recent years has been insignificant: in 1891 there were eleven deaths from this cause, in 1892 there were seven, and in 1893 there were nine. The case mortality is low, varying from 2 to 4 per cent. More males appear to be attacked than females, but more females die than males when so attacked. The fatality of relapsing fever is very Ioav during the early years of life, but increases as age advances. Murchison gives the folloAAdng figures from the London Fever Hospital:— Under 30 years, 1366 cases Avith 7 deaths, or 0*51 per cent. Above 30 „ 745 ,, 32 ,, 4'29 „ „ 50 „ 191 „ 18 „ 942 „ „ 60 „ 72 „ 9 „ 12-50 „ Etiology.—While the predisposing causes of relapsing fever appear to be identical with those of typhus, namely, overcroAvding, filth, and starvation, the actual phenomena of the disease are regarded as being essentially dependent upon the presence in the blood of a particular spirillum, dis- covered by Obermeyer during the febrile stage, and which disappears from 646 THE INFECTIVE DISEASES. the blood immediately before the end of the febrile stage. The spirilla are very thin and about 20 y to 40 y long, their movement being that of rapidly progressing spirals. Immediately preceding the febrile stage of the disease they appear in the blood, groAv more and more numerous during the fever, and disappear again completely from the circulation before the fever quite ceases. During the non-febrile stage they probably take refuge in the spleen and bone marrow, where, perhaps, they undergo germination and reproduction. These spirilla have not as yet been satisfactorily cultivated, but that they are the real microbial causative agents of relapsing fever is proved by the experiments of Vandyke Carter and others, who have pro- duced typical relapsing fever in apes after injection of blood taken from a patient during the febrile stage and containing the spirilla. Exact data as to the incubation period of relapsing fever are Avanting, but from Avhat facts are known, it would seem to be from fourteen to twenty-one ; days. When once established, the disease is highly infectious, the virus being / apparently conveyed through the air, or by fomites, from the sick to the healthy. With free ventilation the disease almost ceases to be communi- 1 cable. Relapsing fever appears to afford httle or no protection against sub- sequent attack, as second attacks are by no means uncommon. Prevention.—Recognising the fact that this disease is one of the most contagious of the infective diseases, preventive measures consist in prompt isolation of the sick, the freest ventilation, and the most thorough disinfec- tion of clothing. Other prophylactic measures of the first importance are those Avhich combat poverty and destitution. ROTHELN. In this and other countries there occasionally occur both sporadic and epidemic cases of an ailment having some of the appearances of measles and some of those of scarlet fever, but stdl not conforming strictly to the clinical and epidemiological characters of either. This malady, seemingly different from measles and from scarlet fever, but having some of the charac- ters of both, is commonly spoken of as " rubeola," " rb'theln," or German measles. Many have regarded it as a hybrid of scarlet fever and measles, but the more generally accepted vieAv is that it is an entirely distinct and specific disease. The disease is undoubtedly infectious, but never very markedly so. The infection is given off probably by the breath and acquired by inhalation. The period of incubation is somewhere about fourteen days, while its period of infectiveness lasts from two to three weeks. The case mortality is low, and there are no very special features in respect of either the influence of age, sex, or race upon its incidence. This malady is of special interest to the public health officer, as the term "German measles "is very loosely employed, and too often is alloAved to serve as a cloak to uncertainty in diagnosis. As Goodhart has pointed out, "a doubtful rash makes its appear- ance, and the medical man, instead of saying he is not certain of its nature, calls it German measles. 'Then it is not scarlatina?' say the parents. ' No,' says the doctor; and the parents, thinking nothing of measles, take no precautions." When we bear in mind that true rotheln is reaUy a very rare disease, it needs httle imagination to realise how many cases of either measles or scarlet fever are probably overlooked annually, and permitted to disseminate their specific infection involuntarily but none the less surely throughout the community. SCARLET FEVER. 647 SCARLET FEVER. We owe the recognition of scarlet fever as a distinct disease to Sydenham, before whose time it was confounded Avith measles, and occasionally with diphtheria. It is most Avidely diffused in Northern and Western Europe and in North America, but has failed to establish itself firmly in Africa or any part of Asia, except Syria and some parts of Asia Minor. The disease occurs sporadically from time to time, and then under unknown conditions becomes widespread. Ransome, from a study of the Swedish scarlet fever mortality records, says that "not only a short cycle of four to six years may be traced, but also a long undulation of fifteen or twenty years or more; Avhich may be hkened to a vast Avave of disease upon Avhich the lesser epidemics show like ripples upon the surface of an ocean swell." Whitelegge, at Nottingham, found that scarlet fever shows a weekly cycle, the notified cases fading to a minimum on Wednesday. This he regards as probably due to the lessened chances of infection through school attendance upon the Sunday. In England scarlet fever is more prevalent in urban than in rural areas, mining and several of the large manufacturing towns being especiaUy affected. In explanation of this it has been suggested that " probably the population in industrial and mining counties live in more than averagely close aggregation, and that the spread of infection is thus facilitated. If, however, this were the true and complete explanation, we should expect the geographical distribution of other infectious diseases to tally with that of scarlet fever." But this, the Registrar-General remarks, "is not true as regards diphtheria; nor does it seem altogether true as regards measles." Both Longstaff and Barnes have shown the marked difference between the distribution of diphtheria and scarlet fever; in fact, broadly speaking, it may be said that Avhere the latter disease is most prevalent there a particularly Ioav diphtheria rate prevails. Influence of Climate and Season.—While climatic influences do not appear to play a very prominent part in determining the geographical distribution of this disease, there is evidence that season does influence its prevalence. In England the mortality is at its minimum in March and April, and rises to a maximum in October. In New York, hoAvever, the curve is almost reversed, the minimum being in September and the maximum in April (Whitelegge). From their analysis of the deaths from scarlet fever registered in London in the thirty years 1845 to 1874, Buchan and Mitchell conclude that this disease has its maximum from the beginning of September to the end of the year, and its minimum from February to July. The period of the highest death-rate is from the beginning of October to the end of November, being nearly 60 per cent, above the average, and the lowest in March, Aprd, and May, Avhen it is about 33 per cent, below its average. In each of the thirty years the deaths increased at the time of mean maximum, and in all except four of the years the increase A\ras considerable. During ten of the years a high death-rate was continued on into the year immediately following, but in every year the deaths became fewer, and diminished steadily, if not rapidly. Whitelegge, by a table based on the notification returns of twelve large Enghsh and Scottish toAvns, has shown that—as was to be expected—the seasonal curve of notified attacks differs little in outhne from the mortality curve; but the seasonal range of variation is greater in the attack curve,—in other AArords, the mortality rises and falls proportionately less than the cases do, indicating that at the season of the year in Avhich the disease is most pre- valent it is least fatal, and vice rersa. 648 THE INFECTIVE DISEASES. As to the meteorological conditions that are most favourable to the spread of scarlet fever and its mortality, there is a wide divergence of opinion. Upon the whole, there appears to be an inverse relationship between the mortality from scarlet fever and the rainfall; or, as Ballard puts it, " a temperature above the average for the season, and a dry state of the atmos- phere with little rain, favour the prevalence of scarlet fever more than the reverse conditions." Influence of Age and Sex.—The influence of age and sex upon liability to attack and death by scarlet fever were fully discussed by the Registrar- General in his 49th Annual Report, 1886, and the important conclusions at which he arrived are thus stated:—"1. The mortality from this disease is at its maximum in the third year of life, and after this diminishes with age, at first slowly, afterwards rapidly. 2. This diminution is due to three contributory causes : (a) the increased proportion in the population at each successive age-period of persons protected by a previous attack; (b) the diminution of liability to infection in successive age-periods of those Avho are, as yet, unprotected; (c) the diminishing risk in successive age-periods of an attack, should it occur, proving fatal. 3. The hability of the unpro- tected to infection is small in the first year of life, increases to a maximum in the fifth year or soon after, and then becomes rapidly smaller and smaller with advance of years. 4. The chance that an attack will terminate fatally is highest in infancy, and diminishes rapidly Avith years to the end of the tAventy-fifth year, after which an attack is again somewhat more dangerous. 5. The female sex throughout hfe, the first year possibly excepted, is more liable to scarlet fever than is the male sex. 6. But the attacks in males, though fewer, are more likely to terminate fatally." These conclusions of the Registrar-General have been largely confirmed by an independent inquiry made by Whitelegge, upon the basis of 6288 cases of scarlet fever notified in the three large towns of Nottingham, Salford, and Leicester. From his investigation, Whitelegge draws the folloAving practical conclusion : " That in shielding a child against infection during the first feAv years of life there is a double gain ; every year of escape from scarlet fever renders him less and less susceptible, until finally he becomes almost insusceptible ; and, secondly, even if he should ultimately take the disease, every year that the attack is deferred reduces the danger to life which it brings." Mortality.—The following table, compiled from the annual reports of the Registrar-General for England and Wales, sIioavs the mortality from scarlet fever during the last twenty years. Year. Total Deaths. Death-rate per million living. Average Annual Death-rate per million living for each Five-Year Period. Year. Total Deaths. Death-rate per million living. Average Annual Death-rate per million living for each Five-Year Period. 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 24,922 20,469 16,893 14,456 18,842 17,613 17,404 14,275 13,732 12,649 1,050 851 691 585 753 694 675 548 521 475 1 1-786 J 1*582 1 J 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 10,863 6,355 5,986 7,859 6,378 6,698 6,974 4,959 5,618 6,982 402 233 218 282 226 235 242 171 190 235 1 J-272 J 1-214 1 J SCARLET FEVER. 649 Even after making allowance for the facts that not only do different out- breaks vary very greatly as regards mortality, but that epidemic prevalences tend to occur in cycles, it is justifiable to regard these figures of so long- continued and marked an abatement in scarlatinal mortality as an indication that some at least of the means conducing to the spread of this very fatal disease are being materially restricted. Even noAV the death-rate from scarlet fever is still unduly high in some counties. The 1893 returns show a death-rate of 308 per milhon in Lancashire, 316 in Monmouthshire, 329 in London, 355 in Nottinghamshire, 356 in Herefordshire, 375 in Leicester- shire, 467 in Middlesex, and 521 in Cornwall. The case mortality or fatality of scarlet fever varies largely in different epidemics and even at times during the different stages of the same epidemic. As a general average it may be said to be about 8 per cent., but may reach at times as high a figure as 30 per cent. The reports of the Metropolitan Asylums Board show that the mortality amongst cases treated in their hospitals was 6*18 per cent, in 1894, against an average of 8*35 per cent. in the six years 1887 to 1892. The case mortality above given (6*18 per cent.) is somewhat high when compared with that of other toAvns. In Brighton the case mortahty in 1894 for home-treated cases Avas 2*56 per cent., for hospital-treated cases 1*3 per cent. In Leicester in the same year it was 3*9 per cent, for home-treated cases, and 2*17 per cent, for the hospital-treated cases. Without an allowance being made for variations of age-distributions of patients comparisons between one locality and another are apt to be fal- lacious. But the relatively high rates in the Metropolitan Asylums Board hospitals suggest the idea of an increased virulence of scarlatinal infection caused by an aggregation of patients on too large a scale. The following table summarises the result of the treatment of 81,350 cases in the Metro- politan Asylums Board hospitals in the years 1871-94. Males. Females. Combined Mortality per cent. for both Sexes. Under 5 18*1 17-0 17*6 5-10 5-6 5-1 5-3 10-15 2 3 2-4 2-4 15-20 3-0 2-3 2-6 20-25 2-3 2-8 2-6 25-30 3-8 2-8 3-3 30-35 5-2 4-3 4-7 35-40 8-1 4-4 6-2 40 and over 8-2 4-5 6-3 Etiology and Infectiveness.—The contagion of scarlet fever is probably not developed until the eruption appears, and is particularly to be dreaded during desquamation. No doubt the poison is spread largely by the fine scaly particles which are diffused Avith the dust throughout the room. Even late in the disease, after all desquamation has apparently ceased, a patient has conveyed the contagion; in these cases, however, there is usually to be detected some discharge from or dried purulent matter attaching to the auditory meatus, which possibly is equally infective as any purely cuticular particles. The poison chngs with great persistence to clothing of aU kinds and to articles of furniture. In no disease is a greater tenacity displayed. Bedding and clothing which have been put away for months or even for years may, unless thoroughly disinfected, convey contagion. The infection 650 THE INFECTIVE DISEASES. of scarlet fever seems to be given off by the breath, the secretions from the nose, mouth, pharynx, ears, and perhaps kidneys, as Avell as by the desquamating cuticle. It may apparently cause the disease either by being inhaled or SAA-allowed. There is no evidence of its being conveyed by water, and inasmuch as the disease does not appear to spread in the neighbourhood of fever hospitals, it is doubtful whether the infection can be conveyed any great distance by air currents. Although Boobbyer has recorded a series of cases of scarlet fever, the incidence of which appeared to be determined by disturbance of soil, there is at present little evidence to shoAV that the disease has any definite relation to the soil. On the other hand, numerous epidemic outbreaks of scarlet fever are now known to have occurred in which milk was the vehicle of the contagium. Until 1882 all such milk epidemics were believed to be brought about by infection of the milk by the virus from a human case of scarlet fever; in fact, in a tabulated account of fifteen milk scarlatinas prepared by Ernest Hart, and published in vol. iv. of the Transactions of the International Medical Congress for 1881, several epidemics are detailed in which this mode of milk infection from a human source was clearly demonstrated. Later investigations by PoAver and Klein seem to show, however, that not only may milk be a medium of disseminating scarlet fever after its infection by virus from a human case, but that human scarlet fever may be produced by milk which owes its infective property to an ailment of the cow. The well-known " Hendon outbreak " constitutes so important and classical an instance of this class of epidemic that it demands some brief reference in detail. In December 1885 a sudden and extensive outbreak of scarlet fever occurred in Marylebone, and was found by Wynter-Blyth, the Medical Officer of Health, to be associated with a particular milk-supply obtained from a farm at Hendon. The milk was also distributed in St John's Wood, St Pancras, Hampstead, and Hendon; in each of these districts, except the first, scarlet fever became prevalent suddenly early in December. On the 15th the milk sent to Marylebone was returned to the farmer, and some of this was given away to poor people at Hendon on the following days; from the 20th onAvards a number of cases of scarlet fever occurred among those who had drunk the milk. There was, therefore, strong presumptive evidence that the disease was conveyed by the mdk. The whole outbreak was investigated by Power and Klein, on behalf of the Local Government Board, with the result that they found the cow itself Avas the source of infection. Their inquiries indicated that there had been no case of scarlet fever among either the employes or the neighbours of the dairyman that could reasonably be suspected of having infected the milk. On attention being next directed to the cows, many of them were found to be suffering, or to have recently suffered, from vesicles or ulcers upon the teats and udders. These were readdy demonstrated to be infectious, and had been first seen upon a coav which was bought on November 15th. The dates of outbreak of scarlet fever in each district being knoAvn, it was found that each outbreak was preceded by a few days by the introduction of this affection into the cow- sheds from which the milk-supply of the district was drawn. The early exemption of St John's Wood Avas explained by the fact that the disease had not appeared in the small shed from which alone its supply Avas drawn • but during the inquiry this shed became affected at last, and an outbreak in St John's Wood immediately followed. All the coavs shoAving any signs of the disease were then isolated, and no further cases of scarlet fever occurred among the consumers of the milk. The' symptoms noticed in the SMALL-POX. 651 cow were chiefly local, but there were bald patches of skin, especially about the tail and back, the epidermis in these patches being scaly and the cutis thickened. There Avas no pyrexia. The vesicles, which were small, were confined to the teats and udder. They extended, and in two days formed flat irregular ulcers covered with brown scabs. Inoculated upon calves, the matter from these ulcers caused local tenderness and swelling in three days, a scabbed ulcer with vesicular margin in six days, and a further extension during the next few days, followed by healing. From these ulcers, and from the diseased portions of the -viscera of these coavs, Klein isolated and cultivated a streptococcus which was identical with that which he had obtained from the skin and blood of scarlatina patients. This streptococcus Klein designates as the Streptococcus scarlatina?, and regards it as the microbe of scarlet fever. Among other cultural character- istics it solidifies milk if kept at 35° C. for two days, and is apparently distinct from the Streptococcus pyogenes and all other streptococci. Inoculation of calves with pure cultures of this Hendon micro-organism produced a constitutional disease that had many points of analogy with human scarlet fever, the condition of the kidneys, in particular, differing in no respect from acute scarlatinal nephritis. This theory of a bovine scarlet fever is rejected by the veterinary profession and by some medical authorities, but, apart from the facts connected with the Hendon outbreak, evidence is slowly accumulating, in association Avith other milk epidemics of scarlet fever, which indicate that there are sources of scarlatinal infection of milk other than those from cases of the human disease. Edington has also described a bacillus which he regards as the true specific microbe of scarlet fever, but his views in this respect are not generally accepted by competent critics. The incubation period of scarlet fever varies from one to six days, and the period of infectiveness extends from the earliest symptoms to the end of convalescence, necessitating an extension of the period of isolation in most cases to some seven or nine weeks. One attack usually confers immunity throughout life, though second and third attacks occasionally occur. ^ This disease is sometimes found closely associated with diphtheria, Avhile its apparent relationship with a form of puerperal fever has already been referred to elsewhere. Prevention.—Strict isolation is of the first importance, to which must be added the proArision of infectious hospitals and the practice of notification of the disease. Arrest of contagious material from the skin may be secured by inunction with vaseline, oil, or glycerin combined with eucalyptus, carbolic acid, or some other disinfectant. Antiseptic inhalations for the throat and nose' are of value. All clothing, bedding, furniture, and dwelling-rooms must be strictly disinfected. Mdk should be boiled, especially for children. The convalescent person should not be permitted to mix with others until all desquamation has ceased, the process being aided by repeated bathing in Avarm water to which a little Condy's fluid has been added, and supple- mented by thorough cleansing of all parts of the body with soap; The hair and scalp should be cleansed Avith a mixture of acetic acid, glycerin, and spirit. SMALL-POX. It is still a disputed point as to the country in which small-pox originated, though the earliest records of its existence are to be found in Hindustan and China, dating many centuries before the Christian era. The pesta magna 652 THE INFECTIVE DISEASES. described by Galen, and of which Marcus Aurelius died, is believed to have been smaU-pox. On the break up of the Abyssinian army at the siege of Mecca in 570 a.d., owing to the excessive prevalence of the disease among the soldiery, smaU-pox Avas gradually disseminated over northern Africa and into Asia Minor. Subsequently it spread to Europe, probably by the Moors through France and Spain, until by the eighth or ninth century it had reached Saxony, SAvitzerland, and England. The first accurate account of the affection was given by Rhazes, an Arabian physician, Avho died about 925 a.d., and Avhose description is available in Greenhill s translation for the Sydenham Society. It was introduced into the West Indies and America by the Spaniards early in the sixteenth century. In the seven- teenth century a study of the disease was made by Sydenham, who still remains one of the most trustAvorthy of the earlier authorities on the disease. In the present day, no part of the world can be said to be exempt from smaU-pox, or rather from epidemic outbreaks; whde in India, the Soudan, and Central Africa it is so constantly prevalent that those countries may be regarded as endemic foci of the disease. From time to time so-called pandemic extensions occur, involving large areas and characterised by a particularly malignant form of the disease. The last of these was that of 1871-2, which overran Europe and America, and was the cause in these islands of something like 40,000 deaths during the two years. Influence of Climate and Season.—As Hirsch says, "not many of the acute infective diseases show in their incidence and diffusion so complete an independence of the conditions of climate and soil." Season does seem to have some effect upon the spread of smaU-pox. In temperate climates, such as England, the mortality curve is above the mean from January to June, and below it from July to December. Taking India as a type of oriental countries, the maximum prevalence is in AprU and May, that is, in the hot season, but the onset of the rains invariably puts a check to the disease. In Europe and North America the maximum prevalence is usually during late Avinter and early spring. Influence of Race, Sex, and Age.—Negroes and all coloured races appear to have a peculiar susceptibility to small-pox, and, moreover, suffer a heavy case mortality. Among aboriginal races the disease is terribly fatal. When it was first introduced into America the Mexicans died by thousands, and among the North American Indians the mortality has been appalling. In respect of sex, at most ages the mortality is greatest among males, but in the second and third years of hfe, and from ten to fifteen years of age, the reverse is, to a slight extent, the case. In relation to age, as we shall see presently, the prevalence and mortality of smaU-pox is essentially a question of vaccination. In pre-vaccination times, about 90 per cent, of the deaths were at ages below five years, the actual maximum being in the second year. In the present day, the deaths under five years, being prac- tically limited to unvaccinated children, constitute about 30 per cent, of the total deaths from small-pox; and in this age-period the greatest mortality is in the first year. From this point it steadily diminishes until about the fifteenth year, rises to a second maximum about the twenty-fifth year, and then steadily falls again (M'VaU). The foUoAving table from the Report of the Medical Officer to the Local Government Board, 1884, Ulustrates this point very clearly, by showing the contributions of various ages to 1000 smaU-pox deaths at aU ages. These figures show that, " with the spread of vaccination, children as a whole, and especially vaccinated children, bear less and less of the total smaU-pox SMALL-POX. 655 mortahty, Avhile among the unvaccinated the distribution approaches more nearly to that of pre-vaccination times." Ages at Death. Vaccination unknown. Vaccination partial. London, 1884, Vaccination general. Geneva, 1580-1760. Kilmarnock, 1728-1761. London, 1848-1851. Unvaccinated Community. Vaccinated Community. Total Inhabitants. 0-10 years, 10-20 ,, 20-30 ,, 30-40 ,, Over 40 ,, 961 26h 10" } * 988 5 7 815 59 83 32 11 612 146 108 72 62 86 173 319 221 201 343 170 213 142 132 Total, 1000 1000 1000 1000 1000 1000 Mortality.—The introduction of vaccination has largely affected the epidemic character of smaU-pox. The "bills of mortality" for London, going back to 1629, show that upon an average some 70 to 90 per 1000 of the persons buried in London during the seventeenth and eighteenth centuries had died of smaU-pox, while in epidemic years the proportion often rose to 130, 150, or even 190 per 1000. The general smaU-pox death-rate per million living in England and Wales is shown in the follow- ing table compiled from the Registrar-General's returns for the last thirty years. It is noticeable that even in the epidemic years, 1871-2, the mortality approached nothing hke the rate of pre-vaccination times. Year. Rate per million. Year. Rate per million. Year. Rate per million. Year. Rate per million. Year. Rate per million. 1864 367 1870 116 1876 103 1882 54 1888 36 1865 303 1871 1015 1877 178 1883 39 1889 1 1866 141 1872 824 1878 79 1884 87 1890 1 1867 116 1873 101 1879 25 1885 107 1891 2 1868 93 1874 91 1880 29 1886 13 1892 15 1869 70 1875 40 1881 124 1887 21 1893 49 Infectivity.—Although the pathogenic micro-organism of smaU-pox has not as yet been identified, it is a well-recognised fact that micrococci abound in the vesicles of the disease and in the adjacent lymphatics. The disease is disseminated from the sick to the healthy mainly by means of the air, and this power of aerial convection is one of the most striking characteristics of small-pox. It, moreover, can be carried by fomites, as by epithelial debris, pieces of clothing, &c.; similarly, the bodies of persons who have died of the disease, the beds on which they have lain, the furniture of sick-rooms, and all such ordinary means of infection have their share in the diffusion of smaU-pox. But, hitherto, neither water nor milk has been shown to convey the infection of the disease, though drinking vessels and other domestic utensils, if used by the infected, may serve as the vehicles of conveying the contagion to others. The well-known investigations of Power regarding the influence of the Fulham SmaU-pox Hospital on the spread of the disease, conducted in 1884-5, have shown that the virus can sometimes retain its activity while passing through a quarter of a mile or more of London air. Power shoAved 654 THE INFECTIVE DISEASES. that, if the district were divided into zones, by means of circles draAvn upon the map from the hospital as a centre, with radii of ^, £, f- and 1 mile respectively, and an enumeration made of all the houses in each belt, and also of all houses invaded by smaU-pox, the proportion of invaded houses •diminished as the distance from the hospital increased, and this relation held good in each quadrant of each zone. Taking the total results over a series of eight years, beginning in 1877, and including some half-dozen •different periods of smaU-pox prevalence in London, it was found that the percentage of houses round the Fulham Hospital in Avhich small-pox had appeared was as follows:—30*1 Avithin a quarter of a mile, 14*5 between a •quarter and a half mile, 9*5 between a half mde and three-quarters, and 4*6 between three-quarters of a mile and one mile. The position of the hospital Avas such that direct communication by traffic could practically be dis- regarded, as the incidence upon the quadrant Avhich included the only approach to the hospital was actually less than upon any of the others. Power concluded that diffusion only occurred when acute cases Avere aggregated, and under foggy conditions of the atmosphere. Possibly only the air of towns or cities may possess the necessary carrying power, as, so far, no good evidence has been adduced of such occurring in connection with hospitals in rural districts ; but the failure here may be as much owing to Avant of population as to atmospheric condition. The practical outcome of this inquiry and of later ones made by others, leading to similar conclusions, has been that the Local Government Board have issued the following instructions:—That a local authority should not contemplate the erection of a smaU-pox hospital (1) on any site where it Avould have within a quarter of a mile of it as a centre either a hospital, Avhether for infectious diseases or not, or a Avorkhouse, or any similar establishment, or a population of 150-200 persons; (2) on any site where it would have Avithin half a mile of it as a centre a population of 500-600 persons, whether in one or more institutions or in dwelling-houses. The incubation period of smaU-pox is practically twelve days, and its period of infectiveness at least six weeks in severe cases. Isolation should be maintained for at least three weeks in the mildest cases, and always until every scab has disappeared. After exposure to infection, a quarantine of seventeen days is usually sufficient, but should not be less than a fort- night. Second attacks are rare, except after some years' interval; third attacks are not unknown. OccasionaUy one meets Avith persons who are entirely insusceptible to the contagion of small-pox,—Avhat is the precise proportion of such insus- ceptible persons to the general population is very difficult to determine, but taking the mean of many observations, we may put the ratio down as 1 in 20 for adults and 1 in 60 among children. Protection and Vaccination.—Individual protection against an attack of smaU-pox can be obtained in three ways : by natural small-pox, by inoculated smaU-pox, and by vaccination. In former years, protection once acquired was looked upon as permanent and absolute; but later experience shows that, from Avhatever cause obtained, the amount of pro- tection varies according to the thoroughness of the protective procedure. Severe small-pox gives more lasting protection than mdd smaU-pox; smaU-pox inoculation gives most protection when followed by an eruption; and a complete, thorough, and multiple vaccination gives more lasting pro- tection than does a vaccination in which only a smaU single vesicle has been produced. At the present time, a second attack of smaU-pox is less frequent than SMALL-POX AND VACCINATION. 655 formerly, because, as a result of the practice of vaccination, a first attack of the disease usually comes later in life, so that the protection it affords does not wear off in time to readily allow of a second attack. Protection from smaU-pox by deliberate inoculation of the disease, or variolation, as it was called, was very generally practised in this country during the last century, and until made illegal in 1840. The chief objections to it Avere the danger to life which attended it, the disfigurement which so generally followed, and the fact that the inoculated Avent about spreading the disease broadcast. The researches and obervations of Edward Jenner, betAveen 1768 and 1798, led to the introduction of vaccination, or the inoculation of man with the smaU-pox of the coav, by Avhich man con- tracted the affection called vaccinia. This vaccinia is, as Jenner always supposed it to be, small-pox of the cow; but OAving to the remarkable change in the cow or calf of smaU-pox into vaccinia, the poison of human or ordinary small-pox is so Aveakened as to be unable to cause, except in rare cases, a general eruption, or to spread by atmospheric convection; in fact, to use the words of M'Vail, the change in the calf from smaU-pox to vaccinia has the effect of "removing the objectionable and retaining only the valuable part of the original disease." Which is the ancestor of the other still remains a moot point, but that smaU-pox and cow-pox are identical was Jenner's firm belief, and the most recent scientific investiga- tions of the subject altogether go to strengthen this vieAv. Vaccination was introduced by Jenner in 1796, when he claimed for it that, "duly and efficiently performed, it Avill protect the constitution from subsequent attacks of small-pox as much as that disease itself will. I never expected it would do more, and it will not, I believe, do less." During the earlier part of the present century it gradually superseded inoculation. It was provided gratuitously by the first Vaccination Act of 1840, made com- pulsory in 1854, and systematically enforced by paid vaccination officers from the time of the pandemic in 1871. FolioAving the introduction of vaccination, there has resulted a remarkable decline in the prevalence of smaU-pox, not only in England, but in various European countries. This decline, it has been urged, Avas due, not so much to the use of vaccination as to the decrease of inoculation and to increased attention to sanitation. That the mere decline in the practice of variolation was not the cause of a diminished small-pox prevalence is Avell shown by the experience of SAveden and Copenhagen, where it so happened inoculation for small-pox was never largely practised; yet the death-rate from smaU-pox per million of popula- tion was in Sweden, in the last century, no less than 2050, and now since the introduction of vaccination the death-rate is but 158 per million; the corresponding figures for Copenhagen are 3128 and 286. As bearing on the question of the influence of sanitation as a factor in the decline of small-pox, it has been pointed out by various writers, principally by M'Vail, that the statistics of all diseases teach that in reference to sanitation each disease has to be considered by itself. Though the removal of faecal impurities has diminished enteric fever, it has not affected measles. The lessening of overcrowding and personal filth has much lowered the typhus fever rate, but without reducing the diarrhoea rate. Vaccination has diminished smaU-pox without similarly affecting whooping-cough, and while general cleanliness and purity of water and food are useful against all diseases, yet " the lessening of smaU-pox cannot beset down to improved drainage any more than can the lessening of enteric fever be set down to vaccination " (M'Vail). The remarkable diminution in the small-pox death-rate, especially Avithin 656 THE INFECTIVE DISEASES. the last fifty years, is shoAvn in the foUoAving table with regard to the London death-rate:— Years. Average Annual Deaths per Averace Annual Deaths per million from all Causes. million from Small-pox. 1660-79 80,000 4,170 1728-57 52,000 4,260 1771-80 50,000 5,020 1801-10 29,200 2,040 1831-35 32,000 830 1838-53 24,900 513 1854-71 24,200 388 1872-82 22,100 262 1883-92 19,800 73 During 1855-64, when vaccination Avas optional in Scotland, the annual death-rate from smaU-pox was 340 per mdlion of inhabitants; but when vaccination Avas made compulsory the death-rate dropped to 80 per million for the years 1865-90. Upon the same point EdAvardes gives some interesting figures from SAveden, Avhere the small-pox statistics go back to 1774. From that date to the beginning of this century the average annual death-rate was 2008 per million of people. From 1801 to 1815 vaccination Avas optional, and the death-rate fell to 631. In 1816 vaccination became compulsory in Sweden, and during the period 1816 to 1885 the death-rate has been 173 per million; Avhile for the last eight years of that period it has been but 41 per million. Perhaps the strongest argument in favour of the view that it is vaccina- tion and not sanitation which has so reduced the prevalence and mortahty of smaU-pox of late years, is the fact that in pre-vaccination times small-pox was very largely a disease of childhood, Avhde now, owing to infantde vaccination, the main incidence of the disease has been transferred to later periods of life. The following table, which gives the mean annual deaths in England and Wales from smaU-pox at successive hfe periods per milhon living, indicates this fact very clearly. Period. All Ages. 0-5 5-10 10-15 15-25 25-45 45 and Upwards. 1. Vaccination optional, 1847- 53, .... 305 1617 337 94 109 66 22 2. Vaccination obligatory, but not efficiently enforced, 1854-71, 223 817 243 88 163 131 52 3. Vaccination obligatory, but more efficiently enforced by vaccination officers, 1872-91, 89 177 95 54 97 83 38 The figures show ^ that, coincidently Avith the gradual extension of the practice of vaccination, there has been, in the first place, a gradual and notable decline in the mortality from smaU-pox at all ages ; and, in the second place, that this decline has been exclusively among persons under ten years of age, and most of all among children under five; and thirdly, that after the age of ten years the mortahty, so far from having declined has actually increased—very shghtly among persons of from ten to fifteen years of age, but very greatly for persons older than this; and lastly, that SMALL-POX AND VACCINATION. 657 the increase has been the greater the more advanced the time of life. Thi3 changed incidence of smaU-pox is one of the most curious and convincing proofs of the efficacy of vaccination, and one which may profitably be studied by a close examination of the facts connected with each and all of the recent smaU-pox epidemics. No such change of age incidence is to be seen in any of the other zymotic diseases as is found to have taken place Avith respect to small-pox since the introduction of vaccination. Confirmatory evidence, if any be needed, is afforded by Barry in his Report to the Local Government Board upon the Sheffield epidemic of 1887-88, in which he showed that, among each 1000 of the children under ten years of age, living under the common conditions of infection in the whole borough, The attack-rate of the vaccinated was......5-00 The attack-rate of the unvaccinated was ..... 101 "00 The death-rate of the vaccinated was......0'09 The death-rate of the unvaccinated was.....44-00 Among 1000 persons over ten years of age living under the common conditions of infection in the borough, The attack-rate in persons twice vaccinated was . The attack-rate in persons once vaccinated was . The attack-rate in persons not vaccinated was The death-rate among persons twice vaccinated was The death-rate among persons once vaccinated was The death-rate among persons not vaccinated was 3-00 19-00 94-00 0-08 1*00 51-00 Under the general circumstances of the Sheffield epidemic, therefore, the vaccinated children had, as compared with the unvaccinated children living in the town, a 20-fold immunity from attack by small-pox, and had a 488- fold security against death by smaU-pox. Among persons at ages above ten years there was a 5-fold immunity from attack, and a 51-fold security against death from small-pox. The twice vaccinated persons over ten years of age, as compared with the unvaccinated persons of the same age living in the town, had a 31-fold immunity against attack by small-pox, and had a 637-fold security against death from smaU-pox. From Leicester very similar facts are forthcoming in respect of the epidemic of 1892-93. Quoting from the official report of the Medical Officer of Health, we get the following suggestive figures :— Under Ten Years of Age. Vaccinated cases, 2 ; death, 0,.......-0 "00 per cent. Unvaccinated cases, 105 ; deaths, 15,......=14 "30 ,, Over Ten Years of Age. Cases once vaccinated, 176 ; death, 1,......= 0*57 per cent. Unvaccinated cases, 48 ; deaths, 4,......- 8 *30 ,, Re-vaccinated cases, 14 ; death, 0, ••..„• * * , % . ~ JkWk " Doubtful as to vaccination—that is, no marks visible—cases, 2; death, 1, = 50 00 „ Whittington, in Derbyshire, suffered from a sharp outbreak of smaU-pox in 1893-94, there being 135 attacks and 13 deaths. The following table by the local'Medical Oflicer of Health is sufficiently instructive to be worth quoting in its entirety. 2 T 658 THE INFECTIVE DISEASES. Age-Period. Number of Persons in Invaded Houses. Attacks. A'accinated in Infancy. Not A'accinated. Not Attacked. Attacked. Died. Not Attacked. Attacked. Died. Under 10 years, 10-20 years, 20-30 30 years and upwards, 177 111 85 109 25 34 37 39 148 77 48 70 11 31 35 39 0 0 2 5 4 14 3 2 5 1 0 6 Totals, 482 135 343 116 7 4 19 Therefore, of 459 persons vaccinated in infancy and hving in houses invaded with small-pox, 25 per cent, were attacked and 1 *5 per cent, died; whilst of 23 persons unvaccinated and in invaded houses, 82*7 per cent. were attacked and 26 per cent. died. No vaccinated person under twenty years of age died. Similar evidence is forthcoming from all other localities. Much valuable evidence has been collected of late years in regard to the duration of the protection which vaccination gives against small-pox. This evidence indicates that although the susceptibihty to the operation of vaccination returns comparatively soon after a primary vaccination, the susceptibdity to smaU-pox returns but slowly; so slowly, in fact, that the power of infantile vaccination against attack by small-pox may be said to remain at least to one-half of its original extent at twenty years of age. On these points the evidence given by Gay ton before the Yaccination Commission (Second Eeport, p. 245) is peculiarly interesting. He found that some 40 per cent, of vaccinated children could be re-vaccinated at the age of from six to ten years; but of vaccinated children of the same age exposed to the infection of smaU-pox by residence with cases of the disease, less than 10 per cent, were attacked, though under the same exposure no less than 92 per cent, of unvaccinated children of the same age contracted the disease. If we compare the attack rates under exposure with the fatahty rates among attacked persons in successive age-periods from birth upwards, as shown by the statistics of the great smaU-pox hospitals, we find that resistance to death by smaU-pox among the vaccinated outlasts very considerably resistance to attack by smaU-pox, and also that the inclination to both attack and death by smaU-pox is much slower in course and much less in ultimate amount in the well vaccinated than in the badly vaccinated. Ages. Vaccinated. Good Marks. Vaccinated. Imperfect Marks. Said to be Vaccinated. No Marks. Unvaccinated. 0-5, 0-10, 10-20, 20-40, Over 40, Case Cases. Deaths. Mor-tality. 51 0 00 267 2 0-7 1045 17 1-6 725 37 5-1 48 6 12-5 Case Cases. Deaths. Mor-tality. 182 21 11-5 714 48 6-7 1976 98 5*0 1898 258 13*6 266 51 19-2 Case Cases. Deaths. Mor-tality. 128 47 36 -7 325 87 26*8 419 81 19-3 420 140 33 5 131 44 33-8 Case Cases. Deaths. Mor-tality. 677 383 56-6 1187 563 47*4 521 160 30*7 382 181 47-4 79 34 43*0 All ages, 2085 62 3 4854 455 9 1295 352 27 2169 938 43 The quahty of vaccination, that is, the number, area, and character of the SMALL-POX AND VACCINATION. 659 cicatrices, has an important bearing upon the degree and permanence of the protection afforded, as well as upon the case mortahty. The preceding analysis of 10,403 cases in the Metropolitan smaU-pox hospitals, by Gayton, makes this point very clear. Marson gives the f olloAving case mortahty in relation to the number of vaccine cicatrices:— Case Mortality (per cent.). Unvaccinated,..........35^ Stated to be vaccinated, but without cicatrices, .... 21| Having one cicatrix, ......... 1\ Having two cicatrices, ......... 4g Having three cicatrices, ........ 12 Having four or more cicatrices,....... I Vaccination is protective against itself as Avell as against small-pox. Any number of insertions may be made at the time of vaccination; whether one vesicle is produced or a dozen, the protection is absolute for the time being, but all experience goes to show that the duration of the protection is limited, and is directly proportionate to the number and size of the vesicles produced. For this reason it is desirable to vaccinate in at least four places, and the total area of the cicatrices should not be less than half a square inch. As the protective influence of the primary vaccination fades, a time arrives when re-vaccination becomes possible. Very few persons are insusceptible to re-vaccination after the lapse of ten or tAvelve years'; many are susceptible within five years, although the primary cicatrices may be good. The course of re-vaccination in the majority of persons is different from that of primary vaccination, being more rapid, and often failing to exhibit some of the typical stages. If, hoAvever, the former protection has entirely disappeared, the course of re-vaccination may be identical with that of a primary vaccination. Re-vaccination renews in all respects the immunity given by primary vaccination. Barry showed that in the Sheffield epidemic the re-vaccinated had a great advantage over the rest. Of 8198 persons re-vaccinated prior to the epidemic, twenty-five were attacked and one died, the attack-rate being therefore 3 per 1000, and the death-rate 0*1. Among 56,233 persons re-vaccinated during 1887-88, tAvo were doubtfully attacked, and none died. The incubation of vaccinia being shorter than that of smaU-pox, it is possible to modify or even entirely prevent an attack of smaU-pox by vaccination performed some days after infection. This is especially the case with re-vaccination, the incubation of which is often shorter than in primary vaccination. Vaccination, if successfully performed within three days after exposure to infection of smaU-pox, Avill prevent the appearance of symptoms, and in all likelihood the attack wUl be arrested or modified by vaccination if performed as late as the fifth day. The proof of this state- ment rests upon the observation that attacks of small-pox may and do •occur within six days of vaccination in persons who have been many days previously exposed to infection, but the few attacks that occur between six and nine days after successful vaccination are mild, and practically none -commence later. The Vaccination Acts require that every child shall be vaccinated within three months of its birth, unless (a) death occurs within this period, or (b) the state of health renders postponement necessary, or (c) the child is attacked by smaU-pox, or (d) three or more unsuccessful attempts at vaccina- tion have been made, in which case insusceptibUity is inferred. Certificates signed by a qualified medical practitioner must be produced in proof of any 660 THE INFECTIVE DISEASES. such exceptions. A certain number of children are lost sight of by the vaccination officers, chiefly OAving to migration. At the same time, it cannot be denied that wholesale evasion of the law is countenanced by the authori- ties responsible for the administration of the Vaccination Acts, and that as a result the " proportion remaining unaccounted for " is annually increasing. In 1891 the percentage of children not finally accounted for as regards vaccination, that is, including cases postponed, Avas 13*4 of the total births throughout the whole of the country; the proportion of cases not finally accounted for in the metropolitan returns for 1891 was 16*4 per cent.; in the provincial returns 12*9. Of the registered births of the tAventy years 1872-91, the corresponding proportion not finally accounted for in regard to vaccination in each year respectively has been as follows:— Year. England and AVales. Metropolis. Provinces. Year. England and AVales. Metropolis. Provinces. 1872 4*6 8-8 4 5 1882 4-8 6*6 4*5 1873 4-8 8-7 4-2 1883 5*1 6*5 4-9 1874 4-8 8-8 4-1 1884 5-5 68 5-3 1875 4-7 9-3 3-8 1885 5-8 70 5-5 1876 4 3 6-5 4-0 1886 6-4 7-8 6-1 1877 4-5 7*1 4-1 1887 7-1 9-0 67 1878 4-7 7*1 4 3 1888 8-5 10-3 8-2 1879 5-0 7-8 4-5 1889 9-9 11*6 9-6 1880 4-9 7-0 4-5 1890 11*3 139 10*9 1881 4-5 5-7 4-3 1891 13*4 16-4 12*9 The administration of the Vaccination Acts is not in the hands of the sanitary authorities, but, subject to the control of the Local Government Board, is entrusted to the Poor Law Guardians. Vaccination may be per- formed, and the certificate signed by any qualified medical practitioner, but the Guardians must provide for the gratuitous vaccination of all chddren. For this purpose Public Vaccinators are appointed, and attend at certain convenient vaccination stations at fixed days and hours. The most scrupu- lous care is necessary in the selection of " vaccinifers," or infants from whom lymph is taken, and in the cleanliness of instruments. The Local Govern- ment Board Instructions prescribe at least four insertions, and the total area of cicatrix should not be less than half a square inch. The vaccination of chddren who are not in good health should be postponed, unless there is some immediate risk of infection by smaU-pox. Be-vaccination is entirely optional, but persons over twelve years of age are re-vaccinated gratuitously at the pubhc stations, and if there is immediate danger of smaU-pox the age-limit is reduced to ten years. Some people profess to be much opposed to the practice of vaccmation, and, m support of this view, allege that (1) vaccination neither prevents nor modifies smaU-pox; (2) that it gives rise to other diseases; (3) that it is unnecessary, as smaU-pox is only slightly infectious, and can be prevented by isolation in hospitals. No one who has studied the statistics, nor any one who has read the few facts explained above as to the real nature of the case, can for one moment honestly believe or think that vaccination neither prevents nor modifies smaU-pox. The truth is, vaccination does both With regard to the second contention, that vaccination gives rise to other diseases, much untruth has been both Avritten and spoken by prejudiced persons. The facts appear to be that, in a very small percentage of cases certam diseased conditions have resulted either from or in consequence of SMALL-POX AND VACCINATION. 661 vaccination having been performed. But when these cases have been closely inquired into, it has been found that grave errors had been com- mitted in the performance of the operation, and that due precautions had not been taken in the choice of the source of the vaccine lymph. Consider- ing the enormous number of vaccinations that have been performed during the past fifty years, it is remarkable how few genuine cases have occurred in which disease has in any way resulted from the procedure. It is pro- bable that with an increased use of vaccine direct from the calf, and the exercise of greater care even than has hitherto been exercised, the alleged risks of vaccination in this direction will quite disappear. Coming now to the third objection to vaccination, or the statement that it is needless because isolation is a better preventive than it, we find that on this particular allegation there is practically no evidence at all. What evidence there is is based upon the experience of Leicester, in which town isolation of the smaU-pox sick has been very rigidly carried out. But this toAvn is not an instance where isolation has been employed as a substitute for vaccination, because the great bulk of the inhabitants of Leicester have been vaccinated at some time or another, with the result that the experience of Leicester really only amounts to an experiment as to the efficacy of isola- tion, plus a certain amount of vaccination. Moreover, the doctors, nurses, and attendants of these isolated small-pox sick are all more or less vac- cinated or otherwise protected individuals, which means simply that the patient has around him a cordon of protected or insusceptible people. Surrounded in this manner with persons protected from the disease, it is not remarkable that diffusion or communication of the affection has been small; but where the immediate attendants are not thus protected by either vaccination or re-vaccination, experience shows that isolation alone, as so understood, rapidly results in an overwhelming increase in the numbers of those attacked with the disease, accompanied by an increased severity of the disease type. There is yet another interesting feature in the Leicester " experiment," and that is the system of "quarantining " for smaU-pox. In his report upon the outbreak of 1892-93, the Medical Oflicer of Health explains that by " quaran- tines " are meant practically persons in small-pox infected houses, for it is clear that such inmates must, more or less, have been exposed to the contagion. He goes on further to say that " such persons may be quarantined (1) in separate hospital wards and reception houses specially pro"vided, a method, by the way, I do not recommend, whether from the point of view of economy or practicabUity; or (2) at their own homes, a method I have found satis- factory, both financially and otherwise. The value of quarantining has been well shown during the Leicester epidemic, and I have been able, with comparative ease, by means of my inspectors to quarantine hundreds of persons at their own homes and Avith a success that has been gratifying both financially and otherwise. 1261 persons were quarantined, and of these 123 sickened (that is, 9*7 per cent.). Each infected house was visited daily by one or other of the inspectors for fourteen to sixteen days. Other persons who had come into contact with smaU-pox were also watched in the same way. These ' quarantines' were strongly urged—practically compelled —not to go to work for the Avhole or part of their quarantine period of fourteen to sixteen days, and during that time have been made such monetary allowances as the Committee have thought fit, the sum advanced in each case being no more than sufficient to cover rent and maintenance." It is clear this is a kind of compulsion Avhich would not be tolerated to any great extent, if it be seriously thought that the system might be made 662 THE INFECTIVE DISEASES. general. In comparison Avith it, the compulsion of infantile vaccination is a trifling interference with individual liberty. Prevention.—The most important measures are : (1) Vaccination, (2) Isolation. To these may be added fixation of contagious matter by smearing the skin with olive oil, vaseline, or carbolised glycerin, to prevent its diffusion into the air. All discharges from the nose, mouth, and else- Avhere should be received into vessels containing some disinfectant. Bags should be used for wiping the nose, &c, and afterwards burnt. All clothing, bedding, furniture, and dAvelling-rooms need to be most scrupu- lously disinfected. No persons should be allowed near the sick, unless vaccinated ; vaccination should be performed upon all individuals occupying the same house in which a case of smaU-pox has occurred. TETANUS. Carle and Battone were the first to produce typical tetanus in animals, and to show it to be a communicable disease. This they succeeded in doing by inoculating rabbits with pus taken from the ulceration of a human being in whom tetanus had set in; infection of a second animal with the sciatic nerve of the first produced the same result, but inoculations of the blood were negative. Nicolaier made the important discovery that garden earth is often capable of producing, Avhen inoculated into the subcutaneous tissue of the mouse or rabbit, a local suppuration and hsemorrhagic effusion about the seat of inoculation, rapidly followed by typical tetanus and death. At the seat of inoculation fine bristle-shaped bacilli were found; these were often SAvollen at one end. If the garden earth Avas previously sterilised by heating it to 110° C, then no effect followed. Bosenbach was the first to demonstrate that the same bacilli exist in the exudation at the place of infection in human tetanus, and that tetanus was produced and propagated through a series of animals by inoculation of matters taken from near the inoculated place. Hochsinger, Beumer, Peiper, and many others confirmed the existence of these bacilli in tetanus, and even succeeded in producing the disease in animals with them by the aid of foreign bodies, yet these cultures were always in an impure state. The first pure cultivations of the tetanus bacilh were obtained by Kitasato. The tetanus bacdh are slender bristle-like rods, having circular spores at one end, and possessing but little power of automatic movement. They are strictly anaerobic, and withstand a tolerably high temperature—about 80° C.—Avithout losing their pathogenic power, but growth takes place best at 37° C. The fact that the spores can be subjected to a high temperature without losing their vitality enabled Blitasato to obtain pure cultures of the tetanus bacillus, since the other bacilli cultivated or groAving along with them are destroyed at a temperature of 80° C. A trace of pus or exudation from a patient suffering from tetanus is smeared upon serum sohdified in a slanting position, or upon agar, and the cultures so made incubated for a few days at 37° C. They are next transferred, for from half an hour to an hour, to a Avater-bath heated to 80° C, in order to kill the micro-organisms which have grown along with the bacilh, after Avhich secondary cultivations must be made in the absence of ah by substituting for it an atmosphere of hydrogen gas, or by planting the bacilli in the depth of the gelatin. One or two per cent, of grape-sugar may be added to the medium with advantage. The colonies have usually a halo radiating in all directions, and liquefaction sets in sloAvly, being combined TETANUS. 663 with the formation of a certain amount of gas. If an infection is made with a pure culture, the bacilli are found only on the site of inoculation and in its immediate neighbourhood. The more exact researches of recent years indicate that the introduction of tetanus bacilh under the skin is followed by the production by them of a chemical virus, which, as it is being produced at the seat of inoculation, is absorbed into the system and sets up the disease; but the baciUi themselves remain limited to the seat of inoculation, and do not enter the blood or any other tissue, and therefore only the seat of inoculation contains the infective principle, that is, the bacilli. Brieger has isolated from the exudation at the seat of infection in human tetanus a toxic principle, tetanin, the injection of which produces tetanus. Eatasato has separated a similar chemical body from the cultures of the tetanus bacillus. According to Vaillard and Vincent, tetanin is neither an alkaloid nor an albumose, but is related in its chemical characters to snake poison. Behrhig and Kitasato have shown that the blood of a rabbit (previously made insusceptible to tetanus), injected into a mouse, otherAvise susceptible to tetanus, neutralises in this latter the action of the tetanus bacillus. Tizzoni and Cattoni have gone further than this by showing that the blood- serum of animals, made previously insusceptible, when injected into animals, possesses a decided anti-toxic action. From such blood-serum a tetanus anti-toxin can be prepared, Avhich is effective in neutralising the vhus of the tetanus bacilh. Several cases are on record in which tetanus seems to have been conveyed by the hands or instruments of the surgeon, especially veterinary surgeons. One of the most striking of these is related by Langer, in Avhich the horses castrated by the same ecraseur died of tetanus, but after boiling the instrument in oil no others died or were affected from its use. Numerous cases are on record of the occurrence of this affection following wounds and injuries in man, the common feature of Avhich has been contamination by dirt, dust, or soil. In view of this fact, that tetanus is produced by a micro- organism to be found in dust, dirt, and adhering to foreign substances, the surgeon Avill naturally take the greatest care to keep wounds and other injuries free from such contaminating influences. Save in the way of dis- seminating information on these points among the public at large, tetanus is a malady against which the sanitary officer can do but little. He may, hoAvever, point out that the discharges from such wounds should be collected on clean rags or simdar materials, Avhich can be either disinfected or burned. From the frequency with which tetanus is met with among grooms and others much in association with horses, some writers have endeavoured to establish an etiological connection between horses and man in respect of this disease. The doctrine of an equine origin of tetanus has as few facts to support it as has the vieAV that chills, exposure to extremes of heat or cold, and other climatic or meteorological conditions are the cause of the disease. That tetanus is frequent amongst those injured by, or in intimate association with horses, mules, and other quadrupeds, is probably to be explained by the simple fact that such injuries and associations commonly involve contamination by earth or soil, a medium which we knoAV to be particularly favourable to the specific bacillus. Prevention.—Extreme cleanliness in regard to all wounds, cuts, or lacerations, especially Avith a vieAv to avoiding access of soil or any kind of dirt thereto. 664 THE INFECTIVE DISEASES. TUBEBCULOSIS. This is a diseased condition which occurs in man in a variety of different forms, the most familiar being phthisis, scrofula, lupus, tabes mesenterica, and meningitis. Tuberculosis is not limited to the human race ; it is very common among oxen and cows as a disease known as "grapes"; it also affects pigs as well as fowls, rabbits, and guinea-pigs. Though there is every reason to believe that tubercular disease, especially phthisis, has occurred in all ages, there are no data on Avhich to form any estimate as to its relative prevalence in the past in respect of either time or place. In the present day, tuberculosis is certainly more common in some countries than in others ; but this geographical limitation does not mean that the infecting virus is not widespread, but rather that the susceptibihty to it is happily far less common. For this reason, the predisposing causes are much more important in this than in any other infective disease. Influence of Climate and Season.—Speaking generally, tuberculosis is more prevalent in temperate climates, especially in the more populous parts of such countries. Neither hot nor cold climates are exempt, but humidity, especially if the daily range of temperature is high, is frequently associated Avith the prevalence of pulmonary tuberculosis or phthisis. Cold, and especially Arctic, countries suffer comparatively httle as a rule, and the exceptions are mostly explicable by social conditions involving overcrowding and want of ventilation. Other things being equal, elevated and mountainous regions are less affected than lowlands, owing, probably, to the greater dryness and purity of the air and soil, and the deeper and fuller respiratory movements. As regards the influence of season, in this country deaths from tuber- culosis, as evidenced by the phthisis mortality, are most frequent in March and April, and least so in September and October. The seasonal curve of mortality is therefore later than in the ordinary respiratory diseases, and serves really to indicate seasonal conditions accelerating death rather than primarily inducing what is generally a disease of long and uncertain course. Influence of Race, Sex, and Age.—Jews are said to enjoy a relative immunity from tubercular disease, but, speaking generally, no race is exempt. The coloured races seem to suffer much from phthisis, particularly if they change their natural and primitive habits of hfe for the conditions associated with a higher civilisation; this is all the more markediif such changed mode of life is synchronous with migration to a colder and more temperate climate. The influence of sex is very marked. In proportion to their numbers, males suffer a higher phthisis mortahty than females at all ages, except between 5 and 25 years. As regards age, deaths registered as due to phthisis faU from the first to the fifth year : after the age-period 5-10, they increase up to the age-period 25-35, subsequently to which they steadily decrease. Tubercular meningitis is most common between the third and eighth years of life, but tabes mesenterica is commonest at an earher age, namely from one to three years. Mortality.—It is a matter of common knowledge that tubercular disease occasions an enormous mortahty. OAving, hoAvever, to the uncertainty which attaches to the actual cause of many of the deaths, especially among chddren, ascribed to tuberculosis, it is very difficult to ascertain accurately the extent of this mortality. It is generally estimated that, among ciAdhsed communities, at least one-seventh of the total mortality is due to tuberculosis TUBERCULOSIS. 665 in some form or another. As regards England and Wales, the following table, compiled from the Begistrar-General's returns, shows the number of deaths recorded during the last tAventy years as due to phthisis, and the corresponding death-rates per mUlion of the population. Year. Total Deaths. Death-rate per million living. A'ear. Total Deaths. Death-rate per million living. 1874 49,379 2081 1884 49,325 1827 1875 52,943 2202 1885 48,175 1770 1876 51,775 2119 1886 47,872 1739 1877 51,353 2079 1887 44,935 1615 1878 52,856 2111 1888 44,248 1563 1879 51,272 2021 1889 44,735 1573 1880 48,201 1869 1890 48,366 1682 1881 47,541 1825 1891 46,615 1599 1882 48,715 1850 1892 43,323 1473 1883 50,053 1880 1893 43,632 1433 From this table it is gratifying to be able to note both a relative and absolute diminution in the deaths recorded. Etiology.—Even by the older physicians, tuberculosis was regarded as an infectious disease, but it Avas not until Koch discovered the tubercle bacdlus that this conception of its nature was very generally recognised. The tubercle baciUi in human tubercle are delicate cylindrical rods, measuring from 1*5 y. to 4 p.; many are straight, Avith rounded ends, but others are slightly curved. When stained, the protoplasm of the bacilli appears segregated into deeply stained, cubical, spherical, or rod-shaped granules ; between the granules the sheath is empty, but these empty places are not to be taken for bright spores, nor is it proved that the bright granules are spores. That the tubercle bacilli contain spores is proved by their behaviour under conditions of drying and heating, but what the character of these spores is, or how they appear in the bacilh, has not been satisfactorily shown. In bovine tubercular matter the bacilli are, as a rule, shorter and thinner, but are in every respect identical with the human species, these minute differences being really differences due to the different soils on which the bacilli were reared. Tubercle bacilli show definite characters in cultivation. On blood-serum, after ten to fourteen days, these bacilli show themselves in the form of whitish points and patches, resembling dry scales. On agar broth, and also in broth, the growth is very limited; but by the addition of 6 per cent, of glycerin to meat broth the tubercle bacilli can be brought into rapid and extensive multiplication. These baciUi will not grow below 30° C. or above 42° C. Koch has shown that by subcutaneous or intra-vascular injection, by inhalation, and by inoculation into the peritoneum or the anterior chamber of the eye, &c, of artificial subcultures removed by many generations from the original source, typical tuberculosis is produced in all animals susceptible to tubercle (guinea-pigs, rabbits, dogs, rats, and mice), and that the tubercular deposits in these experimental animals again contain abundantly the tubercle baciUi; thus, the final and exact proof that the tubercle bacilli are the true cause of the tubercular process is definitely established. The discovery of the tubercle bacillus, although a matter of the highest importance and of the greatest scientific value, by no means exhausts the etiology of tuberculosis. Admitting, however, the constant presence of the bacillus, we have, as in other specific diseases, to determine the power of 666 THE INFECTIVE DISEASES. resistance of the tissues to its invasion, and to note various other conditions as being also requisite for the production of the phenomena Avhich we recognise as tubercular disease. In the case of tuberculosis this is pre- eminently true, and these other conditions or so-called predisposing causes must be regarded as having an importance hardly second to the micro- organism itself. Of these predisposing causes, the most effectual is the fact of parents having suffered from the same disease, wlhch Ave state abstractly as hereditary disposition or diathesis. As regards direct contagion, it-must be I confessed that clinical observation is altogether opposed to the idea that I direct infection from another patient is at all common in the etiology of j tubercular diseases. Some very striking evidence on this point has been [ collected from the experiences and after histories of the resident staff and personnel of the Brompton Hospital, which distinctly indicates that phthisis does not commonly spread from a patient to those in intimate contact with him. At the same time, there can be no doubt that phthisis can spread, and actually does spread at times by infection from case to case. In Italy consumption has always been regarded as a contagious disease. That it is not readily communicated is certain, but it does seem to be so under certain favourable conditions, as in the case of husband and wife and other persons hving in close and habitual contact. The dried, sputum of phthisical persons / preserves the bacillus for a long time, and in crowdea towns there must be abundant opportunities of infection from so common a disease. * Among other conditions influencing tuberculosis, elevation and dampness of soil play an important part; reference to this aspect of the subject has already been made on page 472. To these predisposing factors must be added want of sufficient food, especially Avant of the fatty elements, and the breathing of impure air. The habitual breathing of air rendered impure by overcrowding or by defective ventilation may and probably does act in two Avays: first, indirectly by weakening the resistance of the tissues, and secondly, dhectly by increasing the chance of infection. Strictly speaking, overcrowding and ( defective ventilation are not convertible terms; but in practice we scarcely \. ever meet one of them apart from the other. The proof that impure air is a cause of phthisis rests mainly upon the evidence of statistics as to the frequency of the disease among soldiers, artisans, and inmates of prisons. As regards soldiers, a Boyal Commission upon the Sanitary Condition of the Army, which reported in 1858, brought to light the fact that the death- rate from consumption in all branches of the service was in excess of that of the civU population of large towns, and that overcroAvding had extensively prevaded in the barrack rooms. The overcrowding had been greatest among the Foot Guards, and in that branch of the service the phthisis mortality had been highest. During the ten years 1837-46 it was 11*9 per 1000 of strength. For the seven years 1864-70 it had been reduced to 2*3. The mean of the phthisis mortahty in the army at home for the years 1837-46 was 7*89 per 1000 of strength; since the adequate provision of cubic space and ventilation, this death-rate in the home army has lessened enormously; for the year 1893 the mortality from phthisis in the British Army at home was as httle as 0*76 per 1000 of strength. Similar experience is afforded by the health history of the Navy, and by that of the occupants of prisons. As to workmen we have abundant evidence, the general tenor of which, in the words of Sir John Simon, indicates that "in proportion as the male TUBERCULOSIS. 667 and female populations are severally attracted to indoor branches of industry, in such proportion, other things being equal, their respective death-rates by tuberculosis and lung-disease are increased." But the pernicious effects of defective ventilation, as favouring phthisis, are not only due to the accumula- tion in the air of the products of respiration (including tubercle bacilli), exhalations from the body, and products of imperfect combustion. Experi- ence shows that the loading of the atmosphere of mines, factories, and Avorkshops with special kinds of dust produced in different trades is also a powerful indirect cause of pulmonary tuberculosis. The ability for harm of these dusts is apparently largely dependent upon their hardness and angularity, as favouring a catarrhal or mechanicaUy injured condition of the mucous lining of the lungs, and thereby facilitating the entrance and activity of the tubercle bacillus. Farr long ago stated his belief that the prevalence of phthisis in the armies of Europe, in the Navy, in factories, workshops, and public institutions, such as prisons and workhouses, was probably due in large part to the inhalation of expectorated tubercular matter dried, broken up into dust and floating in the air of close barrack rooms and dormitories. In the light of our present knoAvledge this belief requires no justification or explanation. Indeed, it is obvious that only in very exceptional instances can overcrowding or defective A'entilation be isolated from other injurious conditions, apart from direct contagion, as to be proved the main cause of tubercular phthisis. There still remains to consider the possibility of tubercular infection by the alimentary canal. It has already been stated that cattle suffer in con- siderable numbers from tuberculosis, and that, notwithstanding slight morphological differences between the respective bacilli, we may regard the human and bovine diseases as identical. It is notorious that, apart from imphcation of the flesh, tuberculosis of the udder in the form of softening nodules is not uncommon in milch coavs. Such being the case, the danger to man as regards cattle is a double one, for infection may occur both by the ingestion of flesh and milk. It is now universally acknowledged that the flesh of animals suffering from tuberculosis in a severe form, with fever and emaciation, ought to be absolutely condemned as unfit for human food, and ought not to be given to carnivorous animals, but destroyed, though in America it is allowed to be converted into manure. Differences of opinion arise when we have to deal with animals who have not yet suffered in con- dition, and in whom the disease is limited to certain viscera. Martin's evidence before the recent Boyal Commission on Tuberculosis shows that there is danger even in these minor cases, but that it is a danger which may he obviated. He adduced strong evidence that the flesh itself is not infec- tious, but that it may be rendered so by the process of cutting up and preparing the joints for sale. A knife used for cutting into tuberculous viscera or lymphatic glands will become covered with infective matter, and this may then be smeared on to the joints. That this is a very real danger is further shoAvn by Woodhead's experiments on the effects of cooking. He found that if tuberculous matter were smeared on a piece of meat which was then tightly rolled up, as is done with the rolls of meat sold by butchers, the infective matter Avas not destroyed by roasting, baking, or boiling, though boiling was more effective than baking, and baking than roasting. There is this further element of danger, as pointed out by the Commission, that tuberculous matter from a diseased carcass may be conveyed by the butcher's hands and knives to the meat from perfectly healthy animals cut up subsequently in the same place and with the same tools. With regard to milk, the Boyal Commission found that the milk of a 668 THE INFECTIVE DISEASES. tuberculous cow is not virulent except when the udder is the seat of tuber- culous lesions. Unfortunately, the diagnosis of the nature of the lesions of the udder has not yet attained certainty. Mistakes may be made in both directions. The Commissioners express a hope that the well-considered use of tuberculin in a herd may give valuable aid in picking out the diseased animals, even those as yet in the earliest stages of the disease. The following are the final conclusions of the Commissioners :—" Provided every part that is the seat of tuberculous matter be avoided and destroyed, and provided care be taken to save from contamination by such matter the actual meat substance of a tuberculous animal, a great deal of meat from animals affected by tuberculosis may be eaten without risk to the consumer. Ordinary processes of cooking applied'to meat which has got contaminated on its surface are probably sufficient to destroy the harmful quality. They Avould not avail to render wholesome any piece of meat that contained tuberculous matter in its deeper parts. The boiling of milk, even for a moment, would probably be sufficient to remove the very dangerous quality of tuberculous milk." Prevention.—Of the first importance is the .provision of proper ventilation, the avoidance of overcrowding, and in certain trades the provision of an air supply free from irritating particles. Next is the maintenance of a proper state of nutrition by sufficient and suitable food. Thirdly, the avoidance of I chill, and the removal of all predisposed persons from damp soils and climates, combined with plenty of exercise in the open air. The sputa of phthisical patients should be carefully collected and destroyed. Patients should be urged not to spit about carelessly, but ahvays use a spittoon, or one of the portable cups now on sale. If tuber- cular sputa is not burnt or boiled it should be disinfected. All handker- chiefs should be well boiled, or better still, small rags used, which should be burnt immediately afterwards. All tuberculous persons should occupy single beds. Booms, bedding, and furniture used by the tubercular should be disinfected. A most important general prophylactic measure relates to the inspection of dairies and slaughter-houses for the detection of tuberculous animals, and the granting of full powers to inspectors to confiscate all suspected animals and carcasses. Slaughtering and dressing should be done under skiUed supervision, with the object of securing the removal and destruction of every part of a carcass that contained any tubercle whatever, and also the destruction of the whole carcass in cases where animals are found to have advanced or generalised tuberculosis. AU milk should be boiled, especially that to be used by young children. A mother with tuberculosis should not suckle her child. TYPHUS FEVEE. Historically, this disease is next in importance to the true or Oriental Plague: it is the common pestilence which has accompanied and followed wars from the earhest times. Most probably the plague of Athens, recorded by Thucydides, was what we now call typhus. This name now in use was - ~ ■ - -----jj^xx^. j.ixxo .name xiuvv 111 use Avas first applied to a malady or a group of maladies by Sauvages in 1759 and is synonymous with the older terms, "jail fever," "morbus castrensis" putrid fever, and the modern German term, "typhus exanthematicus " or .blecktyphus. Both in Great Britain and Ireland this disease has prevailed with great TYPHUS FEVER. 669 severity on repeated occasions during the last tAvo hundred years. Since the commencement of the present century there have been epidemics of typhus in 1803, 1817-19, 1826-28, 1836, 1843, 1846-48, 1856, and 1861-70. It must be noted, however, that in some of the earlier epidemics there was a large admixture of cases of relapsing fever, which was not knoAvn to be distinct from typhus until 1843, but can even now be recognised by the small mortality which has always attended it. Typhus is more or less endemic in the poor districts of Edinburgh, Glasgow and Dubhn, and was so until recent years in London. As an epidemic it has again and again left its haunts in cities and invaded the whole country. On the Continent and in the United States its course has been chiefly epidemic, and attendant on armies, especially during the miseries of sieges and of retreat. Typhus is rare even as an occasional visitant in the south of Europe, and appears to be almost unknown in India and the tropics generally. It is not uncommon in Northern China. The disease was introduced into America in 1847 by an infected emigrant ship, and in 1867 by the same means into Australia, but fortunately it has never established itself there. Typhus is unknoAvn among animals : but has been produced by Ziilzer in rabbits by injections of blood taken from a sick person when in the height of the disease. These inoculation experi- ments faded when the blood was drawn from the sick person after the crisis of the disease had passed. Experiments on dogs, made by the same observer, gave negative results. Influence of Climate and Season.—The disease is essentially one of temperate and cold climates, but by no means unknoAvn in many warm countries, but usually at considerable elevation, such for instance as Mexico, Peru, Persia, North China, and Algeria. In England both the prevalence and mortahty of typhus have, on the whole, been greater in the winter and spring than in summer and autumn; but there is a less constant relation to season in respect of this disease than is the case with several of the other epidemic and infective maladies. Influence of Kace, Age, and Sex.—No race is exempt from typhus, but the influence of class and circumstances is shown by the especial incidence of the disease upon the poor and those living under relatively unwholesome conditions. No age is exempt, but the susceptibility to attack is greatest between the ages of 10 and 20. The mortality from typhus increases from child- hood to about 50 years of age, and then declines somewhat. Murchison gives the case mortality of the higher ages as 35*39 in persons between 30 and 40 ; 43*48 in persons between 40 and 50 ; 53*87 in those between 50 and 60 ; and 67*04 per cent, in those over 60. During the first five years of life the fatality is about 6*7 per cent., from 5 to 10 years it falls to 3*6, between 10 and 15 it is not more than 2*3, while from 15 to 20 years of age it rises to about 4*5 per cent. Although sex appears to have little influence upon liability to attack, the actual fatality is usually somewhat greater for males at all ages taken together, than for females. Of 18,268 cases of typhus at all ages" admitted into the London Fever Hospital, 18*9 per cent, ended fatally, or a male fatality of 19*6 per cent, of attacks, and a female fatahty of 18*2 per cent. Murchison points out that these, being hospital cases, were doubtless above the average as regards severity, and he gives 10 per cent, as a general estimate of typhus fatahty; but this naturally varies in different epidemics. Mortality.—The following figures, taken from the Annual Beports of the G70 THE INFECTIVE DISEASES. Begistrar-General, sufficiently indicate the more recent history of typhus fever in England and Wales. Year. Total Deaths. Death-rate per million living. Year. Total Deaths. Death-rate per million living. 1874 1762 74 1884 328 12 1875 1499 62 1885 318 12 1876 1165 48 1886 245 9 1877 1104 45 1887 211 8 1878 906 36 1888 160 6 1879 533 21 1889 137 5 1880 530 21 1890 151 5 1881 552 21 J 1891 137 5 1882 940 36 1892 85 3 1883 877 33 1893 137 4 Etiology.—No materies morbi has yet been detected, though there can be little doubt of its existence. It probably gains entrance in most cases by the breath: the contagion is very sure, but is readily diluted and dissipated, and probably not very persistent. The incubation period is variously stated from six to fourteen days, but there appear to be some well- authenticated cases in which it was not more than from two to five days. As regards the period of infectiveness, it is impossible to speak with any certainty. The general opinion is, that the infection is comparatively slight during the first week, but that the disease is most contagious from the end of the first week up to convalescence. This implies that it Avill probably not be safe to allow a patient to mix with others in less time than a month from the date of attack. In some cases a longer period of isolation may be necessary. That typhus passes directly to other persons from the sick is established by the clearest possible evidence; and the diffusion of the disease can often be traced from point to point in a town or in a district. The contagion is probably exhaled both by the skin and the lungs, and it may perhaps cause the offensive odour which is so perceptible when near to severe cases. The poison, whatever it may be, can certainly attach itself to clothes and bedding, but typhus is not nearly so apt as some of the other contagious exanthemata to be propagated by means of inanimate objects, or of human beings themselves unaffected by it. Moreover, its poison is easily rendered inert by free ddution with air. It has never been shown to be conveyed by water, or by nhlk or other food. The most important etiological factors in this disease are bodily fatigue, mental anxiety, want of sleep, poverty, starvation, and overcrowding. The three last named are among the most certain predisposing causes, and no epidemic of typhus has ever occurred except in association with widespread destitution, and the excessive aggregation of numbers of poverty-stricken, starved, and otherwise morally and physically deteriorated human beings. Besides its obvious influence in increasing the spread of typhus by con- tagion, overcrowding seems speciaUy to augment the susceptibihty of individuals to the poison; but it may safely be inferred from analogy that, without the presence of a specific poison, no intensity of overcrowding or other favouring conditions can originate an outbreak of typhus. A second attack of typhus is as rare as one of smaU-pox, but in exceptional instances the disease appears to confer practically no immunity at all. Such cases, however, are very rare. WHOOPING-COUGH. 671 Prevention.—To prevent the development of the typhus poison, free ventilation and cleanliness are essential and usually sufficient. Although the prevention of poverty is not always possible, the poor may be supplied •with airy, wholesome dwellings, and Avith the means of maintaining personal cleanliness, such as baths and Avash-houses. To prevent the spread of the disease, isolation and disinfection of the sick must be carried out stringently. A typhus patient should be treated in a very freely ventilated ward or building, or under canvas, at least 2000 cubic feet being allowed per bed, and the amount of fresh air supplied practically unlimited. As the contagion is specially virulent near and about the patient, attendants should avoid inhaling the emanations, or exposing themselves (unless protected by a pre-vious attack) unnecessarUy to such inhalation. Visitors should not be allowed, and the isolation most strictly maintained. All clothing worn by the patient before admission and during treatment must be carefully disinfected. Bedding and furniture must also be disinfected. The same observations apply to all rooms occupied by the patient either before or during the attack. WHOOPING-COUGH. Like so many other epidemic diseases, whooping-cough can be traced to only comparatively recent periods—the earliest notice of it is said to have been by Schenck in 1600. It is a very frequent and widespread disease, and, next to scarlet fever, more fatal than any other in childhood; indeed for infants under one year it is probably the most fatal of all. Influence of Climate and Season.—Climate does not appear to have much influence upon the prevalence of this disease, except that perhaps cold and damp countries are more favourable to it. As regards season, the prevalence of whooping-cough in this country, like the mortality, is greatest about the months of March and April. In this respect its curve of preva- lence is almost exactly the reverse of that for scarlet fever. This apparent seasonal prevalence does not probably apply to all countries, as Hirsch, from an analysis of a large number of facts, shows that it is not more apt to be epidemic at one season of the year than another. As regards the effect of weather, Goodhart remarks : " Atmospheric changes have a most important bearing upon pertussis. It has been repeatedly noticed in .the whooping- cough ward at the Evelina Hospital that the children are worse, even Avhen otherwise doing well, when the wind turns cold or suddenly changes ; and it is notorious that the disease runs a much less determined course in summer than in the colder seasons of the year." Influence of Sex and Age.—Female children are decidedly more hable to be attacked than males. The age at which whooping-cough is most common is between the first year and the eighth. Of the total deaths over 90 per cent, at all ages occur during the first five years of life. Of Goodhart's 352 cases, 62 were under a year old, 212 were betAveen one and four, 65 between four and six, and 13 between six and ten. The mortality among females is greater at all ages than among males. The case mortality is about 2*5 per cent., but varies with age. Although Avhooping-cough is most prevalent in the earlier years of life, it is sometimes observed in adults up to forty or fifty, or even a still greater age. Mortality.—In the folloAving table -will be found the mortahty recorded from this disease in England and Wales during the last twenty years. It shows that the mortality from whooping-cough in this country is very con- 672 THE INFECTIVE DISEASES. siderable indeed, and of late years it has destroyed more children than any of the other so-called zymotic diseases, except diarrhoea. Year. Total Deaths. Death-rate per million living. Year. Total Deaths. Death-rate per million living. 1874 10,362 437 1884 11,476 425 1875 14,280 594 1885 13,106 481 1876 10,556 432 1886 12,936 470 1877 11,358 460 1887 11,251 404 1878 17,784 710 1888 12,287 436 1879 12,752 503 1889 12,225 430 1880 13,662 530 1890 13,756 478 1881 10,830 415 1891 13,612 468 1882 15,259 579 1892 13,406 455 1883 10,471 393 1893 10,176 342 It is to be noted that the death-rate in 1893 from this disease showed a considerable dechne from the rates in the preceding years; it is, in fact, the lowest rate on record, the nearest approach having been 389 per million in the year 1840. Etiology.—Becent observations render it probable that the contagious principle of whooping-cough is an organism analogous to those which produce so many other infective diseases, but at present no micro-organism has been satisfactorily shown to stand in causal relation to it. The disease undoubtedly spreads by infection from case to case, but such infection need not necessarily be direct, as the virus may be carried in clothing, &c. On the other hand, it is said to be one peculiarity of the contagion of whooping-cough that it is far less apt than most other contagia to be transmitted to a distance in an active state. We very rarely find the contagion of whooping-cough con- veyed by persons not themselves affected with the disease; but some well- authenticated cases are on record of such having occurred, notably that observed by Bristowe, of a case in which a lady clearly conveyed the contagion of the disease from Sydenham to London upon her dress. Whooping-cough is peculiarly infective in the early stages, and, like measles, is largely spread by the attendance at schools and other public gatherings of children who are sickening for it, but who have not, so far, manifested the characteristic symptoms. There is no evidence that this disease is ever disseminated by the agency of water, milk, food, or domestic animals; neither does it appear to be in any way connected with soil conditions. The incubation period varies from four to fourteen days, and the period of infectiveness is not less than from six to eight weeks after the disease is declared. Prevention resolves itself into isolation of the sick person, combined with destruction of all discharges from the air-passages, and the disinfection of clothing and bed hnen used by the affected persons. The aerial diffusion of 1 some volatUe disinfectant may be a powerful adjunct to these preventive | measures, but cannot replace disinfection or destruction of all discharges from the nose, pharynx, and lungs. YELLOW FEVER. 673 YELLOW FEVEB. This is an acute febrile disease of tropical and sub-tropical countries, charac- terised by jaundice and hamiorrhages, and due to the action of a specific virus. The disease prevaUs endemically in the West Indies, and in certain sections of the Spanish Main, from whence it occasionaUy extends, and, under suitable conditions, prevails epidemically in other countries. The first epidemic on record was in 1647, when it appeared in Barbadoes; a destructive pestilence of the same kind occurred at Philadelphia in 1693, and again in 1762, 1793, and 1802. It visited Mauritius in 1815, and Gibraltar in 1804, 1814, and 1828. It is endemic in the island of San Domingo, and more or less frequent throughout the West Indies and the adjacent coasts of Mexico, Guiana, and the southern United States. It first appeared on the Brazihan seaboard in 1849, at Buenos Ayres in 1858, and at Callao in Peru in 1853. Between 1780 and 1820 it repeatedly occurred in Cadiz and other Spanish ports, in 1821 at Barcelona, and later at Marseilles and Leghorn.^ There was a terrible epidemic in New Orleans in 1878, and in Florida in 1888. Lisbon was affected epidemically in 1857, and Swansea in 1865. The disease exists also on the west coast of Africa. We may say that there are three main areas of infection:—(1) The focal zone, in which the disease is never absent, including Havana, Vera Cruz, Bio, and other Spanish-American ports. (2) Perifocal zone or regions of periodic epidemics, including the ports of the tropical Atlantic in America and Africa. (3) The zone of accidental epidemics, between the parallels of 45° N. and 35° S. latitude. . Influence of Climate and Season.—Yellow fever only flourishes m hot climates, and the regions in which it commonly prevails are all situated near the equator. The occurrence of a local epidemic within the temperate zone seems constantly to be associated with an exceptionally sultry state of the weather at the time. This was the case at St Nazaire in France when it developed itself there in 1861, and also at Swansea in 1865. In its endemic area, the worst months are generally July, August, and September, or periods of great heat and humidity. Although heat is necessary for the development of an epidemic, the disease, when once established, does some- times persist in spite of cool weather, though it is invariablx arrested by frost. But while it is always arrested by frost, its cause is not necessarily destroyed thereby, but may, like cholera, survive the winter and give rise to a fresh epidemic on the return of hot weather. This sequence of events has repeatedly been noticed in the case of infected ships passing from low to high degrees of latitude, and vice versa. According to Hirscli, a high degree of atmospheric moisture is generally favourable to yello\v fever prev- alence, but this is not a factor of universal importance. The possible connec- tion o'f yellow fever to sod has already been considered on page 475. Influence of Race, Sex, and Age.—Although no race can be said to be entirely exempt from yellow fever, there can be no doubt that the negroes are distinctly less susceptible than the whites. Negroes are less hable both to attack and to death in the event of attack. Both attacks and deaths are more numerous among males than females, but this is probably due to neater exposure, and to habits of life. As regards the influence of age, during epidemics in endemic localities, the majority of observed cases occur amongst persons in middle life, because visitors and other unacchmatised persons form a large proportion of the cases, and these people are for the most part adult males. In localities in Avhich yellow fever is not actually Zi U 674 THE INFECTIVE DISEASES. endemic, but occurs in occasional epidemics, large numbers of children are attacked, for, unlike the children in endemic areas, they are not acclimatised. Sternberg quotes the folloAving table from Bemiss, showing the age distribu- tion of 905 cases occurring in XeAV Orleans during the epidemic of 1878. Age. Cases. Deaths. Per cent. Under 5 years of age, . 206 26 12-62 From 5 to 10 years of age, . 233 20 8*58 ,. 10 „ 20 „ ,, . 183 9 4*92 „ 20 „ 40 „ „ . 232 39 16-81 „ 40 „ 60 „ „ . 47 6 12*77 „ 60 „ 80 „ „ . 4 o -> 50-00 The mortality seems to vary Avidely in different epidemics, being some- times as low as 15 per cent., sometimes as high as 75 per cent. Etiology.—With regard to the origin of yellow fever there have been great differences of opinion, and up to the present time the specific germ of the disease has not been satisfactorily demonstrated. Several observers, notably Domingos Freire of Brazil, and Carmona of Mexico, have described different micro-organisms which they regard as standing in causal relation to the disease, but in the face of Sternberg's report on the subject to the United States Government, we are unable to accept the organisms de- scribed by them as being the true cause of the affection. Formerly, yellow fever was regarded as being allied to if not actually a modified form of malaria. It is now, however, universally admitted that it is quite distinct from any form of intermittent or bilious remittent fever of malarial origin; for its geographical range is quite different, it is epidemic, it is trans- missible from place to place, it consists of a single attack and protects against future invasion, albuminuria is constant, the spleen is not enlarged, and quinine, so far from being a specific remedy, is believed to be injurious. ^ Yellow fever is a disease of the sea-coast, and rarely prevaUs in regions with an elevation above 1000 feet. Its ravages are most serious in cities, particularly when the sanitary conditions are unfavourable. It is always most severe in the badly-drained, unhealthy portions of a city, where the population is crowded together in ill-ventdated, badly-drained houses. It has already been stated that yellow fever is endemic only in certain localities, and the evidence seems to show that when it has occurred else- where, its occurrence has been due to importation. There is practically no evidence of the latter day de novo origin of the disease. What was the original cause of the disease is stdl shrouded in mystery, but Audouard's | view, referred to on page 476, may be cited as having much to commend it, namely, that it originated at all its endemic centres from the filth of the slave ships, which filth was the putrid dysenteric discharges of the sick i negro Begarded in this light, yellow fever has been given us in the dejecta of another race, which, brought in considerable quantities in the bUges of ships to ports, has there been discharged into harbour mud and soil. The mud of these harbours, and the foreshores of the adjacent lands, continue to be endemic foci of the disease. One of the most striking features of yeUow fever is that its infectious principle is often transported by ships. It may also be transported by fomites, and also be conveyed from place to place by the sick. The infec- tion has often been found to cling to the hull, or perhaps to the cargo, of a particular vessel, after the creAv have been paid off. It is believed in the YELLOW FEVER. 675 West Indies that a cargo of hides or sugar is favourable, and one of salt unfavourable, to the development of yellow fever on board, or to its transfer from one port to another, even when the crew escape. In not a few instances an outbreak of the disease has followed the arrival of ships which, although coming from infected places, have apparently had no actual sickness on board, either at the time of arrival or during the voyage. Similarly, outbreaks in towns have followed the arrival of apparently healthy people from infected locahties. Strong as is the evidence in favour of the view that yellow fever is a communicable disease, equally strong e-vidence is forthcoming to show that its communicability differs widely from that of smaU-pox, typhus, and other typically infectious maladies, and that in certain important respects yellow fever resembles, as regards communicability, cholera or enteric fever. Thus, when it prevailed in Lisbon in 1857, 182 persons are said to have left the city for different places in Portugal, carrying away with them the disease, and 86 died, but in no instance was it communicated to other persons in the places whither they went. It is a matter of very general experience that those in close attendance upon the sick do not specially contract the disease. In 1865 Buchanan, having investigated with great care the local epidemic at Swansea, came to the conclusion that "the evidence tending to negative personal contagion was about as strong as such evidence can by its nature ever be." Sternberg says this was also the experience of the physicians in charge of the Charity Hospital of New Orleans. " So long as the hospital and its vicinity remain uninfected, cases do not originate in the hospital, although yellow fever patients may be admitted to the wards with unacclimatised persons suffering with other diseases, and be cared for by susceptible attendants." All these facts indicate that the yeUow fever patient does not commonly infect others directly, but that he nevertheless gives off, probably with his discharges, the virus of the disease, and that this, under suitable conditions, is capable of infecting the particular locality, and of thus indirectly giving \ rise to the disease in others. Outside the body the micro-organism prob- 1 ably finds a habitat in the soil. It is also notable that the virus of yellow fever shows a special ability to attach itself to ships and dwellings. There is at present no evidence that yellow fever is spread by infected water or milk, but the absence of evidence on these points must not be taken as excluding these agencies, and, judging from the analogy of cholera and enteric fever, there is an a priori probability that the cause is swallowed also in this case, and that it may possibly enter with the drinking water or food. The incubation period is short, and varies from twenty-four hours to five days. One attack of yellow fever usually confers immunity, though even this immunity seems to be lost by long absence from endemic localities. This matter of those habitually residing in yellow fever localities enjoying a relative immunity raises the question whether such immunity is transmissible by heredity, or whether it is entirely acquired by each indi-vidual for him- self. The weight of evidence is in favour of the view stated by Sternberg that " the Creole child OAves his immunity not to his parents, but to indi- vidual acclimatisation, and not unfrequently, to say the least, to a mild, unrecognised attack of yelloAV fever." Prevention.—Becognising that yellow fever is a filth-begotten disease, the chief prophylactic measures will be (1) to provide adequate arrangements for the removal and disposal of excreta and refuse; (2) to provide free ventUation, and avoid overcrowding; (3) to ensure a pure and Avholesome G7G THE INFECTIVE DISEASES. Avater-supply, with proper means of personal cleanliness. Once a case of the disease has occurred, the f olloAving special measures should be adopted:— (1) Isolation of the sick person; (2) disinfection of all discharges, especially the vomit and excreta, preferably these should be burned; (3) disinfection of all bedding and clothing; (4) free ventilation of the sick-room. If an outbreak has occurred in a house or barrack, fumigation, scraping and hme washing of the walls, flushing of seAvers, and thorough disinfection in every way must be carried out. Similar procedures are necessary in the case of a ship. Owing to the ready transportability of the contagion in fomites, baggage, cargo, &c, all these materials require careful fumigation and disinfection. The creAvs and passengers of ships arriving from infected localities should be medically inspected, and if in good health may be allowed to proceed to their destinations, after note has been taken of their names and addresses, and notification of the same made to the sanitary authorities of the locahties concerned. The sick and apparently sick should be detained until all doubt of possible infectivity has been removed. If an outbreak of yellow fever occur in a barrack, it is impossible then to attempt any cleansing of sewers; the only plan is to evacuate the barracks and isolate the infected body of men. This has been done many times in the West Indies with the best results. As a preventive measure, also, evacu- ation of the barracks and encampment inland, well aAvay from foreshores, is a most useful plan. Before the barrack is reoccupied, every possible means should be taken to cleanse it; sewers should be thoroughly flushed; waUs scraped and limeAvashed, and disinfection of the building, bedding, and clothing most scrupulously carried out. If a barrack cannot be altogether abandoned, the ground floors should be disused. There are several instances in Avhich persons living in the loAvest story have been attacked, while those above have escaped. If it appears on board ship, take the same precautions with regard to evacuations, bedding, &c. Treat all patients in the open air on deck, if the Aveather permit; run the ship for a colder latitude; land all the sick as soon as possible, and cleanse and fumigate the ship. A predisposition to the disease is caused by fatigue, especially when combined with exposure to the sun, by drinking, and by improper food of any kind which lowers the tone of the body. No prophylactic medicine is known, neither has any satisfactory method of preventive inoculation been devised, though at one time Freire's efforts in this direction Avere suggestive of success. BIBLIOGBAPHY AND REFERENCES. Abel and Claussen, " Untersuch. u. die Lebensdauer der Cholervibrionen in Fakalien," Ccntr.f. Bakter., xvii. No. 3, p. 77 ; also No. 4, p. 118. Adami, "Notes upon an Epizootic of Rabies," Brit. Med. Journ., Oct. 12th, 1889. Adams, " The Relation- ship between the Occurrence of Diphtheria and the Movements of Subsoil Water," Proc. 8th Pnternat. Cong, of Hygiene and Demogr., Buda-Pesth, 1894. Anderson, "Tuberculosis and its Prevention," Journ. Amer. Med. Assoc, 1894, p. 300. Andrewes and Parry Laws, On the Micro-organisms of Savage : their relation to Sewer-air, a.nd the relation of the Bacillus of Typhoid Fever to Sewage ; printed by order of Main Drainage Committee of the London County Council, 1894. Ballard, On Epidemic Diarrhoea, Report of Med. Off. to Local Govern. Board, 1887; also Report on Middlesborough Epidemic, Idem, 1889 ; also Report on an Acute Specific Disease Characterised by a Peculiar Diarrhoea—the so-called Welbeck Disease, Supp. to 10th Rep. Local Government Board, 1880-1. Barnes, " On the Etiology of Diphtheria," Brit. Med. Journ., July 28th, 1888. Barry, Report on Small-pox BIBLIOGRAPHY AND REFERENCES. 677 Epidemic at Sheffield, 1887-8, to Local Govern. Board, published 1889 ; also Report on the Origin and Progress of the Western Diffusion of Cholera during 1892, Report of Med. Off. to Local Govern. Board, 1892-3, p. 117 ; also Report on the Prevalence of Enteric Fever in the Tees Valley, Supp. to 21st Annual Report of Local Govern. Board, 1891-2. Belleav, The History of Cholera in India, 1862-81, Lond., 1885. BERAU<;ER-FERArD, TraiU theorique et clinique de la Dysenteric, Paris, 1893. Bruce-Loav, Report on some Localised Occurrences of Cercbro-Spinal Meningitis in certain Parishes of the Eastern Counties, 20th Report of the Local Govern. Board, Report of Med. Off., p. 117. Buchan and Mitchell, " Influence of Weather on Mortality," Journ. Scottish Meteorological Society, July 1874. Carter, "Aspects of the Blood-spirillum in Relapsing Fever," Brit. Med. Journ., ii., 1881, p. 517. Clemow, Epidemic Influenza, April 1890 ; also The Cholera Epidemic of 1892 in Russia, Lond., 1893 ; also "The Spread of Cholera by Water," Brit. Med. Journ., ii., 1894, p. 801. Copeman, "Variola and Vaccine : their Manifesta- tions and Inter-relationship in the Lower Animals," Trans. Epid. Soc, 1892-3, p. 142. _ CorPEN-Jones, " Uber die Morphologie u. Systematische Stellung des Tuber- kelpilzes u. iiber die Kolbenbildung bei Aktinomykose u. Tuberkulose," Centr.f. Bakter., 1895, xvii. No. 1. Creighton, Unconscious Memory in Disease, Lond., 1886 ; also History of Epidemics in Britain, Camb., 1891. Crookshank, History and Pathology of Vaccination, Lond., 1889. Cunningham, "On some Species of Choleraic Commas Occurring in Calcutta," Scientific Memoirs of Med. Off. of Army of India, Part vi., 1891. Cza.tkoavski, "Uber die Mikroorganismen der Masern," Centr.f. Bakter. u. Parasiteulcundc, Bd. xviii, 1895, p. 517. Davidson, Gcograph. Pathology, Edin., 1892 ; also Article on "Malarial Diseases," in Hygiene of Warm Climates, Lond., 1893, p. 113—this article contains good biblio- graphical references on the subject. Daavson-Williams, " The Route of Asiatic Cholera in 1892," Brit. Med. Journ., Sept. 17, 1892. Donovan, " On the Microbian Doctrine of Yellow Fever," Trans. Epid. Soc, N.S., vii., 1887-8, p. 80. Doavnes, "Contribution to a Study of the Causes of Epidemic Diphtheria," Practitioner, vol. xxxi. p. 471 ; vol. xxxii. p. 67. Duncan, The Prevention of Disease in Tropical Campaigns, Lond., 1888. Dunn, "Bacteriological Origin of Puerperal Sepsis," Richmond, U.S.A., Medical Journal, 1894, p. 201. Edavardes, Vaccination and Small-pox, Lond., 1892. Farr, Report cm Cholera Epidemics in England, Supplement to the 29th Annual Report of Registrar-General. Fayrer, Tropical Dyseidcry and Chronic Diarrhoea, Lond., 1881. Fehlelsen, Die JEtiologie des Erysipcls, Berlin, 1883 ; an English translation by Ogilvie, Lond., 1886. Finkler, Die Acuten Lungenentzundungen als Infections- krankheitcn, Wiesbaden, 1891. Golgi, "On the Malarial Parasite," Fortschritte der Mcdicin, 1889, No. 3. Green- field, On the so-called Wool-sorters' Disease, 11th Report Local Govern. Board, Rep. of Med. Off., p. 207. Greenhoav, Report on Districts ivith excessive Mortality from Lung Disease, 3rd and 4th Reports of Med. Off. to Privy Council, 1860-61. Gress- avell, " Diphtheria as a Chronic Malady in Particular Individuals, with Liability in them to Recrudescence," Trans% Epid. Soc, N.S., vol. v., 1885-6; also On the Natural History of Scarlet Fever, Lond., 1890. Hamer, On the Conditions determining Insusceptibility, 21st Rep. Local Govern. Board, 1891-2, Rep. of Med. Off, p. 201. Han kin, "Observations on Cholera in India," Indian Med. Gazette, March 1895, p. 92. Hansen, "On the Leprosy Bacillus," Virch. Archie, Bd. Ixxix. and xc. Hellin, "Das Verhalten der Cholerabacillen in aeroben u. anaeroben Kulturen," Arch. f. Hyg., 1894, Bd. xxi. No. 3, p. 308. Heubner, Article upon " Dysentery," in Ziemssen's Encyclopaedia, vol. i., Lond., 1875. Hinsdale, "The Comparative Rarity of Pulmonary Tuberculosis in the Highlands of Pennsylvania and the adjacent Counties of NeAv York," Amer. Med. News, ii., 1894, p. 113. Hirsch, Geograph. and Historical Pathology, New Syden- ham Society's Translation, Lond., 1886. Hirschberger, Experim. Beitrdge :ur Infektion der Milch tuberculosa- Thicrc, Miinschen, 1889. James, Report on the Epidemic of Bubonic Plague in Hong Kong in 1894, Array Medical Department Report, vol. xxxv. p. 330. Kartulis, " On the Amoeba Coli," Centr.f. Bakter. u. Parasiten, Bd. vii. 2 ; also "Zur xEtiologie der Dysenterie in iEgypten," Yirch. Archiv., 1885. Kellog, "On the Identity of B. coli Avith B. Eberth," New York Mod. Medical aiul Bacteriological 678 THE INFECTIVE DISEASES. Review, No. 2, 1894, p. 29. Kelly, "On the Relation of Soil to Diphtheria," Lancet, ii., 1886, p. 350 ; also "On an Outbreak of Enteric Fever in West Worth- ing apparently due to Pollution of the Water Mains through Hydrants," Public Health, Jan. 1894. Kelsch and Kiener, Traiti des Maladies des Pays chauds, Paris, 1889. Kempner, " Uber den vermeintlichen Antagonismus zwischen dem Choleravibrio u. dem B. coli commune," Ccntr. f. Ball., 1895, Bd. xvii. No. 1. Klein, Article on the " Pathology of the Infectious Diseases," in vol. ii. of Stevenson and Murphy's Treatise on Hygiene, Lond., 1893 ; also On Diseases occurring naturally in Cats in Association with Human Diphtheria, 19th Rep. Local Govern. Board, Rep. of Med. Off., 1889, p. 162 ; also various papers on the Etiology of Diphtheria in 18th, 19th, and 20th Reports, Idem ; also " On Anti-cholera Vaccina- tion," Brit. Med. Journ., March 25th, 1893, p. 632; also "On the Etiology of Typhoid Fever," Brit. Med. Journ., ii., 1894, p. 797 ; also on same subject in App. to Rep. Med. Off. Local Govern. Board, 1892-3, p. 345. Koch, " Further Researches on Cholera," Brit. Med. Journ., Jan. 1886, p. 6 ; also Idem, 1892, ii. p. 540 ; also " Conferenz zur Erbrterung der Cholerafrage," Berliner Klin. Woch., 31, 1884. Lafleur and Councilman, " On Amoebic Dysentery," John Hopkins Hospital Reports, vol. ii. Nos. 7, 8, and 9. Laa'eran, " L'Etiologie du Paludisme," Revue Scicn- tifique, 1894, ii. No. 15, p. 449; also Paludism, NeAv Sydenham Soc, 1893. Leavis, " Cholera in Relation to certain Physical Phenomena," from his Path, and Phys. Researches, London, 1888. Lingard, On the Relation of Scroftda, Lupus, and Tuberculosis, 18th Rep. Local Govern. Board, Rep. Med. Off, 1888, p. 462. Longstaff, The Geographical Distribution of Diphtheria in England and Wales, Supplement to Rep. Med. Off. Local Govern. Board, 1887; also "Phthisis, Bron- chitis, and Pneumonia," Trans. Epidem. Soc, 1883, vol. ii., N.S. ; also Studies in Statistics, Lond., 1890. Losch, "On the Amceba Coli," Yirch. Archiv. f. Path. Anat., 1875, Bd. Ixv. p. 196. Macnamara, The History of Asiatic Cholera, Lond., 1876. Maggiora, "On the Amceba Coli," Centr. f. Bakterien u. Parasit., Bd. xi. Nos. 6 and 7—this article contains a good bibliography. Man .son, "On the Nature and Significance of the Crescentic and Flagellated Bodies in Malarial Blood," Brit. Med. Journ., ii., 1894, p. 1306. Marchiafava and Celli, "Untersuch. iiber die Malaria Infektion," Forlschritte der Medicin, 1885, pp. 339 and 787 ; also two Monographs on Malaria and the Parasites of Malarial Fevers, New Sydenham Soc, 1894. Martin, On the Chemical Pathology of Diphtheria, 21st Rep. Local Govern. Board, Rep. Med. Off., 1891-2, p. 147 ; also On the Chemical Pathology of Anthrax, 19th and 20th Rep. Local Govern. Board, Rep. Med. Off., pp. 255 and 235. Massiatin, "On the Amceba Coli," Centr.f. Bakter. u. Parasit., Bd. vi. Nos. 16 and 17. M'Fadyean, "The Suppression of the Contagious Diseases of Animals," Brit. Med. Journ., ii., 1894, p. 758. M'Vail, Vaccination Vindicated, Lond., 1887. Meavins, "Zur Epidem. der Diphtherie," Berl. Klin. Wochsch., 1894, No. 42, p. 954. Moore, "Pythogenic Pneumonia," Dublin Journ. Med. Sci., May 1875. Munro, "On an Outbreak of Scarlet Fever connected Avith an Udder Disease of Coavs," Public Health, Aug. 1893, p. 345. Neisser, "On the Leprosy Bacillus," Yirch. Archiv., Bd. Ixxxiv. Netten-Radcliffe, On the Modern History of Levantine Plague, Rep. Med. Off. Frivy Council, No. vii., 1875. Obermeyer, "On the Spirillum of Relapsing Fever," Centr.f. d. Med. Wissensch., 1873, No. 10. Ogata, "Uber d. B. Dysenteriae," Centr.f. Bakt. u. Parasit.. March 9th, 1892. Parsons, "On the Association of Diphtheria with Scarlet Fever," Trans. Epidem. Soc, 1883-4 ; also On an Outbreak of Scarlet Fever, with associated Diphtheria and Sore Throat, occurring in the Macclesfield Rural and Urban Sanitary Districts in connec- tion with a particular Supply of Milk, 19th Rep. Local Govern. Board, 1889, Rep. Med. Off., p. 89 ; also Report on an Epidemic of Pneumonia at Scotter, Lincolnshire, 20th Rep. Med. Off. Local Govern. Board, 1890, p. 95 ; also Reports on the Influenza Epidemics, 1889-90, to the Local Govern. Board, 1891 and 1893. Pfeiffer, "On the Bacillus of Influenza," Deutsche Med. Wochsch., No. 2, 1892. Pfihl, " Beitrag zur Lehre von dem Cholera Epidemien auf Schiffen," Zeitch. f. Hyg., xviii. heft 2. Poavell, " On Acute Lobar or Croupous Pneumonia," Brit. Med.'Journ., ii., 1895, p. 1149. Poaver, Report upon an Outbreak of Milk Scarlatina in London in 1885, Rep. Med. Off. Local Govern. Board, 1885, p. 73 ; also Report upon the Influence of the Fulhain Small-pox Hospital upon the Diffusion of the Disease 14th BIBLIOGRAPHY AND REFERENCES. 679 and 15th Rep. of Med. Off. Local Govern. Board, 1884-5 ; also Report upon Epi- demic of Diphtheria in York Town and Camberley, 16th Rep. Med. Off. Local Govern. Board, 1886. Ransome, "On the Form of the Epidemic Wave," Trans. Epid. Soc, 1881-2; also Milroy Lectures " On the Etiology and Prevention of Phthisis," Brit. Med. Journ., vol. i., 1890. Rehn, "Typhoide Erkrankung eines 2-jahrigen Kindes nach dem Genuss unzureichend abgekochter Milch. Infektion durch Bacterium coli," Hyg. Rundschau, 1894, No. 21, p. 964. Report of the English Commission on Pasteitr's Researches on Hydrophobia, 1886. Report of Royal Commission on Tuberculosis, Lond., 1895. Reyburn, " The Life History of the B. Tuberculosis in its relation to the Cure of Tuberculosis in Man," Medical Age, New York, 1894, p. 458. Rodet, Roux, and Arloing, "On the Identity of B. coli with B. Eberth," Trans. Internat. Cong. Hygiene, Lond., 1891, ii. p. 272. Roux, "Upon Preventive Inoculation," .Croonian Lecture before Royal Society, Brit. Med. Journ., i., 1889, p. 1269. J J*> > Schafer, "On the Persistence of Loffler's Bacillus after Diphtheria," Brit. Med. Journ., Jan. 12th, 1895. Seaton, Report on Epidemic Small-pox in the United Kingdom, Rep. Med. Off. Local Govern. Board, 1874. Shakespeare, Report on Cholera in Europe and India, Washington, U.S.A., 1886. Sharman and Lamkin, "The Relationship between Bovine and Human Tuberculosis," Med. Record, ii., 1894, No. 13, p. 412. Simon, Public Health Reports, more especially that contained in 9th Annual Rep. to Privy Council, 1866, and contained in vol. ii. of the Reports as republished by Sanitary Institute, 1887. Sisley, Epidemic Influenza, London, 1891. Sobernheim, " On the Intra-peritoneal Cholera Infection of Guinea-pigs," Revue d'Hygiene, 1893, No. 22 ; also Practitioner, March 1894, p. 223. Spear, Report on the so-called Wool-sorters Disease, Rep. Med. Off. Local Govern. Board, 1880-1, p. 66 ; also Report for 1882, p. 82. Squire, " Measles Epidemics, Major and Minor," Trans. Epidem. Soc, 1892-3. Sternberg, " Report on Yellow Fever to United States Government," Journ. Amer. Med. Assoc, Nov. 30th, 1889. Sykes, " On the Increase of Diphtheria Mortality in London," Practitioner, Aug. 1894. Thompson, "Notes on the Observation of Malarial Organisms in connection with Enteric Fever," Trans, of Assoc. Amer. Physic, 1894, p. 110. Thomson, On an Epidemic of Enteric Fever in Bow, Worthing, and the Villages of Broadwater and West Tarring, Report to Local Govern. Board, 1894. Thorne-Thorne, On an extensive Epidemic of Enteric Fever at Red Hill, CcUerham, and adjoining places, 9th Report Local Govern. Board, 1880, Appendix 8 ; also Report on the Recent Occur- rence of Epidemic Cerebro-Spinal Meningitis in the Basin of the Mediterranean, Rep. Med. Off. in 18th Rep. Local Govern. Board, 1888, p. 365 ; also Diphtheria, its Natural History and Prevention, Milroy Lecture, 1891. Tomkins, " On Epidemic Diarrhoea in Leicester," Brit. Med. Journ., July 27th, 1889. Thresh, "Diph- theria in relation to Manure Nuisances," Practitioner, Sept. 1892; also "On an Epidemic of Diphtheria associated with Scarlet Fever and Measles," Practitioner, Feb. 1893. Turner, On the relation of Diphtheria to the Lower Animals, Report Local Govern. Board, 1886, Supplement by Med. Officer. Yillemin, Etude sur la Tuberculose, Paris, 1868. Washbourn, "On Acute Pneumonia," Brit. Med. Journ., ii., 1895, p. 1154; also "On Immunity," Trans. Epidem. Soc, April 1895, N.S., vol. xiv. Weibel, "Untersuch. u. die Infektiositiit des Cholera vibrio und iiber sein Yerhaltniss zum Vibrio Metschnikovii," Archiv. fur Hygiene, Bd. xxi., 1894, p. 22. Whit- taker, "Predisposition to Phthisis," Trans. Med. and Chir. Faculty of Maryland, 1894, p. 64. Whitelegge, "Changes of Type in Epidemic Diseases," Milroy Lecture, 1893, Brit. Med. Journ., i., 1893; also "On Age, Sex, and Season in Relation to Scarlet Fever," Trans. Epidem. Soc, N.S., vii., 1887-8, p. 153. Willoughby, "Retrospect of the successive Epidemics of Cholera in Europe and America," Trans. Epid. Soc, N.S., vol. x., 1890-1. Woodbridge, "Typhoid Fever," Journ. Amer. Med. Assoc, 1894, p. 311. Woodhead, "An Address on the Channels of Infection in Tuberculosis," Lancet, ii., 1894, p. 957. Wright and Bruce, " On Haffkine's Method of A'accination for Cholera," Brit. Med. Journ. Feb. 4, 1893, p. 227. CHAPTER XIII. DISINFECTION. The term disinfectant, which has now come into popular use, has unfortu- nately been employed in several senses. By some it is applied to every agent which can remove impurity from the air; by others to any substance which, besides acting as an air purifier, can also modify chemical action, or restrain putrefaction in any substance, the effluvia from which may con- taminate the air; while, by a third party, it is used only to designate the substances which can prevent infectious diseases from spreading, by destroying their specific poisons. This last sense is the most correct, and it is that in which it is solely used here. The mode in Avhich the poisons are destroyed, whether it be by oxidation, deoxidation, or arrest of growth, is a matter of indifference, provided the destruction of the poison is accom- plished. To those substances which suspend vitality and the power of propagation of micro-organisms, thereby restraining or absolutely preventing decomposition, the general term antiseptics should be applied. Those substances which merely oxidise the products of decomposition, and thereby destroy or correct offensive odours, are best described as deodorants. In a great many instances the substances Avhich are recommended as disinfectants are little more than deodorants, or, at most-, antiseptics or means of checking and delaying putrefaction. The true principle of disinfection is to attack the specific poisons of disease at their seats of origin, as far as these are accessible to us. It was the instinct of genius which led "William Budd to point out that the way to prevent the spread of scarlet fever is to attack the skin from the very first; to destroy the poison in the epidermis, or, failing that, to prevent the breaking up and passage into the air of the particles of the detached epidermic scales. Oily disinfectant inunctions of the skin, and the most complete disinfection of the clothing which touches the skin of the patient, are the two chief means of arresting the spread of scarlet fever. The rules for small-pox are almost identical, though it is more difficult to carry them out. In enteric fever, cholera, and dysentery the immediate destruc- tion of all particles of infection in the stools and urine by strong chemical reagents, and the prevention of the poison in its active state getting into sewers or drinking water or food, are the measures obviously demanded by the peculiarities of these special diseases. The more completely these points are investigated, and the more perfectly the breeding-places in the body are knoAvn, the more perfect will be our means of disinfection. Disinfectants are physical and chemical: the chief physical agent is heat; the cbief chemical agents are perchloride of mercury, carbolic acid, and chloride of lime, Avith certain gaseous bodies of strong germicidal power. HEAT AS A DISINFECTANT. 681 In actual practice, disinfection proper is largely aided by the preliminary removal of infection by the scraping and stripping of paper from walls, the washing and sweeping of floors, to say nothing of air perflation, and the washing, beating, shaking, and exposure of clothes. These procedures, excellent in their way, are uncertain and incomplete; the destruction of germs, or true disinfection, is only attainable by either heat or chemical means. For articles of small value, the safest plan is to burn them. The value of fresh air and sunlight as aids to disinfection must not be overlooked. Direct sunlight, and especially the most highly refrangible, ultra-violet, rays of the spectrum, have a powerfully restraining action on the growth of bacteria, though neither oxidation nor solar action are actually germicidal, themselves, as to spores. Besides these agencies, a comparative purification of the air can be effected by many substances in use for this purpose, but these latter must be regarded as supplemental to, not as substitutes for, true disinfectants. Heat as a Disinfectant.—Tyndall was the first to shoAV that, whilst prolonged boihng failed to sterilise an infusion, successive heatings for a short time, even below the boiling point, were successful. The explanation proposed is, that during the period of latency the spores are in a hard state capable of resisting high temperature, but that just before the period of active germination they become softened, and therefore amenable to the influence of heat. As, however, spores in various stages may exist in the same fluid, successive heatings are necessary so as to arrest each group ^ at the proper time; but by repeating the heatings sufficiently often an infusion may be sterilised at a point below the boiling point of water. This method of intermittent heating is now in general use for sterilising cultivating fluids. Important in all ways, this question of the nature of contagia is especially so in a practical sense, viz., that of the easy or difficult destruction of these agents. It does not, however, follow that ordinary putrefactive bacteria are identical with those AAdiich may be supposed to produce disease. It is probable that they are quite different, and that disease bacteria (except B. anthracis) are more easily destructible by heat. According to Klein micrococci of scarlatina are killed at 85° C. (185° F.). The experiments by Koch on heat as a disinfectant led him to the folloAv- ing conclusions:— 1. As to dry heat. "Sporeless bacteria are destroyed in 1| hour by hot air at a temperature slightly exceeding 100° C. Spores of fungi require 1^ hour at 110° to 115° G; spores of bacilli require 3 hours at 140° C. Heat penetrates so sloAvly that even for articles of moderate size, such as pillows, 3 to 4 hours' exposure at 140° C. is insufficient. Exposure for 3 hours to 140° C, which is necessary for thorough disinfection, damages most fabrics more or less." 2. As to moist heat. Steam under pressure killed anthrax spores after ten minutes' exposure to a temperature of 110° C. Steam at atmospheric pressure destroyed anthrax spores after exposure of one hour. Koch con- cludes that in every respect exposure to a current of steam at 100° C. is the most satisfactory method. Parsons found that the spores of B. anthracis were killed after 4 hours' exposure to a dry heat of 212° to 216° F. or of 245° F. for 1 hour. Bacteria without spores were killed in 1 hour at 212° to 218° F., while boiling for one minute, or exposure to steam at 212° F. for 5 minutes, was sufficient to destroy spores. The Greater power of moist heat is principally due to the large amount of latent heat in steam. To convert 1 lb of Avater at 212° F. into steam at 682 DISINFECTION. 212° F., requires nearly 1000 times as much heat as it docs to raise 1 It) of water from 211° to 212° F. Conversely, a corresponding amount of heat is liberated when 1 lb of steam at 212° F. is condensed into water at 212° F. When an object is heated by being placed in hot dry air, not only is no latent heat yielded up to it by the air, but, on the other hand, before the object can attain the temperature of 212°, any water which it may contain (and all textile fabrics, even though dried at ordinary temperatures, retain a quantity of moisture) must be evaporated; in this evaporation, heat passes into the latent form, and the attainment of the desired temperature is thus delayed. When steam penetrates into the interstices of a cold body it undergoes condensation in imparting its latent heat to the body. When condensed into water it occupies only a very small fraction* of its former volume. To fill the vacuum thus formed more steam presses forward, in its turn yielding up its heat and becoming condensed, and so on until the whole mass is penetrated. " On the other hand, hot air in yielding up its heat undergoes contraction in volume, but only to a very small extent as compared AA'ith that undergone by steam in condensing into water " (Wynter-Blyth). Dry heat is inferior to moist heat, owing to the difficulty of ensuring the complete penetration of the necessary high temperature throughout the interior of bulky articles. If pillows, bales of goods, &c, are simply placed in a hot-air apparatus, the outside may be scorched, while the inner parts have never reached the proper temperature. Whitelegge, working with Bansom's hot-air apparatus, obtained the folloAving results; the escaping air having a temperature varying from 245° to 260° F.—a registering maximum thermometer being placed beneath layers of blankets within the apparatus. Duration of Exposure. 2 Layers. 4 Layers. C Layers. 12 Layers. 18 Layers. 4 Hours, .... 6 „ . . . . 8 „..... Deg. I". 220 226 230 Deg. l-\ 206 214 221 Deg. F. 190 208 215 Deg. F. 162 174 196 Deg. F. 139 153 182 When moist heat was used, a temperature of 212° F. was obtained beneath sixteen layers of blanket after a maximum exposure of seventeen minutes. This temperature, it is to be noticed, was not reached even after eight hours with dry heat with only tAvelve layers of blankets. As the result of a large number of experimental observations upon the effect of heat as a disinfectant, it may be accepted that thorough penetration is absolutely essential, though the actual amount of heat and the duration of its application may vary. As a general rule, it may be said that boiling for a quarter of an hour, or, .if this is not practicable, exposure to moist heat (steam) of 212° F. at ordinary pressure for one hour, will render any article absolutely safe. Dry heat is neither so safe, nor is it so easy of thorough application; if used, a tem- perature of from 245° to 250° F. should be attained and maintained through- out for four hours, even at the risk of some damage to fabrics. This state- ment is someAvhat in excess of theoretical requirements, or what laboratory experiments indicate to be the needs of the case, but it is always advisable to err on the safe side, and keep up the temperature either rather higher or longer than is found to be the experimental limit. The question of temperature'has been much discussed, and with regard to HEAT AS A DISINFECTANT. 683 dry heat especially, is of much importance. It is desirable to get as high a temperature as possible so as to ensure the destruction of infective matter. On the other hand, the temperature must not be too high, for fear of destroying the fabrics. On the Liability to Injury of Articles Disinfected by Heat.—The possible injuries to fabrics when disinfected by heat are practically the following :— (1) Scorching or partial decomposition of organic substances by heat. In its earliest stage this manifests itself by change of colour, of texture, and of Aveakening of strength. Scorching occurs sooner in woollen materials, such as flannels and blankets, than Avith cotton or linen. Most materials Avill bear a temperature of 230° F. Avithout much injury, but Avhen this temperature is exceeded, signs of damage soon begin to sIioav. Flannel and blankets exposed to steam at 260° F. for half an hour acquire a distinct yellow tinge, and their tensile strength is somewhat diminished. Exposed to dry heat of 220° F. for four hours, or a steam heat of 228° F. for half an hour, white flannel acquires a slight yellow tinge, but its textile strength is not appreciably impaired. Cotton, linen, and silk will bear a dry temperature of 230° F. for four hours Avithout little alteration, and also moist heat of 250° F. for half an hour with little change, beyond a slight loss of glaze. Feathers become yelloAvish and brittle after four hours' exposure to steam at 260° F. (2) Overdrying renders things very brittle; but this injury can be con- siderably minimised by alloAving the materials Avhich have been subjected to dry heat to remain in the air long enough to recover their natural degree of moisture before manipulating them. (3) Fixing of stains so that they will not wash out. This property of heat is a very inconvenient one from our present point of vieAv, and is specially marked in the case of albuminous materials coagulable by heat, such as blood or excreta. In order to remove organic stains, the cloth or garment must be steeped in cold Avater. When the grosser dirt has been removed by soaking and rubbing in cold or tepid Avater, the articles may be boiled Avithout injury. (4) Melting of fusible substances, as glue and Avax. This injury does not often occur, and is most commonly met Avith in attempts to disinfect books and leather goods by heat. (5) Alterations in colour, gloss, and shrinkage of dyed and finished goods. Dry heat causes little shrinkage in Avoven materials. Moist heat, on the other hand, or even Avetting Avithout much heat, causes permanent shrinkage in Avoollen goods, as cloth, flannel, and blankets. To this draAvback must be added another, namely, the loss of elasticity and fluffiness, upon Avhich the warmth and softness of Avoollen materials depend. This elasticity is due to the natural grease of the avooI, and is rapidly removed by boiling in Avater or exposure to moist heat. These materials may be washed in cold Avater, or exposed to dry heat of moderate temperature Avithout much deterioration, but a frequent repetition of these processes brings about in time a change similar to that effected by boiling water. (6) Wetting, as Avhen ordinary steam is used, is often undesirable in the case of some kinds of goods, for it produces shrinkage, and causes the colours to run. This wetting is obviated when the steam is used at high tempera- tures, being superheated by the higher degree of heat corresponding to the extra pressure under which it is applied. Forms of Apparatus for Disinfection by Heat.—From Avhat has been said it Avill be readdy seen in Avhat manner heat as a disinfecting agent is best applied. In the earlier forms of disinfecting chambers, a dry heat 684 DISINFECTION. was employed. In the more modern forms, steam has been used Avith the best results. The most important requisites of a disinfecting chamber are: (a) uniform distribution of heat in the interior; (b) a constant temperature maintained during disinfection ; (c) means for ascertaining the actual temperature of the interior at any given moment (Parsons). In apparatus heated by steam, these three requirements are satisfactorily met, and in some of the best dry- heat chambers the results are also fair, but in the majority of them the first condition is not fulfilled. One of the most generally used in this country, and a typical form of steam apparatus for disinfection by moist heat, is that of Washington Lyon. It consists of an oval chamber with double walls, and a door at each end fastened by screAV-clamps, one for the introduction of infected articles, and the other for their removal when the process of disinfection is complete. Steam is discharged into the apparatus by two pipes, the one communicating Avith the cavity formed by the double Avails, and the other with the interior of the chamber, the amount of pressure in each case being indicated by pressure gauges. The object of surrounding the chamber Avith the "jacket " of steam is to prevent loss of heat, and to check condensation. The articles to be disinfected are conveyed to a room at the inlet end of the apparatus, and which must be completely separate from the receiving room at the other or outlet end. The chamber is fitted Avith a light frame on wheels, or Avire cage, in Avhich clothing, &c, can be placed; these are then pushed into the chamber along rails, and the door closely and strongly fastened. Steam, at a pressure of 30 lb to the square inch, having a temperature of 273° F., is first turned into the outer jacket, so as to raise the temperature of the inner chamber to sufficiently great a heat as to prevent condensation of the steam Avhen subsequently turned into it. At the ordinary pressure of the air, water boils at 212° F., and the moment the temperature falls below that point steam condenses. At a pressure of tAvo atmospheres, or 28 lb on the square inch, water boils at, and steam will not condense at, a loAver temperature than 249° F.; while at a pressure of 44 lb to the square inch, or 30 lb above that of ordinary air, the boiling point of water and condensing temperature of steam is 273° F. If, therefore, the tempera- ture of the inner chamber be kept at this point by steam at this temperature being made to circulate around it in an outer jacket, the steam when turned on into it will be kept constantly superheated, and will not condense into moisture unless the temperature fall below that point. After the temperature of the inner chamber is sufficiently raised by the admission of steam to the outer jacket, the steam is then turned on into it, and kept on for some twenty minutes or so, or even longer, according to the nature and number of the articles within it needing disinfection. When this is done, the steam is cut off from the inner chamber and left on in the outer jacket only. The inner chamber thus becomes a drying cell, and any dampness which the articles, put in for disinfection, may have acquired thoroughly driven off before they are withdrawn. Often the steam pressure employed is not more than 10 Bb per square inch in the cavity of the walls, and only some 5 lb in the interior, but these lessened pressures are only used when high temperatures are not required. To attain and maintain a temperature of 250° F., a pressure of at least 28 lb must be employed, and for higher temperatures even a greater pressure still. A modification of the above disinfecting chamber is that of Alliott and Paton, the principal feature of which is that a vacuum producing apparatus is so attached that the ah is exhausted not only from the inner chamber but DISINFECTING CHAMBERS. 685 from the interstices of the articles to be disinfected, thus facilitating the penetration of steam. Further, on the completion of the process, the steam is exhausted by the air pump, so that no deposit of moisture takes place Avhen the doors are opened, leaving the articles, therefore, quite dry. This same apparatus can be also used as a hot-air or dry-heat disinfector. The apparatus of Geneste-Herscher et Cie, Avhich is extensively used in France, acts also by steam at high pressure. It has been very favourably reported upon. Another form is that of Goddard, Massy, & Warner; in it a pressure of 20 lb is used, the temperature of the steam being 240° F. Unfortunately, all the foregoing high-pressure steam disinfectors are expensive, a fact which renders their general employment by local authorities somewhat difficult. This difficulty seems to have been overcome in the case of Beck's steam disinfector, which is cheaper and at the same time efficient. Its special features are (1) the use of low-pressure steam, delivered to the apparatus by an automatic regulator at a rate which cannot be exceeded; (2) the absence of any steam jacket; and (3) a cold shower introduced into the chamber which has for its object the speedy removal of all steam from the interior. This cold shower is prevented from injuring the clothes by a shielding arrangement which distributes the water over a large surface and completely protects the articles from moisture. The penetrating poAver of the loAv-pressure steam (1| lb), the temperatures reached in various thick- nesses of material, the amount of moisture left in the articles after disinfec- tion, and the destructive power of the apparatus upon bacteria have given satisfactory results. The folloAving table shows the temperature reached in various cases : — In 15 minutes—Folds of Blankets. In 35 minutes. 4 Folds. 8 Folds. 16 Folds. In Chamber. In 16 Folds of Blanket. Between Mattresses. 219° F. 218° F. 212° F. 216° F. 220° F. 211° F. Thirty-five minutes are recommended as a desirable time for articles to remain in the chamber of this apparatus for disinfection. Moreover, its simplicity is likely to be of immense benefit in places and institutions where the more complicated high-pressure disinfectors are often umvorkable. A simple and comparatively inexpensive non-pressure steam disinfecting apparatus has recently been brought out by Thresh, and by means of which it is said that a moist temperature, exceeding that of steam at normal pressure and under ordinary conditions (212° F.), is obtained. The principle is a new one and consists in using Avater to which certain saline ingredients have been added in order to raise its boiling temperature to 225° F. Fi°-. 116 which represents in section a Thresh's disinfector, AAdll enable the reader to understand the construction of the apparatus. The central chamber for infected articles, A, is surrounded by a jacket, B, containing the sahne solution which is heated by the furnace, K. The steam given off is directed either to the chamber or into the chimney by a valve, G, and in the former case is distributed in the disinfecting chamber by a plate, C, before passing off into the chimney by a pipe, D. As the water evaporates, an equivalent supply is introduced automatically from a cistern, I, with a ball valve arrangement supphed by a pipe, L. After the disinfecting process, the steam is turned off from the chamber and alloAved to escape 686 DISINFECTION. DTO CHItflNEY Fie. 116. into the furnace flue, and by means of a cod of tubes, E, immersed in the saline solution, ah, which enters at the valve, F, is heated and passes D through the chamber in order to dry the articles. This appa- ratus is an ingenious one and is likely to come into general use. Experiments indicate that a moist temperature of 225° F. is readily maintained, and disinfection effi- ciently performed within an hour. As regards disinfection by dry heat, the ordinary drying closet in a good laundry will sometimes give heat enough, but not ahvays. A baker's oven can also be used in case of emergency. A Avell- knoAvn dry-heat or hot-air dis- infecting apparatus is that of Bansom, which consists of an iron chamber with an external covering of felt and wood. The heat is supplied by means of a circular gas-burner connected with the under surface of the chamber by a flue which conducts the hot air, together with the products of combustion, into the interior, equal distribution being secured by a perforated plate at the bottom. An outlet flue is placed at the top of the chamber. In both flues a thermometer is fixed to indicate the temperature of the incoming and outgoing air. In addition to this a mercurial regulator is fixed in the inlet flue, by means of which the amount of gas consumed, and consequently the amount of heat produced, can be controlled, and this may be adjusted to any temperature desired. As a precaution against fire, an arrangement is connected with the outlet flue by which, when the temperature reaches 300° F., a link of fusible metal is melted, and by this means a damper is •closed and the supply of gas is shut off. No matter by what form of apparatus carried out, disinfection by hot air or dry heat is not so efficacious as by moist heat, but it is required in the case of some articles, such as leather, bound books, &c. Probably 220° or even 212° F. would be a sufficiently high temperature to destroy all disease germs if thoroughly apphed; but this is the great difficulty in Bansom's disinfector, as in other hot-air stoves, the heat being very much greater at some parts of the interior than at others. Chemical Disinfectants.—If we limit our conception of a disinfectant to that of a substance which is capable, by its own inherent poisonous action upon a pathogenic organism, to destroy the life and power of development of that micro-organism, the number of practical chemical disinfectants is small. Practically, we must set aside all disinfectants that are expensive, as well as all those which are not readily soluble in water, or otherwise are difficult to apply and manipulate. To these conditions Ave may further add that a good disinfectant must be rapid as well as certain in its action. In no case ought more than twenty-four hours to be allowed for the complete destruction of all germs, and in many cases only a very brief exposure can be obtained. Chemical disinfectants may be sohd, hquid, or gaseous; but from the nature of the case it is evident that solids must be brought into the form of CHEMICAL DISINFECTANTS. 687 a solution to enable them to penetrate throughout any substance to be dis- infected. Disinfectants, therefore, are practically useful only as solutions, or as gases. The most reliable disinfectants appear to be the following :— Mercuric chloride, or corrosive sublimate, is a well-known and highly poisonous salt. A cold saturated aqueous solution contains about 10 per cent., but two parts of boiling water dissolve one part of the sublimate. It is also readdy soluble in alcohol or ether. Of a strength of 1 in 1000 in water, mercuric chloride destroys the bacilli of glanders, anthrax, enteric fever, diphtheria, the spirilla of cholera, and the micrococci of erysipelas in ten seconds. Spores are not so readily destroyed, requiring an exposure of ten minutes at least: a 1 in 5000 solution produces the same effect in a feAv hours. As a disinfectant, mercuric chloride has three great disadvantages : (1) it corrodes metals, (2) it forms with albumin an inert insoluble com- pound, (3) it is poisonous. To guard against this latter fact it has been suggested to colour the sublimate solution with aniline blue; thus, mercuric chloride \ ounce, hydrochloric acid 1 ounce, commercial aniline blue 5 grains, water 3 gallons, make a solution of the required strength and of a deep blue colour. A better colour is obtained by adding 1 grain of the blue to 10 gallons; this tint is sufficiently characteristic, and does not permanently colour washing fabrics. In the absence of aniline blue any other colouring agent may be added, such as permanganate of potash. By Schill and Fischer's experiments, it appears doubtful whether the perchloride of mercury can destroy the spores of tubercle bacilli in phthisical sputa, even in the proportion of 1 in 500 solution. This inefficient disin- fectant action is probably due to the fact that the salt enters into chemical combination with the proteids of the sputum, or even forms a coating around the bacilli which protects the contained spores from its further action. This peculiarity of the subhmate somewhat detracts from its general utility as a disinfecting agent in albuminous materials, but may be prevented by accidu- lating the solution. Lingard's experiments shoAV that a solution of sublimate, 1 in 960, destroys the human tubercular virus in from four to eight hours. Experi- ments made at ISTetley on this point indicate that with a 1 in 1000 solution, at least twelve hours' exposure should be alloAved for the absolutely complete destruction of all tubercular virus in sputa by mercuric chloride, and even then the reagent must be well mixed with the infected matter. Not less strength than 1 per cent, was necessary to destroy the spores of anthrax and B. subtilis. One part of subhmate in 5000 of gelatin is antiseptic, or sufficient to inhibit the growth of most micro-organisms. Carbolic acid (phenol), when absolute and pure, is in the form of white crystals which melt at 42°*2 C. or 108° F. The solubility of these crystals in water is about that of 1 in 11; a saturated solution in water will contain about 8*6 per cent, of phenol. It is more soluble in weak alkahne solutions than in water; while, when pure, it is soluble in all proportions in ether, alcohol, benzene, chloroform, and carbon disulphide. The ordinary red or dark broAvn fluid sold as carbolic acid is a mixture of ortho-, meta-, and para-cresol. It is less soluble than phenol; a saturated aqueous solution will contain only about 3 5 per cent.; it is soluble in weak alkaline liquids, but is precipitated with excess of alkali. The chief impurities of commercial carbolic acid are tar oils. Their presence and approximate quantity can be estimated by shaking a measured volume of the acid with twice its volume of pure soda solution of 9 per cent, strength. The cresylic and carbolic acids are dissolved by the alkaline liquid, wlhle 688 DISINFECTION. the oils separate, the heavy oils sinking to the bottom, and the light oils rising to the top ; their respective volumes can be then read off. These tar oils are apparently without any disinfectant properties. Numerous " carbolic acid powders " are in the market; these are for the most part mixtures of cresylate and carbolate of lime, and have no appreci- able disinfecting properties. Calvert's carbolic acid powder is a type of the best form of carbolic acid poAvder, as it has not lime for its basis, but is merely a mechanical mixture of the acid with the siliceous residue resulting from the manufacture of aluminium sulphate from shale. Macdougall's powder is another satisfactory preparation of this kind. It is made by adding a certain proportion of crude carbolic acid to an impure sulphite of calcium prepared from the action of sulphur dioxide on ignited limestone. A considerable number of "carbolic acid soaps," containing more or less free carbolic acid, are also in the market. Soap alone we know to have distinct antiseptic qualities, but it is doubtful whether any of these carbolic acid soaps are of the slightest use for disinfecting purposes, or are in any way superior to ordinary soap. Innumerable experiments have been made as to the action of phenol and cresol as disinfectants. Their general tenor has been to show that 1 per cent, solutions of them are able to destroy the more feeble micro-organisms in twenty-four hours, but to ensure destruction of spores and the more resistant forms of microbial life it is necessary to use at least 5 per cent. solutions in water, and the action must be prolonged over a day at least. Wynter-Blyth aptly remarks that " if specific excreta are treated, it is doubtful whether 5 per cent, solutions are of sufficient strength, because associated with the hurtful material there is a quantity of organic matter which must on the one hand remove some of the phenol from the sphere of action, and on the other impede the contact of the phenol with the substance which we Avish to disinfect." Tubercle bacilli are destroyed by a 5 per cent, solu- tion of carbolic acid in half a minute, but the spores require an exposure of at least two hours, especially when present in phthisical sputa. Closely allied to phenol and the cresols is creasote, which is a mixture of several phenol-like bodies. OAving to its insolubility in water, creasote is of little practical value as a disinfectant. Some experiments made indicate it to be about equal in value to cresol. It possesses marked antiseptic properties, and on this account is largely used in the preservation of timber. The disinfecting value of the aromatic acids, phenyl-propionic and phenyl- acetic, have been investigated by Klein. He found that, as regards sporeless anthrax bacilli, they were killed on exposure, even for a few minutes, to solutions of either of the acids in the strength of 1 in 400 or less. A longer exposure was necessary for weaker solutions. Their action on the virus of SAvine-plague Avas marked when the strength was not less than 1 in 800, but tubercle bacilli and spores of anthrax appeared resistant to even the strong solutions. Both these acids are strongly antiseptic. Izal, which is a comparatively new disinfectant extracted from an unknown oil obtained from certain coke ovens, is a creamy-looking emulsion, having an earthy smell, coupled with a faint odour suggestive of phenol. It is readily mixed with water, forming a milky emulsion. Its disinfecting properties have been extensively investigated by us and found satisfactory. A 20 per cent, emulsion destroyed the highly resisting spores of B. subtilis and B. mesentericus in thirty-five minutes. A 10 per cent, emulsion killed vhulent spores of anthrax baciUi in twenty minutes. Non-spore-bearing specimens of the above baciUi were destroyed after five minutes' exposure to 0*5 per cent., or 1 in 200 emulsion. A 0*3 per cent, emulsion destroyed GASEOUS DISINFECTANTS. 689 the streptococcus of pus; and exposure for half an hour to a 1 per cent. emulsion was sufficient to destroy the enteric fever bacillus and the spirilla of cholera. Our observations dispose us to regard izal as a disinfectant of consider- able practical value, and that for concrete cases of disinfection of morbid materials from the various infectious disorders, an exposure for fifteen minutes in the strength of 1 per cent, will be sufficient. Moreover, izal, being free from poisonous properties when introduced by injection into the tissues, or when administered by the stomach, possesses qualities which practically no other efficient disinfectant affords. The inhibitory or anti- septic value of izal is equally defined, as neither spores, micrococci, or non- sporing bacilli and spirilla can germinate in medicated media if the amount of disinfectant added is 0*1 per cent. Chlorine holds the first place among the gaseous disinfectants in common use. It may be prepared for the purposes of disinfection by heating together a mixture of common salt, manganese dioxide, and sulphuric acid, or simply by the action of hydrochloric acid on manganese dioxide. Both these processes are somewhat inconvenient, and it is more easily evolved from chloride of lime (CaCL,,Ca(C10)2) or bleaching powder by the addition of an acid; thus, CaCI2,Ca(C10).2 + 2H2S04 = 2CaS04 + 2HC1 + 2HC10; then 2HC1 + 2HC10 = 2C12 + 2H20. Theoretically, bleaching powder contains 56 per cent, of chlorine, but it is doubtful whether the whole of this gas is obtained on decomposition. Practically, one pound of the powder, on being treated with sufficient acid to completely decompose it, will evolve about 2*8 cubic feet of chlorine gas. We are indebted to the researches of Fischer and Proskauer, and to Cash for most of our knowledge concerning the disinfectant action of chlorine. In ordinary dry air, 5*38 parts of chlorine per 1000 cubic feet of air appear to be necessary to kill all micro-organisms. If the air be moistened, Avhich may be done by wetting the walls, floors, &c, and by diffusing steam, 0*3 per cent, by volume in each 1000 cubic feet of air is sufficient, disin- fection being complete in from five to eight hours. This quantity of the gas can be generated, practically, by decomposing 1J lb of chloride of lime Avith 6 ounces of strong sulphuric acid for each 1000 cubic feet of space to be disinfected. Or, as an alternative, for the same cubic space the folloAving should be used:—common salt, 8 oz.; manganese dioxide, 2 oz.; sulphuric acid, 2 oz.; water, 2 oz.: the water and acid to be mixed together, and then poured over the other ingredients in a delf basin, which should be placed in a pipkin of hot sand. Or four parts by weight of strong hydro- chloric acid may be poured on one part of powdered manganese dioxide. Chlorine decomposes hydrogen and ammonium sulphides at once, and more certainly than any other gas. It doubtless destroys organic matter in the air, as it bleaches organic pigments, and destroys odours, either by abstract- ing hydrogen, or by indirect oxidation. Its action, however, depends greatly upon the humidity; disinfection by chlorine in dry air being very uncertain. It is an extremely irritant, poisonous gas, and being very heavy tends to faU, necessitating the generating vessel to be placed in an elevated situation, in order to secure anything like equal diffusion. Carpets, curtains, &c, should be removed and disinfected by moist heat, as chlorine fails to destroy organisms in them, and they themselves would be injured by its action. Euchlorine, a mixture of chlorous acid and free chlorine, obtained by o-ently heating (by placing the saucer in Avarm water) a mixture of strong hydrochloric acid and potassium chlorate, has been also used instead of 2 x 690 DISINFECTION. pure chlorine. The odour of euchlorine is more pleasant than that of chlorine; it acts as rapidly on iodide of potassium and starch paper, and appears to have a similar action on organic substances; it is probably inferior to pure chlorine, but the ease of development and its pleasanter smeU are in its favour. Chlorine fumigation, carried out under the best conditions, may fail, and often does fail, to disinfect spore-holding material covered over or lurking in chinks and cracks. Delepine and Bansome's observations, upon the practical disinfection of tuberculous rooms by chlorine, show clearly that, as often perfunctorily carried out, attempts at disinfection by chlorine gas are fallacious. These observers recommend that, in place of evolving the crude gas from inconvenient apparatus, the chlorine in the nascent state may be generated in the places required by thoroughly Avashing aU parts of a room with a 1 in 100 solution of bleaching powder. After the application of the solution, chlorine continues to be evolved so long as all the chlorinated lime has not been decomposed, and that without anything further being required to be done. If necessary, it is easy to increase its activity by adding an acid to the solution, or by saturating the air of the rooms with acid fumes and by raising the temperature for a few hours. This Avashing with chloride of lime-water should for safety be repeated three or four times in succession. By starting each time at the same corner of a room, each layer would have time to penetrate into the wall and partly dry before the next is applied. The room may be closed afterwards, a small safe petroleum stove being first placed in the middle of the chamber, precautions being taken to prevent any chance of fire. Over this stove a large tin basin full of acidified water or chlorinated lime solution should be placed. Disinfection by chlorine in this Avay should be complete in less than three hours. Bleaching powder itself does not spoil things as much as one would expect, and can be used as indicated in rooms from which aU draperies and carpets have been removed without any fear of damage, provided the walls and ceihngs are not decorated with valuable paintings or papers. The quantity of powder required for a room measuring 10 feet in all directions Avould not be more than 8 ounces, and the quantity of water 3 pints for one washing. Sulphurous acid, or sulphur dioxide, has been for many years the most common and favourite disinfecting agent, owing to its cheapness and the ease with which it can be generated. This gas is formed whenever sulphur is burned in air or oxygen. It is usually generated by taking about a pound of roll sulphur, seal up a room as hermetically as possible, light the sulphur in some suitable receptacle, and let it burn as long as it will. A stdl more convenient method is to take an ordinary benzoline lamp, fill it with carbon bisulphide, and light; as the carbon bisulphide is consumed, the sulphur is evolved as sulphur dioxide. The generation of sulphur dioxide by these means is now largely superseded by the employment of sulphurous acid liquefied under pressure, and which is supphed by the manufacturers in cylinders avadable for convenient use. When sulphur is burned in a per- fectly close space, its consumption is limited by the quantity of air in that space : theoretically, a cubic foot of air will burn up 634 grains of sulphur, but it Avill not do this unless freely supphed with air. One pound of sulphur, when completely burnt, gives off 11*2 cubic feet of sulphur dioxide, Avhich for 1000 cubic feet of space gives 1*12 per cent. With the addition of alcohol under careful experimental conditions, 40 per cent, of the possible total quantity of sulphur in a closed space can be burnt, but in ordinary rooms not much more than 20 per cent, is usually consumed. To attain GASEOUS DISINFECTANTS. 691 the maximum consumption, the sulphur must be broken up into pieces not larger than a hazel nut, and divided about a room, never putting more than one pound in any one vessel. Sulphur dioxide is a poAverful reducing agent, uniting Avith the oxygen of many substances to form sulphuric acid. It may occasionally give up oxygen, and Avhen mixed Avith much vegetable matter may itself give rise to sulphuretted hydrogen. Commonly, it destroys hydrogen sulphide, form- ing water and sulphur. The bactericidal or disinfectant value of sulphurous acid has been exten- sively investigated by Cash, Wolffhiigel, Koch, and others. On the whole, their results have been unsatisfactory, though, on the other hand, Dubief and Bruhl found it to be an effectual germicide, especially when the air is moist. It has been proved over and over again that the best results Avith this agent can only be obtained under very strict experimental conditions, such as are quite unattainable in ordinary circumstances. The best results are obtained in imperfectly ventilated places by well moistening the sulphur Avith methylated spirit, Avhen, under the most favourable conditions, the air of the room thus disinfected may contain 10 per cent, of sulphur dioxide. Koch's experiments show that even when present to this extent, and the air saturated Avith moisture, micro-organisms greAV vigorously after twenty-four hours' ex- posure. To obtain this percentage of sulphurous acid gas in the air, even under favourable circumstances, it would require at least 10 lb of sulphur to be burnt for each 1000 cubic feet of air space; as, however, it is impossible to burn up all the sulphur, even this quantity Avould not yield the amount of S02 theoretically required. As the disinfection of any given place is usually a complex operation, involving afterAvards mechanical processes of scrubbing and cleansing, it is possible that a less quantity may suffice, but in any case this should not be placed at a lower hmit than 3 tt> of sulphur for each 1000 cubic feet of space. Too great reliance, however, must not be placed upon disinfection by means of sulphurous acid; at best it is an uncertain agent, and distinctly inferior to either chlorine or nitrous acid. The slightest covering will protect micro-organisms from its action. Nitrous acid or Nitrogen tetroxide can be evolved by placing a piece of copper in nitric acid and a little water. The nitrogen dioxide Avhich is given off takes oxygen from the air, and red fumes, consisting chiefly of nitrogen tetroxide or nitrous acid (N02), are formed. The oxidising action of nitrous acid is very great on organic matter. It removes the smell of the mortuary sooner than any other gas. It is very irritating to the lungs, and in large quantities may cause vertigo, nausea, vomiting, and even death : great care is required in its use. The action of nitrous acid results from the ease with which it parts with oxygen to any oxidisable substance, being converted into nitrogen dioxide, Avhich again at once combines Avith atmospheric oxygen, and so on. For 1000 cubic feet, take copper shavings, 1 oz.; nitric acid, 3 oz.; water, 3 oz.; then pour the mixed acid and water upon the copper in a small jar. If precautions are taken to reduce leakage to a minimum, disinfection by means of fumigation by any of the three gases above mentioned may be able to destroy most, if not all, of the freely exposed and less resistant micro- organisms; more than this cannot be expected. Exact experiments as regards nitrous acid are wanting, but some few observations that have been made indicate that, as a germicidal agent for disinfection purposes, it holds a position someAvhat superior to sulphurous acid but inferior to chlorine. As a deodorant it is undoubtedly superior to both. Formaldehyde is a Avell-known antiseptic for the preservation of milk and 692 DISINFECTION. other foods. Its use in the gaseous state from the incomplete combustion of methyhc alcohol has been suggested for the disinfection of rooms. Experiments, however, indicate that its value for this purpose is in no Avay superior to any of the above-mentioned gases. In addition to the foregoing, numerous chemical reagents have from time to time been suggested as disinfectants. Of these iodine is not well adapted for use as a fumigating agent, chiefly on account of the density of its vapour, Avhich is 8*5 times heavier than air, rendering its equal diffusion very difficult. Iodine trichloride possesses marked disinfectant properties in solution of 1 per cent., but its chief value lies in its antiseptic poAvers, 1 in 3000 prevent- ing the groAvth of a variety of pathogenic organisms; there is one exception, however, that of the enteric fever bacillus, wlhch resists even a solution of 1 in 500. Bromine has been employed as a gaseous disinfectant, but Avith indifferent success. Lime has a powerful germicidal effect, Avhich has been shown to be due to its alkalinity; a 0*1 per cent, solution of quickhme sterilises excreta after five hours' exposure. Of the many other commonly regarded disinfectants, we may mention the sulphates of copper, iron and zinc, also chloride of zinc and potassic permanganate. All these need to be of 5 per cent, strength, and even then either take several days to kill anthrax spores, or fail to do so. Of the many other chemical and patented substances that have been brought forward at various times as disinfectants, none have been proved to be efficacious in the exhaustive way that mercuric chloride, carbolic acid, and izal have been tested. The greater number are reaUy only antiseptics or deodorants, of considerable value as such, but not to be considered as true disinfectants. A practical point in regard to even the most powerful of these disinfect- ants is its effective working strength. If a given reagent has disinfecting poAvers when of 5 per cent, strength by weight or volume, it is absolutely useless to add a httle of a 5 per cent, solution of the salt to any given matter requiring disinfection. We must add the solid reagent, or a highly con- centrated solution of it, until it forms not less than 5 per cent, of the whole substance to be disinfected—not 5 per cent, of the stock solution. In the case of a salt like permanganate of potassium this 5 per cent, would, of course, have to be in addition to the amount required to oxidise any organic matter present. So, too, with mercuric chloride, a similar consideration applies, as, if added, without acidulation, to liquids containing organic matter, it forms a precipitate that carries down part of the mercury in an inert form. Beference has already been made to a corresponding need in the case of carbolic acid. It is scarcely necessary to say that these essential conditions are rarely, if ever, observed in practice, and that, in consequence, what is intended to be disinfection more often than not amounts only to deodorisation, or at most to imperfect anti-septicising. From what has been said, it will be seen that so-called disinfectants and disinfection processes have not all the same value,—the most powerful and rehable being fire, boiling, steam, exposure to dry air at or above 220° F. for from six to eight hours, corrosive sublimate (1 in 1000), carbolic acid of not less strength than 5 per cent., and izal 1 per cent. Among those capable of destroying sensitive but not the more resistant micro-organisms are chloride of lime, nitrous and sulphurous acids, 3 or 4 per cent, solutions of carbohc acid, brief exposures to heat and weak solutions of corrosive sublimate and izal. Finally, among those that have been shown by experiment to be unable to destroy even the more sensitive bacteria, under the conditions occurring in practice, are solutions of chloride of zinc, ferrous sulphate, 1 or 2 per cent, solutions of carbolic acid, and other disinfectants in excessive DISINFECTION OF CLOTHING AND EXCRETA. 693 dilution, boracic acid, hot air, or fumigation applied to bulky objects, or for inadequate periods of time. Disinfection of Clothing and Bedding.—All articles of little value should be burnt. The apphcation of heat in some way is the most sure and at the same time usually the most practicable method of disinfection. For bulky articles, as bedding, blankets, and clothing generally, moist heat or dry steam Avill be found the most efficacious. In the case of bedding, the hair or feathers in mattresses or pillows may be taken out and loosened before expos- ing them to disinfection by heat. Where moist heat cannot be applied or obtained, exposure to dry air at or above 220° F. for from six to eight hours should be secured; but in no case should efforts at disinfection by means of dry heat be substituted for moist heat when the latter procedure is available. In circumstances where no means exist for disinfecting bulky articles of clothing and bedding by these methods, they should, if possible, be destroyed by burning; failing that, they should be boiled, or at least be allowed to soak for tAventy-four hours in some disinfecting liquid, such as one of the following:—(a) Izal, 5 parts to 100 of water, (b) Chloride of lime, 2 ounces to 1 gallon of water, (c) Chloride of lime, 70 grains mixed Avith 6 grains of herring brine to 1 gallon of water, (d) Carbolic acid, 5 parts to 100 of water, (e) Bichloride of mercury, \ ounce; hydrochloric acid, 1 ounce; aniline blue, 5 grains, to 3 gallons of water. After soaking in any one of these solutions, the clothing should be then boiled and thoroughly Avashed Avith soap and water. Disinfection of Excreta and Discharges.—The urine and bowel dis- charges so frequent in enteric fever, cholera, dysentery, and diarrhoea should be received into a vessel containing either carbolic acid solution (1 in 20), or mercuric chloride solution (1 in 1000, as given above), or izal (1 in 20), with a further application of an equal quantity of the disinfectant directly afterwards. The whole should be well mixed, left for a quarter of an hour for the disinfectant to act, and then either burnt, buried, or discharged doAvn the closet; if the latter is done, it should be well flushed afterwards Avith Avater. Chloride of zinc, in the form of Burnett's fluid, is a useful disinfectant for application to alvine discharges. Sulphate of hon, if used in the strength of 1 lb to a gallon of water, makes a valuable disinfectant for drains, but owing to its staining powers is unsuited for soaking linen or clothing. In cholera and yelloAV fever, the vomited matters should be treated in the same way as the stools. The same care needs to be observed in the treatment of all other discharges from the sick. Thus, all discharges from the mouth, throat, nose, and lungs in diphtheria, whooping-cough, scarlet fever, small-pox, measles, and phthisis should be Aviped away with pieces of rag in place of handkerchiefs; these rags to be burnt after use. Faihng this, they should be treated in a similar manner as an infectious stool. In diphtheria and scarlet fever direct application of some disinfectant is advisable. In scarlet fever and small- pox, when the infective matter exists in the skin particles so freely given off, care should be taken to render these particles innocuous. This can, to a large extent, be accomplished by Avashing the skin with warm water and carbolic soap, and then smearing the body surface night and morning with a medicated oleaginous preparation made by mixing 1 drachm of carbolic acid and 3 of eucalyptus oil in 8 fluid ounces of olive or almond od. In the same diseases, much good results by syringing or swabbing out -with pledgets of cotton-wool the mouth and nose, with a Avarm solution of common salt (about 2 drachms of salt Avith half a drachm of boric acid to a pint of water), and then burning the avooI after use. 694 DISINFECTION. Deodorisation of Excretal Discharges.—Apart from their disinfection, it is often convenient and necessary to deodorise excretal discharges. For this purpose, feAv means are better than well-powdered dry earth, especi- ally humus, marly, and clayey soils. Charcoal may be used for the same purpose, but it soon loses its power. Quicklime and chloride of lime are also valuable, the latter, in particular, being most powerful as a deodorant and also as a steriliser. Quicklime, 5 parts, and carbolic acid, 1 part, make a good deodorising mixture. The preparations in the form of special powders are various, the best perhaps being the different carbolic acid powders already aUuded to; to these may be added such preparations as ferratum and cupralum. The latter consists of sulphates of copper and aluminum with potassium dichro- mate and terebene. It is a fairly poAverful deodorant, counteracting ammonia and hydrogen sulphide, and at least masking faecal odour as much as carbolic acid. The substance advertised as Sanitas is a hydrocarbon derived from turpen- tine acted upon by steam. It has the advantage of being easily miscible . Avith Avater, but it is not very powerful either as a deodorant or antiseptic. Chlor-alum is a weak solution of chloride of aluminum; it is not a very poAverf ul deodoriser, and must be used in large quantity, but its cheapness and want of poisonous properties are recommendations, and when in sufficient amount it is effectual. It is efficacious against ammonia, but not against hydrogen sulphide; it acts moderately against faecal odour. Burnett's fluid, which contains 25 grains of zinc chloride to every fluid drachm, if used in strength of 1 pint to a gallon of water (1 to 8), will deodorise excreta. Potassium permanganate, in the form of Condy's fluid, prevents putrefaction for a short time, and removes the faecal odour, but it requires to be used in large quantity. Sodium manganate has similar powers, but needs to be used freely. These substances are all good deodorants and arresters of putrefaction, but must not be regarded as disinfectants. Practically, their use is very limited. Disinfection of Booms and Furniture.—An agent of the first importance for the disinfection of rooms is undoubtedly the free perflation of fresh air, while all woodwork should be well scrubbed with soft soap and hot water, or washed with a corrosive sublimate solution (1 in 5000) or chloride of lime_(l in 100). The walls also should be well washed with the same solutions. The experiments of Chamberland in France, and Delepine in this country, leave little doubt that washing with chloride of lime gives the most satisfactory disinfection of all surfaces to which it can be applied. The difficulty of ordinary room disinfection is that the surfaces and objects to be treated are unduly injured, not merely by this corrosive chemical but by the process of washing with any liquid. An attempt to overcome this objection has been only imperfectly made by means of the Geneste-Herscher sprayer. This is an appliance for mechanically projecting a liquid dis- infectant in the form of a spray sufficiently fine to allow each drop to rest Avhere it strikes, and, where necessary, Avith a velocity sufficient to inject it into any surface irregularities. In order that the velocity may be maintained, the spray nozzle is mounted on a long metal tube, so as to be apphed within 2 or 3 inches of the surface. Experience sIioavs that if the spraying is performed at a greater distance than 4 inches, sterihsation is not secured. Moreover, the apparent sterilisation which seems to result from the spraying is often, as in the case of ordinary Avashing, due merely to the organisms having been mechanically carried DISINFECTION OF PvOOMS AND SHIPS. 695 off the test-surfaces on to some other part which was not at first examined. In white-washed rooms the above difficulties do not arise, as the walls can be readily scraped and then well washed with a solution of chloride of lime. In the case of papered walls all the layers, if there be more than one, should be stripped off and the walls washed with the lime before being re-papered. Ceilings need to be scraped and washed with hme in the same Avay. All fabrics must be removed from infected rooms, and subjected to disinfection by moist heat. All articles of furniture, of wood, or metal must be washed with soft soap and hot water. As an additional precaution, rooms may be fumigated for three or more hours with chlorine, or nitrous acid, or sulphur dioxide, the doors and windows being subsequently opened, and kept open for twenty-four or thirty-six hours. The difficulties in fumigation arising from the slowness of the diffusion of the disinfectant gas into the air and the consequent uncertainty of the composition of the disinfectant atmosphere at any point are obvious from merely physical considerations. Apart from this, exact bacteriological observations have shown that the disinfecting properties of these gases, when employed for the fumigation of rooms, is most uncertain and unreliable. For these reasons, fumigation of rooms has deservedly fallen into disrepute, and unless supplemented by careful washing and scrubbing is practically valueless. If fumigation is performed, it must be clearly understood that it is quite a subsidiary proceeding, and that it can only be done effectually Avhen the room is unoccupied, as the air must be rendered quite unfit for re- spiration. For the purification ordeodorisationof mortuaries and dead-houses, fumigation Avith nitrous acid or chlorine is both useful and practicable, but their actual disinfection will be best secured by complete and thorough washing and scrubbing Avith chloride of lime or corrosive sublimate solutions combined with free perflation of air. Disinfection of Ships.—Disinfection afloat is practically the same as else- Avhere, with the exception that the apparatus commonly employed for the purpose of purifying bedding and clothing on land are too large and cumber- some to be used on ships. Appliances in which the required temperature is obtained by means of gas are, of course, not available on shipboard. These difficulties are overcome by fitting up a hulk or tug with apparatus for means of disinfection by steam, sulphur dioxide, chlorine and nitrous acid, or by means of the mercuric drench. All bedding, ship's linen, cushions, curtains, carpets, rugs, personal baggage, and wearing apparel can be removed from ships and disinfected by steam heat in specially constructed chambers. Leather articles and such as Avould be injured by moist heat can be treated with the bichloride of mercury solution. The disinfection of the actual ship itself can be secured by first wetting or drenching all available surfaces of the vessel, excepting cargo, but including bilge, ballast, hold, saloons, forecastle, decks, &c, with a solution of mercuric chloride conveyed from the disinfect- ing hulk or tug by rubber hose. For this drenching Avith the subhmate, scrubbing and washing Avith chloride of lime may be substituted. If neces- sary, these drenchings and Avashings can be supplemented by fumigations with either chlorine or sulphur dioxide generated on the disinfecting tug and conveyed on board ship by a fumigating pipe and led into the hold. The cargo is not disturbed, but every opening battened down, the process being completed in from three to eight hours. When sulphur dioxide is employed for these fumigations, tubes or tins of the condensed and liquefied gas can be conveniently used in different sections of the vessel. 696 DISINFECTION. BIBLIOGRAPHY AND REFERENCES. Andre, " De I'assainissement par I'acide sulfureux des barraques occupies par le depot du 7e regiment de dragons a Yitry le Francois," Rec. de mem. de M<-d. milit., Paris, 1881,.xxxvii. p. 110. Baxter, Report on an Experimental Study of Certain Disinfectants, Report Med. Off. Privy Council, vi. 1875, p. 216. Blyth, Manual of Public Health, Lond., 1890, p. 313. Bond, "On the Conditions of Efficient Disinfection, and on some New Forms of Disinfectant," Brit. Med. Journ., 1875, i. p. 239. Cash, Report upon the Action of Disinfectants, more particularly the Halogens, Rep. Med. Off. Local Govern. Board, being Supplement to 16th Annual Report, 1886-7. Chamberland and Ferxbach, "La Disinfection des locaux," Annates de VInsti- tut Pasteur, Juin 1893, p. 433. De Chat-jioxt, " Report on the Effects of High Temperatures upon "Woollen and other Fabrics," Lancet, 1875, ii. p. 830. DELKrixE and Ransome, "Report on the Disinfection of Tubercle-infected Houses," Brit. Med. Journ., 1893, ii. p. 990 ; also Idem, 1895, i. p. 349. Duclaux, " Sur Paction antiseptique de I'acide formique," Annates de VInstitut Pasteur, Sept. 1S92, p. 593. Fischer and Proskaxjer, "On the Disinfectant Action of Chlorine and Bromine," Mittheilungen aus dem Kaiserliehen Gesundheitsamte, Bd. ii., Berlin, 1884. Flugge, Micro-organisms in reference to the Etiology of the Infective Diseases, transl. for the New. Syden. Soc. by Watson Cheyne, Lond., 1890. Herscher, " Des Appareils a disinfection par Pair chaud destines a la purification des vetements, des lignes, des objets de literie et de texture," Revue d'Hygiene, Paris, 1881, iii. p. 585. Hofmann, " Uber Desinfectionsmaasregeln," Deutsch. Vrtljschr. f. bffen. Gsndhtspflg., Braunschweig, 1880, xii. p. 41. Klein, Report on the Disinfectant Action of Perchloride of Mercury, Supplement, 15th Annual Report of Med. Off. Local Govern. Board, 1885, p. 155. Koch, "Uber Desinfection," Mittheil. a. d. K. Gesundhsamte., Berlin, 1881, i. p. 1; also '' Versuche iiber die Verwerthbarkeit heisser Wasserdampfe zu Desinfection - zwecken," Ibid., p. 19. Max Jolles, " Weitere Untersuchungen u. die Desinfectionsfahigkeit von Seifen- losungen," Zeitsch. f. Hyg., Bd. xix. hft. 1, 1895. Mehlhausen, " Versuche u. Desinfection geschlossener Raunie," in the Berichte der Cholera-Kommission f. das deutsche Reich., 6, Heft 4, Berlin, 1879, p. 335. Parsons, Report on Disinfection by Heat, Supplement by Med. Off. to 14th Rep. Local Gov. Board, 1884, p. 218 ; also 16th Report, 1886, p. 347. Pottevix. " Recherches sur le pouvoir antiseptique de 1'aldehyde formique," Annales de VInstitut Pasteur, Novembre 1894, p. 796. Ransom, Disinfection by Hot Air, Practitioner, 1878, xxi. p. 67. Reidel, " On the Disinfectant Action of Iodine Trichloride," Arbeit a. d. K. Gsndhtsamte., Bd. ii., 1887. Atallix, Traite des Disinfectants, Paris, 1883; also " De la Desinfection par 1'Air chaud," Mem. de la Societe de Midecine Publique et d'Hyg. Professionelle, 1877. Vixcext, "Sur la desinfection des matieres fecales normales et pathologiques," Annates de VInstitut Pasteur, Jan. 1895. Vogel, "Ein neuer Desinfections- apparat mit starkstromendem, gespanntem Wasserdampf. nebst Bermerkungen iiber die Bedeutung der Stromung, Spannung, Temperatur des Dampfes bei der Desinfection," Zeitsch. f. Hygiene, Bd. xix. Heft 2, 1895, p. 291. Wolffhugel, "Uber den Werth der schwefligen Saiire als Desinfectionsmittel," Mittheil. aus dem Kaiserliehen Gesundhtsamte., Berlin, 1881, i. p. 1. CHAPTER XIV. CLIMATE. The word climate {i<\tya, a slope, from kXivclv, to incline) originaUy signified that obliquity of the sphere with respect to the horizon from Avhich results the inequahty of day and night. In its modern acceptation it may be taken to mean the sum of all the meteorological conditions of a place or region, including not only those of temperature, but the meteorological conditions generally, so far as these exercise an influence on the animal and vegetable kingdoms. There are four principal factors in the production of the climate of any place or country :—(1) Distance from the equator; (2) Height above the sea; (3) Distance from the sea; (4) Prevailing winds. With regard generally to the effect of climate on human life, it Avould seem certain that the facility of obtaining food (which is itself influenced by climate), rather than any of the immediate effects of climate, regulates the location of men and the amount of population. The human frame seems to acquire in time a wonderful power of adaptation. The Esquimaux, when they can obtain plenty of food, are large strong men (though nothing is known of their average length of life), and the dwellers in the hottest parts of the world (provided there is no malaria, and that their food is nutritious) show a stature as lofty and a strength as great as any dwellers in temperate climates. Pecuharities of race, indeed, arising no one knows how, but probably from the combined influences of climate, food, and cus- toms, acting through many ages, appear to have more effect on stature, health, and duration of life than climate alone. Still, it would seem probable that, in climatic conditions so diverse, there arise some special differences of structure which are most marked in the skin, but may possibly involve other organs. How soon the body, when it has become accustomed by length of residence for successive generations to one climate, can accommodate itself to, or bear the conditions of, the climate of another widely different place, is a question Avhich can only be ansAvered when the influences of climate are better known. The hypothesis of " acclimatisation " implies that there is at first an injurious effect produced, and then an accommodation of the body to the new condi- tions within a very limited time; that, for example, the dweller in northern .zones passing into the tropics, although he at first suffers, acquires in a feAv years some special constitution Avhich relieves him from the injurious conse- quences which, it is supposed, the change at first brought with it. There are, therefore, tAvo assumptions, viz., of an injurious effect, and of a relief from it. Is either correct? y It may seem a bold thing to question the commonly received opinion that a tropical climate is injurious to a northern constitution, but there are some striking facts Avhich it is difficult to reconcile -with such an opinion. The army experience shows that, both in the West Indies and in India, the 698 CLIMATE. mortality of the soldier has been gradually decreasing, until, in some stations in the West Indies (as, for example, Trinidad and Barbadoes), the sickness and mortality among the European soldiers are actually less than on home service in years which have no yellow fever. In India, a century ago, people spoke Avith horror of the terrible climate of Bombay and Calcutta, and yet Europeans noAV live in health and comfort in both cities. In Algeria the French experience is to the same effect. As the climate and the stations are the same, and the soldiers are of the same race and habits, Avhat has removed the dangers which formerly made the sickness threefold and the mortality tenfold the ratio of the sickness and deaths at home? The explanation is very simple: the deaths in the West Indies Avere partly owing to the virulence of yelloAV fever (which was fostered, though probably not engendered, by bad sanitary conditions) and the general excess of other febrile and dysenteric causes. The simple hygienic precautions which were efficacious in England have been as useful in the West Indies. Proper food, good water, pure air have been supphed, and, in proportion as they have been so, the deadly effects attributed to climate have disappeared. The effect of a tropical climate is, so to speak, relative. The temperature and the humidity of the air are highly favourable to decompositions of all kinds; the effluvia from an impure soil, and the putrescent changes going on in it, are greatly aggravated by heat. The effects of the sanitary eAdls Avliich, in a cold climate like Canada, are partly neutralised by the cold, are developed in the West Indies, or in tropical India, to the greatest degree. In this way a tropical climate is evidently most powerful, and it renders all sanitary precautions tenfold more necessary than in the temperate zone. But all this is not the effect of climate, but of something added to climate. Take away these sanitary defects, and avoid malarious soils or drain them, and let the mode of living be a proper one, then the European does not die sooner in the tropics than at home. It must be said, however, that an element of uncertainty may be pointed out here. In our tropical possessions the European remains now only for short periods, and during this time he may be for some years on the liiUs, or at any rate in elevated spots. The old statistical reports of the army pointed out that the mortality in the West Indies augmented regularly with prolongation of service, and it may be said that, after all, the lessened sickness and mortality in the tropics is owing, in some degree, to avoidance by short service of the influence of climate. But as the Avhole long service was constantly passed under the unfavourable sanitary conditions now removed, it does not follow that the inference to be drawn from the statistical evidence as to length of service is really correct. Facts prove, then, that under favourable sanitary conditions (general and personal) Europeans, during short service, may be as healthy as at home, as far as shown by tables of sickness and mortality, and it is not certain that long service brings with it different results. It may, however, be urged that, admitting that a non-malarious tropical climate, per se, may not increase sickness or mortality during the most Adgorous years of life, it may yet really diminish health. This practically is the gist of the whole relationship between climate and health, so that a convenient division of the subject is into : (1) How far is climate injurious to health? and (2) How far is it beneficial to health? In attempting to answer these questions, it is necessary to inquire what is known of the effects of climatic agencies on the frame. The influences INFLUENCE OF TEMPERATURE. 699 of locahty and climate, as far as they are connected with soil and water, have already been sufficiently discussed elsewhere. Setting aside the question of the amount of sunlight, and the actual chemical composition of the atmosphere, the chief climatic conditions or elements which influence health are temperature, humidity, air movement or Avind, and atmospheric pressure. Influence of Temperature upon Health.—The amount of the sun's rays; the mean temperature of the air; the variations in temperature, both periodic and non-periodic; and the length of time a high or low temperature lasts, are the most important points. Temperature alone has been made a ground of classification. (a) Equable or insular climates ; i.e., with slight yearly and diurnal varia- tions ; this condition being due to the proximity to the sea, which tends to equalise the temperature; as the specific heat of Avater is great, it takes a long time to be heated, or to be cooled; the heat is slowly absorbed and sloAvly given out, therefore the temperature of the neighbouring air is equalised. (b) Extreme or continental; i.e., Avith great variations; the conditions being the reverse of those just stated. Although the effects of heat cannot be dissociated from the other condi- tions, it is necessary, hoAvever briefly, to notice them. The effect of a certain degree of temperature on the vital processes of a race dwelling generation after generation on the same spot, is a question Avhich has as yet been but imperfectly answered. The problem is generally presented to us under the form of a dweller in a temperate zone proceeding to countries either colder or hotter than his oavii. In this restricted sense Ave shall noAv consider it. With regard to the effect on the Anglo-Saxon and Celtic races of going to live in a climate with a lower mean temperature and greater variations than their own, we have the experience of Canada, Nova Scotia, and some parts of the Northern American States. In all these, if food is good and plenti- ful, health is not only sustained, but is perhaps improved. The agricultural and. out-door life of Canada or Nova Scotia is perhaps the cause of this; but certain it is that in those countries the European not only enjoys health, but produces a progeny as vigorous, if not more so, than that of the parent race. The effects of heat exceeding the temperate standard must be distin- guished according to origin; radiant heat, or the direct rays of the sun, and non-radiant dieat, or that of the atmosphere. In the latter case, in addition to heat, there is more or less rarefaction of the air, and also coincident conditions of humidity and movement of the air, Avhich must be taken into account. The influence, again, of sudden transitions from heat to cold, or the reverse, has to be considered. Europeans from temperate climates flourish, apparently, in countries not much hotter than their OAvn, as in some parts of Australia, NeAv Zealand, and NeAv Caledonia, and apparently the vigour of the race has improved. But there is a general impression that they do not flourish in countries much hotter, i.e., with a yearly mean of 20° F. higher, as in many parts of India; that the race dAvindles, and finally dies out; and, therefore, that no acclimatisation of race occurs. And certainly it Avould appear that in India there is evidence to show that the pure race, if not intermixed with the native, does not reach beyond the third generation. Yet it seems only right to say that so many circumstances besides heat and the other elements of chmate have been acting on the English race in India, that any conclusion opposed to 700 CLIMATE. acclimatisation must be considered as based on scanty evidence. We have not gauged on a large scale the effects of climate pure and simple, uncom- plicated Avith malaria, bad diet, and other influences adverse to health and longevity. {a) Influence of the Direct Rays of the Sun.—It is not yet known to what temperature the direct rays of the tropical sun can raise any object on Avhich they fall. In India, on the ground, the uncovered thermometer will mark 160°, and perhaps 212° F.; and in this country, if the movement of air is stopped in a small space, the heat in the direct sun's rays can be raised to the same point. In a box with a glass top Sir H. James found the thermometer mark 237° F., Avhen exposed to the rays of the sun, on the 14th July 1864. In experiments on frogs, Avhen temperature much over the natural amount is apphed to nerves, the electrical currents through them are lessened, and at last stop. E. H. Weber's observations show that for men the same rule holds good; the most favourable temperature is 30° B. ( = 99°*5 F.). It appears also from Kuhne's experiments that the heat of the blood of the vertebrata must not exceed 113° F., for at that temperature the myosin begins to coagulate. Perhaps this fact may be connected with the pathological indication that a very high temperature in any disease (over 110° F.) indicates extreme danger. To what temperature is the skin of the head and neck raised in the tropics in the sun's rays? No sufficient experiments have been made, either on this point or on the heat in the interior of caps and hats with and without ventilation. Doubtless, Avithout ventilation, the heat above the head in the interior of the cap is very great. It is quite possible, as usually assumed, that Avith bad head-dresses the heat of the skin, bones, and possibly even of the deep nerves and centres (the brain and cord), may be greater than is accordant with perfect preservation of the functions of the nerves, or of the necessary temperature of the blood, or with the proper fluidity of some of the albuminous bodies in the muscles or nerves. The difficulty of estimating the exact effect of the solar rays is not only caused by the absence of a sufficient number of experiments, but by the common presence of other conditions, such as a hot, rarefied, and perhaps impure air, and heat of the body produced by exercise, which is not attended by perspiration. Two points are remarkable in the history of heat stroke, viz., its extreme rarity in mid ocean and at great elevations. In both cases the effect of the sun's rays, per se, is not less, but even greater, than on land and at sea-level; yet in both heat-stroke is uncommon; the temperature of the air, however, is never excessive in either case. The effect of the direct rays on the skin is another matter requiring investigation. Does it aid or check perspiration ? That the skin gets dry there is no doubt, but this may be merely from rapid evaporation. But if the nervous currents are interfered Avith, the vessels and the amount of secretion are sure to be affected, and on the Avhole it seems probable that a physiological effect adverse to perspiration is produced by the direct rays of the sun. If so, and if this is carried to a certain point, the heat of the body must rise, and, supposing the same conditions to continue (intense radiant heat and want of perspiration), may pass beyond the limit of the tempera- ture of possible life (113° F.). In the Turkish bath it may sometimes be observed that, on entering the hottest chamber, the skin, which had previously been acting freely, becomes dry. A feeling of oppression accom- panies tins, but relief is experienced as soon as perspiration is re-established. This would seem to point more to an actual arrest of function than to a mere drying up of the secretion. The same thing in a modified degree may occur INFLUENCE OF TEMPERATURE. 701 in a tropical climate, in which case the intensity of fever wdl depend upon the time that elapses before accommodation is reached. The effect of intense radiant heat on the respiration and heart is another point of great moment which needs investigation. The pathological effect produced by the too intense direct rays of the sun is seen in one or tAvo forms of insolation, and in fatal cases apparently entads paralysis of the heart or respiration. (b) Heat in Shade.—The effect of high air temperature on the native of a temperate climate passing into the tropics has not been very well deter- mined, and some of the conclusions are draAvn from experiments on animals exposed to an artificial temperature. 1. The temperature of the body does not rise greatly—not more than 0°*5 or 1° F. (John Davy); from 1° to 2J° and 3° C. (Eydaux and Brown- Sequard). In some experiments not published, the late Dr Becher deter- mined his own temperature in a very careful way during a voyage round the Cape to India. He found the body-heat increased, and in the propor- tion of 0°*05 F. for every increase of 1° F. in the air. Battray also found a decided increase, varying from 0°*2 F. to 1°*2 F.; the greatest increase Avas in the afternoon. We may conclude that the tropical heat raises the temperature of the body of a new-comer, probably because the evaporation from the skin is not capable of counterbalancing the great additional external heat, but it is now known that in old residents the same fact does not hold good. The temperature of the body is the result of the opposing action of two factors—1st, of development of heat from the chemical changes of the food, and by the conversion of mechanical energy into heat, or by direct absorption from without; and 2nd, and opposed to this, of evaporation from the surface of the body, Avhich regulates internal heat. So accurately is this balance preserved, that the stability of the animal temperature in all countries has always been a subject of marvel. If anything, however, prevents this evaporation, radiation and the cooling effect of moving Avind cannot cool the body sufficiently in the tropics. Then, no doubt, the temperature of the body rises, especially if in addition there is muscular exertion and production of heat from that cause. The extreme discomfort always attending abnormal heat of body then com- mences. In experiments in ovens, Blagden and Fordyce bore a temperature of 260° F. with a small rise of temperature (2|° F.), but the air was dry, and the heat of their bodies was reduced by perspiration; Avhen the air in ovens is very moist and evaporation is hindered, the temperature of the body rises rapidly. 2. The respirations are lessened in number in animals subjected to heat. According to Yierordt, less carbon dioxide and presumably less water are eliminated. Rattray proved by a great number of observations that the number of respirations is lessened in persons passing from a cold to a hot climate. The amount of diminution varies; in some experiments the fall Avas from 16*5 respirations per minute in England, in -winter, to 12*74 and 13*74 in the tropics. In another series of experiments the fall was from 17*3 respirations per minute to 16*1; the breathing is also gentler, i.e., less deep. Rattray has also shoAvn that the spirometric measurements of the expired air increases in the tropics and falls in temperate chmates, the average variation being about 8*7 per cent, of the total spirometric measure- ments. This will hold good at all ages, but is less at either extreme of life, and is most marked in persons of largest frame and most full blooded. The explanation of this spirometric increase in the respiratory action of the lungs, as compared with the lessened number of inspirations, is said to be 70*2 CLIMATE. due to the fact that Avith a high temperature the quantity of oxygen present in the ah is diminished. Thus, a cubic foot of dry air at 32° F. weighs 566*85 grs., Avliich, neglecting the slight amount of carbon dioxide present, gives in that cubic foot of air 436'5 grs. of nitrogen and 130*35 grs. of oxygen. Assuming that a man at rest breathes 16*6 cubic feet of air per hour into his lungs, he Avill at 32° F. receive 2163*8 grs. of oxygen per hour. At a temperature of 100° F. (Avhich is not unusual in the tropics) a cubic foot of dry air weighs 498 grs., and is made up by weight of 383-5 grs. of nitrogen and 114*5 grs. of oxygen. Therefore, in an hour, breathing as before, the man would receive 1901 grs. of oxygen, or nearly 12 per cent, less than he would breathe in at the loAver temperature. 3. The heart's action has been usuaUy stated to be quickened in the tropics, but Battray's numerous observations show that this is incorrect; the average pulse in the tropics was lower by 2 -£ beats per minute than in the temperate zone. In experiments on animals, moderate heat does not quicken the heart, but great heat does. 4. The digestive powers are somewhat lessened, there is less appetite, less desire for animal food, and more Avish for cool fruit. The quantity of bile secreted by the liver is not increased, if the stools are to be taken as a guide, though Lawson believes that an excess of colouring matter passes out with the stools; nothing is knoAvn of the condition of the usual liver Avork. 5. The skin acts much more than usual (an increase of 24 per cent. according to Rattray), and great local hypersemia and sAveUing of the papillae occur in new-comers, giving rise to the familiar eruption knoAvn as "prickly heat." In process of time, if exposed to great heat, the skin suffers apparently in its structure, becoming of a slight yellowish colour from, probably, pigmentary deposits in the deep layers of the cuticle. 6. The urine is lessened in quantity. The urea is lessened, as shown by experiments in hot seasons at home and during voyages. It is probable that this is simply from lessened food. The pigment has been supposed to be increased, but this is doubtful. The chloride of sodium is lessened; the amount of uric and phosphoric acids is uncertain. 7. The effect on the nervous system is generally considered as depressing and exhausting, i.e., there is less general vigour of mind and body. But it is an undoubted fact that the greatest exertions both of mind and body have been made by Europeans in hot climates. Bobert Jackson thought as much work could be got out of men in hot as in temperate climates. It is probable that the depressing effects of heat are most felt when it is com- bined with great humidity of the atmosphere, so that evaporation from the skin, and consequent lessening of bodily heat, are partly or totally arrested. The most exhausting effects of heat are felt when the heat is continuous, i.e., very great, day and night, and especiaUy in sandy plains, where the air is highly rarefied day and night. There is then really a lessened quantity of oxygen in a given cubic space. Add to this fact that the respirations are lessened, and Ave have two factors at Avork which must diminish the ingress of oxygen, and thereby lessen one of the great agents of metamorphosis. 8. Battray made observations on the weight and height of forty-eight naval cadets, aged from 14| to 17 years, during four successive changes of chmate during a voyage. The results shoAV that in the tropics they increased in height more rapidly than in cold climates, but that they lost weight very considerably, and, in spite of their rapid growth, Battray con- cludes that the heat impaired the strength, Aveight, and health of these lads. His figures seem conclusive on these points, and sIioav the beneficial INFLUENCE OF TEMPERATURE. 703 influence of cold on youths belonging to races long resident in temperate climates. On the whole, even when sufficient perspiration keeps the body tempera- ture within the limits of health, the effect of great heat in shade seems to be, as far as we can judge, a depressing influence lessening the nervous activity, the great functions of digestion, respiration, sanguification, and directly or indirectly the formation and destruction of tissues. Whether this is the heat alone, or heat and lessened oxygen, and great humidity, is not certain. So bad have been the general and personal hygienic conditions of Europeans in India, that it is impossible to say Avhat amount of the former great mortality in that country Avas due to excess of heat over the tempera- ture of Europe. Nor is it possible to determine the influence of heat alone on the endemic diseases of Europeans in the tropics—liver disease and dysentery. There is, perhaps, after all, little immediate connection between heat and liver disease. Rapid Changes of Temperature.—The exact physiological effects have not yet been traced out; and these sudden vicissitudes are often met by altered clothing, or other means of varying the temperature of the body. The greatest influence of rapid changes of temperature appears to occur when the state of the body in some way coincides with or favours their action. Thus, the sudden checking of the profuse perspiration by a cold wind produces catarrhs, inflammations, and neuralgia. It is astonishing, however, to find how well even phthisical persons will bear great changes of tempera- ture, if they are not exposed to moving currents of air; and there can be httle doubt that the wonderful balance of the system is soon readjusted. Effects of Cold.—The degree of cold which inhabitants of temperate climates can bear without ill effect is well shown in the experiences of Arctic voyagers. Parry noted the thermometer as low as - 55° F., or 87° below the freezing point; Franklin at - 58° F., or 90° below the freezing point; and Back at - 70° F., or 102° below the freezing point. The actual effects of cold naturally vary in degree and kind. Much depends upon the degree of cold, the duration of the exposure, and the medium or manner of application: to these conditions may be added the extent of surface exposed and the general health or physiological condition of the person exposed. It is a matter of common knowledge that moderate cold, acting during a short time, or even very severe cold, during a still shorter time, when followed by the glow of reaction, exercises a tonic and stimulating influence. In temporary exposure to cold, or even slight exposure, there is first the sensation of cold with pallor of the skin, shivering and tingling, folloAved by numbness: the pulse becomes sloAver, excretion of Avater by the lungs and skin diminishes, while the urine increases in quantity. If the exposure to cold be prolonged, and the circulation and heat-producing powers cannot be maintained, the arterioles become contracted and no longer permit the passage of blood-corpuscles, and thus aU physiological and chemical changes are arrested. The extremities become starved, and hence death of these parts takes place by frost-bite and gangrene. Prolonged exposure to extreme cold gives rise to an overpowering sense of languor, sensibdity becomes loAvered, the individual loses power of reaction and sinks to sleep or becomes dehrious, death usually resulting from coma, though it may occur from syncope or asphyxia. Deprivation of food, partial or complete, materially adds to the hurtful influence of cold. In a well-nourished person, cold air, containing bulk for bulk more oxygen than Avarm air, produces a sensation 704 CLIMATE. of well-being, increased appetite, and an inclination toAvards increased physical and mental activity. It is only in the feeble, or Avhen the cold is pushed to such an extreme as to act as a depressant, that injurious results ensue. In the production of these effects it must be borne in mind that the actual temperature is not the only factor to be taken into consideration : dryness and stillness of the air permit a much lower temperature to be borne Avith comfort than when the air is damp or in motion. Even moderate Avind renders a low temperature unbearable. It is the stillness and dryness of the air in Arctic regions, and at some health resorts at high altitudes, that renders the extreme degrees of cold there prevalent not ouly tolerable but even beneficial. We have no evidence to say with certainty that any diseases are dhectly caused by cold. The specific fevers are generally less prevalent, and micro-organisms generally less active at low than at high or moderate temperatures. Catarrhal affections may be induced by sudden exposures to cold, or the so-called chill, but beyond this general statement we are not justified in going. Influence of Atmospheric Humidity on Health.—According to their degrees of humidity climates are divided into moist and dry. Tyndall's observations show Iioav greatly the humidity of the air influences climate, by hindering the passage of heat from the earth. As far as the body is con- cerned, the chief effect of moist air is exerted on the evaporation from the skin and lungs, and therefore the degree of dryness or moisture of an atmosphere should be expressed in terms of the relative (and not of the absolute) humidity, and should always be taken in connection with the temperature, movement, and density of the air, if this last varies much from that of sea-level. The evaporating power of an atmosphere which contains 75 per cent, of saturation is very different, according as the temperature of the air is 40° or 80° F. As the temperature rises, the evaporative power increases faster than the rise in the thermometer. There is a general opinion that an atmosphere which permits free Avithout excessive evaporation is the best; but there are few precise experiments. The most agreeable amount of humidity to most healthy people is when the relative humidity is between 70 and 80 per cent. In chronic lung diseases, however, a very moist air is generally most agreeable, and aUays cough. The evaporation from the lungs produced by a warm dry atmosphere appears to irritate them. On the other hand, a still, cold atmosphere is dry, without much capacity for holding moisture; so that the bracing effects of the cold are felt, without the irritation produced by too rapid evaporation from the respiratory surface. This may be one cause (among others) of the benefit derived in winter from such places as Davos, &c. The moist hot siroccos, which are almost saturated with water, are felt as oppressive by man and beast; and this can hardly be from any other cause than the check to evaporation, which interferes with elimination of effete matters by transpiration, and the consequent rise in the temperature of the body. It is not yet known Avhat rate of evaporation is the most healthy. Exces- sive evaporation, such as may be produced by a dry sirocco, is well borne by some persons, but not by all. Probably, in some cases, the physiological factor of perspiration comes into play, and the nerves and vessels of the skin are altered; and in this way perspiration is checked. We can hardly account in any other way for the fact that, in some persons, the dry sirocco, or dry hot land wind, produces harshness and dryness of the skin and INFLUENCE OF WINDS. 705 general malaise, Avhich possibly (though there is yet no thermometric proof) may be caused by a rise of temperature of the body. From the experiments of Lehmann on pigeons and rabbits, it appears that more carbon dioxide is exhaled from the lungs in a very moist than in a dry atmosphere. The pathological effects of humidity are intimately connected with the temperature. Warmth and great humidity are borne on the whole more easily than cold and great humidity. Yet in both cases, so wonderful is the power of adaptation of the body that often no harm results. The spread of certain diseases is supposed to be intimately related to humidity of the air. Malarious diseases, it is said, never attain their fullest epidemic spread unless the humidity approaches saturation. Plague is said to be checked by a very dry atmosphere. In the dry Harmattan wind, on the west coast of Africa, small-pox is difficult to inoculate; and cow-pox is kept up with great difficulty in very dry seasons in India, but if care is taken in the storage of lymph and in the manipulative procedures necessary to carry out the operation, there is no actual inability to carry on vaccination during the very hot and dry seasons of India and elsewhere. Yellow fever, on the other hand, seems less dependent on moisture, or will at any rate prevail in a dry air. The observations at Lisbon, Avhich Lyons recorded, show no relation to the dew-point. With regard to other diseases, and especially to diseases of sanguification and nutrition, observations are much needed. Influence of Air Movement on Health.—This is a very important climatic condition. The effect on the body is twofold. A cold wind abstracts heat, and in proportion to its velocity; a hot wind carries away little heat by direct abstraction, but if dry increases the evaporation, and in that way may in part counteract its own heating poAver. Both, probably, act on the structure of the nerves of the skin and on the contractility of the cutaneous vessels, and may thus influence the rate of evaporation, and possibly affect also other organs. The amount of the cooling effect of moving bodies of air is not easy to determine, as it depends on three factors, viz., the velocity of movement, the temperature, and the humidity of the air. The effect of movement is very great. In a calm atmosphere an extremely warm temperature is borne with- out difficulty. In the Arctic expeditions calm air, many degrees below zero of Fahrenheit, caused no discomfort. But any movement of such cold air at once chills the frame. It has been asserted that some of the hot and very dry desert winds will, in spite of their warmth, chill the body; and if so, it can scarcely be from any other reason than the enormous evaporation they cause from the skin. It is very desirable, however, that this observation should be repeated, with careful thermometrical observations both on the body in the usual way and on the surface of the skin. The main action which produces change in the character of winds is their being forced to mount up when they meet with any elevation above the surface of the ground. The ascent of air brings it into levels where the pressure is reduced, and it is therefore rarefied. This rarefaction causes the air to fall in temperature, though this fall is, to a certain extent, counteracted by the latent heat set free by the enforced condensation of moisture. When the air has reached the summit of the obstacle, it has no longer to ascend, and the reverse action sets in. The air descends, comes under constantly increasing pressure, and is thereby warmed, whde, as the mountain side is not a water surface, it cannot obtain moisture on its way doAvn. It therefore arrives at the plains as a warm and dry wind. This explains why, when any Avind sets straight in against a coast line, it is in 706 CLIMATE. general Avet, and that the bolder and more mountainous the coast is the moister the wind will be. The more important local winds Avhich have great influence on the health of the countries in which they prevail are the following:— The Simoom, or poison wind of the desert, is a species of whirl Avind which prevails in Arabia, and sometimes buries whole caravans in sand. The Khamsin of Egypt, from the Arabic word for fifty, as it blows usually for the fifty days from Easter to Whitsuntide, is a hot, dry blast from the desert, laden with sand particles. The Harmattan is another withering desert wind, blowing over the Sahara toAvards the west coast of Africa, bearing clouds of dust, and making its influence felt as far as the Cape Verde Islands. A notoriously dry wind in Western Europe is the Fohn of Switzerland, known also as the Schneefresser, or snoweater; it corresponds to the Chinook winds of the Western States of North America. The intense heat and dryness of this wind are due to its having descended from the passes over which it crossed the Alps. Another dry, descending wind is the Mistral of the Bi-viera, or the Maestro of Italy. It is a north-west wind, intensely dry, rendering places exposed to it most undesirable residences during its prevalence. The first effect of this wind on visitors is agreeable, from its coolness, but from its dryness it soon causes unpleasant sensations in the nose and mouth, and often pains in the limbs. In consumptives its appearance has been sometimes followed by an attack of haemoptysis. Going farther eastward we find a wind from the same quarter, known as the Tramontane, on the lakes of Maggiore and Garda. At Trieste and in Dalmatia it is knoAvn as the Bora, bloAving so furiously that streets are provided with guide ropes to act as bannisters to enable wayfarers to hold on against the blast. At Nice, and in the Biviera generally, the same wind is called the Bise; it is a cold, blustering north-east wind coming straight from the Maritime Alps. The south-east Avind, or Scirocco of the Mediterranean basin, is just the reverse to the Mistral. It is a warm, moist wind, generally preluding rain. It is supposed to arise in the Sahara, and to gather moisture in crossing the Mediterranean. In Syria this wind is regarded as a dry wind; in Malta and Sicily it is hot, moist and very relaxing, while in Corsica it is less so, and in the Genoese Biviera is very moist but not very warm. The names of other local winds are almost countless, most of them being blasts of Ul-repute; the more important being the " Brickfielders " of Sydney, and the "Painter" or "Barber" of Callao, so called from their dust-laden character. The permanent winds, like the north-east and south-east trades, vary their prevalence with the season of the year. Of the seasonal winds, the north- east and south-west monsoons are the most important. These prevail in India and China during certain times of the year, and are really the winter and summer monsoons respectively. The north-east monsoon corresponds to the north-east trade, and is a cool, dry wind, Avhile the south-west monsoon is hot, moist, and accompanied by low barometric pressure and heavy rains. In Western Europe the most frequent wind in winter is the south-west, while both in Eastern Asia and in Eastern South America it is the north- west. As influencing the amount of rise and fall of temperature, as com- pared with the mean, we find the south-west wind is the warmest in Central Europe, raising the temperature 5° F., while the north-east, the coldest wind in Central Europe, lowering the temperature 7° F., is in the west one of the least frequent of winds; whereas on the eastern coasts of Asia and INFLUENCE OF ATMOSPHERIC PRESSURE. 707 America the most frequent wind—the north-west—lowers the temperature as much as 5° F., while the south wind, which raises the temperature more than 10° F., is the rarest of all. In these islands by far the most prevalent wind is the south-west, next the west, these two prevailing three times more frequently than the north- east, and six times more so than the east wind ; though probably the latter makes its prevalence more felt (Glaisher). The north-east is the rarest wind, and next to it come the south-east, the east, and the north. The west and the south-west winds in this hemisphere are the result of the equatorial current and Gulf Stream: they are warm and bring rain; whereas the north- east and east winds, blowing from the continents of Europe and Asia, and only moistened by passing over the narroAv strip of the North Sea, are dry and cold. As bearing upon their influence on health, we may summarise by saying, that warm and moist winds, such as the south-west Avind in these islands, are mild and relaxing; dry, cool winds, such as our east wind, are bracing; but this Avind, on account of its penetrating character, is often dangerous to those having any weakness of the lungs, and is also hurtful to those liable to rheumatism or liver congestion. Influence of Atmospheric Pressure on Health.—When the difference of pressure between two places is considerable, a marked effect is produced, so much so that the influence of mountain localities plays a very important part in modern therapeutics. From the hygienic point of vieAV, this subject involves the consideration of (1) the effects of lessened pressure, and (2) the effects of increased pressure. Effects of Lessened Pressure.—In ascending mountains there is rarefac- tion, i.e., lessened pressure of air; on an average (if the weight of the air at sea-level is 15 lb on every square inch) an ascent of 900 feet takes off half a pound ; but this varies Avith height; about one-eighth of the atmospheric pressure is lost at 2500 feet, a sixth at 5000 feet, a quarter at 7500 feet, and at 16,000 feet about one-half. There are also lowered temperature and lessened moisture above 4000 feet, greater movement of the air, increased amount of light, greater sun radiation if clouds are absent; the air is freer from germs ; owing to the rarefaction of the air and lessened watery vapour, there is greater diathermancy of the air; the soil is rapidly heated, but radiates also fast, as the heat is not so much held back by vapour in the air, hence there is very great cooling of the ground and the air close to it at night. The physiological effects of lessened pressure begin to be perceptible at 2800 or 3000 feet of altitude (= descent of 2| to 3 inches of mercury); they are—quickened pulse (fifteen to twenty beats per minute); quickened respiration (increase = ten to fifteen respirations per minute), with lessened spirometric capacity, increased evaporation from skin and lungs; lessened urinary Avater. At great heights there is increased pressure of the gases in the body against the containing parts; swelling of superficial vessels, and occasionally bleeding from the nose or lungs. A sensation of weight is felt in the limbs from the lessened pressure on the joints. At altitudes under 6000 or 7000 feet the effect of mountain air (which is, perhaps, not owing solely to lessened pressure, but also, possibly, to increased light and pleasur- able excitement of the senses) is to cause a very marked improvement in digestion, sanguification, and in nervous and muscular vigour. It is inferred that tissue change is accelerated, but nothing definite is known. The rapid evaporation at elevated positions is certainly a most important element of mountain hygiene. At Puebla and at Mexico the hygrometer of Saussure will often mark 37°, Avhich is equal to only 45 per cent, of 708 CLIMATE. saturation, and yet the lower rooms of the houses are very humid, so that in the toAvn of Mexico there are ready two climates—one very moist, in the rez-de-chaussee of the houses; one very dry, in the upper rooms and the outside air. The diminution of oxygen, in a certain cubic space, is precisely as the pressure, and can be calculated for any height, if the barometer is noted. Taking dry air only, a cubic foot of air at 30 inches, and at 32° F., contains 130*4 grains of oxygen. An ascent (about 5000 feet) which reduces the /25 x 130*4\ barometer to 25 inches Avill lessen this -J-th, or (----oq---' )= 108*6 grains. But it is supposed that the increased number of respirations compensates, or more so, for this; and, in addition, it must be remembered that in experi- ments on animals, as long as the percentage of oxygen did not sink below a certain point (14 per cent.), as much Avas absorbed into the blood as when the oxygen was in normal proportion. Jourdanet has indeed asserted that the usual notion that the respirations are augmented in number in the inhabitants of high lands is " completely erroneous " ; that the respirations are in fact lessened, and that from time to time a deeper respiration is voluntarily made as a partial compensation. But Coindet, from 1500 observations on French and Mexicans, does not confirm this; the mean number of respirations was 19*36 per minute for the French, and 20*297 for the Mexicans. As a curative agent, mountain air (that is, the consequences of lessened pressure chiefly) ranks very high in all anaemic affections from whatever cause (malaria, haemorrhage, digestive feebleness, even lead and mercury poisoning); and it would appear, from Hermann Weber's observations, that the existence of valvular heart disease is, if proper rules are observed, no contra-indication against the lower elevations (2000 to 3000 feet). Neuralgia, gout, and rheumatism are all benefited by high Alpine positions. Scrofula and consumption have been long known to be rare among the dwellers on high lands, and the curative effect of such places on these diseases is also marked ; but it is possible that the open-air life which is led has an influence, as it is now known that great elevation is not necessary for the cure of phthisis. Weber and others have shown how in the true Alpine region, in Dauphine, in Peru and Mexico, and in Germany, phthisis is decidedly averted or prevented by high altitudes. The more recent experience of Davoz Platz is certainly confirmatory of this. Although on the Alps phthisis is arrested in strangers, in many places the Swiss women on the lower heights suffer greatly from it; the cause is a social one: the women employed in making embroidery congregate all day in small, iU-ventilated, low rooms, A\diere they are often obhged to be in a constrained position; their food is poor in quality. Scrofula is very common. The men, who live an open-air hfe, are exempt; therefore, in the very place where strangers are getting well of phthisis the natives die from it,—another instance that we must look to local conditions and social habits for the great cause of phthisis; that is, that in most cases this disease is due to the breathing of impure air, containing the infective oacdlus. It would even seem possible that, after all, it is not indeed elevation and rarefaction of ah, but simply plenty of pure air and exercise Avhich are the great agents in the cure of phthisis. Jourdanet, who differs from so much that is commonly accepted on this point, gives additional evidence on the effect of elevation on phthisis. At Vera Cruz phthisis is common ; at Puebla and on the Mexican heights it is almost absent (ctpeu pres nulle). INFLUENCE OF ATMOSPHERIC PRESSURE. 709 The diseases for Avhich mountain air is least useful are—rheumatism, at the loAver elevations Avhere the air is moist (above this rheumatism is improved), and chronic inflammatory affections of the bronchial tubes and pleura, and neuralgia. The "mountain asthma" appears, however, from Weber's observations, to be no specific disease, but to be common pulmonary emphysema f olloAving chronic bronchitis. It seems likely that pneumonia, pleurisy, and acute bronchitis are more common in higher Alpine regions than lower down. Effects of Increased Pressure.—The effects of increased pressure have been noticed in persons working in diving-bells, caissons, &c, and in those submitted to treatment by compressed air, especially at Lyons and at Reichenhall. When the pressure is increased to from \\ to 2 atmospheres, the pulse becomes slower, though this varies in individual cases; the mean lessening is ten beats per minute; the respirations are slightly lessened (1 per minute) ; evaporation from the skin and lungs is said to be lessened (?); there is some recession of blood from the peripheral parts; there is a little ringing and sometimes pain in the ears; hearing is more acute; the urine is increased in quantity; appetite is increased; it is said men will Avork more vigorously. When the pressure is much greater (2 or 3 atmos- pheres), the effects are sometimes very marked; great lowering of the pulse, heaviness, headache, and sometimes deafness. It is said that more oxygen is absorbed, and that the venous blood is as red as the arterial; the skin also sometimes acts more, and there may even be sweating. The main effect is to lessen the quantity of blood in the veins and auricles, and to increase it in the arteries and ventricles ; the filling of the ventricle during the relaxation takes place more slowly. The diastolic interval is lengthened, and the pulse is therefore sloAver. In pneumatic chambers and tubes used for pier driving and laying the foundations of bridges the pressure in the air chambers is usually of from 3 to 4 atmospheres, and if due precautions are taken to neither increase nor lower the pressure too rapidly, no symptoms or inconvenience are experienced by workmen when employed in them for hours together. What accidents and ill effects have occurred are chiefly in the form of prickings, muscular pains, nose bleedings, and paralysis, and these have occurred commonly after leaving the high-pressure chambers or tubes, and when the reduction of pressure has been too rapid. Yery few unfavourable effects appear to occur under the actual high pressure. The great danger in all these cases appears to be in the too sudden reduction of pressure. If time be given, the body seems to be quite able to accommodate itself to the extreme variations of pressure; thus, in a balloon ascent made by Glaisher and Coxwell, these observers Avere able to withstand as Ioav a pressure as indicated by 8 inches of mercury, while, on the other hand, men who worked in sinking piers for the Forth Bridge did so in air chambers in which the barometer stood as high as 72 inches. These two instances give a range of atmospheric pressure extending over 64 inches supportable by man. As a curative agent in phthisis, the use of compressed air has so far been unfavourable, but is of more benefit in asthmatic cases. In the " compressed air bath " at the Brompton Hospital the pressure rarely exceeds an addition of 10 lb to the square inch, or § of an atmosphere. Half an hour is given to reach this pressure it is maintained for an hour, and half an hour is occupied in reducing it to the natural pressure; thus all danger of sudden change is taken aAvay. Some observations made by Bert shoAV that oxygen, when it enters the blood under pressure (such as that given by 17 atmospheres of atmos- 710 CLIMATE. pheric air, or 3tl atmospheres of pure oxygen), is toxic to birds, producing convulsions. Convulsions are produced in dogs Avhen the pressure is only 7 or 8 atmospheres and Avhen the oxygen amounts to only double the normal, or, in other Avords, reaches 32 c.c. per 100 c.c. of blood. Bert con- jectured that the toxic influence of oxygen was on the nervous centres, like strychnine. The animal temperature fell 2 or 3 degrees (C.) during the convrdsions, so that excess of oxygen did not cause increased combustion. In the case of a dog kept under a pressure of 9| atmospheres for some time, gas was found in the ventral cavity and in the areolar tissue. In man the pressure of only 5 atmospheres appears to be dangerous. Acclimatisation.—The doctrine of acclimatisation has been much debated, but probably we do not know sufficiently the physiological conditions of the body under different circumstances. In the case of Europeans living till puberty in a temperate region, near the sea-level, and in a moist climate like England, and then going to the tropics, the question of acclimatisation Avould be put in this form,—Does the body accommodate itself to greater heat, to lessened humidity in some cases, or greater in others, and to varying altitudes? There can be little doubt that the body does accommodate itself within certain limits to greater heat, as we have seen that the lungs act less, the skin more, and that the circulation lessens Avhen Englishmen pass into the tropics. There is so far an accommodation or alteration impressed on the functions of the body by unAvonted heat. And we may believe that this effect is permanent, i.e., that the lungs continue to act less and the skin more as long as the Europeans remain in the tropics. Doubtless, if the race Avere perpetuated in the tropics, succeeding generations would sIioav fixed alterations in these organs. We may conclude that the converse holds true, and that the cold of temperate regions will influence natives of the tropics in an opposite Avay, and this seems to be rendered likely by the Avay in Avhich lung affections arise in many of them. We may admit there is an acchmatisation in this sense, but in no other. The process is one of adaptation rather than acclimatisation. The usual belief that the constitution acquires in some Avay a poAver of resisting unhealthy influences—that is, a power of not being any longer susceptible to them—is not supported by any good evidence. The lungs in Europeans Avill not regain their weight and amount of action in the tropics; a change to a cold climate only -will cause this; the skin retains its increased function until the cause producing it is removed. So also there is no acclimatisation in any sense of the word for malaria. From the results of a long extended inquiry into the effects of climate on different races of people, Stokvis concludes "that the poAver of resistance of the healthy adult European living in the tropics quite equals, and in some measure is even superior to, the vital power of the native races." On the other hand, there are certain peculiarities of the race which have been gradually acquired by inheritance from generation to generation, and that the longer the European resides in the tropics the more likely is he to lose his superior resisting powers; and it is possible that the European Creole is both bodily and mentally inferior to the European. Classification of Climates.—The simplest plan of classifying climates is based upon geographical limits, and largely according to latitude. This at best is imperfect unless alloAvance be made for the influence of warm or cold sea-currents, large ocean areas, and the nearness or distance of mountain ranges. These latter in particular greatly affect rainfall and exposure to CLASSIFICATION OF CLIMATES. 711 winds. AlloAving for these modifying influences, and based upon the principle or limits of latitude, a commonly accepted classification of climates is as foUows:— Warm Climates.—These include the greater part of Africa and its islands; Southern Asia, embracing India and China; Polynesia, including all Australia except Victoria; North America south of California; and South America north of Uruguay, with the West Indies. These climates are marked by high temperature, heavy rainfall, and more or less well-defined dry and wet seasons. Such climates are usually met Avith in places lying between the equator and 35° of latitude north or south of it. They can be subdivided into equatorial, tropical, and sub-tropical groups. In the equatorial the mean annual temperature is from 80° F. to 84° F., the minimum being 54° F. and the maximum 118° F. The mean temperature decreases slowly as we recede from the equator. The difference of temperature during the day is slight, but there is a marked fall at night from radiation. The rain- fall is rarely less than 40 inches annually, and. it is this which tempers and reduces the otherwise extreme heat. Though possibly all the diseases usually attributed to the influence of warm climates are not rightly so, still these climates are peculiarly apt to be associated with such affections as heat-stroke, yellow fever, cholera, dengue, hver abscess, dysentery, smaU-pox, and various forms of malarial fever, while scarlet fever and measles are comparatively rare. Temperate Climates.—These have a mean temperature of 60° F., often with great extremes; four well-defined seasons, usually most rainy during autumn and winter; and the geographical limits of from 35° to 50° of latitude. The temperate chmates are inhabited by the most vigorous races of the world, and would seem to have been in all ages specially favourable to the physical and intellectual growth of the human race. The most prev- alent diseases are for the most part the ordinary diseases of Europe and America, especially rheumatism, acute and chronic pneumonia, various affec- tions of the air-passages, and the large group of exanthemata. Pulmonary consumption is common, but cannot be said to be the special production of these climates, " though doubtless immunity from the disease has been shown to exist under various and indeed opposite climatic conditions" (Williams). Cold Climates.—These belong to regions situated between 50° of latitude and the poles. In them the summer is short, often lasting but a few weeks, while the winter is long. SnoAV is extensive, but of rain there is little or none. The temperature falls rapidly between latitudes 55° and 75°, and the fall amounts to 22° F. to 27° F., the coldest region being not at the pole, but about 10° from it north of Behring's Straits, the mean temperature there ranging between 17° F. and 19° F. Scurvy and scrofula are the principal affections Avhich can be directly attri- buted to these climates,—the former arising from a deficient supply of fruit and vegetables, and the latter from the overcrowding and general poor- ness of living which prevails. Ophthalmia and amaurosis are also reported to be present, from the reflection of light from the snow in the polar regions. The extreme and dry cold, Avhich is the feature of these climates, has a bracing effect on the system, improves the appetite, promotes the per- formance of muscular work, and, as it is fatal to all micro-organisms, is a good antiseptic. Mountain Climates.—These are peculiar, being marked by extremes of temperature, great clearness and rarefaction of the atmosphere, and lessened barometric pressure. Among the more important of these climates are (1) 712 CLIMATE. the Alpine, where the Avinter is very cold, dry, and calm, but the sun's rays are most poAverful; (2) the Eocky Mountains of North America, where the climate resembles that of the Alpine resorts, but warmer, drier, less snow, but more dust; (3) the sanitaria of the Andes, Avith a climate generally dry, Avarm, and bracing, except at La Paz, where the winter is cold; (4) Himalayan stations, where the chmate is cool, but subject to considerable extremes, and damp owing to the excessive rainfall; (5) the South African Highlands of Cape Colony, Orange Free State, and the Transvaal, Avhere the climate is Avarm, with seldom any extreme of cold except during the rainy season and a few days of Avinter. Mountain chmates are peculiarly favourable to those having imperfect chest development, with hereditary or other tendencies to consumption; but are unsuitable for those troubled with chronic bronchitis, or acute diseases of the lungs, kidneys, liver, or brain. The peculiar effects of mountain climates appear to be due to the increased aeration of the blood which takes place during the act of breathing mountain air, and, as a result of this, these chmates are best suited for those capable of taking abundant exercise, and distinctly hurtful to the aged and very feeble. Marine climates are those prevailing upon islands, capes, and sea coasts, in which the temperature is remarkably equal, rarely reaching extremes, and in which, owing to the increased moisture and rainfaU, a certain softness of atmosphere is experienced. The climates of Great Britain, Norway, and Iceland may be taken as types of these so-caUed marine chmates. The principal diseases which appear to be in any way peculiar to marine chmates are rheumatism, and the various affections of the lungs and air- passages, the greater part of Avhich may be due to the dampness and con- stant weather changes which are so characteristic of these climates. BIBLIOGRAPHY AND REFERENCES. Blanford, The Climate and Weather of India, 1889. Burdon-Sanderson, " The Salt and Compressed Air Cures of Reichenhall," Practitioner, vol. i. No. 4, p. 217. Cullimore, The Book of Climates, Lond., 1890. Felkin, "The suitability of Tropical Highlands for European settlement," Prov. Med. Journ., Nov. 2, 1891. Foley, " Du Travail dans Pair comprime," Gaz. Hebdom., Paris, 1863, No. 32. Hirschfeld, "Uber das Vorkommen der Lungentuberkulose in der warmen Zone," Deutsches Archiv. f. Klin. Med., Bd. liii. heft 5 and 6, p. 457. Johnston, " Remarks on the Normal Temperature of the Body in the Tropics," A.M.D. Report, xviii. p. 255. Jourdanet, Influence de la pression de Vair sur la vie de I'homme, Paris, 1875. Rattray, "On the Effects of Change of Climate on the Human Economy," Proc. Roy. Soc, 1869-72, Nos. 122-126 and 139. Stokvis, "Address on Colonial Pathology," Transac Internat. Medical Congress, Berlin, 1890. Tait, " On the Mortality of Eurasians," Statistical Journal, Sept. 1864. Weber, On the Climate of the Swiss Alps, Lond., 1864. Williams, " Aero-Thera- peutics," London, 1894; also "Climate in Relation to Health and Geographical Distribution of Disease," Journ. Sanitary Institute, vol. xv. Pt. 2, July 1894. Yeo, Climate and Health Resorts, Lond., 1885. CHAPTER XV. METEOKOLOGY. Meteorology is the science of the Aveather; while the Avord Aveather connotes the general condition of the atmosphere at any particular time, and especially of that portion of the atmosphere near the surface of the earth. These definitions suggest that weather is a general result produced by the combined action of several different elements, each consisting of a special set of phenomena in the physics of the atmosphere, such as those depending on its warmth, motion, dryness, humidity, transparency, and the like; while the leading principles of modern scientific meteorology are first, the making of accurate and systematic observations of these phenomena, and secondly, their practical interpretation. The making of meteorological observations presents for the most part no great difficulty, the essential qualification being " a capacity for doing a small piece of routine work at stated times without losing interest in it, and so becoming careless." To be of any value, the observations made at different places must be comparable; the instruments used must be sinhlar in form, exposed in a similar way, and the errors peculiar to them and to the observer must be known. TEMPERATURE, HOW OBSEBVED AND CALCULATED. Thermometers.—The principle of these instruments is that they measure temperature by the expansion of bodies. The first thermometer is supposed to have been invented by Sanctorio, of Padua, in 1590; but the history of the instrument practically dates from 1714, when Fahrenheit of Dantzic constructed the thermometer known by his name. Liquids are the bodies best suited for the purpose of indicating, by their expansion or contraction, the intensity of heat, in the construction of thermometers; the expansion of gases being too great, and that of solids too small. Of liquids, mercury and alcohol are practically the only ones used; the former because of its equal expansion at different temperatures, its low freezing point (-37°*9 F.), its high-boihng point (675°*1 F.), its high conductivity of heat, and its low specific heat; alcohol is used because at atmospheric pressure it does not solidify at the greatest known cold. For these reasons, mercury is used for recording high degrees of heat, and alcohol for low temperatures. A thermometer consists of a capillary glass tube of uniform bore, hermetically sealed at one end, and blown at the other into a bulb filled with mercury or spirit. The steps in the construction of a thermometer are: (1) calibrating the tube, or dividing it into parts of equal capacity; (2) filhng the bulb and tube Avith mercury or alcohol, and expelling all air 714 METEOROLOGY. by heat; (3) curing, or laying the instrument aside for a year or so after fiUing, so that the glass may assume a permanent shape, and so obviate the error known as " displacement of zero " ; (4) graduation, or the marking of the scale on the thermometer stem, the fixed points of temperature of melting ice, and of boiling water under standard pressure, being duly ascertained by direct experiment in each case. The melting point of ice is used in preference to the freezing point of Avater, because distilled Avater, if perfectly still, may be chilled to a tempera- ture several degrees beloAV that at Avhich, if not perfectly still, it would freeze. Under such circumstances, if it is suddenly agitated, it Avill congeal instantly. Again, Avater which holds a salt in solution has a freezing point considerably below that Avhich has no such salt in solution. The boiling point of water is a stdl more variable quantity than the freezing point; hence the term must be qualified by the Avords "at mean sea-level," the barometer standing at 29*92 inches in the latitude of London, and at 760 mm. in the latitude of Paris. On the continent of Europe the scale of a thermometer is divided into 100 parts or so-called Centigrade, after the method of Celsius, a professor of Upsala, who suggested this in 1742. This division is really the simplest, and now generally used in this country in connection with all scientific work. In this scale the zero or melting point of ice (so-called freezing) is at 0 degree, Avhde the boiling point is at 100 degrees. Another scale introduced by Reaumur, a French physicist, in 1731, has the same fixed points as in the Centigrade, but the interval between them is divided into 80 instead of 100 parts; that is to say, 80 degrees Reaumur equal 100 degrees Centigrade, or 1 degree Reaumur is -f- of a degree Centi- grade, or 1 degree Centigrade is 4 of a degree Reaumur. Consequently, to correct Reaumur degrees into Centigrade ones, it is necessary to multiply them by f. Similarly, Centigrade degrees are converted into those of Reaumur by multiplying them by 4. In England and America, for general use, the thermometric scale invented by Fahrenheit is still employed. In this scale the higher fixed point is, like that in the Centigrade and Reaumur scales, that of boiling water; but the lower fixed point or zero is not the temperature of melting ice, but that obtained by mixing equal parts of snow and sal ammoniac, and the interval between the tAvo is divided into 212 parts or degrees. The zero temperature on this scale is lower than that of melting ice, Avith the result that when a Fahrenheit scale thermometer is placed in melting ice, it stands at 32 degrees, and, therefore, 100 degrees on the Centigrade scale and 80 on the Reaumur equal 212 less 32, or 180 degrees on the Fahrenheit, or 1 degree Fahrenheit equals f of a degree Centigrade, and | of a degree Reaumur. For the con- version of any given number of degrees Fahrenheit into Centigrade or Reaumur degrees, the number 32 must be first subtracted in order that the degrees may count for the same part of the scale, and the result then multi- plied by the relative value of the tAvo degrees. Conversely, Centigrade and Reaumur degrees may be converted into Fahrenheit by adding 32 after multiplying by the ratio value. Thus, |C. + 32 = F. f R. + 32 = F. (F-32)| = C. (F-32)± = R. In the case of the Centigrade and Reaumur scales all temperatures below the melting point of ice have a minus sign. As the zero on the Fahrenheit scale is 32° below the melting point of ice, the minus sign is, therefore, very seldom required for temperatures occurring in the British Isles. The value THERMOMETERS. 715 - 40° represents the same temperature on the Fahrenheit and Centigrade scales. A good mercury thermometer should answer to the folloAving tests. When completely immersed in melting ice, the top of the mercury should exactly indicate zero or 32°, according as to whether the scale be Centigrade and Reaumur or Fahrenheit; and when suspended in the steam of water boiling in a metal vessel with the barometer at 29*92 inches, the mercury should be stationary at either 100° or 212° according to the kind of scale. The value of the. degrees should be uniform, as shoAvn by a detached piece of mercury occupying an equal number of degrees in all parts of the tube. The thermometers used in meteorological observatories are :—standard thermometers, ordinary thermometers, registering thermometers, sometimes called maximum and minimum thermometers, self-recording thermometers, and radiation thermometers. A Standard thermometer is made Avith every precaution to secure accuracy, and is intended less for daily use than for testing from time to time the correctness of the ordinary instruments. Except for use in extremely cold climates, a standard thermometer should be made with mercury. Its scale must be cut on the stem, and should range from far beloAV zero to the boiling point of water. The scale should not be marked for several years after the tube has been filled, in order to guard against the defect knoAvn as the displacement of zero, arising from the gradual contraction of the bulb which results from the sloAvness with which fused glass returns to its original density. As the bulb contracts, it holds less mercury, which is forced into the tube to a higher level than the temperature warrants, Avhereby the instrument tends to read too high. Ordinary thermometers need no special remarks beyond that they should be constructed of mercury, and have a certificate of verification from some recognised scientific institution. At least once a year each instrument should be tested for " displacement of zero " by being plunged into a mass of melting snoAV and ice. Registering thermometers are those instruments Avhich are so constructed as to enable us to read off from them the highest or loAvest temperature to Avhich they have been exposed in a given length of time. The thermometer Avhich is used for registering the highest or maximal temperature of the day or period is called a "maximum thermometer." Similarly, that which registers the lowest or minimal temperature is called a " minimum thermo- meter." In both these instruments the contrivance by means of which we are able to read the extremes of temperature is called the " index." Maximum thermometers are of two kinds, called, after their designers, Phillip's and Negretti's. Both these instruments have mercurial columns, a detached portion of which serves as an index for the highest temperature reached. In Philhp's the detached portion of the mercurial column is separated from the rest by a bubble of air. In Negretti's the detachment is made by means of a slight contraction of the tube, which, Avhile allowing the expanding mercury to pass Avhen the temperature is rising, is sufficient to overcome the natural cohesion of the metal when contracting, to prevent it drawing it back on cooling. Both these instruments are placed horizontally, and both can be reset by lowering the bulb, and then either gently tapping or swinging the thermometer. Minimum thermometers are also of tAvo kinds : Butherford's, a spirit thermometer, and Casella's, a mercurial instrument. The former is the minimum thermometer in almost universal use at home and colonial stations, 716 METEOROLOGY. while the latter is a beautiful instrument especially adapted for use in tropical climates, Avhere the intense heat causes alcohol to volatilise quickly. In Butherford's instrument a small metallic index is immersed in the spirit with which the bulb and part of the stem are filled. When the temperature falls, and the alcohol contracts, the capillary attraction of the liquid draws the index back Avith it toAvards the bulb ; but Avhen the tempera- ture rises again, the alcohol passes the index, and leaves the extremity of it farthest from the bulb at the lowest temperature reached. The instrument, after having been read, is readily set by partially inverting it and letting the index fall to the top of the spirit column; it is then hung up in a horizontal position. Occasionally air bubbles appear in the alcohol and fix the index, whde at other times some of the alcohol volatilises and condenses at the top of the tube. Both these faults can be easily cured by holding the thermometer bulb downwards and swinging it rapidly round; this will usuaUy cause the ah bubbles to disperse, and displace any condensed alcohol from the top of the tube. If, by chance, as the result of this procedure, the index be throAvn into the bulb, a little tapping and patience will bring it out again. To avoid the annoyance arising from breakage of the column by bubbles Fig. 117. of air, and from vaporisation in alcohol minimum thermometers, Casella has invented a mercurial minimum thermometer (fig. 117). In this instrument there is no steel or other index employed; its general form is shown in the figure, c being a tube with large bore, at the upper end of which a flat glass diaphragm is formed by the abrupt junction of the small chamber ab, the inlet to which at b is larger than the bore of the indicating tube. The result of this is that, having set the thermometer, the contract- ing force of the mercury in cooling withdraws the fluid in the indicating stem only ; Avhilst on its expanding with heat, the long or indicating column does not move, the increased bulk of mercury finding an easier passage through the larger bore into the small pear-shaped chamber attached. To set this instrument, it is necessary to raise or lower the bulb end, so as to cause the mercury to flow sloAvly, until the best part of the tube c is full and the chamber ab quite empty; if at any time mercury Avill not readily flow from the small chamber as above, a tap or jerk with the hand wdl cause it to do so. Previous to the invention of these maximum and minimum thermometers, a registering instrument known as Six's thermometer (fig. 118), from the name of its inventor, was much used, and is so now. The tube of the instrument is long and U-shaped. One limb constitutes the cold tube, and THERMOMETERS. 717 has at its extemity a bulb, while the other limb is the heat tube, having at its top or end a small chamber in which is confined some air. The middle portion of the tube contains mercury extending round the bend and part of the way up each limb. The bulb and both tubes or limbs above the mercury contain alcohol. Inside the alcohol are two steel indices, one being in the cold and the other in the heat tube. These are readily set, or caused to rest gently upon either column of mercury by moving them by means of a magnet. This being done, if the temperature rises, the alcohol in the bulb will expand and push doAvn the mercury in the cold leg, but raise that in the heat leg, and by so doing drive up the index in it until the tempera- ture ceases to rise, when the point of maximum heat will be indicated by the lower end of that index. On a fall of temperature precisely the reverse will happen, for then the spirit within the bulb will contract, and the pressure in the air chamber at the top of the heat leg will force the mercury down in it, but up in the cold limb, whde the cold index will continue to go up so long as the tempera- ture continues to fall. Of course the scales read down- wards on the cold leg and upwards in the heat one, and in each the lower end of the index shoAvs respectively the lowest and highest temperature reached since the instrument was last set. The presence of the air chamber makes a Six's thermometer unsuited for travelling, and necessitates the vertical position. The instrument is further liable to error, owing to the fact that sometimes alcohol will ooze round by the side of the mercury, and so pass from the cold to the heat leg. As the scales run in opposite directions, it is obvious that if this defect occurs, it gives rise to a large error in the reading of the temperature. No one but a Fig. 118. skilled optician can rectify this evil. Self-recording thermometers, or thermographs, are so arranged as to record their own readings, independently of the observer, either at frequent intervals in the case of electrical thermographs, or continuously, as in the case of photographic thermographs. Of these instruments those of Cripp or Richard are familiar examples. The bulb is a large curved flattened tube, filled with a liquid which tends to straighten with an increase of heat, and this, being connected with a long lever in such a manner as to rise with increase of temperature and to fall with decrease, marks a tracing line upon a revolving cylinder. This cylinder depends upon a clockwork arrange- ment, and can be wound up, started and left untouched for given periods of time, at the end of which records of temperature will be found for every instant during the period. As the curvature of the tube and the spring mechanism are apt to alter, these instruments need to be corrected and compared periodically with an accurate mercurial thermometer. Radiation thermometers are commonly employed to afford a measure of the intensity of the heat radiations received from the sun, or given off by the surface of the earth. Some idea of the intensity of the sun's heat is obtained by means of what are called solar radiation thermometers or maximum thermometers placed direct in the sun's rays. In order to avoid loss of heat by reflection from the bright glass surface of the bulb, this and one inch of the stem is coated with lamp-black, and this again, to protect it from being Avashed off by rain, 718 METEOROLOGY. is placed in a glass case out of which air has been pumped to make it a vacuum. Unfortunately, the presence of the outer glass covering largely interferes with the cooling influence of Avind, which materially affects the distribution of heat by the sun in nature. NotAvithstanding this theoretical defect, the blackened bulb maximum thermometer in vacuo is the best instrument we have for measuring the amount of heat given out or radiated by the sun. The instrument is exposed freely to the sun and air by fixing it horizontally 4 feet above the ground, well aAvay from trees or walls, and Avith its bulb, in this country, pointing south-east. The heat recorded by such an instrument Avill be the temperature at Avhich an equilibrium or balance is estabhshed between the heat produced by the direct rays of the sun on the bulb, and the cooling caused by radiation or loss of heat from the bulb to the glass jacket or covering; this latter, of course, will have practically the same temperature as that of the air. It follows, therefore, that the excess of the temperature of the black bulb over that of the outer air, as registered by a maximum thermometer in the shade, will be an approximate measure of the poAver of the actual sun's rays, or in other Avords, the power of the sun's radiation of heat. Thus, suppose the black bulb thermometer shows a reading of 116°, and the shade or air maximum be 76°. The difference between them of 40° Avill be the approximate measure of the sun's intensity. As an alternative method, it has been suggested to expose alongside of the black bulb in vacuo a similar ther- mometer also in vacuo, only with its bulb bright, and to register the difference between the readings of the two instruments as the amount of solar radiation. It has been objected, with some reason, to both these methods that the indications of the black bulb or sun maximum thermometer are not of much value, because, in the first place, the sun's rays do not necessarily have their greatest power at the hour of maximum air tempera- ture, but much earher, and that to obtain reliable results we should therefore subtract from the black bulb reading, not the maximum, but the actual air temperature at the moment the black bulb reaches its highest point. What is really wanted is a measure of the total heat received from the sun, not a record of its maximum intensity at any instant. The helio-pyrometer of Southall, and the actinometers of PouiUet, Crova, Langley, Herschel, and Richard, which to a certain extent give this, are, unfortunately, not suited for general use; but " much may be learned from the duration of direct solar radiation, even without attempting to estimate its intensity." Not only is there a constant gain of heat by the earth from the sun, but there is also a more or less constant loss of heat from the earth and from all objects on it. This loss of heat is spoken of as terrestrial radiation, and is very much greater when the sky is clear than when overcast with clouds. The amount of this loss of heat by radiation is determined by placing a minimum thermometer, as already described, on short supports some 4 inches off the ground, preferably on a plot of grass. Should the ground be covered with snow, the instrument should be laid upon the surface of the snoAV. Where a grass plot is not available, the thermometer should be placed on a large black board laid upon the ground. The difference or defect of this minimum temperature below that of the air minimum in the shade is taken as the amount of terrestrial radiation. The bulb of minimum thermometers used for this observation is often modified so as to present the greatest amount of surface relatively to its contents, either by making it in the form of a hollow cylinder, or by arranging it in the form of a fork, or by drawing it out and bending it back upon itself. MEAN TEMPERATURE. 719 Thermometer Exposure.—The method of exposing radiation thermo- meters has been definitely stated, but the proper exposure of other or shade thermometers so that they may indicate the true temperature of the air is a matter of some difficulty. Two conditions are required: (1) a constant circulation must be kept up round the thermometer bulbs, and in its passage to the instruments the air must not have its temperature changed by passing over hot or cold surfaces; (2) the thermometer bulbs must be protected not only from the direct rays of the sun, but from radiations of all kinds from surrounding objects. These conditions are probably most nearly realised by the sling thermometer, which is attached to a cord some 2 feet in length and swung round like a sling in the shade. Obvious objections exist to observa- tions of this kind, and various kinds of thermometer shelter have been devised. Perhaps the best is that used in this country and called after its inventor the " Stevenson" screen. It consists merely of a hut or box made of stout boards, with a ridge roof and louvred sides, open below, and standing some 4 feet off the grass on four legs. It should be placed where it will be freely exposed to the movements of the air, and at least 20 feet away from any house or building. Reading of Thermometers.—All good thermometers can be read by the eye to tenths of a degree. The maximum and minimum thermometers are read once a day, usually at 9 a.m. ; the former marks the highest point reached on the previous afternoon, and must be so entered on the return ; the latter, the lowest point reached on the same morning. For the army returns the ordinary thermometer is read twice a day, at 9 a.m. and 3 p.m. If three read- ings are taken daily, the hours of 6 a.m., 2 p.m., and 10 p.m. are the best. Range of Temperature.—The maximum and minimum in shade give most important climatic indications; the difference between them on the same day constitutes the range of the diurnal fluctuation. The range is expressed in several ways. The extreme daily range in the month or year is the difference betAveen the maximum and minimum thermometer on any one day. The extreme monthly or annual range is the difference between the greatest and least height in the month or year. The mean monthly range is the daily ranges added and divided by the number of days in a month (or the difference between the mean of all the maxima and the mean of all the minima). The yearly mean range is the monthly ranges added and divided by 12. Mean Temperature.—The mean temperature of the day is obtained in the following Avays :— (a) At Greenwich and other observatories, where by means of photography the height of the thermometer at every moment of the day is registered, the mean of the hourly readings is taken. This has been found to accord with the absolute mean (found by taking the mean of the whole curve) to within y^th. of a degree. It may also be recorded by means of a self-registering instrument. (b) Approximately in several Avays. Taking the mean of the shade maximum and minimum of the same day. In this country, during the cold months (December and January), the result is very close to the truth; but as the temperature increases a greater and greater error is produced, until in July the mean monthly error is + 1°*9 F., and in some hot days is much greater. In the tropics, the mean of the maximum and minimum must give a result still further from the truth. Monthly corrections can be applied to bring these means nearer the truth. Lloyd has suggested the folloAving rule for this country, the result being 720 METEOROLOGY. the approximate mean temperature. Multiply the difference betAveen the observed maximum and minimum by the proper factor obtained from the foUowing table, and add the product to the minimum. Month. ¥aK°n January and December,....... February and November, March and October, . April and September, May and August, June and July, . 0-500 0-485 0-476 0-470 0-465 In a great number of places the mean temperature of the day and year, as stated in books, is derived solely from the mean of the maximum and minimum; if a Stevenson's screen is in use this is very nearly the truth. According to Scott, the approximation to the true mean is very close in most parts of the world, especially if the observations be taken as near the end of the period as possible, near midnight, for instance, for the mean of the civil day of twenty-four hours. The approximate mean temperature may also be obtained by taking observations at certain times during the day. If these be taken at 7 a.m., 2 p.m., and at 9 p.m., or at t, t' and t", the t + t' + 2t" folioAving formula by Herschel may be used,----j----= mean temperature of day. If the hours are 8 a.m., 3 p.m., and 10 p.m., the formula is— ----=------= mean of day. If the temperature be taken twice a day at homonymous hours, such as 9 a.m. and 9 p.m., the mean of these is practically the true daily mean. The nearest approach to the mean temperature of the day by a single observation is given at from 8 to 9 p.m. ; the next is in the morning—about 8 o'clock in July and 10 in December and January. The mean monthly temperature is the mean of the daily means : the mean annual temperature is the mean of the monthly means. The nearest approach to the mean annual temperature is given by the mean of the month of October. Observations made from a Aveek before to a week after the 24th April, and again in the corresponding weeks of October, give a certain approximation to the yearly mean temperature. The changes in temperature of any place, during the day or year, are either periodic or non-periodic. The former are dependent on day and night, and on the seasons, i.e., on the position of the place with respect to the sun. The periodic changes are sometimes termed fluctuations, and the differences between day and night temperatures, or the temperatures of the hottest and coldest months, are often called the amplitudes of the daily or yearly fluctuations. Daily Periodic Changes.—On land, the temperature of the air is usually at its lowest about 3 o'clock a.m., or just before sunrise, and at its maximum about 2 o'clock p.m. ; it then falls nearly regularly to 3 o'clock a.m. At sea, the maximum is nearly an hour later. The amount of diurnal periodic change is greater on land than on water; in the interior of continents than by the seaside; in elevated districts than at sea-level. As far as land is concerned, it is least on the sea-coast of tropical islands, as at Kingston in Jamaica, Colombo in Ceylon, Singa- pore, &c. In Sinde and Baluchistan, and throughout the dry tract to the west of the Jumna, the daily range of the thermometer is greatest in October and November, when the difference between sunrise and afternoon averages not RANGE OF TEMPERATURE. 721 much less than 30° F., and sometimes 40°. The same occurs in the northern districts of Bombay in the earlier months of the year, when land winds, from between west and north-west, blow most steadily. In the north-west pro-dnces it averages 28° to 32° F., both in March and April. These varia- tions take place daily, and with much regularity. Yearly Periodic Changes.—In the northern hemisphere the coldest month is usually January; in some parts of Canada it is February. On the sea the coldest month is commonly March. The hottest month is in most places July, in some feAv August; on the sea it is nearly always August. The coldest days in this country are about the 21st January; the hottest about the 21st July. At Toronto the hottest day is about thirty- seven days after the summer solstice; and the coldest fifty-five days after the winter solstice. It is thus seen that both for the diurnal and annual alterations of heat the greatest heat is not simultaneous with, but is after, the culmination of the sun; this is OAving to the slow absorption of heat by the earth. The amplitude of the yearly fluctuation is greater on land than sea, and is augmented by land, so that it reaches its highest point in the interior of great extra-tropical continents. It increases towards the pole for three reasons,— 1. The geographical fluctuation of the earth's position causes a great yearly difference of the angle with which the sun's rays fall on the earth. 2. The duration of incidence of the sun's rays (i.e., the number of hours of sunshine or shade) has greater yearly differences than in the tropics. 3. In the northern hemisphere especially there is a very great extent of land, which increases radiation. The amplitude of the yearly fluctuation is very small in the tropical lands at sea-level. At Singapore it is only 3°-6 F. (Jan. 78°*8, July 82°*4), while it is immense on continents near the pole. At Yakoutsk, in North Asia, it is 112°*5 F. (January-44°*5 and July+ 68°). All fluctuations depend to a large extent upon the distance from the sea, although local causes may have some influence, such as the vicinity of high lands. In any place there may be great undulations and small fluctuations, or great changes in each way. At Brussels, the greatest possible yearly undulation is 90° F. In some parts of Canada immense undulations some- times occur in a day, the thermometer ranging even 50° to 70° F. in one day. The difference between the highest and loAvest readings recorded at Leh, which is the most northerly and driest station where observations are re- corded in India, averages 94° F., and has been as much as 103° F. On the plains of the Punjab it varies from 80° (at Mooltan) to 86° F. at Peshawar, and sometimes reaches 92° F. At the hill stations it is much less, 69° F. at Murree and 63° F. at Simla : at Darjiling it is only 47° F. At Quetta the average range in the course of the year is 80° F., while at Jacobabad the average is 86° F., and the greatest 89° F. At Bombay it averages 31° F., at Madras 48° F., and at Colombo only 25° F. Temperature of the Air of any place.—This depends on the following conditions:— Latitude.—The nearer the equator the hotter the air. For 23^° on either side the equator the sun's rays are vertical twice in the year, and are never more oblique than 47°. The mean yearly temperature of the equator is 82° F.; of the pole, about 2°*5 F. Relative Amount of Land and Water.—The sun's rays passing through the air with but trifling loss fall on land or on water. The specific heat of land being only one quarter that of Avater, it both absorbs heat and gives it 2z 722 METEOROLOGY. out more rapidly. Water, on the other hand, absorbs heat more slowly, stores up a greater quantity, and parts with it less readily. The tempera- ture of the superficial water, even in the hottest regions, seldom exceeds 80° to 82°F., and that of the air is generally beloAV (2° to even 6°) the temperature of the water (J. Davy). Consequently, the more land the greater is the heat, and the Avider the diurnal and yearly amplitudes of fluctuation. The kind of soil has a great effect on absorption. The evaporation from the water also greatly cools the air. Altitude.—The greater the elevation the colder the air, on account (1) of the lessening amount of earth to absorb the sun's rays, (2) of the greater radiation into free space. The decline of temperature is taken as being about 1° F. for each 300 feet of ascent, or 1° C. for each 200 metres. The decline is by no means regular, being influenced by currents, clouds, &c. In Glaisher's balloon ascents in a cloudy sky, it was found to be about 4° F. for each inch of barometric fall, at first; but when the barometer had fallen 11 inches, the decline of temperature was more rapid. Under a clear sky, there was a fall of 5° F. for each of the first 4 inches of descent: then 4° per inch till the thirteenth inch of descent, and then 4°*5 for fourteenth, fifteenth, and sixteenth inches of descent. There are other influencing circumstances of local importance, the chief being aspect and the nature of the soil. To these may be added forests, Avhich, in hot climates especially, greatly moderate the heat, by shielding the soil from the sun's rays, and by evaporation from the leaves. Distribution of Temperature.—The manner in Avhich heat is distributed over the globe is shown by maps on which are drawn isothermal lines, or lines connecting places that have the same mean temperatures : these mean temperatures may be either for the year or for the several months. The region of highest mean monthly temperature, shoAvn by an isothermal hne of 90° F. for July, encloses a tract extending from about 8° W. long, in north Central Africa, to about 72° E. long, in the Punjab, forming a belt of about 18° in width; its southern limit in Africa being about 9° N. lat., its northern limit reaches nearly 35° N. lat. The hottest places on the earth are—in the eastern hemisphere, near the Red Sea^at Massowah, and at Khartoum (15° N. lat.), and on the Nile in Lower Nubia; annual temperature = 90°*5 F.: in the western hemisphere, on the Continent, near the West Indies, the mean annual temperature is 81°*5 F. These are sometimes called the climatic poles of heat. The highest readings of a well-shaded verified thermometer in India have been 123°*1 F. at Pachpadra, in Rajputana, and 122°*2 F. at Jacobabad, both on May 25th, 1886. The poles of cold are in Siberia (Yakoutsk to Usjausk, 62° N.) and near Melville Island. The lowest readings recorded have been-69° F. by Kane at Rensselaer harbour in Greenland, and-81° F. by Govochow at Wenchojausk in Siberia. SUNSHINE. The duration of the sunshine is a very important factor in all chmates, and the extent of this duration is recorded by either (1) the Campbell- Stokes Burning Recorder; (2) the Whipple-Casella Universal Sunshine Recorder; (3) the Jordan Photographic Recorder. The principle of the first two of these instruments is the same, the second being really a modi- fication of the first. They consist mainly of a glass sphere, so mounted that when the sun shmes its rays are focussed as by a lens upon a strip of WIND. 723 cardboard, with the result that a burnt track or hole is left for such periods of time as the sun shines. The cardboard is so placed in the instrument that definite sections of it correspond to periods of time in hours. Jordan's instrument (fig. 119) is, strictly speaking, rather a recorder of sunlight than of sunshine. The im- proved pattern consists of two semi- cylindrical boxes, one to hold the forenoon, the other the afternoon record, and on the inside of each of which a sheet of sensitive cyanotype paper is carefully placed day by day. A slit, through which the beam of sunlight finds entrance, is placed in the centre of the rectangular side of each box, so that the length of the beam within the chamber is the radius of the cylindrical surface on which it is projected. The path of the sunbeam, therefore, follows a straight line on the sensitive paper at all seasons. The instrument must be carefully adjusted to the meridian and to the latitude of the place, and must be firmly fixed. WIND. The facts to be observed relating to winds are practically limited to those connected with direction, force or pressure, and velocity. Direction.—The point of the compass from which the wind is blowing is obviously best ascertained by observing for a few moments the movements of a properly set and freely movable vane or Aveathercock. When a weathercock is not available, the smoke from a chimney will readily give the information, provided, of course, the observer has a precise idea as to where lies his north or south. Under all circumstances, the bearings should be true and not magnetic (by compass). In this country the variation of the compass at the present time ranges from 16s in the extreme east of England to 23° in the extreme north-west of Ireland, the true north lying so many degrees to the east of the compass or magnetic north. Roughly speaking, a true north and south line lies along the line N.N.E. to S.S.W. by compass. In the absence of a mariner's compass, we can ascertain the north by means of the pole star, or the south by means of the sun. The pole star is practically the north in January and July at 6 a.m. and 6 p.m., in February and August at 4 a.m. and 4 p.m., in March and September at 2 am. and 2 p.m., in April and October at noon and midnight, in May and Novem- ber at 10 a.m. and 10 p.m., in December and June at 8 a.m. and 8 p.m. For ascertaining the position of due south, we must know the longitude of a given place and also true local time. As a matter of fact, the sun is not always on the meridian at 12 noon, but in this country it is practically so, or within a minute thereof, during the following periods: April 11th to 18th, June 9th to 18th, August 28th to September 3rd, and December 22nd to 25th. If, therefore, a pole be erected vertically as tested by a plumb line, the shadoAv from it will fall true N.W. at 9 a.m., N. at noon, and N.E. at 3 p.m. But before this observation can be of value it is necessary to know the true local time. This can be always obtained from uniform time, 724 METEOROLOGY. i.e., Greenwich time, by subtracting four minutes for every degree of Avest longitude, or by adding four minutes for every degree of east longitude. Thus, Dublin is 6° 15' W. of GreenAvich. These degrees and minutes of longitude multiplied by 4 give minutes and seconds of time, or 25 minutes. Then, as Dublin is west of GreenAvich, local time is earlier than Greenwich time, and noon at GreenAvich becomes 11 hours 35 minutes a.m. by Dublin, or local time. In other words, on the dates above mentioned the sun at Dublin is due south at 0 h. 25 m. Greenwich time. All Avind direction observations should be recorded to the nearest point of the compass. To calculate the mean direction, it is usual to give an arbitrary numerical value to each observation, and then to analyse them. Thus, suppose we read to 16 points of the compass, and give a numerical value of 4 to each observation; if the Avind be due N., we should give to N. the full value of 4; if the reading were N.W., we should give half the value of the observation, or 2 to N., and the other half to W. If the read- ing were N.N.W., then N. Avould get 3, and W. get 1, as their shares of the numerical value of the observation. Suppose we have the following observations of Avind direction recorded: S., S.E., E., S.S.E., N.W., W.N.W., N.E., E.N.E., N., N.E. The calculation of the mean direction is done in the folloAving way. Giving to each observation a numerical value of 4, we get— s. = S.E. = E. = S.S.E. = ... N.W. = 2 W.N.W. = 1 N.E. = 2 E.N.E. = 1 N. = 4 N.E. = 2 w 12 9 14 5 Then, deducting the opposite directions from each other, we get:— N. 12 S. 9 Net N. 3 E. 14 W. 5 Net E. 9 That is, the mean direction lies in the N.E. quarter of the compass, and nearer E. than N. Since each quarter consists of 90°, the precise mean direction is at a point on the compass f of 90° from N. in favour of E., or at an angle of 67|° from N., which is a mean direction of E.N.E. Pressure and Velocity: Anemometers. — The instruments for the measurement of wind, either as regards pressure or velocity, are called anemometers. The earlier forms of these instruments were rectangular plates hung on hinges on a horizontal axis. The angle which these plates made with the vertical indicated the wind's pressure. In another kind, the movements of the plates, resisted by either springs or weights, recorded upon a chart by means of a connected pencil the degree and amount of their displacement. In another form, the pressure of the wind is measured by making it blow into the mouth of an open tube kept facing the current by means of a vane, and then noting the degree of pressure exerted upon a column of Avater or mercury in an U tube. The later and better forms of anemometer in most general use are those known as Robinson's, consisting FORCE AND VARIATION OF AVIND. 725 of four arms, each provided Avith a hollow cup and rotating horizontally on a vertical axis, which, by means of an endless screw, causes movements to be recorded on a series of dials in terms of miles and parts of a mile. These instruments are graduated on the principle that, allowing for friction, the cups revolve three times slower than the wind moves; so that if the centres of the cups be, as they usually are, 1*12 foot apart, each revolution corresponds to 3*52 feet of movement, or 10*56 feet of actual wind-motion, and that 500 rotations of the cups indicate 1 mile of wind. Owing, how- ever, to the allowance of friction being placed probably too high, and the cup motion being nearer two than three times sloAver than the wind, the velocity of wind movement, as recorded by many of these instruments in general use, is something like 20 per cent, too high. All anemometers to be reliable need to be kept scrupulously clean, well-oiled, and placed in a thoroughly open position at least 20 feet from the ground. Estimation of Wind Force.—Yarious proposals have been made for estimating and describing roughly the force of the Avind. The earliest was that of Admiral Beaufort, who, in 1806, devised a scale having a relation to the pressure of the wind upon the sails of a ship, and the amount of canvas which she could carry. This is given in the folloAving table :— A^elocity in miles per hour. 3 8 13 18 23 28 34 40 48 56 65 75 90 Attempts have been made to express the Avind's force as a pressure of so many pounds to the square foot. From experiments with various kinds of anemometers, Dines calculates the pressure (P) of the wind in pounds per square foot from the recorded velocity in miles per hour, on the assumption that the pressure equals one two-hundredth (^^jf) of the square of the velocity, or P = 0*005 x V2. According to this formula, a wind blowing with a velocity of 50 miles an hour exercises a pressure of 12| K> on the square foot. Unfortunately for the value of this formula, the factor 200 is nearly as doubtful as that of three for the friction ratio of Bobinson's anemometer. Diurnal Variation of Wind.—In this country the wind has an average velocity of 8 miles an hour, and rarely exceeds 40; but its direction and force are subject to certain diurnal variations. As a rule, at mid-day the wind bloAvs from sea to land, and from plains to hills, while in the evening the direction will be reversed. In all parts of the world the upper air currents move faster than the loAver, following in the northern hemisphere a direction shghtly to the right, in the southern to the left. Now during the day the heating of the lower air strata causes them to ascend, thereby increasing the friction betAveen the upper and lower currents, and proportionately reducing the difference of velocity. The lower current, under the influence of the upper, is deflected to the right in the northern hemisphere, to the left in the southern, and has Beaufort Scale. Description of Wind. 0 . . . . Calm 1 Light air 2 Light breeze 3 Gentle breeze 4 Moderate breeze 5 Fresh breeze 6 Strong breeze 7 Moderate gale 8 Fresh gale 9 Strong gale 10 Whole gale 11 Storm 12 Hurricane 726 METEOROLOGY. its speed increased in both cases, while the upper, under the influence of the lower, is deflected in the opposite direction with diminution of velocity. These effects are naturally more marked the greater the diurnal heating of the lower strata relatively to the upper, and the greater the normal angle between the two currents. For these reasons : (1) Near the equator, and over the open sea, there is little diurnal variation of wind either in direction or speed. (2) On plains and similar land surfaces, even at great elevations, the wind shifts with the hands of the clock, and attains its maximum strength during the afternoon, backing and diminishing again at night in the northern hemisphere. The changes of direction are reversed in the southern hemi- sphere. (3) On mountain peaks the wind shifts against the hands of the clock, and diminishes in strength during the afternoon, and veers and increases again at night. The changes in direction are reversed in the southern hemisphere. ATMOSPHEBIC ELECTRICITY. Even in fine Aveather the atmosphere is charged with electricity. Bodies are said to be electrified when, after having been rubbed or placed in com- munication with an electrified object, they exercise an attraction or repulsion upon other bodies. Closer inquiry indicates that the electricity developed by friction from different substances, such as glass on one hand and sealing wax on the other, is not identical, and that there are consequently two electricities varying from each other in some of their characters. In order to distinguish between the two kinds of electricity, the one is called vitreous electricity, from its being generated from glass, and is known as positive; Avhile the other is called resinous electricity, and is known as negative. Electricities of different kinds attract each other, and electricities of the same kind repel each other. It has been found that the atmosphere always contains free electricity, which is almost invariably positive. When the sky is cloudless, the elec- tricity is ahvays positive, but the intensity varies with the height, being greatest in the highest and most isolated situations. Positive electricity is only found at a certain height above the ground; on flat ground it becomes manifest at a height of 5 feet. It is not found in houses, in streets, or under trees. The observations of negative electricity almost all occur during heavy rain. When the sky is clouded, the electricity is sometimes positive and sometimes negative, according to the electrified condition of the clouds. In relation to the atmosphere the earth's surface is always negative. The electricity of the atmosphere is stronger in winter than in summer, increasing from June to January. It is subject to a double maximum and minimum each day. The first maximum occurs from 7 to 8 a.m. in summer, and from 10 a.m. to noon in winter; it then falls slightly to the first minimum between 5 and 6 p.m. in summer, and between 2 and 3 p.m. in winter; it rises to a second maximum a little after sunset, and then decreases to a second minimum which occurs about daybreak. These varia- tions are best observed in clear settled weather. Sources of Atmospheric Electricity.—The chief of these are : (1) Evapora- tion ; (2) Vegetation; (3) Combustion; (4) Friction. Electricity is produced when impure water is evaporating, or water in which some degree of chemical decomposition takes place, none whatever being produced by the evaporation of pure Avater. Vapour rising from water containing a salt or an alkali is charged with positive electricity, while the water retains negative electricity; but Avhen the Avater contains acid, negative electricity is given off, and ATMOSPHERIC ELECTRICITY. 727 positive is left behind. Hence it is supposed that seas, lakes, and rivers are abundant sources of atmospheric electricity, especiaUy positive electricity. ^ The vegetable kingdom is also a source of electricity, (1) from the evapora- tion going on, and (2) from the giving off of oxygen and carbonic acid, which is charged Avith positive electricity. During the process of burning, bodies give off positive electricity, and become themselves negatively electrified. This frequently occurs during volcanic eruptions. Wind, by the friction it produces on terrestrial objects, the particles of dust, and the watery particles in the vesicular state which it carries with it, contributes to the electricity of the air. Electricity is not generated if the moisture be in the form of pure vapour. Atmospheric electricity may, from time to time, reveal its presence by very unequivocal phenomena, of which the chief are: (1) Thunder and Lightning; (2) Hailstones; (3) Aurora—the aurora borealis being peculiar to the northern hemisphere, and the aurora australis to the southern. But apart from these manifestations, observations may be made upon the electricity existing in the air under ordinary circumstances, so as to deter- mine, firstly, Avhether it is positive or negative; secondly, what is its intensity or tension. The Electroscope is intended to demonstrate the kind of electricity present in the air. The most sensitive instrument for this purpose is the gold-leaf electroscope, in. which electricity collected from the atmosphere is made to pass through a metal rod, called a conductor, upon tAvo delicate gold leaves suspended at the end of the rod, and between the poles of two dry piles charged Avith opposite electricities. The leaves, when brought under the influence of the same kind of electricity, will diverge or repel each other. As very little electricity can be observed near the ground, the conductor should be placed in contact with the air at some height above the earth's surface, by means of a collector, which may be a metallic arrow tied to one end of a conducting string and then shot upwards into the air. The electroscope will be found electrified as the arrow mounts. A gilded fishing-rod may be substituted as a conductor, its lower end being insulated by caoutchouc. The Electrometer is an instrument for measuring the amount of electricity, that is, its intensity or tension. There are two chief forms in common use, namely, the Quadrant electrometer for observatories, and the Portable electro- meter. In the quadrant, or modified divided-ring electrometer, a needle of thin aluminium, cut so as to resemble in form a figure 8 with the hollows filled in, and carrying above it a small light mirror, is suspended from its centre by two fine silk threads. The needle swings horizontally inside a shallow cylindrical box, Avhich is, cut into four equal segments or quadrants, each insulated separately by glass supports, but connected alternately by thin Avires. Each pair of quadrants is also connected to wires forming the tAvo electrodes or terminals for the attachment of the collecting and earth Avires. The base of the electrometer contains a Leyden jar, partially filled Avith strong sulphuric acid, and a platinum wire, hung from the lower sur- face of the needle, is made to dip into the acid. A lamp and a divided scale are placed about a yard in front of the instrument, and the light shining through an aperture in the frame of the scale is reflected by the mirror on the scale, where the position of the image of a wire stretched across the hole can be accurately observed. In order to use this electrometer the needle must be charged with electricity from a small electrophorus or electricity bearer, brought into contact with a Avire dipping into the sulphuric acid at the bottom of the Leyden jar. One 728 METEOROLOGY. of the electrodes connected Avith the segments is then joined by a Avire to the collector; the other is placed in communication Avith the earth. The needle will then be deflected towards either one side or the other, according as the electricity of the atmosphere is of the nature to repel or attract it, and the extent of repulsion, as measured by the scale, is proportional to the amount of difference betAveen the potentials of the atmospheric and terrestrial electricities. The scale value of each such electrometer must be experi- mentally determined by means of a galvanic battery of constant intensity, such as Daniell's. Knowing the electro-motive force of the cell employed in the battery, the indications of the electrometer scale may be readily con- verted into terms of the absolute unit of electro-motive force or "volts" (see Scott's Instructions in the use of Meteorological Instruments). The Portable electrometer of Lord Kelvin collects the electricity by means of a burning fuse at the extremity of a vertical Avire. Another electrometer much commended is Peltier's. Thunderstorms are classified into Cyclonic Thunderstorms and Heat Thunderstorms. The former belong to Avinter and to insular climates, the latter to summer and to hot climates. Cyclonic thunderstorms are so called because they accompany atmospheric depressions, such as traverse the Atlantic and north-western coasts of Europe, especially in Avinter. While these cyclonic thunderstorms are not so violent, they are quite as dangerous as the summer thunderstorms, because in them the clouds drift at a Ioav level, whereby the lightning is more likely to strike the ground. Heat thunderstorms are especially associated with sudden and extreme variations in air temperature. As the result of rapid evaporation, clouds surcharged with positive electricity form in the upper air. Subsequently, in the lower strata of the air, negatively electrified cloud strata form. The interaction of these cloud masses result in the phenomena of a thunderstorm. These heat thunderstorms show a diurnal and even an annual periodicity. It is not uncommon to find them breaking over the same line of country on consecutive days, as if there was a direct electrical attraction between the earth of certain localities and the superincumbent atmosphere for the time being; and this no doubt is in reality the case. Speaking generally, much negative electricity in the air forecasts rain; on the other hand, a sudden development of positive electricity in Avet weather is a certain sign of fine Aveather. Lightning is the brilliancy produced by the generation of heat along the path of an electric discharge so intense as to render the various constituents of the air momentardy incandescent. This heat is due to the resistance of non-conductors in the air to the discharge Avhich takes place when clouds charged with different electricities approach each other (Balfour Stewart). Lightning is usually either zigzag or forked ; diffused or sheet; or globular or so-called ball lightning. Thunder is probably due to the instantaneous expansion of the air by the heat produced by the lightning along the path of the electric discharge, and then by an inrush of air to fill up the vacuum so caused. From the rate at which sound travels, if thunder be not heard till five seconds after the flash the distance is about a mile. Thunder has not been heard at a greater distance than 15 miles from the lightning flash. _ St Elmo's Fire is the Castor and Pollux of the ancients. It is an induc- tion phenomenon, occurring when an electrified cloud approaches a prominent obstacle like a flagstaff, the mast of a ship, a tree, or a lightning conductor. The electricity of the cloud and of the earth combine, not in a flash of ozone. 729 lightning, but more sloAvly and continuously, so that a flame seems to rise from the projecting body. Hailstorms are modifications of the thunderstorm, and seldom occur during the night or in Avinter, but are most frequent in summer and during the hottest part of the day. Hail itself is intimately related to atmospheric electricity, its formation requiring (1) an excess of moisture, (2) a tempera- ture below freezing, (3) the presence of electrified clouds. Typical hailstorms are nearly always associated with thunder and lightning, the hailstones being kept in a state of constant oscillation between two oppositely electri- fied clouds, until by continued condensation they grow so heavy that they fall to the earth. Aurora.—This is an electrical phenomenon rarely seen in low latitudes, consisting of a luminous appearance in the northern and southern skies, most frequently in this hemisphere between the parallels of 66° and 75°. The aurora borealis is now generally considered to be due to positive electricity from the sea betAveen the tropics being carried into the upper regions of the air, and thence wafted to the poles by the higher aerial ■currents. In the vicinity of the poles it descends toAvards the earth and meets the terrestrial negative electricity in a rarefied atmosphere. Luminous discharges then take place, being possibly increased in brightness by the presence of masses of ice-particles in the atmosphere. OZONE. If a succession of electric sparks from a powerful electric machine be passed through a tube of oxygen, a peculiarly pungent odour is developed, due to the production of a body to Avhich the name of ozone has been given, from the Greek o£oj, / have a smell. Only a small proportion of oxygen can be converted into ozone by the electric discharge; but a constant and considerable diminution of volume accompanies the change, 100 volumes of oxygen contracting to 92 volumes. Hence ozone must be denser than oxygen. It is now generally considered that ozone is an allotropic condition of oxygen, and that its formation consists in the condensation of another atom of oxygen into each dyad molecule of ordinary oxygen. So that the chemical formula for free oxygen being 02 that for ozone is 03, and the density of ozone is one-half greater than that of oxygen. When 100 volumes of oxygen are reduced by ozonisation to 92, 8 volumes of oxygen combine with 16 volumes to produce 16 volumes of ozone. The chief points of difference betAveen ozone and ordinary oxygen are {1) it possesses a curious smell, like Aveak chlorine, whilst oxygen is odour- less ; (2) it destroys vegetable colours; (3) it rapidly oxidises the precious metals; (4) it liberates iodine from iodide of potassium. Variations in the amount of ozone have been supposed to be a cause of ■climatic difference, but, in spite of all the labour Avhich has been given to this subject, the evidence is very inconclusive. The reaction Avith the ozone paper is liable to great fallacies. Yet it seems clear that some points are made out: the ozonic reaction is greater in pure than impure air; greater at the sea-side than in the interior; greater in mountain air than in the plains; absent in the centre of large towns, yet present in the suburbs; absent in an hospital Avard, yet present in the air outside. In this country it is greater Avith south and west Avinds; greater, according to Moffat, when the mean daily temperature and the deAV-point temperature are above the 730 METEOROLOGY. mean; the same observer found it in increased quantity with decreasing readings of the barometer, and conversely in lessened quantity Avith increas- ing readings. On account of the irritating effect of ozone when rising from an electrode, Schb'nbein believed it had the poAver of causing catarrh, and inferred that epidemics of influenza might be produced by it. He attempted to adduce evidence, but at present it may safely be said that there is no proof of such an origin of epidemic catarrhs. A popular opinion is, that a climate in which there is much ozone (i.e., of the substance giving the reaction with potassium iodide and starch paper) is a healthy, and, to use a common phrase, an exciting one. The coinci- dence of excess of this reaction -with pure air lends some support to this, but, like the former opinions, it still wants a sufficient experimental basis. On the whole, the subject of the presence and effects of ozone, curious and interesting as it is, is very uncertain at present; experiments must be numerous, and inferences draAvn from them must be received with caution. Determination of Ozone.—Papers saturated with a composition of iodide of potassium and starch, and exposed to the air, are supposed to indicate the amount of ozone present in the atmosphere. Schb'nbein, the discoverer of ozone, originaUy prepared such papers, and gave a scale by which the depth of blue tint was estimated. Subsequently, simdar but more sensitive papers Avere prepared by Moffat, and Lowe afterwards improved on Moffat's papers, and also prepared some ozone powders. The papers are exposed for a definite time to the air, if possible with the exclusion of light, and the alteration of colour is compared with a scale. Schbnbein's proportions are 1 part oi pure iodide of potassium, 10 parts starch, and 200 parts of water; Lowe's proportion is 1 part of iodide to 5 of starch; Moffat's proportion is 1 to 2\. The starch should be boiled for ten minutes, and filtered so that a clear solution is obtained; the iodide is dissolved in another portion of Avater, and is gradually added. Both must be perfectly pure; the best arrowroot should be used for starch. The paper, prepared by being cut into slips (so as to dry quicker and to avoid loss of the powder in cutting) and soaked in distilled water, is placed in the mixed iodide and starch for four or five hours, then removed with a pair of pincers, and slowly dried in a cool dark place, in a horizontal position. The last point is important, as otherwise a large amount of the iodide drains doAvn to one end of the paper, and it is not equally diffused. The papers when used should hang loose in a place protected from the sun and rain : a box is unnecessary; they should not be touched with the fingers more than can be helped when they are adjusted. When Schbnbein's papers are used they are moistened with water after exposure,_but before the tint is taken. Moffat's papers are prepared some- what similarly to Schbnbein's, but do not require moistening Avith Avater. The estimation of ozone is still in a very unsatisfactory state, and this arises from tAvo circumstances. 1. The fact that other substances beside ozone act on the iodide of potassium, especiaUy nitrous acid, which is formed in some quantity during electrical storms. If such be suspected, in order to be quite sure that it is ozone only Avhich has turned the paper blue, it is advisable to use a second test, which is to soak red litmus paper Avith a very dilute solution of the iodide of potassium. The potassium oxide produced causes an alkaline re- action, and turns the red paper to blue. 2. The fact that the papers can scarcely be put under the same conditions CLOUDS. 731 from day to day; light, Avind, humidity, and temperature (by expelling the free iodine) all affect the reaction. Chemical objections have also been made. Supposing that iodine is set free by ozone, a portion of it is at once changed by additional ozone into iodozone, Avhich is extremely volatile at ordinary temperatures, and is also changed by contact with Avater into free iodine and iodic acid. Hence a portion of the iodine originally set free never acts on the starch, being either volatilised or oxidised. Again, the iodine and caustic potash set free by the ozone combine in part again, and form iodate and iodide of potassium (£th of the former and f ths of the latter), and in this Avay the blue colour of iodide of starch first produced may be removed. The ozone may possibly act on and oxidise the starch itself, and hence another error. CLOUDS. A cloud is a collection of particles of aqueous vapour condensed into watery particles and floating in the atmosphere at some height above the ground. This height varies from a few hundred feet to several miles. In the words of Tyndall, the minute particles of water, condensed from aqueous vapour, which go to make up a cloud, may be aptly called " water dust." The "cloud line," or that level below which cloud formations seldomor never take place, varies in different parts of the world. In South America it is about 9000 feet; in the Tyrol it falls to about 5000 feet; and in the British Islands it is as low as 2500 feet. Classification of Clouds.—The following is the cloud classification of Hildebransson and Abercromby, as noAv universally accepted, and confirmed by the last meeting of the International Meteorological Committee at Upsala in August 1894. Those marked with (a) are detached or rounded forms, most frequently seen in dry weather; those marked with (b) are wide-spread or veil-like forms, most frequent in Avet weather. A. Highest clouds, mean height 9000 metres. (a) 1. Cirrus. (b) 2. Cirro-stratus. B. Clouds of mean altitude, 3000-7000 metres. , . j 3. Cirro-cumulus. W \ 4. Alto-cumulus. (b) 5. Alto-stratus. C. Loav clouds, below 2000 metres. (a) 6. Strato-cumulus. (b) 7. Nimbus. D. Clouds formed by the diurnal ascending currents. 8. Cumulus. Top, 1800 metres; base, 1400 metres. 9. Cumulo-nimbus. Top, 3000-8000 metres; base, 1400 metres. E. Elevated fog, below 1000 metres. 10. Stratus. The following is the description of the above ten principal forms of cloud, as suggested by the International Committee:— (1) Cirrus (Ci.).—Isolated feathery clouds of fine fibrous texture, generally of a white colour. Frequently arranged in bands which spread, 732 METEOROLOGY. like the meridians on a celestial globe, over a part of the sky, and converge in perspective toAvards one or tAvo opposite points of the horizon. (In the formation of such bands, the two folloAving forms often take part.) (2) Cirro-Stratus (Ci. S.).—Fine whitish veil, sometimes quite diffuse, giving a whitish appearance to the sky, and called by many cirrus haze, sometimes of more or less distinct structure, exhibiting confused fibres. The veil often produces halos around the sun and moon. (3) Cirro-Cumulus (Ci. Cu.).—Fleecy cloud. Small AAdiite balls and Avisps without shadows, or with very faint shadows, Avhich are arranged in groups and often in rows. (4) Alto-Cumulus (A. Cu.).—Dense fleecy cloud. Larger whitish or greyish balls with shaded portions, grouped in flocks or i-oavs, frequently so close together that their edges meet. The different balls are generally larger and more compact (passing into S. Cu.) towards the centre of the group, and more delicate and wispy (passing into Ci. Cu.) on its edges. They are very frequently arranged in stripes in one or tAvo directions. (5) Alto-Stratus (A. S.).—Thick veil of a grey or bluish colour, exhibit- ing in the vicinity of the sun and moon a brighter portion, and which, without causing halos, may produce coronse. This form shows gradual transitions to cirro-stratus, but, according to the measurements made at Upsala, has only half the altitude. (6) Strato-Cumulus (S. Cu.).—Large balls or rolls of dark cloud which frequently cover the whole sky, especially in winter, and give it at times a wave-like appearance. The stratum of strato-cumulus is usually not very thick, and blue sky often appears in the breaks through it. Between this form and the alto-cumulus all possible graduations are found. They are distinguished from nimbus by the ball-like or rolled form, and because they do not tend to bring rain. (7) Nimbus (N.).—Bain clouds. Dense masses of dark formless clouds with ragged edges, from which generally continuous rain or snow is falling. Through the breaks in these clouds there is almost ahvays seen a high sheet of cirro-stratus or alto-stratus. If the mass of nimbus is torn up into smaller patches, or if smaller clouds are floating very much below a great nimbus, the former may be called Fracto-nimbus (" Scud" of the sailors). (8) Cumulus (Cu.).—Piled clouds. Thick clouds whose summits are domes with protuberances, but whose bases are flat. These clouds appear to form in a diurnal ascensional movement which is almost always apparent. When the cloud is opposite the sun, the surfaces wlhch are usually seen by the observer are more brilliant than the edges of the protuberances. When the illumination comes from the side, this cloud shows a strong actual shadow; on the sunny side of the sky, hoAvever, it appears dark with bright edges. The true cumulus shows a sharp border above and below. It is often torn by strong winds, and the detached parts (Fracto-cumulus) present continual changes. (9) Cumulo-Nimbus (Cu. N.).—Thunder cloud; shower cloud. Heavy masses of clouds, rising like mountains, towers, or anvils, generally surrounded at the top by a ved or screen of fibrous texture ("false cirrus "), and below by nimbus-like masses of cloud. From their base generally fall local shoAvers of rain or snow, and sometimes hail or sleet. The upper edges are either of compact cumulus-like outline, and form immense summits, sur- rounded by delicate false chrus, or the edges themselves are drawn out like cirrus. This last form is most common in " spring squalls." The front of storm clouds of great extent sometimes shows a great arch stretching across a portion of the sky, which is uniformly lighter in colour. OBSERVATION OF CLOUDS. 733 (10) Stratus (S.).—Lifted fog in a horizontal stratum. When this stratum is torn by the wind or by mountain summits into irregular frag- ments, they may be called Fracto-stratus. Observation of Clouds.—As the whole subject of our knowledge of clouds is at present in a somewhat elementary condition, considerable efforts have been made to obtain comparable and international observations and reports. To attain this result the following instructions are suggested for observing clouds, so that at each observation there may be recorded :— (1) The Kind of Cloud, designated by the international letters of the cloud name. Those having access to the Hildebransson-Kbppen-Neumayer Atlas of cloud forms may more exactly define their own observations by giving the number of the picture of the Atlas most nearly representing the observed form. (2) The Direction from which the Clouds come.—If the observer remains completely at rest during a few seconds, the motion of the clouds may be easily observed relatively to a steeple or mast erected in an open space. If the motion of the cloud is very sIoav, the head must be supported. Clouds should be observed in this way only near the zenith, for if they are too far aAvay from it the perspective may cause errors. In this case nephoscopes should be used, and the rules followed which apply to the particular instrument employed. (3) Radiant Point of the Upper Clouds.—These clouds often appear in the form of fine parallel bands, which, by an effect of perspective, seem to come from one point of the horizon. The radiant point is that point where these bands, or their direction prolonged, meet the horizon. The position of this point on the horizon should be recorded in the same way as the wind direction, north, north-north-east, &c. (4) Undulatory Clouds.—It often happens that the clouds show regular, parallel and equidistant streaks, like the waves on the surface of water. This is the case for the greater part of the cirro-cumulus, strato-cumulus (roll-cumulus), &c. It is important to note the direction of these streaks. When there are apparently tAvo distinct systems, as is to be seen in clouds separated into balls by streaks in two directions, the directions of the two systems should be noted. As far as possible, observations should be made on streaks near the zenith, to avoid effects of perspective. (5) Density and Position of Cirrus Banks.—The upper clouds frequently take the form of felt or of a more or less dense veil, which, rising above the horizon, resembles a thin Avhite or greyish bank. As this cloud form has an intimate relation to barometric depressions, it is important to note:— (a) The density— 0 meaning very thin and irregular. 1 meaning thin but regular. 2 meaning rather dense. 3 meaning dense. 4 meaning very dense and of dark colour. (b) The direction in Avhich the veil or bank appears densest. Remarks.—All interesting details should be noted, for example:— (1) On summer days all low clouds generally assume particular forms resembling cumulus more or less. In this case, there should be put under Remarks, " Stratus or Nimbus Cumuliformis." (2) It sometimes happens that a cumulus has a mammillated lower surface. This appearance should be described by the name of " Mammato-cumulus." (3) It should always be noted whether the clouds appear stationary, or whether they have a very great velocity. 734 METEOROLOGY. HUMIDITY OF THE AIB. The question of the amount of moisture in the air is somewhat com- plicated, and is usuaUy spoken of as the degree of humidity. Beference has been made elsewhere to the fact that water is constantly evaporating into the ah, and that the amount of water or moisture which the air can hold or retain is constantly varying with its temperature. Thus at 32° F. a cubic foot of dry air can only take up 2*13 grains of water, Avhile at 100° F. it can take up as much as 19*84 grains. When air is so full of moisture that it can contain no more, it is said to be saturated. In this country the air upon an average contains about three-fourths of the amount of water needed to saturate it, that is, it has an humidity of about 75 per cent.; but if the air containing this amount of moisture be cooled down, it will reach a tempera- ture at which that same amount of moisture will suffice to saturate it, and if cooled still more it wdl reach a temperature insufficient to retain that moisture, with the result that it must part with some of it, the amount so parted Avith being precipitated or deposited as rain, snoAV, mist, or deAv. For instance, 100 cubic feet of air, three parts saturated with moisture, at a temperature of 70° F. Avould hold 600 grains of water; if for some cause or other the temperature of that 100 cubic feet of air were reduced to 61° F., that volume of air would become quite saturated, bcause at that temperature it could only hold 600 grains; and if the temperature were still further reduced, say to 56° F., it could only retain 500 grains of moisture; therefore the difference between 600 and 500 grains, or 100 grains of water, would be released or deposited as mist, dew, or rain. Mist, Fog, and Dew.—Aitken and some others have pointed out that occasionally, in perfectly pure ah, a pressure of vapour may be maintained greater than that corresponding to the temperature of saturation. In fact, that condensation will not in general begin unless some nucleus is present to which the particles of water can attach themselves. It is on the presence of solid particles of dust in the ah that the formation of mists and fogs depends; the precise degree of mist or fog depending on the amount of dust present, and on the size and constitution of the particles. When the number of dust particles is large or their size considerable, and the quantity of vapour condensed is small, we get the phenomenon of a town or so- called dry fog. The condensation of Avater upon invisible particles so increases their size as to make them visible. Often in the case of town fogs, their obviousness is not so much due to the action of the moisture condensed on the particles as to the excessive size and quantity of the particles them- selves. What are known as sea fogs probably occur in air which is com- paratively dry, because the dust in their case consists largely of salt grains derived from spray or surf, and which have a great affinity for moisture. If the quantity of condensed moisture is large, or the amount of dust and other solid nuclei small, we get what is called a mist, and it is merely a question of the degree of the moisture present which determines where the mist ends and actual rain begins. The formation of dew is precisely analogous; in this case the solid sub- stance on which the moisture is precipitated or condensed is the surface of the ground, or a blade of grass, and not sohd nuclei like soot or dust floating about in the air, as in the formation of fogs. Owing to the rapidity with which the earth, under certain circumstances, loses heat by radiation, as, for instance, on a fine clear night, the strata of air containing moisture, in eontact with the coohng earth, themselves become reduced so much in HYGROMETERS. 735 temperature that they are no longer able to retain their water vapour, but actually lose it by condensation upon the ground, where it constitutes what we call dew. The particular temperature at which air saturated or loaded with moisture deposits its water is called the dew-point. Hygrometers.—For the determination of the temperature of the dew- point, certain instruments called hygrometers are used ; these are either direct or indirect. All direct hygrometers experimentally illustrate the principle or theory •of the dew-point, or that critical temperature at which dew begins to be deposited. We have seen that the capacity of the atmosphere for taking up and holding aqueous vapour in suspension varies with the temperature, or m other words, with what is called the elastic force or tension of aqueous vapour. If the temperature falls, and with it the tension of aqueous vapour, a point is reached eventually at which the air is saturated with moisture. If the cooling process continues, a deposition of dew takes place —in fact, the temperature has fallen to or below the dew-point. Now, in direct hygrometers the cooling process is continued until a film of condensed moisture or dew develops on a surface of glass or polished metal. At this moment an attached thermometer is read off, giving the temperature of the dew-point. Three direct hygrometers call for notice: they are Daniell's Regnault's, and Dine's. ' Daniell's Hygrometer—-This consists of a bent tube with a globe at each «nd, and is partly filled with ether, the rest of the space in the tube being filled with the ether vapour, all the air having been expelled. One globe is made of blackened glass, and contains a thermometer, while the other is -covered with muslin. Before using the instrument, the ether is made to pass into the blackened globe containing the thermometer, whde the muslin surrounding the second globe is moistened with ether. This ether rapidly evaporates, causing a condensation of some of the ether vapour inside the tube; this in its turn produces an evaporation of the ether in the blackened hulb. Now, whenever evaporation occurs, there is absorption of heat, so that the black bulb gradually becomes colder and colder, and the moment is soon reached when the air in contact with it begins to deposit dew on its surface. So soon as this happens, the temperature shown by the contained thermometer is read off and recorded as the dew-point. Regnault's Hygrometer is a modification of Daniell's. In it are two thermometers; one shows the temperature of the air, the other dips through •a stopper into a small vessel of polished silver, and is exposed during an experiment to the influence of a current of air made to bubble either by means of an aspirator or by blowing through ether contained in the silver vessel. As the air bubbles through the ether it causes it to volatilise, and hy so doing so reduces the temperature that dew is deposited on the outside of the polished silver vessel, at which instant the temperature of the contained thermometer is read off as that of the dew-point. Dine's^ Hygrometer consists of a wooden stand, on Avhich is a vessel to contain ice-cold water; from this a pipe proceeds along the wooden stand into a space in which rests the bulb of a thermometer. The roof or cover- ing of this space or chamber consists of a plate of polished metal or of blackened glass. By means of a tap the ice-cold water is allowed to flow into the space beneath the glass or metal plate, and immediately dew is seen to be deposited on the polished surface the temperature of the adjoining thermometer is read off as that of the dew-point. The necessity for ether in Daniell's and Regnault's instruments renders them costly and inconvenient, especially in tropical countries; for this 736 METEOROLOGY. reason, of the direct hygrometers, that of Dine is in most general use. Of indirect hygrometers there are tAvo principal kinds, namely, the hair hygrometer of Saussure, and the Avet and dry bulb thermometer. Saussure's Hygrometer consists of a human hair that has not been roughly handled, and that has been freed from grease by digestion in ether or liquor potassae. Such a hair elongates Avhen moist and contracts when dry. It is fixed at one end, and stretched by a small weight at the other, the connecting cord being passed round a pulley to which is attached an arm or pointer marking on a scale. This scale is graduated by wetting the hair to complete saturation, and marking the point 100, then placing it over sulphuric acid and marking 15° of saturation; the intervening space is then marked off in degrees, indicating degrees of relative humidity. This instrument is fairly sensitive, but needs frequent comparison and verification with a more precise hygrometer. Wolpert's hygrometer is of horsehair. The wet and dry bulb thermometer, or psychrometer, really consists of two ordinary thermometers mounted on a frame side by side. One of these has its bulb covered with muslin, and kept constantly moist by being connected with a small vessel containing distilled Avater, by means of the capillary action of a piece of cotton wick, Avhich has been previously well freed from grease by being boiled in ether. The dry bulb gives, of course, the temperature of the air, while the wet one, in consequence of the evaporation constantly going on from its surface, gives a lower reading. The difference betAveen the two temperatures recorded indicates the rapidity with which evaporation is proceeding, and, moreover, since evaporation is faster as the air is drier, the indication of the degree of evaporation is a measure of the dryness or moistness (otherwise humidity) of the air. If the ah be saturated with moisture, of course no evaporation is going on, and the two thermometers will record the same temperature. In frosty weather, fre- quently the muslin covering and the water in the vessel will freeze, with the result that evaporation will not take place. In such case, it suffices to brush the frozen muslin over with a brush dipped in cold water and allow this to freeze; at such time evaporation will be going on from the ice surface, so that it will be equivalent to its having a damp but unfrozen bulb. Occasionally in thick fog, or during very calm cold weather, the wet bulb may read higher than the dry; the latter temperature is then to be taken as that of saturation. From the respective readings of the wet and dry bulb thermometers many valuable deductions may be made; for example, the dew-point, the tension or elastic force of vapour (or the amount of barometric pressure due to the vapour in the air), the relative humidity, the weight of vapour in a cubic foot of air, the amount of vapour required to saturate the air, and the weight of a cubic foot of air at the prevailing atmospheric pressure. Calculation of the Dew-Point.—The dew-point has already been ex- plained as being that temperature at which the air is saturated with moisture, so that the least further fall in temperature causes a deposit of water in the form of dew. Its determination is obvious by means of a direct hygrometer; its calculation from the readings of the dry and wet bulb thermometers can be roughly made by taking it to be as much below the wet bulb reading as that is itself beloAV the dry; but for greater accuracy it is better calculated out in either of the two following ways :— (a) By Glaisher's Factors.—By comparison of the results of Daniell's hygrometer and the dry and wet bulb thermometers for a long term of years, Mr Glaisher has deduced an empirical formula, which is thus Avorked. Take the difference of the dry and Avet bulbs, and multiply it by the factor ELASTIC FORCE OF VAPOUR. 737 Avhich stands opposite the dry-bulb temperature in the preceding table, deduct the product from the dry-bulb temperature; the result is the dew- point. From this formula Glaisher's tables are calculated. Glaisher's Factors. Reading Reading Reading Reading of Dry-bulb Factor. of Dry-bulb Factor. of Dry-bulb Factor. of Dry-bulb Factor. Therm. Therm. Therm. Therm. 10 8-78 33 3*01 56 1-94 79 1*69 11 8-78 34 2*77 57 1-92 80 1*68 12 8-78 35 2-60 58 1-90 81 1*68 13 8*77 36 2*50 59 1-89 82 1*67 14 876 37 2*42 60 1*88 83 1-67 15 8*75 38 2-36 61 1*87 84 1*66 16 8 70 39 2*32 62 1*86 85 1*65 17 8-62 40 2-29 63 1-85 86 1*65 18 8*50 41 2-26 64 1*83 87 1*64 19 8*34 42 2-23 65 1*82 88 1-64 20 8*14 43 2-20 66 1*81 89 1*63 21 7*88 44 2*18 67 1*80 90 1*63 22 7-60 45 2*16 68 1-79 91 1*62 23 7-28 46 2*14 69 1*78 92 1-62 24 6-92 47 2*12 70 1*77 93 1-61 25 6*53 48 2*10 71 1*76 94 1-60 26 6*08 49 2*08 72 1*75 95 1-60 27 5-61 50 2*06 73 1*74 96 1*59 28 5*12 51 2-04 74 1-73 97 1*59 29 4-63 52 2*02 75 1-72 98 1*58 30 4-15 53 2*00 76 1-71 99 1*58 31 3-60 54 1*98 77 1-70 100 1*57 32 3-32 55 1-96 78 1-69 (b) Apjohn's Formula.—From a most philosophical and exhaustive analysis of the conditions of this complicated problem, Apjohn derived his cele- brated formula, which is now in general use. Eeduced to its most simple expression, it is thus worked :—A table of the elastic tension of vapour, in inches of mercury at different temperatures, must be used. From this table take out the elastic tension of the temperature of the wet thermometer, and call it /'. Let (t -1') be the difference of the two thermometers, and p the observed height of the barometer. Apjohn's formula then enables us to calculate the elastic tension of the dew-point, which we will call /"; and, this being known, by looking in the table we obtain, opposite this elastic tension, the dew-point temperature. The formula is :— /"=/'-0*01147(*-O-^- The fraction ^i~- differs but little from unity, and may be neglected; the formula then becomes, for the temperature above 32° F., If below 32° the formula is : /" =/ - 87 ' 96 ' The constants 87 or 96 represent the specific heat of air and vapour. Elastic Force of Vapour.—In an atmosphere of pure steam or aqueous vapour its force, or tension, at the earth's surface is the pressure it exerts— 3 A 738 METEOROLOGY. that is, its Aveight. So, in an atmosphere composed partly of dry air and partly of steam or vapour, the elastic force of each is the Aveight of each. This is commonly expressed either in inches or mdlimetres of mercury. The tension e of aqueous vapour in the atmosphere may be calculated from the indications of the tAvo thermometers by means of the following empirical formula :— e = e'-0*00077 (t-t')xh, in which e' is the maximum tension corresponding to the temperature of the wet bulb, h is the barometric reading in millimetres, and t and t' are the respective readings of the dry and wet bulb thermometers in Centigrade degrees. To express inches as millimetres, multiply by 25*4. The tension or elastic force of aqueous vapour is, however, more conveniently obtained by direct reference to the following table :— Temp. Fahr. Tension in inches of Mercury. Temp. Fahr. Tension in inches of Mercury. Temp. Fahr. Tension in inches of Mercury. Temp. Fahr. Tension in inches of Mercury. 0 0*044 24 0-129 48 0-335 72 0-785 1 0-046 25 0-135 49 0-348 73 0*812 2 0-048 26 0-141 50 0-361 74 0-840 3 0-050 27 0-147 51 0-374 75 0-868 4 0-052 28 0-153 52 0-388 76 0 897 5 0-054 29 0*160 53 0*403 77 0-927 6 0-057 30 0*167 54 0-418 78 0-958 7 0-060 31 0-174 55 0*433 79 0-990 8 0*062 32 0181 56 0-449 80 1*023 9 0065 33 0-188 57 0*465 81 1*057 10 0*068 34 0-196 58 0*482 82 1-092 11 0-071 35 0 204 59 0-500 83 1-128 12 0074 36 0-212 60 0-518 84 1-165 13 0-078 37 0-220 61 0-537 85 1*203 14 0-082 38 0*229 62 0-556 86 1*242 15 0-086 39 0-238 63 0*576 87 1-282 16 0-090 40 0-247 64 0-596 88 1*323 17 0-094 41 0-257 65 0-617 89 1-366 18 0-098 42 0-267 66 0-639 90 1*410 19 0-103 43 0 277 67 0-661 91 1*455 20 0-108 44 0-288 68 0-684 92 1-501 21 0-113 45 0*299 69 0-708 93 1-548 22 0*118 46 0*311 70 0733 94 1-596 23 0*123 47 0-323 71 0-759 95 1-646 The tension or elastic force of vapour represents the pressure of all the aqueous vapour in the air above the place of observation. It is greatest near the equator, least near the poles; greater over the ocean than over dry land, in summer than in winter, by day than by night, and at sea-level than in the upper strata of the atmosphere. Relative Humidity.—This is merely a convenient term used to express comparative dryness or moisture. Complete saturation being assumed to be 100, any degree of dryness may be expressed as a percentage of this, and is obtained at once by dividing the weight of vapour actually existing by the weight of vapour which would have been present had the air been saturated. In other words, the hygrometric state or relative humidity (H) may be expressed as the ratio of the elastic force of aqueous vapour at the temperature of the air (E) to the elastic force of the vapour at the tem- g perature of the dew-point (e); that is, H= -ft x 100. RELATIVE HUMIDITY. 739 To find the relative humidity, therefore, we require to know, (1) the actual temperature of the air; (2) the dew-point; (3) the elastic tension of vapour present in the air, which is the tension of the dew-point, and is found in the table of tensions or by formula; (4) the tension of vapour saturated at the air temperature, also found in the table. Example.—The dry-bulb thermometer reads 62° F., the wet-bulb 56° F.; required the relative humidity. The dew-point=62- {(62-56)x T86} =50o,84. A reference to the table shoAvs the tension at 62°, or the tension which would exist if the air Avere saturated with moisture, to be 0*556 in. (E); the same table gives the tension of vapour actually present in the air, or the tension at the temperature of the dew-point, 50°*84, to be 0'372 (e). From these facts, H or the relative humidity = 0*372 Q.rrfi x 100, or 66*9, say 67 per cent, of saturation. Relative humidity is greatest near the surface of the earth during night, when the temperature, being at or near the dady minimum, approaches the dew-point; it is also great in the morning, when the sun's rays have evaporated the dew, and the vapour is as yet only diffused a little way upwards; and it is least during the greatest heat of the day (Buchan). This percentage saturation of the air is practically an inverse measure of the drying power of the air, and as such has a most important bearing upon ■climatic conditions, more particularly the degree of radiation from the earth's surface. We are all familiar Avith the peculiarly unpleasant effects of a hot moist atmosphere, and with the invigorating influence of dry and crisp air. A saturated atmosphere at from 35° to 50° F. will be found to be intolerably chilly, and although the evaporation may be checked, and this source of heat-loss removed, yet the conduction and radiation due to the vapour in the air will be enormous. A temperature of 50° to 65° F. in a nearly saturated atmosphere seems to be not uncomfortable, as under those conditions an equihbrium seems to be established between the cooling action by conduction and radiation, due to the vapour in the air, and the supply of heat from checked skin evaporation. A saturated atmosphere with a temperature of from 65° to 80° F. becomes oppressive and sultry. Above 80° F. a saturated air becomes most oppressive, and it is doubtful whether life could be long sustained in a saturated atmosphere of 90° to 100° F., as the surplus heat cannot be removed by conduction or radiation, while at the same time the natural effort of the system to produce evaporation is •enormously exaggerated. Humidity of the air is very generally supposed to be associated with the spread, or rather prevalence, of disease; much moisture in the air certainly favours the continuance of colds, but at the same time appears to relieve bronchitis by assisting expectoration and the general discharge of mucus. Malarial diseases are said never to attain their Avorst form except the air be saturated with moisture, but on this point the evidence is not very strong. The differences between the temperatures marked in the sun and shade by two maximum thermometers are chiefly dependent on the amount of humidity. The maxima of insolation (measured by the difference between the sun and shade thermometers) occur in those stations and on those days Avhen humidity is greatest. Thus, at Calcutta, the relative humidity being 80 to 93, the insolation (or difference between the thermometers) is 50° F.; at Bellari, the relative humidity being 60 to 65, the insolation is 8° to 11° F. These results are explained by Tyndall's observations, Avhich show that the transparent humidity Avill scarcely affect the sun's rays striking on the sun thermometer, Avhile it greatly obstructs the radiation of invisible heat from the thermometer; when the air is highly charged Avith moisture, the sun 740 METEOROLOGY. thermometer is constantly gaining heat from the sun's rays, Avhile it loses little by radiation, or, if it does lose by radiation, gains it again from the air. The Weight of Vapour required to saturate a cubic foot of air at varying temperatures is given in the table which foUoAvs; and, knowing the relative humidity, it is easy to calculate from it the weight of vapour actually present in any given volume of the atmosphere. Temp. Fahr. AVeight in grains of a cubic foot of Vapour. Temp. Fahr. AAreight in grains of a cubic foot of Arapour. Temp. Fahr. AVeight in grains of a cubic foot of Vapour. Temp. Fahr. AAreight in | grains of a cubic foot of Vapour. . 0 0*55 26 1*68 51 4-24 76 1 9-69 ; 1 0*57 27 1-75 52 4*39 77 9*99 2 059 28 1-82 53 4*55 78 10*31 3 062 29 1*89 54 4*71 79 10*64 4 0-65 30 1*97 55 4-87 80 10*98 ! 5 068 31 2*05 56 5-04 81 11*32 6 0-71 32 2*13 57 5-21 82 11*67 7 0*74 33 2*21 58 5-39 83 12*03 ,i 8 0*77 34 2*30 59 5*58 84 12-40 j 9 0 80 35 2*39 60 5*77 85 12-78 10 0-84 36 2*48 61 5*97 86 13*17 11 0*88 37 2-57 62 6*17 87 13-57 13*98 ! 12 0-92 38 2-66 63 6*38 88 13 0-96 39 276 64 6*59 89 14*41 14 1-00 40 2-86 65 6-81 90 14*85 15 1*04 41 2-97 66 7*04 91 15*29 16 1*09 42 3*08 67 7-27 92 15*74 17 1*14 43 3*20 68 7-51 93 16*21 18 1*19 44 3*32 69 7*76 94 1669 19 1*24 45 3*44 70 8*01 95 17*18 20 1*30 46 3*56 71 8-27 96 17-68 ' 21 1*36 47 3*69 72 8*54 97 18*20 22 1-42 48 3-82 73 8*82 98 18*73 23 1*48 49 3-96 74 9-10 99 19*28 24 1*54 50 4*10 75 9*39 100 19*84 25 1*61 ■ Thus, if 5*77 grains of vapour are required to saturate a cubic foot of air at 60° F., and the relative humidity of a given volume is 70 per cent., the weight of vapour actually present, per cubic foot of that air, is 5*77 x 0*7 or 4*03 grains. The difference between this and the weight of Avater required to saturate a cubic foot of the air at the given temperature, or 5*77 - 4*03 = 1*74 grain, is a measure of the drying power of the atmosphere under those conditions. The Weight of Air at a given temperature, pressure, and humidity can be determined from similar data. Thus, say it is required to know the weight of a cubic foot of air containing 60 per cent, of moisture at 60° F. and 29*92 inches barometric pressure. Now, a cubic foot of moist air at 60° F. is nothing more than a mixture of (1) a cubic foot of dry air at 60° F. under the existing barometric pressure minus the tension of the vapour present, and (2) a cubic foot of aqueous vapour at that temperature. The tension of the vapour present will be that corresponding to the vapour pressure at the dew-point. Reference to the table on page 738 shows that the maximum tension of vapour at 60° F. is 0*518 inch, and the relative humidity being 60 per cent., the maximum vapour pressure at the dew- point, or actual vapour tension in the air, is 0*518x0*6 = 0*31 inch. As- EVAPORATION. 741 the barometer stands at 29*92 inches, therefore, 29*61 inches would be supported by the pressure of the dry air, and the remaining 0*31 inch by the vapour. Now, the weight of a cubic foot of dry air at 32° F. and 29*92 inches is 566*85 grains; and remembering that (see page 128) density varies inversely as absolute temperature, and directly as pressure, it is obvious that the weight of 1 cubic foot of dry air at 60° F. and 29*61 iMheS ™U * 2992 x (1 "(0^8Ma0 - 32))) " ™™ *** The weight of a cubic foot of vapour at 60° F. is 5*77 grains, but as the relative humidity is 60 per cent., its weight under those circumstances is 5*77 x 0*6 = 3*46 grains. The weight of 1 cubic foot of air containing 60 per cent, of moisture at 60° F. will, therefore, be 530*72 + 3*46 = 534*18 grains. EVAPORATION. Evaporation is the process by which water is changed from the hquid or solid state into vapour, and is carried off as such into the atmosphere. Various instruments termed atmometers or atmidometers (aryo^, vapour; pirpov, a measure) have been suggested for the determination of the amount of evaporation, but with indifferent success. Evaporation takes place most quickly into dry air at a high or increasing temperature. It is also favoured by high wind and by a low barometric pressure. In these islands and in Western Europe generally it is most active during spring, when the capacity of the atmosphere for moisture is increasing under the influence of dry easterly winds and a sun of daily increasing power. On the other hand, in the late autumn evaporation is practically non-existent, because the temperature of the air is falling, and its capacity for moisture is diminishing, until it virtually becomes so charged with vapour as to be saturated. When this latter condition is reached, evaporation ceases absolutely, and the slightest further fall in temperature causes condensation of the watery vapour into fog, cloud, or rain. The rate of evaporation may be calculated from the depression of the wet-bulb thermometer, by deducting the elastic force of vapour at the deAV- point temperature from the elastic force at the air temperature, and taking the difference as expressing the evaporation. Thus, Avith the dry-bulb temperature at 53° F., and that of the deAV-point at 45° F., the difference of the tensions of vapour at those respective temperatures will be 0*403- 0*299 = 0*104 inch of mercury. This difference expresses the force of the escape of vapour from any moist surface under those conditions. Various atmometers have been devised, the principles of which have been either the measurement of the evaporation by the volume of water removed from some exposed vessel, or by the loss in weight of a similar vessel containing water in a given period, of time. A manifest fault in these instruments exists in the exposure of the water to gusts of wind at all seasons, and to frost in winter. In de la Rue's atmidometer the water evaporates from a surface of moistened parchment paper, stretched over a shallow drum kept full of water, which is supplied from a cylindrical reservoir giving about 6 inches of head. " Into this vessel dips a narrow metal tube forming the only opening into a graduated cylinder of glass about 6 inches high and 1J inch in diameter. The glass cylinder is in the first instance filled Avith water, and the tube leading from it, Avhich dips into the reservoir, is perforated laterally. The water in the reservoir is therefore maintained at a constant 742 METEOROLOGY. level by a Aoav from the glass cylinder AAdienever the lateral _ opening becomes exposed to the air. The amount of water evaporated is indicated by the graduations on the glass cylinder, Avhich are so drawn as to express the evaporation in hundredths of an inch." Richard Freres, of Paris, have invented another form of atmidometer Avhich consists of a pah of scales, one of which bears a basin of water or a plant. Weights are placed in the opposite pan to establish an equilibrium. A pen is attached to the scale beam, which records its movements on a revolving drum. The amount of vapour annually rising from each square inch of_ Avater surface in this country has been estimated at from 14 to 24 inches. Symons, from his OAvn observations, calculated the average annual evapora- tion from a water surface in London in the years 1885-91 to have been 14*5 inches. In the tropical seas evaporation has been estimated at from 80 to 130, or even more inches. In the Indian Ocean it has been estimated to be as much as an inch in tAventy-four hours, or 365 in the year, an almost incredible amount. No doubt, however, the quantity is very great. This distillation of water serves many great purposes. Mixing with the air it is a vast motive power, for its specific gravity is very low (0*6230, air being 1), and it causes an enlargement of the volume of air; the moist air is therefore much fighter, and ascends Avith great rapidity; the distdlation also causes an immense transference of heat from the tropics, where the evaporation renders latent a great amount of heat, to the extra-tropical region, Avhere this vapour falls as rain, and consequently parts with its latent heat. The evaporation also has been supposed to be a great cause of the ocean currents (Maury), which play so important a part in the distribution of winds, moisture, and Avarmth. RAINFALL. The physical cause of rain is the sudden cooling of comparatively warm ah, more or less laden with moisture, either (1) by its ascent into the upper and colder regions of the atmosphere, or (2) by its impact against cold mountain slopes, or (3) by its impact against the colder surface of the ground, as in the case of our own west coasts in winter, where the land is colder than the sea surface. The mixture of masses of air of different temperature is generally supposed to be a cause of rain, but from a com- parison between the units of heat set free by condensation and the weight of aqueous vapour per cubic foot of air at any two given temperatures, one high and the other low, it seems very probable that the mere mixture of volumes of air cannot be very effective in causing precipitation. In fact, Hann has demonstrated that the latent heat set free in the process of condensation largely prevents that fall of temperature Avhich is assumed to take place and to be the cause of rainfall. Of the more immediate causes producing rain, winds are the most important. Winds blowing from high latitudes to low ones are generally dry, those nuyving in the opposite direction are generally moist. Winds bloAving off shore are dry, those bloAving from the sea are damp. For these reasons we find the wettest regions of the globe to be the equatorial belt of calms, and certain localities Avhere damp winds meet mountain ranges, and are there suddenly chilled. The greatest rainfalls known are on the Western Ghats on the Malabar coast of India, as at Mahableshvvar, Avhere the fall is 263 inches yearly, so again at Cherrapunji, in the Khasia hills to the north RAINFALL. 743 of the Bay of Bengal, the rainfall averages 600 inches annually—in 1861 it was as much as 805 inches. Even in our own country the warm moist air over the Gulf Stream, impinging on the Cumberland Hills, causes, in some districts, a fall of 80, 100, 150, or even more inches in the year. On the other hand, the regions with least rainfall are the desert tract reaching from the Sahara through Arabia and Persia to Central Asia, the Kalahari desert in South Africa, and the Great Salt Lake region in North America. The amount of rain which falls varies, of course, very much with the place; but in determining the average fall at any station, it is necessary to deal with observations extending over long periods. In England and Wales the average rainfall each year is 33*76 inches; in Scotland 46*56 inches; in Ireland 38*54 inches. The average annual rainfall for the United Kingdom is 37*30 inches, for Great Britain 36*69 inches. On the east coast of England not much more than 20 inches of rain falls in a year, while on the west coasts of both Scotland and Ireland it averages as much as 60 or 80 inches; in some parts of Cumberland as much as 150 inches a year have been known to fall. It is very rarely that more than 1 inch of rain falls anyAvhere in Great Britain in one day; though occasionally as much as 5 inches have been known to fall. For furnishing meteorological returns, a minimum record of 0*01 inch is considered as characteristic of a rainy day in this country. Observation of Rainfall.—Rain is estimated in inches; that is, the fall of an inch of rain imphes that on any given area, say a square yard of surface, rain has fallen equal to an inch in depth. The amount of rain is determined by a rain-gauge. The most convenient rain-gauge for practical purposes consists of a copper or japanned tin cylinder, at the upper end of which is fixed a turned brass ring Avith a sharp edge whose diameter is accurately known (fig. 120). Some 6 inches below the ring the cylinder narrows to a funnel, terminating in a long and narrow tube which leads to a metal collecting vessel. Very often the lower end of this tube is curled upward to check evaporation. In this country a rain-gauge is usually circular, with a diameter of either 5 or 8 inches, so that its area in square inches is accu- rately known. The rain, having been collected in the receiver, is measured in a graduated glass vessel, the divisions of which correspond to hundredths of an inch. The measuring vessel is divided proportionately to the area of the gauge, the diameter of which should always be some simple unit, like 5 or 8 inches, so that, if the original measure get broken, a new one can be readily improvised and gradu- Fig. 120. ated. Thus, take an 8-inch gauge, the diameter being 8 inches, its receiving area is 50*26 square inches; therefore, 1 inch of rainfall, or rain 1 inch deep over a town, would deposit in that particular rain-gauge 50*26 cubic inches of water, or 29 fluid ounces, or 12,688 grains of water. It is found in practice more convenient to make 334933 744 METEOROLOGY. the measuring glass hold half an inch. Therefore, if 14| fluid ounces, or 6344 grains, of water be poured into the proposed measuring glass, and the vessel be marked Avith a line at the level of its top, that line will represent the graduation of 0*5 inch of rain; fifty subdivision markings are similarly made, or one for each y^th inch of rain, the graduations being marked at 0*10, 0*20, 0*30, 0*40, and 0*50. The best place for a rain-gauge is on the ground in a well exposed position, Avith the rim about 1 foot above the earth. A rain-gauge should never be placed upon a house roof, unless, as in towns, no sufficiently open space is available. The spot on Avhich a rain-gauge is exposed should, be clear of all objects whose height is greater than their distance from the gauge. Rain should not be collected in the measuring glass, as this is liable to break, especially during frosts. Snow or hail can be measured by thaAving the quantity collected and measuring the water which results. When snow faUs, its measurement demands constant attention. Should the wind be high and the temperature very low, drifting of snoAV dust will be apt to vitiate the measurements. SnoAV -will be drifted into the gauge on the one hand, or blown out of it on the other. The depth of snow in a sheltered place, free from drifting, should be carefully measured by a two-foot rule. On a very rough estimate, 1 foot of dry snow may be taken to represent an inch of rain. Should the snow have been lifted out of the funnel by the Avind, a good plan is to take the outside cylinder of the gauge, wlhch has the same diameter as the funnel, and to insert it in the snow where it lies level and of an uniform depth. The solid cylinder or section of snow, thus cut out, should then be melted and the resulting water measured. All observations should be made every day at 9 a.m., and the amount coUected entered as having fallen on the previous day. Theoretically, square gauges are simpler than circular ones, but in practice the latter are mostly used because they are not so apt to get out of shape as the former, and the least denting of the rim of a rain-gauge would affect its accuracy of measurement (Moore). Besides the foregoing instrument, or, as it is sometimes called, the Meteorological Office Gauge, there are several other kinds; the more important are the following:— The Mountain Gauge, as suggested by G. J. Symons, is intended for rough mountain work. It really is a " float-gauge," and can hold 48 inches of rain ; if may be read off to tenths of an inch by means of a rod attached to the cup of the float. Another variety is Symon's Storm Rain-Gauge. It is not intended for general use, or for continuous records, but rather to record in detail the rate at which heavy rains fall during thunderstorms. In this instrument the rain passes into a copper cylinder in which is a float, which rises as the rain falls. The float has a string passing round a pulley, and kept tight by a weight: therefore, when the float rises, the pulley turns. The axle of the puUey is connected with two hands or pointers which, on a graduated dial, complete revolutions when 1 and 5 inches of rain have fallen respectively. With this gauge it is easy to read from a window the rainfall to hundredths of an inch, and if this is noted at short intervals of time, the minutest detads of the fall of rain can be recorded. Crosley's rain-gauge is self-registering, and has an area of 100 square inches. It was invented in 1829. Beneath the tube leading from the funnel there is a divided bucket, balanced on a pivot. When one compartment of this bucket has received a cubic inch of Avater, that is, when 0*01 inch of rain has fallen, the bucket tips, the index advances ATMOSPHERIC PRESSURE. 745 on the first dial, and the second compartment begins to fiU, and so on indefinitely. Yeates' electrical self-registering rain-gauge is a modification of the preceding, having as its essential feature the arrangement that at each turn of the bucket an electrical contact is made, whereby an index hand moves one division. Richard Freres, of Paris, have invented a float pattern, and a tipping bucket pattern of self-recording rain-gauges. In them a style, carrying a writing pen, foUows the motion of the float and oscdlating tipping bucket, with the result that the amount of rain which falls is graphicaUy recorded on a revolving drum. Seasonal and Diurnal Fall of Rain.—In these islands and on the western shores of Europe the winter rainfall exceeds that of summer. This is mainly due to the prevalence of westerly winds laden with moisture, and to the relative coldness of the highlands and coast-line on the Atlantic sea-board. In the middle of Europe the summer rainfall is in excess of that in winter, apparently OAving to the heavy rains which accompany summer thunderstorms. These summer rains are really evaporation rains Avhich fall from cumuli formed by evaporation and their ascent above the saturation or condensation line. The seasonal rains of India, accompanying the south-west monsoon, are caused by the condensation of the vapour in those Avinds blowing in from over the Indian Ocean, condensing against the cold highlands of the Himalayas. The diurnal fall of rain is dependent on season. As a rule, in winter more rain falls by night than by day, Avhile in summer the reverse is the case; in spring and autumn there is not much difference. According to Hellmann, the diurnal variation of rainfall, like that of cloudiness, can be classified according to a number of typical curves. An afternoon maximum occurs in many places, especially in summer, corresponding to the hour of maximum frequency of thunderstorms; and another maximum late at night or in the very early hours of the morning is connected with peculiarities in the diurnal variations of pressure, temperature, and even wind. This latter maximum is more or less characteristic of Western Europe at all seasons, and is specially marked in winter. ATMOSPHERIC PRESSURE. We have already seen in Chapter II. that the atmosphere has weight, and by -virtue of that weight exercises pressure. The instrument used for ascertaining this effect is called the barometer (/3 means W., \L means N., <- means E., and so on. The force of the wind is indi- cated by the number of barbs or feathers on the arrow, thus:— \ light breeze ; ^ fresh breeze ; | strong wind; X a gale; and O signifies calm. Temperature and Moisture, being usually given as numerical results of instrumental observations, are omitted for the present. The remaining elements Avhich go to make weather are described by letters and symbols as follows, a bar or dot under a letter denoting intensity. b = blue sky: Avhether with clear or hazy atmosphere. c = cloudy, but detached opening clouds. d = drizzling rain. 760 METEOROLOGY. f = focrcrv ~COSC g = dark gloomy weather. h = hail, ^. 1 = lightning, <£ m = misty hazy atmosphere, ;^; or oo. o = overcast, the whole sky being covered with an impervious cloud. p = passing temporary showers. q = squally. r = rain, continued rain, #. s = snow, -)f. t = thunder, T. u = "ugly," threatening appearance of the weather. v = " visibility " of distant objects, whether the sky be cloudy or not. w = dew, ■»-. The above notation, devised by Admiral Beaufort, has long been in universal use in this country. The folloAving symbols have been added more recently, and are officially recognised by the various European meteorological institutions. Thunderstorm, Soft Hail (" Graupel "),. Hoar Frost, . Silver-thaw ("Bauh-frost, "Duft"), . Glazed Frost (" Glatteis "), Snow Drift, . Ice Crystals, . A V Strong Wind, ■ s Solar Corona, . o „ Halo, . © Lunar Corona, • w ,, Halo, . • G> Bainbow, Aurora, .... ■ A Dust-haze (" Hohen-rauch ") OO In these symbols intensity is to be indicated by the exponents 0 and 2 attached to the symbols, thus, ■X-0 means slight snow, -}f-2 heavy snow. BIBLIOGBAPHY AND BEFEBENCES. Abercromby, Principles of Forecasting by means of Weather Charts, Lond., 1885 ; also Weather, Lond., 1887; also Instructions for observing Clouds (with photographs), Lond., 1888. Aitken, " On Dust, Fogs, and Clouds," Trans. Roy. Soc. Edin., vol. xxx. i., 1883, p. 337. Babber, von, Hygienische Meteorologie, Stuttgart, 1895. Blanford, Instructions to Meteorological Observers in India, Calcutta, 1876 ; also The Climate of India, Calc, 1889; also "On the Rainfall of Cherrapunji," Quart. Journ. Roy. Meteor. Soc, July 1891, p. 146. Buchan, Introductory Text-Book of Meteorology, Lond., 1871; also "The Mean Temperature of the British Islands," Journ. Scottish Meteor. Soc, vol. vi. N.S., 1882, p. 22. Daniell, Meteorological Essays and Observations, Lond., 1823. Dickson, Meteorology, Lond., 1893. Dines, "On Wind-Pressure on an Inclined Surface," Proc. Roy. Soc. Lond., vol. xlviii. pp. 233 and 257. Dove, The Law of Storms, translated by Scott, Lond., 1862. Fitzroy, The Weatlver Book, Lond., 1863. Fox, Ozone and Antozone, Lond., 1873. Frankland, E., "On Dry Fogs," Proc Roy. Soc. Lond., 1878. Gaster, "On Fog, Cloud, and Sunshine," Journ. Sanit. Institute, vol. xv., July 1894. Glaisher, Hygrometrical Tables, Lond., 1877. Guillemin, La MMorologie, Paris, 1885. BIBLIOGRAPHY AND REFERENCES. 761 Hann, Allgemeine Erdlcunde, Tempsky, Prague, 1881; also Handbuch der Klimatologie, Stuttgart, 1883. Haughton, Six Lectures on Physical Geography, Lond., 1880. Hellmann, Die Anfdnge der meteorologischen Bcobachtungen und Instrumente, Berlin, 1889. Herschel, Meteorology, London, 1862. Laughton, Air Temperature, its Distribution and Range in Modern Meteorology, Lond., 1879. Lemstrom, VAurore Boreale, Paris, 1886. Ley, Aids to the Study and Forecast of Weather, Lond., 1880. Lloyd, "Notes on the Meteorology of Ireland," Trans. Roy. Irish Academy, xxii., Science, 1854. Mann, Modern Meteorology, Lond., 1879. Marcet, "Atmospheric Electricity," Quart. Journ. Roy. Meteor. Soc, vol. xiv. p. 197, 1888. Marriott, "Moisture, its Determination and Measurement," Journ. San. Institute, vol. xv., July 1894. Mascart, La Mitiorologie appliquAe a la Prdvision du, Temps, Paris, 1881. Mohn, Grwndzuge der Meteorologie, Berlin, 1879. Moore, Meteorology, Practical and Applied, Lond., 1894. Scott, Principles of Forecasting by means of Weather Charts, Lond., 1885; also Elementary Meteorology, Lond., 1887 ; also Instructions in the Use of Meteorological Instruments, Lond., 1892 ; also Weather Charts and Storm Warnings, Lond., 1887; also "Barometrical Conditions and Air Movements," Journ. Sanit. Institute, xv., July 1894. Sprung, Lehrbuch der Meteorologie, Hamburg, 1885. Symons, British Rainfall, published annually ; also Monthly Meteorological Maga- zine ; also Pocket Altitude Tables, Lond., 1880; also "Meteorological instruments and Sanitary "Work," Journ. Sanit. Institute, xv., July 1894. Toynbee, The Meteorology of the North Atlantic during August 1873, Lond., 1878. Tyndall, Heat, a Mode of Motion, Lond., 1880. Umlauft, Das Luftmeer, "Wien, 1891. Wild, Uber Fbhn und Eiszeit, Bern, 1868. Williams, " Climate in Relation to Health and Geographical Distribution of Disease," Journ. Sanit. Institute, xv., July 1894. CHAPTER XVI. VITAL STATISTICS. An accurate basis of facts, derived from a sufficient amount of experience and tabulated with the proper precision, lies at the very foundation of hygiene, as of all exact sciences. It is desirable, therefore, that all persons interested in sanitary science should know what data are at their disposal, how to collect them, and how to use safely the various facts placed before them. Probably no single cause has contributed more to the attention now paid to questions of Public Health than the careful collection of the statistics of births and deaths, and of the causes of death, which have been collected and published by the Begistrar-GeneraPs Office during the past fifty years. These collections of figures and facts are usually spoken of as vital or health statistics, because they are so intimately associated with the various problems relating to the health and chances of life which the community enjoys. So- valuable has been the work done, that we are now able to determine with some precision the causes and limits of mortahty, and, by the study and analysis of the collection of facts known as vital statistics, to apply them as tests of the health of the communities to which they refer. The chief vital statistics, bearing upon public health, relate in detail to- past and present facts concerning populations, age and sex distribution, births, marriages, deaths, diseases, duration of the hours of occupation and general social conditions, such as the health of each class of the community as judged of by the expectation of life at given ages. Statistics of sickness, apart from mortality, have as yet not been attempted, chiefly on account of the difficulty in collecting the data with accuracy. Population, as the natural basis of all vital statistics, necessarily demands prehminary consideration. Our knowledge upon this point in each place in Great Britain depends primarily upon the census returns which have been made regularly and with increasing care every ten years since 1801. The foUo-wing table gives the results of each successive census, and shows the enormous increase in the population of England and Wales, and of London, in the present century :— Population of England and Wales and in London in each Census. Year of Enumeration. England and Wales. London. Persons in London to 100 in England and Wales. 1801 8,892,536 958,788 10*78 1811 10,164,256 1,138,746 11*20 1821 12,000,236 1,378,853 11*49 1831 13,896,797 1,654,870 11-91 1841 15,914,148 1,948,293 12-24 1851 17,927,609 2,362,105 13*18 1861 20,066,224 2,803,847 13-97 1871 22,712,266 3,253,785 14-33 1881 25,974,439 3,815,544 14-69 1891 29,002,525 4,211,452 14-52 POPULATION. 763 The chief data collected at each census are the total number of inhabi- tants in each area, the numbers living of each sex and at certain age-periods, and the numbers employed in certain callings. It will be at once obvious that the facts relating to the numbers hving of each sex and age-periods and the numbers employed in certain callings can only be accurately known in actual census years, and making from them estimates for intermediate years. An interval of ten years betAveen the takings of the census is now acknowledged to be too long, and it is probable that, if our population statistics are to remain in any way accurate, more frequent enumerations of the people will need to be taken, and even then certain inaccuracies are sure to exist, due chiefly to the still imperfect education of large numbers of householders and heads of families; these defects of information collected relate especially to occupations and ages. It is remarkable what a large number of people do not know their precise age; these persons generally giving their age in census returns in some multiple of ten. Another source of error and perplexity in all census returns is the too frequent wilful mis- statements made by women, owing to their desire, for various reasons, to be thought between 20 and 25 years of age. This is shown by the fact that, in each successive census, the number of women returning themselves as between 20 and 25 is larger than the number of girls returned in the census of ten years before as between 10 and 15 years of age. The former being only the survivors, after the lapse of ten years of these latter, they should of necessity be fewer in number. The male sex is not altogether free from blame in the same matter, though the bias goes in the opposite direction. Thus, men of the poorer classes, avIio have passed the age of 60, constantly overstate their age for the sake of certain definite advantages, such as getting outdoor relief, or, if entering the poorhouse, gaining some special privileges not granted to their juniors. Some really old people often exaggerate their age in order to appear as centenarians. In attempting to estimate the population of any given locality for any year intermediate between the collection of census returns, it is necessary to calculate the probable decrease or increase of the particular population by comparing the numbers of the latest enumerations. Thus, say a town had in 1881 a population of 35,626, and in 1891 one of 38,754, and it was required to knoAV its estimated population in June 1896: it is only fair in such a case to assume that the 1896 population will be greater than the 1891, and. if we further assume that the increase will be at the same rate as between 1881 and 1891, by taking the difference betAveen the 1881 and the 1891 populations and dividing by 10 Ave get the annual increase of popula- tion for that toAvn. Inasmuch as the census is always taken in the first quarter of the year, and we require the population at the end of June 1896, an interval of 5£ years will have elapsed since the last census; if, therefore, Ave multiply the annual increase of population, which in this example is 38,754-35,626 = ^ ^ an increase of 1642 to be added to 10 ' J ° the 1891 population, giving an estimated population of 38,754 + 1642, or 40,396 for the middle of 1896. The foregoing method of calculating an estimated population is fallacious, as it presumes the increase or decrease will be as in an arithmetical pro- gression. The true laAv of population increase or its decrease is that of a geometrical progression, and is very suitably compared to the increase of a sum of money at compound interest. The increase in x years is derived from the increase in one year by multiplying 1 plus the annual rate of increase x times into itself If the increase in one year be 1*5 per cent., 1 764 VITAL STATISTICS. becomes 1*015 in one year, and 1*015 multiplied x times into itself Avill give the increase in x years. To obtain, therefore, the annual rate of increase in a* years, the xth root, and not the xth part of the x rate of increase, must be taken. If a population of 100,000 in 1891 becomes 101,000 in 1892, it is evident that the 1893 population wiU be greater than 102,000, for the yearly increase has noAV to be reckoned upon 101,000, not upon 100,000. If p be the population in any given year, say 1891, and r be the factor of annual increase (in this case r= 1*01), then in 1892 or in one year the population Avill become px.r, in 1893 or in two years p x r2, and in n years p x rn. In the above instance the correct estimate for 1893 would be 102,010, for 1894 it would be 103,030, and so on. In mathematical language the increase is geometrical, not simply arithmetical, and on this assumption the Begistrar- General calculates the estimated populations for London and other large toAvns, as well as for the whole country, for intercensal years. On this basis the calculations are more conveniently performed by logarithms in the following manner. Taking the same example as above, in which a toAvn had in 1881 a population of 35,626 and in 1891 one of 38,754, Ave find the logarithm for the 1891 population, or log 38,754 = 4*5883165, and deduct from it the logarithm for the 1881 population, or log 35,626 = 4*5517671; this gives 0*0365494, Avhich is the logarithm of the decennial increase. Dividing this by 10 gives us 0*00365494, or the logarithm of the annual increase, and a quarter of this is 0-0009137, or the logarithm of the quarterly increase. By adding together the logarithm of the 1891 population and five times the logarithm of the annual increase and the logarithm of the quarterly increase we get the logarithm of the mid-year 1896 population, or 4*6075049, which by reference to a set of tables = a population of 40,504, or somewhat higher than the estimation made by that of a simple arithmetical progression. On the other hand, supposing the census of 1891 to have given a lower figure than that of 1881, the population for any year subsequent to 1891 might be similarly calculated upon an assumption of a uniform decrease. Unfortunately, these assumptions as to a uniform increase or decrease of numbers are largely arbitrary or conjectural, and but rarely agree with the actual facts as found by the next census. Thus the population of London as estimated in 1891 by the Begistrar-General was 4,441,993, but when actually enumerated by that year's census was found to be nearly a quarter of a million less, or only 4,211,452 ; that is, the rate of increase of popula- tion during the ten years 1882-91 had been much less than in the preceding decennial period. In a similar way the total population of England and Wales at the census of 1891 was found to show a rate of increase during the ten years 1882-91 of 11*65 per cent, as against 14*36 between 1872- 81, giving in fact the lowest rate of increase recorded since the systematic taking of a census was begun in 1801. Had the 1882-91 rate of increase been the same as in 1872-81, the population at the last census Avould have been greater than it proved to be by more than 701,000. The same thing was found to have occurred in regard to the populations of most of the large towns, with the result that their calculated death-rates had been returned too Ioav. It is chiefly owing to errors in either under or over estimating the population that faulty estimates of the birth and death rates have occurred; so true is this, that any very excessively high or low birth or death rate is to many persons highly suggestive of the estimated popula- tion figure being wrong. The case of Liverpool in 1890-1 is interesting as illustrating this point. The death-rates were supposed, on the assumption that the population was increasing at the same rate as in the previous decade, POPULATION. 765 to have fallen from 26*7 in 1881 to 23*6 in 1890 ; the truth, as discovered by the actual enumeration in 1891, being, that instead of increasing, the population had decreased, and that the death-rate, instead of falling to 23*6, had risen to 27*8. The only true remedy for these possible errors is a more frequent census. The following table shows the difference between the estimated and enumerated populations of some large towns in 1891, as taken from the Begistrar-General's returns, as well as the actual increase or decrease in their populations which had taken place in the period 1882-91. Enumerated Enumerated Estimated Excess or Actual Town. population population population defect of increase or at census of at census of in middle of column 2 over decrease of 1881. 436,971 1891. 189], column 3. population. Birmingham, . 478,113 469,003 + 9,110 + 41,142 Blackburn, 104,014 120,064 125,874 -5,810 + 16,050 Bolton, 105,414 115,002 117,034 -2,032 + 9,588 Bradford, 194,495 216,361 246,101 -29,740 + 21,866 Brighton, 107,546 115,873 125,539 -9,666 + 8,327 Bristol, . 206,874 221,578 235,171 -13,593 + 14,704 Cardiff, . 82,761 128,915 121,477 + 7,438 + 46,154 Derby, 81,165 94,146 103,269 -9,123 + 12,981 Halifax, . 81,117 89,832 82,998 + 6,834 + 8,715 Huddersfield, . 86,502 95,420 101,080 -5,660 + 8,918 Hull, 165,690 200,044 219,812 -19,768 + 34,354 Leeds, 309,119 367,505 370,261 -2,756 + 58,386 Leicester, 136,593 174,624 158,266 + 16,358 + 38,031 Liverpool, 552,508 517,980 620,443 -102,463 -34,522 Manchester, 462,303 505,368 506,325 -957 + 43,065 Newcastle, 145,359 186,300 165,016 + 21,284 + 40,941 Norwich, 87,842 100,970 96,202 + 4,768 + 13,128 Nottingham, . 186,575 213,877 252,217 -38,340 + 27,302 Oldham, . 111,343 131,463 151,158 -19,695 + 20,120 Plymouth, 73,858 84,248 79,339 + 4,909 + 10,390 Portsmouth, 127,989 159,251 144,671 + 14,580 + 31,262 Preston, . 96,537 107,573 106,141 + 1,432 + 11,036 Salford, . 176,235 198,139 251,024 -52,885 + 21,904 Sheffield, . 284,508 324,243 338,543 -14,300 + 39,735 Sunderland, 116,526 131,015 138,859 -7,844 + 14,489 Wolverhampton, 75,766 82,662 84,277 -1,615 + 6,896 As the Begistrar-General has pointed out, the official method of calculat- ing populations by the assumption of an equable rate of growth is only trustAvorthy in the case of very large communities, where any abnormal increase in one direction is sure to be counterbalanced by an abnormal decrease in another. It is hardly reliable for very small communities, AAdiere groAvth is very often most irregular and spasmodic. A moment's reflection will show that many circumstances may help to quicken or slow the increase of a population. The increase in any given population may be either natural or actual. The former is merely the excess of births over deaths, Avhile the latter is dependent upon the balance between births and immigration on the one hand, and deaths and emigration on the other. The facts revealed by the last census, in 1891, showed a decline in the natural increase of population for England and Wales; this Avas not due to any increased mortality, but rather to a decline in the birth- rate which was low beyond precedent. Eor the whole country the actual increase as shoAvn by the last census, also showed a dechne, due mainly to an excess of emigration over immigration during the last decennium. As a 766 VITAL STATISTICS. general rule, in toAvns the actual increase is greater than the natural, simply because there is a natural tendency for people to migrate from rural to urban districts; and with regard to such local migrations, at present Ave have no available or systematic record. It is Avell knoAvn that in times Avhen trade is bad in certain localities, a considerable movement of the population occurs to other parts, and vice versd. Although not officially recognised by the Begistrar-General, there are several methods of checking estimated populations, which, if used judiciously, are of great value. Amongst such are examinations of inhabited houses as ascertained from the rate-books, and then, assuming the density to remain the same, to multiply the number of inhabited houses by the average number of persons per house. Care, however, must be taken to allow for any marked change in the class of new houses built, whether containing fewer or more occupants than others, and, too, to alloAV for block buildings, flats and large hotels, aU of which are liable to seriously affect statistical results. Another useful method for checking the calculation of a present population, suggested by Newsholme, may be derived from the birth-rate of a place. It is based on the assumption that the birth-rate remains the same for a series of years as it was found to be at the time of the last census. Thus, in Wandsworth, the average birth-rate for the decennium 1872-81 was 35-68 per 1000, and the number of births in 1881 was 7582, therefore, assuming that 35*68 was the number of births from one thousand of population, 7582 was the birth-rate of 212,500 people; or, —Jt 1 215 1000 = 32*3 birth-rate per 1000, and ,,-, „9, x 1000 = 15*7 marriage-rate per 1000. This method of stating the ratio of births, marriages, or deaths in one year, as per thousand persons living in a place, is the most usual and convenient, but occasionally it may be necessary to compare these rates for shorter periods, say weeks, months, or quarters; in which case it is done in the foUowing way. Suppose it is requhed to know the birth-rate during — part of a year, then— Number of births during the period in question x n x 1000 = birth-rate of Population in the middle of the year period in question. Taking the preceding example, and requhed the birth-rate 1 during one week or k9.177 ,7 part of a year, during which period ten births have taken place; we get 13 621 x52'17747 x 1000 = 38*3, or birth-rate. When comparing one community with another, to be strictly fair the birth-rate should be calculated on the total population only after it has 3c 770 VITAL STATISTICS. been reduced to a common or normal constitution as regards sex, age, and marriage. This is best secured by calculating the birth-rate on the number of women between twenty and forty years of age who constitute the great majority of childbearing mothers. More males appear to be born than females, in the proportion of 104 to 100. The number of illegitimate children born is diminishing; formerly it was as much as 5 per 1000 ; in 1893 the proportion was as low as 1*3 per 1000 persons living, or 42'per 1000 births. This illegitimate birth-rate varies much in different districts; thus, the registration counties in which the proportion of illegitimate to total births was highest, were, the North Biding of Yorkshire, Herefordshire, Shropshire, Cumberland, Westmoreland, and North Wales. There is reason to beheve that in France and some foreign countries the production of children is deliberately restricted in relation to the possible maintenance of them at home; with the result that the total populations are diminishing. In this country we have no need to discourage the expan- sion of the population, for our colonies are in need of more inhabitants, and our industries of more work-people. In fact it is the absence of 'such restrictions on population in Great Britain which has enabled us to establish our colonial empire and extend the British nation all over the world. It is as much a mistake to suppose that the inhabitants of a country are in proportion to their food as it is to think that the productions of a country are in proportion to the number of its inhabitants. The truth is, the population that a country sustains does not depend exclusively on the amount of subsistence existing in it at any one time, but rather that the produce of a country is limited chiefly by the number and character of its inhabitants, and the more numerous, cultured, and civilised they are, the greater will be the products of their industry. Unfortunately, population is often out of the place where it is wanted or could be most productive • but at no time can it be said that the population of any country is excessive or out of ratio with means of subsistence. In Great Britain the means of subsistence have increased faster than the numbers of the people; for whde the population has doubled, the value of capital has more than trebled itself Thus, at 3 per cent, per annum, compound interest, capital doubles itself in twenty-four years. A birth-rate of 3 per cent., which is near the actual present rate in England and Wales, would imply, in the absence of deaths that the population would be doubled in the same period. But as the death- rate is 1*9 per cent, of population, the real increase per 100 at the present birth-rate is 1*1 or 0*011 per unit. Nowi? = PBre, where, as in compound interest, p is the amount when increased, or principal + interest • P is the principal or original population; R is 1+the rate of increase per unit or r, that is, R = 1 + r; n is the number of years. It is required to know the time necessary to double the population. In this case, p = 2 and P = 1 Th^r, if P = PR", 2 = lxE- = E*-(l+r)"f or 2-(l +0-011)" or (1-011)--? Therefore, n log 1-011 = log 2, and w =,J°g_l_ = Pj3010300 * ' log 1*011 0*0047512 = 634 years. The population, therefore, doubles itself in about sixty-four years a much longer period than capital takes to double itself, and money capital mav be taken as representative of subsistence or other working materials Each member of the population, when the balance between expense of subsistence and wages earned through life is worked out, represents enormous wealth. And as for any need to restrict the production of chddren, as advocated by Malthus, for fear of over-populatingthe world it is as uncalled for as it is mischievous; and amounting as it does to a policy of depopulation, it means the gradual reduction of this country in the DEATH-RATES. 771 presence of the great continental nations, to the level of a second-rate poAver. Apart from this aspect of the question, to the sanitarian, the Malthusian doctrine, Avhich assumes that the fewer the people the happier they will be, is of very serious and far-reaching import. If sanctioned or encouraged, it would involve practically the relaxation of all efforts to improve the public health, Avhile all efforts to remove insanitary conditions and obviate unhealthy employments would necessarily be regarded as attempts to evade an inevitable and, from the Malthusian point of view, a beneficial law. Possibly few Avould carry the doctrine so far as to propose the actual destruction of life, but its advocates are logically bound to welcome a high death-rate as being prima facie favourable to a reduction of numbers. Even this idea is fallacious, for Ave shall see later on that the births almost invariably increase when the mortality increases, and where the mortality is greatest there the population is multiplying most rapidly (Newsholme). Death-Rates.—By the Births and Deaths Begistration Act of 1874 all deaths must be registered within five days of their occurrence. In 1893 the deaths registered in England and Wales were in a proportion of 19*2 to 1000 persons living. This rate was 0*2 per 1000 higher than the rate in the preceding year, but was identical with the mean annual rate in the ten years 1883-92. In 1894 the death-rate dropped to 16*6 per 1000 living, or the lowest on record. The death-rate is obtained in exactly the same way as that for births: by multiplying the actual number of deaths from all causes into 1000, and dividing the product by the population; this is known as the general or gross death-rate. In a similar way, as explained above for calculating the weekly or quarterly birth-rate, so is the annual death-rate for the week, month, or quarter obtained. Thus, take a town with a population of 20,000 and the deaths in any Q week being 8, the annual death-rate for that week will be 21, or 9„ ~~~ x 52*17747x1000 = 20*87. These so-called weekly death-rates are con- venient for reports, but are not reliable data on which to compare the relative conditions of places, as much of the mortality often depends upon epidemics, weather, and other causes of a temporary nature. These death- rates, as published for each week by the Begistrar-General, must therefore not be regarded as actual rates, but rather as annual rates per 1000, repre- senting the number who would die supposing the same proportion of deaths to population held good all through the year. Their chief value is for contrasting mortality rates of any given place at corresponding periods of some previous year. The Begistrar-General makes his death-rates for each quarter refer to the thirteen weeks most nearly corresponding with the natural quarter; and the quarterly population is obtained by multiplying by thirteen the population of one week. The value of the general death- rate has been much criticised on the ground that it is much influenced by movements of the populations, by the presence of large institutions, such as hospitals, by the age and sex distribution of the population, and by the birth-rate. All this is quite true, but still, if due correction be made, it is probably in the case of large populations the most trustworthy test we have of relative vitality. The corrections most advantageously applied to general death-rates are : (1) for non-resident, or migratory people; (2) for sex and age distribution. The correction for a migratory population is most difficult to apply, as it is not easy to trace and control the facts relating to visitors and immigrants. In the case of Avatering-places and favourite residential towns, corrections in 772 VITAL STATISTICS. this direction are most important, and are largely made by the officials from materials obtainable from the sub-registrars ; but, even under the best super- vision, considerable disturbance and fallacies to the statistics occur. Closely allied to the consideration of migration is the effect which public institutions, such as poorhouses or hospitals, exert on local death-rates, as the disturbance arising from them is due to migration into them from neighbouring districts. To meet this difficulty, the rule is to deduct the deaths of those inmates drawn from outside areas, at the same time adding the deaths of proper inhabitants of the place which may have occurred in other institutions out- side the district. In this connection reference may be made to the statistical table A., given in Appendix XII. Each sanitary authority in London is supplied quarterly by the Registrar-General with particulars of death of their inhabitants in outlying districts, so that the deaths in all these cases may be apportioned to their proper districts. Unfortunately, such accuracy does not pertain to rural districts, but it is to be hoped, in course of time, even this wdl be done. All general death-rates require to be corrected for sex and age distribution. Sex.—The death-rate among males in England and Wales during 1893 Avas 20*3, and that among females 18*1, per 1000 living of the corresponding sex. Out of equal numbers living there were 1117 deaths of males to 1000 of females, as compared with an average proportion in the decennium 1883-92 of 1122 to 1000. As a class, females live longer than males, the death-rate among the males being uniformly higher than among females, except at the ages betAveen ten and tAventy years; both death-rates, how- ever, are decreasing, owing to the great saving of life in the earlier years of age. Since females live longer than males, it follows that if two toAvns Avere in an equally healthy state, but that one of them contained a larger proportion of females than the other, the one with the lower proportion of females would have the higher death-rate. Ages.—The following table shows the mean annual death-rates in England and Wales, during recent years, per thousand persons living, at each age- period :— AgeG •oups All Persons. Males. Females. 1871-80 1881-90. 1891-93. 1871-80. 1881-90. 1891-93. 1871-80. 1881-90. 1891-93. 0- 5, 5-10, 10-15, 15-20, 20-25, 25-35, 35-45, 45-55, 55-65, 65-75, 75-85, Over 85, 63 4 6 5 3-7 5 4 7 1 9-0 127 17-8 31-8 65 0 143-1 3119 56-8 5-4 31 4-4 5-6 7-6 11-5 17-3 316 65-4 138-6 288-3 58-5 4-7 2-7 41 5-2 7-2 11-8 18-4 345 71-0 1477 288-0 68 6 a 5 7 9 13 20 34 69 150 327 5 7 7 3 4 4 8 1 9 7 8 4 61-6 5-4 3-0 4-3 5-7 7-8 12-4 19-4 34-7 70-4 146-6 305-8 63-7 4-7 2-6 4-1 5-4 7-4 12-8 '20-8 37-9 75-8 155-3 301-2 58-4 6-3 37 5-5 6-8 8-6 11-6 15-6 28-7 610 135-4 296-4 52-0 5-3 31 4-4 55 7-4 10-6 151 2H-5 60-4 130-6 270-8 53-3 4-7 28 41 5-0 7-0 10-8 16-0 31-2 66-2 1402 274-8 All ages, . 21-4 19-2 19-5 22-7 20-3 20-6 20-1 18-1 18-4 The above table clearly shows that there is a great tendency to death among young persons; this liabdity to die reaching its minimum from betAveen ten to fifteen years of age, and afterwards steadily increasing throughout life. In this latter respect there was a remarkable increase of mortality at the advanced ages in 1890-91, due to the prevalence of epidemic influenza. CORRECTED DEATH-RATES. 773 It foUoAvs, therefore, that a town, a large proportion of whose inhabitants were at the most viable age, would have a loAver death-rate than a toAvn equaUy healthy, but in which the ages of the people were less favourable to long life; just as it would be if the one town had a much larger population of females than the other. Corrected Death-rates.—In order to neutrahse the errors in death-rates arising from sex and age constitution of the population, the Registrar- General has devised a method by which they can be corrected. This method, based primarily upon the death-rate of each sex at different ages throughout England and Wales, provides a series of factors by which the recorded death-rates of the great towns can be each multiplied so as to make them comparable with that of England and Wales. By the use of these factors the recorded gross death-rate of any of these towns can be lowered or raised to what it would be if the age and sex distribution of that par- ticular town were the same as that of England and Wales generally. This new rate is called the corrected death-rate. The factor employed is practi- cally the expression of the ratio which the recorded death-rate bears to an empirical (arbitrary) standard death-rate calculated on the hypothesis that deaths at each age-period were at the same rate as in England and Wales during the decennium 1881-90, the death-rate at all ages in England and Wales during that period having been 19*15 per 1000. Owing to the proportions of persons of low mortality being excessive in most towns, their recorded death-rates are too low, and in consequence the factor for their correction is in most cases above unity, the only exceptions for last year being Norwich and Plymouth. The table below gives these factors for the chief toAvns as issued by the Registrar-General in 1895, along with their recorded and corrected death- rates per 1000 living in 1894. Towns, in the order of their Standard Factor for Correction for Recorded Corrected Comparative Corrected Death-rates. Death-rate. Sex and Age Distribution. Death-rate, 1894. Death-rate, 1894. Mortality Figure, 1894. Cols. England and Wales, 1. 2. 3. 4. 5. 19-15 1-0000 1659 16-59 1000 England and Wales, \ less the 33 ToAvns, / 19-45 0-9845 15-78 15-54 937 33 Towns, 17*71 1-0813 1812 19*59 1181 Croydon, 18-37 1-0424 13*19 13-75 829 Portsmouth, 18-73 1-0224 1515 15-49 934 Leicester, 17-64 1-0855 14-65 15-90 958 Derby, 17-36 1-1031 15-01 16-56 998 Brighton, 18-94 1-0110 16-41 16-59 1000 West Ham, . 17-75 1-0788 16-17 17*44 1051 Plymouth, . 19-70 0-9720 18-30 17-79 1072 Norwich, 19-99 0-9579 18-74 17-95 1082 Bristol, 18-33 10447 17-26 18-03 1087 Cardiff, 17-16 1-1159 16-22 18-10 1091 Hull, .... 18-23 1-0504 17-36 18-23 1099 Halifax, 17'20 11133 16 48 1835 1106 Huddersfield, 16-47 1T627 15-80 18-37 1107 774 VITAL STATISTICS. Toinis, in the order of their Corrected Death-rates. Standard Death-rate. Factor for Correction for Sex and Age Distribution. Recorded Death-rate, 1894. Corrected Death-rate, 1894. Comparative Mortality Figure, 1SH4. Cols. 1. 2. 3. 4. 5. Nottingham, Swansea, London, Gateshead, . Bradford, Sheffield, Leeds, . Birkenhead, Newcastle, . Blackburn, . Birmingham, Bolton, Oldham, Burnley, Wolverhampton, Sunderland, Preston, Manchester, Salford, Liverpool, . 17-81 17-53 17*97 17*83 16-73 17*22 17*28 17*42 17*58 17*05 17*33 16 90 16-72 16-67 18-30 18-25 17-42 16-90 17-03 17-26 1-0752 1-0924 1-0656 1*0740 1*1446 1-1120 1-1082 1-0993 1-0892 1-1231 1-1050 1-1331 1-1453 1-1487 1-0464 1-0493 1-0993 1-1331 1-1244 1-1094 17-24 17-04 17-76 17-66 17-00 17-77 17-87 18-06 18-29 17-89 18-59 1879 18-61 18-70 20*70 20-78 20-81 20-42 21'00 23-85 18-54 18-61 18-93 18-97 19-46 19-76 19 80 19-85 19-92 20-09 20*54 21-29 21-31 21-48 21-66 21-80 22-88 23-14 23-61 26-46 1118 1122 1141 1143 1173 1191 1193 1197 1201 1211 1238 1283 1285 1295 1306 1314 1379 1395 1423 1595 If the corrected death-rate in each town be compared with the death- rate at aU ages in England and Wales, taken as 1000, it gives a number known as the comparative mortality figure, as shown in the last column of the preceding table. These figures may be expressed in another way, by saying that after correction has been made for differences of age and sex distribution, the same number of people that gave 1000 deaths in England and Wales in 1894 gave 958 in Leicester, 1193 in Leeds, and 1379 in Preston. Or we can say that in 1894 the death-rate for the whole of England and Wales was 16*59 ; and the recorded death-rate for Black- burn is 17'89, with its factor for correction as 1*1231. Then 17*89 x 1*1231 20*09 = 20*09 as the corrected death-rate for Blackburn, and^-g^ x 1000 = 1211 as its figure of comparative mortality. Infantile Mortality.—The calculations of infant and child mortalities demand special remark; particularly as it is by no means uncommon to find them worked out on the population, or on the number of deaths at all ages. The proper, the most simple and most accurate way is rather to utilise the birth returns, and calculate out the ratio of deaths of infants under one year to the number of actual births in the latter half of the pre- ceding year and the former half of the current year. The greatest care should be given to child mortality, or the death-rate of those under five years of age, as it constitutes an important and instructive index of health conditions. In 1894 the infantile death-rate or proportion of deaths of infants under one year of age to registered births in England and Wales was 137 in 1000. In 1893 it Avas 159 per 1000 births, or higher than in any year since 1870, Avhen the proportion had been 160 in 1000. The average mortality of infants from all causes in the four decennia ending with 1890 has been in the proportions of 154, 154, 149, and 142 respec- INFANT MORTALITY. 775 tively to 1000 births. The rate differs widely in different counties and towns ; the general rule being that the rate is lowest in purely agricultural, and highest in the mining districts, and in those with textile industries. For the past ten years three towns in particular have been especially bad in this respect; they are Preston, Burnley, and Leicester, the infantile mortality of which during the ten years 1884-93 has been 229, 215, and 207 per 1000 births respectively. The following table gives the number of survivors after a lapse of 3, 6, and 12 months out of 100,000 births respec- tively in three agricultural counties (Herts, Wilts, and Dorset); in five mining or industrial counties (Stafford, Leicester, Lancashire, West Biding, and Durham); and lastly, in the three selected towns of Preston, Burnley, and Leicester. The figures are based upon the returns for the years 1891-2 and 1893. Age. Of 100,000 bom, the Numbers Surviving at each Age. Annual Death-rates per 1000 living in each successive Age-period. Three Rural Counties. Five Mining and Manu-facturing Counties. Three Selected Towns. Three Rural Counties. Five Mining and Manu-facturing Counties. Three Selected Towns. At birth, ,, 3 months, >» 6 >> ,,12 „ • 100,000 94,760 93,144 90,306 100,000 92,110 88,605 83,126 100,000 90,896 85,628 78,245 211 75 60 330 155 126 378 238 181 It will be seen from these figures how high is the mortality among young chUdren in these particular towns and industrial counties, as compared with the rural counties ; put into round numbers, it means that for 10,000 deaths in the agricultural counties there would be 26,000 in the towns in each case out of 100,000 children born alive. The chief causes of infantile mortality, common to every locality, are briefly : premature birth, congenital defects, hereditary tendencies, inex- perience and neglect of mothers, industrial conditions, improper food, and overlaying. Infant mortality is more particularly influenced by the prev- alence of epidemic diarrhoea, and by epidemics of measles or whooping- cough. A high infant death-rate does not necessarily imply a high tendency to death among the rest of the population, as it is often high in towns that have a low general death-rate; thus Leicester has had an infantde death-rate for the ten years 1884-93 of 207 per 1000 births, but during the same period its general death-rate has been only 20*3 per 1000 living. It is always high in districts Avhere female labour is largely employed in manufactures. Combined Beath-rates.—A very frequent source of error in vital statistics is made in calculating the mean death or other rate of two popula- tions or communities; these are often spoken of as combined death-rates. The error usually arises from failing to take into account the proportion which the two populations or groups bear to one another. Thus, suppose tAvo towns each contain 30,000 inhabitants, and have respectively mortalities of 22 and 16, their mean or combined death-rate would be -—>---0r 19. But suppose one of the toAvns have 42,000 inhabitants and the other 18,000, and have respectively the above mortalities, their combined death- rate will then not be the mean of their two separate death-rates, but as follows :— 776 VITAL STATISTICS. One toAvn of 42,000 people with a death-rate of 22 per 1000 = 924 deaths. „ „ „ 18,000 „ „ „ 16 „ =288 „ or 60,000 people give 1212 deaths, and —12—1- — = 20*2, the true combined death-rate per 1000. 60,000 Influence of Birth-rate on Beath-rate.—With regard to the influence of the birth-rate upon the death-rate much controversy has prevaded. To a great extent this has been unnecessary, and has arisen from a misconception as to the true meaning of the relation between the birth and death rates. Practi- cally, the birth-rate affects the death-rate only in so far as it alters the age constitution of the population. If we imagine a population in which there has been a high birth-rate for one or more years, it is clear such must contain a larger proportion than usual of young children, and inasmuch as the death- rate of young children is higher than that of all others except the aged, the general death-rate of that population will be raised; but this condition is to a large extent counterbalanced by the fact that a high birth-rate implies the presence in that particular population of a large proportion of persons of the childbearing age, that is, of an age-period when the mortality is un- usually low. So, again, if the high birth-rate be continued for any length of years, it means not only a large proportion of children and of persons at reproductive ages, but also of young adults, among whom a low rate of mortality also prevails. In the same way a continuously low birth-rate may bring about a Ioav death-rate. A striking illustration of this kind is afforded by the case of Aston Manor, which enjoys a very low death-rate, and where the age constitution of the population per 1000 at the last two censuses was as f oIIoavs :— Age-Periods, .... 0-5. 5-10. 10-15. 15-25. 25-35. 35-45. 45-55. Over 55. Census of 1881, „ 1891, 157 127 131 123 110 119 191 204 156 162 113 113 74 68 68 74 In this town the enormous reduction in the child population, and relative increase of ages between fifteen and thirty-five or those of loAver mortality, is wholly due to a continuous decline in the birth-rate during the last fifteen years, which has shown itself in a reduced death-rate, and more palpably in the fact that, though the population has increased between 1881 and 1891 from 53,842 to 68,639, the demand for school accommodation has been stationary. Thus far the change in the constitution of the population has had an apparently favourable influence on the death-rate, but, if it con- tinue to operate, it will lead to an accumulation of persons over forty-five years of age, and be followed by a steady rise in the death-rate, however excellent the sanitary condition of the district may be ; when the authorities doubtless will be as eager as they are now unwdhng to have the recorded death-rate " corrected." The real influence of the birth-rate upon the death-rate, therefore, is not one which can be well expressed as a low birth-rate causing a low death- rate, or a high birth-rate producing a high death-rate, but rather that the average age of a population governs the death-rate, and that the lower the mean age of the hving, the lower should be the death-rate, and, by inference that the death-rate really controls the birth-rate, because the lower it is, the more chance is there of there being a large proportion of persons at the URBAN AND RURAL MORTALITY. 777 child-producing ages. If a high death-rate follows a high birth-rate, it reasonably suggests an excessive infantile mortality; very often low death- rates and low birth-rates co-exist, but it must not be supposed that the one is always necessarily caused by the other. Relation of Bensity to Mortality.—The influence exerted by density of population on mortality and death-rates has long been recognised. The density may be either expressed as so many persons to a square mile, or as acres to a person, or we may state the distance Avhich would separate each indi-vidual from his next neighbour if the whole population were spread as uniformly as possible over the surface of the country. The gradual increase of density of population in this country at each successive census is shown in the foUowing table :— Date of Census, 1801. 1811. 1821. 206 3-11 132 1831. 238 2-69 123 1841. 1851. 1861. 1871. 1881. 1891. 499 1-29 85 Persons per square mile, Acres per person, . Proximity in yards, 153 4-20 153 174 3-67 143 273 2-34 114 307 2-08 108 344 1-86 102 390 1-64 96 445 1-44 90 The late Dr Farr found that the mortality increases with the density of a population; not in direct proportion to the density, but as the twelfth root. This rule, however, is of very hmited practical application, as many variable conditions are involved. According to Ogle, this influence of density does not affect the mortality unless there be more than four hundred persons to the square mile. ISTeAVsholme regards the number of persons per room as the most reliable index of density; and shows that in 1889 the vital statistics of the 20,000 inhabitants of Peabody Buildings, with a density of 750 per acre, compared favourably with those of London generally (average density 49 per acre) as regards infant mortality, total death-rate, and death-rate from diarrhoea and enteric fever; though there was a higher mortality from phthisis, scarlet fever, diphtheria, measles, and whooping-cough. The practice of building back-to-back houses so prevalent in Yorkshire and Lancashire, and without provision for through ventilation, illustrates very clearly the evil effects of crowding populations, and has been well sifted by the reports of Barry and Gordon Smith to the Local Government Board in 1888. Increased density of population gives rise to filth conditions, to the more rapid spread of infectious diseases, phthisis, accident, and other evil conditions, the outcome of co-existent poverty and occupation. It is probably by and through these, rather than from mere overcrowding, that density of population in any way influences the death-rate of a community. Urban and Rural Mortality.—Closely connected with the influence of density of population upon mortality is the question of the respective death- rates in urban and rural districts. The following table gives the death-rates for town and country districts. The death-rate is evidently diminishing in both urban and rural areas, but more rapidly in the former than in the latter, so that the difference between them grows less. The increased excess of the urban over the rural death-rate in 1893, as compared Avith the rates in 1891 and 1892, was in part due to the high mortality from diarrhoea, a disease affecting town in greater degree than country populations. The rates in 1891 and 1892, how- ever, in the rural districts had been unusually high, doubtless on account of epidemic influenza, thus reducing the difference between the urban and 778 VITAL STATISTICS. rural rates, so that in 1893 the ratio of urban to rural mortality only reverted to its normal figure. Year. Persons to a Square Mile in England and AVales. Annual Deaths to 1000 Persons living in Deaths in Town Districts to 100 Deaths in Country Districts, in equal Numbers living. England and AVales. Town Districts. Country Districts. 1851-60 1861-70 1871-80 1881-90 1891 1892 1893 1894 325 22-2 365 - 22-5 416 i 21-4 470 i 19'2 499 20*2 504 I 19*0 510 19*2 514 16-6 1 247 24-8 23-1 20-3 21*9 19*5 20*6 17*4 19*7 20*2 19-8 18-1 18-5 18*5 17*8 15*9 124 126 1 122 1 117 , 114 i 108 1 116 109 ! f As ISTeAvsholme has pointed out, the true difference between urban and! rural mortality is greater than is shown in the preceding table, if due allow- ance be made for age and sex distribution. There is in the town districts a much larger proportion of females, a larger proportion of adults of both sexes in the prime of life, and a much smaller proportion of very aged persons. "There is a slight counterbalancing influence of a large number of infants in toAvns, but these, as we have already seen, are followed by an increase of young adults, and, therefore, apart from any excess of infant mortality, ought not to raise the general death-rate." The extent of the correction required on these accounts may be gathered from an example. In 1893 the urban death-rate was 20*2 ; the rural death-rate 17*4. Owing, however, to the great differences of age and sex distribution of the respective populations,, the urban death-rate ought, with equal healthiness, to have been nearly 12 per cent, lower than the rural death-rate, instead of being, as it was, 16 per cent, above it. The figures for 1894 are much more satisfactory. Causes of Beath.—It is not sufficient to know the death-rate of a com- munity ; it is necessary to know and inquire what rates the different causes of death give Avhen the deaths are distributed to their several classes. Although the death-rates obtained from registrars are principally derived from certificates signed by either doctors or coroners, and, as such, should be clear statements of the precise cause of death, still even now the cause of death in many cases is both vague and ill-defined. Each year, however, shows improvement in this direction, with the result that the registration of causes of death is becoming more and more accurate and complete. Some idea of the mortality in England and Wales from the several classes of diseases during the last few years will be gathered from the following table :__ Causes of Death. Rate per Thousand living. 1884. 1S85. 1886. 1887. 1888. 1889. 1890. 1891. 1892. 1893.' Zymotic diseases,. . . Parasitic- diseases, . Dietetic diseases, . . . Constitutional diseases, . Local diseases, . . Violence, .... Developmental diseases, Ill-defined and not specified \ causes, . . . . J 3116 0-039 0-058 3-431 9-618 0-656 1-586 1-160 2-531 0030 0060 3-310 10-007 0-634 1-614 1-019 2-679 0-036 0061 3 370 10040 0-634 1-638 1-064 2-702 0-030 0-064 3213 9-867 0652 1-578 0-968 2133 0-025 0-063 3-166 9-643 0-622 1-569 0-891 2-456 0-024 0 067 3-223 9-394 0-614 1-550 0-893 2-541 0-024 0-081 3-374 10364 0653 1-611 0-900 2-706 0 023 0083 3-339 10807 0670 1-690 0-899 2-785 0 021 0079 3-168 9-801 0-651 1-624 0-853 3-165 0-020 0-088 3-210 9-536 0-675 1-593 0-883 All causes, .... 1966 j 19-20 19-52 1907 1811 18-22 19-54 20-21 18-98 19-17 ZYMOTIC DEATH-RATES. 779 Some of these groups of causes of death are deserving of closer analysis. The Zymotic death-rate, or death-rate from special febrile diseases, is an important fact to be noted among all communities, as it furnishes a very popular standard as to their general healthiness. But it will be readily understood that it is liable to great fluctuations according to the greater or less prevalence of one or other of those diseases, with the result that a so- called mean zymotic death-rate is often of little value. Thus, say in a given community the zymotic death-rate be excessive owing to the epidemic preva- lence of the two zymotic diseases, measles and whooping-cough. Owing to these diseases not being either usually or truly dependent upon defective sanitary conditions, their excessive prevalence, as evidenced by an increased zymotic death-rate, furnishes less clue as to the health condition of the com- munity than would an equally high zymotic mortahty rate owing to such diseases as diphtheria or enteric fever, which are more directly the expression of faulty sanitary states. Of late years the zymotic death-rate has shown a steady tendency to fall; in 1894, for England and Wales, it was 1*76 per 1000 living; but so far the best endeavours of sanitarians in this country have not been able to get the death-rates of the chief diseases of this class beloAV the following rates per 1000 hving :— Zymotic Diseases. 1884. 1885. 1886. 1887. 1888. 1889. 1890. 1891. 1892. 1893. Small-pox, .... 0-083 0-104 0010 0018 0-036 o-ooi o-ooi 0-002 0-015 0 049 Measles, .... 0 419 0-533 0 436 0 602 0-347 0-518 0-439 0-436 0-460 0 374 Scarlet fever, 0 402 0-233 0-218 0 282 0-226 0-235 0-242 0-171 0-190 0 235 Typhus, .... 0 012 0-012 0-009 0 008 0-006 0005 0-005 0-005 0-003 0 005 Enteric fever, 0 236 0175 0-184 0 185 0-172 0176 0-179 0-168 0-137 0 229 Simple continued fever, 0 028 0-024 0022 0 018 0 015 0-015 0-013 0-011 0-008 0 009 AVhooping-cough, . . 0 425 0-481 0-470 0 404 0-436 0430 0-478 0-46S 0-455 0 342 Diphtheria, . . . 0 186 0-164 0-149 0 160 0-171 0-189 0-179 0-173 0-222 0 318 Influenza, .... 0 003 0-005 0-003 0 003 0-003 0002 0-159 0-574 0-534 0 325 Cholera, .... 0 030 o-oii 0-019 0 017 0-008 0012 0-014 0 011 0-150 0 045 Diarrhoea, .... 0 978 0-492 0-899 0 727 0-455 0-G48 0-606 0-469 0-505 0 954 Erysipelas, .... 0 079 0-073 0-055 0 067 0-0-38 0-043 0-048 0-043 0-050 0 065 Puerperal fever, . 0091 0-089 0-076 0 088 0-085 0-065 0-068 0-068 0-080 0-102 Of the so-called Parasitic Diseases the greater number are attributed in the Eegistrar-General's returns to thrush. The deaths from diseases of this class in 1893 were fewer than in any previous year on record. The deaths Causes of Death. 1884. 18S5. 1886. 1887. 1SSS. 18S9. 1890. 1891. 1892. 1893. Thrash..... 0032 0 025 0029 0-024 0-019 0 019 0-019 0-018 0-016 0-015 Alcoholism, 0047 0-049 0-051 0052 0-051 0-055 0-070 0 071 0-063 0-073 Rheumatic fever, 0 101 0-107 0-092 0-095 0-096 0-079 0-084 0-08S 0-086 0-104 Rheumatism, 0-032 0-032 0-032 0-035 0-033 0-032 0-033 0-037 0-037 0-030 Cancer, .... 0-563 0-572 0-590 0-615 0-621 0-656 0-676 0-692 0690 0-711 Phthisis, .... 1-827 1-770 1-739 1-615 1-568 1-573 1-682 1-599 1-468 1-468 Diabetes, .... 0-055 0-056 0-059 0-063 0-063 0-0G2 0-065 0-066 0-068 0070 Convulsions, 0-854 0-808 0-831 0-778 0-736 0-756 0-749 0-763 0-701 0-701 Diseases of nervous system, 1-824 1-823 1-858 1-806 1-772 1-715 1-745 1-748 1-622 1-612 Diseases of circulatory system, 1-506 1-613 1-647 1-666 1-695 1-664 1-757 1-826 1-684 1-630 Diseases of respiratory system, 3-342 3-737 3-641 3-626 3-502 3-309 4-120 4-474 3-884 3-536 Croup, .... 0-176 0-156 0-134 0-143 0-129 0-114 0-109 0-091 0-076 0-071 Dentition, .... 0-183 0-171 0-178 0-152 0-150 0-153 0-158 0-160 0-144 0-136 Diseases of liver, . 0-362 0-360 0-358 0-337 0316 0-311 0-302 0-294 0-274 0-276 Other digestive diseases, 0599 0 563 0-617 0-596 0-586 0630 0-652 0-651 0-641 0-791 Diseases of urinary system, 0442 0-444 0-450 0-446 0-445 0-441 0-451 0-468 0-449 0-451 Diseases of parturition, . 0-070 0075 0 065 0-061 0-063 0-061 0-080 0-097 0-097 0-098 Diseases of organs of locomotion, 0-092 0-092 0-092 0-091 0-085 0-084 0-079 0-075 0-065 0-060 Diseases of skin, . 0-067 0-064 0-066 0-063 0-063 0 059 0-062 0-063 0-066 0-06S Accident and negligence, 0 567 0-549 0-540 0-558 0-528 0-528 0-565 0-574 0-553 0-576 Homicide, .... 0-012 o-on 0-011 0-013 0011 o-oio o-oio o-on o-oio o-on Suicide, .... Ill-defined causes,. 0076 0-074 0-082 0-080 0-082 I 0-076 0-077 0-085 0-0S8 0-087 1160 1019 1-064 0-968 0-891 . 0893 0-900 0-899 0-S53 0-883 780 VITAL STATISTICS. due to Dietetic Diseases are mainly the result of intemperance, and returned under the head of Alcoholism. The annual death-rates per 1000 living from the chief causes of death, other than the zymotic, in England and Wales, during recent years is given in the preceding table. The foregoing tables indicate that, in regard to certain well defined diseases, the death-rate has changed in the direction of increase or decrease. The increase in mortality is manifest in respect of cancer, diabetes, diphtheria, influenza, suicide, and diseases of the circulatory and respiratory systems. It is probable that some real increase has occurred in respect of nervous diseases also, possibly due to improved methods of diagnosis and greater care in certification of cause of death. There has been a true increase in diphtheria in the last feAv years, especially in urban districts. Puerperal fever has apparently increased, but it is not improbable that this is due to more correct certification, arising from the systematic inquiry now made by the Begistrar-General in respect of doubtful entries. Measles and whooping- cough show a high average mortality, with little tendency to decrease, but these diseases have no demonstrated relation to insanitary conditions, and as yet have not been seriously combated either by hospital isolation or dis- infection. A decrease is manifest in the mortahty from small-pox, scarlet fever, diarrhoea, typhus, enteric fever, simple continued fever, thrush, phthisis, convulsions, croup, and ill-defined causes. The reduction in regard to the first five is real, and mainly attributable to improved sanitation. Phthisis has been undoubtedly lessened by better drainage and ventilation, but improved diagnosis is probably responsible for the transfer of some cases to the category of other respiratory diseases. The gradual disappearance of simple continued fever, croup, convulsions, and ill-defined diseases as causes of death may be explained by better diagnosis and better certification, but nearly all these cases have involved transference to other headings, and. are not true reductions in mortality. Other influences Avhich have an important bearing upon the mortahty of certain diseases are sex, age, and occupation. The mortality among women appears to be higher than among males for such diseases as rheumatism, anaemia, chlorosis, erysipelas; while for affections connected with childbirth, it is, of course, limited to the female sex. On the other hand, men die more than women when affected with such diseases as syphilis, diabetes, rickets, typhus, meningitis, and hydrophobia. The influence of age upon mortality rates is very marked in certain diseases. Thus, phthisis or consumption is at its lowest prevalence between the ages of 5 and 12, but increases up to 47 years of age, after which it lessens. SmaU-pox mortality is highest in the first and twenty-fifth years, while diarrhoea, Avhooping-cough, measles, and diphtheria all have their highest death-rates during the first few years of life. Cancer is a disease which appears rarely to affect the young, but tends to increase after 28 years of age. Diseases connected with the heart and circulatory system increase in their mortality rates from birth upwards. The total death-rate, and the death-rates from affections of the nervous system, lungs, and bladder, all appear to be at their lowest between the tenth and fifteenth years of life. Occupation.—The more recent investigations of Ogle and Arlidge have thrown considerable light upon the influence Avhich occupation has upon mortahty. Some callings are much less favourable to health than others; some again, whde being relatively healthy, are dangerous. The chief cir- cumstances which render certain employments more or less hurtful to health are, bad ventilation and overcrowding of work-rooms ; exposure to weather, OCCUPATION IX RELATION TO MORTALITY. 781 or extremes of heat and cold; inhalations of vapours, gases, or metallic, mineral and organic dust; overstrain and mental anxiety; also temptations to intemperate habits. Many difficulties and fallacies underlie all com- parative statistics of class mortalities, unless due allowance be made for the age at which such employments are followed, as well as the question of the class of person actually engaged, and the importance of differentiating between employer and employed. Thus, a death-rate of 10 per 1000 among factory girls aged 15-25 in a town where the general death-rate was 22 would be very high, since that for females at that age-period is about 5. This precaution is sufficient Avhen, in the absence of anything specially unfavourable to health in the occupation, any excessive mortality must be ascribed to insanitary surroundings or irregular habits. As Farr says, " it Avould be obviously unfair to expect that all trades could be rendered equally healthy; and when a certain amount of danger to life or unhealthi- ness is unavoidable, the death-rate should also be compared with that of some other group of workers in the same or similar industry, thus giving a practicable as well as an ideal standard." Again, the healthiness or unhealthiness of an occupation may be obscured by the fact that those who folloAv the several industries do not start on equal terms as regards health. A weak, weedy lad will not become a navvy, but a tailor or shopman by preference. The occupations demanding great muscular strength and activity to some extent, then, consist of picked men. So, again, there are some callings only attainable late in life, Avhile, on the other hand, some are only suited to young persons, who after a few years seek more lucrative employments. In all these cases the mean age at death is delusive. Most females follow their employments only until by marriage they cease to be self-supporting, consequently, the mean age at death of female clerks, domestic servants, and shop assistants is valueless. To give that of ladies' maids as 36 and of nurses as 60, or to say that the mean age at death of a judge is 68 and that of a solicitor is 50, is merely an abuse of statistics. The following table shows the comparative mortahty and death-rates for two age-periods of various occupations, as gathered from Ogle's figures for the three years 1880-1-2, which is the latest period for which an analysis has been made. In his larger table Ogle gives the death-rate per 1000 living at five age-periods, but of these the groups between the 26th and 46th birthdays are the largest, and show the influence of occupation most markedly. Before 25 the influence of occupation has not had time fully to develop, and after 65 the influence of retirement comes into play. The comparative mortality figure is derived in this way. During 1880-1-2, when this table Avas constructed, there were in England and Wales 1000 deaths per 64,641 males aged 25-65, of whom 41,920 were under and 22,721 were over 45 years of age. The comparative mortality fio-ures are the number of deaths that would have occurred in the several occupations out of 64,641 males, distributed according to age, as in England and Wales. For instance, 41,920 butchers aged 25-45, and 22,721 aged 45-65, with a death-rate respectively of 12*16 and 29*08 per 1000, gave 1170 deaths. Thus the figure 1170 represents the mean mortahty of butchers betAveen 25 and 65 as compared with the mortality of all males of similar ages in England and Wales, which is 1000. It is of interest to note that the death-rate of more than three-fifths of the industries is below the mortality fio-ure for " all males." The standard furnished by " all males," however, is°a very unsatisfactory one, as it includes an enormous number perman- ently enfeebled in health and not engaged in any definite occupation. 782 VITAL STATISTICS. Mean Annual Death-rate per 1000 living. Comparative Mortality Figure. Occupation. Age Age Age 25-45. 45-65. 25-65. All males, ...... 10-16 25-27 1000 Occupied males, 9*71 24-63 967 Unoccupied males, . 32-43 36-20 2182 Males in selected healthy districts, 8-47 19-74 804 Inn and hotel servants, . 2263 55-30 2205 General labourers in London, . 20-62 50-85 2020 Costermongers and hawkers, . 20-26 45-33 1879 Cornish miners, 14-77 53-69 1839 Potters and earthenware manufacturers, . 13*70 51*39 1742 Filemakers,...... 15-29 45*14 1667 Watchmen, porters, and messengers, 17-07 37*37 1565 Licensed victuallers and innkeepers, 18-02 33-68 1521 Chimney-sweeps, ..... 13-73 41-54 1519 Cabmen and omnibusmen, 15 39 36-83 1482 Brewerymen, .... 13-90 3425 1361 Hairdressers, .... 13-64 33-25 1327 Professional musicians, . 13-78 32-39 1314 Bargemen and watermen, 14-25 31-13 1305 Carters and carriers, 12-52 33*00 1275 Cutlers and tool and needle-makers, 11-71 34-72 1273 Plumbers, glaziers, and painters, 11-07 32-49 1202 Glass-blowers, .... 11-21 31*71 1190 Butchers, .... 12-16 29*08 1170 Law clerks, .... 10-77 30*79 1151 Medical men, .... 11-57 28*03 1122 Cotton operatives in Lancashire, 9-99 29*44 1088 Wool and worsted operatives, . 9-71 27-50 1082 Printers,..... 11-12 26-60 1071 Tailors, ..... 1073 26-47 1051 Chemists and druggists, . 10-58 25-16 1015 Tobacconists, .... 11-14 23 46 1000 Commercial travellers, 10-48 24*49 996 Blacksmiths, .... 9-29 25-67 973 Builders and bricklayers, 9-25 25-59 969 Bakers and confectioners, 8-70 26-12 958 Corn millers, .... 8*40 26 62 957 Insurance agents, 9-04 25-03 928 Artists, sculptors, and architects, 8-39 25-07 921 Shoemakers, .... 9-31 23-36 921 Tanners and fellmongers, 7 97 25-37 911 Watch and clockmakers, . 9-26 22-64 903 Plasterers and whitewashes, . 7-79 25-07 896 Coal miners, .... 7-64 25-11 891 Grooms and private coachmen, 8-53 23-28 887 Drapers and warehousemen, . 9-70 20-96 883 Barristers and solicitors, . 7-54 23*13 842 Booksellers and stationers, 8 53 20-57 825 Carpenters and joiners, . 7*77 21*74 820 Fishermen,..... 8*32 19-74 797 Grocers,..... 8*00 19-16 771 Schoolmasters and teachers, 6*41 19-98 719 Agricultural labourers, . 7*13 17-68 701 Farmers and graziers, 6*09 16-53 631 Gardeners and nurserymen, 5-52 16-19 599 Clergy, priests, and ministers, 4-64 15-93 556 SICKNESS RATES. 783 In the preceding table the selected occupations are given in the order of the greatness of their mortality, as shown by the comparative mortahty figure. Jnn-servants, inn-keepers, and brewers all have an excessive mortality chiefly due to intemperance, but a large proportion of this class must be of temperate habits, as the comparative mortality figure for recognised in- temperate persons is, according to Neison, 3240. Pubhcans and inn-keepers show also the highest mortality from gout and urinary diseases, with the exception of occupations dealing with lead. Plumbism as well as alcoholism would appear to be a cause of some forms of heart disease, as diseases of the circulatory system are most fatal among brewers, publicans, coster- mongers, cabmen, fishermen, painters, plumbers, filemakers, and potters .Nervous diseases give rise to a high mortality among those addicted to -intemperance, and appear to be most fatal in the same occupations as are associated with a marked mortality from alcoholism. The same is the case with diseases of the hver; while suicide also has a fairly close relation to intemperance. Eespiratory diseases, especially phthisis, cause a high mortality amon^ the debilitated, and those exposed to the weather, to impure air, and to certain forms of dust. For these reasons we find a high mortality figure among oostermongers, tailors, drapers, cutlers, filemakers, potters, printers wool and cotton workers, and in some miners, such as the Cornish miners.' Coal miners, as a class, have a relatively low mortahty figure, probably'due to the fact that coal mines are well ventilated, and that the nature of the employment excludes weakly persons. Lead-poisoning is prevalent amonc printers, earthenware makers, painters, plumbers, glaziers, and filemakers3 The two latter calhngs show also an extremely high mortahty from renal diseases. The high mortality of printers is due less to plumbism than to phthisis. Butchers show a high mortality, which is apparently due to excessive indulgence; the same remark apphes to commercial travellers The shopkeeper class have a relatively Ioav mortality; among them grocers suffer much less than drapers from phthisis and respiratory diseases but more from diseases of the circulation, and slightly more from alcoholism and suicide. The clergy enjoy the lowest mortality, being closely pressed in this respect by gardeners, farmers, and agricultural labourers; the latter appear to suffer much from phthisis and respiratory diseases. Farmers have a somewhat high mortality from gout, alcoholism, and liver disease. Fisher- men appear to have a low mortality from diseases of the nervous and respiratory systems, but suffer largely from accidents. Sickness Bates.—Our information on this point is somewhat unsatis- factory, as the materials [are wanting for a complete study of the amount of illness in the community. What statistical evidence we have is drawn from the experience of friendly societies, certain industrial organisations the police, the navy, and the army. All these, however, are more or less selected bodies, and cannot be regarded as fairly representing the General population. The following figures have been obtained from, and are based upon, the experience of certain friendly societies, more particularly the Manchester Unity of Oddfellows and the Foresters. These figures indicate that after mid-life the average duration of each illness increases, and with it the " expectation of sickness " and the propor tion of number of cases of illness to each death. On the basis of these data it may be calculated that, inasmuch as in 1893 there were in England and Wales 569,958 deaths, there were 1,598,882 constant sufferers from sickness, and nearly 2,000,000 sufferers from such illness as would require 784 VITAL STATISTICS. medical rehef, or throw the members of friendly societies on their funds. The economical loss to the community represented by this amount of sick- ness is enormous ; and, assuming that a large proportion of it is preventible, the necessity of still further improving the sanitary condition of the people is manifest. Ages. Xumher of Years of constant Sickness corresponding to one annual Death. Annual average amount of Sickness per head, in weeks. Average duration of each Illness, in weeks. Males. Females. 10-20 2-47 0-75 3-43 3 30 20-30 2-53 0-93 3-80 3-90 30-40 2-17 1-00 4-74 5-20 40-50 2-45 1-80 5-58 5-80 50-60 2-64 2-60 7-80 7*00 60-70 4-00 4-36 9-54 9 50 70-80 5-53 7-50 12-12 12-60 Over 80 4-80 10-50 10-00 11-00 Statistical Evidence of the Health of Communities.—In attempting to judge the health of a community by statistical evidence, the greatest impor- tance is attached to the foUowing points, namely, the total corrected death- rate, the zymotic death-rate, and the infant mortality. All these have been discussed, and the various sources of error connected with them explained. Equally significant with the zymotic death-rate and the infant mortality is the phthisis death-rate, which, if excessive, indicates dampness of soil, unhealthy work-rooms, or overcrowding of tenements. The death- rate from respiratory diseases, other than phthisis, is also important. But, besides these, certain other evidence is usually considered, mainly as a test of the mean or average longevity of the population. This evidence consists of facts relating to what is known as " the mean age at death," " the prob- able duration of life," and " the expectation of life." The mean age at death of a population is the sum of the ages at death divided by the number of deaths. It is no good test of the relative healthi- ness of populations unless due corrections be made for age and sex distri- bution. As Farr says, a population of ensigns might show a mean age at death of 22, and a population of generals over 48, but the latter population would not be more healthy than the former, it would merely consist of persons of a different age. A high birth-rate may reduce the age, though the health of the community may be extremely good. If the birth-rate be high, there will be in consequence a greater proportion of infants or young children in the population. These, we know, have a relatively high death- rate, with the result that the average age of death wdl be proportionately reduced. In this country the mean age at death averages 42 for males and 45 for females. Farr has shown that it is nearly equivalent to the reciprocal of the death-rate minus one-third of the difference betAveen the reciprocal of the death-rate and that of the birth-rate; or two-thirds the reciprocal of the death-rate plus one-third that of the birth-rate. Suppose the death-rate to be 1 in 46, and the birth-rate 1 in 29, we have _*L*? + ^ o o = 40*3 as the mean age at death. The probable duration of life is practically the age at which exactly half of any given number of children born alive wUl have died; or, in other LIFE-TABLES. 785 words, there are equal chances of their dying before and after that age. It is sometimes spoken of as the equation of life, or vie probable of French writers. All these terms are more or less unfortunate, as there is a prob- ability for every possible duration of life. Begarded strictly as defined above, the probable duration of life is of no great value as a test of longevity ; it can only be obtained from what is called a life-table, and as so determined for England and Wales, gives the probable duration of life for each male 47 years, and for each female 52 years. The probable duration of life is often confounded with another statistical expression, called the mean dura- tion of life, which is the probable or likely duration of life from birth, and, by French writers, called the vie moyenne. If we imagine an absolutely stationary population, that is, one in which age and sex distribution does not change, then, starting from birth, the mean duration of life would be identical with the mean age at death, and with the expectation of life as determined by means of life-tables. But such a stationary population is rare, and in an ordinary community, whose numbers are constantly being disturbed by migration or other causes, the mean duration of life really signifies the present age in years plus the probable duration of life after ha\dng attained a given age, and which is more commonly called the mean after lifetime, or expectation of life. For comparative purposes, it is often more convenient to employ the term mean duration of life as indicating the expectation of life at birth; but if it is required to remove the disturbing influence of infant mortality, then the mean after lifetime, or expectation of life at a later age, must be taken. This expression, expectation of life, must not be taken to imply that any individual may reasonably expect to live a given number of years, because it has no true relation to the most probable duration of the lifetime of any given person. It merely shows the average number of years which a person, at a given age, lives, and in that sense constitutes the true measure of the chances of living which a mixed community has. Its estimation is made by means of what is called a life- table, and which is nothing more than a table constructed from census figures on the basis of the number living and the number dying at each age. Such a table shows how many out of, say, 1,000,000 persons supposed to be born at the same time will survive at the end of each year or term of years. The same table will also show the sum of the number of years which they live, and if this sum of these years be divided by the number living at any given age, the result wiU be the expectation of life for that given age. Life-tables.—Farr called a life-table a biometer, because it really repre- sents " a generation of indi-viduals passing through time," and measures the probabilities of life and death of this generation at birth, and of survivors at each successive age-period, until the whole generation is extinct. In order to construct a life-table it is necessary to have (1) particulars from a census return of the number, age, and sex distribution of a popula- tion ; (2) returns of deaths for one or more years among this same population, grouped in the same ages or age-periods as have been adopted for stating the census population. A separate table is required to be constructed for each sex, and for this reason the death returns must be distinct for the two sexes. A life-table can be constructed for either annual or quinquennial intervals; in most tables an annual interval is adopted for the first five years, and after that five-year periods are taken. The first step is to ascertain from the census returns the mean population, or the number of lives at risk at the centre of each year of life, and the number of deaths in the correspond- ing years of life. By dividing the former into the latter we obtain the rate of mortahty per unit of population, better known to actuaries as the central 3d 786 VITAL STATISTICS. death-rate, because it represents the rate at which people are dying in the centre of a given year. Let this be expressed per 1000, and call it D. These deaths may be assumed to be evenly distributed over the Avhole age- period, so that half the deaths will occur in the first portion of the period, and the other half in the second portion; and the ratio of the final to the 1000 - AD 2000 - D initial population is 10Q0 + ID> which, when simplified, becomes ^OOO + D* This ratio is practically identical with the probability of living through one number of survivors at end of year year, or px equals number iiving at beginning of year" For the construction of a hypothetical life-table, let us suppose that the mortality among infants in a given population is 100 for every 1000. It will be at once evident that, if there be 1,000,000 babies born and living at the commencement of a given year, these will be reduced to 900,000 in the course of the year, and this number will commence the second year. Pre- suming that the data show that the death-rate among children in the second year of life is as high as 50 per thousand living, then applying the foregoing formula, we get f0^~l°0 or^ or 0*951219, and the 900,000 children at the beginning of the second year are reduced to 900,000 x 0'951219, or 856,097 at the beginning of the third year. In the same way, knowing the death-rates for the third, fourth, and fifth years of life, the actual numbers of children surviving at the end of those age-periods is calculated. Suppose now, by the end of the fifth year only 650,000 survive out of the original million, and we propose to continue constructing the hfe-table for quin- quennial or five-year periods in place of annual intervals. The calculation is practically the same, substituting for the death-rate of each year the death- rate for each quinquennium. Presume the death-rate among persons aged 5-10 years to be 7, then applying the formula for the reduction of the /2000 — 7\5 population during this five-year period, we get L.. J or 0*965632, and at the end of this quinquennium, or by the end of the tenth year, the 650,000 wdl be reduced to 650,000 x 0*965632 = 627,660. This calculation can be repeated for each five-year period until there are no more survivors left. Such an ideal life-table will consist of a series of columns, in the first of Avhich will be entered the various years of life or age-periods headed by the symbol x. The second column would be marked D, or as it is sometimes written mz. The entries in this column Avould be obtained by dividing the deaths during each year or age-period by the corresponding mean population, and represent the rate of mortality. From the entries in the second column, those of the third or px column would be obtained. These represent the probability of living one year for each age or age-period, as calculated from the formula px = onnn—^.. The next column, lx, is obtained by multiplying the number living at the immediately preceding year by px. The entries in this column Avill represent the number surArhdng at each successive age, or in other words lx represents the number who reach the precise age x. The next column required in a life-table is one shoAving the mean number living in each year of life, and technically called P^. Thus the mean number hving in the tenth year = — --15. LIFE-TABLES. 787 The next column in the table is known as the Q,. column. The number opposite any age in this column is the sum of all the numbers in the Vx column from that age to the end of the table, that is, until all the lives become extinct; and it shows, therefore, the aggregate number of years which the persons at each age in the table will live. The last column is that marked Ex; in it, opposite each age, is placed the mean after lifetime, or expectation of life at each age. This is obtained from the formula Er = -^ h' The following table represents the headings of a typical life-table, pre- pared in accordance with the foregoing principles; it will serve to shoAV a complete view of the results obtainable from a life-table. Each year of age should be inserted to make it complete, but in order to economise space, the intermediate years have been omitted. The table is practi- cally an epitome of Farr's English Life-Table, No. 3, for Males, published in 1864. Age or Age-Period. X. Annual Mor-tality per Unit at Age x. D or M^ Probability of Living one Year from each Age. Px. Number Born and Living at each Age. Mean Popu-lation in each Year of Age. Years of Life Lived at Age x and upwards. %. Mean After Lifetime at each Age x. E*. 0 5 10 15 20 25 35 45 55 65 75 85 95 105 0-18326 0-01369 0-00563 0-00519 0-00832 0-00920 001105 0-01554 0-02485 004698 0-10391 0-21966 0-42035 0-83212 511,745 0-98640 370,358 0-99438 353,031 0-99482 344,290 0-99171 333,608 0-99084 319,442 0-98901 ; 288,850 0-98458 , 253,708 0-97644 1 209,539 0-95410 150,754 0-90122 75,777 080208 | 16,877 0-65265 : 833 4 456,820 367,672 352,007 343,415 332,231 317,892 287,229 251,763 206,984 147,315 72,012 15,151 678 3 20,426,138 18,410,252 16,608,936 14,866,429 13,169,656 11,536,677 8,492,601 5,774,489 3,447,708 1,631,508 491,685 63,030 1,806 5 39-91 4971 47-01 43-18 39-48 36-12 29-40 22-76 16-45 10-82 6-49 3-73 2-17 Besides the preceding life-table, several others have been constructed, the more important being : " The Healthy Districts Life-Table," prepared by Farr on the basis of the mortality during the five years 1849-53 in sixty-three selected districts which showed, during the decennium 1841-50, a mean annual death-rate not exceeding 17 per 1000 persons living. This table expresses very accurately the actual duration of life among the clergy and other classes of the community living under favourable circumstances. The " Upper Class Experience Table," constructed by Ansell from data collected by him as to men of the upper and professional classes. The " Healthy Males Table," based on the experience of the principal insurance offices. The "Clerical Experience Table," based on data respecting over 5000 clergymen hving between 1760 and 1860. The " NeAv Enghsh Life-Table " by Ogle, and constructed on the death- rates of 1871-80. The "Brighton," "Manchester," "GlasgoAV," and "London" Life-Tables, prepared by the medical officers of health of those respective towns on the basis of the census of 1891 and death-rates of recent years. 788 VITAL STATISTICS. The folio-wing table gives a portion of Ogle's " NeAv English Life-Table," as issued in 1885 :— Males Female . Age. Survivors at each Age Expectation of Survivors at each Age Expectation of out of 1,000,000 Born. Life in Years. out of 1,000,000 Born. Life iu Years. 0 1.000,000 41-4 1,000,000 44 6 1 841,417 48-1 871,266 50*1 2 790,201 50 1 820,480 52-2 3 763,737 50-9 793,359 53-0 4 746.587 51 0 775,427 53-2 5 734,068 50-9 762,622 53-1 10 708,990 47*6 738,382 49-8 15 696,419 43-4 724,956 45-6 20 680,033 39-4 707,949 41-7 25 657,077 35-7 684,858 38-0 30 630,038 32-1 658,418 34-4 35 598,860 28-6 628,842 30-9 40 563,077 25-3 596,113 27-5 45 522,374 22-1 560,174 24-1 50 476,980 18-9 520,901 207 55 424,677 16-0 477,440 17-3 60 365,011 13-1 422,835 14-2 65 297,156 10-6 356,165 11*4 70 222,056 8-3 277,225 9*0 75 144,960 6*3 190,566 6-9 80 77,354 4*8 108,935 5-2 85 30,785 3-6 47,631 3 9 90 8,015 2-7 14,225 2-9 95 1,183 2-0 2,533 2-2 100 82 1-6 225 1-6 Having stated the data on which a life-table is based, and described the method of its construction, we are in a position to study the life history of the persons to which it has reference. The essential points for such a study are the three following:— (a) The probability of living a given period for each age-period in the two sexes separately. This is commonly written px, and equals, as we have , 1 number of survivors at end of period already seen, -----r—t^~-----rr—;—;----i • ■■ • Thus, bv the above J ' number living at beginning of period ' J New English Life-Table, at birth the probability of a male child living one . 841,417 /A1 . , . . year is fQOO 000 ' certainty of surviving to the end of the first year of life being taken as unity), and therefore the probability of his dying during the . 1,000,000-841,417 rtnr.or „ . year is - —., nnn nnn----= 0*158583. At 25 the probability of a male 630,038 1,000,000 living five years, by the same life-table, is q^'q^, and the probability of his dying during the quinquennium being 657>077 -630^038 27,039^ J ° 8 H H 5 657,077 ' ° 657,077 0*04115 ; and so on. (b) The number of survivors out of 1,000,000 children born of each sex, at each succeeding year, or quinquennial period of life, until the whole number becomes extinct by death. The above table starts with a million boys and a million girls assumed to be born at the same time, and shows how many EXPECTATION OF LIFE. 789 survivors there Avould be at each successive period. Thus, of 1,000,000 males born, 476,980 are still alive at the end of fifty years from birth; and of 1,000,000 females born, 520,901 sur-vive to the same age. (c) The expectation of life, or mean after lifetime, of males and females at the end of each given period. To find the expectation of life at any age .»•, the rule is, add together the years of life lived through by the whole of the life-table population after that age, and divide by the number of survivors at that age, or Ex = -y5. Suppose it is requhed to find the expectation of life for males at the age 35, on the basis of Ogle's English Life-Table. If we refer to that table, and add together the numbers surviving at each age later than 35, we obtain the figure 3,133,710, which is the number of complete five-year periods lived through by the whole of the life-table population after 35 years of age. These five-year periods equal 15,668,550 years, and as this number of years is lived by 598,860 males, the number of complete years lived by each male is 26*16 years. This result is known as the "curtate expectation of life." In the above remarks we have confined our attention to the complete quinquennia of life, and have not taken into account that portion of lifetime lived by each person in the quinquennium of his death. In some instances this may be only a few months or days, in others one or more years; but it may be assumed with a fair degree of accuracy, taking one person with another, that the duration of life in the quinquennium of death will be half such a period, that is, 2*5 years. If we add this 2*5 to the curtate expec- tation of life, the complete expectation of life is obtained. Thus, the complete expectation for males at 35 = 26*16 + 2*5 = 28*66 years. In life- tables where the age-periods are given in single years of life, the addition to be made to the curtate expectation will be 0*5 year. Usually, only the complete expectation of life is given in life-tables. If reference be made to Farr's table or the earlier English life-table given on page 787, it will be readily seen that the seventh or last column is obtained in the same way, and that the mean future lifetime of any person Q» can be obtained by the formula -y-. <>x From Avhat has here been explained, it will be gathered that life-tables can be constructed for individual towns as well as districts or countries, provided the necessary facts are available. And OAving to the important conclusions Avhich may be drawn from it, a local life-table must henceforth be regarded as indispensable to every medical officer of health. As Tatham has said, it is to him what the two-foot rule is to the mechanic. " In a Avord, the life-table is the one and only means by which the vague expres- sions ' more or less' of the sanitarian can be reduced to an exact comparative standard." Although the most recent life-table for the whole of England and Wales is that for the decennium 1871-80, known as Ogle's "New Enghsh Life-Table," that for 1881-90 not being yet published, still we have available for comparison four local life-tables based on the death-rates for 1881-90, namely, those for Manchester (Tatham), Brighton (Newsholme), Glasgow (Bussed), and London (Shirley Murphy). These recent tables are of the greatest interest as showing the immense difference in the expecta- tion of hfe in large and croAvded manufacturing centres, in the metropolis, and in a typical seaside health resort of magnitude. Beference should be made to all these tables by those desirous of constructing similar local tables for themselves, as details are therein given for AAdiich space is not available in a general work of this kind. 790 VITAL STATISTICS. A comparison betAveen the old and new life-tables for England and Wales shows that there is a greater expectation of life under the neAv table up to 19 years of age for males, and 45 for females. After these ages the improvement appears to be less, possibly due to a greater death-rate under new conditions amongst the elderly people • but this is so much counter- balanced by the saving in life during the earlier years, that the total number of sur-vivors up to about 70 for males and 90 for females is greater under the new table than in the old. The mean after lifetime at birth for both sexes is about 43\ years in this country ; while the probable duration of life lies betAveen 45 and 50 for males, and between 50 and 55 for females. The following comparative tabular statement gives the expectation of life at the end of each five years of life, and for each sex in London, Manchester, Glasgow, and Brighton, as worked out by their recent life-tables (1881-90), as well as for England and Wales (1871-80). Males. Females. England Man ■ Chester. England and AVales. London. Glasgow. Brighton. and AVales. London. Chester. Glasgow. Brighton. 0 41-35 40-66 34-71 35-18 43-59 44-62 44 91 38-44 37-70 49-00 5 50 87 50-77 45 59 46-97 52-87 53-0S 54 42 48 06 48 27 56-92 10 47 60 47'22 42 75 44-32 49 12 49-76 50 95 45 43 45 44 53-15 15 43 41 42-88 38 78 40-51 44 67 45-63 46 65 41 50 41 59 49-07 20 30 40 38-70 34 62 36-90 40-55 41-66 42 45 37 33 38 00 44-76 25 35 68 34-70 30 69 33-29 36 51 37-98 38 34 33 38 34 60 40-48 30 32 10 31-80 27 08 29-60 32-67 34-41 34 95 29 73 29 88 36 39 35 28 66 27-39 23 76 26-06 29-02 30-90 30 69 26 30 28 06 32-48 40 25 30 25-22 20 68 22-44 25-60 27-46 26 80 22 99 23 45 28-71 45 22 07 21-00 17 80 19-54 22-36 24-06 23 80 19 79 21 61 25-07 50 18 93 18-75 15 06 16-35 19-33 20-68 20 65 16 74 17 50 21-79 55 15 05 15-31 12 49 13-99 16-48 17-33 17 34 13 91 15 60 18-48 60 13 14 13 00 10 16 11-40 13-67 14-24 14 50 11 35 12 88 15-26 65 10 55 10-59 8 15 9-38 1096 11-42 11 78 9 11 10 69 1219 70 8 27 8-30 6 48 7-50 8-69 8-95 9 00 7 25 8 00 9-32 75 6 34 7-20 5 11 6-25 6-64 6-97 7 79 5 76 6 45 6-97 85 356 5-50 316 3-30 333 3-88 5-70 376 3-62 3-72 It is interesting to note from this table that at each age and for each sex the expectation of hfe in London exceeds that in Manchester and Glasgow, but is less than that of Brighton. The expectation of life for males at birth at Brighton is shown to be 43*59 as compared with 34*71 years in Man- chester, and 41*35 years in England and Wales. In other words, it was 20*4 per cent, higher in the seaside health resort than in the industrial centre, and 5*1 per cent, higher than in the country at large. Similarly for females the expectation of life at birth in Brighton was 49*00 years as compared with 38*44 in Manchester, and 44*62 years in England and Wales, an excess in favour of Brighton of 21*5 and 8*9 per cent, respec- tively. When speaking of the general English life-table, 1871-80, it was pointed out that the share in the gain of life of recent years was not uniform for each age-period. The local hfe-tables for Manchester and Brighton, 1881- 90, show that this experience is shared by these towns with the rest of the country. That the expectation of life has not improved for ages beyond 20 in males and 45 in females is usually explained by the two following hypo- theses :—(1) That, owing to the saving of life in the earlier years of life, a saving which has been especiaUy in zymotic diseases and phthisis, there has been a larger number of weakly survivors, who Avould under the former conditions have been carried off by these diseases. It is extremely doubtful LIFE-CAPITAL. 791 whether there is any real evidence in support of this view that the operation of the laAv of the survival of the fittest has been impeded, with results unfavourable to the health and vigour of adult life. It is not unlikely that the weeding out of weakly lives, caused by the greater mortality among weakly children suffering from an infectious disease, is almost entirely counterbalanced by the greater number of children made weakly in former times by non-fatal attacks of an infectious disease. In regard to phthisis and tubercular diseases, it is reasonable to suppose that much at least of the deteriorating effect of the survival of tubercular persons is counterbalanced by the large number of persons who are prevented by improved sanitary and social conditions from becoming tubercular. (2) The increased strain of modern life is supposed by many to explain the increasing death-rate among adults. It is doubtful whether such increased strain exists in the community as a whole. The majority of the population belong to the wage-earning classes, and it is beyond dispute that the moral, physical, and financial condition of the masses is infinitely better now than fifty years ago. We are disposed to think that much of the failure of the later ages to participate in the improved expectation of life is due to the effects of increasing " urbanisation " and the associated increase of manufacturing and indoor occupations, with a decline in agricultural and outdoor pursuits and callings. To these considerations may be added that we are, so far as sanitation is concerned, in a transition period ; the benefits from the Public Health Acts of 1871, 1875, and 1891 not having been fully reaped, even yet. Possibly in another tAventy years the improved conditions of life will have endured sufficiently long to enable their full force and value to be determined and felt; for the present we must suspend judgment, and leave " the complete solution of the problem to a time when the statistical experience of our country is more mature." In the absence of proper life-tables, the late Dr Farr shoAved that the mean duration of life, or mean after lifetime, could be approximately calculated from the birth and death rates by the following formula, in which B = birth-rate and D = death-rate, Avhile x = the expectation of life at birth. _2 1000 1 1000 X~3X "D~+3X~TT* Say a town has a birth-rate of 32 and a death-rate of 28 per 1000, then ,. , n x 2000 1000 2000 1000 ni applying this formula, Ave get „^ + -™- or „ + - - = o4, as the mean expectation of life at birth under those conditions. Wilhch gives another formula, in which # = the expectation of life at any 2 age a, between 25 and 75 years, then : x = ^ (80 - a), and applying this, say 2 for calculating the expectation of life at 53 years of age, Ave get o(80 - 53) = x or 18 years. Life-Capital.—If we apply the figures of a life-table to the existing or estimated population of a community in groups of ages at a given period, we obtain the aggregate future lifetime of each of those populations, or, as it has been appropriately called, the life-capital of the community in that particular period or year (Tatham). Taking Manchester as an example, as we have available for that city a life-table based upon the most recent 792 VITAL STATISTICS. facts as gained at the last census, Ave are able to construct the following table :— Expectation of Life. Population. Life-Capital. Ages. Males. Females. Males. Females. Miilos. Females. 0, . . . 34*71 38-44 31,796 32,539 1,103,639 1,250,799 5, 45-59 48-06 28,622 29,444 1,304,877 1,415,078 10, 42-75 45-43 27,756 28,699 1,186,569 1,303,795 15, 38-78 41-50 25,960 27,580 1,006,728 1,144,570 20, 34-62 37-33 23,460 26,700 812,185 996,711 25, 30-69 33-38 22,632 22,695 694,576 757,560 30, 27-08 29-73 18,188 21,051 492,531 625,846 35, 23 76 26-30 17,550 18,675 416,988 491,152 40, 2068 22-99 13,724 14,167 283,812 325,699 45, 17-80 19-79 11,648 12,861 207,334 254,519 50, 15-06 16-74 9,275 10,576 139,681 177,042 55, 12-49 13-91 7,522 9,188 93,950 127,805 60, 10-16 1135 3,422 4,346 34,767 49,327 65, 8-15 9-11 2,820 3,550 22,983 32,340 70, 6-48 7-25 1,541 2,796 18,118 20,271 75, 5-11 5-76 819 1,381 4,185 7,954 85 and upAvards, 3-16 376 69 144 218 541 All ages, . 246,804 513, 266,392 7,807,441 8,979,009 Total, 196 16,786,450 These figures have a direct and an important bearing on the vital statistics of the community to which they apply ; and this may be shoAvn in either of two Avays. In the first place-----~— = average life-capital or future lifetime of each member of the population; and, in the second place, since mean population is equal to years of life expended in a year, population x 100 —i:fe car)it,al— = ProPor^lon Per cent, of life-capital expended in a year. On the basis of these calculations Ave can construct the following table in reference to the city of Manchester :— Average Life-Capital of the Population. Proportion per cent, of Life-Capital expended in a Year. Persons. Males. Females. Persons. Males. Females. 2-953 3270 31-63 33-77 3-057 3-161 This table is in reality the application of the Life-Table for Manchester to the existing population of that city. It shoAvs that so long as the age constitution remains as at the last census enumeration, and the death-rates at the various ages continue as in the decennium 1881-90, the average life- capital of the population of Manchester, taking young and old together, is 32*70 years; and that under the same conditions the ordinary expenditure of this capital per annum is 3-057 per cent. If noAV we calculate for any period the number of deaths Avhich should have occurred in each age-group at the rates of 1881-90, and compare them STATISTICAL METHODS. 793 with the deaths which actually occurred during the period, the differences between the two sets of figures will be the numbers of lives saved or lost by the fluctuations of mortahty in the given period; and by means of the resulting figures we can ascertain the gain or loss of life-capital due to these fluctuations of mortality. The gain or loss of life-capital depends not simply on the number of lives saved or wasted, but on the value of those lives to the community. Thus, say in a given community it is found that 262 lives under 5 years of age have been lost, each being Avorth from a life- table 38*3 years, while 422 lives betAveen 5 and 65 years of age have been gained worth only 22*87 years each. It is at once obvious that there will have been in this case an actual loss to the particular community of 383 years of future lifetime. This is a consideration of the very greatest importance, and adds new force to the contention that the infantile death-rate is one of the best tests of sanitary condition. Not only is it such a test, but a heavy death-rate among children represents an enormous waste of the life-capital of the population. The method here indicated in a simple form is capable of considerable extension and application, particularly if life-tables for given cities, towns, or large areas be prepared. From them it would not be difficult to compute the average years of life that will be lived between any specified ages. For instance, if 20 to 65 be taken as the Avorking period of hfe, Ave can calculate how many years of Avorking life will, on an average, be lived by children now under 5, between 5 and 10, &c. In this way Ave could estimate what may be called the working life-capital; and in the same way we could calculate the number of years of working life-capital gained or lost in any year or series of years. Considerations of space render it impossible to follow out here all the possible and practical uses to which life-tables readily lend themselves. It is sufficient to have indicated some of the most important and striking of these uses, and to have shown that, in a properly prepared life-table for its district, the sanitary authority possesses a poAverful instru- ment for statistical investigation. By its aid we can learn hoAv much of the best and most useful part of human life is wasted OAving to the life conditions of the community, and Ave can also use it as a measure of future sanitary progress or regress. Statistical Methods, and Tabulation of Mortality Facts.—The elements of statistical inquiries are individual facts, or so-called numerical units, which, having to be put together or classed, must have precise, definite, and constant characters. For example, if a number of cases of a certain disease are to be assembled in one group Avith a definite signification, it is indispens- able that each of these cases should be what it purports to be, an unit not only of a definite character, but of the same character as the other units. In other words, an accurate diagnosis of the disease is essential, or statistical analysis can only produce error. If the numerical units are not precise and comparable, it is better not to use them. A great responsibility rests on those who send in inaccurate statistical tables of disease; for it must be remembered that the statist does not attempt to determine if his units are correct; he simply accepts them, and it is only if the results he brings out are different from prior results that he begins to suspect inaccuracy. These items or numerical units being furnished to the calculator, are by him arranged into groups; that is to say, he contemplates the apparently homogeneous units in another light, by selecting some characteristic which is not common to all of them, and so divides them into groups. To take the most simple case :—A certain number of children are born in a year to a given popidation. The children are the numerical units. They can 794 VITAL STATISTICS. then be separated into groups by the dividing character of sex, and then into other groups by the dividing characters of "born alive" or "still- born," &c. Or, a number of cases of sickness being given, these numerical units (all agreeing in this point, that health is lost) are divided into groups by diseases, &c.; these groups, again, are divided into others by the character of age, &c, and in this way the original large group is analysed, and separated into minor parts. This group-building seems simple, but to properly group complex facts,. so as to analyse them, and to bring out all the possible inferences, can only be done by the most subtle and logical minds. The dividing character must be so definite as to leave no doubt into which group an unit shall fall; it must be precise enough to prevent the possibility of an unit being in two groups at the same time. The rule is of the greatest importance, and many examples could be pointed out of error from inattention to it. Statistical results are iioav frequently expressed by graphic representations, a certain space drawn to scale representing a number. The most simple plan is that of intersecting horizontal and vertical lines. Two lines, one horizontal (axis of the abscissas) and the other vertical (axis of the ordinates), form two sides of a square, and are then divided into- segments, draAvn to scale—vertical and horizontal lines are then let fall on the points marked ; the axis of the ordinates representing, for example, a certam time, and the axis of the abscissa? representing the number of events occur- ring at any time. A line drawn through the points of intersection of these tAvo quantities forms a graphic representation of their relation to each other, and the surface thus cut can be also measured and expressed in area if required, or the space can be plotted out in various ways, in columns, pyramids, &c. In the same Avay circles cutting radii at distances from the centre draAvn to scale are very useful; the circles marking time (in the example chosen), and the radii events, or the reverse. Such graphic representations are most useful, and allow the mind to seize more easdy than by roAvs of figures the connection between two conditions and events. For the medical officer of health a systematic and simple method of keeping his statistical facts is of the first importance. This is particularly the case in regard to the tabulation of the causes of death. He may append to his annual report a table of the deaths at all ages and from all causes on the model of the Begistrar-General or of those given in Appendix XII. as requhed by the Local Government Board. But for practical purposes connected Avith pubhc health, and for weekly or monthly issue, a simpler form is often preferable. Individual ingenuity wdl readily be able to draw up a suitable table, which should be divided into a few well-marked age- periods, as infancy, early and late chddhood, adolescence, early and late adult life, and old age, each of which has its several dangers to health, and social or industrial conditions. These periods would be, under 1 year, 1 to 5, 5 to 10, 10 to 20, 20 to 40, 40 to 70, and over 70. Care should be taken to give all the zymotic diseases, phthisis and the pre- ventable diseases generally in detail; under diphtheria may be grouped croup and any fatal cases of so-called putrid sore throat, but in the present day, with increased facilities for bacteriological observation, the errors in diagnosis of these cases should be reduced to a minimum ; in any case where doubt exists, a short explanatory note in the column of remarks should be given. So also "cholera" Avhen reported in the absence of an epidemic, " cholera infantum," and the so-called " dysentery," except in the case of persons returning invalided from the tropics, are best grouped VALUE OF STATISTICAL FACTS. 795 together under the heading of " diarrhoea and enteritis." Where possible, tubercular phthisis should be distinguished from the non-tubercular, but in most cases phthisis will be found most conveniently noted as a single item, while " all other respiratory diseases" may constitute a second heading. Scrofula may be included under the general term of phthisis and tuber- culosis. Syphilis should, when possible, be separately noted and efforts made to trace and clear up ambiguous cases where there is reason to suspect that this disease is the original cause of death. This is especially import- ant in regard to the congenital form, as the reported mortality from it does not represent the truth, many cases being returned as " marasmus," " tabes," &c. Diseases of the heart, kidneys, and liver, except cancer, may be bracketed in a comprehensive class of " diseases of the internal organs," Avith the omission of separate headings for so-called "dropsy " and "jaundice," these latter really being only symptoms and without importance to questions of public health. Cancers of all kinds and parts should form a single and separate group, so also should puerperal fever. Diseases of the nervous system must form a distinct heading, but it is advisable to exclude " teeth- ing " and "convulsions" from it, unless it is clear that they are not the pathological expression of gastro-intestinal derangement, the result of improper feeding. These causes of death constitute a serious source of error in infantile mortality returns, but a tactful medical officer of health can often, by judicious inquiry, obtain sufficient information to correct such returns, so as practically to allocate them to their proper position under the heading of " improper or defective feeding of infants." Some excellent statistical forms for public health purposes have been suggested and draAvn up by the Society of Medical Officers of Health. The tabular form given on page 796 has been prepared and modified from one in use in Germany by the health officials of that country. From its remarkable compactness and comprehensiveness, it appears to us to be well Avorthy of adoption in this country, and might serve as a basis for a scheme of international vital statistics. Value of Statistical Series and Averages.—We have now discussed the chief kinds of statistical material generally at the disposal of the sanitarian, but before closing the subject it is necessary to indicate the chief sources of fallacy in statistics, and the general limits within which they may be used. In an ideal mass of statistics the facts must (1) be all correctly observed ; (2) they must be of the same kind and order; (3) they must be all locahsed both in regard to time and place ; (4) they must be sufficiently numerous to give correct averages, and extend over sufficient length of time. It Avill be at once obvious that these various essentials are not easy to obtain. It has already been explained that Avhile it is easy enough to ascertain correctly the numbers of a people during the census year, it is less simple to do so during intermediate years. Similarly, differences of degree or intensity, causation or -virulence of diseases, render their comparison, by reducing their statistics to the same order and kind, extremely difficult. So, too, the importance of localising statistics, both in respect of time and place, is made clear by pointing out the absurdity of attempting to construct a particular disease- rate for some health resort from the deaths of persons occurring there from that special affection. The fourth essential for an ideal statistical series is Avell expressed in the mathematical statement that the error diminishes as the square root of the number of observations; in other Avords, the smaller the total number of facts the larger Avill be the relative percentage of errors T) h January, . February. March, April, . . May, . . June, . . July, . . August, . September, October, . November, December, Month. Illegitimates. M. 1 F. 1 T. of the Births. Fli ' | Male. S ' | Female. I | [ Total. --■ Male. o Female. Total. __ 7 ------ ct> >s — cy , o 1 (3 — s» a. . 2, ---- c+ ___ CD 1 *ti __ o , ^ 1 B i P* 5* _ o _ 5 i C --- (T 1 P 1 ^ -— — 1 Legitimate. o o S Illegitimate. 1 | Legitimate. n *o B i 5 i"1 1 | Illegitimate. ' | 6-15 Years. ' 16-20 Years. ' | 21-30 Years. 1 | | 31-40 Years. 1 | 41-50 Years. I | 1 51-60 Years. 1 | 61-75 Years. I 1 j Over 75 Years. ~---- — I 3 O 1 o o 1 1 | | ----- — 1 ci ' 1 — --------- o » CD 5° £x 3 ----- — ' 1 1 Accident. ^ 1 | Suicide. — Homicide. ;/ "■ ~ !■ | Uncertificated Deaths. | Death-Rate per 1000 on the | Estimated Monthly Population. 1 Mean Estimated Population for the Year. 'SOIISIXVIS TVXIA 96Z MEANS OR AVERAGES. 797 displayed by them, and the larger the number of facts collected the smaller will be the margin of error. There being a number of facts, each of which can be expressed by a numerical value, an average or mean number is obtained by adding all the numerical values and dividing by the number of facts. The mean or average is really a number which lies between the highest and lowest of a series of numbers, and has a definite dependence upon the whole of the series. The terms, mean and average, are often used synonymously ; regarded mathematically, there are several kinds of means. Thus, the simple average, or arithmetic mean of four numbers, such as a, b, c, d, is conveniently . a+b+c+d _____ written as -----^----, but their geometric mean would be tfabcd, while ________4 their harmonic mean stands thus : 1 1 1 17 and their quadratic abed a2 + 02 + c2 + d2 mean is— k/ t Of course, if the terms of the series of numbers are unequal, then the quadratic mean will be the highest, next the arithmetic, and then the geometric and harmonic means; but if all the terms of the series are equal, then their means are equal too. The chief practical question in vital statistics is not so much either the value of a true or pure average, or arithmetical mean, or even the probable value of a fixed quantity, but rather the probable value of an average or variable quantity ; the question being in most cases, how far the mean is a trustworthy approximation to the true value sought. Its degree of approximation may be determined by Avorking out the mean and probable errors ; the smaller the latitude of error the more trustworthy the series from which the mean number is drawn. The mean error, that is, the divergence of the individual terms of the series from its mean, is conveniently performed in the following Avay : (1) find the mean of the series, then find the mean of all the observations above the mean, and subtract the mean from it; this gives the mean error in excess; (2) find the mean of all the observations below the mean and subtract it from the mean; this gives the mean error in deficiency. Add the two quantities, and take the half; this is the mean error. It will be at once obvious that the greater the mean error the greater is the need for the series to be extended, in order to compensate for the unreliability of each term of the series; and that the value of any series of observations increases with their number and with their equality. The probable error of a mean result may be conveniently obtained by apphcation of the following rules as given by Jevon :— 1. Draw the mean of all the observed results. 2. Find the excess or defect, that is, the error, of each result from the mean. 3. Square each of these reputed errors. 4. Add together aU these squares of the errors. 5. Take the square root of the sum. 6. Divide the square root by the number of results. 7. Multiply the quotient by 0*67449, or by f. Thus, suppose of the series 21, 32, 27, 25, 18, 33, Avhose mean is 26, we Avant to know the probable error of that mean. Now, the apparent errors of each number of the series from the mean are 5, 6, 1, 1, 8, 7; their 798 VITAL STATISTICS. squares are 25, 36, 1, 1, 64, 49 ; and the sum of the squares is 176. The nearest square root in Avhole numbers of this sum is 13, and this, divided by 6, or the number of the series, gives 2*16, which, multiplied by the factor 0*67449, yields 1*45 as the probable error of the mean of the series. This calculation of the probable error may be described in another way, by saying that it is the error of mean square multiplied by the mathematical constant0*67449. The error of mean square is the quadratic mean of the apparent errors, or the result of dividing the square root of the sum of the squares of the apparent errors by the number of terms. To compare two or more similar groups together, the probable error of each may be first ascertained, then the relative values of each Avill be as the reciprocals of the squares of the probable errors; that is -,—p, where (pe) is the probable error. Thus, if we have two groups, A and B, A having a probable error of 10 per cent, and E one of 2 per cent., the value of A will be ^2 = ^xt;- and the value of B will be -^ = -j-, or the group B Avill have a value 25 times as great as A. The relative values of two or more series are also as the square roots of the numbers of units of observation. So also, by increasing the number of observations in any inquiry, the value (or accuracy) increases as the square root of the number. Thus a group of 10 observations is to a group of 100 as >/l0 to J100, or as 3*16 to 10. In many cases the method by successive means is very useful. This con- sists in taking the mean of the mean numbers successively derived from a constantly repeated series of events (say the mortality to a given population yearly). Supposing, for example, the annual mortality in England to be, in successive years, 22, 23, 21, 26, 23, 21, 22, 28, 22, 21 per 1000 living, the successive means would be— 22 + 23 22 + 23 + 21 22 + 23 + 21 + 26 2 3 ~^T~ —' and so on, until the numbers are so great as to give every time the same result. It is useful to calculate the successive means in both the direct and inverse order, viz., from first to last, and then from last to first, i.e., putting the two last together, then the three last, &c, so as to see if the variation was greater at the end of a series than at the beginning. The degree of uncertainty is then the mean variation between the successive means. A plan almost the same as this has been used; a certain number of facts being recorded, the sum is divided into two, three, or more parts, and it is then seen whether the results drawn from the lesser groups agree with that drawn from the larger group and with each other. If there is any great difference of results, the numbers of the lesser groups are not sufficient. In the instance given above, the mean of the ten years is 22*9; the mean of the first three years is 22; of the second three years is 22*33; of the third three years is 24. The term of three years is therefore far too short to allow a safe conclusion to be drawn. The mean of five years again is 23, and of eight years is 22*8, numbers which are much nearer each other and the mean of the whole ten years. "What is known as Poisson's formula is very frequently employed to determine the liabihty to error in vital statistics. Thus, say 500 persons BIBLIOGRAPHY AND REFERENCES. 799 are sick with a certain disease, and 165 of them, or 33 per cent., have died, and it is required to know whether these numbers are sufficiently great to say that this mortality rate is approximately constant and reliable for the particular disease in question; or whether the figures are too small to accept this death-rate as correct. Poisson's formula says if y, = the total number of observations, made up of m in the direction of recovery, and n in the direction of death, then m + n = y,; and that the true proportion of each group to the whole number of cases will be in the proportions represented by the formula — +------g----- In the case cited, the probability of recovering is represented by — or ——- [A 100 n 33 and of dying by — or —-. J s J tL 100 The possible error is expressed by the second part of the formula ~^^-—-----, and the smaller will be the value of this possible error the y,A larger the total number of cases, or y. A , . .i . x- * 4.1 t i *. 2\/2 x m x n 2>j2 x 67 x 33 Applying this portion of the formula, Ave get -----------= _-----.------ y y6 = 0*1330 to unity, or 13*3 per cent., as the probable error—a figure which is very high, and suggestive of the vieAV that the number of cases is too few for us to accept the mortality rate of 33 per cent, as found, as being approximately correct. The application of averages or means, when obtained, it will be seen, are of great importance, but only Avhen founded on a sufficient number of cases. There is always a danger of attaching too much value to means or averages, forgetting how great a range there may be above and below them, and it is by reminding us constantly of this that calculations of the mean and probable errors, as well as the use of Poisson's rule, are so useful. In addition to averages, it is always desirable to note extreme values, that is, the two ends of the scale of which the average is the middle. To use Guy's pointed expression, "averages are numerical expressions of probabilities; extreme values are expressions of possibilities." BIBLIOGRAPHY AND REFERENCES. Ansell, Statistics of Families, Lond., 1874. Block, Traite" de Statistique, Paris, 1878. Bristoave, "The Mutual Relations of the Birth-rate and Death-rate," St Thomas's Hospital Reports, vol. vii., 1876. De Chaumont, Lectures on State Medicine, Lond., 1875. De Morgan, An Essay on Probabilities, and on their Application to Life Contingencies and Insurance Offices, Lond., 1838. Farr, Vital Statistics, a Memorial Volume of selections of Avritings, edited by Noel Humphrevs for the Sanitary Institute, Lond., 1885 ; also English Life-Table, No. 3, Lond.,"1864. e readily collected. In some places it has been found an advantage to have on the floors of workshops and elsewhere quantities of tin-fod or other metal, which, by readily forming an amalgam, reduces loss by waste and also lessens the danger of volatilisation. Phosphorus, both as white phosphorus and in its amorphous (red) form, is used on an enormous scale in various manufactures. For industrial purposes phosphorus is prepared from bone-ash, the latter being decom- posed by sulphuric acid, sulphate of calcium being formed. Most of the phosphorus is found in the liquid as superphosphate of calcium. The liquid is evaporated to the consistence of a syrup, then mixed with one- fourth its weight of charcoal, and dried by heating in an iron vessel. The resulting dry mass is heated to redness, half the phosphorus distils over and is collected into the Avater, while the other half remains combined Avith calcium in the retort as pyrophosphate. At this stage the phosphorus is impnre, containing compounds of arsenic, carbon, sulphur, silicon, and red amorphous phosphorus. It is subsequently purified by either pressing, when heated under hot water, or by chemical treatment with bichromate of potassium and sulphuric or nitric acids. It is usually sold in the form of sticks, the melted phosphorus being sucked into glass tubes. The red or amorphous phosphorus is formed by heating phosphorus in a closed vessel. It consists of red scales, Avhich do not become ignited on coming in contact with the air until it reaches a temperature of 260° C. or 500° F., Avhen it becomes reconverted into the ordinary form. This red phosphorus is largely used in the preparation of " safety" matches. During the purification of phosphorus arseniuretted and sulphuretted hydrogen, also phosphuretted hydrogen and phosphoric anhydride, are given off in large quantities. Hence great precautions need to be taken by work- men to avoid risks involved in the inhalation of these fumes. The manufacture of red phosphorus may lead to the development of similar •oases owing to the impurities in the phosphorus which is used for conversion into the red form. The most obvious sanitary precaution in all these operations is the careful closing of the digester, the making of it air-tight, and the exercise of care during opening to avoid the escape of the noxious fumes. The chief business in which phosphorus is employed is that of making matches. After being cut to the required shape and size, the wooden stems 816 OFFENSIVE TRADES. of the matches, to the number of from 3000 to 6000 at a time, are fixed in a frame, are Avarmed on a hearth and then dipped to the required depth into melted sulphur, whose temperature is not much above 235° F. By giving the frame a shake, superfluous sulphur is removed; the sulphur-tipped stems are next dipped into the igniting material; this material is formed of white phosphorus, which should not amount to more than 8 per cent, of the mass, though in England the proportion is usually much larger, melted under hot water and mixed with oxidising materials (such as peroxide of manganese, nitrate of potassium, htharge, or even chlorate of potassium), and some kind of material to fix it on the match (usually glue or gum), and some colouring- matter (such as umber, aniline colours, or ultramarine) ; this mixture is used either hot or cold. Subsequently the matches are left in the frames in warm air (85° F.) until they are quite dried, Avhen they are taken out of the frames, and made up in bundles or put direct into boxes. In "safety" matches, the red phosphorus which is employed for them is contained in the rough rubbing substance on the box, and not in the igniting material on the match-heads. This igniting material is fixed by glue to the matches, and is composed of chlorate of potash (10 to 40 per cent.), iron pyrites, peroxide of manganese, poAvdered glass, sulphide of antimony, and some adhesive matter, such as glue. The dangers attending the purification and distillation of phosphorus have been mentioned. The storage and carriage of phosphorus demands care. It should ahvays be kept in glass or stoneware vessels contain- ing water, and be placed in cool chambers away from all risk of breakage. For transport, all the vessels should be provided with handles, and be invariably labelled to show which is the upper side. As might be expected, the operations of match-making are by no means free from danger. This arises from the presence of phosphorus in the match-heads, and from the sulphur employed as a medium between it and the wood. Owing to the constant evolution of sulphurous acid, the pans in which the sulphuring is done should be covered with a proper lid, and be provided with a pipe to conduct the fumes into a tall chimney. Owing to the danger of explosion, the preparation of the igniting material must be conducted in proper vessels heated by steam or water, with air-tight covers, means of carrying off offensive vapours, and safety-valves for the ready escape of gases suddenly produced. The removal of the finished matches from the frames, the making of them into packets, and the placing in boxes, all involve risks of ignition. The need of great caution in these operations is manifest, and vessels of water should always be close at hand. The sanitary precautions required in this business are the provision of large roomy workshops Avith good ventilation, assisted by fans or flues, and the exercise of extreme personal cleanhness, especiaUy before partaking of food. The same clothing should not be worn at home as in the workshops. The hours of dangerous labour should be reduced to a minimum consistent with industrial economy. The inhalation of turpentine vapour, to favour oxidation of the phosphorus, and the Avashing out of the mouth with weak alkaline solution of carbonate of sodium or lime-water and charcoal are all to be recommended. As a substitute for turpentine, an aqueous solution of copper sulphate may be employed, as it precipitates the phosphorus as a phosphate, along with metallic copper. Charcoal is of value as a powerful absorbent of phosphorus. Fortunately, owing to an adequate recognition of the dangers attending the making of matches and other industries in which phosphorus is em- ployed, poisoning by this element is by no means common now in this HORSE-HAIR FACTORIES. 817 country. The complete suppression of the use of white phosphorus is the surest preventive. Zinc is chiefly met Avith either as a carbonate (calamine), or as a sulphide (blende), or as a red oxide, the colour of which is due to mixture with oxides of iron and manganese. Zinc is not absorbed by the skin, and its effects are limited to absorption of its vapour by inhalation, or inhalation of the dust. Zinc vapours are largely given off during extraction of the metal from its ores, also during the preparation of " galvanised " iron sheets for roofing, of galvanic iron wire, and the preparation of alloys. Iron is " galvanised" either by dipping it into molten zinc, and covering Avith a layer of sal-ammoniac Avhich dissolves the oxide which forms on the zinc; or by first coating the iron with tin, by galvanic action, and then dipping in molten zinc. Galvanic zincing is performed by placing the metal to be galvanised in a zinc bath filled with a saturated solution of sulphate of zinc. Brass and copper are sometimes zinced. Zinc is much used as an alloy; thus, brass consists of equal parts of zinc and copper; and German silver is merely brass to which some nickel has been added. Zinc dust is created in large quantities in the grinding of the oxide, and every precaution is needed to carry out this operation in suitable closed chambers, and to protect workmen by respirators. The proper con- densation of all zinc vapour is imperative, combined with vigorous ventila- tion to free the workrooms from it. The symptoms following exposure to the action of vapour of zinc are,— cough, difficulty of breathing, headache, giddiness, stiffness in the limbs, sickness, and vomiting. Excessive perspiration is not infrequent. The cohc and itching of the skin which is frequently observed in persons ex- posed to zinc dust is often due to the action of impurities, especially of lead or of arsenic. Apart from this, however, zinc powder may mechani- cally cause irritation. Manufacture of Horse-hair.—A large industry exists for the preparation of hair for mattresses, chairs, brush-making, &c. The hair so used is not limited to that of the horse, as cow and pig-hair are also employed. The manes and tails of horses and the tails of cows are the parts chiefly used. Except the best quality of horse-hair, all these are more or less filthy and dusty, from the intermixture of dung, pieces of skin, and earth. The first procedure is to sort the hair into the long and short, the coloured and the Avhite; usually this is a very dusty operation. The hair is then washed, and AAdien dry is combed; this latter process removes the short hairs which have been previously overlooked. The long Avhite hairs are bleached by exposure to burning sulphur in a closed chamber; the long coloured hairs are dyed, usually black, with log- wood and protosulphate of iron. The short hairs are sometimes dyed and sometimes not. If very dirty they are teazed and dusted in a " winnowing " machine; the resulting fine dust is commonly discharged into the air instead of into a furnace flue; the heavier dust is utilised for manure. The short hair Avhen dyed is commonly so treated with the dirt on ; sometimes it is AvinnoAved first. The hair is curled by being twisted into a sort of rope by a curling machine, it is then steeped in cold Avater, and on removal placed in ovens at a high temperature, after which the curl is permanent. The chief sources of nuisance in connection with hair-works are the stench from the vapours of the dye-vat, and from the hot liquor discharged into drains. The statutory limit of temperature, above which liquids are inadmissible into seAvers, is 110° F. The only remedy against the stenches 3f 818 OFFENSIVE TRADES. from the dye-vats is the use of a water-sealed lid, Avith hood and a flue conducting the vapours into a scrubber or cold-Avater tank. Mere discharge into a chimney is rarely effective against annoyance, unless the chimney is very high, say 150 feet. As regards the nuisance from the discharge of hot hquors into drains, the only remedy is not to so discharge them until cold. Another evil in connection with this industry is the possibility of infec- tion with anthrax. It is due to infection by means of virus attached to the hair from animals which have suffered from the disease, and is practically identical with the subject of the succeeding section upon Avool-sorting. Wool-sorting.—A wool-sorter is a person AAdio divides the wool of a fleece into " sorts" or classes of various qualities, that is, the coarser and finer portions are placed apart in separate bundles. In connection with the woollen industry this sorting constitutes an important form of labour. When a dry, dusty material is being sorted, such as mohair, alpaca, and camel's hair, there is always much dust in the air of the sorting-room; but when sheep's wool is being sorted, OAving to the greasiness of the fleece, this is not the case. The sorting of avooI is usually performed over a mov- able wire grating covering an opening, through and into Avhich dust and the other fine matter falls. Dust is generated not only during the actual sorting of wool, but also during the opening of bales or other large packages of wool. OAving to the prevalence of anthrax, malignant pustule or charbon among certain animals, a great liabihty to the infection of this disease exists among herdsmen, skinners, slaughtermen, unloaders of cargoes of hides, and the manipulators of various wools and hairs. In this respect, the most dangerous wools imported into this country are those from the districts around Lake Van and from Persia. There is liability to infection by the spores and bacilli of anthrax in any of three Avays—either by inocu- lation through wounds of the skin, by swallowing, or by inhalation. In serious cases a fatal termination may result in twenty-four hours, and is rarely postponed beyond three to four days. In other cases the attacks are relatively slight. As illustrating the sanitary precautions necessary in the conduct of this business, the folloAving regulations modified from those originally drafted by Hime, and adopted by the ToAvn Council of Bradford, may be conveniently quoted in this place :— 1. All bales of wool or hair shall be opened by some person skilled in judging the condition of the material. If he find the contents unobjectionable, they shall be sorted in the ordinary way. If, on opening any bale, dead or fallen fleeces or damaged materials are found, such bale shall be at once taken from the room where opened, and dealt with as noxious. All Van, Persian, damaged wool, fallen fleeces, and foreign skin, wool, or hair shall be deemed noxious, and shall not be opened in the sorting-room. All wool or hair shall, before sorting, be thoroughly saturated with water and then washed in hot suds, rolled and sorted while damp, or if steeping would be injurious to the article, then it shall be disinfected. 2. InTo noxious material (alpaca, pelitan, or East Indian cashmere) shall be opened in the sorting-room, but in a place specially set apart for the purpose, separate and distinct from the sorting-room, and all such material shall be opened over a fan by some person capable of judging the condition of the material. 3. The sorting-rooms for all dry and dusty materials shall be provided Avith extract- ing fans so arranged that each sorting board shall be independently connected with the extracting shaft, in order that the dust arising from the material being sorted may be drawn horizontally or downwards, and thus prevented from injuring the sorter. 4. The dust collected by the fan must not be discharged into the open air, but be received into properly constructed catch-boxes. It must be afterwards burnt. The WOOL-SORTING. 819 catch-boxes should be emptied at least tAvice a week. The sweepings from floors, walls, and from under the wire gratings or " hurdles " shall be similarly treated. All pieces of dead skin, scab, and clippings must be removed weekly from the sorting-room, and must not be dealt with or sold until they have been disinfected. 5. All bags or coverings in which wool or hair has been imported shall be picked clean and not brushed, and;such bags shall not be sold or used for any other purpose until they have been disinfected. 6. No sorter having any exposed open cut or sore upon his person shall be allowed to sort. 7. A suitable room, outside the sorting-room, shall be provided in which the sorters can leave their coats during working hours. 8. Proper provision shall be made for the keeping of the sorters' food out of the sorting-room. No meals shall be taken in the sorting-room. 9. The sorting-rooms shall be well ventilated, by fans or otherwise ; but as this can- not be effectually accomplished by open windows only, power shall be employed to secure downward or horizontal ventilation, so arranged as to protect the workmen from draught. The sorting-rooms shall be warmed during cold weather. Windows shall be kept open during meal hours. 10. No wool or hair shall be stored in the sorting-rooms. 11. The floor of the sorting-room shall be thoroughly sprinkled with a disinfectant, so as to allay dust, and swept daily after work is over. The sorting-room shall be thoroughly disinfected and the walls thereof limewashed at least once a year. 12. Requisites for disinfecting and treating scratches and slight wounds should be at hand in the sorting-room. 13. Proper provision shall be made for the sorters to wash in or near the sorting- room. 14. A copy of these precautionary regulations shall be hung up in a conspicuous place in every sorting-room. CHAPTER XVIII. SANITARY LAW. In this chapter it is proposed to summarise and review the most impor- tant features of the law in respect of the chief matters which concern the public health. While the main basis of so-called sanitary laAv as now in force in the different parts of the United Kingdom are the various Public Health Acts of 1867 (Scotland), 1875 (England and Wales), 1878 (Ireland), and 1891 (London), there are in addition a large number of other Acts of Parliament Avhich, in various ways, strengthen or otherwise modify the foregoing. This condition of affairs naturally renders the whole subject of sanitary law a matter of some complexity. In the following pages we have deemed it more convenient rather to consider the general effect of these various legislative enactments, as a whole, upon each sanitary matter of importance, than to analyse each Act separately. At the same time, under each section of the subject, references will be made to the peculiarities of the legislation in force in the different parts of the kingdom; that is to say, hoAv far the law, as affects England and Wales, differs from that in London, and how far that of Scotland and Ireland differs from either, both, or each other. By this arrangement, it is hoped that a comprehensive view may be obtained, consistent with the space at our command, of the general bearing of the laAv in respect of sanitary matters in all parts of the United Kingdom. The essential and primary element in the administration of the sanitary law is the division of the country into sanitary areas, each of which is controlled by a " Sanitary Authority." Before considering the powers and duties of these authorities in connection with the public health, it will be more convenient, in the first instance, to explain their nature and areas of authority, and, secondly, to consider what are the statutory provisions with reference to the appointment by them of Medical Officers of Health, Surveyors, and Inspectors of Nuisances, and the general scope of the duties of these sanitary officials. LOCAL SANITARY AREAS AND AUTHORITIES. In England and Wales.—The whole of England and Wales outside the city of London is divided into (a) administrative counties, and (b) county boroughs. By the Local Government Act, 1894, the administrative counties are divided into county districts, some of which are urban, and others rural districts. For sanitary administration the county boroughs are deemed to be urban districts, and, with the other urban districts, constitute urban sanitary districts; while the rural districts, each consisting of one or more parishes, are rural sanitary districts. LOCAL SANITARY AUTHORITIES. 821 In every administrative county there is a County Council, who may appoint one or more Medical Officers of Health for the county, and who have various other poAvers and duties in connection with the sanitary super- vision and administration of the county, more particularly of complaining under section 299, Public Health Act, 1875, in cases where a Sanitary Authority is not doing its duty, and of enforcing the provisions of the Rivers Pollution Prevention Act. They have also considerable poAvers under the Isolation Hospitals Act, 1893, and as appeal authorities under the Local Government Act, 1894. In county boroughs the mayor, aldermen, and burgesses, acting by the council, constitute the urban Sanitary Authority. In all other boroughs, the same, acting as the Municipal Council, become, for sanitary purposes, an urban District Council, and as such are an urban Sanitary Authority. In urban districts, other than county and municipal boroughs, the District Council constitutes the Sanitary Authority; but they may appoint com- mittees, consisting either wholly or partly of their members, for the exercise of sanitary powers; but no such committee will hold office beyond the next annual meeting of the District Council, and the acts of every such committee must be submitted to the council for their approval (Local Government Act, 1894, section 56). Similarly, in rural districts the District Council is the rural Sanitary Authority. Where the number of councillors of any such district shall be less than five, the Local Government Board may, by order, nominate such number of persons as are necessary to make up that number from owners or occupiers of property situated in the rural sanitary district. The persons so nominated are entitled to act and vote as members of the rural Sanitary Authority, but not further or otherwise. An alternative procedure is for the Local Government Board to order the affairs of the district to be administered by the District Council of an adjoining district in another county Avith which it may or may not have been united before the passing of the Local Government Act, 1894 (see section 24). Each rural District Council has all the powers, duties, and habilities as a rural Sanitary Authority as were exercised by the old Boards of Guardians. They have also the same powers for appointing committees as have the District Councils of urban dis- tricts other than boroughs (Local Government Act, 1894, section 56). The Local Government Act, 1894, creates new authorities in the shape of Parish Councils in every rural parish which has a population of 300 or more. Also, by order of the County Council, providing the "Parish Meeting" so resolve, a Parish Council may be established in any rural parish having a population of 100 and upwards, and, Avith the consent of the Parish Meeting in any rural parish having a population of less than 100. Also, with the consent of the respective Parish Meetings, neighbouring parishes may be grouped under a common Parish Council, but with a separate Parish Meeting for every parish so grouped. Although, by the Local Government Act, 1894, section 8, some feAv sanitary powers are possessed by Parish Councils, such as the utilisation of wells, springs, streams within its parish, and poAver to drain, clean, cover, or remedy the condition of ponds and stagnant pools, also to acquire or hire land for allotments, make official representation to the District Council under the Allotments Act, or to the Medical Officer of Health under the Housing of the Working Classes Act, or to the Local Government Board for granting of urban provisions to their parish or any part of it, these poAvers in no Avay derogate from the sanitary obligations of a District Council, which is the true rural Sanitary Authority. 822 SANITARY LAW. The Parish Council may complain (section 16) to the County Council if the rural District Council have faded to provide or to maintain sufficient drainage or water-supply for the parish, or to enforce any provision of the Public Health Act, and in that event the County Council may take over to themselves the poAvers of the District Council for the purpose, or may make an Order for the necessary works to be carried out by the District Council, or by some person appointed by the County Council. Apart from expendi- ture under adoptive Acts, a Parish Council must not incur expenses involving more than a 6d. rate in any year, nor more than a 3d. rate without the consent of the Parish Meeting. They may raise money on loan, but only with the approval of the Parish Meeting, the County Council, and the Local Government Board. The Parish Meeting has the exclusive power of adopting certain optional Acts, including the Burial Acts, 1852 to 1885, the Baths and Wash-houses Acts, 1846 to 1882, the Lighting and Watching Act, 1833, and the Public Improvements Act, 1860. In large rural districts the District Council may appoint parochial committees for outlying parishes to act as a resident subordinate authority, and as its agents in the exercise of the powers delegated to them. If such exist, the members of these committees must be selected from the members of the Parish Council. These parochial committees are completely under the control of the rural Sanitary Authority which made them, and have no jurisdiction beyond the places for which they were respectively formed. By section 15 of the Local Government Act, 1894, a rural District Council may delegate to a Parish Council any power which it may delegate to a parochial committee under the Public Health Acts, and thereupon those Acts wdl apply as if the Parish Council were a parochial com- mittee. The duties which, in the opinion of the Local Government Board, may properly be assigned to a parochial committee are:—(1) Inspection of their district periodically as to need of works of construction, and the presence or abatement of nuisances; (2) Superintendence of works of repair or con- struction ; (3) To inquire into and report upon nuisances; (4) To examine and certify all accounts relating to expenditure within their district; (5) To report to the rural Sanitary Authority on all matters requiring attention, and upon the manner in which their officers and servants have discharged their duties. Although the powers conferred on urban and rural Sanitary Authorities are in many respects identical, they are not invariably so. By section 276 of the Public Health Act, 1875, the Local Government Board may, on application of a rural Sanitary Authority, or-of persons rated to the relief of the poor, whose assessments amount to one-tenth of the nett rateable value of the district, declare, by order, any provision of that Act in force in an urban sanitary district to be in force in such rural sanitary district, or part thereof. In like manner, the Private Street Works Act, 1892, and the Public Health Acts Amendment Act, 1890, may be put in force in the whole or part of any rural sanitary district. In amplification of the fore- going, by section 25 (7) of the Local Government Act, 1894, similar powers may be exercised by the Local Government Board, on application of a County Council, Or with respect to any parish or part thereof on application of the Parish Council. Experience has shown that the provisions of the Public Health Act hitherto most frequently put in force are, sections 42, 44, 157, and 158, relating to cleansing and watering of streets, and making of bye-laAvs as to nuisances and neAv buildings. Other sections which are LOCAL SANITARY AUTHORITIES. 823 occasionally put in force are 112 and 114, relating to offensive trades, and 169, 170, which regulate the sanitation of slaughter-houses. «? °rde^ t0 simPlify sanitary administration, the Local Government Act, 1894, section 36, requires every County Council to make such orders as will cause— (1) The whole of each parish, and, unless the County Council for special reasons otherwise direct, the whole of each rural district, to be within the same administrative county. (2) The Avhole of each parish, unless the County Council for special reasons otherwise direct, to be Avithin the same county district. (3) Every rural district which has less than five elected councdlors, unless the County Council for special reasons otherAvise direct, to be united to some neighbouring district or districts. After March 5, 1896, these powers of the County Council pass to the Local Government Board. The constitution of neAv boroughs can only be made by the grant of a charter by the CroAvn, on the advice of the Privy Council: notice of appli- cation, however, must be sent to the County Councd and the Local Govern- ment Board (Local Government Act, 1888, section 56). In London.—While the Public Health Act, 1875, and the Acts passed from time to time amending it, form the basis of the greater part of the sanitary law in the provinces, comparatively few sections of these Acts apply to the metropolis. Among the sections Avhich do apply are sections 108 and 115, relating to the abatement of nuisances ; sections 130, 134, 135, and 140 (as amended by section 2 of Public Health Act, 1889), relating to powers of the Local Government Board with respect to cholera and other infectious diseases ; also sections 182 to 186, relating to bye-laws; and section 336, defining the relations of new Sanitary Authorities to completed sewage AA^orks of the old Metropolitan Board of Works. In the rest of England and Wales it has been shown that there is prac- tically one Sanitary Authority acting for each district. In London, with the exception of the Port of London which is under the City Corporation, there is no part where there is not more than one public body exercising the functions of a Sanitary Authority. It is impossible in this Avork to give a full account of the powers and duties exercised by such diverse bodies as the County Council, the Metropolitan Asylums' Board, the Corporation of the City, the Commissioners of Sewers of the City, the Vestries, the District Boards, the Woolwich Local Board of Health, the Police Commis- sioners, and the Commissioners of Baths and Workhouses. By the Public Health (London) Act, 1891, section 99, the authority, hereafter called the Sanitary Authority, is (a) in the city, the Commissioners of Sewers ; (b) in the parishes of Schedule A. of the Metropolis Management Acts, 1855 and 1885, the Vestry, except in Woolwich, where it is the Local Board of Health; (c) in the districts in Schedule B. the District Boards ; and (d) in places in Schedule C. the Guardians, or, if there be none, the overseers for such place, defraying their expenses as if they Avere poor-rates. In Scotland.—Every burgh is a separate area for public health purposes. Of the rural or " landward " parts of Scotland, the primary di-vision is the county, which again is divided into parishes, which, as a rule, are much larger than in England. These parishes are in most counties diA'ided into groups, knoAvn as County Districts, and each district is a unit for highway and rural public health administration. There are, on the average, about four districts in each dhdded county, and about eight parishes in each county 824 SANITARY LAW. district. The boundaries of a district may be altered from time to time, but a parish may not be partly in one county district and partly in another. In counties not divided into districts, the public health area of adminis- tration is the county, Avhich of course in this connection does not include the burghs comprised Avithin its geographical.limits. Eight Scottish counties are undivided. By the Local Government (Scotland) Act, 1894, the central public health authority in Scotland is the Local Government Board (Scotland). In each burgh the provost, magistrates, and town council, acting as " Burgh Com- missioners," are the local authority for public health purposes, and as such exercise the powers conferred by the Public Health (Scotland) Acts on a local authority, and by the Burgh Police (Scotland), Act, 1892, on burgh commissioners. In the landward or rural districts the pubhc health authority, where a county is undivided into districts, is the County Council, acting together Avith one representative from the Parish Council of each parish in the county. Where a county is divided into districts, the local authority is the District Committee, consisting of the county councillors and of one representative from each Parish Council within the district. In divided counties, certain powers are reserved to the County Council, namely, the appointing of a Medical Officer of Health and Sanitary Inspector, also representing matters to the Local Government Board, and making bye-laws, regulations, and levying rates. The County Council, in addition to the District Committee, has power to enforce the provisions of the Rivers Pollution Prevention Act. County Councils and District Committees may appoint sub-committees to exercise their public health functions. In some counties, a sub-committee is appointed for each parish. By section 44, Local Government (Scotland) Act, 1894, District Com- mittees can constitute special districts in landward areas for lighting, scavenging, and provision of baths, wash-houses, and drying grounds. The cost of these services fall upon the special district, and is limited to a rate of ninepence in the pound. Though the same Act abolishes the old parochial boards, and constitutes in their place in each parish a Parish Council, this body has no important duties of sanitary administration. There is nothing in the Scottish Statutes on the lines of section 276 of the Enghsh Public Health Act, 1875, or of section 25 (7), Local Government Act, 1894, with the result that there are no means of conferring burghal powers on landward local authorities, except by the constitution of a new police burgh, whereby the authority of the District Committee ceases, and the burgh is for most purposes taken out of the county, to be henceforth governed by elected commissioners. It is anticipated that the application of section 44 of the Scottish Act of 1894, above mentioned, will largely remove the disabilities attaching to the older and somewhat inelastic provision. By the powers described, part of a landward sanitary area may be con- verted into a burghal area. By order of a County Council, however, the area of a whole landward district, that is, a county district, may from time to time be altered ; and this even Avithout reference to a central authority. The Secretary of State for Scotland is, however, apprised of the formation of any new police burgh. In Ireland.—The public health administration in Ireland is governed mainly by the provisions of the Pubhc Health Acts of 1878 and 1890, and the special Orders issued by the Local Government Board for Ireland in pur- suance of the first of these Statutes. Though many of the urban areas are under the Act of 1878, still a great number are governed by special Acts, LOCAL SANITARY AUTHORITIES. 825 particularly the Towns Improvement (Ireland) Act, 1854, and the Towns Improvement Clauses Act, 1847. It would be a great advantage if the various Acts bearing upon public health administration in Ireland were con- solidated. In the main, the Irish Act of 1878 is;draAvn on the lines of the English Act of 187o, but there are some differences in the provisions, as will be seen subsequently. By the Public Health Act, 1878, the whole of Ireland is divided into (a) urban sanitary districts, and (b) rural sanitary districts, and each district is subject to the jurisdiction of a Sanitary Authority. Urban sanitary districts consist of: — 1. The city of Dublin. 2. Toavus corporate (except Dublin). 3. Town of Carrickfergus, which has Municipal Commissioners under the Municipal Corporations Act (Ireland), 1840. The foregoing are boroughs Avithin the meaning of the Act of 1878, and the boundary of each urban sanitary district is conterminous Avith the borough boundary. 4. Eight toAvns under the Lighting of Towns (Ireland) Act of 1828. 5. ToAvns under the Towns Improvement (Ireland) Act of 1854. 6. Twelve towns under various local Acts. _ 7. Towns which have been constituted urban sanitary districts by Pro- visional Orders of the Local Government (Ireland) Board, and confirmed by Parliament. The rural sanitary districts are those portions of a poor-law union which are not included in an urban sanitary district. There are 159 of these rural sanitary districts in Ireland. In the various urban sanitary districts, above detailed, the urban Sanitary Authorities are the Corporations of the city of Dublin and of the corporate towns, and the various town or municipal commissioners of the other town- ships. These urban Sanitary Authorities have the same power as similar bodies in England to form and appoint committees. By section 6, Public Health (Ireland) Act, 1878, the guardians of the union as a corporate body are constituted the rural Sanitary Authority. These rural Sanitary Authorities cannot delegate their powers to committees. By an unfortunate omission in the Irish Act of 1878, no power is given to the Local Government Board to invest a rural Sanitary Authority in Ireland Avith urban powers. An exception exists in the case of a lapsed urban district, Avhich, on becoming absorbed as part of the rural sanitary district in which it is situated, may, by order of the Local Government Board, be declared subject to any provisions of the Pubhc Health (Ireland) Act, 1878, applicable to an urban district, the rural Sanitary Authority, so far as that particular area, being invested Avith the powers, duties, and obligations of an urban Sanitary Authority. The Irish Local Government Board may also, by Provisional Order, separate from a rural district any municipal toAvn or district Avholly situated therein, Avhether the population be more than 6000 or not, and constitute it an urban sanitary district; or include any such toAvn or district in an adjoin- ing urban sanitary district. The Local Government Board may also add any town, constituted an urban sanitary district, to the rural sanitary district in which it lies. No such provisional order may be made except on petition from one or other toAvn or district, nor, in the event of objection, until after due local inquiry. The Provisional Order is of no force unless and until it is confirmed by Parliament. 826 SANITARY LAW. MEDICAL OFFICERS, SURVEYORS, AND INSPECTORS OF NUISANCES. In England and Wales.—Section 189 of the Public Health Act, 1875, requires every urban Sanitary Authority to appoint one of each of these* officers, and provides that the officers so appointed are to be fit and proper persons. A rural Sanitary Authority is not requhed to appoint a Surveyor, but by section 190 of the same Act must, from time to time, appoint fit and proper persons to be Medical Officers of Health and Inspector of Nuisances ; the latter may also be the Surveyor. No special power has yet been given to County Councils to appoint county Inspectors of Nuisances, although such a course has been adopted in some cases. Tavo or more Sanitary Authorities may appoint the same Medical Officer of Health or the same Inspector of Nuisances; and, apart from this, the Local Government Board is empowered (section 286) compulsorily to unite districts for the purpose of appointing these sanitary officials to act in such special united districts. County Councils are authorised, by section 17, Local Government Act, 1888, to appoint county Medical Officers of Health, who are forbidden to hold other appointments or engage in private practice without the written consent of the council. Under this same section, Sanitary Authorities have power to avaU themselves of the services of these county Medical Officers on such terms as to contribution to his salary as may be agreed with the County Council. So long as such an arrangement is in force, the obligation of the Sanitary Authority under the Act of 1875 to appoint a Medical Officer of Health is to be deemed to be satisfied without the appointment of a separate- Medical Officer. If any part of the salary of the Medical Officer of Health to a local authority is repaid, the Local Government Board has the same powers in regard to qualification, appointment, duties, salary, and tenure of office as it has in the case of a Poor-Law Medical Officer (Pubhc Health Act, 1875, section 191). Qualifications of Medical Officer.—Section 18 of the Local Government Act, 1888, requires (except when the Local Government Board, for reasons brought to their notice, may see fit in particular cases especially to aUoAv) every Medical Officer of Health appointed after the passing of the Act to be legally qualified in medicine, surgery, and midwifery; and further, if appointed after the 1st of January 1892 to a district having at the last census 50,000 inhabitants or more, to be the registered holder of a diploma in Public Health under section 21 of the Medical Act, 1886; or have been, during some three consecutive years prior to 1892, a Medical Officer of a district with a population, at the last census, of not less than 20,000; or have been for not less than three years a Medical Officer or Inspector of'the Local Government Board. Tenure of Office_ by Medical Officer.— Unless a portion of the salary is repaid to the Sanitary Authority out of imperial revenue, transferred to the county and borough councils by the Local Government Act, 1888, the Local Government Board have no control over the tenure of office.' If appointed under these conditions, the Medical Officer of Health may continue to hold office for such period as the Sanitary Authority may, with the approval of the Local Government Board, determine, or until he die, resign, or be removed by such authority with the consent of the Local Government Board or by that Board. The Sanitary Authority may suspend him, but must fortliAvith report their action, together with the cause, to the MEDICAL OFFICERS OF HEALTH. 827 Local Government Board, the latter Board having poAver to remove the suspension. In the event of disagreement as to either salary or duties, a Sanitary Authority have power to give six months' notice to determine the appointment, but only Avith the consent of the Local Government Board. Where no part of a Medical Officer's salary is repayable, none of these approvals is necessary; the authority may fix his salary at as Ioav a sum as they please; and if he is appointed by an urban Sanitary Authority, section 189 of the Public Health Act, 1875, permits of his removal from office at their pleasure. Duties of the Medical Officer—The duties of a Medical Officer of Health are the same whether a contribution is made to his salary or not by the Local Government Board, except that in the latter case he must report his appointment to the Board Avithin seven days. " A copy of the annual report and of every special report must be sent to the Local Government Board, Avhether there is any repayment of salary or not; but there is no compulsion in this respect as regards Medical Officers of Health appointed prior to March 1880, if no repayment of salary is claimed by the authority. County Councils are entitled to receive copies of all annual and other reports which the Medical Officer of any district within the county is required to send to the Local Government Board ; and in default may refuse to pay any contribution to his salary which otherwise they would be liable to pay." The regulations of the Local Government Board, issued March 23, 1891, and still in force, provide that the following shall be the duties of a Medical Officer of Health in respect of the district for which he is appointed, viz.:— (1) He shall inform himself as far as practicable respecting all influences affecting, or threatening to affect, injuriously, the public health within the district. (2) He shall inquire into and ascertain by such means as are at his disposal the causes, origin, and distribution of diseases within the district, and ascertain to what extent the same have depended on conditions capable of removal or mitigation. (3) He shall, by inspection of the district, both systematically at certain periods, and at intervals as occasion may require, keep himself informed of the conditions injurious to health existing therein. (4) He shall be prepared to advise the Sanitary Authority on all matters affecting the health of the district, and on all sanitary points involved in the action of the Sanitary Authority ; and in cases requiring it he shall certify for the guidance of the Sanitary Authority or of the Justices as to any matter in respect of Avhich the certificate of a Medical Officer of Health or a medical practitioner is required as the basis or in aid of sanitary action. (5) He shall advise the Sanitary Authority on any question relating to health in- volved in the framing and subsequent Avorking of such bye-laws and regulations as they may have poAver to make, and as to the adoption by the Sanitary Authority of the Infectious Disease (Prevention) Act, 1890, or of any section or sections of such Act. (6) On receiving information of the outbreak of any contagious, infectious, or epidemic disease of a dangerous character within the district, he shall visit without delay the spot where the outbreak has occurred, and inquire into the causes and circumstances of such outbreak, and in case he is not satisfied that all due precautions are being taken, he shall advise the persons competent to act as to the measures which may appear to him to be required to prevent the extension of the disease, and take such measures for the prevention of disease as he is legally authorised to take under any Statute in force in the district, or by any resolution of the Sanitary Authority. (7) Subject to the instructions of the Sanitary Authority, he shall direct or superin- tend the work of the Inspector of Nuisances in the Avay and to the extent that the Sanitary Authority shall approve, and on receiving information from the Inspector of Nuisances that his intervention is required in consequence of the existence of any nuisance injurious to health, or of any overcrowding in a house, he shall, as early as practicable, take such steps as he is legally authorised to take under any Statute in force in the district, or by any resolution of the Sanitary Authority, as the circumstances of the case may justify and require. (8) In any case in Avhich it may appear to him to be necessary or advisable, or in which lie shall be so directed by the Sanitary Authority, he shall himself inspect and 828 SANITARY LAW. examine any animal, carcass, meat, poultry, game, flesh, fish, fruit, vegetables, corn, bread, flour, or milk, and any other article to which the provisions of the Public Health Act, 1875, in this behalf shall apply, exposed for sale, or deposited for the purpose of sale or of preparation for sale, and intended for the food of man, Avhich is deemed to be diseased, or unsound, or unwholesome, or unfit for the food of man ; and if he finds that such animal or article is diseased, or unsound, or unwholesome, or unfit for the food of man, he shall give such directions as may be necessary for causing the same to be dealt with by a Justice according to the provisions of the Statutes applicable to the case. (9) He shall perform all the duties imposed upon him by any bye-laAvs and regulations of the Sanitary Authority, duly confirmed where confirmation is legally required, in respect of any matter affecting the public health, and touching which they are authorised to frame bye-laAvs and regulations. (10) He shall inquire into any offensive process of trade carried on Avithin the district, and report on the appropriate means for the prevention of any nuisance or injury to health therefrom. (11) He shall attend at the office of the Sanitary Authority or at some other appointed place, at such stated times as they may direct. (12) He shall from time to time report in writing to the Sanitary Authority his pro- ceedings, and the measures which may require to be adopted for the improvement or protection of the public health in the district. He shall in like manner report with respect to the sickness and mortality Avithin the district, so far as he has been enabled to ascertain the same. (13) He shall keep a book or books, to be provided by the Sanitary Authority, in which he shall make an entry of his visits, and notes of his observations and instructions thereon, and also the date and nature of applications made to him, the date and result of the action taken thereon and of any action taken on previous reports; and shall produce such book or books, Avhenever required, to the Sanitary Authority. (14) He shall also prepare an annual report, to be made to the end of December in each year, comprising a summary of the action taken during the year for preventing the spread of disease, and an account of the sanitary state of his district generally at the end of the year. The report shall also contain an account of the inquiries which he has made as to conditions injurious to health existing in his district, and of the proceedings in Avhich he has taken part or advised under the Public Health Act, 1875, so far as such proceedings relate to those conditions ; and also an account of the supervision exercised by him, or on his advice, for sanitary purposes, over places and houses that the Sanitary Authority have power to regulate, Avith the nature and results of any proceedings which may have been so required and taken in respect of the same during the year. It shall also record the action taken by him, or on his advice, during the year, in regard to offensive trades, and to factories and workshops. The report shall also contain tabular statements (on forms to be supplied by the Local Government Board, or to the like effect) of the sickness and mortality Avithin the district, classified according to diseases, ages, and localities. (See Appendix XII.) (15) He shall give immediate information to the Local Government Board of any outbreak of dangerous epidemic disease Avithin the district, and shall transmit to the Board a copy of each annual and of any special report. He shall make a special report to the Local Government Board as to any advice he may give to his Sanitary Authority as to the closure of any school or schools. (16) When giving information to the Local Government Board of the outbreak of infectious disease, or transmitting to them a copy of his annual or any special report, he must give the like information, or transmit a copy of such report, to the County Council of the county in which his district is situated. (17) In matters not specifically provided for in this Order he shall observe and execute the instructions of the Local Government Board on the duties of Medical Officers of Health, and all the lawful orders and directions of the Sanitary Authority applicable to his office. (18) Whenever the Local Government Board shall make regulations for all or any of the purposes specified in section 134 of the Public Health Act, 1875, relating to the Prevention of Infectious Diseases, and shall declare the regulations so made to be in force within any area comprising the whole or any part of the district, he shall observe such regulations so far as the same relate to or concern his office. The duties of the Medical Officer of Health to a Port Sanitary Authority are defined by the Local Government Board in terms Avhich are very similar to those given above, omitting the references to regulated trades and inspection of food, and substituting " ships " for " houses," and " shipping Avithin the district" for " district." SANITARY INSPECTORS. 829 " He shall inform himself as far as practicable respecting all conditions affecting or threatening to affect injuriously the health of crews and other persons on ship-board within the district.....He shall inquire into and ascertain by such means as are at his disposal the causes, origin, and distribution of diseases in the ships and other vessels within the district, and ascertain to what extent the same have depended on conditions capable of removal or mitigation.....He shall, by inspection of the shipping in the district, keep himself informed of the condition injurious to health existing therein.....On receiving information of the arrival within the district of any ship having any infectious or epidemic disease of a dangerous character on board, or of the outbreak of any such disease on board any ship within the district, he shall visit the vessel without delay, and inquire into the causes and circumstances of such outbreak, and advise the persons competent to act as to the measures which may appear to him to be required to prevent the extension of the disease, and so far as he may be lawfully authorised to assist in the execution of the same.....On receiving infor- mation from the Inspector of Nuisances that his intervention is required in consequence of the existence of any nuisance injurious to health, or of any overcrowding in a ship, he shall, as early as practicable, take such steps authorised by the Public Health Act, 1875, on that behalf, as the circumstances of the case may justify and require .... also when any vessel within his district has had dangerous infectious disease on board, he shall give notice thereof to the Medical Officer of Health of any port in the United Kingdom whither such vessel is about to sail." The Duties of a Sanitary Inspector.—In the Public Health Act, 1875, this officer is always spoken of as the Inspector of Nuisances, and he must be formally appointed under that title; the .Act does not recognise the title Sanitary Inspector, Avhereas, as will be seen subsequently, the Pubhc Health (London) Act, 1891, does so. Practically, the two titles are indifferently employed to indicate one and the same official. His duties are closely connected Avith those of a Medical Officer of Health, but the broad lines separating them will be apparent from the following definition of his duties formulated by the Local Government Board. (1) He shall perform, either under the special directions of the Sanitary Authority, or (so far as authorised by the Sanitary Authority) under the directions of the Medical Officer of Health, or in cases Avhere no such directions are required, without such directions, all the duties specially imposed upon an Inspector of Nuisances by the Public Health Act, 1875, or by any other Statute or Statutes, or by the Orders of the Local Government Board, so far as the same apply to his office. (2) He shall attend all meetings of the Sanitary Authority when so required. (3) He shall by inspection of the district, both systematically at certain periods, and at intervals as occasion may require, keep himself informed in respect of the nuisances existing therein that require abatement. (4) On receiving notice of the existence of any nuisance within the district or of the breach of any bye-laws or regulations made by the Sanitary Authority for the suppres- sion of nuisances, he shall, as early as practicable, visit the spot, and inquire into such alleged nuisance or breach of bye-laAvs or regulations. (5) He shall report to the Sanitary Authority any noxious or offensive businesses, trades, or manufactories established Avithin the district, and the breach or non- observance of any bye-laAvs or regulations made in respect of the same. (6) He shall report to the Sanitary Authority any damage done to any works of water-supply, or other Avorks belonging to them, and also any casf of wilful or negligent waste of Avater supplied by them, or any fouling by gas, filth, or otherwise, of water used for domestic purposes. (7) He shall from time to time, and forthwith upon complaint, visit and inspect the shops and places kept or used for the preparation or sale of butchers' meat, poultry, fish, fruit vegetables, corn, bread, flour, milk, or any other article to which the provisions of the Public Health Act, 1875, in this behalf shall apply, and examine any animal, carcass, meat, poultry, game, flesh, fish, fruit, vegetables, corn, bread, flour, milk, or other article as aforesaid Avhich may be therein ; and in case any such article appear to him to be intended for the food of man, and to be unfit for such food, he shall cause the same to be seized, and take such other proceedings as may be necessary in order to have the same dealt with by a Justice: Provided, that in any case of doubt arising under this clause, he shall report the matter to the Medical Officer of Health, with the view of obtaining his advice thereon. (8) He shall, when and as directed by the Sanitary Authority, procure and submit 830 SANITARY LAW. samples of food, drink, or drugs suspected to be adulterated, to be analysed by the analyst appointed under "The Sale of Food and Drugs Act, 1875," and upon receiving a certificate stating that the articles of food, drink, or drugs are adulterated, cause a complaint to be made, and take the other proceedings prescribed by that Act. (9) He shall give immediate notice to the Medical Officer of Health of the occurrence within the district of any contagious, infectious, or epidemic disease ; and whenever it appears to him that the intervention of such Officer is necessary in consequence of the existence of any nuisance injurious to health, or of any overcrowding in a house, he shall forthwith inform the Medical Officer of Health thereof. (10) He shall, subject to the directions of the Sanitary Authority, attend to the instructions of the Medical Officer of Health with respect to any measures which can be lawfully taken by an Inspector of Nuisances under the Public Health Act, 1875, or under any Statute or Statutes, for preventing the spread of contagious, infectious, or epidemic disease of a dangerous character. (11) He shall enter from day to day, in a book provided by the Sanitary Authority, particulars of his inspections, and of the action taken by him in the execution of his duties. He shall also keep a book or books, to be provided by the Sanitary Authority, so arranged as to form as far as possible a continuous record of the sanitary condition of each of the premises in respect of which any action has been taken under the Public Health Act, 1875, or under any other Statute or Statutes, and shall keep any other systematic records that the Sanitary Authority may require. (12) He shall, at all reasonable times, when applied to by the Medical Officer of Health, produce to him his books, or any of them, and render to him such information as he may be able to furnish with respect to any matter to which the duties of Inspector of Nuisances relate. (13) He shall, if directed by the Sanitary Authority to do so, superintend and see to the due execution of all works which may be undertaken under their direction for the suppression or removal of nuisances within the district. (14) He shall, if directed by the Sanitary Authority to do so, act as officer of the said authority as local authority under the Contagious Diseases (Animals) Act, 1886, and any orders or regulations made thereunder. (15) In matters not specially provided for in this Order he shall observe and execute all the lawful orders and directions of the Sanitary Authority, and the Orders of the Local Government Board which may be hereafter issued, applicable to his office. Under section 191 of the Public Health Act, 1875, the Medical Officer of Health may exercise the poAvers Avith Avhich an Inspector of Nuisances is invested by that Act. Section 192 of the same provides that the same person may be both Surveyor and Inspector of Nuisances. In common Avith other sanitary officials, Medical Officers of Health, Surveyors, and Inspectors of Nuisances are prohibited by section 193 from being concerned in contracts Avith the Sanitary Authority. Section 2 of the Public Health (Members and Officers) Act, 1885, has to some extent qualified these provisions for exceptional cases; but independently of any of the above, very severe pains and penalties are imposed by the Public Bodies Corrupt Practices Act, 1889, on every person who solicits, receives, or agrees to receive corruptly any gift, fee, loan, or reward on account of any member, officer, or servant of any public body doing or forbearing to do any- thing in respect of any matter or transaction in Avhich such public body is concerned. The duties of county Medical Officers of Health and of Surveyors have not yet been authoritatively defined; neither have the qualifications of Inspectors of Nuisances in the provinces been prescribed. In London, under section 106 of the Public Health Act, 1891, every Sanitary Authority is required to appoint one or more Medical Officers of Health for its district. The same person may, with the sanction of the Local Government Board, be appointed Medical Officer of Health for two or more districts; but, except in cases allowed by the Board, every such person must reside in that district, or within one mile of its boundary. A Medical Officer of Health in London may exercise any of the powers with which a Sanitary Inspector is invested; and his annual report to SANITARY INSPECTORS. 831 the Sanitary Authority must be affixed to the annual report of that authority. The qualifications necessary for a Medical Officer of Health in London are similar to those required for similar officers in the provinces; and subject to the provisions of the Public Health (London) Act, 1891, as to "existing officers, the Local Government Board have the same powers as they have in the case of those in the rest of England and Wales, with regard to appointment, salary, duties, and tenure of office. This enactment (section 108) is, however, subject to the following provisions : (a) a Medical Officer will be removable by the Sanitary Authority with the consent of the Local Government Board, or by that Board, and not otherwise: (b) any such officer must not be appointed for a limited period only. Every Sanitary Authority must appoint an adequate number of fit and proper persons as Sanitary Inspectors, and every one of them appointed after January 1, 1895, must be a holder of a certificate of such body as the Local Government Board may approve (at present the examining and certifying body is the Sanitary Institute), or must have been, during three -consecutive years preceding 1895, a Sanitary Inspector or Inspector of Nuisances of a district in London, or of an urban sanitary district out of London containing, according to the last census, a population of not less than 20,000 inhabitants (Public Health (London) Act, 1891, section 108). The regulations prescribed by the Local Government Board as to the •duties of Medical Officers of Health and Sanitary Inspectors in London are very similar in terms to those which apply to Medical Officers and Inspectors ■of Nuisances in the provinces. It is noticeable that, under the Acts in force •outside the metropohs, no qualification is demanded for this latter office; whereas, in London, such qualification is definitely explained. It is probable that a similar provision Avill be inserted in any future consolidation .•of the Public Health Acts for the country generally. In Scotland, every County Council must appoint and pay one or more I, Medical Officers and Sanitary Inspectors, Avho shall not hold any other i appointment, or engage in private practice without the express written / consent of the council. "These officers may be re-appointed by the District I •Committees as district officers, every District Committee being empowered „r to appoint one or more Medical Officers and Sanitary Inspectors for their •districts, or for any part of it." If they think necessary, the Local Govern- ment Board for Scotland may compel a District Committee as local authority to appoint a Medical Officer or Sanitary Inspector; and under their regulations, Sanitary Inspectors must be appointed wherever there is a town or village population exceeding 2000. A Medical Officer must be a registered practitioner, and may not now be appointed for a county, district, or parish with a population of 30,000 or upAvards unless he holds a diploma in Public Health under the Medical Act, 1886 ; and no person may, except with the special consent of the Local Government Board, be appointed Sanitary Inspector of a county unless he has "been, during the three consecutive years preceding his appointment, the Sani- tary Inspector of a local authority under the Public Health (Scotland) Acts. Burgh Commissioners must appoint a Sanitary Inspector and a Medical Officer of Health. The latter officer must be registered, and if appointed after May 15, 1894, must also have the special qualification reqiured in oounties since the beginning of 1893. " No Medical Officer or Sanitary Inspector, whether for a county, land- ward district, or burgh, can be removed from office without the sanction of the Scottish Local Government Board." 832 SANITARY LAW. The model bye-laAvs recommended by the Local Government Board for Scotland to the various Sanitary Authorities for regulating the duties of Medical Officers and Sanitary Inspectors do not materially differ from those of the English Board. In Ireland.—By section 11 of the Public Health (Ireland) Act, 1878, the dispensary medical officers are ex officio Medical Officers of Health for their respective districts. In addition to the Medical Officers of Health, the Local Government Board for Ireland requires each rural Sanitary Authority, when directed by them, to appoint a consulting sanitary officer or a medical superintendent officer of health, and for either of these posts the medical officer of the union workhouse, or any other duly qualified medical practitioner, is eligible. The officials in England called Inspectors of Nuisances or Sanitary Inspectors are in Ireland known as sanitary sub-officers, and for these posts the relieving officers, or the rate collectors of the several unions or other persons are eligible. Urban Sanitary Authorities are to appoint so many sanitary sub-officers as they, with the consent of the Local Govern- ment Board, may determine; also, when directed by the Board, they are to appoint one consulting sanitary officer or one medical superintendent of health, Avho must be a qualified medical practitioner; and an executive sanitary officer, with such qualification as the Sanitary Authority shall, with the consent of the Local Government Board, determine. The appointments held by sanitary officers of both urban and rural authorities shall continue for such period as the Sanitary Authority may, with the approval of the Local Government Board, decide, or until the holder thereof die or resign. The regulations as to the duties of the several. sanitary officers are similar to those of the English Local Government Board. There is no provision in the Irish Public Health Act for the appointment of; a " Surveyor," but there is nothing to prevent a Sanitary Authority employ-* ing a Surveyor temporarily in order to execute any special work. There is, further, no poAver given to Sanitary Authorities to combine for the appoint- ment of sanitary officers. Parliamentary grants are made annually in recoupment of portions of the salaries of sanitary officers; the amounts recouped to local funds is one-half of the salaries. There is no provision in the Irish Act prohibiting sanitary officials being concerned in contracts made with the authority for any of the purposes of the Public Health Act, nor does the Public Health (Members and Officers) Act, 1885, extend to Ireland. The Public Bodies Corrupt Practices Act, 1889, hoAvever, does apply to Ireland as well as to England. DEFINITIONS. There are certain definitions of terms in the various Sanitary Acts which give to those terms meanings which are not the same as the common mean- ing. The more important of these definitions are the following :— Building.—This Avord has a very Avide significance. It includes wooden structures on wheels, also those without foundations, but resting simply on the ground. Under the Infectious Diseases Notification Act, 1889, the term building applies to boats, vessels, ships, tents, vans, sheds, and other similar structures used for human habitation. House.—Though not absolutely defined, the term " house " is so extended as to include schools, factories, and other buddings in which persons are employed. Eor a structure to be a " house " it is not necessary that persons reside in it. DEFINITIONS. 833 OAvner.—Under the Public Health Acts, the term "owner" means the person who, for the time being, receives the rack-rent of the lands or premises in connection with which the word is used, whether on his own account or as agent or trustee for any other person, or who would so receive the same if such premises were let at a rack-rent. By rack-rent is meant the rent that is not less than two-thirds of the full nett annual value of the property. Under Part II., Housing of the Working Classes Act, the owner of a property is held to be any person or corporation who has at least a twenty- one years' interest in it. Drain means any drain of, and used for the drainage of one budding only, or premises within the same curtilage, and made merely for communicating therefrom with a cesspool or like receptacle for drainage, or with a sewer into Avhich the drainage of two or more buildings or premises occupied by different persons is conveyed. Sewers include sewers and drains of every description, except drains to which the word "drain," as above defined, applies. In other words, a sewer is a drain receiving the drainage of two or more buildings; and may be an open channel, such as a polluted water-course, as well as an under- ground culvert. Under the Metropolis Local Management Act, 1862, this distinction between drain and sewer is not accepted, but a combined drain is deemed to remain a drain. So again, in urban districts which have adopted section 19 of the Public Health Acts Amendment Act, 1890, the interpreta- tion of "drain" is different. Whereas under the Public Health Act, 1875, if one or more houses drain into a common pipe, such common pipe or combined drain is a sewer; but under section 19 of the Amended Act this common pipe is deemed to be a sewer only if all the houses belong to one oivner ; if they belong to more than one owner, then the combined drain is a drain repairable at the owners' expense, and not a sewer repairable at the expense of the Sanitary Authority. Canal.—Under the Canal Boats Acts, 1877 and 1884, the term "canal" includes any river, lake, water, or inland navigation "being within the body of a country, whether it is, or is not, within the ebb or flow of the tide." Canal Boat.—This includes any and every vessel, however propelled, used for conveyance of goods along a canal, as above defined, but does not include a ship registered under the Merchant Shipping Act, 1894, unless the Local Government Board orders otherwise, which it may do on the representation of a Sanitary Authority or any of its inspectors. Curtilage is defined as a "court-yard, backside or piece of ground lying near to a dwelling-house." Slaughter-house includes the buildings and places commonly called slaughter-houses and knackers' yards, and any building or place used for slaughtering cattle, horses, or animals of any description. Sanitary convenience includes urinals, water-closets, earth-closets, privies, ashpits, and any similar convenience. Ashpit includes any ashtub or other receptacle for the deposit of ashes, faecal matter, or refuse. Lands and premises include messuages, buildings, lands, casements, and hereditaments of any tenure. Dwelling-house means any inhabited building, and includes any yard, garden, outhouses, and appurtenances belonging thereto, or usually enjoyed therewith, and includes the site of the dwelhng-house as so defined. Street includes any highway (not being a turnpike road), and any pubhc bridge (not being a county bridge), and any road, lane, footway, square, 3 G 834 SANITARY LAW. court, alley, or passage, whether a thoroughfare or not (Public Health Act, 1875, section 4). The Public Health (London) Act, 1891, section 141, adds to this definition of a street the words " whether or not there are houses in such street." Under the Housing of the Working Classes Act, 1890, section 29, the word "street" is restricted to a road, &c, with houses budt in it, and does not include highways or roads without houses. Earth-closet is defined " as any place for the reception and deodorisation of faecal matter, constructed to the satisfaction of the local authority." BYE-LAWS AND REGULATIONS. In respect of certain matters, and under certain conditions expressly stated in the various Acts dealing with the Public Health, Sanitary Authorities may make bye-laws having the force of law. These bye-laws are intended rather to supplement than to summarise, vary, or supersede the express provisions of the statute law. All bye-laws made by Sanitary Authorities under and for the purposes of the Public Health Acts must be under their common seal; and any such bye-law may be altered or repealed by a subsequent bye-law made pursuant to the provisions of the Acts. But no bye-law is of effect if repugnant to the laws of England or to the provisions of the Acts. A Sanitary Authority may, by any bye-laws made by it, impose such reasonable penalties as it thinks fit, not exceeding £5 for each offence, and, in the case of a continuing offence, a further penalty not exceeding 40s. for each day after written notice of the offence; but all such bye-laws imposing any penalty must be so framed as to allow of the recovery of any sum less than the full amount of the penalty. Bye- la avs do not take effect unless and until they have been confirmed by the Local Government Board, who have power to allow or disallow the same as they think proper. The bye-laws, when confirmed, must be printed and hung up in the office of the Sanitary Authority, and a copy of them must be delivered to any ratepayer of the district who apphes for them (see Public Health Act, 1875, sections 182 to 185). Some bye-laws must be made by a local authority; there are others which may be made by both urban and rural authorities, and others also which urban Sanitary Authorities are alone empowered to make. In the greater number, the power to make them is permissive. Regulations differ somewhat from bye-laws, because, with few exceptions, they do not require the approval of the Local Government Board. They may be simply passed as a resolution at a meeting of the authority, and may be amended or rescinded at a subsequent meeting. In certain cases, as, for instance, under section 125, Public Health Act, 1875, relating to the removal to hospital of infected persons brought by ships, a regula- tion, just like a bye-law, has to be approved by a superior authority, and its breach involves liabdity to a money penalty. Urban Sanitary Authorities are empowered to make bye-laws in respect of the following:— 1. Common Lodging-houses.—For fixing and varying the number of lodgers; for the separation of the sexes; for promoting cleanliness and ventdation; for giving of notices and taking precautions in the case of infectious diseases; for the general weU-ordering and sanitation of such houses (Public Health Act, 1875, section 80). 2. Cleansing and Scavenging.—Fox the cleansing of footways; for the removal of house refuse; for the prevention of nuisances arising from snow, BYE-LAAVS AND REGULATIONS. 835 dust, ashes, rubbish, and the keeping of animals (Public Health Act, 1875, section 44). 3. Tenement Houses.—For regulating the number of persons and separation •of the sexes; for promoting cleanliness, ventilation, and prevention of the spread of infectious diseases; besides the general well-ordering of such houses (Public Health Act, 1875, section 90). So far as relates to seamen's lodging-houses, the power to make bye-laws is derived from the Merchant Shipping Act, 1894, section 214. 4. New Streets and Buildings.—With respect to the level, width, con- struction, and sewerage of new streets; and to the structure, stability, ventilation, general sanitary arrangement, alteration, removal, and closure of huildings unfit for habitation (Pubhc Health Act, 1875, section 157, and Part III., Public Health Amendment Act, 1890). 5. Slaughter-houses.—For the licensing, registering, and inspection of slaughter-houses and knackers' yards; for ensuring their cleanliness and proper supply of water, as well as to prevent cruelty therein (Public Health Act, 1875, section 169). 6. Markets and Fairs.—For the prevention of nuisances, the inspection of slaughter-houses and the daily removal of refuse, the prevention of the exposure or sale of unAAdiolesome food, and various other purposes (Public Health Act, 1875, section 167). 7. Offensive Trades.—To control, prevent, or lessen the injurious effects of various or any offensive trade (Public Health Act, 1875, section 113). 8. Hop and Fruit-pickers.—For securing these workers decent lodgings and accommodation while so engaged (Public Health Act, 1875, section 314, and Public Health (Fruit-pickers) Act, 1882). 9. Tents and Vans.—For the promotion of cleanliness, prevention of nuisances in connection with, and the spread of infectious disease by the occupants of these structures (Housing of the Working Classes Act, 1885, section 9). 10. Mortuaries and Cemeteries.—For the regulation of charges, and management (Public Health Act, 1875, section 141, and the Public Health (Interments) Act, 1879). 11. Open Spaces.—For the regulation of pubhc grounds and walks, including churchyards or burial-grounds over which the Sanitary Authority may have control (Pubhc Health Act, 1875, section 164, and the Open Spaces Act, 1887). The Municipal Corporations Act, 1882, section 23, gives power to municipalities or borough councils to make bye-laws for the suppression and prevention of nuisances not already punishable in a summary manner by any other Act in force throughout the borough. County Councils have simdar powers under the Local Government Act, 1888, section 16. Urban authorities can further make bye-laws under the Housing of the Working Classes Act, 1890, for the regulation of all buildings provided under that Act or the Acts which it supersedes. Rural Sanitary Authorities have similar powers for making byedaws in respect of the following:— (1) Private scavenging, (2) Common lodging-houses, (3) Tenement houses and Seamen's lodging-house*, (4) Hop and fruit pickers, (5) Tents and vans, (6) Mortuaries, and (7) under the Housing of the Working Classes Act, 1890. Further, by adopting portions of the Public Health Acts Amendment Act, 1890, which are not expressly hmited to urban districts, rural Sanitary Authorities can make certain bye-laws as to neio and old buildings. The Local Government Board may confer on them any other 836 SANITARY LAW. poAvers as to bye-laws Avhich the Public Health Acts give to urban authori- ties (Public Health Act, 1875, section 276). Every Sanitary Authority must make bye-laws as to common lodging- houses ; every urban Sanitary Authority must do the same as to slaughter- houses : the exercise of power as to other bye-laws is optional. The London County Council have poAver to make bye-laws for the regulation of the plans, levels, width, surface, inclination and materials of new streets and roads; for the plan and sites of buildings; as to the dimensions, form, construction, cleansing and repairing of pipes, drains, and traps connected with sewers; and as to the construction, ventilation and cleansing of sewers (London Building Act, 1894, section 164, and certain unrepealed clauses of the Local Management Acts). Also under the Public Health (London) Act, 1891, for regulating the conduct of offensive trades, and the structure of the premises (section 19). For prescribing the times for removal of any faecal or offensive matter in or through London, so as to avoid the creation of a nuisance (section 16). As to the closing of cesspools and privies, the removal and disposal of refuse, and as to the duties of the occupier of any premises in connection with house refuse (section 16). As to water-closets, earth-closets, ashpits, cesspools, receptacles for dung, and the proper accessories thereof in connection with buildings (section 39). The power to make bye-laAvs under section 19 is permissive, but under sections 16 and 39 is compulsory. The Metropolitan Sanitary Authorities must make bye-laws for the control of nuisances arising from snow, ice, salt, dust, rubbish, ashes, carrion, fish, or filth in the streets; or from offensive matters running from any manufactory, brewery, slaughter-house, or dung-hill; for the prevention of keeping animals on any premises in such place or manner as to be a nuisance or dangerous to health; and as to the paving of yards and open spaces in connection with dwelling-houses (section 16). For the keeping of water-closets supplied with sufficient water for their effective action (section 39). For the cleansing and protecting of all cisterns, tanks, &c, used for storing water for domestic purposes, drinking, or the manu- facture of beverages (section 50). The same authorities may make bye-laws for the removal to hospital or detention therein of persons suffering from infectious disease (section 66). For preventing the fouling of tents, vans, sheds, and similar structures used! for human habitation, and the spread of infectious disease by the inhabi- tants thereof (section 95). In relation to tenement houses, under section 8 of Housing of the Working Classes Act, 1885. These same authorities must also enforce any bye-laws made by the County Council under sections 16 and 39 of the Public Health (London) Act, 1891. In the city of London, similar powers are vested in the Commissioners of Sewers, under the City of London Sewers Acts, 1848 and 1851, the- Pubhc Health (London) Act, 1891, the Gardens in Towns Protection Act, 1863, the Metropolitan Open Spaces Acts, 1877 and 1881, and the Open Spaces Act of 1887. Under the Dairies Order, 1885, any Sanitary Authority may make regulations for any of the following purposes:—(a) For the inspection of cattle in dairies; (b) for prescribing and regulating the lighting, ventdating, draining, cleansing and water-supply of dairies and cow-sheds'; (c) for prescribing precautions to be taken by purveyors of milk against infection; (d) for securing the cleanliness of milk stores, milk shops, and milk vessels used for containing milk for sale. A Sanitary Authority, subject to approval by the Local Government SEWERAGE AND DISPOSAL OF SEWAGE. 837 Board, may make regulations for the removal to hospital and detention there as long as necessary of all persons who may be brought within their district by either boat or ship, and Avho may be infected Avith an infectious disease (Public Health Act, 1875, section 125). They have also power to make regulations for the management of places provided by them for making post-mortem examinations ordered by a coroner (section 143). The Local Government Board has power to make regulations under sections 130 and 134 of the Public Health Act, 1875, in relation to cholera and other dangerous infectious diseases. The provisions as to making bye-laws in Scotland and Ireland are somewhat similar to those above mentioned. Where offering any marked differences from the English procedures, the fact will be indicated in the following pages. From time to time the Local Government Board have prepared and issued " Model Bye-laAvs " to serve as guides to Sanitary Authorities Avhen seeking to frame bye-laws. As these models have been very generally adopted, subject to occasional modifications, by various Sanitary Authorities, a summary of them will be given under each heading where, in respect of certain matters, the Public Health Acts give the Sanitary Authority power to frame them. Supplementary to these model bye-laAvs, various regulations in regard to the management of mortuaries and cemeteries have been issued by the Home Secretary : these will be detailed in their appropriate places. SEWERAGE AND DISPOSAL OF SEWAGE. In England and Wales.—By the Public Health Act, 1875, section 13, it is enacted that all sewers except certain private sewers are vested in the Sanitary Authority of the district. The exceptions mentioned in the section are :—(1) Sewers made by a person or persons for his or their profit. (2) SeAvers made and used for draining or improving land under any local or private Act, or for irrigation. (3) Sewers under any Commissioners of Sewers appointed by the Crown. The Sanitary Authority may purchase (section 14) or construct (section 15) sewers. They must provide such sewers as are necessary for effectually draining their district, having, by section 16, powers of taking them through, across, or under lands and streets. Section 308 provides for compensation for damage, to be ascertained by arbitration. The seAvers must be so constructed, covered, ventilated, and kept as not to be a nuisance or injurious to health, and must be properly cleansed (section 19). The performance of these duties by a Sanitary Authority can be enforced on complaint by individuals (section 299), Avhile further powers, in this respect, are given by sections 16 and 19 of the Local Government Act, 1894, to County Councils, on complaint by a Parish Council of a defaulting rural Sanitary Authority. Under section 7, Rivers Pollution Prevention Act, 1876, every Sanitary Authority must give facilities for factories to drain into sewers, but provision is o-iven for the protection of seAvers from injurious matters, such as anything which may impede the Aoav of their contents, any chemical refuse, waste steam, or Avater or liquid heated above 110° F., by sections 16 and 17, Public Health Acts Amendment Act, 1890. The restrictions imposed by sections 32, 33, and 34 of the Public Health Act, 1875, on the execution of sewerage works by a Sanitary Authority outside its OAvn district, involve the giving of a public notice, and in case of objection, the Avork not to be 838 SANITARY LAW. commenced Avithout sanction of the Local Government Board, avIio may appoint an inspector to make inquiry and report. For the protection of the seAvers of an urban Sanitary Authority, section 26, Public Health Act, 1875, pro Aides a penalty for unauthor- ised buildings over them; and sections 150 and 151 give power to the Sanitary Authority to compel the seAvering of private streets, subject to any bye-laws the authority can get confirmed by the Local Government Board. Powers are given by section 27 of the same Act for the treatment and disposal of sewage, but section 17 expressly insists that such disposal of sewage must not be into streams, unless purified before discharge : this latter section, however, needs to be read in connection with the Rivers Pollution Prevention Acts, 1876 and 1893, which give a certain amount of protection to Sanitary Authorities in respect of the pollution of streams and rivers by seAvage channels used, constructed, or in process of construction at date of passing of the Act of 1876. Sections 28, 29, and 30 of the Public Health Act, 1875, further give powers to the Sanitary Authority to deal Avith land appropriated to sewage purposes, to contribute to works executed by others for the disposal of the sewage, and to agree for communication of sewers Avith sewers of adjoining districts. The incidence of the charge of sewerage and other public sanitary Avorks in urban districts is usually made by a general district or borough rate. In rural districts, the incidence of charge of expense of sewerage and other sanitary works are not made on the entire district, but constitute a separate charge on the parishes or parts of parishes for wlhch the works have been carried out, and the areas liable to contribute are termed " contributory places " (section 229). There are four kinds of contributory places :—(1) A rural Sanitary Authority may, subject to approval by the Local Government Board, constitute any portion of its area a " special drainage district" for the purpose of charging thereon exclusively the expenses of sanitary works, the cost of which is not spread over the entire district, and thereupon such area becomes a "contributory place." (2) Where no part of a parish is situate in a special drainage district, or in an urban sanitary district, the entire parish is a contributory place. (3) Where no part of a parish is in an urban sanitary district, but part of it is in a special drainage district, the part not in a special drainage district is a contributory place. (4) Where part of a parish is in an urban sanitary district, and part in a rural sanitary district, so much of it as is not in an urban district or special drainage district is a contributory place (section 229). In London.—The County Council, as the successors of the Metropolitan Board of Works, are the local authority for the purposes of the main seAverage and disposal of the sewage of London, while the Vestries and District Boards are the local authorities for the purposes of the seAverage and drainage other than the main seAverage. The powers of the late Metro- politan Board of Works, and consequently of their successors, the County Council, as regards main sewerage are derived from the Metropolis Manage- ment Act, 1855, taken in conjunction Avith a similar Act of 1862, and the Metropohtan Main Drainage Act, 1858. While the main sewers are to be constructed and kept so as not to be a nuisance, the County Council have power to declare sewers to be main sewers, and to take jurisdiction over seAverage and drainage matters belong- ing to the Vestries, also to control these bodies in the construction of sewers, &c, by means of bye-laws. The general poAvers of the County Council in respect of seAverage and sewage disposal are very similar to those of the Sanitary Authorities in the provinces under the Public Health Act, 1875. SEWERAGE AND DISPOSAL OF SEWAGE. 839 As relates to procedures for the prevention of floods, the powers of the County Council, by inheritance from the Metropolitan Board of Works, are derived from the Metropolitan Management (Thames River Prevention of Floods) Amendment Act, 1879. All sewers, &c, within the city are vested in the Commissioners, avIio have full powers over them and all drains com- municating with the public sewers, under the City of London Sewers Act, 1848. By the Metropolis Management Act, 1855, section 68, all sewers, other than those now vested in the County Council and the Commissioners of Sewers, are vested in the Vestries and District Boards, who, from time to time, must repair, maintain, alter, or extend as may be necessary; but no new sewers can be made Avithout the approval of the County Council. The powers given by the above provisions are extended in certain cases to areas outside the metropolis by section 58 of the Metropolis Management Act, 1862. The Act of 1855 (sections 73 to 75) further provides for the ventilation, trapping, cleansing, inspection, and proper connection of drains with sewers on the part of the Sanitary Authorities : while section 202 of the same Act gives the local authorities power to make bye-laws as to drains. For the purposes of their sewers, and for other purposes of the Metropolis Management Acts, every Vestry or District Board has the same power as the County Council to purchase lands. These purchase powers, however, are not compulsory (sections 151, 152). In Scotland.—While the Scottish Acts do not draw any formal distinc- tion between drains and seAvers, the duties of local authorities in regard to their provision and maintenance do not materially differ from those of the English Sanitary Authorities; the powers being derived from the provisions of the Public Health (Scotland) Act, 1867, the Burgh Police (Scotland) Act, 1892, and the Local Government (Scotland) Act, 1889. Though the pollution of a stream by sewage is an offence as a nuisance under the common law of Scotland, it is also so under section 21 of the Rivers Pollution Prevention Act, 1876, which applies to Scotland, with the substi- tution of the Secretary for Scotland for the Local Government Board as central authority. A County Council may enforce this Act as if it were a Sanitary Authority Avithin its meaning. In Ireland.—The provisions of the Irish Public Health Act, 1878, in respect of sewerage and sewage disposal are identical with those of the English Act of 1875. The Rivers Pollution Prevention Acts, 1876 and 1893, extend also to Ireland, but in their practical application there is some doubt whether the definition of Sanitary Authority contained in the Act of 1876 can be held to include a Sanitary Authority constituted by the Irish Public Health Act of 1878. In respect of the incidence of taxation to meet loan charges for sanitary works, it is noticeable that the definition of a contributory place in the Irish Act is different from that contained in the English Act. By section 232 of the Public Health Act (Ireland), 1878, a contributory place may be (1) the dispensary district; (2) the electoral division; (3) the toAvn-land; (4) such portion of the town-land or town- lands as may be determined by the Local Government Board of Ireland. Another distinction between the two Acts is that there are no " special drainage districts" in Ireland, their place being taken by the " area of charge," consisting of a contributory place or a number of contributory places benefiting by proposed sanitary improvements. An area of charge differs from a special drainage district, inasmuch as it may be, and usually is fixed for one particular Avork, and the same area need not be adopted for the expenses of another sanitary Avork for the same place. 840 SANITARY LAW. HOUSE DRAINAGE AND REMOVAL OF EXCRETA FROM HOUSES. In England and Wales.—The Public Health Act, 1875, sections 21 to 25, gives every Sanitary Authority poAver to enforce drainage of undrained houses, and in certain cases to close existing drains on condition of provid- ing others. These drains must lead to the public sewer if there be any Avithin 100 feet of the site of the house; if not, to a covered cesspool in such position (not under a house) as the Sanitary Authority may direct. Failing compliance, the authority may carry out the work and recover in a summary manner the expenses incurred from the oAvner, or may by order declare the same to be " private improvement expenses." These private improvement expenses may be made payable by instalments with interest. They may, moreover, be levied on the occupier, AAdiereas the expenses, if recovered summarily, will only be recoverable from the OAvner. It occasion- ally happens that, OAving to delay in construction of sewers, houses have been supplied with cesspools and effectual drains leading thereto. In those cases, the Sanitary Authority are under no obligation to pay the costs of drains necessary for enabling the house to discharge its seAvage into the new sewers. Where the sewer is in the same sanitary district as that in which the premises are situate, the owner or occupier, upon giving due notice and complying with the regulations of the authority as to how the communica- tion is to be made, is entitled to carry drains into the public sewer. In places where Part III., Public Health Amendment Act, 1890, has been adopted, by section 18 of that Act, the owner or occupier has a right to require the Sanitary Authority to make the communication at his cost. Where the sewer is in another sanitary district, the communication must be made on such terms and conditions as may be agreed upon between the owner or occupier and the authority to whom the sewer belongs. Where any drain or cesspool is a nuisance, or injurious to health, the Sanitary Authority may take proceedings to remedy the matter either under section 41, Public Health Act, 1875, or under the provisions of the same Act relating to nuisances. All the foregoing provisions apply to existing houses and drains, without regard to the date of their construction, in both urban and rural districts. In urban districts, and in rural districts, or contributory places endowed with urban powers by section 276, Public Health Act, 1875, not only may no house be built or rebuilt after having been pulled down to or below the ground floor, or be occupied after having been built or so rebuilt until proper covered drains have been constructed and duly connected with either a sewer or cesspool, as above indicated, to the satisfaction of the Sanitary Authority (section 25, Act of 1875), but the authority may make bye-laws as to the mode in which connections between drains and seAvers are to be made (idem, section 157). This 157th section of the 1875 Act is only of limited extent, as it provides that no bye-law made under it shall affect any building erected in any place which, on August 11, 1875, was included in an urban sanitary district before the Local Government Acts came into force in such place, or any building erected in any place which, on that date, was not included in any urban sanitary district before such place became constituted or included in an urban district, by virtue of any order of the Local Govern- nent Board, subject to this Act. Nor may any bye-law made under the section apply to buildings belonging to any railway company, and used for the purposes of such raihvay under any Act of Parliament. In places HOUSE DRAINAGE. 841 where Part III., Public Health Amendment Act, 1890, has been adopted, section 23 of this same Act has extended the operation of this 157th section of the 1875 Act to buildings erected before the time mentioned, and to rural sanitary districts. Rural Sanitary Authorities can therefore now, by adopting this part of the 1890 Act, obtain these very important powers throughout their districts without the intervention of any order of the Local Government Board. The law relating to privies, water-closets, excrement and refuse disposal, resembles that relating to house drainage, inasmuch as it is contained partly in statutory enactments applicable to both urban and rural sanitary districts, and partly in bye-laws applicable only to urban districts and to those rural sanitary districts or contributory places to which it has been specially applied by order of the Local Government Board. The general statutory enactments in regard to these matters of excrement and refuse disposal are contained in the Public Health Act, 1875, sections 35 to 45, and practically amount to the following :—It is unlaAvful to erect any house Avithout a sufficient Avater-closet, earth-closet, or privy, and an ashpit with proper doors and coverings; and the same must be provided for any existing house on the order of the Sanitary Authority, who may require a separate closet for each house (sections 35, 36, and 37). The Sanitary Authority may order sanitary conveniences in factories where persons of both sexes are employed (section 38), Avhile the Coal Mines Regulation Act, 1887, section 74, makes the same provision applicable to parts of mines above ground in which Avomen and girls are employed. Every Sanitary Authority must see that all drains, closets, ashpits, and cesspools are properly constructed and kept (section 40); Avhile urban Sanitary Authorities may provide public urinals, closets, or receptacles for refuse (sections 39 to 45). On the Avritten applica- tion of any person that any drain, closet, ashpit, or cesspool is a nuisance, the Sanitary Authority may, by writing, empower their surveyor or inspector, after giving twenty-four hours' notice, to enter the premises and open the ground; if any defect is found, the Sanitary Authority must serve notice upon the OAvner or occupier to do the necessary Avork, but if there is no defect, the Sanitary Authority must close the ground and make good any damage. The Local Government Board have issued a series of Model Bye-laws relating to the various matters for which bye-laAvs may be made by a Sanitary Authority under the foregoing provisions. Their general pro- visions are sufficiently indicated in the following summary:— Drainage.—Damp sites must be drained by earthenware field pipes properly laid to a suitable outfall, but not directly communicating with any sewer or cesspool or drain containing sewage. Rlin pipes must be provided to carry away all water falling on the i-oof without causing dampness of the walls or foundations. The level of the lowest storey must be such as to allow of the construction of a drain sufficient for the drainage of the building communicating with a sewer at a point above the centre of the sewer. All drains for sewage must be made of impervious pipes 4 inches or more in internal diameter, laid with a proper fall in a bed of concrete, and with water-tight joints. Every drain inlet not intended for ventilation must be trapped. No drain conveying seAvage must pass under a building unless no other mode of construction is practicable ; in that case it must be laid in a direct line for the Avhole distance beneath the house, and must be embedded in and covered with concrete 6 inches thick all round, and must be laid at a depth below the surface at least equal to its diameter, and lastly, must be ventilated at each end of the portion beneath the building. The main drain must be trapped at a point within the curtilage, but as distant as practicable from the building. Branch drains must join other drains obliquely in the direction of the flow. There must be at least two untrapped ventilating openings into the drains, according to one of the folloAving alternative arrangements:—(1) One opening consists of a shaft or disconnecting chamber opening at or near the ground level, and situated as close as possible to the trap specified above, but on the house side of it; the other opening is a 842 SANITARY LAW. pipe or shaft carried from a point as far distant as possible from the said trap, that is, as near as possible to the head of the drain, vertically upwards in such manner and to such height (in nocase less than 10 feet) as to prevent any escape of foul air into any building j but (2) if more convenient, the relative positions of these openings maybe reversed, the shaft being placed near the trap, and the opening at the ground level at the head of the drain. The ground-level opening must have a grating, with apertures equal in total area to the sectional area of the drain. The pipe or shaft at the other end of the drain (whether used as a soil pipe or not) is required to have a sectional area equal to that of a drain, and in no case to be less than 4 inches ; all bends and angles- are to be avoided as far as practicable. No drain inlet is permitted within a building except the inlet necessary for a water- closet. _ Every soil pipe must be at least 4 inches in diameter, must be placed outside- the building, and must be continued upwards in full diameter, without bends or angles, to such a height and such a point as to afford a safe outlet for sewer air. This height and point will usually be above the highest part of the roof of the building to which the soil pipe is attached, and, where practicable, not less than 3 feet above any window Avithin 20 feet measured in a straight line from the open end of such soil pipe. There must be no trap between the soil pipe and the drain to which it leads, nor in any part of the soil pipe except such as may be necessary in the construction of the water-closet. The waste pipe from a slop sink must conform to the same requirements as a soil pipe. The waste pipes from any other sink, bath, or lavatory, the overflow pipe from any cistern and from any " safe " under a bath or water-closet, and every pipe for conveying waste water, must be taken through an external wall, and must discharge in the open air over a channel leading to a trapped gully grating at least 18 inches distant. _ Water-closets must have a window opening directly into the external air, and measur- ing 2 feet by 1 foot clear of the frame ; and, in addition to the window, adequate means of constant ventilation by air-bricks, air-shafts, &c. Such closets, if within the ouildmg, must adjoin an external wall. The water must be supplied to a water-closet by means of a special cistern. The apparatus must be suitable for effectual flushing and cleansing of the basin ; the basin must be made of non-absorbent material, and of such shape and capacity as to receive and contain a sufficient quantity of water, and to. allow all filth to fall free of the sides directly into the water. "Containers" and "D-traps" are forbidden. Earth-closets are subject to the same conditions as water-closets, so far as regards- position, lighting, and ventilation. Proper arrangements must be made for the supply of dry earth, and its effectual and frequent application to the excreta; also for con- venience of scavenging, and for exclusion of rainfall and drainage. The receptacle for excreta, whether fixed or movable, must be so constructed as to prevent absorption or escape of the contents, and to exclude rainfall and drainage ; if fixed, its capacity must not be greater than may suffice for three months, nor in any case greater than 40> cubic feet, and it must in every part be 3 inches above the ground. In the case of earth-closets placed mside houses, the maximum limit of size may with advantage be reduced to 2 cubic feet. B Privies must not be erected within 6 feet of a dwelling, public building or place of business, nor withm 50 feet of any water likely to be used for drinking or domestic: purposes or for manufacturing drinks, nor otherwise in such a position as to entail danger of the pollution of such water. Privies must be built so as to admit of con- venient scavenging without carrying the contents through any dwelling, public building, or place of business. There must be an opening for ventilation at the top • the floor must be paved, and raised 6 inches above ground in all parts, with a fall of half an inch towards the door. The receptacle may be fixed or movable. If movable as in pail-closets, the floor of the area beneath the seat must be flagged or asphalted* and raised 3 inches above the ground level, and all the sides of the said area must be made of flag, slate, or brick, at least 9 inches thick, and rendered in cement If the receptacle is fixed, it must be in every part 3 inches above the ground level' and its. capacity not exceeding 8 cubic feet, presuming that the scavenging will be done weekly : suitable means or apparatus must be provided in connection with the mivv for the application of ashes dust, or dry refuse to the filth deposited ; and the receptacle must be so constructed that the contents may not at any time be exposed to rainfall or to the drainage of any waste water or liquid refuse from any adjoining premises, while at the same time conveniently accessible for scavenging ; the materials and construction mustbe such as to prevent any absorption by any part of it of any filth deposited therein or any escape by leakage or otherwise of its contents. It must in no wav be connected Avith a dram. -> Cesspools must not be constructed within 50 feet of any dwelling, public building or place of business, nor withm 100 feet of an water likely to be used for drinking or domestic purposes, or for manufacturing drinks, or otherwise in such a position as to entaiS HOUSE DRAINAGE. 843 danger of pollution of such water. Cesspools must be so constructed and placed as to con- veniently admit of scavenging and cleansing without carrying the contents through any dwelling, public building, or place of business. They must not be connected with any sewer. They must be covered over by an arch, or otherwise, and adequately ventilated. They must be constructed of brick in cement, rendered inside with cement, and with a backing of at least 9 inches of clay. Ashpits must not be constructed within 6 feet of any dwelling, public building, or place of business, nor within 50 feet of any water likely to be used for drinking or domestic purposes, nor otherwise in such a position as to entail danger of the pollution of such water. Ashpits must be so placed and constructed as to conveniently allow of scavenging without carrying the contents through any dwelling, public building, or place of business. The capacity must not exceed 6 cubic feet, or such less capacity as may suffice for a period not exceeding one week. The walls must be of flag, slate, or brick, at least 9 inches thick, and rendered inside with .cement ; the floor must be flagged or asphalted, and raised at least 3 inches above the ground level. The ashpit must be roofed and ventilated, and provided with a door so arranged as to allow of the convenient removal of the contents, and to allow also of being closed and fastened. The ashpit must not be connected with any drain. In London.—In regard to house drainage, water-closets, privies, cesspools, ashpits, the removal and disposal of refuse, the receptacles for dung, and the proper accessories thereof in connection with new buildings or old, by section 39 (1) of the Public Health (London) Act, 1891, the County Council are empowered to make bye-laws, which it is the duty of every Sanitary Authority in London to enforce and observe. Bye-laAvs made by the County Council under the Act do not, however, extend to the city. These bye-laws and any others made by the County Council, under this Act, are subject to the provisions of sections 182 to 185 of the Public Health Act, 1875, as already explained in connection with bye-laws made by any Sanitary Authority in England and Wales: in their main provisions the bye-laws made by the County Council accord closely with those given above as models by the Local Government Board. Earth-closets, privies, and receptacles for dung must, by the London County Council bye-laws, be emptied and cleansed weekly; Avhile cesspools must be similarly treated every three months. The obligations and poAvers of a Sanitary Authority in London in relation to house drainage and the removal of refuse are very similar to those of a Sanitary Authority in other parts of the country. A new house must have "one or more Avater-closets, as circumstances may require," with proper Avater-supply, trapped soil-pan, and other accessories. The same applies to all houses, irrespective of date, under notice from the Sanitary Authority (section 37). A privy or earth-closet may only be substituted if the available sewerage and water-supply is insufficient for a water-closet. Any person who may think himself aggrieved by any notice or act of the Sanitary Authority may appeal to the County Council, whose decision is final. These appeals are governed by section 126. Penalties are prescribed for (a) constructing or re-constructing water-closets, &c, not in accordance with this Act or any bye-laws, or in defiance of notice or prohibition; (b) for dis- continuing any such water-supply without lawful authority; (c) illegaUy or wilfully injuring or constructing a drain or Avater-closet so as to create a nuisance or danger to health (section 41). In Scotland.—When no house drain exists, an owner may, under the Public Health (Scotland) Act, 1867, section 16, be compelled to make one, or provide a cesspool; but there is no provision for compelling or insuring that neAv houses are properly drained. This defect in the Act is practically minimised by the elasticity of the term nuisance under the same Act, Avhich includes any insufficiency of drainage and Avater-closet accommodation. In the towns, the Burgh Police Act, 1892, gives poAvers to the burghal 844 SANITAKY LAAV. authorities, Avhich do not materially differ from the English provisions (sections 238 to 245), except that Avhat are contained in detailed regulations in the Scottish Acts are, in England, left to be prescribed in the form of bye-laws. In Ireland, a Sanitary Authority is empoAvered to enforce the drainage of undrained houses, but it is not compulsory on them to do so, as in England. The Sanitary Authority may also, by the Irish Public Health Act, 1878, require drains and cesspools to be ventilated as may appear necessary (section 25 et seq.). As to drainage in the case of newly built or rebuilt houses, a rural Sanitary Authority cannot enforce it; but it can make bye-laws with respect to the drainage of buildings, a provision which to some extent covers the same ground. This power of making building bye-laAvs is, in Ireland, given to rural as Avell as to urban Sanitary Authorities, without requiring, as in England, an order by the Local Government Board (section 41). The Irish Board has not issued any special model bye-laAvs, as those of the English Local Government Board are fully applicable to Ireland. The general provisions in the Irish Act (section 44 et seq.) relating to sanitary conveniences, &c, are almost the same as those in the English Act of 1875. CLEANSING AND SCAVENGING. In England and Wales.—By section 42, Public Health Act, 1875, every Sanitary Authority may, and when required by the Local Government Board shall, undertake or contract for the removal of house refuse and cleaning of privies, ashpits, &c. Moreover, every urban Sanitary Authority and every rural Sanitary Authority invested with requisite powers may, and when required by the Local Government Board shall, themselves undertake the cleaning of streets; they may also undertake the watering of the same. AU refuse, so collected, shall be the property of the local authority, to be sold or otherwise disposed of, any profits to be applied to the expenses of the Act in urban and rural districts respectively. Eurther, if Part III. of the Public Health Acts Amendment Act, 1890, has been adopted in their district, the Sanitary Authority may, under section 26 (2) of that Act, make byedaws imposing on occupiers duties to facilitate the removal of refuse. Any person obstructing removal to be liable to a penalty not exceeding £5, except as regards refuse, &c, which the occupier intends to employ for his own use, unless he meanwhile suffer it to become a nuisance. If the Sanitary Authority neglect, without reasonable excuse, to remove any refuse within seven days of receiving a remonstrance from the occupier, they shall be liable to pay him 5s. for each further day's neglect (section 43, Act of 1875). An urban Sanitary Authority may, by section 45, provide receptacles and places for the temporary deposit of the matter collected. By section 44, Public Health Act, 1875, the Sanitary Authority has poAver to make bye-laws imposing the duty of cleansing footways, pave- ments, ashpits, privies, cesspools, and removing house refuse when they do not themselves contract or undertake to do the same, and may make bye- laws for the prevention of nuisances from accumulations of snoAV, filth, ashes, &c, and from the keeping of animals. The following is a summary of the Model Bye-laAvs suggested by the Local Government Board in connection with the terms of this section. (a) Private Scavenging.—The occupier of any premises must cleanse the footways and pavements adjoining his premises daily except Sunday. He must remove the house- CLEANSING AND SCAVENGING. 845 refuse once a week, and excreta at intervals not exceeding the folloAving maximum limits:— Earth-closets, Avith fixed receptacle, " >> movable ,, ... Privies, whether the receptacles are fixed or mo\'able, Ashpits, whether receiving excreta or not, Cesspools, .... Must be cleansed at least once in three months. once a week. once a week. once a week. once in three months. (b) Clearing away Snow.—The occupier of any premises must clear away snow from the footways and pavements adjoining his premises as soon as possible after it ceases to tall. (c) Removal of Refuse.—The refuse from any premises shall only be removed in a suitable covered receptacle or carriage, and if removed from premises within 20 yards of any dwelling, place of business, or public building, only between 7 a.m. and 9 a.m. from November to February, and between 6 a.m. and 8 a.m. from March to October. Refuse must not be deposited upon any road, and any refuse accidentally falling upon a road must be immediately gathered up and the place cleansed. ' (d) Deposit of Night-soil and other Refuse.—No load of filth must be deposited for more than twenty-four hours within 100 yards of any street, dwelling, public building or place of business. Night-soil deposited for agricultural purposes upon land withuflOO yards of a street, dwelling, &c, and not deodorised, must at once be dug or ploughed into the ground. (e) Keeping of Animals.—Swine must not be kept within 100 feet of any dwelling nor cattle where they may pollute water likely to be used for drinking, domestic, or dairy •purposes, or for manufacturing drinks. The same prohibitions apply to storage of dung. Premises wherein are kept any swine, cattle, horses, &c, must be provided with proper receptacles for manure, and with efficient drainage ; the receptacle must be water-tight, covered, and entirely above the level of the ground, and it must be cleansed at least once a week ; the drain must be properly constructed and kept in order at all times, so as to convey all liquid filth to a sewer, cesspool, or other suitable receptacle. If the Medical Officer of Health or two medical practitioners certify that any house or part thereof is so filthy as to endanger health, or that the Avhitewashing and purifying thereof would tend to prevent infectious disease, the Sanitary Authority may require the owner or occupier to cleanse, &c.| and in his default may themselves do what is necessary (section 46 Pubhc Health Act, 1875). Section 47 of the same Act prohibits not only keeping swine in dwelling- houses so as to be a nuisance within an urban district, but also suffering stag- nant water to he in cellars or dwellings twenty-four hours after written notice from the Sanitary Authority, and allowing contents of privies and cesspools to overflow or soak out, on a penalty not exceeding 40s., and a daily penalty not exceeding 5s., after notice, and authorises the abatement of the nuisance by the Sanitary Authority at the expense of the occupier. Moreover, a Sanitary Inspector in an urban district may give notice to the owner of any offensive accumulation of matter, or to the occupier of the premises whereon it exists, to have it removed within twenty-four hours, failing which the Sanitary Authority may remove the same (section 49). An urban Sanitary Authority may give public notice requiring the periodical removal of manure from mews, and other public premises, and enforce the same under penalty (section 50). In cases where Part III., Public Health Act Amendment Act, 1890, is in force, by section 27 of the same, the Sanitary Authority have powers for keeping common courts and passages clean, apportioning the expenses incurred to the occupiers of the adjacent buildings. Further, by section 48 of the Public Health Act, 1875, provision is made for obtaining a justice's order for cleansing offensive ditches or water-courses lying near to or forming the boundaries of districts. In London. — The provisions for cleansing and scavenging under the 346 SANITARY LAW. Public Health (London) Act, 1891, are someAvhat more stringent than those of the Public Health Act, 1875, Avhich controls the main actions of Sanitary Authorities in the provinces. By sections 29 and 30 of the London Act, the local authorities must cleanse streets, footpaths, cesspits, earth-closets, and privies. They must remove house refuse at proper inter- vals, and trade refuse also, if required to do so, on payment. As to what is or is not trade refuse, shall, on complaint of either party, be determined by a petty sessional court, such decision being final (section 33(2)). The Sanitary Authority, further, may undertake the collection of manure and other refuse, on request; or may by order require periodical removal by owner (section 36). Section 16 (2) of the same Act empowers the County Council to make bye-laws (a) for prescribing the times for removal of faecal or other offensive matter through London, and for providing that the vessel or carriage there- for is properly constructed so as to prevent any nuisance; and (b) as to the closing and filling of privies, removal of refuse generally, and as to the duties of the occupier in relation to facilitating the removal of it by the scavengers of the Sanitary Authority. Further, a constable may arrest Avithout warrant and take before a justice any person found committing an offence against such bye-laws, and who refuses to give his true name and address. Swine must not' be kept within 40 yards of a street or public place, nor be allowed to stray in any public place. The Court may prohibit the keeping of any animal in any specified place shown to be unfit for the purpose (section 17). In Scotland.—By the Public Health (Scotland) Act, 1867, there is no direct provision, either by bye-law or otherwise, for securing the scavenging or cleansing of the whole or part of a landward district. As a rule, this difficulty is overcome by a landward local authority levying a rate on the whole district for the supply of a scavenger for such parts as need one; Avhile to some extent a County Council may deal with the matter by means of bye-laws for the prevention of nuisances. Burgh scavenging and cleansing is fully regulated by the Burgh Police (Scotland) Act, 1892, sections 107, 127, 316, which vest the Burgh Commis- sioners with powers similar to those in force in England and Wales. The occupiers are required to sweep and wash common stairs, and the owners to Avhitewash and paint them once a year if required by the Sanitary Inspector. In Ireland.—Section 52 of the Irish Public Health Act of 1878 is the same as section 42 of the English Act of 1875, and contains simdar provisions. It practically, however, only applies to urban Sanitary Authorities, as there is no section in the Irish Act corresponding to section 276 of the English Act, Avhich empowers the Local Government Board to invest a rural Sanitary Authority with all or any of the powers and duties of an urban authority. Under section 54 of the Irish Act (corresponding to section 44 of the Enghsh Act) power is given to the Local Government Board for Ireland to require urban Sanitary Authorities to make bye-laws for the prevention of nuisances arising from snow, dust, ashes, filth, &c, and by section 55 the power to provide receptacles for the deposit of rubbish, which in England is permissive and confined to urban Sanitary Authorities, is in Ireland compul- sory and entrusted also to a rural Sanitary Authority. The same extension of powers to rural authorities is given as to penalties for keeping swine in dwelling-houses, and for allowing soakage or overflow from cesspools {section 57). WATER-SUPPLY. 847 Although section 28 of the ToAvns Police Clauses Act, 1847, imposes a penalty of 40s. for keeping a pig-sty in front of any street, or in or near any -street, so as to be a common nuisance, this does not apply generally to "•urban districts in Ireland, as this enactment is not incorporated in the Public Health Act, 1878, and is incorporated in only a few of the local Acts in force in certain urban districts of Ireland. In other respects the provisions as to cleansing and scavenging are similar in both the English Act of 1875 and the Irish Act of 1878. WATER-SUPPLY. In England and Wales.—Owing to the privileges Avhich, from time to time, have been granted to companies and other corporate bodies, Sanitary Authorities are under certain restrictions as to their supplying water. Where a water company has Parliamentary poAvers to supply water over any given area, the Sanitary Authority must give notice to the company stating the purposes for which and extent to which it requires water ; and if the company are able and willing to supply sufficient and proper water for the purposes of the local authority, this latter body may not -construct any water-works within that area (Public Health Act, 1875, section 52). Moreover, section 332 of the Act provides that where the supply of water must be taken from a running stream, the Sanitary Authority, before abstracting water from such stream, river, or source, must obtain the consent in writing of any person or persons who have prior claims upon those streams. When not hampered by either of the foregoing restrictions, any Sanitary Authority may construct works for supplying any part of their district with water, or may take on lease, or hire, or purchase works (with the sanction of the Local Government Board), or contract for the supply -{section 51). When a Sanitary Authority supply water within their district, they have the same powers and are under the same restrictions for carrying their mains within and without their district as they have and are subject to in respect of their sewers (section 54). The water supplied must be pure -and wholesome, and under sufficient pressure as will carry the same to the top storey of the highest dwelling-house in the district supphed. There is, however, no obligation to provide a constant supply under pressure (section 55). The Sanitary Authority have power to charge water-rates and rents in respect of premises to Avhich they supply water, while all pubhc cisterns, pumps, wells, &c, used for the gratuitous supply of water to the inhabitants ■of a district, vest in and are under the control of such authority (sections 56 and 64). The same Act, section 62, gives any Sanitary Authority power to require houses which are without a proper water-supply to be so supplied, if it can he furnished at a cost not exceeding the water-rate authorised by any local Act, or twopence a week, or such other cost as the Local Government Board /may, upon application, determine to be reasonable. In order to guard against the pollution of sources of water-supply, the Sanitary Authority have power to proceed against offenders (sections 68, 69). If the water of any well or ■cistern is deemed to be injurious to health, a justice's order may be obtained ior its being permanently or temporarily closed, or the water to be used for certain purposes only, and for the payment of any necessary analysis of the sample at the cost of the Sanitary Authority (section 70). The general provisions of the Public Health Act, 1875, in respect of 848 SANITARY LAAV. water-supply may be briefly summarised by saying that it is the duty of the Sanitary Authority to provide their district with Avater, Avhere danger exists to the health of the inhabitants from either the unwholesomeness or the insufficiency of the existing supply, and a proper supply can be got at reasonable cost. If the Sanitary Authority neglect to do this duty, the same proceedings can be taken to make them perform it, under section 299 of the Act of 1875, or, if they are a rural Sanitary Authority, under the Local Government Act, 1894, sections 16 and 19, just as can be taken in the case of their failing to supply the district with sewers. But cases arise where it is impossible for the Sanitary Authority to supply water at a reasonable cost; under these circumstances they may require the owner to do so, if he can at reasonable cost (Public Health (Water) Act, 1878, section 3). If neither the Sanitary Authority nor the owner can provide water at a reasonable cost, then, if the absence of a proper water-supply creates a nuisance that the house is unfit for habitation, steps may be taken to obtain a justice's order prohibiting its being so used for human habitation (section 97, Pubhc Health Act, 1875). It was largely to meet difficulties of this kind, especially in rural districts, that the Public Health (AVater) Act, 1878, was designed. It applies to every rural Sanitary Authority, and also to such urban Sanitary Authorities as the Local Government Board may order (section 11). Under section 3 of this Act, it is the duty of the local authority to provide or require the provision of sufficient water-supply to every occupied dwelling-house within their district. From time to time they may take steps, by means of systematic inspections on the part of their officers, to see that these conditions are fulfilled. The same powers of entry upon premises are given as are conferred by sections 102 and 103 of the Public Health Act, 1875, in respect of nuisances (section 7); and if the Medical Officer of Health reports that an occupied house is without a proper water-supply, and the Sanitary Authority are of opinion that such a supply can be provided at a reasonable cost (the interest on which, at 5 per cent., shall not exceed twopence a week, or as the Local Government Board may, on the application of the Sanitary Authority, decide to be reasonable in the circumstances), the Sanitary Authority may require the owner, subject to appeal to the Local Government Board, to provide such supply within a specified time, and, in case of default, may themselves carry out the necessary works at his expense. The authority may, on cause being shown why the requirements of the notice served by them should not be complied with, withdraw the notice or modify the terms thereof. Nothing, however, in this Act must be deemed to relieve the Sanitary Authority from the duty imposed upon them by the Public Health Act, 1875, of providing their district or any contributory part of it with a supply of water, where danger arises to the health of the inhabi- tants from the insufficiency or unwholesomeness of the existing supply, and a general scheme of supply is required, and can be got at a reasonable cost (sections 3 and 4). In order to prevent houses being built in situations where they cannot be provided with water, the Water Act, 1878, has prohibited (section 6) the OAvner of any dwelling in a rural district that may be erected or rebuilt from the ground floor after July 4, 1878, from permitting such house to be occupied without a certificate from the Sanitary Authority that it is provided with a sufficient and available supply of Avholesome water; such certificate to be based upon the report of the Medical Officer of Health or Sanitary Inspector. Section 9 of the same Act provides that, if the Sanitary Authority furnish a stand-pipe for water-supply, they may make Avater- WATER-SUPPLY. 849 charges upon every dwelling Avithin 200 feet, just as if the supply Avere actually given on the premises; but they may not make this levy upon houses which have a good supply within reasonable distance from another source, unless the water from the stand-pipe is used by the inmates. The Local Government Act, 1894, section 8 (1) (e) empowers a Parish Council to utilise any well, spring, or stream within the parish, and to provide facilities for obtaining Avater therefrom, consistent with the just rights of any person or corporation; but these powers do not in any Avay derogate from the obligations of a rural Sanitary Authority in respect of supplying water. Under the Rivers Pollution Prevention Act, 1876, proceedings may be instituted, in respect of pollution of streams by sewage or solid matters, by any private person or aggrieved local authority (section 8); but in respect of manufacturing or mining effluents, Sanitary Authorities only can take action, and subject to the approval of the Local Government Board. The Board, in giving or withholding consent, must have regard to the industrial interests involved, and the circumstances and requirements of the locality. They shall not give their consent to proceedings by a Sanitary Authority of a district wlhch is the seat of any manufacturing industry, unless they are satisfied, after due inquiry, that means for rendering harmless the effluents from such manufacturing processes are reasonably practical and available, and that no material injury to the interests of such industry will be caused by the proceedings (section 6). It is owing to the extensive safeguards which it contains that this Act is so largely inoperative. But it cannot be too clearly understood that, by its provisions, the discharge of solid or liquid sewage, or of any solid matter, into streams, is illegal. Neither may the water-waste of houses, which have no water-closets, be discharged without treatment into streams. The discharge of sewage-farm effluents into rivers is a special question, and permissible, provided the effluent is of a certain purity, and not likely to either create a nuisance or pollute any stream or water-course. In London, the water-supply is in the hands of eight companies, whose powers and rights are regulated by their local Acts and by the Metropolis Water Acts of 1852 and 1871. These companies control the water-supply not only in London, but also over a large extra-metropolitan area. Practi- cally, the water companies in the metropolis have the same position as they have in the provinces, and so far as this question is concerned, neither the County Council nor any other local authority in London has any direct power. The controlling authority, as affecting the public health, over the Avater companies is the Local Government Board, Avho have the water supplied examined periodically, approve or disapprove of new sources of supply, of various regulations made by the companies for preventing waste, misuse or contamination, and who also inquire into complaints made to them as to the quality or quantity of the water supplied by any company for domestic use. The Metropolis Water Act, 1871, section 19, gives the County Council power to ask for the repeal or alteration of any of the regulations for the above purposes, and, if the companies refuse to do so, to appeal to the Local Government Board, who, on inquhy and report of some impartial engineer or person of engineering knowledge, may make such repeal or alterations as they think fit. Sections 8 and 9 of the same Act have similar provisions as to the County Council asking for a constant supply in any given district. No company can, hoAvever, be compelled to give a constant supply to any 3h 850 SANITARY LAW. ptemises in any district until its regulations, as approved by the Local Government Board, are in operation in the district, nor if the company can show that, at any time after tAvo months from the date of the service of any requisition for a constant supply, more than one-fifth of the premises in the district are not supphed Avith the prescribed fittings. The County Council have power to supply the prescribed fittings on default of OAvner or occupier. The Local Government Board have power to order a constant supply with- out apphcation from the County Council, where they think that, by reason of the insufficiency of the existing supply in the district, or the unwhole- someness of such water in consequence of its being improperly stored, the health of the inhabitants is, or is likely to be, prejudicially affected (section 11). The London County Council (General Powers) Act, 1890, section 38, gives the County Council authority to conduct inqmries and negotiations as to water-supply in or near London, and to pay out of the county fund the costs and expenses of such inquiries, not exceeding £5000. So far as relates to the poAver of Yestries and District Boards in connection Avith the water-supply, the Public Health (London) Act, 1891, indicates the absence of a proper water-supply, or of proper fittings in a house, to render such house unfit for habitation. A new house must not be occupied until the Sanitary Authority grant a certificate that it has a proper water-supply (section 48). A water company cutting off the supply of water to any house must give immediate notice to the Sanitary Authority (section 49). For the closure of polluted wells, &c, the Sanitary Authority have only to satisfy the justice that the water is " so polluted, or likely to be so polluted, as to be injurious or dangerous to health " (section 54). It must be noted that this section gives a Sanitary Authority somewhat greater poAvers than section 70 of the Pubhc Health Act, 1875, inasmuch as it says not only when the water is so polluted as to be injurious to health, but when it is so polluted, or likely to be so polluted, as to be injurious or dangerous to health. Moreover, it gives the Court no power to allow the water to be used for certain purposes only, and imposes a fine not exceeding £20 for disobedience to any order under the section. Every Sanitary Authority under the Act must make bye-laws for cleans- ing and guarding tanks, cisterns, and other receptacles for storing water, likely to be used for drinking or domestic purposes, from pollution (section 50). The Model Bye-laws framed by the Local Government Board in connection with this section demand : (1) the emptying and cleansing of cisterns and tanks once at least in every six months, and at such other times as may be necessary to keep them clean; (2) every such tank, cistern, or receptacle to be provided with a proper cover, and to be kept at all times properly covered. In cases where two or more tenants of a premises are entitled to the common use of any tank, cistern, or receptacle to Avhich this bye-laAv applies, the foregoing requirements apply to the OAvner instead of to the occupier of the premises. In Scotland, the difficulty Avhich exists in England in acquiring a compulsory water-supply by means of a provisional order is not felt, because the Public Health (Scotland) Amendment Acts, 1882 and 1891, apply certain compulsory clauses of the Land Clauses Acts not only to the construction of sewers, but also to the provision of a water-supply in landAvard or rural districts. So soon as a local authority considers a pubhc supply expedient, on representing the facts to the Secretary for Scotland, he is empowered to issue provisional orders (subject to Parliamentary confirmation) to bring those clauses into action for the purposes mentioned. WATER-SUPPLY. 851 The cost of the water-supply either falls, in the form of a water-rate, upon the Avhole district, or upon any special district according to the circum- stances. Special districts may be combined, their area may be altered, and in some cases the special water-rate may be supplemented by a general rate over the whole district. Burghal Avater-supplies may be obtained either under the Public Health {Scotland) Act, 1867, or under the Burgh Police (Scotland) Act, 1892. Under the former Act, in towns with a population under 10,000, or in burghs where the local Police Act makes insufficient provision, a water- supply may be obtained as in landAvard districts, proceeding by provisional order where any compulsory clauses are necessary. If a Avater company exists, the local authority may contract with it, or purchase it, but may not enter into competition with it. In larger towns with a population over 10,000, or having a local Police Act, the local authority may provide a water-supply either by contract with a water company, or, where there is no company, directly. Under the Burgh Police Act, 1892, which does not for these purposes apply to burghs supplied with water before 1895 under local Acts, the Burgh Commissioners of towns having a population below 5000 may apply the compulsory clauses of the Land Clauses Acts with the consent of the sheriff only, and without a pro-visional order. The Public Health (Water) Act, 1878, does not extend to Scotland, hence there is no poAver to prevent a new house being built without a proper water-supply; but in respect of houses already built, the Sanitary Authority is required by the Public Health (Scotland) Acts " to compel an owner to obtain a water-supply at or near his house, and, in a burgh, may ■compel him to take it into his house." In Ireland.—The Public Health (Ireland) Act, 1878, enables all Sanitary Authorities to require all houses to be supphed with water " at such cost as the Local Government Board may determine under all the circum- stances to be reasonable," there being no limit of cost prescribed as in England (section 72). If the owner, Avhen required by the Sanitary Authority, does not execute the necessary works, the Sanitary Authority may do them, and recover the cost summarily, or, if it be an urban Sanitary Authority, the cost may be declared to be private improvement expenses. The Public Health (Water) Act, 1878, not being in force in Ireland, the provisions therein offered cannot be applied. Another important difference between the Irish and English Acts is that, by section 61 of the Irish Act, a Sanitary Authority can acquire the right to abstract Avater from a running stream or other source otherAvise than by agreement. By section 202 every Sanitary Authority is endoAved with -compulsory poAvers to acquire water rights for drinking and domestic purposes : there is a saving clause for the existing water companies (section 62, corresponding to section 52 of the English Act), but it has not stood in the way of amicable arrangements being made between the Sanitary Authorities and the water companies, as to the acquirement by the former of new and additional supplies. The laAv as to water-rates in Ireland is similar to that in England, except that the levying of such rates is entirely -optional with the Sanitary Authority, and who, moreover, cannot levy them in respect of either public stand-pipes or street-fountains (section 66). 852 SANITARY LAW. NUISANCES. In a legal sense, nuisances are of two chief kinds, namely (1) nuisances at common laAv; (2) nuisances under the Public Health Acts, commonly called " statutory nuisances." At common laAv a nuisance may be public, private, or both. A public nuisance is thus defined by Stephen in his Digest of Criminal Laiv (art. 176):—"An act not Avarranted by laAv, or an omission to discharge a legal duty, which act or omission obstructs, or causes inconvenience or damage to the pubhc in the exercise of rights common to all Her Majesty's subjects." As examples of public nuisances may be quoted the pollution of the ah by smoke or by noxious fumes from a factory, obstruction of a highway, and exposure of infected persons in the public way. A private nuisance is anything done to interfere with the proprietary rights of another in land, not amounting to a trespass (Wynter-Blyth). As examples of private nuisances one may mention special annoyance from steam-hammers or engines making a noise, and the special annoyance from smoke. A mixed nuisance is obviously a nuisance which belongs to both of the above- mentioned varieties. Statutory nuisances under the Public Health and Sanitary Acts alone concern the officers of Sanitary Authorities. As relating to the Public Health, these statutory nuisances have been Avell defined by Wynter-Blyth as being " something Avhich either actually injures, or is likely to injure, health, and admits of a remedy, either by the individual whose act or omission causes the nuisance, or by the local authority." It is important to bear in mind that in the Public Health Act sense, as now understood and interpreted, the idea of a nuisance embraces future as well as present consequences. The Public Health Law, in respect of nuisances, may be summarised, for the various parts of the United Kingdom, in the following manner. In England and Wales.—The provisions of the Public Health Act, 1875, sections 91 to 111, apply to every urban and rural sanitary district, and are "deemed to be in addition to, and not to abridge any right, remedy, or proceeding under any other provisions of the Act, or under any other Act, or at laAv or in equity." But no person may be punished for the same offence both under these provisions and under any other law or enactment. Under this Act of 1875 "nuisance" is regarded as likely to arise in con- nection with: (a) Sewers, sections 18 and 19; (b) SeAvage, section 27; (c) Construction of drains, closets, ashpits, and cesspools, sections 40 and 41; (d) In connection with snow, filth, dust, ashes, and rubbish, section 44; (e) Swine, pig-styes, and stagnant Avater in ceUars, or the overfloAving of pri-vies and cesspools, section 47; (f) Offensive trades, sections 112, 113, and 114. In regard to some of these cases, remedies are given by other provisions of the Act, more particularly by sections 41, 49, and 50. It Avill rest Avith the Sanitary Authority to determine under which provisions they will pro- ceed, having regard to the circumstances. The main section deahng Avith nuisances is, hoAvever, section 91, which defines the folloAving to be nuisances to be dealt Avith summarily under the Act:— (1) Any premises, including buildings and lands, in such a state as to be a nuisance or injurious to health. (2) Any pool, ditch, gutter, water-course, privy, urinal, cesspool, drain, or ashpit so foul, or in such a state as to be a nuisance or injurious to health. (3) Any animal so kept as to be a nuisance or injurious to health. (4) Any accumulation or NUISANCES. 853 deposit which is a nuisance or injurious to health. (5) Any house, or part of a house, so overcrowded as to be dangerous or injurious to the health of the inmates, whether or not members of the same family. (6) Any factory, workshop, or workplace, not kept in a cleanly state, or not ventilated in such a manner as to render harmless as far as practicable any gases, vapours, dust, or other impurities generated in the course of the work carried on therein, that are a nuisance or injurious to health, or so overcrowded as to be dangerous or injurious to the health of those employed therein. (7) Any fireplace or furnace which does not, as far as practicable, consume the smoke arising from the combustible used therein, and which is used for working engines by steam, or in any manufacturing or trade process whatever ; and any chimney (not being the chimney of a private dwelling- house) sending forth black smoke in such quantity as to be a nuisance. In defining these nuisances, the same section, however, provides that there is no penalty if the accumulation or deposit mentioned in (4) is necessary for, and has not been kept longer than is necessary for, the carrying on of any business or manufacture, and if the best available means have been taken for preventing injury to the public health. The pro-visions of subsection (6) apply to all buildings, including schools, factories, and workshops, except such as are subject to the special provisions, relating to cleanliness, ventilation, or overcrowding, of the Factories and Workshop Acts. In respect of (7), there is no penalty if the Court is satisfied that the fireplace or furnace is constructed in such manner as to consume as far as practicable, having regard to the nature of the manufacture or trade, all smoke arising therefrom, and that such fireplace or furnace has been care- fully attended to by the person in charge thereof. Under the smoke sections, it is not necessary in taking action to prove anything with regard to health, it being sufficient to prove that on such and such a day and hour the chimney emitted black smoke. Urban Sanitary Authorities have some other powers Avith regard to smoke under section 171 of this Act, and under the Railway Regulation Act, 1868, and the Highways and Locomotives Act of 1878. For interpreting the term "overcroAvded" in subsection 5 of section 91, Public Health Act, 1875, a sanitary officer usually takes as his guide the minimum standards laid down by the Local Government Board in their bye- laAvs, namely, 400 cubic feet for rooms in which persons both live and sleep, and 300 cubic feet for rooms solely used for the waking life of the tenants. In the event of a second conviction for overcrowding within three months, the Court may order the closing of the premises (section 109). Another point to be noted in connection with this subsection is that the words " tent, van, shed, or similar structure " may be included within it by section 9 of the Housing of the Working Classes Act, 1885. Unfenced quarries and abandoned coal-mines are deemed to be nuisances under section 91 of the Public Health Act, 1875, by the Quarry Fencing Act of 1887, and the Coal-Mines Regulation Act, 1887. It is the duty of every Sanitary Authority to cause their district to be in- spected for the detection of nuisances and to enforce the provisions of the Public Health Act, 1875, in order to abate the same (section 92), but the authority may be put in motion by any person aggrieved, or by any two inhabitant householders of such district, or by any officer of the Sanitary Authority, or by the relieving officer, or by any police officer (section 93). If satisfied of the existence of a nuisance, the Sanitary Authority is required by the Act to serve a notice on the person responsible, or, if he cannot be found, on the OAvner or occupier of the premises on which the nuisance arises, requiring him to abate the same within a time to be specified in the notice, and to execute such works as are specified in the notice as being necessary. Where the nuisance arises from the Avant or defective construction of any 854 SANITARY LAW. structural convenience, or Avhere there is no occupier, the notice must be served on the OAvner. If the person causing the nuisance cannot be' found, and the OAvner or occupier is not responsible for its occurrence, the Sanitary Authority may themselves abate the same Avithout further order (section 94). On non-compliance Avith the notice, or if the nuisance, although abated, is likely to recur, the Sanitary Authority may apply to a justice, who must thereupon summons the person responsible to appear before a Court of summary jurisdiction (section 95). If the Court is satis- fied that the alleged nuisance exists, or that, although abated, it is likely to recur on the same premises, it must make an order requiring him to comply Avith the notice, or prohibiting the recurrence of the nuisance, and directing the execution of any necessary Avorks. The Court may further impose a penalty not exceeding £5 (section 96). Where the nuisance is such as to render the house unfit for habitation, the Court may order the house to be closed, and may cancel this by a further order when satisfied that the house has been made fit for habitation (section 97). Any person not obeying the order of the Court, or failing to use diligence, is liable to a penalty not exceeding 10s. per day during his default; and the Sanitary Authority may carry out the order and charge him with the expenses (section 98). Where the person responsible for the nuisance cannot be found, the order of the Court may be carried out by the Sanitary Authority; and any matter or thing removed by the authority in abating any nuisance may be sold (sections 100, 101). Where any nuisance under the Act is caused by the acts or defaults of tAvo or more persons, the Sanitary Authority may institute proceedings against any one or more of such persons (section 255). Where a nuisance within a district is caused by some act or default beyond its limits, the Sanitary Authority may institute proceedings, provided that these be taken before a Court having jurisdiction in the district Avhere the act or default is alleged to be committed or take place (section 108). For the purpose of the provisions of this Act of 1875 relating not only to nuisances but also for infectious diseases and hospitals, any ship or vessel lying in any water within the district of a Sanitary Authority is subject to their jurisdiction, as if it were a house. If in any other water, it is deemed to be Avithin such district as the Local Government Board may prescribe, and in the absence of any such prescription then within the nearest sanitary district (section 110). The master or other officer in charge of any such ship will be deemed to be the occupier; but these provisions do not apply to any of Her Majesty's ships, or to those of any foreign government. The Sanitary Authority and their officers have rights of entry between 9 a.m. and 6 p.m. upon private premises, and, in the case of a nuisance arising in respect of any business, at any hour Avhen such business is in progress. If admission is refused, a justice's order may be obtained (sections 102, 103). Where Sanitary Authorities fail to take proceedings for abatement of nuisances, individuals may obtain a remedy in one of three Avays, either (1) by complaining to the Local Government Board, who may issue an order, enforceable by mandamus in a High Court of Justice (section 299); or (2) on it being proved to the satisfaction of the Local Government Board that a Sanitary Authority have made default in relation to nuisances under the Public Health Act, 1875, that Board may authorise any police officer, acting within the district of the defaulting authority, to institute proceedings which the defaulting authority might institute with regard to such nuisance (section 106); or (3) an individual may complain direct to a justice as to the existence of a nuisance, and the Court may make orders, penalties for NUISANCES. 855 disobedience of orders, &c, as in the case of a complaint relating to a nuisance made to a justice by a Sanitary Authority (section 105). This latter mode of procedure is obviously the most expeditious for any individual to take where he feels aggrieved by the neglect of a Sanitary Authority to take proceedings, and Avhere the existence of a nuisance within the meaning of the Act is clear. In London.—The powers and duties of the Vestries and District Boards, in the capacity of Sanitary Authorities in London, with respect to nuisances under the Public Health Act (London), 1891, in the main correspond with those relating to nuisances under the Public Health Act, 1875, as explained under England and Wales. But they embody several amendments and extensions of the law which have materially strengthened the hands of the Sanitary Authorities in London in dealing with nuisances. Section 2 of the London Act extends the definition of "nuisance," making it include not only that which is injurious to health, but also that which is dangerous to health. It also makes it include any cistern, water-closet, earth-closet, or dung-pit, so foul or in such a state as to be a nuisance or injurious or dangerous to health, and any such absence from premises of water-fittings as is a nuisance by virtue of section 3 of the Metropolis Water Act, 1871. Further, any person may give information to the Sanitary Authority of a nuisance, and it is the duty of every officer of the authority and of the relieving officer so to do, and to give written notice to the persons Avho may be required to abate it. In giving notice requiring abatement of a nuisance, it is optional to specify the works to be executed: also, where the persons responsible for causing the nuisance cannot be found, the Sanitary Authority may not only themselves abate the nuisance, but also do what is necessary to prevent its recurrence. In cases of overcroAvding, the Sanitary Authority must take proceedings to abate the nuisance. The penalty for wilful nuisance or non-abatement is a fine of £10 for each offence, whether an order to abate it or prohibiting its recurrence is made or not (section 4). SimUarly, the maximum fines for failing to comply with an order for the abatement of a nuisance or for acting contrary to a prohibition order are increased from the amounts fixed by the Public Health Act, 1875, to 20s. a day and 40s. a day respectively during default or contrary action, as the case may be (section 5 (9)). Wilful damage to drains, water-closets, &c, so as to create nuisances involve a fine not exceeding £5 (section 15). Groundless appeals to Quarter Sessions against nuisance orders are checked by daily fines of 20s. (section 6 (3) (4)). The Sanitary Authority, moreover, are required by section 16 of the London Act to make bye-laws for the prevention of nuisances arising from (1) any snoAV, ice, salt, dust, ashes, rubbish, offal, carrion, fish, filth, or other matter in the street; (2) from any offensive matter running out of any manufactory, brewery, slaughter-house, knacker's yard, butcher's or fishmonger's shop, or dung-hill, into any uncovered place, whether or not surrounded by a wall or fence; (3) from keeping of animals; (4) as to the paving of yards and open spaces in connection with dwelling-houses. It is, moreover, the duty of the Sanitary Authority to enforce any bye-laws made, in respect of these matters, by the County Council. As regards the prevention of smoke, section 24 of the Public Health (London) Act, 1891, corresponds closely Avith section 91 of the Act of 1875; but the main provisions against nuisances arising from smoke in the metropolis are contained in section 23 of the London Act of 1891, Avhich provides that "every furnace employed in the working of engines by steam, 856 SANITARY LAW. and every furnace employed in any public bath or wash-house, or in any mill, factory, printing-house, dye-house, ironfoundry, glass-house, distillery, brew-house, sugar refinery, bakehouse, gas-Avorks, water-Avorks, or other budding used for the purpose of trade or manufacture (although a steam- engine be not used or employed therein) shall be constructed so as to consume and burn the smoke arising from such furnace." Sanitary Authorities must carry out these provisions of this section, and, moreover, any information under it is not to be laid except under the direction of a Sanitary Authority. This section extends to the Port of London, where it must be enforced by the port Sanitary Authority, which is the City Corporation. In Scotland.—The statutory enumeration of nuisances which may be summarily dealt with, as contained in the Public Health (Scotland) Act, 1867, is somewhat more comprehensive than that of the English Act of 1875 or the London Act of 1891. This is somewhat fortunate, especially in landward districts, as, owing to "the absence of specific powers of prevention, a local authority is obliged, as a rule, to rely upon its powers of prosecution Avith a view to the removal of nuisances" (sections 16, 30, 96, 122). Except in certain cases as regards fireplaces, furnaces, and chimneys sending forth smoke so as to be injurious to health, and also churchyards or cemeteries so situated, or so crowded with bodies, or so conducted as to be offensive or injurious to health, the summary decision of a sheriff, magis- trate, or justice upon the alleged existence of a nuisance is final. As regards manufactories, trades, and businesses injurious to the health of the neighbourhood, or so conducted as to be offensive or injurious to health, or any collection of bones or rags, as well as factories not under any general Act for the regulation of factories or bakehouses, a medical certificate or requisition by ten inhabitants is required before the justice can give an interdict of the nuisance. The sheriff, magistrate, or justice may order remedial works to be carried out, or ordain the local authority to do so and to recover expenses from the owner of the premises or person responsible for the nuisance. There are no saving clauses at all correspond- ing to those in the English Act. A County Council, subject to the approval of the Secretary for Scotland, to make bye-laws " for prevention and suppression of nuisances not already punishable in a summary manner by virtue of any Act in force throughout the country"; and Burgh Commissioners, subject to the approval of the Local Government Board, have similar powers in respect of the burghs (Burgh Police (Scotland) Act, 1892). If a local authority refuse to enforce the provisions of the Public Health (Scotland) Act as to nuisances or otherwise, any two householders, or the inspector of the poor, or the local procurator fiscal, or the Local Government Board may apply to the sheriff for a summary decision and decree. The subsequent course of action is similar to that under similar circumstances in England. In Ireland.—The nuisance prevention provisions are almost, if not quite, identical in the Public Health (Ireland) Act, 1878, section 107 et seq., Avith those of the English Act of 1875; consequently, the explanations already given as to the law of nuisances in England and Wales hold good for that in Ireland. The Coal-Mines Regulation Act, 1887, applies to Ireland, but the Quarry (Fencing) Act of the same year does not apply. CELLAR DAVELLINGS. 857 CELLAR DWELLINGS. In England and Wales.—The Public Health Act, 1875, section 71, prohibits the separate occupation as a dwelling of any cellar (including any vault or underground room) built or rebuilt after the passing of the Act, or which was not lawfully so let or occupied at the time of the passing of the Act. Anyone passing the night in a cellar is deemed to occupy it (section 74). No cellar could be considered to be lawfully let or occupied at the time of passing the 1875 Act which was not so let or occupied previously to August 7, 1866; and in the case of some few urban sanitary districts, where section 67 of the Public Health Act of 1848 was still in force in 1875, no cellar could be lawfully let or occupied as a dAvelling which Avas not so let or occupied prior to August 31, 1848. Cellar dwellings, the letting or occupation of Avhich are not forbidden under section 71, are prohibited by section 72 from being let or occupied unless they comply with the following requirements :—(a) The height must in every part be at least 7 feet, 3 feet of which must be above the level of the adjoining street, (b) An open area at least 2\ feet wide in every part, and 6 inches below the level of the floor, must extend along the whole frontage. It may be crossed by steps, but not opposite the window, (c) The cellar must be drained by a drain at least 1 foot below the floor, (d) There must be proper closet and ashpit accommodation, (e) There must be a fireplace and chimney, and (/) a Avindow at least 9 square feet in area, made to open. The window of a back cellar let or occupied along with a front cellar need only be 4 square feet in area. Any person AAdio lets, occupies, or knowingly suffers to be occupied for hire or rent any cellar contrary to the Act is liable for every offence to a penalty not exceeding 20s. for every day of default (section 73). Where two convictions relating to the occupation of a cellar as a separate dwelling have taken place Avithin three months, a Court of summary jurisdiction may close, either temporarily or permanently, the premises, as it deems to be necessary (section 75). In London.—The provisions as to cellar dwellings by sections 96 to 98 of the Public Health (London) Act, 1891, differ somewhat from those given in the preceding section. A cellar dwelling or underground room must not be occupied in London unless:—(a) Every part is 7 feet high, and the ceiling is at least 3 feet above the surface of the adjoining street; but, if the area outside is as much as 6 feet in width, or not less wide than the depth of the floor below the ground level, then the height may be 1 foot above the street, (b) Every wall has a damp-course, and, if in contact with the soil, is effectually secured from damp from the soil, (c) There is an open area outside along the frontage, 4 feet icide in every part, and 6 inches below the floor level. It may be crossed by steps but not opposite a window- (d) The area and the soil immediately below the room are effectually drained, (e) The holloAV space (if any) below the floor is ventilated to the outer air. (/) Any drain passing under the room is properly constructed of gas-tight pipe, (g) The room is effectually secured against the rising of any effluvia or exhalation. (k) There is a proper water-closet and ashpit in a convenient place, (i) There is effectual ventilation. (/) There is a fireplace, with chimney, (k) There are one or more windows opening directly into the open air; the -windoAV-area being at least one-tenth of the floor-area, and so constructed that at least half of each AvindoAv can be opened, and in each case opening to the top. 85S SANITARY LAAV. The same conditions apply to underground rooms occupied separately as dAvellings before January 1, 1892 ; but the Sanitary Authority, either by" general regulations or upon special application by the OAvner, may modify any- con ditions neAAdy imposed by this Act Avhich involve structural alteration, of the building. The poAver as to closure of underground rooms after tAvo convictions is the same as under the 1875 Act. In Scotland.—Under the Public Health (Scotland) Act, 1867, sections 45 to 47, the occupation of cellars or underground rooms is regulated under similar conditions to those in force in England and Wales: " but there is no prohibition of the occupation of such dAvellings, provided the conditions be observed, even if built after the passing of the Act." In Ireland.—Practically there are no differences between the provisions- of the Irish and English Public Health Acts under this heading : section 82: of the former corresponding to section 71 of the latter. COMMON LODGING-HOUSES. In England and Wales.—While the Public Health Act, 1875, does not give any definition of the expression " common lodging-house," it is commonly taken to mean, for the purposes of the Act, those lodging-houses " in which persons of the poorer class are received for short periods, and, though strangers to each other, are allowed to inhabit one common room." The term does not cover rooms common to the members of one family or household, nor inns, nor lodgings let to the middle or upper classes. Section 76 of the Act requires every urban and rural Sanitary Authority to keep a register of common lodging-houses in their district, in which shall. be entered the names and residences of the keepers thereof, and the situation. of every such house, and the number of persons authorised by such authority to be received therein. It is unlawful to keep a common lodging-house' unless it is registered (section 77), and this can only be done after it has- been inspected and approved for the purpose by some officer of the Sanitary Authority (section 78). If required, the notice of registration must be affixed to the house (section 79). Before any premises are approved as suitable for a common lodging-house they should— "(1) Possess the conditions of Avholesomeness needed for dAvelling-houses in general p and (2) should have arrangements fitting it for its special purpose of receiving a number of lodgers." Thus, the house should have dry foundations, and have proper drainage, guttering, and spouting, with a well-laid and paved yard abutting on it. The drains must beproperly connected, the soil pipe ventilated, the water-closets trapped, and all waste pipes from sinks, basins, &c, discharging over gullies outside the house. The- closets, privies, and receptacles should be in convenient situations, of proper construc- tion, and adapted to the scavenging arrangements of the district. The walls, roof, and floors should be in good repair. Inside Avails should not be papered. Every registered! room should have special means of ventilation, by chimney if possible, and a windoir opening freely and directly upon the outer air. There should be kitchen and day-room accommodation apart from the bedrooms. Rooms partially underground should not bs- registered as sleeping rooms. There should be a supply of pure water, allowing at least 10 gallons per head per day for the maximum number of inmates, and one closet for every twenty registered lodgers. The Avashing accommodation should, wherever practicable, be in a special place, and not in the bedrooms ; the basins for personal Avashing being. fixed, trapped, and fitted with disconnected waste pipes. No premises, failing to fulfil the above indicated requirements, should be> approved by the Sanitary Authority for registration as a common lodging- house. COMMON LODGING-HOUSES. 859 When the lodging-house is without a proper water-supply, and this can be furnished at a reasonable rate, the Sanitary Authority may enforce it (section 81). The keeper is required to limeAvash the walls and ceilings in the first week of April and October in every year (section 82). The Sanitary Authority have poAver to require the keeper of a house in which vagrants or beggars are received to make returns of persons who have slept there the night before (section 83), and the keeper must always give notice to the Medical Officer of Health and to the relieving officer of any case of infectious disease (section 84). In any urban or rural sanitary district in which Part III. of the Public Health Acts Amendment Act, 1890, has been adopted, any keeper of a common lodging-house who fails to give the notice required by the last mentioned section is liable to a penalty not exceeding 40s., and to a daily penalty not exceeding 5s. Free access must be allowed to officers of the Sanitary Authority to a common lodging-house or any part thereof, and any person avIio refuses such access will be liable to a penalty not exceeding £5 (section 85). Section 80 of the Public Health Act, 1875, requires all Sanitary Authori- ties to make bye-laavs (1) for fixing and varying the number of lodgers who may be received into a common lodging-house, and for the separation of the sexes therein; and (2) for promoting cleanliness and ventilation; and (3) for the giving of notices and the taking of precautions in a case of any infectious disease; and (4) generally for the Avell ordering of such house. The Local Government Board have issued a series of Model Bye-laAvs for the purposes of this section, of which the following is a summary:— (a) A greater number of lodgers than the maximum from time to time fixed by the Sanitary Authority by a notice served on the keeper of the house must not be accommo- dated in each room ; it is usual to require at least 300 cubic feet of air-space per head, but to count two children as one adult. (6) In general, no person above ten years of age must occupy the same sleeping room as persons of the opposite sex, but rooms may be set apart for the sole use of married couples, to the exclusion of other persons over ten years of age, on condition that every bed is screened off. No bed must be occupied by more than one male above ten years of age. (c) The yards, &c, must be kept clean and in good order ; all floors swept daily, and washed once a week ; all windows, painted sur- faces, and fittings of Avood, stone, or metal kept clean, (d) Closets must be kept clean and in good and efficient order, (c) Ashpits must be kept clean and in good order ; no filth or Avet refuse being thrown into ashpits designed for dry refuse only. (/) The windows must be opened fully for an hour in the morning and an hour in the afternoon, except in case of bad weather or occupation of the room by a sick person, or other suffi- cient cause. Beds must be stripped of clothes and fully exposed to the air for an hour each day, and must not be re-occupied within eight hours after being vacated. All refuse and slops must be removed every day before 10 a.m., and all utensils cleansed daily. Every sleeping room must be provided with sufficient bedsteads, beds, bed-clothes, and utensils for the use of the maximum number of lodgers to be received therein, {g) A sufficient supply of suitable basins, Avater, and toAvels must be provided for the use of lodgers, and must be kept clean and renewed as required, (h) If the keeper finds that any lodger is suffering from an infectious disease, he must at once take all necessary precautions. No person, except a relative or attendant, must occupy the same room as the sick person. If the patient is removed to hospital by the Sanitary Authority, the keeper must afford all facilities for removal, and must adopt all precautions directed by the Medical Officer of Health. He must, if required to do so, temporarily cease to receive lodgers into any infected room. At the end of the case, by removal, recovery, or death the keeper must at once give notice to the Medical Officer of Health, and must cleanse and disinfect every part of the infected rooms and their contents, and in doing so must comply Avith all the instructions of the Health Officer. When the cleansing and disinfection are completed, he must give notice thereof to the Medical Officer of Health, and must not receive any lodger into the rooms in question until two days after such notice has been given, (i) A copy of the bye-laws in force Avith respect to common lod°ing-houses, supplied by the Sanitary Authority, and a statement of the prov-isions of sections 75 to 89 of the Public Health Act, 1875, must be placed in some conspicuous place in the house, and must not be concealed, altered, obliterated, or injured. 860 SANITARY LAAV. In London.—Outside the city of London the metropolitan common lodging-houses are regulated by the Common Lodging-houses Acts, 1851 and 1853, which, "except as regards the Metropolitan Police District, Avere repealed by section 343 of the Public Health Act, 1875." Section 3 of the Act of 1851 provided that the Act should be executed Avithin and for all parts of the Metropolitan Police District by the Commissioners of Police. By a provisional order, however, of the Local Government Board, dated May 7, 1894, since confirmed by Parliament, these powers and duties of the Police Commissioners under those Acts have been transferred to the London County Council, from November 1, 1894. Under the Common Lodging-houses Acts of 1851 and 1853, the powers for the control and management of those places are practically the same as those of Sanitary Authorities in other parts of the country under the Public Health Act, 1875; power being given to make regulations for them, subject to con- firmation of the Home Secretary (section 9). In the city of London the provisions of the Public Health Act, 1875, as to common lodging-houses appear to apply, the Commissioners of Sewers being the local Sanitary Authority. In Scotland.—By the Public Health (Scotland) Act, 1867, sections 59 to 70, the provisions respecting common lodging-houses are similar to those in force in England. The definition, hoAvever, of a common lodging-house is peculiar, it being defined " as a house or part thereof where lodgers are housed at an amount not exceeding fourpence per night for each person, Avhether the same be payable nightly or weekly, or at any period not longer than a fortnight, or Avhere the house is licensed to lodge more than twelve persons." The amount charged may, with the approval of the Sanitary Authority, be diminished or raised, but not to exceed sixpence. In Ireland.—The Irish Public Health Act of 1878, section 2, defines a common lodging-house to mean " a house in Avhich, or in any part of which, persons are harboured or lodged for hire for a single night, or for less than a week at a time." The provision empowering a Sanitary Authority to remove a lodging-house from the register until a proper water-supply has been provided is compulsory, and not merely permissive as in England (section 92). In the case of failure on the part of the keeper to limewash the AvaUs in the first weeks of April and October in each year, the work can be executed by the Sanitary Authority, and the cost recovered in a summary manner (section 93). Excepting some other minor differences, the provi- sions of the Irish Act, in respect of common lodging-houses, conform closely with those of the English Act; while the Model Bye-laws, issued by the Local Government Board for use in England, will also apply, with some small modifications, to Ireland. TENEMENT HOUSES. The term " tenement houses" is here used to express houses which, while not being common lodging-houses as defined in the last section, are let in lodgings' or occupied by members of more than one family. So far as relates to sanitary enactments hereafter to be explained, these tenement houses, as above defined, are assumed to be only those houses occupied by persons belonging to the poorer classes, and do not embrace houses of higher rateable value. In England and Wales.—Every Sanitary Authority, in respect of so- called "tenement houses," has poAver to make bye-laws for their control and TENEMENT HOUSES. 861 management by the Public Health Act, 1875, section 90, and the unrepealed 8th section of the Housing of the Working Classes Act of 1885. These bye-laws should be framed for (1) fixing, and from time to time varying, the number of persons who may occupy a house or part of a house, which is let in lodgings or occupied by members of more than one family, and for the separation of the sexes in a house so let or occupied; (2) for the registration of such houses; (3) for their inspection; (4) for enforcing drainage, and the provision of privy accommodation, cleanliness, and ventilation; (5) for cleansing, limewashing at stated intervals, and for the paving of the yards; (6) for the giving of notices, and the taking of precautions in case of infec- tious disease. Practically, the general tenor of these bye-laws is the same as those pro- posed for common lodging-houses; but in the absence of any express limitation, in the sanitary Acts, of their scope, Sanitary Authorities are advised by the Local Government Board to insert a clause in their bye-laws relating to these houses, providing for the exemption of lodging or tenement houses, as to which it may be reasonably inferred that such supervision, as elsewhere a Sanitary Authority alone can sufficiently exercise, will be exercised, in fact, by the lodgers themselves. In other words, it is assumed that bye-laAvs are unnecessary in the case of tenement houses occupied by well-to-do persons. The Local Government Board have issued Model Bye-laws, dealing Avith these houses, which are somewhat lengthy. The nature of some of them may be inferred from the models relating to common lodging-houses; but in respect of one or two points, special notice is necessary. Thus, it is suggested that every room should have a notice or placard indicating hoAV many inmates may be received in each sleeping or other apartment. The minimum free air space allowed, for rooms used exclusively for sleeping, should be 300 cubic feet for every person exceeding ten years of age, and 150 cubic feet for those under ten years. Where a room is not used exclusively for sleeping purposes, these spaces may be increased to 400 and 200 cubic feet respectively. The Model Bye-laws do not contain provisions for the separation of the sexes. This omission arises from a reasonable doubt whether this is practicable under the ordinary conditions of life in lodgings of the poorer class. Where, however, a Sanitary Authority are satisfied that a rule on this subject can be enforced Avithout hardship, it should be framed and enforced. Another point is that, considering the registration of these houses is not laid down by the laAv as for common lodging-houses, the landlord should furnish a statement, on requisition by the Sanitary Authority, as to (a) the total number of rooms in the house; (b) the total number let in lodgings or occupied by members of more than one family; (c) the manner of use of each room; (d) the number, age, and sex of the occupants of each sleeping room; (e) the name of the lessee of each room; and (/) the amount of rent or charge payable by each lessee. The other Model Bye- laws relating to inspection, drainage, privy accommodation, &c, do not materiaUy differ from those proposed for common lodging-houses. In sea-port towns, under section 214 of the Merchant Shipping Act, 1894, the Sanitary Authority may make bye-laws as to seamen's lodging-houses, subject to sanction of the President of the Board of Trade. Such bye-laws must, amongst other things, proAride for licensing, inspection, general sanitation, pubhcation of the fact of a house being licensed, due execution of bye-laws and regulations, the prevention of persons not duly licensed purporting to keep licensed houses, the exclusion of persons of improper 862 SANITARY LAW. character, and sufficient penalties for breach of such bye-laAvs, not exceeding £50. If a Sanitary Authority do not make, revoke, or alter bye-laAvs in respect of these matters, after notice from the Board of Trade, that body may do so; and an Order in Council may be made requiring all seamen's lodging- houses to be licensed, and none but persons duly licensed shall keep seamen's lodging-houses or let lodgings to seamen in any sea-port town or part thereof. Section 259 of the same Act enables the corporations of municipal boroughs being ports in the United Kingdom to appropriate, with the consent of the Local Government Board, lands belonging to them as sites for saUor's homes. In London, the regulation of tenement houses or lodgings other than common lodgings, is within the jurisdiction of the metropolitan Vestries and District Boards in the administrative county of London, and of the Com- missioners of SeAvers in the city, who respectively, by section 94 of the Pubhc Health (London) Act, 1891, are requhed to make and enforce bye- laws for the several purposes for which Sanitary Authorities may make bye- la avs under section 90 of the Public Health Act, 1875. The County Council are the Local Authority in the administrative county of London for the purposes of the Merchant Shipping Act, 1894, and are under the same obligations to make bye-laws and regulations with reference to seamen's lodgings under that enactment as attaches to Sanitary Authorities in Avhose districts sea-port toAvns are situated. In the city of London the same duties devolve on the Commissioners of Sewers. In Scotland.—As regards lodging-houses other than common lodging- houses, section 44 of the Public Health (Scotland) Act, 1867, says that, Avith the consent of the Local Government Board, regulations may be made " by the local authorities of burghs with not less than 2000 inhabitants, for pur- poses similar to those which may be regulated in England"—not specifically including drainage, and the notification of, or taking of precautions against infectious disease cases. Although the Housing of the Working Classes Act, 1885, section 8, empowering every local authority to regulate lodging- houses by bye-law, appears to be intended to apply to Scotland, it is doubtful whether, OAving to imperfect drafting, its provisions could be enforced. The provisions of the Merchant Shipping Act, 1894, sections 214 and 259, respecting seamen's lodging-houses, apply to Scotland. In Ireland.—Section 100 of the Public Health (Ireland) Act, 1878, corresponds to section 90 of the English Act, and empowers Sanitary Authorities to make bye-laws as to houses let in lodgings. Owing to ambiguity of phraseology, it is doubtful whether that section of the Act is in force in the districts in respect of such houses, without a declaration by the Local Government Board. The Housing of the Working Classes Act, 1885, section 8, enabled the Sanitary Authorities in England to make " these bye-laAvs -without any declaration by the Local Government Board, and section 15 of the same Act applied the provisions of section 8 to Ireland." The Act of 1885, with the exception of a few sections which include section 8 but not section 15, was repealed by the Housing of the Working Classes Act of 1890, so that it is very problematical whether section 8 of the 1885 Act is really now in force in Ireland. The provisions for making bye-laAvs and granting sites for seamen's lodging-houses are the same in the case of Ireland as for England. UNHEALTHY AREAS. 863 HOUSING OF THE WORKING CLASSES. The legislative enactment which enables Sanitary Authorities to deal with ^his important branch of the Public Health is the Housing of the Working '"Classes Act, 1890. This Act repealed and consolidated fourteen Acts •dealing with the important but large subject of dwellings for the labouring ■ classes. The Act is divided into seven parts; of these, the last four are supplemental to the first three, hence the natural division of the Act is into three parts only. Part I. is headed " unhealthy areas," being an amendment and consolida- tion of the Artisans' and Labourers' Dwellings Acts, formerly known as * Cross's Act. The essential point of this part of the Act is to give poAvers to a Local Authority to clear some well defined unhealthy area in an urban 1 district, and having removed the offending dAvellings, narrow courts, &c, to ^replace the dAveUings so removed by structures in all respects fit for human ^'habitation, and to re-arrange the streets on an improved plan, admitting of fplenty of air and light. Part II. deals Avith the individual house, or with small groups of houses. ' The basis of this part is the Act known formerly as Torren's Act, but the 'leading idea is practically the same as that characteristic of Part I.: the chief distinction between them being, that while Part I. is applicable only to nrban districts and deals with large areas including many houses, Part II. applies to both urban and rural districts and deals with the individual house, ■or small groups of houses. Part III. is an embodiment of the Shaftesbury Acts, and is adoptive. It : gives to Authorities facilities for acquiring or appropriating land for the purposes of erecting thereon buildings suitable for lodging-houses for the working classes. Under this part they can also convert any buildings into I lodging-houses for the working classes, and may "alter, repair, enlarge, and improve the same respectively, and fit up and furnish and supply the same • with requisite furniture, fittings, and conveniences." Of the remaining or purely supplemental portions of the Act, Part IV. • contains the following important provision. " In any contract made after August 14, 1885, for letting for habitation by persons of the working ■ classes a house or part of a house, there shall be implied a condition that ' the house is at the commencement of the holding in all respects reasonably fit for human habitation." The Act thus readily lending itself to division into three main parts, or those dealing Avith " unhealthy areas," " unhealthy dwellings," and " working- • class lodging-houses," it will be more convenient to consider the law relating to the whole question of the housing of the working classes under those 'three main sections. UNHEALTHY AREAS. Part I. of the Housing of the Working Classes Act, 1890, Avhich deals -with this subject, is applicable to England and Wales, the metropolis, •Scotland, and Ireland; and enables the various urban Sanitary Authorities, the London County Council, and the Commissioners of Sewers of the City ■of London to carry out by means of provisional orders, confirmed by Parlia- ment, improvement schemes for the reconstruction and re-arrangement of '4he streets and houses in unhealthy areas. 864 SANITARY LAAV. To put the Act in motion, it is the duty of the Medical Officer of Health to make " an official representation " in Avriting to the Sanitary Authority, Avhenever he sees cause to do so, that within a certain area either any houses or courts are unfit for habitation; or the bad arrangement or condition of the streets or houses, or want of light, ventilation, or proper conveniences, or any other sanitary defects, are dangerous to the health of the hihabitants ; and that the evils cannot be effectually remedied other- wise than by re-arrangement and reconstruction of some or all of the streets or houses. Similarly, .upon complaint by two justices of the peace, or twelve ratepayers, the Medical Officer of Health must make an inspec- tion and report upon any area alleged to be unhealthy and dangerous to health. If he fads to do so, or reports that it is not an unhealthy area, such ratepayers may appeal to the confirming authority (which in the case of all urban districts is the Local Government Board, and as regards the metropolis is the Home Secretary), avIio, upon receiving satisfaction as for costs, may then appoint a medical practitioner to inspect the area, and to make representation to them, stating the facts of the case, and whether, in his opinion, the area, or any part thereof, is or is not an unhealthy area. The representation so made must be transmitted by the confirming authority to the Local Authority, who must treat it in the same manner as if it were an official representation made direct to them in the other or more ordinary Avay by their own officer (section 16). The Sanitary Authority must consider this or any representation, and if satisfied of the truth thereof, and of the sufficiency of their resources, must declare the area to be an unhealthy area, and frame an improve- ment scheme. In any case, if the Sanitary Authority refuse or fail to prepare a scheme upon receipt of an official representation, they must report the facts to the confirming authority, who may then order a local inquiry to be held. The Act, however, does not authorise any action to be taken on the information thus obtained (section 10). Having passed a resolution to carry out an improvement scheme, the Sanitary Authority may prepare it, with maps, plans, and elaborate details as to sanitary arrangements, widening the approaches and streets, or other- wise opening out the area. It may exclude any part of the area, or include neighbouring lands ; but must provide such dwelling accommodation, if any, for the working classes displaced by the scheme as is requhed by the Act (section 6). Due publicity must be given to the scheme by publishing advertisements in a local newspaper in either September, October, or November, naming a place within such area or in the vicinity where a copy of the scheme may be seen at all reasonable hours; and during the month next following the month in which advertisements were pubhshed, notices must be served on all the persons interested (section 7). This being done, apphcation must be made by the Sanitary Authority to the confirming authority for a provisional Order. If this authority think fit to proceed with the case, it must direct a local inquiry to be held respecting the correctness of the official representation, and the sufficiency of the scheme. On receiving the report made by this inquiry, the confirming authority may grant a provisional Order declaring the limits of the area to which the scheme relates, and authorising the scheme to be carried into execution. The Order has no validity unless and until it has been confirmed by Act of Parhament, and such Act must be a pubhc general Act (section 8). In London, accommodation must be provided in or near the area for the Avhole number displaced, unless the Order decrees otherwise; under certain conditions the Order may accept in substitution equally convenient UNHEALTHY AREAS. 865 accommodation not in or near the area, and may dispense with the obligation to any extent not exceeding one-half. Outside the metropolis such proAdsion is only compulsory if (and to the extent) prescribed by the Order (section 11). In assessing the value of property, no additional allowance for com- pulsory purchase is to be made in regard to any unhealthy portion of the area ; and e-vidence may be given showing that any premises are (1) unfit for habitation, and cannot reasonably be made fit; or (2) in bad repair, or in an insanitary condition ; or (3) that the rental is enhanced by reason of overcrowding or use for illegal purposes. In the first case the compensa- tion is to be based upon the value of the land and building materials only ; in the second, upon the value after alloAving for the cost of necessary repairs; in the third, upon the value apart from such illegal use (section 21). The Sanitary Authority must, not less than thirteen Aveeks before taking any fifteen houses or more, give notice to the occupiers by placards, hand- bills or other notices, and must also, before actually clearing, obtain a certificate from a justice that they have made known their intention of taking the houses in the manner specified in the Act (section 14). The time taken by all these steps is often considerable. It rarely happens that an area is cleared and built upon under four years. If Avithin five years after the removal of any buildings on the land set aside by any scheme authorised by a confirming Act as sites for working men's dAvellings the Sanitary Authority fail to complete it, the Local Government Board have power to sell the land and complete the scheme (section 13). Reference may conveniently here be made to a practical difficulty which occasionally arises, in connection with this matter of unhealthy areas, in London. Owing to the County Council being the local authority outside the city for the purposes of Parts I. and III. of the Housing of the Working Classes Act, 1890, and the Vestries and District Boards and the Woolwich Local Board the local authorities for the purposes of Part II. of the Act, in cases where the area to be dealt with is neither very large nor very small, differences of opinion arise whether it should be dealt with under Part I. or II. of the Act. When Part I. is put in force, the expenses are necessarily borne by the whole of London exclusive of the city. When recourse is had to Part II., the cost primarily falls on the parish or district subject to the Sanitary Authority. To avoid this difficulty, section 72 says that when official representation deals with not more than ten houses, the case is to be dealt with under Part II. It is obvious, however, that this enactment only solves the difficulty in a limited number of cases, hence a further attempt has been made to remove doubts and differences on this matter that may arise betAveen the County Council and the Sanitary Authorities, by leaving the question to be settled in each case by the Home Secretary (section 73). Another point of importance, in London, is that the official representation by means of which the County Council are to be set in motion must be made either by the Medical Officer of Health of the Council, or by any Medical Officer of Health in London (section 5 (1)). Parti, of the Housing of the Working Classes Act, 1890, applying equally to Scotland and Ireland as to England and the metropolis, no special remarks as to its working in the tAvo former countries are necessary. 3i 866 SANITARY LAW. UNHEALTHY DWELLING-HOUSES. The enactments dealing with this matter are practically the Public Health Act, 1875, sections 91 to 111, and Part II., Housing of the Working Classes Act, 1890. It has already been shown (page 854) that any house or part of a house so overcrowded as to be dangerous or injurious to the health of the inmates, no matter whether members of one family or not, and any premises in such a state as to be a nuisance or injurious to health may be dealt with in any urban or rural sanitary district under the provisions of the Pubhc Health Act, 1875, relating to nuisances, and if so deemed necessary may be closed as unfit for habitation. Where the only object of a Sanitary Authority is to close a house, either for the purpose of checking over- crowding or to induce the owner to make certain necessary improvements in it, it is generally better to proceed under the provisions of the Act of 1875. But Avhere the authorities propose to go further, and to take steps to obtain the demolition of the house, they must proceed, under the Housing of the Working Classes Act, 1890. Part II. of this latter Act, which is applicable to all urban and rural Sanitary Authorities in England and Wales, and also, with some minor modifications, to Scotland and Ireland, lays a definite duty upon the Medical Officer of Health to represent to the local authority of his district any dwelling-house " which appears to him to be in a state so dangerous or injurious to health as to be unfit for human habitation " (section 30). He may also be moved to inspect and make a representation by complaints in writing from any four or more householders (section 31 (1)); and in the case of an urban district, should the Sanitary Authority let three months pass away after receiving such representation without doing anything, the householders may petition the Local Government Board to hold an inquiry, and the Board, after such inquiry, may make a binding order on the authority (section 31 (2)). It is further the duty of the authority to make, from time to time, inspection of their district to ascertain Avhether any dwelling-house therein is in a state so dangerous or injurious to health as to be unfit for human habitation; and, if so satisfied that such is the case, to either take measures to close the house by a magistrate's order, under section 97, Public Health Act, 1875, or to give notice to the owner to do certain work, so as to put the premises in proper order, and, on his failing to comply, summon, and at the hearing ask, for the premises to be closed (section 32). In connection with the use of the term " owner " in this Act, reference should be made to the definition of that term (page 833), as under this Act the Local Authority has only to deal with freeholders and leaseholders, or other persons who have at least a twenty-one years' interest in the property. If the closing Order of the Court is not terminated by a further Order declaring the dwelling-house habitable, the Sanitary Authority may proceed to make a resolution for demolition, giving notice to owner of same and opportunity for him to present objections. If upon the consideration of the resolution and objections, the Sanitary Authority decide that it is expedient so to do, then, unless an owner undertakes to execute at once the Avorks necessary to render the premises fit for human habitation, they must order the demolition of the building (section 33). It may be, however, that the OAvner undertakes to execute the said works. If so, the Authority may order the execution of the Avorks within a specified time, and if the works are not completed within that time, or any extended time allowed by the Authority or a Court of summary jurisdiction, the Authority must order UNHEALTHY DWELLING-HOUSES. 867 the demolition of the building. When an order for demolition has been made, the owner must comply Avith it Avithin three months; if he fad to do so, then the local Sanitary Authority may demolish, sell the materials, and, after deducting expenses, pay over the balance to the owner. Moreover, no building likely to be dangerous or injurious to health can be erected on the vacant site or any part of it (section 34). There is power of appeal against any of the Orders under this part of the Act, by any aggrieved person to Quarter Sessions; but notice of appeal must be given Avithin one month after notice of the Order of the Sanitary Authority has been served (section 35). Section 38 raises the interesting question of what are known as " obstruc- tive buildings," or those buildings Avhich, although not in themselves unfit for human habitation, are so situated that by reason of their proximity to or contact Avith any other buildings they stop ventilation, or make other build- ings insanitary, or prevent proper measures from being carried into effect for remedying nuisances. In any of the above cases, it is the duty of the Medical Officer of Health to make "a representation" of the particulars to his Sanitary Authority, stating that in his opinion it is expedient that it should be pulled doAvn. A similar representation may be made by any four or more inhabitant householders. In either case, the Sanitary Authority must make inquiries as to the facts, and as to the cost of acquiring the land and pulling doAvn the building. If they decide to proceed, the Authority can make an order for the demolition of the budding, after giving the OAvner notice and an opportunity of stating his objections, and subject to appeal to Quarter Sessions. When such an Order has been made, and there is no appeal, or the appeal fails or is abandoned, the Sanitary Authority may compulsorily purchase the site within a year from the date of the Order, or if it were appealed against, from the date of its confirmation, unless the owner pulls down the obstructive building; in such case he is compensated for the building only. In case of difference as to price the matter goes to arbitration. The OAvner cannot subsequently re-erect an obstructive building on the vacant site, nor one that is dangerous or injurious to health. Where the Authority purchase land compulsorily under the above powers, a part only of the building can be taken if, in the opinion of the arbitrator, no material detriment Avill be suffered; but in assessing compensation, the value of the part and also the severance of the part are both taken into consideration. As probably the value of the buildings, Avhich previously had been injuriously affected by the obstructive buddings, will be increased by the removal of the latter, the principle of " betterment" is adopted, and a Local Authority may apportion the compensation on such buildings, declaring them to be private improvement expenses, and levy improvement rates (section 38 (8)). Where the lands are purchased by the Sanitary Authority, they may keep the site Avholly or partly as an open space, higliAvay, or other public place, or, Avith the consent of the Local Government Board, sell such portion of the site as is not required. Section 39 empowers the Sanitary Authority to prepare a scheme for dedicating as a higliAvay or open space, or appropriating or exchanging for the erection of working-class dwellings, the site of any building ordered to be demolished under this part of the Act, if it appear to them that it would benefit the health of the inhabitants of the adjoining houses; they may also prepare an improvement scheme for any unhealthy area too small to be dealt Avith under Part I. of the Act. Notice of the scheme must be (b) At least 16 square feet of floor space must be alloAved in them for each adult and for every two children under ten years cf age. (c) When intended for the reception of adults of different sexes, the habitations must be so furnished or provided that every bed is properly separated from any adjoining bed by a suitable screen or partition to secure adequate privacy to the occupants, (d) There must be a separate cooking-place for every fifteen persons authorised to be received, (e) There must be a sufficient supply ■of good Avater for drinking, cooking, and washing, if) There must be adequate privy accommodation for the separate use of each sex. (g) Every lodger or occupant shall be provided with a sufficient supply of clean dry straw, or other clean, dry, and suitable bedding, Avhich must be changed or properly cleansed from time to time, as occasion may require, (h) Every part of the interior of the premises, the cook-houses, and privies must be thoroughly cleansed immediately before any person is received to lodge therein, the internal surfaces limeAvashed, and all offensive accumulations cleared aAvay ; this ■cleansing and limeAvashing must be done at least annually, and repeated as required from time to time during the period of occupation. 874 SANITARY LAW. In the Metropolis, the various Sanitary Authorities have simdar poAvers and duties to those of other authorities in England and Wales in relation to tents, vans, sheds, or other similar structures used for human habitations, but their action in this matter will be taken by applying section 95 of the Public Health (London) Act of 1891, read in conjunction with section 9, Housing of the Working Classes Act, 1885. As regards Scotland and Ireland, these provisions of the Working Classes Act are of very doubtful application; while those of English Statutes dealing Avith hop and fruit-pickers' lodgings do not apply. NEW STREETS AND BUILDINGS. In England and Wales.—The Public Health Act, 1875, and the Amend- ment Act, 1890, give Sanitary Authorities, especially urban Authorities and such rural Authorities as have obtained urban powers, considerable control over the arrangements, construction, and planning of streets and buildings Avithin their districts. By the Act of 1875 all public streets in urban districts are vested in the Sanitary Authority, avIio must cause them to be levelled, paved, and repaired as occasion may require (section 149). All oAvners of property abutting on any private street or part of a street may be required by an urban Authority to level, pave, sewer, light, or make good such street or part of a street; and in case of default the Sanitary Authority may carry out the work and recover expenses from the owners according to the frontage of their respec- tive premises (section 150). Section 157 of the same Act enables every urban Authority to make bye-laws Avith respect to the structure of Avails, foundations, roofs, and chimneys of neAv buildings for securing stabihty, and the prevention of fires, and for purposes of health, and with respect to the sufficiency of the space about buildings to secure a free circulation of air, and Avith respect to the ventilation of buildings. For the purposes of the Act, the re-erection of any building puUed down to or below the ground floor, or the conversion into a dwelling-house of any budding not originally con- structed for human habitation, or the conversion into more than one dwelling-house of a building originally constructed as one dwelling-house only, shall be considered the erection of a new building. These powers have been extended by section 23 of the Public Health Acts Amendment Act, 1890, so as to enable any urban Sanitary Authority to make further bye-kws concerning new buildings upon the following points :—(a) adequate Avater-supply to closets; (b) construction of floors, hearths, and staircases ; (c) height of rooms intended for habitation; (d) paving of yards and open spaces in connection with houses ; (e) provision of secondary approaches to houses, for the purpose of removing refuse. It is further provided that bye-laws respecting closets and drainage may be made applicable to old as well as new houses. Similar power of framing and enforcing bye-laws for each of the above purposes, with the exception of the prevention of fires, has been given to rural Authorities adopting Part III. of the Act. Apart from this, hoAvever, the Local Government Board can, as already stated, grant fidl urban poAvers to rural Authorities. This same section 23 enables any Sanitary Authority to make bye-laws to prevent buildings erected in accordance Avith bye-laAvs from being altered in such Avay that if at first so constructed they would have contravened the bye- laAvs. Other sections of the same Act of 1890 (sections 25 and 24) prohibit any NEW STREETS AND BUILDINGS. 875 new building being erected upon ground impregnated Avith animal or vegetable matter, or upon Avhich such matter has been deposited, unless such matter has been properly removed or has become innocuous. Similarly, if in an urban district, any portion of a room is immediately over any privy (not being a water-closet or earth-closet), cesspool, midden, or ashpit, it is illegal to occupy it, or suffer it to be occupied, as a dwelling place, sleeping place, workroom, or place of business. Another enactment is, that build- ings described in deposited plans otherwise than as dwelling-houses must not be used as such, under a penalty not exceeding £5, and a daily penalty not exceeding 40s. (section 33). These provisions are, hoAvever, subject to the exception, that if the building has in rear thereof, and adjoining and exclusively belonging thereto, such an open space as is required by Act of Parliament or bye-law for the time being in force with respect to buildings intended to be used as dAvelling-houses, and if such part of the building as is intended to be used as a dwelling-house has undergone such structural alterations as, in the opinion of the Sanitary Authority, render it fit for that purpose. Further, an urban Sanitary Authority, if satisfied that any building or wall is in a ruinous state so as to be dangerous to passengers or to the inmates of neighbouring houses, shall cause a fence to be put up, and shall order the owner forthwith to secure or pull down such building; and in default thereof the surveyor may obtain a justice's order to carry out the necessary Avorks, and may recover the expenses. The Authority may also compel the owner of any building adjoining or near to a street to provide within seven days efficient eaves-gutters and rain-pipes (ToAvns Improvement Clauses Act, sections 74 to 78; Public Health Act, 1875, section 160). For the guidance of Sanitary Authorities in framing bye-kuvs in respect of new streets and buildings, the Local Government Board have issued Model Bye-laws; of these models the following is a summary :— (a) No new street must be less than 36 feet wide, if it exceeds 100 feet in length or is intended to be a carriage road : nor less than 24 feet in any case. One end at least must be quite open, (b) No buildings must be erected upon soil polluted with animal or vegetable matter. Sites in low and damp situations, near rivers or in excavations, must be elevated artificially. The site of a new house must be entirely asphalted or covered with 6 inches of concrete, (c) Walls of all new buildings must be constructed of good bricks, stone, or other hard and incombustible materials, properly bonded and solidly put together with good mortar compounded of good lime and clean sharp sand or other suitable material, or Avith good cement, or with good cement mixed with clean sharp sand. Every wall must have a proper damp course of durable and impervious material beneath the level of the lowest timbers, and at least 6 inches above the ground. If the ground is to be in contact Avith a wall above the level of the floor of the loAvest storey, that Avail must be made double, with a cavity 2\ inches AA-ide extending from the base of the Avail to 6 inches above the surface of the adjoining ground ; and damp courses must be inserted both at the base of the wall and at the level of the top of the cavity. The minimum thickness of the Avail of a new house should be as folloAvs:— Where' a wall is not over 25 feet in height, if it does not exceed 35 feet in length, and does not comprise more than tAvo storeys, it shall be 9 inches for its whole height; but if it do comprise more than two storeys, or exceed 35 feet in length, it shall be 13| inches below the topmost storey, and 9 inches for the rest. Where Avails are over 25 feet high, and not exceeding 35 feet in length, they should be 13^ inches thick beloAv the topmost storey and 9 inches for the rest; but if they be longer than 35 feet, then they must be 18 inches thick for the height of one storey, then 13£ inches thick for the rest of the height beloAV the topmost storey, and 9 inches thick for the rest of its height. Walls over 35 feet high must be 18 inches thick for the first two storeys, and 13^ inches for the rest. If over 50 feet in height, walls should be 22 inches thick for the height of one storey, then 18 inches for the next two storeys, and finally 13| for the rest of the height Party walls must be carried up at least 15 inches above the roof, the distance to be measured at right angles to the slope of the roof, (d) Roofs must be made of 876 SANITARY LAAV. incombustible materials, and provided with gutters leading to rain-pipes, (e) A new house must have along its whole frontage an open space measuring at least 21 feet to the boundary of any land or premises immediately opposite or to the opposite side of the street. In the rear there must be an open space exclusively belonging to the house, at least 150 square feet in area, and free from any erection above the ground level, except a closet and an ashpit; the open space must extend along the entire width of the house, and must measure in no case less than 10 feet from every part of the back Avail of the house ; if the house is 15 feet high, the distance must be 15 feet; if 25 feet, then 20 feet; and if 35 feet or more, then 25 feet at least. (/) If the floor of the loAvest storey is boarded, there must be a clear space of at least 3 inches between the boards and the impervious covering of the site, and the space must be ventilated, (g) Every habitable room must be provided with AvindoAvs opening directly into the external air. The Avindow area must be at least one-tenth of the floor area ; at least half of each window must be made to open, and it must open at the top. Every habitable room must, further, either have a fireplace and chimney, or a special ventilating aperture or air-shaft Avith an unobstructed sectional area of at least 100 square inches. Every neAv building must be provided with adequate means of ventilation, and to secure this, so far as dwelling rooms in general are concerned, the minimum height should be 9 feet in every part, except in attics used as bedrooms, when a minimum height of 5 feet is per- mitted, if in two-thirds of the area the height is not less than 9 feet. The provisions as to closets, privies, ashpits, and cesspools given in these Model Bye- laAvs have already been detailed on page 842. They are intended to specially apply to new buildings. The same models proceed to suggest that (h) the Sanitary Authority may, under certificate from the Medical Officer of Health'or Surveyor, declare any.building or part of a building erected after .... unfit for habitation, and order it to be closed until rendered fit for habitation. Opportunity must be given to the owner to show cause Avhy such order should not be made, (i) Plans and sections must be submitted, shoAving in detail the construction of all proposed neAv streets or buildings. (The Authority must signify their approval or disapproval within a month after receiving them, by section 158, Public Health Act, 1875.) (?) Notice must be given to the Surveyor of the dates upon which any sewer, drain, or foundation is to be covered up ; notice must also be given of the completion of the work ; Avhile free access for inspection must, be afforded to him at all times during the progress of the work, {k) If any work to which the bye-laws apply is done in contravention of such bye-laws, the Sanitary Authority are empowered to remove, alter, or pull doAvn such work. In London, the control, regulation, and management of all matters relating to the planning and laying out of new streets and the constructing of new buildings is governed, saving in respect of certain matters in connec- tion Avith the city of London, by the provisions of The London Building Act, 1894. This Act consolidates and amends the previous Metropolitan Building Acts, and also certain provisions relating to the formation and widening of streets, the lines of building frontage, dwelling-houses on low-lying lands, sky-signs, and the naming and numbering of streets, most of Avhich provisions Avere formerly included in the various Metropolis Management Acts and General Powers Acts of the London County Council. The Act is not, in itself, an absolutely complete code regulating building operations in London, as it is still necessary to refer to existing enactments of the Management Acts for provisions as to drainage of houses, as to the construction of vaults and cellars under streets, and as to the erection of hoardings during building. The sanitary arrange- ments in houses, the construction of underground rooms, and the structure of premises on Avhich any offensive business is carried on, are regulated by the Public Health (London) Act, 1891, and the bye-laAvs in forco thereunder; and in the city of London, such jurisdiction as was exercise- able by the Commissioners of SeAvers, under the SeAvers Acts previous to the passing of this 1894 Act, still remains in force. The Commissioners of Sewers are the local authority within the city for the purposes of this Act, but the city is expressly exempted from certain provisions of the Act; these are sections 9 (4) and (5), 11 (4) and (5), 22 to 31, 84, 164 in part, 165, and 199, Avhereby the Commissioners of NEW STREETS AND BUILDINGS. 877 Sewers retain jurisdiction, within the city, over the altering and planning of streets, lines of frontage, the erection of hoardings, dangerous structures, and sky-signs, the placing of lamps, signs, or other structures overhanging the public way, the making of bye-laws with respect to sites and foundations, prevention of fires, the materials of walls, and duties of district surveyors in relation to general house construction. In respect of these matters, the Sewers' Commissioners hold special poAvers under the Metropolitan Build- ing Acts, 1855 to 1882, and the City of London Sewers Acts, 1848 and 1851; but, as already stated, with these exceptions the provisions of the London Building Act, 1894, apply within the city of London as in other parts of the metropolis, the Commissioners of SeAvers being the local authority under the Act. A considerable advance upon the previous legislation affecting London has been made, in the power given to the County Council to increase the Avidth of certain new streets, not within 2 miles of St Paul's Cathedral, from 40 to 60 feet (section 12), and to refuse, if they think fit, to sanction plans for streets formed for carriage traffic of less width than 40 feet clear, and those formed for foot traffic, less than 20 feet clear (section 9). Similarly, no new buildings shall be erected with reference to streets intended for carriage traffic or with reference to footways, unless their external wall, fence, or boundary be at least 20 and 10 feet respectively from the centre of such street or footway (section 13). Sections 22 to 31, which do not apply to the city, empower the County Council under certain conditions to move back buildings which do project, and to prevent any neAv buildings being erected so as to project beyond the frontage line of the street. Part V. of the Act, or sections 39 to 52, contains provisions Avith reference to open spaces about buildings, which are a great advance upon any previously existing law. The application of the principle of measurement by angles (section 41) for the purpose of determining the height, in relation to the space required at the rear of houses, is novel, so far as regards London, though it has been in operation in Liverpool under bye-laws framed with the sanction of the Local Government Board. Every domestic building (that is, a building which is neither a public building nor of the warehouse class) abutting upon streets formed or laid out after January 1, 1895, must have an open space of an aggregate extent of not less than 150 square feet in its rear, and exclusively belong- ing thereto; this space must extend throughout the entire width of the building, and be at least 10 feet in depth in every part. This open space must be free from any erection thereon above the level of the adjoining pavement, except a water-closet, earth-closet, or privy, and a receptacle for ashes, and enclosing Avails, none of which erections shall exceed 9 feet in heio-ht. The building itself may be erected to a height equal to tAvice the width of the open space provided at the rear of the building, but an increase of height is allowed in cases where there is a street or permanent open space in the rear of the building. This result is obtained by confining, except as in the section provided, the height of a building within an imao-inary diagonal line, to be drawn at an angle of 63^° from an imaginary horizontal line draAvn at right angles to the roadAvay, and at the level of the pavement in front of the centre of the building. The point in the hori- zontal, from Avhich the diagonal springs, will be the intersection of the horizontal line Avith the rear boundary of the open space, except Avhere the boundary of such space is not parallel Avith the rear wall of the building. In the case of certain corner buildings, the space in the rear may be 878 SANITARY LAAV. occupied by buildings not exceeding 30 feet in height, and the return front of such buildings may be carried up to the fuU height of the front elevation. As regards buildings abutting upon a street formed or laid out before the commencement of the Act, the height of such buildings, in relation to the open space required at the rear, Avill be determined by the same method of drawing diagonal and horizontal lines as provided above, except that the horizontal line may be drawn at a level of 16 feet above the level of the adjoining pavement; and the required open space, except in the case of working-class dwellings, may be above the level of the ceihng of the ground-floor storey, or above a level of 16 feet above the pavement. Certain savings for domestic buildings on old sites, Avhen evidenced by plans certified by the district surveyor, and a provision for cases Avhen an area is cleared of existing buildings, and new streets laid out thereon, are provided by sections 43 and 44. Special provision is made by section 45 for providing adequate light and ventilation for courts constructed within buildings, and for habitable rooms looking on to such courts. If the depth of such court from the eaves to the ceihng of the ground storey exceeds the length or breadth of the court, adequate pro- vision for ventilation must be made by means of a communication betAveen the loAver end of the court and the outer air. No habitable room, without a window directly opening into the outer air, otherAvise than into a court enclosed on every side, shall be constructed in any building unless the width of such court, measured from such AvindoAv to the opposite wall, shall be equal to half the height measured from the sill of such AvindoAv to the eaves or top of the opposite Avail. The general limit of the height of buddings is fixed at 80 feet (sections 47 to 52). All matters, relating to the provision of open spaces about buildings, and the height of buildings, are subject to the supervision of the district surveyor (section 138). Every neAv building exceeding 60 feet in height must be provided, on the storeys the upper surface of the floor whereof is above 60 feet from the street level, Avith such means of escape in the case of fire as can be reasonably required under the circumstances of the case; and no storeys of such buddings may be occupied until certified by the Council that these pro- visions have been complied with (section 63). No building may be built nearer than 50 feet to any other building used for dangerous and noxious businesses, such as match factories, turpentine, varnish, tar, resin, or BrunsAvick black manufactories, blood' and bone-boilers, soap-boilers, tallow-melters, fell-mongers, tripe-boilers, and slaughter-houses for cattle or horses (sections 118 to 121). Similarly, no building may be erected upon land of which the surface is beloAV the level of Trinity high-Avater mark, and Avhich is so situate as not to admit of being drained by gravi- tation into an existing seAver, except with the permission of the County Council (sections 122 to 124). The first schedule of the Act gives elaborate tables as to the permissible limits for the thicknesses of Avails, proportionate to height; these in the main follow the general rules already given in the Model Bye laws of the Local Government Board, but are more compre- hensive. Before closing this necessarily brief reference to this important London Building Act, 1894, it may be convenient to specifically state that the Statutes, other than this Act of 1894, which are still in force, and which affect building operations in the metropohs, especially in the city, are :— The Act for Better Paving, Improving, and Regulating the Streets of the Metropolis, &c, commonly knoAvn as 57 Geo. III. cap. xxix.; the NEW STREETS AND BUILDINGS. 879 Metropolis Management Act, 1855, sections 73 to 123, 202 to 204, 211, 212, 227, 231, 242, 247, and 250 ; the Metropolis Management Amendment Act, 1862, sections 47, 48, 49, 61, 63 to 65, 68, 69, 88, 96, 97, 102, 104 to 107, and 110 to 112 ; the Metropolis Management Buildings Acts Amend- ment Act of 1878, Parts I. and III. ; the Metropolis Board of Works Act, 1882, sections 1, 3, 45, and 48 ; the Metropolis Management Amendment Act, 1890 ; the London Council (General PoAvers) Act, 1890, sections 1, 2, 32, 39, 40, and 41 ; the Factory and Workshop Act, 1891, sections 7 and 41 ; the Public Health (London) Act, 1891; and the City of London SeAvers Acts of 1848 and 1851. In Scotland.—-By the Local Government (Scotland) Act, 1895, section 9, in the rural or landward districts, the County Councils have poAvers to make bye-laws for regulating the erection and construction of neAv buildings. The section is based upon sections 157-8-9 of the English Public Health Act, 1875. It contains a drastic and advanced definition clause whereby " any alteration of the structure of any house " brings it within the category of a " neAv house." The Avording of the subsections deahng with the purposes for which bye-laws may be made foUoAvs the lead of the English Act in failing to distinguish in these instances betAveen new and existing houses. Apart from powers under the Act of 1895, local authorities can deal with any defects in respect of buildings as nuisances under the Pubhc Health (Scotland) Act, 1867, or under the Housing of the Working Classes Act, 1890. In the rural or landAvard districts the local authorities have practically no powers of supervision over the construction and general arrangements of new dwellings; but they can, as already intimated, deal Avith any defects in these respects as nuisances under the Public Health (Scotland) Act, 1867, or under the Housing of the Working Classes Act, 1890. In the burghs, the Burghal Commissioners have elaborate poAvers under the Burgh Police (Scotland) Act, 1892, sections 166-180, 201-209. Some of the provisions are embodied in the Act, while others appear as rules in the schedules. The chief distinctive provisions are that (a) all rooms in neAv or altered dwelling-houses must be sufficiently lighted and ventilated from the street, or from an open space equal to three-fourths of the area in Avhich the house stands, (b) Not more than twelve flat tenements may open from an inside stair, nor more than tAventy-four from an outside stair, (c) In neAv dwellings, rooms on the ground floor must be 9 h feet in height, and on other floors 9 feet, except attics, Avhich must be 8 feet high over one-third of their area, and noAvhere less than 3 feet, (d) Every neAv habitable room of less area than 100 feet, built without a fireplace, must have special means of ventilation. There are further provisions as to ventilation of common stairs, and for the prohibition of the erection of any building upon polluted sites. In buro-hs, Avhere there is a Dean of Guild Court, this body is practically a committee of the Burghal Commissioners, and discharges all the functions in respect of buildings. In Ireland.—Under section 41 of the Irish Public Health Act of 1878, urban and rural Sanitary Authorities have very similar poAvers for making bye-laAvs, and in respect of the same matters as have the Enghsh urban Authorities under section 157 of the Act of 1875. Any bye-laavs made under this section 41 are not applicable to buildings erected before August 8 1878. Although section 23 of the Public Health Amendment Act of 1890 extends to Ireland, its general apphcation is little called for, as sections 41 and 42 of the Irish Act of 1878 apply to both rural and urban 880 SANITARY LAW. Authorities, thus differing from sections 157 and 158 of the English Act of 1875, AA-hich apply only to urban Authorities. Sections 25 and 33 of the Amendment Act, 1890, may be applied to rural and urban districts, and section 24 to urban districts in Ireland as Avell as in England. Section 36 provides that aU buildings, being places of public resort in urban districts, must have proper means of egress and ingress; Avhile in towns constituted under the Towns Improvement (Ireland) Act, 1854, the ToAvn Commissioners have full control over the erection and planning of all places of public entertainment. OFFENSIVE TRADES. In England and Wales.—The " offensive trades " are defined by section 112, Public Health Act, 1875, as those of "blood-boiler, bone-boiler, fell- monger, soap-boUer, tallow-melter, tripe-boiler, and any other noxious or offensive trade, business, or manufacture." By the same section it is illegal to establish any of these offensive trades within an urban sanitary district, Avithout the consent in writing of the Authority. As regards the prohibition of the establishment of any given trade without their consent, it is incumbent upon the prosecuting Local Authority to shoAV that the trade in question is either one of those specifically mentioned above, or ejusdem generis with them ; that is, that it is necessarily an offensive trade apart from neglect or mismanagement. It will be necessary, therefore, in determining whether a business comes within the definition of " offensive trade" to consider whether the materials used in its processes are identical with or similar to those dealt with in the six trades specified in the definition, and also whether the trade is, or must be, carried on in such manner as to be noxious or offensive. The higher Courts have held that this is the case with rag and bone stores for example, but not in brick-making,. manure works, or fish-frying. An urban Sanitary Authority may make bye-laavs with respect to these trades, Avhen they have been established with their consent, so as to prevent or diminish any nuisance arising therefrom (section 113); but a rural Authority would, have to apply to the Local Government Board for power, under section 276, to apply these provisions. The Local Government Board have issued Model Bye-laws in regard to not only the six trades mentioned in section 112 of the Act of 1875, but also in reference to the trades of a leather-dresser, tanner, fat-melter or fat- extractor, glue-maker, size-maker, blood-drier, and gut-scraper. The same general provisions appear in all, with numerous additions or variations as: required by the conditions of the particular trade in question. The following summary wUl show their general scope and character :— (a) All materials not required for immediate use or treatment shall be so stored as to prevent effluvium. (6) The best practicable means must be adopted for rendering any offensive vapours emitted during melting, boiling, &c, innocuous. The vapour must be either discharged into the external air in such a manner and at such a height as to admit of its diffusion without injurious effects; or shall be passed directly from the pan, &c, through a fire; or into a condensing apparatus; or through a condensing apparatus and then through a fire, in such a manner as effectually to consume the vapour or deprive it of all noxious or injurious properties, (c) The drainage on the premises must be kept in efficient order. Bone-boilers must cool all hot liquid refuse before passing it into any drain, (d) Floors must be kept in good order so as to prevent the absorption of filth. In the majority of these trades it is advisable to require the floors to be either swept, Avashed, scraped, or otherwise cleansed at the close of every working day. All refuse so collected, by scraping or sweeping, shall be removed forth- OFFENSIVE TRADES. 881 with from the premises in covered receptacles, unless intended to be forthwith subjected to further trade processes on the premises, (e) Walls must be kept in good order so as to prevent the absorption of filth, and, if necessary, be scraped. Limewashing of walls and ceilings twice a year is necessary in regard to these trades. (/) All apparatus, including implements and vessels, must be kept clean ; where possible, this should be done daily, (g) Waste lime resulting from the businesses of fell-mongers and tanners must_ be removed at once, and under close cover, (h) Tanks used by fell-mongers for Avashing or soaking skins must be emptied and cleansed as often as may be necessary to prevent effluvia, (i) Every facility must be allowed for the access to the premises of the Medical Officer of Health, Inspector of Nuisances, Surveyor, or any Committee appointed by the Authority, for the purpose of inspection at all reasonable times. Section 114 enacts that, if the Medical Officer of Health, or two legally qualified medical practitioners, or ten inhabitants of a district, certify that any of the following places are a nuisance, or injurious.to health, it is the duty of the Sanitary Authority to take proceedings against the offender, who is liable to a penalty not exceeding £5, nor less than 40s., unless he can show that he has used the best practical means for abating such nuisance, or preventing or counteracting such effluvia. The premises mentioned in this section are " any candle-house, melting-house, melting-place, or soap-house, or any slaughter-house, or any building or place for boiling offal or blood, or for boiling, burning, or crushing bones, or any manufactory, building, or place used for any trade, business, process, or manufacture causing effluvia." The same powers are applicable Avhere a nuisance, affecting the inhabitants of a district, arises from offensive trades carried on in premises situated beyond the limits of the district (section 115). In London.—The provisions as to offensive trades under the Public Health (London) Act, 1891, are more stringent than the corresponding provisions of the Act of 1875 in force outside the metropohs. Section 19 of the London Act prohibits any one, under penalty of £50 per day or less, establishing within the metropohtan area the business of a blood-boiler, a bone-boUer, a manure manufacturer, a soap-boiler (if the soap is made from animal fats), a tallow-melter, or a knacker ; but old-established businesses of this kind are permitted to remain, subject to the bye-laws of the County Council. A new soap-boiling business may, however, be established with the sanction of the Council, provided the soap is made from olein, or any vegetable fat or oil (ibid. (2)). Certain other businesses may, with the consent of the County Council, be estabhshed anew: these are those of a fell-monger, tripe-boiler, slaughterer of cattle or horses, or any other business which the Council may declare by Order, confirmed by the Local Govern- ment Board, to be offensive. The expression " establishment anew " means reopening after discontinuance of work for nine months, removal to new premises or extension of existing buildings, but not reconstruction, partial or complete, without extension of area. The granting of sanction to establish any new businesses of these kinds, on the part of the Council, is subject to the proviso that at least fourteen days before making any such Order they notify to the Authority, within whose district the premises on which the business is proposed to be established are situate, that application has been made, so that the inhabitants may have an opportunity of opposing it (section 19 (3)). Subsection (4) of the above mentioned section enables the County Council to make bye-laws as to the arrangement of premises and conduct of such businesses. Any such bye-laws (5) may empower a Petty Sessional Court to prohibit any person from following the same temporarily or permanently subject to a daily penalty not exceeding £50 : but any Sanitary Authority or person aggrieved by the enactment, alteration, or repeal of any such bye- law may give notice to the Local Government Board. The Metropohtan 882 SANITARY LAW. and Deptford cattle-markets are exempted from these bye-laAvs. Section 20 authorises the licensing of coAv-houses and slaughter-houses, such licences being made annuaUy. Section 22 of the Act provides that the removal, storage, and disposal of house and street refuse by a Sanitary Authority is to be deemed to be an offensive trade, and any complaint or proceeding made under section 21 may be made or taken by the County Council in like manner as if the Council Avere a Sanitary Authority. This provision enables the County Council to deal with a class of nuisance which is not unfrequently alleged to be committed by Sanitary Authorities themselves in the discharge of their duties Avith respect to the removal and disposal of house and street refuse. With these exceptions, the provisions of the London Act of 1891 as to offensive trades are practically the same as those of the Public Health Act, 1875, sections 114 and 115. In the city of London the Commissioners of Sewers take the place of the County Council for applying these enactments in connection with offensive trades. In Scotland.—The Public Health (Scotland) Act, 1867, section 30, classifies as offensive trades "the business of a blood-boiler, bone-boiler, tanner, slaughterer of cattle, horses, or animals of any description, soap- boUer, skinner, talloAAr-melter, tripe-boUer, or other business, trade, or manufacture injurious to health." The Local Government Board have power to determine whether a business, trade, or manufacture is injurious to health; and no such business may be established or enlarged within 500 yards of any burgh or -village without the consent of the Local Authority. Any business so conducted as to be offensive and injurious to health is deemed to be a statutory nuisance. In the towns the Burghal Commissioners have power to pass bye-laws " for reducing or removing the noxious or injurious effects attending these offensive trades" (Burgh Police (Scotland) Act, 1892, section 316). There are no provisions in the Scottish Pubhc Health Acts corresponding to sections 114 and 115 of the English Act of 1875. In Ireland.—Section 128 of the Irish Public Health Act of 1878 includes the business of a gut-manufacturer among the offensive trades, in addition to those given in section 112 of the English Act. As a rural Sanitary Authority in Ireland cannot be invested with urban powers, it follows that only urban Authorities can prevent the establishment of an offensive trade within the meaning of the Pubhc Health Act. The powers of these urban Authorities to make bye-laAvs as to offensive trades is imperative in Ireland, and not permissive as in England, subject, of course, to the sanction of the Local Government Board of Ireland (Public Health (Ireland) Act, 1878, section 129). In other respects the provisions of the Irish and English Acts on this matter are similar. FACTORIES, WORKSHOPS, AND BAKEHOUSES. The sanitary legislation in respect of these places is somewhat compli- cated. A reference to page 853 wiU show that section 91 of the Public Health Act, 1875, includes as a nuisance any factory, workshop, or work- place not kept in a cleanly state, or not ventdated in such a manner as to render harmless as far as possible any gases, vapours, dust, or other impurities generated in the course of the work carried on therein, or so overcrowded whde work is carried on as to be dangerous or injurious to the health of those employed therein. These provisions, however, do not FACTORIES AND WORKSHOPS. 883 apply to a factory which is subject to the provisions of the Factory and Workshop Acts of 1878, 1883, 1891, and 1895. These Acts are in force in England and Wales, the metropolis, Scotland, and Ireland, conse- quently references as to their working under the special headings of these geographical areas is not necessary. With a view to clear up any mis- conception as to what are the factories and workshops to which the provisions of the Public Health Act, 1875, as to nuisances apply, section 61 ■of _the Factory and Workshop Act, 1878, declares that the provisions of this latter Act do not apply where persons are employed at home, that is to say, to a private house, room, or place which, although by reason of the Avork carried on there is a factory within the meaning of the Act, is used ■as a dwelling, and in which neither steam, water, or other mechanical power is used, and in which the only persons employed are members of the same family dwelling there. Consequently, it is to these places only that section 91 of the Public Health Act, 1875, applies. The general effect of the Factory and Workshop Acts is to place all factories and workshops under a dual control, namely, the Home Office and the various Sanitary Authorities. The Home Secretary appoints Factory Inspectors, whose primary duty is to inspect factories. On the other hand, the primary duty of inspecting workshops and workplaces rests with the Local Authorities; this statement, however, must not be interpreted as meaning that the local Sanitary Authorities have no right to inspect a factory under the operation of these Acts, for there is a general duty cast upon the Sanitary Authorities to inspect all parts of their district (see also page 841). Under the Act of 1878, factories are divided into textile and non- ■textile; they comprise, practically, all workplaces where mechanical power is used, and also the folloAving, whether power is used or not:— "blast-furnaces, copper-mills, iron-mills, foundries, manufactories of earthen- ware, lucifer matches, percussion-caps, cartridges, tobacco, paper, glass, print-works, fustian-cutting, printing, bookbinding, and flax scutch mills. Subject to the foregoing special exceptions, workshops are places where any manufactures are carried on, but where no mechanical poAver is employed. By the Act of 1895, section 22, steam laundries are treated as factories, and other laundries as workshops. This law only applies to laundries carried on for purposes of trade or gain, and not where the persons carrying on the laundry are members of the same family. In every laundry worked by steam, water, or other mechanical power, (a) a fan or other means must be maintained for regulating temperature in ironing rooms, and for carrying away the steam in the wash-houses; (b) all stoves for heating irons must be sufficiently separated from the ironing rooms; (c) the flooring shall be kept in good condition, and drained in such manner as will allow the water to flow off freely. AU factories and workshops must be kept clean and free from effluvia arising from any drain, closet, urinal, or other nuisance. They must not be so overcrowded as to be dangerous or injurious to the health of the workers, and must be ventilated in such manner as to render harmless as far as practicable aU gases, vapours, dust, or other impurity generated in the course of the Avork that may be injurious to health. For the sanitary supervision of these places, Factory Inspectors have exceptional powers of entry, inspection, and of taking legal proceedings. By the Act of 1895, section 1, overcroAvding of a factory or workshop is statutorily defined as a minimum of 250 cubic feet of space for every person, and 400 884 SANITARY LAAV. cubic feet for every person doing overtime; moreover, the Home Secretary has poAver to add to this minimum during hours in Avhich artificial li^ht is employed. If the Home Secretary is not satisfied that any factory or workshop is sufficiently ventilated, he may, if he think fit, by Order authorise an Inspector of Factories to take, during the period mentioned in the Order, such steps as appear necessary or proper for enforcing them (Act of 1891, section 1). In the case of premises which are in an unfit state for manufacturing purposes, section 2 of the Act of 1895 gives poAver to a Court of summary jurisdiction, on the complaint of an Inspector, to make an Order prohibiting the premises from being so used until the necessary changes have been made to put them in a proper condition. When an Inspector deems that there is any act or default in relation to the sanitary arrangements or other matters in a factory or Avorkshop, which is punishable or remediable under the Public Health Act, but not under the Factory and Workshop Acts, he shall give notice of the same to the Sanitary Authority; and it is the duty of the Sanitary Authority to make such inquiry, and take such action, within one month, as may be proper for the enforcement of the law, duly notifying the Inspector of the proceedings taken. In case of default, after notice, of the Authority, the Inspector may himself take proceedings, recovering expenses from the Sanitary Authority (Act of 1878, section 4; Act of 1891, section 2; Act of 1895, section 3). Upon receipt of a certificate from the Medical Officer of Health or Inspector of Nuisances that cleansing, limewashing, or purifying is necessary for the health of the workers in a workshop, the Sanitary Authority must give notice to the owner or occupier; if he makes default, he incurs a daily penalty of 10s., and the Sanitary Authority may carry out the Avork and recover expenses (Act of 1891, section 4; also see Pubhc Health (London) Act, 1891, sections 25 and 26). If it comes to the knoAvledge of the Factory Inspector that work is being done in an unsanitary place, not necessarily a factory or workshop in the meaning of these Acts, it is his duty to give notice to the employer Avho gives out the work that such is the case, and if, one month after receiving that notice, the employer continues to give out work to be carried on in the place complained of, and nothing has been done in the meantime to remedy the insanitary conditions to which his attention has been drawn, he becomes hable to a penalty of £20. A similar penalty is incurred if any occupier of a factory or workshop knowingly causes or allows Avearing apparel to be made, cleaned, or repaired in any building any inmate of which is suffering from scarlet fever or small-pox (Act of 1895, sections 5 and 6). A Medical Officer of Health must give written notice to the Factory Inspector if he becomes aware that any "child" under fourteen years of age, " young person" of that age and under eighteen years, or "woman" of eighteen years of age or upwards is employed in any workshop (Act of 1891, section 3; also see Public Health (London) Act, 1891, section 27). The Act of 1895 prohibits the employment in any factory or workshop of chUdren under eleven years of age, and of women within four weeks after confinement. Overtime is prohibited in the case of all persons under eighteen years of age in non-textUe factories and workshops. For women working in factories and workshops other than laundries, overtime is limited to three days a week, and thirty days in the year; in the case of trades in which the goods are perishable, overtime is extended to sixty days in the year. After January 1, 1897, overtime at night is limited to male young persons of fourteen years of age or upwards (Act of 1895, FACTORIES AND WORKSHOPS. 885 section 14). Home work is noAV prohibited altogether for children who are employed in factories or workshops; and also women or young persons who have been employed for full hours in factories or workshops are prohibited from being afterwards employed in the shop (idem, section 16). "Women employed in laundries may work overtime, subject to the following conditions:—No woman shall work more than fourteen hours in any day; the overtime worked shall not exceed two hours in any day; •overtime shall not be worked on more than three days in any week, or than thirty days in any year" (section 22 (4), Act of 1895). As to dangers from fires, which are more common in workshops than factories, section 7 of the Act of 1891 places the duty of providing adequate means of escape from fire upon the Sanitary Authorities. Owing to the neglect of this duty, section 10 of the Act of 1895 enables an Inspector to require structural alterations where there are defects in relation to this matter, and a Court of summary jurisdiction may, on the apphcation of the Inspector, order the provision of movable fire-escapes and the making of structural alterations wherever the Inspector is able to show that the pro- visions made are not sufficiently practicable in that respect. By section 29 of the Act of 1895 every medical practitioner attending on or called in to visit a patient Avhom he believes to be suffering from lead, phosphorus, or arsenical poisoning, or anthrax, contracted in any factory or workshop, must (unless the notice required by this section has been previously sent) send to the Chief Inspector of Factories at the Home Office, London, a notice stating the name and full postal address of the patient and the disease from which he is suffering. The remuneration for this notification is 2s. 6d., and the penalty incurred in default of furnishing the notice is 40s. In every factory or workshop where lead, arsenic, or any other poisonous substance is used, suitable washing conveniences must be provided for the workers (idem, section 30). If the Home Secretary certifies that any particular process or kind of work is dangerous to the life or health of the workers in any factory, or that the provision of fresh air is insufficient, or that the quantity of dust generated or inhaled in any factory or Avorkshop is dangerous to health, the Chief Inspector may prescribe special rules, or the adoption of special pre- cautionary measures (Act of 1891, section 8). The folloAving industrial processes have been scheduled by the Home Secretary as dangerous under this section:—the manufacture of Avhite lead, paints, and colours; the extraction of arsenic; the enamelling of iron plates; the manufacture of lucifer matches, except such as are made Avith red or amorphous phosphorus ; the manufacture of earthenware, and of explosives in Avhich di-nitro-benzole is used; chemical works; quarries; the making of red, orange, or yelloAV lead; lead smelting; tinning or enamelling of iron hollow ware; electric accumulator works; flax mills and linen factories. Factory Inspectors have poAver to require the provision of fans, or other mechanical appliances, if necessary, for preventing inhalation of dust, gas, vapour, or other injurious impurities by workers; also to require all ceilings, Avails, passages, and staircases to be limewashed every fourteen months, but the Home Secretary may grant exemptions. He may also make special regulations as to cleanliness and ventilation which may, from time to time, appear to him to be necessary in the interest of the workers (Act of 1878, sections 33 and 36, as amended by the Factory Acts, 1891 and 1895). By section 31, Act of 1895, all textile factories, in which the atmospheric humidity is artificially increased for trade purposes, and Avhich are not for the time being subject to special rules under section 8 of the Act of 1891, 886 SANITARY Lk\\. come under the provisions of the Cotton Cloth Factories Act, 1889. By this Act, special arrangements must be made for admitting at least 600 cubic feet of fresh air per hour per occupant. Tavo sets of standard Avet and dry-bulb thermometers must be provided and maintained in Avorking order, and so placed as to be in full vieAV of the operatives. Readings are to be taken betAveen 10 and 11 a.m., and again betAveen 3 and 4 p.m., daily, and records kept. A schedule of this same Act specifies, among other details, for each dry bulb temperature a maximum permissible reading of the wet bulb, and a copy of this table has to be placed near to each hygrometer. The temperature must not be artificially raised above 70° F. In workshops and factories where wearing apparel is made, the temperature must be kept at not less than 60° F. Bakehouses occupy a someAvhat unique position among factories and workshops, owing to the fact that they have received a certain amount of special legislation. In the first place, a distinction must be made betAveen " Avholesale" and "retail" bakehouses. A wholesale bakehouse is repre- sented by such premises as those of Peak & Frean or of Huntley & Palmer; in the eye of the law these are not bakehouses, but factories (Act of 1891, section 36). A "retail" bakehouse is defined by section 18 of the Factory Act, 1883, as meaning "any bakehouse or place, the bread, biscuits, or confectionery baked in which are not sold wholesale but by retail, in some shop or place occupied together with such bakehouse." The same Act places the sanitary supervision of these " retail" bakehouses in the hands of the Sanitary Authorities; these Authorities, outside the metropolis, are the urban and rural Sanitary Authorities, in London, they are in the city the Commissioners of SeAvers, and elsewhere the Vestries and District Boards. The powers and duties of a Medical Officer of Health in connection with the sanitary regulation of retail bakehouses are somewhat exceptional. By section 18 of the Factory Act, 1883, he has all the powers of entry, inspec- tion, taking legal proceedings and otherwise, of a Factory Inspector. He is also required, if he becomes aAvare of the employment of any child or young person under eighteen years of age, or woman in any retad bakehouse, to forthwith give written notice thereof to the Factory Inspector of the district. The poAvers of entry and inspection conferred on the Medical Officer of Health are such that he may enter, inspect, and examine any retail bake- house at any reasonable time by day or by night, without any special written authority or warrant (Act of 1878, section 68, and Act of 1891, sections 25 and 39). In all summary proceedings for offences and fines, the information must be laid within two months, or, where the offence is punishable by imprisonment, Avithin three months after the commission of the offence. There is poAver of appeal to Quarter Sessions (Act of 1878, sections 89, 90, 91). By section 27 of the Act of 1895, Avhich amends sections 34 and 35 of the Act of 1878, the statutory requirements for all bakehouses, Avhenever or Avherever erected, are the same as for other factories or workshops. All the inside walls, ceihngs, staircases, and passages must be limewashed once at least every six months, or painted every seven years, and if so painted, washed Avith soap and hot water every six months. And further, there must be no sleeping-place on the same level in the same building, unless there be complete separation from ceihng to floor, and unless the sleeping- room have an external window nine square feet in area, half of Avhich is made to open (Act of 1878, section 35). The fine for not keeping a bake- house in conformity with these provisions is a penalty not exceeding £10, ALKALI AND CHEMICAL WORKS. 887 recoverable in a Court of summary jurisdiction, and if the order to conform to the requirements of the Act is not obeyed Avithin a specified time, to a daily penalty of £1 (idem, section 81). Sections 15 and 16 of the Factory Act, 1883, as amended by section 27 of the Act of 1895, make it illegal to let or occupy as a bakehouse any place, except under the following conditions:—(a) No Avater-closet, earth-closet, privy, or ashpit to be within the bakehouse, or communicate directly with it. (b) Any cistern for supplying water to the bakehouse to be separate from any cistern supplying a water-closet, (c) No drain or pipe carrying off sewage to have an opening within the bakehouse. Any person contravening these provisions will be liable on summary conviction to a fine not exceeding 40s., and a further fine not exceeding 5s. for every day during which any room or place is occupied in contravention of the section after a conviction. No place under ground may be used as a bakehouse unless so used before January 1, 1896, and if so used must not be in contravention of the above conditions (Act of 1895, section 27 (3)). As regards London, apart from special mention in section 25 of the Public Health (London) Act, 1891, of the duty of every Sanitary Authority to enforce the limewashing, cleansing, and general sanitary supervision of workshops, section 26 of the same Act particularly makes it the duty of every Sanitary Authority in London to enforce sections 34, 35, and 81 of the Factory Act, 1878, and sections 15 and 16 of the similar Act of 1883 as respects bakehouses which are workshops within the meaning of those Acts. For the purpose of enforcing these provisions, the London Sanitary Authorities are made the Local Authorities within the meaning of those sections, and their Medical Officers of Health have all the excep- tional powers and duties as already explained in the previous pages. The provisions of the Factory and Workshop Acts apply fully to both Scotland and Ireland; in the former country, the central jurisdiction is vested in the Home Secretary. ALKALI, CHEMICAL, AND OTHER WORKS. It has already been shoAvn that the provisions of the Public Health Acts relating to Avhat are called offensive trades apply only to a limited class of trades. Outside that class are a number of other trades, works, and businesses in Avhich various noxious and offensive gases are evolved. These latter are placed under the inspection and regulation of officers of the Local Government Board, subject to the Alkali, &c, Works Regulation Acts, 1881 and 1892. These Acts are to be regarded as cumulative, and nothing contained in either of them is to be construed as legalising any act or default which would otherwise be deemed to be a nuisance, or be contrary to law, had these Acts not passed (Alkali Act, 1881, section 31). Further, where it appears to any Sanitary Authority, on the written representation of their officers, or of any ten inhabitants of their district, that any work (either within or without their district) to which these Acts apply is carried on in contravention to them, or that any alkali waste is deposited (either within or without their district), and that a nuisance is occasioned by any such contravention of the Acts, such Sanitary Authority may complain to the Local Government Board, who, after inquiry, are empowered to direct such proceedings to be taken by an Inspector as they think just (section 27). The same Act of 1881, section 29, defines an "alkali Avork" to be "every work for the manufacture of alkali, sulphate of soda, or sulphate of potash, 888 SANITARY LAAV. in which muriatic gas is evolved; and for the purpose of this definition the formation of any sulphate in the treatment of copper ores by common salt or other chlorides will be deemed to be a manufacture of sulphate of soda." These Acts of 1881 and 1892 apply to all alkali Avorks and to the follow- ing scheduled works:—sulphuric acid Avorks, chemical manure works, gas- liquor Avorks, nitric acid works, sulphate ] of ammonia Avorks, muriate of ammonia Avorks, chlorine Avorks, Venetian red Avorks, lead deposit works, arsenic works, nitrate and chloride of iron works, muriatic acid works, fibre separation Avorks, tar Avorks, zinc works; also the following, unless the pro- cess adopted be such that no sulphuretted hydrogen is evolved, namely, alkali waste Avorks, barium works, strontium Avorks, antimony sulphide works, and bisulphide of carbon Avorks (Act of 1881, section 29, and Act of 1892, section 1). No alkali work, or scheduled work, or Avork for the extraction of salt from brine, or cement work, may be carried on unless it has been certified to be registered by the Local Government Board. The certificate of registry is in force for one year from April 1st, following the day of the application for the certificate, such apphcation being required to be made in January or February (Act of 1881, section 11). No neAv works can be registered unless furnished with satisfactory and proper appliances (section 12). The folloAA'ing are the requirements of the Act of 1881 with respect to alkali works. By section 3, every such work must be carried on in such a manner that 95 per cent, of the hydrochloric acid gas evolved must be con- densed, and not more than one-fifth of a grain of hydrochloric acid gas per cubic foot of air, smoke, or chimney gases must escape from the works into the atmosphere. Nor must there be more of the acid gases of sulphur and nitrogen than the equivalent of four grains of sulphuric anhydride per cubic foot of air. The OAvner of any alkali work which is carried on in contraven- tion of these provisions is liable to a fine in the case of a first offence not exceeding £50, and in the case of every subsequent offence £100. Acid drainage must not be allowed to mix with alkali Avaste so as to cause a nuisance: the penalties for the contravention of this provision are similar to the above, with a continuing penalty of £5 a day (section 5). The owner may require the Sanitary Authority to provide and maintain, at his expense, a drain for carrying the acid Avaste into the sea, or any watercourse into which it can be taken without breach of the Rivers Pollution Prevention Act, 1876. Alkali waste must not be deposited or discharged without the best practicable and available means being used to prevent nuisance (section 6). Simdar regulations apply to sulphuric acid works. The gases escaping into the atmosphere must not have an acidity equivalent to more than four grains of sulphuric anhydride per cubic foot (section 8). The other works scheduled in the Acts must employ the best practicable means for preventing the escape of noxious and offensive gases, and for rendering them harmless and inoffensive, subject to the qualification in the case of sulphuric acid works as to the degree of aerial vitiation by the escaping gases (section 9). In calculating the proportion of acid to a cubic foot of air, smoke, or gases, for the purposes of the Act, such air, smoke, or gases are to be calculated at a temperature of 60° F. Avith a barometric pressure of 30 inches (section 21). The Alkali Acts apply to Scotland, being locally administered by the public health authorities. The Secretary for Scotland is the central authority in place of the Local Government Board. The same Acts apply equally to Ireland, but the English Local Government Board has the appointing of the Inspectors; while in all other respects the Irish Board is the central authority. SLAUGHTER-HOUSES. 889 SLAUGHTER-HOUSES. In England and Wales.—By section 4 of the Public Health Act, 1875, the expression " slaughter-house " includes the buildings and places commonly called slaughter-houses and knackers' yards, and any place or building used for slaughtering cattle, horses, or animals of any description for sale. Section 169 of the Public Health Act, 1875, Avhich incorporates certain provisions of the ToAvns Improvement Clauses Act, 1847, enacts that any urban Sanitary Authority may provide abattoirs or slaughter-houses, and if they do so, must make bye-laws with respect to their management and charges. They may also license slaughter-houses and knackers' yards, and without their licence no place shall be used for such purposes which was not so used at the time of the passing of the Act in 1875. Every place used as a slaughter-house or knacker's yard before the passing of the Act, and still continued to be so used, shall be registered by the OAvner or occupier in a book kept by the Sanitary Authority. The distinction, therefore, between a registered and licensed slaughter-house is dependent upon the fact that in the one case the place Avas used as such before the passing of the Act in 1875, Avhile in the other case it has been established since that date. A legible notice bearing the Avords Licensed Slaughter-House or Registered Slaughter-House must be attached and displayed in some conspicuous place on every slaughter-house by the owner or occupier (section 170). Prior to the adoption of Part III. of the Public Health Acts Amendment Act, 1890, in any district, licences granted under the above enactment will not be annual licences, but granted once for all; nor in those cases is a fresh licence necessary when part of the premises is rebuilt, or when any addition is made to them. The continuance of use is of great importance, as it is frequently found that slaughter-houses are disused as such, and applied to other purposes. In that case they cannot again be used as slaughter-houses without application for a licence. But in urban districts in which Part III. of the Act of 1890 is in force, licences, granted after the adoption of that Act, wUl be for not less than twelve months, or such periods as the licensing urban Sanitary Authority may deem fit to specify in it. As regards slaughter-houses and other similar premises for Avhich a hcence is sought, the Local Government Board, in a Memorandum dated July 25, 1877, have suggested that the folloAving rules as to site and structure should influence the decision of a Sanitary Authority before granting a licence:— "1. The premises .... should not be Avithin 100 feet of any dwelling-house ; and the site should be such as to admit of free ventilation by direct communication Avith the external air on two sides at least of the slaughter-house. " 2. Lairs for cattle in connection with the slaughter-house should not be within 100 feet of a dwelling-house. " 3. The slaughter-house should not in any part be below the surface of the ground. " 4. The approach to the slaughter-house should not be on an incline of more than one in four, and should not be through any dAvelling-house or shop. " 5. No room or loft should be constructed over the slaughter-house. " 6. The slaughter-house should be provided Avith an adequate tank or other proper receptacle for water, so placed that the bottom shall not be less than 6 feet above the level of the floor of the slaughter-house. '' 7. The slaughter-house shall be provided Avith means of thorough ventilation. " 8. The slaughter-house should be well paved Avith asphalte or concrete, and laid with proper slope and channel toAvards a gulley, which should be properly trapped and covered with a grating, the bars of which should not be more than three-eighths of an inch apart. Provision for the effectual drainage of the slaughter-house should also be made. " 9. The surface of the walls in the interior of the slaughter-house should be covered with hard, smooth, impervious material to a sufficient height. 890 SANITARY LAAV. " 10. No water-closet, privy, or cesspool should be constructed within the slaughter- house. "There should be no direct communication between the slaughter-house and any stable, Avater-closet, privy, or cesspool. "11. Every lair for cattle in connection Avith the slaughter-house should be properly- paved, drained, and ventilated. "No habitable room should be constructed over any lair." It is the duty of the Sanitary Authority to make bye-laAvs for the licens- ing, registering, and inspection of slaughter-houses and knackers' yards, and preventing cruelty therein, for keeping the same clean, for the daily removal of filth, and for the proper supply of Avater. The folloAving Model Bye-laAvs, issued, by the Local Government Board, are applicable to the above requirements. (a) Licences.—Applications for licence of existing premises, or erection of new slaughter-houses, must be made upon a specified form, and must include full par- ticulars as to the position, form, area, cubic space, &c, of the buildings and appendages ; materials and construction of walls and floors ; means of Avater-supply, drainage, lighting, and ventilation ; means of access for cattle ; number, position, and size of stalls or lairs, and number of animals to be accommodated therein, distinguishing oxen, calves, sheep, and swine. The boundaries must also be shown, and, in the case of old premises, particulars as to the ownership and the applicant's tenure must be given. (b) Registration.—If the Sanitary Authority approve the application, a licence shall be issued to the applicant, and must be registered by him at the office of the Sanitary Authority. (c) Inspection.—Free access to every slaughter-house for the purpose of inspection must be afforded at all reasonable times to the Medical Officer of Health, Inspector, Surveyor, and Committees appointed by the Sanitary Authority. (d) Water must be supplied to every animal kept in a lair prior to slaughter. (e) Mode of Slaughter.—Cattle must be secured by the head so as to be felled with as little pain as practicable. (/) Drainage, water-supply, and ventilation must be kept in efficient order. (g) Cleanliness.—The walls and floor must be kept in good order and repair, and must be thoroughly cleansed within three hours after any slaughtering ; the walls and ceiling must be limewashed four times yearly, that is to say, within the first ten days of March, June, September, and December respectively. (h) Animals not to be kept.—No dog may be kept in a slaughter-house: nor other animal, unless intended for slaughter upon the premises, and then only in proper lairs, and not longer than may be necessary for preparing it for slaughter by fasting or otherwise. (i) Removal of Refuse.—Suitable vessels made of non-absorbent materials, and provided with close-fitting covers, must be provided for the reception of blood, manure, garbage, and other refuse; all such matters must be placed in these vessels immediately after +he slaughtering ; the refuse must be removed within twenty-four hours, and the vessels fortliAvith cleansed. All skins, fat, and offal must be removed Avithin twenty-four hours. If any person is convicted of killing or dressing any cattle contrary to the provisions of the Public Health Act, or of the non-observance of any of the bye-laws or regulations made under the Act, the justices before whom he is convicted may suspend the licence for two months or less, and in the event of a second offence may revoke the licence (Towns Improvement Clauses Act, 1847, sections 125 to 130, incorporated in section 169 of the Public Health Act, 1875). A similar revocation of licence may folio av on conviction for sale of meat unfit for food (Public Health Acts Amendment Act, 1890, section 31). In London, by section 20 of the Public Health (London) Act, 1891, it is provided that a person carrying on the business of a slaughterer of cattle or of horses, knacker or dairyman, may not use any premises in London (outside the city) as a slaughter-house Avithout a licence from the County Council. In the city, the licensing authority is the Commissioners of Sewers. The section does not extend to slaughter-houses erected before or after the com- mencement of the Act in the Metropolitan Cattle Market, under the UNSOUND FOOD. 891 authority of the Metropolitan Market Act, 1851, or the similar Act of 1857. The general provisions as to slaughter-houses are the same as in the provinces, particularly Avhen read in conjunction with section 47 relating to the sale of unsound food. Conviction under this section entails cancellation of licence. In Scotland.—The Public Health (Scotland) Act, 1867, does not specially deal with slaughter-houses, but the business of a "slaughterer of cattle, horses, or any animals of any description " is included under other offensive trades, and is practically subject to the regulations which govern them both in burghs and landward districts (section 30). In the burghs, the Commissioners have full control over the slaughter- houses, and none can be used without their licence; moreover, if they provide premises of this kind, no others may be used (Burgh Police (Scot- land) Act, 1892, sections 278 to 287). In Ireland, the provisions of the Public Health Act are practically the same as those in force in England. In towns constituted under the ToAvns Improvement (Ireland) Act, 1854, if section 47 of that Act has been adopted, the provisions of the Towns Clauses Act, 1847, incorporated into the Public Health (Ireland) Act by virtue of section 105, with regard to slaughter- houses, Avill be in force although such towns may not be urban sanitary districts : and the Town Commissioners " may by special order purchase, rent, build, or otherwise provide such slaughter-houses and knackers' yards as they think proper for slaughtering cattle within the town." UNSOUND FOOD. In England and Wales.—Under the Public Health Act, 1875, the Medical Officer of Health and Inspector of Nuisances have poAver, at all reasonable times, including Sunday, to examine or inspect any animal, carcass, meat, poultry, game, flesh, fish, fruit, vegetables, corn, bread, flour, or milk exposed for sale, or deposited for the purposes of sale, or of preparation for sale, and intended for the food of man; and may seize the same if diseased, unsound, or unwholesome, and take it to a magistrate (section 116), who may order it to be destroyed or so disposed of as to prevent it from being exposed for sale or used for the food of man, and inflict a penalty not exceeding £20, or a term of imprisonment of not more than three months (section 117). The proof that it was not intended for the food of man rests Avith the person charged. Any person hindering these officers from inspecting meat, &c, is subject to a penalty of £5 (section 118). On complaint made by oath by any officer of a Sanitary Authority that there is reason to believe that there is kept or concealed on any premises any articles to which these sections apply, a justice may grant a search Avarrant, and any person hindering the execution of this warrant is liable to a penalty of £20 (section 119). In the foregoing provisions there are tAvo great defects, namely, (1) that no proceedings can be taken in regard to articles already sold, and (2) that eggs, butter, cheese, and other important articles of food are not included in the scope of these sections of the Act. In districts Avhere Part III. of the Public Health Acts Amendment Act, 1890, is in force, these defects have been remedied by section 28 of the same, which enacts that sections 116 to 119 of the Act of 1875, above mentioned, shall extend to "any article intended for the food of man, sold or exposed for sale, or preparation for sale," and a justice may order destruction under section 117, although it has not been seized as under section 116. 892 SANITARY LAAV. In markets and fairs under the control of a Sanitary Authority the sale of unwholesome meat or provisions is subject to similar provisions under section 15 of the Markets and Fairs Clauses Act, 1847, Avhich is incorporated with the Public Health Act, 1875. Where the market or fair does not belong to the local authority the above provisions Avill not apply, unless a local Act is in force, with which the Market and Fairs Clauses Act is incorporated. A Sanitary Authority can make bye-laAvs for preventing the sale of unwholesome provisions in a market or fair by section 42 of the Act of 1847, also incorporated in the Public Health Act, 1875; but owing to the stringency of sections 116 to 119 of this latter Act, these bye-laAvs Avill be rarely necessary. In London, under section 47 of the Public Health (London) Act, 1891, the provisions as to the sale of unsound food are someAvhat more stringent. The London Act not only closely follows the lines of section 28 in Part III. of the Amendment Act, 1890, but renders the offender liable, on conviction, to a fine not exceeding £50, or imprisonment for six months with or without hard labour. The section further enforces the liability of the previous \Tendor of the food, and also renders anyone obstructing an officer acting under a Avarrant for entry Avithin twelve months after a previous conviction for obstruction, or evidently with intent to prevent detection, liable to imprisonment for a month in lieu of fine. The Sanitary Authority have further the duty placed upon them of removing unsound food, as if it were trade refuse, on the receipt of written notice from a person having possession of the same. In Scotland, the list of articles of unsound food liable to seizure does not include corn, bread, flour, or milk (Public Health (Scotland) Act, 1867, section 26). This defect is not remedied, so far as relates to Scotland, by the Amendment Act, 1890. In the burghs, there is power to "seize and destroy diseased cattle, whether offered for sale or not, and to prosecute the original sellers of diseased meat or animals intended for human food, Avhether within or without the burgh" (Burgh Police (Scotland) Act, 1892, sections 428-9). In Ireland.—Sections 132 to 135 of the Public Health (Ireland) Act, 1878, contain very simdar provisions as to unsound food as are contained in the corresponding English Act, with the addition of butter in the classification of articles. Section 42 of the Markets and Fairs Clauses Act, 1847, is not incorporated in the Irish Act, but section 108 of this latter Act enables an urban Authority to make bye-laws for the prevention of the sale of unwhole- some food in all markets and fairs belonging to it. Section 15 of the Markets and Fairs Clauses Act, 1847, "applies only in the case of an urban Authority." With these exceptions, the Irish and English enactments in respect of this matter are similar. HORSE-FLESH. The provisions controlling the sale of horse-flesh for human food are the same in all parts of England, Wales, Scotland, Ireland, and the metropolis. They are contained in the Sale of Horse-flesh, &c, Regulation Act, 1889, which defines " horse-flesh " to be such flesh cooked or uncooked, alone or mixed with other substances, and includes the flesh of asses and mules (section 7). This Act (section 1) provides that the flesh of horses, asses, or mules must not be sold or kept for sale for human food, except in a shop or stall ADULTERATION OF FOOD. 893 over or upon which is placed conspicuously, in legible characters four inches long, an announcement that horse-flesh is sold there. It also prohibits the sale of horse-flesh for human food to any purchaser asking for other meat, or for a compound article not usually made of horse-flesh (section 2). Any person offending against these provisions is liable to a penalty not exceeding £20, to be recovered summarily (section 6). The machinery and procedure for the inspection, obtaining of a search warrant, seizing and taking of suspected meat before a justice, is simdar to that contained in sections 116 to 119 of the Public Health Act, 1875, and already detaded under the heading of unsound meat. The principal point of difference is that the power of inspect- ing is given not only to the Medical Officer of Health and Sanitary Inspector, but also to any other officer of the Sanitary Authority (sections 3 to 5). In London, the Vestries and District Boards, and the Commissioners of Sewers in the City, are the local authorities for the administration of this Act. In the rest of England and Wales, and in Ireland, the local authorities are the urban and rural Sanitary Authorities under the re- spective Public Health Acts. In its application to Scotland, the expression "justice" includes a Sheriff and Sheriff-Substitute, and "local authority" means any local authority authorised to appoint a Public Analyst under the Sale of Food and Drugs Act, 1875. ADULTERATION OF FOOD. The legislative enactments relating to this matter, in respect of the whole of Great Britain and Ireland, are contained in the Sale of Food and Drugs Act, 1875, the Sale of Food and Drugs Act Amendment Act, 1879, the Margarine Act, 1887, and, so far as concerns England and Wales, also the Local Government Act, 1888. Section 2 of the Act of 1875 defines "food" as including every article which is used by man for food or drink, except water and drugs; it defines " drug " as including medicine for external as Avell as internal use. The Act further provides that " no person shaU mix, colour, stain, or powder (or order or permit any other person to mix, colour, stain, or powder) any article of food with any ingredient or material so as to render the article injurious to health, with intent that the same may be sold in that state; and no person shall sell any article so mixed, coloured, stained, or powdered under a penalty not exceeding £50 for a first offence, and on a subsequent conviction of imprisonment Avith hard labour for a period not exceeding six months " (section 3). The same prohibitions and penalties apply to the hke treatment of drugs (section 4), but no hability is incurred if the accused person can show that he was unaware of the admixture, and could not "with reasonable diligence" have known that the food or drug was so adulterated (section 5). Further, "no person shall sell, to the prejudice of the purchaser, any article of food or any drug which is not of the nature, substance, and quahty of the article demanded by such purchaser, under a penalty not exceeding £20 ; but no offence shall be deemed to be committed under this section in the following cases :—(1) Where any matter or ingredient not injurious to health has been added to the food or drug because the same is required for the production or preparation thereof as an article of commerce in a state fit for carriage or consumption, and not fraudulently to increase the bulk, Aveight, or measure of the food or drug, or conceal the inferior quality thereof; (2) Avhere the drug or food is a proprietary medicine, or is the 894 SANITARY LAW. subject of a patent in force, and is supplied in the state required by the specification of the patent; (3) Avhere the food or drug is compounded .... [and the provisions of the seventh and eighth sections are observed]; (4) Avhere the food or drug is unavoidably mixed with some extraneous matter in the process of collection or preparation " (section 6). As regards these exemptions, the onus probandi rests Avith the defendant (section 24). No person shall sell any compound, drug, or article of food Avhich is not composed of ingredients in accordance with the demand of the purchaser, under a penalty not exceeding £20 (section 7); but no offence under this section is committed in respect of the sale of a drug or article of food mixed with an ingredient not injurious to health if it is labelled as " mixed " at the time of the sale (section 8). Section 9 of the Act provides that "no person shall (with the intent that the same may be sold in its altered state without notice) abstract from an article.of food any part of it, so as to affect injuriously its quality, substance, or nature; and no person shall sell any article so altered without making disclosure of the alteration, under a penalty not exceeding £20." In any prosecution under this Act, the defendant is to be discharged if he proves to the satisfaction of the Court (a) that he bought the article as being the same in nature, substance, and quality with that demanded by the purchaser, and Avith a written warranty to that effect; (b) that at the time of sale he had no reason to beheve it to be otherwise; and (c) that he sold it in the same state as when he purchased it (section 25). In order to carry out the provisions of this Act, in every district a com- petent person may be, and if required by the Local Government Board must be, appointed as Public Analyst (section 10). In the case of boroughs having a separate Court of Quarter Sessions, or a separate police force, this appointment is made by the ToAvn Council; wlhle for all other parts of the country the appointment is made by the County Council (Local Govern- ment Act, 1888, sections 3, 38, and 39). All these appointments and re- appointments are subject to the approval of the Local Government Board. Where a Public Analyst is thus appointed, any purchaser of an article of food or drug within the district shall be entitled to have it analysed for a fee of 10s. 6d., otherwise by another Public Analyst at such fee as he may require, and in either case to have a certificate of the result (section 12). The Medical Officer of Health, Inspector of Nuisances, or any officer charged by the Sanitary Authority with the execution of the Act, may procure samples of food and drugs, and submit them to the Pubhc Analyst (section 13). The quantities of the samples purchased under section 13 should not be less, in the case of milk, than 1 pint; butter, f of a Sb ; lard, f of a Bb; coffee, f of a lb; spirits, f of a pint. Any person purchasing an article for analysis shall, upon the completion of the purchase, forthwith notify to the seUer his intention to have it analysed by the Public Analyst, and shall offer to divide it into three parts, to be then and there separated, and each part to be marked and sealed or fastened up, and shall, if required to do so, proceed accordingly, and shall dehver one of the parts to the seller. One of the three parts must be retained for future comparison, and the third dehvered up to the Pubhc Analyst (section 14). If the seller does not accept the offer of division, the Analyst must divide the sample into two parts, seahng and delivering up one of them to the purchaser (section 15). Samples may be sent by registered parcel post to the Public Analyst, if his residence is two miles from that of the purchaser (section 16; see also Post- Office Act, 1891, section 11). Any person refusing to sell to an officer of the Sanitary Authority any ADULTERATION OF FOOD. 895 article of food or drug on sale by retail, the price being tendered and the quantity demanded not being greater than is reasonably requisite, is liable to a penalty not exceeding £10 (section 17). The certificate of the Analyst must be in the following prescribed form (section 18) :— " To [name of person submitting the article']. "I, the undersigned, Public Analyst for the [County, Borough, of air, or 477,637 cubic feet of air 1° F.; or, to put it in another way, the evaporation of 1 gaUon ' of water will reduce 26,216 cubic feet of air from 80° to 60° F. If ' thoroughly utihsed, 1£ gallon per head would be the allowance for twelve hours, but as the full work is never got out of any material, this quantity ought in practice to be doubled. In India the temperature of a hot dry wind is often reduced 15° to 20° F. by blowing through wet khus-khus tatties; merely sprinkling water on the floors has a perceptible effect on the temperature. When the air is stagnant cooling is less easy. In India it is often attempted, in a still atmosphere, to insure coolness by creating currents of air either by the simple punkah or by thermantidotes; these act by in- creasing evaporation from the body, and they certainly do away with the oppressiveness of a still atmosphere. But evaporation of water must be also employed if the atmosphere is dry. In the case of a thermantidote, thin wet mats made of khus-khus grass are suspended in a short discharge-tube, or ice placed in the channel, through which the heated air passes, will answer equally well. Hut Barracks..—Of late years the use of wooden huts, both in peace and war, has greatly extended in several of the European armies. In peace, their first cost is small, and they are very healthy. In war, they afford the means of housing an army expeditiously, and are better adapted for winter quarters than tents. The ground occupied by a hut should be cleared, levelled, and drained. The hut should be provided with ridge ventUation and projecting eaves to carry off the rain-water from the foundations; it should have the requisite number of windows, and should be raised sufficiently above the ground to allow a free current of ah to pass underneath the flooring. In hot climates .the roof and sides should be double, if these latter are not protected from the sun by verandahs. Huts are best placed en echelon, so as to receive the full advantage of winds. Ventilation is effected.by openings in the ridge, or outlet shafts may be used, passing through the roof and terminating in louvres and inlets under the eaves. 932 MILITARY HYGIENE. Warming may be effected by the use of stoves or an open grate. The latter is preferable, as it assists in ventilation. The construction of huts depends on whether they are used for temporary purposes or whether they are intended to be of a more or less permanent character. In the latter case the sides are usually buUt of brick. In the German Army the Docker huts are largely used, and are said to answer well. They have recently been favourably reported on in this country. They are made of wooden or iron frames, covered with a special kind of felt, lined with canvas. They are very portable, and the fastenings are so arranged that they can be put together in a very short time. These huts are well ventilated by windows, cross louvres, and ridge ventUation, and can be easily warmed, if this is desired. Lord Wolseley recommends that temporary huts on service should be constructed to hold twenty-eight men, and be of the following proportions : Length, 32 feet; breadth, 16 feet; height to eaves, 6 feet; height to ridge, 16 feet. The cubic space should be 400 cubic feet per man. Tavo such huts are placed end to encfwith one chimney between them. Fig. 130. The roof may be made of felt or tarred calico, secured by strips of wood. In the tropics, if the rainfall is heavy, the roof should be made steep, to throw off the rain. If the flooring is made of wood, it should be fastened by screws and not nads. This wUl aUow the boards to be taken up, if necessary, and the space beneath cleaned. If the floor is of earth, a httle of the surface earth may be removed occasionally and replaced by clean gravel. Ashes from wooden fires, well rammed down, make an excellent floor. Trenches should be carried round huts as in the case of tents. Fig. 130 shows a plan much used by the Germans in 1870-71 for temporary sheds; the crossing of the rafters permits thorough roof venti- lation, and the raising from the ground where practicable is very important. Bamboo was used in the Ashanti Expedition, on the north-east frontier of India, also at Suakim, and made excellent huts. In the Nile Expedition huts were buUt of sun-dried brick, which gave great protection from the sun. The " Berthon" huts are portable and circular structures made on the same principle as the coUapsible Berthon boats, with timbers radiating from an apex, and which extend two phes of waterproof canvas. The hut waUs are composed of two thicknesses of board, with glass windows in each TENTS AND MARQUEES. 933 segment. The floor is made in segments of board, stained and thickly varnished. The ventilation in them is good, as fresh air enters between the ■double sides, and passing upwards between the two skins of the roof escapes by ventilators at the apex. These huts can be heated in the winter by a stove placed in the centre with a stove-pipe projecting through the apex, nowhere touching any wood or canvas. In extreme climates, additional warmth can be obtained by means of additional felt inner linings. As these huts can be readily taken down and removed, their employment on service, especially for hospital use, presents many advantages. Tents.—A good tent should be light, so that it may be easily transported, readily and firmly pitched, and easily taken down. It should completely protect from weather, be well ventilated, and durable. It is perfectly easy to devise a tent with some of these characteristics, but not to combine them all. The tents used in our army are as follows:— The Circular or Bell Tent.—A round tent with sides straight to 1 foot high, and then slanting to a central pole. Angle at apex, 70°. Diameter of base, 12*5 feet; height, 10 feet; area of base, 123 square feet; cubic space, 492 feet; weight, when dry, including poles, about 721b. The •canvas of the new pattern is made of cotton or hnen. The ropes extend about 1J foot all round. It holds from twelve to sixteen men; and in war time eighteen and even twenty have been in one tent. The men lie with their feet towards the pole, their heads to the canvas. With eighteen men the men's shoulders touch. Formerly, there was no attempt at ventilation; but afterwards a few holes were made in the canvas near the pole. Ventila- tion, however, is most imperfect, as the holes are so small that the movement of the air is almost imperceptible. There is little ventilation through the canvas, and none at all when it is wet with dew. The new chcular tent is somewhat improved as regards ventUation. The Hospital Marquee.—An improved hospital marquee was issued in 1866. It is in principle the same as the old marquee, but with improved ventilation. This tent is two-poled, with double canvas. It is made of a lower, almost quadrangular part, and an upper part, sloping from the top of the straight portion to the ridge. Length, 30 feet; breadth, 15; height of sides, 5 ; height to ridge, 15; area about 385 square feet; cubic space, 3336 cubic feet. It is intended for sick, and can accommodate eight men. There are ventUators, and a large flap at the top can also be opened for ventilation, and the fly can be raised. The weight of this hospital marquee (includ- ing the valise) is about 512 ft). A waterproof sheet is supplied, to put on the ground, and this weighs 145 ft>. It is a good tent when care is taken with ventilation; but there should be a way of raising one whole side, so as to expose every part of the tent; ■and if the height of the upright part were 6 feet, it would be more con- venient. These tents are used for hospitals on the lines of communication and at the base, but form no part of the movable field equipment: they are used when buildings or bell tents are not available. This hospital marquee is cumbersome, excessively heavy, and difficult to pitch. It might advantageously be replaced by a smaUer tent, known as the officers' marquee, and which weighs but 168 ft) complete. Circular Tents.—Two double circular tents, with higher walls and without lining, weighing about 75 lb and 85 lb, have been approved of for hospital purposes, into which four sick or wounded men are placed. These form part of the new field equipment. Five such tents accommodate twenty 934 MILITARY HYGIENE. men well, whereas the marquee of the same weight only serves for eight, unless unduly crowded. Shelter Tent.—There is no official shelter tent for the English Army on home service, but one was formerly issued for service at the Cape, and one is still occasionaUy issued on campaigns, Aveighing 11 lb, for two or three men. Each man at the Cape carried a canvas sheet, made up of a quad- rangular (5 feet 9 inches x 5 feet 3 inches) and of a triangular piece (2 feet 8 inches height of triangle x 5 feet 3 inches base). Buttons and button- holes were sewn along three sides, and a stick (4 feet long, and divided in the middle) and three tent pegs and rope also were provided. Tavo or four of these sheets could be put together, the triangles forming the end flaps. A very roomy and comfortable shelter tent, 4 feet in height, was formed, which would, Avith a little crowding, accommodate six men, so that two sheets could go on the ground. The objection to this tent was its weight, viz., 6 lb 14 oz. per man. Lord Wolseley condemns the shelter tent as too heavy and not fulfilling its purpose. If a thinner material could be obtained, and if the size could be a little lessened in all directions, it would be a very good tent. A plan for making a shelter tent with blankets is given in the Instructions for Encampments, 1895, plate xviii. The tents in use by the Indian Army are as follows:— British Privates.—With two poles and ridge, double fly. Length, 20 feet; breadth, 16 feet; height of walls, 5 feet 6 inches; height to ridge poles, 10 feet 6 inches. Cubic space, 2373 cubic feet. This tent is used for inland service, and accommodates 16 healthy men or 8 sick. Mountain Service.—With two poles and ridge. Length, 12 feet; breadth, 8 feet; height of walls, 10 inches ; height to ridge poles, 8 feet. Cubic space 544 cubic feet. This tent is used for field hospitals to accommodate 4 sick. General Service.—With three poles and ridge. Weight, 160 lb ; length, 14 feet; breadth, 14 feet; height of walls, 1 foot; height to ridge pole, 7 feet. Cubic space, 686 cubic feet. This tent is used for field service, and accommodates 16 British or 20 native soldiers, or 25 followers. General Service (small).—With two poles and ridge. Weight, 80 ft>; length, 8 feet; breadth, 14 feet; height of walls, 1 foot; height to ridge pole, 7 feet. Cubic space, 392 cubic feet. This tent is used for field service, and accommodates 8 British or 10 native soldiers, or 12 followers. French Tents.—In the French Army two chief kinds of soldiers' tents have been used. 1. The tente-abri, or shelter tent of hempen canvas, which was intended for three or four men. This is now given up, on account of its weight, except in campaigns beyond the confines of Europe. 2. Tente de Troupe, or Tente Taconnet.—This is a two-poled tent, with a connecting ridge pole ; for sixteen men. It is considered cumbersome and unstable, and is now abandoned. 3. Two conical tents are now used, like the English beU tent; one (tente conique, also tente turque, or ct marabout) a cone, and the other having an upright wall 16 inches high, and then being conical above (tente conique et a murailles). This last tent is ventilated at the top; a galvanised iron ring, 12 inches in diameter, receives the canvas, which is sewed round it. An opening is thus left of 113 square inches, which can be closed by a wooden top which rests on the top of the pole, and is buckled to the ring. Each tent holds sixteen men. The tente conique is the one now chiefly used. Its weight is 129 ft), and its capacity 1059 cubic feet. Small tents, called tentes de marche, are now issued to officers, who formerly provided their own various forms. TENTS AND ENCAMPMENTS. 935 _ French Hospital Tent.—This is constructed on Toilet's principle and con- sists of a metal frame with a double envelope, the outer casing being of Hnen, the inner of cotton. The framework is in seven pieces and tortoise- shaped. It measures 15 metres in length, is 5 metres broad and 5 metres high in highest part. It affords a cubic space of 200 cubic metres, which for 16 beds gives about 12 cubic metres for each sick person. German Tent.—This is a conical tent, with a single pole, like the bell tent of the English Army; it is nearly 15 feet in diameter; the pole is 12 feet high : it holds fifteen men, and weighs 83 lb avoir. The floor space is 12 square feet, and the cubic space 70 cubic feet per head. In the German Army bivouac tents are in use. The component parts of the tent poles and canvas are distributed among as many men (two at least) as are meant to be sheltered by it. The canvas part, which has the appearance of tanned waterproof flax, is rolled round the soldier's overcoat, which is strapped down on the top and sides of the knapsack, and in bad weather this tent section may be unrolled and Avorn as a watertight poncho by the bearer. German Hospital Tent.—The ground floor of the tent is a rectangle 29£ feet long and 24J feet broad; the tent is 13 feet 9 inches high; the area is 723 square feet, and the weight 952 lb. It is di-vided by curtains into three parts, a central one for the sick, and two rooms for attendants, utensils, &c. The tents are made with a wooden framework, and there is a good hood for ventilation. Each tent could contain ten to twelve beds, but only six patients are placed in it. It stands on an area of 53 feet by 43 feet. At the chief dressing stations, if no suitable building can be found, a bandaging tent is erected in which to perform operations. This is also rectangular in shape; length, 13£ feet; breadth, 11^ feet; height, 8 feet. It is very simply constructed, and has a single fly made entirely of water- proof canvas. Russian Tent.—The infantry tent is quadrangular, 14 feet square and 7 feet high to the slope; there is a centre pole and four corner poles ; it is intended for fourteen men, but only twelve are usually placed in it. Round the tent is a bench 1^ foot broad, and covered Avith straw mattresses and sheets (in the summer camps) for sleeping. A wooden rack round the centre pillar receives the rifles. The canvas can be partly or entirely hfted up. The officers' tents have double canvas. United States Army.—Four styles of tent are issued:— (1) Conical (modified Sibley), 16 feet 5 inches in diameter at base; wall, 3 feet; apex, 10 feet; floor, 212 square feet; air-space, 1450 feet; allowance, 20 infantry or 17 cavalry; comfortable for camp or slow march with half that number. (2) Common (" I" or modified " A "), wall, 2 feet; base, 8 feet 4 inches x 6 feet 10 inches; ridge, 6 feet 10 inches from ground; floor, 57 square feet; air-space, 250 feet; allowance, 4 mounted or 6 foot men. Each infantry man would have 17 inches to lie in. (3) Wall, 9 feet square x 3 feet 9 inches; to ridge, 8 feet 6 inches; floor, 81 feet; air-space, 500 feet; covered by fly or false roof. (4) Shelter tent. Hospital tents are larger wall tents (14 x 15 x i\ feet wall, 12 feet to ridge), that may be opened at each end and thrown together in extension. Camps.—The worst site for a camp is clay soil, or a clay subsoil coming near the surface. Such soils are retentive of water, and keep the atmo- sphere over them damp. They should therefore, if possible, be avoided. Ground immediately at the foot of a slope is apt to be damp and unhealthy, on account of receiving Avater from the higher levels. In tropical climates, 936 MILITARY HYGIENE. localities exposed to winds blowing over Ioav marshy ground are unsafe on account of malarial fevers; for the same reason elevated sites on the margin of steep ravines, up which malaria may be carried by air-currents, are apt to be unhealthy, as are also deep narrow valleys or gorges covered with dense vegetation. Ground covered with rank vegetation, especially in the tropics, is un- healthy, partly on account of the. amount of decaying matter in the soil, partly because the presence of such vegetation is in itself a mark of the presence of a high subsoil water or of a humid atmosphere. In hot chmates, the banks of rivers, especially if the water is stagnant, marsh lands, lands subject to periodical floodings, and especially if covered with mixed salt and fresh water, are particularly unhealthy. A porous subsoil, not encumbered with vegetation, with a good fall for drainage, not receiving or retaining water from any higher ground, and the prevailing winds not blowing over a marsh, will afford the best sites. Regulations have been issued by the Quartermaster-General's Department, and the Queen's Regulations contain several orders which will be noticed hereafter. The Barrack Improvement Commissioners also lay down certain rules which must be attended to. Encampments are divided into two kinds—those of position, which are intended to stand for some time, and incidental camps. The camps are arranged in the same way in peace and war, as a means of training the men; but, of course, in peace the war arrangements need not be adhered to. In the Regulations and Instructions issued in 1895 by the Quartermaster- General's Department, the following points are laid down as of import- ance :— 1. The length of time troops are to occupy the camping-ground. 2. That order, cleanhness, ventilation, and salubrity are to be ensured. 3. That means of passing freely through the camp are essential. 4. That a straggling camp increases labour of fatigue duties, and impedes delivery of supplies and circulation of orders. 5. That the more compact the camp, the easier it is to defend. Troops are ordered to be encamped in such a manner that they can be rapidly formed in a good position for action. This does not involve the necessity of encamping on the very position itself. Although purely strate- gical or tactical considerations are of the first importance before an enemy, yet sanitary advantages must always be allowed great weight, and will, in most cases, govern the choice of ground if military reasons permit. Cavalry and infantry camps are directed to be formed with such intervals between their troops or companies as circumstances may require, or the general com- manding may direct. Open column is usually the most extended order used. In front of an infantry camp is the battalion parade, the quarter-guard being in front of all. Behind the men's tents, on the left side, are the kitchens, and on a hne to the right the tents of the officers; then come the waggons, horses, drivers, and batmen; next the ashpit and latrines, and on the boundary line the rear-guard. In fixed camps the latrines and kitchens may be pitched elsewhere, if found advisable. The distances between different corps are, as a rule, to be 10 yards. Measurements in camps are made in yards : 5 yards = 6 paces. ^ Cavalry are encamped in columns of troops or squadrons, the horses being picketed between every second row of tents; 5 feet of space is allowed to each horse. ArtiUery encamp with the guns in front, the waggons in two lines behind, CAMPS. 937 and the horses and men on the flanks, the men being outside, the officers' tents being in rear. There are 3,097,600 square yards in a square mile, and assuming that there are fifteen men to each bell tent, the folloAving table gives the surface area per tent for different densities of population per square mile:— No. of Square Yards per Tent. No. of Tents per Square Mile. No. of Troops per Square Mile at 15 Men per Tent. 50 61,953 929,280 100 30,976 464,640 200 15,488 232,320 400 7,744 116,160 800 3,872 58,080 1000 3,097 46,464 Assuming the strength as in column one, and using these measurements, the following table gives the density of population:— Strength. Square Yards. Acres. Men per Acre. Men per Sq. Mile. Infantry battalion, full size, . 1011 21,600 4*46 226 144,640 ,, minimum, 1011 7,800 1*61 628 401,920 Cavalry regiment, full size, 630 34,000 7-02 89 56,960 ,, minimum, . 630 15,000 3-09 204 130,560 Battery...... 154 11,200 2 31 67 42,880 Field company, R.E., 182 7,500 1-54 118 75,520 Bearer company, .... 66 8,400 1-73 38 24,320 Field hospital, .... 145 11,200 2-31 62 39,680 The above tables show that a cavalry regiment encamped upon its maximum area is nearly as densely populated as Liverpool, which has a population density of 97*3 persons to an acre; and when occupying its minimum space would have as dense a population as the most crowded part of London, namely Whitechapel. The compression of any camp must depend on the size of the ground and the nature of the service on which troops are employed, but these tables clearly show that camps in the most " open order," as laid down in regula- tions, are densely populated. In laying out a camp, tents should never be arranged in double line; short single lines are best. The tents in line should be separated from each other by a space at the very least equal to a diameter and a half of the tent, and the further the lines can be conveniently placed from each other the better. The floor of a tent should never be excavated, with a view to increase the space; water is apt to lodge in the cavity; the space is nearly always damp, and the occupants are exposed to ground-air emanations. Men should never sleep below the level of the ground, but if possible above it. To prevent the subsoil beneath the tent becoming saturated with filth, tents should occasionally be shifted to fresh ground within the same hnes, so as to expose the vacated sites to sun and air. It is well known that tents occupying the same ground for a length of time become unhealthy. The German regulations order that the soil underneath, if not absolutely 938 MILITARY HYGIENE. clean and firm, should be dug out to the depth of one foot, and replaced by gravel, coal-dust, &c, shghtly watered, and covered by a few boards until dry and hard. Whenever possible, the floors of tents should be boarded, the boards being loose, so as to be easily removed. If boards cannot be obtained, Avaterproof sheets should be used; the soil should be beaten down, so as to render it less permeable; the surface scraped from time to time and replaced by clean gravel or ashes from the wood fires. If straw is used for bedding, it is best to make it into mats of a triangular shape and two or three inches in thickness. These can be taken up during the day and exposed to the sun and ah. As there is almost no ventilation in tents, the sides should be raised during the day and to leeward at night. The tent door should never be closed. Camp latrines should be placed to leeward of prevailing winds, and as far- removed from the tents as is compatible with convenience. They should be dug deep and narrow, and their contents covered over every evening with several inches of fresh earth. Care should be taken not to place them near existing weUs, nor to dig wells near where latrines have been placed. When the latrines are filled within two or three feet of the surface, earth should be thrown in and well raised so as to mark the site. It is well to> screen off the latrines with any available material. Horses or other animals should always be placed to leeward of the men's tents. All refuse material that can be disposed of by burning should be got rid of in that way. If this cannot be done, it should be removed daily to some- spot at a safe distance from the camp. Dead animals and the debris from the slaughter-houses, &c, should be buried in dry earth at sufficient depth, and at a distance to leeward of the camp. Military Hospitals.—In the construction of hospitals, the great points to- be secured are: (1) purity of internal atmosphere; (2) abundance of pure air and sunlight within the building; (3) facility of administration and discipline. The reahsation of these principles involves the selection of a healthy site for the building, simplicity of plan and construction, a suf- ficient number of wards properly placed, a certain arrangement of wards,. proper ward proportions, a suitable number of offices, stores, &c, and easy means of communication throughout the building. The first of these con- ditions is met by placing the sick in detached buildings, with such an aspect as will afford the freest air and the greatest light; this is best effected in hospitals built on the pavilion plan, in which the sick can be treated in small detached and perfectly ventilated buddings, and where there is no possibihty of the air of one ward passing into another. The ventilation of wards in a military hospital is on the same plan as for barracks, except the dimensions are nearly doubled. The ward unit is the foundation of the hospital plan, and the ward con- struction and proportions must be based on the number of cubic feet to be allowed per bed. In Avards each man should have at least 90 square feet I of superficial space and 1200 feet of cubic space. This is the amount 1 allowed by regulations at home, but, if possible, a larger space should be given. In tropical climates (exclusive of India) 1500 feet of cubic space is allowed to each man, or an amount as may be specially authorised for each command. The Instructions for the Royal Engineer Department, 1887, state the size HOSPITALS. 939 and construction of hospital wards in the United Kingdom to be as follows:— Ward.—Normal size for twenty-four beds, 87 ft. x 24 ft. x 14 ft. high. Ward for two beds, 20 ft. x 13 ft. x 14 ft. high. 1. The regulations direct that the walls for hospitals shaU be constructed on the same plan as those for barracks. 2. The bed space for two beds between two windows must not be less than 9 ft., or 3 ft. per bed and 3 ft. between them. The bed space between a window and an end wall should be 4 ft. 6 in. With the minimum distance between the windows, their maximum interval width should be 5 ft. 6 in., giving for each bed in the large wards a floor space of 7 ft. 3 in. x 12 ft., which, with a height of 14 ft., allows 1218 cubic feet. The windows of large wards should face east and west. The windows should be 2 ft. 6 in. from the floor to the top of the stone sill, about 10 feet high, and should run up to within 12 inches of the ceihng; the inner sills to be bevelled to prevent accumulation of dust. Blinds should be provided to the windows of wards. Doors to large wards to be 4 feet wide, hung in two, and glazed with a swing fanlight above. Fig. 131. The arrangement of water-closets and urinals is a matter of the greatest importance. The best plan is to throw out from one end of the ward a building to contain th& closets, and connect it to the ward by an inter- cepting lobby. This is the plan adopted in the Cambridge Hospital at Aldershot and in all the neAv station hospitals (see fig. 131). The foUowing plans show the general arrangements adopted in the con- struction of mihtary hospitals. The Herbert Hospital, Woolwich, consists of four double and three single pavilions of two floors each, aU raised on basements. The administration is in a separate block in front. The wards are warmed by two central open fire-places with descending flues, round which are air-passages, so that the entering air is warmed. The floors are iron beams filled in with concrete and covered with oak boarding (fig. 132). The Cambridge Hospital at Aldershot is much on the same plan, but the closets and lavatories are thrown out in separate turrets and connected by intervening lobbies (fig. 133). Military Hospitals in India.—The Indian Army Regulations direct for each sick man from 102 to 120 square feet of superficial area, and from 1630 cubic feet of space (in the hills) to 2400 (in the plains). 940 MILITARY HYGIENE. Hospital Organisation, &c.—Military hospitals are classified as f oUoavs I. In Districts and Commands. (a) General Hospitals. (b) Station Hospitals. (c) Lunatic Hospitals. (d) Hospitals on board ships conveying troops. (e) Hospitals for soldiers' wives and children. > "■■■ ri-----------»N' "*°° ' . ,..,.; ... V :§iii^ Q o: ^ci II. With an Army in the Field. (a) General Hospitals. (b) Hospital Ships. (c) Hospitals on the lines of communication. (d) Field Hospitals. HOSPITALS. 941 Subject to the officer commanding the district or station, the senior medical officer in charge of a hospital commands aU officers of the Army Medical Staff, and soldiers of the Medical Staff Corps attached to the hospital, as well as all patients in hospital and officers and soldiers of other corps attached to the medical staff corps for duty. He is responsible for the discipline of the whole establishment. The medical officer in charge of a military hospital is directly responsible for all the duties of the hospital: he will take care that all the instruments, medicines, hospital equipments, clothing, and stores held on inventory are in good condition, sufficient according to regulation, and kept in safe custody ; that the supplies are of good quality, and that the cooking and distribution of the diets are properly carried out. The nursing duties in general and station hospitals are carried out by nursing sisters, under the immediate supervision of the superintendent or acting superintendent: they receive orders and instructions relative to the nursing arrangements from the medical officers. Nursing sisters are re- sponsible for the personal cleanliness of the patients in their wards and that all medicines, diets, &c, are properly issued. They also assist in training, as hospital attendants for nursing duties, the men of the medical staff corps. no 5b o IO» SOP SCO or 21"3 Per 1000, Of course the numbers furnishing the sick are constantly reduced by the sick entering hospital; as a rule, an equivalent number usually leave hospital; if the numbers are very different, a calculation must be made to equalise them. It is always desirable to express what would be the admissions in a year into hospital, supposing that the strength remained the same, and furnished every week the same number of sick. This result is obtained by taking the daily admission per 1000 and multiplying by 365. In this case = 1109 per 1000. Therefore, the whole regiment, or what would be equivalent to it, would pass through the hospital if 23 men were admitted weekly. There are here, of course, 3 variables— (a) The successive days or weeks. (b) The strength of the regiment. (c) The number of sick. But to simplify matters, it is sufficient to take the first and last, and to leave out the varying strength, unless this is considerable. The admissions into hospital are advantageously considered from the point of view of age, to show whether the younger or the older men are suffering most. For this Ave require to know the number of men in the regiment at every age :— 18 to 20 years. 28 to 30 years. 20 „ 22 „ 30 ,, 35 ,, 22 ,, 24 ,, 35 „ 40 „ 24 „ 26 ,, 40 „ 50 ,, 26,, 28 „ Then reduce to a comparable standard. As the number of men at a given age are to the number of sick at that age, so is 1000 for example. Supposing that between the ages of twenty to twenty-tAvo there are 163 healthy men furnishing 22 sick in one Aveek, Avhile betAveen the ages of twenty-six to twenty-eight there are 115 men furnishing 7 sick, then, ^^0 = 134-9 per 1000, and 1^0 = 60*8 per 1000; therefore, the younger men are more than tAvice as sickly as the older ones. (2) The deaths in hospital must be considered, as compared Avith the number of cases treated. In a given time we have to state—How many persons have been treated ? How many have died ? and then to reduce this to a comparable standard. To get the number of persons treated, Ave may adopt several Avays. (a) Take half of the cases admitted and discharged. Supposing in one Aveek 40 cases were admitted and 10 discharged, then 40 + 10 = 50 -f- 2 = 25, the average number treated. (b) This same result may be obtained in another Avay. Supposing Ave have in hospital— 30 Remained,.....call that R 40 Admitted,.....,, A 60 Remaining......,, L 10 Died or discharged,. ... ,, D 972 MILITARY HYGIENE. Then to get the average sick treated in the time, add half the remained to the admissions and deduct half the remaining :— T> T A + ~0---_- = number treated, A = 40 + |° = 55-f~25; or, deduct from the discharged half the remained and add half the remaining:— Then reduce the mortality to a comparable standard. Supposing in a hospital 557 are admitted and 237 are discharged in a given time, say 63 days, then 557 + 237 = 794 4- 2 = 397 cases treated in the time in which the mortality is to be calculated. Then supposing that the mortality has been 15, reduce this to a percentage :— 15 x 100 —^— =3*78 per cent., or 37*8 per 1000. To make this still more intelligible, let us reduce it to a uniform time, say, as given above, 63 days; then if the mortahty continued, let us see Avhat it would be in a year:— 365x37*8 Mn ,nnn ---^---=219 per 1000 ; that is, if instead of 397 men only, 1000 had been in hospital constantly, 219 would have died in a year if the mortality had been the same as in the 63 days. Instead of the cases treated, the sick popidation may be taken; that is, the number of patients in hospital on each day as an average. To get the sick population add the numbers put doAvn as remaining on each day or on each week and divide by the number of days or weeks. This gives the average number in hospital on any one day. The mortality may be calculated on the sick population, by dividing the deaths by the sick population and reducing to a uniform standard of time, say one year. (3) The next point is to determine the number of days a patient is in hospital. (a) Add all the days together and divide by the cases treated; or, (b) Multiply the sick population by the number of days over which the return extends and divide by the cases treated. For example, say the sick population is 23, number of days 7, and the cases treated 39, then 23 x 7 oq = 4*1. Each patient Avas therefore in hospital rather over four days. If in any individual case we Avish to know the number of days Ave must, of course, have the dates of admission and discharge of the individual. A rough estimate may at any moment be made by remembering that if in the above example the sick population and the cases treated had been equal, each man must have been seven days in hospital. If the sick population had been, as above, 23, but the cases treated 46, each man would have been half a week in hospital, or 3"5 days. The returns required to be furnished by the medical officer in charge of a station or general hospital are as foUoavs :— 1. Daily Return.—This is a daily state of the numbers admitted, dis- charged, remaining in hospital, or died. It is sent to the officer commanding STATISTICAL RETURNS. 973 the station for his information. A return of the men admitted and dis- charged is also forwarded to the officer commanding each corps. 2. Weekly Return.—This return contains the details for seven complete days, including the average strength by corps, the admissions to and dis- charges from hospital, the numbers remaining in hospital, the deaths, remarks on all important cases, also on any infectious diseases, and on the sanitary condition of the station. All deaths occurring during the period have to be briefly noted, as well as any important cases under treat- ment. This return is furnished by all hospitals except those for soldiers' Avives and children, hospitals on board ship, and hospitals in the field. 3. Annual Return.—This return is completed and forwarded by each officer who is in medical charge of a hospital on December 31. It includes all the details given in the Aveekly returns, and, in addition, the average number of daily sick, the average sick time to each soldier, and the average duration of each case of sickness is given. It must include the statistics of all the sick of the regular forces who have been admitted during the year. With this return is attached a report in manuscript of medical transactions, and prevailing diseases, which should show the bearings of sanitary arrangements thereon. An annual report is also furnished by the officer in charge of the hospital for soldiers' wives and children. 4. Special Returns.—During the prevalence of epidemics, special weekly returns are furnished. 5. Returns on Board Ship.—The statistics of the folloAving classes of troops are required :— (a) Troops proceeding on service abroad. (b) Troops returning home from abroad. (c) Troops proceeding from one station to another. (d) Invalids returning home. 6. Returns of Troops on Active Service in the Field.—These include (a) daily state of sick and wounded, (b) special return of officers and men who have received wounds or injuries in battle, specifying as tersely and accu- rately as possible the kind of wound or injury and the degree of severity. Weekly returns are also required for hospitals in the field. The mortality of the army has undergone an enormous diminution during later years. This is probably due in some measure to a closer selection of the men enlisted, to the lesser difficulty in invaliding under the short- service system, and to the comparative youth of the army taken as a whole. But there can be little doubt that this result is also the outcome in a large measure of the sanitary improvements which have of late years been introduced, and which have lessened the death-rate and invahding both at home and abroad. The following table shows this decrease :— Mortality per 1000 in the United Kingdom. From all causes. Mean of 10 years 1861-70,........9*45 1870-79,........8*18 1878-87,........6*52 Mean of 7 years 1886-92.........5*24 1893.............5*13 This gross mortality must now be compared Avith that of the civil male population at the soldier's age :— Mortality per 1000 of population. From 20 to 25 years of age,........5*4 „ 25 „ 35 „ ........74 .. 35 „ 45 „ • ■.......12*8 974 MILITARY HYGIENE. The soldier's mortality, taken as a Avhole, is therefore under that of the civil population, but this is not taking into account the invaliding, for which some addition should be made. As regards the influence of age on mortality, statistics show that between the ages of twenty and thirty-four the mortality is in favour of the soldier; after thirty-five years the proportion is reversed, and the civilian mortality is lower. The inference which must be drawn is that military life, if prolonged, has an injurious effect—probably, in some measure, the result of climate and of personal habits acquired in it. Causes of Mortality.—As regards the causes of mortality the disease Avhich is most fatal is phthisis: the number of cases invalided during the year 1893 was 1*60 per 1000, and the average ratio per 1000 from 1886 to 1892 was 1*75 : the mortahty being 2/72 per 1000 for each period—making a total loss by death and invaliding during 1893 of 4*32 per 1000, and for the seven years 1885 to 1892 an average of 4*42 per 1000 annually. The mortality is only slightly below the whole male civil population at the soldier's age, and must be considered excessive when we remember that the soldier is especially selected and undergoes a strict examination before he is enlisted. The diminution over former years is exceedingly large, and there is still evidence of further decrease, so that we may reasonably hope for still further improvement in this direction. Heart disease and diseases of the circulatory system come next in order of frequency. The mortality is about the same as that of the civil population. There is here also a considerable improvement over former years, due to the close attention given to the dress of the soldier and to the careful distribution of the weights he has to carry, which are now arranged so as not to press unduly on the chest walls. Excessive smoking has also been assigned as a possible cause, as well as the excessive use of alcohol. The real cause of the "soldier's heart" appears, however, to be due to sudden and violent exertion, undertaken by lads of immature growth under unfavourable conditions of food and clothing. The next most fatal forms of disease are those referred to the digestive system; from these soldiers suffer in about the same ratio as the civil popula- tion. Diseases of the nervous system are also in about the same ratio as the civil population; this class includes apoplexy, meningitis, paralysis, mania, &c, and accounts for 3*4 per cent, of the total deaths. Acute diseases of the lungs come next in order. It is extremely difficult to say Avhether in military life these are more common than among the civil population, but from the crude information we possess, the mortality appears to be less than in civil life. The next group are the continued fevers. Practically, the mortality from these is nearly all due to enteric fever. The mortality is about one-half that of the civil population. Other diseases, such as diphtheria, scarlet fever, diabetes, &c, account for nearly 23 per cent, of the total deaths which take place yearly. Although there has been great improvement in the health of the army during recent years, still much remains to be done. Tubercular diseases, those of the circulatory system, and " fevers," aU more or less preventible] are stUl excessive in the mortality returns. Loss of Strength from Invaliding.—In 1893 the invahding at home was 15*70 per 1000 : this is lower than the decennial average rate by 1*50 ; for the Avhole army it was 13*30 per 1000, the decennial average, 1883 to 1892, being 15*54. During the seven years 1860-67 there were invalided 37 per CAUSES OF MORTALITY. 975 1000, and a total loss by death and invaliding from disease nearly 46 per 1000. Thus the loss by invaliding has been reduced more than one-half •compared to what it was in former years. The chief reason for this reduction is the system of short service. Circulatory diseases account for about one- fifth, phthisis and respiratory diseases, in round numbers, account for about one-sixth, and nervous diseases for about one-eighth of the invaliding. Loss of Service from Sickness.—On an average, 1000 soldiers furnish from 700 to 800 hospital admissions: the seven years 1886-92 gave 777; 1893, 751*6. The cavalry of the line and the artillery furnish the largest number, whilst the household cavalry and engineers give the least number; in the latter, many of the men are married, and Avhen admitted to hospital are •deprived of their working pay, so they seldom seek admission until compelled to do so. The cavalry of the line and artillery are also subject to accidents incidental to the nature of their work. A very large number of admissions are the result of venereal disease, of which there is no immediate prospect of any considerable decrease. It is not possible to compare the loss occasioned by sickness Avith that occurring in other armies, as the conditions of service are not the same. Causes of Sickness.—Venereal Diseases.—This class of disease causes a large amount of inefficiency in the army. It is impossible to compare the numbers who are affected in the military and naval services with those in the civil community, as there are no morbidity statistics relating to the latter. We have, however, no reason to believe that the civil population is exempt from these diseases in a greater degree than the military and naval -services are. The large amount of inefficiency in the army and navy caused by venereal - disease Avas brought prominently to notice shortly after the systematic issue of the Army Medical Department Reports in 1859. In 1864 the first Act •of Parliament was passed which had for its object the prevention of these diseases, and caused those females who were the sources of its diffusion to be subjected to medical treatment in hospital Avhile they Avere in a state capable of communicating it. The first Act passed was found to be more or less ineffectual, and this was amended by the Acts of 1866 and 1869, Avhich remained in force until May 1883, when compulsory examination was abolished by a resolution of .the House of Commons, at Avhich time the Acts practically ceased. These Acts gave rise to much controversy, and there has been a wide- spread and active opposition to them. Apart, hoAvever, from the saving of much misery and suffering which they were the direct means of averting, they were no doubt useful as affording a wholesome influence on the class : subjected to them, and were the means of raising the moral tone of those towns which were placed under them. It is not likely that these Acts Avill ever be passed in the same form again, but it is not unreasonable to hope that the time is not far distant when venereal diseases will be included in the list of those of which notification is required, and that men and women suffering from this objectionable disease shall be placed under super- vision and control. The prevalence of venereal diseases in armies has recently been the subject of a communication to the Academy of Medicine in Paris by Commenge. He shows how prevalent these diseases are, and especially so in the British Army. In 1892 out of 196,336 soldiers, 52,155—that is to say, upwards of a quarter of the entire British Army—were admitted to ~ hospital on account of venereal disease. The foUowing tables show the relative prevalence of venereal disease in 976 MILITARY HYGIENE. the British, French, and Russian Armies, the figures giving the cases per 1000 of strength:— England. France. Russia. 1889, . 217*1 45-8 40*7 1890, . 212-4 43-8 43-0 1891, . 197-1 43*7 41-5 1892, . 201-1 44-0 44-6 The foUowing table shoAvs the comparative prevalence of syphilis alone England. France. Russia. 1889, . 35-7 9 1 12-9 1890, . 37 3 9 1 13-4 1891, . 32 2 8 9 12-2 1892, . 33-8 9 2 13-7 Commenge states that venereal diseases are ahvays far more numerous in countries where there is free trade in prostitution than in those Avhere regulations are in force. On the other hand, it cannot be denied that since the abolition of the Acts there has been a progressive diminution in the admissions from these diseases in the army at home, and this has been used as an argument against their reinforcement by those who are opposed to any legislation on the subject. But that this occurred in former years before the introduction of the Acts must also be admitted, although the reason for this being the case is not apparent. The following table shows the admissions for venereal diseases for five years before the introduction of the Acts:— Year. Ratio per 1000 1859, . 422*0 1860, . 368*9 1861, . 353*8 1862, . 329-9 1863, . 3068 A similar diminution in the admissions for all venereal diseases during the decennial period 1884-93 has also taken place, as shown in the foUow- ing table:— Year. Admissions for Primary Syphilis. All Venereal Disease. 1884, 1885, 1886, 1887, 1888, 1889, 1890, 1891, 1892, 1893, 125*2 127-4 118*8 107-5 93-2 83-5 69-1 63-1 667 56 9 2707 275-4 261-1 252-9 224-5 212-1 195-8 183 4 188-8 177-0 VENEREAL DISEASE. 977 There is some evidence that during later years a diminution has occurred among the civil population, and the death-rate during the last quinquennial period, 1890-94, sIioavs a large decrease over previous years. The folloAV- ing table is compiled from the Registrar-General's returns for England and Wales:— Years. 1865-69, 1870-74, 1875-79, 1880-84, 1885-89, 1890-94, Deaths per 1,000,000. 90 90 97 94 85 80 There is no doubt that, as shown by the above tables, there has been a decline in the prevalence of these diseases since 1885. The last twenty years has seen many changes in this country. Since the passing of the Education Acts, when school attendance was made com- pulsory, there has been a gradual but increasing improvement in the moral character, of the whole population, and the various sanitary Acts have in no small degree assisted to bring this about. It is evident also that the Con- tagious Diseases Acts have, of themselves, been beneficial, inasmuch as they proved to individuals the necessity for medical treatment Avhen diseased, and inculcated the benefits to be gained from cleanly habits. It is seldom that the same abandoned class of prostitutes are to be seen in garrison towns that formerly frequented them, and there is every reason to believe that this is due to the general social improvement of the masses, and not to the abolition of the Acts, which served their time and purpose, and were in no small measure instrumental in bringing about this change. On the contrary, we are justified in believing that this diminution in venereal disease would have been greater had the Acts remained in force and their sphere of usefulness been more widely extended. The advantages gained by the passing of these Acts at a time when education was neglected and feAv sanitary Acts dealing with the surroundings of the working classes were in existence, is shoAvn in the following table, which gives the admission ratio per 1000 in fourteen stations under the Acts, and fourteen stations not under the Acts, since 1860. Year. 14 Stations under the Acts. 14 Stations not under the Acts. 1860-63, . 1864-69, . 1870-73, . 1874-79, . 1880-82, . 1883-84, . 129-8 87-1 86-0 38-7 75-6 123*9 120*6 133*9 107-9 97-4 175-9 174-0 In India, where the same rapid advance in sanitary progress has not been possible, and where the education of the natives has been narrowed by caste prejudices, and especially of the female population, which has always been relegated to an inferior position in that country, there have not been the same influences at Avork; and consequently we find that the sus- pension of the Acts has had a directly opposite effect to what has taken place in this country. 3 Q 978 MILITARY HYGIENE. The foUoAving table sIioavs the comparison betAveen the year 1866, before the Contagious Diseases Acts were imposed, the year 1884, Avhile they were in force, and the years 1891-92-93, Avhen the Acts had been abandoned, the figures giving the cases per 1000 of strength. Presidency. Average Strength. 1866. 1884. 1891. 1892. 1893. Bengal, . . Madras, Bombay, 42,304 13,440 12,903 217-7 231-1 206-6 290-6 307*7 291-6 303-8 322-0 354-6 315-0 333-0 321-6 357-8 414-8 386-9 The history of the subject in Calcutta is even more convincing. The Acts were put in force in that city in 1869; they were suspended in part of the city in November 1881, and in the entire city in March 1883. The following figures show the results of this change:— Cases of Venereal Diseases.—Ratio per cent of Garrison. Year. Primary Syphilis. Venereal of all Kinds. 1868, 10-0 25-06 1869, 9-0 25-08 1870, 60 14-4 1871, 2-7 8'1 NeAv regiment. 1872, 5-7 13-9 1873, 1-4 7-4 1874, 1-4 9'4 New regiment. 1875, 1-3 10*3 ,, 1876, 2 3 12*6 „ 1877, 4-3 10-7 1878, 4-0 11-7 New regiment and drafts. 1879, 2-7 9*3 1880, 1-7 12*8 New regiment. 1881, 3-1 8-7 1882, 3*7 14"5 New regiment. 1883, 10-9 28-0 1884, 30-2 58*1 New regiment. 1885, 15-1 31*6 „ „ From these figures it is apparent that syphihtic disease had sunk from a high ratio, 10 per cent, in 1869, to a low one, 1*7 per cent, in 1880, and for two years it had only been 1*4. In 1883 it rose to 11 per cent., and in 1884 to 30 per cent., while 58 per cent, of the garrison were admitted to hospital for one form or other of venereal disease. CHAPTER XX. MARINE HYGIENE. Marine Hygiene may be defined as the application of the principles of general hygiene to the conditions and exigencies of sea life. These con- ditions, so far as they affect life and health, contrast markedly with the corresponding circumstances on land. The importance of the subject, and the extent of the interests involved, will be apparent from a consideration of the following statistical facts. Nature and Extent of the Marine Population.—The total population afloat belonging to this country may be stated in round numbers as being not less than 400,000 persons. It may be divided conveniently into (a) that belonging to the mercantUe marine, including the crews of fishing-boats registered under both the Merchant Shipping Act and under the Sea Fisheries Act, and (b) that constituting the personnel of the Royal Navy. According to the Annual Statement of the Navigation and Shipping of the United Kingdom issued by the Board, of Trade, the number of persons employed in the mercantile marine of the United Kingdom in the year 1894 was as foUoAvs:— Mercantile Marine, Britishers. Lascars. Other Nationalities. Total. In sailing-ships, .... In steamships, .... In fishing-boats (approximate), 62,915 120,318 104,761 79 26,096 11,857 19,193 74,851 165,607 104,761 Total, . 287,994 26,175 31,050 345,219 The table on page 980, prepared from the same source as the foregoing, shows the number and tonnage of sailing and steamships belonging to and registered in the United Kingdom, with the distribution of the mercantile marine population in ships of different sizes. In the Royal Navy, the total force afloat, corrected for time in the year 1893, was 60,120 officers and men, of whom 33,940, or 56*45 per cent., were betAveen the ages of fifteen and twenty-five; 18,430, or 30*65 per cent., were between the ages of twenty-five and thirty-five; 6820, or 11*34 per cent., were between the ages of thirty-five and forty-five; and 930, or 1*54 per cent., were above forty-five years of age. Marine Sanitary Regulation and Supervision.—From the foregoing statement of the diverse composition of the general population afloat it will be apparent that the subject of Marine Hygiene is by no means simple, and it is further comphcated by the fact that the health of the seafaring 980 MARINE HYGIENE. community is committed to the care of a variety of departments acting under the authority of different Acts of Parliament. Classification of Tonnage. Sailing. Steam. Vessels. Tonnage. No. of Crew per Ship. Vessels. Tonnage. No. of Crew per Ship. Under 50 tons, Of 50 and under 100 tons, ,, 100 „ 200 ,, ,, 200 „ 300 „ 300 „ 400 „ ,, 400 „ 500 „ 500 „ 600 „ 600 ,, 700 „ 700 ,, 800 „ ,, 800 ,, 1000 „ ,, 1000 ,, 1200 „ ,, 1200 ,, 1500 ,, ,, 1500 „ 2000 „ ,, 2000 „ 2-500 „ ,, 2500 ,, 3000 ,, ,, 3000 and upwards, . 3672 3614 878 184 62 65 52 53 92 170 187 336 406 186 4S 6 129,742 258,479 127,889 44,109 21,250 30,092 29,160 34,663 69,486 152,306 207,994 452,208 704,042 411,329 130,380 19,096 3-6 4-4 5-8 8-0 10 0 122 13-6 15-3 16-7 18-0 21-S 23-7 28-1 31-4 34-5 37 0 1,002 I 24,857 652 44,413 353 53,11.5 211 | 52,854 222 ' 77,94.5 263 118,2U3 227 | 124,213 218 141,690 234 175,407 454 406,584 498 546,623 724 978,312 813 1,409,-526 349 773,385 17-5 473,975 14L | 492,898 6-2 9 0 139 18-0 196 196 22-0 211 20-0 23-0 24 0 28-4 33 8 55-8 760 120-3 Totals, 10,011 2,822,225 74,851 6,536 5,894,060 16.5,607 Thus, the Board of Trade have the control of the mercantile marine,. including both passenger and emigrant services, and, by virtue of the Merchant Shipping Act, 1894, are able to require that certain provisions as to cubic space, hghting, and ventilation shall be made on all British vessels. Under other portions of the same Act, the food to be supplied to seamen may be inspected by medical inspectors appointed for that purpose by the Board. The Commissioners of Her Majesty's Customs apply such of the clauses of the Quarantine Act, 1825, as now remain in force; while the Local Government Board make Regulations dealing with cholera and other infectious diseases by authority of section 130 of the Public Health Act, 1875, and by the Pubhc Health (Ships, &c.) Act of 1885 can apply sections 120, 121, 124,125, 126, 128, 131, 132 and 133 of the Act of 1875 to ships. These sections are, by Local Government Board Orders made in pursuance of section 287 of the same Act, enforced by Port Sanitary Authorities (see also page 912, et seq.). The personnel of the Royal Navy is controlled in all matters bearing on the province of naval hygiene by the Queen's Regulations and Admiralty Instructions. The Seaman or Sailor.—If we accept the definition given in section 742 of the Merchant Shipping Act, 1894, the term seaman or sailor includes every person (except masters, pilots, and apprentices duly indentured and registered) employed or engaged in any capacity on board any ship; and further, if we take into consideration their numbers, and the peculiar nature and importance of their calling, the personal hygiene of these men is of ex- ceptional importance to the country. The careful attention paid to hygiene in the Royal Xavy testifies to the appreciation of this fact now shoAvn by those officially responsible for the efficiency of that service. The same can hardly be said of the mercantile marine; the seamen of that service are a somewhat variable body, especially in respect of their antecedents. " The sea is too often the last resort of the idle, the careless, and the ne'er- do-Avell." Why this should be, is difficult to say; but it is probably the THE VESSEL OR SHIP. 981 effect of a variety of causes, more particularly official and national apathy, want of organisation among owners, and general economic causes. The seaman should have a good physique, though height, apart from good development, is of no advantage. Excepting it be a somewhat faulty exami- nation of masters and mates as to ability to distinguish colours, there are no physical tests of fitness for service demanded by the Board of Trade in respect of those desirous of entering the mercantile marine. It is other- wise in the navy, where every man or boy desirous of joining is submitted to a rigid physical examination by one or more medical officers. Xone but promising lads are accepted for the training ships, while persons of whatever ■class or age, found to be labouring under any of the under-mentioned physical defects or deformities, are, by Article 1154 of the Admiralty Instructions, considered unfit for Her Majesty's Navy:— {a) A Aveak constitution, imperfect development, or malformation or physical weak- ness, either hereditary or acquired. (b) Skin disease, temporary or trivial; marks of cupping, leeching, blistering, or of issues. (c) Malformations of the head, deformity from fracture, impaired intellect, epilepsy, paralysis or impediment of speech. (d) Blindness or defective vision; imperfect perception of colours or any chronic ■disease of the eyes or eyelids. (e) Impaired hearing, or any discharge from or disease of either ear. (/) Disease of nasal bones or cartilage, and nasal polypus. (g) Disease of throat, palate, tonsils or mouth ; cicatrices of neck, whether from scrofula or suicidal wounds ; unsound teeth, or seven teeth deficient or defective. (h) Functional or organic disease of the heart or blood-vessels. Deformity of chest, phthisis, bronchitis, haemoptysis, asthma, dyspnoaa, chronic cough, or any evidence of lung disease or tendency thereto. (i) Undue swelling or distension of abdomen ; disease of liver, spleen, or kidneys; hernia or tendency thereto, incontinence of urine, syphilis or gonorrhoea. (/) l\Ton-descent of either or both testicles, hydrocele, varicocele, or any other disease or malformation of the genital organs. (k) Fistula of anus, haemorrhoids, or any disease of stomach and boAvels. (I) Paralysis, weakness, or impaired motion or deformity of either extremity, includ- ing varicosity of veins and distortion or malformation of hands, feet, fingers, or toes. (m) Distortion of the spine, of the bones, chest, or pelvis, no matter whether from injury or disease, or from constitutional defect. Artificers, over 18 years of age, when first entered, are not to be less than 5 ft. 4 in. in height, with a chest measurement of at least 32 inches. For stokers the same standard of height is required, with the following chest measurements :—Between 18 and 19, not less than 32 inches; between 19 and 20, not less than 33 inches; over 20, not less than 34 inches (Article 348). The Vessel or Ship.—Section 742 of the Merchant Shipping Act, 1894, ■defines the term "vessel" as including any ship or boat, or any other description of vessel used in navigation. Similarly, " ship " includes every description of vessel used in navigation not propelled by oars. Boyd, quoted by Armstrong, says that " the criterion as to whether a vessel falls under the category of ship, is whether the vessel be one whose real habitual business is to go to sea; if so, though propelled by oars as well as saUs, it is a ship within the meaning of the Act. If she does not go to sea at all she is not a ship in this sense." The simplest classification of ships is into (a) men-of-war, (b) merchant ships. These classes can be further divided into groups according as to Avhether they are either wooden or iron ships, or whether they are steam- ships or sailing-ships. Men-of-war, in the present day, are practically all iron ships and also steamships; they comprise battleships of the first, second and third class; 982 MARINE HYGIENE. first, second and third class cruisers; sloops; gunboats; torpedo-boats; torpedo-boat destroyers; troopships; storeships; and stationary harbour ships. Merchant ships are naturally divided into steamers and sailing-ships. Steamers may be further classified into passenger ships, trading or cargo ships, trawlers or fishing vessels, whaleships, cattleships, and colliers. The majority of these are built of iron and propelled by steam. Sailing-ships, in the present day, are practically limited to the conveying of cargoes only, or to the carrying out of special industries, such as fishing, sealing, or whaling. Any precise classification of sailing-ships is founded primarily upon their rig. For example, we have full-rigged ships, brigs, brigantines, barques, barquentines, schooners, topsad schooners, cutters, yawls, barges, luggers, ketches and other small vessels. A fuU-rigged ship has three masts, each fitted with topmast, topgallant- mast and royal mast, all being square-rigged. A barque is a three-masted vessel, the two foremost being square-rigged as above, the hindmost, or mizzen, having only topmast Avith gaff sail. The barquentine resembles the barque in having three masts, but only one of them (the foremast) is square-rigged. A brig is a square-rigged two-masted vessel. The brigantine has also two masts, but only one, the foremast, is square- rigged, the other or aftermast carrying a mainsail or boomsail, with top- mast and gaff topsail. A schooner may be either three or two masted; the lower masts being long Avith short topmasts and no yards, and carrying mainsails and gaff topsails only. The topsail schooner is a two-masted vessel with long loAver masts, the foremast having a loose square foresail, the aftermast having mainsail and topmast, &c, as in a brigantine. Some topsail schooners have three masts ; in them the foremast is the same as in the foregoing, the two aftermasts having mainsails and gaff topsails. A cutter is one-masted with running bowsprit, carrying jib, foresail and boom-mainsail. Sailing and steam ships may also be classified according to their build or arrangement of decks. Thus we may speak of one, two, or three decked vessels; or, if lightly built, of spar-decked ships. Other terms in common use are flush-decked, well-decked, hurricane-decked, shade-decked, awning- decked or shelter-decked; all these expressions have reference to the character of the decks and the structures upon them. While the rig of a ship has practically no relation, beyond that of general size, to its general hygienic character, it is far otherwise with the build or construction. Ventilation becomes more and more complex in proportion to the number of compartments into which the ship is divided either verticaUy or horizontally, transversely or longitudinally. These conditions vary considerably according to the material of which the vessel is constructed. Ships are built either wholly of wood or metal, such as iron or steel; or they are composite, that is, composed partly of wood and partly of metal. The principal facts connected Avith. the construction of both wooden and iron ships demand some detailed reference. Construction of Wooden Ships.—The frame or skeleton of a wooden ship consists principally of the following parts:—keel, keelson, stem, stern- post, timbers, planking, beams and stanchions. The keel may be regarded as the back-bone of a ship and runs the entire length of the bottom of the vessel. It is usually, in Avooden ships, made of CONSTRUCTION OF SHIPS. 983 elm, square in section, and consisting of a number of segments connected together by a joint or splice. The keel in front terminates in the stem, with which it forms an angle of from 80 to 100 degrees; behind it joins the sternpost, to Avhich is attached the rudder. To the keel at regular intervals, and curving outwards like the ribs of an animal, are fixed the timbers ; those Upper Deck, '///>_± -^ 'V^^5i^^j^///fe-^fega^l\^y/^/A, . U~>T~^;g|a f] C"W Main Deck Kl« _________________ DP__________________vv_^ Lower Deck. man W/immwvw/^^^^^^ Hold Fig. 135.—F.K., False keel; K.S., Keelson; B., Bilge; L.B., Limber board; L.S., Limber strake ; S.Ks., Sister keelson; B.S., Binding strakes; D.T., Diagonal trusses; G.S., Garboard strake; B.P., Bottom planking; S., Shelf-piece; W., "Waterway; D.P., Deck planking and diminishing plank externally; K., Iron knee ; B., Beam ; R,., Rough tree rail; H.B., Hammock berthing; C, Channel ; S.S., Sheer strakes ; C.W., Channel wales ; M.W., Main wales. in the front or bow of the ship are called " cant timbers," those aft of the cant timbers are the frames. To the timbers are attached the inner and outer plankings; these generally run horizontally the entire length of the ship. These inner and outer plankings constitute the "skins" or walls of the ship. BetAveen the skins in the intervals of the frames is a space in the 984 MARINE HYGIENE. Avails, closed at the top by a covering board and extending downward to the bottom of the vessel, where it ends in the limber or bilge, a longitudinal channel parallel to, and one on each side of, the keelson—a kind of inner or upper keel. In order to strengthen the Avails, the "skin spaces" are often occupied by " fiUings " of seasoned wood, first introduced by Seppings and often caUed after his name. The outside planking of a ship's wall is known by certain technical names, varying with different parts of the vessel. Thus, the term " garboard strake " is applied to those planks next to the keel; the planks from the garboard strake to the bulging portion of the ship's side are called the "bottom planking" ; the name "main Avales " is given to the planks at the water line; those near the main deck are called the "channel wales," while those on the bulwarks are spoken of as the " sheer strake." These technical terms and parts of a ship's structure Avill be readily understood by a reference to fig. 135, which gives a midship section of an ordinary wooden ship. In addition to the foregoing special structures, the framework of a wooden ship is made up of beams or substantial pieces of timber running horizontally across the vessel from timber to timber. These are secured to the timbers above and below by structures known respectively as waterway-pieces and shelf-pieces, and which run from end to end of the ship, forming a kind of internal horizontal strengthening band. The waterway-pieces are similar in structure to the shelf-pieces, and are so called because their upper and inner surfaces are so shaped as to form gutters to receive the drainage of the decks. The decks practically consist of planking laid across the beams in a fore-and-aft direction. In the middle line of the ship the beams rest upon stanchions or pillars, the lower deck stanchions springing from the keelson, while the upper ones rise from deck to deck. Construction of Iron or Steel Ships.—These vessels have more or less the same essential structures as wooden ships, but all are made of metal. In general principles the construction of an iron ship is the same as that of a wooden one, but there is this essential difference, that in iron ships the keel and ribs are not such prominent structures as in wooden vessels, and that the strength of the whole ship depends as much upon the quahty of the metal and upon the rigidity with which the various parts of the framework or shell are secured together as upon the strength of such individual parts as keel, ribs, beams, &c. Perhaps the most conspicuous feature of iron and steel ships is the sub- division of their hulls into a number of watertight compartments and the provision of cellular double bottoms or water-ballast tanks. These arrange- ments are obviously great safeguards against accident, and are met with in aU modern men-of-war as well as in the better class of mail and passenger steamships. In purely cargo vessels, watertight bulkheads are not very generally provided, as they interfere with the loading and unloading and the storage of bulky articles; the greater number of such vessels, however, have double-bottom compartments, which serve not only as a safeguard against flooding in the event of the shell being penetrated, but also as water-ballast tanks when the vessel is empty or loaded with a light cargo. Interior Economy of Ships.—With regard to the comparative salubrity of the different kinds of ship, there is much to be said both for and against sailing and steam ships or in respect of wooden and iron or steel vessels. Sailing-ships appear to be more liable than other vessels to accidents by loss of men overboard and the general dangers of the sea. On the other hand, INTERIOR ECONOMY OF SHIPS. 985 accidents connected Avith machinery, scalding, &c, and the sickness resulting from continuous Avork in high temperatures, are characteristic of steamships. From a mere health point of view, the substitution of iron or steel for wood in the construction of ships has rendered easier the cleansing and dis- infection of vessels, but has made it more difficult to maintain a suitable temperature, in cold weather and to prevent excessive heat in the tropics; to these disabilities of metal ships must be added the disagreeable effects of condensation on metal surfaces from moisture-laden air between decks. When compared with vessels of the merchant service, men-of-war have both advantages and disadvantages. Though the crews of men-of-war are, in most respects, exceedingly well cared for, the proportionately large numbers of men on board and the general construction of the ships imply crowding and defective ventilation. Of late years, in the mercantile marine, the tendency has been in the direction of undermanning, Avith of course an attendant increase of cubic space per head. The forecastles of these ships are, as a rule, more easily and possibly better ventilated than the crew's quarters in a battleship. Passenger and. emigrant ships are quite a class of their OAvn, and vary largely from the magnificent liners, with full accommoda- tion and every luxury, to the dark, dirty, overcrowded emigrant ships characterised often by discomfort and cheerlessness. Of this latter kind of vessel the most objectionable are the few carrying both emigrants and cattle. The same difficulties met with in these ships occur sometimes in naval transports carrying cavalry. From a sanitary point of view, the most important features of the interior economy of ships which demand special reference are the bilge, the fore and after peaks, the stokeholds, the lavatories, the closets, the forecastle, deck- house, cabins and general accommodation for crews and passengers, the ventilation and the heating. The Bilge.—In marine language this term has a double meaning. By a shipbuilder it is applied to the curved part of the outside and bottom of the vessel, below the waterline, which bulges. By a sailor it is applied to that cavity or cavities in which offensive liquid, known as bilge-water, collects. In this latter sense only is it used in this article, and constitutes, therefore, that part of a ship to Avhich all internal drainage gravitates. From what has been detailed already regarding the construction of ships, it is apparent that, in wooden vessels and such iron ones as have a keelson, the bilge is a double channel. In men-of-war and other iron vessels without a keelson the bilge is merely that portion of the upper surface of the inner skin about the median line on which drain fluid naturally collects. Closely connected with the bilge is the main drain; this is a large pipe running nearly the whole length of the ship and may be placed either above or beneath the inner bottom of the vessel. This pipe receives the drainage from the bilge, and is further connected with the bilge-pumps, and also receives any water which may have gained access to the bunkers. Fore and After Peaks.—These are spaces right forward and right aft; and next to the bilges, perhaps, the most insanitary parts of a ship. These places are separated from the hold, &c, by bulkheads; but are frequently in a most foul condition, and in the case of the fore-peak in small ships materi- alty affect the air of the lower forecastles, where the crew are housed, and through Avhich alone entry is gained to it. The hatch rarely fits tightly, in spite of the Board of Trade's regulation, which requires it to be fastened ■doAvn on to a ring of rubber or other elastic material, hence any effluvium passes readily into the creAv space. Where there is sufficient beam for the 986 MARINE HYGIENE. purpose, the forecastles should be separated by a passage-Avay leading to the fore-peak hatch, and any spare space so left utilised as a store for oilskins or other Avet clothing, which it is ob\dously desirable to keep out of the fore- castle. Where the beam of the vessel will not admit of this arrangement, the hatch might be placed in the middle line and a corresponding hatch placed in the top-gallant deck; these tAvo hatches being connected by means of a wooden casing. Stokeholds.—In steamships the engine-room and boilers are usually placed amidships, extending downAvards to the floor, and separated from the hold between decks by bulkheads, thus preventing the free circulation of air from end to end of the vessel below deck. From a health point of vieAV, important parts of such ships are the stokeholds. These places are situated at the bottom of the ship, deeply below water, and from them the furnaces are coaled. In the smaller vessels there is only one stokehold, but large ships have two or more. In these parts of the ship the heat may be and is often excessive. For economy of space, the stokehold is rarely made Avider than is absolutely necessary, often not more than from 8 to 10 feet; the stokers, therefore, have to Avork in a sort of deep well, exposed to great heat from the furnaces, and from which they are unable to withdraw whdst on duty. The air at the bottom of the stokeholds tends to become very foul, Avhile the temperature not unfrequently recorded is from 115° F. to 140° F. In a properly ventilated stokehold this should not be the case; in fact, if sufficient air be supplied for the combustion of the furnaces there will be a constant and rapid current, and the atmosphere be actually purer than in other parts of the ship. Engine-rooms and stokeholds should be supplied with fresh air by means of large ventilators carried from above deck and fitted with cowls turned to the wind. In other cases, windsails may be found of advantage. In the Royal Navy, where everything is of necessity protected, and where forced draught is the exception, the question of the ventilation of the engine- rooms and stokeholds becomes a very difficult matter. In the majority of vessels of this kind fresh air is of necessity supplied by special apparatus, such as fan-blasts, &c. As may be readily imagined, firemen as a class are unhealthy, the effect of the stokehold on its occupants being detrimental to a high degree. Lavatories.—In every ship proper provision should be made to enable men to keep themselves clean. There is no need for any elaborate arrange- ment, but there are few vessels where space cannot be spared for a reason- able lavatory and bath-room, while there is abundant evidence to show that seamen greatly appreciate and make good use of such accommodation. As a general principle, everything provided for the use of seamen should be of the simplest and strongest description possible. A comparatively small space will provide all that is required; Avater can be supplied by means of a tap, and in steamers there should be no difficulty in arranging for a hot supply. A few basins can be readily fixed, with galvanised iron buckets provided for the washing of clothes. A galvanised iron bath of sufficient size and depth should be provided also. It is not necessary that this should be of sufficient length for a man to he down, as thorough cleansing can be carried out in a squatting position provided the bath be deep enough for the purpose. The floor of such a lavatory should be covered with sheet lead, carried up the side for a short distance, and efficient means of drainage provided. While this question of provision for the personal cleanliness of seamen and others in the mercantile marine is not specifically laid doAvn either in LAVATORIES AND CLOSETS. 987 Regulations of the Board of Trade or by schedule in the Merchant Shipping Act, it is otherwise as regards the Royal Navy. In that service there is a daily issue of fresh water every morning for personal cleanliness; moreover, by Article 531 of the Admiralty Instructions, the captain of every ship is directed to take care that all officers and men have ample opportunities to avail themselves of the special fittings provided in the ship for personal Avashing, and that bath-rooms when so fitted are kept supplied with both hot and cold Avater, and also kept open for the use of those who desire it every evening after quarters. All commanding officers must see that proper times are appointed for washing the person, so that it may be a part of the daily routine. Special facilities are given in the Navy to stokers and firemen for personal cleanliness, and in the larger ships special bath-rooms with an unlimited supply of fresh water are at the disposal of these men. The consumption of fresh water in the Navy for personal Avashing averages about one gallon daily per man. Article 529 of the Admiralty Instructions directs that bedding be aired once a Aveek when the weather will permit, each article being exposed separately to the air by being tied up in the rigging or upon girt lines. Twice in every year the blankets must be washed Avith soap in Avarm Avater; and once a year the bed tickings are to be washed, and the hair beaten and teazed. Hammocks are usually washed every fourteen days; the alloAvance of fresh water for the washing of clothes and bedding in the Royal Navy is about tAvo gallons weekly per man. Closets and Removal of Excreta.—On ships, closets should be of the simplest description, as any complicated apparatus is certain to go Avrong Avhen used by the ordinary seaman. They should be provided on every vessel, and in the case of steamships can be always furnished with an efficient water-flush. The floor of the closet should be impermeable, the surface being finished Avith a good fall outwards. The structure should be of sufficient size for a man to stand upright in, and should be provided with ample light. The ventilation should be free and secured by louvred panels or simple holes in the door, with a scuttle out-board. The best form of apparatus is a short hopper made of galvanised iron attached to an iron soil- pipe, the apparatus being open to the air beneath. If the seat be made to lift up, the closet may be used as a urinal, thus obviating the necessity for Avhat is always a source of trouble on ships. Passenger ships and the better class of vessels are usually provided with valve closets flushed Avith Avater from a cistern, and having a valve fitted to the loAver end of the soil-pipe so as to prevent the entrance of sea-water. In these vessels the latrines for the crew are ordinary trough closets. In many of the small cargo-boats, the pail is the only form of convenience in use. In small yachts and some fishing-boats special kinds of closet are in use, especially Avhere these conveniences must be placed below the water line and where the ordinary discharge by gravity is impossible. In these closets the flush-water ia draAvn directly from the sea by the user pulling the handle of a pump at Ins right side; the contents of the basin are discharged by a valve opened by a handle near his left hand. Any quantity of water may be used for flushing, and Avith ordinary care these closets ansAver their purpose well. The soil-pipes of all ships' water-closets should discharge at a proper distance from the deck and out of sight. Where possible, closets should be in the after part of ships, so that the soil-pipe may shoot over or through the counter near the sternpost. The closets for the crew should be near the men's quarters, but not so close as to cause any nuisance. Where a closet actually adjoins a forecastle, 988 MARINE HYGIENE. the bulkhead, if Avooden, should be doubled Avith a layer of felt betAveen the two thicknesses, and extra ventilation arranged for. The proportion of privies or closets on passenger and emigrant ships required by the Board of Trade in their Instructions as to Survey of Pas- senger Accommodation, Masters' and Crew Spaces, 1895, is at the rate of tAvo for twenty of creAv. Under the eleventh schedule of the Merchant Ship- ping Act, 1894, every passenger or emigrant ship must be provided with at least two privies, and with two additional privies on deck for every 100 passengers; and in ships carrying as many as fifty female passengers Avith at least tAvo water-closets under the poop or elsewhere on the upper deck for the exclusive use of Avomen and young children. The privies must be placed in equal numbers on each side of the ship, and need not in any case exceed twelve in number. All such privies and water-closets must be firmly con- structed and maintained in a serviceable and cleanly condition throughout the voyage, and may not be taken down until the expiration of forty-eight hours after the arrival of the ship at the final port of discharge, unless all the steerage passengers quit the ship before the expiration of that time. In ships, other than emigrant ships, AAdien lying in dock, the usual regulation is that the closets should be cleaned and kept fastened, the crew, if remain- ing on board, going on shore for accommodation. In the Royal Navy the usual form of closet for officers is that knoAvn as the " Duplex valve closet." The outlet of the pan is closed by two metal valves so arranged that while one is open the other is shut, and vice versa. The outlet of the soil-pipe is further protected by an automatically acting leather or metal valve. The escape of compressed or pent-up air in the soU-pipe is provided by means of a vent delivering outside the bulwarks. In torpedo-boats, Avhere the closet is below the water line, the special form of closets already described are provided. For seamen and the crews of Avarships ordinary trough closets or latrines are supplied at the rate of three for every hundred seamen and marines. These latrines are usually placed forAvard on one or both sides of the forecastle, and completely disconnected therefrom. Urinals are commonly put on the opposite side of the deck to the latrines. Closets for officers are placed either on the upper deck or on the fore part of the main deck. Accommodation for Crew.—In merchant ships the crew are berthed either in forecastles or deck-houses. Forecastles are of two kinds, according to situation. The upper or top-gallant forecastle is placed upon the upper deck, right forward; it has side lights or scuttles and is entered by a door- way. Lower forecastles are found only in small vessels. They are below deck, and are entered by a hatch, measuring usually 2\ feet square and sometimes covered with a scuttle. Leading from the hatch into this fore- castle is a ladder or flight of steep steps. This lower forecastle is a most unsatisfactory lodging, and one which it is scarcely possible to keep in a sanitary condition. The top-gallant forecastle is far preferable, but the ideal accommodation for seamen is undoubtedly the deck-house, now met with on the better class of British vessels, but most frequently seen on Danish and Norwegian merchantmen. Deck-houses are placed amidships, and have the sanitary advantages of light, air, accessibility, and possibilities for the greater convenience and comfort of their occupants. Even on small sailing-vessels it is found that the erec- tion of deck-houses does not materially interfere with the working of the ship. In some boats engaged in the cattle trade, the animals occupy the whole tore part of the vessel, while the crew are berthed below in the after part with the officers placed amidships in a deck-house. ACCOMMODATION FOR CREWS. 989 The legitimate contents of crew spaces are hammocks or bunks, bedding, lockers, chests, a table, stove and lamp. Unfortunately, many crew quarters too frequently contain other articles, which, to say the least, are improper. These articles embrace all the different materials and implements on board which it is possible to stow away, notably, sails, cordage, spare blocks, cans, buckets, brushes, paint, tar, oil, paraffin, wet clothes, boots, and even provi- sions. These various articles not only pollute the air, but materially occupy space, and that illegaUy. The principal defects of sailors' quarters may be summed up as insufficient height, light, ventUation, and means of heating; to these may be added effluvia from cargo or bUge-water, improper storage, and overcrowding. The Merchant Shipping Act, 1894, section 210, requires that every seaman shall have 72 cubic feet of air space and 12 square feet of floor area, and that such space shall be entirely free from stores, &c. This, the legal minimum limit, is certainly too small. Fortunately, in the larger vessels, there is a tendency rather to underman than to overcrowd; hence it is not unusual to find fewer men occupying a given crew space than could be allotted to it. On the other hand, there are a certain number of vessels on Avhich the minimum only is proAdded, and the opinion prevails that this allowance should be increased to not less than 100 cubic feet per head. If the height of the forecastle Avere 6 feet, this would allow 16 square feet per man, or a fairly reasonable allowance. It is noticeable that the Act of 1894 does not specify that a creAv space shall be of any particular height, but merely provides that every such place shall be such as to make the space " available for the proper accommodation of the men Avho are to occupy it"; it also provides for a minimum amount of cubic capacity, as well as a minimum amount of floor space per man. In iron ships, moisture frequently condenses from the air of the creAv's quarters on to the metal plates and beams overhead, rendering the apart- ment damp generally, and also dropping into the bunks and wetting the seamen's bedding. This evil can be remedied by sheathing the metal with wood, or covering it with thick varnish and dusting thereon finely granulated cork. Where wood sheathing or sweat-boards are used, this lining often serves as a resting-place for filth and vermin. The surveyors of the Board of Trade are instructed not to sanction wood lining unless fitted quite close to deck and sides. Seamen's bunks should be arranged so as to leave a clear space between them and the ship's side. This space should be wide enough for a man to pass round for cleaning and painting purposes. In no case should a crew space be certified for a greater number of seamen than there are bunks fitted for. The bunks themselves should be made of iron covered Avith a non- conducting composition. They should be not less than 6 feet long by 2 feet Avide, and arranged in two tiers only; the distance between each tier and betAveen the upper tier and the deck should be not less than 2 feet 6 inches. The bottom of the lower bunk should be at least 12 inches above the floor level, so as to permit of thorough cleansing underneath. Hammocks are pre- ferable to bunks as sleeping accommodation for seamen, on account of their being more cleanly and occupying less space. In all forecastles and crew spaces the decks or floors must be of wood, not less than 2| inches thick, properly laid and caulked. Planks laid on quartering over an iron deck, or loose boards on an iron deck, are inadmis- sible. The floor or deck should slope to a well-constructed water-way, Avhich should be efficiently drained by trapped scuppers so placed that they can be readily seen and cleaned. 990 MARINE HYGIENE. In the Royal Navy the crews of battleships and first class cruisers are commonly berthed between decks; but in some of the smaller cruisers there is accommodation in the top-gallant forecastle. As in the merchant vessels, these forecastles are apt to be damp and unhealthy, OAving to water gain- ing access through the hawse pipes when the ship is under way. There appears to be no exact scale of berthing accommodation for seamen and marines laid down by the Admiralty. The number berthed in any given space is mainly determined by the so-called hammock space; the usual interval between the hammock hooks as seen projecting doAvnwards from the beams or girders being 18 inches. The cubic space actually avail- able in the crew spaces varies in different classes of ship and often in different parts of the same ship; it may be roughly stated to vary from 100 to 200 cubic feet per man. In the naval transports or troopships, the ship's company are berthed separately in the forecastle, while the troops are placed in the main deck and in the fore part of the loAver deck. In these ships the actual cubic space available for both sailors and soldiers is little in excess of 80 cubic feet per man. Accommodation for Passengers.—As regards accommodation for passen- gers and emigrants there are special provisions in the Board of Trade's Regulations and in the tenth and eleventh schedules of the Merchant Shipping Act, 1894, which direct " that the height between decks must not be less than 6 feet, that there must not be more than two tiers of berths on any one deck, and that the height betAveen the tiers and betAveen the upper tier and the deck overhead must not be less than 2\ feet. In respect of floor area, it is laid down that on the upper passenger deck there must be at least 15 square feet, and on the loAver passenger deck 18 square feet for each adult; but if the height betAveen decks on the lower passenger deck be less than 7 feet, and if the apertures (exclusive of side scuttles) through which light and air are admitted together are less in size than in the proportion of 3 square feet to every 100 superficial feet of that deck, then the floor area of each adult must be at least 25 square feet." per square inch, and the discharge of a cubic foot of this compressed ah is said to induce the discharge of 25 cubic feet of ordinary air. This system can be used for either propulsion or extraction. 7. Perkin's automatic ventilator is an exhaust arrangement which in various forms has been tried with indifferent success in the Navy, and VENTILATION OF SHIPS. 995 depends for its action upon the rolling or pitching motions of the ship. It consists of two cylindrical tanks placed one on either side of the deck, and connected below by a horizontal tube. From the upper part of each vessel pass two tubes; one leads upwards to the outer air, the other downwards to the space to be ventilated. Each of these tubes is fitted with valves. Each cylinder is filled half full with water. As the ship rolls, water gravitates from one tank to the other, and by so doing sucks foul air into one vessel and expels it from the other. It is practically an automatic air-pump, but only capable of action when the ship is rolling or pitching. It is placed diagonally in the ship, but owing to the small volume of air operated upon does not give results commensurate with the space which the apparatus occupies. The same principle has been adopted in the ventUating pumps of Thiers of New Orleans and of Roddy of New York; neither of these arrangements have been altogether satisfactory. 8. Rotary fans of various kinds. The general principle and power of these appliances has already been considered at page 211. Their use is very general in the Royal Navy, especially in the form of centrifugal fans varying from 3 to 6 feet in diameter. Blackman's fans, which are not centrifugal, are not much used in H.M. ships, except for moving air in comparatively small spaces, such as cabins. The following hst shows the relative number of supply and exhaust fans fitted in some of H.M. ships; it clearly shows that, while the principle of extraction is not altogether ignored in the Navy, the preference is given to supply methods of ventilation. Exhaust Fans. Supply Fans. Name of Ship. Number. Diameter. Numher. Diameter. Devastation, .... 4 4'6" 4 5'6" Thunderer, .... 4 4'6" 4 5'6" ' Trafalgar,..... 3 two / 6' 0" one \ 4' 0" 4 4'0V ; Nile,...... 3 4'6" 4 4'6" Imperieuse, .... 2 3'6" 4 4'6" Edinburgh, .... 2 3'0" 6 4' 1" Colossus, ..... 2 3'0" 6 4'6" Inflexible, ..... 1 3'3" 8 4'0" Vulcan, ..... 2 4'0" 2 4'0" Polyphemus, .... 1 3'6" 2 one/ 4' 0" „ \3'0" Howe,..... 1 3'0" 5 4'0" Anson...... 1 3'0" 4 4'0" Camperdown, .... 1 3'0" 4 4'0" Royal Sovereign, 12 six \ 6' 0" „ |5'6" Royal Arthur, .... 5 four \ 5' 0" one \ 3' 0" Dreadnought, .... 6 4'0" Neptune,..... 4 4'0" Collingwood, .... 4 4'0" Severn, ..... 2 4'0" Galatea,..... 2 3'0" Barossa,..... 2 3'0" Barham,..... 2 3'0" Bellona...... 2 3' 0" Calliope,..... 1 3'0" 996 MARINE HYGIENE. Heating and Lighting.—Apart from considerations of climate, the temperature or Avarmth of a ship depends upon the material of Avhich she is constructed, Avhether she is propelled by steam or not, and upon the condition and nature of her cargo. Sailing-ships are as a rule colder than steamers; this is mainly due to the large amount of coal used on these latter vessels. This extra heat is naturally greatest near the furnaces, and not unfrequently is conveyed to distant parts of the vessel by steam-pipes, from which, if not suitably covered by some non-conducting material, an enormous waste of heat takes place. AUusion has previously been made to the excessive temperatures which often prevail in engine-rooms and stokeholds. In many cases this condition, arises from insufficient ventilation, and, unless suitable provision for the admission of fresh air to the stokeholds is made, the fires will not burn properly. If adequately ventUated, in tropical climates, the stokeholds of large vessels are often the coolest part of a ship. The holds of ships, especially sailing-ships, are frequently warmer than other parts. This is partly due to its depth from the external air, but more commonly depends on heating of the cargo. Certain cargoes, such as coal, grain, lime, sugar and many others, are apt to undergo various chemical changes attended with the evolution of much heat; this is particularly the case if the cargoes- be stowed Avhen damp, or if the holds in which they are placed be insuf- ficiently ventilated. In steamships, a common source of increased tempera- ture in the holds is the blowing out of hot water from the boilers into the bilges. Iron ships are peculiarly liable to extremes of temperature, owing to the readiness Avith Avliich the metal conducts heat. As regarding the efficient heating of crew spaces on ships, there appears to be no official ruhng. The various parts of ships are usually warmed artificially by fireplaces, stoves, or by steam-pipes or radiators. In the fore- castles of merchant vessels there is usually a " bogey " or small square stove, constructed of thin cast-iron with a movable cover. It has many disadvan- tages : it requires constant attention, when heated allows the products of combustion to pass freely through its substance, readily cracks, is dangerous as a constant source of accident, is dirty, and from its shape clumsy and; inconvenient. One of the rarest sights on board ships is a bogey stove in perfect condition. Much improvement might be made in crew spaces were a more rational stove made compulsory in these parts of ships. Probably the best and most economical stove would be a well-constructed circular wrought-iron slow-combustion one, lined with fire-clay. The flue should be of iron, connected to the stove by means of a curved pipe. The funnel should pass through the deck by a properly constructed flange and terminate in a cowl. When not in regular use, the stove might be dis- connected and the cowl remain as a ventilator. Or the funnel of the stove might be made to pass up through the centre of an ordinary ventilator aUowing the smoke to escape at a higher level; the general effect of this arrangement would be to heat the ah in the ventilator and so cause a considerably increased discharge by the outlet shaft. While the lighting of the cabins of ships' officers and saloon passengers may be said to be fairly good, the reverse is too often the case in respect of emigrants and seamen. These deficiencies are commonly more apparent to occupants during the day than at night, as during this latter period Ulumination is effected by means of oil, candles, or electricity. The foUowing are the official instructions to surveyors of the Board of Trade upon this important point. "Every space appropriated to crew CLEANSING AND DISINFECTION OF SHIPS. 997 space should be properly lighted. To ensure that such will be the case under the ordinary conditions of a vessel's employment, it will generally be necessary to have so much provision for light when the ship is new and the paint clean, that if one-third of it be closed it will be possible to read the print of an ordinary newspaper in any part of the space." Although the necessity at times of supplying light to forecastles by means of glass prisms or bull's-eyes in the deck is recognised, the Board of Trade discourage their use, except in cases where it is impracticable to obtain the requisite amount of light by other means, or in small vessels where side scuttles would be too near the water. The maximum diameter for side scuttles is fixed at 10 inches, as a larger size may weaken the structural strength of the side plating of a vessel. Cleansing and Disinfection of Ships.—The unclean condition of ships, more particularly small ships, cattle-boats and fishing-vessels, is very common, not only in parts which are out of sight, but on their decks, forecastles, cabins, and holds. In the Royal Navy and on the better vessels of the mercantile marine, daily inspections are made by the ship's officers of the various parts in order to ensure their being kept thoroughly clean, and this routine needs to be strictly carried out. Merchant ships, as a rule, are not kept so clean as warships, which, in the Royal Navy, by Article 529 of the Queen's Regulations, it is the duty of the captain to strictly super-vise and also to cause the holds to be whiteAvashed every six months or oftener if necessary. In the Royal Navy the decks are cleaned by holy-stoning (wet or dry), and in the berthing parts by scraping and scrubbing with hot water, wetting only small portions at a time and drying thoroughly. The two former methods are open to objection in the inhabited parts of the ship, one from filling the air with dust, the other from loading it with vapour. The commonest fault committed in cleansing ships is to employ water too frequently and in unnecessarily large quantities. Thorough scrubbing and cleansing can be effectively carried out without the use of large quantities of water, which very often, by accumulation charged with organic matter in out of the way corners, are productive of more trouble than the original dirt. There is much reason to believe that the unhealthiness of many ships in tropical parts is due to this cause; the more ships wash their decks in these places, the more sickly they are; the organic matter in suspense in the Avater is left upon the decks as they dry, with disastrous results. Great care should be taken to see that all superfluous water is removed, and that the forecastle is dried as quickly as possible; in wet or damp weather dry scrubbing should always be resorted to. It cannot be too clearly understood that "a damp ship is an unhealthy ship." Flushing with water or wet scrubbing should not be carried on when there is less than three degrees difference between the readings of the dry and wet bulb thermometers placed under a screen in the open air. It should also be a rule that, when- ever the weather will permit, all bedding should be removed from the forecastle or crew berth spaces and exposed to the sun and wind for a certain time every day. As regards the details necessary for the proper drainage and cleansing of merchant ships, their provision and supervision rests with the surveyor of the Board of Trade. His instructions upon this matter practically amount to this:—That he will see that there are holes, sufficient in number and size, through the cant or coaming of upper forecastles and deck-houses, to admit of a ready escape of water, and that there are plugs, with lanyards or chains attached, fitted to each hole. Where such drainage passes through a 998 MARINE HYGIENE. privy or other compartment, it is necessary to have a pipe for the drainage to pass through such privy or compartment, with the pipe made perfectly tight through the cant or coaming. The most difficult parts of a ship to keep sweet or fairly clean are the bUges; that this is the case is readily understood from the nature of the material and refuse which they constantly receive. Bilges should not be flushed out with sea-water, neither should reliance be placed upon the use of deodorants or antiseptics; the only efficient means of keeping the bilges sweet is to pump them dry periodically and completely remove overboard the bilge-water itself. After being pumped dry, they may be flushed with fresh sea-water or with water mixed with a disinfectant or antiseptic. The question of the disinfection of ships need not be reconsidered in this place, as it has already been discussed on page 695. Water-supply of Ships.—Except in small sailing-vessels, the question of supply is no longer a difficult one, inasmuch as condensation and subsequent aeration can always be resorted to; hoAA'ever, difficulties often exist in regard to source and storage. In ports, ships are usually furnished with water by " water-boats " fitted with tanks, from which the supply is pumped to the vessel requiring it; or direct from companies' mains. The former method has grave objec- tions, owing often to the water-boats being dirty or having leaking decks, also owing to the difficulty, in cases of enteric fever, &c, of ascertaining the source from which the water-boat derived its supply. Where water- boats are the means of supply, a responsible ship's officer (the surgeon, if one is carried) should always inspect the barge and examine the water before allowing it to be delivered on board, and should further insist upon the hose being washed by the first pumpings before the end is put into the ship's tank. Under no circumstances should water be taken from a wooden water-barge. In the Royal Navy the rule is that no water is to be taken or used on board ship until it has been examined and passed by the surgeon. In foreign ports the water is often of doubtful and in some cases of absolutely harmful quahty. In many such ports in place of methods of supply, as above detailed, recourse has to be made to fetching the water from shore, either in casks and barrels, or by clearing the ship's boats of all removable gear and then filling them with water ; finally towing them back to the vessel, where the water is pumped on board. Sometimes this latter method is improved upon by fitting each boat with a collapsible canvas bag. These methods are obviously objectionable, since the water may be and often is fouled by leakage of sea-water through the boat's sides, or by Avashing in over the gunwale. As an alternative to the foregoing sources of water-supply, all large steamships and vessels of the Royal Na-vy rely upon the distillation of water from sea-water. There are a large number of distilling apparatus which have been approved by the Board of Trade; those of the first class will distil as much as 800 gallons in ten hours. Well-knoAvn kinds are those of Normandy, Kircaldy, and Caird & Rayner, all of which are employed in various ships of the naval service and mercantile marine. The Board of Trade's regulations as to the survey of steamships carrying passengers state that the distilling apparatus should, with certain exceptions, be taken to pieces every voyage and tested. "The water should be cold, pure, and fit to drink immediately after it is drawn off from the filter. No distiUing apparatus should be passed unless fitted with a suitable sized filter, charged with animal charcoal." The storage of water on ships is a difficult and unsatisfactory matter. In ^VATER-SUPPLY OF SHIPS. 999 small vessels, casks are still in common use; they should be abolished altogether except in cases of emergency. The alternate wetting and drying rapidly sets up decomposition of the wood, and this being favoured by want of ventilation pollutes the water, rendering it unfit for dietetic purposes. If wooden casks are used, they should be properly charred inside, and not capable of containing more than 300 gallons; the staves should not be made of fir, pine, or soft Avood. In large ships water is stored in galvanised iron tanks, holding often 600 gallons or more each. These, painted outside and cement washed within, form the most economical, and at the same time fairly sanitary receptacles. They need to be furnished with large manholes for the purpose of cleansing, which should be carried out as a matter of routine after every voyage. If possible, the manhole should be placed in such a position that natural light finds its way into every part of the tank when the cover is removed. Unfortunately, too often these water tanks are placed in most awkward and inaccessible parts of the ship, with the result that their supervision and cleansing are frequently neglected. On ordinary merchant ships the supply carried must be equal to a daily allowance of 3 quarts per statute adult, exclusive of the quantity necessary for cooking, which latter must be shipped at the rate of at least 10 gaUons for every day of the prescribed length of the voyage for every 100 statute adults on board (section 295, Merchant Shipping Act, 1894, read in con- junction with the twelfth schedule of same Act). Passenger ships provided with proper distilling apparatus, however, are required to store only half the above amount of water. In the Royal Navy, the Queen's Regulations and Admiralty Instructions, Appendix XXL, state that for troops or third-class passengers water " is to be issued on the most liberal scale possible; and the minimum daily allow- ance of water is to be for each individual embarked, 6 pints when out of the tropics, and 1 gallon when within the tropics, which quantities are to suffice for all purposes." For the crews and complement of Avarships there is no definite enactment in the Admiralty Instructions as to the amount of water to be issued daily. General precautions are taken to prevent waste, but practically the saUor receives an unlimited supply. The daily average consumption of water on ships of the Royal Navy is 4 gallons per man, and of this some 2 \ gallons are used for personal and clothes washing. For the purification of water in the mercantile marine, various filters charged with animal charcoal are in use. For the same purpose, in the Navy, Morris' filter containing manganous carbon, Crease's filter charged with carbalite, and a special form of filter charged also with carbalite, and usuaUy fitted in the bottom of a water tank, appear to be chiefly employed. The general conditions and principles of water purification on board ship do not differ from those explained on page 45, et seq.; it is probably merely a question of time and the dissemination of a better knowledge con- cerning the fallacies and dangers attaching to the use of imperfect filters, for the use of those of the Pasteur-Chamberland type to be officiaUy required not only on vessels of the Royal Navy but in the greater number of those belonging to the mercantile marine. Food on Shipboard.—The true economy and importance of providing the saUor with good and adequate food is sufficiently self-evident to need no special arguments in this place. Yet notAvithstanding a practically unani- mous opinion on this point, it is astonishing how little attention is really given to the feeding of seamen by those who employ them. For the merchant service there is no official dietary scale; what food a seaman shall receive in any given ship or for any given voyage is entirely a 1000 MARINE HYGIENE. matter of contract between the master and the man and the Board of Trade merely see that the scale is inserted in the articles of agreement. The Merchant Shipping Act simply requires that a diet scale shall form part of the agreement, but in no way (except so far as lime-juice and sugar are concerned) indicates what such diet scale should be. The following tabular statement practically represents the diet scale signed for by the crew in the majority of British ships. Bread. Flour. Beef. Pork. Peas. Sugar. , Coffee. Tea. Water. Sunday, Monday, Tuesday, Wednesday, . Thursday, Friday, Saturday, lb. It>. h "i "i tb. i'i i'i i'i tt). i'i i'i i'i pts. 1 3 "i "i oz. 2 2 2 2 2 2 2 oz. 4 4 4 4 4 4 4 oz. 5 1 8 i 4 i 8 1 8 qts. 3 3 3 3 3 3 3 This dietary has a mean daily nutritive value of: proteids, 5*2 oz.; fats, 0-9 oz.; carbo-hydrates, 13*2 oz.; and salts, 3 oz. On some ships extras are alloAved; thus, very often a fresh mess, composed chiefly of soup-bouilli, is given on Sundays in addition; occasionally preserved meat is substituted once a week for salt; sometimes a certain quantity of butter is served out instead of a portion of meat, while a few owners issue marma- lade and pickles. In some coasting vessels, in which the labour is hard, the dietary is practically unlimited. In addition to the foregoing or other articles of ordinary diet, the Merchant Shipping Act, 1894, section 200, demands the issue of lime or lemon juice with sugar (the sugar to be in addition to any sugar acquired by agreement with the crew). This lime or lemon juice must be served out daily at the rate of an ounce per day to each member of the crew, so soon as they have been at sea ten days, and during the remainder of the voyage, except during such time as they are in harbour and are there supplied with fresh provisions. Before being served out, the lime or lemon juice must be mixed with a due proportion of water; further, no lime or lemon juice may be taken on board ship for issue to the crew unless it has been obtained from a bonded Avarehouse for and to be shipped as stores; moreover, it may not be so obtained or delivered unless it contain 15 per cent, of proper and palatable proof spirit, to be approved by the Board of Trade inspector, or by the proper officer of customs. Whilst fully admitting the grave difficulties in the Avay of securing satisfactory food on board ships, there appears much necessity for having the rations of coasting as well as ocean-going ships fixed by law. The chief defects apparent in the customary diet are: (1) monotony, (2) excess of salt meat, (3) deficiency of vegetable food, and (4) improper proportion of the different ingredients, more particularly an excess of proteids with a deficiency of fats and carbo-hydrates. The regulations of the Board of Trade for the inspection of the previsions and water of ships are sufficiently comprehensive. They relate to notice being given to the inspector for the inspection of stores, and for supplying him Avith a list of all stores; they also provide for the inspection of all surplus stores left over after a previous voyage, and for turning out the contents of all casks of Avet provisions among such surplus stores. The SHIP DIETARIES. 1001 requisite condition of beef, pork, preserved meats and vegetables, vegetables in tins, flour and biscuits is defined. Briefly stated, " animal food is to be sweet and properly packed and pickled in pickle of full strength; vegetables are to be sound and fresh, properly preserved, and in strong and suitable tins. Flour is to be of fine grade, milled from fully-matured, good sound wheat, containing a proper proportion of nutritious matter, and packed in suitable casks or tanks. Biscuits are to be thoroughly baked and dried, and made of fully-matured wheat-flour. When stored in tanks, these are to be thoroughly cleansed, lined with fresh hme and dried before being refilled. The water left in the ship's tanks from a former voyage must all be completely emptied, and the tanks thoroughly cleansed and refiUed with good fresh water." A noticeable defect on board many merchant vessels is the want of proper places in which to store provisions; the result being that they are often exposed to unwholesome exhalations. It is not at all unusual to find on some vessels that the bread store opens into the crew's quarters, or that portions of the crew's food are kept in the forecastle. Such arrangements are obviously in violation of all sanitary teaching, and need not only official condemnation but legislative prohibition. AVeekly Allowance per Statute Adult. Scale A. Scale B. For Voyages not Exceeding 84 For Voyages Exceeding 84 Days in Sailing-Ships or 50 Days in Sailing-Ships or 50 Days in Steamers. Days in Steamers. tt) oz. tt) oz. Bread or biscuit, . 3 8 3 8 Wheaten flour, 1 0 2 0 Oatmeal, 1 8 1 0 Rice, . 1 8 0 8 Peas, . 1 8 1 8 Potatoes, 2 0 2 0 Beef, . 1 4 1 4 Pork, . 1 0 1 0 Tea, . 0 2 0 2 Sugar, . 1 0 1 0 Mustard, 0 04 0 0i Black or white pepper, g round, 0 Oi o o| Vinegar, One gill. One gill. Lime juice, . 0 6 Preserved meat, . 1 0 Suet, . ... 0 6 Raisins, ... 0 8 Butter, ... 0 4 Salt, .... 0 2 0 2 Scale of Substitutes. 1 lb preserved meat «= 1 lb flour, bread, or biscuit or 4 ft beef \ = or pork J 1 lb rice = i lb preserved potatoes = 10 oz. currants = 34 oz. cocoa or coffee = :§ lb treacle = 1 gill mixed pickles = 1 lb salt beef or pork. Ii lb oatmeal or 1 lb rice or 1 lb 1J lb oatmeal. 1 lb potatoes. 8 oz. raisins. 2 oz. tea. \ lb sugar. 1 gill vinegar. 1002 MARINE HYGIENE. In some small ships, particularly coasters, a system prevails of giving pay in lieu of food; this is bad, inasmuch as the men have neither proper storage for their provisions nor often enough money to provide themselves with sufficient food or of adequate quality. In cases where the food or water supphed on board a merchant ship is deemed to be either bad or insufficient, any three or more of the crew may complain to any officer in command of any of Her Majesty's ships, or to any British consular officer, or to a superintendent or a chief officer of customs, who, after examining the food or water and finding it defective, must signify the same in writing to the master of the ship; in case of failure to proAn.de proper provisions, &c, in place thereof, the master is liable to a penalty of twenty pounds. The provisions for the crews of passenger ships are not to be inferior to those of the passengers. The table on page 1001 illustrates the scales of dietary authorised by the Board of Trade for passengers; these scales, it will be observed, vary according to the length of the voyage. In the case of failure to supply issues of good and wholesome pro-visions in accordance with the above scales, the master is liable to a penalty of fifty pounds. In the Royal 2STavy the seaman's dietary is in accordance with the follow- ing scale as laid down in Appendix XXI. of the Queen's Regulations and Admiralty Instructions, 1893. When to be Issued. Seamen. Articles. Officers, Crew, and Supernumeraries at others, at a Seaman's two-thirds of a 1 Full Allowance. Seaman's Allowance. ) ( C Biscuit, . It. 1? * ! 2 1 ^-Daily, . . \ i ( Soft bread, lz i 3 4 Spirit, Sugar, pint. oz. i 28 i* 5 Chocolate—Ordinary, . 1 i ?!J I „ Soluble, 1-2 Tea, "i 9 ! Uveekly, . J 10 J [ Oatmeal, . 3* 2 Mustard, . Pepper, . ;; i Vinegar, . pint. k i 11 ) Daily, when/ 12 ./ procurable, \ Fresh meat, lb. I* 1 i Vegetables, i When fresh provisions c annot be secured:— 13 14 15 16 ) Every other 1 > ^y, • j f On one alter-J Salt pork, Split peas, Celery seed, Salt beef, . £ oz. to lb. 1 1 every 8 lb of split peas 1 * put Into the coppers. § 6 17 Flour, oz. 9 18 19 f nate day, . j Suet, Raisins, . f li i 20 \ j Preserved meat, It). 4 with either * 21 (1) Preserved potato, . oz. 4 2 22 (2) Bice, . 4 2 21 Jon the other alternate day," or (Preserved potato, (3) 1 and » 14 22 (Rice, 2 1 17 18 19 J or (Flour, (4) J Suet, (Raisins, 9 1 1* 6 i 1 NAVAL DIETARIES. 1003 Scale of Substitutes. In case it should be necessary to issue substitutes for any of the articles in this scale of victualling, the folloAving propor- tion is to be adopted, viz. :— Biscuit, . I pound} Flour, I pound> Rice, . 1 pound) AVine,. . . . i pint ) 4 gi" \ 1 pint ) Spirit, Porter, Coffee, 1 ounce A Cocoa, 1 ounce Chocolate, ordinary 1 ounce > ,, soluble, 1*2 ounce 1 Tea, . £ ounce J are to be considei'ed equal to each other. do. The following, when issued with meat rations, are to be considered equal to each other:— /"Split peas, | Peas (whole), . J pound. J pint. ./Flour,.....i pound. \ Calavances, .... J pint. iDholl,.....I pint. {.Rice......If- pound. (Vegetables, . i pound. 2 1 Compressed mixed vegetables, 1 ounce. (Preserved potato, ... 2 ounces. „/Oatmeal......J pint or 2 ounces. \ Split peas, .... f pound. When the men desire it, i lb of flour may be issued in lieu of i lb of biscuit; and ships proceeding to sea are to fill up on this basis. Article 1726 of the Admiralty Instructions directs that, whenever practicable, whether at home or abroad, sea-going ships are to be supplied with fresh meat and vegetables. Fresh beef is to be received in quarters, and mutton in carcasses. Salt meat is not to be issued on board H.M. ships in harbour, or when fresh meat and vegetables can be obtained, except abroad, when an issue may take place once a week (Article 1727). No person is to receive a spirit ration in kind unless he is twenty years of age (Article 1729). Those not receiving or declining the rum ration are allowed by Article 1732 either the savings price of the rum or one of the following substituted rations :— ["Tea, . . i oz. (1)-! Soluble chocolate, | ,, t Sugar, . . l| „ f2JTea, . W\ Sugar, i oz. 14 . ,„> j Soluble chocolate, % Wt Sugar, . . 2 When required by the medical officer half an ounce each of lime-juice and sugar are to be issued daily to each individual (Article 1735). Oatmeal or a ration of lime-juice and sugar is allowed to men working in the engine-rooms or stokeholds (Article 1736). Prisoners receive no spirit ration or allowance in lieu, either in kind or money. Those sentenced to cell punishment receive either low diet, con- sisting of 1 lb of biscuit daily, or full diet, consisting of half the ordinary ration, omitting meat and rum. Loav diet is hmited to the first three days of punishment, and, in the case of an award of fourteen days cells, to the last three days (Article 742). The nutritive value of the saUor's daily ration in the Eoyal Navy is, practically, proteids, 4*8 oz.; fats, 1*3 oz.; carbo-hydrates, 18 oz.; salts, 2*5 oz. As in the case of the soldier's ration, considerable and variable additions are made by the men themselves, by private purchase from the canteen, to the regulation allowance; these being entirely a matter of personal selection, are difficult to express in terms of food-principles, but their nature is such as to considerably increase the nutritive value of the daily food-supply. In the training-ships of the Eoyal Navy a special dietary is provided for the boys. It permits of more variety than that of the ordinary seaman. It is given in detail in the folloAving table :— 1004 MARINE HYGIENE. Sunday and Thursday. Monday and Friday. Tuesday and Saturday. AVednesday. Total for 7 Days. Quantity Issued Daily. Soft Bread, lb. 14 1 3 li H Hi Sugar, oz. If If If If 12i Chocolate, j> 3 S 3 S 4 s H Tea, • »> * 4 i 4 i Fresh beef, lb. 3 1 3 ,, mutton, • >> «" ... 14 Corned pork, . • > j i i i l" 24 Mixed vegetables, • >) 4 1 Potatoes, or other vegetables 1 according to season, . j " i o 3 3 H * •i ¥ Flour, .... ,, 4 1 14 Suet, fresh, oz. 1 4 3 Raisins, . • ») 2 4 Split peas, >> 4 4 Celery seed, J J ih i 7T* Mustard, >l r "j Pepper, . Vinegar, . pt. i > Every four days Salt, oz. 1 ) The nutritive value of this ration may be taken to be, proteids, 5 oz.; fats, 2*1 oz.; carbo-hydrates, 20 oz.; and salts, 2 oz. On board H.M. troopships special dietary scales are authorised by the Admiralty Instructions. These are given in detail for men, women and children respectively on pages 1005 and 1006. The mean nutritive daily value of those for adults may be taken to be, proteids, 3*5 oz.; fats, 1*5 oz.; carbo-hydrates, 13 oz.; salts, 1*5 oz. Boys of 10 years and under 14 years of age receive the woman's ration; boys of 14 years of age or upwards receive the man's ration; girls of 10 years of age or upwards receive the woman's ration. Disease, Accident, and Death at Sea.—The statistical facts at our disposal in respect of these matters are not very satisfactory. "While those having reference to the Eoyal Navy may be deemed fairly complete, those relating to the mercantile marine are far from reliable; this arises from the fact that many merchant vessels do not carry a surgeon, and that in many cases the information respecting both sickness and death is derived from unprofessional sources. In accordance with the Births and Deaths Eegistration Act, 1874, com- manding officers of ships trading to or from British ports are required, under penalty, to transmit returns of all births and deaths occurring on board their ships to the Eegistrar-General of Shipping and Seamen, who furnishes certified copies of such returns to the Eegistrars-General of England, Scotland, and Ireland. Similar returns are furnished by persons having charge of Her Majesty's ships directly to the Eegistrars-General of Births and Deaths. Mercantile Marine.—That even this service has shared in the general reduction of death-rates which so peculiarly characterises this generation, is shoAvn in the summary on page 1007 of the number and mortahty of sea- men employed in vessels registered in the United Kingdom, under the Merchant Shipping Acts. Transport or Troopship Dietaries. Scales of Rations for Her Majesty's Troopships. Troops or Third-Class Passengers. SCALE OF RATIONS per Man. Days of the AA'cck. Sunday, . Monday,. Tuesday, Wednesday, Thursday, Friday, . Saturday, 12 12 pint. S.2 a> AVith Fresh Meat an additional 4 oz. of Bread, or 3 oz. of Biscuit, is to be issued to each Man. 12 12 12 T3 O oz. oz. 2 4 2 2 2 pint. [ 4 o P< SCALE OF RATIONS per Woman. Sunday, . Monday, Tuesday, Wednesday, Thursday, Friday, . Saturday, 8 6 12 ........... ................. 8 ........... 8 * ... 1 8 6 12 ........... ................. 8 ........... 8 | ... 1 ................. 8 ■3 S So -* r- a) hj e o s ;rt ea r i 2 4 4 1 1 3 4 2 it 1 4 2 i -1 2 2 4 4 I * i. 6 A 3 5 2 2 4 4 2 4 I 1 2 2 2 J o o en Transport or Tuoorsinr Dietaries—continued. SCALE OF RATIONS per Child of 5 Years and under 10 Yea s of Age SCALE OF RATIONS per Child of 1 and under 5 "i ears of A go- Daily. Weekly. Daily. Days of the Week. "3 co o ^ y* CJ Seq u 3 1 *3 o M § P. 8 i OJ m OJ o o 3 S ° oj § x. 03 M 3 a o •3 c .W S A u OJ 13 's OJ s a O u o ■a § CO o E 3 co '3 o CO s OJ £ x. 3 CO 0J *3 CO S ■ 60 3 CO OJ £ 3 w OH co CJ « OJ x. Sunday, . OZ. 6 oz. 3 oz. 4 oz. 2 OZ. oz. 2 OZ. ih. 4 oz. oz. 3 OZ. i pint. 4 OZ. 1 ( oZ. 4 OZ. 2 pint. 2 pint. r 4 OZ. 4 lb. i Monday, . 4 4 2 2 i 4 4 2 2 ea a 4 4 4 Tuesday, . 10 2 4 2 4 i 2 4 2 2 4 4 i Wednesday, 6 3 4 2 4 1 2 i 4 \ 1 - 4 2 2 +j - 4 4 i Thursday, 4 4 2 2 i 4 4 2 2 'o 4 4 i Friday, . 10 2 4 2 i 4 4 2 2 4 4 i Saturday, 4 4 2 2 i 4 J 4 2 2 - 4 4 i Note.- -Each infant under 1 year of age to be provided with milk, corn-flour, sago or arrowroot and sugar at discretion of Medical Officer. If condensed milk be used, sufficient to make half a pint for children over five years of age, and sufficient to make 2 pints for children over one but under five years of age. In using soup and bouilli, it is reckoned that 5 J ounces may be cooked with i pint of Avater, or 10 ounces Avith \ pint. In using essence of beef half of a quarter pint canister should be cooked with half a pint of water. DISEASE, ACCIDENT, AND DEATH AT SEA. 1007 Persons Deaths Death-rate Year. Persons Deaths Death-rate Employed. Reported. per 1000. Employed. Reported. per 1000. 1873 202,239 5,393 26-6 1884 199,654 3,757 18-8 1874 203,606 4,602 22-6 1885 198,781 3,286 16-5 1875 199,667 4,076 20-4 1886 204,470 3,546 17*3 1876 198,638 4,151 20-9 1887 220,266 3,384 15*4 1877 196,562 4,181 21*3 1888 223,673 3,114 13*9 1878 195,585 3,870 19*8 1889 230,263 3,018 13*1 1879 193,548 3,692 19*0 1890 236,108 3,305 14*0 1880 192,972 4,100 21*2 1891 240,480 3,263 13*6 1881 192,903 4,464 23-1 1892 241,735 3,452 14*3 1882 195,937 4,659 23-8 1893 240,974 3,172 13*1 1883 200,727 4,451 22-2 The improvement in the rate of mortality shown in the foregoing table is mainly due to reductions of deaths on steam-vessels—that on board sailing- vessels in the year 1893 having been 18*8 per 1000, and in steamships 7*4 per 1000. No returns are issued by the Board of Trade relative to non-fatal forms of sickness among seamen. The chief source of loss of life at sea is due to wreck, drowning, or accident. The exact proportions of these losses in the mercantile marine are shown in the following table issued as Parliamentary Paper No. 430 of Session 2, 1895, and having reference to the year 1894. 1 f 1. 1 1 Masters and Seamen Em-ployed. (D Lives Lost. Percentages and Proportions. Total Number of Lives Lostin Merchant Ships Registered in the United Kingdom. Drowned. Masters and Seamen Lost by Accident other than Drown-ing. (5) Total Number Lost by Drown-ing and other Accident. (6) Lives Lost by Drowning of Persons employed. (7) Lives Lost by Drowning and other Accident of Persons employed. (8) Crew. (9) Pas-sengers (lost by Wreck only). (10) Total. Masters and Seamen Lost by Wrecks and Casualties. (2) Masters and Seamen Lost when Vessel was not Damaged. (3) Total. (4) \ Sailing, Steam, 58,537 159,257 622 444 261 300 883 744 91 141 974 885 1-51 or 1 in 66 •47 or 1 in 214 1-66 or lin 60 •56 or 1 in 180 974 885 7 *1,183 981 *2,068 Total, 217,794 1,066 561 1,627 232 1,859 ■75 or 1 in 134 ■85 or 1 in 117 1,859 *1,190 *3,049 * These figures include about 1,150 persons lost from the ss. " Kowshing," which was sunk by a Japanese man-of-war. Royal Navy.—The latest returns in connection with this force, at present available, are those for 1893; in that year, the average daily sick-rate was 41*32 per 1000; the number finally invalided out of the service was 1626, or in the ratio of 27*04 per 1000 of strength; the total number of deaths was 679, or a ratio of 11*29 per 1000; this mortality rate exhibits an increase of 5*71 per 1000 in comparison with 1892, and of 4*69 on the aver- age of the last six years. This high death-rate, however, Avas due mainly to the sinking of H.M.S. "Victoria," in which no less than 358 persons 1008 MARINE HYGIENE. were drowned. If the deaths consequent on the loss of the "Victoria " are excluded, the total number would be 317, equal to a death-rate of 5*27 per 1000, or 0*31 below that of the preceding year. The death-rate from disease alone was 4*07 per 1000, and from injury and accident 7*22 per 1000. A summary of the mortahty in the Navy during the past twenty years is given below:— Year. Death-rates per 1000. Year. Death-rates per 1000. All Causes. Disease. Violence. All Causes. Disease. Violence. 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 9*4 8*8 9 2 7-1 14*4 8*6 12*6 10*9 7*5 5*9 6*7 6*9 6*0 5*0 5*3 6*2 4-6 5-3 6-9 4*1 2*7 1*9 3*2 2*1 9*1 2*4 8*0 5*6 2*6 1*8 , 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 9*0 7*0 6*9 8*3 5*7 5*3 8*5 6*2 5*6 11*3 5*8 4'7 5*1 4*9 3*9 3-8 4-1 4*7 4*4 4*1 3 2 2*3 1*8 3*4 1*8 1*5 4*4 1*5 1*2 7, The Navy, like the Army, must be regarded as a force of specially selected, and presumably healthy, men in the prime of life ; a comparison, therefore, of the death-rates of this picked body of males at varying age-periods with the rates for males in civil Hfe for the same ages is of interest. The facts are as follow :— Death-rates per 1000, at the following Age-periods. 15 to 25. 25 to 35. 35 to 45. 45 to 55. Royal Navy (1892), .... Males in civil life, .... 4*14 4*7 6*03 7-4 9*56 12*8 19*23 20*8 In the above table the year 1892 has been taken for the Eoyal Navy, as the year 1893 yielded an exceptional mortality owing to special accidental causes. The civil death-rates are those for England and "Wales. The comparative statement clearly shows that the conditions of life in the Navy are distinctly favourable to health. Special Causes of Sickness among Sailors.—When we come to analyse the statistics of sickness and mortality of seafaring people, we find that sea hfe is apt to give rise to certain ailments which are more or less charac- teristic of, or peculiar to, the sailor's surroundings. Thus, sea-sickness is an ailment of marine life only, while formerly scurvy was especially associated with life on board ship. Cholera and yellow fever are diseases closely connected with ships; the contagion of both being not infrequently carried by them from one country to another. The chief ailments to which sailors as a class are subject are, constipation, boils, erysipelas, lymphangitis, ennui, diarrhoea, sea-sickness, nostalgia, melan- cholia, hypochondriasis, colic, scurvy, the contagious fevers, itch, the effects of vicissitudes of climate, catarrhs, rheumatism, dysentery, and venereal affections. Many of these are of exceptional prevalence, while one or two, notably scurvy and dysentery, are so much the effect of faulty dietaries, that atten- DISEASE, ACCIDENT, AND DEATH AT SEA. 1009 tion to the food-supply of sea-going ships has practically removed these causes of death from the sea-casualty returns. Some of the disorders prevalent among seamen appear to be closely associated with their duties. Thus, men engaged in the interior of ships, such as cargo-men, cooks, bakers, and storekeepers, are commonly anaemic and debilitated; so too are painters, who, like their fellow-workers on shore, are apt to suffer from colic and other symptoms of lead-poisoning. Look-out- men are said to suffer from weak sight, amblyopia, circumorbital pains, and loss of visual accommodation. Steersmen are liable to accidents from the wheel, and often suffer from auditory troubles, presumably effects of exposure, and prolonged efforts to keep on the alert for signals and words of command. Men engaged aloft generally suffer from traumatic lesions of the hands, feet, and inner parts of the thighs and legs ; also from cardiac hyper- trophy and hernia, the results of violent exertion. Boatmen and fisher- men suffer much from rheumatism and other effects of frequent Avettings and long exposure to weather. Boiler-cleaners are liable to asphyxia, while firemen, stokers, and engine-room artificers, who constantly work under con- ditions of high temperature, are usually anaemic, debilitated, and subject to vertigo, stupor, or convulsions. Phthisis is also common among these men. Firemen and stokers, as a class, are often morbid and prone to suicide. Statistics showing the general prevalence of these and other forms of illness in the mercantile marine are unfortunately non-existent. Hoav far these diseases and injuries prevail in the Boyal Navy are shown in the folloAAdng table, prepared from the Statistical Reports on the Health of the Navy, and based on the average ratios for the six years, 1887-92. Average Ratio per 1000, for Six Years, 1887-1892. Disease or Injury. Cases. Daily Sick. Invalided. Deaths. Small-pox, ..... 0*18 0*01 o-oi Other eruptive fevers, 5-64 0*34 0-04 Enteric fever, . 2-85 0*4 0-35 0-67 Other continued fevers, 33-97 0-8 0*32 Yellow fever, 0-02 o-oi Cholera, . 0-18 o-i Dysentery, 1-28 0*08 0*17 0-05 Influenza, 41-93 0'78 0-04 Malarial fevers, 25-77 1-53 2*68 0-24 Septic diseases, 0-88 006 0-02 0*05 Syphilis—primary, . 57-16 5-1 ,, secondary, 23-97 2*48 1-97 0*05 Gonorrhoea, 76-21 5-09 0-69 0*02 Alcoholism, 1*27 0-02 o-oi 002 Rheumatism, . 44*64 1-97 1-54 0*07 Tubercular diseases, . 0*65 0-06 0-22 0*17 Diseases of the nervous system, 12*75 0-66 2-75 0*24 ,, circulatory system, 5*22 0-41 2-82 0*41 ,, respiratory system, . 89*13 3-22 4*03 1*34 ,, digestive system, 120-4 2-51 2-8 0-29 ,, urinary and generative system, . 9*8 0-56 0*82 0*19 >> eye> • 9-43 0-42 0*75 ,, ear, . 4-33 0-18 0*69 Poisoning, .... 0-85 0*02 0*02 0*04 Wounds and injuries, general, . 3-87 0-06 0*16 1*83 ,, local, 197-51 6-57 1-92 0*28 Suicides,..... o-i 0*1 3 s 1010 MAHINE HYGIENE. BIBLIOGBAPHY AND EEFEEEXCES. Armstrong, Article on "Marine Hygiene" in Stevenson and Murphy's Treatise on Hygiene, vol. ii. p. 513. This article gives a copious bibliography on this subject. Cane, "The Hearing of Seamen," Lancet, April 13th, 1889. Collingridge, Annual Reports as Medical Officer of Health of the Port of London; also "Practical Points on the Hygiene of Ships," Proc. Shipmasters' Soc, Lond., 1894; also "On Port Sanitary Administration," Journ. Sans. Instit., vol. xvi. p. 40. Fonssagrives, Traili d'Hygiene Navale, Paris, 1877. Froud, "Heating of Ships and Cargoes," Proc. Shipmasters' Soc, Lond., 1891. Gihon, Practical Suggestions on Naval Hygiene, Washington, 1871. Holt, Review of the Principles of Maritime Sanitation, New Orleans; 1892. Leach, Hygienic Condition of the Mercantile Marine in the Port of London, 1871. Lewes, Service Chemistry, Lond., 1892. MacDoxald, Naval Hygiene, Lond., 1881 ; also "On Ship Ventilation," Journ. Royal United Service Instit., July 1895. Mahe, Manual Pratique d'Hygiene Navale, Paris, 1874. Paasch, From Keel to Truck, Antwerp, 1885. Spooner, "Dietary Scales in connection with the Health of Seamen," Trans. Vllth Internat. Congress of Hyg. and Demog., Lond., 1891, vol. viii. p. 41. Taylor, "The Medical Supervision of the Mercantile Marine," Trans. Vllth Internat. Congress of Hyg. and Demog., Lond., 1891, vol. viii. p. 18. Turner, Article on " Marine Hygiene" in Buck's Hygiene, New York, 1878. Wilson, A Manual of Naval Hygiene, Philadelphia, 1879. APPENDIX I. MEASURES OF LENGTH. The Standard Metre is |||;§§g of the distance, at the temperature of 16°*3 C, betAveen the ends of a certain bar, called the " Toise of Peru," kept in the French Archives, and is approximately the ten-millionth part of the distance from one of the earth's poles to the Equator, at the meridian of Paris. This measure, and those founded on it, is lawful in this country, and a copy of the standard metre is kept in the Exchequer Office at Westminster. The English Standard Yard is the distance, at the temperature of 62° F., between two marks on a certain bar which is kept in the Office of the Exchequer. The relative values of the Metric and English measures of length can be gathered from the following table :— Metres. Inches. Feet. Yards. Miles. Kilometre, Hectometre, . Decametre, Metre, .... Decimetre, Centimetre, . Millimetre, 1000 100 10 1 0*1 0*01 0*001 39*37 0*03937 3*28 10936 0*6214 APPENDIX II. MEASURES OF AREA. Square Metres. British Measures of Area. Square Kilometre, 1,000,000 0-3861 sq. mile. Hectometre, or Hectare, . 10,000 2-4711 acres. „ Decametre, or Are, 100 119*6 sq. yards. „ Metre, . 1 10*764 sq. feet. „ Decimetre, 0*01 15*5 sq. inches „ Centimetre, . 0*0001 0-155 „ „ Millimetre, 0*000001 0-00155 „ 1012 APrENDIX. APPENDIX III. SOLID MEASURES. 1 Cubic Decametre, or Kilostere, equals 35,316'5 „ Metre, or Stere, „ 35316 „ Decimetre, or Millistere, „ 61*025 „ Centimetre „ 0'061 Millimetre „ 0-000061 cubic feet. cubic inches. APPENDIX IV. MEASURES OF WEIGHT. The metric Standard Kilogramme is the weight, at the temperature of the maximum density of water (4° C), and under the atmospheric pressure of 760 millimetres of mercury, in the latitude of Paris, of a certain piece of platinum Avhich is kept in the French Archives. A copy of this standard kilogramme is kept in our Exchequer Office. The kilogramme was at first intended to be the weight of one cubic decimetre of pure water at its maximum density, but it is in actual fact shghtly greater. The Enghsh Standard Pound Avoirdupois is the weight, at the temperature of 62° F., and under the atmospheric pressure of 30 inches of mercury, in the latitude of London, and at or near the level of the sea, of a certain piece of platinum which is kept in the Exchequer Office at Westminster. The relative values of the Metric and English weights is shown in the following table:— Grammes. Grains. Avoir, ozs. Avoir, it). Kilogramme, . Hectogramme, Decagramme, Gramme, . . Decigramme, Centigramme, Milligramme, lOOO 100 10 1 o-i o-oi 0001 15,432 15*432 6*0154 35-3 0*0353 2-204 0*0022 APPENDIX V. MEASURES OF CAPACITY. The metric Standard Litre is the volume of a kilogramme of pure water at its temperature of maximum density (4° C), and under the atmospheric pressure of 760.miUimetres of mercury. It was originally intended to he a cubic decimetre, but is actually a little greater. Under the above mentioned conditions, a litre of pure water Aveighs one kilogramme. The English Standard Gallon is the volume of 10 ft avoirdupois of pure 5S of m temperature of 62° F-> and uuder tlie atmospheric pressure of 30 tJfoW*VetaVbleU-0f ^ ^^ ^ EngUsl1 measures of caPacity is sho™ in APPENDIX. 1013 Cubic centimetres. Fluid ozs. Pints. Gallons. Cubic ins. Kilolitre, Hectolitre, Decalitre, Litre, .... Decilitre, Centilitre, Millilitre, 1,000,000 100,000 10,000 1000 ido 10 i 35:3 1:76 0*22 61*027 APPENDIX VI. TABLE OF FACTORS FOR CALCULATING EQUIVALEXTS OF WEIGHT, VOLUME, LENGTH, &c. To convert grammes . to pounds, multiply by 0-0022 15-432 0-0353 0-0648 28-349 453-592 2-204 353 0-22 353 1-76 0-354 61-027 0-1605 4-5434 0-5679 568-1818 34-6592 0-0036 0-0288 0-5813 16-4 0-0283 28-2153 6-2322 1-72 28-35 0-0924 0-111 10-7641 0-0254 25-4 3937 0-30479 0-000187 0-00057 2-54 0-3937 0-03937 1-6 square kilometres to square miles, „ 2*5899 hectares . to acres, „ 0*4046 glclxxxxxxCE » UU IJUU11U.O, X11LIAL to grains, )5 to ounces, grains . to grammes, ounces . to „ pounds to „ kilogrammes to pounds, 3) to ounces, litres to gallons, » ■ to fluid ounces, >j to pints, to cubic feet, to cubic inches, gallons to cubic feet, » to litres, pints to „ • to cubic centimetres, 5) ' to cubic inches, cubic metres to gallons, » to pints, to fluid ounces, to cubic centimetres, cubic feet to cubic metres, 55 to litres, 5) to gallons, fluid ounces to cubic inches, )) to cubic centimetres, square feet to square metres, » to square yards, square metre s to square feet, inches . to metres, J? to millimetres, metres to inches, to feet, feet to miles, yards to „ 3, to centimetres, centimetres to inches, millimetres to „ kilometi -es to miles, 1014 APPENDIX. APPENDIX VII. Table showing the Daily Yield of Water from a Roof with varying Rainfalls. Area of House, 10 feet by 20 feet, or 200 square feet. Mean Rainfall. Loss from Evaporation. Requisite capacity of Tank. Mean daily yield of Water. Mean daily yield of Water in wettest year. Mean daily yield of Water in driest year. inches. per cent. cubic feet. gallons. gallons. gallons. 20 25 100 4-3 6-7 3*2 25 20 135 57 7*5 3*9 30 20 145 6-8 9-4 4*5 35 20 155 7-9 11*0 5-0 40 15 165 97 13*1 7*2 45 15 170 10-9 14*2 8*6 For any other size of Roof or amount of Rainfall, the numbers will be pro- portional. One inch of rain = 101 tons per acre = 22,624 gallons. APPENDIX VIII. The Chemical Symbols and Atomic Weights of Elementary Bodies. Names of Elements. Chemical Symbols. Atomic Weights. Names of Elements. Chemical Symbols. Atomic Weights. Aluminium, . Al 27-5 Nitrogen, N 14 0 Antimony, Sb 120*0 Oxygen, O 16 0 Arsenic, As 75-0 Palladium, Pd 105*7 Barium, Ba 137-0 Phosphorus, P 31-0 Bromine, Br 80-0 Platinum, Pt 197-2 Cadmium, Cd 112-0 Potassium, K 39*0 Calcium, Ca 40-0 Rubidium, Rb 85*3 Carbon, C 12 0 Selenium, Se 78*8 Chlorine, CI 35*5 Silicon, Si 28-0 Chromium, Cr 52*5 Silver, . Ag 108-0 Cobalt, Co 59*0 Sodium, Na 23*0 Copper, Cu 63*2 Strontium, Sr 87*4 Fluorine, F 19-0 Sulphur, S 32*0 Gold, . Au 196 2 Tantalum, Ta 182*0 Hydrogen, H 1-0 Tellurium, Te 125*0 Iodine,. I 126-6 Thallium, Tl 203*7 Iridium, Ir 192-7 Thorium, Th 231*5 Iron, . Fe 56 0 Tin, . Sn 118-0 Lead, . Pb 206*5 Titanium, Ti 48*0 Lithium, Magnesium, Li Mg 7*0 24*0 Tungsten, Uranium, W u 184-0 240*0 Manganese, Mn 55-0 Vanadium, V 51*3 Mercury, Hg 200-0 Yttrium, Y 88*0 Molybdenum, Mo 95-5 Zinc, . Zn 65*0 Nickel, Ni 59-0 Zirconium, Zr 89*4 APPENDIX. 1015 APPENDIX IX. Table showing the amount of Oxygen capable of being dissolved in Distilled Water, at varying temperatures, under standard pressure. Temperature Centigrade. Cubic centimetres of Oxygen per litre of distilled Water. Temperature Centigrade. Cubic centimetres of Oxygen per litre of distilled Water. 5-0 8-68 18-0 6*54 5*5 8-58 18*5 6-47 6-0 8-49 19*0 6*40 6-5 8*40 19*5 6-34 7*0 8*31 20-0 6-28 7-5 8*22 20-5 6-22 8-0 813 21-0 6-16 8*5 8*04 21*5 6-10 9-0 7*95 22-0 6*04 9 5 7*86 22*5 5*99 10-0 7-77 23 0 5-94 10-5 7*68 23*5 5-89 11*0 7*60 24-0 5-84 11*5 7*52 24-5 5-80 12*0 7*44 25-0 5-76 12 5 7*36 25-5 5-72 13*0 7*28 26-0 5-68 13*5 7*20 26-5 5-64 14*0 7*12 27-0 5-60 14*5 7*04 27-5 5-57 15*0 6*96 28*0 5*54 15*5 6-89 28*5 5-51 16*0 6-82 29-0 5*48 16*5 6-75 29-5 5-45 17*0 6-68 30-0 5-43 17*5 6-61 APPENDIX X. THE STAINING AND MICROSCOPIC EXAMINATION OF MICRO-ORGANISMS. Staining constitutes an indispensable aid to the study of micro-organisms, and a knowledge of the composition and preparation of various stains is essential to those making bacteriological examinations of either water or animal tissues. The various stains or dye-stuff's in common use in pathological work are practi- cally divided into two great classes, namely, the basic and the acid. The former exhibit a strong affinity for the protoplasmic contents of bacterial cells as well as for the nuclei of animal tissues; the latter or acid coal-tar colours do not exhibit this special affinity for the nuclei and bacteria, but stain animal tissues more or less uniformly throughout their entire extent. These two classes of dye-stuffs, therefore, are sharply distinguished from each other, the basic dyes being alone avaOable for the exact exhibition of micro-organisms, while the acid colours are best suited for the demonstration of other elements in the microscopic specimen. The basic aniline dyes in most common use for the staining of bacteria are :— fuchsine, methylene blue, Bismarck brown, gentian violet, and methyl violet. The chief acid coal-tar colours are :—eosine, acid magenta, picric acid, safranine, &c. The natural acid stains, such as hcematoxylin and cochineal, have a similar action. 1016 APPENDIX. For bacteriological work, it is most convenient to prepare saturated alcoholic solutions of the basic dyes, which can be kept in stock ; these stock solutions are then diluted with about ten times their volume of distilled water for actual use. Small quantities only of the diluted solutions shordd be made at a time as they keep badly, with the one exception of methylene blue, which keeps well. Owing to the fact that the staining powers of these aqueous alcoholic solutions may be greatly increased by the addition to them of certain substances, a large number of special stains have been devised; the principal of these special stains are the following:— Loffler's Methylene Blue.—To 100 c.c. of a solution of caustic potash (1 in 10,000) add 30 c.c. of a saturated alcoholic solution of methylene blue. Kuhne's Carbolic Methylene Blue.—In a mortar rub 1*5 gramme methylene blue with 10 c.c. of absolute alcohol, and add 100 c.c. of a 5 per cent, aqueous solution of carbolic acid. Weigert's Gentian Violet.—To 90 c.c. of distilled water add 0-5 c.c. of liquor ammoniae, 10 c.c. of absolute alcohol, and 2 grammes of gentian violet. Ziehl's Fuchsine Solution.—Five grammes of carbolic acid and 1 gramme of fuchsine are added to 100 c.c. of distilled water to which 10 c.c. of absolute alcohol is gradually added. Ehrlich's Solution.—The distinctive feature of this staining solution is that, in place of diluting the alcoholic solution of the basic dye with pure water, the con- centrated stock solution is diluted with water which is saturated with aniline oil. Four to five c.c. of aniline oil are shaken up with 100 c.c. of distilled water. This oily mixture is passed through a damp filter, whereby the excess of undissolved oily aniline is retained by the filter, and to the clear filtrate, or " aniline water " as it is called, are added 11 c.c. of a concentrated alcoholic solution of either fuchsine, methyl violet, or gentian violet. The whole is then frequently shaken during twenty-four hours, at the end of which time the liquid becomes clear and ready for use. This solution will keep about three weeks. Ehrlich-Lbffler Solution.—This is a modification of the foregoing. Dissolve 5 grammes of solid fuchsine or any other basic colour in 100 c.c. of aniline water prepared as above. If kept in a stoppered bottle in the dark, this solution will keep for some six weeks. Its staining powers may be increased by adding a solution (1 in 1000) of caustic soda drop by drop, until the previously clear solu- tion just begins to become cloudy, but not actually precipitated. Ehrlich-Weigert-Koch Solution.—To 100 c.c. of aniline water add 11 c.c. of a concentrated alcoholic solution of fuchsine or methyl violet, and 10 c.c. of absolute alcohol. This solution will only keep some ten days or so. Simple Staining of Cover-glass Preparations of Micro-organisms.—All cover-glasses and slides must be scrupulously clean and free from grease. This cleansing is best secured by dipping them in pure sulphuric acid, then washing them with distilled water. The glasses and slides should be afterwards transferred to a mixture containing equal parts of alcohol and ammonia, and then dried with a perfectly clean soft rag. A sample of the matter to be examined is conveyed on to a cover-glass with the point of a sterilised platinum needle, and diluted, if needful, with water, after which the organisms suspended in the water are spread out over the surface of the glass by means of the needle ; or, a better way is to press another cover-glass upon the prepared one, and then slide it off, so that the material appears equally distri- buted on both cover-glasses. Care must be taken that there is not too much material on the cover-glass, and that, in examining cultivations of micro-organisms, none of the culture medium is introduced along with the organisms, otherwise the preparation will be indistinct and dirty. When the cover-glass, with its thin film of material, has become perfectly air-dried it should be taken up with a pair of forceps by the edge and passed three times through a flame to fix the micro-organisms to its surface, after which the staining is effected by depositing a few drops of dye on the infected surface of the cover- glass, or by floating it with the prepared side downwards upon some of the staining solution in a watch-glass. After from one to five minutes it is freed from super- fluous stain by washing in water, and then turned, prepared side downwards, on to a clean slide, gently pressed with blotting-paper, so that all moisture on the upper surface is removed, and examined with an oil immersion lens, a drop of cedar oil APPENDIX. 1017 being first placed on the dried surface. If a permanent preparation is required, the cover-glass, after staining and washing, must be aUowed to become quite dry, and he then pressed down on to a drop of canada balsam, previously placed on the slide. Decoloration and Double-staining.—In order to obtain greater definition of bacteria, it is often necessary to stain in two colours. Decoloration is the essential principle of double-staining ; whilst one part of the specimen remains coloured, the other portion is made to yield up its colour, after which it is treated with some other stain, the application of which does not affect in any way the already stained portion of the specimen. The strongest agents for decoloration are acids combined with alcohol. The following are the principal decolourising agents in use :—5 per cent, aqueous solution of acetic acid ; 20 per cent, aqueous solution of nitric acid ; 3 per cent, alcoholic solution of hydrochloric acid. Spores in bacteria are very conveniently demonstrated by an apphcation of these principles. A cover-glass preparation, having been simply stained with a heated Ehrhch's solution of fuchsine, is treated with a decolourising agent, and then thoroughly washed with water, and finally stained with the ordinary aqueous solution of methylene blue. The spores, which are not affected by the latter aqueous stain, will still remain red whilst the bacilli have assumed the blue colour. Gram's method of staining consists in staining a cover-glass preparation or section in an aniline-water solution of gentian violet for about five minutes, after which it is placed in a solution of iodine and potassium iodide (1 iodine, 2 potas- sium iodide, 300 parts water) for two minutes, and then washed with alcohol until no more colour is removed ; it is then placed in clove oil, by means of which some more colour is extracted. The bacteria come out stained with gentian violet. Gram's method is useful as an aid to the diagnosis of some micro-organisms. Thus, the Pneumococcus Friedldnder shows no staining after going through the process, and similarly the spirilla of cholera and relapsing fever, the bacilli of enteric fever and glanders, and gonococci, cannot retain the colouring matter, but give it up, as do the nuclei of cells. It is important to bear in mind that fuchsine, methylene blue, and Bismarck brown cannot be used for Gram's method, but only the so-called para-rosaniline colours, to which belong methyl violet, gentian violet, and Victoria blue ; all these latter have a strong affinity for iodine. Staining of Flagella.—For the purpose of rendering visible the flagella of motile micro-organisms, Loffler recommends the use of a mixture of 10 c.c. of a 20 per cent, solution of tannin with 5 c.c. of a cold saturated solution of ferrous sul- phate, and 1 c.c. of a concentrated aqueous or alcoholic solution of fuchsine. The above solution is called " the mordant." After the preparation has been stained or mordanted with the above solution, it is dyed with the Ehrlich-Loffler solution of fuchsine, above described, to which a 1 per 1000 solution of caustic potash has been added. After the dye has been washed off in water the preparation is ready, and may be examined in the usual way under the microscope. For many organisms the treatment with the simple mordant is sufficient, but for bacteria, which form alkalies, the mordant must be rendered correspondingly acid • for those which form acids, alkaline. To render the mordant alkaline, Loffler recommends the use of a 1 per cent, aqueous solution of sodium hydrate, whilst for the acidification of the mordant he employs dilute sulphuric acid of such strength that a given volume is exactly neutralised by the same volume of the 1 per cent. solution of caustic soda. The following are the additions of acid and alkali respectively made to the mordant, as recommended by Loffler, for particular micro-organisms :— Spirillum cholera? Asiaticae, 1 drop of acid to 16 c.c. of mordant. „ Metchnihovi, 4 drops „ „ „ Bacillus pyocyaneus,' 5 „ „ „ „ „ mesentericus vulgatus, 4 „ alkali „ „ „ typhi abdominalis, 22 „ „ „ „ „ subtilis^ 30 „ „ „ „ „ cedematis maligni, 36 „ „ „ „ „ anthracis, 35 „ „ „ „ Micrococcus agilis, 20 „ „ „ „ 1018 APPENDIX. Loffler's method not only stains the flagella but the whole micro-organism. Nicolle and Morax have recently and successfully modified the above details, whereby the addition of an acid or alkali is omitted ; their method is simply to apply the mordant three or four times, instead of only once. This procedure takes a httle longer to carry out, but is certainly simpler, and equally effective in demon- strating the flagella. APPENDIX XI. PREPARATION OF AMMONIA-FREE DISTILLED WATER. This is a matter of very considerable importance in the preparation of standard solutions, particularly as ordinary distiUed water is rarely free Irom ammonia, To overcome this difficulty, the Society of Public Analysts recommend that ordinary distilled water be boiled with 1 per 1000 of pure ignited sodium carbonate. A more preferable method is to fix all the ammonia present in the original water by the addition of pure phosphoric acid to the water before distillation, in the pro- portion of 1 c.c. of the acid to each gallon of water to be distilled. The distillate, as a ride, comes over quite free from ammonia, but it should be always tested with a little of Nessler's reagent. APPENDIX. 1019 APPENDIX XII. STATISTICAL TABLES A AND B REQUIRED BY THE LOCAL GOVERNMENT BOARD TO BE APPENDED TO THE ANNUAL REPORTS OF MEDICAL OFFICERS OF HEALTH. 60 < o u a > u ■a s 3 e x. 3 IS u o ■ J <3 O o to c -§ 1 c *3 3 cj ■a s "8 "3" 3 s p a in Woj, | ■ M M M M ; : | 0 5 "2 e3 CC CU O 3 _o ■> s 0 -3 0 O 3 "Sb •e _3 _B "s 0 u c3 O .5 3 a> J< 03 a> ^= O O *3 3 E 3 3 >3 (U 3 0 "S 3 O J= H ,H 1 "S8Sl?3SI<7 | i M 1 : M 1 * 1 : ; 1 i § -sannfui | : 1 | : | : 1 : : | j ilil | * i 1 i 0> •asuasio: ?.reaH | 1 1 i 1 I 1 i 1 i 1 i MM | : i 1 1 CO •jfsunatj •■Biuouiuauj •Sl|iqouo.ig t~ ■sisiinHtl to ■anSy x-> | M9A9J 1 "-1 | oijurananjj | 1 * 1 * i | ; : | i ^, 1 •XiajuasXg 1 ■^ | pun BaDq-unia 1 1 : | j • 1 i CO •qSnog 1 SuidooqAV 1 1 * 1 i 1 1 : ■S8[SB3K 1 \ 1 : : 1 ! S •sts[9djSA-.ia 1 : | •: : 1 i S "Bjaioqo 1 1 ! \ • 1 i CD •X •Ituadjanj 1 : | j ■Suisdtqajr 1 : I : : 1 : •panuijuoo ! 1 1 * i 1 i ■pioqd^x 1 .10 ouajug 1 1 i 1 i i 1 i '■ •snqd^x j 1 i 1 i Mil 1 -dno.io snoutuquiajj « •uuaq^qdia e>< •bui;b[.it!ds - •xod-nBins \ 1 i s 3:3. 3:3 »c5 :^3 S :S ■a: P =. p. •o Its 3:3, £>:3 :x"3 «5 :>a 53 i g •a g :xo "2:5 « :ft x^ «5 :^ S: g c:A «S :>3 •0: ? b:p-:xo O ;3 s ■ a. 3:^ 0 :*§ •a : £ 3:3-10 S: g ■3 ■ f 3:0. ;x-^ "5 S ■a C3 : P. :3 Under 5 5 upwards Under 5 5 upwards a V to ^< c .2 c ■sp.iBAvdn put? eg 3 1 1 •59 aapun puB es S 1 1 1 : 1 i •gg .lapun pun et S 1 1 | ; •gi aapun pun 0 S 1 1 | •g .iapun pun 1 g 1 | | \majC x japun. S | ■saStf nu ;y g ■3 3 < Names op Localities adopted for the purpose of these Statistics; public institutions being shown as separate localities. See Note 4. (a) CO 0 0 3 "3 cu Q (B)—TABLE OF POPULATION, BIRTHS, AND OF NEW CASES OF INFECTIOUS SICKNESS coming to the knowledge of the g Medical Officer of Health, during the year 18......, in the............Sanitary District of..................; classified according to Diseases, Ages, £? and Localities. f Names of Localities adopted for the purpose of these Statistics; public institutions being shown as separate localities, See Note 2. Population at all Ages. M ■a ■£b cu « Aged under 5 or over 5. 0) New Cases of Sickness in each Locality coming to the knowledge of the Medical Officer of Health. Number of such Cases removed from their Homes in the several Localities for Treatment in Isolation Hospital. Ci OO 3 3 ■3 (6) B ° e 1 2 3 4 5 | 6 | 7 1 8 | 9 10 | 11 12 1 13 1 2 3 4 5 | G 1 7 | 8 1 9 10 11 12 13 o 3. S CO .5 S -> u W 3 j= 3. >> H 03 If 5 3 0 ci 3 p. "3 cu O, 5 3 •Ph 3 3. 03 CU 'S 'S .3 CU p. •a 3 3 O O 3 P. _C3 -CU « "3 p. x. 3 Cl,- Under 5 5 upwards -- Under 5 5 upwards — Under o 5 upwards -- -- Under 5 5 upwards Under o 5 upwards f -- Under •"> 5 upwards Under 5 5 upwards ....!.... -- -- 1 Under i> 5 upwards 1 Under 5 o upwards ...J.... 1 Under 5 i 5 upwards ! Under 5 ...J.... 1 5 upwards 1 1 1 i Totals Under 5 l | ....1.... ...J... 5 upwards 1 1 1 1 1 1 i State here whether "Notification of Infectious Disease" is compulsory In the District.......... Since when?........................ Besides the above-mentioned Diseases, insert In the columns with blank headings the names of any that are notifiable in the District, and fill the columns accordingly. State here the name of the Isolation Hospital used by the sick of the District. Mark (II) the Locality in which such Hospital is situated; and if not within the District, state where it Is situated........................................ APPENDIX. 1021 Notes on Tables A and B. Note 1. Medical Officers of Health of "combined districts" must make a separate Return for the District of each Sanitary Authority. 2. Medical Officers of Health, acting for a portion only of the District of a Sanitary Authority, should write, in the heading of the Table, the designa- tion of the Division for which they act. 3. The words " Urban," or " Rural," or " Metropolitan" must be inserted in the appropriate space in the heading, according as the Sanitary Authority for the District is Urban or Rural, or is within the Metropolitan area. 4. The " Localities" adopted for the purpose of these statistics should be areas of known population; such as parishes, groups of parishes, townships, or wards. As stated at the head of the first column in each Table, Public Institu- tions should be regarded as separate localities, and the deaths in them should be separately recorded. Workhouses, Hospitals, Infirmaries, Asylums, and other establishments into which numbers of people, and especially of sick people, are received, are Public Institutions for the purpose of these statistics. 5. The deaths that have to be classified in this Table, and summed up in the horizontal line of " Totals," are the whole of those registered as having actually occurred in the several localities comprised within the Division or District. But the registered number of deaths frequently requires correction before it can give an exact view of the mortality of a Division or District; and the two lowest horizontal lines are provided for the purpose of enabling Medical Officers of Health to indicate, to the best of their ability, what the extent of such corrections should be. Details concerning the corrective figures, e.g., the Institutions that have been considered, or the particular localities to which corrections apply, may appear in the text of the report or in supplementary tables. Area and Population of the District or Division to which this Return relates. Area in Acres,.............................. Population (1891), In recording the facts under the various headings of Tables A and B, attention has been given to the notes endorsed on the Tables. ....................................Medical Officer of Health. (Date)................................. Notes on Table B. (See also Notes to Table A.) Note 1. The present Table B is concerned with Population, Births, and Sickness (not with Mortality) in the Sanitary District or Division to which the Table relates. 2. As stated in the heading of column (a), Public Institutions should be regarded as separate localities, and the new cases of sickness in them should be sepa- rately recorded. Workhouses, Hospitals, Infirmaries, Asylums, and other establishments into which numbers of people, and especially of sick people, are received, are Public Institutions for the purpose of these statistics. 3. Comments on any unequal incidence of notifiable disease upon the several localities, and considerations as to the local incidence of consumption and other prevalent diseases, should be made in the text of the report. INDEX. A.B. C. treatment of sewage, Ablution rooms in barracks, Absorbability of proteids, Acarus far ince, . scabiei, Accessory foods, . Acclimatisation, . Accoutrements of soldier, weight of, Achorion Schonleinii, . Acid, boracic, in milk, . ------carbolic, as disinfectant, ------carbonic. See Carbon dioxide ------hydrochloric, effects of vapour ------nitric, in water, . . 56 ------nitrous, in water, . 56 ------------as a disinfectant, ------phosphoric, in water, . 58; ------salicylic, in milk, ------silicic, in water, ------sulphuric, in water, ------sulphurous, detection of, in air, as a disinfectant, PAGE 543 925 270 331 566 247, 367 710 vegetable, Acids, beer of, ------bread of, ------vegetables of, ------wine of, . Actinomycosis, . Adulterations of arrowroot, ------of beer, . ------of bread, . ------of butter, ------of cocoa, . ------of coffee, . ------of flour, . ------of lime juice, ------of milk, ------of mustard, ------of pepper, ------of tea, ------of vinegar, of wine, Aerated waters, fate of micro-organisms 111 Aeroscopes, . . . .175 Agar-agar, preparation of, . . 94 A?r, . • • • • 121 ------amount of, required, . . 181 .--------;----for animals, . . 186 --------:----for lights, . . 185 -------------for removal of moisture, 187 -------------for the sick, . . 185 ------bibliography of, . . 178 ------calculation of amount required, 133 ------collection of samples of, . 167 ------composition of, . . . 122 cooling of, . . 235, 931 957 560 321 687 of, 152 75,87 72,87 691 79,89 321 58 56,89 174 690 251 375 338 356 382 561 353 372 337 323 402 399 332 403 309 406 407 397 405 383 ditfusion of, effects of air of combustion, 128, 194 137 PAGE Air, effects of air of respiration, 143, 162 ------------effluvia from brickfields, 155 offensive trades, ----:— gases and effluvia in, ------impurities, increased pressure of, lessened pressure of, suspended matters in, unequal weights of, electrical conditions of, estimation of carbon dioxide in, monoxide in, ------of micro-organisms in, ------of organic matter in, ------of oxidisable matter in ------of oxygen in, ------of ozone in, ------of sulphuretted hydro gen in, ------of sulphurous acid in, examination of, . ------bacteriologically, — chemically, microscopically, 156 152 148 709 707 148 197 726 169 174 175 172 172 168 174, 729 forces concerned in movement heating of, humidity of, influence on health, impurities of, ------from combustion, ------from respiration, ------from sewage effluvia, 135, from trade processes, 175 174 167 175 168 175 of, 194 216 125, 734 704 129 137 143 156, 160 133 movement, how determined, 240, 724 195 705 137 133 135 438 125, 172 how obtained, influence on health, ------of marshes, ------of mines, . ------of sewers, ------of soil, ------organic matter in, ------supplies, source, and distribu tion of, ------suspended matter in, . ------temperature of, . ------watery vapour in, ------weight of, Air-meters, Albuminoids. See Proteids. Alcohol as an article of diet, . ------estimation of, ------physiological action of, ------use of, in bodily labour, ------------great heat or cold ------------mental work, Alcoholic beverages, Algae in water, 193 125,130 713 125 127, 740 240 387 374 387 389 390 388 387, 947 367 91 1024 INDEX. Alkali works, Alluvial soils. law relating to, water from, Altitudes, correction of barometer for ------measurement of, Alum as a purifier of water, ------in beer, . ------in bread, . ------in flour, . ------in wine, . Aluminium process for determination of nitrates, Aluminous substances as sewage pre cipitants, Amines process for treating sewage, Ammonia in air, . ------albuminoid, in water, — free, in water, vapour, effects of, PAGE 811 887 435 26 750 751 46 377 339 336 384 75 Amceba dysenterice, Amjjhistomum hominis, Anaerobic cultures, preparation of, Analysis, hygienic value of water, ------of air, ------of soil, ------of water, . ----:-----tables illustrating, volumetric, principles of, Anchylostomum duodenale, Anemometers, Angus Smith's coating for water- pipes, • . Animals, amount of fresh air for, ------cubic space for, . ------determination of age of, ------diseases of, ------distinction of sex of, ------inspection of, ------nuisance arising from keeping, slaughtering of, — water necessary for, Anthomyia canicularis, Anthrax, .... 284, Anticalcaire for purifying water, Anticyclone, Antiseptics, Apjohn's formula, Aqueous rocks, . Aqueous vapour, tension of, . Arachnids, parasitic, Argaspersicus, . Argon, .... Army statistics, . Arrowroots, Arsenic in trades, ------in water, . Artesian wells, . Artificial cooling of air, . ------improvement of wine, . ------ventilation, Artisans' dwellings, Asbestos-as filtering medium, . Ascaris lumbricoides, ------mystax, Aspergillus, Ashes for mixing with excreta, Asses' milk, Atmometers, Atmospheric electricity, ------pressure, . . Atomic weights, table of, Aurora, . . . 543 544 172 71,87 57, 69, 87 152 562, 619 584 96 111 167 477 52 114 60 571 240, 721 22 186 192 286 283 287 282 801 802, 889 6 564 294, 595 46 757 680 737 434 126, 737 565 566 123 970 351 812 58,80 11 235 380 207 494 50 43, 568 568 560 514 300 741 726 707, 745 1014 729 44 Austro-Hungarian soldier, rations of Averages and means, Bacon curing, nuisance from, . . 806 Bacteria in air, . . . 131, 177 ------in soil, ------in water, . Bacteriological examination of air, -------------of filters, -------------of ice, -------------of milk, . -------------of soil, -------------of water, Bakehouses, sanitary law relating to Baking, . ' . Ball-traps, ' . Barffs coating for water-pipes, Barley, . . Barometers, construction of, ------corrections for reading, ------fluctuations of, . ------reading of, Barracks on home service, ------in hot climates, . ------inspection of, ------ventilation of, at home, -------------in tropics, ------warming of, Baths and wash-houses, law as to, Beans, . . Bedding, disinfection of, Beef-broth, preparation of, for bacterial cultures, ------extracts, nutritive value of, Beer, .... ------adulterations of, ------examination of, . ------nutritive value of, ------varieties of, Beet-sugar, Berkefeld filters, Berlier system of sewage removal, Berthon huts, Beverages, alcoholic, ------non-alcoholic, . " . Bibliography of air, ------of beverages, ------of climate, ------of clothing, ------of disinfection, . ------of excreta removal, ------of exercise, ------of food, . ------of habitations, . ------of infectious diseases, . ------of marine hygiene, ------of meteorology, ------of parasites, ------of soil, ------of ventilation and heating, ------of vital statistics, ------of water, . Bilges of ships, . Bilharzia hcematobia, . Birth-rates, . . . 759 Biscuits, . ' . Blaps mortisagd, Blastomycetes, . Bleaching powder as a disinfectant, Blood-utilisation, trades involving, Boiling as a means of cooking, ------of tripe, . ------point of water, . INDEX. 1025 Bond's Euthermic stove, Bone-boiling, Boots and shoes, . Bbracic acid in milk, Bothriocephalus latus, . Bovril, nutritive value of, Boyle's law, Brandy, ..... Brassfounder's ague, Braxy in sheep, .... Bread, ..... ------examination of, . ------quality of, and diseases arising from, ..... Brickfields, effluvia arising from, Buckwheat, . Buildings, new, law relating to, Burial Boards, law as to formation of, ------of dead, law relating to, Butter, ..... ------adulteration of, . ------examination of, . Buys Ballot's law, Bye-laws, .... ------model, as to burial-grounds, . -------------------canal boats, PAGE . 227 804 418, 957 321 582 360 128 384 151 295 334 338 336 155 346 874 902 901 322 323 323 755 834 903 872 ----------cleansing and scavenging, . 845 -------------------common lodg- ing-houses, . 859 -------------------mortuaries and cemeteries, . 901 -------------------movable dwellings, 873 -------------------new streets and houses, . 875 -------------------offensive trades, 880 -------------------privies and mid- dens, . 514,842 -------------------slaughter-houses, 889 -------------------tenement houses, 861 Cabbage, ..... 356 Calculation, diets of, . . . 269 ------discharge from sewers of, . 537 ------work done of, . . . 428 Calorigen stove, .... 327 Camps, ..... 935 Cancer and soil, .... 458 Cane-sugar, . . . 250, 355 ------in milk, . . . .320 Capillarity, correction for, . . 749 Carbalite as a filtering medium, . 50 Carbide, magnetic, . . 50,544 Carbo-hydrates, . . . 249, 253 Carbolic acid as a disinfectant, . 687 Carbon, amount required daily in food, ------dioxide in the air, -------------------of barracks, ------of marshes ------of mines, ------of prisons, ------of respiration, ------of schools, ------of sewers, ------of soil, . ------of stables, ------of towns, effects of, elimination of, . estimation of, in air, in water, 264 123 145 137 133 145 143 124, 145 135 disulphide as a disinfectant, ------effects of, — manganous, 124 145 124 163 419 169 83 690 152 50 PAGE Carbon monoxide, estimation of, in air, 174 ------------poisoning from, . 153 ------organic, in water, . 11, 68, 88 Carbonates in water, ... 84 Carbonic acid. See Carbon dioxide. Carboniferous soils, . . . 435 Cattle, diseases of, . . . 283 Cavalry, weight of dress and equipment, 957 Cellar dwellings, law relating to, . 857 Cellular cloth, . . . .417 Cement works, air of, . . . 155 Cemeteries, air of, . . . 137 ------law relating to, . . . 901 ------water from near, . . 26 Cerebro-spinal fever, . . . 597 Cesspits, ..... 542 Cestoda, ..... 577 Chalk soils, . . .435 ------water from, . . .25 Chamberland-Pasteur filters, . . 50 Charcoal closets, . . . 515 ------filtering medium as, . . 49 Charles' law, .... 127 Charqui, ..... 369 Charts, notation of meteorological, . 752 Cheese,.....327 Chemical works, law relating to, . 887 ------disinfectants, . . . 686 Chemiotaxis, .... 592 Chicken-pox, .... 598 Chicory, ..... 399 Chloralum, . . . .694 Chlorine as a disinfectant, . . 689 ------in water, . . 23, 56, 65, 86 Chocolate, .... 402 Choke-damp, .... 134 Cholera, natural history of, . . 599 ------in relation to air, . . 149 ------------milk, . . .306 ------------soil, . . 458,604 ------------water, . . 30, 604 ------powers of Local Government Board to make regulations for, 913 ■------prevention of, . . 605, 913 preventive inoculation for, — spirillum of, ------------detection of, in water, Chrome works, . Cirrus clouds, Cisterns, cleansing of, . materials for, 606 602 103 812 731 20 19 Clark's process for softening water, . 46 Classification, climates of, . . 710 ------clouds of, ... 731 ------food-stuffs of, . . 247, 257 ------waters of, . . 14, 114 Clay soils, .... 435 ------water from, ... 25 Cleansing and scavenging, law relating to, 844 Climates, classification of, ------effects of, * Closets, charcoal, ------ earth, ------slop, ------trough, ------tub and pail, ------water, Clothing, . ------principles of selection, ------soldier, of the, . Clouds, Coal, combustion of, Coal gas, . . 710 697 515 515 517 520 514 520 410 416 953 731 137 139 3T 1026 INDEX. PAGE Coca,.....401 Cocoa, ..... 401 Coffee......397 Coir,......416 Collection, air, samples of, . . 167 ------water, samples of, . . 53, 95 ------■-----supplies of, . 15 Cols,.....758 Combustion, air vitiated by, . . 137 Comma bacilli of cholera, . . 602 Common lodging-houses, law relating to, 858 Comparison, heating methods of, . 237 ------sewage disposal methods of, . 555 ------ventilation methods of, . 214 Concentrated and preserved foods, . 357 Condiments, .... 404 ------dietetic uses of, . . 409 Conduction, heating by, . . 218 Constant supply of water, . . 20 Construction of dwellings, . . 488 ------of ships, .... 982 Contagion, .... 587 Contagious Diseases (Animals) Act, powers of a Sanitary Authority under, ..... 896 Contagious Diseases Acts, effects of repeal upon venereal disease in the army, Convection, heating by, Cooking of food, . Cooling of air, Copper in food, . in water, . Cotton, Cowls, .... Cream, . Cubic space for animals, ------in barracks, ------in dwellings, ------in hospitals, ------in ships, . ------measurement of, ------relation to ventilation, Culex anxifer, Culture manipulations, . ------media, ------phenomena of water bacteria Cumulus clouds, . Cupralum, Curcuma arrowroot, Cuterebra noxialis, Cyclones, .... Cysticercus cellulosa>, 976 219 272 235, 931 363 44, 57, 80 413 197 300, 309 192 189 188 91, 501 988 238 191 564 96 94 105 732 694 352 564 755 579 Dairies, cow-sheds, and milkshops, law relating to, ... 896 Death, causes of, ... 778 ------mean age at, . . . 784 ------rates, .... 771 ------------combined, . . 775 ------------corrected, . . 773 ------------influence of birth-rates upon, . . .776 ------------ urban and rural, . 777 ------------zymotic, . . . 779 Definitions of sanitary terms, . . 832 Delhi boil, relation to water, . . 41 Dengue, ..... 607 Density of population, . . . 777 Deodorants, . . . 680, 694 Deodorisation of excreta, . 513, 515, 694 Desmids in water, ... 91 Dew.......-734 Dew-point, Diarrhoea, causes and prevention of, ------in relation to sewer air, ------------to soil, . ------------to water, Diatoms in water, Diet, general principles of, Diets, calculation of, ------on board ship, . ------standard. ------table for calculating, Diffusion of air, . Digestibility of food, Diphtheria, causes and prevention of, ------in relation to milk, ------------to sewer air, — to soil, . to water, prevention of, 13 Disaccharids, Disinfection, ------apparatus for, ------by chemical means, ------by heat, . ------of clothes and bedding ------of excreta, ------of rooms, . ------of ships, . Disposal of sewage, ------of sludge, Distillation of water, Distomum crassum, ------hepaticum, ------heterophyes, ------lanceolatum, ------Ringeri, . ------sinense, . Distribution of water, Dochmius duodenale, Docker huts, Dolomite, . Donkin's formula, Dracunculus medinensis, Drainage of houses, ------law relating to, . Drains, cleansing of, ------connection of, with house-pipe ------construction of, ------definition of, ------examination of, — fall of, . laying of, Drills, Dry closets, Dry methods of removing excreta, Dust in air, Dysentery, causes and prevention of, ------in relation to food, ------------to soil, ------------to water, ------prevention of, Dyspepsia and drinking water, 461. PAGE 735 608 157 609 36 91 251, 264 269 999 264 268 128 271 611 306 159 462, 612 41 616 249 680 684 686 681 693 693 694 695, 998 542 545 45, 998 583 43, 583 584 583 584 583 20 44, 571 932 435 191 569 523 840 531 , 531 528 528 532 532 529 963 513 513 130, 148 616 617 464, 617 38, 617 619 38 Earth-closets, .... 515 Echinococcus hominis, . . . 580 Effects of air from graveyards, . 162 -------------------manufactories, . 162 ------------vitiated by respiration, 162 ------of emanations from faecal matter, 161 ------of exercise, . . . 419 Effluents from sewage after precipita- tion, ..... 544 .....299 INDEX. 1027 Egg-shaped sewers, Elastic force of vapour, Electrical condition of air, Electricity as an illuminant Electrolysis for precipitation of sewage, . Electroscopes, Emergency foods, Encampments, Energy obtainable from food, Enteric fever, cause and prevention of ------bacillus of, ------------detection of, in water, etiology of, in relation to milk. sewer air, -. s°il) water, Entomostraca in water, . Entozoa and drinking water, Ephestia elutella, Epidemic cerebro-spinal fever, Erbswurst, Ergot, Error, mean, ------of mean square, . ------probable, Erysipelas, Euchlorine, Evaporation, Examination of air, ------of bread, . ------of beer, . ------of coffee, . ------of flour, . ------of lime or lemon juice, ------of milk, . ------of soil, ------of starches, ------of sugar, . ------of tea, ------of ventilation, ------of vinegar, ------of water, . ------of wine, . Excreta, amount of, ------deodorisation of, -----disinfection of, . ------disposal of, ------law relating to removal of, ------removal of, ------------by Berlier method, -----.------by dry method, ------------by Liernur method, -----.------by separate system, -----.------by Shone method, ------------■ by water, Exercise, . ------amount that can be taken, ______effects of, on elimination carbon, ___________________nitrogen, Expectation of life, Extraction, ventilation by, PAGE 536 737 726 141 of 552 727 358 935 259 620 622 102 622 306, 624 158 465, 621 34, 624 92 43 332 597 358 343 797 798 797 625 689 741 167 338 373 400 332 403 308 477 354 355 396 238, 243 405 52 382 511 694 693 511 840 513, 987 552 513 551 551 552 517 419 427 419 423 785, 789 207 Factories, air of, . . . 132, 150 ------law relating to sanitation of, . 882 Factors, table of, for calculating equi- valents of weight, volume, length, &c,.....1013 Faecal emanations, effects of, . 156, 160 Fans, ventilation by, . . . 211 Fasciola hepatica, . • 43, 583 Fatigue, law of, . Fats, . ' . ------melting of, ------nutritive value of, Feathers, . Fell-mongering, . Ferralum, . Ferrozone, Filaria Bancrofti, -----loa, ------sanguinis hominis, Filters, domestic, ------examination of, . ------sand and gravel, Filtration of sewage, ------of water, . Fireplaces, open, Fires, impurities in air from, Fish, ------parasites of, ------poisoning from, . Flax, Floors and flooring, Floor space in barracks, ------------in hospitals, ------------in schools, Flour, Flushing of sewers, Flush tanks, Fog, Food, ------adulteration of, law relating ------amount of, required, -----■ bibliography of, ------classification of, ------concentrated, ------cooking of, ------deficiency of, its effects, ------digestibility of, . ------diseases connected with, ------energy obtainable from, ------ excess of, its effects, ------nutritive functions of, ------------value of, . ------of the sailor, ------of the soldier, ------prepared, ------preserved, ------unsound, law relating to, Foot-and-mouth disease, Formalin in milk, Fresh air for animals, . ------for artificial lights, ------for removal of moisture ------for the healthy, . ------for the sick, Friction in ventilation, . Frying of food, . Fumigation, Fungi in water, . Furs, Gas, coal, .... ------amount of air required for, ------impurities produced by com bustion of, ------stoves, Gases, offensive, from trades, 133, Gelatin-peptone, preparation of, Geological origin of soils, George's calorigen stove, Gin, .... Glaisher's factors, to, PAGE 429 249 805 253 412 807 694 544 576 577 573 49 112 47 546 47 219 137 297 298 298 415 493 920 501, 938 495 330 541 531 734 246 893 263 364 247, 257 357 272 277 271 275 259 275 251 258 999 944 358 361 891 84, 295 321 186 185 187 181 185 198 275 689 90 412 139 185 140 225 152, 156 94 432 227 385 737 1028 INDEX. 137 Glanders, . Ghssina morsitans, Glue-making, Goat's flesh, ------milk, Goitre, in relation to soil ------------water, Graham's law, Gram (kind of pea), Granite, . ------soils from the, ------water, Grates, Gravel, water from the, Graveyards, air of, ------law relating to, ------water from, Grease traps, Griess' test for nitrites, Ground water, Guinea worm, Gut-cleaning, Habitations, ------bibliography of, ------construction of, ------examination of, ------sites for, Hailstorms, Hardness of water, Head, calculation of, for air currents, Heat as a disinfectant, ------as a ventilating agent, ------distribution of, . ------effects of, on air, ------------on health, ------------on water, ------equivalent of, ------production and measurement of, specific, PAGE 296, 627 565 808 300 Heating by means of fires, ------------of hot air, --------of stoves, of water and steam, ------of houses, ------of ships, . Heights, barometric correction for, measurement of, Hemp, Hempel's gas apparatus, Hermite process of treating sewage, Hesse's tube for examination of air bacteria, Hominy, . Honey, Horse-hair, manufacture of, Horses, amount of fresh air for, of water for, cubic space for, flesh of, . law as to sale of, Hospitals, ------air of, 467 42 128 348 434 436 25 219 26 162 901 26,38 525 73 442 569 804 484 510 488 497 486 729 65,89 213 681 207, 993 218 127 699 2 259 216 217 219 229 223 230 180, 216 996 750 751 416 168 553 176 346 355 817 186 6 192 288 892 498 132 510 191, 501 502 bibliography of, cubic space required in heating of, huts for . . . .932 infectious, . . . 506 ------powers of Sanitary Authority to provide, 906 military, .... 938 naval, .... 991 on board ships, . . . 990 Hospitals, plans of, ------provision of, for infectious diseases, ------special, . ------tents for, ------ventilation of, . House, drainage of, law relating to, Humidity, air of, ------estimation of, ------influence on health, ------relative, . Huts and hut barracks, Hydraulic mean depth, Hydrocarbons, . Hydrochloric acid, effects of vapoui from, .... Hydrogen sulphide, effects of, ------------estimation of, in air, -------------------in water, Hydrometers, Hydrophobia, Hygrometers, Hyphomycetes, . PAGE 509 906 506 933 501, 507 513 840 125, 734 738 704 738 931 537 249 152 153 175 37,89 386 628 735 560 Ice, bacteriological examination of Igneous rocks, Illuminants, comparison of, Illumination, artificial, . Ilosvay's test for nitrites, Immunity, Impurities in air, effects of, in water, effects of, Incubation periods, Index error, India-rubber, ------------making of, Industrial gases, effects of, Infantile mortality, Infantry equipment, Infection, . Infectious diseases, ------------hospitals for, ------------law relating to, ------------and milk supplies, ------------and schools, ------------notification of, Inferences from water analyst- Influenza, . . . Infusoria in water, Inlets for fresh air, Insects, parasitic, Inspection of animals, . ------of meat, . ------of sewers, Intermittent downward filtration, ------supply of water, Invaliding from army, . ------------ navy, Iodine as a disinfectant, Iron, detection of, in water, ------in water, . ------magnetic, for filters, ------pipes for water, ------soils, ------spongy, for filtration, Irrigation, Isobars, Isolation hospitals, 58, 39 10 112 434 141 138 74 590 129 148 25 29 589 749 416 809 152 774 953 588 587 506, 907 905 896, 908 909 910 86, 111 630 91 201 563 282 285 541 546 20 974 1007 692 57,79 57,79 49 22 471 49,50 547 754 506 INDEX. 1029 Isolation Hospitals, powers of Sani- tary Authority to prov Isothermals, Izal, Jute, Kefir, Kit of soldiers, Kjeldahl's process for o Knackeries, Kola, Koumiss, . Lactosazone, Lactose, . Lathyrus sativus, Latrines on board ship, Lavatories, Lead, action of water ur ------detection of, ------in cisterns, ------in flour, . ------in water, . ------pipes for water, de, 907 722 41£ 308 953 ganic nitrogen, 71 802 401 301, 308 320 301, 313 348 987 on, 23 57, 80 19 337 24 23 poisoning by, in relation to soils, 468 to water, works, sanitary supervision of, Leather as an article of clothing, ------making, . Leeches in drinking water, Iieguminosce, Lemon juice, ------------examination of, - issue of, on ships, Lentils, Leprosy, .... Liebig's extract of meat, Liernur's system of sewage removal, Life capital, 24 813 412 807 44 347 402 403 1000, 1003 348 632 360 551 791 — expectation of, . . 785, 789 ------loss of, at sea, . . . 1007 ------mean duration of, . . 785 ------probable duration of, . . 784 ------tables, .... 785 Lights, artificial, impurities in air from, 137 ------amount of air for, . . 185 Lime juice. See Lemon juice Lime in water, Lime salts as sewage precipitants, Limestone soils, . -------------water from, Lime water as a purifier for water, Linen, .... Linoleum making, Linseed, .... Lodging-houses, common, -------------for working classes, Lolium temulentum, London water-supply, Lucilia hominivora, law relating to, . 36, 56 . 543 435 25 46 415 809 332, 415 858 869 332 3 849 564 Macaroni, .... 341 Made soils, . . . .455 Magnesia in water, . . 42, 57, 65 Magnesian limestone soils, . . 435 -------------------water from, . 26 Magnetic carbide, ... 50 Main sewers, . . . . . 536 Maize, ..... 346 Malaria, ..... 633 —.----and air, . . . .149 Malaria and soil, ------and water, ------parasite of, Malignant oedema in relation to soil, Manganous carbon as a filtering medium, Man-holes, Manihot arrowroot, Manure manufactories, Marches and marching of soldiers Mare's milk, Margarine, ------law as to sale of, Marine hygiene, . ------mortalities, ------populations, Marriage rates, . Marshes, . ------air from, . ------water from, Mate, Means, Mean age at death, ------error, ------duration of life, ------population, ------square, error of, Measles, Measures of area, ------of capacity, ------of length, ------of solidity, ------of weight, Measurement of cubic space, ------of discharge of water, — of sewage, M eat, ------biscuits, . ------cooking of, ------diseases arising from, . ------dried, ------extracts, ------frozen, ------inspection of, ------■ microscopic examination of, ------preservation of, . ------salt, ------tuberculous, Medical Officer of Health, duties of, Melampyrum arvense, . Mercantile marine, food-supply of, ------------mortality of, ------------population of, . ------------sanitary supervision of Mercurial poisoning, Mercuric chloride as a disinfectant, Mercury, use of, in trades, Metallic poisoning by air, ------------by water, Metamorphic rock soils, -------------------water from, Meteorology, Meteorological charts, notation of, Methods, statistical, Metrical weights and measures, Micro-organisms, culture phenomena of. ------in air, ------in milk, ------in sewers ------in soil, ------in water, ------vitality of, in aerated waters, ------.------in ordinary water, 50 528 353 162, 808 963 300 323 895 979 1004 979 767 470 137 26 401 797 784 797 785 787 798 637 1011 1012 1011 1012 1012 238 17 537 280 359 272 291 362 360 289 285 289 362 289 292 827 332 999 1007 979 979 152 687 814 151, 812 44 435 25 713 759 793 1011 105 175 . 316 136,157 450 93 99 1030 INDEX. Middens, . . . Midfeather traps, M icscher's tubes, Military hospitals, ------hygiene, . ------service, effects of, Milk, . . ------adulterations of, -----as an article of diet, ------as a culture medium, ------examination of, ------from asses, goats, and mares, ------from diseased cows, ------law relating to sale of, ------powers of Sanitary Authority to control sale of, ------preservation of, ------variations in composition of Millet, .... Mines, air of, . ventilation of, Miners, mortality among. Mist, . . .' . Monosaccharids, Montgolfier's formula, . Mortality, causes of, ------------in army, ------------in mercantile marine, in navy, facts, how recorded, infantile, . in relation to birth-rates, ------to density of popula- tion, . to occupation, . rates, urban and rural, PAGE 513 524 5(12 938 916 968 300 309 301 95 308 300 304 896 307 302 346 133, 149 208 149 734 249 197 778 974 1007 1007 793 774 776 Mortuaries, law as to, Movement of air, causes of, ------------determination of, ------------in sewers, Mumps, .... Mushrooms as articles of diet, Mustard, Myrbane, effects of, Natural ventilation, Naval hygiene, . —■.----mortality, Nematoda, Nervous diseases, mortality from. Nessler's reagent, Nimbus clouds, . Nitrates in water, how determined, Nitric acid. See Acid. Nitrification in soil, Nitrites in water, how determined, Nitro-benzol, effects of, Nitrogen, elimination of, ------in air, ------in food, . ------in soil, ------in water, . Nitrogenous aliments. See Proteids. Nitrous acid. See Acid. Normal standard solutions, Notification of infectious diseases, Nuisances, inspector of, ------law relating to, . Numerical determination of micro organisms in water, . Nutritive value of the food-stuffs, 777 780 771 777 901 129 240 539 639 357 406 154 200 979 1007 567 783 57 732 56, 75 450 56, 72 154 423 122 252 480 68,71 62 910 829 852 97 258 Oats, .... Occupation and mortality, Ochromyia anthropophaga, CEstrus hominis, . ... Offensive gases from trades, 133,152, ------trades ------------law as to nuisance fron oidium lactis, Oil, amount of air needed for illumina tion by, ------as an illuminant, ------boiling, . ------impurities yielded by, on com bustion, ------stoves, Oleo-margarine, . . . Oolite, water from, Orders of Local Government Board in regard to Dairies, Organic matter in atmospheric air, ------------in respired air, . ------------in water, Oriental sore, in relation to. water, Osazones, .... Outlets for foul air, Oxidisable matter in air, ------------in water, Oxygen in air, ------------estimation of, . ------consuming power of water for, — dissolved in water, table of, PAGE 344 780 564 564 156, 811 801 57 Oxyuris vermicular is, Ozone, ------estimation of, 123, Paper-making as an offensive trade, Paraguay tea, Parasites, .... Parish Councils, sanitary powers of, Parks, open spaces, and powers of Sanitary Authority thereto, Parliament Houses, ventilation of, Peas as articles of diet, . Pea-sausage, Pellagra, .... Pemmican, Pentastomum constrictum, ------denticulatum, ------tcenioides, \ Pepper, .... Permanganate of potassium as purifier of water, Phagocytosis, . . . Phenol-sulphuric acid method for estimating nitrates Phosphates in water, Phosphorus, use of, in the manufactures Phthisis among miners, . ------in relation to air vitiation. ------------to dust in air, . ------------to meat, . — to milk, . to soil, Physical examination of soil, . ------------of water, Pipes for water, . Plague, . ... Plate-cultures, Pneumatic methods of sewage removi Pneumonia, . . . ------from sewer gas, . ------from vitiated air, 317 186 139 810 139 228 323 25 897 125 146 68 41 320 204 172 76,88 123 168 76 80 1015 44, 568 74, 729 730 810 401 558 821 899 208 348 358 346 363 567 566 566 407 46 590 75 58,79 815 150 164 149 292 306 472 477 54 20 639 96 551 640 157 165 \v ,vW*\ ^ INDEX. 1031 Poisoning from fish, ------from meat, Poisson's formula, Polarite as a filtering medium, ------as a sewage precipitant, Polysaccharids, . Population, age and sex distribution of, 766 ------density of, 777 ------estimation of, . . . 763 ------normal constitution of, . 767 Port sanitary authorities, . 828, 912 PAGE 298 291 798 49 544 249 of London, 823 Potassium permanganate for purifying water, ------------process in analysis of air. of water, Potatoes as articles of diet, ------as culture media, Potato-gelatin, preparation of, Potential energy of the food-stuffs, Precipitation of sewage, Preservation of food, ------of meat, . ------of milk, . Preserved foods, . Prevention of anthrax, ------cerebro-spinal fever, ------cholera, . ------diarrhoea, ------diphtheria, ------dysentery, ------enteric fever, ------erysipelas, ------hydrophobia, ------influenza, ------leprosy, . ------malaria, . ------measles, . ------mumps, . ------plague, ------pneumonia, ------relapsing fever, ------scarlet fever, ------small-pox, ------tetanus, . ------tuberculosis, ------typhus fever, ------whooping-cough, ------yellow fever, Probable duration of life, Proof spirit, Propulsion, ventilation by, Protection from infectious diseases. Proteids, .... ------nutritive value of, Protozoa, parasitic, Psorosperms, . Puccinia graminis, Puerperal fever, . Pulex pen etra n s, Purification of air by infectants, ------ of sewage, ------of water, . Rabies, Radiation of heat, ------solar, ------ terrestrial, thermometers, Rain, gaseous dis as source of water-supply, 46 172 76 349 95 95 258 543 361 362 307 361 597 598 605 610 616 619 625 627 630 632 633 636 639 639 640 643 646 651 662 663 668 671 672 675 784 797 385 211 590 247 252 561 290, 562 331 643 565 543 45 628 218 717 718 717 742 Rain, calculation of fall of, Rainfall, . . . . . ------table showing daily yield from Rain-gauge, Rain-water, composition of, Rations, emergency or iron, ------of Austro-Hungarian soldier ------of Belgian soldier, ------of English sailor in mercantile marine, in navy, soldier at home, — in India, on board ship, ------French soldier ------German soldier, . ----- Italian soldier, . ------Japanese soldier, -----Russian soldier, . ------Sepoy in India, . ------Spanish soldier, ------United States soldier, ------war, Reek's disinfector, Recruits, selection of, Refreshment, law of, Regulations, sanitary, . Relapsing fever, . Removal of excreta, ------------law relating to, Reservoirs for water-supply, Respiration, air vitiated by, -------------------effects of, Respiratory diseases due to dust, ------■------------to vitiated air, ------------of miners, impurity, Rest, diet for, Rhabdonevw, intestinale, Rheumatism and soil, . Rhizopoda in water, Rice, Rickets in relation to soil, Rivers, discharge of sewage into, 534, River-water as a source of supply, ------measurement of yield, . Roasting, .... Roburite, effects of, Roofs, construction of, . Rotheln, . . Rum, .... Russian soldier, rations of, Rye, .... Saccharin, Saccharometer, use of, . Sago, .... Sailors, mortality and sickness anion, Salicylic acid in milk, . Salt, .... ------meat, Salts, mineral, ------nutritive value of, Sand and gravel as filtering media, Sandstone, water from, Sandy soils in relation to malaria, ------water from, Sanguisuga hcemopis, . ------tagella, Sanitary Authorities in England and Wales, ------------in Ireland, ------------in London, PAGE 16, 743 742 , 1014 743 8 358 951 952 999 1002 944 946 1004 949 950 952 953 952 953 952 952 946 685 916 429 834 645 ■13, 987 840 19 143 162 149 164 149 182 266 r.72 474 91 345 475 837, 849 12 17 275 154 491 646 385 952 342 355 313 353 1004 321 408 289 251 255 47 25 470 567 567 820 824 823 1032 INDEX. Sanitary Authorities in Scotland, ------bye-laws and regulations, ------definitions, ------inspection of houses, ------inspectors, ------law, .... — in relation to adultera- tion of food, PAGE 823 834 832 497 829 820 893 887 alkali works, baths and wash houses, . 904 canal boats, . 871 cellar dwellings, 857 cleansing and scavenging, . 844 common lodg- ing-houses, . 858 dairies and cow- sheds, . 896 drains of houses, 840 factories, . 882 horse-flesh, . 892 infectious diseases, 905 lodgings for the working classes, 869 mortuaries and cemeteries, . 901 movable dwellings, 873 new buildings, nuisances, offensive trades, parks and open spaces, port sanitation, sewers_ slaughter-houses, tenement houses, unhealthy areas, dwellings. Saprolegnia, Sausages, . Scarlet fever, ------disinfection in, . ---in relation to milk, to water, unsound food, water-supply, 861 863 866 891 847 560 288 647 651 306, 650 41 Scavenging, law relating to, Schools, sanitary construction of, ------air of, . ------influence of, in spread of diph theria, . ------power of Sanitary Authority to close, Scott-Moncrieff process of sewage treatment, Scurvy, .... Sea, discharge of sewage into, . Seamen, selection of, Sea-water, composition of, Search after water, Sediment of water, Separate system of sewage removal Sepoy diet, Service, military, effects of, naval, effects of, Sewage, composition of, ------disposal of, ------discharge of, into rivers, - sea, farms, law relating to disposal of, 874 852 899 912 837 844 495 145 615 909 ------precipitation of, 553 277 542 980 13 57 89 534, 551 953 968 1007 511 542 544 542 546 837 543 PAGE Sewage treatment, comparison of methods, 555 Sewers, air of, effects of. ------calculation of discharge from, ------choking of, ------inspection of, ------law relating to, . ------movement of air in, ------powers of Sanitary Authorities over, ------ventilation of, . Sherringham valves, Ships, .... ------classification of, . ------cleansing of, ------closets and latrines on, ------construction of, ------crew spaces in, . ------dietaries on board of, . ------disinfection of, . ------heating and lighting of, ------hospital accommodation on, ------impurities of air of, ------interior economy of, ------sanitation of, ------ventilation of, ------water-supply of, Shoddy, detection of, Shoes and boots, Shone system of sewage removal, Sicherheit explosive, effects of, on air Sickness-rates, ------in army, . ------in mercantile marine, . ------in navy, . Silica in water, . Silk, .... Siphon traps, Sites, .... Slaughter-houses, ------law as to, Slop-closets, Small-pox, ------and vaccination, ------hospitals for, ------protection from, Smoke, prevention of nuisances from ------test for drains, . Snow-water, Soap-making, Soap-test for hardness of water, Sodium manganese for purifying watei Soil-pipes, Soils, .... ------air of, . ------examination of, . ------formation of, ------geological origin of, ------heat of, . ------in relation to anthrax, ------------to calculus, ------------to cancer, ------------to cholera, ------------to diarrhoea, ------------to diphtheria, . ------------to dysentery, ------------to enteric fever, ------------to goitre, ------------to lead in water, ------------to malaria, ------------ to malignant cedema -------------to phthisis, 528 135 156 r>:$7 541 541 837 539 837 539 203 981 981 997 987 982 988 999 695, 997 996 990 991 984 979 991 998 412 418 552 154 783 971 1004 1007 80 412 524 486 802 889 517 651 654 506 654 853 533 10 806 65 46 523 432 438 477 436 432 446 456 457 458 458 461 462 464 465 467 468 469 471 472 INDEX. 1033 Soils in relation to rheumatism, -------------to rickets, -------------to tetanus, -------------to yellow fever, ------micro-organisms in, ------water in, Soldier, barracks of the, ------clothing of the, . ------effects of service upon the ------food of the, ------ hospitals for the, ----— invaliding of, ------mortality of the, ------recruiting of the, ------sickness of the, . Solids in water, determination of, Solutions, preparation of standard, Spirillum of cholera in water, . -------------general character of, Spirits, .... Sponge as a filtering medium, Spongy iron as a filtering medium, Spring water, Springs as sources of water-supply. Stables, ventilation of, . Staining of micro-organisms, . Standard diets, . ------solutions, Starch, .... ------grains, table of, . Statistics of the army, . -------------mercantile marine, navy, vital, Statistical evidence of health of com munities, ------methods, ------series, value of a,, ------tables, -------------required by Local Government Board PAGE 474 475 475 475 450 442 918, 938 953 970 944 938 974 974 916 976 63 62 103 602 384 50 49 11 10 193 015 264 62 250 354 971 79, 1004 1007 762 Steam, disinfection by, . Steam-jet, ventilation by, Sterilisation, apparatus for, Stewing of meat, Storage of water, -------------impurities from, - on board ships, . Stoves, oil, 543 544 56,89 Stratus clouds, . Streets, new, law as to, Subsistence diet, . Suctoria, parasitic, Sugars, .... ------examination of, . Sulphate of alum as a sewage precip itant, .... ------of iron as a sewage precipitant Sulphates in water, Sulphur as a disinfectant, ------dioxide in air, . . 174, 154 -------------in water, . . 45, 89 Sunshine,.....722 Suspended matter in air, 125, 130, 148, 175 --------------in water, Tables, statistical, . . .796 Tacca arrowroot, . . . 352 Tunia acanthotrias, . . . 580 ------cucumerina, . . . 582 ------echinococcus, . . . 580 793 795 796 1019 681 210, 994 93, 683 273 19 28 999 223 225 228 733 874 266 567 250 355 Ttunia flavo-punctata, . ------madagascariensis, ------nana, . ------saginata, ------solium, Tapioca, .... Tasajos, .... Tea, .... Temperature, how observed and cal culated, ------daily periodic changes of, ------distribution of, . ------influence on health, ------mean, ------yearly changes of, Tenement houses, law as to, . Tents, .... Tetanus, .... ------in relation to soil, Thermantidote, . Thermometers, . Thresh's disinfector, oxygen process, PAGE 581 582 581 577 578 383 362 394 713 720 722 699 719 721 860 933 662 475 213, 931 713 685 81 728 77 Thunderstorms, Tidy's oxygen process, Tin for water-pipes, ... 24 Tobacco smoke, vitiation of air by, . 143 Tobin's tubes, .... 204 Tous les mois arrowroot, . . 353 Trades, offensive, . . 150, 801 Training, ..... 430 Traps for sewers, . . . 523 Trematoda, parasitic, . . . 583 Tricocephalus dispar, . . . 568 Trichina spiralis, . . 296, 569 Tripe-boiling, .... 803 Trough-closets, .... 520 Tub and pail closets, . . . 514 Tubercular diseases, . . . 664 -------------in relation to vitiated air, . . 164, 666 Tube wells, . . . .51 Typhoid. See Enteric fever. Typhus fever, .... 668 Tyrotoxicon, .... 322 Unhealthy areas, law as to, . . 863 ------dwelling-houses, law as to, . 867 United States soldier's food, . . 952 Unsound food, law as to sale of, . 891 Upland surface water, ... 10 Vaccination, .... 654 Vapour, effects of, on temperature, . 739 ------elastic force of, . . 126, 737 ------weight of, ... 740 Varnish-making, . . . 810 Vegetable acids, . . . 251 Vegetables, composition of, . . 356 ------dried and preserved, . . 362 Velocity of air, how calculated, 129, 197 ------discharge from sewers, . 537 Venereal disease in the army, . 975 Ventilation, .... 180 ------artificial, . . . 207 ------calculation of head of air in, 212 ------comparative value of methods of, 214,237 ------examination of sufficiency of, 238 ------extraction by fans, . . 211 -------------by heat, . . .207 ——------by steam jets, . 210, 994 ------forces concerned in, . . 194 3 u 1034 INDEX. Ventilation, friction in, ------natural, . ------of barracks abroad, ------------at home, ------of hospitals, ------of schools, ------of sewers, ------of ships, . ------of soil pipes, practical examination of, Vinegar, Vital statistics of the army, ------------of the mercantile marine, ------------of the navy, Vitiation, respiratory, . Volumetric analysis, theory of, V-shaped depressions, . Walls, War, rations for, Warming by fireplaces, ------by hot air, ------by hot water, ------by steam, ------by stoves, ------of barracks, ------of houses, ------of ships, . Washington Lyon's disinfector, Waste pipes, Water, ------action of, on lead pipes, ------amount required, -----------------— for animals, -------------------for domestic purposes, -------------------for hospitals, -------------------for trade purposes, -------------------for water-closets, ------------supplied to cities, -------------------to sailors, to soldiers, PAGE 198 200 930 924 501 237 539 991 523 240 404 762 970 1004 1007 143, 182 60 756 489 946 219 229 230 230 223 924 216 996 684 523 1 23 3 6 7 5 4 998 4 52 92 747 2 14 520 15 53 analysis of, bacteriological examination of, barometers, boiling points of, classification of kinds of, closets, collection of, ------of samples of, . comparative value of different sources of, . . 13 composition of, . . . 1 constant supply of, . . 20 diseases produced by impure, 30 dissolved solids in, . . 63 distillation of, . . 45, 998 distilled, ... 13, 1018 distribution of, . . . 20 effects of impure, . . 29 examination of, ... 52 ------of bacteriological, . 92 ------chemical, . . 56 ------microscopic, . . 89 ------physical, . . 54 ------qualitative, . . . 56 Water examination, quantitative, -------------suspended matter, ------filtration of, ------impurities of, ------in relation to cholera, -------------diarrhoea, -------------diphtheria, ------------■ dysentery, ------------dyspepsia, -------------enteric fever, -------------entozoa, . -------------goitre, . -------------lead poisoning -------------malaria, . -------------parasitic diseases, -------------yellow fever, ------in soil, ------insufficient supply of, ------intermittent, ------purification of, . ------rain, ------river, ------sea, ------search after, ------snow, ------spring, ------upland surface, . ------sources of, ------storage of, ------supplies, law relating to, 4, PAGE 60 89 47 25 30, 604 36, 609 41, 615 38, 617 38 34, 624 43 42 23 39, 636 43 38 442 28 20 45 8 12 13 51 10 10 10 8 18 18, 998 847 Weather. See Climate Weather forecasting, Weevil in flour, . Weights of soldier's equipment, Wells as sources of water-supply, Wheat, ------diseases connected with altered qualities of, ------diseases of, ------examination of, Whisky, . Whooping-cough, Wind, — action of, in ventilation, influence on health, Wines, adulteration of, artificial improvement of, examination of, 754 331 958 11, 18 » 328 336 331 332 385 671 723 195 705 377 383 380 382 410 818 428 266 Wool as an article of clothing, Wool-sorting, Work. See Exercise. ------calculation of, . ------diets for various degrees of, Working classes, law as to housing of, ... . 863, 869 Workshops, sanitary legislation of, . 882 Worms in water, . . .43 Yellow-fever, . . . .673 ------in relation to soil, . . 475 -------------to water, . 38, 675 Zinc chloride as a disinfectant, . 694 ------poisoning through water, . 44 ------works, hygiene of, . . 817 NEILL AND COMPANY, PRINTERS, EDINBURGH. READ » SPECIAL NOTE " BELOW. CATALOGUE No. 1. DECEMBER, 1895. CATALOGUE Medical, Dental, Pharmaceutical, and Scientific Publications, WITH A SUBJECT INDEX, OF ALL BOOKS PUBLISHED BY P. BLAKISTON, SON & CO. (Successors to Lindsay & Blakiston), PUBLISHERS, IMPORTERS, AND BOOKSELLERS, 1012 WALNUT ST., PHILADELPHIA. SPECIAL NOTE. The prices as given in this catalogue are absolutely net, no discount will be allowed retail purchasers under any consideration. This rule has been established in order that everyone will be treated alike, a general reduction in former prices having been made to meet previous retail discounts. Upon receipt of the advertised price any book will be forwarded by mail or express, all charges prepaid. We keep a large stock of Miscellaneous Books relating to Medicine and Allied Sciences, published in this country and abroad. Inquiries in regard to prices, date of edition, etc., will receive prompt attei tion. The following: Catalogues sent free upon application:— CATALOGUE No. 1.—A complete list of the titles of all our publications on Medicine, Dentistry, Pharmacy, and Allied Sciences, with Classified Index. CATALOGUE No. 2.—Medical Books. Illustrated with portraits of prominent authors and figures from special books. CATALOGUE No. 3.—Pharmaceutical Books. CATALOGUE No. 4.—Books on Chemistry and Technology. CATALOGUE No. 5.—Books for Nurses and Lay Readers. CATALOGUE No. 6.—Books on Dentistry and Books used by Dental Students. CATALOGUE No. 7.—Books on Hygiene and Sanitary Science; Including Water and Milk Analysis, Microscopy, Physical Education, Hospitals, etc. SPECIAL CIRCULARS.—Morris' Anatomy; Gould's Medical Dictionaries; Moullin's Surgery; Books on the Eye; The ? Quiz Compends? Series, Visiting Lists, etc. We can also furnish sample pages of many of our publications. P. Blakiston, Son & Co.'s publications may be had through booksellers in all the princi- pal cities of the United States and Canada, or any book will be sent by them, postpaid, upon receipt of the price. They will forward parcels by express, C. O. D., upon receiving a remittance of 25 per cent, of the amount ordered. Money should be remitted by express or post office money order, registered letter, or bank draft. THE PRICES OF ALL B CLASSIFIED LIST, WITH PRICES, OF ALL BOOKS PUBLISHED BY P. BLAKISTON, SON & CO., PHILADELPHIA. When the price is not given below, the book is out of print or about to be published. Cloth binding, unless otherwise specified. For full descriptions see following Catalogue. ANATOMY. Ballou. Veterinary Anat. Jo.80 Campbell. Dissector. - 1.00 Heath. Practical. 7th Ed. 4.25 Holden. Dissector. Oil-cloth, 2.50 ----- Osteology. - - 5.25 ----- Landmarks. 4th Ed. 1.00 Macalister's Text-Book. - 5.00 Marshall's Phys. and Anat. Diagrams. $40.00 and 60.00 Morris. Text Book of. 791 Illus. Clo , 6.00; Sh., 7.00; % Rus., 8.00 Potter. Compend of. 5th Ed. 133 Illustrations. - .80 Wilson's Anatomy, nth Ed. 5.00 ANESTHETICS. Buxton. Anaesthetics. - 1.25 Turnbull. 3d Ed. - 3.00 BRAIN AND INSANITY. Blackburn. Autopsies. - 1.25 Gowers. Diagnosis of Dis- eases of the Brain. 2d Ed. 1.50 Horsley. Brain and S. Cord. 2.50 Hyslop. Mental Physiology. 4.25 Lewis (Bevan). Mental Diseases. 2d Ed. - --- Mann's Psychological Med. 3.00 Regis. Mental Medicine. - 2.00 Stearns. Mental Dis. Illus. 2.75 Tuke. Dictionary of Psycho- logical Medicine. 2 Vols. 10.00 Wood. Brain and Overwork. .40 CHEMISTRY. See Technological Books. Water. Allen. Commercial Organic Analysis. 2d Ed. Volume I. --- ----- Volume II. - - — ----- Volume III. Part I. --- ----- Volume III. Part II. 4.50 ----- Volume III. Part III.--- -----Diabetic Urine. - 2.25 Bartley. Medical and Phar- maceutical. 4th Ed. - 2.75 Bloxam's Text-Book. 8th Ed. 4.25 Caldwell. Qualitative and Quantitative Analysis. - 1.50 Clowes. Qual. Analysis. - 1.00 Groves and Thorp. Chemi- cal Technology. Vol. I. Fuels 5.00 -----Vol.11. Lighting. - 4.00 Holland. Urine, Gastric Con- tents, Poisons and Milk Anal- ysis. 5th Ed. ... 1.00 Leffmann's Compend. - .80 ----- Progressive Exercises. 1.00 ----- Milk Analysis. - - 1.25 Mliter. Pract. and Anal. 1.25 Richter's Inorganic. 4th Ed. 1.75 ----- Organic. 2d Ed. 4.50 Smith. Electro-Chem. Anal. 1.25 Smith and Keller. Experi- ments. 3d Ed. Illus. .60 Stammer. Chem. Problems. .50 Sutton. Volumetric Anal. 4.50 Symonds. Manual of. 2.00 Trimble. Analytical. - 1.50 Watts. (Fowne's) Inorg. 2.00 ----- (Fowne's) Organ. 2.00 Woody. Essentials of. 4th Ed.--- CHILDREN. Goodhart and Starr. - --- Hale. Care of. - .50 Hatfield. Compend of. .80 Meigs. Infant Feeding and Milk Analysis. - .50 Money. Treatment of. - 2.50 Muskett. Treatment of. 1.25 Power. Surgical Diseases of. 2.50 Starr. Digestive Organs of. 2.00 -----Hygiene of the Nursery, i.co CLINICAL CHARTS. Griffiths. Graphic. Pads. $0.50 Temperature Charts. " .5° COMPENDS And The Quiz-Contpends. Ballou. Veterinary Anat. .80 Brubaker's Physiol. 7th Ed. .80 Fox and Gould. The Eye. .80 Hall. Pathology. Illus. .80 -----Nose and Ear. - .80 Hatfield. Children. - .80 Horwitz. Surgery. 5th Ed. .80 Hughes. Practice. 2 Pts. Ea. .80 Landis. Obstetrics. 5th Ed. .80 Leffmann's Chemistry. 4th Ed. .80 Mason. Electricity. - .75 Potter's Anatomy, 5th Ed. .80 -----Materia Medica. 6th Ed. .80 Stewart, Pharmacy. 5th Ed. .80 Warren. Dentistry. 2d Ed. .80 Wells. Gynaecology. - .80 DEFORMITIES. Reeves. Bodily Deformities and their Treatment. Illus. 1.75 DENTISTRY. Barrett. Dental Sure. - 1.00 Blodgett. Dental Pathology. 1.25 Flagg. Plastic Filling. - 4.00 Fillebrown. Op. Dent. Illus. 2.2s Gorgas. Dental Medicine. 4x0 Harris. Principles and Prac. 6.00 -----Dictionary of. 5th Ed. 4.50 Heath. Dis. of Jaws. - 4.50 -----Lectures on Jaws. Bds. .50 Richardson. Mech. Dent. 4.00 Sewell. Dental Surg. - 2.00 Taft. Operative Dentistry. 3.00 -----, Index of Dental Lit. 2.00 Talbot. Irregularity of Teeth. 3.00 Tomes. Dental Surgery. 4.00 ----- Dental Anatomy. 3.50 Warren's Compend of. - .80 ----- Dental Prostheses and Metallurgy. Illus. - 1.25 White. Mouth and Teeth. .40 DICTIONARIES. Cleveland's Pocket Medical. .50 Gould's Illustrated Dictionary of Medicine, Biology, and Al- lied Sciences, etc. Leather, Net, $10.00; Half Russia, Thumb Index, - Net, 12 00 Gould's Medical Student's Dic- tionary. U Lea., 2.75; %Mor. Thumb Index. ... 3.50 Gould's Pocket Dictionary. 12,000 medical words. Lea., 1.00: Thumb Index, - 1.25 Harris'Dental. Clo.4.50; Shp.5.50 Longley's Pronouncing. .75 Maxwell. Terminologia Med- ica Polyglotta. - - 3.00 Treves. German-English. 3.25 EAR. Burnett. Hearing, etc. .40 Dalby. Diseases of. 4th Ed. 2.50 Hall. Compend. - - .80 Hovell. Treatise on. - 5.00 Pritchard. Diseases of. 1.25 ELECTRICITY. Bigelow. Plain Talks on Medi- cal Electricity. 43 Illus. 1.00 Mason's Electricity and its Medical and Surgical Uses. .75 Steavenson & Jones. Medi- cal Electricity. Illus. - --- EYE. Arlt. Diseases of. - - 1.25 Fick. Handbook of Dis. --- Fox and Gould. Compend. $0.80 Gower's Ophthalmoscopy. 4.00 Harlan. Eyesight. - .40 Hartridge. Refraction. sthEd. 1.00 —— Ophthalmoscope. - 1.23 Hansell and Bell. Clinical Ophthalmology. 120 Illus. 1.50 Higgins. Practical Manual. 1.50 Macnamara. Diseases of. 3.50 Meyer. Text-Book. - 3.50 Morton. Refraction. 4th Ed. 1.00 Phillips. Spectacles and Eye- glasses. 49 Illus. .2d Ed. 1.00 Swanzy's Handbook. 4th Ed. 2.50 Walker. Student's Aid. 1.50 FEVERS. Collie, On Fevers. - 2x0 HEADACHES. Day. Their Treatment, etc. 1.00 HEALTH AND DOMESTIC MEDICINE. Bulkley. The Skin. - .40 Burnett. Hearing. - .40 Cohen. Throat and Voice. .40 Dulles. Emergencies. 4th Ed. 1.00 Harlan. Eyesight. - .40 Hartshorne. Our Homes. .40 Osgood. Dangers of Winter. .40 Packard. Sea Air, etc. .40 Richardson's Long Life. .40 Westland. The Wife and Mother. ... 1.50 White. Mouth and Teeth. .40 'Wilson. Summer and its Dis. .40 Wood. Overwork. - .40 HEART. Sansom. Diseases of. - 6.00 HYGIENE. Canfield. Hygiene of the Sick- ' Room. .... 1J25 Coplin and Bevan. Practi- 1 cal Hygiene. Illus. - 3125 Fox. Water, Air, Food. 3150 Kenwood. Public Health 1 Laboratory Guide. ■ - 2.00 Lincoln. School Hygiene. . 40 McNeill. Epidemics and Iso- lation Hospitals. - - 3.jo Parke's (E.) Hygiene. 8th Ed. 4.50 ----- (L. C.), Manual. 2.yo ----- Elements of Health. 1.25 Starr. Hygiene of the Nursery. 1.00 Stevenson and Murphy. A Treatise on Hygiene. In 3 Vols. Circular Vol. I, 6.00 upon application. Vol. II, 6.00 Vol. Ill 5.00 Wilson's Handbook. 7th Ed. 3.C0 Weyl. Coal-Tar Colors, 1.25 JOURNALS, Etc. Ophthalmic Review. 12 Nos. 3.00 New Sydenham Society's Publications, each year. - 8.00 KIDNEY DISEASES. Ralfe. Dis. of Kidney, etc. 2.00 Thornton. Surg, of Kidney. 1.50 Tyson. Bright's Disease and Diabetes, Illus. - 2.50 MASSAGE. Kleen and Hartwell. - 2.25 Murrell. Massage. 5th Ed. 1.25 Ostrom. Massage. 87 Illus. 1.00 MATERIA MEDICA. Biddle. 13th Ed. Cloth, 4.00 Bracken. Materia Med. 2.75 Davis. Essentials of Materia Med. and Pres. Writing of. 1.50 Gorgas. Dental. 5th Ed. 4.00 Potter's Compend of. 5th Ed. .80 RICES ARE NET. CLASSIFIED LIST OF P. BLAKISTON, SON 6- CO.'S PUBLICATIONS. Potter's Handbook of. Fifth Ed. Cloth, 4.00 ; Sheep, $;.oo Sayre. Organic Materia Med. and Pharmacognosy. - 4.00 White & Wilcox. Mat. Med., Pharmacy, Pharmacology, and Therapeutics. 3d Ed. Enlarged. Cloth, 2.75; Sh. 3.25 MEDICAL JURISPRUDENCE. Mann. Forensic Med. - 6.50 Reese. Medical Jurisprudence &Toxicology,4th Ed.3.00; Sh. 3.50 MICROSCOPE. Beale. How to Work with. 6.50 ----- In Medicine. - 6.50 Carpenter. The Microscope. 7th Ed. 800 Illus. - 5.50 Lee. Vade Mecum of. ' - 4.00 MacDonald. Examination of Water and Air by. - 2.50 Reeves. Medical Microscopy. Illustrated. - - - 2.50 Wethered. Medical Micros- copy. Illus. - - - 2.00 MISCELLANEOUS. Black. Micro-organisms. .75 Burnet. Food and Dietaries. 1.50 Davis. Text-book of Biology. 3.00 Duckworth. On Gout. - 6.00 Garrod. Rheumatism, etc. 5.00 Gowers. Dynamics of Life. .75 Haig. Uric Acid. - - 3.00 Hare. Mediastinal Disease. 2.00 Harris and Beale. Consump- tion. - --- Henry. Anasmia. - - .50 Leffmann. Coal Tar Products. 1.25 Powell. Lungs, etc. - - 4.00 Treves. Physical Education. .75 NERVOUS DISEASES, Etc. Flower. Atlas of Nerves. 2.50 Gowers. Manual of. 2d Ed. 530 Illus. Vol. 1,3.00; Vol. 2,4.00 -----Syphilis and the Nerv- ous System. - - - 1.00 ----- Diseases of Brain. 1.50 ----- Clinical Lectures. 2.00 Horsley. Brain and Spinal Cord. Illus. - - - 2-5° Obersteiner. Central Nervous System. - - - - 5-5° Ormerod. Manual of. - 1.00 Osier. Cerebral Palsies. 2.00 -----Chorea. - - 2.00 Page. Injuries of Spine. --- -----Railway Injuries. - 2.25 Thorburn. Surgery of the Spinal Cord. - - - 4-°° Watson. Concussions. 1.00 NURSING. Canfield. Hygiene of the Sick- Room. ... - 1.25 Cullingworth. Manual of. .75 ----- Monthly Nursing. .40 Domville's Manual. 7th Ed. .75 Fullerton. Obst. Nursing. 1.00 _____ Nursing in Abdominal Surg, and Dis. of Women, 1.50 Humphrey. Manual. i^thEd. 1.00 Shawe. District Nursing. 1.00 Starr. Hygiene of the Nursery. 1.00 Temperature Charts. - .50 Voswinkel. Surg. Nursing. 1.00 OBSTETRICS. Bar. Antiseptic Midwifery. 1.00 Cazeaux and Tarnier. Text- Book of. Colored Plates. 4.50 Davis. Obstetrics. Illus. 2.00 Landis. Compend. 5th Ed. .80 Schultze. Obstetric Diagrams. 20 Plates, map size. Net, 26.00 Strahan. Extra-Uterine Preg. .75 Winckel's Text-book. 5.00 PATHOLOGY & HISTOLOGY. Blackburn. Autopsies. 1.25 Blodgett. Dental Pathology 1.25 Gilliam. Essentials of. - .75 Hall Compend. Illus. - .80 Stirling. Histology. 2d Ed. 2.00 Stohr's Histology. - --- Virchow. Post-mortems. #0.75 PHARMACY. Beasley's Receipt-Book. - 2.00 -----Formulary. - - 2.00 Coblentz. Manual of Pharm. 3.50 Proctor. Practical Pharm. 3.00 Robinson. Latin Grammar of. 1.75 Sayre. Organic Materia Med. and Pharmacognosy. - 4.00 Scoville. Compounding. 2.50 Stewart's Compend. 5th Ed. .80 U. S. Pharmacopoeia. 7th Revision. CI. 2.50; Sh., 3.00 Select Tables from U. S. P. .25 White and Wilcox. Materia Medica and Phar. 2d Ed. 2.75 PHYSICAL DIAGNOSIS. Tyson's Manual. 2d Ed. Illus. 1.25 PHYSIOLOGY. Brubaker's Compend. Illus- trated. 7th Ed. - - .80 Kirkes' New 13th Ed. (Au- thor's EdJ Cloth, 3.25; Sh., 4.00 Landois' Text-book. 845 Illus- trations. - - --- Starling. Elements of. - 1.00 Stirling. Practical Phys. 2.00 Tyson's Cell Doctrine. - 1.50 Yeo's Manual. 254 Illustrations 6th Ed. Cloth, 2.50 Sheep, 3.00 POISONS. Murrell. Poisoning. - 1.00 Reese. Toxicology. 3d Ed. 3.00 Tanner. Memoranda of. .75 PRACTICE. Beale. Slight Ailments. 1.25 Charteris, Guide to. - 2.00 Fagge's Practice. 2 Vols. 7.00 Fowler's Dictionary of. - 3.00 Hughes. Compend. 2 Pts. ea. .80 ----- Physicians' Edition. 1 Vol. Morocco, Gilt edge. 2.25 Roberts. Text-book. 9th Ed. 4.50 Taylor's Manual of. - 2.00 PRESCRIPTION BOOKS. Beasley's 3000 Prescriptions. 2.00 ----- Receipt Book. - 2.00 Davis. Materia Medica and Prescription Writing. - 1.50 Pereira's Pocket-book. .75 Wythe's Dose and Symptom Book. 17th Ed. - - .75 SKIN. Anderson's Text-Book. 3.00 Bulkley. The Skin. - .40 Crocker. Dis. of Skin. Illus. 4.50 Van Harlingen. Diagnosis and Treatment of Skin Dis. 3d Ed. 60 Illus. - - 2.75 STIMULANTS & NARCOTICS. Lizars. On Tobacco. - .40 Parrish. Inebriety. - 1.00 SURGERY AND SURGICAL DISEASES. Caird and Cathcart. Surg- geon's Pocket-Book. Lea. 2.50 Dulles. Emergencies. - 1.00 Hacker. Wounds. - - .50 Heath's Minor. 10th Ed. 1.25 -----Diseases of Jaws. - 4.50 ----- Lectures on Jaws. .50 Horwitz. Compend. 5th Ed. .80 Jacobson. Operations of. - 3.00 Macready on Ruptures - 6.00 Moullin. Complete Text- book. 3d Ed. by Hamilton, 600 Illustrations and Colored Plates. CI. 6.00; Sh. 7.00 Porter's Surgeon's Pocket- book. - - Leather 2.00 Smith. Abdominal Surg. --- Voswinkel. Surg. Nursing. 100 Walsham. Practical Surg. 2.7s Watson's Amputations. 5.50 TECHNOLOGICAL BOOKS. Cameron. Oils & Varnishes. 2.25 ----- Soap and Candles. 2.00 Gardner. Brewing, etc. $1.5° Gardner. Bleaching and Dyeing. - - . - 1.50 Groves and Thorp. Chemi- cal Technology. Vol. I. Mills on Fuels. - CI. 5.00 Vol. II. Lighting. - 4.00 Vol. III. Lighting Contin'd.--- Overman. Mineralogy. - 1.00 THERAPEUTICS. Allen, Harlan, Harte, Van Harlingen. Local Thera. 3.00 Biddle. 13th Edition - 400 Field. Cathartics and Emetics. 1.75 Mays. Therap. Forces. 1.25 —— Theine - - - 50 Napheys' Therapeutics. Vol. 1. Medical and Disease of Children. - Cloth, 4.00 -----Vol. 2. Surgery, Gynaec. & Obstet. - Cloth, 4.00 Potter's Compend. 5th Ed. .80 -----, Handbook of. 4.00 ; Sh. 5.00 Waring's Practical. 4th Ed. 2.co White and Wilcox. Mat. Med., Pharmacy, Pharmacol- ogy, and Thera. 3d Ed. 2.75 THROAT AND NOSE. Cohen. Throat and Voice. .40 Hall. Nose and Throat. - 2.50 ----- Nose and Ear. - .80 Hutchinson. Nose & Throat. ——- Mackenzie. Throat Hospital Pharmacopoeia. 5th Ed. 1.00 McBride. Clinical Manual, Colored Plates. 2d Ed. - 6.00 Murrell. Bronchitis. - 1.50 Potter. Stammering, etc. 1.00 Woakes. Post-Nasal Catarrh. 1.00 TRANSACTIONS. Trans. College of Physicians. 3.50 ----- Assoc. Amer. Phys. 3.50 URINE & URINARY ORGANS. Acton. Repro. Organs. 1.75 Allen. Diabetic Urine. 2.25 Beale. Urin. Deposits. Plates. 2.00 Holland. The Urine, Milk and Common Poisons. 5th Ed. 1.00 Legg. On Urine. 7th Ed. 1.00 Memminger. Diagnosis by the Urine. Illus. - - 1.00 Moullin. The Prostate. - 1.50 Thompson. Urinary Organs. 3.00 ----- Calculous Dis. 3d. Ed. .75 Tyson. Exam, of Urine. 1.25 Van Niiys. Urine Analysis. 1.00 VENEREAL DISEASES. Cooper. Syphilis. 2d Ed. - 5.00 Gowers. Syphilis and the Nervous System. - - 1.00 Hill and Cooper's Manual. .75 Jacobson. Diseases of Male Organs. Illustrated. - 6.00 VETERINARY Armatage. Vet. Rememb. 1.00 Ballou. Anat. and Phys. .80 Tuson. Pharmacopoeia. 2.25 VISITING LISTS. Lindsay & Blakiston's Reg- ular Edition. 1.00 to 2.2s ----— Perpetual Ed. 1.25 to 1.50 ----- Monthly Ed. .75 to 1.00 Send for Circular. WATER. Fox. Water, Air, Food. 3.50 Leffmann. Examination of. 1.25 MacDonald. Examination of. 2.50 WOMEN, DISEASES OF. Byford (H. T.). Manual. 2.50 Byford(W. H). Text-book. 2.00 Duhrssen. Gynecological Practice. 105 Illustrations. 1.50 Lewers. Dis. of Women. 2.co Wells. Compend. Illus. .80 Winckel,by Parvin. Manual of. Illus. Cloth 3.00; Sh. 3.50 ffS> BASED ON RECENT MEDICAL LITERATURE. Gould's Medical Dictionaries BY GEORGE M. GOULD, A.M., M.D., Ophthalmic Surgeon to the Philadelphia Hospital, Editor of "The Medical News." THE STANDARD MEDICAL REFERENCE BOOKS. The Illustrated Dictionary of Medicine, Biology, and Allied Sciences. INCLUDING THE PRONUNCIATION, ACCENTUATION, DERIVATION, AND DEFINITION OF THE TERMS USED IN MEDICINE AND THOSE SCIENCES COLLATERAL TO IT : BIOLOGY (ZOOLOGY AND BOTANY), CHEMISTRY, DENTISTRY, PHARMACOLOGY, microscopy, etc. With many Useful Tables and numerous Fine Illustra- tions. Large, Square Octavo. 1633 pages. Full Sheep, or Half Dark-Green Leather, #10.00; with Thumb Index, $11.00 Half Russia, Thumb Index, #12.00 The Student's Medical Dictionary. INCLUDING ALL THE WORDS AND PHRASES GENERALLY USED IN MEDICINE, WITH THEIR PROPER PRONUNCIATION AND DEFINITIONS, BASED ON RECENT MEDI- CAL literature. With Tables of the Bacilli, Micrococci, Leucomains, Ptomains, etc., of the Arteries, Muscles, Nerves, Ganglia, and Plexuses; Mineral Springs of the U. S., Vital Statistics, etc. Small Octavo. 520 pages. Half Dark Leather, $2.75 ; Half Morocco, Thumb Index, $3.50. " We know of but one true way to test the value of a dictionary, and that is to use it. We have used the volume before us, as much as opportunity would permit, and in our search have never suffered disappointment. The definitions are lucid and concise, and are framed in the terms supplied by the latest authoritative literature, rather than by purely philological method. Obsolete words are omitted, and this has made the dimensions of the book convenient and com- pact. In making a dictionary, the author confesses that he has found out the labor consists in eliminating the useless, rather than adding the superfluous. The value of the work before us is increased by the large number of useful reference tables in anatomy, ptomains, micrococci, etc."—The Physician and Surgeon, Ann Arbor. The Pocket Pronouncing Medical Lexicon. 12,000 "WORDS PRONOUNCED AND DEFINED. Double the Number in any Other Similar Book. Containing all the Words, their Definition and Pronunciation, that the Student generally comes in con- tact with; also elaborate Tables of the Arteries, Muscles, Nerves, Bacilli, etc., etc.; a Dose List in both English and Metric Systems, etc., arranged in a most convenient form for reference and memorizing. Thin 64mo. Full Limp Leather, Gilt Edges, #1.00; Thumb Index, #1.25 These books may be ordered through any bookseller, or upon receipt of price the publishers will deliver free to the purchaser's address. Full descriptive circulars and sample pages sent free upon application. 4r,000 COPIES OF GOULD'S DICTIONARIES HAVE BEEN SOLD. ■** The Prices of all Books are absolutely Net. gST" All prices are net. No discount can be allowed retail purchasers. P. BLAKISTON, SON & CO.'S JYJedical and Scientific publications, No. 1012 Walnut St., Philadelphia. ACTON. 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